考虑流变特性的水力冲孔孔径变化规律及防堵孔技术

通过分析水力冲孔周围煤体的受力特征，建立了考虑煤的塑性软化和扩容特性的水力冲孔周围煤体黏弹塑性模型，分析了水力冲孔的卸压增透效果和孔径变化规律，制定了防止钻孔堵塞和注气驱替技术。研究结果表明：① 水力冲孔措施可以大幅度提高周围煤体的渗透率，冲煤量越多，水力冲孔的卸压范围越大，煤体的渗透率提高的幅度越大；② 由于煤的流变特性水力冲孔钻孔会产生缩孔现象，地应力越大，煤体强度越低，钻孔周围煤体的蠕变变形越剧烈，钻孔就越容易被堵塞，一旦抽采通道被堵塞，瓦斯抽采效果就会大幅度的降低；③ 采用下套管防堵孔技术，人工保留一条抽采通道，可长时间抽取高浓度瓦斯，抽采效果提高了2.7倍；④ 注气驱替与水力冲孔技术结合，单孔抽采纯量增加了8.1倍，可有效的提高瓦斯抽采效果。

Hydraulic flushing aperture variation and anti-blocking technology considering rheological property

By analyzing the stress characteristics around boreholes，the visco-elastic plastic model of coal around hydraulic flushing considering plastic softening and dilatancy was established，the pressure-relief and permeability improvement effect of hydraulic flushing and aperture variation were analyzed，thus the anti-blocking technology and the measures for gas drainage improvement were formulated.The results show that：① Hydraulic punching measures can greatly improve the coal permeability around boreholes，the more punching coal amount，the greater relief range of hydraulic flushing，the higher the permeability of coal is increased；② Shrinkage phenomenon of borehole occurs over time because of rheological properties，the greater the stress，the lower the coal strength，the more intense the creep deformation of coal，once drainage channels are blocked，gas extraction effect will be greatly reduced；③ Anti-blocking technology by installing casting pipe reserves a drainage channel，thus high concentrations gas can be extracted for a long time，the effect of gas drainage increase by 2.7 times；④ By gas injection combined with hydraulic flushing technique，the gas drainage amount of single hole increases by 8.1 times，which can effectively improve gas drainage effect.