基于CT扫描试验的砒砂岩孔隙分布特征研究

Microstructure and Pore Distribution of the Siltstone Based on X-Ray Scanning

岩石的孔隙分布特征是影响相关地质条件下岩质边坡稳定性的潜在因素。为了研究分布于黄河中游地区砒砂岩的微观结构特点,开展X射线断层CT扫描,获取砒砂岩的孔隙模型,提取图像信息并进行孔隙尺寸分布和分形特征研究。结果表明:砒砂岩试样的孔隙率达9.451%,连通孔隙占总孔隙的比例超过了60%,说明砒砂岩孔隙的连通性很强;砒砂岩孔隙的尺寸范围较大,将孔隙划分为大、中、小3类,其中大孔隙虽然数量只占1.50%,但其孔隙体积占比超过了52%,故大孔隙是决定砒砂岩孔隙发育程度的主要因素;试样不同高度处孔隙图像的分形维数在1.298~1.735之间波动,表明不同高度处的孔隙不规则度存在较大差异,反映了砒砂岩内部孔隙分布的不均匀性,这对力学指标的确定有较大影响,因而易导致砒砂岩边坡渗透和力学设计参数选取不准确。

The pore distribution characteristics of rock are potential factors affecting the stability of rock slope under relevant geological conditions. In order to study the microstructure characteristics of siltstone, which are distributed in the Middle Yellow River, X-ray CT scanning tests were carried out to acquire its pore model. Meanwhile, the image information and pore size distribution curves and fractal characteristics were researched. The results show that the pore distribution of siltstone samples is well developed and the porosity is up to 9.451%. The connected pores account for more than 60% of the total pores, which indicates the strong connectivity of soft sandstone pores. Although the number of macropores accounts for only 1.50%, the pore volume accounts for more than 52%. Therefore, macropores are the main factors that determine the development degree of pores. The pore fractal dimension of images at different height ranges from 1.298 to 1.735, which reflects that a large difference between different heights of the pore, The phenomenon means the pore distribution characteristics of siltstones is inhomogeneity, with a great influence on the determination of the mechanics index. As a result, it is easy to cause inaccurate penetration and mechanical parameters to design the slopes.