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为了探明采掘应力作用下顺层钻孔抽采负压分布规律,基于钻屑法分析得到预抽工作面煤体采掘应力分布规律。根据煤体塑性软化特性,建立了钻孔周围煤体蠕变模型;运用煤层瓦斯赋存与流动相关理论,建立了钻孔周围瓦斯流动模型;借鉴管道气体流动相关理论,建立了钻孔内瓦斯流动模型,分别得到了孔径变形规律、涌入钻孔瓦斯量、钻孔内负压计算公式。以鹤壁八矿为例,解算了3103工作面顺层钻孔抽采负压分布。结果表明:瓦斯抽采第1天~第5天,孔口孔底压差从260 Pa增加到3.3 k Pa;随抽采时间推移,第7天,钻孔内出现负压值为0区段,即瓦斯抽采空白段;第9天,钻孔内几乎无抽采负压。
In order to find out the negative pressure distribution law of borehole drainage under the action of mining stress, the law of mining stress distribution of pre-pumping face is obtained based on the analysis of drill cuttings method. According to the characteristics of plastic softening of coal, a creep model of coal around the borehole was established. By using the theory of gas occurrence and flow in coal seam, the gas flow model around the borehole was established. Based on the theory of gas flow in the pipeline, Flow model were obtained pore deformation, influx of drilling gas volume, borehole negative pressure formula. Taking Hebi No.8 Mine as an example, the negative pressure distribution of the vertical drilling of 3103 working face is solved. The results show that on the first day to the fifth day of gas drainage, the pressure difference at the bottom of the hole increases from 260 Pa to 3.3 kPa. With the passage of the extraction time, on the seventh day, the negative pressure value in the borehole is 0 , That is, a blank section of gas drainage; the first 9 days, there is almost no negative pressure in the borehole.