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<p>Sand-Bentonite (SB) cutoff walls have been widely employed to contain contaminant migration at polluted sites. However, previous research has primarily addressed individual effects of drying-wetting cycles or heavy metal contamination, while the coupled influence of multiple environmental factors on mechanical behavior and microstructure remain insufficiently understood. In this study, the durability and pore structure of SB cutoff walls subjected to coupled drying-wetting cycles and ZnCl<sub>2</sub> contamination were investigated through unconfined compressive strength (UCS), X-ray computed microtomography (CT), and scanning electron microscopy (SEM). Quantitative analyses were performed to characterize changes in strength, porosity, and pore fractal dimension. The results indicate that increasing drying-wetting cycles led to mass loss ratio increasing to 6.56% and UCS decreased by up to 78.47%, accompanied by irreversible plastic deformation. ZnCl<sub>2</sub>-contaminated samples exhibited higher porosity (up to 31.97% in ZnCl<sub>2</sub>-6) and a higher mesopore proportion, reduced cementation, and multiple vertical through cracks. The pore characteristics evolving toward greater complexity and orientation. Furthermore, mesopores evolution were identified as the dominant factor contributing to pore structure complexity and strength reduction. The deterioration mechanism of ZnCl<sub>2</sub> contamination under drying-wetting cycles differed from distilled water, mainly due to coupled physico-chemical interactions induced by Zn(II). Crystal formation with sizes comparable to mesopores transformed larger pores into mesopores, thereby increasing pore complexity and ultimately reducing macroscopic strength. This study provides new insights into the coupled effects of drying-wetting cycles and heavy metal contamination, offering a theoretical basis for predicting the engineering performance and durability of SB cutoff walls.</p>

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Study on the durability and pore structure fractal characteristic of sand-bentonite cutoff wall under ZnCl2-contamination and drying-wetting cycles

  • 期刊论文

  • 发表日期：

    2026年3月23日

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  • Xinyi Hu,
  • Yanan Sun,
  • Jianyong Shi,
  • Xinmiao Shi

摘要

Sand-Bentonite (SB) cutoff walls have been widely employed to contain contaminant migration at polluted sites. However, previous research has primarily addressed individual effects of drying-wetting cycles or heavy metal contamination, while the coupled influence of multiple environmental factors on mechanical behavior and microstructure remain insufficiently understood. In this study, the durability and pore structure of SB cutoff walls subjected to coupled drying-wetting cycles and ZnCl2 contamination were investigated through unconfined compressive strength (UCS), X-ray computed microtomography (CT), and scanning electron microscopy (SEM). Quantitative analyses were performed to characterize changes in strength, porosity, and pore fractal dimension. The results indicate that increasing drying-wetting cycles led to mass loss ratio increasing to 6.56% and UCS decreased by up to 78.47%, accompanied by irreversible plastic deformation. ZnCl2-contaminated samples exhibited higher porosity (up to 31.97% in ZnCl2-6) and a higher mesopore proportion, reduced cementation, and multiple vertical through cracks. The pore characteristics evolving toward greater complexity and orientation. Furthermore, mesopores evolution were identified as the dominant factor contributing to pore structure complexity and strength reduction. The deterioration mechanism of ZnCl2 contamination under drying-wetting cycles differed from distilled water, mainly due to coupled physico-chemical interactions induced by Zn(II). Crystal formation with sizes comparable to mesopores transformed larger pores into mesopores, thereby increasing pore complexity and ultimately reducing macroscopic strength. This study provides new insights into the coupled effects of drying-wetting cycles and heavy metal contamination, offering a theoretical basis for predicting the engineering performance and durability of SB cutoff walls.