Influence of shallow coal seam mining on the surface in loess gully region: insights from numerical simulation and discrete physical model experiments

Abstract

The extraction of coal resources can greatly affect surface ecology. This impact is particularly seen in loess gully regions (LGRs), where surface cracks form and expand, threatening land stability and ecological safety. To tackle these concerns, this study combines discrete physical simulation experiments with numerical simulations. It focuses on the 135,201 working face of a typical coal mine in the LGR. A 1:100 discrete physical model is created to simulate surface crack generation and expansion across different mining stages. This model enables the analysis of overburden fissure evolution, surface crack development, and surface movement patterns. The research reveals that the development of surface cracks is jointly influenced by the characteristics of mining—induced overburden pressure and the surface topography. During the second mining stage (the Bottom of the Gully Mining Stage), underground mining has a relatively small impact on the surface. However, in the third stage (the Back of the Gully Mining Stage), the surface is more frequently and severely affected by underground excavation, with the same underground mining distance causing more intense surface disturbance. Numerical simulations are also used to study the failure, stress, and surface movement and deformation of the overlying rock layer in the mining area. Field observations further analyse the initiation, active, and recession stages of surface subsidence in the LGR during coal mining. Calculations of tilt and curvature variations between adjacent measurement points show that surface tilt and curvature changes along the inclination observation line are more regular, with maximum tilt values reaching 61.7 mm/m and 60.8 mm/m. However, variations along the strike observation line are influenced by the complex local topography and geomorphology. Overall, the results offer useful insights for coal mining and surface protection in similar geological settings, especially through the physical model experiments applied in this study.