Abstract:In order to ensure the safety of workers and equipment in the middle area of the two faults. Using the structural mechanics analysis method, the overlapping roof and floor of the goaf are simplified as a mechanical structure model of the fixed beam, and the total potential energy equation of the system is established. Based on the cusp catastrophe theory, the cusp catastrophe model of the instability of the overlapping roof and floor in the goaf is constructed, and the instability criterion of the overlapping roof and floor in the goaf is obtained and verified by engineering examples. The results show that the special fault will increase the tensile stress and X direction displacement of the roof beam, and in the case of a certain thickness of the overlapping roof and floor, the greater the tensile stress and X direction displacement of the roof, the more prone to instability of the overlapping roof and floor .