No abstract

One of the promising soil improvement techniques that have recently gained increased attention in Geotechnical and Civil Engineering is microbial induced carbonate precipitation (MICP). The MICP is mediated by ureolytic bacteria through a chain of biochemical reactions which lead to the formation of calcium carbonate cement in soil matrix and persuades the substantial bonds between the soil particles. The study presented herein focuses on surficial stabilization of slope soil (Hokkaido, Japan) by mediating industrial-grade chemicals through two different scales of preliminary laboratory investigations: small-scale columns and bench-scale slopes. Locally isolated Psychrobacillus sp. was cultivated in both industrial-grade media (beer yeast) and laboratory-grade media (NH4-YE: tris-buffer, ammonium sulfate and yeast extract), and the urease activities were compared. The results showed that the cultivation of bacteria in beer yeast resulted in higher urease activity (0.9 U/mL) compared to that in conventional laboratory media (0.4 U/mL). Also, UCS of the specimen treated using industrial-grade chemicals (urea fertilizer, beer yeast and snow melting reagent) was about two times higher than the specimen treated using conventional laboratory-grade chemicals (urea, CaCl2 and nutrient broth). The benchtop-scale test revealed that the highest surface strength (UCS of 1.02 MPa) was achieved while treating the soil by 0.5 M cementation solution at 30ºC. Sets of colorimeter measurements were undertaken on treated slope models to compare precipitation profile at different locations. These findings suggest that industrial-grade chemicals can contribute as potential candidates in MICP applications from the perspective of cost reduction.

Biogrouting is a method employed for ground improvement based on microbially induced calcium carbonate precipitation. It is commonly believed that biogrout has environmental and economic benefits. However, there remains the need to clearly understand the internal structure of biogrouted soil. In this study, we use microfocus X-ray computed tomography (CT) to evaluate the porosity in biogrouted sand. X-ray CT is useful as a non-distractive inspection tool. First, we prepare small specimens using coral sand at different dilution rates of culture solution. After carrying out a solidification test for 2 wks., we perform an unconfined compressive strength (UCS) test and measure the porosity of the specimens. Our aim is to investigate the influence of the dilution rate on the UCS and the porosity of sand specimens. The results show that a lower dilution rate resulted in a lower sand-specimen porosity and an increase in the UCS. We investigate the precipitation that fills a void. Then, we investigate the relationship between UCS and the ratio of porosity. There was a negative correlation between UCS and porosity, which closely agrees with previous research. We confirm the validity of the result, and we determine the UCS from the porosity.

Pharmacokinetic relationships have been developed to characterize a one-compartment drug disposition model which includes perfusion limited elimination processes. The derived expressions have been applied to plasma concentration and urinary excretion data obtained after rapid intravenous administration of 4-aminoantipyrine to rabbits. The mathematical relationships and experimental data demonstrate that dose dependent disposition of 4-aminoantipyrine is a result of reduced renal and hepatic blood flow caused by the drug itself.