基于体视学原理的煤岩裂隙三维表征试验研究

EXPERIMENTAL STUDY OF THREE-DIMENSIONAL CHARACTERIZATION OF COAL FRACTURES BASED ON STEREOLOGY

基于体视学原理,运用工业CT试验系统对煤样进行单轴加载扫描试验。对得到的CT扫描图像采用不同阈值求取其裂隙张量特征值平方和的曲线,选取曲线图拐点处所对应的阈值作为图像二值化的阈值,并验证该阈值是计算二阶张量的最佳阈值。同时实现体视学中对二值化后的图像测线及特征区域参数的提取,提出特征值平方和的概念作为描述煤样破损程度的参数。在从三维角度重构出的裂隙煤样中,选取3个正交面构造出二阶张量特征值平方和与孔隙率之间的关系,为进一步从三维角度描述煤样裂隙损伤奠定基础。

Scanning experiments under uniaxial loading for coal samples were carried out using the industrial computerized tomography（CT） experiment system based on the principle of stereology. The curves were obtained by calculating the sum of squared eigenvalues of crack tensor with different threshold values for CT images. The inflection point of the curve was taken as the threshold which was verified to be the best threshold value for calculation of the second order tensors. The binary image line and the eigenvalues of regional parameters by the binary stereological image were obtained. The sum of squared eigenvalues was proposed as the parameter of coal specimen damaging. Three orthogonal surfaces of fractures of the reconstructed three-dimensional coal specimen were selected to calculate the relationship between the squared eigenvalues of second order tensor and the porosity, which could provide a reference for describing crack damage in three dimensions.