Research On Construction Risk And Control Technology Of Large Bias Tunnel Zero Excavation Under The Condition Of Half-embedded And Half-uncovered

Based on Shi Zilong Tunnel of Chang Xiang expressway, this paper studies Zero Excavation method in Tunnel Portal Construction in condition of half-embedded and half-uncovered. The study was performed by means of risk analyses, numerical simulation and dynamic monitoring scheme. The main content is as follows:(1) Taking advantage of fuzzy comprehensive method and R=P C method, the main risk sources of the tunnel portal section was evaluated with qualitative and quantitative. The initial risk and residual risk of portal section construction of Shi Zilong Tunnel, as well as construction risk control measures of half-embedded and half-uncovered structure were discussed.(2) Inverse algorithm was used to obtain the strength parameters of the surrounding rock of the tunnel portal section. Then the mechanical characteristics of surrounding rock and support structures of large span biased tunnel were studied by using ABAQUS finite element software. The displacement, stress and mechanical weaknesses of support structures were analyzed.(3) By real time risk monitoring, the data of settlement of umbrella arch, horizontal convergence, crown settlement and the horizontal and vertical displacement of retaining wall were determined. Variation of stress and deformation under the conditions of constructing phase of large span biased tunnel with half-embedded and half-uncovered structure were discussed.(4) With risk analysis, numerical simulation and dynamic monitoring scheme, the construction program and risk control measures of large bias tunnel with zero excavation and half-embedded and half-uncovered structure were put forward based on mechanical characteristics of surrounding rock and support structures.