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

The cyclic test for the determination of resilient modulus ( MR) is often too complex and time-consuming to be applicable on a production basis. Therefore, the development of a simple and reliable alternative MR testing tech- nique is essential for the application in the mechanistic design of a flexible pavement system. Seven disturbed subbase soils were collected from the actual pavement projects for testing. To evaluate the effect of particle size on MR, stan- dard MR tests with various maximum particle sizes and specimen diameters were performed using three subbase soils. The resilient moduli determined from various specimen sizes with the same particle-size distribution were almost iden - tical. However, the value of the slope parameter k2 in the bulk stress model was constant, but the value of k1 increased with a decrease in maximum particle size. The effects of mean effective stress, loading frequency, and number of load- ing cycles on modulus were evaluated from torsional shear (TS), triaxial (TX), and MR tests. The alternative MR testing procedure using the static TX test was proposed considering deformational characteristics of subbase soils. The pre - dicted MR values from the proposed method matched well with those determined by the standard MR test, showing the capability of the proposed method for determining MR.