Experimental Study on Microbial Solidification of Gravel-Containing Silty Clay under Different Calcium Sources

Abstract

Crushed silty clay is widely distributed in engineering foundations. Because of its local hardness and uneven soil distribution, it is not a good foundation material. Based on microbial solidification technology, microbial solidification tests of silty clay containing crushed stone were carried out by selecting cementing liquids with different calcium sources to study the effect of the calcium source on the solidification effect. With Pasteurella as the main solidified bacterial solution, calcium chloride, calcium acetate, and calcium gluconate were mixed into urea to prepare cementing solutions with different calcium sources at concentrations of 0.6, 1.0, and 1.4 mol/L. Microbial solidification tests were carried out under different calcium source concentrations, the calcium carbonate formation of the samples after solidification was examined, and unconfined compressive strength and triaxial tests were conducted. When calcium chloride and calcium acetate were used to solidify the clay, the solidification strength gradually decreased with the increase in the concentration, while the solidification strength of calcium gluconate was the highest at 1.0 mol/L. When calcium chloride with a concentration of 0.6 mol/L was used as the calcium source, the curing effect was the best. The internal friction angle and cohesion of the triaxial test were increased by 35.19% and 99.1%, respectively, and the unconfined compressive strength was increased by 37.94%. The yield ratio was 3.76%. The concentration of 1.0 mol/L was the best concentration of calcium gluconate as the calcium source, and the reinforcement effect was slightly less than that of 0.6 mol/L calcium chloride.