Numerical simulation of plant lateral root stress perturbation during shallow coal seam mining in the semi-arid region of Western China

Abstract

Plant lateral root damage is an important ecological problem of vegetation degradation in semi-arid mining areas in western China. The damage mechanism and influencing factors of plant lateral roots caused by stress changes in root-soil layer induced by mining urgently need to be explored in depth. Based on the field survey data of plant roots, combined with quasi-cohesion theory and anchoring theory, and through the control variable method, a numerical model considering four key parameters, namely mining height, advancing distance, mining speed and coal seam burial depth, was established by FLAC3D software to analyze the macroscopic mechanical disturbance characteristics of root-soil complex and plant lateral roots. The research results show that: the stress on the bottom of the root-soil layer above the goaf area is higher than that on the surface; During the advancement of the working face from 60 m to 110 m, the failure range of the plastic zone of the root-soil layer and the stress on the lateral roots of plants showed an increasing trend, and the stress on lateral roots increases up to 3.3 MPa when the working face advances from 80 m to 110 m; in the disturbance zone, the maximum stress of the lateral roots and the failure range of the plastic zone of the root-soil layer increase with the increase of mining height, but decrease with the increase of coal seam burial depth; the change of the mining speed has little effect on the stress of the lateral roots and the failure range of the plastic zone of the root-soil layer, the maximum stress difference on the lateral roots between the maximum and minimum mining rates is only about 0.58 MPa. In addition, compared with plant roots with only the main root, plant roots with lateral root structure show better tensile and shear resistance in the root-soil layer, which shows that the presence of lateral roots help to enhance the overall stability and damage resistance of plant roots. FLAC3D was used to construct a three-dimensional visualization numerical simulation model of plant lateral root, which revealed the macroscopic mechanical response mechanism of plant lateral root damage induced by mining, and clarified the influence of various factors on plant lateral root stress damage induced by mining.The research findings enrich the understanding of plant damage mechanisms induced by underground coal mining in semi-arid areas.