Reducing Compressibility of the Expansive Soil by Microbiological‐Induced Calcium Carbonate Precipitation

Abstract

Most of the research studies on the improvement of expansive soils are focused on reducing their expansive properties; however, there are few studies on the impact of the soil compressibility after the improvement. In this paper, through indoor high-pressure consolidation tests, the recent microbial-induced calcium carbonate precipitation (MICP) technology is studied to improve the compression characteristics of the expansive soil. The significant effect of different microbial concentrations (achieved by different number of treatments) on the compression deformation is revealed with the hyperbolic function that involves two parameters with clear physical meanings. In particular, after 6 times of treatment with the microbial solution, the compression characteristics of the expansive soil reach the best improvement effect; continuing to increase the number of microbial treatments is, otherwise, not conducive to improving the soil compression performance. Also, a dramatical increase of the structural strength of the microbial-treated expansive soil is presented and investigated. Moreover, we performed a scanning electron microscope (SEM) experiment and confirmed the existence of crystals due to mineralization. This study shows that MICP is an effective and environmentally friendly means of reducing the compressibility of the expansive soil.

Failure Mechanisms and Protection Measures for Expansive Soil Slopes: A Review

“…However, actinomycetes have not played a role in improving the cohesion of expansive soils [174]. Microbially induced calcite precipitation (MICP) has attracted more attention as a new soil modification method, as the swelling-shrinkage, compressibility, hydrophilicity, and soil strength of expansive soils can be improved using this technology [176][177][178][179]. Nevertheless, research is still needed regarding the required nutrition of strains in engineering applications and the long-term effects of soil modification.…”

Experimental Study on Microstructure of Unsaturated Expansive Soil Improved by MICP Method

“…Calculated the mass of loose soil required for the sample and made it into a ring-knife sample of size 61.8 × 20 mm. Based on relevant studies by Jiang [19] and Li [20] on the microbiological improvement of expansive soil, the admixture of cementation liquid and bacterial liquid in the experimental scheme was designed [19]. In the three groups of improved expansive soil samples, the content of cementation liquid was 100, 125, and 150 mL respectively, and the content of bacterial liquid was 50 mL.…”

“…Some scholars investigated the swelling properties, strength properties, and microstructure of MICP modified expansive soils through a series of tests such as one-dimensional swelling tests, tensile tests, consolidation tests and compression tests. The MICP method of improved expansive soils can control the swelling and shrinking characteristics of the soil and improve the strength of the soil, and the calcite produced by the reaction can also provide a linkage to the soil particles [19][20][21]. Expansive soil in nature is usually unsaturated.…”

Experimental Study on the Influence of Microbial Content on Engineering Characteristics of Improved Expansive Soil

“…However, there is less literature related MICP method is used to improve expansive soil. Therefore, based on the current studies (Qin et al, 2020;Jiang et al, 2021;Li et al, 2021;Yao et al, 2021;Yu et al, 2021;Yu et al 2021;Yu et al, 2022), the effect of different microbial contents on the mechanical properties, expansibility and shrinkage of expansive soil improved by MICP method has been investigated. The influence mechanism of MICP method on the microstructure of improved expansive soil has been revealed through the testing of scanning electron microscope imaging.…”