大断面隧道开挖稳定性数值模拟分析

Numerical Simulation Analysis of Excavation Stability of Large-section Tunnel

为了确保大断面隧道开挖的稳定性,采用数值模拟方法,以某大断面隧道开挖支护为例,通过介绍隧道地表沉降和塑性区来判断隧道的稳定性。隧道开挖支护后正上方沉降最大,向两侧沉降逐渐减小,地表沉降基本沿隧道中心左右对称,且呈现出抛物线形状;初次开挖时隧道外环周围出现小范围剪拉,随着与掌子面距离增大,塑性区范围不断扩大,且扩大位置主要发生在拱肩和拱脚部位;从塑性区分布可以看到,拱顶和拱底主要为剪拉屈服,其他部位主要为剪切屈服。

In order to ensure the stability of large-section tunnel during excavation,numerical simulation method was adopted,and the excavation and support of a large-section tunnel was taken as an example to judge the stability of the tunnel by introducing the surface settlement and plastic zone of the tunnel.After the tunnel excavation and support,the settlement above the support is maximum,and the settlement on both sides is gradually reduced.The surface settlement is basically symmetrical around the center of the tunnel and exhibits a parabolic shape.During the initial excavation,a small range of shearing around the outer ring of the tunnel occurs.As the distance from the tunnel heading increases,the range of the plastic zone expands continuously,and the enlarged position mainly occurs at the shoulder and the arch.It can be seen from the distribution of the plastic zone that the vault and the arch bottom are mainly tensile yielding,while the other parts are mainly shear yielding.