非凝材料恒压注浆技术在松软煤层封孔中的应用

Application of Constant Pressure Grouting with Non-condensable Material to Soft Coalbed Sealing

为解决松软低透气性煤层抽采钻孔的密封质量差、预抽瓦斯浓度低等问题,提出无机非凝材料恒压注浆封孔技术.采用COMSOL Multiphysics多物理场数值模拟软件构建底抽巷穿层钻孔注浆扩散流固耦合模型,探究底抽巷及钻孔围岩松动圈的范围,分析不同注浆压力下非凝浆液的渗流能力并验证该注浆技术的封孔效果.结果表明:新型无机非凝注浆材料具有低析水性、高渗透性、高悬浮稳定性和较好的封堵性能,可作为“两堵一注”带压封孔材料;2164底板抽采巷及穿层钻孔施工后,巷道肩角部位及钻孔孔底处易产生应力集中,钻孔的始封深度为6 m;浆液在砂岩段的渗流范围比泥岩段大,随着注浆压力的增加,浆液的有效渗流半径也逐渐增大,合理的注浆压力为3 MPa.采用非凝材料恒压注浆技术后,浦溪井的钻孔平均瓦斯抽采体积分数为51.5%,平均抽采纯流量为0.005 m^(3)/min,分别是水泥注浆封孔的1.34倍和1.67倍.

To solve the problems of bad sealing effect and low pre-drainage gas concentration of boreholes in soft coalbeds,the constant pressure grouting technology with inorganic non-condensable material is proposed.The seepage model of slurry in layer-through borehole is built with COMSOL Multiphysics simulation software,to explore the scope of loosening zone around drainage roadway and borehole,and to analyze the seepage capacity of slurry under different grouting pressures.Eventually,the sealing quality is investigated.Results show that the inorganic non-condensable material has low water separation,high permeability,suspension stability and good plugging performance.After the excavation of No.2164 drainage roadway and the borehole,stress concentration is easy to occur at the shoulder of roadway and the borehole bottom;and the reasonable initial sealing depth of borehole should exceed 6 m.The seepage range of slurry in the sandstone section is larger than that in the mudstone section,and the effective seepage radius of slurry gradually increases with the grouting pressure.Adopting the constant pressure grouting technology with the slurry,the average drainage concentration of boreholes in Puxi coal mine is 51.5%,and the average gas flowrate is 0.005 m^(3)/min,which are 1.35 times and 1.67 times than those with the cement grouting method.