Study on laws of water inrush and sand burst migration based on LBM-DEM coupling method

Due to the special geological conditions and high-intensity mining methods in the western mining areas, it is easy to induce water inrush and sand burst disasters, so it is urgent to study the mechanism of the disaster. In order to understand the law of water and sand migration under water burst and sand burst and the key causes of disasters, the problem of water and sand two-phase migration in the single-fracture open channel model was preliminarily explored with the aid of the LBM-DEM coupling simulation method. Compared with the change of section flow rate and the sand break rate per unit time, the influence of different boundary pressure, crack opening width and sand layer thickness were analyzed and the numerical calculation results of maximum unit mass flow rate at different boundary pressures were fitted based on the Bulsara formula. The results show that with the increase of boundary pressure, the cross-sectional flow rate and the maximum sand bursting rate increase monotonously. Under high pressure, sand particles are more likely to accumulate at the crack opening and form a temporary compact structure to hinder the migration of water and sand. The cross-sectional flow rate and maximum sand break rate decrease gradually. As the opening width increases, the cross-sectional flow rate, the maximum sand break rate and the volume of the compact structure formed by sand particles at the opening all increase monotonically, but but the increase decreases gradually. The modified formula based on Bulsara equation can fit the maximum unit mass flow curve well. It is found that one of the key factors affecting the disaster is the volume of dense sand structure; as the thickness of the sand layer increases, the duration of sand dense structure increases and the hindering effect gradually increases. The cross-sectional flow rate and the maximum sand break rate gradually decrease and the decline gradually decreases. The disaster occurred from the initial water-driven sand flowing out of the crack orifice stage to the stage of sand-grain compact structure instability caused by sand-grain dumping.