X-Ray CT Investigation on Fractal Characteristics of Fine-Grained Tailing Sand in Fujian’s Makeng: Insight into the Mesoscopic Seepage Failure

Abstract

This work is aimed at revealing the mesophysical process and mechanical behaviors of fine-grained tailing sand during seepage failure. The macroscopic seepage tests combined with posttest X-ray computed tomography (CT) were employed to study the fractal characteristics of mesostructure. Results show that before and after the seepage failure of fine-grained tailing sand, fractal of pore distribution ( $D_{\text{pd}}$ ) and fractal dimension of pore size ( $D_{\text{ps}}$ ) show a relatively obvious positive correlation with porosity. Tailing particles migrate along the seepage direction during the seepage process, resulting in the gradual decrease of $D_{\text{pd}}$ and pore distribution area. The $D_{\text{ps}}$ reflects the variation characteristics of pore number distribution with different pore sizes. The increase in $D_{\text{ps}}$ leads to a decrease in the uniformity of pore size and an increase in the size difference between pores. The mass fractal dimension ( $D_m$ ) of fine-grained tailing sand samples ranges from 1.6472 to 1.8256. With the increase of $D_m$ , the coefficient of uniformity ( $C_u$ ) of tailing sand tends to increase. The $D_m$ method can discern the seepage failure type of fine-grained tailing sand, and it is more accurate than the traditional method. This study provides a reference for the prevention and control of the seepage failure of tailing dam.