Abstract: When relative humidity of surface of surrounding rock mass is higher than that of internal surrounding rock mass, the humidity gradient between two zones is seen as a driving force which can make water diffuse into low humidity zone, while mechanical properties of surrounding rock mass is weaken. Surrounding rock mass is in a new humidity condition when underground cavern is excavating, which will change mechanical properties. Numerical simulation was done on humidity diffusion of rectangular coal tunnel by RFPA humidity diffusion edition. Disturbance status of stress field in rectangular coal tunnel rock affected by humidity diffusion and displacement situation with time passing of tunnel inner wall because of the humidity diffusion effect was obtained. The forming, development process and failure pattern of surrounding rock mass in humidity diffusion of tunnel of different stratum distribution were simulated.

Key words: Rectangular coal tunnel, Humidity diffusion, Failure of surrounding rock mass, Numerical calculation