Analysis On Construction Process Of Weak Surrounding Rock Tunnel Expansion

With the rapid development of the social economy,the links between various regions are closer,and the task of rebuilding and expanding the highway tunnel is imminent.With the development of the larger span of the tunnel,the security of the structure is more difficult to be guaranteed.In order to better understand the stress and stability of surrounding rock and supporting structure during the tunnel expansion construction process,based on the expansion project of Houci tunnel of the Xiarong expressway in Fujian,based on the ANSYS finite element software platform,the expansion process of soft surrounding rock tunnel is analyzed.The main contents and main conclusions of this paper are as follows:The research status of tunnel expansion in weak surrounding area at home and abroad is reviewed,according to the principle of reconstructing and expanding highway tunnels and combining the actual conditions of the project,selecting the in-situ expansion form of tunnels in weak surrounding rocks suitable for supporting projects: The reconstruction and extension of the right-line of the Houci tunnel should use the in-situ unilateral extension form.A brief summary of the basic principles of elastic-plastic mechanics involved in the finite element simulation,the implementation method of the tunnel expansion construction process in ANSYS is introduced.The construction method of tunnel expansion in weak surrounding rock is studied in detail,the ground settlement,displacement around the cave,stress of the surrounding rock,and the stress of the supporting structure under different construction methods were analyzed.The research indicates: In order to ensure the safety of the construction process,the cross partition method(CRD method)should be used.According to the selected construction method,the finite element analysis of the tunnel expansion construction process was conducted.The stress and deformation laws of the surrounding rock during construction and the impact on the existing tunnels were analyzed,The results show: The surface sedimentation tank is slightly offset,and the settlement curve has asymmetry;the tunnel section shows distinct uneven settlement and horizontal displacement;the compressive stress concentration is generated at the foot of the cross section of each guide hole of the tunnel;the displacement generated by the existing tunnel is small,and the expansion excavation has little effect on the existing tunnel.The monitoring and measuring technology of tunnel expansion is used to monitor and measure the surface slope,surrounding displacement and vault settlement of the weak surrounding rock tunnel at the right side of the Houci tunnel,showing the data and analysis results in monitoring during construction,and compared with numerical simulation.According to the monitoring results,the following construction process is optimized,suggestions on the expansion are put forward,and the best construction technology and construction method are determined.The research results provide a reference for the engineering practice and the similar engineering construction.