Study On Calculation Method Of Loose Zone Of Tunnel In-situ Expansion Process Based On Pressure Arch Theory

In recent years,with the rapid development of China's economy,increased traffic,in order to ensure the smooth passage of the highway,the highway tunnel traffic capacity must be higher requirements.In some areas,the two-way four lane tunnel has been unable to meet the current requirements of traffic.In order to improve the traffic capacity,it is necessary to enlarging excavate the original tunnel in situ.Based on the current domestic rare Damaoshan in-situ expansion tunnel of the Shen Hai high-speed Quanzhou Xiamen section as the engineering background,Analyzed the mechanical characteristics of surrounding rock of Damaoshan tunnel excavation in situ by two kinds of methods:analytical solution and numerical simulation,put forward the method for calculating the range of load and loose zone.And through the actual engineering monitoring data and ABAQUS three-dimensional numerical simulation results to verify the applicability of the tunnel,the construction of the tunnel to provide analytical support The main research work and achievements are as follows:1.Using complex function Schwarz alternating method,considering the influence of the supporting force of the tunnel lining on the surrounding rock,The analytical solution of tunnel in situ expansion is perfected and the analytical solution is obtained under the consideration of support resistance.Inquiring into influence of support resistance.2.Based on the unloading theory,the ABAQUS software is used to simulate the excavation of the tunnel.The mechanical properties of the surrounding rock caused by the construction of the in-situ tunnel are analyzed,and the size of the loosening circle is determined.The safety factor is analyzed by the strength reduction method.3.Based on the analysis of CD construction method and the large section construction of tunnel in-situ expansion,the load calculation method based on pressure arch theory is studied and calculated by ABAQUS three-dimensional numerical simulation.The load calculation method suitable for the tunnel in situ expansion is obtained.4.Based on the pressure arch theory,the theoretical calculation method of the surrounding rock loosening circle considering the tunnel in-situ expansion process is studied by using the Castner approximation formula.And the influence factors of cohesion and Platts coefficient are analyzed for the range of loosening circle.