Cementation of sand soil by microbially induced calcite precipitation at various degrees of saturation

Abstract

A newly emerging microbiological soil stabilization method, known as microbially induced calcite precipitation (MICP), has been tested for geotechnical engineering applications. MICP is a promising technique that utilizes the metabolic pathways of bacteria to form calcite precipitation throughout the soil matrix, leading to an increase in soil strength and stiffness. This paper investigates the geotechnical properties of sand bio-cemented under different degrees of saturation. A series of laboratory experiments was conducted, including sieve analysis, permeability, unconfined compressive strength, consolidated undrained triaxial, and durability tests. The results indicate that higher soil strength can be obtained at similar CaCO3 content when the treatment is performed under a low degree of saturation. The experimental results are further explained with a mathematical model, which shows that the crystallization efficiency, i.e., actual volume of crystals forming at the contact point where they contribute the most to strength, can be calculated from the degree of saturation and grain size. Fine sand samples exhibited higher cohesion, but lower friction angle than coarse sand samples with similar CaCO3 content. The results also confirm the potential of MICP as a viable alternative technique for soil improvement in many geotechnical engineering applications, including liquefiable sand deposits, slope stabilization, and subgrade reinforcement. The freeze–thaw and acid rain resistance of MICP-treated sand has also been tested.

Microbially Induced Sand Cementation Method Using <i>Pararhodobacter</i> sp. Strain SO1, Inspired by Beachrock Formation Mechanism

“…Moreover, the CaCO 3 precipitation from n ¹ 1 to n days (X pn (g/g sand)) was calculated using eq. (9).…”

“…Aqua marina, 7) NO-A10 strain isolated from the soil in Niwase, Okayama, 8) Bacillus sphaericus 9) and Bacillus sp. strain VS1 10) have been shown to induce sand cementation using the same mechanism.…”

Upscaling Effects of Soil Improvement by Microbially Induced Calcite Precipitation by Surface Percolation

“…In comparison to the saturated flow MICP application, the unsaturated zone created in the surface percolation MICP treatment provided environmental conditions more conducive to the formation of effective crystals (Cheng et al 2013). …”

Improving the Strength of Sandy Soils via Ureolytic CaCO&lt;sub&gt;3&lt;/sub&gt; Solidification by &lt;i&gt;Sporosarcina ureae&lt;/i&gt;

“…This may guide future research on ureolytic MICP with B. subtilis, particularly where cementation media do not contain nutrient rich additives such as yeast extract. This has been the case in some literature solutions for inducing ureolytic MICP (Cheng et al, 2013;van Paassen et al, 2010). In this study B. subtilis was included in sand solidification as a non-ureolytic strain control as cementation media contained yeast extract, intended for maximum biomass support and CaCO 3 production rates (van Paassen et 560 al., 2010).…”

“…The group of Cheng and Cord Ruwisch (2013) has modeled a novel idea that plentiful cell nucleation could provide best soil strengths. Although the current study's findings suggest higher cell number, having theoretically 620 more nucleation sites, did not factor into meaningful strength increases as S. ureae gave rise to non-significantly (p Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-517 Manuscript under review for journal Biogeosciences Discussion started: 7 February 2018 c Author(s) 2018.…”