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针对煤层瓦斯抽采钻孔稳定性差、抽采率低等问题,结合广义Hoke-Brown强度准则、有效应力原理及非线性孔隙压力分布特征,推导了钻孔围岩弹塑性区半径和应力表达式,得到了钻孔周围塑性区半径随各影响因素的变化规律。基于理论分析,采用囊袋式注浆封孔技术,在山西某矿310207工作面回风巷进行了现场试验。结果表明:地质强度指标(GSI)和不均衡系数(λ)相比扰动性系数(D)对钻孔周围塑性区范围影响更大;当原始瓦斯压力点距离钻孔中心小于1 m时,塑性区半径受瓦斯压力影响开始显著上升。以瓦斯抽采体积分数大于30%作为衡量封孔效果的标尺,在3个月左右的观测时间内囊袋式注浆钻孔相比聚氨酯钻孔,瓦斯抽采有效时间可以延长约2个月,瓦斯平均体积分数提高约58.2%。
Aiming at the problems such as poor stability and low pumping rate of gas drainage in coal seam, the radius and stress expression of the elastic-plastic zone of the surrounding rock are deduced based on the generalized Hoke-Brown strength criterion, effective stress principle and nonlinear pore pressure distribution , The law of the radius of plastic zone around the borehole with each influencing factor was obtained. Based on the theoretical analysis, a pocket-type grouting sealing technique was used to conduct field tests on the air return tunnel of a 310207 working face in a mine in Shanxi. The results show that the perturbation coefficient (D) of geologic strength index (GSI) and unbalance coefficient (λ) have a greater influence on the plastic zone around the borehole. When the original gas pressure point is less than 1 m from the borehole center, District radius under the influence of gas pressure began to rise significantly. Taking the volume fraction of gas drainage greater than 30% as a gauge to measure the sealing effect, the effective time of gas drainage can be prolonged by about 2 months compared with that of polyurethane drilling within 3 months observation time , The average volume fraction of gas increased by about 58.2%.