钻屑暴露时间误差对解吸指标△h2误差的影响

Effects of the exposure time error of drilling cutting on the desorption index Δh_2

钻屑瓦斯解吸指标△h_2是预测煤与瓦斯突出的重要方法之一。通过分析钻屑瓦斯扩散的过程,建立了钻屑瓦斯扩散的数学物理模型,推导出了钻屑解吸指标△h_2的解析解。对钻屑瓦斯放散量随时间的变化规律、△h_2的绝对误差和相对误差随钻屑暴露时间误差的变化规律进行了研究。结果表明:钻屑瓦斯放散量随放散时间的增长而增加,且增加幅度随时间逐渐减小;△h_2的绝对误差和相对误差都随钻屑暴露时间误差的增大而增加。因此,暴露时间的准确性对获得真实的△h_2至关重要。

The present paper is to study the effects of the exposure time error of drilling cutting in coal-mining on the desorption index △h2（the drilling cutting gas desorption index△h2is one of the signif- icant iridexes for predicting the coal and gas outburst or flame acci- dents）. For the research purpose, we have first of all established a mathematical and physical model governing the gas diffusion of coal particles and deduced the analytical solution of △h2. And then we have studied the variation of gas diffusion amounts and the variation of gas diffusion rate with the diffusion time and that of the absolute error and relative error of △h2 with exposure time error. The results of our study indicates that the gas diffusion amount increases with the in- crease of the diffusion time but decrease of the increasing rate with the exposure time going on. On the other hand, with the coal particles instantly exposed to the air, the gas from the mining coal-face would first diffuse, and then it begins to diffuse with that of deeper level with the time going on. At the same time, the resistance to the gas movement increases with the gas flow interface and the flow channel prolonging, the gas radiation velocity would drop with the time e- lapse. Or put it simply, gas diffusion rate decreases with the diffusion time elapse, which tends to be in accordance with the negative-power variation regularity. And since the drilling cutting gas desorption in- dex △h2 follows the rule of the diffusion reduction with the exposure time going on, both absolute error and relative error of △h2 tends to increase with the error of exposure time, which virtually prolongs the gas absorption time and leads to the reduction of the gas diffusion amount per unit time. Thus, it can be concluded that △h2 tends to reduce and the absolute error and relative error of △h2 would increase with the exposure time elapse, which is essential to gain the authentic △h2 to ensure the accuracy of the exposure time.