Abstract:
Microbially Induced Carbonate Precipitation (MICP) is a new kind of green and low-carbon soil modification technique. At present, this technique is mainly applicable to sandy soil with good permeability. A two-phase treatment method is commonly used, where the bacterial solution and the cementation solution are applied separately. However, for clayey soils with relatively poor permeability, the traditional two-phase treatment method is difficult to apply. Therefore, a new one-phase cementation method is introduced in this paper. It is a mixed application of bacterial solution and cementation solution. It provides a lag period for bacterial hydrolysis by adjusting the initial pH value of the solution, avoids microbial flocculation blocking the pore, makes the mixed solution evenly distributed in a certain depth range of soil, and thus significantly improves the cementation quality. The mixed liquid is sprayed to the surface of soil to have it treated by MICP. After the treatment, the initial structural strength of soil surface at different depths is tested by SMP-1. The spatial difference of soil mechanical properties is analyzed. The cementation quality of soil is quantitatively evaluated. In addition, the effects of cementation solution concentration (0.2 M, 0.5 M and 1.0 M) and cementation method (adjusting pH or not) on soil structural strength and MICP modification quality are investigated. The results show that the one-phase MICP technique can significantly improve the structural strength of clay and has good applicability. Within the range of cementation solution concentration not higher than 1.0M, the cementing effect of clay increases with the increase of cementation solution concentration. Comparatively the one-phase cementation method of adjusting pH can improve the depth and homogeneity of soil cementation proactively. One-phase MICP technique is simple and easy to implement, can save costs, and has potential application value on strengthening the surface of clayey soil.