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Rock and Soil Mechanics

Abstract

Soil cementation technology based on microbially or enzymatically induced calcium carbonate precipitation (MICP/EICP) is one of the hot topics in the field of geotechnical and geological engineering in recent years. In this study, a systematic review was performed on this technology, focusing on advances in the cementation mechanisms of MICP/EICP and the influence of soil pore structures, properties of bacterium, urease and cementation solution, and cementation methods on characteristics of calcium carbonate (CaCO3). The results indicate that the smaller the soil pores are, the more difficult the infiltration of microorganisms or urease is and the worse the cementation uniformity is. More contact points among soil particles will produce more deposition points for CaCO3, resulting in stronger bonding and bridging effects and better cementation effects. The generation rate and total amount of CaCO3 increase as the concentration of bacterium or urease and the activity of urease increase in a certain range. However, too high concentration or activity will induce a too high generation rate of CaCO3, resulting in clogging near the injection end. The calcium carbonate crystals obtained from low concentration cementation solution are relatively small and evenly distributed in the soil. The use of appropriate grouting saturation can increase the proportion of CaCO3 with bonding effect. Multilayer alternating injection or one-phase low pH injection can improve the distribution uniformity of CaCO3 in the sample. Based on influencing factors of CaCO3 precipitation characteristics, the improvement of cemented soil uniformity, durability verification, and the adaptability and improvement scheme of applying the laboratory test results to the field scale should be the focus points of the future research.

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