松软煤层瓦斯抽采钻孔裂隙扩展及声发射特性研究

Crack Propagation and Acoustic Emission Characteristics of Boreholesin Gas Drainage in Soft Coal Seams

为研究钻孔角度和气体压力对瓦斯抽采钻孔裂隙扩展的影响,利用自主研发的固-气耦合物理相似模拟实验台,监测稳压密闭条件下,不同钻孔角度和气体压力对声发射能量、计数和事件的影响。研究表明:瓦斯抽采钻孔钻进过程中声发射信号分为3个时期,即发育期、增长期和衰减期;钻孔角度由0°增加到30°时,累计能量增加437.3%,累计计数增加540.2%,事件数增加80.9%;气体压力由0.13 MPa增加到0.50 MPa时,累计能量增加140.4%,累计计数增加231.6%,事件数基本不变;钻孔孔周裂隙分布特征由钻孔中部区域裂隙集中分布变为钻孔中部下方区域裂隙集中分布,钻孔前端和上方区域分布较少。

To study the influence of borehole angle and gas pressure on crack propagation during gas extraction,this study utilized a self-developed solid-gas coupled physical similar simulation experimental platform to monitor the effect of the borehole angle and gas pressure on acoustic emission energy,counts,and events under constant pressure and closed conditions.The results show that the acoustic emission signals during the drilling of gas extraction boreholes can be divided into three periods:development period,growth period,and attenuation period.As the borehole angle increases from 0°to 30°,the cumulative energy increases by 437.3%,cumulative counts by 540.2%,and event numbers by 80.9%.When the gas pressure increases from 0.13 MPa to 0.50 MPa,the cumulative energy increases by 140.4%and the cumulative counts by 231.6%,while the event numbers remains relatively constant.The distribution of cracks around the borehole changes from the concentrated distribution in the middle area to the concentrated distribution in the lower part of the middle area,with fewer cracks in the front and upper part of the boreholes.