Key Technology Research Of The Construction Of Large Section Tunnel Under The Complicated Condition

This paper relies on a highway tunnel project in Qingdao tunnel project, which has large cross section for its mainline and ramp cross with the conditions of complex geological conditions, shallow buried depth and buried beneath a building, and carrys out a large section tunnel construction technology research. Nowadays large multi-stage section tunnel at present use excavation by steps, which leds to numerous disturbance of the rock, mutual interference between the various processes, and invert can not be closed into a ring, longer duration and number of problems and poor economy. So this paper also combine Taoshuping tunnel engineering, it also take a research on the development of new method in the construction of large sectional tunnel. The research of the large sections tunnel construction method has also been the focus.The research of the paper mainly contains as following:(1) It firstly make a research on the large section of the tunnel construction at home and abroad, and points out the value and importance of research of the large cross section tunnel construction technology;(2) This paper summarizes the mechanical properties of large section tunnel. Then, it analsys the mechanics stepwise mechanism of large section tunnel excavation method combined with the shaft change theory, and prove theoretically that large section tunnel should be excavated by steps rationality. Finally, it propose appropriate construction technology and summarizes the large section tunnel construction method;(3) By using the finite element analysis software, a numerical model that the a large section tunnel is excavated by three construction method is established. And it makes a detailed analysis on the tunnel surrounding rock stability, between supporting structure and surrounding rock deformation for every step of the construction. Then it will make a conclusion for the key steps of the construction method and the weak position of the tunnel, and make recommendations for the construction and monitoring. From the mechanical mechanism and economic perspectives into account, it finally obtains optimal excavation method for each tunnel section;(4) Combined with tunnel engineering in our country, pre-convergence of the working face is treated as the analysis index by the numerical analysis. When the face is not suppot in advance, it will analysis the relationship between the total deformation and the convergence ahead of tunnel, and prove that is important of controlling pre-deformation of the core soil of the tunnel face.(5) Because large cross section tunnel excavation method exsit many fractional problems, this paper combines with the idea of ADECO and propose feasibility whole section excavation. Through researching on the TaoShuping tunnel engineering, it make use of the numerical simulation tools and analsys the efficiency, cost and the deformation of control, which is proved that the innovative method has great advantage in large section construction.(6) By numerical simulation method, two indicators which are the tunnel face extrusion deformation and vault settlement are treated as the evaluation tool, it will analyze the impact on the stability of the tunnel by the three excavation way and optimiz reinforcement parameter settings.(7)Making the field monitoring measurement by all kinds of excavation methods, and conduct a comprehensive analysis of surrounding rock and primary support, grasp the stress state, further verified the rationality of excavation scheme. So some useful conclusions are obtained.