Research progress of microbial reinforcement technology

Biological reinforcement is a new branch that has developed in the field of engineering geology in recent years, among which, the microbially induced calcium carbonate precipitation (MICP) reinforcement technology is an effective method. MICP reinforcement technology utilizes the metabolic activity of widely existing microorganisms in nature to induce the precipitation of calcium carbonate with cementing and filling effects, thereby improving the strength of soil, reducing its permeability, and enhancing its engineering performance. Over the past two decades, significant progress has been made in theoretical research, model experiments, and field trials of MICP reinforcement technology. To promote a deeper understanding of MICP reinforcement technology, this paper systematically introduced the reinforcement mechanism and influencing factors of microbial-induced calcium carbonate reinforcement technology based on the current research on MICP reinforcement technology. In addition, the application of MICP reinforcement technology was discussed thoroughly. The current problems and challenges of MICP technology were analyzed in depth. The results show that the strengthening mechanism of MICP is formed based on microbial-induced mineralization, which includes the filling and cementation of soil pores by calcium carbonate precipitation. The influencing factors of the solidification effect of MICP mainly are the properties of bacterial solution and cementing solution, pH , temperature, soil type, and reinforcement method, by influencing the formation of calcium carbonate and cementing effect. The MICP reinforcement technology has shown great potential in soil reinforcement, crack resistance, impermeability, wind erosion resistance, and remediation of contaminated water/soil. At present, the MICP reinforcement technology still has some problems, including solidification uniformity, soil durability, economic benefits, environmental safety, and sustainability. To solve these problems, it is necessary to further integrate microbiology, soil mechanics, materials science, environmental science, and other disciplines to conduct in-depth research, which will help deepen the understanding of MICP reinforcement technology, promote MICP technology to achieve more comprehensive development in the engineering geological field, and further promote application of this technology.