Abstract: The thickness of rock mass for prevention of water inrush between tunnel and karst cave is one of the important factors in selecting a tunnel site in karst mountain area. In the process of karst tunnel construction,karst water gushing often leads to some accidents,economic losses or construction delay if the wall thickness is too thin. The classification of water inrush failure types is simple. Most classification studies ignore that the structure of tunnel surrounding rock can affect the thickness of rock mass for prevention of water bursting. This paper studies the inrush model in rock mass failure from three aspects: the structure type of surrounding rock of karst tunnel,the relative size and relative position between karst cave and tunnel. Then the failure modes can be subdivided into many mechanical models including beam model,rectangular or circular thin plate model,punching shear column model,wing crack tension through model,tension shear composite fracture model,bedding slip model. Finally,the different failure models are used to summarize the calculation formulas of the thickness of rock mass for prevention of water inrush. The findings can provide suggestions for tunnel route selection in karst area,and provide reference for predicting water inrush geological disasters during tunnel construction.