近断层速度脉冲地震动对边坡滑移的影响分析

SLIDING DISPLACEMENTS OF SLOPES UNDER NEAR-FAULT PULSE-LIKE GROUND MOTIONS

采用基于小波变换的多向地震动速度脉冲特性鉴定方法,从NGA(next generation attenuation)数据库及汶川地震动记录中选取196条速度脉冲地震动;基于Newmark非耦合滑动模型,考虑土体动力非线性,通过对比近断层脉冲及非脉冲地震动引起的不同参数边坡的滑移特征,分析近断层地震动速度脉冲特性及边坡本身参数对滑动位移值的影响;同时对近断层速度脉冲地震动参数与边坡滑移量的相关性做了对比分析。结果表明:(1)近断层速度脉冲地震动引起的边坡滑动位移值远大于近断层非脉冲地震动,对长周期边坡影响尤为明显;(2)相比非脉冲地震动,脉冲地震动引起的边坡滑动时间较短,且主要发生在地震动起始阶段的较短时间内(速度脉冲段),滑移的坡体具有更大的滑移速度,携带更高的能量,从而对周边环境产生更强的破坏作用;(3)近断层速度脉冲地震动引起的边坡滑移特征与其速度脉冲特性(持时短、周期长、速度峰值大)密切相关,且峰值地震动速度PGV与边坡滑移量具有高度相关性。最后,通过比较原始速度脉冲地震动及相应的等效脉冲作用下不同参数边坡的滑动位移值,对提取出的等效脉冲预测原始地震动引起的滑动位移的有效性进行分析,并基于此建立脉冲参数–滑动位移曲面。

Based on the procedure to identify velocity pulse for multi-component ground motions,196 ground motions from NGA（next generation attenuation） database and Wenchuan earthquake are classified as pulse-like ground motions. Newmark decoupled method considering the nonlinear soil property is used to compare the sliding displacements of slopes caused by near-fault pulse-like and non-pulse-like ground motions. Effects of pulse characteristics and slope parameters on sliding displacement are analyzed;and the efficiency of different pulse-like ground motion parameters for predicting the displacement is also investigated. The analyses indicate that the near-fault pulse-like ground motions result in much larger displacement than non-pulse-like ground motions,especially significant effect on long-period slopes. Also,displacements induced by pulse-like ground motion commonly have shorter duration and larger sliding velocity compared with non-pulse-like ground motion. It is shown that sliding displacement characteristics caused by pulse-like ground motion are closely related to its velocity-pulse feature,and peak ground velocity is the most efficient parameter for predicting sliding displacement. The effectiveness of the equivalent wavelet pulse on representing the original pulse-like ground motions in terms＆amp;nbsp;of sliding displacement value is investigated. Finally,sliding displacements of slope to pulse-like ground motions is summarized in terms of a response surface.