A new numerical method for calculating residual deformation in mined-out areas considering water–rock interaction and its application

Globally, extensive land regions have fallen victim to coal mining subsidence, rendering the reuse of goaf sites a crucial concern. The residual deformation amount of these sites is the linchpin for determining their reusability. Presently, numerical computations of residual deformation in goafs, which overlook water-rock coupling, breed significant errors, posing severe threats to the safety of on-site structures. To remedy the situation, this research hinges on the mechanical experiment results of fractured rock masses under water-rock interaction within the goaf. By leveraging an embedded programming language, it pinpoints the irregular damage range of overlying strata due to water-rock effects. Then, corresponding mechanical parameters are allocated to the surrounding rocks at diverse spatial positions, with the erosive impact of water-soaked coal pillars also factored in. This gives rise to a novel numerical method that more precisely gauges groundwater's influence on strata movement and surface subsidence. Using the 01 working face of a Shandong mine as a practical backdrop, the new method verifies its reliability and accuracy. When contrasted with traditional approaches, be it neglecting water filling or assuming full saturation in the goaf, it slashes the calculation error by 20%, furnishing new approaches for residual deformation calculation and novel perspectives for evaluating site stability under complex geological conditions.