There is a ground improvement technology that utilizes carbonate calcium precipitated from carbon dioxide generated by microbial metabolism and calcium sources in pore of soil. It is known that the mechanical properties of improved grounds correlate with the amount of calcium carbonate precipitation. However, the relationship between mechanical properties and permeability has yet to be clarified. In this study, we estimated the apparent coefficient of permeability from the injection speed of nutrient and performed triaxial compression tests (CD condition) on specimens, aiming to assess the relationship between the mechanical properties and permeability of Toyoura sand, which is compacted by microbial metabolism. Through the study, we confirmed that the Young's modulus and peak strength tend to increase as a function of the amount of precipitated calcium carbonate, with little change in the coefficient of permeability.
Under current circumstances, where the efficient maintenance of civil engineering structures is at issue, ground improvement technologies that can be applied to the maintenance and reinforcement of existing structures are required. The ground improvement technology that utilizes carbonate calcium precipitated from carbon dioxide generated by microbial metabolism and calcium sources in pore of soil is expected to be a technology applicable to ground directly under existing structures, because the viscosity of the injected grout is low. It is known that the mechanical properties of grounds improved by this method correlate with the amount of calcium carbonate precipitation (Inagaki et al. 2011), but the relationship between mechanical properties and permeability has yet to be clarified. In this study, we used Sporosarcina Pasteurii (ATCC11859) as the microorganism and conducted tests utilizing the reactions indicated below, which are caused due to ureolysis by the microorganism, aiming to assess the relation between the mechanical properties and permeability of Toyoura sand, which is compacted by microbial metabolism.
