Residual shear strength of guar gum amended granular bentonite under chemo-mechanical loading

¹ Department of Civil Engineering, Indian Institute of Technology Guwahati, Guwahati, India
² Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, India

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Bentonite clay is widely used as a liner material at the base and along the side slopes of municipal solid waste (MSW) landfills due to its low hydraulic conductivity and high swelling capacity. However, the granular form of bentonite (GB) often fails to seal effectively in the presence of leachate chemicals, compromising its barrier performance. Several recent studies have explored the use of biopolymers to enhance the physicochemical and mechanical behavior of granular bentonite. Among these, guar gum has emerged as a promising stabilizer because it forms a thick, viscous gel in aqueous and saline environments, improving particle bonding. Understanding the residual shear strength behavior of GB and guar gum-amended GB is crucial, as it defines the minimum shear resistance mobilized after large deformations. This study investigates the influence of guar gum inclusion on the residual and peak shear strength of granular bentonite clay using a torsional ring shear test under drained conditions, following ASTM D6467. Samples were compacted to a target density and tested under normal stresses of 300, 500, and 700 kPa, with shearing applied at a constant rate until steady-state conditions were achieved. The shear stress-displacement response was analyzed to determine the residual shear strength at the plateau region. Results revealed a significant improvement in residual shear strength with guar gum addition, attributed to enhanced interparticle bonding and matrix cohesion.