煤岩不同含水状态下瓦斯渗流特性试验研究

Experimental study of gas permeability of coal under different moisture state

水力增透技术在瓦斯抽采中的作用效果常常受到水的影响,为更客观地了解煤层不同含水状态下的瓦斯渗透特性,利用三轴渗流试验机,在恒定有效轴向应力和有效围压条件下,对四川省白皎煤矿试样,进行干燥煤样、自然含水煤样、液态水润湿煤样、压力水注水煤样等不同湿润方式煤样的渗流试验。试验结果表明:1)压力水注水煤样(含裂隙)的无因次渗透率随瓦斯压力的增大而逐渐减小,干燥煤样、自然含水煤样、液态水湿润煤样及压力水注水煤样的无因次渗透率均随瓦斯压力的增大呈现先减小后增大趋势,且在瓦斯压力为1.00 MPa左右时存在相对较为明显的变化拐点。2)在干燥煤样、自然含水煤样及液态水湿润煤样的含水率范围内,煤样渗透率与含水率呈线性减小关系。3)在试验范围内,随着含水率的增加,水分对瓦斯压力敏感性的影响越显著,而对压力水注水煤样,水压主要通过产生裂隙来影响煤样瓦斯压力敏感性。

The permeability enhancement effect of hydraulic technology in gas drainage is often influenced by water. For more objective understanding of the gas permeation properties of coal seam with different moisture state, gas seepage experiments are carried out with different coal samples（drying coal samples, natural water coal samples, liquid water wetting coal samples and pressure water injection coal samples） from Baijiao mine in Sichuan province by using the triaxial gas-seepage test machine under constant effective axial stress and effective confining stress. The results show as follows： 1） The dimensionless permeability of water injection coal samples（cracked） decrease with the increase of gas pressure, the dimensionless permeability of drying coal samples. The natural water coal samples, liquid water wetting coal samples and pressure water injection coal samples decrease firstly and then increase with the increase of gas pressure and there is a relatively obvious inflection point near gas pressure of 1.00 MPa. 2） Within the moisture content range of the drying coal samples, natural water coal samples and liquid water wetting coal samples, permeability of coal samples decrease linearly with the increase of moisture content. 3） In the scope of this experiment, with the increase of moisture content, the effect of moisture on the gas pressure sensitiveness is more significant. The hydraulic pressure affects the gas pressure sensitivity mainly by hydraulic fracture in pressure water injection coal samples.