Numerical simulation of the effect of root-soil layer slope on plant lateral root damage and its mechanical response under shallow coal seam mining

In the arid and semi-arid regions of western China, where shallow coal seam mines are located, vegetation degradation has become a key bottleneck constraining ecological restoration, and damage to plant lateral roots is a major contributing factor to this degradation. Therefore, as the slope of the root-soil layer is a critical factor influencing the distribution of mining-induced stresses, there is an urgent need for in-depth investigation into the mechanisms by which it affects stress-induced damage to plant lateral roots. This study takes the Daliuta Coal Mine in the Shendong Mining Area as its engineering context. Based on quasi-cohesive theory and anchorage theory, a numerical model of lateral root stress damage is developed using FLAC^3D, and the control variable method is combined to simulate the macroscopic mechanical disturbance characteristics of the root-soil complex and lateral roots under different root-soil layer slope conditions. This analysis aims to investigate the influence of mining-induced stresses on lateral root damage and the evolution of the plastic zone within the root-soil layer, while also exploring the mechanism of the root-soil composite layer’s shear strength. The results indicate: ①as the slope increases, both the maximum shear stress in the lower soil layer and the maximum stress experienced by lateral roots rise significantly. ②Stress concentration occurs at the toe of the slope, with θ=6.1° serving as the critical point for stress concentration; stress values in the left root system（near the slope shoulder） are higher than those in the right, and the peak stress in the left root system reaches 13.78 MPa at θ=9.1°. ③Tensile failure dominates in the surface layer of the root-soil system, while shear failure dominates in the lower layer; furthermore, the extent of failure in the plastic zone expands with increasing slope gradient. ④Compared to a system with a single taproot, a plant root system with lateral roots can enhance the overall stability of the root-soil composite. The inclusion of lateral roots improves the shear strength of the slope soil. This study innovatively incorporates the coupling of lateral root networks with slope topography into a mining-induced damage model, clarifies the critical influence of slope gradient on root system stress distribution, and reveals the buffering and reinforcement mechanisms of lateral roots in stress transfer. The findings provide a theoretical basis for vegetation conservation and ecological restoration in western mining areas.