In this paper, it was determined that all of the three-dimensional principal stresses increase with depth and that both the maximum and the minimum stresses tend to be aligned in the horizontal orientation. The numerical simulation model was built using the software FLAC<Superscript>3D</Superscript> to simulate two times,...</superscript>

Gas drainage not only ensures safety in coal mine but also produces clean energy and reduces emission of greenhouse gases. However, a good method to evaluate the efficiency of gas drainage is still absent. In this study, we firstly propose a definition of gas drainage efficiency which is defined...