Study On Entrance Technology With Micro-excavation In Portal Of Highway Tunnel

The construction of tunnel entrance is very difficult and important in tunnel engineering, Reasonable way of tunnel entrance can not only reduce the engineering problems, but also reduce the damage to the environment. thus,choose a suitable way to achieve tunnel entrance becomes particularly important. Micro-excavation entrance is an advance concept of construction method, witch can make tunnel entrance faster 、 safer and more environment-friendly.This paper take topography and geology conditions as key point, use the methods of data collection and summary, theoretical analysis and numerical simulation, to study tunnel entrance by micro-excavation.The main contents are as follows:(1) Summarize and analyze tunnel entrance and the excavation methods corresponding to different topographic and geological conditions. Give the proper way of tunnel entrance under different terrain conditions and surrounding rock。(2)Given the trapezoid umbrella arch method of tunnel entrance, from the force of structure and terrain adaptability analysis the advantages of umbrella arch method.(3)According to the actual terrain, use finite element software analyzes Dujuangu tunnel under zero slope conditions, by umbrella arch method, analysis the force and deformation of initial support and surrounding rock. Discussed the used of orthogonal micro-excavation in small clear-distance tunnel in this paper.(4)By the whole process simulation of trapezoid umbrella arch Shallow-buried bias tunnel, analysis the force and deformation of trapezoid umbrella arch and initial support, skew entering is feasible to Wuyashan tunnel. By the support of trapezoid umbrella arch, skew entering method can work very well in Shallow-buried bias tunnel, skew entering method has great advantage in reducing the scale of slope excavation.