Movement and failure law of slope and overlying strata during underground mining

Overburden deformation has a considerable influence on slope stability during underground mining works. A simulation experiment for underground mining is performed in this study. The movement of the overlying strata caused by mining during the mining process is observed using a three-dimensional optical displacement monitoring system. Based on the simulation experiment results, a particle contact-based meshfree method (PCMM) is proposed. The elastoplastic analysis and sliding process simulation of the slope are realized by introducing the softening Mohr–Coulomb model and maximal tensile stress model into continuous media elements. The deformation process and slope failure are analyzed by using the PCMM numerical simulation method. The results showed that the overburden gradually degraded as the work face continuously pushed forward. Furthermore, the basic roof bore the force generated by the upper rock mass. Hence, a 'rock beam' force distribution developed. The farther the distance from the coal seam, the smaller the subsidence. The rock strata subsided and induced a 'beam' structure effect when the work face continued to advance past the design stop line, causing a rock mass partial settlement on the slope and a serious horizontal movement on the free face. This behavior significantly affected the slope stability, even inducing cracks and potential slip and sliding surfaces. The numerical simulation results indicated that the deformation process of the overlying strata is as follows: 'the roof immediately starts to collapse → the rock mass of the main roof collapses → overlying strata generate an abscission layer → a fracture of the free surface develops → the overlying strata begins to sink'. Meanwhile, the slope deformation and failure process is as follows: 'overlying rock mass exhibits shear failure → the overburden is completely sheared → the overburden collapses → the slope surface exhibits a tensile crack → the stepped crack is connected → the slope begins to slide to the outside.' The research results provide guidance for underground mining. (paper)