Quantitative microstructural characterization and seepage visualization of biocemented sand

Abstract

Microbial-induced carbonate precipitation (MICP) is a novel geotechnical reinforcement method that can be used for slope protection, erosion mitigation and seepage control without compromising the soil structure. Based on computed tomography (CT) 3D reconstruction, pore parameters such as the connected porosity, pore equivalent diameter and coordination number are extracted to quantitatively evaluate the effect of the calcium carbonate content on the microstructure of biocemented sand. Then, simulations are conducted to analyze the seepage characteristics of single-phase water flow in the pore space, and 3D visualization of porous seepage in biocemented sand is achieved. The results indicate that as the calcium carbonate content increases, there is a noticeable decrease in total porosity, which is accompanied by an increase in the number of isolated pores and a decrease in the number of connected pores. Concurrently, the average pore equivalent diameter increases, while the pore coordination number decreases. Seepage simulation shows that the permeability of biocemented sand has strong anisotropy, and the pore structure has a strong control effect on the seepage. With increasing calcium carbonate content, the biocemented sand streamlines gradually develop from a network to a branching shape until several main stems remain.