Numerical Simulation Of The Pre-consolidation And The Excavatio N Of Large Cross-section Tunnel

ABSTRACT:In China, many tunnels are large section shallow-burried tunnel which were constructed in weak rock areas. During the construction process of this kind of tunnel, tunnel collapse, roof collapse and other accidents happened a lot and it caused great distress to the tunnel construction. Pre-reinforcement large section tunnel construction method can solve such kinds of problems efficiently and easily. With the size increase in the cross-section of a tunnel, the stability of the tunnel face will be a critical controlling factor to ensure the construction process safely constructed.This thesis used FIAC3D numerical simulation software as a tool, mainly researched the construction technology of shallow-burried tunnel and the work focus on the following areas:1. Summarizes the research experience of pre-reinforcement large-span tunnel, briefly describes the basic concepts of ADECO-RS method.2. Based on the numerical simulation analysis, this paper researched the deformation performance of the tunnel face; this paper also researched the distribution of plastic area of the tunnel surrounding rock and the displacement of the apex of the tunnel arch corresponding to different grade of rock. And the rock grade various from grade II to gradeVI. During the research, this paper also discussed the influence on the stability of the tunnel face caused by different section size and depth. Some kinds of measures were given in this paper to strength the tunnel face. Those are tent retaining method, hydrofracture grouting method and, fiberglass anchor grouting methods.3. During the excavation process of large section tunnel which locates in the soft rock area, if there is no initial support or other measures to strengthen the advanced core rock, just using the pre-bassoon shed beams, the arching effect is not obvious, the deformation of the advanced core rock is still large. The tunnel face cannot maintain stability. On the contrary, advanced glass bolt and hydrofracture grouting could significantly improve the strength and stiffness of the core soil, which greatly reduces the depth of the plastic zone.Propose a suitable way of the advanced pre-reinforcement. This paper use the FIAC3D numerical simulation software to simulate the deformation, the tunnel convergence, the plastic zone and surface subsidence effects of the tunnel face after the advanced pre-reinforcement were conducted. The result shows that through the reinforcement of core soil in front of the tunnel face and pre-grouting support outside the tunnel face, it can significantly improve the strength of the core soil and its mechanical property. And it can also markedly reduce the deformation and plastic zone of the tunnel face, to improve its stability during the construction process.