型煤与原煤全应力–应变过程渗流特性对比研究

COMPARATIVE RESEARCH ON PERMEABILITY CHARACTERISTICS IN COMPLETE STRESS-STRAIN PROCESS OF BRIQUETTES AND COAL SAMPLES

利用自主研制的自压式三轴渗流装置对型煤和原煤试样进行三轴压缩渗流试验,得到不同围压下2种煤样的全应力–应变曲线,并利用流量计和环向引伸计自动采集整个试验过程中煤样的渗流速度和横向变形。从细观损伤力学的观点分析2种煤样不同的破坏形式以及煤样的变形破坏对渗流速度的影响;讨论渗流速度对外部变量的敏感性和煤与瓦斯突出的突发性。研究结果表明,2种煤样的全应力–应变曲线都可以分为5个阶段,并与渗流速度–轴向应变曲线具有良好的对应关系。由于型煤与原煤的结构特性不同,致使2种煤样受力以后具有不同的损伤机制,渗流速度–轴向应变曲线差异较大,尤其在破坏阶段。型煤变形主要在前2个阶段影响煤的渗流特性,而原煤在整个试验过程中都受影响;型煤的渗流速度对轴向压力和轴向变形最敏感,而原煤的渗流速度对体积变形和横向变形比较敏感。原煤全应力–应变–渗流试验的5个阶段可以较好地解释煤与瓦斯突出过程的准备、发动、发展和终止4个阶段,可以间接地利用煤体瓦斯渗流速度变化进行煤与瓦斯突出预测预报。研究结果对探索煤层真实的瓦斯运移规律具有一定的参考价值。

Triaxial seepage tests of briquettes and row coal specimens are implemented by self-developed triaxial seepage test system. The complete stress-strain curves under different confining pressures are obtained. Seepage velocity and transverse deformation in the whole test process are automatically collected by flowmeter and ring extensormeter. The different destructional forms of two types of samples are analyzed by microscopic damage mechanics theory;and the relation of seepage velocity and the process of deformation and destroy is presented. The sensitivity of seepage velocity is effected by the external variables;and the coal and gas outbursts are also discussed. The results show that the complete stress-strain curves of two kinds of samples could be divided into five stages. It has a good relationship with the curve of seepage velocity-axial strain. Due to different structural characteristics,the two types of coal specimens have different damage mechanisms under axial pressure. Seepage velocity-axial strain curves have great difference,especially in the destructional phase. The deformation of briquettes will affect seepage velocity in the first two stages,but it will have certain effects on coal in the whole compression process. The seepage velocity of briquettes is sensitive to axial pressure and axial strain,but it is sensitive only to transverse strain and volume strain for row coal. The five stages in the compression stress-strain-seepage curves of row coal could be explained by four stages（preparation,initialization,development,and completion） of coal and gas outbursts processes. The variety of seepage velocity in coal bed could be used for forecasting coal and gas outburst indirectly. The results have a certain referential value for exploring the real laws of gas migration.