Numerical study on movement of dynamic strata in combined open-pit and underground mining based on similar material simulation experiment

The characteristics of the movement of dynamic strata in combined open-pit and underground mining based on similar material simulation experiments were studied in this study. To get more accurate test parameters, a similar material, based on a sheet of brittle material, was developed. We then used the Anjialing coal mine as our case study sample. The characteristics for movement of dynamic strata and development of bed-separated fissure in working faces including 24,207, 24,208, and 29,210 were investigated by experimental simulation and numerical simulation, which was based on a similar simulation test system and Fast Lagrangian Analysis of Continua 3D (FLAC(3D)) statistical analysis software. Results from the experimental simulation demonstrated that the movement of dynamic strata during the mining process could be expressed as follows: underground mining -> submerged rock -> arch-shaped rock -> pit-type subsidence region -> perforation of slope fractures. When the working face 29,210 was advanced to the mining stop line, the overlying rock strata generally slid towards the slope with less separation cracking in the vertical direction. With the continuous advancement of working face 29,210 , the slope stress increased significantly and formed a slip surface or potential slip surface in the sloping rock. Moreover, the numerical analysis, similar material simulation experiment, and actual mining results were all similar, indicating that a similar material simulation experiment based on a sheet of brittle material well reflected the characteristics for the movement of dynamic strata in combined open-pit and underground mining.