Micro-mechanical performance evaluation of expansive soil biotreated with indigenous bacteria using MICP method.

Area of Science:

• Geotechnical Engineering
• Environmental Engineering
• Microbiology

Background:

• Expansive soils pose significant challenges in civil engineering due to their swelling and shrinkage behavior.
• Current stabilization methods often involve chemical additives with potential environmental drawbacks.
• Microbial Induced Calcite Precipitation (MICP) presents a promising bio-based approach for soil improvement.

Purpose of the Study:

• To investigate the efficacy of indigenous bacteria and MICP for stabilizing expansive soil.
• To assess the impact of MICP on swelling-shrinkage behavior and shear strength of clayey soils.
• To develop and optimize a procedure for applying MICP in low-permeability clay soils.

Main Methods:

• Isolation and culturing of indigenous soil bacteria.
• Application of MICP technique to expansive soil samples with varying plasticity.
• Macroscale and microscale analysis including plasticity, strength, swelling, and mineralogical tests.
• Statistical assessment using multivariate analysis and hierarchical clustering.

Main Results:

• MICP treatment significantly increased calcite content by up to 205%.
• Substantial improvements in unconfined compressive strength and split tensile strength were observed.
• A notable reduction in swelling pressure and swell strain was achieved.
• The method proved effective in improving engineering properties without disrupting the natural soil ecosystem.

Conclusions:

• Biostimulation using indigenous bacteria and MICP is a cost-effective and eco-friendly method for stabilizing expansive soils.
• This technique offers a sustainable alternative for improving road pavement subgrades.
• The optimized MICP procedure is suitable for clayey soils, addressing a key challenge in current literature.