Effect of wetting and drying cycles on the durability of bio-cemented soil of expressway slope

Abstract

Cyclic wet-dry is one of the influential weathering agents which can rapidly alter the mechanical properties of soils, limiting their durability and consistent performance. This study investigates the effect of wet-dry cycles on the mechanical behaviour of bio-cemented soil. Microbial-induced carbonate precipitation-based bio-cementation is an innovative soil improvement method, which is gaining increasing attention as a potential alternative for stabilizing slope surface. As the treated surfaces are exposed to repeated rainfalls and draughts, durability analysis is essential; cyclic wet-dry tests were therefore performed as a credible indicator of durability. The soil obtained from the Hokkaido expressway slope was treated at laboratory to varying cementation levels (% CaCO3) and subjected to 50 subsequent wet-dry cycles. Physical and mechanical changes were monitored using mass loss, shear wave velocities and needle penetration tests during wet-dry cycles. The results showed that the wet-dry cycles deteriorated the physical and mechanical at two stages. The mass and S-wave velocity of specimens significantly dropped after first few cycles and then tended to reach equilibrium. The second stage of notable deterioration was observed between 30 and 50 wet-dry cycles. It is suggested that the erosion of weak and powdery deposition of CaCO3 causes the degradation at the early stage, whereas the degradation in the late stage was attributed to the microstructural deformations of intact carbonate bonds. It was also found that the increase in cementation level decreases the deterioration of bio-cemented soil under wet-dry cycles.

Effect of Scallop Powder Addition on MICP Treatment of Amorphous Peat

“…The quantification of precipitated CaCO 3 is often an important part in MICP-related soil improvement studies. Most of the researchers evaluated the amount of CaCO 3 by the acid-washing method; two approaches are widespread: (i) measuring the difference between dry mass of soil before and after dissolving CaCO 3 (Neupane et al, 2015) and (ii) measuring the pressure of CO 2 gas released during the reaction of CaCO 3 with HCl (Fukue et al, 2011;Gowthaman et al, 2021a). However, the acid-washing methods are less applicable to the soils that already consist of carbonates in their mineralogy.…”

Durability Improvement of Biocemented Sand by Fiber-Reinforced MICP for Coastal Erosion Protection

“…Micrococcus yunnanensis (hereafter referred to as G1) was isolated from the coastal regions of Porto Rafti, Greece, and was employed in this investigation [ 22 ]. The key characteristics of this bacterium are elevated urease activity with salt-tolerant prominence, the ability to survive for long periods of time at different temperatures and pH levels, and the capacity to thrive in nutrient-deficient situations [ 23 ].…”

Feasibility of bacterial-enzyme induced carbonate precipitation technology for stabilizing fine-grained slope soils

“…Few researchers evaluated the feasibility of implementing the MICP treatment for the mitigation of coastal sand dunes (Liu et al, 2020;Imran et al, 2022). Moreover, the longevity of MICP treated slope surface under possible environmental deteriorations such as cyclic freeze-thaw actions (Gowthaman et al, 2020), cyclic wet-dry actions Gowthaman et al, 2022) and acid-rain induced losses (Gowthaman et al, 2021b) was also comprehensively studied in the recent past.…”