The contribution of physical-chemical effects of abandoned mine water to the deterioration of Mode-I fracture toughness- based on CT-DEM integrated modeling

The fracture zone of abandoned mining sites is prone to Mode-I fractures. In coal rock layers with more aquifers, the erosion and dissolution of abandoned mine water will accelerate this process. To investigate the respective effects and contributions of swelling and erosion on Mode-I fracture in abandoned mine water, this study combines laboratory experiments and discrete element simulations to explore the macro- and micro-fracture processes of samples under the coupled action of erosion and swelling. Five time gradients were set for treating the prepared NSCB samples (0, 7, 14, 21, 30 days), and the degree of deterioration of the Mode-I fracture toughness of the coal samples was explored. A mechanical model for mineral dissolution-swelling was established by combining Computed Tomography(CT) scanning and the discrete element grain-based model (GBM). The Swelling/ dissolution expansion coefficient were defined, by adjusting the expansion coefficient, the model simulates the damage process of coal particles and minerals undergoing dissolution-swelling. The research results indicate that the failure behavior transitions from brittle fracture to ductile fracture. Simulation results indicate that the initial stage of contact between abandoned mine water and coal is primarily characterized by hydraulic swelling, with corrosion starting to affect the sample in the later stages of contact. It is observed that corrosion leads to an increase in transgranular cracks during Mode-I fracture processes, whereas the original sample primarily experiences slip fracture along mineral crystal boundaries.