冻融循环下红砂岩的微观孔隙结构与分形特征

Microscopic pore structure and fractal characteristics of red sandstone under freeze-thaw cycle

为研究冻融作用下红砂岩的内部微观孔隙结构演化规律,利用冻融循环试验、压汞试验和CT扫描试验,基于图像处理技术和分形理论,分析了冻融循环下红砂岩的孔隙结构和分形特征。试验结果表明:随着冻融次数增加,红砂岩内部大孔孔隙数量增加最为突出,孔径分布曲线连续性增强,孔隙连通性增大,孔隙度呈指数函数增大;通过最佳值阈值对CT图像进行二值化处理,以微孔隙、裂隙等缺陷的“面积”为参数,得到了红砂岩的统计孔隙度;盒维数法计算得到的红砂岩孔隙分形维数,随着冻融次数的增加而降低;通过数据回归分析可知,由Menger海绵模型预测得到的红砂岩孔隙度和孔隙分形维数之间呈指数函数关系。

This paper is an effort to investigate the evolution law behind the internal microscopic pore structure of red sandstone under freeze-thaw action.The study conducts freeze-thaw cycle test,mercury injection test and CT scan test,and analyzes the pore structure and fractal characteristics of red sandstone under freeze-thaw cycle based on image processing technology and fractal theory.The experimental results show that with the increase of freeze-thaw times,the most prominent change characteristics in the red sandstone is the number increase of the big pores,along with the continuely enhanced pore distribution curve,the increased pore connectivity,and the increased porosity by exponential function;The CT image is binarized by the optimal threshold value,and the statistical porosity of red sandstone is obtained by taking the"area"of micro pores,fractures and other defects as the parameter;The fractal dimension of red sandstone pores calculated by the box dimension method decreases with the increase of freeze-thaw times;The porosity of red sandstone is predicted by Menger sponge model,and the exponential function relationship exists between porosity and fractal dimension by analyzing data regression.