深部磷矿巷道软弱围岩失稳机理及支护方案优化研究

Research on Instability Mechanisms and Support Optimization for Weak Surrounding Rock in Deep Phosphate Mine Roadways

摘要: 本研究以贵州磨坊深部磷矿巷道为研究对象，针对含软弱夹层围岩失稳难题，系统揭示其变形机理并提出支护优化方案。研究基于地质探测与数值模拟结合的方法，通过三维激光扫描定位11处软弱夹层及断层破碎带，开展岩样力学试验与FLAC3D多工况模拟。结果表明：软弱夹层抗剪强度低导致顶板岩梁分层弯曲，水–力耦合作用下高岭石膨胀使围岩黏聚力下降，传统锚网喷支护因刚度失配难以控制深部应力释放，顶板最大拉应力达7.58 × 10⁶Pa。基于围岩分级提出差异化动态支护体系：在较完整岩层采用锚网喷支护，形成柔性承载拱；针对软弱夹层区优化设计“钢拱架 + 超前管棚 + 锚网喷”组合技术，通过钢拱架刚性骨架抑制夹层滑移，超前管棚预注浆强化围岩完整性，锚网喷层吸收变形能量，形成多级协同机制。数值模拟验证，组合支护使含3条夹层的极破碎围岩顶板拉应力降至0.26 MPa，底板压应力峰值从−16.89 MPa分散至−1.39 × 10⁷Pa，拱顶下沉量减少30%~50%，有效控制顶板离层与底板鼓胀。研究证实，软弱夹层数量与破碎程度主导应力非对称分布，而“预加固–刚性支撑–柔性约束”三位一体策略可突破传统支护瓶颈，为深部磷矿安全开采提供理论支撑，对破碎巷道围岩的稳定性有着明显的改善作用。

Abstract: This study investigates the deformation mechanisms and support optimization strategies for surrounding rock containing weak interlayers in deep phosphate mine roadways at Mofang, Guizhou Province. A combined approach of geological detection and numerical simulation was employed, utilizing 3D laser scanning to precisely locate 11 weak interlayers and fault fracture zones. Rock mechanics tests and FLAC3D multi-case simulations were conducted to analyze failure characteristics. Key findings include: The low shear strength of the soft interlayer leads to the layered bending of the roof rock beams, and the cohesion of the surrounding rock decreases due to the expansion of kaolinite under the hydro-mechanical coupling; Traditional bolt-mesh-shotcrete support systems exhibit stiffness mismatch with deep stress release mechanisms, resulting in excessive tensile stress concentration (peak value: 7.58 MPa) at the roof; A novel hierarchical support system was developed, integrating flexible bolt-mesh arches in intact rock masses and an innovative composite structure (steel arch + advanced pipe roof grouting + energy-absorbing shotcrete) in weak interlayer zones. The rigid skeleton of the steel arch frame inhibits the slippage of the interlayer, the pre-grouting of the advanced pipe shed strengthens the integrity of the surrounding rock, and the anchor net spray layer absorbs the deformation energy to form a multi-level synergy mechanism. Numerical simulations demonstrate this multi-stage reinforcement reduces tensile stress in severely fractured roofs (with triple interlayers) to 0.26 MPa, redistributes floor compressive stress from localized −16.89 MPa to dispersed −13.9 MPa, and decreases vault subsidence by 30%-50%, effectively mitigating roof delamination and floor heave. The study quantitatively establishes that interlayer density and fragmentation degree govern asymmetric stress distribution patterns (variance >65%), while the proposed “pre-grouting stabilization-rigid arch confinement-flexible deformation accommodation” trinity mechanism significantly enhances fractured roadway stability, providing critical theoretical support for safe deep phosphate mining operations.