基于CT扫描的煤岩细观损伤特性研究
Study on microscopic damage features of coal-rock based on CT scanning
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摘要: 为了研究煤岩在加载前后各扫描断面的图像分形维数以及孔隙度的变化规律,利用工业CT探测技术及三轴加载试验系统,在三轴条件下对初始煤岩及加载破坏后煤岩进行CT扫描观测,分析煤岩CT断面的密度分布图像以及荷载作用下煤岩的动态损伤过程。研究结果表明:煤岩在不同断面破坏前后的分形维数与孔隙度的变化不同,在相同应力状态下,煤岩的不同层面有着不同的损伤扩展特性,在荷载作用下煤岩的损伤演化局部化和不均匀。通过分析煤岩的灰度概率密度曲线,得出曲线中出现多峰分布,反映出在煤体内存在多种损伤因素;曲线中存在单个突出的尖峰,反映出某种因素占主导地位。由试验结果及煤岩的动态损伤过程,并结合煤岩的变形损伤特征,选取合适的损伤参量建立了在荷载作用下煤样的损伤本构模型,证明理论曲线与试验曲线能够较好地吻合。Abstract: In order to study the image fractal dimension of each scanning section and the variation law of the porosity before and after the loading on the coal-rock,the industrial CT detection technology and the triaxial loading test system were applied to the CT scanning observations on the initial coal-rock and the loading damaged coal-rock under the triaxial condition. An analysis was conducted on the density distribution images of the coal-rock CT sections and the dynamic failure process of the coal-rock under the role of the loading. The study results showed that the fractal dimension and porosity of the coal-rock before and after the failure of different section were different in variation. Under the same stress state,the different section of the coal-rock would have different damage expansion features. Under the role of the loading,the damage evolution of the coal-rock would be a localization and inhomogeneity. With an analysis on the density curve of the coal-rock grey probability,a multimodal distribution occurred in the curves was obtained and could explain the multi damage factors existed in the coal-rock. A single protruding peak existed in the curves could explain one factor in the leading position of a factor. The test results and the coal-rock dynamic damage process combined with the deformation damage features of the coal-rock and with the selection of the suitable damage parameters were applied to establish a damage constitutive model of the coal samples under the role of the loading. The results showed that the theoretical curve and the test curve could be well fitted.
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Keywords:
- triaxial loading test /
- industrial CT /
- fractal dimension /
- coal-rock damage
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