煤体吸附瓦斯膨胀变形效应的试验研究

为了探讨煤体吸附瓦斯产生膨胀变形效应这一特有的力学行为,利用自行研发的含瓦斯煤岩细观力学试验系统,进行不同瓦斯压力下的吸附膨胀变形试验。试验结果表明:(1)同一煤样在不同瓦斯压力下随时间的变形曲线具有相同的变化规律,煤样的应变变化率随时间逐渐减小,直至一个相对稳定值;(2)煤样的吸附膨胀变形呈各向异性,垂直于层理方向和平行于层理方向的应变整体变化趋势呈现一致性,但由于煤体内部裂隙分布差异,垂直层理方向的变形值明显大于平行层理方向;(3)煤体瓦斯吸附量与体应变量呈现较好的线性关系,以此建立考虑温度、水分、灰分和各向异性等因素的吸附膨胀变形计算方程;(4)利用吸附变形应力与制约吸附变形量的线性关系,以及吸附变形量与瓦斯压力的关系得出吸附膨胀应力计算方法;(5)煤体的吸附膨胀变形具有不可逆性,且吸附气体压力越大,其残余变形值也越大。煤体的膨胀变形效应具有重要的工程应用价值,可作为煤层突出危险性测定的辅助指标,以及应用于煤层透气性的研究。

EXPERIMENTAL STUDY OF SWELLING DEFORMATION EFFECT OF COAL INDUCED BY GAS ADSORPTION

In order to investigate the unique mechanical behavior of swelling deformation effect of coal induced by gas adsorption，the self-developed meso-mechanical testing apparatus of coal containing gas is used to perform the adsorbed swelling deformation test under different gas pressures. The results show as follows：(1) The swelling deformation and time curves of the same coal specimen under different gas pressures have the same variation law. The strain change rate of coal specimen decreases with time until it reaches a stable value. (2) The swelling deformation of coal specimen shows anisotropy. The total trends of strains perpendicular to the bedding and parallel to the bedding are consistence. Because crack distributions are different in the coal，the deformation perpendicular to the bedding is greater than that parallel to bedding. (3) The gas adsorption quantity of coal and its volumetric strain present a good linear relationship. Based on this，the swelling deformation equation is established considering temperature，moisture，ash，anisotropy and other factors. (4) Using the linear relationship between absorbed deformation stress and constrained deformation，and relationship of adsorption deformation and gas pressure，the calculation method of absorbed swelling stress is obtained. (5) The adsorbed swelling deformation of coal is irreversible；and the value of residual strain increases as the adsorbed gas pressure becomes larger. Swelling deformation effect of coal induced by gas adsorption is important for engineering application. It can be used as an assistant index of coal seam outburst risk assessment，and also can be used in gas permeability study of coal seam.