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

Nitin Tiwari,Meghna Sharma,Neelima Satyam

doi:10.1038/s41598-021-89687-2

Abstract

This study explored the effect of indigenous bacteria present in the soil to stabilized swelling behavior and improving the mechanical property of expansive soil. The objective of the research is to investigate the effectiveness of the biostimulation microbial induced calcite precipitation (MICP) for controlling the swelling-shrinkage behavior and improving shear strength of expansive soil. An attempt was made to develop an effective procedure to culture the indigenous bacteria for treating clays with varying plasticity and improve their engineering behavior. The detailed procedure has been investigated to effectively apply the MICP technique in clay soil, considering its low permeable nature. The applicability of biostimulation to clayey soils in minimizing their swelling potential and improving the strength is assessed. Both macroscale and microscale studies were conducted on untreated and biostimulated soils to observe changes in plasticity, strength, swelling, mineralogical, chemical characteristics. The present method has shown an effective alternative to improve the road pavement subgrade without affecting the eco-system of natural soil. The method investigated the effective way of providing the enrichment and cementation solution in clayey soil, which is the major concern in current literature. The study confirms that the calcite content has been increased with biostimulated MICP treatment up to 205% in the treated specimens and which future increased the unconfined compressive strength and split tensile strength. A reduction in the swelling pressure and swell strain is also observed. The results show that a cost-effect and eco-friendly method can be deployed for stabilizing the road pavement subgrades. The statistical assessment using multivariate analysis and hierarchical clustering dendrogram has been carried out to investigate the effect of the MICP treatment protocol on different soil and engineering parameters.

Highlights

microbial induced calcite precipitation (MICP) is the multidisciplinary, well-recognized, potentially sound, environmentally friendly, and sustainable method for strength enhancement of soil
The results reported are taken from an average of three identical specimens with similar experimental conditions
The cementation mineral formed in the soil improves the adhesion of soil particles and increases the cohesion, which reduces the liquid limit of the expansive soil

Summary

Introduction

MICP is the multidisciplinary, well-recognized, potentially sound, environmentally friendly, and sustainable method for strength enhancement of soil. Effective use of MICP technique from lab scale to field scale has been demonstrated to improve the engineering characteristics of sand due to ease in treatment m ethod[38,39,40,41]. Gomez et al.[39] explore the potential of native bacteria to investigate the biocementation effect on sand. Past studies (Burbank et al 2011; Burbank et al 2013; Gomez et al 2018; Tsesarsky et al 2018) showed that biostimulation is a superior alternative because the bacteria are already accustomed to the soil environment compared with augmented bacteria. The method is still underexplored for strength improvement of clayey soils. A few studies have been carried out to investigate the biostimulation and mechanical stabilization of clays

Objectives

Methods

Results

Conclusion