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掌握钻孔瓦斯流量峰值出现的时间,可有效提高钻孔瓦斯涌出初速度(q值)测定的准确性,实现更深的钻孔的q值准确测定。根据煤层瓦斯流动理论和质量守恒定律,构建q值测量室的气体压力平衡微分方程,并推导出该压力的解析表达式;绘制测量室气体压力随时间的变化曲线,并进行实践应用。结果表明,钻孔前方瓦斯室初始气体压力呈先上升后下降趋势,且上升的速率相对较大。在不同条件下,钻孔瓦斯流量峰值出现时间是不一样的,只有在峰值出现之前完成测定准备工作,才能确保钻孔瓦斯涌出初速度测定结果的准确性;测定钻孔越深,流量峰值出现时间越晚,q值测定可利用的准备时间越长,便可实现更深孔的q值测定。
Grasping the peak time of gas flow in the borehole can effectively improve the accuracy of gas velocity measurement (q value) of borehole, and achieve accurate determination of q value of deeper borehole. According to gas flow theory and mass conservation law in coal seam, gas pressure balance differential equation of q-value measuring room is constructed and the analytical expression of pressure is deduced. The curve of gas pressure in measuring room with time is plotted and practiced and applied. The results show that the initial gas pressure in the gas chamber in front of the borehole first increases and then decreases, and the rate of ascent increases relatively. Under different conditions, the peak time of the gas flow in the borehole is not the same, and the accuracy of initial gas velocity measurement results can be ensured only when the measurement preparation is completed before the peak appears. The deeper the borehole, the peak flow rate appears The later, the longer the preparation time available for the q value determination, the deeper q values can be determined.