Alternative method of determining resilient modulus of subgrade soils using a static triaxial test

The resilient moduli (M-R) of subgrade and subbase soils are very important properties in the analysis and design of a flexible pavement system. However, difficulties and complexities in performing cyclic M-R testing and the high cost of the testing system have prevented the cyclic M-R test from becoming a routine test. Therefore, the development of an alternative simple and reliable M-R testing technique is essential to the application of the mechanistic design of a flexible pavement system. In this study, an alternative M-R testing technique for subgrade soils was developed using a static triaxial compression (TX) test. For the development of the alternative testing method, the effects of strain amplitude, loading frequency, mean effective stress, and number of loading cycles on the resilient modulus of subgrade soils were fully investigated. Cyclic M-R, static TX, and resonant column - torsional shear tests were performed to evaluate the deformational characteristics. Synthetic specimens of known stiffnesses ranging from those of soft subgrade soils to those of subbase materials were developed, and all of the testing systems used in this study were calibrated. The alternative M-R testing procedures were proposed considering deformational characteristics of subgrade soils. The reliability of the proposed test method was verified by comparing the moduli determined by the proposed alternative M-R testing method with those determined by the standard M-R tests.