Abstract To understand the gas penetration properties during unloading confining pressures and permeability enhancement mechanism in coal, temperature shocks, seepage tests, NMR, CT and SEM scanning tests were carried out with trimmed coal samples. The results showed that the coal permeability increased with the decrease of confining pressures after temperature shocks performed, and that the coal permeability fully followed an exponential change law. To achieve a higher gas permeability, heating-cooling shocks should be executed in low stress regions and stress-releasing areas in coal. According to the NMR results, the increase in pore volume improved the gas diffusion coefficient of coal. The CT and SEM scanning results declared that the growth and extension of internal and surface cracks eventually enhanced the coal permeability. After temperature shocks performed, it can be concluded that coal anisotropy and excessive thermal stresses are the essential causes of the coal damage and gas permeability enhancement.

中文翻译：

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卸围压温度冲击下煤的渗流特性及增渗机理

摘要 为了解煤体卸围压过程中的瓦斯渗透特性和增透机理，对煤样进行了温度冲击、渗流试验、核磁共振、CT和SEM扫描试验。结果表明，经过温度冲击后，煤的渗透率随着围压的降低而增加，且煤的渗透率完全遵循指数变化规律。为了获得更高的气体渗透率，应在煤的低应力区和应力释放区进行加热冷却冲击。根据核磁共振结果，孔隙体积的增加提高了煤的气体扩散系数。CT 和 SEM 扫描结果表明，内部和表面裂缝的生长和扩展最终提高了煤的渗透性。