空间变异液化夹层位置对盾构隧道地震响应影响规律研究

Study on the Influence of Spatial Variation Liquefaction Interlayer Location on Seismic Response of Shield Tunnel

基于随机场理论,在考虑土体剪切模量空间变异性的基础上,采用数值模拟方法研究了液化夹层与盾构隧道的相对位置变化对隧道和土体地震响应的影响规律.通过对液化夹层土体超静孔压比、隧道顶点上浮位移及地表土体竖向位移的监测数据进行分析发现:在地震作用下,当液化夹层的位置不低于隧道埋深时,忽略土体空间变异性会低估液化夹层土体的超静孔压比;当液化夹层环绕在隧道周围时,隧道顶点上浮位移和地表土体竖向位移最大,此时的隧道安全性最差;当液化夹层位于隧道上方时,通过随机性计算得到的隧道顶点上浮位移的值有高达60%的概率超过通过确定性计算得到的隧道顶点上浮位移的值,此时地表土体的最大竖向位移为沉降变形,这表明将土体视为均质材料的传统分析方法会高估隧道在地震作用下的安全性.

Based on random field theory,and considering the spatial variability of soil shear modulus,the influence of the relative position of liquefaction interlayer and shield tunnel on the seismic response of tunnel and soil is studied by using numerical simulation method.The data of excess static pore pressure ratio of liquefied interlayer soil,floating displacement of tunnel apex and vertical displacement of ground surface soil are monitored.The results show that ignoring the spatial variability of soil will underestimate the excess static pore pressure ratio of liquefied interlayer soil when the location of liquefied interlayer is not lower than tunnel burial depth under seismic conditions.When the liquefied interlayer surrounds the tunnel,the floating displacement of tunnel apex and the vertical displacement of ground surface soil are the largest,and the safety of tunnel is the worst.When the liquefaction interlayer is located above the tunnel,there is a 60%probability that the value of the tunnel apex floating displacement obtained by random calculation exceeds the value obtained by deterministic calculation.At this time,the maximum vertical displacement of ground surface soil is settlement deformation,which indicates that conventional analysis methods that treat the soil as a homogeneous material can overestimate the safety of the tunnel under seismic conditions.