Deformation properties of rock strata based on angular displacement and its hydrogeological significance

The deformation behavior of the roof and floor strata during coal seam mining plays a critical role in the development of mining-induced fractures and is an intrinsic factor in the prevention and control of coal and rock dynamic disasters, such as mine water hazards. This study investigates the critical values of the rock failure angle displacement based on the deformation performance of the strata through both laboratory and field experiments. A method for assessing the strata failure condition using the differences in deformation performance is proposed. The results indicate that the critical value of the rock failure angle displacement is closely related to the lithology, thickness, and cross-sectional area of the strata. Strata with higher strength can withstand greater loads, exhibiting larger critical angle displacements, whereas strata with lower strength experience greater angle displacements under the same load, resulting in more significant deformations. Strata with larger thicknesses and cross-sectional areas tend to have smaller critical angle displacements, indicating a reduced capacity for deformation. The angle displacement ( θ _i ) and the critical angle displacement ( θ ₀ ) under unit stress differ, leading to temporal and dynamic differences in the horizontal and vertical fracture formation during strata deformation and failure. This results in the manifestation of “anisotropic seepage” behavior in groundwater, which gives rise to various forms of water hazards, including sequential water inflow, delayed water outbursts, and backflow. By using the critical values of angle displacement under unit stress as a criterion for determining strata deformation and failure, the extent of fracture development and the range of mining-induced damage zones can be more conveniently assessed compared to traditional mechanical criteria. The findings of this study are of significant practical importance for the prevention and control of mine water hazards and the protection of groundwater environments.