Abstract:In order to study the reasonable filling time of goaf, based on creep theory, the improved Nishihara model was used to determine the best filling time; FLAC3D software was used to build the 3D model of stope and surrounding rock, the stope stability of different grades of rock under different filling lag time was analyzed, and the reasonable filling lag time of different grades of surrounding rock and determined. The results indicated that: 1) The filling mining method can effectively restrain the deformation of surrounding rock and improve the stope stability. 2) Under the condition of grade III, IV and V rock mass, the stope deformation can be minimized and effectively controlled. 3) The filling lag time of class III surrounding rock should not exceed 80 h, the filling lag time of class IV surrounding rock should not exceed 60 h, and the filling lag time of class V surrounding rock should not exceed 30 h.