Effectiveness of Microbially Induced Calcite Precipitation for Treating Expansive Soils

Abstract

Expansive soil is a high-plasticity clay that expands rapidly when wetted or soaked with water and shrinks and cracks when it dries. Soil expansion often causes instability problems during construction of roadbeds or embankments. Microbially induced calcite precipitation (MICP), a novel soil treatment method, has drawn increased attention in recent decades because of its environmental friendliness and good performance in soil solidification. In this paper, the expansive soil slope treatment with MICP for the Yangtze-Jiangxi-Huaihe River Diversion Project in China is presented. The effectiveness and mechanism of Sporosarcina pasteurii bacteria for inhibiting soil expansion were investigated experimentally. The results indicated that MICP treatment can significantly reduce the swelling and deformation of expansive soil and showed that the MICP treatment was feasible and effective in inhibiting soil expansion. X-ray diffraction and scanning electron microscopy were adopted to study the changes in soil mineralogy after MICP treatment. These techniques helped to reveal the mechanism of MICP in treating expansive soils.

Spatial Distribution Characteristics of Microbial Mineralization in Saturated Sand Centrifuge Shaking Table Test

“…Sodium hydroxide solution was added to adjust the pH of the medium to 9.0, and the medium was sterilized at 120 °C for 40 min. After inoculation, the bacterial culture was placed in a shaking incubator at 30 °C and shaken at 170 rpm for 24 h [ 27 , 28 , 29 , 30 ]. After oscillation, while kept at an indoor temperature of 22 °C, the measured biomass OD 600 of the bacterial solution was 2.293 on average, and the urease activity was 2.0 ms/min/cm on average.…”