海底和陆地地震动作用下沉管隧道地震响应研究

Seismic Response of Immersed Tube Tunnel Between Offshore and Onshore Ground Motions

海水层和海底沉积土层的存在影响地震动的传播,导致海底地震动与陆地地震动特征存在明显差异,选取合理的地震动输入是进行沉管隧道抗震性能分析的重要前提,因此,对比分析沉管隧道在海底和陆地地震动作用下的动力响应具有重要意义。基于饱和粘弹性人工边界理论,将地震动输入转化为等效节点力来实现三向地震波的输入。利用ABAQUS软件建立海水-海床-隧道的三维有限元模型,并考虑地震动作用下海水产生的动水压力影响。对沉管隧道在两种地震动作用下产生的相对层间位移、加速度和最大主应力进行对比分析。结果表明:海底地震动作用下的各向相对层间位移小于陆地地震动作用下;在海底和陆地地震动作用下沉管隧道出现最不利的位置不同;在海底地震动作用下产生的峰值加速度相比于原始输入地震波,其数值有所减小,而在陆地地震动作用下其数值有所增加。

The existence of sea water layer and seabed sedimentary soil layer affects the propagation of ground motion which result in the obvious difference of ground motion characteristics between seabed and land. Selecting reasonable ground motion input is an important prerequisite for seismic performance analysis of immersed tube tunnel. Therefore, it is of great significance to compare and analyze the dynamic response of immersed tube tunnel under seabed and land ground motion. Based on the theory of viscoelastic artificial boundary, the input of ground motion is transformed into equivalent nodal force to realize the input of three-way seismic wave. A three-dimensional finite element model of seawater, seabed and tunnel was established by using ABAQUS software, and the hydrodynamic pressure caused by seawater under the action of ground motion was considered. The relative interlayer displacement, acceleration and maximum principal stress of immersed tube tunnel under two kinds of ground motion are compared and analyzed. The results show that the relative interlayer displacement under the action of seabed ground motion is smaller than that under the action of land ground motion. The most fragile position of the submerged tube tunnel is different between submarine ground motion and land ground motion;compared with the original input seismic wave, the value of peak acceleration produced by seabed ground motion decreases, while it increases under land ground motion.