Research on Simulation and Field Measurement Technology of Floor Mining Failure Depth

Aiming at the detection problem of floor mining failure zone after mining, in order to grasp the failure law of floor strata caused by mining and ensure the safe mining on confined water, in this paper, the methods of the theoretical prediction and FLAC(3D) numerical simulation was adopted to study floor mining failure depth of the 41303 working face in Huafeng coal mine, and then the system of double ends borehole plugging device in measuring leakage was applied to the field measurement to verify the theoretical prediction and numerical simulation results, and the results of the three methods were compared. The research shows that: (1) the prediction depth of floor mining failure depth is 16.89 similar to 21.24mm, and the numerical simulation results are 15m, and the measured depth is 13.15m; (2) Through comparison, it can be seen that the numerical simulation result is basically close to the field measured result. The result of empirical formula is expected to be conservative. In summary, the maximum floor mining failure depth of the 41303 working face is 13.15m. It provides scientific basis for the safe mining of coal resources under the pressure of the confined water; (3) With the advancing of the 41303 working face, the plastic zone of the bottom plate is increasing. When the working surface reaches 90m, the depth of the floor mining failure reaches the maximum value of 15m, and the depth is no longer increased and its shape is a straight line which is approximately parallel to the floor. the change trend of plastic zone is consistent with the maximum principal stress.