穿黄隧洞抗震安全分析

南水北调中线穿黄工程是一期总干渠的关键性工程,其抗震安全备受关注。本文采用动态三维有限元方法,分析研究穿黄隧洞北岸竖井及相邻隧洞段的地震响应。分析中采用等价线性法计入基础土体在地震动作用下的模量下降及阻尼增加变化。分析计算模型包含竖井和隧洞结构以及结构周边一定范围的土体以有效模拟土体与结构间的动力相互作用,同时,计算模型采用阻尼边界模拟有限土体以外地基的辐射阻尼效应、采用非线性接触算法模拟隧洞管段间在地震时的开合与错动。分析结果显示,由于竖井和隧洞结构的显著差异,靠近竖井的隧洞接缝在地震中较易发生张开与错动,应予以高度重视,采取必要的抗震措施。分析研究结果为穿黄隧洞竖井段抗震安全评价提供科学依据。

Analyses on seismic safety of tunnel close to a shaft

The tunnel crossing the Yellow River is the key project for the central route of South-to-North Water Diversion in China.The seismic response of part of tunnel close to the shaft of the north end was analyzed with three-dimensional FEM.The nonlinearities of the soil under dynamic load were approached with equal linear method with SHAKE.The converged modulus and ratio of damping were used in the three dimensional dynamic analyses,where the interactions between the soil and structure were taken into account,the effect of energy radiation was simulated with damping boundary on the outsides of the finite region,the opening and sliding between the sections of the tunnel were simulated with direct contact method. The results of the study show the prevailing swing motion of the shaft creating opening and sliding between the tunnel sections.The results also provide valuable data for the judgment of seismic safety of the part of tunnel close to the shaft.