q值测量室气体压力初始演变规律及其应用

Initial evolvement rule of gas pressure in q value measuring chamber and its application

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。

The authors believe that a correct expectation of the time for borehole gas flow rate reaches its peak value is helpful to improve the accuracy of measuring the initial velocity （q value ） of gas emission from borehole and to increase the depth of borehole in which q value can be measured accurately. Accord- ing to the gas flow theory in coal seams and mass conservation law, a balance differential equation of gas pressure was established for q value measuring chamber. An analytical expression of such pressure was deduced. Gas chamber pressure-time curves were drawn and put into practical application. Results show that initial gas pressure in the gas chamber presents a tendency of firstly increasing and then decreasing in the front of borehole, and the increasing velocity is bigger comparatively, that under different conditions, the peak time is also different, that only when mensuration preparations are completed before the peak val- ue appears can measurement results of initial velocity be accurate, that deeper the measured borehole is, the later the peak time will be, the longer the available preparation time will be tbr q value measurement, and deeper the borehole is, in which q value can be measured accurately.