Desiccation crack and volumetric shrinkage of magnesium oxide-treated compacted soil liner in landfill

Abstract

This study investigates the failure mechanisms of compacted clay barriers used to prevent the leakage of hazardous fluids from landfill sites, bentonite clay (BC) alone is prone to significant desiccation fractures following wetting and drying cycles, undermining its effectiveness as a barrier material. This research explores the root causes of these failures by analyzing the interaction between Bentonite and Magnesium Oxide (B-M) mixtures in improving the liner's performance. Specifically, the study examines how the addition of 15% Magnesium Oxide (MgO) to bentonite-modified soil impacts geotechnical properties such as plasticity index, liquid limit, optimum moisture content, permeability, swelling, swelling pressure, volumetric shrinkage, and desiccation cracking. In addition, the objective of this paper was to shed light on the mechanisms that were responsible for the change in the hydro-mechanical behavior of the clay material that had been treated with MgO by conducting scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) testing. The results indicate that MgO treatment significantly reduces the free swell, hydraulic conductivity, plasticity index, liquid limit, optimum moisture content, volumetric shrinkage and desiccation cracking, thus enhancing the material's stability and integrity under environmental stresses. Based on these findings, the study recommends using MgO-treated expansive soils as a more reliable alternative to traditional bentonite liners, offering better long-term performance and reduced risk of failure in landfill applications.