Study on soil solidification based on microbiological precipitation of CaCO3

The soil solidifying technology started booming from the 1940s and formed an integrated cross-discipline. This paper aimed to study the effect and mechanism of soil solidification by microorganisms. Soil specimens treated by different methods were designed. Then the compressive strengths of these specimens on day 7 were tested and the situ bacteria culturing technique in soil was investigated. Finally the mechanism of soil solidification by microorganisms was explored according to the decomposition rate of substrate, pH value and the SEM and XRD analysis. Experimental results showed that the soil could be solidified by filling enhancement and precipitation of microorganisms. The compressive strength increased with bacteria A but decreased with substrate B, and soil specimen got a higher strength with bacteria situ cultured. The suitable pH value for bacteria A was 8-9, and the delay of lime addition could make substrate decomposition more completely, lower the influence by the existence of substrate, and improve the strength. In XRD and SEM images, precipitation of CaCO3 could be speculated.