A Study on Erosion Resistance for Microbially Induced Calcite Treated Beach Sand

Microbial induced calcite precipitation (MICP) was used to treat several sandboxes filled with naturally occurring beach sand collected from Atlantic Beach, FL. Unlike most previous MICP studies, a surface-spray technique was used to treat these sandboxes where relatively high-concentration bacteria solution and high concentration calcium chloride/urea solutions were applied directly to the boxes’ surfaces. Several different treatment combinations were tested whereby bacterial optical density, bacteria/urea/calcium chloride volume relative to void space, and bacteria/urea/calcium chloride ratio were manipulated. Treated sandboxes were tested for erodibility using a pocket erodometer and for calcification using a wash method. In addition, sandboxes were dissected after calcification/erosion testing to examine calcification depth. Results showed that higher optical densities, higher bacteria quantities relative to void volume, and higher bacteria quantities relative to urea led to higher calcification. By maximizing these three variables, calcium carbonate precipitation of approximately 6% was achieved after one treatment. After five treatments, calcification approached 15%. However, even with significant calcification like this, erodibility improvements were relatively moderate. In addition, correlations were developed that appeared to show indirect relationships between erodibility and calcite content; and direct relationships between calcification depth and calcite content. Overall, results seem to present a roadmap for upscaling microbial treatment for erosion control – generally, “more is better” and adding as much bacteria, urea, and calcium carbonate as possible to soil appears to produce the most erosion resistance

ARTEFACTS OF CITIZENSHIP: EVOLUTION OF THE SINGAPORE IDENTITY CARD FROM 1948-1966

Bachelor'sBACHELOR OF ARTS (HONOURS

Evaluation of Factors Affecting Erodibility Improvement for MICP-Treated Beach Sand

Microbially induced calcite precipitation (MICP) was used to treat several sandboxes filled with naturally occurring beach sand collected from Atlantic Beach, Florida. A surface-spray/percolation technique was used to treat these sandboxes where a relatively high-concentration bacteria solution and high-concentration calcium chloride/urea solutions were applied directly to the boxes\u27 surfaces. Several different treatment combinations were tested whereby bacterial optical density, bacteria/urea/calcium chloride volume relative to pore volume, and bacteria/urea/calcium chloride ratio were manipulated. Treated sandboxes were tested for erodibility using a pocket erodometer. In addition, sandboxes were dissected after erosion testing to examine crust depth. Results showed that higher optical densities, higher bacteria quantities relative to void volume, and higher bacteria quantities relative to urea led to lower erodibility and greater crust depth. When MICP constituent quantities were maximized to give the best erosion/crust-depth results, erodibility improvements began to approach what may be considered adequate erosive resistance. Further investigation is required to better classify this behavior more quantitatively