Cyclic deformation behavior of soft clay subjected to mainshock-aftershock sequence loading

Sequential earthquakes can cause incremental damage to underground structures and surrounding soils. It is necessary to investigate the dynamic behavior of soil under mainshock and aftershock loading. In this study, the mainshock-aftershock sequence is converted into equivalent loading under varying maximum accelerations. The recovery of effective stress is controlled to achieve varying levels of reconsolidation. A series of cyclic simple shear tests are performed to study the influence of reconsolidation degree on cyclic deformation behavior. The cyclic shear strain increased from 3.58% to 5.92% under the two-stage aftershock loading of 31.7 kPa without reconsolidation, exhibiting a destructive growth trend. As the degree of reconsolidation U increases from 50% to 100%, the reduction of effective stress and the growth of shear strain are significantly suppressed. However, the dissipation rate of the effective stress accelerates, and the reconsolidation strain exhibits a marked increase. OCR_eq (equivalent overconsolidation ratio) shows a linear relationship with the cyclic strain. The incremental deformation induced by aftershock loading increases with OCR_eq.