深埋隧道复合式衬砌承载规律及其力学解答

Distribution rules and mechanical solutions of loads on composite linings in deep-buried tunnels

为研究深埋隧道复合式衬砌荷载的分布规律及其形成原因,首先,统计52座隧道围岩与初支、初支与二衬间的接触荷载监测数据,并分析各监测点荷载分布范围以及二衬荷载分担比分布区间;其次,将传统的[BQ]法等效于GSI分值,基于Hoek-Brown强度准则给出了计算支护荷载的理论方法;最后,将理论方法与实测数据对比分析,以验证理论方法的可行性,并对影响支护荷载以及主承载结构的重要因素进行分析。分析结果表明:不同围岩级别隧道支护荷载存在一定差异,且围岩越差,二衬荷载分担比呈越大的趋势;Ⅰ,Ⅱ,Ⅲ,Ⅳ和Ⅴ级围岩对应GSI分值区间分别为100~78,77~62,61~48,47~36和35~10;理论计算更适合埋深大于100 m的情况,而埋深小于100 m时,部分软弱围岩断面荷载表现为松动荷载;Ⅲ,Ⅳ,Ⅴ级围岩二衬荷载分担比例区间分别为17.43%~37.96%,27.42%~51.89%,37.52%~66.6%;二衬施作时机、支护厚度和围岩条件均对支护荷载有较大影响,几个因素的结合可能改变主承载结构。研究成果为山岭深埋隧道支护设计提供一定参考。

In order to study distribution rules and formational reasons of loads on composite linings in deepburied tunnels,firstly,the contact loads between the surrounding rock and the primary support as well as between the primary support and the secondary lining,monitored in 52 tunnels,were counted,and the load distribution range of each monitoring point and the load sharing ratio of the secondary lining were analyzed. Secondly, by equating BQ to GSI, a theoretical method for calculating the support load was developed based on the Hoek-Brown strength criterion. Finally,the theoretical method was compared with the monitoring data to verify its feasibility, and the important factors affecting the support load and the main load-bearing structure were analyzed. The analysis results show that there is a certain difference in the tunnel support loads for different surrounding rock grades, and that the lower the surrounding rock grade, the greater load sharing ratio of the secondary lining will be. The corresponding intervals of the GSI for classes Ⅰ,Ⅱ,Ⅲ,Ⅳ,and Ⅴ of the surrounding rock are 100–78,77–62,61–48,47–36 and 35–10,respectively. The theoretical calculation is more suitable for the burial depth greater than 100 m,and for the burial depth less than 100 m,some of soft surrounding rock section loads are reflected as loose loads. The load sharing ratio of the secondary lining of classes Ⅲ, Ⅳ and Ⅴ surrounding rock ranges from 17.43% to 37.96%,from 27.42% to 51.89% and from 37.52% to 66.6%,respectively.The installation time of the secondary lining,the support thickness and the surrounding rock conditions have great influence on the support loads,and the combination of these factors can change the main load-bearing structure.The research results provide some reference for the design of deep-buried tunnel support in mountains.