Elasto-plastic Behavior of Sandy Soil under Cyclic Loading Conditions

The number of loading cycle, amplitude and frequency are the important factors that affect the elasto-plastic behavior of a granular soil under cyclic loading conditions. Studies found in the literature are mainly based on the behavior of resilient modulus and cumulative permanent strain. However, studies regarding the modulus of elasticity in the unloading and reloading phase, the permanent strain and their variation with number of load cycles are rather limited in the literature. In this study, an attempt was made to investigate the elastic and plastic responses of a dense sandy soil by conducting laboratory cyclic load triaxial tests with different combinations of confining pressures and loading amplitudes. Based on the test results, the unloading and reloading modulus were calculated separately for each cycle and observed their behavior with respect to the number of load cycles. To predict permanent strain behavior, a relatively simple equation was proposed. The test results showed that, for a particular combination of confining pressure and loading amplitude, the unloading modulus was almost consistent with respect to the number of load cycles. Similar observation, with a lower value than unloading modulus for the corresponding tests, was found for reloading modulus. The proposed equation for the permanent strain was used to calculate the cumulative permanent strain values at any number of load cycles. The calculated results agreed well with the experimental results.