Numerical Simulation of Longwall Face Mining Stress Evolution Based on the Nonlinear Compression Characteristics of Goaf Gangue

The nonlinear compression mechanical properties of broken gangue in goaf directly affect the stress, deformation, and failure characteristics of mining strata. A numerical simulation is an effective approach when analyzing engineering issues during coal seam mining. Therefore, the appropriate material model and reasonable material parameters of the goaf gangue are critical in the study of the mechanical properties and mining stress evolution law. This paper adopted the double-yield (D-Y) material model to characterize the mechanical properties of goaf gangue. It established the corresponding relationship between the Salamon constitutive equation and D-Y material model parameters. Then, the numerical simulation of roof caving, gangue stack, and gangue compression during coal seam mining was realized using FLAC3D. A numerical model of longwall working face mining was established based on typical coal mining geological conditions to determine the stress evolution law in the roof and floor strata. The synchronous variation law in the vertical (σz) and horizontal stresses in the roof strata was opposite, and it was consistent in the floor strata. Finally, the evolution laws were equivalent converted into the mining triaxial compression (MTC) path, in which the mining roof triaxial compression (MRTC) path presented an S-shape, and the mining floor triaxial compression (MFTC) path presented a reverse S-shape. The results of this paper could be a basis for the study of the mechanical properties when mining rock and strata control.