瓦斯抽采PC-CAS基封孔材料优化及其膨胀作用分析*

为了研制以硅酸盐/铝酸盐水泥、生石灰、生石膏为主的PC-CAS基封孔材料，采用正交试验优化材料配比、开展膨胀力研究，并用扫描电镜观测料-煤胶结形貌。研究结果表明:材料的最优配比为A2B2C4，其具备优良的流动性、强度及致密性，造浆量达2 100 mL/kg；PC-CAS基材料具有显著的膨胀性，其膨胀力随时间先增大而后趋于稳定，并且该膨胀力随着径向约束的提高而增大；相比于FP材料，PC-CAS基材料产生的膨胀力能够显著降低材料-煤岩界面的空隙并在一定程度上压密煤体内部的裂隙；该材料产生的膨胀力可压密封孔段围岩、提高封孔质量，并为后期“二次注浆”提供保压条件。工业试验结果表明，采用PC-CAS基材料进行封孔可显著改善抽采效果，将原有平均浓度10.11%提升至20.08%。

Optimization on PC-CAS based borehole sealing material for gas extraction and analysis of its expansion effect

In order to develop a PC-CAS based borehole sealing material with the portland/aluminate cement,lime and gypsum as the main components,the orthogonal test method was used to optimize the material mixture ratio and carry out the expansive force study,then the SEM was used to observe the morphology of material coal cementing.The results showed that the optimal material mixture ratio was A2B2C4,and it had the preferable fluidity,strength and tightness,with the slurry production capability of 2 100 mL/kg.The PC-CAS based material had the prominent expansibility,its expansive force increased first and then tended to be stable with time,and the expansive force increased with the increase of radial constraint.Compared with FP material,the expansive force generated by the PC-CAS based material could significantly reduce the gap on the interface between material and coal rock,and compress the fracture in the coal to a certain extent.The expansive force generated by this material could compress the surrounding rock at the borehole sealing section,improve the quality of borehole sealing,and provide the holding pressure condition for the “secondary grouting” in the later period.The results of industrial test showed that adopting the PC-CAS based material to carry out the borehole sealing could significantly improve the extraction effect,and the original average concentration increased from 10.11% to 20.08%.