近断层滑冲效应脉冲地震动对场地液化的影响

利用开源有限元平台OpenSees，建立一个20 m长的土柱模拟自由场地的地震响应.通过分析近断层滑冲效应脉冲地震动作用下场地产生的变形、应力，结合其地震动持时，衡量滑冲效应脉冲地震动对场地液化的影响.研究表明，滑冲效应脉冲地震动由于其独特的脉冲特性，较无脉冲地震动使土柱产生更大的孔隙水压力比、循环应力比，相应的等效循环周数值也较大，这三方面共同增大了场地发生液化的可能性.滑冲效应脉冲地震动产生的高孔压持续时间较短，使液化后的变形量较小.
Abstract: A soil column of 20 m was established to simulate the seismic responses of free site by using the open source finite element software OpenSees. Then the influence of fling-step effect on site liquefaction was evaluated by the stress and strain induced in the soil column, coupling with the collected ground motion duration of each simulation. Results show that the ground motion with fling-step effect is more likely to induce larger pore water pressure ratio and cycle stress ratio than non-pulse ground motions due to its special pulse characteristics. Besides, the ground motion with fling-step effect could generate higher number of equivalent cycles in comparison to the non-pulse motions. All these factors increase the occurrence of site liquefaction and cause a larger permanent vertical deformation. However, the ground motion with fling-step effect induced high pore pressure duration is relatively limited, which is detrimental to the liquefaction deformation.