Influence of Key Environmental Conditions on Microbially Induced Cementation for Soil Stabilization

TLDR

Microbially induced calcite precipitation (MICP) is a sustainable biological ground‑improvement technique that can alter and improve soil mechanical and geotechnical properties. The study investigates how urease concentration, temperature, rainwater flushing, oil contamination, and freeze–thaw cycling affect ureolytic MICP in soils. Laboratory column experiments were conducted to assess the influence of these parameters on MICP‑mediated soils. The experiments showed that low urease activity and ambient temperature produce effective crystal precipitation that markedly increases UCS, while rainwater flushing impairs biocementation, two‑phase injection fails on oil‑contaminated soils but premixed bioflocs enhance UCS and stiffness, and MICP‑treated soils exhibit strong freeze–thaw durability due to crystal bridging.

Abstract

Microbially induced calcite precipitation (MICP) is a sustainable biological ground improvement technique that is capable of altering and improving soil mechanical and geotechnical engineering properties. In this paper, laboratory column studies were used to examine the effects of some key environmental parameters on ureolytic MICP mediated soils, including the impact of urease concentrations, temperature, rainwater flushing, oil contamination, and freeze–thaw cycling. The results indicate that an effective crystal precipitation pattern can be obtained at low urease activity and ambient temperature, resulting in high improvement in soil unconfined compressive strength (UCS). The microstructural images of such crystals showed agglomerated large clusters filling the gaps between the soil grains, leading to effective crystals formation. The rainwater flushing was detrimental to the biocementation process. The results also indicate that traditional MICP treatment by the two-phase injection method did not succeed in treatment of oil-contaminated soils, and the proposed premixing of bioflocs with soil can significantly improve UCS and stiffness of oil-contaminated soils. Finally, MICP-treated soils showed a high durability to the freeze–thaw erosion, which is attributed to the interparticle contact points and bridging of crystals formation.