基于松动区理论的高速铁路浅埋隧道初支变形处理方法

Abstract

高速铁路浅埋隧道开挖断面较大，围岩强度低，隧道开挖后难以形成承载拱，常引起地表塌陷、初期支护变形过大、掉块、开裂等现象。当初期支护变形侵入二次衬砌限界后，为确保后续施工正常进行以及二次衬砌质量，需对这一部分初期支护进行拆换，并采取相应的加强措施。为确定隧道开挖对围岩的扰动作用，以某高速铁路浅埋隧道初支变形为例，进行无支护开挖条件下围岩应力的数值模拟，利用开挖外轮廓径向分布的特定临界破坏点的集合求出各施工阶段松动区范围。以此为依据，结合相似工程处理措施，最终确定了后续开挖过程中的初期支护型式，后续施工的各项监测指标均满足设计要求。工程实践证明，考虑了一定安全储备的松动区分析方法是可行且有效的。 Featured by larger excavated section and lower strength of surrounding rock, it’s not easy for HSR (High Speed Railway) shallow buried tunnel to form load-bearing arch after excavation, thus always prone to surface subsidence, and resulting in serious deformation, chipping and cracking of the ini-tial support. To ensure normal subsequent construction and the quality of secondary lining, the de-formed part of the initial support intruding into the secondary lining needs to be replaced and rein-forced. In order to determine the impact of tunnel excavation on surrounding rock, taking the initial support deformation of a certain HSR shallow buried tunnel for example, this paper carries out stress numerical simulation of surrounding rock in the case of support-free excavation, and finally works out the scope of disturbed zone in each construction stage, by determining the set of specific critical failure points radially distributed along the outer excavation contour. On this basis, combin-ing the treatment measures of similar projects, the initial support modal suitable for subsequent excavation can be determined, and all the monitoring indicators during subsequent construction can meet the design requirements. Engineering practices has proved that the disturbed zone analysis method considering certain emergency capacity is effective and feasible.