Failure analysis and countermeasures of highway tunnel crossing fault fracture zone in coal-bearing strata: A case study

Abstract

Collapse occurs frequently during the construction of highway tunnel crossing fault fracture zone in coal-bearing strata. This paper presents a case study on the failure mechanism and treatment measures of the collapse of a tunnel. In-situ investigation indicates that the continuous looseness of surrounding rock caused by the crushing of coal seam is the main cause of collapse. The uniaxial compressive strengths of coal and rock was subsequently determined based on point load test. The in-situ stress measurement results show that the tunnel is in the extremely high stress zone. In addition, the collapse mechanisms were analyzed in aspects of in-situ stress, groundwater, surrounding rock mechanical properties and geology. The countermeasures of grouting and support strengthening were taken to improve the stability of surrounding rock. The effects of countermeasures were discussed by analyzing monitoring data. The lesson learned from the collapse case study can provide a reference for similar tunnels.