倾斜采场覆岩非对称载荷传递路径倾角效应

Effects of coal seam dip angle on asymmetric load transfer paths in the overburden of inclined stopes

  • 摘要:
    目的 煤层倾角是导致倾斜采场覆岩载荷传递路径远较一般煤层复杂的根本原因,明确倾斜采场覆岩载荷传递路径倾角效应,对实现该类煤层围岩稳定性控制具有重要意义。
    方法 以新疆某矿为工程背景,综合采用物理相似模拟、有限元数值仿真及理论计算等方法,分析倾斜采场覆岩非对称变形破坏特征,并构建顶板应力特征量,研究不同维度条件下覆岩载荷传递路径及其倾角效应。
    结果和结论 结果显示:(1)倾斜煤层开采过程中,顶板应力特征量传递路径为倾向“m”形和走向双“n”形的分布,在平行煤层方向,顶板应力特征量传递路径为双“v”形分布,使采动影响范围以内、应力分界线以外的覆岩载荷,向采场四周煤壁作双向传递,而应力分界线以内的覆岩载荷则向工作面倾向两侧煤体单向传递。(2)随着煤层倾角的增大,采场顶板应力特征量的偏转界线范围逐渐减小,使采场四周支承压力峰值呈逐渐减小的演化趋势。(3)受此影响,倾斜采场顶板破断形态呈中上部大于下部的非对称分布形态,造成工作面倾向中部、上部支架工作阻力及其离散程度较大,支架偏载、空载现象频发,而工作面倾向下部支架工作阻力及其离散程度相对较小。(4)覆岩载荷传递路径的非对称性是导致倾斜采场顶板力学行为区域性分布的根源,且这一现象随着煤层倾角的增加而愈发突出。研究成果可指导倾斜采场支架设计与布置,预防偏载、空载,提升围岩稳定性,提高开采效率,保障煤矿安全。

     

    Abstract:
    Objectives The coal seam dip angle is recognized as the root cause of far more complex load transfer paths in the overburden of inclined stopes compared to those of common coal seams. A clear understanding of the effects of the coal seam dip angle on the load transfer paths holds great significance for the stability control of surrounding rocks in inclined coal seams.
    Methods Based on the engineering background of a certain coal mine in Xinjiang, this study investigated the asymmetric deformations and failure of the overburden in inclined stopes using physical similar material simulation experiments, finite element numerical simulations, and theoretical calculations. Furthermore, this study developed roof stress characteristic components and investigated the load transfer paths in the overburden, along with the effects of coal seam dip angle on the paths, under varying dimensions.
    Results and Conclusions The results indicate that during the mining of the inclined coal seam, the transfer paths of roof stress characteristic components exhibited an M-shaped distribution along the roof inclination but a shape of double Ns along the roof strike. Meanwhile, in the direction parallel to coal seams, these components were transferred in the shape of double Vs. Consequently, the load in the overburden within the mining influence range and outside the stress boundary transferred bidirectionally toward coal walls around the stope, while that within the stress boundary transferred unidirectionally to coals on both sides along the inclination of the mining face. With an increase in the coal seam dip angle, the deflection boundary ranges of the roof stress characteristic components gradually decreased, leading to a gradually decreasing trend in the peak abutment pressure around the stope. Consequently, the roof of the inclined stope exhibited an asymmetrical fracture morphology characterized by a larger fracture extent in its middle and upper parts than its lower part. Therefore, supports in the middle and upper parts of the mining face along its inclination exhibited high working resistance with a high degree of dispersion, leading to their frequent eccentric load and no-load phenomena. Conversely, supports in the lower part of the mining face along its inclination were subjected to relatively small working resistance with a low degree of dispersion. The asymmetric transfer paths of the overburden were identified as the underlying reason for the regional distribution of the mechanical behavior of the roof in the inclined stope, with the asymmetry increasingly pronounced with an increase in the coal seam dip angle. The findings of this study can serve as a guide for the design and layout of supports in an inclined stope, serving the purposes of preventing eccentric loading and no-load phenomena, enhancing the stability of surrounding rocks, improving the mining efficiency, and ensuring the safety of coal mines.

     

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