Search for: All records

Biocementation is a biomediated ground improvement method that can improve the engineering behavior of granular soils through the precipitation of calcium carbonate minerals. Although cemented bonds and particle coatings generated from biocementation can enable large increases in soil initial shear stiffness, peak shear strength, and liquefaction resistance; emerging strategies such as soil desaturation have shown the ability of alternative mechanisms to enable large improvements in liquefaction behaviors. This article highlights outcomes from recent experiments which have investigated the potential of novel treatment processes to enable the generation and entrapment of gases within biocementation. We hypothesize that these entrapped gases may provide a secondary mechanism to improve soil undrained shearing behaviors by enabling the release of gases following cemented bond deterioration and related increases in pore fluid compressibility. Our study employs a series of batch experiments to identify new methods to both generate and entrap gasses within an organic polymer layer applied intermittently between biocementation treatments. Biocemented composites resulting from this work may enable large improvements in the environmental and financial efficacy of biocementation and the resilience of treated soils to extreme loading events. 

Microbially induced calcite precipitation (MICP) or biocementation is a bio-mediated process that can be used to improve the engineering properties of granular soils through calcium carbonate precipitation. Although most commonly this process is accomplished using microbial urea hydrolysis, other microbial metabolic pathways can be used to enable biocementation with the potential to eliminate ammonium byproducts. Microbial organic acid oxidation presents one alternative pathway by which increases in solution carbonate species can be generated to enable calcium carbonate mineral formation. While past studies have considered the potential of this microbial pathway to enable biocementation for surficial applications, to date few studies have examined the feasibility of this pathway for subsurface applications wherein dissolved oxygen is more limited. In this study, 18 small-scale batch experiments were performed to investigate the ability of microbial organic acid oxidation to enable biocementation soil improvement. Experiments investigated the feasibility of using both acetate and citrate oxidation to mediate biocementation as well as the effect of differences in techniques used to supply dissolved oxygen, the effect of supplied growth factors, bicarbonate salt additions, and solution sampling frequency. Results suggest that aerobic oxidation of acetate and citrate can be used to enable calcium carbonate biocementation, though ensuring dissolved oxygen availability appears to be critical towards enabling this process.