Reasonable width of waterproof coal pillar under the condition of different fault dip angles

Using the Mol-Coulomb rule, we calculated the critical angle of water-burst fault to determine the reasonable width of waterproof coal pillar under different fault dip angles. Based on the stability of coal pillar underground a certain pressure and on the relationship of water conducting fractures with fault and aquifer, we obtained the formula for calculating the width of waterproof coal pillar by applying the theory of elastic-plastic limited equilibrium, the theory of fluid mechanics and on the basis of this formula, the waterproof coal pillar's width of Tuo shan mine is calculated by MATLAB, with the width of coal pillar being shortened by 4 m, not only ensuring the safety production but also increasing the the recovery ratio of coal.