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特厚煤层采动应力演化与动力灾害防控关键技术

Key technologies for mining-induced stress evolution and dynamic disaster prevention in extra-thick coal seams

  • 摘要: 针对我国特厚煤层深部开采面临的采掘扰动易诱发动力灾害及瓦斯防治存在的钻孔控制盲区、效果检验可靠性不足等问题,以窑街矿区金河煤矿单一特厚突出煤层为工程背景,系统研究了采掘全过程应力场动态演化规律、采掘工作面区域防突关键技术及掘进工作面局部高应力区高效卸压增透技术。通过FLAC3D数值模拟揭示了大采放比综放工作面弧形卸压区发育特征:初采期宽度5~7 m、构造区3~5 m、正常区10~15 m;同时,发现多重采动应力叠加下掘进工作面存在超高应力集中现象,应力集中系数λ高达2.4~3.0;据此提出了基于应力主控因素的风险分级管控方法:回采工作面划分一级风险区(λ>2.0)、二级风险区(1.5≤λ≤2.0),掘进工作面增设三级风险区(1.0≤λ<1.5),并制定了差异化防控对策。针对采掘工作面采用传统区域防治技术存在的难题,研发应用了4项关键技术以提升防突可靠性:区域措施钻孔三维反演系统,实现钻孔轨迹三维可视化与风险区域识别,消除区域措施钻孔“立体薄弱区”;抽采达标分层立体预测模型,以顶分层最小抽采半径为布孔标准,确保中上部煤体充分抽采;内胆贴壁式瓦斯含量取样装置,减少瓦斯逸散,实测可解吸瓦斯含量较传统孔口取样提高6.25%~20.59%;“分区−分带−分层”全覆盖检验方法,对构造区、软煤带等高风险区域加密检测,重点层位分层验证,减少检验盲区。针对掘进工作面高应力区(如16219−1掘进工作面七重采动影响带),应用改进的超高压水力割缝技术装备(高刚度轻质钻杆、防滑装置、水质过滤器);结果表明,16219−1掘进工作面高应力区应力集中系数由3.0降至1.6,煤层透气性系数提升近10倍,抽采达标时间缩短1/3,残余瓦斯含量降至4.73 m3/t,掘进期间CH4、CO2涌出平稳(最大CO2体积分数为0.48%)、高能量微震事件减少,实现了消突和应力降低“双重”目标。

     

    Abstract: Addressing the challenges in the deep mining of China’s extra-thick coal seams—where mining disturbances readily induce dynamic hazards, and gas control is hindered by issues such as blind spots in borehole coverage and the insufficient reliability of effectiveness verification—this study was conducted with the single extra-thick, outburst-prone coal seam at the Jinhe Coal Mine in the Yaojie Mining Area as its engineering context. It systematically investigated the dynamic evolution of the stress field throughout the entire mining process, the optimization of key technologies for regional outburst prevention at the working face, and techniques for high-efficiency pressure relief and permeability enhancement in local stress zones at the driving face.FLAC3D numerical simulations revealed the developmental characteristics of the arc-shaped pressure relief zone in a fully-mechanized top-coal caving face with a large mining-to-caving ratio: the zone's width was 5~7 m during the initial mining period, 3~5 m in tectonic zones, and 10~15 m in normal zones. Concurrently, it was discovered that under the superposition of multiple mining-induced stresses, an ultra-high stress concentration phenomenon occurs at the driving face, with the stress concentration factor (λ) reaching as high as 2.4~3.0. Accordingly, a graded risk management and control method based on dominant stress factors was proposed: the longwall face was zoned into a Grade I risk area (λ>2.0) and a Grade II risk area (1.5≤λ≤2.0), while a Grade III risk area (1.0≤λ<1.5) was established for the driving face, for which differentiated prevention and control countermeasures were developed. To address the challenges associated with traditional regional prevention techniques at the working faces, four key technologies were developed and applied to enhance the reliability of outburst prevention: A 3D inversion system for regional measure boreholes, which achieves 3D visualization of borehole trajectories and identification of risk areas, thereby eliminating “3D weak zones” in regional borehole coverage; A stratified and three-dimensional prediction model for gas drainage compliance, which uses the minimum drainage radius of the top slice as the standard for borehole layout to ensure the middle and upper parts of the coal body are fully drained; An inner-liner, wall-clinging gas content sampling device that reduces gas desorption loss, increasing the measured desorbable gas content by 6.25% to 20.59% compared to traditional borehole collar sampling; A “by-zone, by-band, by-layer” full-coverage verification method, which intensifies testing in high-risk areas like tectonic zones and soft coal bands and validates key horizons layer by layer, reducing verification blind spots. For high-stress zones at the driving face (such as the 16219−1 driving face, affected by sevenfold mining influence), an improved ultra-high-pressure hydraulic slotting technology and its associated equipment (including high-rigidity lightweight drill rods, an anti-slip device, and a water quality filter) were applied. The results showed that in the high-stress zone of the 16219−1 driving face, the stress concentration factor decreased from 3.0 to 1.6, the coal seam’s permeability coefficient increased 10-fold, the time required to meet drainage standards was shortened by one-third, and the residual gas content was reduced to 4.73 m3/t. During driving, CH4 and CO2 gushing remained stable (with a maximum CO2 concentration of 0.48%), and high-energy microseismic events decreased, achieving the “dual” objectives of outburst elimination and stress reduction.

     

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