Simulation study on the mechanism and influencing factors of water and sand inrush in the working face of thin bedrock with laterite layer

In response to the roof of a thin bedrock working face under a loose aquifer in a coal mine being cut off, resulting in the water and sand inrush disaster, taking the 30108 working face of Haojialiang Coal Mine in Shaanxi Province as the background, the mechanism of water and sand inrush is theoretically analyzed. Through numerical simulation methods, the process of water and sand inrush in the working face is reproduced when the bedrock is 20 meters thick, the laterite layer is 40 meters thick, the mining height is 6.5 meters, and the advance is about 20 meters. And an analysis of influencing factors is conducted. The research has found that under the conditions of thin bedrock and thick laterite layer, the inherent characteristics of laterite layers have a significant inhibitory effect on the development of fracture zones, the development of water conducting fracture zones is incomplete and insufficient. However, during the continuous mining of multiple adjacent working faces, the strength of laterite layer gradually decreases due to the influence of mining and water infiltration erosion, and the height of the fracture zone gradually increases. When the strength of laterite layer reduces by about 47%, the roof is prone to cutting and causing water and sand inrush accidents. The further simulation indicates that, in addition to the inherent characteristics of the laterite layer, the main factors affecting the water and sand inrush in the working face caused by overburden failure also include bedrock thickness, laterite layer thickness, mining height. Therefore, studying the mechanism of water and sand inrush and the main influencing factors is of great practical significance for preventing similar accidents in mines under similar conditions.