浅埋煤层过沟谷开采覆岩“三场”演化致灾研究

Study on the evolution of the "three fields" and disaster of overburden in shallow coal seam through trench mining

  • 摘要: 为进一步揭示沟谷区浅埋煤层开采覆岩应力场、位移场和裂隙场演化规律及致灾特征,以柠条塔煤矿N1120工作面为工程背景,采用数值模拟、实地探查和综合分析的方法,研究了浅埋煤层过沟开采覆岩破坏过程及特征,覆岩应力场、位移场和裂隙场动态演化特征,揭示了导水裂隙带高度动态变化特征,分析了N1120工作面开采致灾特征。研究结果表明:非充分采动阶段覆岩以“逐层破断”和“岩块铰接”的方式分别沿垂向和回采方向扩展,充分采动阶段,覆岩以整体协同破断的方式演化;采动覆岩“应力场”由应力集中区和应力释放区组成,并呈“拱形”扩展;采动覆岩位移场呈滞后回采的“梯形”演化,下沉量由下至上逐渐递减,地表下沉曲线逐步由“V”型转变为“U”型,且受关键层控制。采动覆岩“裂隙场”形态随开采呈“半圆拱形—梯形—类双曲线形”演化,裂隙数量(N)与开采距离(L)呈高度正相关的线性函数关系。N1120工作面采后导水裂隙带发育高度30.3~50.1 m,裂采比为17.82~29.74。基于研究成果,N1120工作面开采过程中理论上不会发生切顶压架和沟道溃水灾害,但可能会诱发滑坡,工作面开采前及开采过程中,需根据研究成果进一步系统分析工作面地质条件,并对地表可能发生滑坡位置和地表构筑物进行系统调查,消除致灾因素,避免成灾。

     

    Abstract: To further reveal the evolution laws and disaster characteristics of the stress, displacement, and fracture fields during shallow buried coal seam mining in valley areas, this study takes the N1120 working face of Ningtiaota Coal Mine as the engineering background. Numerical simulation and comprehensive analysis methods are employed to investigate the overburden failure process and characteristics in shallow buried coal seam mining across ditches, clarify the dynamic evolution features of the overburden stress, displacement, and fracture fields, and uncover the dynamic variation of the water−conducting fracture zone (WCFZ) height. The disaster characteristics of mining in the N1120 working face are also analyzed. The research findings show that during the insufficient mining stage, overlying strata undergo vertical expansion via "layer−by−layer fracturing" and expansion along the mining direction through "rock block hinge rotation", respectively. In the sufficient mining stage, overlying strata evolve in a coordinated manner through overall fracturing. The mining−induced overlying strata "stress field" comprises stress concentration zones and stress release zones, expanding in an "arch" shape. The overlying strata displacement field during mining evolves in a "trapezoidal" pattern with delayed recovery, and subsidence gradually decreases from the coal seam floor to the surface. The surface subsidence curve gradually transitions from a "V" shape to a "U" shape, which is primarily controlled by key strata. The "fracture field" morphology in overlying rock evolves into a "semi−circular arch−trapezoid−hyperbolic shape" as mining proceeds. The fracture number (N) exhibits a strong positive linear correlation with mining distance (L), following a linear function. The measured WCFZ height ranges from 30.3 m to 50.1 m, and the ratio of the WCFZ height to the coal seam mining height is between 17.82 and 30.30. Based on the research results, roof cutting and channel collapse disasters are theoretically unlikely to occur during mining of the N1120 working face; however, landslide hazards are easily induced. Prior to mining the working face, it is necessary to further systematically analyze the working face’s geological conditions in accordance with the research findings, conduct a comprehensive investigation of potential landslide−prone areas and surface structures, and eliminate causative factors to prevent disasters.

     

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