The roof caving characteristics of the mining face significantly influence gas migration in old goafs, underground tunnel excavation, and the stability of surface structures. The mining length and the width of the retained coal pillar are crucial parameters affecting roof deformation and caving. By fabricating irregular-shaped specimen with varying mining lengths, conducting uniaxial compression tests, collecting defor-mation data using acoustic emission and VIC monitoring systems, and performing numerical simulations with ABAQUS, the mechanical properties and deformation characteristics of these irregular-shaped specimen were re-vealed. The findings indicate that: (1) Under uniaxial compression, the peak stresses of specimens with mining lengths of 50 mm, 60 mm, 70 mm, and 80 mm were 14.166, 9.738, 7.160, and 6.524 MPa, respectively. As the mining length increased, the peak stress of the specimens gradually decreased, with the rate of decrease slowing down. (2) The ring count and cumulative ring count of acoustic emissions exhibited distinct stage characteristics under uniaxial compression. The cumulative ring count decreased with increasing mining length of the irregular-shaped specimen, indicating a reduction in the internal damage area. (3) The ABAQUS numerical simulation results demonstrate that an increase in vertical loading stress leads to the gradual expansion of the plastic zone. When the proportion of the plastic zone is similar, the stress decreases with increasing mining length, suggesting that a longer mining length reduces the bearing capacity. Additionally, there is a linear decrease in both peak strength and the proportion of the plastic zone. The research findings can serve as a reference for studies on the failure mode and mechanical properties of roof caving in mining faces.
Zhang et al. (Tue,) studied this question.