交替加卸载条件下原煤的变形及渗透特性研究

    Study on deformation and permeability properties of raw coal during alternate loading and unloading

    • 摘要: 采用热流固耦合伺服实验系统,开展了变轴压加载速率条件下交替加卸载过程中原煤的变形及渗透性实验,分析了交替增轴压、卸围压过程中含瓦斯原体的变形及渗透特性。结果表明:增轴压、卸围压过程中试样轴向呈压缩变形、径向呈膨胀变形,轴向压缩变形量和径向膨胀变形量随围压应力水平的降低均逐渐增大;增轴压过程中试样渗透率缓慢降低,卸围压过程中试样渗透率缓慢增大,满足二次函数关系;采用单位应力条件下试样轴向应变、径向应变和渗透率的变化率分析轴压和围压对试样变形参数的影响特征,采用单位时间内试样轴向应变、径向应变和渗透率的变化速率分析变轴压加载速率对试样变形参数的影响特性;随着轴向荷载强度和轴压加载速率的增大,试样轴向应变和径向应变变化速率的绝对值逐渐增大,渗透率变化速率的绝对值先增大后减小;相反,随着轴压加载速率的减小试样轴向应变、径向应变和渗透率的变化速率的绝对值均先增大后减小;卸围压过程中2个试样轴向应变和径向应变变化速率的绝对值均逐渐增大,而渗透率变化速率的变化规律相反。

       

      Abstract: The deformation and permeability experiments of raw coal in the process of alternating loading and unloading under variable axial pressure loading rate are carried out by using the thermal fluid structure coupling servo experimental system, and the deformation and permeability characteristics of coal containing gas in the process of alternating increasing axial pressure and unloading confining pressure are analyzed. The results show that during the process of loading axial stress and unloading confining pressure, the specimen presents axial compression deformation and radial expansion deformation, and the axial compression deformation and radial expansion deformation gradually increase with the decrease of confining pressure stress level. It is considered that the sample shows axial compression deformation and radial expansion deformation in the process of loading axial stress and unloading confining pressure, and the deformation of axial compression and radial expansion gradually increase with the decrease of confining pressure stress level. The permeability decreases slowly during loading axial stress and increases slowly during unloading confining pressure, which satisfies the quadratic function relationship. The change rate of axial strain, radial strain and permeability under unit stress state are used to analyze the influence characteristics of axial stress and confiningpressure on the deformation parameters of the sample. The variation rates of axial strain, radial strain and permeability in unit time are used to analyze the influence of variable axial compression loading rate on the deformation parameters of the sample. With the increase of axial load strength and axial stress loading rate, the absolute value of variation rate of axial strain and radial strain gradually increases, and the absolute value of permeability variation rate first increases and then decreases. On the contrary, with the decrease of axial stress loading rate, the absolute values of axial strain, radial strain and permeability first increase and then decrease. In the process of unloading confining pressure, the absolute values of axial strain and radial strain change rate of the two samples gradually increase, while the change law of permeability change rate is opposite.

       

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