浅埋煤层开采下根土层坡度对植物侧根损伤的影响及力学响应特征数值模拟

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

    • 摘要: 在我国西部干旱半干旱浅埋煤层矿区,植被退化已成为制约生态修复的关键瓶颈,而植物侧根损伤更是导致矿区开采植被退化的重要诱因。因此,根土层坡度作为影响采动应力分布的关键因素,其对采动诱发植物侧根应力损伤的影响规律亟待深入探讨。本文以神东矿区大柳塔煤矿为工程背景,依据准黏聚力理论和锚固理论,构建基于FLAC3D的植物侧根应力损伤数值模型;结合控制变量法,模拟不同根土层坡度条件下根土复合体及侧根的宏观力学扰动特征,以分析采动应力对植物侧根损伤及根土层塑性区演化的影响规律,并探讨了根土复合层抗剪强度机理。结果表明:①随坡度增加,根土底层最大剪应力和侧根所受最大应力均显著上升;②侧根应力在坡脚处产生应力集中,且θ=6.1°为应力集中临界点,左侧根系(靠近坡肩)应力值高于右侧,θ=9.1°时左侧根系应力峰值达13.78 MPa;③根土表层以拉伸破坏为主,底层以剪切破坏为主,且塑性区破坏范围随坡度增加而扩展;④相较于单一主根,侧根网络的加入不仅能增强根土复合体的整体稳定性,还能通过其锚固作用,有效提升斜坡土体的抗剪强度。本研究创新性地将侧根网络与斜坡地形耦合纳入采动损伤模型,明确了坡度对根系应力分布的关键影响,揭示了采动应力在斜坡根土层中的坡脚应力集中-侧根应力缓冲-根土复合承载的三重力学响应机制,提出了侧根通过分担拉应力和增加抗剪强度增量延缓根系损伤的力学认知。研究结果可为西部矿区植被保护与生态修复提供理论依据。

       

      Abstract: 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 FLAC3D, 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.

       

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