大倾角煤层采动诱发煤壁破裂演化规律与片帮孕育机制研究

Coal face spalling is a key factor to restricting the safe and efficient mining of working face in steeply dipping coal seams. The applicant preliminary studies show that coal face failure is progressive, periodic and the deformation is large. Recent studies have found that, with mining disturbance, the influence of boundary conditions, stress environment and fracture development on coal face stability in steeply dipping stope is more significant, and the shape of coal face spalling is three-dimensional development. Based on that, taking the coal face rupture and instability and the coalface spalling mechanism of the steeply dipping coal seams as research object and the great influence that stress environment, boundary conditions, crack development degree on coal face spalling in steeply dipping coal seams as research breakthrough point, besides, taking the interaction relationship among the roof, the support and the coal face of a large inclined stope as the research link. First, based on the similar simulation platform, the mining mechanical response of coal face and roof structure in large inclined stope are studied using the digital speckle technology. Secondly, the fracture constitutive model is constructed and the 3DEC software mechanics model is developed to studied the criterion for judging the failure and instability of the coal face under the steep inclined strip is studied. Then the three-dimensional mechanical model for "Roof-coal face-support" is established to describe the rupture instability and inoculation mechanism of coal face spalling. At last, based on the internal relationship among the stiffness of the support, coal face and roof, the support resistance to ensure the stability of the coal face is determined. The research results can not only solve the coal face spalling and end face roof caving for steeply dipping coal seams, but also lay a foundation for realizing intelligent coal mining.

煤壁片帮是制约大倾角采场安全高效开采的一大难题。申请人前期研究表明煤壁破坏具有渐进性、周期性、大变形的特点，近期研究发现，随着开采扰动，大倾角采场煤壁受边界条件、应力环境、裂隙发育影响更加显著，且片帮形态是三维发育的；基于此，本项目以煤壁破裂演化与片帮孕育机制为研究目标，同时以应力环境、边界条件、裂隙发育程度对煤壁片帮的影响为研究的切入点，把大倾角采场顶板、支架、煤壁三者作用关系作为研究的纽带，首先，基于相似模拟平台，借助数字散斑系统研究大倾角采场顶板结构与煤壁采动力学响应；其次，构建裂隙本构模型与开发3DEC软件力学模型，研究大倾角煤壁破坏失稳判别准则，然后，建立“顶板-煤壁-支架”三维力学模型，获得大倾角片帮孕育机制；在此基础上，基于支架、煤壁煤体、顶板三者刚度之间的内在联系，确定保证煤壁稳定合理的支架阻力。该研究能够解决大倾角煤层煤壁片帮、端面冒顶难题，为实现智能化煤矿开采打下基础。

煤壁片帮是制约大倾角采场安全高效开采的一大难题。课题综合运用现场调研、实验、数值模拟以及理论分析等方法，针对大倾角采场煤壁采动力学响应与裂隙演化规律、大倾角采场顶板-煤壁-支架三者相互作用关系的两大关键科学问题，开展了深入系统的研究。结果表明：当煤壁处于单向应力状态下，煤壁失去应力和位移边界约束成为自由面，其承载能力减小，极易导致煤壁片帮。大倾角煤层顶板沿倾向先于工作面中上部开始垮落，并下滑充填至下部采空区，呈分区、非对称破坏特征。未垮落顶板处最大主应变值不断增长可达1.39，且应变集中位置不断向上覆岩层转移。上覆岩层在一定跨度内，沿走向开采顶板周期来压之前，煤壁水平位移量整体较小且增大过程缓慢；但当顶板周期来压之后，低位顶板来压频繁，煤壁水平位移量瞬间大幅度增大。采动影响下煤壁发生一定程度的剪切破坏，并以工作面中上部煤壁裂隙发育及变形破坏较为频繁和严重，并不断蔓延至工作面下部，其破坏形态多呈现“棱锥体”、“楔形体”。沿倾向由于煤壁破坏程度不同而导致应力释放情况不同，工作面中上部位置煤壁应力得到充分释放，应力值较小；工作面下部煤壁应力未得到充分释放，应力值较大，最终沿倾向出现了明显的应力释放区及塑性破坏区非对称分布特征。建立大倾角“煤壁-顶板-支架”系统力学模型，明确了煤壁片帮、端面冒顶、支架支护系统失效三者相互影响、恶性循环的采场围岩失稳致灾机制。构建大倾角工作面煤壁三维破坏力学模型，进一步表明了大倾角煤壁片帮滑移体呈不规则的四棱锥体形态，且该滑移体先于上层面开始断裂破坏，最终形成片帮。同时，确定了大倾角工作面煤壁片帮的影响因素及各影响因素与煤壁稳定性之间的量化关系，并获得了煤层采高、倾角、内聚力、节理间距对大倾角煤壁破坏失稳的影响规律以及煤壁位移预测模型。基于此，根据云理论建立了大倾角工作面煤壁稳定性云模型，对其煤壁稳定性进行综合辨识并进一步提出合理的煤壁片帮防治措施。