Tunnel collapse mechanism and numerical analysis of its influencing factors

A large number of engineering facts of tunnel collapse were stated and analyzed through consulting references and field investigation.Through the analysis of the statistical materials,a new classification scheme was proposed,and geological condition,buried depth,form and size of cross section,ground water,blasting disturbance and incorrect construction measures were considered as the main influencing factors of the tunnel collapse.The contributions of these factors to the tunnel collapse were analyzed comprehensively while the ratio of collapse height,buried depth,width of surface subsidence to tunnel span and angle of rupture were taken as the parameters indicating the degree of collapse.The applicability of some calculating methods for determining surrounding rock pressure was studied through the comparison with the statistical materials.The whole process of tunnel collapse was simulated by PFC2D.The contribution of the influencing factors to the tunnel collapse was studied through the results of the numerical simulation which matched the results of statistical materials perfectly.