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<p>Marl soils are among sedimentary deposits that are composed of clay minerals and calcium carbonate. The presence of clay minerals and calcium carbonate in marl soils significantly influences and alters the soil’s engineering behavior. The geotechnical and geo-environmental characteristics of marl soils change when exposed to consecutive freeze-thaw test cycles. The formation of ice in the marl soil structure during freezing and the addition of extra moisture during thawing influence the marl soil microstructure, which may significantly impact the engineering characteristics of marl soil. Accordingly, this study investigates the effects of freeze-thaw test cycles on marl soil’s engineering behavior. After determining the geotechnical characteristics of marl soil, some samples of marl soil were exposed to 0, 1, 3, 5, 7, 10, 15, 20, and 30 freeze-thaw test cycles. Marl soil characteristics changed as a result of the conducted freeze-thaw test cycles, which were analyzed using both macrostructural (gradation, Atterberg limits, Unconfined Compressive Strength (UCS), and permeability coefficient) and microstructural (pH, EC, soil particle size distribution by PSA analysis, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM)) investigations. According to microstructural observations, the presence of zeolite channels in the structure of palygorskite and sepiolite minerals may stabilize these two minerals when exposed to the freeze-thaw test cycles. Increasing the number of freeze-thaw test cycles reduced UCS values due to the growth of microcracks, hole formation, destruction of the primary structure, and the formation of a new structure. The UCS value of the original natural marl soil, measured after 30 freeze-thaw test cycles, was found to be 140&#xa0;kPa, representing a 57% reduction. This research provides novel insights into the freeze–thaw resilience of marl soils, a topic scarcely addressed in existing literature. The findings are particularly significant for the design and stability assessment of geotechnical structures in cold regions, where cyclic freezing and thawing can critically affect soil behavior.</p>

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Microstructural Investigation of the Effect of Freeze-Thaw Cycles on Engineering Characteristics of Southern Iran Marl Soil

  • 期刊论文

  • 发表日期：

    2025年6月24日

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  • Mohammad Amiri,
  • Sakineh Shahriari,
  • Fatemeh Porhonar

摘要

Marl soils are among sedimentary deposits that are composed of clay minerals and calcium carbonate. The presence of clay minerals and calcium carbonate in marl soils significantly influences and alters the soil’s engineering behavior. The geotechnical and geo-environmental characteristics of marl soils change when exposed to consecutive freeze-thaw test cycles. The formation of ice in the marl soil structure during freezing and the addition of extra moisture during thawing influence the marl soil microstructure, which may significantly impact the engineering characteristics of marl soil. Accordingly, this study investigates the effects of freeze-thaw test cycles on marl soil’s engineering behavior. After determining the geotechnical characteristics of marl soil, some samples of marl soil were exposed to 0, 1, 3, 5, 7, 10, 15, 20, and 30 freeze-thaw test cycles. Marl soil characteristics changed as a result of the conducted freeze-thaw test cycles, which were analyzed using both macrostructural (gradation, Atterberg limits, Unconfined Compressive Strength (UCS), and permeability coefficient) and microstructural (pH, EC, soil particle size distribution by PSA analysis, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM)) investigations. According to microstructural observations, the presence of zeolite channels in the structure of palygorskite and sepiolite minerals may stabilize these two minerals when exposed to the freeze-thaw test cycles. Increasing the number of freeze-thaw test cycles reduced UCS values due to the growth of microcracks, hole formation, destruction of the primary structure, and the formation of a new structure. The UCS value of the original natural marl soil, measured after 30 freeze-thaw test cycles, was found to be 140 kPa, representing a 57% reduction. This research provides novel insights into the freeze–thaw resilience of marl soils, a topic scarcely addressed in existing literature. The findings are particularly significant for the design and stability assessment of geotechnical structures in cold regions, where cyclic freezing and thawing can critically affect soil behavior.