Dynamic disaster evolution mechanism of high mine pressure at hard roof and advance area prevention and control technology
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摘要: 工作面上覆坚硬顶板往往不易垮落，破断后易形成动压灾害。以神东矿区布尔台煤矿为背景，针对典型坚硬顶板造成的强矿压动力灾害问题，采用数值模拟、理论分析的方法分析并揭示坚硬顶板弱化前后的应力演化特征及顶板破断机理，提出超前区域防治技术并应用于现场实践。结果表明：坚硬顶板破断演化特征分为3个阶段，即“长悬臂梁”阶段—“砌体梁滑落失稳”阶段—重新压实阶段，其中“长悬臂梁”阶段支架上方顶板应力显著增大至6.8 MPa，破断前支架上方顶板应力为破断后的2倍，其临界破断产生的应力释放是引起强矿压的根本原因，这也是弱化改造控制的主要阶段。基于坚硬顶板灾害发生机理，提出“广域大空间”超前区域防治技术，阐述了绿色、精准、广域的防治优势，以及钻孔轨迹控制、封孔质量控制、多孔联动效应的关键技术及治理评价体系。结合数值模拟进一步验证防治技术的可靠性，当“长悬臂梁”结构弱化后，其破断前支架上方顶板应力为4.6 MPa，降幅32.4%，顶板破断演化特征3个阶段演变为来压前阶段—“砌体梁滑落失稳”阶段—重新压实阶段，弱化后顶板各阶段支架上方顶板应力降幅达到32.4%~79.4%，表明预成裂隙弱面和降低坚硬层完整性能够有效改变顶板破断结构，显著降低来压强度。实践表明：压裂过程产生多次压降，降幅均达到3 MPa以上，探测裂缝发育长度达到30 m以上，压裂前后工作面周期来压步距降幅44.9%，支架来压载荷降幅18.1%，治理效果良好。研究结果可为类似矿区动力灾害治理提供借鉴。Abstract: The overlying roof on the hard roof working bench is usually not likely to fall off, while tends to form dynamic pressure disaster. The stress evolution characteristics and roof breaking mechanism before and after hard roof weakening were analyzed and revealed using the methods of numerical simulation and theoretical analysis, and the advance area prevention and control technology were proposed and applied in the field practice, for the typical dynamic disaster problem of high mine pressure that was caused by the hard roof against the background of the Buertai Coal Mine in the Shendong Mine Area. As indicated by the results, there were three stages of the hard roof breaking evolution characteristics, i.e. the “long cantilever” stage — “masonry beam falling and destabilization” stage — re-compaction stage. At the “long cantilever” stage, which was also the main stage of weakening modification and control, the roof stress at the upper support was increased significantly to 6.8 MPa; the roof stress at the upper support before breaking was twice of that after breaking; the stress relief resulted from the critical breaking was the root cause of the high mine pressure. On the basis of the occurrence mechanism analysis of the hard roof disaster, the advance area prevention and control technology of "wide-range large space" was proposed, and the green, accurate and wide-range prevention and control advantages, the key technologies of drilling trajectory control, hole plugging quality control and multi-hole linkage effects as well as the governing evaluation system were elaborated. The reliability of the prevention and control technologies were verified in combination of the numerical simulation. After the "long cantilever" structure weakening, the roof stress at the upper support before breaking was 4.6 MPa, with the drop rate of 32.4%. The three stages of the roof breaking evolution characteristics were pre-weighting stage — “masonry beam falling and destabilization” stage — re-compaction stage. After weakening, the drop rate of the roof stress at the upper support for each stage was 32.4%–79.4%, which indicated that the preformed fissure weak surface and the hard stratum integrity reduction can effectively change the roof breaking structure and significantly decrease the weighting intensity. As indicated by the practice, the pressure drop occurred several times during fracturing, the drop rate was over 3 MPa, and the detection fracture developed to more than 30 m; the drop rate of the periodic weighting interval of the working bench before and after fracturing was 44.9%, and the drop rate of the support weighting load was 18.1%. The governing effect was good. The study result can provide references for the dynamic disaster governing in the similar mine areas.
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图 1 试验区坚硬顶板钻孔柱状分布特征
Fig. 1 Column distribution characteristics of hard roof drilling in the test area
图 3 弱化前工作面顶板破断特征及应力分布
Fig. 3 Roof fracture characteristics and stress distribution of working face before weakening
图 5 超前分段区域防治与传统技术优势对比
Fig. 5 Comparative study of prevention and control advantages in advanced sublevel regions
图 8 弱化后工作面顶板破断特征及应力分布
Fig. 8 Roof fracture characteristics and stress distribution of working face after weakening
图 12 压裂后区域瞬变电磁探测分布特征
Fig. 12 Distribution characteristics of transient electromagnetic detection before and after fracturing
图 13 压裂区域支架载荷分布特征
Fig. 13 Distribution characteristics of support resistance before and after fracturing
表 1 研究区煤岩物理力学参数
Table 1 Physical and mechanical parameters of coal rocks in the study area
层位 岩性 厚度/m 抗压强度/MPa 密度(kg·m−3) 泊松比 内摩擦角/(°) 底板 砂质泥岩 4.84 81.60 23.90 0.25 26.60 4−2煤 煤 5.96 24.00 15.00 0.20 28.20 基本顶 粉砂岩 20.67 101.70 24.10 0.25 24.70 间隔层 砂质泥岩 14.51 81.60 23.90 0.25 26.60 
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表 2 压裂前后区域矿压显现特征对比
Table 2 Comparison of regional ore pressure characteristics before and after fracturing
对比区域 来压步距/m 来压周期/次 来压时支架载荷/MPa 未压裂区域 9.6 1 57.9 18.4 2 57.4 16.0 3 57.3 18.4 4 57.6 均值 15.6 均值 57.6 压裂区域 8.0 1 49.2 6.4 2 46.4 8.0 3 47.7 11.2 4 45.2 9.6 5 44.4 7.2 6 51.9 6.4 7 47.4 均值 8.6 均值 47.2
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