Study on Deformation and Failure Mechanism of Stratified Mining Slope Based on Bending Mode

In order to explore the deformation and failure mechanism of anti-dip slope in goaf, the constraint models of the fixed beam were proposed for the layered rock mass of goaf roof. The stress criterion of bending and fracture based on structural mechanics was derived respectively from the constraint models. In order to verify the constraint models, it took Zuojiaying collapse in Nayong county, Guizhou, China as an example. On the basis of the detailed geology survey, typical geological 1-1′ section was selected to verify the models. The bending fracture stress of the largest gob roof was calculated at every 10 m point using the constraint model of the fixed beam. At the same time, the FLAC^{3 D} was used to numerically simulate the bending process. Finally, the mechanism of Zuojiaying collapse was analyzed by combining the results of structural mechanics calculation, numerical simulation and geological survey. The results show that the stress characteristic of the inverted stratified rock mass in the goaf is a fixed beam, and the stress characteristic of the inverted stratified rock mass away from the goaf is a cantilever beam. The stress concentration on both sides of the goaf is obvious, and deviated towards the dip direction. Meanwhile, the stress concentration in the dip direction is more obvious than the anti-dip direction. The middle part of the roof and floor of the goaf is in tension, and the plastic area is mainly in shear failure. Hard and soft lithology combination and developed joint fissures cause rock mass structure broken. It is the crucial factor for the formation of collapse. High and steep topography of slope provides a favorable terrain for collapses. The goaf stress adjustment results in crack fracture expanding, and cutting through. Finally, it aggravates slope instability and collapse.