山岭隧道洞口段衬砌结构地震响应数值分析

隧道洞口段由于所处地质环境较差,是山岭隧道最容易失稳的部位之一。特别地,地质条件对隧道稳定性的不利影响会在地震过程被进一步放大。基于混凝土塑性损伤模型,建立隧道-围岩系统三维非线性有限元模型,采用该模型对横琴长湾隧道洞口段结构进行地震响应过程分析。结果显示:距离洞口越近,衬砌结构的位移响应越大;衬砌拱肩和拱腰的最大主应力峰值明显大于其他部位,并且拉裂破坏是衬砌结构主要破坏模式;损伤区主要分布在距离洞口70 m范围内,并且距离洞口越近,衬砌结构的损伤系数越大;衬砌结构的拱肩和拱腰是其抗震的薄弱部位。

Numerical analysis of seismic response of lining structure forportal section in mountain tunnel

Tunnel portals are well known to be more vulnerable to damage during earthquakes because they are generally located in areas of poor geological conditions. In particular, the adverse effects of poor geological conditions on tunnel stability can be further amplified during earthquakes. In this paper, a three-dimensional nonlinear finite element model of tunnel-surrounding rock system is established based on the plastic damage model of concrete. The model is used to analyse the seismic response process of the portal section of the Changwan Tunnel, and the results show that: (1) the closer to the entrance, the larger displacement response of the tunnel; (2) The peaks of the maximum principal stress of the arch spandrel and arch waist are significantly larger than that of other positions, and the tensile failure is the main failure mode of the lining structure; (3) the damage zone is mainly distributed within 70m from the entrance, and the closer to the entrance, the larger damage coefficient of the lining structure; (4) the arch spandrel and arch waist e are the weak positions of tunnel portals during earthquakes.