1、Standard Method of Test for Determining the Resilient Modulus of Soils and Aggregate Materials AASHTO Designation: T 307-99 (2012)1American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1a T 307-1 AASHTO Standard Method o
2、f Test for Determining the Resilient Modulus of Soils and Aggregate Materials AASHTO Designation: T 307-99 (2012)11. SCOPE 1.1. This method covers procedures for preparing and testing untreated subgrade soils and untreated base/subbase materials for determination of resilient modulus (Mr) under cond
3、itions representing a simulation of the physical conditions and stress states of materials beneath flexible pavements subjected to moving wheel loads. 1.2. The methods described are applicable to undisturbed samples of natural and compacted subgrade soils, and to disturbed samples of subgrade soils
4、and untreated base/subbase prepared for testing by compaction in the laboratory. 1.3. In this method, stress levels used for testing specimens for resilient modulus are based upon the location of the specimen within the pavement structure. Samples located within the base and subbase are subjected to
5、 different stress levels as compared to those specimens that are from the subgrade. Generally, specimen size for testing depends upon the type of material based upon the gradation and the plastic limit of the material as described in a later section. 1.4. The value of resilient modulus determined fr
6、om this procedure is a measure of the elastic modulus of untreated base and subbase materials and subgrade soils recognizing certain nonlinear characteristics. 1.5. Resilient modulus values can be used with structural response analysis models to calculate the pavement structural response to wheel lo
7、ads, and with pavement design procedures to design pavement structures. 1.6. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard t
8、o consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Note 1Test specimens and equipment described in this method may be used to obtain other useful and related information such as the Poissons ratio and rutting charac
9、teristics of subgrade soils and base/subbase materials. Procedures for obtaining these are not covered in this standard. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: T 88, Particle Size Analysis of Soils T 89, Determining the Liquid Limit of Soils T 90, Determining the Plastic Limit and Plasticity
10、 Index of Soils T 99, Moisture-Density Relations of Soils Using a 2.5-kg (5.5-lb) Rammer and a 305-mm (12-in.) Drop 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 307-2 AASHTO T 100, Specific Gr
11、avity of Soils T 180, Moisture-Density Relations of Soils Using a 4.54-kg (10-lb) Rammer and a 457-mm (18-in.) Drop T 190, Resistance R-Value and Expansion Pressure of Compacted Soils T 191, Density of Soil In-Place by the Sand-Cone Method T 233, Density of Soil In-Place by Block, Chunk, or Core Sam
12、pling T 265, Laboratory Determination of Moisture Content of Soils T 296, Unconsolidated, Undrained Compressive Strength of Cohesive Soils in Triaxial Compression T 310, In-Place Density and Moisture Content of Soil and Soil-Aggregate by Nuclear Methods (Shallow Depth) 2.2. IEEE/ASTM Standard: SI10,
13、 American National Standard for Metric Practice 3. TERMINOLOGY 3.1. untreated granular base and subbase materialsthese include soil-aggregate mixtures and naturally occurring materials. No binding or stabilizing agent is used to prepare untreated granular base or subbase layers. These materials may
14、be classified as either Type 1 or Type 2 as subsequently defined in Sections 3.3 and 3.4. 3.2. subgradesubgrade soils are prepared and compacted before the placement of subbase and/or base layers. These materials may be classified as either Type 1 or Type 2 as subsequently defined in Sections 3.3 an
15、d 3.4. 3.3. Material Type 1for the purposes of resilient modulus testing, Material Type I includes all untreated granular base and subbase material and all untreated subgrade soils that meet the criteria of less than 70 percent passing the 2.00-mm (No. 10) sieve and less than 20 percent passing the
16、75-m (No. 200) sieve, and that have a plasticity index of 10 or less. Soils classified as Type 1 will be molded in a 150-mm diameter mold. 3.4. Material Type 2for the purpose of resilient modulus testing, Material Type 2 includes all untreated granular base/subbase and untreated subgrade soils not m
17、eeting the criteria for material Type 1 given in Section 3.3. Thin-walled tube samples of untreated subgrade soils fall into this Type 2 category. 3.5. resilient modulus of untreated materialsthe modulus of an untreated material is determined by repeated load triaxial compression tests on test speci
18、mens of the untreated material samples. Resilient modulus (Mr) is the ratio of the amplitude of the repeated axial stress to the amplitude of the resultant recoverable axial strain. 3.6. haversine-shaped load formthe required load pulse form. The load pulse is in the form (1 cos )/2 as shown in Figu
19、re 1. 3.7. maximum applied axial load (Pmax)the total load applied to the sample, including the contact and cyclic (resilient) loads. Pmax= Pcontact+ Pcyclic(1) 3.8. contact load (Pcontact)vertical load placed on the specimen to maintain a positive contact between the specimen cap and the specimen.
20、Pcontact= 0.1Pmax(2) 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 307-3 AASHTO Figure 1Definition of Resilient Modulus Terms Cyclic Axial Load (Resilient Vertical Load, Pcyclic) Repetitive Loa
21、d Applied to a Test Specimen Pcyclic= Pmax Pcontact(3)3.9. maximum applied axial stress (Smax)the total stress applied to the sample including the contact stress and the cyclic (resilient) stress. Smax= Pmax/A (4) where: A = initial cross-sectional area of the specimen. 3.10. cyclic axial stress (re
22、silient stress, Scyclic)Cyclic (resilient) applied axial stress. Scyclic= Pcyclic /A (5) 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 307-4 AASHTO 3.11. contact stress (Scontact)axial stress a
23、pplied to a test specimen to maintain a positive contact between the specimen cap and the specimen. Scontact= Pcontact /A (6) Also, Scontact= 0.1Smax(7) 3.12. S3is the total radial stress; that is, the applied confining pressure in the triaxial chamber (minor principal stress). 3.13. eris the resili
24、ent (recovered) axial deformation due to Scyclic. 3.14. ris the resilient (recovered) axial strain due to Scyclic. r= er/L (8) where: L = original specimen length. 3.15. Resilient modulus (Mr) is defined as Scyclic /r. 3.16. Load duration is the time interval the specimen is subjected to a cyclic st
25、ress (usually 0.1 s). 3.17. Cycle duration is the time interval between the successive applications of a cyclic stress (usually 1.0 to 3.1 s, depending on type of loading device; see Section 6.2). 4. SUMMARY OF METHOD 4.1. A repeated axial cyclic stress of fixed magnitude, load duration (0.1 s), and
26、 cycle duration (1.0 to 3.1 s) is applied to a cylindrical test specimen. During testing, the specimen is subjected to a dynamic cyclic stress and a static-confining stress provided by means of a triaxial pressure chamber. The total resilient (recoverable) axial deformation response of the specimen
27、is measured and used to calculate the resilient modulus. 5. SIGNIFICANCE AND USE 5.1. The resilient modulus test provides a basic relationship between stress and deformation of pavement materials for the structural analysis of layered pavement systems. 5.2. The resilient modulus test provides a mean
28、s of characterizing pavement construction materials, including subgrade soils, under a variety of conditions (i.e., moisture, density) and stress states that simulate the conditions in a pavement subjected to moving wheel loads. 6. APPARATUS 6.1. Triaxial Pressure ChamberThe pressure chamber is used
29、 to contain the test specimen and the confining fluid during the test. A typical triaxial chamber suitable for use in resilient testing of soils is shown in Figure 2. The deformation is measured externally with two spring-loaded linear variable differential transducers (LVDT) as shown in Figure 2. 2
30、015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 307-5 AASHTO Note: LVDT tips shall rest on the triaxial cell itself or on a plate/bracket that is rigidly attached to the triaxial cell. Figure 2Typ
31、ical Triaxial Chamber with Eternal LVDTs and Load Cell (not to scale) 6.1.1. Air shall be used in the triaxial chamber as the confining fluid. 6.1.2. The chamber shall be made of polycarbonate, acrylic or other suitable “see through” material to facilitate the observation of the specimen during test
32、ing. 6.2. Loading DeviceThe loading device shall be a top-loading, closed loop, electrohydraulic or electropneumatic testing machine with a function generator that is capable of applying repeated cycles of haversine-shaped load pulse of the following durations. Type of Loading Device Load Pulse (s)
33、Rest Period (s) Pneumatic 0.1 0.9 to 3.0 Hydraulic 0.1 0.9 Repeated Load ActuatorLoad CellChamber Piston Rod13-mm min. dia. forType 2 SoilsLVDTCell Pressure InletCover PlateChamber(lexan or acrylic)Tie RodsSpecimen BaseVacuum InletBall Seat (divot)Steel Ball51 mm max.LVDT Solid BracketThompson Ball
34、BushingO-Ring SealsSample CapPorous Bronze Discor Porous StoneFilter PaperSpecimen MembraneSpecimenFilter PaperPorous bronze discor porous stoneBase PlateVacuum InletSection View38-mm min. dia. forType 1 SoilsSolid Base 2015 by the American Association of State Highway and Transportation Officials.A
35、ll rights reserved. Duplication is a violation of applicable law.TS-1a T 307-6 AASHTO 6.2.1. The haversine-shaped load pulse shall conform to Section 3.6. All preconditioning and testing shall be conducted using a haversine-shaped load pulse. The system-generated haversine waveform and the response
36、waveform shall be displayed to allow the operator to adjust the gains to ensure that they coincide during preconditioning and testing. 6.3. Load and Specimen Response Measuring Equipment: 6.3.1. The axial load-measuring device should be an electronic load cell located between the actuator and the ch
37、amber piston rod as shown in Figure 2. The following load-cell capacities are required: Specimen Dia. (mm) Max. Load Cap. (kN) Req. Accuracy (N) 71 2.2 4.5 100 8.0 10.0 152 22.24 22.24 The above requirements for load capacity and accuracy are approximately linear when plotted versus specimen cross-s
38、ectional area. Requirements for load cells used with other specimen diameters should be approximately on the same linear relationships. Note 2During periods of resilient modulus testing, the load cell shall be monitored and checked once every 2 weeks or after every 50 resilient modulus tests with a
39、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 the original load cell to ensure accurate loadings. Additionally, the load cell shall be ch
40、ecked at any time if the laboratorys in-house QA/QC testing indicates noncompliance or 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 or if the load cell does not meet the manufacturers tolerance r
41、equirements stated above for accuracy, whichever of the two is of the higher accuracy. 6.3.2. Test chamber pressures shall be monitored with conventional pressure gages, manometers, or pressure transducers accurate to 0.7 kPa. 6.3.3. Axial DeformationMeasuring system for all materials shall consist
42、of 2 LVDTs fixed to opposite sides of the piston rod outside the test chamber as shown in Figure 2. These two transducers shall be located equidistant from the piston rod and shall bear on hard, fixed surfaces, which are perpendicular to the LVDT axis. Spring-loaded LVDTs are required. The following
43、 LVDT ranges are required: Specimen Dia. (mm) Range (mm) 71 1 100 2.5 152 6 Both LVDTs shall meet the following minimum specifications: Linearity, 0.25 percent of full scale Repeatability, 1 percent of full scale Minimum Sensitivity, 2 mv/v (AC) or 5 mv/v (DC) The above requirement for range is appr
44、oximately linear when plotted versus specimen cross-sectional area. Requirements for LVDTs used with other specimen diameters are approximately on the same linear relationships. A digital or other type of deformation measurement system with equivalent linearity and repeatability specifications may b
45、e used in place of LVDTs. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1a T 307-7 AASHTO 6.3.3.1. A positive contact between the vertical LVDTs and the surface on which the tips of the transducers
46、rest shall always be maintained during the test procedure. In addition, the two LVDTs shall be wired so that each transducer can be read and reviewed independently and the results averaged for calculation purposes. Note 3Misalignment or dirt on the shaft of the transducer can cause the “sticking” of
47、 the shafts of the LVDT. The laboratory technician shall depress and release each LVDT prior to each test to assure that there is no sticking. An acceptable cleaner/lubricant (as specified by the manufacturer) shall be applied to the transducer shafts on a regular basis. 6.3.3.2. The response of the
48、 LVDTs shall be checked daily with the laboratorys in-house QA/QC program. Additionally, the LVDTs shall be calibrated every 2 weeks, or after every 50 resilient modulus tests, whichever comes first, using a micrometer with compatible resolution or a set of specially machined gauge blocks. Resilient
49、 modulus testing shall not be conducted if the LVDTs do not meet the manufacturers tolerance requirements for accuracy. 6.3.4. Suitable signal excitation, conditioning, and recording equipment are required for simultaneous recording of axial load and deformations. The signal shall be clean and free of noise. Use shielded cables for connections. If a filter is used, it shall have a frequency that cannot attenuate the signal. The LVDTs shall be wired separately so each LVDT signal can be monitored independently.
