GINEERING
F
r
TECHNICAL
FIELD NOTES
DATA
INFORMATION
RETRIEVAL
PROFESSIONAL
TECHNICAL
REPORTS
MANAGEMENT
DEVELOPMENT
SYSTEM
NUMBER
PP
Field
3
N-ý-Otes
The Problems of Using Standard Specifications
Without Adjusting for Specific Design Conditions
Polypropylene Fabric
Subgrades
1
as a
Reinforcement
1
Muskeg
Construction
Washington
FOREST SERVICE
MARCH
ftST SgPq
UýS
ma
U.S.
DEPARTMENT OF AGRICULTURE
1977
S
ENGINEERING FIELD NOTES
Volume
Information
contained
Number
9
has
3
been developed
of employees
for guidance
respon-sibility
of
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United
cooperating
States
Federal
in
this
publication
Department
and State
of
The
agencies.
for the interpretation or use
The
Agri culture-Forest
Service
its
Department of Agriculture
of this information
by other than
contractors
and
its
assumes no
its
own
employees.
of trade firm or corporation
names in this publication is for the information and
of the reader. Such use does not constitute an official endorsement or approval
use
convenience
of any
product
of others that
The
text in
or service
may be
the
publication
must not
be construed
or policy
except
engineers
not
by the United
States
as
represents
the
recommended
personal
or approved
Because
by FSM references.
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technicians
should
intended
Department of Agriculture
to the exclusion
suitable.
exclusively
opinions
of the respective
procedures
of the type
read each
of material in the
issue
however
for engineers.
FOREST SERVICE
U.S.
DEPARTMENT OF AGRICULTURE
Washington
D.C. 20013
author and
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are
R-1
Bill
McCabe
R-4
Ted
Wood
R-9
Norbert
R-2
Royal M. Ryser
R-5
Jim
McCoy
R-10
Frank Muchmore
R-3
Bill
Coordinators
Strohschein
should
direct
R-6
Kjell
R-8
Ernest
questions
Bakke
concerning
WO
Forest
Engineering
Attn
format editing
publishing dates and other
P.O.
Service
Staff
Rm. 1108 RP-E
L.
Rome
D.C.
20013
Gordon
or Rita E. Wright
Box 2417
Washington
Telephone
Al Colley
Quinn
problems to
USDA
Smith
Area Code 703-235-8198
it
THE PROBLEMS OF USING STANDARD SPECIFICATIONS
WITHOUT ADJUSTING FOR
Gerald
T.
SPECIFIC DESIGN CONDITIONS
Skip
Chugach N.F.
CoghZan
R-101
camp-ground
INTRODUCTION
In
1976
Forest Service awarded a $165703 contract to pave a
Final contract
the Kenai Peninsula in south-central Alaska.
was complicated because all measured asphalt densities were
This report discusses how this problem was resolved.
specified.
the
road
acceptance
below that
on
PROJECT DESCRIPTION
recon-ditioned
project included paving 0.97 mile of single-lane campground road
The typical section provided
parking areas and 26 camping spurs.
of base on a
for 2 inches
of hot mix asphalt-concrete
over
4 inches
Forest Service Standard Specifications were
existing surface.
used and Supplemental Specifications required that the contractor provide
a mix design by the Marshall Method for light
traffic as described by the
The Marshall Method for light and medium
Asphalt Institute Manual MS-2.
The
three
Specifi-cations
requires 500 pounds minimum stability for the standard 4-inch
diameter by 2 1/2-inch
thick design specimen.
The Supplemental
also required that quality tests be provided by the Contractor
through an independent materials testing
laboratory.
traffic
progressed well with a commercial test lab furnishing the quality
the core
test results received
Following the Final Inspection
showed
The densities of nine
adequate thickness but inadequate density.
as shown on table 1 ranged from 92.5
samples
percent to 96.0 percent
while the specifications required 97 percent.
Although a small roller had
been necessitated by the tight quarters
rolling operations had appeared
to meet standard construction methods and the same roller had just been
used on another non-Forest Service project.
Therefore
the low densities
Work
tests.
came
as
a surprise.
1Mr.
CoghZan has
recently
transferred to R-9 as Regional Materials
Engineer-1
Table
1.
Core No.
Densities of nine samples
Thickness
Adjusted
Compaction
stability
%
inches
pounds
21/4
95.0
13/4
93.2
523
7/8
96.0
1075
4
23/8
95.2
714
5
2
94.2
690
6
23/8
93.2
530
7
2
94.0
622
8
1
1/2
92.5
510
9
23/4
95.0
712
Contract
requirement was
1
2
3
1
837
97% compaction.
ef-fort
ANALYSIS
At
this
The
point
contractor
to
The
several alternatives were open
gain
surface
attempt to cold-roll the
additional density.
could
the
could
be
heated
in
place and
Replacement or supplemental thickness
Reduced payment could.be
asphalt in an
receive
could
further rolling.
be required.
considered.
rea-sonable
Any of these could
have produced
it difficult to resolve claims.
questionable results and
What stood out were the
construction procedures followed and the question
we needed 97 percent compaction.
made
of
why
primary purpose of the density test is to indicate constructed strength
compared to the design strength
or stability.
The higher the density
the higher the strength
however the actual correlation between density
and stability was not known.
The specified 97 percent was chosen from
other
rather than based upon the design criteria.
contracts
If stability
tests were run on the as-built asphalt results could be compared directly
The
as
to
The
the
design criteria.
possibility of running Marshall Stability Tests on the density core
was discussed with the Contracting Officer the Contractor and
samples
2
Measured stabilities would be adjusted by the ratio of
testing lab.
design standard thickness to the actual thickness for comparison to the
A final decision on acceptance or rejection
design standard stability.
would be based on the results.
his
the
RESULTS
Table
500
AND DISCUSSION
summarizes the test results.
minimum design stability.
1
As
adjusted
all samples exceed
the
pounds
sample densities with the adjusted stabilities
From the plot it
relationship.
strength-stability
expected
can be seen that 92 percent or 93 percent would have been a more reasonable
the Marshall Method requires a minimum
For heavy traffic
specification.
of
A
94
700
percent
compaction specification would have
stability
pounds.
Figure
and
1
shows
the
compares
field
the
The specified
been adequate for even the heavy traffic design criteria.
97 percent would have given
a stability of 1250 pounds or 250 percent of
the minimum design stability.
Because the 4-inch stability samples were
made from the 6-inch field cores the specimens most likely received undue
disturbance
causing these test results to be conservative.
correla-ting
concluded that the in-place asphalt-concrete
adequately met the
The
situation
also
and
should
be
clearly showed
criteria
accepted.
design
the importance of properly selecting specifications and better
design and construction criteria.
It was
98
97
O
96
p
8
95
O
94
93
92
91
90
400
Figure
1.
500
600
700
800
900
Stability
pounds
1000
1100
Field sample densities with adjusted
3
1200
1300
stabilities.
POLYPROPYLENE FABRIC AS A REINFORCEMENT OF MUSKEG
SUBGRADE
IN
ROAD CONSTRUCTION
Morris Lively Civil Engineering Technician
Stikine Area Tongass National Forest R-10
and
William A. Vischer
Materials Engineer
Willamette National Forest R-61
in-volved
extensive
construction in southeast Alaska involves
Most of the roads are constructed using
crossings of muskeg terrain.
The costs
or pit-run embankments.
overlay techniques and shot-rack
in crossing such weak
subgrades increase rapidly due to excessive
The majority of the road
deformation and settlement of the subgrades.
and
construction cost i.e. 80 percent involves
the production
As a result economical
of the shot-rock embankments.
techniques which provide reductions in rock quantities can
reduce construction costs.
Any method of reinforcement bridging
Forest Service road
instal-lation
construc-tion
signifi-cantly
floating over the peat deposits may be feasible depending on the
particular peat characteristics
applicable rock costs and construction
Because of the relatively low cost of fabrics
i.e.
techniques used.
50G to $1 per square yard even a slight savings in rock quantities can
easily justify this type of reinforcement in terms of economics.
or
construc-tion
moni-tored
reinforce-ment
for this type of road
benefits of such fabrics
section using the low cost fabric was constructed and
on the Tongass National Forest 20 miles south of Petersburg
Alaska.
Various embankment sections with and without the fabric
were constructed and monitored to determine the differences in
To
evaluate
a
the
test
performance.
needle-punched
The project site and subgrade characteristics
are
prior to construction
The
fabric used was a
shown in figures 1 and 2 respectively.
spun-bonded
polypropylene material having a weight of 420 gm/m2
and a strip tensile strength of 86 pounds
The trade name of the
per inch.
product is Fibretex 400 distributed by Crown-Zellerbach Corporation.
Vischer was the Regional Materials Engineer in R-10 at the
test project.
He has since transferred to R-6 Willamette N.F.
1Mr.
4
time
of the
0
Y
h
ýýý
ti
r
ý
t
ý
ý
ýr
Figure
ý
to
51
ýpkR-
1.
yvýBy
ký
r
ýY
Project
tt
site
ý
4
ý
e
c
prior to construction.
5
3
zth Yýiý
Station
3000
3100
3300
60
272
--
w._-
_
_
may
-
250-3510
980
Q
-ýtý
_
-
206
258
300
272
232
d
03
LU
3400
__-__
65
ý
3200
232
172
103
136
168
55
210
156
Fine fibrous muskeg
very
soft
50
350
saturated
50
Dense
9w
moisture sample
and
zoo
Vane
and
Top
result
shear
result
till
unyielding
location
in
test
in
glacial
and bedrock
Legend
%
2
Summary
Average
location
psf
Average
dia
saturated
mat
vegetative
1/2-lthick
Scale
Vertical
Horizontal
1
1
5
50
Figure
2.
Soil profile and
test
shear
results.
strength
-200
moisture content
psf
960%
The overlay construction techniques are illustrated in figures 3 and 4.
A Cat-loader Model 977L with a gross weight of 41000 pounds was used
for spreading the rock embankment
while dump trucks
tandem axle/dual
wheel with a gross weight of 80000 pounds were used for hauling the rock.
For a more
Figures 5 and 6 summarize the as-built conditions of the road.
of
footnote2.
detailed discussion
the techniques
see
sub-stantially
6
reduced rock quantities
a
some areas.
Based on the as-built road cross-sections
could
have
been
potential reduction in rock quantities of about 23 percent
realized throughout this area if fabric reinforcement had been used over
As
indicated by figures
in
5
and
the
fabric
the
full length.
On subgrades requiring
results in significant savings.
3
feet
of
fill
and
more
this
dis-placements
In
two
where reinforcement was not used substantial
bearing capacity failures occurred as indicated by the
59 and 32
cross-sections at stations 30
60.
separate cases
due
to
devel-oped
profiles and
of the fabric-reinforced peat have not been fully
explained in terms of the stress-strain relationships
in each material.
instrumentation
This is due to the limited field
and materials testing data
Based upon the
available on such projects.
limited documentation on this project a theoretical analysis of the results
was made by D.R. Greenway and J.R. Bell of Oregon State University3.
The
intent
was to obtain a better understanding of the reinforcement mechanism.
Their
report as well as the documentation report by W. Vischer2 suggests
that the decreases in settlement of the fabric
sections were not due to
decreases in consolidation type settlements but rather to settlement or
The
exact
documented
mechanics
or
The fabric
displacement associated with local bearing capacity failures.
apparently provided sufficient tensile strength on the weak peat to enable
the embankment to act as a unit rather than
allowing localized bearing
failures.
The negligible difference in settlement between
the
section from stations
31
75 to 32
00 and the single-matted
section between stations 32
00 and 32
40 appears to indicate also
that a single mat layer was sufficient to preclude these localized failure
displacements
hence the additional layer in the double-mat section
provides no additional benefits.
double-matted
ap-parently
in-dicate
this test section has provided some general direction to R-10
summary
future muskeg subgrade reinforcement with fabrics.
The results
that if the peat is relatively strong i.e. shear
strength of 250
few benefits would be derived by using fabric to reinforce
psf or better
In
for
Con-struction
Em-bankment
Univer-sity
2Vischer
W.A.
USDA
of Synthetic Fabrics on Muskeg Subgrades in Road
Forest Service Report Region 10 November 1975.
Use
D.R.
and Bell J.R. Analysis of a Low Fabric Reinforced
on Muskeg Department of Civil Engineering
Oregon State
Corvallis
Oregon June 1976.
3Greenway
7
muskeg subgrades on roads in southeast Alaska.
Fabric however could
probably produce some benefits on amorphous peat deposits or weak silt or
clay deposits which are highly susceptible to pumping.
The fabric would
serve as a filter barrier against pumping to preclude contamination and
weakening of the rock embankments or base course.
J.E. Stewards report
on Plastic Filter Cloth4 discusses this in detail.
The peat
deposits
in southeast Alaska for the most part
to
be
the
appear
organic
the
rather than the
not foreseen.
amorphous type
benefits
significant
thus
in
type
this
area are
For analytic approaches on predicting the benefits of fabric reinforcement
on muskeg terrain
the reader is again referred to the reports by Vischer2
and Greenway and Be113.
Based on the test section data these authors
prescribe design analysis and prediction methods for engineers involved
in such designs.
4
y my
L
ý..
f
4.d
3y
O
ý
N
em-bankment
End dumping pit-run rock.
Figure 3.
The area shown illustrates the results
a
of
typical bearing capacity failure.
Severe subsidence of the road
and upheaval of the adjacent muskeg occurred
Note the
immediately.
Zack
of water on the unvegetated muskeg in the foreground
that bare area
had about 6 inches of groundwater covering it
immediately prior to end
dumping.
4Steward
J.E. Use of Woven Plastic Filter Cloth as a Replacement for
Graded Rock Filters USDA Forest Service Report Region 6 June 1976.
8
vial
ý
\
yý
Figure
bý
f
4
q
VkAt
Spreading the pit-run rock.
4.
Station
3100
3000
l
1
1
I
11
I
3300
3200
3400
I
1
I
I
I
1
1
l
1
I
I
i
I
I
I
I
L
I
1
1
1
i
t
1
1
1
11
1
I
65
64
63
62
61
ft Profile
after
3 months
60
c
0
59
w
57
Natural
ground
profile
tt after
5 months
58
56
Single
Double
55
mat
mat
54
53
t
52
Profile
Bottom
of rock
fill
51
50
Scale
Vertical
Horizontal
5
1
1
50
Figure
5.
Embankment
and soil
9
profile after construction.
11
a
a
a
a
a
a
A
Fl
0
a
a
a
a
a
3125
3a
A
a
a
a
a
Station
Station
3175
3225
3260
a
a
a
a
a
a
4
a
a
p
3420
Scale
10
Figure
6.
As-built
--Ml-ankment
4.5
Station
3350
cross-sections.
a
a
a
p
Station
3300
a
a
a
5.1
Station
a
a
a
Station
3059
TA
a
5.75
a
Station
Station
1
a
a
3025
A
a
a
Station
A
I
a
a
p
WASHINGTON OFFICE NEWS
TECHNOLOGICAL IMPROVEMENTS
Heyward T. Taylor
Assistant Director
DOCUMENTATION
OF ROAD DESIGN SYSTEM
RDS
progress report on our cooperative agreement with Colorado State
has
a joint effort to document the Road Design System
University
been received.
indicated
that
in
the
RDS
The
addition to making
report
easily transportable from one machine to another and efficiently
on all machines the corrected documented version will produce
in machine costs regardless of which machine it operates
savings
The
first
maintain-able
con-siderable
RDS
on.
con-ducted
docu-mented
The information is in the first quarterly report of the first phase of the
documentation.
We anticipate three phases will be required to complete
RDS documentation.
The report gives the results of benchmark tests
the
on
original RDS and tests conducted on the implemented
version.
These tests indicate that on the documented version a
of
savings
$14000 in machine time will be made this year additional
will be realized in subsequent years.
The progress report also
savings
indicates considerable savings can be realized in the time required to
maintain and keep RDS operating.
The RDS modules modified by the
have cleared up ambiguities.
They have also eliminated redundant
or obsolete codes
and improved
results of data manipulations which have
been implemented.
documen-tation
cooperative agreement continues at the same level we can expect
complete RDS documentation and have a system less costly to operate
easier to maintain and ready for efficient transport to the new USDA
scheduled for delivery in 1979.
computer hardware
If
the
11
to
CONSULTATION
AND STANDARDS
C.R. Weller
Assistant Director
COMPATIBILITY OF ELECTRICAL
EQUIPMENT WITH
ELECTRIC
SERVICE
One problem we often have in the field is that electrical equipment does
not match the characteristics of the electric service supplied by the
This most often occurs
when the electric supply is rated
power company.
three-phase
volts
120/208
three
phase
four
wire.
volt system permits the use of both single-phase and
We should make sure that the equipment to be used with
equipment.
kind
of
service
is rated 120 or 208 volts and not the more common
this
240
volts.
Electric
motors should operate satisfactorily on plus
230 or
of
the
rated
motor should
or minus 10 percent
voltage e.g. a 230-volt
In rural areas however the voltage often
run sufficiently on 207 volts.
The
120/208
drops
try
below
its
to operate
volt rating and this can cause problems if you
or 240-volt equipment on a nominal 120/208-volt
120/208
230-
system.
Check with your power company to make sure that the equipment to be used
matches the voltage and phase characteristics of the electric supply.
12
OPERATIONS
Harold L. Strickland
Assistant Director
EMERGENCY
RELIEF FUNDS
cat-astrophic
23 U.S.C. Section 125 the Secretary of the Department of
Transportation is authorized to repair or reconstruct roads and trails
that have suffered serious
damage resulting from natural disasters or
Under Title
Fed-eral
failures.
fol-low
As a result of a major storm in California
the Administrator of the
Highway Administration and the Chief of the Forest Service entered
into a Memorandum of Understanding on March 14
1969 to expedite the
repair of roads and trails damaged by natural disasters.
The Memorandum
of Understanding outlines administrative procedures each
agency will
in the event
a disaster affects forest
roads
and trails.
Basically
1.
the
procedures
are
Immediately after a disaster the Chief
asks
for
a
the
Administrator
doing
finding
of
of
the
eligibility.
The
date
The
location
The
approximate cost
by State
of
the
he
Administrator
must provide
disaster.
of
Information on whether
proclamation
In so
the
county
and forest.
repairs.
or
not
there
is a State
or
Presidential
disaster.
pro-gram
Chief is asking for a finding Regions or Forests begin
individual
preparing
project damage descriptions and cost estimates.
While
2.
The
the
Administrator
issues
a finding.
If the damage is eligible for
Repairs Federally-Owned ERFO funding he approves the
usually in the amount of the Chiefs request and asks for a
The summary must contain preliminary estimates
summary of projects.
and descriptions of damage.
Emergency
3.
The Region submits the
summary to the Chief who submits it to the
Administrator. The Administrator approves
individual projects and
13
trans-ferred
adjust-ments
notifies the
to
Chief
that
funds
for
approved
projects will be
FS.
Regions promptly initiate repairs and inform the Chief of actual
This enables
the Chief
to request program
project costs.
from the Administrator.
4.
5.
As
work progresses
6.
At
conclusion
submits
show
a
of
final
FHWA makes
spot
checks.
work associated with
construction report to
a
storm
specific
the
Chief.
the Region
report must
the Administrator
The
project by project the amount approved by
amount actually spent repairing the project.
Adminis-trato
7.
and
the
The
Chief
will request a final program adjustment
based on the information in item 6.
from
the
Regions and Forests are experienced in the ERFO program area
however others who need to apply for ERFO funds may find the following
information helpful
Several
1.
eligi-bility
trans-mittal
Federal-Air Highway Program Manual
1976.
The transmittal outlines the
transmittal
196
dated
June
9
purpose limitations
etc.
of the ERFO
requirements
program and should be used
in conjunction with the 1969 agreement.
2.
Natural Disaster Manual
Portland
Oregon.
This
Part 2 written for Region 8 FHWA
manual goes into more detail than
196.
3.
Work of an emergency nature done during or immediately following
or to keep critical access
a disaster to protect lives and property
is
reimbursable
FHWA.
fully
by
open
con-tribute
This
roads
relatively simple procedure has made it possible for FHWA to
towards
the repair of damaged forest
over
$77 million since 1969
and
trails.
14