Research On Ground Stress Field Evolution Rule After Earthquake Of DuWen Road And Soft Rock Tunnel Floor Heave Prevention And Treatment

DuWen road with complex geological conditions passes through the Longmen mountain fault zone. During the construction, it would encounter many adverse geological phenomena, such as high gas, high ground stress, hard rock burst, soft rock deformation, water outburst and so on; all of these bring great difficulties to the highway construction.5.12Wenchuan earthquake shocked the whole world and which made DuWen road construction suffered heavy losses, the second-level sections have been buried or destroyed completely, and soon-to-be-completed Dujiangyan-Yingxiu highway has also been serious damaged. Before the Wenchuan earthquake, the stress values of project area was measured up to26-27MPa, but after the earthquake, Wenchuan highway tunnel still occurred a rock burst when built the Futang tunnel, and still exists the phenomenon of high ground stress and the stress values was20Mpa. It doesn’t match the knowledge of people that ground stress after the earthquake will be a substantial release. It’s a worthy issue to explore on the evolution of ground stress field before and after earthquake.According to the data of ground stress before and after earthquake in support project area, this paper adds a group of the measured ground stress data, additional tests to stress the value of a group of post-earthquake FLAC3D software for finite element simulation, formation lithology and tectonic framework of the project area, to carry out extreme seismic zone earthquake before and after the crustal stress field before and after to the stress field inversion, using the measured stress data regression analysis, the project area earthquake. Geological Survey, the theoretical analysis and numerical simulation, and other means to analyze the reasons of Wenchuan highway Zipingpu tunnel floor heave and the drum by the end of the control measures were studied to obtain the main results are as follows:(1) through the analysis of ground stress inversion before and after earthquake in the project area, to get the project area regional stress field distribution characteristics, on this basis, summarizes the project area before and after the earthquake stress field evolution is:after the earthquake Basin, the Longmenshan central fault zone under the stress release, stress magnitude is lower the stress state. Disk in the the Longmenshan central fault, before the earthquake, the background of high field stress, stress magnitude earthquake Heights fell less in the region is still a high field stress range. In the direction of principal stress before the earthquake, the maximum principal stress direction of the project area small changes to the deflection from the NE-NNE to NNE.(2) According to the previous summary of the causes of kick drum, combined with the real Zipingpu tunnel project situation, and use the rock mass of kick drum as the research object, through on-site investigation and analysis, come to the drum end of the tunnel are mainly:rock strength is extremely low and jointed development, the role of hydrodynamic impact and strength of weak governance measures to support post-earthquake. FLAC3D software to create three-dimensional numerical simulation model of deformation of the bottom drum, kick drum amount calculated under the tunnel before and after the earthquake on retaining scheme, the analysis of tunnel surrounding rock plastic zone and the tunnel surrounding displacement and stress distribution.(3) Introduced in the drum reason the end of the tunnel in-depth analysis and numerical simulation based on the drum end of the tunnel control technology, the base plate grouting reinforcement, floor bolting and invert support invert+base plate bolting retaining four various control tunnel at the end of drum programs, and by numerical simulation to further explore its supporting effect, considering the floor bolt grouting support Zipingpu tunnel floor heave control.