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<p>As a widely distributed volcanic rock in the Earth's crust, dacite is extensively exposed in regions of northwest China, North China, the Qinghai–Tibet Plateau, and southwestern China. The dacite investigated in this study is weathered dacite from the BD hydropower station area, as indicated by XRD results showing that clay minerals account for approximately 40% of its mineral composition. Under freeze–thaw cycling, water migration and ice–water phase changes within the clay-rich weathered dacite induce progressive deterioration of its meso-structure, leading to a significant reduction in load-bearing capacity. To investigate these effects, this study examines the mechanical behavior and microstructural evolution of dacite subjected to freeze–thaw cycles through field sampling and laboratory testing. Triaxial compression tests were conducted to analyze the compressive strength, deformation characteristics, and failure mechanisms of the rock after cyclic freezing and thawing. Additionally, CT scanning and three-dimensional reconstruction techniques were employed to quantify the damage and microstructural degradation. Results indicate that as the number of freeze–thaw cycles increases, the pore structure parameters change markedly: both the number of pores and porosity increase, along with a notable rise in pore throat count and coordination number, enhancing pore connectivity and developing a more extensive pore network. Fractures evolve from isolated and dispersed forms into an interconnected network, substantially reducing the overall structural integrity. These results clarify the linkage between freeze–thaw-induced microstructural degradation and macroscopic mechanical deterioration of weathered dacite under triaxial stress conditions.</p>

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Study on the macro-microscopic damage deterioration mechanism of weathered dacite under freeze–thaw cycles

  • 期刊论文

  • 发表日期：

    2026年6月27日

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  • Junqi Yu,
  • Hui Deng,
  • Chenglong Yang

摘要

As a widely distributed volcanic rock in the Earth's crust, dacite is extensively exposed in regions of northwest China, North China, the Qinghai–Tibet Plateau, and southwestern China. The dacite investigated in this study is weathered dacite from the BD hydropower station area, as indicated by XRD results showing that clay minerals account for approximately 40% of its mineral composition. Under freeze–thaw cycling, water migration and ice–water phase changes within the clay-rich weathered dacite induce progressive deterioration of its meso-structure, leading to a significant reduction in load-bearing capacity. To investigate these effects, this study examines the mechanical behavior and microstructural evolution of dacite subjected to freeze–thaw cycles through field sampling and laboratory testing. Triaxial compression tests were conducted to analyze the compressive strength, deformation characteristics, and failure mechanisms of the rock after cyclic freezing and thawing. Additionally, CT scanning and three-dimensional reconstruction techniques were employed to quantify the damage and microstructural degradation. Results indicate that as the number of freeze–thaw cycles increases, the pore structure parameters change markedly: both the number of pores and porosity increase, along with a notable rise in pore throat count and coordination number, enhancing pore connectivity and developing a more extensive pore network. Fractures evolve from isolated and dispersed forms into an interconnected network, substantially reducing the overall structural integrity. These results clarify the linkage between freeze–thaw-induced microstructural degradation and macroscopic mechanical deterioration of weathered dacite under triaxial stress conditions.