Study On The Best Supporting Opportunity And Surrounding Rock Stability In A Conveyance Tunnel

Along with the fast development of economy and engineering, a lot of tunnels were excavated by the construction of water conservancy, railway and highway’s projects. The following problems of high in situ stress and low surrounding rock strength brought difficulties to the process of construction. The stability of surrounding rock excavated is becoming a key to engineering design, construction safety and later’s operating.This paper selected an outlet section of a water conveyance tunnel as a research object, studying the best supporting opportunity and surrounding rock stability. The mainly results are achieved as the following points:(1) A true 3D numerical model was built to calculate the relation between the surrounding rock’s deformation and the drilling distance of tunnel face. And then, a quasi-3D numerical model was built to simulate the relation between the rock’s stress release and deformation in detail, which could be used to deduce the relation between the force loaded on the supporting structure and the rock’s deformation. Then the best deformation of the surrounding rock could be confirmed, compared with the consequences calculated by the true 3D modeling, the drilling distance of tunnel face could be determined as a sign of the best supporting opportunity.(2) Through the outlet section of the water conveyance tunnel,5 sections are selected based on the variations of geological features, rock types and buried depth. Numerical models combined with the supporting construction and the surrounding rock were built, which had concerned the supporting scheme, to calculate the displacements of the surrounding rock after excavation, the force loaded on the supporting structure, and the distribution of the yield zones. The stability of surrounding rock of the tunnel was evaluated.(3) Based on the calculation results of numerical modeling, compared with the original support design, suggestions are given for the supporting opportunity during excavation. Moreover, based on the analysis results of the surrounding rock stability, the rationality of the supporting scheme is verified.