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基于多类型四双法的煤层顶板突水预测评价研究

Prediction and evaluation study on coal seam roof waterinrush based on multi-type four-double method

  • 摘要: 富水性和导通性是评价预测顶板突水的2个关键判据。基于GIS的多源信息复合叠加方法评价富水性,存在数据来源不足、评价过程烦琐、评价手段过于专业等问题;采用冒裂安全性分区图来评判含水层的导通性,存在两极值区间过大、精度较低问题;采用疏干开采技术时,采前疏干程度评价缺少量化判据。实践中,顶板突水条件千差万别,目前缺少一套适用于各种地质条件的技术评价体系预测顶板突水,为此提出了“多类型四双法”评价预测技术,简称MTFD法。首先,依据煤层与上部岩层(含水层)空间组合关系以及岩层自身富水性强弱,将顶板分为A、B、C、D四种评价类型,确定了每种类型的评价对象和评价准则,并形成了完整的技术评价路线。再次,基于钻孔柱状图信息建立了双表,即基础数据表和工作表,获取评价和预测工作的数据源;其次,引入了双指数概念,即富水性指数和突水危险性指数评价参量,通过双指数绘制双图,即富水性等值线图和突水危险性等值线图,富水性指数用来表征地层的富水性,将砂岩厚度和脆塑性比值2种最重要地学信息指数,可省去繁琐的多源信息归一化处理过程;突水危险性指数用来衡量间接充水含水层水导入采场可能性大小,由于两极值区间范围小,有利于提高评价的精准度和灵敏度,同时能够克服经验公式的不足。最后,提出了双水量预测方法,即疏干水量预测或涌水量预测,以富水性指数为主控因素预计的疏干水量,可以作为采前安全开采评价的量化判据;以富水性指数为主控因素预计工作面涌水量,可以作为涌水量传统预计方法的有益补充。应用结果表明:MTFD工作法在内蒙古上海庙矿区、宁夏鸳鸯湖矿区、山东济宁矿区均已得到广泛应用,指导了约60个采煤工作面的疏放水钻孔设计和施工。富水性指数法预测富水性指数与实测钻孔放水量呈正相关关系,预计水量的偏差率约4%;利用“双图”科学揭示了多起典型的突水溃沙事故的机理。

     

    Abstract: Water-rich and conductivity are two key criteria for evaluating the prediction of water inrush from the roof. The method of multi-source information superposition method based on GIS is more advanced, but there are problems such as insufficient data sources,complex evaluation process and over-professional evaluation methods. The difference between thickness of aquifer and height of water conducting fracture is used to evaluate the connectivity between aquifer and stope, but evaluation accuracy is low because of the large extreme values. It is necessary to pre-drain roof water under the conditions of water-bearing aquifer, but there is no quantitative criterion for pre-mining safety evaluation after drainage. In practice,the water inrush conditions of the roof are very different. At present, a set of technical evaluation system suitable for various geological conditions is used to predict the water inrush from the roof. For this reason, the ‘multi-type four-double’evaluation and prediction technology is proposed, which is referred to as the MTFD working method. Firstly, according to spatial combination relationship between the coal seam and the upper aquifers and water-bearing characteristic, the water inrush from the roof can be divided into evaluation types of A, B, C and D , and each type has specific applicable conditions and evaluation criteria, and it forms an integrated evaluation technical route. Secondly, basic data table and worksheet (Double Tables) can be established based on the borehole histogram information, and data sources for evaluation and prediction also can be obtained, which is used to complete the calculation tasks required for the evaluation. Thirdly, the water abundant index and danger index of water inrush(Double Indexes)are introduced and calculated in worksheet through calculation formula. In the meanwhile, contour map of water abundant and of water inrush danger (Double Diagrams) can be obtained correspondingly. Water abundant index is used to show the aquifer of water-bearing, including two kinds of extensive and dependable geoscience information which are the thickness of sandstone and the ratio between the thickness of sand and mud, eliminating the need for complex multi-source information normalization.The water inrush risk index is used to measure the possibility of water diversion from indirect aquifer into stope. Because the range of the two-pole interval is small, it is conducive to improve the accuracy and sensitivity of the evaluation, and at the same time overcome the deficiency of the empirical formula. Finally, the double predictions, namely the prediction of the dewatering volume or the prediction of the water inflow, the amount of the dewatered water predicted by the water-rich index as the main controlling factor, can be used as the quantitative criterion for the pre-harvest safe mining evaluation. The new estimation method of water inflow quantity based on water abundant index can be seen as a useful supplement of traditional evaluation method. In recent years, the MTFD work method has been widely used in Shanghaimiao Mining Area in Inner Mongolia, the Ningxia Wuhu Mining Area, and the Jining Mining Area in Shandong. It has guided the design and construction in 60 drilling holes in coal mining face. The application results show that MTFD method predicted by water abundant index is positively correlated with the measured water discharge, and the deviation rate of water inflow is about 4%. Furthermore, some typical mechanisms of water-sand inrush have been revealed by contour map of water abundant and of water inrush danger.

     

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