Numerical Investigation of the Release and Motion Behavior of Top Coal and Rock During the Advancement of a Coal Mining Face Using SPH

The top-coal caving mining techniques are an effective method for extracting thick coal seams and play a crucial role in achieving efficient and safe top-coal extraction. Numerical simulations are essential for modeling top-coal caving behavior under complex geological conditions. This paper employs the Smoothed Particle Hydrodynamics (SPH) method to investigate coal release and support movement during the advancement of multi-layer caving faces, addressing the parameter uncertainty issues commonly associated with traditional discrete element methods. A coal release model based on elastoplastic constitutive relations was developed. Leveraging the advantages of the SPH method for simulating large deformation problems, this study combines the elastoplastic model with the Drucker–Prager yield criterion to analyze the effects of various material parameters (e.g., friction angle, thickness, and density) on the evolution of the coal–rock interface during mining face advancement. Experimental validation confirmed the model’s effectiveness in simulating the coal–rock interface evolution and granular coal flow. The study also examined how rock cohesion and elastic modulus affect the pressure and amount of coal released during the cyclic coal release and support movement process. Results show that the noncohesive model effectively simulates bulk coal particle flow, with SPH simulations aligning well with experimental data. By activating and deactivating virtual boundary particles at the coal release port, the opening and closing of the release port were modeled, while a movable boundary was implemented for the support’s tail beam to simulate its vertical movement along the mining face. Under the operational parameters of a 2[Formula: see text]m coal release step and 15 release cycles, the evolution of the coal–rock interface during mining face advancement was simulated. As coal release occurred continuously along the strike of the mining face, the bimodal stress trends on either side of the release port gradually weakened. The material’s friction angle and cohesion significantly influence the top-coal caving process, as changes in shear strength and bonding affect the migration of coal and rock particles. During the coal release-support movement cycle, the initial pressure on the support’s top plate decreased overall, stabilizing with periodic oscillations. The research provides theoretical insights that can improve the efficiency of top-coal caving in practical applications.