MINING-INDUCED OVERBURDEN FAILURE AND HEIGHT PREDICTION IN JURASSIC WEAKLY CEMENTED ROOF
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摘要: 煤层采动后形成的顶板导水裂隙带是沟通顶板充水含水层的主要通道之一,同时也是顶板水害防治需要重点研究的关键问题。近年来,西部矿区已成为我国煤炭资源主要开采区,其主采侏罗系含煤地层与东部石炭-二叠系有着明显差异,并具有典型的孔隙度高、胶结程度差等特征,顶板采动导水裂隙的演化特征也与东部矿区具有较大差异,相关的研究尚未形成普适性成果。因此,本文选取典型的弱胶结地区——新疆哈密大南湖矿区为例,采用UDEC数值模拟、现场三维钻孔电视成像等方法,并结合“S-R”稳定理论,以垮落带高度为自变量,建立砌体梁承载强度与垮落带高度关系式,全面揭示该区煤层开采过程中顶板的采动破坏过程与演化特征,并以此为依据确定顶板导水裂隙带的发育高度。在此基础上,通过收集侏罗系同类型煤矿导水裂隙带高度的实测数据,采用回归分析方法,拟合并修正现有经验公式。研究表明:研究区顶板导水裂隙带发育高度的范围是60.07~62 m,裂采比为17.67~18.24,整体形态呈“梯台”型特征,结合邻矿现场实测对比证实了此次实测结果的可靠性;开采范围内导水裂隙带发育高度受垮落带高度增量、岩块回转角变化的影响呈现:“快速增加-缓慢增加-逐渐稳定”的发展与演化规律;验证计算结果表明,论文提出的回归公式预测精度一般在10.30% ~17.25%之间,相较于传统经验公式平均误差降低了51.84%,显著提高了导水裂隙带高度的预测精度。论文的相关研究成果可为新疆地区相似开采条件下顶板导水裂隙带发育高度计算提供理论依据。Abstract: The water-conducting fractured zone of roof after mining is an important pathway to connect the overlying aquifer. It is also a key problem to be studied in the prevention and control of roof water disaster. In recent years,the western mining area has become the main mining area of coal resources in China. Its main mining Jurassic coal-bearing strata are obviously different from the eastern Carboniferous-Permian,and have typical characteristics such as high porosity and poor cementation. The evolution characteristics of water-conducting fractures in rock roof are also quite different from those in the eastern mining area. Relevant research has not yet formed universal results. Therefore,this paper selects the typical weak cementation area-the Dananhu mining area in Hami,Xinjiang as an example. Using UDEC numerical simulation,on-site three-dimensional borehole TV imaging and other methods,combined with 'S-R'stability theory,taking the height of caving zone as an independent variable,the relationship between the bearing strength of masonry beam and the height of caving zone is established. The mining failure process and evolution characteristics of roof in the process of coal seam mining in this area are fully revealed,and the development height of roof water-conducting fractured zone is determined based on this. On this basis,by collecting the measured data of the height of the water-conducting fractured zone in the same type of the Jurassic coal mines,based on the regression analysis method,the existing empirical formula is fitted and corrected as a reference for the prediction formula of the height of the roof water-conducting fractured zone in the Jurassic weakly cemented coalfield. The results show that the development height of the roof water-conducting fractured zone in the study area is 60.07~62 m,the ratio of the height of the fractured zone to the cutting height is 17.67~18.24,and the overall shape is 'terrace' type. The reliability of the measured results is confirmed by the comparison with the field measurement of adjacent mines. The development height of the water-conducting fractured zone in the mining area is affected by the height increment of the caving zone and the change of the rock block rotation angle. The development and evolution of 'rapid increase-slow increase-gradually stable' is presented. The verification calculation results show that the prediction accuracy of the regression formula proposed in this paper is generally between 10.30% and 17.25%,which is 51.84% lower than the average error of the traditional empirical formula. The prediction accuracy of the height of water-conducting fractured zone is significantly improved. The relevant research results of the paper can provide a theoretical basis for the calculation of the development height of the water-conducting fractured zone under similar mining conditions in Xinjiang.
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表 1 工作面数值模型工程地质类型及物理力学参数
Table 1. Engineering geological types and their physico-mechanical parameters in the numerical model of the panel
序号 岩性 密度/kg·m-3 体积模量/GPa 剪切模量/GPa 抗拉强度/MPa 黏聚力/MPa 内摩擦角/(°) 法向刚度/GPa 切向刚度/GPa 1 18煤 1300 3.71 1.91 1.1 1.0 24 0.01 0.01 2 粉砂岩 2400 28.33 18.20 9.0 9.6 32 0.40 0.40 3 粗粒砂岩 2400 26.00 17.03 5.6 6.0 30 0.05 0.05 4 粉砂岩 2400 28.33 18.20 9.0 9.6 32 0.40 0.40 5 泥岩 2430 4.00 2.10 2.2 1.7 28 0.04 0.04 6 中砾岩 2400 12.45 7.11 4.2 2.5 36 0.09 0.09 7 泥岩 2430 4.00 2.10 2.2 1.7 28 0.04 0.04 8 粉砂岩 2400 28.33 18.20 9.0 9.6 32 0.40 0.40 9 中砾岩 2400 12.45 7.11 4.2 2.5 36 0.09 0.09 10 细砂岩 2400 13.05 9.00 3.8 3.6 32 0.08 0.08 11 中砾岩 2400 12.45 7.11 4.2 2.5 36 0.09 0.09 12 泥岩 2430 4.00 2.10 2.2 1.7 28 0.04 0.04 13 覆岩 2400 28.33 18.20 9.0 9.6 32 0.40 0.40 14 底板 2400 28.33 18.20 9.0 9.6 32 0.40 0.40 表 2 cg-1钻孔数据
Table 2. Cg-1 borehole datasheet
cg-1孔标高/m cg-1孔底标高/m 煤层顶板标高/m cg-1孔深/m +480.408 +235.51 +232.407 +244.898 表 3 实测结果的对比分析
Table 3. Contrast with real test results
参数 沙吉海矿 国神一矿 1801工作面 采厚/m 6 6.3 3.0 裂隙高度/m 78.52~81.54 94~98 46~47 裂采比 13.09~13.59 14.92~15.56 15.33~15.67 表 4 软弱覆岩导高计算公式
Table 4. Calculation formula of the height of water-conducting fractured zone in weak overburden
岩性 计算公式之一/m 计算公式之二/m 软弱 $H_{\mathrm{L}}=\frac{100 \sum M}{3.1 \sum M+5.0} \pm 4.0$ $H_{\mathrm{L}}=10 \sqrt{\sum M}+5$ ∑M为累计采厚(m);HL为导水裂隙带高度(m) 表 5 导水裂隙带计算高度
Table 5. Calculated height of water-conducting fracture zone
预测方法 “三下”规范 数值模拟 三维钻孔成像 计算高度 公式一
25.88公式二
23.4462 60.07 最大裂采比 7.61 6.89 18.24 17.67 表 6 矿井导水裂隙带高度实测数据统计
Table 6. Statistics of height measurements water-conducting fractured zone in different mines
序号 煤矿 煤层采厚/m 实测高度/m 1 榆树岭矿 8.6 86.0 2 榆树泉矿 6.9 70.1 3 塔什店二井田矿 9.6 129.3 4 伊犁四矿 7.1 74.2 5 陈家沟煤矿 10.6 124.0 6 下沟矿 8.7 97.5 7 崔木煤矿 8.2 90.5 8 红柳煤矿 5.3 62.5 9 上湾煤矿 5.8 63.0 10 鄂尔多斯东胜矿 6.0 63.4 11 布尔台煤矿 3.0 36.8 12 寸草塔二矿 2.8 31.1 13 乌兰木伦煤矿 2.5 43.2 14 上湾煤矿 3.4 46.0 15 补连塔煤矿 4.4 64.2 表 7 导水裂隙带高度对比
Table 7. Comparison of the height of water-conducting fractured zones
煤矿 煤层采厚/m 实测高度/m 经验公式计算高度 与实际值误差/% 回归公式计算高度/m 与实际值误差/% 察哈素煤矿 4.75 67.10 24.08 64.11 59.41 11.46 大南湖五号井 3.00 47.59 20.98 55.92 40.54 14.81 活鸡兔煤矿 3.70 54.00 22.47 58.41 48.44 10.30 红庆河煤矿 6.00 86.10 25.42 70.48 71.25 17.25 多伦协鑫煤矿 9.58 112.00 27.61 75.35 99.40 11.25 -
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