大倾角煤层覆岩应力非对称传递时空演化特征

Spatiotemporal evolutionary characteristics of asymmetric stress transfer in overburden of steeply dipping coal seams

  • 摘要:
    目的 大倾角煤层安全高效开采的关键是对围岩的有效控制,而发现并揭示覆岩应力传递路径的时空演化特征是围岩稳定性控制的基础。
    方法 以新疆某矿25221工作面为例,采用现场实测、物理相似模拟实验和数值计算相结合的研究方法,在综合厘定工作面矿压显现特征、覆岩变形破坏规律基础之上,构建以切应力与正应力为主的应力特征量,研究覆岩应力传递路径时空演化特征。
    结果和结论 结果显示:工作面回采过程中,顶板倾向围岩结构呈中上部垮落高度较大、下部垮落高度较小的非对称分布特征,顶板走向围岩结构则随工作面推进呈周期性演化规律。受此影响,顶板采动应力随工作面推进呈现倾向非对称、走向对称的传递演化特征。在工作面倾向与走向剖面内,顶板应力特征量以切应力分界线为界沿采空区四周煤体传递,其传递路径呈现出“m”形分布特征。随着工作面推进距离的增加,应力传递路径由“m”形向中部相连的双“n”形转变,采空区两侧煤体支承压力峰值呈现增大→稳定的演化趋势。在平行煤层剖面内,顶板应力分界线为“w”形分布特征,应力分界线至采空区中心处,顶板应力呈单向传递特征,分界线至煤壁处,顶板应力呈双向传递特征。且随着顶板层位的增加,应力分界线演化至“v”形,研究结果揭示了大倾角煤层顶板应力非对称传递时空演化特征,对丰富大倾角煤层岩层控制理论具有重要意义。

     

    Abstract:
    Objective The key to the safe and efficient mining of steeply dipping coal seams is the effective control of the stability of surrounding rocks, while the effective control is underpinned by identifying and revealing the spatiotemporal evolutionary characteristics of the stress transfer path of the overburden.
    Methods This study investigated mining face 25221 of a coal mine in Xinjiang through field measurement, physical simulations using similar materials, and numerical computation. This study determined the rock pressure behavior of the mining face, along with the deformation and failure patterns of the overburden, through a comprehensive analysis. Accordingly, it established stress characteristic components dominated by shear and normal stresses and explored the spatiotemporal evolutionary characteristics of the stress transfer path of the overburden. Results and Conclusions The results indicate that in the mining process along the mining face, the surrounding rock structure along the roof inclination exhibited an asymmetric distribution characterized by large collapse heights in the middle and upper parts but small collapse heights in the lower part. In contrast, the surrounding rock structure along the roof strike manifested a periodic evolutionary pattern as the mining face advanced. Consequently, the mining-induced stress in the roof exhibited transferred asymmetrically along the roof inclination but symmetrically along the roof strike as the mining face advanced. As shown in the profiles along the mining face inclination and strike, the stress characteristic components of the roof, which were bounded by the shear stress boundary, transferred along the coals around the goaf, manifesting an n-shaped transfer path. With an increase in the advancement distance of the mining face, the stress transfer path shifted from an m-shaped pattern to a double n-shaped pattern connected at the center. The peak abutment pressure of the coals on both sides of the goaf increased initially and then stabilized. Within the profile where the roof was parallel to the coal seams, the roof stress boundary displayed a w-shaped distribution. Specifically, the roof stress transferred unidirectionally from its boundary to the goaf center but bidirectionally from its boundary to the coal wall. With an increase in the roof horizon, the stress boundary evolved into a v-shaped pattern. The results of this study reveal the spatiotemporal evolutionary characteristics of the asymmetric roof stress transfer of steeply dipping coal seams, holding great significance for enriching the rock-layer control theory of steeply dipping coal seams.

     

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