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<p>This study quantifies the hydraulic conductivity k of compacted loess–bentonite mixtures (0–10% bentonite) under varying mechanical and chemical conditions to optimize geoenvironmental barrier designs. A comprehensive experimental program evaluated the coupled effects of compaction state (dry and wet of optimum), vertical effective stress (up to 400&#xa0;kPa), and pore fluid chemistry (distilled water vs. real Municipal Solid Waste (MSW) leachate). Results indicate that k decreases significantly as bentonite content increases, with this reduction being more pronounced for specimens compacted on the dry side of optimum. Specifically, the addition of 10% bentonite reduced k by approximately one to two orders of magnitude in water-permeated samples. Furthermore, increasing the effective vertical pressure from 50 to 800&#xa0;kPa resulted in an additional reduction of k by up to 80%, highlighting the role of mechanical densification and particle rearrangement. However, the introduction of MSW leachate (ionic strength up to 31,100 µS/cm) produces an increase in k by one to two orders of magnitude in the 10% bentonite mixtures. This sharp increase is attributed to the contraction of the diffuse double layer and a microstructural transition toward a flocculated fabric. While vertical stress contributes to reducing k through densification, the chemical impact remains the dominant factor for high-bentonite mixtures. These findings are synthesized into a design framework that defines the minimum bentonite content and compaction energy required to maintain regulatory performance under realistic chemical exposure.</p>

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Hydro-Mechanical Behavior and Design Criteria of Compacted Loess–Bentonite Mixtures for Geoenvironmental Barrier Applications

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Pablo M. Nieva,
  • Franco M. Francisca

摘要

This study quantifies the hydraulic conductivity k of compacted loess–bentonite mixtures (0–10% bentonite) under varying mechanical and chemical conditions to optimize geoenvironmental barrier designs. A comprehensive experimental program evaluated the coupled effects of compaction state (dry and wet of optimum), vertical effective stress (up to 400 kPa), and pore fluid chemistry (distilled water vs. real Municipal Solid Waste (MSW) leachate). Results indicate that k decreases significantly as bentonite content increases, with this reduction being more pronounced for specimens compacted on the dry side of optimum. Specifically, the addition of 10% bentonite reduced k by approximately one to two orders of magnitude in water-permeated samples. Furthermore, increasing the effective vertical pressure from 50 to 800 kPa resulted in an additional reduction of k by up to 80%, highlighting the role of mechanical densification and particle rearrangement. However, the introduction of MSW leachate (ionic strength up to 31,100 µS/cm) produces an increase in k by one to two orders of magnitude in the 10% bentonite mixtures. This sharp increase is attributed to the contraction of the diffuse double layer and a microstructural transition toward a flocculated fabric. While vertical stress contributes to reducing k through densification, the chemical impact remains the dominant factor for high-bentonite mixtures. These findings are synthesized into a design framework that defines the minimum bentonite content and compaction energy required to maintain regulatory performance under realistic chemical exposure.