Study On Stability Of Surrounding Rock And Supporting Structures Of Deep Buried Tunnel

In the tunneling stability, the interaction of the surrounding rock and supporting structures has been considered as a tough problem, there are many factors which impact the stability of surrounding rock-supporting system, the main ones are the supporting way, geological factors and supporting parameters. Grasping the influence of the change of each factor on the surrounding rock and supporting structures has a great significance to the safety and economical efficiency of tunnel construction.Based on the predecessor’s research about the new austrian tunnel method, this paper summarizes the criterion of surrounding rock stability and the factors that affect the stability of surrounding rock, characteristics and mechanism of the supporting structures are described. The calculation principle of finite difference software FLAC3 D is introduced in detail. On the background of the No.1 water conveyance tunnel of Jiaofenling section in east lines which is part of the Central Yellow River Diversion Project in Shanxi Province, the three-dimensional numerical model has been built with FLAC3 D. The supporting structures such as bolts and sprayed concrete are simulated by structural elements, the main research work and achievements are as follows:(1)Surrounding rock stability conditions under supporting or not have been analyzed and compared when the tunnel was excavated. Surrounding rock deformation, stress field distribution and plastic zone size of two different conditions are compared. The results show that it is necessary to take supporting measures timely after tunnel excavation, which can control further deformation of surrounding rock and further expansion of plastic zone area.(2)Surrounding rock deformation, stress field distribution, plastic zone size,stress and deformation of supporting structures have been analyzed when the tunneldepth, the later pressure coefficient of surrounding rock, the level of surrounding rock,physical and mechanical parameters of surrounding rock, the thickness of sprayed concrete change. Some useful conclusions have been given, which will have guiding significance for the design and construction about similar engineering.(3)The paper studied the sensitiveness of the main mechanic parameter to get the most sensitive factor and sub-sensitive factor of the surrounding rock, stress field and plastic zone. The result indicates that in the numerical simulation, the selecting ofφ, с value should pay more attention to ensure the simulation reliability.(4)The stability of surrounding rock-support system has been analyzed when the thickness of sprayed concrete changed. It is not obvious that increasing the thickness of sprayed concrete improves the support effect for surrounding rock, but the stress of the sprayed concrete increase significantly. Therefore, the design thickness of the sprayed layer should be a reasonable choice, not too large.