Evaluation of Porosity in Biogrouted Sand Using Microfocus X-Ray Ct

Abstract

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.

Effects of Cationic Polypeptide on CaCO3Crystallization and Sand Solidification by Microbial-Induced Carbonate Precipitation

“…Ureolytic bacteria Pararhodobacter sp. isolated from beach sand in Sumuide, Nago, Okinawa, Japan, was used in this study. , Bacterial cells were precultured in Zobell 2216E medium (polypeptone (Nihon Seiyaku Co., Ltd., Tokyo, Japan) 5.0 g/L, yeast extract (BD Biosciences Advanced Bioprocessing, Miami, FL, USA) 1.0 g/L, and FePO 4 (Junsei Chemical Co., Ltd., Tokyo, Japan) 0.1 g/L in artificial seawater, pH 7.6–7.8; 5 mL) by shaking at 30 °C and 160 rpm for 24 h. The preculture (1 mL) was inoculated into fresh Zobell 2216E medium (100 mL). The mixture was kept in the shaking incubator under the same conditions as those used for preculturing for 48 h. The cells were collected by centrifugation of the bacterial culture.…”

Microbial Induced Slope Surface Stabilization Using Industrial-Grade Chemicals: A Preliminary Laboratory Study

“…Similar to the previous studies [5,7,12,13], needle penetrometer (SH-70, Maruto Testing Machine Company, Tokyo, Japan) was used to estimate the UCS of the treated specimens. Regression relationship given in Eq.…”

Enhancement of Microbially Induced Carbonate Precipitation Using Organic Biopolymer

“…was isolated from the beach sand in Sumuide, Nago, Okinawa, Japan [15] and cultivated using Zobell2216E medium ( Polypeptone 5.0 g/L, Yeast extract 1.0 g/L and FePO4 0.1 g/L, prepared by using artificial sea water, pH 7.6-7.8). Bacteria cells were precultured using 5ml of Zobell2216E medium and kept in the shaking incubator at 30 ο C and speed of 160rpm for 24 hours.…”