底板岩巷穿层钻孔一孔多用瓦斯抽采时效性研究

为了提高穿层钻孔的利用率,基于煤岩动力学行为下的采动裂隙场和应力场演化规律,提出全生命周期的底板岩巷穿层钻孔一孔多用瓦斯抽采技术,即按先后顺序实现采前预抽、边采边抽以及采空区瓦斯抽采功能。以古汉山矿1604综采工作面为例,进行现场试验。结果表明:一孔多用试验钻孔的抽采效果具有明显的时变特性,为定性定量分析试验钻孔的抽采时效性规律,根据抽采纯量变化将抽采全生命周期划分为初始预抽增流期、高效预抽期、预抽快速衰减期、高效卸压增流期、低流枯竭期、采后纯量回升期和采后衰减低流期7个阶段;高效预抽期是全生命抽采周期中最关键的阶段,其次为高效卸压增流阶段,平均瓦斯抽采纯量可达到在预抽高效期钻孔平均瓦斯抽采纯量的61.4%;确定前方距离工作面70 m至后方距离工作面40 m范围内为穿层钻孔受采动卸压影响区,工作面超前35~40 m,抽采浓度和纯量最大;在边采边抽阶段,距离采面前方20~70 m的试验钻孔平均抽采纯量比卸压前提高5倍;古汉山矿底板岩巷穿层钻孔采前预抽合理抽采天数为260 d,边采边抽有效抽采期为46 d,采空区瓦斯抽采有效抽采期为26 d。通过一孔多用的底板岩巷穿层钻孔瓦斯抽采实现了预抽达标和降低工作面瓦斯涌出的目标,具有良好的推广应用价值。

Study on time effectiveness of gas drainage by crossing layer drilling in floor rock roadway with one hole and multi-purpose

In order to to improve the utilization rate of cross-layer boreholes,based on the evolution law of mining fracture field and stress field under the dynamic behavior of coal and rock,a multi-application gas drainage technology with one hole in floor rock roadway with full life cycle was proposed.It can realize the functions of pre-draining coal seam gas before mining,draining coal seam gas during min?ing,and draining coal seam gas from goaf.Taking the No.1604 fully-mechanized mining face of Guhanshan Mine as an example,field tests have been carried out and the results show that:the gas drainage effect of one hole multi-application test drilling hole has obvious timelines characteristics.In order to to analyze the timelines effect law of test boreholes qualitatively and quantitatively,the whole life cycle of gas drainage can be divided into seven stages,namely,initial pre-draining period,high-efficiency pre-draining period,rapid attenuation pre-draining period,high-efficiency pressure relief and flow increase period,low flow depletion period,after mining gas volume recovery pe?riod,and after mining gas volume decline flow period.High efficiency pre-draining period is the most critical stage in the whole life cycle,the second stage is the high-efficiency pressure relief and flow increasing period,and the average gas drainage volume can reach 61.4%of the average gas drainage volume in the pre-drainage high-efficiency period.The range from 70 m in front of the working face to 40 m be?hind the working face is the area affected by mining pressure relief.In the range of 35 to 40 m in front of the working face,the concentra?tion and volume of gas drainage reached the peak.In the stage of mining while pumping,the average gas drainage volume capacity of the test boreholes 20 to 70 m in front of the mining face is 5 times higher than that before pressure relief.In Guhanshan Mine,the reasonable pre-draining period is 260 d,the reasonable drainage while mining period is 46 d,and the reasonable goaf gas drainage period is 26 d.Through a multi-application drill hole in the rock roadway at the bottom of the coal seam to drainage coal seam gas,the goal of reaching the pre-drainage standard and reducing the gas emission from the working face was realized,which has good popularization and applica?tion value.