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<p>This study evaluates the applicability of the marl-bentonite (MB%) mixture as a low-permeability, durable landfill liner material exposed to mature leachate. Natural marl collected from the Ghardaïa region of Algeria was mixed with 3% to 10% bentonite and characterized using a series of tests, including Atterberg limits, oedometer swell tests, permeability tests, unconfined compression tests, and direct shear tests. Chemical interactions with mature leachate were studied using immersion protocols, with measurements of pH, electrical conductivity (EC), and carbonate and quartz contents. Exposure to leachate resulted in changes in the textural and hydraulic properties, leading to increased ionic strength, decreased carbonate content, increased quartz content, decreased pH, increased EC, increased plasticity index and liquid limit, decreased bentonite swelling, and decreased <i>k</i><sub><i>v20°</i></sub>. The incremental addition of bentonite decreased saturated hydraulic conductivity (<i>k</i><sub><i>v20°</i></sub>) by up to three orders of magnitude. Mixtures containing 8% and 10% bentonite (MB8% and MB10%) met standard liner permeability criteria. Mechanical strength, expressed as unconfined compressive strength (UCS) and cohesion (<i>C</i><sub><i>UU</i></sub>), improved with increasing bentonite content, while the apparent friction angle decreased moderately. Although leachate exposure reduced UCS, the residual liner strength remained sufficient according to the design requirements. Under long-term conditions, uncontaminated MB8% and MB10% mixtures showed a decrease in internal friction angle φ′ from 37.52° to 34.79° and an increase in internal cohesion <i>C</i>′ from 24.55 to 33.18&#xa0;kPa. Leachate-contaminated specimens followed the same trend, but with higher <i>φ</i>′ values of 39.20° to 36.86° and lower <i>C</i>′ values of 16 to 22.40&#xa0;kPa. Therefore, chemo-mechanical interaction determines the shear strength of MB% mixtures. MB8% and MB10% mixtures provide a practical compromise between hydraulic sealing and mechanical stability for landfill liner applications under chemically aggressive conditions.</p>

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Assessment of the Impact of MSW Leachate on the Geotechnical and Geochemical Characteristics of Marl-Bentonite Liners

  • 期刊论文

  • 发表日期：

    2026年7月30日

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  • Abdellah Demdoum,
  • Elhadj Guesmia Daheur,
  • Zhong-Sen Li,
  • Rüdiger Anlauf,
  • Said Taibi

摘要

This study evaluates the applicability of the marl-bentonite (MB%) mixture as a low-permeability, durable landfill liner material exposed to mature leachate. Natural marl collected from the Ghardaïa region of Algeria was mixed with 3% to 10% bentonite and characterized using a series of tests, including Atterberg limits, oedometer swell tests, permeability tests, unconfined compression tests, and direct shear tests. Chemical interactions with mature leachate were studied using immersion protocols, with measurements of pH, electrical conductivity (EC), and carbonate and quartz contents. Exposure to leachate resulted in changes in the textural and hydraulic properties, leading to increased ionic strength, decreased carbonate content, increased quartz content, decreased pH, increased EC, increased plasticity index and liquid limit, decreased bentonite swelling, and decreased kv20°. The incremental addition of bentonite decreased saturated hydraulic conductivity (kv20°) by up to three orders of magnitude. Mixtures containing 8% and 10% bentonite (MB8% and MB10%) met standard liner permeability criteria. Mechanical strength, expressed as unconfined compressive strength (UCS) and cohesion (CUU), improved with increasing bentonite content, while the apparent friction angle decreased moderately. Although leachate exposure reduced UCS, the residual liner strength remained sufficient according to the design requirements. Under long-term conditions, uncontaminated MB8% and MB10% mixtures showed a decrease in internal friction angle φ′ from 37.52° to 34.79° and an increase in internal cohesion C′ from 24.55 to 33.18 kPa. Leachate-contaminated specimens followed the same trend, but with higher φ′ values of 39.20° to 36.86° and lower C′ values of 16 to 22.40 kPa. Therefore, chemo-mechanical interaction determines the shear strength of MB% mixtures. MB8% and MB10% mixtures provide a practical compromise between hydraulic sealing and mechanical stability for landfill liner applications under chemically aggressive conditions.