Critical criterion and physical simulation research on progressive ascending water inrush in hidden faults of coal mines

In order to solve the problem of concealed hidden fault water inrush in the coal floor,the simplified fracture mechanical principle model of buried fault progressive ascending was established in this study. The critical mechanical analytical formula was deduced and the minimum safe distance between fault and damage area of footwall was calculat- ed. Experiments were conducted to simulate the process of buried fault progressive ascending by employing the similar material. There was stress concentration in the tip of buried fault under the mining effect. The stress intensity factor in- creased beyond the critical value,consequently,the expansion happened,which led to lift height increase and released random stress. With the face advancing,the stress concentrated,the intensity factor increased and exceeded a critical value once again. Water inrush would occur when the lift height increased and reached the minimum distance of foot- wall destruction area. The intensity of water inrush increased with the increase of the initial water conduction height and the decrease of the rock strength. If the natural initial lift height of blind fault was higher,the progressive lift destruction would be stronger,which would easily lead to the water inrush in the footwall of coal seams.