Mode-I-crack compression modeling and numerical simulation for evaluation of in-situ stress around advancing coal workfaces

The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to greatly increase probability of accident occurrence. To reveal the distribution of high stress around working faces, we put forward the mode-I-crack compression model. In this model, the goaf following a working face is regarded as a mode-I crack in an infinite plate, and the self-gravity of overlaying strata is transformed into an uniform pressure applied normal to the upper edge of the model crack. Solving this problem is based on the Westergaard complex stress function. For comparison, the software RFPA-2D is also employed to simulate the same mining problem, and furthermore extendedly to calculate the stress interference induced by the simultaneous advances of two different working faces. The results show that, the area close to a working face or the goaf tail has the maximum stress, and the stress is distributed directly proportional to the square root of the advance and inversely proportional to the square root of the distance to the working face. The simultaneous advances of two neighboring working faces in different horizontals can lead to extremely high resultant stress in an interference area.