改良微生物诱导碳酸钙沉淀技术加固粉性土力学性能

微生物诱导碳酸钙沉淀技术(microbially induced calcite precipitation,MICP),是近年来在国内兴起的一项多学科交叉的技术,工程技术人员将它引入到土木工程中,使得土体各项性能得以改良;黄河中下游的粉性土水稳定性差,毛细水作用大,干燥时强度高但潮湿时强度显著下降,利用MICP技术加固粉性土值得研究.以粉性土为研究对象,首先研究了不同糯米浆浓度下土样的力学性能,以最优糯米浆浓度作为改良材料对MICP技术进行改良;其次控制胶菌质量比为2∶1,研究了不同胶结液浓度下MICP技术的产碳酸钙量以及Ca2+转化率,得出MICP技术的最佳配比,结合最优糯米浆浓度形成改良MICP技术;最后研究了素土、MICP加固土、改良MICP加固土土样养护7d后的力学性能.研究表明:土样最优糯米浆浓度为3％,此时土体无侧限抗压强度与内摩擦角达到最大;MICP技术最佳配比为2:1胶菌质量比、0.5 mol/L胶结液浓度,此时产碳酸钙量最多且Ca2+转化率在80％以上,添加3％糯米浆浓度的改良MICP技术Ca2+转化率在90％以上,比MICP技术高10％;通过土的直接快剪试验和无侧限抗压强度试验,MICP加固土的黏聚力提高了约30％,内摩擦角变化不大,改良MICP加固土的黏聚力提高了约50％,内摩擦角提高了约17％.

Study on mechanical properties of soil strengthened by improved MICP Technology

In recent years, MICP technology is a multi-disciplinary interdisciplinary technology rising in China, which is introduced into civil engineering by engineers and technicians, so that the mechanical properties of soil can be strengthened. In this paper, the core technology is MICP, the glutinous rice slurry is used as the improved material to improve the MICP technology, and the plain soil is used as the reference group to compare and analyze the strengthening effect of MICP technology and improved MICP technology on the mechanical properties of soil. The results showed that the unconfined compressive strength and internal friction angle of the samples reached the maximum at the concentration of 3% glutinous rice slurry, and the concentration of 3% glutinous rice slurry was used as the improved material of the improved MICP technology; the OD value and conductivity of the improved bacterial solution were higher than those of the common bacterial solution after 48 hours of culture; When the quality ratio of glue bacteria is 2:1 and the concentration of cement solution is 0.5m, the amount of calcium carbonate produced by MICP technology is the most and the conversion rate of Ca2+ is more than 80%. The conversion rate of Ca2+ of improved MICP technology is more than 90%, which is 10% higher than that of MICP technology. Based on the results of direct shear test and unconfined compressive strength test of soil under the optimum ratio, compared with the plain soil sample, the cohesion of soil under the MICP technology is increased by about 30%, the internal friction angle changes little, the cohesion of soil under the improved MICP technology is increased by about 50%, and the internal friction angle is increased by about 17%.