Abstract
The soil water characteristic curve and microstructure evolution of unsaturated expansive soil improved by microorganisms in Nanning, Guangxi were studied by means of filter paper method and scanning electron microscope imaging (SEM). Based on Fredlung & Xing model, the influence law of different cement content on the soil water characteristic curve of improved expansive soil is proved. According to the analysis of SEM test results, the influence mechanism of MICP method on the engineering characteristics of improved expansive soil is revealed. The results show that with the increase of cement content, the saturated water content and residual water content of the improved expansive soil gradually increased. At the same time, the water stability gradually increased while the air inlet value gradually decreased. The improved expansive soil changes from the superposition of flat particles and flake particles to the contact between spherical particles and flake particles, which indicates that the aggregate increases significantly. With the increase of the content of cement solution, the contact between particles tends to be smooth and the soil pores gradually tend to be evenly distributed. The particle size and microstructure of soil particles was changed and the connection between particles was enhanced in the improved expansive soil. Eventually the strength and water stability of expansive soil were improved. The conclusions above not only provide a theoretical basis for the in-depth study of engineering characteristics of unsaturated expansive soil improved by MICP method, but also offer theoretical evidence for perfecting engineering technology of expansive soil improved by MICP method.
Highlights
Expansive soil is special catastrophic clay composed of strong hydrophilic minerals such as montmorillonite, illite, and kaolinite, which usually exhibit significant overconsolidation, multiple fissures, and swell-shrink characteristics
Soil-water Characteristic Curves (SWCC) obtained from unsaturated soil tests can be used to study the hydrophilicity, swell-shrinkage and strength characteristics of expansive soil improved by the microbially induced carbonate precipitation (MICP) method
The SWCC of the expansive soils improved by the MICP method was obtained using the filter paper method under different conditions of cementation liquid content
Summary
Expansive soil is special catastrophic clay composed of strong hydrophilic minerals such as montmorillonite, illite, and kaolinite, which usually exhibit significant overconsolidation, multiple fissures, and swell-shrink characteristics. In terms of applying the MICP method to improve the engineering characteristics of soft soils, scholars from home and abroad have mainly researched in improving sandy soils and made great progress [10,11,12,13,14]. A few scholars have used the MICP method to improve expansive soil and other soft clays, which has made gratifying research progress. Soil-water Characteristic Curves (SWCC) obtained from unsaturated soil tests can be used to study the hydrophilicity, swell-shrinkage and strength characteristics of expansive soil improved by the MICP method. From the perspective of microstructural changes in soil samples, the mechanism of the effect of different cementation liquid content on the water stability and water sensitivity of improved expansive soil during the MICP process was revealed. Each 100 mL of cementation liquid contained 21.91 g of CaCl2·6H2O and contained 6.01 g of urea
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
