Mechanical Behavior Of Surrounding Rock And Supporting Structure Of Twin Arch Tunnel Under Unsymmetrical Pressure

With the development of highway construction in China, twin arched tunnels are being widely used as new tunnel structural form. Due to the complex section form,the mechanical behaviour of the surrounding rock and the supporting structure of a twin arch tunnel is more complicated than one of a single arch tunnel.At present,the investigation on the mechanical behaviour of the surrounding rock and the supporting structure of a twin arch tunnel has become a focus task in engineering.Generally speaking,the pressure on a twin tunnel caused by the complex topograghical condition and the construction sequence is unsymmetrical.The existing studies on the influence of this unsymmetrical pressure on the behaviour of the surrounding rock and the supporting structure of a twin arch tunnel are not only systematic but also deep-going.This paper takes a practical twin arch tunnel as the engineering background and simulates the construction process of tunnel by using Finite Element Method.The focus of analysis is on the influence of the unsymmetrical pressure on the behaviour of the surrounding rock and the supporting structure in typical construction steps.Firstly, the theory of New Austrian Tunneling Method and the main method of the construction of twin arch tunnels were introduced.The basic theory of Finite Element Method for simulating the construction of tunnel was discussed in a deep-going way and the significance of output results was pointed out.The steps of simulating the excavation of tunnel were described in detail.Secondly,the elastic-plastic plane analysis of the construction process of a twin arch tunnel located near a steep slope was employed by using ANSYS to study the regularity of influence of the topograghical condition and the construction sequence on the mechanical behaviours of the surrounding rock,the interval wall and the supporting structure.In addition,the 3D finite element elastic analysis for simulating the construction of twin arch tunnel was carried out and the space effect of the tunnel structure under unsymmetrical pressure was studied emphatically.Finally, the mechanical behaviours of the surrounding rock and the supporting structure of a twin tunnel under unsymmetrical pressure were summarized and some useful conclusions were obtained.The problems meriting to study deeply were also presented.