隧道可液化场地围岩液化势评判及有限元分析

Liquefaction Evaluation of Liquefiable Field Surrounding Circular Tunnel under Seismic Excitation and Finite Element Analyses

目的为对隧道围岩抗震性能进行准确有效评价,研究地震作用下可液化地基震动液化对地下隧道震害规律影响.方法基于总应力法对隧道可液化围岩进行液化势的判别和有限元分析,采用NCEER建议的动剪应力液化判别简化方法,分析隧道尺寸、衬砌厚度、隧道埋深及剪切波速对可液化围岩震动液化势的影响.结果改变隧道尺寸和衬砌厚度对土体加速度影响不大,而隧道埋深对土体液化势指数影响较大,增大隧道埋深则围岩不易发生液化.结论可液化场地隧道建设时应考虑增大埋深从而减小土体液化后产生的破坏.

The purpose of this study is to explore the influence of liquefiable foundation on seismic damage of underground tunnel under earthquake action. This paper introduced the liquefaction potential evaluation of soil and the finite element analysis for liquefiable foundation of underground tunnel under earthquake based the total stress analyses method. The effect of tunnel diameters, support thickness, depth of tunnel center, and shear wave velocity are discussed in detail on liquefaction potential of surrounding soils based on dynamic shear stress correlation method, the discriminant method suggested by NCEER. Results show that changes of the diameter and support thickness of tunnels have little influence on surface acceleration. However, the most important parameter defining the liquefaction potential is the depth of the tunnel from the ground surface. If the tunnels are deeper, they are less vulnerable to liquefaction compared to shallow tunnels. Therefore, If the surrounding soil is easy for liquefaction under earthquake, increasing the depth of tunnel center should be considered in tunnel construction to decrease the soil liquefaction that can caused damage potential in larger.