Evaluation of the Ability to Control Biological Precipitation to Improve Sandy Soils

Biological soil improvement is a novel improvement technique in which chemical and biological processes leads to an improvement of physical and mechanical soil properties. Since this method is environmentally compatible and applicable to various soil types using different materials, it has turned into an efficient soil improvement method in numerous ground treatment projects. Microbiologically induced calcite precipitation (MICP) is one of the most well-known biological soil improvements method in which after the injecting bacterial suspension, reaction solution (cementation solution) into soil particles, calcium carbonate sediment is formed, and thereby soil properties are improved. In this paper, the ability to manage time and location when calcium carbonate sediments are biologically formed was investigated in sandy soil. The electrical conductivity method, unconfined compressive strength test and X-ray diffraction examinations were sequentially used to determine urease bacterial activity, measure the amount of the increased strength of treated soil and determine crystal type. The results showed good ability of this method to control time and location of biological precipitating. Furthermore, unconfined compressive strength of Caspian Sea coast sandy soil was increased up to 400 kPa. The ability to manage time and location of biological precipitating indicates this method can be potentially used in different application such as mitigation of liquefaction, soil erosion control, immobilizing of pollutions in soil and other soil improvement projects.