THE INFLUENCE OF MINERALOGY, CHEMISTRY AND PHYSICAL
ENGINEERING PROPERTIES ON SHEAR STRENGTH PARAMETERS OF
THE GOATHILL ROCK PILE MATERIAL,
QUESTA MOLYBDENUM MINE, NEW MEXICO
by
Luiza Aline Fernandes Gutierrez
Submitted in partial fulfillment of the requirements for the
Degree of Master of Science in Mineral Engineering
with Specialization in Geotechnical Engineering
New Mexico Institute of Mining and Technology
Department of Mineral Engineering
Socorro, New Mexico
March, 2006
ABSTRACT
This thesis develops information regarding the engineering characteristics (direct
shear, Atterburg Limits, particle size) of the Goathill North (GHN) rock pile material at
the Questa molybdenum mine in New Mexico and examines correlations with chemistry,
mineralogy, particle size distribution and weathering indexes (SWI – simple weathering
index, WPI – weathering potential index, MI – Muira index). Results of peak internal
friction angle () ranged from 40º to 47º and residual friction angle varied between 37º
and 41º. These high values of peak internal and residual friction angle are attributed to
grain shape (subangular to very angular) and relative density of the test specimens.
Correlations of  from GHN samples with chemistry and mineralogy are shown to be
weak or absent. Correlation of  with lithology was not observed. Negative correlations 
were observed for %Fines, liquid limit, plasticity index, LOI (lost of ignition), SWI, WPI,
and MI. The  decreased as these parameters increased.
Direct shear tests were performed using a 2-inch square shear box and air-dried
samples with a maximum particle size of 3.36 mm (U.S standard sieve No. 6). A
displacement rate of 0.5 mm/min (0.02 in/min), and normal stress varying from 159 to
800 kPa (23 to 116 psi) were adopted for all the tests. These tests were conducted on
disturbed samples. The  values determined from these tests should not be used for slope
stability considerations.
GHN rock pile samples were classified according to the United Soil Classification
System (USCS as poorly- to well-graded gravel with fines and sand). The percent of fines
(silt + clay size) and percent of clay varied from 3 to 19 and 0.3 to 6, respectively. Most
of the fines were identified as CL-group (inorganic clay with low swell potential).
ACKNOWLEDGEMENTS
Support for this research was provided by the Molycorp Corporation. in the form
of a Research Assistantship, by the WAAIME (The Woman’s Auxiliary to the American
Institute of Mining, Metallurgical, and Petroleum Engineers), and by the New Mexico
Bureau of Geology and Mineral Resources. I gratefully acknowledge this support.
I would like to express my sincere appreciation to Dr. McLemore and Dr.
Aimone-Martin for providing guidance, insight, and support throughout the course of this
research. Appreciation is also extended to Dr. Mojtabai who is on the thesis advisory
committee and who encouraged me to do my thesis research at New Mexico Tech.
I would like to thank many people who provided insight and suggestions on this
research: Dr. Virgil Lueth, Kelly Donahue, Erin Phillips, Fernando Junqueira, Dr.
Fakhimi, Dr. Gundiler, Prof. Ward Wilson, Mike Smith, and other members of the
Molycorp project weathering study. I especially want to thank Rick Lynn, Lynne
Kurilovitch, Farid Sariosseri, Pedro Martin Moreno, Erico Tabosa, Vanessa Viterbo,
Heather Shannon, Claudia Duarte, Alexandre, Igor, Armando and Jario for assistance
with the laboratory testing program. Last but not least, I would like to thank Remke van
Dam for all his support by reviewing my thesis thousand times, and literally going
through this experience with me.
This thesis is dedicated to my parents Marta Gutierrez and Zenon Gutierrez,
my sisters Norma Gutierrez Ventura, Kelly Gutierrez Alves, Adela Gutierrez Branco, and
to my lovely husband.
TABLE OF CONTENT
List of Tables………………………………………………………………...…………...iv
List of Figures…………………………………………………………………...………...v
1.
2.
3.
INTRODUCTION ...................................................................................................... 1
1.1.
Background ......................................................................................................... 1
1.2.
Thesis Objective.................................................................................................. 2
1.3.
Site Description................................................................................................... 3
1.4.
Thesis Outline ..................................................................................................... 8
REVIEW OF STUDIES AT GOATHILL NORTH ROCK PILE.............................. 9
2.1.
Past Geotechnical Studies (Before Regrading) ................................................... 9
2.2.
Present Work and Preliminary Results ............................................................. 14
LITERATURE REVIEW OF CONCEPTS RELATED TO THIS RESEARCH .... 20
3.1.
Strength of Granular Materials ......................................................................... 20
3.2.
Weathering Process ........................................................................................... 27
3.3.
Effect of Weathering on Geotechnical Properties of Mine Rock ..................... 30
3.4.
Published Grain Size distribution and Shear Strength Parameters for Mine Rock
........................................................................................................................... 34
4.
METHODOLOGY ................................................................................................... 38
4.1.
Sampling ........................................................................................................... 38
4.2.
Particle Size Analysis ....................................................................................... 39
4.3.
Direct Shear Test Under Consolidated Drained Conditions ............................. 44
4.3.1.
4.4.
5.
Initial Test ................................................................................................. 47
Index Properties and Mineralogy ...................................................................... 54
RESULTS AND DISCUSSIONS ............................................................................. 55
i
5.1.
Indices Testing .................................................................................................. 55
5.2.
Direct Shear Test Results .................................................................................. 59
5.3.
Verification of Direct Shear Test Results ......................................................... 61
5.4.
Correlations of Direct Shear Results with Geological and Geotechnical
Parameters ..................................................................................................................... 64
5.5.
6.
Correlations of Direct Shear Test Results with Weathering Indices ................ 73
CONCLUSIONS AND RECOMENDATIONS ................................................... 7978
REFERENCES ............................................................................................................. 8180
APPENDIX A – SAMPLE LOCATION...................................................................... 8685
APPENDIX B – GRAIN SIZE DISTRIBUTION CURVES AND SUMMARY TABLE ..
............................................................................................................................... 8887
APPENDIX C – DIRECT SHEAR STRESS-STRAIN DIAGRAMS ..................... 118117
APPENDIX D – MOHR COULOMB DIAGRAMS................................................ 156154
APPENDIX E – DESCRIPTION OF GEOLOGIC UNITS, SUMMARY OF
GEOLOGICAL AND GEOTECHNICAL DATA USED FOR CORRELATIONS 176174
APPENDIX F – STANDARD OPERATING PROCEDURES ............................... 186184
LIST OF TABLES
ii
Table 2.1. Summary of geotechnical properties at GHN rock pile ................................... 10
Table 2.2. Summary of friction angle of Molycorp mine rock piles and “weak zone” at
GHN and their gradation results. ...................................................................................... 10
Table 3.1. Weathering field survey used to characterize the weathering sequence in the
gneiss................................................................................................................................. 32
Table 3.2. Main engineering-geological features of weathered horizons near Acri (after
Calcaterra et al., 1998). ..................................................................................................... 32
Table 3.3. Shear strength parameters of sedimentary residual soil with weathering grades
varying from III to V......................................................................................................... 34
Table 3.4. Grain size distribution of rock piles around the world. ................................... 35
Table 3.5. Summary of mine rock values of friction angle and cohesion. ....................... 37
Table 4.1. The minimum specimen size required for particle size analysis according to
the diameter of the largest particle (U.S. Army Corps of Engineers, 1970). .................... 41
Table 4.2. Summary of results of the 3 methods for particle size analyses. ..................... 43
Table 4.3. Summary of the results from direct shear tests using different maximum
particle size and shear box size. ........................................................................................ 50
Table 4.4. Summary of the results from direct shear test using different maximum particle
size. ................................................................................................................................... 52
Table 4.5. Summary of direct shear test results for samples at dry and moist state. ........ 52
Table 5.1. Summary of particle size analysis of samples from GHN by geologic unit. ... 56
Table 5.2. Summary of Atterberg limits results of samples from GHN by geologic unit. 57
Table 5.3. Summary of moisture content and paste pH results of samples from GHN by
geologic units. ................................................................................................................... 57
Table 5.4. Summary of direct shear test results of samples from GHN by geologic units.
........................................................................................................................................... 60
iii
LIST OF FIGURES
Figure 1.1. Location of Molycorp Questa mine, northern Taos County, New Mexico. ..... 4
Figure 1.2. Aerial photo of Questa mine showing the nine rock piles adjacent to the open
pit. ....................................................................................................................................... 4
Figure 1.3. Goathill North rock pile before regrading. ....................................................... 6
Figure 1.4. One of the trenches (LFG-004) excavated on stable portion of Goathill North
rock pile during the regrading. ............................................................................................ 6
Figure 2.1. Friction angle of GHN mine rock based on triaxial test results ..................... 12
Figure 2.2. Grain size distributions from triaxial samples from Sugar Shack rock piles
and typical Goathill North mine rock. .............................................................................. 13
Figure 2.3. Friction angle versus confining stress. ........................................................... 14
Figure 2.4. Example of a geologic map. ........................................................................... 15
Figure 2.5. Geologic cross section of bench 9, trench LFG-006. ..................................... 15
Figure 2.6. Plot of QSP hydrothermal alteration intensity................................................ 17
Figure 2.7. Plot of authigenic gypsum across bench 9, trench LFG-006.......................... 18
Figure 2.8. Results of paste pH and NAG pH across bench 9, trench LFG-006. ............. 18
Figure 3.1. Examples of sphericity and roundness charts. ................................................ 23
Figure 3.2. The effect of particle shape on internal friction angle for sand. ..................... 24
Figure 3.3. Correlations between the effective friction angle and relative density for
different soil type. ............................................................................................................. 25
Figure 3.4. Variation of peak internal friction angle with effective normal stress for direct
shear tests on standard Ottawa sand.................................................................................. 26
Figure 3.5. Physical break up of a boulder by transformation of anhydrite to gypsum
minerals at Questa mine site. ............................................................................................ 29
Figure 3.6. Evidence of chemical weathering process (oxidation) at Questa mine site. .. 30
iv
Figure 3.7. Correlation of weathering grade with dry density and porosity. .................... 33
Figure 4.1. Generalized geologic cross section of GHN showing the location of the
samples analyzed in this thesis. ........................................................................................ 39
Figure 4.2. Comparison of three different approaches for estimation of particle size
distribution using sample GHN-LFG-0003. ..................................................................... 43
Figure 4.3. Manually direct shear equipment. .................................................................. 46
Figure 4.4. Example of a shear stress versus shear strain plot.. ........................................ 47
Figure 4.5. Example of a shear diagram showing the best fit line for the peak internal
friction angle and the residual internal friction angle. ...................................................... 47
Figure 4.6. Shear box size effects on direct shear test. ..................................................... 49
Figure 4.7. Results of effect of particle size on direct shear test using a 2-inch shear box.
........................................................................................................................................... 51
Figure 4.8. Results of influence of moisture on direct shear test. ..................................... 53
Figure 5.1. Range of grain size distribution for samples from GHN rock pile................. 58
Figure 5.2. Distribution of the samples from GHN rock pile on the plasticity chart........ 58
Figure 5.3. Direct shear test results for a dry sample versus a sample with gravimetric
moisture content of 12.4%. ............................................................................................... 61
Figure 5.4. Mohr-Coulomb diagram for sample GHN-KMD-0014 using two direct shear
test equipments.................................................................................................................. 62
Figure 5.5. Mohr-Coulomb diagram for sample GHN-KMD-0017 using two direct shear
test equipments.................................................................................................................. 63
Figure 5.6. Mohr-Coulomb diagram for sample GHN-KMD-0027 using two direct shear
test equipments.................................................................................................................. 64
Figure 5.7. Stratigraphic position of the geologic units for bench 9 (Trench LFG-006). . 65
Figure 5.8. Cross plots of internal friction angle versus paste pH.. .................................. 65
Figure 5.9. Cross plots of internal friction angle versus NAGpH .................................... 65
Figure 5.10. Cross plots of internal friction angle versus percent of fines.. ..................... 66
Figure 5.11. Cross plots of internal friction angle versus plasticity index.. ..................... 66
Figure 5.12. Cross plots of internal friction angle versus liquid limit.. ............................ 67
v
Figure 5.13. Cross plots of internal friction angle versus percent Amalia Tuff.. ............. 67
Figure 5.14. Cross plots of internal friction angle versus percent Andesite.. ................... 68
Figure 5.15. Cross plots of internal friction angle versus quartz-sericite-pyrite (QSP)
alteration.. ......................................................................................................................... 69
Figure 5.16. Cross plots of internal friction angle versus propylitic alteration. ............... 69
Figure 5.17. Cross plots of internal friction angle versus LOI (lost of ignition). ............. 70
Figure 5.18. Cross plots of internal friction angle versus percent epidote. ...................... 70
Figure 5.19. Cross plots of internal friction angle versus percent illite...... ...................... 71
Figure 5.20. Cross plots of internal friction angle versus percent MgO.. ......................... 71
Figure 5.21. Cross plots of internal friction angle versus percent CaO. ........................... 72
Figure 5.22. Cross plots of internal friction angle versus percent Al2O3.......................... 72
Figure 5.23. Plot of WPI and MI with distance across bench 9, trench LFG-006. ........... 75
Figure 5.24. Plot of WPI and MI for all GHN samples. ............................................... 7675
Figure 5.25. Cross plot of Friction angle versus simple weathering index (SWI) for bench
9 samples, trench LFG-006. .............................................................................................. 76
Figure 5.26. Cross plot of Friction angle versus weathering potential index (WPI) for
samples from bench 9, trench LFG-006. .......................................................................... 77
Figure 5.27. Cross plots of Friction angle versus Miura Index (MI) for samples from
bench 9, trench LFG-006. ................................................................................................. 77
vi
This thesis is accepted on behalf of the
Faculty of the Institute by the following committee:
_________________________________________________________
Research Advisor
__________________________________________________________
Academic Advisor
__________________________________________________________
Committee Member
___________________________________________________________
Date
I release this document to the New Mexico Institute of Mining and Technology.
_____________________________________________________________
Student's Signature
Date
1. INTRODUCTION
1.1. Background
This thesis develops information regarding the engineering characteristics of
Goathill North rock pile material at the Questa molybdenum mine in New Mexico and
examines correlations of internal friction angle with mineralogy, chemistry and
weathering indexes. Molycorp Inc. is funding a multidisciplinary study to investigate the
potential effects of chemical and physical weathering on the slope stability of Goathill
North rock pile, one of the nine rock piles at the mine. The project is a unique
opportunity to sample and study the internal material of this rock pile. The ultimate goal
of the study is to assess the risk of mass failure of the mine rock pile over at least 100
years. Another way to state this goal simply is to ask: Will the mine rock piles become
gravitationally unstable with time due to weathering? The weathering aspects of the rock
pile and stability analyses are being studied by other members of the team to the same
end. This thesis research will complement the weathering studies by examining the shear
strength using a direct shear apparatus with a 2-inch shear box.
Rock piles are disposal facilities for overburden (also termed “mine rock”).
Overburden or mine rock is the barren or uneconomic mineralized rock that must be
removed in order to mine the mineral resource. Surface mine operations create rock piles
that by weight, volume, or height represent some of the largest structures built by man.
Compared with other engineered structures, little or no characterization of the material
has been performed before, during, or especially after construction of the rock piles
(Robertson, 1982). Since the 1980s, environmental regulations forced mine operators to
1
consider the design of rock piles and in some cases enforced requirements for maximum
slope angles, factors of safety for slope stability, and site reclamation. These
considerations have led to the need for information on the strength characteristics of the
materials that comprise rock piles. Unfortunately, little detailed information has been
published on this topic. Thus, a secondary goal of this thesis is to add to the base of
knowledge in this area.
1.2. Thesis Objective
The purpose of this work is to interpret data on the engineering characteristics of
the Goathill North (GHN) rock pile at the Molycorp Questa Molybdenum mine, and to
examine correlations of internal friction angle with mineralogy, chemistry and
weathering indexes. The key elements of this research are to:

Investigate the variation of shear strength within the GHN rock pile by
performing a series of direct shear tests.

Investigate the variation of Geotechnical index properties within the GHN rock
pile by performing particle size analyses and by measuring Atterberg limits,
specific gravity, and moisture content.

Investigate the effect of gradation, chemistry, and mineralogy on shear strength
by correlating mineralogy, chemistry, and the data from particle size analyses
with friction angle.
2
1.3. Site Description
The Questa molybdenum mine (Figure 1.1), owned and operated by Molycorp,
Inc., is located 5.6 km (3.5 mi) east of the Village of Questa, in Taos County, northern
New Mexico, in the western portion of the Taos Range of the Sangre de Cristo
Mountains. The mine site is located in an area of high relief with elevations varying from
2,310 to 3,295 m (7,580 to 10,812 ft) in an area of about 15.54 km2 (6 mi2). The main
headframe of the mine is located on the south-facing slopes of the Red River Valley at
approximately 2,438 m (8000 ft) above sea level.
The Questa molybdenum mine has been in operation, though not continuously,
since 1918, during which time several mining methods have been used to extract
molybdenite (“moly” - MoS2) from this “Climax-type” porphyry molybdenum deposit.
Initially, the mine was a small underground working, with donkey-hauled ore cars
delivering ore to the surface that was broken up by workers. Later, from 1965 to 1982,
large-scale open pit mining methods were used to extract the ore. Currently the mine
operates underground using block caving mining methods.
During the open-pit period of mining, approximately 320 million tons of
overburden rock overlying and surrounding the ore body were excavated and deposited in
steep valleys adjacent to the open pit (URS Corporation, 2000). The resulting nine rock
piles are shown in Figure 1.2. In general, the mine rock piles are at the angle of repose
(35º to 40º) and have long slope lengths (up to 600.5 m or 1970 ft) and comparatively
shallow depths (~30-60 m or ~98-196 ft) (Shaw et al., 2002).
3
Figure 1.1. This image shows the location map of Molycorp’s Questa molybdenum
mine, which is in northern Taos County, New Mexico.
Goathill North &
Goathill South Rock Piles
Sulphur Gulch Rock
Pile
Figure 1.2. This image shows an aerial photo of Questa mine showing the nine rock
piles adjacent to the open pit.
4
The GHN rock pile is one of the nine rock piles created during open-pit mining.
Before reclamation GHN contained approximately 4.2 million m3 (5.5 million yds3) of
overburden material with slopes similar to the original topography (Norwest Corporation,
2004).
Studies by Norwest Corporation (2003) revealed that the GHN rock pile was
constructed in an area characterized by hydrothermal alteration scars. These
hydrothermal alteration scars are natural, colorful (red to yellow to orange to brown),
relatively unstable landforms that are characterized by steep slopes (greater than 25
degrees), moderate to high pyrite content (typically greater than 1 percent), little or no
vegetation, and extensively fractured bedrock (McLemore et al., 2004; Meyer and
Leonardson, 1990). The toe of the GHN rock pile is founded on a colluvium bench
underlain by pre-sheared material. Foundation movements associated with the initial
development of the slide occurred between 1969 and 1973 (Norwest Corporation, 2003;
Norwest Corporation, 2004), and continued to occur for more than 30 years untilthe
initial reclamation of that pile was completed in 2005.
GHN rock pile can be divided into two areas - a stable area and an unstable area,
as shown in Figure 1.3. In 2004-2005, Molycorp stabilized this rock pile by removing
material off the top portion of both areas to the bottom of the pile (Norwest Corporation,
2003). This regrading decreased the slope, reduced the load, and created a buttress.
During the progressive down-cutting (regrading) of the top of GHN, trenches were
constructed to examine, map, and sample the undisturbed internal geology of the rock
pile as shown in Figure 1.4. Samples collected from these trenches form the basis for this
thesis.
5
Figure 1.3. This image shows Goathill North rock pile before re-grading, looking
east. Solid line indicates approximate location of trenches completed in summer-fall
2004; dashed line indicates the boundary between the stable and unstable portions
of the rock pile (after McLemore et al., 2006).
Figure 1.4. This image shows one of the trenches (LFG-003) excavated on the stable
portion of the Goathill North rock pile during the re-grading.
6
The geology at the Questa mine includes four main lithologies, all of which are
hydorthermally altered to varying degrees: andesite porphyry, aplite porphyry, andesite
to quartz latite porphyry flows, and rhyolite tuff (Amalia Tuff). Most of the mined rockpile material consists of andesite, rhyolite tuff and porphyritic aplite. Several studies of
the Questa mine have used the term ‘mixed volcanics’ to describe the lithology of the
rock piles. These ‘mixed volcanics’ consist of andesite, latite, quartz latite, and
volcaniclastic rocks all of which have been subjected to varying amounts of hydrothermal
alteration (Shaw et al., 2002).
The climate at the mine is semi-arid with mild summers and cold winters(Wels et
al., 2002). The long-term average annual precipitation at the mill site (located at the base
of the mine site) is approximately 401 millimeters (15.8 in). Temperatures vary greatly
both annually and diurnally. The average daily maximum temperatures range from 2.7º to
25º C (37º to 77º F) with average daily minimum temperatures ranging from -14.4º to 5º
C (6º to 41º F). During five months of the year (November through March) the average
monthly temperature is below freezing (Robertson GeoConsultants Inc., 2000). Hot days
and cool nights characterize summer. The rainy season is during July and August. Heavy
localized rainfalls during July and August often cause flash floods and mudflows, which
sometimes block the highway between the Village of Questa and the Town of Red River
(Molycorp Inc., 2002).
7
1.4. Thesis Outline
Chapter 2 contains a critical literature review of past and present studies on the
Goathill North rock pile. Chapter 3 discusses the factors that influence strength of a
granular soil, such as those found in the GHN rock pile. Chapter 4 presents the
methodology used in this thesis. Chapter 5 presents both the results of the physical
measurements and a discussion of those results. Chapter 6 contains conclusions and
recommendations. Appendices and references are located at the end of this thesis.
8
2. REVIEW OF STUDIES AT GOATHILL NORTH ROCK PILE
Past Geotechnical Studies (Before Re-grading)Past evaluations of the
geotechnical properties of the GHN rock pile were completed by several consulting
companies hired by Molycorp, Inc. These projects included stability evaluations and the
development of closeout and mitigation plans. The characterization of geotechnical
properties included laboratory tests of particle size distribution, Atterberg limits, dry unit
weight, specific gravity, moisture content, and shear strength. Samples were collected
from the surface in test pits or from deeper in the pile from drill holes. Drill hole depths
range from 9 to 70.4 m (30 to 231 ft). Drill hole logs indicated four different units, listed
in descending order as follows (Norwest Corporation, 2004):

Mine rock

Colluvium (and “weak zone”)

Weathered bedrock

Bedrock
Laboratory results from different projects are summarized in Table 2.1 and Table
2.2. Although the laboratory results included all four units, this thesis research examined
only the mine rock (first unit). Therefore, this document will be focused on describing the
mine rock.
The previous studies’ particle size analyses indicate that the GHN rock pile has a
wide variation in gradation ranging from cobble-sized material to silty sands and clayey
sands. The mine rock is mostly sandy gravel with less than 20% fines, clay contents less
9
than 12%, and plasticity indexes (PI) less than 10%. Dry unit weights of 21 mine rock
samples indicate an average of 1.82 g/cm3 (113.3 pcf) with standard deviation of 0.13
g/cm3 (8 pcf) (Norwest Corporation, 2004). The specific gravity of the mine rock based
on 15 samples ranges from 2.66 to 2.80 g/cm3 (166 to 175 pcf) (Norwest Corporation,
2004; URS Corporation, 2003).
Table 2.1. Summary of geotechnical properties at GHN rock pile
Particle size distribution
Reference
Sampling
method
Sample description
% Gravel
Norwest
Corporation, 2004
Atterberg limits
mine rock
%Sand
%Fines
55.1
33.9
(Ave.)
(Ave.)
19.2
13.9
(STDEV)
(SDTEV)
42
42
(#samples) (#samples)
% Clay
colluvium
-
-
Norwest
Corporation, 2004
"weak zone"
of the colluvium
-
-
36-65
11-34
(range)
(range)
7
7
(#samples) (#samples)
URS Corporation,
2003
mine rock
Norwest
Corporation, 2004
35-54
36-49
(range)
(range)
28
28
(#samples) (#samples)
Plasticity
index
Comments
11.1
5.6
27.7
9.5
6.7
(Ave.)
(Ave.)
(Ave.)
(Ave.)
(Ave.)
6.6
2.5
3.6
3.4
3.9
sandy gravel
(SDTEV)
(SDTEV)
(SDTEV)
(SDTEV)
(SDTEV) with cobbles
42
17
36
36
42
(#samples) (#samples) (#samples) (#samples) (#samples)
24.1
8.5
(Ave.)
(Ave.)
10.7
4.8
(SDTEV)
(SDTEV)
91
50
(#samples) (#samples)
split tube drill
Liquid limit
(%)
Natural
Moisture
Content, w
(%)
11.2
(Ave.)
3.6
(SDTEV)
84
(#samples)
-
-
14-25.3
(range)
7
(#samples)
-
-
6-28
2.1 -12.8
24-37
4-18
2.6-13.1
sandy and
(range)
(range)
(range)
(range)
(range)
clayey gravel
28
28
28
28
28
with cobbles
(#samples) (#samples) (#samples) (#samples) (#samples)
test pits
URS Corporation,
2003
Robertson
GeoConsultants
Inc., 2000
drill hole
bedrock
(highly
altered/weathered
andesite)
-
-
30-49
(range)
4
(#samples)
mine rock
59
( 1 sample)
19
(1 sample)
5
(1 sample)
30-36
12-21
11.4-12
(range)
(range)
(range)
4
4
4
(#samples) (#samples) (#samples)
2
28
(1 sample) (1 sample)
12
(1 sample)
2.7
(1 sample)
-
sample
(GT-18)
Table 2.2. Summary of friction angles of Molycorp mine rock piles and the “weak
zone” at GHN and their gradation results.
10
Reference
Mine rock /
Norwest Inc.,
2004 and
URS
Corporation
Inc., 2003
Mine rock/
Robertson
GeoConsultant
s Inc., 2000
Sample location
% Fines
(-0.75mm)
%Clay
(-0.002mm)
Plasticity
index
SSW-3
Sugar Shack
West rock pile
18.8
6.6
8
Friction
angle
(degrees)
Cohesion
36
average
Test
Comments
Norwest suggested friction angle of
Consolidated
undrained triaxial test GHN rock pile is the same as the
average friction angle of this two
samples from Sugar Shack rock
piles at Questa. The tests were
Consolidated
performed by URS Corporation Inc.,
undrained triaxial test
2003.
SSM-6
Sugar Shack
Middle rock pile
29.1
7.7
11
GT-18
GHN rock pile
5
2
12
31
561psf
direct shear test
Shear box size= 2.4" diameter
Test conditions=saturated
# of tests considered = 3 different
normal load
TH-GH-04S
60.0-61.0'
36
11
16.6
39.8
0.0
direct shear test
Sample size= 2.41" diameter
Test conditions= saturated
# of tests considered = 3 different
normal load
TH-GH-04S
69.0-71.0'
65
34
25.3
22.3
0.0
direct shear test
Sample size= 2.41" diameter
Test conditions= saturated
# of tests considered = 3 different
normal load
TH-GH-02S
137.5-138.5'
49
21
18.5
19.7
-
direct shear test
# of tests considered = 3 different
normal load
44
18
15.6
30.0
-
direct shear test
# of tests considered = 1 normal
load
TH-GH-10S
44.7-45.5'
39
20
24.8
27.0
-
direct shear test
# of tests considered = 1 normal
load
TH-GH-14S
90.5-91.0'
39
15
18.2
25.0
-
direct shear test
# of tests considered = 2 different
normal load
TH-GH-14S
94.2-95.0'
40
14
14
29.5
-
direct shear test
# of tests considered = 2 different
normal load
Weak Zone/
Norwest Inc., TH-GH-02S
2004
141.0-141.8'
-
Robertson GeoConsultants (RGC) Inc. (2000) performed a series of fourteen 12inch saturated direct shear tests on Questa rock pile material including one mine rock
sample from the GHN rock pile. Their results showed a range of friction angles and
cohesion from 41º to 47º and 9.6 to 96 kPa (200 to 2000 psf). Results from a 2.4-inch
saturated direct shear test on a mine rock sample from the GHN rock pile showed an
average friction angle of 31º and cohesion of 26.9 kPa (561 psf) (Robertson
GeoConsultants Inc., 2000).
Robertson GeoConsultants Inc. (2000) reported that all direct shear tests exhibited
evidence of strain hardening. The effect of strain hardening is that shear strength
11
continues to increase at very large strains under the conditions of the test and no sudden
reduction in shear strength as strain occurs (Robertson GeoConsultants Inc., 2000).
A study performed by Norwest Corporation in 2004 on GHN concluded that the
friction angle of the mine rock is an average of two triaxial test results performed on
samples from the Sugar Shack rock piles at Questa mine (Norwest Corporation, 2004).
The Mohr Coulomb diagram combined for the two samples gives a friction angle of 36º
as is shown in Figure 2.1. The assumption was justified by the similarity in particle size
distribution of these samples with the particle size distribution of the mine rock from
GHN as can be seen in Figure 2.2. The testing was conducted over a confining stress
range up to about 2,750 kPa (57,435 psf). The results show that the friction angle
decreases somewhat with confining stress from about 40º at low stresses to 35º at 2,750
kPa or 57,435 psf as shown in Figure 2.3.
Figure 2.1. This graph shows the friction angle of GHN mine rock based on triaxial
test results for samples from Sugar Shack rock piles that have gradations lying
towards the finer range of materials sampled at GHN rock pile (from Norwest
Corporation, 2004).
12
Figure 2.2. This graph shows the grain size distributions from triaxial samples from
Sugar Shack rock piles and typical Goathill North mine rock (from Norwest
Corporation, 2004).
13
Figure 2.3. This graph shows friction angle versus confining stress showing a
decrease in friction angle as confining stress increases (from Norwest Corporation,
2004).
2.1. Present Work and Preliminary Results
The present work on the GHN rock pile is being performed by a multidisciplinary
group of engineers and scientists with the following main objectives:
1. Understanding weathering processes, both at the surface and within the
mine rock pile which could affect the geotechnical properties of the pile.
2. Measuring the rate at which such weathering processes occur over time.
3. Determining the effect of these processes on the geotechnical properties of
the pile (e.g., grain size, grain shape and textures, cementation, shear
strength, moisture content) for further long-term stability analyses. (This
thesis research is complementing this work by providing initial
geotechnical data).
During the regrading of the GHN rock pile, several trenches were excavated into
the interior of the pile. For every trench, geologic maps and logs of each bench were
created to describe the different subsurface mine rock units. Subsurface units were
defined based on grain size, color, texture, stratigraphic position, and other physical
properties that could be determined in the field. Examples of a geologic map and the
subsurface units for trench LFG-009 are shown in Figures 2.4 and 2.5, respectively. Units
were correlated between benches and on each side of a trench, and several units were
correlated downward through the series of five successively excavated trenches. A
detailed description of each unit for all the trenches is presented in McLemore et al.
(2006) and in Appendix E.
14
Figure 2.4. This figure shows an example of a geologic map like those created for
each trench at GHN rock pile. Geologic map of trench LFG-009 (from McLemore et
al., 2005).
Figure 2.5. This figure shows a geologic cross section of bench 9, trench LFG-006
showing the identified subsurface units. See Appendix E for description of the
subsurface units.
Field and laboratory analyses reveal that the GHN rock pile consists primarily of
hydrothermally altered andesite and Amalia Tuff (McLemore et al., 2005). The andesite
and Amalia Tuff rock fragments are comprised primarily of quartz and feldspar.
However, andesite contains less quartz and more plagioclase than the rhyolitic Amalia
15
Tuff. In addition, Amalia Tuff commonly contains quartz phenocrysts, which are usually
absent in the andesite. The andesite and Amalia Tuff have been subjected to variable
intensities of hydrothermal alteration as well as weathering. Hydrothermal alteration is
the change in original composition of the rock in place by hydrothermal (warm to hot
aqueous) solutions associated with mineralization and associated ore-forming events such
as granitic intrusions. Hydrothermal alteration is a pre-mining condition and includes
both hypogene (primary) and supergene (secondary) processes. Hypogene alteration
occurred during ore-formation. Supergene alteration, a type of weathering, occurred at
low temperatures near Earth’s surface after the formation of the ore deposit, but before
mining commenced. The major hypogene alteration types at GHN include quartz-sericitepyrite (QSP), propyllitic, argillic, and potassic alteration (Carpenter, 1968). Weathering
can be defined as the process of rock and mineral alteration to more stable forms under
the variable conditions of moisture, temperature, and biological activity that prevail at the
surface (Birkeland, 1999). Most rocks and minerals exposed at and immediately beneath
the earth’s surface are in an environment quite unlike that under which they are formed
(Birkeland, 1999).
Preliminary results of petrographic analysis of samples from bench 9, trench
LFG-006, show that both hydrothermal alteration of fragments within the pile varies
according to the predominant lithology (rhyolite typically shows more QSP alteration
than andesite) and that weathering increases from the interior of the pile to the edge of the
pile, as shown in the Figures 2.6 and 2.7. The QSP alteration intensity was defined by the
percentage of hydrothermal alteration minerals (quartz, sericite, pyrite))that have
replaced primary minerals and ground mass. A major indicator of weathering is the
16
abundance of authigenic gypsum crystals, which indicates that some weathering of
sulfide minerals (essentially all pyrite) and calcite occurred after emplacement of the rock
pile (Campbell et al., 2005).
Results from paste pH and net acid generation (NAG pH) show a range from 2.1
to 10. Paste pH and NAG pH typically increase with distance from the outer, oxidized
zone (west) towards the interior, unoxidized zone (east) of the GHN rock pile as shown in
Figure 2.8 (Tachie-Menson, 2006). These results can be attributed to a number of factors,
including (1) the different lithologies of the stratigraphic units that comprise the rock pile,
(2) the amount of weathering and leaching that had occurred before the material was
mined and dumped (deposited) onto the pile, and (3) the differences among variables,
such as oxygen concentration, moisture content, and presence of bacteria, that influence
weathering of the rock pile both at the surface and within the pile (Tachie-Menson,
2006).
Figure 2.6. This graph shows a plot of QSP hydrothermal alteration intensity
(defined by the percentage of hydrothermal alteration minerals that have replaced
primary minerals) across bench 9, trench LFG-006 (from McLemore et al., 2005).
Refer to Figure 2.5. for geologic units.
17
Figure 2.7. This graph shows a plot of authigenic gypsum across bench 9, trench
LFG-006 (from McLemore et al., 2005). Refer to Figure 2.5. for geologic units.
Bench 9, LFG-006
12
10
pH
8
6
4
Paste pH
NAG pH
2
0
0
20
40
60
Distance from 9NW (ft)
80
100
Figure 2.8. This graph shows the results of paste pH and NAG pH across bench 9,
trench LFG-006 (after Tachie-Menson, 2005).
18
A post-mining weathering index for the rock pile is currently being developed. A
weathering index is a measure of how much the sample has weathered. McLemore (2005)
described a simple, descriptive weathering index (SWI) that is based upon field
observations (color, grain size, mineral texture, and the presence or absence of certain
minerals indicative of weathering) for the purpose of identifying the relative intensity of
weathering of samples collected for the project. Other weathering indexes found in the
literature are being evaluated as well. Most weathering indexes are based on geochemical
parameters that restrict their applications to the type of environment that they were
developed for.
19
3. LITERATURE REVIEW OF CONCEPTS RELATED TO THIS RESEARCH
3.1. Strength of Granular Materials
A granular soil is composed of particles larger than approximately 0.075 mm or
No. 200 standard U.S. sieve size. Typically it is assumed that these soils do not exhibit
significant effective cohesion (resulting from electrostatic particle attractions) and are
free-draining (water not bound inside particle structure), with low retention of water
between particles. Coarse granular soil is composed of at least 50 percent by weight of
gravel (1/4-inch diameter) or larger particles (Holtz and Kovacs, 2003; Quine, 1993). The
shear strength of a granular soil can be defined by equation 3.1,
  c   tan 
(3.1)
where c is cohesion (in kPa, MPa or psf),  is total stress ( in kPa, MPa or psf), and  is
the internal angle of friction of the soil (in degrees) (Das, 1983). This equation is
generally referred to as the Mohr-Coulomb failure criteria. For saturated soils, the stress
carried by the soil solids is the effective stress and equation 3.1 is modified to equation
3.2:
  c  (  u ) tan   c' ' tan 
20
(3.2)
where u is the pore water pressure, c’ is the effective cohesion, and ’ is the effective
stress on the failure plane at the failure. Since it is assumed that granular material does
not present any effective cohesion, equation 3.2 is generally simplified to equation 3.3 in
many references (Das, 1983; Holtz and Kovacs, 2003; Terzaghi et al., 1996).
   ' tan 
(3.3)
Therefore, the shear strength of granular soil is frequently characterized by its
internal friction angle (). The internal friction angle is a function of the following
characteristics (Hawley, 2001; Holtz and Kovacs, 2003):

Particle size (friction angle increases with increase in particle size)

Grain quality (weak rock such as shale verses strong rock such as granite)

Particle shape and roughness of grain surface (friction angle increases with
increasing angularity and surface roughness)

Grain size distribution (well graded soil has a higher friction angle than a
poorly graded soil)

State of compaction or packing (friction angle increases with increasing
density or decreasing void ratio)

Applied stress level (decreasing with increasing stress, resulting in a
curved strength envelope passing through the origin)
Various studies have successfully evaluated how the parameters listed above
affect internal friction angle. Findings from these studies are presented in the following
paragraphs.
21
It has been recognized (Holtz, 1960; Holtz and Gibbs, 1956) that an increase in
the proportion of coarse material in an otherwise fine-grained granular soil can result in
an increase in friction angle. Typical  values for medium-dense sand can range from 32º
to 38º, while typical  values for medium-dense sandy gravel can range from 34º to 48º
(Das, 1983). Triaxial strength testing of large-size (up to 200 mm or 7.87 in) rockfill
particles suggested that rock piles are expected to have internal friction angles in the
range of 40º to 50º, the lower end of the range corresponding to fine-grained material,
and the upper end of the range corresponding to coarse-grained material (Leps, 1970).
Particle size and shape reflects material composition, grain formation and release
from the mineral matrix, transportation, and depositional environments. Chemical action
and physical abrasion increase with weathering and more weathered sands tend to be
rounder regardless of particle size (Cho et al., 2004). Particle shape is characterized by
three dimensionless ratios (Barrett, 1980; Krumbein, 1941): sphericity (eccentricity or
platiness), roundness (angularity), and smoothness (roughness). Sphericity and roundness
can be estimated visually using the comparison charts shown in Figure 3.1. The use of
these charts makes it easier to examine the influence of particle shape on geotechnical
properties (Cho et al., 2004). The relationship between particle shape and friction angle is
presented in Figure 3.2. Open circles are for sand with sphericity > 0.7, and closed circles
are for sand with sphericity < 0.7. The plot shows a negative correlation between internal
friction angle and roundness. As roundness varied from 0.1 (very angular) to 1 (well
rounded), the internal friction angle decreased from 40º to approximately 28º. Particles
with a higher sphericity generally had lower friction angles. Surface roughness will also
have an effect on internal friction angle, although surface roughness is very difficult to
22
measure. Generally, the greater the surface roughness, the greater will be the internal
friction angle (Holtz and Kovacs, 2003).
(a)
(b)
Figure 3.1. This figure shows examples of sphericity and roundness charts (a) from
(Cho et al., 2004) and (b) from AGI (American Geological Institute) data sheet 18.1
comparison chart for estimating roundness and sphericity, by Maurice C. Powers,
copyright 1982. These charts were used for this project.
23
Figure 3.2. This graph shows the effect of particle shape on internal friction angle
for sand ( from Cho et al., 2004). Open circles and closed circles are for sand with
sphericity higher than 0.7 and sphericity lower than 0.7, respectively.
The effects of grain size distribution on internal friction angle can be observed on
samples with the same relative density. Figure 3.3 shows the correlation between the
effective friction angle from triaxial compression tests and both relative density and soil
classification. When two sands have the same relative density, the soil that is better
graded (for example, an SW soil as opposed to an SP soil) has a larger  (Holtz and
Kovacs, 2003).
24
Figure 3.3. This graph shows the correlations between the effective friction angle
and the relative density for different soil types (from Holtz and Kovacs, 2003). ML:
Silt, SM: Silty sand, SP: Poorly graded sand, SW: Well-graded sand, GP: Poorly
graded gravel, GW: Well-graded gravel.
The influence of void ratio (state of compaction or packing) and of applied stress
level are illustrated in Figure 3.4 (Das, 1983). Figure 3.4 is a plot of the results of direct
shear tests on standard Ottawa Sand. For loose sand (initial void ratio approximately
0.66), the value of  decreases from about 30º to less than 27º when the normal stress is
increased from 45 to 766 kPa (0.5 to 8 ton/ft2). Similarly, for dense sand,  decreases
from approximately 34.5º to about 30.5º due to an increase in normal stress from 45 to
766 kPa (0.5 to 8 ton/ft2).
25
Figure 3.4. This graph shows the variation of peak internal friction angle with
effective normal stress for direct shear tests on standard Ottawa sand (from Das,
1983).
The determination of the internal friction angle () and the effective cohesion (c)
is commonly accomplished by the direct shear test or the triaxial test. The direct shear
test is preferred because of its simplicity and lower cost. The advantages and
disadvantages of direct shear tests are given below.
Advantages of direct shear testing are as follows:

The test is relatively inexpensive and quick to perform.

It requires less sophisticated equipment than other methods and it is easier
to reduce the data and interpret the results.
26

It has been found that soil parameters  and c obtained by direct shear
testing are nearly as reliable as triaxial values. Typical values obtained
with the direct shear test are 1 to 2 degrees larger than values obtained
with the triaxial test (Bowles, 1979).

It is good for measuring residual strength values (Quine, 1993).
Disadvantages or limitations of the direct shear test (Holtz and Kovacs, 2003) are
as follows:

Shearing stress is not uniformly distributed across the sample. Initial
failure occurs at the corners and ends of the box, and propagates towards
the center.

The test forces failure to occur along a fixed zone or plane.

There is an uncontrolled rotation of principal planes and stresses that
occurs between the start of the test and failure.

Pore water pressures for fine-grained soils are neither controlled nor
monitored.
3.2. Weathering Process
Weathering is the process of rock and mineral alteration to more stable forms
under the variable conditions of moisture, temperature, and biological activity that prevail
at or near the surface (Birkeland, 1999). Two main types of weathering are recogonized:
physical weathering, in which the original rock disintegrates to smaller-sized material
with no appreciable change in chemical or mineralogical composition, and chemical
27
weathering, in which chemical and/or mineralogical composition of the original rock and
minerals are changed (Clark and Samall, 1982).
The mechanism common to all processes of physical weathering is the
establishment of sufficient stress within the rock so that the rock breaks (Clark and
Samall, 1982). The most common processes associated with physical weathering are
unloading by erosion of overlying material; by expansion of cracks or along grain
boundaries by crystallizing open-space-filling minerals or freezing water; and by thermal
expansion (associated with fire, for example) and contraction of the constituent mineral
(Birkeland, 1999). Physical weathering results in a decrease in grain size, which increases
surface area that in turn leads to greater chemical reactivity and the exposure of fresh
mineral surfaces. As shown in Figure 3.5, the fragments of andesite within the rock piles
at the Questa mine are affected by a physical break up of the rock caused by the volume
change produced by the transformation of anhydrite to gypsum or other crystal growth
along fractures.
28
Figure 3.5. This image shows the progressive physical break up boulders by the
transformation of anhydrite to gypsum common at the Questa mine site.
Chemical weathering processes include dissolution, carbonation, hydration,
hydrolysis, oxidation and reduction (Birkeland, 1999; Clark and Samall, 1982; Gerrard,
1988). Evidences of chemical weathering are shown by several field and laboratory
criteria including: (1) change in color due to oxidation of iron-bearing minerals as shown
in Figure 3.6, (2) depletion of original minerals (non-clay and clay), (3) alteration of
original clay minerals or neo-formation of clay minerals, (4) neo-formation of iron or
aluminum oxides and oxyhydroxides, (5) changes in major-element chemistry versus that
of the assumed parent material, (6) the chemistry both of the waters that move through
the soil and that of the streams draining a particular basin (Birkeland, 1999).
29
Figure 3.6. This image shows evidence of chemical weathering process (oxidation of
iron ) at Questa mine site.
The rate of weathering is complex; it involves not only particle size, but also
types of material, climate, moisture, exposure conditions, and plant, animal, and
microbial activities. Generally, in an acidic environment, both the rate and the amount of
weathering increases with time due to the reduction of grain size, which allows more
surface area of the material to be exposed to the process (Bowles, 1979).
3.3. Effect of Weathering on Geotechnical Properties of Mine Rock
Few studies exist on the effect of weathering on the geotechnical properties of
material found in mine rock piles. However, natural hillslopes and rockfill dams have
general similarities to rock pile material (Leps, 1970; Quine, 1993; Robertson, 1985;
30
URS Corporation, 2003). Therefore, in this literature review of the effect of weathering
on the geotechnical properties of mine rock, studies on natural hillslope and rockfill
material will be included as well.
Seedsman and Emerson (1985) studied the role of clay-rich rocks in spoil pile
failures at the Goonyella Mine in Australia. They observed a reduction of the friction
angle by 6º to 12º due to chemical weathering and by 2º to 3º caused by the presence of
fines generated by physical weathering. According to Seedsman and Emerson, the
reduction of the friction angle caused by physical weathering does not occur gradually as
the fines fraction (silt + clay) increases but, insteadrelatively suddenly at a fines content
of about 10%. At this fines content, the larger particles in the spoil are no longer in direct
contact with each other but instead tend to be supported in a matrix of silt- and clay-sized
particles.
Calcaterra et al. (1998) studied the weathering processes in crystalline rocks of
the Sila Massif, Calabria, Southern Italy. Weathering grades were identified using a
weathering field survey classification scheme proposed by the Hong-Kong Geotechnical
Control Office. Descriptions of completely to moderately weathered gneissic rocks are
presented in Table 3.1. Laboratory results of geotechnical properties in Table 3.2 showed
that strength, density, specific gravity, and porosity decreased as weathering grade
increased. Specific gravity did not significantly decrease with an increase in weathering
grade. Thuro and Scholz (2003) presented density and porosity results in agreement with
the findings from Calcaterra et al. (1988) shown in Figure 3.7.
31
Table 3.1. This table shows the weathering field survey used to characterize the
weathering sequence in the gneiss (after Calcaterra et al., 1998). Weathering grades
I, II, and VI were unavailable to survey.
Weathering
grade
V
Field survey
Parent rock
Gneiss
(corestones)
brownish to reddish-orange coarse-grained soils, retaining original
mass structure and material fabric (less than 30% rocks, as
"corestones"); slake in water, easily crumbled by hand and finger
pressure into grains, indented by geologic hammer. Relict
discontinuities are recognizable.
IV
Gneiss
III
Gneiss
completely discolored (brownish-red) weak rocks. Do not slake in
water, can be broken by hand into smaller fragments. Discontinuities
are clearly visible, original fabric is present.
greenish-grey rocks stained and discolored along discontinuities and
original fabric are wholly preserved.
Table 3.2. This table shows the main engineering-geological features of weathered
horizons near Acri (after Calcaterra et al., 1998).
Weathering
grade
V
V
Parent rock
Granitoids
(soil)
Gneiss
(corestones)
IV
Gneiss
III
Gneiss
Specific
gravity
(kN/m3)
Bulk
density
(kN/m3)
Dry
density
(kN/m3)
26.3-27.6
(7)
26.0-26.5
(5)
26.1-26.7
(6)
26.3-29.9
(5)
19.3-20.0
(7)
22.1-25.2
(5)
23.1-25.4
(6)
25.3-28.6
(5)
18.3-19.4
(7)
21.2-24.4
(5)
22.7-25.2
(6)
25.2-28.6
(5)
Saturated
density
(kN/m3)
Porosity
(%)
21.4-22.2 28.7-32.2
(7)
(7)
23.0-25.5 8.2-15.5
(5)
(5)
24.0-25.7 5.0-13.1
(6)
(6)
25.6-29.0 2.2-4.7
(5)
(5)
Point load
strength
(MPa)
n.d.
0.7-1.1
(4)
0.4-2.9
(6)
0.5-4.1
(4)
The numbers in brackets refer to the number of samples tested, and n.d. = not determined
32
Figure 3.7. This graph shows the correlation of weathering grade with dry density
and porosity. High/mean/low values are plotted for each grade (from Thuro and
Scholz, 2003).
Huat et al. (2005) studied the strength parameters in a profile of sedimentary
residual soils of various weathering grades. The weathering grades varied from III to V,
where the lower end is for less weathered material and the higher end is for more
weathered material. The site comprised residual soil of weathered sandstone, overlying
schist and quartzite. The soils were generally yellowish brown and consisted mainly of
fine sands, silt and clay. Results of triaxial tests are shown in Table 3.3. The results show
an increase in cohesion but a decrease in angle of friction as the soil/rock becomes more
weathered. An increase in fines content with weathering grade was also observed, which
according to the authors was the reason for a decrease in friction angle.
Lumb (1962; 1965) conducted extensive work on residual soils in Hong Kong.
They successfully used particle size parameters to indicate the degree of weathering
based on field observations that most soil profiles exhibit trends of decreasing particle
size and increasing clay content towards the surface.
33
Even though most literature presents similar results and indicates a reduction of
strength with increasing weathering, it cannot be generalized that weathering will always
decrease mine rock/soil strength. Most of these studies are based upon soil profiles that
ranged from unweathered rock to weathered soil that formed over a long period of time.
Cementation was not a factor in these studies. Chemical weathering can produce cements,
such as hematite, that will join grains together and that are not easily dissolved in water.
According to (Pernichele and Kahle, 1971) field studies of rock piles indicate that the
cementing action of iron precipitates formed within the piles as a result of natural or
production leaching tends to improve the strength of the piles over time. Generally, the
cementation is so complete that vertical cuts are capable of standing for years without
signs of failure.
Table 3.3. This table shows the shear strength parameters of sedimentary residual
soil with weathering grades varying from III to V. The lower end is for less
weathered material and the higher end is for more weathered material
Weathering grade
V
IV
IV-III
III
Cohesion, c
(kPa)
10
8
4
0
Angle of friction, 
(degrees)
26
28
31
33
3.4. Published Grain Size distribution and Shear Strength Parameters for Mine
Rock
34
Table 3.4 summarizes values of grain size distribution for different rock piles
from around the world. Percentages of gravel, sand and fines in the mine rock piles range
from 45 to 70, 20 to 43, and 3 to 29, respectively. These distributions support the
generalized classification “sandy gravel with cobbles” attributed to rock piles in the
literature (Hawley, 2001; Leps, 1970; Quine, 1993; Robertson, 1985). Table 3.5
summarizes values of internal friction angle and cohesion from different rock piles.
Typical values of cohesion vary between 0 to 239 kPa (0 and 5000 psf) and friction
angles vary between 21º and 55º, with most values reported between 38º and 45º.
Table 3.4. This table shows the grain size distribution of rock piles from around the
world.
35
Mine and Location
Cobbles
(%)
Gravels
(%)
Sand
(%)
Fines
(%)
Silt
(%)
Clay
(%)
reference
Ajo mine, Arizona
Copper mine
5
67
20
8
7
1
Savci and
Williamson
(2002)
Aitik Mine, Sweden
Copper mine
6
45
34
15
n.d.
n.d.
URS
Corporation
(2003)
Midnite Mine,
Washington
Uranium Mine
n.d.
50-65
(range)
21-43
(range)
11-29
(range)
n.d.
n.d.
URS
Corporation
(2003)
Bonner Mine San
Juan County,
Colorado
n.d.
70
20
10
8
2
Stormont and
Farfan (2005)
Kidston gold mines,
Australia
30
37
30
3
n.d.
n.d.
URS
Corporation
(2003)
Morenci mine,
Arizona
Copper mine
n.d.
50-56
(range)
30-34
(range)
10-20
(range)
n.d.
n.d.
URS
Corporation
(2003)
n.d.= not determined
36
Table 3.5. This table shows a summary of mine rock friction angle and cohesion
data from around the world.
Mine and location
Lubelskie, Poland
Mine rock material/
rock type or
Deposit type
n.d.
Internal
friction angle
(degrees)
Fresh
32-55
5 years old
34-35
7 years old
27-37
Fresh
36-41
8 years old
21-29
Apparent cohesion
(kPa)
Comments
References
Friction angle decreases,
cohesion increases with age
Filipowicz and Borys
(2005)
Friction angle decreases,
cohesion increases with age
Filipowicz and Borys
(2005)
0
Triaxial test 6-inch diameter
dmax=3/4"
samples comprised of
moderately to slightly
weathered rock with 20% fines
URS Corporation
(2003)
British Columbia Mine
Waste Rock Pile
Research Committee
(1991), URS (2003)
20-32
21-35
25-40
18-23
Upper Silesian,
Poland
n.d.
Bouganville Copper
Ltd., Papua New
Guinea
Fractured rock
(Panguna andesite)
Endako
British Columbia,
Canada
Molybdenum mine
100% Quartz
monzonite
36
24
Material properties
30% > 300mm and
2% < No.200 sieve
Bald Mountain gold,
Nevada
Dundrberg Shale
39
172
Direct shear test
shear box size 15in x 15in
dmax = 3 inch
Quine (1993)
Barrick gold, Nevada
Argillized
granodiorite
38-40.3
83-139
Direct shear test
shear box size 15in x 15in
dmax = 3 inch
Quine (1993)
Big Spings gold,
Nevada
Argillaceous siltstone
47-50
206-239
Direct shear test
shear box size 15in x 15in
dmax = 3 inch
Quine (1993)
Candelaria gold,
Nevada
Siltstone and shale
43-47
90-239
Direct shear test
shear box size 15in x 15in
dmax = 3 inch
Quine (1993)
Newmont gold,
Nevada
Siltstone/sandstone
Siltstone/ argillized
sandstone
35-51
69-205
Direct shear test
shear box size 15in x 15in
dmax = 3 inch
Quine (1993)
Round Mountain
gold, Nevada
Rhyolitic tuff
40-41.5
77-96
Direct shear test
shear box size 15in x 15in
dmax = 3 inch
Quine (1993)
PT Freeport
Indonesia’s Gasberg
Open –Pit Mine
37.6-42.2
34-64
Direct shear test
n.d.
39.6-40.4
0-11
Triax compression
consolidated, undrained
Bonner Mine San
Juan County,
Colorado
n.d.
37
5
direct shear test shear box size
30in x 30in x 16in tall
Midnite Mine,
Washington
Uranium Mine
Porphyritic quartz
monzonite, and calcsilicate rock and
marble
32.6-43.7
0-29
trixial test 4-inch diameter
dmax =3/4"
37
31
trixial test 6-inch diameter
dmax =1 1/2"
29-45
27-37
n.d. = not determined
37
Walker, W.K. and J.
M.J (2001)
Stormont and Farfan
(2005)
URS Corporation
(2003)
4. METHODOLOGY
4.1. Sampling
A multifaceted sampling program was carried out by the principal investigators of
the Molycorp Project Weathering Study. The sampling program was conducted from
Spring 2004 through April 2005. A total of 36 samples from the GHN rock pile were
analyzed during this thesis project. Samples were comprised mainly of a combination of
Amelia Tuff and andesite mine rock.
The sampling occurred during the re-grading period of the GHN rock pile when
the trenches were excavated. Approximately 5 gallons of solid material was collected for
geotechnical analyses for each sample. Samples for gravimetric moisture content,
mineralogy, and chemical analyses were also collected at the same locations. All samples
were collected as disturbed material Samples examined for this thesis project were used
to determine the effects of physical and chemical properties on the direct shear test and
were not used to calculate slope stability. Because all samples are a subset of the original
material, the resulting shear tests are not representative of the entire rock pile and cannot
be used to calculate friction angle for the pile.
Figure 4.1 shows a cross section of the GHN rock pile before re-grading including
locations of the samples that were analyzed in this thesis. A list of all the samples and
their respective coordinates (UTM easting, UTM northing, and elevation) is given in
Appendix A.
38
3000
Elevation (m)
2950
2900
2850
2800
2750
0
50
100
150
200
250
300
350
400
450
Easting (m)
Original Topographic
2003 profile
1967
profileprofile
1967
Sample location
Figure 4.1. This figure shows a generalized cross section of GHN with the location of
the samples analyzed for this thesis project.
4.2. Particle Size Analysis
Particle Size Analysis was performed to evaluate the sieving procedure most
appropriate to the samples from the GHN rock pile. Generally, the distribution of particle
sizes larger than 75 m (retained on the No. 200 U.S. standard sieve) is determined by
sieving, while the distribution of particle sizes smaller than 75 m is determined by a
sedimentation process with a hydrometer. This combined particle size analysis can be
performed using different approaches, such as dry sieve and wet sieve (or wash sieve).
Wet sieving is used instead of dry sieving when the material is not soluble in water and is
difficult to screen due to the presence of extremely fine particles that either agglomerate
or cause binding on the coarser sieves (U.S. Army Corps of Engineers, 1970). To
39
determine the most appropriate procedure for the samples from the GHN rock pile, initial
tests of wet and dry sieving were performed, with separations made on the No. 10 (2 mm)
and No. 200 (75 m) U.S. standard sieves using sample GHN-LFG-0003. The results
were compared and the influence of aggregate fines on particle size distribution for this
kind of material was studied. All sieves used in this thesis research were U.S. standard
sieves.
Method 1, “Dry sieving with separation made on No. 200 sieve,” consisted of
mechanical dry sieving for particles larger than 75 m, and applying a sedimentation
process using a hydrometer for particles smaller than 75 m. These combined particle
size analyses (mechanical sieving and hydrometer) were performed in accordance with
U.S. Army Corps of Engineers (1970) methods.
Method 2, “Dry sieving with separation made on No. 10 sieve,” consisted of dry
sieving for particles larger than No. 10 sieve (2 mm). The material smaller than 2 mm
was analyzed using a sedimentation process (hydrometer) followed by the dry sieving for
the part larger than 75 m. First, hydrometer analysis was performed on all material
passing the No. 10 sieve (2 mm). The weight used was approximately 115 g for sandy
soils and approximately 65 g for silt and clay soils. The dry sieving of oven-dried
material between 75 m and 2 mm was performed after the fines (passing No. 200 sieve)
were washed out using wet sieving. The method No. 2 combined particle size analysis
was performed in accordance with the American Society for Testing and Material
standard procedures (ASTM, 2002a).
Method 3, “Wet sieving,” consisted of washing particles larger than 75 m
through a series of sieves, and performing a sedimentation process using a hydrometer for
40
particles smaller than the No. 200 sieve. This combined particle size analysis for method
3 was performed in accordance with the U.S. Army Corps of Engineers (1970) method.
All three methods were applied to the same sample in order to compare the
procedures. First, the sample was air dried and two representative splits were taken by the
method of cone and quartering (ASTM, 1987). The minimum mass of the sample used
for particle size analysis was related to the maximum particle size present in the bucket.
Table 4.1 shows different size particles and the corresponding minimum mass of sample
necessary to perform the test (U.S. Army Corps of Engineers, 1970).
One sample split was used for dry sieving (method 1, followed by method 2); the
second split was used for wet sieving. The sample preparation for dry sieving consisted
of breaking up the aggregates thoroughly with a mortar and pestle. The sample
preparation for wet sieving consisted of soaking the specimen in water for 24 hrs.
Table 4.1. This table shows the minimum specimen size required for particle size
analysis according with the diameter of the largest particle (U.S. Army Corps of
Engineers, 1970).
Nominal diameter of the Approximate minimum
largest particle
mass of the sample
inches (mm)
(g)
3 (76.2)
6000
2 (50.8)
4000
1 (25.4)
2000
1/2 (12.7)
1000
0.18 (4.75)
200
0.079 (2mm)
100
41
Results of the three methods are summarized in Table 4.2. The coefficient of
curvature (Cc) is defined as the ratio (D30)2/(D10 x D60), where D60, D30, and D10 are the particle
diameters corresponding to 60, 30, and 10% fines on the cumulative particle size distribution
curve. The coefficient of uniformity (Cu) is defined as the ratio D60/D10.
Figure 4.2 is a plot showing a comparison of the particle size distributions for the
three methods. A comparison of methods 1, 2 and 3 shows that wet sieving analysis
provided more fines than the other two methods. The fines are removed from the surface
of coarse grains by water. These results indicate that wet sieving is the best method for
particle size analysis. However, the duration of method 3 was a concern because it
required more time (about 6 hours) than either method 2 (about 2 to 3 hours) or method 1
(about 2 hours). Method 2 is preferred over method 1 because method 2 produced results
that were considerably closer to method 3 (e.g., % of fines: method 1 = 2.53, method 2 =
11.59, and method 3 = 17.78). Furthermore, no problems were encountered during the
testing using method 2. Using method 1, it was observed that aggregates of fines were
plugging the sieve openings, and this condition was even worse for sieves smaller than
No.10 sieve (2 mm).
Based on the results of these tests, method 2, “dry sieving with separation on No.
10 sieve” (ASTM, 2002a), was selected for particle size analysis of all the samples
described in this thesis.
42
Table 4.2. This table is a summary of results of the 3 methods for particle size
analyses.
GHN-LFG-0003
Dry sieve w/ Dry sieve w/
separation on separation on
No200 sieve
No10 sieve
Fines (%)
Sand (%)
Gravel (%)
D10 (mm)
D30 (mm)
D60 (mm)
Cu
Cc
2.53
67.05
30.42
0.27
1
3.1
11.48
1.19
11.59
42.59
31.00
0.019
0.59
3.1
163.16
5.91
SP-SC
Poorly graded
sand with clay
and gravel
SW
well graded sand
with gravel
USCS
classification
Wet sieve
17.80
65.51
16.69
0.004
0.35
1.5
375.00
20.42
SC
Clayey sand
with gravel
U.S. STANDARD SIEVE SIZE
100
4
6
3
2 1-1/2
1 3/4
1/2 3/8
1/4
4
8 10
16 20
30
40
50 60
100 140 200
90
PER CENT FINER BY WEIGHT
80
70
Wash sieve, Fines= 17.41%
60
50
Separation No10, Fines = 11.59%
40
30
Separation No200, Fines = 2.53%
20
10
0
1000.0000
100.0000
10.0000
1.0000
0.1000
0.0100
0.0010
GRAIN SIZE MILLIMETERS
BOULDERS
COBBLES
SAND
GRAVEL
Coarse
Fine
Coarse
Medium
SILT OR CLAY
Fine
Figure 4.2. This graph shows a comparison of the grain size distribution for the
three different approaches tried for the estimation of particle size distribution using
sample GHN-LFG-0003.
43
4.3. Direct Shear Test Under Consolidated Drained Conditions
All direct shear tests were conducted at the Soils Mechanics Laboratory in New
Mexico Institute of Mining and Technology following Standard Industrial Practice
(ASTM, 1998) and using standard manual equipment as shown in Figure 4.3. Prior to
testing, all samples were air-dried and a mortar and pestle was used to break up the
aggregates. Samples at field moisture contents were created by adding water and then
allowed to cure for 24 hrs. Strain rates of 1% and 0.5% were used to perform direct shear
tests on dry samples and samples at field moisture contents, respectively.
The sample density for the direct shear tests was based on measurements from a
nuclear gauge. The dry density ranged from 1.06 to 2.31 g/cm3 (66.5 to 144.8 pcf) with
an average of 1.69 g/cm3 (106 pcf) and standard deviation of 0.15 g/cm3 (9.6 pcf). The
wet density ranged from 1.16 to 2.43 g/cm3 (72.4. to 151.9 pcf) with an average of 1.8
g/cm3 (112.5 pcf) and standard deviation of 0.18 g/cm3 (11 pcf). Therefore, a dry density
of 1.7 ± 0.2g/cm3 (106 ± 10pcf) or a wet density of 1.8 ± 0.2 g/cm3 (112.5 ± 11 pcf) was
selected for the shear box tests. The purpose of using only one value of dry density or wet
density for all samples was to reduce the number of variables that could affect the friction
angle. The specimens were prepared by lightly compacting the soil in three lifts so that
each lift had the same relative compression.
Normal stresses required for testing were estimated by dividing the applied load
by the area of the shear box. Loads represented the weight of the rock pile overburden
44
consistent with the depth of the sample in the rock pile. Using a 2-inch shear box, the
normal stress varied between 50 kPa (1044.27 psf) and 800 kPa (16708 psf). These
values duplicate depths in the rock pile between 3 m and 48 m (9.8 ft to 157.6 ft)
considering sample density of 1.7 g/cm3 (106 pcf). For a 4-inch shear box the maximum
normal stress that could be applied (due to equipment limitations) was less than half of
the value ( 350 kPa or 7310 psf) obtained for a 2-inch shear box. This value duplicates a
maximum depth in the rock pile of 21 m (69 ft) considering sample density of 1.7 g/cm3
(106 pcf).
Peak shear strength and residual shear strength were determined from plots of
shear stress versus shear strain. One example is shown in Figure 4.4. Internal friction
angle was obtained using a linear best-fit line from the plot of peak shear strength versus
normal stress. An example plot is given in Figure 4.5. The residual friction angle was
obtained using a similar best-fit line.
45
Figure 4.3. This image shows the manual direct shear equipment used, with views
showing the 2-inch square shear box, displacement dials and load frame.
800
Peak shear strength
Residual shear
strength
700
Shear stress (kPa)
600
500
400
300
200
Normal stress = 754kPa
Normal stress = 562kPa
100
Normal stress = 356kPa
Normal stress = 159kPa
0
0
2
4
6
8
10
12
Shear strain (%)
46
14
16
18
20
Figure 4.4. This graph shows an example of a shear stress versus shear strain plot.
The test was conducted at four different normal stresses 159, 356, 562, and 754 kPa.
The arrows indicate the peak shear strength and the residual shear strength.
Peak internal friction angle
Residuall friction angle
800
700
 peak
Shear strength (kP
600
500
400
 residual
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
Figure 4.5. This image show an example of a shear diagram showing the best fit line
for the peak internal friction angle and the residual internal friction angle.
4.3.1. Initial Test
A series of trial direct shear tests were performed to define the best conditions for
testing. Results of the effect of shear box size, maximum particle size, and moisture
content were studied to define the appropriate test conditions. The effects of particle size
and shear box size on friction angle were investigated using dry samples and three
maximum particle sizes: material passing the No. 3/8 (9.5 mm)sieve, material passing the
No. 4 (4.75 mm) sieve, and material passing the No. 6 (3.35 mm) sieve. The investigation
on the effect of shear box size was performed on dry samples passing the No. 4 and the
No. 6 sieves. Each sample was tested in 2- and 4-inch square shear boxes. The direct
47
shear tests for samples at field moisture content were performed using a 2-inch shear box
on material passing a No. 6 sieve.
The effects of shear box size, maximum particle size, and moisture are presented
in plots of shear stress versus normal stress shown in Figures 4.6 through 4.8 and in
summary Tables 4.3 through 4.5. Figure 4.6 shows the results of initial direct shear tests
for two samples from GHN, using 2- and 4-inch shear boxes. Table 4.3 summarizes the
results for both samples. The difference in internal peak friction angle with shear box size
was statistically insignificant as shown by the high correlation (R2) values. Therefore, the
selection of the shear box size was based on the surface area of shearing that provided the
range of normal stresses that encompassed the field normal stresses. The 2-inch shear box
provided a range of normal stress between 50 kPa (1044.27 psf) to 800 kPa (16708 psf).
The 4-inch shear box provided a range of normal stress between 50 kPa (1044.27 psf) to
350 kPa (7310 psf). Therefore, the 2-inch shear box size was selected for this study rather
than the 4-inch shear box.
48
600
Sample ID: GHN-KMD-0056
dmax = 4.76mm
500
 = 1.03 n
Shear stress(kPa)
400
R2 = 0.99
 peak = 45.8o
300
200
4inch shear box
100
2inch shear box
0
0
100
200
300
400
500
600
Normal stress (kPa)
(a)
600
Sample ID: GHN-LFG-0003
dmax = 4.76mm
Shear stress(kPa)
500
400
 = 0.95 n
R2 = 0.98
 peak = 43.2o
300
200
4inch shear box
100
2inch shear box
0
0
100
200
300
400
500
600
Normal stress (kPa)
(b )
Figure 4.6. Shear box size effects on direct shear test (a) for sample GHN-KMD0056 with dmax = 4.76 mm, (b) GHN-LFG-0003 with dmax = 4.76 mm.
49
Table 4.3. Summary of the results from direct shear tests using different maximum
particle size and shear box size.
Sample ID
Maximum
particle size
mm
GHN-KMD-0056
4.76
GHN-LFG-0003
Shear box
Size
(in)
Peak internal
friction angle
(degrees)
R2
2
46.12º
0.9955
4
45.57º
0.9978
2
43.5º
0.9858
4
43.5º
0.9913
4.76
Figure 4.7 shows the effects of maximum particle size for samples GHN-KMD0056 and GHN-LFG-0003. There was little difference in internal peak friction angle with
variations in maximum particle size (dmax). Both samples showed correlation (R2) values
of 0.98 for the best fit lines. When each series of direct shear tests are considered
separately, the results show an increase in correlation (decrease of data scatter) with a
decrease in dmax as shown in Table 4.4. Based on these results, a conservative maximum
particle size of 3.36 mm was selected for testing the remainder of the samples to
minimize possibility of data scatter.
50
600
Sample ID: GHN-KMD-0056
2-inch shear box size
Shear stress(kPa)
500
R2 = 0.98
 peak = 47.4o
400
300
200
dmax = 9.52 mm
dmax = 4.76 mm
100
dmax = 3.36 mm
0
0
100
200
300
400
500
600
Normal stress (kPa)
(a)
600
Sample ID: GHN-LFG-0003
2-inch shear box size
Shear stress(kPa)
500
R2 = 0.98
 peak = 45o
400
300
200
dmax = 4.76 mm
dmax = 3.36 mm
100
0
0
100
200
300
400
500
600
Normal stress (kPa)
(b )
Figure 4.7. This figure shows the results of the effect of particle size on direct shear
tests using a 2-inch shear box for (a) sample GHN-KMD-0056 with maximum
particle sizes (dmax) of 9.52, 4.76, and 3.36 mm and (b) sample GHN-LFG-0003
with dmax of 4.76 and 3.36 mm.
51
Table 4.4. This table summarizes the results from direct shear test using different
maximum particle sizes.
Shear Maximum particle
size
box Size
(mm)
(in)
Sample ID
GHN-KMD-0056
GHN-LFG-0003
2
2
Peak internal
friction angle
(degrees)
R2
9.52
48.8º
0.9654
4.76
47º
0.9901
3.36
46.05º
0.9963
4.76
43.5º
0.9840
3.36
45.5º
0.9891
Direct shear results for different moisture contents are given in Table 4.5 and
Figure 4.8. Adding water decreased the peak internal friction angle and increased the
apparent cohesion component, as shown in Table 4.5. The cohesion component is
estimated from the plot of shear stress versus normal stress by the interception of the
trendline with the y-axis. Measurements of pore water pressure were not done because of
limitations of the testing equipment. The remaining tests were conducted on dry samples.
Table 4.5. This table is a summary of direct shear test results for samples at dry and
moist states.
samples air-dried
Sample ID
Peak internal
friction angle
(degrees)
Apparent
cohesion
(kPa)
GHN-KMD-0017
42.15º
0
GHN-KMD-0018
44.43º
0
Trying to achieve field moisture content
Moisture
Peak internal
friction angle
(degrees)
Apparent
cohesion
(kPa)
14.97
12.40
34.27º
34.09
13.45
11.00
33.9º
41.33
Field moisture
content
content
(%) achieved (%)
52
GHN-KMD-0017
700
600
Shear stress (kPa)
dry
note:
shear box size: 2 inches
max. part. Size: 3.36mm
moisture 12.4%
500
2
R = 0.96
 peak = 42o
400
300
200
2
R = 1.00
 peak = 34o
100
0
0
100
200
300
400
500
600
700
Normal stress (kPa)
(a)
GHN-KMD-0018
600
note:
shear box size: 2 inches
max. part. Size: 3.36mm
Shear stress (kPa)
500
dry
moisture 11%
400
2
R = 0.99
 peak = 44.4o
300
2
R = 0.96
 peak = 33.9o
200
100
0
0
(b )
100
200
300
400
500
600
Normal stress (kPa)
Figure 4.8. This figure compares the results of the influence of moisture on the
direct shear test for samples (a) GHN-KMD-0017 and (b) GHN-KMD-0018.
53
The remaining direct shear tests were performed in a 2-inch shear box using dry
samples. Samples were first sieved on a No. 6 sieve (3.35 mm), then a minimum of four
fractionsof approximately 120 g (~ 4 oz) ofeach specimen were used for the tests. A dry
density of 1.7 ± 0.2g/cm3 (106 ± 10pcf) was achieved for all samples. A small density
range was desired to reduce the number of variables affecting the friction angle. All the
specimens were prepared by lightly compacting three lifts to attain the same relative
compression. A strain rate of 1% and normal stress varying from 159 to 800 kPa (23 to
116 psi) were adopted for all the tests.
4.4. Index Properties and Mineralogy
Other physical properties characterized in this study include moisture content,
liquid limit (LL), plastic limit (PL), plasticity index (PI), and specific gravity. Definitions
of theses terms as used in this document are given in appendix G. Tests were conducted
according to ASTM standard procedures (ASTM, 2001a; ASTM, 2001b; ASTM, 2002b).
Mineralogy of the samples was determined using a modal mineralogy analysis provided
by geoscientists at the New Mexico Bureau of Geology and Mineral Resources. The
modal mineralogy combines results from various chemical and mineralogical analyses,
including petrography, electron microprobe, clay mineralogy, pyrite concentrations using
the Reitveld method, and whole rock chemistry from X-ray fluorescence (XRF)
spectrometry. More information regarding the methodologies used to determine the
modal mineralogies can be found in project reports (McLemore et al., 2006) and project
standard operating procedures (Appendix F).
54
5. RESULTS AND DISCUSSIONS
Results of the measurements performed for this study are found in Appendices B
through E. Particle size analyses are located in Appendix B. Appendix C contains direct
shear stress-strain plots. Mohr Coulomb diagrams are given in Appendix D. In Appendix
E, sample mineralogy, measurements of Atterberg limits, direct shear test results, specific
gravity, particle size distribution, and moisture content are summarized.
5.1. Indices Testing
Tables 5.1 through 5.3 present results of particle size analysis, measurements of
Atterberg limits, moisture content, paste pH, and direct shear test results for samples
from the GHN rock pile arranged according to geologic units. Geologic units were
defined based on grain size, color, texture, stratigraphic position, and other physical
properties that could be determined in the field. Their characteristics are described in
Appendix E and in McLemore et al. (2005, 2006).
Based on gradation and Atterberg limits, the majority of samples from the GHN
rock pile are classified as poorly- to well-graded gravels with fines and sand according to
the United Soil Classification System (USCS). The table given in Appendix B shows the
USCS symbols for all soils that were classified. Soil ranged from GW, GW-GC, GWGM, GP, GP-GC, GP-GM, SC, SM, SW-SC, and SP-SC. Figure 5.1 shows the range of
particle size distributions for all the samples listed in Appendix B. Most of the fines were
55
identified as CL-group using the plasticity chart shown in Figure 5.2. The CL-group is an
inorganic clay with low swell potential. The remaining samples fall in the ML category,
which is an inorganic silt.
Table 5.1. This table is a summary of particle size analyses for samples from GHN
indexed by geologic unit.
Number
of
Samples
Geologic unit
Gravel (%)
Sand (%)
Fines (%)
Silt (%)
Clay (%)
Ave
Max
Min
Ave
Max
Min
Ave
Max
Min
Ave
Max
Min
Ave
Max
Min
C
41.83
-
-
46.95
-
-
11.22
-
-
5.51
-
-
5.57
-
-
1
I
46.45
55.69
37.21
37.99
43.66
32.32 15.56 19.13 11.99 12.72
14.57
10.87
2.84
4.56
1.12
2
J
56.77
63.40
49.84
35.29
41.01
29.36
7.94
10.70
4.70
6.25
8.34
4.42
1.69
3.97
0.28
5
54.55
57.57
51.53
35.88
38.95
32.80
9.45
9.99
9.36
8.13
8.18
8.07
1.46
1.46
1.45
2
K
54.90
69.62
45.06
35.24
44.20
24.97
9.86
12.54
5.41
6.16
7.97
3.12
3.69
5.71
2.28
4
O
55.25
70.45
41.56
35.45
47.93
24.21
9.31
12.64
5.34
6.26
8.20
3.23
3.04
4.89
2.10
10
M
61.18
-
-
28.83
-
-
9.99
-
-
5.58
-
-
4.41
-
-
1
R
54.51
63.12
45.90
35.09
41.12
29.07 10.40 12.98
7.82
7.41
8.78
6.05
2.89
4.20
1.77
2
Oxidized,
outter zone
Intermediate
zone
N
Unoxidized,
internal zone
S
64.90
74.83
54.98
26.64
33.68
19.59
8.46
11.34
5.58
5.87
7.04
4.70
2.59
4.31
0.88
2
U
69.49
87.39
60.06
24.10
32.33
9.66
6.41
8.66
2.95
3.77
5.05
1.70
2.63
3.61
1.25
3
V
61.44
65.12
58.75
30.69
33.31
28.11
7.87
8.90
6.77
4.97
5.31
4.57
2.90
3.58
2.20
3
56
Table 5.2. This table is a summary of Atterberg limit results for samples from GHN
indexed by geologic unit.
Plastic limit, PL
Geologic unit
Liquid limit, LL
Plasticity index, PI
Number of
Samples
Average
Maximum
Minimum
Average
Maximum
Minimum
Average
Maximum Minimum
I
23.28
24.67
21.88
32.62
35.28
29.95
11.60
17.91
5.28
2
J
19.84
22.08
17.96
34.12
38.44
28.73
14.29
17.24
9.26
3
22.66
24.88
20.44
34.73
35.58
33.88
14.72
15.14
14.29
2
Oxidized,
outter zone
Intermediate zone
N
Unoxidized,
internal zone
K
19.30
19.56
19.04
30.60
34.68
26.51
11.80
15.13
8.47
3
O
20.09
23.50
16.55
33.21
37.81
29.55
13.34
17.82
9.15
7
M
19.02
-
-
30.03
-
-
11.01
-
-
1
R
16.80
-
-
35.51
-
-
18.76
-
-
1
S
20.94
-
-
28.11
-
-
11.01
-
-
1
U
22.39
26.45
18.33
33.62
34.52
32.71
11.23
14.38
8.07
2
V
22.00
25.64
18.36
32.44
35.34
29.54
10.44
16.98
3.90
2
Table 5.3. This table is a summary of moisture content and paste pH results for
samples from GHN indexed by geologic unit.
Geologic Unit
Number of
samples
Moisture Content (%)
Average Maximum Minimum
Number of
samples
Paste pH (s.u.)
Average Maximum Minimum
Oxidized, outer zone
C
6.97
9.33
5.48
3
2.85
3.43
2.33
12
I
15.47
23.89
10.72
5
3.07
4.77
2.19
28
J
10.39
17.13
6.61
16
3.37
5.75
2.14
52
13.13
17.25
9.6
17
3.39
4.71
2.15
58
K
10.16
11.77
8.34
9
4.83
7.2
2.36
36
L
8.62
1
6.46
8.74
2.25
9
O
11.2
18.01
6.15
50
5.49
8.98
2.43
163
M
10.45
15.09
5.54
13
4.45
9.56
2.41
57
R
10.51
11.46
9.91
3
6.05
9.6
3.17
16
S
10.43
13.36
7.43
6
6.25
9.47
2.61
20
U
10.61
13.23
7.99
2
3.86
5.52
2.45
15
V
9.23
9.6
8.59
3
4.39
5.77
3.37
11
W
9
9.58
8.41
2
6.65
6.68
6.62
2
Intermediate zone
N
Unoxidized, internal zone
57
U.S. STANDARD SIEVE SIZE
4
6
100
3
2 1-1/2
1 3/4
1/2 3/8
1/4
4
8 10
16 20
30
40
50 60
100 140 200
90
PER CENT FINER BY WEIGHT
80
70
60
50
40
range of grain size
distribution
30
20
10
0
1000.0000
100.0000
10.0000
1.0000
0.1000
0.0100
0.0010
GRAIN SIZE MILLIMETERS
BOULDERS
COBBLES
SAND
GRAVEL
Coarse
Fine
Coarse
SILT OR CLAY
Medium
Fine
Figure 5.1. This graph shows the range of grain size distribution for samples from
the GHN rock pile.
60
U
IN
E
-L
IN
CH or OH
40
A
Plasticity index (PI)
E
50
-L
CL
30
ML
CL or OL
20
MH or OH
CL-ML
10
ML or OL
0
0
10
20
30
40
50
60
70
80
90
100
Liquid limit (LL)
Figure 5.2. This graph shows the distribution of samples from the GHN rock pile on
the plasticity chart.
58
5.2. Direct Shear Test Results
The peak internal friction angle () and the residual friction angle (residual) were
measured by direct shear tests using dry samples with maximum particle sizes of 3.36
mm (0.13 in). The test results are given in Table 5.4. The peak internal friction angle
ranged from 40º to 47º and the residual friction angle varied between 37º and 41º.
Correlation coefficients (R2) for tests on peak angles ranged from 0.95 to 1.00 and
averaged 0.99 for a minimum of four tests. High correlations demonstrated that
individual test conditions were reproducible, therefore high confidence can be placed on
the results.
Dry densities obtained during the tests ranged from 1.48 to 1.82 g/cm3 (92.4 to
113.6 pcf). The maximum dry density obtained for the relative density test was 1.82g/cm3
(113.6 pcf). Therefore, the maximum and minimum relative test densities were 100% and
81%, respectively. The average test relative density was 95%. Typical values of internal
friction angle and residual friction angle for sand-sized material are 28º to 60º (Holtz and
Kovacs, 2003) and 26º to 35º (Das, 1983), respectively. The lower range applies to round,
loose sand and the higher range is for angular, dense sand.
The values for internal friction angle are higher than the values reported for
saturated conditions ( average = 31º and 36º) in past geotechnical studies conducted on the
GHN rock pile (Norwest Corporation, 2004; Robertson GeoConsultants Inc., 2000). The
difference in  between dry and saturated conditions is to be expected. Figure 5.3 shows
normal stress versus shear stress for one sample tested both dry and at 12.4% moisture
content. It is clear that the addition of water to soil with an appreciable amount of non-
59
clay fines (19.3% in this case) produced an apparent cohesion. As such,  was reduced
from its value in the dry soil case.
Table 5.4. This summary table shows direct shear test results of samples from GHN
indexed by geologic unit.
In te rn a l fric tio n a n g le (d e g re e s )
R e s id u a l fric tio n a n g le (d e g re e s )
A v e ra g e
M a x im u m
M in im u m
A v e ra g e
M a x im u m
M in im u m
I
43
43
42
38
38
38
2
J
44
43
45
39
39
38
3
44
44
44
38
39
37
2
K
44
47
42
38
39
37
3
O
44
47
42
38
41
37
13
M
44
-
-
41
-
-
1
R
44
45
43
40
40
39
2
S
45
-
-
37
-
-
1
P
46
-
-
37
-
-
1
U
44
46
43
38
39
37
4
V
46
47
44
40
40
39
2
G e o lo g ic u n it
Num ber of
S a m p le s
O x id iz e d ,
o u tte r z o n e
In te rm e d ia te z o n e
N
U n o x id iz e d ,
in te rn a l z o n e
60
GHN-KMD-0017
700
600
Shear stress (kPa)
dry
note:
shear box size: 2 inches
max. part. Size: 3.36mm
moisture 12.4%
500
2
R = 0.96
 peak = 42o
400
300
200
2
R = 1.00
o
 peak = 34
100
0
0
100
200
300
400
500
600
700
Normal stress (kPa)
Figure 5.3. This graph shows direct shear test results for a dry sample versus a
sample with gravimetric moisture content of 12.4%.
In the case of saturated soils,  is often further reduced if small amounts of clay are
present in the fines.
Internal friction angles were correlated with weathering, chemistry, and
mineralogical effects. As such, the reader is reminded that these tests were conducted on
disturbed samples. The  values determined from these tests should not be used for slope
stability considerations.
5.3. Verification of Direct Shear Test Results
Additional direct shear tests were conducted using a calibrated Ele direct shear
testing apparatus borrowed from Kleinfelder Laboratory in Albuquerque. The proving
ring for this motorized machine is annually calibrated. A 2.5-inch round shear box was
used to test three samples from the GHN rock pile: GHN-KMD-0014, GHN-KMD-0017,
61
and GHN-KMD-0027. The purpose of these tests was to provide validation of the tests
conducted with the manual Soiltest shear box machine in the Mineral Engineering
Department at New Mexico Tech.
The Mohr-Coulomb diagrams for these tests using both machines are shown in
Figures 5.4 through 5.6. The shear test results using the Ele machine fell along the trend
lines defined by data generated with the machine at New Mexico Tech (NMT). The
addition of the corroborating data did not change the  values. Therefore, all test results
obtained at New Mexico Tech are considered to be representative and reproducible.
Friction angle-NMT
Residual Friciton angle- NMT
Kleinfelder Lab.
Kleinfelder Lab.
800
Sample ID. GHN-KMD-0014
Shear strength (kPa)
700
2
600
R = 1.00
500
400
300
2
R = 0.92
200
100
0
0
100
200
300
400 500
Norma stress (kPa)
600
700
800
Figure 5.4. This graph shows the Mohr-Coulomb diagram for sample GHN-KMD0014. Data points generated by both the automatic Ele and the manual NMT shear
box machines are included.
62
Friction angle- NMT
Residual friction angle - NMT
Kleinfelder Lab
Kleinfelder Lab
600
Sample ID. GHN-KMD-0017
Shear Strength (kPa)
500
2
R = 0.96
400
300
200
2
R = 0.97
100
0
0
100
200
300
400
500
600
Normal load (kPa)
Figure 5.5. This graph shows the Mohr-Coulomb diagram for sample GHN-KMD-0017.
Data points generated by both the automatic Ele and the manual NMT shear box
machines are included.
Friction angle - NMT
Kleinfelder Lab
600
Sample ID. GHN-KMD-0027
Shear strength (kPa)
500
400
2
R = 0.97
300
200
100
0
0
100
200
300
400
Normal Load (kPa)
63
500
600
Figure 5.6. This graph shows the Mohr-Coulomb diagram for sample GHN-KMD0027. Data points generated by both the automatic Ele and the manual NMT shear
box machines are included.
5.4.Correlations of Direct Shear Results with Geological and Geotechnical
Parameters
The influence of geological and geotechnical parameters on internal friction angle
() were evaluated and correlated. Correlations were made with respect to geologic units.
An example of these units is given in Figure 5.7 for bench 9 from Trench LFG-006.
Similar stratigraphic positions of the units were evident at other elevations where samples
were collected. The geological and geotechnical parameters examined included texture
(lithology and alteration), modal mineralogy, chemistry, % fines, and Atterberg limit
(liquid limit and plasticity index). The geological and geotechnical data used in this
section are summarized in tables in Appendix E.
Correlations are presented in Figures 5.8 through 5.22. In these plots, the samples
are presented according to geologic unit. For all the plots in this section, the outer zone
(oxidized zone) of the pile included unit I, the intermediate zone included units N and J,
and the internal zone (unoxidized zone) included units O, K, M, S, P, R, U, and V.
Graphs on the left represent correlations for bench 9 and graphs to the right
represent all samples tested in this study, including bench 9.
64
Figure 5.7. This diagram shows the stratigraphic positions of the geologic units for
bench 9 (Trench LFG-006).
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
Paste pH
5
6
7
8
9
10
Paste pH
Figure 5.8. These graphs show cross plots of internal friction angle versus paste pH.
Plot on the left side includes samples only from bench 9. Plot on the right side
includes all GHN samples tested in this study.
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
1
2
3
4
5
6
7
8
9
10
0
NAGpH
1
2
3
4
5
6
7
8
9
10
NAGpH
Figure 5.9. These graphs show cross plots of internal friction angle versus NAGpH.
Plot on the left side includes samples only from bench 9. Plot on the right side
includes all GHN samples tested in this study.
65
J-N
O
K
M-S-P
I
R-U-V
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
41
40
40
0
2
4
6
8
10
12
14
16
18
20
22
0
2
4
6
8
10
%Fines
12
14
16
18
20
22
%Fines
Figure 5.10. These graphs show cross plots of internal friction angle versus
percentage of fines. Plot on the left side includes samples only from bench 9. Plot on
the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
I
R-U-V
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
41
40
40
0
2
4
6
8
10
12
14
16
18
0
20
2
4
6
8
10
12
14
16
18
20
Plasticity index
Plasticity index
Figure 5.11. These graphs show cross plots of internal friction angle versus plasticity
index. Plot on the left side includes samples only from bench 9. Plot on the right side
includes all GHN samples tested in this study.
66
J-N
O
K
M-S-P
I
R-U-V
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
41
40
40
20
22
24
26
28
30
32
34
36
38
40
20
42
22
24
26
28
30
32
34
36
38
40
42
Liquid limit
Liquid limit
Figure 5.12. These graphs show cross plots of internal friction angle versus liquid
limit. Plot on the left side includes samples only from bench 9. Plot on the right side
includes all GHN samples tested in this study.
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
20
40
60
80
100
0
%Amalia Tuff
20
40
60
80
100
%Amalia Tuff
Figure 5.13. These graphs show cross plots of internal friction angle versus
percentage of Amalia Tuff. Plot on the left side includes samples only from bench 9.
Plot on the right side includes all GHN samples tested in this study.
67
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
20
40
60
80
100
0
20
40
%Andesite
60
80
100
%Andesite
Figure 5.14. These graphs show cross plots of internal friction angle versus
percentage of Andesite. Plot on the left side includes samples only from bench 9. Plot
on the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
10
20
30
40
50
60
70
80
90
100
0
%QSP alteration
10
20
30
40
50
60
%QSP alteration
68
70
80
90
100
Figure 5.15. These graphs show cross plots of internal friction angle versus quartzsericite-pyrite (QSP) alteration. Plot on the left side includes samples only from
bench 9. Plot on the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
10
20
30
40
50
60
70
80
90
100
0
10
20
30
%Propylitic alteration
40
50
60
70
80
90
100
%Propylitic alteration
Figure 5.16. These graphs show cross plots of internal friction angle versus
propyllitic alteration. Plot on the left side includes samples only from bench 9. Plot
on the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
1
2
3
4
5
6
7
0
8
1
2
3
4
LOI
LOI
69
5
6
7
8
Figure 5.17. These graphs show cross plots of internal friction angle versus LOI (lost
of ignition). Plot on the left side includes samples only from bench 9. Plot on the
right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
I
R-U-V
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
41
40
40
0
2
4
6
8
10
12
14
16
18
0
20
2
4
6
8
10
12
14
16
18
20
%Epidote
%Epidote
Figure 5.18. These graphs show cross plots of internal friction angle versus
percentage of epidote. Plot on the left side includes samples only from bench 9. Plot
on the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
I
R-U-V
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
41
40
40
0
2
4
6
8
10
12
14
16
18
0
20
2
4
6
8
10
%Illite
%Illite
70
12
14
16
18
20
Figure 5.19. These graphs show cross plots of internal friction angle versus
percentage of illite. Plot on the left side includes samples only from bench 9. Plot on
the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
I
R-U-V
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
41
40
40
0
0.5
1
1.5
2
2.5
3
0
3.5
1
2
3
4
%MgO
%MgO
Figure 5.20. These graphs show cross plots of internal friction angle versus
percentage of MgO. Plot on the left side includes samples only from bench 9. Plot on
the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
0
0.5
1
1.5
2
2.5
3
3.5
0
%CaO
1
2
3
%CaO
71
4
5
Figure 5.21. These graphs show cross plots of internal friction angle versus
percentage of CaO. Plot on the left side includes samples only from bench 9. Plot on
the right side includes all GHN samples tested in this study.
J-N
O
K
M-S-P
R-U-V
I
48
47
47
46
46
Internal friction angle (degrees)
Internal friction angle (degrees)
I
48
45
44
43
42
41
J-N
O
K
M-S-P
R-U-V
45
44
43
42
41
40
40
12
12.5
13
13.5
14
14.5
15
15.5
16
12
%Al2O3
12.5
13
13.5
14
14.5
15
15.5
16
%Al2O3
Figure 5.22. These graphs show cross plots of internal friction angle versus
percentage of Al2O3. Plot on the left side includes samples only from bench 9. Plot
on the right side includes all GHN samples tested in this study.
Variations in  values with paste pH and NAGpH are shown in Figures 5.8 and
5.9. A positive correlation of paste pH and NAGpH with  is apparent only for bench 9
data. In Figures 5.10 through 5.12 correlations with geotechnical properties show a
decrease in  as PI, LL, and percent fines increase. These correlations are expected and
documented in the literature (Das, 1983; Holtz and Kovacs, 2003). The increase of fines
reduces the contacts between coarse grains, thereby reducing the interlocking contacts
that results in a decrease in . Although test results are for dry samples, the effects of
72
fines with atmospheric moisture (1-3% in the laboratory) are apparent. If tests had been
conducted at field moisture contents, these correlations would be far stronger.
Correlations of  with lithology (andesite and Amalia Tuff), shown in Figure 5.13
and 5.14, are not apparent. Alteration of these rock types is given in Figures 5.15 and
5.16. QSP alteration shows a weak negative trend with . The negative trend is probably
caused by the presence of the clay mineral sericite.
The negative correlation of  with LOI (Figure 5.17) may be explained by the
presence of clay minerals. An increasing in LOI can be translated in an increasing in clay
minerals. Figures 5.18 and 5.19 show that there are weak trends to no correlations of 
with mineralogy. The same is true with MgO, CaO, and Al2O3 chemistry data (Figures
5.20 through 5.22). When each of these elements is plot separately correlations are week
to absent.
In summary, correlations of  with geological parameters are weak or nonexistent. The weak correlations might be due to the small range in  values obtained.
Results from direct shear tests showed that  varies from 42 to 47 degrees, with an
average of 44 degrees, as summarized in Table 5.4. Considering a maximum error of ±2
degrees in friction angle (W. Wilson, personal communication, 2005), there is only a
small statistical variation in friction angle within the rock pile.
5.5. Correlations of Direct Shear Test Results with Weathering Indexes
A weathering index is a measure of how much the sample has weathered.
Numerous weathering indexes have been proposed and used over the years, but most of
73
them are based only on geochemical parameters, which restricts their application to the
type of environment for which they were developed. Therefore, there is a need to develop
a weathering index for the rock piles at the Questa mine. For the purpose of identifying
relative intensity of weathering of samples collected in the project, McLemore (2005)
described a simple, descriptive weathering index (SWI) that is based upon field
observations (color, grain size, mineral texture, and presence or absence of certain
minerals indicative of weathering).
Together with SWI, other published chemical weathering indexes are being
evaluated as well.
WPI – Weathering Potential Index (Reiche, 1943, Infran, 1996, 1999)
WPI = 100*(K2O+Na2O+CaO+MgO-H2O) / (SiO2 +Al2O3
+Fe2O3+ FeO + TiO2+CaO+MgO +Na2O+K2O)
MI – Miura Index (Miura, 1973)
MI = (MnO +FeO+CaO +MgO+Na2O+K2O) /
(Fe2O3+Al2O3+3H2O)
The Weathering Potential Index, WPI (Reiche, 1943, Infran, 1996, 1999) and the
Miura index, MI (Miura, 1973) had shown to be applicable in this study. These
weathering indexes show a trend similar to paste pH (Figures 5.23 and 5.24). The paste
pH and the weathering indexes show a trend of increasing weathering from the inner
portion (less oxidized) to the outer portion (oxidixed egde). These weathering indexes are
calculated based on chemical data reflecting changes in mineralogy (i.e. feldspar to clay,
calcite-pyrite to gypsum-jarosite). The data and graphs in Figure 5.23 and 5.24 were
generated by geoscientists at the New Mexico Bureau of Geology and Mineral
Resources.
74
11121314151617181920-
20
bedrock
rubble zone
shear zone
R,U,V and W
M,S,P
K
O
N
J
C and I
0.7
0.5
MI
WPI
0.6
10
0.4
0.3
0
0.2
0
100
200
0
100
Hfrom
200
Hfrom
Figure 5.23. This figure shows plots of the WPI and MI weathering indexes with
distance across bench 9, trench LFG-006. The outer oxidized edge is at Hfrom=0
and the inner zone of the bench is at Hfrom=105. Weathering increases towards the
left.
0.7
20
0.6
10
MI
WPI
0.5
0
0.4
0.3
-10
0.2
0.1
-20
2
3
4
5
6
7
8
9
2
10
3
4
5
6
7
pastepH
pastepH
75
8
9
10
Figure 5.24. This figure shows plots of WPI and MI vs. paste pH for all GHN
samples. WPI and MI are explained in Figure 5.23.
Figure 5.25 through 5.27 are plots of weathering indexes (SWI, WPI and MI)
versus internal friction angle for samples from bench 9, trench LFG-006. A general trend
of decreasing friction angle with increasing degree of weathering is apparent for all of
these weathering indexes. A similar trend was observed in friction angle and weathering
by Ifran (1996, 1999). The effects of weathering are not linear because weathering is so
complex and dependent upon, lithology, composition of original rock, composition of
fluids interacting with the rock pile material.
I
J-N
O
K
M-S-P
R-U-V
Internal friction angle (degrees)
48
47
46
45
44
43
42
41
40
5
4
3
2
1
0
SWI
Figure 5.25. This figure shows a cross plot of Friction angle versus simple
weathering index (SWI) for bench 9 samples, trench LFG-006. Weathering intensity
increases towards the left.
76
I
J-N
O
K
M-S-P
R-U-V
48
Internal friction angle (degrees)
47
46
45
44
43
42
41
40
0
2
4
6
8
10
12
14
WPI
Figure 5.26. This figure shows a cross plot of Friction angle versus weathering
potential index (WPI) for samples from bench 9, trench LFG-006. The weathering
intensity increases towards the left.
I
J-N
O
K
M-S-P
R-U-V
48
Internal friction angle (degrees)
47
46
45
44
43
42
41
40
0
0.2
0.4
0.6
0.8
MI
Figure 5.27. This figure shows a cross plot of Friction angle versus Miura Index
(MI) for samples from bench 9, trench LFG-006. The weathering intensity increases
towards the left.
77
78
6. CONCLUSIONS AND RECOMENDATIONS
This study presents an investigation of the influence of physical, geological,
mineralogical, and chemical properties on shear strength properties of the GHN rock pile
at Questa molybdenum mine, New Mexico. Representative samples were collected based
upon visible changes in the weathering characteristics and were not collected for the
purpose of slope stability analysis. Shear strength was analyzed using dry samples to
eliminate the effects of cohesion. The influences of the physical, geological,
mineralogical, and chemical properties of rock pile samples on friction angle were
studied. The synthesis of these analyses leads to the following conclusions:

The majority of samples from the GHN rock pile are classified as poorly
to well graded gravels with fines and sand.

Most of the fines (silt &clay) are classified as inorganic clay with low
swell potential.

The peak internal friction angle ranged from 40º to 47º and residual
friction angle varied between 37º and 41º. These high values of peak
internal and residual friction angle are attributed to grain shape
(subangular to very angular) and relative density of the test specimens.

The lowest  were for materials near the face of the pile.

Correlations of  from GHN samples with chemistry, and mineralogy are
shown to be weak or absent.
79

Negative correlations  were observed for %Fines, LL, PI, LOI. The 
decreased as these parameters increased.

Correlation of  with lithology was not observed.

The internal friction angle for samples from bench 9, trench LFG-006
showed some trends with three different weathering indexes. Friction
angle decreased as degree of weathering increased.
Recommendations for future work include:

Determine the effects of cementation on friction angle. (Based on
laboratory observations it may be possible to test the cementation by
allowing the sample to air dry in the shear box. After the test is performed
the sample would be broken down and tested again. The difference
between the two friction angles is an estimation of the effect of
cementation on friction angle.)

Determine the effects of cohesion on the strength of the mine rock.

Examine the mineralogy and chemistry on the same size fraction
that is used in the direct shear test (i.e. test the assumption that the
analyses on the entire sample reflect the particle size fraction used in the
shear tests).
80
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85
APPENDIX A – SAMPLE LOCATION
86
Sample
GHN-KMD-0013
GHN-KMD-0014
GHN-KMD-0015
GHN-KMD-0016
GHN-KMD-0017
GHN-KMD-0018
GHN-KMD-0019
GHN-KMD-0026
GHN-KMD-0027
GHN-KMD-0051
GHN-KMD-0052
GHN-KMD-0053
GHN-KMD-0055
GHN-KMD-0056
GHN-KMD-0057
GHN-KMD-0062
GHN-KMD-0063
GHN-KMD-0065
GHN-KMD-0071
GHN-KMD-0072
GHN-KMD-0073
GHN-KMD-0074
GHN-KMD-0078
GHN-KMD-0079
GHN-KMD-0081
GHN-KMD-0082
GHN-KMD-0088
GHN-KMD-0092
GHN-LFG-0085
GHN-LFG-0088
GHN-LFG-0090
GHN-VTM-0450
GHN-VTM-0453
GHN-VTM-0454
UTM east UTM north
(meters)
(meters)
Units
O
K
R
S
I
J
O
M
N
O
K
contact between Unit N
I
V
O
N
J
V
Unit U, V contact
coarse zone in Unit O
O (coarse sand)
U
U
U
R
O
O
O1
K
O
P
O (coarse layer)
O (clay rich)
O
87
453696
453677
453723
453698
453772
453685
453708
453682
453708
453711
453727
453695
453696
453705
453657
453734
453647
453643
453648
453667
453667
453671
453672
453718
453676
453731
453657
453729
453740
453734
453740
453723
453676
453680
4062143
4062146
4062142
4062143
4062140
4062146
4062147
4062140
4062148
4062142
4062144
4062145
4062139
4062140
4062127
4062140
4062115
4062115
4062115
4062137
4062137
4062137
4062134
4062144
4062138
4062143
4062127
4062141
4062141
4062141
4062142
4062141
4062137
4062137
Elevation
(ft)
9731
9691
9736
9731
9688
9694
9738
9689
9739
9734
9739
9698
9694
9697
9635
9755
9600
9599
9601
9644
9644
9646
9644
9737
9650
9760
9635
9736
9758
9736
9758
9736
9650
9650
APPENDIX B – GRAIN SIZE DISTRIBUTION CURVES AND SUMMARY
TABLE
88
89
C
H
I
I
J
J
J
J
K
K
K
K
M
N
N
N-J contant
O
O
O
O
O
O
O
O (clay rich)
O (coarse sand)
O (coarse)
R
R
S
S
U
U
U
U- V contact
V
V
Geologic Units
0.25
0.47
0.09
0.064
0.054
0.35
GHNJRM0029
GHNKMD0018
GHNKMD0063
GHNKMD0096
GHNJRM0028
GHNKMD0014
0.1
0.16
GHNKMD0065
0.11
GHNKMD0079
0.26
2.85
GHNKMD0078
GHNKMD0056
0.19
GHNKMD0074
GHNKMD0071
0.425
GHNKMD0015
GHNKMD0016
0.17
GHNVTM0450
0.049
0.55
GHNKMD0073
0.056
0.079
GHNVTM0453
GHNKMD0080
0.07
GHNKMD0072
GHNKMD0081
0.16
0.0395
GHNLFG0088
0.06
0.1
GHNKMD0019
0.115
0.15
GHNJRM0031
GHNKMD0057
0.08
GHNJRM0030
GHNKMD0051
0.03
0.14
GHNKMD0053
GHNKMD0027
GHNKMD0028
0.075
0.075
GHNKMD0026
0.04
0.055
GHNKMD0055
0.067
0.013
GHNKMD0017
GHNLFG0085
0.05
GHNKMD0052
0.054
2.6
3.3
2.8
2.8
27
2.75
7.2
1.65
0.97
3
4.9
2.35
0.83
0.99
2.9
2.55
1.4
2.4
2.5
2
2.6
0.23
2.45
2.55
2.1
1.15
4.7
1.6
1.6
1.4
3.3
3.5
1.8
0.22
0.73
1.05
(mm)
(mm)
GHNLFG0037
D30
D10
GHNKMD0095
Field_id
20
17
14.8
19.5
320
15
47
13
6.7
11.6
10.7
12
5.1
7.9
15
11.6
8
10.2
10
8
19
2.9
10.3
19.2
12.5
7
10.7
6
6
9
10.3
10.2
10.3
4.0
6.3
5.1
(mm)
D60
125
65
148
177
112
79
111
232
137
68
20
152
73
200
94
101
133
102
67
100
136
97
137
256
187
175
31
111
94
100
22
41
187
308
125
94
Cu
2.1
2.5
5.3
3.7
0.8
2.7
2.6
3.7
2.9
4.6
4.1
5.8
1.9
3.1
3.5
4.9
4.1
5.6
4.2
6.3
2.5
0.6
7.8
4.5
5.3
4.7
5.9
7.9
6.7
2.4
2.3
4.8
5.7
0.9
1.7
4.0
Cc
58.75
65.12
60.45
61.03
87.39
60.06
74.83
54.98
45.9
63.12
70.45
58.39
41.56
48.51
62.53
59.56
49.81
53.25
56.94
51.48
58.77
51.53
57.57
61.18
56.95
47.97
69.62
45.06
50.13
49.84
61.71
63.4
55.69
37.21
45.98
41.83
(%)
Gravel
33.31
28.11
30.65
30.31
9.66
32.33
19.59
33.68
41.12
29.07
24.21
31.97
47.93
38.85
29.42
31.69
39.48
37.82
35
38.1
33.34
38.95
32.8
28.83
32.32
39.49
24.97
44.2
39.17
41.01
33.59
29.36
32.32
43.66
40.3
46.95
(%)
Sand
7.94
6.77
8.9
8.66
2.95
7.61
5.58
11.34
12.98
7.82
5.34
9.64
10.51
12.64
8.05
8.75
10.71
8.93
8.06
10.42
7.89
9.53
9.36
9.99
10.74
12.54
5.41
10.74
10.7
9.15
4.7
7.24
11.99
19.13
13.72
11.22
(%)
Fines
5.03
4.57
5.31
5.05
1.7
4.57
4.7
7.04
8.78
6.05
3.23
6.09
8.2
7.75
5.92
5.31
6.54
5.82
5.84
7.88
5.06
8.07
8.18
5.58
6.73
6.83
3.12
7.97
6.74
8.34
4.42
6.67
10.87
14.57
10.37
5.51
(%)
Silt
2.91
2.2
3.58
3.61
1.25
3.04
0.88
4.31
4.2
1.77
2.1
3.55
2.3
4.89
2.13
3.44
4.17
3.11
2.22
2.54
2.83
1.46
1.45
4.41
4
5.71
2.28
2.77
3.97
0.82
0.28
0.57
1.12
4.56
3.34
5.71
(%)
Clay
CL
ML
ML
CL
CL
n.d.
CL
n.d.
CL
n.d.
n.d.
n.d.
CL
CL
CL
CL
CL
ML
n.d.
n.d.
CL
n.d.
ML
CL
CL
CL
CL
n.d.
CL
CL
n.d.
CL
ML
ML
n.d.
CL
GW-GC
GW-GM
GP-GM
GP-GC
GP
n.d.
GW-GC
n.d.
SC
n.d.
n.d.
n.d.
SW-SC
SP-SC
GP-GC
GP-GC
SP-SC
GP-GM
n.d.
n.d.
GW-GC
n.d.
GW-GM
GP-GC
GP-GC
SC
GP-GC
n.d.
GP-GC
SW-SC
GW
GP-GC
GP-GM
SM
n.d.
SP-SC
Classification
USCS
from plasticity
Classification
chart
Well graded
Well graded
Poorly graded
Poorly graded
Well graded
Well graded
Well graded
Poorly graded
Well graded
Poorly graded
Poorly graded
Poorly graded
Well graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Well graded
Well graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Poorly graded
Well graded
Well graded
Poorly graded
Poorly graded
Well graded
Well graded
Poorly graded
Comments
90
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution- GHN-JRM-0037
SILT
0.0100
HYDROMETER
CLAY
0.0010
91
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution- GHN-KMD-0014
SILT
0.0100
HYDROMETER
CLAY
0.0010
92
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0015
SILT
0.0100
HYDROMETER
CLAY
0.0010
93
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution- GHN-KMD-0016
SILT
0.0100
HYDROMETER
CLAY
0.0010
94
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0017
SILT
0.0100
HYDROMETER
CLAY
0.0010
95
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0018
SILT
0.0100
HYDROMETER
CLAY
0.0010
96
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0019
SILT
0.0100
HYDROMETER
CLAY
0.0010
97
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0026
SILT
0.0100
HYDROMETER
CLAY
0.0010
98
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0027
SILT
0.0100
HYDROMETER
CLAY
0.0010
99
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0051
SILT
0.0100
HYDROMETER
CLAY
0.0010
100
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0053
SILT
0.0100
HYDROMETER
CLAY
0.0010
101
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0055
SILT
0.0100
HYDROMETER
CLAY
0.0010
102
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0056
SILT
0.0100
HYDROMETER
CLAY
0.0010
103
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0057
SILT
0.0100
HYDROMETER
CLAY
0.0010
104
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0063
SILT
0.0100
CLAY
HYDROMETER
0.0010
105
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0065
SILT
0.0100
HYDROMETER
CLAY
0.0010
106
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0071
SILT
0.0100
HYDROMETER
CLAY
0.0010
107
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0072
SILT
0.0100
HYDROMETER
CLAY
0.0010
108
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0073
SILT
0.0100
HYDROMETER
CLAY
0.0010
109
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0074
SILT
0.0100
HYDROMETER
CLAY
0.0010
110
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0078
SILT
0.0100
HYDROMETER
CLAY
0.0010
111
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0079
SILT
0.0100
HYDROMETER
CLAY
0.0010
112
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-KMD-0081
SILT
0.0100
HYDROMETER
CLAY
0.0010
113
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-LFG-0037
SILT
0.0100
HYDROMETER
CLAY
0.0010
114
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-LFG-0085
SILT
0.0100
HYDROMETER
CLAY
0.0010
115
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-LFG-0088
SILT
0.0100
HYDROMETER
CLAY
0.0010
116
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-VTM-0450
SILT
0.0100
HYDROMETER
CLAY
0.0010
117
PER CENT FINER BY WEIGHT
BOULDERS
0
1000.0000
10
20
30
40
50
60
70
80
90
100
COBBLES
100.0000
3
2
Fine
10.0000
3/8
GRAVEL
1 3/4
Coarse
1-1/2
U.S. STANDARD SIEVE NUMBERS
4
1.0000
16
30
40
50
Coarse
Medium
SAND
GRAIN SIZE MILLIMETERS
10
200
Fine
0.1000
60 100
Particle Size Distribution - GHN-VTM-0453
SILT
0.0100
HYDROMETER
CLAY
0.0010
APPENDIX C – DIRECT SHEAR STRESS DIAGRAMS
118
Shear strain (H)
Shear strain is obtained considering the following equation:
H = (Horizontal deformation/ Sample length)*100
Horizontal deformation (in. 10-3)
Sample length, Lo (in)
Direct Shear Test Data Sheet
Name
Date
Project
Molycorp
Specimen
No.
Visual Description
notes
12/9/2005
GHN-EHP-0002
_1d_2_152
sample sieved with No. 6
2
Loads no.
25.81 Frame+Hanger
Sample Length, Lo (in)
2
Sample area, Ao (cm )
Strain rate,L/Lo (100)/min (%/min)
Deformation rate, L/min (in/min) (Lo x strain rate)
1
0.02
LC-8 dial gage divisions per min.
20
116.27
2.54
dry
1.77
Mass of sample(g)
Sample height (cm)
Moisture content (%)
Dry density (Mg/m3)
3
Moist/saturated density (Mg/m )
Normal load (kg)
Normal stress, n (kPa)
Shear stress at failure,(kPa)
Shear stain at failure, H (%)
Horizontal
deformation
(sec)
LC-8 (in.10 )
0
15
30
45
60
75
90
105
120
135
150
165
180
195
210
225
240
-3
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
6
7
8
9
10
11
41.96
159.46
159.15 Residual shear strength (kPa)
132.79
5.00 primary
none
-1.01 secondary
Vertical stain at failure, V (%)
Elapsed
Time
2
3
4
5
Mass(Kg)
check mark
9.96
1
8.46
0
8.12
0
8.13
0
8.14
0
8.15
0
16
1
1
16
16
0
0
16
14.33
0
Vertical
deformation
Load Dial
Gage
(in.)
LC-2 (in.10 )
0.2932
0.2953
0.297
0.2983
0.2994
0.3001
0.3009
0.3025
0.3041
0.305
0.3058
0.306
0.306
0.306
0.306
0.306
0.3057
Shear Strain
H
Vertical Strain
V
Shear Load
P
Shear Stress
P(98.07)/Ao


(kg)
(kPa)
-4
0
117
145
171
195
215
231
244
258
268
274
280
286
288
290
293
295
0
0.250
0.500
0.750
1.000
1.250
1.500
1.750
2.000
2.250
2.500
2.750
3.000
3.250
3.500
3.750
4.000
119
0
-0.2100
-0.3800
-0.5100
-0.6200
-0.6900
-0.7700
-0.9300
-1.0900
-1.1800
-1.2600
-1.2800
-1.2800
-1.2800
-1.2800
-1.2800
-1.2500
0
16.33
20.24
23.87
27.22
30.01
32.25
34.06
36.02
37.41
38.25
39.09
39.93
40.20
40.48
40.90
41.18
0
62.07
76.92
90.72
103.45
114.06
122.55
129.44
136.87
142.18
145.36
148.54
151.73
152.79
153.85
155.44
156.50
GHN-KMD-0013
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0013
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
2
Vertical strain (%)
Shear stress (kPa)
600
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
120
14
16
18
20
GHN-KMD-0014
800
700
600
Shear stress (kPa)
Normal stress = 637kPa
Normal stress = 457kPa
500
Normal stress = 303kPa
Normal stress = 159kPa
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0014
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
121
14
16
18
20
GHN-KMD-0015
800
700
Normal stress = 754kPa
Normal stress = 562kPa
Normal stress = 356kPa
600
Shear stress (kPa)
Normal stress = 159kPa
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0015
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
122
14
16
18
20
GHN-KMD-0016
800
Normal stress = 453kPa
Normal stress = 368kPa
700
Normal stress = 243kPa
Normal stress = 152kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0016
4
Normal stress = 152kPa
Normal stress = 243kPa
Normal stress = 368kPa
Normal stress = 453kPa
3
Vertical srain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
123
14
16
18
20
GHN-KMD-0017
800
Normal stress = 460kPa
Normal stress = 368kPa
700
Normal stress = 243kPa
Normal stress = 122kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0017
4
Normal stress = 122kPa
Normal stress = 243kPa
Normal stress = 368kPa
Normal stress = 460kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
124
14
16
18
20
GHN-KMD-0018
800
Normal stress = 453kPa
Normal stress = 368kPa
Normal stree = 243kPa
Normal stress = 152kPa
700
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0018
4
Normal stress = 152kPa
Normal stree = 243kPa
Normal stress = 368kPa
Normal stress = 453kPa
3
Vertical strain(%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
125
14
16
18
20
GHN-KMD-0019
800
700
Shear stress (kPa)
600
500
Normal stress = 754kPa
400
Normal stress = 562kPa
Normal stress = 356kPa
300
Normal stress = 159kPa
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0019
4
3
Vertical strain (%)
2
1
0
-1
-2
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
126
14
16
18
20
GHN-KMD-0026
800
Normal stress = 427kPa
Normal stress = 368kPa
700
Normal stress = 243kPa
Normal stress = 152kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0026
4
Normal stress = 152kPa
Normal stress = 243kPa
Normal stress = 368kPa
3
Normal stress = 427kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
127
14
16
18
20
GHN-KMD-0027
800
Normal stress = 453kPa
Normal stress = 368kPa
Normal stress = 243kPa
700
Normal stress = 122kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0027
4
Normal stress = 122kPa
Normal stress = 243kPa
3
Normal stress = 368kPa
Normal stress = 453kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
128
14
16
18
20
GHN-KMD-0051
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0051
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
129
14
16
18
20
GHN-KMD-0052
900
Normal stress = 637kPa
Normal stress = 457kPa
800
Normal stress = 303kPa
Normal stress = 159kPa
700
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0052
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical Strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
130
14
16
18
20
GHN-KMD-0053
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0053
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
131
14
16
18
20
GHN-KMD-0053_DUPLICATE
800
Normal stress = 637kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0053- DUPLICATE
4
Normal stress = 159kPa
Normal stress = 303kPa
3
Normal stress = 637kPa
Shear stress (kPa)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
132
14
16
18
20
GHN-KMD-0055
800
700
600
Normal stress = 754kPa
Shear stress (kPa)
Normal stress = 562kPa
500
Normal stress = 356kPa
Normal stress = 159kPa
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0055
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
133
14
16
18
20
GHN-KMD-0056
800
Normal stress = 504kPa
Normal stress = 368kPa
Normal stress = 274kPa
700
Normal stress = 152kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0056
4
3
Vertical strain (%)
2
1
0
-1
Normal stress = 152kPa
-2
Normal stress = 274kPa
Normal stress = 368kPa
-3
Normal stress = 504kPa
-4
0
2
4
6
8
10
12
Shear strain (%)
134
14
16
18
20
GHN-KMD-0057
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0057
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
135
14
16
18
20
GHN-KMD-0057-DUPLICATE
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0057-DUPLICATE
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical Strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
136
14
16
18
20
GHN-KMD-0062
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0062
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
137
14
16
18
20
GHN-KMD-0063
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0063
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
138
14
16
18
20
GHN-KMD-0071
Normal stress = 754kPa
800
Normal stress = 562kPa
Normal stress = 356kPa
Normal stress = 159kPa
700
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0071
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
3
Vertical stress (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
139
14
16
18
20
GHN-KMD-0072
800
Normal stress = 754kPa
Normal stress = 562kPa
700
Normal stress = 356kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0072
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
140
14
16
18
20
GHN-KMD-0073
Normal stress = 754kPa
Normal stress = 562kPa
800
Normal stress = 356kPa
Normal stress = 159kPa
700
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0073
4
Normal stress = 159kPa
Normal stress = 303kPa
3
Normal stress = 457kPa
Normal stress = 754kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
141
14
16
18
20
GHN-KMD-0074
800
700
Shear stress (kPa)
600
500
Normal stress = 754kPa
Normal stress = 562kPa
400
Normal stress = 356kPa
Normal stress = 159kPa
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0074
4
Normal stress = 159kPa
Normal stress = 303kPa
3
Normal stress = 457kPa
Normal stress = 754kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
142
14
16
18
20
GHN-KMD-0078
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0078
4
Normal stress = 159kPa
Normal stress = 303kPa
3
Normal stress = 457kPa
Normal stress = 637kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
143
14
16
18
20
GHN-KMD-0079
800
Normal stress = 754kPa
Normal stress = 562kPa
700
Normal stress = 356kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0079
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
3
Normal stress = 754kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
144
14
16
18
20
GHN-KMD-0079-DUPLICATE
800
Normal stress = 754kPa
Normal stress = 562kPa
Normal stress = 356kPa
700
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
Shear strain (%)
GHN-KMD-0079-DUPLICATE
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
14
Shear strain (%)
145
16
18
20
22
24
26
GHN-KMD-0081
800
Normal stress = 430kPa
Normal stress = 368kPa
700
Normal stress = 274kPa
Normal stress = 152kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0081
4
Normal stress = 152kPa
Normal stress = 274kPa
3
Normal stress = 368kPa
Normal stress = 430kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
146
14
16
18
20
GHN-KMD-0081-DUPLICATE
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
22
24
16
18
20
22
24
Shear strain (%)
GHN-KMD-0081-DUPLICATE
4
3
Vertical strain (%)
2
1
0
-1
-2
Normal stress = 159kPa
Normal stress = 303kPa
-3
Normal stress = 457kPa
Normal stress = 637kPa
-4
0
2
4
6
8
10
12
14
Shear strain (%)
147
GHN-KMD-0088
900
Normal stress = 637kPa
Normal stress = 457kPa
800
Normal stress = 303kPa
Normal stress = 159kPa
700
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-KMD-0088
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
148
14
16
18
20
GHN-LFG-0037
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
22
24
Shear strain (%)
GHN-LFG-0037
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
14
Shear strain (%)
149
16
18
20
22
24
GHN-LFG-0085
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-LFG-0085
4
Normal stress = 159kPa
Normal stress = 303kPa
3
Normal stress = 457kPa
Normal stress = 637kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
150
14
16
18
20
GHN-LFG-0088
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-LFG-0088
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
151
14
16
18
20
GHN-LFG-0090
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-LFG-0090
4
Normal stress = 159kPa
Normal stress = 303kPa
3
Normal stress = 457kPa
Normal stress = 637kPa
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
152
14
16
18
20
GHN-VTM-0450
800
700
Shear stress (kPa)
600
500
Normal stress = 754kPa
Normal stress = 562kPa
400
Normal stress = 356kPa
Normal stress = 159kPa
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-VTM-0450
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
3
Shear stress (kPa)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
153
14
16
18
20
GHN-VTM-0453
800
Normal stress = 754kPa
Normal stress = 562kPa
Normal stress = 356kPa
700
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-VTM-0453
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 754kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
154
14
16
18
20
GHN-VTM-0454
800
Normal stress = 637kPa
Normal stress = 457kPa
700
Normal stress = 303kPa
Normal stress = 159kPa
Shear stress (kPa)
600
500
400
300
200
100
0
0
2
4
6
8
10
12
14
16
18
20
Shear strain (%)
GHN-VTM-0454
4
Normal stress = 159kPa
Normal stress = 303kPa
Normal stress = 457kPa
Normal stress = 637kPa
3
Vertical strain (%)
2
1
0
-1
-2
-3
-4
0
2
4
6
8
10
12
Shear strain (%)
155
14
16
18
20
APPENDIX D – MOHR COULOMB DIAGRAMS
156
Maximum Particle
Size
Sample ID
Dry Density
Minimum
GHN-KMD-0056
GHN-LFG-0003
GHN-KMD-0071
3
(mm)
(g/cm )
(g/cm )
No. 6 sieve
(3.36mm)
1.42
1.85
1.38
1.76
1.43
1.84
1.41
1.82
No. 6 sieve
(3.36mm)
No. 6 sieve
(3.36mm)
Average
Geologic Units
Maximum
3
Sample ID
Peak Friction
Residual
Angle
Friction Angle
(degrees)
(degrees)
41
38
42
38
43
38
Test(1)
Density
(g/cm3)
1.75
1.72
1.78
Relative
Density
(%)
96
95
98
H
I
I
GHN-LFG-0037
GHN-KMD-0017
GHN-KMD-0055
J
J
contact between Unit N-J
N
N
GHN-KMD-0018
GHN-KMD-0063
GHN-KMD-0053
GHN-KMD-0027
GHN-KMD-0062
44
45
43
44
44
39
39
38
37
39
1.48
1.61
1.59
1.62
1.76
81
88
87
89
97
O
O
O
O
O
O
O
O
O
O
O
O
O
GHN-KMD-0013
GHN-KMD-0019
GHN-KMD-0051
GHN-KMD-0057
GHN-KMD-0082
GHN-KMD-0088
GHN-LFG-0088
GHN-VTM-0454
GHN-VTM-0453
GHN-VTM-0450
GHN-KMD-0073
GHN-KMD-0092
GHN-KMD-0072
43
45
43
43
44
45
42
43
44
44
43
44
43
38
39
38
40
37
38
39
35
38
41
39
39
38
1.62
1.77
1.63
1.61
1.75
1.74
1.78
1.77
1.79
1.71
1.8
1.77
1.78
89
97
90
88
96
96
98
97
98
94
99
97
98
K
K
K
GHN-KMD-0014
GHN-KMD-0052
GHN-LFG-0085
47
43
42
39
37
39
1.73
1.73
1.74
95
95
96
M
P
S
GHN-KMD-0026
GHN-LFG-0090
GHN-KMD-0016
44
46
45
41
37
39
1.64
1.68
1.68
90
92
92
R
R
U
U
U
Unit U, V contact
V
V
GHN-KMD-0015
GHN-KMD-0081
GHN-KMD-0074
GHN-KMD-0078
GHN-KMD-0079
GHN-KMD-0071
GHN-KMD-0056
GHN-KMD-0065
45
43
44
46
43
43
47
44
40
39
39
38
38
37
40
39
1.76
1.79
1.79
1.78
1.75
1.79
1.82
1.77
97
98
98
98
96
98
100
97
Average
44
38
1.72
95
Maximum
47
41
1.82
100
Minimum
41
35
1.48
81
(1) Test density for one sample is an average of the achieved density from 4 specimens.
157
GHN-KMD-0013
Peak internal friction angle
Residuall friciton angle
800
700
2
R = 0.99
o
 peak =42.6
500
400
2
R = 0.99
o
 residual =38
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0014
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
Shear stress (kPa)
600
R2 = 1.00
o
peak =47.3
600
500
400
R2 = 0.92
 residual =40.1
300
o
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
158
600
700
800
GHN-KMD-0015
Peak internal friction angle
Residual friciton angle
800
700
2
R = 0.99
o
 peak =45.3
Shear stress (kPa)
600
500
400
2
R = 0.99
o
 residual =39.8
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0016
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 1.00
o
 peak =44.9
500
400
300
2
200
R = 0.99

residual
=39.1
o
100
0
0
100
200
300
400
500
Normal stress (kPa)
159
600
700
800
GHN-KMD-0017
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
500
400
2
R = 0.96
o
 peak =42.1
300
200
2
R = 0.97

residual
=37.9
o
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0018
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
500
400
2
R = 0.99
o
 peak =44.4
300
2
200
R = 0.98

residual
=38.7
o
100
0
0
100
200
300
400
500
Normal stress (kPa)
160
600
700
800
GHN-KMD-0019
Peak internal friction angle
Residual friciton angle
800
700
2
R = 0.95
o
 peak =45.2
Shear stress (kPa)
600
500
400
2
R = 0.81
o
 residual =38
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0026
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
500
400
2
R = 0.99
o
 peak =44
300
2
R = 0.97
o
 residual =40.7
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
161
600
700
800
GHN-KMD-0027
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
500
2
R = 0.97
400
 peak =44.4
o
300
200
2
R = 0.99

100
residual
=37.2
o
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0051
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.98
o
 peak =42.7
500
400
2
R = 0.99
o
 residual =37.9
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
162
600
700
800
GHN-KMD-0052
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
500
 peak =42.3
o
400
2
R = 0.99
300

residual
=36.9
o
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0053
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
o
 peak =43.3
500
400
2
R = 0.99
o
 residual =38
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
163
600
700
800
GHN-KMD-0053-DUPLICATE
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
o
 peak =42.8
500
400
2
R = 0.99
o
 residual =37.7
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0055
Peak internal friction angle
Residual friciton angle
800
700
2
R = 0.99
Shear stress (kPa)
600
 peak =43.2
o
500
400
300
2
R = 0.99
o
 residual =37.7
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
164
600
700
800
GHN-KMD-0056
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
500
2
R = 1.00
o
 peak = 47
400
300
2
R = 0.99
o
 residual = 40
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0057
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 1.00
o
 peak =43.1
500
400
2
R = 0.98
o
 residual =38.5
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
165
600
700
800
GHN-KMD-0057-DUPLICATE
Peak internal friction angle
800
700
Shear stress (kPa)
600
2
R = 1.00
o
 peak =43.7
500
400
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0062
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
o
 peak =43.9
500
400
2
R = 0.97
o
 residual =38.9
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
166
600
700
800
GHN-KMD-0063
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 1.00
o
 peak =44.9
500
400
2
R = 0.99
o
 residual =38.9
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0071
Peak internal friction angle
Residual friciton angle
800
700
2
R = 1.00
Shear stress (kPa)
600
 peak =43.2
o
500
400
2
300
R = 0.99
o
 residual =36.9
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
167
600
700
800
GHN-KMD-0072
Peak internal friction angle
Residual friciton angle
800
700
2
R = 0.99
Shear stress (kPa)
600
 peak =42.5
o
500
400
2
R = 1.00
o
 residual =37.6
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0073
Peak internal friction angle
Residual friciton angle
800
700
2
R = 1.00
Shear stress (kPa)
600
 peak =43
o
500
400
2
R = 0.98
o
 residual =39
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
168
600
700
800
GHN-KMD-0074
Peak internal friction angle
Residual friciton angle
800
700
2
R = 0.98
Shear stress (kPa)
600
 peak =43.6
o
500
400
300
2
R = 0.96
o
 residual =38.8
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0078
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
o
 peak =46
500
400
2
R = 0.99
o
 residual =37.9
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
169
600
700
800
GHN-KMD-0079
Peak internal friction angle
Residual friciton angle
800
700
2
R = 1.00
Shear stress (kPa)
600
 peak =42.7
o
500
400
2
R = 0.99
o
 residual =37.6
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0079-DUPLICATE
Peak internal friction angle
Residual friciton angle
800
700
2
R = 1.00
Shear stress (kPa)
600
 peak =42.8
o
500
400
2
R = 1.00
o
 residual =39.8
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
170
600
700
800
GHN-KMD-0081
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
500
2
R = 0.99
400
 peak =44.1
o
300
200
2
R = 0.97

100
residual
=39.2
o
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-KMD-0081-DUPLICATE
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
o
 peak =41.7
500
400
2
R = 0.99
o
 residual =37.1
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
171
600
700
800
GHN-KMD-0088
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
500
R = 0.99
 peak =42.1
o
400
300
2
200
R = 0.95

residual
=38.7
o
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-LFG-0037
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
500
2
R = 0.98
o
 peak =40.8
400
2
R = 0.99
o
 residual =37.9
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
172
600
700
800
GHN-LFG-0085
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
o
 peak =42.4
500
400
2
R = 0.99
o
 residual =39
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-LFG-0088
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
500
R = 0.99
o
 peak =42.1
400
300
2
200
R = 0.95

residual
=38.7
o
100
0
0
100
200
300
400
500
Normal stress (kPa)
173
600
700
800
GHN-LFG-0090
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.98
 peak = 45.7
500
o
400
300
200
2
R = 1.00

100
residual
=37
o
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-VTM-0450
Peak internal friction angle
Residual friciton angle
800
700
2
R = 1.00
 peak = 44
Shear stress (kPa)
600
o
500
400
2
R = 0.99
o
 residual =40.6
300
200
100
0
0
100
200
300
400
500
Normal stress (kPa)
174
600
700
800
GHN-VTM-0453
Peak internal friction angle
Residual friciton angle
800
700
2
R = 1.00
 peak =44.1
Shear stress (kPa)
600
o
500
400
2
R = 1.00
o
 residual =38.3
300
200
100
0
0
100
200
300
400
500
600
700
800
Normal stress (kPa)
GHN-VTM-0454
Peak internal friction angle
Residual friciton angle
800
700
Shear stress (kPa)
600
2
R = 0.99
500
 peak = 43
o
400
300
200
2
R = 0.99
100

residual
=35.2
o
0
0
100
200
300
400
500
Normal stress (kPa)
175
600
700
800
APPENDIX E – DESCRIPTION OF GEOLOGIC UNITS, SUMMARY OF
GEOLOGICAL AND GEOTECHNICAL DATA USED FOR CORRELATIONS
176
Descriptions of geologic units at GHN. No relative age relationships can be determined
between surface units A-H. (McLemore et al. 2005)
Geologic
Unit
in
this
report
A
Description
Structure
Lithology
Light brown unit with approximately
60% covered by cobbles or larger
sized rocks with vegetation growing
upon the surface.
Massive, light brown to gray to
yellow brown unit containing crusts
of soluble acid salts. Approximately
65% is covered by cobbles or larger
sized rocks. Consists of clayey sand
with gravel and cobbles and is locally
cohesive.
Grayish brown to yellowish gray unit
consisting of fine-grained materials
(sand with cobbles and gravel) and
approximately 15% boulders. Locally
is cohesive and well cemented by
clays and soluble minerals.
Yellow-brown gravely sand unit that
differs from Unit C by a marked
increase in cobbles and boulders
(approximately 30-40%).
Orange brown unit with patches of
gray sandy clay with approximately
15% cobbles and boulders.
Layered in some
of the rills near
the base.
mixed
rocks
volcanic
Southern-most
surface unit of the
stable part
Shallow
rills
(0.2-1 m deep)
of finer grained
material are cut
into the surface.
quartz-sericitepyrite (QSP) altered
Amalia Tuff (70%)
and andesite (30%).
Surface unit of
stable portion of the
GHN rock pile
Massive
alternating
zones, up to 10
ft thick.
Amalia Tuff (70%)
and andesite (30%)
Surface unit of
stable portion of the
GHN rock pile
Massive
Amalia Tuff (80%)
and andesite (20%).
Surface unit of
unstable portion of
the GHN rock pile
Massive
Surface unit of
unstable portion of
the GHN rock pile
F
Similar to Unit A, consists of dark
brown, silty sand with some gravel.
Massive
70 % moderate to
strong QSP altered
Amalia Tuff and
30% weakly altered
Amalia Tuff
andesite
G
Orange brown to yellow brown sandy
gravel with some cobbles, includes
colluvium material.
Dark gray to red-brown V-shaped
unit with oxidized orange zones and
consists of poorly sorted, well graded,
weakly cemented, gravel sand with
some fine sand to fine sand with clay,
approximately 80% cobbles or
boulders.
Light-gray, poorly sorted, well graded
clayey to sandy gravel, medium hard
with weak cementation, and no
plasticity. The matrix is locally sandy
clay with medium to high plasticity.
The unit is less cemented and finer
grained than the overlying unit C.
Massive
andesite
Massive
andesite
Overlain by Unit
C, up to 10 ft
thick
Andesite
Amalia Tuff
B
C
D
E
H
I
177
Location
and
Surface unit of
unstable portion of
the GHN rock pile
Surface unit of
unstable portion of
the GHN rock pile
Surface unit at the
top of stable portion
of the GHN rock
pile
Subsurface oxidized
unit of stable portion
of the GHN rock
pile
Geologic
Unit
in
this
report
J
Description
Structure
Lithology
Location
Dark orange-brown, poorly sorted,
well graded, coarse gravel with clay
matrix and weak cementation. The
top of the unit locally is a bright
orange oxidized layer, 2-4 inches
thick.
Overlain by unit
I, 3-12 ft thick
Primarily andesite
Subsurface oxidized
unit of stable portion
of the GHN rock
pile
N
Light to dark brown moderately
sorted, uniformly graded, moderately
hard sandy clay with cobbles, with
moderate to high plasticity and well
cemented by clay, zones of bright
orange to punky yellow oxidized
sandy clay.
Distinctive purplish-brown gravelly
sand with cobbles and is weakly
cemented and very coarse, almost no
clay. Cobble layer is locally overlain
and underlain by finer gravelly sand
layers and contacts are gradational.
Brown gray, poorly sorted, well
graded gravelly sand with cobbles.
Heterogeneous
with numerous
coarse and fine
layers, 5-10 ft
thick
andesite and Amalia
Tuff
Subsurface
intermediate unit of
stable portion of the
GHN rock pile
grades into Unit
O, 0-4 ft thick
Primarily andesite
Subsurface
unoxidized unit of
stable portion of the
GHN rock pile
Grades into Unit
O
andesite
Brown, poorly sorted, sandy gravel
matrix in coarse gravel and cobbles.
Numerous coarse and fine layers at
varying dips and thicknesses appear
in the mass of the unit. The unit has
cobbles
and
clay
layers.
Heterogeneous, deformed layer with
numerous S-shaped clay lenses and
coarse layers.
Orange brown to brown, poorly
sorted, well graded sandy gravel with
boulders (up to 1 m diameter). Sandy
gravel forms a matrix between
boulders and cobbles. The fines are
generally gritty.
dark brown, poorly sorted, well
graded, sandy gravel with medium
hardness and no to weak cementation
Variable dip of
individual beds
Primarily andesite
Subsurface
unoxidized unit
stable portion of
GHN rock pile
Subsurface
unoxidized unit
stable portion of
GHN rock pile
Unit
locally
flattens with 20
degree dip
andesite and Amalia
Tuff
Subsurface
unoxidized unit of
stable portion of the
GHN rock pile
Pinches out, 0-3
ft thick
andesite
Dark brown, poorly sorted, well
graded, sandy gravel with cobbles
with medium hardness and no to low
cementation.
Orange gray, poorly sorted, well
graded sandy gravel to gravel with
cobbles with medium to weak
cementation by clay.
Steeply dipping
andesite
Subsurface
unoxidized unit
stable portion of
GHN rock pile
Subsurface
unoxidized unit
stable portion of
GHN rock pile
Subsurface
unoxidized unit
stable portion of
GHN rock pile
K
L
O
M
P
Q
R
Pinches out, 0-3
ft thick
178
Primarily andesite
of
the
of
the
of
the
of
the
of
the
Geologic
Unit
in
this
report
S
Description
Structure
Lithology
Location
Dark gray, poorly sorted, well graded
sandy silt with no cementation or
plasticity.
Pinches out, 0-4
ft thick
Primarily andesite
Subsurface
unoxidized unit of
stable portion of the
GHN rock pile
T
Dark gray, poorly sorted, well graded
sandy gravel.
andesite
Subsurface
unoxidized unit
stable portion of
GHN rock pile
Subsurface
unoxidized unit
stable portion of
GHN rock pile
Subsurface
unoxidized unit
stable portion of
GHN rock pile
Subsurface
unoxidized unit
stable portion of
GHN rock pile
U
V
W
Brown, poorly sorted well graded,
sandy gravel with cobbles.
Pinches out, 0-2
ft thick
andesite
Gray to brown gray poorly sorted,
sandy gravel.
Pinches out, 010 ft thick
andesite
Olive gray clay zone, similar and
possibly correlated to Unit S.
andesite
179
of
the
of
the
of
the
of
the
Sample
GHN-KMD-0013
GHN-KMD-0014
GHN-KMD-0015
GHN-KMD-0016
GHN-KMD-0017
GHN-KMD-0018
GHN-KMD-0019
GHN-KMD-0026
GHN-KMD-0027
GHN-KMD-0051
GHN-KMD-0052
GHN-KMD-0053
GHN-KMD-0055
GHN-KMD-0056
GHN-KMD-0057
GHN-KMD-0062
GHN-KMD-0063
GHN-KMD-0065
GHN-KMD-0071
GHN-KMD-0072
GHN-KMD-0073
GHN-KMD-0074
GHN-KMD-0078
GHN-KMD-0079
GHN-KMD-0081
GHN-KMD-0082
GHN-KMD-0088
GHN-KMD-0092
GHN-LFG-0085
GHN-LFG-0088
GHN-LFG-0090
GHN-VTM-0450
GHN-VTM-0453
GHN-VTM-0454
Units
O
K
R
S
I
J
O
M
N
O
K
contact between Unit
I
V
O
N
J
V
Unit U, V contact
coarse zone in Unit O
O (coarse sand)
U
U
U
R
O
O
O1
K
O
P
O (coarse layer)
O (clay rich)
O
FrictAngle ResidFrictAngle
43
38
47
39
45
40
45
39
42
38
44
39
45
39
44
41
44
37
43
38
43
37
43
38
43
38
47
40
43
40
44
39
45
39
44
39
43
37
43
38
43
39
44
39
46
38
43
38
43
39
44
37
45
38
44
39
42
39
42
39
46
37
44
41
44
38
43
35
n.d. = not determined, LL= Liquid limit, PI= Plastic index
180
LL
37.81
26.51
n.d
28.11
35.28
28.73
29.55
30.03
33.88
31.67
n.d
35.2
29.95
29.54
32.75
35.58
38.44
35.34
34.52
32.99
n.d
n.d
n.d
32.71
35.51
n.d
n.d
n.d
34.68
36.06
n.d
n.d
31.63
n.d
PI
14.31
8.47
n.d
7.17
17.91
9.26
6.69
11.01
14.29
14.29
n.d
17.24
5.28
3.9
14.69
15.14
16.36
16.98
8.07
16.44
n.d
n.d
n.d
14.38
18.76
n.d
n.d
n.d
15.13
17.82
n.d
n.d
9.15
n.d
NAGpH pastepH
6.06
2.49
8.55
3.19
6.78
4.92
8.36
5.74
2.43
2.19
3.88
3.5
n.d
5.84
n.d
3.8
n.d
2.49
8.51
7.19
n.d
5.08
6.26
4.32
n.d
4.27
7.05
4.85
n.d
7.96
n.d
4.43
n.d
3.95
n.d
5.77
2.53
4.35
n.d
7.15
8.62
6.55
6.59
3.36
n.d
3.26
6.4
3.07
3.15
3.29
n.d
3.3
n.d
2.63
n.d
3.72
4.2
2.98
8.99
5.43
8.43
6.71
7.18
6.7
8.49
4.55
3.33
3.56
Sample
GHN-KMD-0013
GHN-KMD-0014
GHN-KMD-0015
GHN-KMD-0016
GHN-KMD-0017
GHN-KMD-0018
GHN-KMD-0019
GHN-KMD-0026
GHN-KMD-0027
GHN-KMD-0051
GHN-KMD-0052
GHN-KMD-0053
GHN-KMD-0055
GHN-KMD-0056
GHN-KMD-0057
GHN-KMD-0062
GHN-KMD-0063
GHN-KMD-0065
GHN-KMD-0071
GHN-KMD-0072
GHN-KMD-0073
GHN-KMD-0074
GHN-KMD-0078
GHN-KMD-0079
GHN-KMD-0081
GHN-KMD-0082
GHN-KMD-0088
GHN-KMD-0092
GHN-LFG-0085
GHN-LFG-0088
GHN-LFG-0090
GHN-VTM-0450
GHN-VTM-0453
GHN-VTM-0454
WPI
4.18
12.01
6.65
9.34
1.37
4.13
9.2
4.82
3.53
8.36
6.47
4.31
0.65
6.93
n.d
n.d
n.d
6.45
6.36
7.82
8.95
7.33
n.d
6.4
6.29
7.98
4.56
n.d
6.11
6.83
7.89
7.97
6.34
4.81
MI
0.39
0.7
0.49
0.58
0.31
0.37
0.54
0.41
0.37
0.55
0.46
0.39
0.26
0.48
n.d
n.d
n.d
0.5
0.43
0.52
0.57
0.52
n.d
0.46
0.44
0.51
0.37
n.d
0.45
0.45
0.53
0.55
0.46
0.37
SWI
3
2
2
2
4
3
2
2
3
2
2
3
4
2
2
3
3
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
181
GravMoist Amalia
13.67
25
8.34
10
9.91
0
9.18
0
14.97
80
7.27
35
10.05
0
12.7
60
17.25
50
7.86
60
9.81
n.d.
9.35
50
10.72
n.d.
8.59
70
7.89
n.d.
13.54
n.d.
10.3
n.d.
9.49
60
9.6
40
7.35
n.d.
11.39
10
20
n.d.
20
50
11.05
95
11.76
n.d.
9.75
n.d.
90
0
0
10
0
35
Andesite
75
90
100
100
20
65
100
40
50
40
n.d.
50
n.d.
30
n.d.
n.d.
n.d.
40
30
n.d.
90
80
n.d.
80
50
5
n.d.
n.d.
10
100
100
80
75
60
Intrusive
0
0
0
0
0
0
0
0
0
0
n.d.
0
n.d.
0
n.d.
n.d.
n.d.
0
30
n.d.
0
0
n.d.
0
0
0
n.d.
n.d.
0
0
0
10
25
5
Sample_id
Sphericity
Roundness
GHNKMD0013
GHNKMD0014
GHNKMD0015
GHNKMD0016
GHNKMD0017
GHNKMD0018
GHNKMD0019
GHNKMD0026
GHNKMD0027
GHNKMD0051
GHNKMD0053
GHNKMD0056
GHNKMD0071
GHNKMD0073
GHNKMD0074
GHNKMD0079
GHNKMD0081
GHNVTM0450
GHNVTM0453
subprismoidal
subprismoidal
subdiscoidal
subprismoidal
spherical
spherical
subprismoidal
spherical
subdiscoidal
subprismoidal
subdiscoidal
spherical
spherical
subdiscoidal
subdiscoidal
subdiscoidal
subdiscoidal
subprismoidal
subprismoidal
subangular
very angular
angular
subangular
subangular
subangular
subangular
angular
subangular
subrounded
angular
subangular
angular
subangular
subangular
subrounded
subangular
subangular
subangular
Field_id
Specific_Gravity
(g/cm3)
GHNKMD0014
2.68
GHNKMD0015
2.66
GHNKMD0017
2.65
GHNKMD0018
2.65
GHNKMD0019
2.75
GHNKMD0026
2.67
GHNKMD0027
2.66
GHNKMD0071
2.62
182
Percent of Hydrothermal Alteration. QSP = quartz-sericite-pyrite
Sample
GHN-KMD-0017
GHN-KMD-0013
GHN-KMD-0014
GHN-KMD-0015
GHN-KMD-0016
GHN-KMD-0018
GHN-KMD-0019
GHN-KMD-0026
GHN-KMD-0027
GHN-KMD-0051
GHN-KMD-0052
GHN-KMD-0053
GHN-KMD-0055
GHN-KMD-0056
GHN-KMD-0057
GHN-KMD-0062
GHN-KMD-0063
GHN-KMD-0065
GHN-KMD-0071
GHN-KMD-0072
GHN-KMD-0073
GHN-KMD-0074
GHN-KMD-0078
GHN-KMD-0079
GHN-KMD-0081
GHN-KMD-0082
GHN-KMD-0088
GHN-KMD-0092
GHN-LFG-0085
GHN-LFG-0088
GHN-LFG-0090
GHN-VTM-0450
GHN-VTM-0453
GHN-VTM-0454
QSP
Propylitic
50
30
25
25
25
20
10
40
30
25
n.d
30
n.d
30
n.d
n.d
n.d
20
25
n.d
25
35
n.d
50
55
30
n.d
n.d
25
25
25
15
55
40
2
5
20
12
20
8
25
1
7
15
n.d
5
n.d
7
n.d
n.d
n.d
5
10
n.d
12
10
n.d
7
10
15
n.d
n.d
2
12
8
8
15
6
183
Argilic
20
3
0
3
0
0
0
0
0
3
n.d
0
n.d
2
n.d
n.d
n.d
0
0
n.d
2
0
n.d
3
3
0
n.d
n.d
4
3
3
5
4
3
184
Sample
GHN-KMD-0013
GHN-KMD-0014
GHN-KMD-0015
GHN-KMD-0016
GHN-KMD-0017
GHN-KMD-0018
GHN-KMD-0019
GHN-KMD-0026
GHN-KMD-0027
GHN-KMD-0051
GHN-KMD-0052
GHN-KMD-0053
GHN-KMD-0055
GHN-KMD-0056
GHN-KMD-0057
GHN-KMD-0062
GHN-KMD-0063
GHN-KMD-0065
GHN-KMD-0071
GHN-KMD-0072
GHN-KMD-0073
GHN-KMD-0074
GHN-KMD-0078
GHN-KMD-0079
GHN-KMD-0081
GHN-KMD-0082
GHN-KMD-0088
GHN-KMD-0092
GHN-LFG-0085
GHN-LFG-0088
GHN-LFG-0090
GHN-VTM-0450
GHN-VTM-0453
GHN-VTM-0454
SiO2 TiO2
63.68
0.6
61.05 0.82
63.83
0.7
61.88 0.79
61.34 0.61
70.45 0.36
61.78 0.81
69.83 0.32
68.03 0.43
67.83 0.59
61.82
0.6
70.62 0.33
71.86 0.27
68.34 0.59
n.d
n.d
n.d
n.d
n.d
n.d
66.82 0.66
67.81 0.49
63.63 0.65
62.63 0.72
65.16 0.71
n.d
n.d
67.58 0.55
66.8
0.43
60.3
0.74
64.35 0.49
n.d
n.d
62.66 0.69
61.25 0.77
60.36 0.77
63.45 0.77
59.8
0.71
64.87 0.48
Al2O3 Fe2O3T FeOT FeO Fe2O3 MnO MgO CaO Na2O K2O P2O5 S
14.59
6.23
n.d
3.48
2.4
0.07 1.46 1.17 2.42 3.68 0.23 0.24
14.79
5.1
n.d
2.72
2.11
0.22 2.74 3.12 3.31 4.65 0.29 0.08
14.36
5.72
n.d
3.15
2.25
0.37 2.05 1.38 2.49 4.07 0.25 0.18
14.44
5.51
n.d
3
2.21
0.31 2.83 2.97 3.36 3.12 0.29 0.13
14.37
6.03
n.d
3.35
2.35
0.08 1.51 1.15
2.5
3.49 0.23 3.06
12.95
3.48
n.d
1.73
1.58
0.22 1.23 0.81 1.29 4.81 0.08 0.8
14.94
5.35
n.d
2.88
2.18
0.32 3.14 3.59 3.48 2.92 0.26
0
12.81
3.86
3.52 1.98
1.68
0.15 0.76 0.5
2.59 4.26 0.13 0.17
12.93
4.57
4.15 2.45
1.88
0.21 1.05 0.56 2.03 4.15 0.19
0
14.44
4.32
n.d
2.22
1.88
0.29
1.8 1.94 3.22 3.96 0.16
0
14.16
5.34
4.85
2.9
2.15
0.37 2.23 2.32 2.48 3.44 0.27
0
12.82
3.73
n.d
1.9
1.64
0.3
0.91 0.53 1.78 4.54 0.06
0
12.19
3.49
3.17 1.77
1.54
0.06 0.63 0.76 0.38 3.88
0.1
0
14.53
4.31
n.d
2.2
1.89
0.22 1.64 1.21 3.21
3.8
0.16
0
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
14.69
6.12
n.d
3.4
2.38
0.52 2.15 1.29 2.76 3.73
0.2 0.11
14.77
3.85
n.d
1.89
1.77
0.13 1.35 1.28
3.1
3.75 0.13 0.29
14.26
5.25
4.77 2.84
2.13
0.4
2.25 2.1
3.09 3.57 0.29
0
14.38
5.14
n.d
2.76
2.1
0.34 2.65 2.28 3.33 3.37 0.26 0.04
14.68
5.7
n.d
3.12
2.27
0.33 2.26 1.66 2.86 3.53 0.22 0.16
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
14.22
4.56
n.d
2.38
1.94
0.23 1.49 1.26
2.8
3.82 0.16 0.12
14.17
3.82
3.47
1.9
1.73
0.13 1.32 1.11 2.79 3.87 0.19 0.13
14.32
5.31
4.83 2.88
2.14
0.64 2.74 2.74 3.46 3.05 0.34
0
14.19
4.19
3.81 2.14
1.84
0.16 1.51 1.13 2.92
3.8
0.21
0
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
n.d
14.68
6.13
n.d
3.41
2.38
0.28 2.48 2.08 2.62 3.56 0.24 0.37
14.44
5.04
n.d
2.69
2.08
0.3
2.77 2.96 3.31 3.41 0.27 0.14
14.7
6.52
n.d
3.66
2.49
0.46 2.55 2.3
3.32 3.37 0.29 0.55
14.62
6.38
n.d
3.57
2.45
0.36
2.6 1.68 3.27
3.3
0.25 0.19
14.49
6.18
5.47 3.45
2.38
0.46 2.57 2.26 2.61 3.53 0.29 1.46
15.32
4.11
n.d
2.04
1.87
0.19 1.61 1.46 2.68 3.68 0.13 0.96
F
CO2
0.0112
0
0.0081
0
0.0138
0
0.0099
0
0.0151
0
0.0122
0
0.0103
0
0.0075
0
0
0
0.0071
0
0
0
0.0096
0
0
0
0.0088
0
n.d
n.d
n.d
n.d
n.d
n.d
0.0121
0
0.0127
0
0
0
0.0093
0
0.0091
0
n.d
n.d
0.0113
0
0.0087
0
0
0
0
0
n.d
n.d
0.0109
0
0.0084
0
0.0103
0
0.0091
0
0.0134
0
0.0953
0
LOI
4.81
2.34
3.7
3.42
7.4
4.2
4.3
3.53
4.48
2.72
4.49
3.65
5.04
3.09
n.d
n.d
n.d
3.59
3.35
3.6
3.17
3.23
n.d
3.21
3.16
4.6
5.14
n.d
4.94
6.03
4.13
3.19
5.13
4.9
185
Sample
GHN-KMD-0013
GHN-KMD-0014
GHN-KMD-0015
GHN-KMD-0016
GHN-KMD-0017
GHN-KMD-0018
GHN-KMD-0019
GHN-KMD-0026
GHN-KMD-0027
GHN-KMD-0051
GHN-KMD-0052
GHN-KMD-0053
GHN-KMD-0055
GHN-KMD-0056
GHN-KMD-0057
GHN-KMD-0062
GHN-KMD-0063
GHN-KMD-0065
GHN-KMD-0071
GHN-KMD-0072
GHN-KMD-0073
GHN-KMD-0074
GHN-KMD-0078
GHN-KMD-0079
GHN-KMD-0081
GHN-KMD-0082
GHN-KMD-0088
GHN-KMD-0092
GHN-LFG-0085
GHN-LFG-0088
GHN-LFG-0090
GHN-VTM-0450
GHN-VTM-0453
GHN-VTM-0454
18
17
16
34
15
14
13
14
13
6
18
14
13
20
16
15
12
13
8
13
41
47
43
40
26
39
37
33
45
43
33
36
34
49
50
35
32
33
47
40
11
6
10
11
13
11
11
0
12
0
11
0
11
10
5
14
12
11
13
10
12
11
13
11
8
8
2
9
14
1
12
11
6
10
9
10
12
4
16
9
5
5
7
0
0
0
1
1
1
0.001
0
3
1
4
2
2
0
0
2
2
0.001
1
0
0.65
0.001
0
0
0.001
0.91
0.001
0.95
0.001
0.001
2
0
0.001
0
0.67
0
0
0
0
0.25
6
3
5
2
6
4
2
3
4
3
1
5
3
7
8
3
5
3
4
4
0.16
0
0
0.04
0
0
0
0
0
0
0
0.17
0.12
0.06
0
0
0.35
0
0.75
0
0
0
0
0
0.3
0.08
8
5
8
0
6
10
2
6
8
3
8
5
8
8
4
12
6
2
3
3
0.9
3.78
2
2
1.95
1
1
2
1.95
3
1
0.2
2.04
1.29
2
2
0.001
0.9
1
1
2.1
2.22
2
2
1.05
1
1
2
1.05
1
1
0.8
0.96
1.71
3
1
3
2.1
1
1
14
18
11
14
13
6
14
14
15
19
12
13
11
13
11
13
Quartz k-feldspar Plagioclase epidote calcite
pyrite
FeMnOxide goethite hematite chlorite AuthGyp DetritGypTotalClay
46
7
40
0
0
2.87
0
0.01
0.04
0
0.001
8
32
0
APPENDIX F – STANDARD OPERATING PROCEDURES FOR
PETROGRAPHIC ANALYSES
186
STANDARD OPERATING PROCEDURE NO. 24
PETROGRAPHIC ANALYSES
REVISION LOG
1.0
Revision Number
Description
Date
24.0
Original SOP
24.1
Revisions by PJP
1/14/04
24.2
Revisions by PJP
5/19/2004
PURPOSE AND SCOPE
This Standard Operating Procedure describes the method for petrographic analyses
involving optical examinations and mineral identification, which are the basis for all
geologic models and characterization, specifically in differentiating various rock units,
determining rank and intensity of alteration, determining chemistry of alternating fluids,
describing cementation, and determination of paragenesis of mineralization, alteration,
and cementation. Mineralogical data is required in selecting samples for weathering cells
(Lapakko), and for developing geotechnical models (Wilson), weathering models
(Trujillo), and geologic (mineralogy, stratigraphy, internal structure) models of the rock
piles. Alteration rank is based upon the mineral assemblages, which infers temperature,
pressure, and permeability conditions at the time of formation. Forms are in Appendix 1.
Digital photographs will be taken (SOP 4).
2.0
RESPONSIBILITIES AND QUALIFICATIONS
The Team Leader and Characterization Team will have the overall responsibility for
implementing this SOP. They will be responsible for assigning appropriate staff to
implement this SOP and for ensuring that the procedures are followed.
All personnel performing these procedures are required to have the appropriate health and
safety training. In addition, all personnel are required to have a complete understanding
187
of the procedures described within this SOP, and receive specific training regarding these
procedures, if necessary.
All environmental staff and assay laboratory staff are responsible for reporting deviations
from this SOP to the Team Leader.
3.0
DATA QUALITY OBJECTIVES
This SOP address objectives 2-7 and 9 in the data quality objectives outline by Virginia
McLemore for the "Geological and Hydrological Characterization at the Molycorp
Questa Mine, Taos County, New Mexico”.
 Determine how mineralogy, stratigraphy, and internal structure of the rock piles
contribute to weathering and stability.
 Determine if the sequence of host rock hypogene and supergene alteration and
weathering provides a basis to predict the effects weathering can have on mine rock
material.
 Determine how weathering of the rock pile affects the geotechnical properties of the
rock pile material.
 Determine if cementation forms in the rock piles and the effect of such cementation
on the stability of the rock piles.
 Determine the concentrations of pyrite and carbonate minerals so that a representative
sample goes into the weathering cells.
 Determine how the concentration and location of pyrite and its weathering products in
the waste rock piles affect the weathering process.
 Determine if the geotechnical and geochemical characteristics of the bedrock
(foundation) underlying the rock piles influences the rock pile stability.
4.0
RELATED STANDARD OPERATING PROCEDURES
The procedures set forth in this SOP are intended for use with the following SOPs:
 SOP 1 Data management (including verification and validation)
 SOP 2 Sample management (chain of custody)
 SOP 4 Taking photographs
 SOP 5 Sampling outcrops, rock piles, and drill core (solid)
 SOP 6 Drilling, logging, and sampling of subsurface materials (solid)
 SOP 8 Sample preparation (solids)
 SOP 9 Test pit excavation, logging, and sampling (solid)
5.0
EQUIPMENT LIST
The following materials are required for petrographic analyses:
 Petrographic microscope

Camera

Forms
188
6.0
PROCEDURES
Petrography will be performed using standard petrographic and reflected ore microscopy
techniques. Mineral concentrations will be estimated using standard charts and data are
summarized. Estimates of both primary and alteration minerals will be determined,
cementation described, diagenesis described, porosity estimated, and the alteration
intensity will be determined from the concentration of alteration minerals. Any special
features will be noted on the forms (Appendix 1). Photographs will be taken and the thin
section photograph subform will be filled out.
Description of alteration
Alteration is a general term describing the mineralogic, textural, and chemical
changes of a rock as a result of a change in the physical, thermal, and chemical
environment in the presence of water, steam, or gas (Bates and Jackson, 1980; Henley
and Ellis, 1983). The nature of the alteration depends upon (a) temperature and pressure
at the alteration site, (b) composition of the parent rock, (c) composition of the alteration
(invading) fluids, (d) permeability of the parent rock, and (e) duration of the alteration
process. Recognition and genesis of alteration are important in mineral exploration and
understanding the formation of ore deposits, because specific alteration types are
associated with specific ore deposits. Furthermore, alteration halos surrounding ore
deposits are typically more widespread and easier to recognize than some of the
orebodies themselves (Guilbert and Park, 1986).
Intensity of alteration is a measure of how much alteration has occurred and can
be estimated by determining the percentage of newly formed secondary minerals by
visual estimation (P. R. L. Browne, unpubl. report, Spring 1992). For example, a parent
rock that has not been affected by any alteration would have zero intensity of alteration,
whereas a parent rock in which all primary minerals have been replaced by secondary
minerals would have an alteration intensity of 100%.
Alteration rank is based upon the identification of new secondary minerals and
their significance in terms of alteration conditions such as temperature, pressure, and
permeability. The intensity of alteration is independent of rank of alteration (Browne,
1978; Simmons et al., 1992). It is possible to have rocks with a high rank but low
intensity (hot, impermeable zones) or other rocks of low rank, but high intensity (cooler,
permeable zones; P. R. L. Browne, unpubl. report, Spring 1992).
Alteration of parent rock occurs by several processes: (1) direct deposition, (2)
replacement, (3) leaching, and (4) ejecta (Browne, 1978). All four processes are found in
the Questa district. Direct deposition occurs by precipitation of new minerals in open
spaces, such as vugs or fractures. Replacement occurs when one mineral is converted to a
new mineral by fluids entering the rock. These two processes are common and depend
upon permeability and duration of the process. Complete fluid/mineral equilibrium is
rarely achieved because of these factors. Leaching and supergene enrichment occurs
locally where steam condensate reacts to form acidic solutions by the oxidation of H2S or
CO2 which then attacks the parent rock and dissolves primary or secondary minerals.
189
Silica residue is a common result of leaching and is a spongy or vuggy altered rock
consisting of predominantly quartz, iron and titanium oxides. Direct deposition or
replacement may occur after leaching, thereby producing overlapping alteration types.
Ejecta, hydrothermal brecciation, and hydrofracturing are another form of alteration,
where hot water and/or steam physically breaks the parent or even altered rock apart. If
this forceful ejection of fluids occurs at or near the surface, hydrothermal eruptions of
water, steam, and rock can occur. Silicification following the brecciation is common.
The term mineral assemblage implies mutual equilibrium growth of mineral
phases, whereas mineral association implies that the mineral phases are only in physical
contact. A number of terms are applied to various alteration assemblages. Deuteric
alteration refers to the interaction between volcanic or magmatic rocks and magmatichydrothermal fluids during the cooling of the igneous rocks. A variety of alteration
minerals may be produced. Propylitic alteration is the mineral assemblage consisting of
epidote, chlorite, pyrite, quartz and carbonate minerals. Sericitic alteration is defined by
the dominance of illite, sericite, and/or muscovite. The major difference between these
three K-micas is size: illite is a clay-size K-mica, whereas muscovite is larger. Sericite is
of intermediate size. Some minor compositional differences also occur between the three
minerals. Argillic alteration consists of kaolinite, smectite (montmorillonite clays),
chlorite, and sericite. Advanced argillic alteration consists of kaolinite, quartz, alunite,
pyrophyllite, and other aluminosilicate minerals. Silicic alteration is produced by the
addition of silica, predominantly as quartz. Then the rock and minerals are subjected to
supergene alteration and finally weathering, which continues today. It may be difficult to
distinguish between supergene alteration and modern weathering.
Description of pyrite and carbonate minerals
Pyrite and carbonate minerals are described in detail because of their importance
in generating or preventing acid drainage. The abundance, texture, grain size, contact
relationships, shape, integrity, paragenesis, composition, surface area, and occurrence or
association are described in detail in the petrographic form. Specific carbonate minerals
are identified.
7.0
COLLECTION OF SAMPLES
Samples are collected according to the sample plan and SOP 5, 6, and 9 and prepared
according to SOP 8. Thin sections are preferred, but grain mounts can be used for
unconsolidated material.
8.0
QUALITY ASSURANCE/QUALITY CONTROL PROCEDURES AND
SAMPLES
9.0
SAMPLE HANDLING
Thin sections, grain mounts and other samples are archived after petrographic
description.
190
APPENDIX F – TERMINOLOGY
191
Terminology
Liquid Limit
Definition
The liquid limit is the dividing line
between the liquid and plastic states.
The liquid limit is reported in terms of
the water content at which a soil
changes from the liquid to the plastic
state (Liu and Evett, 2003).
NAG pH(Net Acid Generation)
The NAG pH measures the net acid
remaining, if any, after complete
oxidation of the material with
hydrogen peroxide and allowing
complete reaction of the acid formed
with the neutralizing components of
the materials (Lewis et al., 1997). After
neutralization
is
complete,
the
remaining H2SO4, if any, is titrated
with NaOH. The amount of NaOH
needed is expressed as kg of CaCO3
equivalents per ton of material and is
equal to the NAG of the material.
Paste pH
Paste pH is the pH measured on a
mixture of soil and deionized water
which forms a slurry or
paste.
Plasticity Index
The plasticity index is the difference
between the liquid and the plastic
limits (Liu and Evett, 2003).
Plastic Limit
Plastic limit is the dividing line
between the plastic and semisolid
states. It is quantified for a given soil
as a water content at which the will
begin to crumble when rolled into
small threads (Liu and Evett, 2003).
Specific gravity
The term specific gravity is defined as
the ratio of the mass of a given volume
of material to the mass of an equal
volume of water. Equation: Gs =
(Ms/Vs)/w, where Ms is the mass of
solids, Vs is the volume of solids, and
w is the density of water (Liu and
Evett, 2003).
1
2