INFLUENCE OF TESTING PROCEDURE AND LVDT LOCATION ON RESILIENT MODULUS OF SOILS

Several transportation agencies use the AASHTO-recommended resilient modulus as the fundamental parameter in the mechanistic analysis and design of pavements. At present there are several types of dynamic testing devices calibrated to measure resilient modulus. The repeated triaxial device is popular because of its repeatability, reliability, and ease of operation. Testing procedures and internal deformation measurements play a crucial role in testing. A statistically designed experiment was used to compare the influence of these factors. Two testing procedures, AASHTO T-294-1992 and AASHTO T-292-1991, were evaluated, and two separate measurement systems inside the triaxial cell were used to measure the axial deformations. Both cohesive and granular soils were tested. The influence of testing procedures and measurement systems are presented in the form of normalized factors, which are discussed with respect to the test variables and confining and deviatoric stresses. The testing procedure appears to influence test results for sand specimens, possibly due to the variation in magnitudes of testing stresses. The measurement system has a greater influence on clay specimens due to a combination of several factors such as soil fabric, stress dependency behavior, and end friction effects. The type of soil, testing procedures, and location of the internal, linear variable differential transformers and their influence on the regression model constants are discussed and graphically presented.