Study on Failure Law and Failure Depth of Floor in Deep Mining

Aiming at the problem of floor failure in deep mining nowadays, taking a certain working face of a deep mine in Shandong, China as the engineering background, the method of numerical simulation and similar simulation are used to study the failure law of floor in the mining process. The numerical simulation results show that the vertical stress increasing area of deep mining is “bubble-shaped”; shearing stress is generally “butterfly-shaped”; plastic zone distribution is “rectangular-shaped”, shearing failure is dominant in the surrounding and middle parts, the range of plastic zone decreases with the increase of the depth from the coal seam; when the working face is advanced to 100 m, the floor failure depth reaches 30 m and tends to be stable state no longer increase. The similar simulation results show that that with the increase of floor rock depth, the stress value decreases, and the stress propagation of floor rock mass to deep depth has a lag effect, and the lag time is longer with the increase of depth. Finally, the depth of floor failure in working face is measured by the method of subsection water injection in the downhole. The measured result shows that the maximum floor failure depth is 31.6 m, which is similar to the result of numerical simulation. The two results were verified each other. The numerical simulation can provide a reference for the study of floor failure law in similar mines, and it can also provide some guidance for the prevention and control of water inrush in deep mines.