考虑流固耦合效应的海底隧道地震响应分析

Seismic Response Analysis of Subsea Tunnels Considering Fluid-Solid Coupling Effect

为研究上覆海水影响下海底隧道地震响应规律,考虑衬砌塑性损伤及流固耦合作用,以汕头海底盾构隧道为工程实例,基于ABAQUS软件建立海水-海床-隧道结构体系有限元模型,分析不同地震激励以及不同海水深度条件下海底隧道动力响应及损伤情况。结果表明:1)在只考虑垂直SV波入射时,应力主要集中在隧道拱脚、拱肩部位,海水深度对海底场地水平运动及海底隧道的作用影响很小;2)在只考虑垂直P波入射时,随海水深度增加,上覆海水整体上会抑制海底场地竖向运动,隧道拱腰以下的应力增大更明显;3)考虑P-SV波延时入射时,隧道能量耗散及损伤具有一定的叠加效应,隧道拱脚及拱肩部位应力集中明显,海水深度小于20 m时,隧道断裂能及损伤较小,SV波占主导地位,海水深度大于20 m时,隧道断裂能及损伤会显著增加,P波起主要作用,在海底隧道抗震设计时有必要考虑海水对隧道地震安全的不利影响。

In this study,a case study is conducted on the Shantou Bay tunnel and a finite element model of a seawater-seabed-tunnel system is established using the ABAQUS software to investigate the seismic response and damage of subsea tunnels under various seismic excitations and seawater depths.The results are summarized as follows:(1)Considering vertical SV waves only,the stress is mainly concentrated at the arch foot and shoulder and the seawater depth exerts a minimum effect on the horizontal motion of the seabed site and the subsea tunnel.(2)Considering vertical P waves only,the overlying seawater inhibits the vertical motion of the seabed site with increasing seawater depth and the stress below the arch waist of the tunnel increases considerably.(3)Considering the delayed incidence of P-SV waves,the fracture energy and damage of the tunnel exert a certain superposition effect and the stress concentration at the arch foot and arch shoulder of the tunnel is obvious.When the depth of seawater is less than 20 m,the fracture energy and damage of the tunnel are small and the SV wave is dominant;furthermore,when the depth of seawater is greater than 20 m,the fracture energy and damage of the tunnel increase considerably and the P wave is dominant.Therefore,it is essential to consider the adverse effect of seawater on the seismic safety of the tunnel.