The Xigeda Strata Tunnel With Weak Surrounding Rock Deformation Mechanism And Supporting Techology Research

Against the background of China’s high-speed railway "going out", Trans-Asian Railway has been put on the agenda, which drives the construction of the railway in southwest China into a new climax, including Chengdu-Kunming Line Ⅱ. This may bring us more convenience, but Xigeda strata in western Panzhihua Area of Sichuan can also imposes great challenges since we barely have any construction technology in light of this strata. In other words, deformation control and safety construction will be the key and the hardest part for speedy drivage and safe pass-through. We should take the newly-built Miyi-Panzhihua Section of Chengdu-Kunming Line Ⅱ as a opportunity to dig further of Xigeda strata and produce more outputs, with which, we may contribute more data for such projects in light of railway construction.This paper takes Zhujia Tunnel, part of Miyi-Panzhihua Section of Chengdu-Kunming Line Ⅱ, as an example. With consideration of geological condition, designing scheme, construction method, surrounding rock deformation, etc., this paper studies the deformation mechanism, support parameter and tunnel face stability technology with various methods, such as theoretical analysis, field research, and laboratory test. The paper is constructed as follows:(1) Identify physical and mechanics parameters of the Xigeda strada based on laboratory test and related literature, in an attempt to ensure the numerical modeling value is reasonable.(2) As for deformation behavior and deformation mechanism of Xigeda strata, we consider them from surrounding rock stress release rate, scale effect and tunnel depth, while simulating the process of surrounding rock changing from elasticity to plasticity, in an attempt to contribute data for the best supporting timing choosing. Deformation law may expand to other cases since that of different size or depth of cross-sections differentiate from each other in a not obvious way.(3) Emphasis has been put on steel frame support when referring to support parameters of Xigeda strata. We take it from two aspects, i.e. impacts brought about by distances between steel frames to surrounding rock deformation and internal force improvement; by this, we analyze the support effect of steel frame to further introduce standards for reasonable steel frame distance.(4) Tunnel face stability control is mainly about the stability of excavation face under the effect of front anchor of fiber reinforcement. This section outlines its role in improving conditions of tunnel face slippage, vault crown settlement, stress state improvement of surrounding rock, in an attempt to find out the best scenario of setting of anchors for tunnel face stability control and further obtain design parameters for support technology of rock anchor bolted to tunnel face.