Abstract: Widely distributed in south China, granite residual soil often brings about landslide and other geological disasters as it disintegrates obviously when confronted with water. In this research, the engineering properties and engineering techniques of cemented granite residual soil were improved by adding bacillus pasteurii using microbial induced calcite precipitation (MICP) technology. The influence of MICP technology on the mechanical properties of cemented-soil such as strength and stress-strain relationship was examined when factors such as cement mixing ratio, calcium ion concentration and calcium source were taken as variables. Unconfined compressive strength (UCS) test was conducted to analyze the mechanical strength of cemented-soil strengthened by MICP, and conclusions were obtained as follows: 1) MICP technology significantly enhanced the engineering properties inclusive of strength, stiffness and toughness of cemented granite residual soil; 2) compared with the control group, the maximum growth rate of strength in the test group amounted to 87.5%, and the most economical cement mixing ratio was 15%; 3) calcium chloride and calcium acetate could both improve the toughness of test specimens, and the effect of calcium acetate was superior; compared with the control group, the maximum growth rate of the toughness of the test group reached 69.67% when the calcium ion concentration was 0.5 mol/L.

Key words: cement-soil, bacillus pasteurii, microbial induced calcite precipitation (MICP), mechanical properties, unconfined compressive strength