Document Type : ORIGINAL RESEARCH ARTICLE

Authors

1 Laboratoire de Physique et de Chimie de l’Environnement, Université Joseph KI-Zerbo, BP 7021 Ouagadougou 03, Burkina Faso

2 Ecole Supérieure d’Ingénierie, Université de Fada N’Gourma, BP 46 Fada N’Gourma, Burkina Faso

3 Building Architecture and Town Planning Department, Université Libre de Bruxelles, Avenue F.D. Roosevelt 50, CP 194/2, 1050 Bruxelles, Belgique

4 Ecole Polytechnique de Ouagadougou, 08 BP 143 Ouagadougou 08, Burkina Faso

5 UMR 6294 CNRS, Laboratoire Ondes et Milieux Complexes, Normandie Université, Unihavre, 53 rue Prony, 76600 Le Havre, France

10.22034/GJESM.2022.02.01

Abstract

BACKGROUND AND OBJECTIVES
In landfills, containment is provided by natural or artificial clayey materials known for their low permeability and for their pollutant retention capacity. However, the properties of these media are modified by leachates, whose migration they are supposed to limit. This study aims to reconsider the criteria for choosing suitable materials to make a bottom liner through both their long term hydraulic and mechanical performances.
METHODS
Two fine materials sampled in Burkina Faso (West Africa) have been characterized in order to compare their hydro-mechanical behavior in the presence of household waste leachates. The first material is classified as an inorganic clay of low to medium plasticity according to Casagrande plasticity diagram, it is mainly kaolinitic with some traces amounts of smectites. The second one is classified clayey sand of low to medium plasticity, the predominant mineral clay being kaolinite. Hydro-mechanical tests were performed on both sampled materials to judge the sealing properties of these materials, as well as the characteristics of deformation and rupture which have an important effect to ensure the durability of a bottom liner. All these tests were performed first with distilled water then with leachates as interstitial fluids in order to understand the modification of the hydro-mechanical properties of the clayey soils.
FINDINGS
Leachate contamination always alters hydraulic properties of the materials. However, between the two soils, the most clayey and the most impervious (soils from Nouna) undergo the deeper weathering. Indeed, hydraulic conductivity of these soils in contact with a synthetic leachate increases from 1.71x10-10 to 1.51x10-9 m/s. In contrast to soils from Boudry, these soils also undergo very significant settlements over the long term with compressibility indexes varying from 0.164 to 0.225. For both soils, the shear strength increases showing that, from this point view, the leachate work in the sense of of the bottom liner stability. For soils from Nouna, the effective cohesion increases from 3 to 21 kPa with a slight decrease of friction angle; for soils from Boudry a slight increase of cohesion is noticed while friction angle increases from 34 to 37°.
CONCLUSION
This comparative study is of practical use to environmental geotechnics professionals because it shows that the choice in designing a bottom liner must be a compromise between long term hydraulic and mechanical behaviors of soils. It is also important to know the nature of the flows to contain in order to ensure the durability of the structure.

Graphical Abstract

Hydro-mechanical behavior of two clayey soils in presence of household waste leachates

Highlights

  • Hydro-mechanical tests show that if leachates are still harmful to the sealing of a bottom liner, it is not necessarily the case for its mechanical behavior;
  • The criteria of choosing clays constituting bottom liners should be the result of a compromise between hydraulic and mechanical performance taking into account the composition of the leachate;
  • Designing a bottom liner is a complex process that requires extensive investigations.

Keywords

Main Subjects

Open Access

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