A Study on the Migration Law of Overburden and Fracture Fractal Evolution Characteristics Under the Influence of Remaining Coal Pillar in Gently Inclined Multi-Coal-Seam Mining

To address the challenge of intense pressure manifestation induced by remaining coal pillar from gently inclined multi-coal seam mining, a physical similarity simulation experiment was conducted using microseismic, thermal infrared, and borehole television monitoring. The overlying strata movement process, energy release characteristics, and fracture fractal evolution patterns were systematically investigated. The 3DEC numerical simulation was employed to evaluate the effectiveness of roof cutting measures. The results indicate that the overburden movement can be divided into three stages: formation of remaining coal pillar, suspension and fracturing of interlayer rocks, and subsidence and migration of overburden. The suspension of rock strata and the load transfer from uncollapsed strata are the key factors inducing dynamic disasters. Furthermore, the occurrence of disaster-causing energy events exhibited concentration and suddenness; only two IV high-energy events were recorded, accounting for 3.62% of the total energy, corresponding to the sudden fracturing of rock strata and the collapse of the entire overburden. A threshold of 250 J can serve as a criterion for identifying high-energy disaster events in similar models. Combined with the fractal dimension evolution process of fractures, it followed a pattern of growth, stabilization and renewed growth. After the upper-seam and W1121 working face were mined, the fractal dimension increased to 1.324. It remained within 1.372–1.377 during interburden suspension and reached 1.417 after interburden failure. These changes indicate that repeated multi-seam mining promotes upward fracture-zone propagation, potentially affecting the height of the water-conducting fracture zone. Finally, roof cutting was simulated in potentially hazardous coal-rock zones to evaluate pressure relief. Following pressure relief, suspension and hinging of fractured rock beams were largely eliminated. Overburden subsidence became more uniform, while lateral compression on one side of the panel coal pillar decreased markedly. Compaction within the goaf also became more uniform. These findings provide a theoretical basis for safe and efficient multi-seam mining and dynamic hazard control in mines with similar conditions.