基于CT图像砂岩峰后损伤特征研究

发布时间：2019-03-04 10:54

【摘要】：本文根据峰后砂岩CT试验，对峰后砂岩在不同围压下进行加载，通过CT图像研究峰后砂岩的损伤特征。目前CT技术为研究峰后岩石的损伤提供了十分有效的技术手段，但是现有的CT图像分析并没有充分地利用峰后岩石的CT图像资料。文中基于峰后砂岩CT图像的数字图像处理技术，对峰后砂岩的CT图像进行图像降噪，图像伪彩色增强，及边缘检测等处理，得到了峰后砂岩内部损伤的清晰图像，且分析了峰后砂岩内部损伤裂隙的分布特征。本文在一些专家学者研究的基础上，对峰后砂岩试验后的力学参数进行了分析，以损伤力学与细观力学为理论依据，建立了峰后砂岩损伤理想数学模型，对其损伤进行定义，通过CT图像计算求得峰后砂岩的CT数与方差，，由CT数的定义推导出了岩石峰后损伤变量与CT数之间的关系，求得峰后砂岩在不同轴压下的损伤变量，发现从开始加压到荷载达到极限前，试件的体积都是减小的，这样使得峰后砂岩的平均密度实际上在增大，这样扫描图像的平均CT数也就增大了，这其实会抵消由于微裂隙的出现所引起CT数减小的事实，其损伤也不是很大，不过在峰值以后由于试件破坏严重，裂隙变宽，导致峰后砂岩的体积增加，密度变小，使得扫描图像的平均CT数也就开始变小，相对于初始扫描图像的平均CT数减小的幅度很大，损伤度却增大了，这充分说明在峰值以后的试件已完全破裂，失去支撑能力，能够定量的研究其损伤程度及损伤演化过程。文中最后以分形理论及分形模型为理论基础，获得了峰后砂岩裂隙的分形维数，并根据获得的相关分形维数来描述峰后砂岩裂隙的分布情况，根据自定义的峰后岩石损伤建立了与分形维数的关系，用分形维数来定量的描述峰后砂岩的损伤，发现随着荷载的增大，峰后砂岩裂隙分布分维数F越来越大，这是因为随着荷载的加大，砂岩内部逐渐有新裂隙产生并且原裂隙也在变大，使得统计的区域内裂隙数量越来越多的缘故。揭示了峰后砂岩裂隙分布具有分形分布特征及其损伤演化规律，补充了谢和平在岩石峰后的研究。
[Abstract]:Based on the CT test of post-peak sandstone, the damage characteristics of post-peak sandstone under different confining pressures were studied by CT image. At present, CT technology provides a very effective technical means to study the damage of post-peak rock, but the existing CT image analysis has not fully utilized the CT image data of post-peak rock. Based on the digital image processing technology of post-peak sandstone CT image, the CT image of post-peak sandstone is processed by image denoising, image pseudo-color enhancement and edge detection, and a clear image of interior damage of post-peak sandstone is obtained. The distribution characteristics of the damage fractures in the sandstone behind the peak are also analyzed. Based on the research of some experts and scholars, the mechanical parameters of post-peak sandstone test are analyzed in this paper. Based on the theory of damage mechanics and meso-mechanics, an ideal mathematical model for damage of post-peak sandstone is established and its damage is defined. The CT number and variance of sandstone behind peak are calculated by CT image, and the relation between damage variable after peak and CT number is deduced from the definition of CT number, and the damage variable of sandstone behind peak under different axial pressures is obtained. It is found that the volume of the specimen decreases from the beginning of the compression to the limit of the load, so that the average density of the sandstone behind the peak is actually increasing and the average CT number of the scanned image is also increased. This will actually counteract the fact that the number of CT decreases due to the appearance of micro-cracks, and the damage is not very great. However, after the peak value, due to the serious damage of the specimen, the crack becomes wider and the volume of the sandstone behind the peak increases and the density of the sandstone decreases. The average CT number of the scanned image begins to decrease, and the average CT number of the scanned image decreases greatly compared with the initial scan image, but the degree of damage increases, which fully indicates that the specimen after the peak value has completely cracked and lost its supporting capacity. It can quantitatively study the damage degree and damage evolution process. Finally, on the basis of fractal theory and fractal model, the fractal dimension of post-peak sandstone fracture is obtained, and the distribution of post-peak sandstone fracture is described according to the obtained correlation fractal dimension. The relationship between rock damage after peak and fractal dimension is established. The fractal dimension is used to describe the damage of sandstone behind peak quantitatively. It is found that with the increase of load, the fractal dimension F of fracture distribution in post-peak sandstone becomes larger and larger. This is because with the increase of load, there are new cracks in the interior of sandstone and the original cracks are also increasing, which makes the number of cracks in the statistical area more and more. It is revealed that the fracture distribution of sandstone behind the peak has the characteristics of fractal distribution and its damage evolution, which complements the study of Xie Heping after the peak of rock.
【学位授予单位】：内蒙古科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD313

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