The Calculation Of Surrounding Rock Pressure And The Study Of Supporting Structure Mechanics Of Neighborhood Tunnel

In long tunnels connected with bridges and tunnels,with narrow topography or with special requirements,small clearance tunnels are preferred for tunnel openings.In practice,small clearance tunnels generally have engineering safety problems such as serious bias pressure,complex construction and structural instability,which are mainly rooted in the inaccurate calculation of tunnel envelope pressure and unreasonable construction methods under such working conditions.In this paper,a deviated small clearances tunnel of Jing-Qin Expressway is used as the engineering background,and a combination of theoretical analysis and numerical simulation is used to study the surrounding rock pressure and initial support of the deviated small clearances tunnel under different surrounding rock levels.The main research contents are as follows.(1)Considering the spatial construction sequence and terrain direction,the cavern on the side away from the mountain was excavated as a priority,and a model for calculating the envelope pressure of the deviated small clearances tunnel was established to derive the vertical envelope pressure and horizontal envelope pressure of the tunnel.(2)The influence of tunnel clearances,surface slope,excavation span and tunnel burial depth on the surrounding rock pressure is analyzed,and the results are compared and analyzed with the calculation results of the standard method.(3)Analyze the optimal construction method for a tunnel of Jing-Qin Expressway in Class III-V surrounding rock,and provide reference suggestions for the construction of this tunnel.(4)Based on the theory of pressure calculation of the surrounding rock in a tunnel with small clearances under bias pressure,numerical simulation is used to analyze the distribution law of displacement and stress under different surrounding rock levels in a tunnel of the Jing-Qin Expressway,and the distribution law is compared and analyzed with the theoretically deduced one.(5)Based on the finite element numerical model,the effects of initial support anchor diameter,spray layer thickness,steel arch type and steel arch spacing support parameters on vault displacement,structural internal force and surrounding rock stress are analyzed,and the optimal combination of support parameters for a tunnel of Jing-Qin Expressway is given.