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基于微震监测的采场覆岩破坏时空演化模式

Spatiotemporal evolution patterns of overlying rock damage based on microseismic monitoring under mining influence

  • 摘要: 为了解决开采我国西部侏罗系煤层广泛面临洛河组砂岩水威胁的问题,采用理论模型与微震监测手段分析了采动影响下导水裂隙带随回采进尺变化的时空演化特点。一方面,通过求解假设模型的应力场解释了单一岩梁在工作面推进方向的运动规律,进而提出了破坏覆岩纵向上的“四带”划分结构,并限定了导水裂隙带的发育上界。另一方面,以邵寨煤矿首采工作面为工程实例,分析微震事件与“四带”的关系,依据微震事件的时空分布特征,通过奇异谱分析技术提取的数据变化表达成分与距离加权能量法绘制的微震事件密度云图划分了能反映覆岩破断明显变化的关键回采进尺,依据研究区沉积特征、各进尺下的微震事件密度及研究区综合地层柱状图确定了不同监测区间顶板“四带”的分带情况以及导水裂隙带的发育上限。将理论分析结果与现场实测结果进行对比,结果表明:监测74 d、197 d、320 d、407 d时的导水裂隙带发育上界分别为地层编号21、编号14、编号4和编号4,导水裂隙带最大发育至厚度37.46 m的泥岩,宜君组、洛河组在“四带”中处于原始隔水层带上部,采煤并未扰动宜君组、洛河组的砂岩含水层。研究揭示了我国西部侏罗系煤层开采过程中导水裂隙带的时空演化规律,并界定了“四带”结构及其与洛河组砂岩水层的关系,研究结果为制定有效的防治水措施提供了理论基础。

     

    Abstract: To address the threat of the Luohe Formation sandstone aquifer to Jurassic coal seams in western China, this study employed theoretical analysis and microseismic monitoring to research the spatio-temporal evolution of water-conducting fracture zone (WCFZ) as they change with mining footage. Firstly, by solving the stress field of a hypothetical model, the movement patterns of a single rock beam in the advancing direction were explained, leading to the proposal of a "four-zone" classification structure for overburden failure in the vertical direction and defining the upper boundary of WCFZ development. Additionally, Using Shaozhai Coal Mine as an example, based on singular spectrum analysis, and energy-weighted maps, it identified key mining footage reflecting significant overburden failure. The "four-zone" structure and WCFZ upper limit were determined according to the sedimentary characteristics, the density of microseismic events, and a comprehensive stratigraphic column. A comparison between theoretical analysis and field measurements revealed that the upper boundary of WCFZ was determined in stratum No.21, No.14, No.4, and No.4 at 74 days, 197 days, 320 days, and 432 days, respectively. The WCFZ developed up to a maximum thickness of 37.46 m in mudstone, without disturbing the Yijun and Luohe formations' aquifers. This study uncovers WCFZ evolution laws and delineates the "four-zone" structure, providing a basis for water prevention measures.

     

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