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.

To improve the utilization rates of soda residue (SR) and fly ash (FA), reduce environmental pollution, and enhance the mechanical properties of marine clay (MC), this study proposes mixing SR, FA, and MC with cement and /or lime to prepare soda residue-fly ash stabilized soil (SRFSS). Using an orthogonal design for the proportions, the study analyzes the compaction performance, unconfined compressive strength (UCS), and shear strength of SRFSS. The influence of various factors on the mechanical properties of SRFSS was investigated through range and variance analyses. The mechanical mechanism was revealed from the perspectives of grading and cementation. The results indicate that SR and FA significantly impact the mechanical properties of SRFSS. The range and variance analysis results are consistent: SR content of 30% and 70% has the most significant impact on compaction performance and UCS, respectively, while 20% FA content has the greatest effect on shear strength. The recommended base proportion is 70% SR + 20% FA + 10% MC. The gradation and cementitious properties jointly influence the mechanical performance and microstructure of SRFSS, G8 has the lowest planar porosity, at only 0.89%. The calcium (Ca) content in SRFSS specimens with different proportions shows significant variation, from 5.0 to 53.6 wt%, while the silicon (Si)/Al ratio (0.76-2.73) shows relatively small fluctuations. The primary hydration products include calcium hydroxide (Ca(OH)2), calcium silicate hydrate (C-S-H), and ettringite (AFt).

Improving the engineering and mechanical properties of marine clay (MC) by modifying it with soda residue (SR) and fly ash (FA), and stabilising with cement and /or lime to create Soda residue-Fly ash stabilised soil (SRFSS). Using the orthogonal design, the mechanical properties of SRFSS were analyzed, recommending a basic proportion of 70% SR + 20% FA + 10% MC. Results showed SR significantly impacted optimum water content (OWC), unconfined compressive strength (UCS), and water absorption quality. FA influenced the maximum dry density (MDD), while cohesion (c) was mainly affected by lime and cement. Cement had a higher unit contribution rate to mechanical indices than lime, except for MDD and OWC. The excellent properties of SRFSS were derived from good gradation and the cementation action of the materials. This research provides a solution for improving MC properties and promoting solid waste reutilisation.

To broaden the sources of subgrade filler and the utilization of Soda Residue (SR), SR was employed to modify clay by adding a small amount of lime for further stabilization, forming a Lime-Soda-Residue-Stabilized Soil (LSRSS). A set of intensive research paths was established, from testing of laboratory mechanical property, mechanism disclosure, and field verification to operational effect. Through Unconfined Compressive Strength (UCS), California Bearing Ratio (CBR), and Resilient Modulus (MR) experiments, it was concluded that with the increase in SR content, the UCS, CBR, and MR values of LSRSS showed an increasing trend then followed by a decrease, reaching their peak values, respectively of 0.62 MPa, 65.0%, 78.83 MPa, all at 30% SR content. An optimal proportion was determined for LSRSS as 6% lime, 30% SR, and 70% clay. The UCS, CBR, and MR values of optimal proportion all increased with the increase of compaction degree, but increased first and then decreased with the increase of water content. Their maximum values did not correspond to the OWC of 23% but to 27%, called the compaction water content, which was suitable for application in the actual LSRSS subgrade. Field test results showed that the UCS, CBR, and MR values were 0.85 MPa, 86.5%, and 135.7 MPa, which all were higher than the laboratory values, and the long-term road performance was outstanding. The analysis demonstrates that the better strength and road performance of LSRSS are mainly determined by the superior gradation and the reaction of three materials. The laboratory and field test results collectively provide data evidence for excellent performance and lay a solid foundation for the wider application of the LSRSS subgrade.