地震动持时对可液化场地管道上浮反应影响分析

Influence of ground motion duration on the seismic uplift response of buried pipe in liquefiable site

地震作用下可液化场地埋地管道易发生上浮破坏。为分析地震动持时对管道上浮反应的影响,首先采用谱匹配方法选取具有一致谱形的长短持时地震动,然后基于OpenSees软件开展二维动力响应分析,从管道上浮位移和土体液化严重程度两个方面分析并量化地震动持时的影响,同时分析了与持时相关的地震动强度参数与管道上浮位移的相关性。结果表明:地震动持时对土体液化和管道上浮影响显著。长持时地震动作用下土体液化持续时间约为短持时地震动作用下液化持续时间的2~3倍,其管道上浮位移均值约为短持时地震动作用下的2~2.5倍。以超孔压比大于等于0.8为标准的土体液化持续时间可较好反映地震动持时对管道上浮反应的影响。此外,累积绝对速度CAV可优先作为用于管道上浮破坏风险评价的地震动强度参数。

Pipes buried in liquefiable sites would be damaged from uplift response subjected to seismic shaking.To quantitatively investigate the influence of ground motion duration on the seismic uplift response of pipes,longer-duration and shorter-duration ground motion records with consistent spectral shape are selected by the spectral-equivalent method.Two-dimensional dynamic response analyses are then carried out based on OpenSees.The influence of ground-motion duration is analyzed from the aspects of soil liquefaction severity degree and uplift displacements.Correlation analyses are also conducted between several duration-related ground motion intensity measures(IMs)and the resultant uplift displacements.Comparative results indicate that the influence of duration on soil liquefaction and pipe uplift is significant.Using the selected longer-duration ground motion suits,the mean duration of soil liquefaction and the mean uplift displacement of pipes are increased to 3 and 2.5 times,respectively.The duration of soil liquefaction defined by metric of excess pore pressure ratio greater than or equal to 0.8 can reflect the effect of duration on uplift response of pipes.In addition,cumulative absolute velocity can be used as a promising IM for the risk assessment of uplift-induced damage of pipelines.