基于CT图像的煤吸附甲烷细观变形分形特性研究

    Study on microscopic deformation fractal characteristics of methane adsorbed by coal based on CT images

    • 摘要: 为了定量化研究煤吸附甲烷过程细观变形的各向异性特征,通过ACTIS-CT扫描实验系统,开展了恒定温度下方型无烟煤吸附甲烷过程的吸附变形CT扫描实验;根据CT图像,采用质点追踪应变计算算法定量计算了吸附过程中煤内部细观结构的应变变形,讨论了其变化规律。在此基础上,提出了一种基于CT技术煤吸附气体细观变形的非均质性定量化研究方法,应用盒计数维数法计算了分形维数,定量评价了煤细观变形的非均质性,并基于分形几何和细观应变变形分布的物理描述,讨论了分形维数和甲烷吸附各向异性变形特性的关系。研究结果表明:煤吸附气体膨胀变形首先挤压孔隙或裂缝以获得更大的膨胀空间;煤吸附甲烷后引起的细观变形,其非均质性符合分形特征;分形维数与煤吸附甲烷后的膨胀变形率呈负相关性关系,膨胀变形率值越高,分形维数越低,即煤吸附甲烷后越膨胀,煤整体的非均质应变变形的不规则程度越低;相反,膨胀变形率值越低,则分形维数越高,煤整体的非均质应变变形的不规则程度越高。

       

      Abstract: In order to quantify the anisotropic characteristics of mesoscopic deformation during the process of coal adsorbing methane, the CT scanning experiment of adsorption deformation was conducted during the methane adsorption process of anthracite coal under constant temperature using the ACTIS-CT scanning experimental system, the strain deformation of meso-structure of coal was quantitatively calculated during the adsorption process based on the particle tracking strain calculation algorithm of CT image, and the change regulation was discussed. On this basis, a quantitative research method for the heterogeneity of micro deformation of coal adsorbing methane based on CT technology was proposed, and the fractal dimension D was calculated using the fractal dimension method to quantitatively evaluate the heterogeneity of micro deformation of coal. Based on the physical description of fractal geometry and micro-strain deformation distribution, the relationship between fractal dimension D and anisotropic deformation characteristics of methane adsorption was also discussed. The results indicate that: the expansion deformation of coal adsorbing gas first compresses pores or cracks to obtain a larger expansion space; the heterogeneity of microscopic deformation caused by coal adsorbing methane conforms to the fractal characteristics; the fractal dimension is negatively correlated with the expansion and deformation rate of coal after methane adsorption; the higher the expansion and deformation rate is, the lower the fractal dimension is. In other words, the larger the expansion of coal after methane adsorption is, the lower the irregularity of the overall heterogeneous strain deformation of coal is. On the contrary, the lower the value of expansion deformation rate, the higher the fractal dimension, and the higher the irregularity of the whole heterogeneous strain deformation of coal.

       

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