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APPENDIX E TEST PROCEDURE FOR RESILIENT MODULUS OF UNSTABILIZED AGGREGATE BASE AND SUBGRADE MATERIALS E-1
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
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
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
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
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
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
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
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
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
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
gravel hanging on the edge of the tube. 7.3 Laboratory Compacted Specimens - Reconstituted test specimens of both Type ~ and Type 2 materials shall be prepared to the specified or in-situ dry density (Yd) and moisture content (w). Laboratory compacted specimens shall be prepared for all unbound granular base and subbase material and for ah subgrade soils for which undisturbed tube specimens could not be obtained. 7.3.! Moisture Content - For in-situ materials, the moisture content of the laboratory compacted specimen shall be the in-situ moisture content for that layer obtained in the field using T238. If data is not available on in-situ moisture content, refer to Section 7.3.3. 7.3.~.! The moisture content of the laboratory compacted specimen should not vary from die required value by more than ~ I.0% for Type ~ materials or ~ 0.5% for Type 2 mat,enals. 7.3.2 Compacted Density - The density of a compacted specimen shall be the in-place dry density obtained in the field for that layer using T239 or over suitable methods. If this data is not available on in-situ density, then refer to Section 7.3.3. 7.3.2.1 Me dry density of a laboratory compacted specimen should not vary more than ~ 2 % from Me target dry density for that layer. 7.3.3 If either the in-situ moisture content or the in-place dry density is not available, then use the optimum moisture content and 95 % of the maximum dry density by using TI8O for the base/subbase and 95 % of T99 for the subgrade. 7.3.3.! The moisture content of a laboratory compacted specimen should not vary form the target value by more than ~ I.0% for Type ~ materials or ~ 0.5% for Type 2 materials. Also, the dry density of the laboratory compacted specimen should not vary more than ~ 2% of the target dry density. 7.3.4 Sample Reconstitution Reconstitute the specimen for Type ~ and Type 2 materials in accordance with the provisions given in Annex Al. The target moisture content and density to be used in determining needed material quantities are given in Section 7.3. Annex Al provides guidelines to obtain a sufficient amount of material to prepare the appropriate specimen type at the designated moisture content and density. After this step is completed, specimen compaction can begin. 7.4 Compaction Methods and Equipment for reconstituting specimens 7.4.! Compacting Specimens for Type ~ Materials - The general method of compaction for Type ~ materials is given in Annex A2. 7.4.2 Compacting Specimens for Type 2 Materials - The general method of compaction for Type 2 materials is given in Annex A3. 7.4.3 The prepared specimens should be protected from moisture change by immediately applying the biaxial membrane and testing within ~ day of preparation unless saturation , drying or curing of the specimen is to be carried out. E-12
S. Test Procedure 8. ~ Initial System Calibration - The testing system including loading apparatus and biaxial cell, if used, must be calibrated before each major test series including · · · · · · - mlnlmlzlng system camp lance, insuring accurate specimen and system alignment and by using synthetic specimens to establish overall test accuracy (refer to Appendix D). 8.2 Test Methods - Following this test procedure, the resilient modulus test is performed on cohesionIess and low cohesion materials using a Biaxial cell. An unconfined resilient modulus test is used for cohesive subgrade soils. S.3 Granular and Low Cohesion Subgrade Soils - This procedure is used for laboratory compact specimens of subgrade soils. This includes all Type ~ subgrade materials (152 mm - 6 in. or 102 mm - 4 in. diameter specimens) and Type IT subgrade materials having a PI ~ 10. Reconstructed specimens will usually be compacted directly on the pedestal of the Biaxial cell. 8.3. ~ Assembly of Tr~axial Chamber Specimens Rimmed from undisturbed samples are placed in the biaxial chamber and loading apparatus in the following steps. Reconstituted specimens can be compacted directly on the pedestal of the biaxial cell. Measure Specimen dimensions to verify their initial density. 8.3. I. ~ Place presoaked porous stones no more than 6.25 mm (0.25 in.) thick on both the base and top of the specimen. If clogging of the porous stones is found to be a problem, presoaked filter paper cut to size can be used between the porous stone and specimen. 8.3. ~ .2 Place vacuum grease on the sides of the end platens to facilitate a good seal between the membranes and end platens. 8.3. I.3 Carefully place the specimen on the porous stone/base. Place the membrane on a membrane stretcher, apply vacuum to the stretcher, then carefully place the membrane on the sample and add the top platen. Remove the membrane from the stretcher, cut off the vacuum and remove the membrane stretcher. Seal the membrane to the top and bottom platens with rubber O- rings. A second membrane can be added if puncturing of Be membrane is a problem due to the presence of sharp aggregate. 8.3. I.4 If the specimen has been compacted or stored inside a rubber membrane and the sample, porous stones and rubber membrane are in place on the biaxial cell pedestal, omit step 8.3. 1.3. 8.3. I.5 Test for Leaks - Connect the specimen's bottom drainage line to the vacuum source through the medium of a bubble chamber. Apply a vacuum of 35 kPa (5 psi). If bubbles are present, check for leakage caused by poor connections, holes in the membrane, or imperfect seals at the cap and base. The existence of an airtight seal ensures that the membrane will remain firmly in contact with the specimen. Leakage ah rough holes in the membrane can frequently be eliminated by coating the surface of the membrane with liquid rubber latex or by using a second membrane. 8.3. I.6 When leakage has been eliminated, disconnect the vacuum supply line. Carefully clean the O-rings/gaskees used to seal the chamber; also clean all surfaces which the O-rings will contact. Place the chamber on the base plate, and the cover plate on the chamber. Insert the loading E-13
piston and obtain a firm connection with the cell. Tighten the chamber tie rods firmly to a uniform tension using a torque wrench. 8.3. ~ .7 Slide the assembled biaxial cell into position under the axial loading device. Positioning of the chamber is extremely critical in applying a concentric load to the specimen and minimizing friction forces on the piston rod. 8.3.~.S Set up the axial displacement measurement system (refer to Section 6.3.3) and verify it is working properly. 8.3.2 Conduct We Resilient Modulus Test - The following steps are required to conduct the resilient modulus test on a subgrade specimen which has been insured in the Biaxial chamber and placed under Me loading frame. 8.3.2.l Open all valves on drainage lines leading to the inside of the specimen. This is necessary to develop confining pressure on the specimen. 8.3.2.2 If not already connoted, connect the confining air pressure supply line to the biaxial chamber. Apply the specified conditioning confining pressure of 41.4 Lila (6 psi) to the test specimen. A contact stress equal to 20 % of the confining pressure shall be applied to the specimen so that the load piston stays in contact with the top platen at all times. S.3.2.3 Conditioning - Begin the test by applying a minimum of 500 repetitions of a load equivalent to a maximum axial stress of 59.4 Lila (~.6 psi) and corresponding cyclic stress of 55.2 kPa (~.0 psi) using a haversine shaped, 0. ~ second load pulse followed by a 0.9 second rest period. If the sample is still decreasing in height at the end of the conditioning period, stress cycling shall be continued up to 1000 repetitions prior to testing. Note 9 -- Conduct appropriate comparative checks of the individual displacement output from the two vertical displacement transducers during the conditioning phase of each Mr test to identify and minimize specimen misalignment. The two measured resilient vertical displacements should have an acceptable vertical displacement ratio. An acceptable displacement ratio ~) is defined es Rot Yma,,/Y,,,,, < ~ 10 where Ye,,, equals the largest of the two measured displacements and Y...... the smaller value. If unacceptable vertical deformation ratios are obtained, then the test should be discontinued and specimen alignment difficulties corrected., Very slightly tapping the tnaxial cell base in the correct direction or tightening the tension rod nuts on one side of the cell may reduce the eccentricity ratio. Proper equipment alignment is essential. The top of the specimen (and top cap) must be at right angles to the axis of the specimen. Once acceptable vertical deformation values are obtained, then the test should be continued to completion. Specimen alignment is critical for good Mr results. 8.3.2.3. ~ If the vertical permanent strain reaches 5% during conditioning, the conditioning process shall be terminated. A review shall be conducted of the compaction process to identify any reasonks) why the sample did not attain adequate compaction. If this review does not provide an explanation, the material shall be E-14
recompac~ and lest a second time. If the sample again reaches 5 96 total vertical permanent shin during preconditioning, then the test shad be terminal and the appropriate item on the data sheet shall be complex. No further testing of this material is necessary. S.3.2.4 Specimen Testing - Perform Me resilient modulus test following the load sequence shown In Table E-2. Begin by Using the maximum social stress ~ 16.6 kPa (2.4 psi) (Sequence No. I, Table E-2) and set Be confining pressure to 13.8 Lila (2 psi). 8.3.2.5 Apply 50 mpetitions of the corresponding cyclic asocial stress using a haversine shaped load pulse consisting of a 0.1 second load followed by a 0.9 second rest period. Record the average recovered deformations for each EVDT separately for the test five cycles on Me Report Fonn X1. 1. S.3.2.6 Increase the maximum Cal stress to 23.5 kPa (3.4 psi) (Sequence No. 2 and repeat step 8. 1.2.5 at this new stress level. S.3.2.7 Continue We test for due remaining load sequences in Table E-2 (3 ~ 12) recording the Verdi recovery deformation. If at any time the permanent strain of Me sample exceeds 5%, stop the test and report Me result on the appropriate worksheet. g.3.2.S After completion of the resilient modulus test procedure, check the total vertical permanent strain that the specimen was subjected to during the resilient modulus portion of Me test procedure. If the total vertical permanent swain did not exceed 59G, continue with the quick shear test procedure (Section 8.3.2.9~. If the total vertical permanent strain exceeds 5%, the test is complete. No additional testing is to be conduct on the specimen, other than In 8.1.2.11. J E-15 8.3.2.9 Quick Shear Test - Apply a con- fining pressure of 27.6 kPa (4 psi) to the specimen. Apply a load so as to produce an axial strain at a rate of 1 % per minute under a strain controlled loading procedure. Continue loading until either (~) the load values decree with Increasing strain, (2) 5 9` strain is reached or (3) the capacity of the load cell is reached. Data from the intemally mound deformation transducer In the actuator shaft and fonn the load cell shall be used to record specimen deformation and loads at a maximum of 3 second ~n~rvals. S.3.2. 10 At the completion of the biaxial shear test, reduce the confining pressure zero and remove Be sample from the tribal chamber. S.3.2. I} Remove Be membrane from Be specimen and use the entire specimen to determine moisture content in accordance with T265. 8.3.2. 12 Plot the stress-strain curve for the specimen for the biaxial shear test procedure. 8.4 Unconfined Resilient modulus Test for Cohesive Subgrade Soils - The unconfined repeated load ~ procure described in this section applies to all undisturbed or laboratory compact specimens of cohesive subgrade soils. These soils include specimens classified as Type 2 material (71 mm - 2.S in. or 102 mm - 4 in. diameter specimens). To be used in this test, Be specimen must have a plasticity index 2 10 and hold together during Be test. Also, We soil should exhibit stress softening characteristics (i.e., the resilient modulus
decreases with increasing deviator stress). Store compacted specimens, wrapped in Saran wrap and placed in a sealed container, for 2 days In a moisture room before testing. In this test, art unconfined specimen (S3=0) is first conditioned and then subjected to 5 levels of repeal axial loading. Solid end platens of aluminum steel are used. 8.4.1 Stiff to very stiff Specimens - For skiff and very skiff cohesive specimens (Su > 37.9 kPa; 750 psf3, actual deformation should preferably be measured either directly on the specimen or else between the solid end platens using grouted specimen ends. The symbol Su denotes the undrained shear strength of the soil. These stiff to very stiff specimens generally have a resilient modulus greater than 10,000 psi. If the specimen ends are not grouted, axial deformation measurement between end platens can still be performed. Following this less reliable approach, however, the measured resilient modulus must be empirically increased to account for die presence of irregular specimen end contacts. The empirical correction factors should be developed for each category of subgrade soil to be tested. To do this, use either specimens with grouted ends and top to bottom axial deformation measurement or specimens having axial deformation measurements made directly on them. 8.4.2 Soft Specimens - The axial deformation of soft subgrade soils (Su ~ 37.9 kPa; 750 psf) should not be measured using clamps placed on the specimen. If the measured resilient modulus is less than 69,000 lips (10,000 psi), axial deformation can be measured between the top and bottom platens. An empirical correction is not required for irregular specimen end contacts of these low moduli soils. If the resilient modulus is greater than 69,000 Lila (10,000 psi), follow the procedures given in 8.4. I. 8.4.3 Specimen End Grouting - All grouted test specimens shall be grouted to the top and bottom end platens using a Hydrostone paste (or equivalent) having a thickness no greater than 3.0 mm (0.12 in.~. The hydrostone paste allows adjustment of the level of the top cap and base pedestals to accommodate or eliminate any imperfections in the specimen end surfaces. The grout also helps to improve both the uniformity of the applied repeated stress and the accuracy of the deformation measurements of the specimen. 8.4.3.! The grout paste shall be prepared using potable water and hydrostone cement mixed in a (W/C) ratio of 0.40. Once the water is mixed with the grout, the hydration begins, with consistency rapidly obtained. A minimum of 120 min. is recommended as a curing time; this assures that the grout will be strong enough to withstand the applied stresses in the resilient modulus test without risking the accuracy and reliability of the measurements. 8.4.3.2 To expedite this operation, the grouting can be performed on a pedestal frame, similar to the one used in capping concrete cylinders, with additional steel caps that can be bolted to Me original end platens. Refer to Appendix G for detailed grouting procedures for specimen ends. 8.4.4 Assembly of Apparatus - Place the specimen wig end platens into position under the axial repeated loading device. Proper positioning of the specimen is extremely critical in applying a concentric load to the specimen. Couple the loading device to the specimen using a smooth steel ball. To center He specimen, slowly rotate the ball as the clearance between the load piston and E-16
ball decreases and a small amount of load is applied to the specimen. Be sure the ball is concentric with the piston which applies the load (watch the gap around the ball). Shift the specimen laterally to achieve a concentric loading. S.4.5 Insect Axial Displacement Devices - Carefully install the axial displacement instrumentation selected under S.4. ~ or 8.4.2. For top to bottom displacement men surement, attach Me LVDTs or proximity gages on steel or aluminum bars extending between the top and bottom platens. If an optical extensometer is to be used, attach the two targets directly to the specimen using at least two smaIt pins for each target. If clamps are used, place the clamps at the I/4 points of the specimen using two height gages to insure the clamps are positioned horizontally at the correct height. Each height gage can consist of two circular aluminum rods macliined to the correct length. These rods are placed on each side of He clamp to insure proper location. Then insure He displacement instrumentation is working properly by displacing each device and observing the resulting voltage output as shown by the data acquisition system. 8.4.6 Conduct Resilient Modulus Test - The following steps are required to conduct the unconfined resilient modulus test on a cohesive subgrade specimen placed in a loading frame as described in 8.4.4 and 8.4.5. 8.4.6.1 Conditioning - Apply a minimum of 200 repetitions of SOCK = 303 kPa (4 psi). The contact stress ScO',,ct shall be 6.9 kPa (! psi). Use a 0. ~ sec., haversine shaped load pulse with a 0.9 sec. rest period between pulses. If the vertical permanent strain reaches 5 % during conditioning, He test shall be terminated. 8.4.6.2 Eccentricity of Load - Minimizing eccentricity of the loading to an acceptable level is extremely important in resilient modulus testing. To do this, observe the output from the two independent measurement gages during conditioning. Then satisfy the requirements given in Note 9. An optical extensometer may be used with axial deformation being measured on only one side of the specimen. For this condition, set up two EVDTs or proximity gages between the top and bottom platens. 8.4.6.3 Specimen Testing - The resilient modulus test is performed using cyclic stresses Scyc,ic of 13.S, 27.6, 41.3, 55.1 and 68.9 kPa (2, 4, 6, ~ and 10 psi). For each deviator stress, apply 50 repetitions of loading using a contact stress (SCO'l - I) of 6.9 kPa (l psi). Since the confining pressure is zero, the principle stress (~) applied to the specimen equals (ScO~tac~l + Scyc~c ~ 8.4.6.4 Permanent Deformation Tests - Perform the rapid shear test as described in 8.3.2.9 except do not use a confining pressure. This test gives an indication of the tendency of the soil to undergo rutting. 8.5 Resilient Modulus Test for Base/ Subbase Materials - The procedure described in this section applies to ad unbound Granular base and subbase materials. This includes specimens classified as Type ~ or Type 2 material. 8.5. ~ Assembly of the Tnaxial Chamber Compact the specimen directly on the base of the biaxial cell. To reduce clogging of the porous disk, place a thin circular piece of filter paper on top of it. before compacting E-17
Table E-2. Testing Sequence for Granular Subgrade Materials Sequence Number , Confining Max. Axial Cyclic Stress Contact Stress Pressure, S3 Stress, Smax ScyCnc Sco~act kPa psi kPa psi kPa psi kPa psi 41.3 6 63.4 9.2 55.1 8 8.3 1.2 13.8 2 16.6 2.4 13.8 2 2.8 0.4 13.8 1 2 1 23.5 1 3.4 20.7 1 3 1 2.8 1 0.4 13.8 2 30.4 4.4 27.6 4 2.8 0.4 20.7 3 24.8 3.6 20.7 3 4.1 0.6 20.7 1 3 1 31.7 1 4.6 27.6 1 4 1 4.1 1 0.6 l 20.7 3 45.4 6.6 41.3 6 4.1 0.6 27.6 ~4 ~ 33.1 ~4.8 27.6 ~4 ~5.5 ~0.8 27.6 1 4 146.8 T6.S 41.3 T 6 T5.5TO.8 27.6 ~ 4 ~ 60.6 ~ 8.S 55.1 ~ 8 ~ 5.5 ~ 0.8 41.3 ~ 6 ~ 35.9 ~ 5.2 27.6 ~ 4 ~ 8.3 ~ 1.2 41.3 | 6 1 49 6 T 7 2 41.3 | 6 T 8.3 | 1.2 41.3 6 63.4 9.2 55.1 8 8.3 1.2 No. of Load Applications lo 500-1000 1 50 2 SO 3 50 1 4 50 5 50 6 SO 7 50 8 50 9 50 1 0 50 1 1 50 12 SO E-18
the sample. When compaction is complete, place a second piece of filter paper on top of the specimen, Men add a porous disc and top cap. For tests performed at or below optimum moisture content, a solid top platen, if desired, can be used to minimize system compliance. Roll the rubber membrane off the rim of the mold and over the sample cap. If the sample cap projects above the rim of the mold, the membrane should be sealed tightly against the cap with the Owing seal. If it does not, the seal can be applied later. Install the axial displacement measurement system and verify it is working correctly. Satisfy the requirements given in Note 9. 8.5.~.1 Connect the chamber pressure supply line and apply a confining pressure of 103.4 kPa (15 psi). 8.5.~.2 Remove the vacuum supply from the drainage inlet, and open the top and bottom cap drainage ports to atmospheric pressure. 8.5.2 Conduct the Resilient Modulus Test - After the test specimen has been prepared and placed In the loading device as described in 8.4. I, Me following steps are necessary to conduct the resilient modulus test: 8.5.2.1 If not already done, adjust the position of the biaxial chamber base support as necessary to couple the load-generation device piston and Me ~ al chamber piston. The tnaxial chamber piston should bear firmly on the load cell. The contact stresses shown in Table E-3 shall be maintained during the test. 8.5.2.2 Adjust as required the axial displacement measurement system, load cell and data acquisition system. 8.5.2.3 Conditioning - Set the confining pressure to 103.4 kPa (15 psi) and apply a minimum of 200 repetitions of a cyclic load (Scyc~c) equivalent to a 103.4 kPa (15 psi) cyclic axial stress. The contact stress shall be 20.7 Ma (3 psi). Use a haversine shaped load pulse consisting of a 0.1 sec. load followed by a 0.9 sec. rest period. If the sample is still decreasing in height at the end of the conditioning period, stress cycling shall be continued up to 1000 repetitions prior to testing. 8.5.2.3.! The foregoing stress sequence constitutes sample conditioning. That is simulating loading during construction and minimizing initial loading effects including seating and imperfection contact between the sample cap and base plate and the test specimen. The drainage valves on lines leading to the inside of the specimen should be open to atmospheric pressure throughout the resilient modulus test. 8.5.2.3.2 If the total vertical permanent strain reaches 5% during conditioning, the conditioning process shall be terminated. A review shall be conducted of the compaction process to identify any reason ks) why the sample might not have attained adequate compaction. If this review does not provide an explanation, the material shall be refabncated and tested a second time. If the sample again reaches 5!¢o total vertical permanent strain during conditioning, then the test shall be terminated and a notation added to the report form. 8.5.2.4 Specimen Testing - The resilient modulus test is performed following the loading sequences in Table E-3 using a haversine shaped load pulse as described above. Decrease the cyclic axial stress to 20.7 kPa (3 psi);and set the confining pressure to 20.7 kPa (3 psi); apply a contact stress of 4. ~ kPa (0.6 psi) (Sequence No. I, E-19
Table E-3. Testing sequence for base/subbase materials ~ Confinin 3 | Max.Axial | Cyclic Str' as| Contac~Suess ~ No. of Sequence Press ure, S3 Stress, Smax So ~ctic Scc knead Load No. kN/m2 psi kN/m2 ps' kN/m2 psi kN/m2 psi Applications 0 ~ 103.4 ~1 hi ~ 124.0 ~16.0 ~ 103.4 ~1 i ~20.7 ~30 ~200-1004 1 207.0 3 24.8 3.6 20.7 3 4.1 0.6 50 2 - 1 20.7 ~ : 145.5 ~6 6 1 41.3 ~1 4.1 ~06 r~50 _ 3 20.7 3 66.1 9.6 62.0 9 4.1 0.6 50 4 31.0 4.5 37.2 5.4 3t.0 4.5 6.2 0.9 50 5 31.0 4.5 68.2 9.9 62.0 9 6.2 0.9 50 6 31.0 4.5 99.2 1 4.4 93.0 1 3.5 6.2 0.9 50 7 41.3 6 49.6 7.2 41.3 6 8.3 1.2 50 . . 8 41.3 6 90.9 1 3.2 82.7 1 2 8.3 1.2 50 . 41.3 6 1 32.3 1 9.2 1 24.0 1 8 8.3 1.2 50 . 1 0 62.0 9 _ _74.4 1 0.8 62.0 9 1 2.4 1.8 50 1 1 62.0 1 36.4 1 9.8 1 24.0 1 8 1 2.4 1.8 50 . 1 2 62.0 . 9 1 98.4 28.8 1 86.0 27 1 2.4 1.8 50 1 3 96.5 1 4 81.3 1 1.8 62.0 9 1 9.3 2.8 50 1 4 96.5 1 4 1 1 5.8 1 6.8 96.5 1 4 1 9.3 2.8 50 l 1 5 96.5 1 4 212.2 30.8 1 92.9 28 1 9.3 2.8 50 E-2:0
Table E-3). 8.5.2.5 Apply 50 repetitions of the corresponding cyclic stress using a haversine shaped load pulse consisting of a 0. ~ second load pulse followed by a 0.9 second rest period. Record the average recovered axial deformations for each EVDT separately for the last five load cycles on the report form. 8.5.2.6 Continue with test Sequence No. 2 increasing the maximum cyclic stress to 41.3 kPa (6 psi) and repeat 8.5.2.5 at this new stress level. S.5.2.7 Continue the test for the remaining load sequences given in Table E-3 (sequences 3 to 15) recording the axial recovered deformation. If, at any time the axial permanent deformation exceeds 5 %, stop the test and report the results on the report form. 8.5.2.X Permanent Deformation Evaluation - Permanent deformation characteristics of a material are not evaluated when measuring the resilient modulus. Therefore, either the permanent deformation test (Step X.5.2.9) or the less reliable quick shear test (Step 8.5.2.10) must be performed to evaluate permanent deformation behavior which can be more impor ant Man We resilient modulus. After completion of the resilient modulus test, determine the total axial permanent strain that the specimen underwent during that test. The permanent deformation test (Section 8.5.2.9) can be performed if permanent strain is less than 0.5%. If the permanent strain did not exceed 5%, the quick shear test can be performed (Section 8.5.2. 10~. If permanent strain did not exceed 0.30%, the optional environmental moisture cycle MR test can be performed (Section 8.2.~.~. If the axial permanent strain exceeds 5 %, the test is complete. 8.5.2.9 Permanent Deformation Test - The permanent deformadon test is performed by continuing to apply cyclic load to the specimen after Me completion of the resilient modulus test. 8.5.2.9. ~ Immediately after completing test sequence number 15 (Table E-3), stop loading the specimen. Then apply a confining pressure to the specimen (S3) of 41.3 kPa (6 psi). Resume cycling the load using a cyclic axial stress (Scythe) of 120.00 kPa (~.0 psi) and contact stress (Scontac`) of 8.3 kPa (~.2 psi). Apply a total of 50,000 load repetitions measured from the beginning of the resilient modulus test. In addition to permanent deformations measured during the resilient modulus test, record the axial permanent deformation, measured between load pulses, at about 5,000, 10,000 and 50,000 repetitions. 8.5.2.9.2 To reduce the time required to perform this test, if desired, the time between load pulses can be reduced to 0.5 sec. To apply 50,000 load applications, the permanent deformation part of Me test can be ~ fed out using a pneumatic testing system after completing the resilient modulus test using a closed loop testing system. By applying one 0.1 sec. pulse every second using the pneumatic testing system, 50,000 repetitions can be applied to the specimen over night. 8.5.2.9.3 Make a plot of the permanent strain as a function of the log of number of load cycles for the specimen. On the plot indicate the soil type, degree of saturation and percent of TIED density of the specimen. 8.5.2.10 Quick Shear Test - The quick shear test can be performed as an alternative to the Permanent Deformation Test given in 8.4.2.9. Apply a confining pressure of 34.5 E-21
kPa (5 psi) to the specimen. Apply a load so as to produce an axial strain at a rate of ~ % per minute under a strain controlled loading procedure. Continue loading until either (~) the load decreases with increasing swain, (2) 5% strain is reached of (3) the capacity of the load cell is reached. Data from the internally deformation transducer in the actuator shaft and from the load cell can be used to record specimen deformation and load at a maximum of 3 second intervals. 8.5.2. 10. ~ Plot the rapid shear test stress- strain curve. 8.5.3 Remove the membrane from the specimen and use the entire specimen to determine moisture content in accordance with T265. 8.6 Modeling Environmental Moisture Cycle- An environmental moisture cycle test can, if desired, be performed before the permanent deformation or rapid shear test. A base/subbase in the field continually undergoes wetting and drying cycles which can cause the resilient modulus to change by more than 100%. To duplicate these effects, a single specimen can be tested at two or more different moisture conditions. First perform the resilient modulus test on the specimen in the as-compacted condition. Now increase Me water content to give the desired level of saturation by passing water through the specimen. Usually 88 to 95% saturation is adequate to indicate moisture sensi~v~`cy. Perform another resilient modulus test with all drainage lines open. Finally, dry the specimen to a low degree of saturation (usually less than about ~ %) and again test the specimen. The same specimen or a replicate can be tested at a high degree of saturation. Fit the data from each test to a resilient modulus model. Plot resilient modulus as a function of water content or degree of saturation for the stress state selected for design. The normal test procedures are followed for each resilient modulus test. 8.6. ~ Drying. Dry the specimen for 24 to 48 hours by placing the biaxial cell, with drainage lines open, in a room heated to between 41°C and 49°C (105°F - 120°F). To increase warm air circulation through the specimen and speed up drying, apply a vacuum of 51 mm (2 in.) of mercury to the lower drainage line of the specimen. Remove the biaxial cell from the high temperature and allow it to cool for at least 4 hours before testing. 8.6.2 Flushing Wig Water. Before flushing with water, use the bubble chamber to find and eliminate any air leaks in the system. Apply a 2.5 ft. static head of water measured to the center of the specimen. Introduce this water to the bottom of the specimen through the drainage line and allow it to exit the tnaxial cell from Me top platen drainage line. Pass water through the base/subbase specimen for 24 to 48 furs. before testing. Leave the drainage lines open and collect the water coming out of them as the specimen is tested. Estimate the degree of saturation using the measured water content at the end of the test and the quantity of water that flows from the specimen during testing. 9. Calculations 9.! Perform the calculations to obtain resilient modulus values using the tabular arrangement similar to Cat shown on Report Form XI. I. As indicated on the work sheet, the resilient modulus is computed for each of the last 5 cycles of each load sequence and then averaged. The data acquisition and data reduction processes should be fully automated to eliminate (or minimize) the E-22
chance for human error. 9.2 Fit, using regression techniques, the following resilient modulus mode! to the data obtained from test sequence I-15 (Table E-2 or Table E-3~: -r = K1 Scyc~K2 S3K3 ~-la) MR-SCYCIC/Cr ~-lb) where K1, K2 and K3 are the regression constants and the other terms are defined in Section 3. Give the constants Kit, K2 and K3 and the square of the correlation coefficient on Report Form X1. 1. Note lo: The following equation given in SHRP P46 (19963 can be used as an alternate to equation (E-la) and (E-Ib): MR = K 1 (scyc,ic) . ( 1 + S3) 10. Report 10. 1 The resilient modulus test report shall consist of the following: 10.1.1 Hard copy of Report Form X1.1. The acquisition system data used to generate this report, as well as the report, shall be stored on a computer diskette in ASCII format. 10.~.2 Report Form X1.2 (recompacted specimens) or Report Form X1.3 (thinwall tube specimens). 10.2 The following general information is to be recorded on all of the Report Forms: 10.2. ~ The specimen identification, the material type (hype ~ or Type 2) and test date. 10.3 Report the following information on the appropriate data sheet: ~ 10.3.1 Report Form X1.2 shall be used to record general information concerning the specimen being tested. This form shall be completed only for those specimens that are recompacted from bulk samples. This form shall not be used to record information for thinwall tube samples. 10.3. 1. 1 Item 4 - Record a "Y" (Yes) or "N" (No) to denote whether the sample reached 5% total vertical permanent strain during the conditioning stage of the test procedure (Sections 8.1.2.3 and 8.2.2.31. Also, note with a "Y" (Yes) or "N" (No) whether or not the sample reached 5 % total vertical permanent strain during the testing sequence. Record the number of test sequences completed, either partially or completely, for the given sample. 10.3.~.2 Item 5 - Record the specimen dimensions and perform the area and volume calculations. 10.3. 1.3 Item 6 - Record the compaction masses as outlined in Annex A2 (hype 1) or Annex AS (Type 2~. 10.3.~.4 Item 7 - Record the in-situ moisture content/density values used as He basis for compaction of the specimen as per sections 7.3. 1 and 7.3.2. These values were obtained from nuclear methods in the field. If these values are not available, record the optimum moisture content, maximum dry density and 95 % maximum dry density values used as the basis for compaction of the specimen as per section 7.3.3. 10.3.~.5 Item ~ - Record the moisture E-23
content of the compacted material as per section B3.16 of Annex A2 (type I) or section C3. 12 of Annex AS Type 2~. Record the moisture content of the material after the resilient modulus test as per section 8. I.3. ~ ~ (Subgrade3 or section X.4.3 (Base/ Subbase). Also, record the target density used for specimen recompaction. 10.3. ~ .6 Item 9 - Record the results and accompanying information for the quick- shear test procedure as per section 8.3.2.9 (Subgrade) or 8.4.2. 10 (Base/Subbase). 10.3.2 Report Form XI.3 shall be used to record general information concerning the specimen being tested. This form shall be complete only for thinwall tube specimens. This form shall not be used to record information for recompacted samples. 10.3.2. ~ Item 4 - Record the approximate distance from the top of the subgrade to the top of the specimen (if known). 10.3.2.2 Item 5 - Record a "Y" (Yes) or "N" (No) to denote whether the sample reached 5% total vertical permanent strain during the conditioning stage of the test procedure (Sections 8.3.2.3. ~ and 8.4.2.3.2~. Also, note with a "Y" (Yes) or "N" (Not whether or not the sample reached 5% total vertical permanent strain during the testing sequence. Record the number of test sequences completed, either partially or completely, for the given sample. 10.3.2.3 Item 6 - Record the specimen dimensions ant] perform the area and volume calculations. Record the mass of the specimen. 10.3.2.4 Item 7 - Record the moisture content (in-situ) prior to resilient modulus testing. Record the moisture content at the completion of resilient modulus testing as per section 8.1.2.12. Record the wet and dry density of the thinwall tube sample. 10.3.2.5 Item 8 - Record the results and accompanying information for the quick- shear test procedure as per section 8. 1.2. 10 (Subgrade). 10.3.3 Record the test data for each specimen In a format similar to Report Form X1 . 1 and attach with Report Form XI.2 or Report Form XI.3. The following information shall be recorded on Report Form X1.1: 10.3.3.1 Column 1 - Record the chamber confining pressure for the testing sequence. Only one entry need be made for the last five load cycles. This entry should correspond exactly with the confining pressure levels shown in Table E-2 (granular Subgrade3 or Table E-3 (Base/subbase). 10.3.3.2 Column 2 - Record the nominal axial cyclic stress for the testing sequence. Only one entry need be made for the last five load cycles. this entry should correspond exactly with the nominal axial cyclic stress required in Table E-2 (granular Subgrade3 or Table E-3 (Base/ subbase). 10.3.3.3 Column 4 Trough 9 - Record the actual applied loads and stresses for each of the last five load cycles as shown on the worksheet. 10.3.3.4 Columns 10 through 12 - Record the recoverable axial deformation of the sample for each EVDT independently for each of the last five load cycles. Average the response from the two EVDT's and record this value in column 12. This value will be used to calculate the axial strain of the material. E-24
10.3.3.5 Column 13 - Compute the axial strain for each of the last five load cycles. This value is computed by dividing column 12 by He original length of the specimen, L0 which was recorded on Report Form XI.2 (recompacted specimens) or Report Form XI.3 (thinned tube specimens). 10.3.3.6 Colunnn 14 - Compute He resilient modulus for each of He last five load cycles. This value is compute by dividing column by column 13. 10.3.3.7 Avenge - Compute the average of the last five load cycles for each column. 10.3.3.8 Standard Deviation - Compute the standard deviation of the values for each column for the las five load cycles using the equation: s =N AX - X)2 n-1 = 2_ (I X,.)2 n (n-l) 10.3.3.9 Summary Resilient Modulus - Calculate and report on Form XI. ~ a summary resilient modulus (MRR) using equation (E-la) and (E-Ib) of Section 9.2. For aggregate base/subbase materials calculate and report on this form the resilient modulus using the above equations for S3 35 1~/m2 (5 psi) and Scyc,ic = 103 kN/m2 (15 psi). For cohesionIess and low cohesion subgrade soils calculate and report the resilient modulus using equation (E-la) and (E-Ib) for S3 14 kN/m2 (2 psi) and Scyc,ic = 41 kN/m2 (6 psi). For cohesive subgrade soils report the resilient modulus for a deviator stress (Scyclic) equal to 41 kN/m2 (6 psi) and confining pressure (S3) equal to zero. E-25
~ 8 ~ &.,O, - r8 A` g o o Z . o z o A Z o - P: ~ ~ a\ Z ~ ~ e Us Us ~1 D| | - C~ 1 1 1 1 1 1 1 ~ ._ 8 _ l 1 1 11 1 1~ ~ - ·^ 1 ~ 1 ~ . I 1 1 11 A: A: - U, O Z ~e4 ~ ~ k U. Cal Z ~3 Z ~ CO ~ Cal O ~ O A) ~3 E_ · · · - ~ ~ U) \0 I' tie] ]'~t Il' a~' 10111 At; ~8 it ~ `8 t: `. _ ~. = . , 8~ 8- 8§ It E-26 on
AA~rO ~ Rat Modulus of Sub~de SolB ad Undated BY theta CRECOMp4~ ~ 1. S`WL~G DATE: 2. ~NU=ER -19 3. MAILERS mE ~pc 1 o: 1)pc 2) 4. TEST INFORMATION pREcoNDmo~G - GREATS IN S X PEW. ST1UIN? (Y - YES OR N ~ NO) lESTINO - GREATS DUN 5X PERM. SnUlN? (Y-YES OR lt ~ NO) MAESTRO - ~= OF w~ LACY m~ ~ 1 5. SPECIE INPO.: ~EC. DL'W., mm TOP ADDLE BOT1~01~S WAGE ~BR,WE UnC~ESS(I). ~ BRUCE ~BCKNESSO), mm NET DI - , mm HEIGHT OF SP&CI~1, CAP AND BASE, mm lIEIGHT OF CAP JWD BASE, mm INITIAL I=ro1H L. mm l~rnAL AREA, An, mm' INTEL VOLE, - , 6. SOD SPECIMEN OUGHT: INrllAL WEIGHT OF CONNER AD WET SOIL, Stems FOUL WEIGHT OF CONTAINER AND WET SOIL, WEIGHT OF WET SOIL USED, am 7. SOL PROPERllES: SmJ bSOISrURE COGENT (NUCL~), X ~ SI-I.U WET DENSITY (NUCLEAR), limp or OPTIMUM MOISTURE CONVICT, % MAX. DRY DENSITY, Dime 9SX ~X. DRY.DENSITY, 4t~ 8. SPEC~ PROPERTIES: COLON MOD Ad, X MOISTURE COST AFT RESET MODULUS IES1ING, COMPACIlON DRY DENSITY, at,, ~m, 9. QUICK SHEAR 1ESr SIRESS-S17~ PLOT ATrAC~ (Y ~ YES OR N ~ NO) 1R~AL SHEAR MAXIMUM S1~ENG IN ~X. LOADIX-SECllON AREA), ~ SPECIMEN Few DURING lRW~AL SHEAR? (Y ~ YES, to Is NO) 10. TEST DATE I 1. GENERAL REMARK: _ ESnED BY DATE Report Fonn X12 E-27 - 9t94
ALTO ~ Ram lUod~ of Q~c Sow "d Upton Wets M, - ~h (T~AI1~ TUBE SAMPLE ' 1. S~L~C] DANE: 2. S.W~;NU - ER - -19 3. CAL TYPE ~pc 1 or ~pc 2) 4. APPROX. DIST-CE FROM TOP OF St3BC]~DE TO SAMIB, m r 5. T=wINPO~TION PRECONDmO~C] - Cam 1RW 5X PERM. So? (Y ~ ~ OR ~ ~ NO) lESrlNG - GRBAT" 1~W SO PERM. SlRA~t (Y ~ YES OR N ~ NO) Isle - NUMBER OF MAD SEQUENCES COMPLETED (0 IS) 6. SPECWENINI:O.: SPEC. DL - ., no TOP ADDLE Saran AVERAGE CRANE l~CKNESS(l), ma R,ME ~CKNESS(2), mm ~ D1 - S. mm JNm,L L^GTYs As, LULL, A,, ~ JNITL.U, VOLUb'E, Am., it ~lllAL WF]G~, grams 7. SOL PROFIT: IN S1lU MoIsrurRE COt~NT, X bSOISIURE CONTEST ~ RESET MODULUS ll5SIINCI, % WET DENSITY, A,, tom, DRY DENSrlY, A,, ~~ 8. QUICK SHEAR TESr SIRESS-SIRAIN P~ AUAC~ ~-~ OR N-NO) CAL Sow MAXIMUM SrR~GlH ~X. LOADD`-SECDON At), ~ SPECIMEN Fob DURING 1RL~ SCAR? (Y - YES, ~ ~ NO) 9. TEST DATE 10. GENERAL Ram: . TESTED BY _ DATE RIEPORT PORM X1~3 E-28 gl94
ANNEX Al - Sample Preparation (Mandatory Information) Al.1 The following provides guidelines for reconstituting the material to be tested so as to produce a sufficient amount of material needed to prepare the appropriate sample type (Type ~ or Type 2 sample) at the designated moisture content and density. Al.~.! Sample Conditioning - If the sample is damp when received from the field, dry it until it becomes friable. Drying may be in air or by use of a drying apparatus such that the temperature does not exceed 60°C (140°F). Then thoroughly break up the aggregations in such a manner as to avoid reducing the natural size of individual particles. Moderate pressure using a rubber covered Implement to push the particles through a 4.75 mm (No. 4 sieve) has been found to be adequate to break down clay lumps. Al.~.2 Sample Preparation - Determine the moisture content twit of the sample as per T265. The mass of the sample for moisture determination shall weigh not less than 200 g for samples with a maximum particle size smaller than the 4.75 mm (No. 4) sieve and not less than SOO g for samples with a maximum particle size greater than the 4.75 mm (No. 4) sieve. Al. ~ .2. ~ Determine the appropriate total volume (V) of the compacted specimen to be prepared. The total volume must be based on a height of the compacted specimen slightly greater than that required for resilient testing to allow for trimming of the specimen ends if necessary. Compacting to a height/diameter ratio of 2. ~ to 2.2 will provide adequate material for this purpose. A1.~.2.2 Determine the mass of oven-dry soil solids (Ws) required to obtain the desired dry density (yg and moisture content (w) as follows: WS=453.5976V E-29 Ws = mass of oven-dry solids, g, ad = desired dry density, Ib/ft3, V = total volume of compacted specimen, ft3. Al.~.2.3 Determine the mass of the dried sample, (Wad), with the moisture content twit, required to obtain Ws plus an additional amount Was of at least SOO grams to provide material for the determination of moisture content at the time of compaction. Wail = (Ws + WaS) (1 + W,/IOO) where: Wad = Mass of sample at water content wit, g, Was = Mass of moisture content specimen (usually 500 g), g, W. = Water content of prepared material, percent. A. ~ . ~ .2.4 Determine the mass of water (Wang) required to change the water content from the existing water content, w,, to the desired compaction water content, w. Waw = (Ws + WaS)~(W ~ Wi)/IOO] where: Waw = Mass of water needed to obtain water content w, g, w = Desired water content of compacted material, percent. Al.~.2.5 Place a sample of mass Wad into a . mixmg pan. Al. 1.2.6 Add the mass of water (Waw), needed to change the water content from w, to w, to the sample in small amounts and mix thoroughly after each addition. Al.~.2.7 Place the mixture in a plastic bag. Seal the bag, place it in a second bag and seal it. Cure the sample for 16 to 48 hours, determine
the mass of the wet soil and container to the nearest gram and record this value on Report Form XI.2. Al. I.2.S The material is now ready for compaction. E-30
ANNEX Al - Sample Preparation (Mandatory Information) Al.! The following provides guidelines for reconstituting the material to be tested so as to produce a sufficient amount of material needed to prepare the appropriate sample type (Type ~ or Type 2 sample) at the designated moisture content and density. Al.~.1 Sample Conditioning - If the sample is damp when received from the field, ply it until it becomes friable. Drying may be in air or by use of a drying apparatus such that the temperature does notexceed60°C(140°F). Then thoroughly break up the aggregations in such a manner as to avoid reducing the natural size of individual particles. Moderate pressure using a rubber covered implement to push the particles through a 4.75 mm (No. 4 sieve) has been found to be adequate to break down clay lumps. A1.~.2 Sample Preparation - Determine the moisture content swig of the sample as per T265. The mass of the sample for moisture determination shall weigh not less than 200 g for samples with a maximum particle size smaller than the 4.75 mm (No. 4) sieve and not less than 500 g for samples with a maximum particle size greater than the 4.75 mm (No. 4) sieve. A1.1.2.! Determine the appropriate total volume (V) ofthe compacted specimen to be prepared. The total volume must be based on a height of the compacted specimen slightly greater than that required for resilient testing to allow for trimming of the specimen ends if necessary. Compacting to a height/diameter ratio of 2.1 to 2.2 will provide adequate material for this purpose. Al.1.2.2 Determine the mass of oven-dry soil solids (W) required to obtain the desired dry density cyst and moisture content (w) as follows: ws=453.59y,dV where: Ws = mass of oven-dry solids, g, E-31 Y,d - desired dry density, Ib/0c3, V = total volume of compacted specimen, id. Al. 1.2.3 Determine the mass ofthe dried sample, (Wad), with the moisture content (sy ), required to obtain Ws plus an additional amount Was of at least 500 grams to provide material for the determination of moisture content at the time of compaction. Wail = (Ws + WaS) (l + Wi/IOO) where: Wad = Mass of sample at water content wit, g, Was = Mass of moisture content specimen (usually 500 g), g, We = Water content of prepared material, percent. A.~.~.2.4 Determine the mass of water (Wang) required to change the water content from the existing water content, wit, to the desired compaction water content, w. Waw = (Ws + WaS)~(W ~ W,)/IOO] where: Waw = Mass of water needed to obtain water content w, g, w - Desired water content of compacted material, percent. Al.~.2.5 Place a sample ofmass Wad into a mixing pan. Al. 1.2.6 Add the mass of water (Waw), needed to change the water content from w, to w, to the sample in small amounts and mix thoroughly after each addition. Al.~.2.7 Place the mixture in a plastic bag. Seal the bag, place it in a second bag and seal it. Cure the sample for 16 to 48 hours, determine the mass of the wet soil and container to the nearest gram and record this value on RepoIt Form X! .2. Al.~.2.S The material is now ready for compaction.
ANNEX A2 - Compaction of Type 1 Soils (Mandatory Information) A2.1 Scope A2.~.! This method covers the compaction of Type ~ soils for use in resilient modulus testing. A2. I.2 Type ~ soils will be recompacted using a 152 mm (6.0 inch) split mold and vibratory compaction. Split molds with an inside diameter of 12 mm (6 inches) shall be used to prepare 305 mm (12 inch) high test samples for all Type ~ materials with nominal particle sizes less than or equal to 37.5 mm (l I/2 inches). The material greater than the 37.5 mm (1.5 inch) sieve shall be replaced by an equal quantity of material between 32 and 37.5 mm (1.25 - I.5 inches) in size prior to testing. A2. 1.3 CohesionIess soils shall be compacted in 6 lifts in a split mold mounted on the base of the biaxial cell as shown in Figure A2. 1. Compaction forces are generated by a vibratory impact hammer without kneading action powered by air or electricity and of sufficient size to provide the required laboratory densities while minimizing particle breakage and damage to the sample membrane. Use a special compaction head on the final lift to insure proper specimen alignment (Figure A2. 1 b). A2.2 Apparatus A2.2. 1 A split mold, with an inside diameter of 152 mm (6 inches) having a minimum height of 38 ~ mm (15 inches) (or a sufficient height to allow guidance of the compaction head for the final lift). A2.2.2 Vibratory Compaction Device - Vibratory compaction shall be provided using electric rotary or demolition hammers with a rated input of 750 to 1250 watts and capable of 1800 to 3000 blows per minute. A2.2.3 The compactor head shall be at least 25 mm (1 in.) thick and have a diameter of not less than 146 mm (5.75 in.~. A2~3 Procedure E-32 A2.3. ~ For removable platens, tighten the bottom platen into place on the biaxial cell base. It is essential that an airtight seal is obtained and that the bottom platen interface with the cell constitutes a rigidjoint. A2.3.2 Place the two porous stones and the top platen on the bottom platen. Determine the total height of the top and bottom platens and stones to the nearest 0.25 mm (0.01 inch). A2.3.3 Remove the top platen and porous disc if used. Measure the thickness of the rubber membrane with a micrometer. A2.3.4 Place the rubber membrane over the bottom platen and lower porous disc. Secure the membrane to the bottom platen using an O-ring or other means to obtain an airtight seal. A2.3.5 Place the split mold around the bottom platen and draw the membrane up through the mold. Tighten the split mold firmly in place. Exercise care to avoid pinchingthe membrane. During equipment calibration, insure by indexing with a dial indicator that the top ofthe mold is parallel to the base ofthe biaxial cell. A2.3.6 Stretch the membrane tightly over the rim ofthe mold. Apply a vacuum to the mold sufficient to draw the membrane in contact with the mold. If wrinkles are present in the membrane, release the vacuum, adjust the membrane and reapply the vacuum. The use ofa porous plastic tormingjacket liner helps to ensure that the membrane fits smoothly inside the mold. The vacuum is maintained throughout the compaction procedure.
777 74/ - - ~ Mold (b) Recommended head for final compaction vet Low Get Rubber htemb~ - Alun~wm or Stool- Spat Sample Mdd Porous ~ffC cod ~. C~or Head beacon ~ r udd Cramp 1 , 1 11 Bee Disc or See ~4 non max Ida) p2s'~) ~ __1 -i ll ' 1 H 8atom PI (a) Compaction Mold Assembly Compacdon Head Chat at ~ As. m leg ~ Figure A2.~. Typical apparatus for vibratory compaction of Type 1 unbound materials A2.3.7 Measure, to the nearest 0.2S mm (0.01 inch), the inside diameter of the membrane lined E-33 mold and the distance between the top ofthe lower porous stone and the top of the mold.
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
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.
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
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
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
(( ~ 2291 ) she ~'b'9~ - Hote: S.D. - Spat DIa~ -Is Shan be See Sted orange ~ Seth) I-D. ~ 8.D. ~ 71.1 men Am) 71.1 mn~l.D. 1 Booth, 7~7 ~ ~10, O.D.I ~ oobr 7t.t mrn ~ I.D. 7~7 - #A ~10 - 60 OLD. 81 t~20- S.SO ) No - : 1` ~ng ~ d den . 1~ m" nry duo ~ a~labJ~ ~ them paw h ~ buy. NOT TO STALE _~ Dla - - .9 mm ~7~ en, ~7 ~ 76 i 1 1 l l 1 1 1. t I 1 1 . add (1) Red ~7~ AS 1 - ma H | Spew no EN Ram (1) Rid ' 1 203. 22S' mm i, oh - - .. ~ ~ - Specer ·P". Needed H - D~dons ~ dumn on F~6-9or" 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
steppes Lifts: COIT pardon ~tO be solid c~lodere of speckled heath' and 70.' mm (2.7~ dear. .. . ~ 2x.~:. ............... ...... . * ..... ......... ........ .......... ........... . . ........... s ~ .. .. ....... .............. ......... ......... . . . ........... ...... ....... ............ .......... ............. ............ ............. ............. ........... ............. . ..... .... .... . . .. .~.~. 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
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
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
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
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