采空区采动覆岩空隙率分布规律及分区治理方法

Distribution pattern of overburden void ratio induced by mining in goaf areas and corresponding zoning-based control measures

  • 摘要: 针对我国煤炭资源规模化开发中遗留的大量采空区地表土地资源利用需要及工程建设安全问题,研究基于焦作某矿采空区形成和分布。采用数值模拟、理论分析、钻孔探测以及物理勘探相结合的方法,分析了采空区域的采动覆岩裂隙发育及空间分布特征,引入分形分析方法构建采动区域空隙率分析模型,分析采动覆岩空隙率空间分布和演化规律,针对研究区采空区现状提出多段位治理方案和不同段位的工程治理方法。研究表明:随着工作面推进,裂隙整体呈“向上—向前—稳定”演化趋势,伴随张开、闭合与压实的周期性变化;采动初期覆岩分形维数呈现快速递增趋势(增幅达10.9%),裂隙网络复杂度与分形维数呈显著正相关,离层对分形维数影响显著;采空区开切眼侧分形维数由1.7降至1.3,工作面推进侧维持在1.3左右,充分采动阶段呈“八”字型分布,揭示了高位裂隙闭合与低位压实的协同演化机制;基于分形图像特征的空隙率提取模型,提出空隙率定量表达公式,实现了裂隙几何复杂性与空隙特征的耦合表达;根据空隙率分布呈区域性差异,划分为结构裂隙区与压实裂隙区,空隙率分别为0.75、0.62与0.25,为不同区域提供分级治理的基础;模拟结果与现场钻孔、物探资料高度吻合,验证了模型的可靠性;基于垮落带残余空洞及裂隙分区特征,提出“分形‒空隙率协同识别的多段位注浆治理方法”,实现多段位的精确注浆和浆液在不同裂隙类型的渗透与扩散。研究结果对于类似采空区作为工程建设用地的治理具有指导意义。

     

    Abstract: In response to the pressing need for surface land resource utilization and engineering safety associated with large-scale coal mining in China, the study is based on the formation and spatial distribution of goafs in a mine located in Jiaozuo. A combined approach of numerical simulation, theoretical analysis, borehole detection, and physical exploration was adopted to analyze the development and spatial distribution characteristics of overburden fractures induced by mining in the goaf areas. The fractal analysis method was introduced to construct a void ratio analysis model for the mining-affected region, examining the spatial distribution and evolution of overburden void ratios. Based on the current conditions of the goaf areas in the study region, a multi-segment treatment scheme and engineering control methods for different segments were proposed. The study indicates that, as the working face progresses, the fractures exhibit an overall “upward-forward-stable” evolution pattern, accompanied by periodic changes of opening, closing, and compaction. In the early stages of mining, the fractal dimension of the overburden exhibits a rapid increase (with an increment of 10.9%). The complexity of the fracture network shows a significant positive correlation with the fractal dimension, and the interlayer significantly affects the fractal dimension. The fractal dimension on the side of the goaf opening decreases from 1.7 to 1.3, while the side of the working face remains around 1.3. During the full mining stage, the distribution presents a “八” shape, revealing the synergistic evolutionary mechanism of high-position fracture closure and low-position compaction. A void ratio extraction model based on fractal image features is proposed, along with a quantitative expression formula for the void ratio. This model realizes the coupling expression of fracture geometric complexity and void characteristics. Based on the regional differences in void ratio distribution, the area is divided into structural fracture zones and compaction fracture zones, with void ratios of 0.75, 0.62, and 0.25, respectively. This provides a basis for graded management in different regions. The simulation results are in high agreement with field borehole and geophysical data, verifying the reliability of the model. Based on the residual cavities and fracture zoning characteristics of the collapse zone, a multi-stage grouting treatment method based on the fractal-porosity synergistic identification approach is proposed, achieving precise grouting in multiple stages and the penetration and diffusion of the grout in different fracture types. The research findings have significant guiding implications for the management of similar mined-out areas as construction sites.

     

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