Damage mechanism of sandstones subject to cyclic freeze–thaw (FT) actions based on high-resolution computed tomography (CT)

• Published in: Bulletin of engineering geology and the environment Vol. 81; no. 9
• Main Authors: Li, Bo, Zhang, Guanghua, Ma, Wei, Liu, Minghao, Li, Anyuan
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2022
• Subjects: Earth and Environmental Science; Earth Sciences; Foundations; Geoecology/Natural Processes; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Nature Conservation; Original Paper; CT scanning; 3D reconstruction; Pore; Freeze–thaw action; Micro-crack; Unconfined compressive strength
• DOI: 10.1007/s10064-022-02872-z
• ISSN: 1435-9529

Freeze–thaw (FT) action is a major cause of rock deterioration in alpine regions. To explore damage evolution of sandstones in cold environment, artificial FT experiments were conducted in the laboratory. Saturated and dry sandstone specimens were subjected to 0, 7, 14, and 28 FT cycles. X-ray computed tomography (CT) images and 3D visualization were obtained to analyze changes in the inner microstructure along with FT cycles. Results show that the peak stress of sandstone decreases to different extents with the increasing number of FT cycles; compared with dry specimens, saturated specimens deteriorate more significantly and show obviously different stress–strain curves under loading. The saturated medium-grained sandstone (MGS) and fine-grained sandstone (FGS) specimens exhibit different damage patterns: initiation and coalescence of micro-cracks for MGS, and expansion and fusion of pores for FGS. Under the action of FT cycles, the frost heave of pore water causes initiation of micro-defects that mainly develop along relatively weak areas such as places close to inherent defects (pores and fractures) and boundaries between different mineral crystals, resulting in intergranular and transgranular cracking. For dry rock specimens, the non-uniform contraction and expansion of minerals are main causes for deterioration inside the rock. The porosity and elastic modulus were incorporated into a damage index to assess the evolving damage degree. The prediction is in good agreement with the developing trend of pores and micro-cracks and can effectively reflect the strength deterioration induced by cyclic FT actions.