隧道大跨段施工围岩变形及受力特征分析

Analysis on deformation and stress characteristics of surrounding rock in large span section of tunnel

以重庆樵坪山隧道大跨段为研究对象,应用有限元法,对CD法(中隔壁法)和双侧壁导坑法两种隧道开挖工法进行数值模拟研究,对比分析了两种不同开挖工法条件下,隧道围岩竖向位移、应力分布以及支护结构受力特征。结果表明,采用双侧壁导坑法进行隧道施工开挖,其拱部沉降要低于CD法,双侧壁导坑法的拱顶最大沉降和最大上鼓比CD法分别低57%和48%。双侧壁导坑法的锚杆拉应力、初支的最大主应力和临时支撑最大压应力均低于CD法,双侧壁导坑法具有更高的安全系数,因此,在该隧道工程中采用双侧壁导坑法进行施工在安全性上优于CD法。

Taking the long span section of Qiaopingshan tunnel in Chongqing as the research object,numerical simulation is carried out for two kinds of tunnel excavation methods:the CD method(center diaphragm method)and the double-side-drift method.And the vertical displacement,stress distribution and supporting structure of surrounding rock under the two excavation methods are compared and analyzed.The analysis results show that the arch settlement of the tunnel excavated by the double-side-drift method is lower than that of the CD method,and the maximum settlement and the maximum upper heave of the double-side-drift method are 57%and 48%lower than that of the CD method,respectively.The tensile stress of bolt,the maximum principal stress of the initial support and the maximum compressive stress of temporary support of the double-side-drift method are all lower than those of the CD method,and safety factor of the double-side-drift method is higher than that of CD method.Therefore,the double-side-drift method is superior to the CD method in safety.