Theoretical models for simulating the failure range and stability of inclined floor strata induced by mining and hydraulic pressure

There is a risk of floor failure within mining of coal seams above aquifers, therefore investigating the processes involved is of great significance for the prediction and prevention of mine water hazards. With consideration of the effects of mining pressure and non-uniformly distributed hydraulic pressure, the two-dimensional (2D) hydraulic-mechanical calculation (HM) model and the key-strata stability analysis (KS) model were proposed to analyze the theoretical range of failure and the stability of inclined floor strata after mining. To validate the model, a numerical simulation of the failure characteristics of inclined floor above a confined aquifer was conducted along with an in-situ investigation. The results showed approximate agreement between the theoretical and simulated failure ranges of the inclined floor along the strike and inclination, with their characteristics being approximate to "spoon-shaped" and "inverted saddle-shaped with upper-small-lower-large", respectively. The theoretical failure depths of the floor around the mining face side and the upper and lower parts were 13 m, 12.5 m and 14 m, respectively, with general agreement between simulated and measured results. Moreover, the zones prone to water intrusion were indicated to be mainly distributed near the upper end, lower end and mining face side of the inclined key strata, in good agreement with the distribution of the area disturbed by mining and the risk of groundwater inrush induced by the vertical failure depth. The research results could provide an improved understanding of the mechanism of water inrush from underlying aquifers.