桃树垭隧道初期支护大变形分析与工程处理

Large deformation analysis and engineering treatment of Taoshuya tunnel supporting structure

桃树垭隧道隧址区地质条件较差,主要为Ⅴ和Ⅵ级围岩。隧道建设过程中,产生强烈变形和严重破坏。围岩初期变形迅速,变形速率大,变形持续时间长,隧道破坏严重,主要表现为拱顶下沉、边墙内挤、喷混凝土剥落、钢拱架扭曲、衬砌开裂等等,变形破坏具有重复性和相似性。通过某一段初期支护大变形事故处置技术分析,从围岩的岩性条件、地下水条件、地应力条件以及隧道设计参数等方面,探讨了该隧道大变形的原因和机制,认为它是围岩塑性流动与围岩膨胀变形综合作用的结果。基于对围岩动态演化机制的正确认识,从围岩控制角度,修正并制定新的返修方案,对大变形段实施返修并取得了成功,同时将研究成果用于指导相同地质条件的后洞段施工,确保了隧道安全顺利贯通。

Taoshuya tunnel is located in the Fengjie - Wushan section of Yu - Yi Freeway, the geology condition is very bad. Large deformation and serious damage happened on the tunnel under construction. The primary deformation of rock has the characteristics of large deformation rate, long duration time and serious damage on tunnel. And the main expression forms are arch settlement, wall crushing, shotcrete flaking, S- shape twisted steel support, broken lining, etc. By analyzing surrounding rocks, groundwater, earth stress as well as deformation characteristics, the reason and mechanism of large deformation of this tunnel were discussed. It is plastic flow and swell of surrounding rocks that are resulted in large deformation jointly. Based on correct understanding of dynamic evolution mechanism of the surrounding rocks, a new reinvention and reinforcement program was adopted from the viewpoint of controlling surrounding rocks. Those parts include large deformation and serious failure was repaired successfully. The construction of the tunnel through the bad surrounding rocks benefited from the research results.The Taoshuya tunnel is finished safely and successfully at last.