重复采动作用下覆岩采动应力演化特征

    Mining-induced stress evolution characteristics of overlying strata under repeated mining

    • 摘要: 采动应力集中是采场煤岩发生变形失稳的主要原因之一,掌握采场煤岩采动应力演化规律,对防控煤岩发生动力灾害具有重要意义。采用物理模拟与数值模拟相结合的研究方法,分析了重复开采作用下覆岩宏观变形破坏特征,研究了间隔岩层主应力传递演化路径与方向偏转特征,揭示了重复采动作用下工作面采动应力演化机理。结果表明:下层煤开采过程中,间隔岩层变形破坏范围呈先增大后逐渐稳定的演化趋势,位于上层煤底板下方间隔岩层处出现大量微裂隙,裂隙未与上层煤底板贯通,覆岩未发生二次变形破坏;重复采动作用下,间隔岩层应力释放范围与主应力偏转程度不断增加,受上层煤底板卸压与覆岩变形破坏范围的影响,工作面前方煤岩的采动应力集中程度变化不同;受下层煤顶板卸压−上层煤底板增压−重复卸压−下层煤顶板增压−两煤层增压影响,间隔岩层第一主应力角度偏转具有区域性,在此过程中,在覆岩载荷传递与上层煤底板应力释放范围作用下,工作面前方煤体的支承压力峰值呈先稳定后缓慢增加到快速增加的演化趋势,当工作面推进距离与工作面长度之比大于1.2时,工作面采动应力峰值增长率快速增加,工作面极易发生变形失稳。

       

      Abstract: Mining-induced stress concentration is one of the main reasons for the deformation and instability of coal and rock in stope. It is of great significance to master the evolution law of mining-induced stress of coal and rock in stope for preventing and controlling the dynamic disaster of coal and rock. In this paper, the macroscopic deformation and failure characteristics of overlying strata under repeated mining are analyzed by combining physical simulation with numerical simulation. The evolution path and direction deflection characteristics of principal stress transfer in interbedded rock layer are studied, and the evolution mechanism of mining-induced stress in working face under repeated mining is revealed. The results show that during the mining process of the lower coal seam, the deformation and failure range of the interbedded rock layer increases first and then gradually stabilizes. A large number of micro-cracks appear in the interbedded rock layer below the upper coal floor, and the cracks are not connected with the upper coal floor. There is no secondary deformation and failure of the overlying rock. Under the action of repeated mining, the stress release range and principal stress deflection degree of the interbedded rock layer are increasing. Affected by the pressure relief of the upper coal floor and the deformation and failure range of the overlying rock, the stress concentration degree of the coal and rock in front of the working face is different. Affected by the pressure relief of the lower coal roof-pressurization of the upper coal floor-repetitive pressure relief-pressurization of the lower coal roof-pressurization of the two coal seams, the deflection of the first principal stress angle of the interbedded strata is regional. In this process, under the action of overburden load transfer and upper coal floor stress release range, the peak value of coal abutment pressure in the front of the working face shows an evolutionary trend of first stable, then slowly increasing to rapidly increasing. When the ratio of working face advancing distance to working face length is greater than 1.2, the growth rate of mining stress peak value of working face increases rapidly, and the working face is prone to deformation and instability.

       

    /

    返回文章
    返回