主余震序列荷载作用下软黏土循环变形特性试验研究

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

    • 摘要: 考虑到主余型地震诱发地下结构及周围土体产生增量损伤的风险,有必要探究主余震荷载作用下土体的动力特性。本文将主余震序列转化为不同峰值加速度对应的等效主余震序列荷载,并通过控制有效应力的恢复量实现不同再固结度;采用循环单剪试验研究了主余震序列荷载作用下再固结程度对软黏土变形特性的影响。研究表明,未经历再固结时,循环剪应变在两阶段31.7 kPa余震荷载作用下由3.58%发展至5.92%,呈现出破坏型增长的趋势;再固结程度由50%增大至100%后,有效应力的下降程度和循环剪应变的发展受到显著的抑制;但有效应力衰减速率加快且再固结应变增长明显;等效超固结比与循环剪应变呈现线性关系,等效超固结比增大会加剧余震荷载诱发的增量变形。

       

      Abstract: 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. OCReq (equivalent overconsolidation ratio) shows a linear relationship with the cyclic strain. The incremental deformation induced by aftershock loading increases with OCReq.

       

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