Improving the stability of slopes of earth drainage ditches by microbially induced calcium carbonate precipitation

Abstract

【Objective】 Microbially induced calcium carbonate precipitation (MICP) is an eco-friendly and innovative technique for improving soil stability. This paper investigates the potential of MICP for improving the stability of slopes of earth drainage ditches. 【Method】 Bacillus pasteurii with OD600=0.97 and consolidation solution with concentration of 1 mol/L (CO(NH2)2∶ CaCl2 = 1∶1) were used in the study. The solid - bacteria ratio was 5∶3, and a urease inhibitor at concentration of 15% was added to the consolidation solution. The experiment was conducted in boxes filled with soil. We sprayed the soil surface with the consolidation solution and the bacterial liquid alternatively for the infiltration to reach the depth of 5 cm (C1), 10 cm (C2) and 15 cm (C3), respectively. The control was to spray water over the soil surface. The mechanical properties of the soils were measured using direct shear tests when soils were air-dried, saturated, and naturally dried, respectively. 【Result】 The shear strength of the soils treated by MICP were all increased; the decrease of internal friction angle of CK, C1, C2, and C3 after saturation treatment were 46.67%, 39.73%, 28.98%, and 27.85%, and the decrease of cohesion were 76.37%, 62.83%, 39.09%, and 51.62%, the soil slope of CK was in the understability, and the slopes of C1, C2, and C3 met the safety requirements C1, C2 and C3 slopes meet the safety requirements, cohesion is the main factor affecting the stability of slopes. 【Conclusion】 Our findings suggest the optimal consolidation depth was 10 cm and demonstrate the efficacy of MICP for reinforcing the slopes of earth drainage ditches.

Keywords

• micp consolidation
• soil slope
• consolidation depth
• slope stability