Coal seam gas is a critical substance because it can be a source of a large quantity of clean energy as well as a dangerous source of risk. A pressure relief gas drainage is an effective and widely used method for coal seam gas recovery and gas disaster control in coal mines. A series of pressure relief gas drainage experiments were conducted using large-scale coal samples under different unloading stress paths in this study to explore the unloading stress paths. From the experimental results, the dynamic evolutions of gas pressure, coal temperature, and gas production were analyzed. The trends of gas pressure and coal temperature during pressure relief gas drainage were similar: dropping rapidly first and then slowly with time. Correspondingly, gas production was fast in the early stage of pressure relief gas drainage and became stable thereafter. Meanwhile, gas flow characteristics were significantly affected by the unloading stress paths. Gas pressure and coal temperature had the maximum descent by unloading stress in three directions simultaneously, and the unloading stress of the direction had the minimal impact when only unloading in one direction of stress. However, the influence of unloading stress paths on gas production was complex and time dependent. The difference coefficient parameter was proposed to characterize the influence degree of unloading stress paths on the pressure relief gas drainage effect. Eventually, the selection of unloading stress path under different situations was discussed based on time, which is expected to provide the basis for pressure relief gas drainage.

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不同卸荷应力路径下气体流动特性及泄压泄放效果试验研究

煤层气是一种关键物质，因为它既是大量清洁能源的来源，又是危险的危险源。泄压瓦斯抽采是煤矿煤层瓦斯回收和瓦斯灾害防治的有效方法。本研究利用大型煤样在不同卸荷应力路径下进行了一系列卸压瓦斯抽采实验，探索卸荷应力路径。从实验结果分析了瓦斯压力、煤温、产气量的动态演化。卸压瓦斯抽采过程中瓦斯压力和煤温的变化趋势相似，均随时间先快速下降后缓慢下降。相应地，卸压瓦斯抽采前期产气速度快，之后趋于稳定。同时，卸载应力路径显着影响气体流动特性。同时卸载三个方向的应力对瓦斯压力和煤温的影响最大，仅向一个方向卸载时，该方向的卸载应力影响最小。然而，卸荷应力路径对产气量的影响是复杂的和时间依赖性的。提出了差异系数参数来表征卸荷应力路径对卸压瓦斯抽采效果的影响程度。最后，基于时间讨论了不同情况下卸荷应力路径的选择，有望为泄压瓦斯抽采提供依据。同时卸载三个方向的应力对瓦斯压力和煤温的影响最大，仅向一个方向卸载时，该方向的卸载应力影响最小。然而，卸荷应力路径对产气量的影响是复杂的和时间依赖性的。提出了差异系数参数来表征卸荷应力路径对卸压瓦斯抽采效果的影响程度。最后，基于时间讨论了不同情况下卸荷应力路径的选择，有望为泄压瓦斯抽采提供依据。同时卸载三个方向的应力对瓦斯压力和煤温的影响最大，仅向一个方向卸载时，该方向的卸载应力影响最小。然而，卸荷应力路径对产气量的影响是复杂的和时间依赖性的。提出了差异系数参数来表征卸荷应力路径对卸压瓦斯抽采效果的影响程度。最后，基于时间讨论了不同情况下卸荷应力路径的选择，有望为泄压瓦斯抽采提供依据。仅在一个方向卸载时，该方向卸载应力的影响最小。然而，卸荷应力路径对产气量的影响是复杂的和时间依赖性的。提出了差异系数参数来表征卸荷应力路径对卸压瓦斯抽采效果的影响程度。最后，基于时间讨论了不同情况下卸荷应力路径的选择，有望为泄压瓦斯抽采提供依据。仅在一个方向卸载时，该方向卸载应力的影响最小。然而，卸荷应力路径对产气量的影响是复杂的和时间依赖性的。提出了差异系数参数来表征卸荷应力路径对卸压瓦斯抽采效果的影响程度。最后，基于时间讨论了不同情况下卸荷应力路径的选择，有望为泄压瓦斯抽采提供依据。