Response of saturated cohesionless soil subjected to irregular seismic excitations

Irregular stress waves generated during an earthquake induce irregular shear stresses in the soil, which affect the dynamic behaviour of soil significantly. Laboratory investigations on the response of soils during real earthquake scenario are very limited. This paper reports about the response of saturated sandy soils subjected to irregular cyclic stress histories using stress-controlled cyclic triaxial tests. Tests were conducted at different relative densities (30–90%) and confining stresses (50–150 kPa) representing varying compactness of soil obtained from different confining depths. Cyclic loading was applied as per the three different earthquake motions considered having different peak ground accelerations (PGAs). The responses are presented in terms of stress–strain variations, excess pore-water pressure ratio and shear strain accumulation in the soil specimen. The results indicated that the accumulated shear strains and excess pore-water pressures get significantly affected by the increase in confining stress and simultaneous changes in the relative density. Further, the study emphasized that the strong motions scaled to the same PGA levels produce substantially differing soil responses due to the variation in the associated strong-motion parameters.