A Laboratory and Numerical Simulation Study on Compression Characteristics of Coal Gangue Particles with Optimal Size Distribution Based on Shape Statistics

Gangue particles (GP) are an important part of solid filling materials in coal mines. The compression characteristics (CC) of gangue determine whether it can effectively control roof subsidence. The particle size distribution (PSD) of GP is the main factor affecting the CC; therefore, it is important to find the optimal size distribution of GP and to investigate the macrodeformation and micromotion characteristics of gangue compression. Here, Talbol theory was used to study the compression resistance of gangue granules. It is concluded that the compression modulus of continuously graded gangue is the largest when the Talbol coefficient n is 0.4. The engineering discrete element method was used to simulate and analyze the optimum PSD (n = 0.4) and to study the stress transfer of GP during compression. The results show that with the increase of stress, the microstructure of gangue particles changes in the support skeleton, the skeleton is destroyed and particles flow, thus forming a more stable support skeleton. The resultant force direction of particles changes from the initial vertical downward to the scattered distribution of the central axis and finally to a generally scattered distribution. The number of strong chains and weak chains increases, and the main conductive stress on strong chains becomes a uniform conductive stress on the weak chains. Most of the particles in the upper and middle parts of the model exhibit linear motion. The trajectories of the middle and lower particles in the model are clustered, undergoing only small displacement.