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OCR for page 343
APPENDIX E
TEST PROCEDURE FOR RESILIENT MODULUS OF UNSTABILIZED
AGGREGATE BASE AND SUBGRADE MATERIALS
E-1
OCR for page 344
RECOMMENDED STANDARD METHOD FOR ROUTINE
RESILIENT MODULUS TESTING OF UNBOUND GRANULAR
BASE/SUBBASE MATERIALS AND SUBGRADE SOILS
1. Scope
~ . ~ This test method describes the laboratory
preparation and testing procedures for the routine
determination of the resilient modulus (Mr) of
unbound granular base/sub-base materials and
subgrade soils for pavement design. The stress
conditions used in He test represent the range of
stress states likely to be developed beneath
flexible pavements subjected to moving wheel
loads. This test procedure has been adapted
from the standard test methods given by
AASHTO DESIGNATION: T29~92I, TP46 and
T292-9I.
I.2 The mesons described are applicable to:
(~) undisturbed samples of natural and compacted
subgrade soils, and (2) disturbed samples of
unbound base, subbase and subgrade soils
prepared for testing by compaction in the
laboratory.
I.3 In this test procedure, stress states used
for resilient modulus testing are based upon
whether the specimen is located in the base/
subbase or He subgrade. Specimen size for
testing generally depends upon the type of
material and is based upon its gradation and the
plastic limit as described in a later section.
I.4 The value of resilient modulus
determined from this procedure is a measure of
He elastic modulus of unbound base and subbase
materials and subgrade soils recognizing certain
nonlinear characteristics.
I.5 Resilient modulus values can be used
with structural response analysis models to
calculate He pavement structural response to
wheel loads, and with pavement design
procedures to design pavement structures.
I.6 The values stated in ST unites are to be
regarded as He standard.
I.7 This standard may involve hazardous
materials, operations, awl equipment. This
standard does not purport to address aR of the
safety problems associated with its use. It is the
responsibility of whoever uses this standard to
consult arm establish appropriate safety and
health practices arm determine the applicability
of regulatory limitations prior to use.
Note ~ -- Test specimens and equipment
described in this method may be used to
obtain other useful and related
information such as the Poisson's ratio
and rutting characteristics of subgrade
soils and base/subbase materials.
Procedures for obtaining these are not
covered in this standard.
2. Referenced Documents
2. ~ AASHTO Standards
T88
T89
T90
T99
T233
T265
T238
E_2
Particle Size Analysis of Soils
Determining the Liquid Limit of Soils
Determining the Plastic Limit and the
Plasticity Index of Soils
The Moisture-Density Relations of Soils
Using a 5.5 Ib. Rammer and 12-Inch
Drop
TI00 Specific Gravity of Soils
TI80 Moisture-Density Relations of Soils
Using a 10-lb. (454 kg) Rammer and an
IS in. (457 mm) Drop
Density of Soil-in-Place by Block,
Chunk or Core Sampling
T234 Strength parameters of soils by Triaxial
Compression
Laboratory Determination of Moisture
Content of Soils
Density of Soil and Soil-Aggregate in
Place by Nuclear Methods (Shallow
Depth
OCR for page 345
T239 Moisture Content of Soil and Soil-
Aggregate in Place by Nuclear Me~ods
(Shallow Depth
3. Terminology
3.! Unbound Granular Base and Subbase
Materials: These include soil-aggregate mixtures
and naturally occurring materiels. No binding or
stabilizing agent is used to prepare unbound
granular base or subbase layers. These materials
may be classified as either Type ~ or Type 2 as
subsequently defined in 3.3 and 3.4.
3.2 Subgrade: Subgrade soils may be
naturally occurring or prepared and compacted
before Me placement of subbase and/or base
layers. These materials may be classified as
either Type ~ or Type 2 as subsequently defined
in 3.3 and 3.4.
3.3 Material Type I: For the purposes of
resilient modulus testing, Material_Type ~
includes all unbound granular base and subbase
material and all untreated subgrade soils which
meet Me criteria of less than 70% passing Me
2.00 mm (No. 10) sieve and less Man 20%
passing the 75 Am (No. 200) sieve, and which
have a plasticity index ~ 10. Type la material
shall have 100% passing 37.5 mm (1.5 in.) sieve
and Type lb the 25.4 mm (1.0 in.) sieve.
Materials~ciassified~ype la shall be molded
in a 152 man (6 inch) diameter mold. Materials
classified as lb can be molded in either a 102
mm (4 in.) or 152 mm (6 in.) diameter mold.
Note 2 - If logo or ~ of a Type la
sample is retained on the 37.5 mm (1.5
in.) sieve, Me material greater than the
37.5 mm (~.5 in.) sieve shall be scalped
and replaced by 25.4 to 37.5 mm (1.0-
1.5 in.) material prior to testing.
3.4 Material Type 2: Material Type 2
includes all unbound granular base/subbase and
untreated subgrade soils not meeting the criteria
for material Type ~ given above in 3.3.
Generally, thin-walled tube samples of untreated
subgrade soils fall in Me Type 2 category.
Remolded Type 2 specimens can be compacted in
either a 71 xnm (2.8 in.) or a 102 mm (4 in.)
diameter mold.
Note 3 -- Type 2, 71 mm (2.8 in.)
Specimens: If 10% or ~ of a Type 2
sample is retained on the 12.5 mm (0.5
in.) sieve, the material greater than 12.5
mm (0.5 in.) shall be scalped off and
replaced by 9.5 mm to 12.5 mm (0.375
in. to 0.5 in.) material prior to testing.
3.5 Resilient Modulus of Type I and Type lI
Materials: The resilient modulus of Type I and
Type I! material is determined by repeated load
compression tests on test specimens of the
unbound material. Resilient modulus (Mr) is the
ratio of Me peak axial repeated deviator stress to
the peak recoverable axial strain of the specimen.
3.6 Loading Wave Form - Test specimens
are loaded using a haversine load pulse as shown
in Figure Eel.
3.7 Maximum Applied Axial Load (Pmax) ~
the load applied to the sample consisting of the
contact load and cyclic load (confining pressure
is not included):
Pm" Poon~, + Pcyclic
3.S Contact Load (PCon~¢ac~) ~ vertical load
placed on Me specimen to maintain a positive
contact between the loading ram and the
specimen top cap. The contact load includes the
weight of the top cap and the static load applied
by the ram of the testing system.
3.9 Cyclic Axial Load - repetitive load
applied to a test specimen:
P`~rclic = Pmax Pconta~
3.10 Maximum Applied Axial Stress (Sm=) -
the axial stress applied to Me sample consisting
of the contact stress and the cyclic stress (~e
confining stress is not included):
Sma,c = Pmax/A
E-3
OCR for page 346
Do
O gO 180 270 360
i ' I ' i ' I ' I ~
1.0-
0.8-
-
co
-
0.6-
C)
o
C'
0.2-
0.0
,` 0.1 seG
/ Load Duration
.,___________. .
Cyclic (Resilient)
Load Pulse
(Pi )
, ~
~
\ Maximu nil App' ed
\ Load (Pmac )
\
O.9S~
Rest
Pedod
Haversine
Load Pulp
(1-CDS 8)
.
\
Contact Lt lad (POOl~ )
1 1
~ r1 1 ~
O .02 .04 .OB .08 JO
Time, Seconds (t)
Figure Eat. Definition of resilient modulus terms
E-4
- 100
- 90
-80
-70
:-
- 60 ~
m
_ 50 O
S.
-40
-30 ~
-
-20
- 10
o
OCR for page 347
where: A = cross sectional area of the sample.
3 . ~ ~ C ye! ic Axial Stress - cyc! ic (res i! ient)
applied axial stress:
S~,C,ic = PCyclidA
3. 12 Contact Stress (SoOn~ - axial stress
applied to a test specimen to maintain a positive
contact between the specimen cap and the
specimen:
Scone, = PCon~,/A
The contact stress shall be maintained so as to
apply a constant an~sotropic confining stress ratio
(SO>n~ + S31/S3 I.2.
where: S3 iS the confining pressure.
3.13 S3 IS the applied coding pressure in the
biaxial chamber (i.e., the minor principal stress,
(731
3.14 er is the resilient (recovered) axial
deformation due to S~c~ic.
3.15 Er is the resilient (recovered) axial strain
due to S~c~ic:
Cr = er/L
where: ~ = distance between measurement
points for resilient axial deformation, en
3.16 Resilient Modulus (Mr) is defined as
SFyctic/Er
3.17 Load duration is the time interval Me
specimen is subjected to a cyclic stress pulse
(usually 0. ~ sec.~.
3.~S Cycle duration is Me time interval
between the successive applications of a cyclic
stress (usually I.0 sec.~.
4. Summary of Method
4. ~ A repeated axial stress of fixed
magnitude, load~uration (0.l sec.), and cycle
duration (l sec.) is applied to a cylindrical test
specimen. Me test is performed on cohesioniess
materials in a biaxial cell and the specimen is
subjected to a repeated (cyclic) stress and a
constant confining stress provided by means of
cell air pressure. For cohesive subgrade soils a
similar repeated cyclic stress is applied to an
unconfirmed cylindrical specimen. The total
resilient (recoverable) axial deformation response
of the specunen is measured and used to calculate
the resilient modulus.
5. Significance and Use
5. ~ The resilient modulus test results
provides a basic constitutive relationship between
stiffness and stress state of pavement materials
for use in pavement design procedures and the
structural analysis of layered pavement systems.
The resilient modulus test simulates the
conditions in a pavement due to application of
moving wheel loadings. As a result, the test
provides an excellent means for comparing the
behavior of pavement construction materials
under a variety of conditions (i.e., moisture,
density, gradation, etc.) and stress states.
6. Resilient Modulus Test Apparatus
6. ~ Triaxial Pressure Chamber: CohesionIess
Materiads - The pressure chamber is used to
contain Me test specimen and Me confining fluid
during Me test. A typical biaxial chamber
suitable for use in resilient testing of soils is
shown in Figure E-2a. The axial deformation is
measured internally directly on the specimen
using either an optical extensometer, noncontact
sensors or clamps (Figure E-2a).
6. I. ~ Air shall be used in the biaxial chamber
as the confining fluid for all testing.
E-5
OCR for page 348
LOADING CON
\\ ~
COYER PLATE -
CHAMBER
CLAMP MOUNTED LYDT
TEST SPECIMEN ~
SPECIMEN METER - E -
THOMPSON UNEAR
~onoN BEARINGS
_ RUBBER GASKET
LOAD An L CONNECTOR
_ LOAD (:aL
E ROD
-LVOT J" BOSOM
_ CHAIJiDER
_ ALUMNUS ROD
_ BRONZE POROUS STONE
EXTERNAL=NNE=OR ~ ~ ^\\\~= ~ IN~NAGE ONE
'' A' ~
RUBBER GASKET ~ ~ ~ BOhOM C"
~ RING SEAL
(a) Triaxial Cell
L" LVDT AND LOAD
CEl1 CONNECT - S
2~ ~ LOAD RAM
STEEL BALL
/ ATOP PLATEN
3~4/ (SOLID)
A, , ~ in , ,,
aid
~-LVDT
CAL
l
T ~ SPECIMEN
~ ,
, ~ BOTTOM
/ PLATEN
(SOLID)
\ \ \ \ \ ~
BASE OF LOAD FRAME
(b) Unconfined compression test
Figure E-2. Triaxial and unconfined test apparatus
E-6
OCR for page 349
6.~.2 The chamber shall be made of Lexan,
Acrylic or other suitable "see-through" material.
If an optical extensometer is used the line of
sight must pass Trough a flat face of the
chamber. Hence, a standard cylindrical chamber
cannot be used with an optical extensometer.
6.2 Unconfined Test: Cohesive Subgrade
Soils - An undrained, unconfined compression
test shall be performed on cohesive subgrade
soils (Figure E-2b). Solid, rigid steel or
aluminum platens are placed on the top and
bottom of the specimen which may be enclosed
in a rubber membrane. The specimen is
subjected to only atmospheric air pressure, and
hence a biaxial cell is not required in the test.
The axial deformation of firm or stiff subgrade
specimens, except as noted, is measured on the
specimen using one of the me~ods given in
Section 6. For soft and very soft subgrade
specimens (i.e., Su ~ 361d'a or 750 psf), clamps
should not be used since they may damage He
specimen. However, a pair of EVDTs extending
between He top and bottom platens can be used
to measure axial deformation of these weak soils.
6.3 Loading Device - The loading device
shall be a top loading, closed loop
electrohydraulic testing machine with a function
generator which is capable of applying repeated
cycles of a haversine-shaped load pulse. Each
pulse shall have a 0. ~ sec. duration followed by
a rest periods of 0.9 sec. duration. For
nonplastic granular materials, it is permissible, if
desired, to reduce He rest period to 0.4 sec. to
shorten testing time: He load pulse time may be
increased to 0. 15 sec. if required.
6.3.] The haversine shaped load pulse shall
conform to Section 3.6 except as noted above.
All conditioning and testing shall be conducted
using a haversine-shaped load pulse. The
electro-hydraulic system generated haversine
waveform and He response waveform shall be
displayed to allow the operator to adjust He
gains to ensure they coincide during
conditioning and testing.
6.4 Load and Specimen Response Measuring
Equipment:
6.4. ~ The asocial load measuring device should
be an electronic load cell located inside the
biaxial cell as shown in Figure E-2a. The
following load cell capacities are required:
Sample Dia. Max. Load Cap. Req. Accuracy
mm. (in.) kN (lbs.) ~ fibs.)
71~2.8) 2.2~500) i4.5(il)
102 (4.0) 8.9 (2000) il7-8 (i 4)
152 (6.0) 22.24 (5000) i 22.24 (i 5)
Note 4 -- Since applied stress levels
are low, a non-fatigue rated load cell
can be used to obtain a greater
voltage output and higher accuracy
than for a fatigue rated cell. Do not
load a non-fatigue rated load cell to
more than 50% of its rated capacity.
During periods of resilient modulus
testing, the load cell shall be
monitored and checked once every
two weeks or after every 50 resilient
modulus tests with a calibrated
proving ring to assure that the load
cell is operating properly. An
alternative to using a proving ring is
to insert an additional calibrated load
cell and independently measure the
load applied by Me original load cell.
Additionally, the load cell shall be
checked at any time there is a
suspicion of a load cell problem.
Resilient modulus testing shall not be
conducted if the testing system is
found to be out of calibration.
6.4.2 The test chamber pressures shall be
monitored wig conventional pressure gages,
manometers or pressure transducers accurate
to 0.7 kPa (O. ~ psi).
E-7
OCR for page 350
6.4.3 Axial Deformation - Axial
deformation is to be measured on the
specimen using one of the following devices:
(~) optical extensometer, (2) noncontact
sensors or (3) clamps attached to the
specimen. Table E-! summarizes the
specifications for noncontact and clamp
measurement devices. Deformation shall be
measured over approximately the middle 1/2
of the specimen For methods (2) and (3)
above, deformation shall be measured
independency on each side of the specimen
using gages having the maximum practical
sensitivity.
6.4.3.! Optical Extensometer - The optical
extensometer should have at least the
following minimum requirements: (~)
resolution - 0.0002 in.; (2) frequency
response - 200 hz bandwidth; (3) linearity -
O. ~ %; (4) displacement range - 0.5 in.; (5)
gage length range: 2.5 in. to 5.0 in.; (6)
analog or digital output signal. If
displacement is measured on a single side of
the specimen, two external or internally
mound EVDTs or dial indicators should be
used to determine specimen eccentricity
under loading.
6.4.3.2 Noncontact Proximity Sensors -
Proximity gages shall have the minimum
voltage output given in Table Eel.
6.4.3.3 Clamps Mounted EVDTs -
EVDTs shall have the minimum voltage
output indicated in Table E-! A pair of
spring loaded clamps are placed on the
specimen et I/4 point. (Figure Ebb. Each
clamp shall be rigid with the clamp weight
not exceeding the following values: 6 in.
clamp - 2.4 N (0.55 Ibs.~; 4 in. clamp - I.8
N (0.40 Ibs.~; 2.8 in. clamp - I.0 N (0.22
Ibs.~. Minimize clamp weight by Uniting
small holes in the clamp. Clamp spring
force should be as follows: 6 in. clamp
44.5 N (10.0 Ibs.~; 4 in. clamp - 33.4 N (7.5
Ibs.~; 2.8 in. clamp- 18.2 N (4.1 lbs.~. Use
two pairs of 12 mm (0.5 in.) diameter rods,
cut to the correct length, to position the
clamps in a horizontal plane at the correct
location on the specimen.
6.4.3.4 Spring loaded EVDTs shall be used
to maintain a positive contact between the
EVDT's and the surface on which the tips of
the transducers rest. If the specimen is soft
enough to be damaged by clamps or slippage
of clamps is suspected, use one of the other
alternative axial displacement measurement
techniques. Slippage of clamps may be a
problem for soft and very soft subgrade soils
which undergo large deformations.
Specimen damage due to clamps and clamp
slippage should not be a problem for
reasonable quality base and subbase
specimens. The two EVDT's, or proximity
gages, shall be wired so that each transducer
is read, and the results reviewed,
independency. The measured displacements
shad be averaged for calculating the resilient
modulus.
Note 5 -- Misalignment, or dirt on
the shaft of the transducer can cause
the shafts of the EVDTs to stick.
The laboratory technician shall
depress and release each EVDT back
and forth a number of times prior to
each test to assure that they move
freely and are not sticking. A
cleaner/lubncant specified by the
manufacturer shall be applied to the
transducer shafts on a regular basis.
E-8
OCR for page 351
Table Eat. Specifications for axial EVDT and noncontact proximity
deformation measurement instrumentation
I - 1
hlATERIAL~oECIMEll
SIZE
hilts APPROX. ~INUW~
Row RESILIENT Am.
(IN.) SPEC - N OUTPUT
(+I-) D~P. ~.) (MV)
TYPICAL LVDT
M~. S~
O 3Y,
MVNI0.001 In.
.
TYP CAL
PROX MrrY GA~
u'u. sENsmvlrY
(IUVI0.001 In.)
AG=£GATE BASE
.
6 IN. D~ SP~CIMEN 0.25 0.001 ~
. DIA SPECII4EN 0.1 0.0006S 5
.
2.1
2..
SIJ - FIAD£ SOILSAND
0.25 0.0014 2.1
0.25 0.001 2.1
4.0 IN. ~ SPECIM~
2 8 IN. DIA. SPECIMEN
SURGRADE SOIL
_ _ _
COHESIVE. 2.8 IN. t)lA.
0.1 1 0.008 1 20
0.1 0.002 1 0
0.1 0.0004 3.5
.
SOFT (not. 2)
1 ..
2 -5.0
FRM
2.1
s
STlFF- YERY snFF
(nots 3)
2.8 (note 4)
s
NOTES:
1. MINUdUM P`ESILENT DISPUCEMENTS, EXCEPT AS NOTED, ARE MEASURED OYER THE
CENTRAL ONE~AU OF A SP£CJM£H HAVWG A HEJGHr 1 W1CE rRs DUIAETER. CORRECT
THIS DiSPLACEM£NT IF ANOTHER GAUGE LENGTH IS USED. MINIMUM RESIUEt4T
DlSPLACEMEtU GIYEN IS APPROXINIATE AND YARIES ~TH THE MATE~t S TESTED.
RESILIENT DISPLACEM£NT hIEsSl IRED OVER ENTIRE SPECIMEH i1E~.
3. CONSIDER USING GROUT ED ENDS AND TOP TO BO11OM LYI)TS OR 4.0 In. DIAIUETER
SP£CIMENS BECA13SE OF POTENTIALLY VERY SMALL DISPLACEI IENTS AT SUALL
D£\4ATOR STRESSES.
4. P~ MEASURMEN~ SYSTEM TO MAXIbSUM OUTPUT: COt4SID£R EXCEEW40
RECOIlMEHDED VOLTAGE.
J O
oo l
.~ .
~o~7
Figure E-3. Typical cIamps used to measure axial deformation
E-9
OCR for page 352
Note 6 -- The response of the deformation
measurement system shall be checked daily
during use. Additionally, the deformation
measurement system shad be calibrated every
two weeks, or after every 50 resilient
modulus tests, whichever comes first.
Calibration shall be accomplished using a
micrometer with compatible resolution or a
set of specifically machined, close tolerance
gauge blocks. Resilient modulus testing shall
not be conduct if the measurement system
do not meet the manufacturer's tolerance
requirements for accuracy.
6.4.4 Data Acquisition - An analog to
digital data acquisition system is required.
The overall system should include automatic
data reduction to minimize the chance for
errors and maximize production. Suitable
signal excitation, condidon~ng, and recording
equipment are required for simultar~eous
recording of axial load and deformations.
The system should meet or exceed the
following additional requirements: (~) 25ps
A/D conversion time; (2) 12 bit resolution;
(3) single or multiple channel throughput
(gain-I), 30 kH3; (4) software selectable
gains, (5) measurement accuracy of full scale
(gain I) of + 0.02%; and (6)
nonlinearity GISTS) of ~ 0.5. The signal
shad be clean and free of noise (use shielded
cables properly grounded). Filtering the
output signal during or after data acquisition
is discouraged. If a filter is used, it should
have a frequency greater than 10 to 20 Hz.
A supplemental study should be made to
insure correct peals readings are obtained
from the filtered data compared to the
unfiltered data.
A minimum of 200 data points from each
EVDT shall be recorded per load cycle. A
supplemental study is also suggested to
establish the optimum number of data points
to use for each specific data acquisition
system.
6.5 Specimen Preparation Equipment A
variety of equipment is required to prepare
undisturbed samples for testing and to
prepare compacted specimens that are
representative of field conditions. Use of
different materials and different methods of
compaction in the field requires the use of
varying compaction techniques in the
laboratory. Specimen preparation is given in
Annex Al, specimen compaction equipment
and compaction procedures for Type ~
materials in Annex A2 and for Type 2
materials in Annex A3.
6.6 Equipment for trimming test
specimens from undisturbed thin-wal1 tube
samples of subgrade soils shall be as
described in AASHTO T234.
6.7 Miscellaneous Apparatus - This
includes calipers, micrometer gauge, steel
rule (calibrated to 0.5 mm (0.02 Intel), rubber
membranes from 0.25 to 0.79 mm (0.02 to
0.031 in. thickness, rubber O-nngs, vacuum
source with bubble chamber and regulator,
membrane expander, porous stones
(subgrade3, 6.4 mm (0.25 in.) thick porous
stones or bronze discs (base/subbase3, scales,
moisture content cans and data sheets.
6.8 Periodic System Calibration - The
entire system (transducers, signal
conditioning and recording devices) shall be
calibrated every two weeks or after every
fib resilient modulus tests. Daily and other
periodic checks of the system may also be
performed as necessary. No resilient
modulus testing will be conducted unless the
entire system meets the established
calibration requirements.
E-10
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7. Preparation of Test Specimens
7.! The following guidelines, based on
the sieve analysis test results, shall be used to
determine the test specimen size:
7.~.1 Use 71 mm (2.S in.) diameter
undisturbed specimens from ~ walled tube
samples for cohesive subgrade soils (Material
Type 2~. The specimen length shall be at
least two times We diameter (minimum
length of 142 mm (5.6 in.~) and the specimen
shah be prepared as described in section 7.2.
If undisturbed subgrade samples are
unavailable or unsuitable for testing, then 71
mm (2.8 in.) diameter molds shall be used to
reconstitute Type 2 test specimens.
Note 7 -- If 10% or less of a Type
2 sample is retained on the 12.5 mm
(0.5 in.) sieve, the material greater
than the 12.5 mm (0.5 in.) sieve shall
be scalped off and replaced by 9.5
mm to 12.5 mm (0.375 in. to 0.5 in.)
material prior to testing. If more
than 10% of Me sample is retained on
the 12.5 mm (0.5 in.) sieve, the
material shall be tested using either
102 mm (4 in.) or 152 mm (6 in.)
specimens following previously given
criteria.
7. 1.2 Use a split mold 152 mm (6.0 in.) in
diameter to prepare 305 mm (12 in.) high
specimens for all Type 1 materials with
maximum particle sizes less than or equal to
37.5 mm (~.5 in.~. Alternately, 102 mm (4
in.) diameter molds can be used to prepare
all Type lb materials having maximum
particle sizes less than 25.4 mm (1 in.~.
Note ~ -- If 10% or less of a Type ~
sample is retained on the 37.5 mm
(1.5 in.) sieve, the material greater
than the 37.5 mm (1.5 in.) sieve shall
be scalped and replaced by 25.4 to
37.5 mm (~.0-1.5 in.) material prior
to testing.
7.2 Undisturbed Subgrade Soil Specimens
- Trim and prepare thin-walled tube samples
of undisturbed subgrade soil specimens as
described in former T234 (now deleted).
The natural moisture content (w) of a tube
sample shall be determined after tnaxial Mr
testing following the procedure T265.
Record w in the test report.
The following procedure shall be followed
for the thin-walled tube samples:
7.2. 1 Standard penetration tests (ASTM D
1586) or cone penetration tests (ASTM D
3441) performed adjacent to thin-walled tube
sample locations and elsewhere along the
route is encouraged. The results obtained
from penetration testing is used to aid in
establishing representative subgrade
conditions and selecting a representative
sample for testing. The sample selected
should be of acceptable quality,
representative of the subgrade conditions
near the surface, and preferably taken from
the uppermost tube pushed into the subgrade.
7.2.2 To be suitable for testing, a specimen
cut from the tube sample must have a length
equal to at least twice its diameter after
preparation. The sample must be free from
defects that would result in unacceptable or
biased test results. Such defects include
sampling/trimming induced cracks in the
specimen, corners broken off that cannot be
repaired during preparation, presence of
particles much larger than that typical for the
material (for example, + 19.0 mm ~ + 3~4
in.) stones in a fine-grained soil), the
presence of foreign objects not representative
of the subgrade such as large roots, wood
particles, organic material and gouges due to
E-11
OCR for page 376
A2.3.8 Determine the volume, V, ofthe specimen
to be prepared using the diameter determined in step
B3.7 and an assumed value of height between 305
and 318 mm (12 and 12.5 inches) for 152 mm (6
inch) diameter specimens and between 203 and 216
mm (8 and 8.5 inch) for 102 mm (4 inch) diameter
specimens.
A2.3.9 Determine the mass of material, at the
prepared water content, to be compacted into the
volume (V), to obtain the desired density.
A2.3.10 For 152 mm (6 inch) diameter specimens
(specimen height of (305 mm, 12 inches)) 6 layers
of 2 in. per layer are required; for 102 mm (4 in.)
diameter specimens 6 layers of 33.9 mm (1.33 in.)
per layer shall be used. Determine the weight of wet
soil, WE required for each layer.
We= Wit
where:
W' = total weight of test specimen to produce
appropriate density,
N = number of layers to be compacted.
A2.3.11 Place the total required weight of soil for
all lifts, Wad into a mixing pan. Add the required
amount of water, Waw and mix thoroughly.
A2.3.12 Determine the weight of wet soil and the
· -
mixing p an.
A2.3.13 Place the required amount of wet soil
(Wry' into the mold. Avoid spillage. Using a
spatula, draw soil away from the inside edge of the
mold to form a small mound at the center.
A2.3.14. Insert the vibrator head and vibrate the
soil until the distance from the surface of the
compacted layer to the rim of the mold is equal to
the distance measured in step A2.3.7 minus the
thickness ofthe layer selected in step A2.3.10. This
may require removal and reinsertion ofthe vibrator
several times until experience is gained in gaging the
vibration time which is required. Use a small
circular spirit level to assist in keeping each layer
level.
A.2.3.15 Repeat steps A2.3.13 and A2.3.14 for
each new layer after first scarifying the top surface
of the previous layer to a depth of about 6.4 mm
(1/4 inch). The measured distance from the surface
of the compacted layer to the rim of the mold is
successively reduced by the layer thickness. The
final surface shall be a smooth plane parallel to the
base of the biaxial cell. Use the special compaction
head shown in Figure A2. I(b) for the final lift. As
a final step, the top plate shall be placed on the
sample and seated firmly by vibrating with the
compactor for about lO seconds. If necessary, due
to degradation of the first membrane, a second
membrane can be applied to the sample at the
conclusion ofthe compaction process.
A2.3.16 When the compaction process is
completed, determine the mass of the mixing pan
and the excess soil. This mass subtracted from the
mass determined in step A2.3.12 is the mass ofthe
wet soil used (mass of the specimen). Verify the
compaction water, ~ of the excess soil using care
in covering the pan of wetted soil during compaction
to avoid drying and loss of moisture. The moisture
content of this sample shall be conducted using
AASHTO T265.
A2.3. 17 Proceed with Section 8.2 ofthis method.
Note ~ - As an alternative for soils lacking
in cohesion, a mold with the membrane
installed and held by vacuum, as in Annex
A2, may be used.
E-34
OCR for page 377
ANNEX A3 - Compaction of Type 2 Soils
(Mandatory Information)
A3.l Scope
A3. ~ . ~ This method covers the compaction of
cohesive Type 2 soils for use in resilient modulus
testing.
A3. ~ .2 Resilient modulus test results are
affected by the spec~men's soil structure.
Different type compaction methods impart
different soil structures to the specimen.
Therefore, the compaction method selected
should simulate field conditions. Selection of the
compaction method depends upon the field soil
moisture at the time of compaction and the later
post-construction moisture condition. Either the
impact or static method of compaction may be
used depending upon moisture conditions. If
testable thin-walled tubes are available,
specimens shall not be recompacted.
E-35
A3. ~ .3 When the range of these conditions are
known, specimens may be prepared at specific
moisture contents and densities. Select the
appropriate compaction method using Table
A3. I. If in doubt about the moisture condition,
assume the post-construction moisture will be
greater than at the time of construction which is
usually true.
A3.~.4 Impact Compaction - The procedure
for impact compaction is described in AASHTO
T99 and AASHTO TISO. Upon completion of
impact compaction, proceed with Section 8.2 of
this test method.
A3. ~ .5 Static Compaction - The procedure for
static compaction is given in Annex A4.
OCR for page 378
ANNEX A4 - Static Compaction
(Mandatory Information)
A4.! Scope
A4.1.1 This method covers the compaction of
cohesive Type 2 soils using static compaction.
Table A3. I, Annex A3, defines when static
compaction is an acceptable method.
A4.~.2 A modified version is used of the double
plunger static compaction method. Specimens shall
be recompacted in a 71 mm (2.8 inch) diameter
mold. The process is one of compacting a known
mass of soil to a volume that is fixed by the
dimensions ofthe mold assembly (mold shall be of
a sufficient size to produce specimens 72 mm (2.8
inches) in diameter end 12 mm (6 inches) in height).
A typical mold assembly is shown in Figure A4. 1.
As an alternative for soils lacking in cohesion, a
mold with the membrane installed and held by
vacuum, as in Annex A2, may be used. Several
steps are required for static compaction as given in
Section A4.3 of this Annex and as illustrated in
Figures A4.2 to A4.6.
A4.2 Apparatus - The apparatus is shown in
Figure A4. 1.
A4.3 Procedure
A4.3. ~ Five layers of equal mass shall be used to
compact the specimens using this procedure.
Determine the mass of wet soil, We to be used per
layer where We = W,/5.
A4.3.2 Place one of the spacer plugs into the
specimen mold.
A4.3.3 Place the mass of soil, WE determined in
Step C3. 1 into the specimen mold. Using a spatula,
draw the soil away from the edge of the mold to
form a slight mound in the center.
A4.3.4 Insert the second plug and place the
assembly in the static loading machine. Apply a
small load. Adjust the position of the mold with
respect to the soil mass, so that the distances from
E-36
the mold ends to the respective spacer plugs are
equal. Soil pressure developed by the initial loading
will serve to hold the mold in place. By having both
spacer plugs reach the zero volume change
simultaneously, more uniform layer densities are
obtained.
A4.3.5 Slowly increase the load untilthe plugs rest
firmly against the mold ends. Maintain this load for
a period of not less than one minute. The amount of
soil rebound depends on the rate of loading and load
duration. The slower the rate of loading and the
longer the load is maintained, the less the rebound
(Figure A4.2~.
Note 2 - Use of compaction by measuring
the plunge movements to deter reline that the
desired volume has been reached for each
layer is an acceptable alternative to the use
of the spacer plugs.
A4.3.6 Decrease the load to zero and remove the
assembly from the loading machine.
A4.3.7 Remove the loading ram. Scarify the top
surface ofthe compacted layer to a depth of 3.2 mm
(~/8 inch) and put the mass of wet soil WL for the
second layer in place and form a mound. Add a
spacer plug of the height shown in Figure A4.3.
A4.3.S Slowly increase the load untilthe plugs rest
firmly against the top of the mold end. Maintain
load for a period of not less than one minute (Figure
A4.3).
A4.3.9 Remove the load and flip the mold over end
remove the bottom plug keeping the top plug in
place. Scarify the bottom surface of layer 1 and put
the mass of set soil WL. for the third layer in place
and form a mound. Add a spacer ring ofthe height
shown in Figure A4.4.
A4.3.10 Place the assembly in the loading
machine. Increase the load slowly until the spacer
plugs firmly contact the ends ofthe specimen mold.
Maintain this load for a period of not less than one
OCR for page 379
TABLE A3. i Selection of Compaction Method for Laboratory Compacted Specimens
i 1
IN-PLACE CONDITIONS Applicable
Saturation at Time | Post-Constructi n | Compaction l
of Compaction In-Service
(GO) Moisture Content Methods
<80 less than the moisture content at impact
time of construction static
>80 greater than or equal to the impact
moisture content at time of
construction
<80 | greater then the moisture
at time of construction
E-37
OCR for page 380
minute.
A4.3.~! Follow the steps presented in Figures
A4.5 and A4.6 to compactthe remaining two layers.
A4.3. 12 After compaction is completed, determine
the moisture content of the remaining soil using
AASHTO T265. Record this value on Report Form
X1.2.
A4.3. 13 Using the extrusion ram, press the
compacted soil out of the specimen mold and into
the extrusion mold. Extrusion should be done
slowly to avoid impact loading the specimen.
A4.3. 14 Using the extrusion mold, carefully slide
the specimen off the ram, onto a solid end plane.
The platen should be circular with a diameter equal
to that of the specimen and have a minimum
thickness of 13 mm (0.5 in). Platens shall be of a
material which will not absorb soil moisture.
A4.3. 15 Determine the mass of the compacted
specimen to the nearest gram. Measure the height
and diameter to the nearest 0.25 mm (0.01 inch).
Record these values on Report Form XI.~.
A4.3.16 Place a platen similar to the one used in
step A4.3. 13 on top of the specimen.
A4.3.17 Using a vacuum membrane expander,
place the membrane over the specimen. Carefully
pull the ends ofthe membrane over the end platens.
Secure the membrane to each platen using O-rings
or other means to provide an airtight seal.
A4.3. ~ ~ Proceed with Section B.2 ofthis method.
E-38
OCR for page 381
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2- 100.1 non {3.9W) herald mad by
2 - 71.6 mm 2.820. helg ~bay
2 - 43.2 mm 1.700' height 28~4 mm (1.1Z. a)
Figure A4. I. Typical apparatus for static compaction of type 2 materials
E-39
OCR for page 382
steppes Lifts:
COIT pardon ~tO be solid
c~lodere of speckled heath'
and 70.' mm (2.7~ dear.
.. . ~
2x.~:.
...............
......
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LJIt 1
· Manure ~ wet ma" of HI to
use for a layer.
place In mold, spade.
Insert pIL'gS of gIven height.
Double plunge until plows are fl - h
who tog arid b=orn ~ mold.
Remove~p~-
Scarly Me exposed surface of [m 1.
Pod web new pep.
Figure A4.2. Compaction of type 2 soil, liR I
E-40
OCR for page 383
Step 3.7 ~ UR 2:
· Measure ~ wet maw of HI to
use for ~ layer.
· Place In mom, ~e.
· Hansen 71.6 mm (~8201 pap.
· Plunge until phases are flush wan top
and bosom of mad.
· FUp mod over arm remove 100.1 mm
(3.9W) plug, keeping He 71.~ man
(~820' pAq7h placo.
By He ted surface d IJft 1
· Pad why new asp.
.
IJft 2
LIft 1
_
1
Figure A4.3. Compaction of type 2 soil9 lift 2
E-41
OCR for page 384
St" 3.. - ~ 3:
a.' >:s
i.
........
..........
Uft2
lit 1
IJft3
.
· Manure cod wet weight of ~ to use
for ~ layer.
· Place In mold. spade.
· Insert 71.8 mm (~ pi-.
· Plunge unto pled are flush wan top and
bottom of mold.
Fnp mold over and remove 71.6 nun
(2.~) play,, from ~ top d Let 2,
keeping Me 71.6 mm ~820~) plug
ton Em 3) In place.
~ We exposed surface of Oft 2.
Figure A4.4. Compaction of type 2 soil, liR 3
E-42
OCR for page 385
Step 3.11 - ~ 4.
· Measure sorry wet welds of 801 to use
for ~ lay - .
· Phco In mo d, spay.
· Insert 43~ mm (1.7003 poop.
· Plunge unfit pings are flush w th top and
bosom of mold.
Flip mod over and rem~e 71.6 mm
~8201 pay, keeping me 432 An
t1.700~ Phil h plans.
by ~ ~ ~faos d Lift 3.
Proceed Ash new step.
_ .
:
L#t4
lift 2
tat 1
Im3
,,,,~,~,,,,,,,,,~,.....
........
Figure A4.5. Compaction of type 2 soil' lift 4
. .
E-43
OCR for page 386
lot 4
left 2
Uft1
1~3
Uft6
I.
-
Step 3.13 - Lm 5:
Measure Wet weight of ~ ~ use
for ~ layer.
Pi,.
Insert 432 mm (1~7008) PIED
Plunge until pings are flush web top and
bosom of mold.
Denude Compacted samp e from mold
mIng extruding ah or ex~on
mold.
· Place h rubber menbre`~.
. T - tfor Or
Figure A4.6. Compaction oftype 2 soil, lift 5
E-44
Representative terms from entire chapter:
moisture content
