Study on Key Steps of Three-lane Weak Surrounding Rock Tunnel Construction

Abstract

For tunnel excavation with poor stability of surrounding rock, controlling the construction of key steps in each construction method is of great significance to tunnel construction. Taking Fengshuao and Daping tunnels as examples, this paper uses FLAC software to simulate three construction methods, i.e. double sides heading tunnel method, three-step method and CRD method. Through the analysis of displacement deformation in the numerical simulation results of three construction methods, it is concluded that the corresponding steps of maximum displacement deformation in different construction methods are the key steps in construction: the both sides heading method needs to strictly control the excavation of double-sided upper steps, the excavation of inverted arch and the dismantlement of middle-wall; the three-step method mainly controls the excavation of curved guide tunnel of upper steps, the excavation of inverted arch and the strike of locked bolts. The control steps of CRD method are the excavation of upper steps on the left wall, the excavation of upper steps on the right wall and the dismantlement of the middle wall. Therefore, strictly controlling the key steps of each construction method can improve the safety and efficiency of this kind of highway tunnel construction, and provide reference for future construction.