特厚煤层综放沿空巷道顶煤挤压破裂机理研究

The large-scale fully-mechanized caving mining in an extra thick coal seam may bring out roof-coal mass squeezing deformation and failure in plumb direction in a gob-side entry. A comprehensive method including laboratory tests, theory analysis, numerical simulation and field monitoring is employed in this study. Based on the practical excavation and mining disturbance process roof-coal mass underwent, mechanical response properties of coal mass under the real stress path induced by mining is investigated, and as a result, a constitutive model reflecting nonlinear deterioration law of strength and dilatancy mechanical characteristics of post-peak coal mass is built. The critical mechanical condition of catastrophe and instability of roof-coal mass is revealed, and the evolution law of stress and displacement field in roof-coal mass is also studied, thus the mechanical evolution mechanism from squeezing to failure to instability of roof-coal mass is clarified. The optimization methods of the time-space relationship of mining and excavation are investigated, and the reinforcement principles of roof-coal mass in gob-side entry are also proposed, and the control mechanism of support structure to the squeezing deformation of roof-coal mass in the plump direction is further clarified. Consequently, a control principle and approach for roof-coal mass of gob-side entry with fully-mechanized caving mining in an extra thick coal seam is set up. All these results have important theoretical significance and broad application prospect for the stability control and disaster prevention of roof-coal mass of gob-side entry and the efficient mining of thick coal seam resources.

针对特厚煤层大型综放开采条件下沿空巷道顶板煤体沿水平方向发生的挤压变形与破裂问题，本项目拟采用室内试验、理论分析、数值模拟、现场实测等相结合的研究方法，基于特厚煤层综放沿空巷道顶煤经历的实际开采扰动过程，探索采动应力路径下煤体力学响应特性，构建反映煤体峰后强度非线性劣化与扩容力学特性的本构模型；探讨顶煤灾变失稳的临界力学条件及应力位移场时空演化规律，揭示顶煤由挤压→破裂→失稳的力学演化机理；探究综放沿空巷道采掘时空关系优化方法与顶煤加固准则，分析支护结构对顶煤水平方向挤压变形的控制原理，形成特厚煤层综放沿空巷道顶煤控制原理与方法。本项目研究成果集特厚煤层综放沿空巷道顶煤力学响应特性、挤压破裂机理与控制方法于一体，对于综放沿空巷道顶煤稳定性控制及其灾害防治、厚煤层资源高效开采具有重要的理论意义和广阔的应用前景。

大型综放开采尤其是工作面长度在200~300m以上、开采煤层厚度8~12m以上的特厚大型综放面已成为我国厚及特厚煤层高效开采的重要发展方向。与之相匹配的综放回采巷道却面临着巷道大变形、厚煤顶等围岩控制难题。大量现场工程实测发现，特厚煤层综放沿空巷道顶板煤岩体变形破坏以水平挤压破裂为主，顶板岩层自煤柱侧向实体煤侧发生明显水平挤压运动形成挤压—松扩破碎带，严重影响综放开采高产高效。本项目以特厚煤层综放沿空巷道顶板煤岩体为研究对象，进行如下研究内容研究：（1）特厚煤层综放沿空巷道顶板挤压破裂特征；（2）特厚煤层沿空巷道顶煤力学响应特性及本构模型；（3）综放沿空巷道顶板煤岩体挤压破坏机制研究；（4）综放沿空巷道顶煤采掘时空关系及控制原理与方法。主要研究结论：（1）特厚煤层综放沿空巷道顶板挤压破裂变形特征突出，沿水平方向顶板岩层水平运动剧烈，存在围岩错动形成的明显挤压破碎带；（2）Double-yield本构模型能够较好地还原采空区冒落矸石的力学行为，应变软化模型可以模型顶板煤体力学行为，两种本构模型结合可以有效模型特厚煤层开采过程中沿空煤巷挤压破裂变形过程；（3）数值模拟揭示了煤柱宽度和强度是沿空巷道顶板挤压破裂变形破坏的关键因素；（4）在关键块回转下沉运动过程中，将会对沿空巷道顶板产生较高的不均衡支承压力和偏斜挤压力，并造成煤柱帮的严重压缩变形，最终导致沿空巷道应力分布和围岩性质沿巷道中轴线的挤压变形特征，这是沿空巷道顶板挤压变形的直接原因。（5）提出了以“不对称式锚梁结构”为核心的综放沿空巷道调控系统，该调控系统不但具有控制大范围塑性破坏、抗剪性能强的优点，且能对巷道顶板煤岩体变形的不对称性做出积极响应并能对其进行有效的控制。课题研究对于丰富和完善矿山压力与岩层控制理论，推动煤矿巷道支护技术发展，实现特厚煤层综放开采的安全高产高效具有重要的理论意义和实用价值，论文研究成果对于类似条件下综放沿空巷道围岩稳定性控制和支护设计具有重要借鉴价值。