i.
EFFECT OF ORGANIC MATTER ON THE
ENGINEERING PROPERTIES OF FORT BELVOIR
SANDY CLAY
by
GEORGE C.
TSO
Submitted in Partial Fulfillment of the
Requirements for the Degree of
BACHELOR OF SCIENCE
from the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
1953
Signature redacted
.. .. .. .. .. ..
.. ......
Civil and Sanitary Engineering.
.
Signature of Author.........
Department
/1
September 1, 1953.
Signature redacted
..............
sis Supervisor.
*
Certified by...............................
T
Ui
Massachusetts Institute of Technology
Cambridge, Massachusetts
August 24, 1953
Mr. L. F. Hamilton
Secretary of the Faculty
Massachusetts Institute of Technology
Cambridge, Massachusetts
Dear Sir:
In partial fulfillment of the requirements for the
degree of Bachelor of Science in Civil Engineering, this
thesis entitled, "Effect of Organic Matter on the Engineering Properties of Fort Belvoir Sandy Clay," is
hereby submitted.
Respectfully submitted.
Signature redacted
George C. Tso
iii
ACKNOWLEDGMENTS
The author wishes to express his sincere gratitude to Professor T. W. Lambe for his guidance, his
encouragement and advice in the research stage of this
investigation.
The author also wishes to express his
appreciation to Dr. R. T. Martin whose valuable suggestions and constructive criticisms made this thesis possible.
Thanks to his colleagues in Soil Mechanics Laboratory at the Massachusetts Institute of Technology for their
kindly suggestions in the laboratory technique.
TABLE OF CONTENTS
Page
Title Page
Letter of Transmittal
Acknowledgment
I.
II.
IV.
iii
Abstract
Introduction
A.
B.
C.
D.
E.
III.
ii
Geheral
Purpose
Scope
Materials
Assumptions
Testing Program
5
A.
Atterberg Limit Tests
1. Specimen
2. Procedures
5
B.
Compaction Tests
1. Specimen
2. Procedures
5
C.
Unconfined Compression Tests
1. Specimen
2. Procedures
6
Discussion of Results
8
A.
Effect on Atterberg Limits
1. General
2. Liquid Limit
3. Plastic Limit
8
B.
Effect on Compaction
1. General
2. Optimum Water Content
3. Optimum Dry Density
10
C.
Effect on Compressive Strength
1. General
2. Background
3. Analysis of Results
4. True Increase in Strength
17
Page
V.
VI.
Conclusion
24
Recommendation
25
26
Appendix--Data
1.
2.
3.
4.
Bibliography
Tests on Peat
Atterberg Limit Tests
Compaction Tests
Unconfined Compression Tests
27
28
29
31
33
I.
ABSTRACT.
The thesis is a part of an investigation which aims to
find out the efffect of organic matter on engineering properties of soil.
In this study, Fort Belvoir sandy clay and peat were
used as the principal materials.
The properties of their
various mixtures, such as Atterberg Limits, Compaction, and
Comkressive Strength were tested.
The data, which in most cases compared to the absolute
values
i. e. considering the exact contributions of the
constituents, show that peat has a significant influence
on the liquid limit, optimum water content, maximum ultimate shear strength and water content at maximum strength
of the clay, whereas in the case of plastic limit and optimum dry density, no appreciable effect is produced.
The amount of peat in the clay is very crucial at
around 2%.
Peak values occur at liquid limit, and ultimate
shear strength when the specimen contains 2% peat.
1.
II.
A.
INTRODUCTION
General:
Soils may generally be classified as inorganic and
organic.
The latter which contains carbonized vegetable
matter or decaying animal life is generally considered to
be a poor matetial in the sense of its engineering properties.
However, very few studies have been made in determing the
exact influence imposed on soil by the organic matter.
Con-
sidering the rapid development in the science of soil
mechanics,, such an investigation seems now justified.
B.
Purpose:
The effect of organic matter on the engineering pro-*
perties of soil is to be investigated.
The purpose of this
thesis is only a preliminary -study to be followed by a detailed investigation based on the results of this preliminary
work.
A general theory can only be developed after further
searching studies.
C.
Scope:
Fort Belvoir sandy clay was taken as a basic soil and
peat was used as the organic matter.
Their various mixtures,
having peat from 0.1% to 10%* were investigated.
Properties
such as their Atterberg Limits, Compactions and Compressive
Strengths were tested.
*
Ratio of dry weights
2.
D.
Materials:
Sandy clay is from Fort Belvoir, Virginia, and was in
oven-dry state.
It contains 60 percent less than 0.1/mm size
material and 25% of its particles are smaller than 0.OQ.jmm.*
Its specific gravity is 2.71.
soil to make specimens.
Water was added to the dry
The engineering characteristics of
the pure clay can be found in the data of each test for the
purpose of comparison.
(Photo 1 shows the clay sample.)
The peat used was a common one.
The raw material was
dug from a depth of 4 feet on a lot behind Melrose Highschool, Melrose, Massachusetts.
It was partly submerged
under water, as the water table of the place was about the
same depth.
odor.
Its color was totally black and had a decaying
It contained a large amount of vegetable remains and
small stones.
The mass was then washed through Tyler No. 10
Sheave in the laboratory to remove foreign materials.
was then sealed in a jar for use.
in a liquid state.
It
The final material was
It was tested and found to be 85% organic,
and had a specific gravity of 1.61.
It has a plastic limit & Liquid limit of
261%
375% respectively (data see Appendix 1)..
Data from T. W. Lambets2"Cold Room Studies Third Interim
Report of Investigation. 2
** 1. Percentage of organic matter was determined by the
ignition of peat in a platinum crucible. After ignition,
the weight of the remaining material in the crucible was
found. The percent of organic matter is then equal to
original weight--remaining weight/original weight.
2.. By the use of H2SO4 - K2 Cr 2 O7 digestion the organic
matter determined was 7%
*
3.
Photo 1.
Fort Belvoir Sandy Clay in a dry state (left)
Peat used in experiments.
(right)
4.
E.
Assumptions:
Throughout the whole experiment, the following
assumptions were made:
1.
The different water content of specimens at the
time of aging does not affect the test data.
2.
The test results are not affected by the variations
in room temperature when the test is performed.
A.full scale. study is necessary in order to determine
the accuracy of Assumption No. 1.
It is also anticipated that the "time" of aging of
specimens will also influence their characteristics.
How-
ever this variable is eliminated by aging all specimens for
a fixed period.
5.
III.
A.
TESTING PROGRAM
Atterberg Limit Tests:
1.
Specimen:
Dry Fort Belvoir sandy clay was mixed thoroughly
with peat which had been prepared.
Six specimens- with dif--
ferent amounts of peat, 0%, .1%, 1%, 2%, 5%, and 10%, were
made.
They were then sealed in a jar in a wet state and stored
for two weeks before they were taken out to be tested.
2.
Procedures:
Procedures used were recommended by Prof. T. W.
Lambe's "Soil Testing For Engineers," Chapter III.
B.
Compaction Tests:
1.
Specimen:
Specimens were prepared in the same manner as in
Atterberg limit tests, except that they were aged for four
weeks due to conflict of schedule.
It was pointed out that
"
as long as they had the same period of aging, the "time
variable does not enter the picture.
2.
Procedures:
Procedure used was recommended by S. D. Wilson,
"Comparative Investigation of a Minuture Compaction Test
With Field Compaction," which was presented before the
Annual Meeting, A.S.C.E., January, 1950.
Mold of 1.306 in
diameter, 2.816" in height was used throughout the tests.
Since this method is considered quite new, the equipment is
shown in Photo 2.*
*
Courtesy of Messers. Keller and Heyman
I
A. Compaction of the Specimen
Photo No. 2
B. Removal of the Mold Extension Collar
6.
C.
Unconfined Compression Tests:
1..
Specimen:
Specimens Wed were those which had been tested in
compaction tests.
Therefore, they had a diameter of 1.306
in. and a height of 2.816 in.
2.
Procedures:
The procedure given by Prof. W. T. Lambe,
Testing for Engineers," Chapter XII was used.
"Soil
Specimens of
same percentage of organic matter were so planned that a
maximum value of compressive ultimate strength could be obtained.
The ultimate' strength was taken at point of failure,
where the strain (a) was between 10-15% in most cases.
The apparatus used is shown in Photo 3.*
*
Courtes- of Messers. Killer and Heyman
I
T
Extrusion of Specimen from Mold
Photo No. 3
B. Strength Test of Specimen in Unconfined
Compression Apparatus
B.
IV.
A.
DISCUSSION OF RESULTS
Effect on Atterberg Limits:
1.
General:
Illustrated in Figure 1 are the liquid limit and
plastic limit of specimens which had various amounts of
organic matter.
The complete data are given in Appendix 2.
The theoretical values, that is,
considering the additive
effect of clay and peat, calculated from the fractional
contribution, and based on the amount of each present, are
plotted as dotted lines.
2.
Liquid Limit:
The illustration shows clearly that the presence
of organic matter raises the liquid limit of the clay.
It
was observed that in a homogeneous mixture, the soil particles
were infiltrated with small masses of organic matter, which
is believed to be capable of absorbing water.
At the most,
the water content in peat can only reach liquid limit of the
peat when the mixture reaches its liquid limit.
only amounts to the theoretical value.
All this
The departure from
the theoretical value suggests that the presence of organic
matter may have some effect on the cohesion force of the
clay.
The addition of organic matter seems to increase the
intermolecular attraction of the soil particles.
is most outstanding when the amount is around 2%.
The effect
The ex-
det reason of the phenomena is not known, but a microscopical
-
.
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3.
Plastic Limit:
The curve has the same trend as that of liquid
limit, but to a lesser extent.
The departure from the theo-
retical value is not as significant (the largest is only
about 3.5%).
The result may be caused by the fact that
peat does not have enough water to reach its own plastic
limit or, in other words, theoretical value which is based
on plastic limit of both constituents is too high to represent the actual condition.
B.
A departure may still exist.
Effect on Compaction:
1.
General:
The test data can be found in Appendix 3.
Figure
2 shows plots of dry density versus water content of each
specimen.
The optimum values of which were interpreted
from these curves and can be found in Appendix 3a.
They
will be discussed under the following headings:
2.
Optimum Water Content:
For the sake of easy reference, Figure 3 shows
the optimum water content of specimens having different percentages of organic matter.
The dash line in Figure 3 represents the value
which considers the water required for optimum water content by the fractional volume of clay in the specimen.
Et
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11.
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The plot shows that optimum water content is raised
by adding organic matter.
It means that more water is needed
in order to get the same effectiveness of compactive effort.
As it has been pointed out, the peat is able to absorb part
of the water, and, of course, reduces the "lubricating"
effect that ordinarily should be produced by the additional
The distance between the two lines can roughly
water.
measure the water that is absorbed by peat.
3.
Optimum Dry Density:
Figure 4 shows the optimum dry density of specimens
having different percentages of organic matter.
It was felt
that these values are insignificant unless some modifications
are made about the various water contents at which optimum
dry densities occur, and the volume of clay replaced by peat.
Line ab in Figure 4 represents the calculated
values of optimum dry density, if the optimum water contents were constant and equal to that of pure clay.
The
method of obtaining it can be better described by the use
of Table 1.
Columns 1, 2, and 3 are self-explanatory.
Using the water content, and the percentage of organic matter,
the weights of the three constituents were computed in
Column 5 is the average specific gravity of the
Column 4.
soil-peat and clay.
Adjusted densityiwas obtained by adding to the
original desnity the increased weight that resulted from
replacing water by soil.
the values.
ttab" is the best line drawn through
TABLE 1 --
ADJUSTMENT FOR CONSTANT WATER CONTENT
Specimen
% of O.M.
Optimum
Dry Density
lb./cu.ft.
Weight lbs
Soil
Clay
Peat
Water
6
5
4
2
Optimum
Water
Content
Ave.
Density
of Soil
A
Adjusted Densit
107.9
0
17.5
107.9
16.0
0
91.9
2.71
.1
17.9
107.8
16.4
.1
91.3
2.71
107.8+(-1.71x'4)=108.5
18.*0
106.8
16.3
.9
89.6
2.70
106.8-P (1.70x.3)=107.3
2
18 0 2
105.2
l16 *2
1.8
87.2
2.67
105.2-r (I.67x.2)=105 5
5
19. 0
103.'6
16.5
4.4
82.7
2.65
103.6+(1.65x.5)s*104.4
10
21.0
99.2
17.2
8.2
73.8
2.58
TABLE 2 -1
2
99.2+ (1.58x1.2)mlOl.l
ADJUSTMENT FOR CONSTANT VOLUME OF CLAY
3
Wt. of
4
Equal Vol.
of Clay
lbs 0'
5
Wt.
Increased
lbs.
Ad justed Density
6
Soecimen
Constant Water
Content Density
Peat
lbs.
0
107.9
0
0
0
107.9
.1
108.5
.1
.2
.1
108 6
107.3
.9
1.5
.6
107.9
2
105.5
1.8
3.00
1.2
106.7
5
104.4
4.4
7.4
3.0
101.1
8.2
13.8
5.6
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106.7
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Line ac in Figure 4 represents the optimum dry
density if,, in addition to the correction made for water
content, the volume of peat in the specimen were repla'ced by
clay.
The method of obtaining the values is self-explanatory
in Table 2.
Line ac is the line best drawn through the
points.
It is seen that ac is nearly a horizontal line.
(Error of 1%)
Considering the inconsistency of the experi-
mental method, such as hamriner force, inconsistent thickness
of layers, the error is negligible.
This means that the difference of optimum dry
density is only caused by different water content, and the
lower specific gravity.of peat.
17.
C.
Effect on Compressive Strength:
1.
General:
The complete data of the tests are given in Ap-
pendix 4*
The results are plotted in Fig. 5 as ultimate
shear stress versus water content for each specimen having
different amounts of Organic matter.
The maximum ultimate
shear stress and the water content at which the maximum
strength occurs, are interpreted from the curves.
Fig. 6
shows the values plotted against the organic matter content of the specimens (data see Appendix 4a)
2.
Background:
Since the exact nature of the strength theory of
soil is not known, it is better to mention the assumptions
that will be used when analyzing the results.
It is generally assumed that shearing resistance
within soil masses is commonly attributed to the existence
of "internal friction" and "cohesion."
Internal friction
is to include the resistance to sliding of the soil particles
over one another and any interlocking that may have to be
overcome before a slip can occur.
Cohesion is supposed to
include both true cohesion, that due to intermolecular attraction, and apparent cohesion, that due to surface tension
effects in the water contained in the clay mass. 1
3.
Analysis of Results:
In Fig. 6 the maximum ultimate strength has a peak
value for a specimen having about 2% organic matter.
The
occurrence of the peak may be explained in the following
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The fact that peat has a very low shearing strength
suggests that smal-1 chunks of it fail before the whole speci-o
men does.
This failure will cause a sudden drop within the
specimen.
The sudden displacement may reduce the cohesion
force greatly by damaging the intermolecular attraction of
the soil.
The damaging Is not appreciable compared to the
specimen's frictional force, where the amount of peat does
not exceed 2%.
Beyond this amount, the reducing of the
cohesion force comes into effect.
The curve of water con"
tent at maximum strength in Fig. 6 shows a correspondente
but reverse shape which gives further proof that the variation of the strength is of a cohesive nature*
4. Tiqle Difference in Strength:
Because of the various water contents at *hich
the maximum ultimate strengths -of each specimen occur, it
was suggested that a plot be drawn showing the comparison
of maximum ultimate strength of specimens to the strength
of the pure clay at the same water content.
is shown in Fig. 7.
Such a plot
The distance between the two curves
in Fig. 7 is the true difference in strength that is produced by the addition of organic matter.
and plotted in Fig. 8.
It is interpreted
The curve has a similar shape to
the maximum ultimate shear strength in Fig. 6.
The slight
deviations in shear strength in 5-10% organic matter range
shown in Fig. 6 and 8 are within experimental errors.
Far
*Cohesion is generally great when the water content of a soil
is low and much lower when the soil is in a saturated condition. 3
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The
theory that the sudden failure of peat, reducing the
molecular attraction and causing a peak value at 2% o.m.
is still valid.
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.. SMU..
..... 2t ...-...
..
.-....---................-..............
, .............................. . ..............
MU. HMSH. .
:.:,
luH
. . .. . . .. . . .. . . .. . . .. . . .. . . I88 .
.. .. .. .. .. .. .. . .. .. .. .. .. .. .. . -....U M ...... .. . . . .............
.' i.....
.....e- e. =. @ee e. .. .= .. .e~e~~e~e.. .e .. s. .. .. .. .. ... .... .. .... ... e. .. ... 1 .. m u. ... ... .....
. . .
. . . . . . . . . .. . . .. . . . .. . . . .. . . .. . . .i.f.t..
.. . . .. . . . ..U . . . .. . . .. . . . .. . . . . .
.:....
..........................
g.. . . . . . . -. . .
a- s...
..
..- e ., .........
........................................... . ..3 ... ........................ .....
.........................................
......
......
3......................................
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.............................. . .....,3 ....... ......................
........................ ..............
...................... .....................'.a...................................
....................... ................ ..............-....... :::.......................1.1.0......
................ .......................... M..,........s................. i mu n m n........... .........
..............
........ ...............................
...
.........
. .. .
.... .......................... .................
........-...
........ ..............
.. ...
. . . . . . . . . . . . . . . O. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......
........ .....0...................=..............0@....0....... ................... ..................
.............e...e..e....e...
................................
......................... .......................
un .. ...
..................
~~e..eee.~ ........... ~...
.... .... .e...... s............... ........ ..@.8@...@...... ... ..........e. a... ........e. ...e.~
...
.e
o
=..
"
.0...m0
=o.
..=.... .....
..
0.*.0.=..=
.=0..=N.U....
.
...ee.e~.
..e~
...e.ee.
.....0..0. . .=. .@.. . .=................
......=.......
. e ....
. v...-a.......
ee.a..... .,- -e w, .. e e .. . .g ...,. ..,ea e . .. . ..................
0..0.e.ee.
............................................. ...............................
=...=......0..s.. e.. ..0 .. s .... ........ e.e.-e...ee.
#4 -
Iu
+
I~
-~
+~~
t
it
a1
+o
+
fi
-
IT
TT
.......
4
I
+
fT
it
..
tt
til
rr
ttt
++-
t
1
44 H t+
i
+
4
4
t
1
r
+1+
14u
4+ q 0
41 ttt
t
4t4
i
t i
ma t -a
Y=
7 t--
-a II
i
4
I--
........
23.
-H4uit:
t 11
24.
V. CONCLUSION
Generalization at such an early stage of work is
dangerous, but one is tempted to make a tentative step.
It would seem that under the conditions imposed by the
experiments,
1.
the following conclusions can be made.
Liquid limit increases as percentage of
organic matter increases.
The experimentally observed
increase was 2 - 3 times that which would be predicted
from mixtures of Fort Belvoir sandy clay and peat.
2.
Plastic limit increases as amount of organic
matter increases.
This increase is proportional to the
increase in limit expected from mixtures of Fort Belvoir
sandy clay and peat.
3.
In compaction, the optimum water content
increases as organic matter increases.
Difference in
optimum dry density is caused only by difference in water
content and lower specific gravity of organic matter.
4.
The ultimate shear stress is raised as percen-
tage of organic matter increases.
There is a peak value
(45% above the stress of pure clay) at the 1-2% organic
matter range.
5.
The test results strongly suggest that (a)
The presence of organic matter tends to increase the molecular attraction of the clay.
The amount depends largely
on the percentage of organic matter present. (b) The organic
matter is capable of absorbing part of the water that is
added to the clay.
25.
VI.
RECOMMENDATION
Although the result of this experiment can only be
taken as preliminary, yet it
does show that influence
brought by organic matter on the engineering properties
of soil in some cases is desirable while in other cases
it
is not, and that further study of the problem will be
The author wishes to suggest some possible in-
rewarding.
vestigations that can be made in a future study.
1.
Properties such as consolidation and permea"
bility can further be investigated for this particular
mixture.
2.
The influence on the properties by different
water content at time of aging should be investigated.
3.
The effect of. time of aging on the engineering
properties of the specimen may be of interest.
4.
Other mixtures should be studied in order to
develop a general theory.
26.
APPENDIX
TEST DATA
27.
1.
Specific Gravity*
TESTS ON PEAT
1.61
Plastic Limiti
Wp Ave.f%
Determination
1st
271
2nd
252
261
Liquid Limit
Water Content
No. of Blows
W'j
30
360
28
375
14
406
374
*Procedure recommended by W. T. Lambe ."Soil Testing for
Engineer."
28.
2.
ATTERBERG LIMIT TEST
Plastic Limits
Organic Matter
Water Content
WpAve.
0
.1
1
2
5
10
23.4
24.2
24.8
24.5
27.4
24.6
30.1
29.1
24.0
24.2
24.8
24.5
27.4
29.5
Liquid Limits
Organic Matter
0
No. of
Blows
16
30
44
.1
23
25
40.
20
23
47
2
5
10
Water
Content
Liquid
Limit
36.4
34.8
3207
3501
3704
-35*6
32.7
35.6
42.8
44.2
3904
42.6
19
32
45
39.8
37.0
3902
22
24
42
43.8
41.0
39.4
42
11
27
50
59.0
54.0
4508
53.3
3806
29.
3.
COMPACTION TEST
Relationships of water content to dry density
for various percentages of organic matter.
0% of Organic Matter
W
11
13
d lbs/cu.ft.
91.0
97.1
15*3
101.0
17.4
19.0
21.5
108.0
106.0
101.0
1% of Organic Matter
d lbs/cu.ft.
14.4
17.0
19.8
22.9
26.1
99.3
106.0
105.3
99.9
95.6
5% of Organic Matter
d lbs/cu.ft.
14.9
17.2
18.0
21.6
23.5
89.6
93.3
101.5
100.0
97*7
.1% of Organic Matter
%
,
11.8
13.8
14.6
19.4
21.1
d lbs/cu.ft.
94.8
100.3
102.3
107.0
103.5
2% of Organic Matter
W_
.d lbs/cuoft.
13.3
13.9
93.6
96.0
16 7
104.5
18.8
21.6
105.0
102.5
10% of Organic Matter
]y
18
18.9
20.8
21*0
23.8
28.4
d lbs/cu.ft.
85.9
94.5
97.1
99.0
98*1
90.0
30.
3a.
RESULTS FROM COMPACTION TESTS*
Optimum Dry Density Vs. Percentages of O.M. Contained.
of Organic Matter
0
.1
2
5
10
Optimum Dry Density
lbs./cu.ft.
10709
107.8
106.8
.(10502)
103.6
99.2
Optimum Water Content Vs. Percentages of 0.M. Contained.
of Organic Matter
0
.1
2
5
10
Optimum Water Content
17.5
1709
18.0
(18.2)
19.0
2100
31.
UNCONFINED COMPRESSION TEST*
Relationships of shear stress peak P#.
to water content
-
4.
for various amounts of organic matter.
O% of Organic Matter
.-L lbs./sq.in.
WX
1% of Organic Matter
W%
2
lbs./sq.in.
%
A
11. 9
14.6
16.0
12.4
2108'
20.2
12.7
9.6
5.1
19.0
2105
23.0
0.1% of Organic Matter
P lbs./sq.in.
W %
2A
8 5
15.5
18.7
19.1
22.7
30*8
16.3
9.6
5.2
14.4
17.0
1908
22.9
26.1
2% of Organic Matter
W%
P lbs./sq.in.
2A.
8.35
1008
16.4
18.8
21.6
9.8
21.6'
20.0
14.7
2308
31.3
19.9
20.4
9.4
5% of Organic Matter
10% of Organic Matter
W%
W
P lbs./sq.in.
P lbs/sq.in.
__2A
#
o
x
1409
17.2
18.0
21.6
16.4
18
2005
23.0
1902
18.9
23.5
6.3
2804
20.8
23.8
P = Compressive force
A = Average cross-sectional area of the specimen
W = Water content
1209
21.6
25.1
13.8
6.3
32.
4a.
RESULTS FROM UNCONFINED COMPRESSION TEST*
-Maximum Ultimate Shear Stress Vs. Amount of O.M. Contained
Organic Matter
0
.1
2
5
10
Maximum Shear Stress
. in lbs./sq. in.
2A
21.7
22.4
30.p8
31,5
25.9
25.5
Water Content at Ultimate Shear Stress Vs. Amount.of 0.M. Contained.
Organic Matter
0
.1
2
5
10
*See
Fig. 8
Water Content
14.6
14.3
16.7
11.4
19.2
20.2
33.
BIBLIOGRAPHY
1.
Ritter and Paquette, "Highway Engineering," New York,
The Ronald Press Co., page 173.
2.
T. W. Lambe, "Frost Investigations," Fiscal year 1952
and 1953, Arctic Construction and Frost Effects Lab.,
New England Division.
3.
Ibid.
4.
M. Peechts method suggested in U.S.D.A. Circular #757.