Mechanical Analysis of the Failure Characteristics of Stope Floor Induced by Mining and Confined Aquifer

Abstract

Mining above confined aquifer has become an important task for water inrush prevention in China. To study the failure characteristics of stope floor along the strike, a mechanical model under combined action of mining and confined aquifer was constructed, and the distribution of vertical stress, horizontal stress, and shear stress was obtained. Based on the Mohr–Coulomb criterion, the failure range of the floor is determined and verified by the in situ test. The results indicate the following. (1) Both vertical stress and horizontal stress in the stope floor take the junction of stress increasing area and stress decreasing area as the dividing line, forming two groups of “convex arches” at the solid coal side and the goaf side, respectively. (2) The vertical stress gradient in the solid coal side is significantly higher than that in the goaf side, while the horizontal stress gradient in the solid coal side is similar to that in the goaf side. The shear stress distribution is divided into three regions by the boundary between positive and negative shear stress, which makes the stope floor in this area to show compression shear or tension shear failure. (3) According to the in situ test, the maximum floor failure depth of 41503 working face is 11.38 m, which is quite close to the theoretical calculation result of 9.68 m. (4) Applying the mechanical model to five other coal mines with different mining conditions and stress states, the maximum absolute error between the measured and theoretical values of floor failure depth is 1.1 m, the average absolute error is 0.8 m, the maximum relative error is 8.2%, and the average relative error is 6.5%. The study provides a certain mechanical basis and reference for the floor failure mechanism induced by mining and confined aquifer.

Experimental Study on Floor Damage and Slurry Material Ratio Optimization in Deep and High Confined Water Mining

“…In recent years, domestic and foreign experts and scholars have used theoretical analysis, numerical simulation, and other research methods to evaluate and predict the risk of water inrush from the mechanism of floor water inrush and the development of floor fissures and have achieved remarkable results [12][13][14][15][16]. For example, Yu, Xu et al [17,18] used BP neural network, linear regression, and other methods to predict the depth of floor damage and predicted and analyzed the possibility of floor water inrush.…”