三轴应力下原煤吸附CH_(4)/N_(2)变形时空特性

Temporal and spatial characteristics of raw coal deformation during the adsorption of CH_(4)/N_(2) under triaxial stress

为深入研究受载煤体与CH_(4)/N_(2)相互作用时的变形时空特性,开展了三轴应力加载下原煤吸附CH_(4)/N_(2)及其二元混气时的吸附量与吸附变形动态测试试验.结果表明:恒定三轴应力下,原煤对CH_(4)的吸附能力大于N_(2);二元混气吸附量介于纯气体吸附量之间.三轴应力下原煤吸附膨胀变形存在各向异性.不同注气压力下,原煤轴向/环向应变随吸附时间整体呈现相同演化规律,注气端轴向应变可划分为5个阶段,煤样中部、排气端轴向/环向应变均可划分为3个阶段.相同注气压力下,原煤吸附气体时各测点轴向应变由负转正时间由长到短的顺序为:CH_(4),CH_(4)/N_(2)混气,N_(2).原煤吸附CH_(4),N_(2),CH_(4)/N_(2)混气时,轴向/环向应变随吸附量增加依次呈指数函数、一元一次函数、一元二次函数增长.三轴应力加载后,原煤轴向/环向初始应变呈两端小中间大分布;三轴应力下原煤吸附CH_(4)时膨胀变形能力较强,煤体表面自由能降低量大,煤体强度削减明显,越易发生变形破坏.

In order to further study the temporal and spatial characteristics of coal deformation during the interaction between loaded coal and CH_(4)/N_(2). The dynamic test of adsorption capacity and adsorption deformation of raw coal adsorbing CH_(4)/N_(2)and its binary mixture under triaxial stress loading were carried out. The results showed that the adsorption capacity of CH_(4)in raw coal was greater than that of N_(2)under constant triaxial stress. The adsorption capacity of binary mixed gas was between that of pure gas. There was anisotropy in the adsorption expansion deformation of raw coal under triaxial stress. Under different gas injection pressure conditions,the axial/circumferential strain of raw coal presented the same evolution law with the adsorption time. The axial strain of the gas injection end could be divided into 5 stages,and the axial/circumferential strain in the middle and exhaust ends of the coal sample could be divided into 3 stages. Under the same gas injection pressure,when raw coal adsorbed gas,the time order of axial strain changed from negative to positive in each measuring point was CH_(4),CH_(4)/N_(2)mixed gas,N_(2). When the raw coal adsorbed CH_(4),N_(2)and CH_(4)/N_(2)mixed gas,the axial/circumferential strain of raw coal increased with the increase of adsorption capacity in the order of exponential function,unary linear function and unary quadratic function. After triaxial stress loading,the axial/circumferential initial strain of raw coal was different,and the initial strain of the raw coal was distributed was small at both ends and large in the middle. When raw coal adsorbed CH_(4)under triaxial stress,the expansion deformation ability was stronger,it had large reduction of surface free energy,and obvious reduction of coal strength,which made it more prone to deformation and failure.