Dynamic behaviour of Kutch soils under cyclic triaxial and cyclic simple shear testing conditions

The dynamic behaviour of soils from Kutch (seismically active region of Gujarat, India) was explored under cyclic triaxial (CTX) and cyclic simple shear (CSS) testing conditions. Under both the CTX and CSS conditions, the soil specimens exhibited cyclic strength that decreased rapidly at lower plasticity index and lower fines content. The reduction in cyclic strength was evaluated to be higher and faster for the clayey-sand specimens as compared to clayey specimens. Specimens with low plasticity index and lower fines content showed higher pore pressure response in both CTX and CSS tests. Pore pressure ratio under CSS conditions was observed to be higher as compared to CTX conditions. Degradation in shear modulus was found to be higher and quicker for clayey-sand specimens as compared to clayey specimens. Degradation index increased with plasticity index and fines content at a given number of loading cycles under both CSS and CTX conditions.