Study on the Influence of Saturation on Freeze–Thaw Damage Characteristics of Sandstone

Abstract

In order to explore the evolution mechanism of freeze–thaw disasters and the role of water in the freezing–thawing cycles of rocks, the macro mechanical indexes and microstructural characteristics of seven different saturation sandstones after certain freeze–thaw cycles were analyzed. Electron microscope scanning, nuclear magnetic resonance, and uniaxial compression tests were employed to study the migration law of water in the rock, the crack growth law, and the damage mechanism during freeze–thaw cycles. The results showed that when the saturation was 85%, the peak load curve of sandstone with different saturation appeared at the minimum point, and the porosity of sandstone reached the maximum. The damage variable increased sharply when the saturation was 75–85%. This proves that 85% saturation is the critical value of sandstone after five freeze–thaw cycles. The water migration freezing model is established, and the migration direction of capillary film water during freezing is micropore → mesopore → macropore. The migration of water is accompanied by the expansion and generation of cracks. Then we study the mechanism and law of crack expansion, and the crack propagation rate is positively related to the theoretical suction. The theoretical suction and theoretical ice pressure increased linearly with the decrease in temperature, which accelerated the crack propagation. The crack propagation rate in decreasing order is Vmacropore > Vmesopore > Vmicropore. The research results can provide a theoretical basis for evaluating the stability of rocks under the action of freeze–thaw cycles in cold regions.

Multi-Scale Analysis of the Damage Evolution of Coal Gangue Coarse Aggregate Concrete after Freeze–Thaw Cycle Based on CT Technology

“…The response exhibited by macroscopic mechanical properties serves as an indicator to characterize the extent of concrete’s damage deterioration. Traditional macro freeze–thaw damage variables ( S n ′) for concrete are typically represented through alterations in the elastic modulus of the material, as follows [ 53 ]: S n ′ = 1 − ( E n /E 0 ), …”

Effect of Freeze–Thaw Cycles on Microstructure and Hydraulic Characteristics of Claystone: A Case Study of Slope Stability from Open-Pit Mines in Wet Regions

“…Weakly consolidated rocks, such as mudstone, claystone, and expansive softrock, in water-rich regions, are susceptible to structural degradation due to F-T cycles in seasonally frozen environments. Extensive experimental studies, which include unconfined compressive tests [13], triaxial shear tests [14], Brazilian tensile tests [15], point loading tests [16], and split Hopkinson pressure bar tests [17] on weakly consolidated rocks, have consistently demonstrated a noteworthy decline in its mechanical properties with an increasing number of F-T cycles. Hong et al (2021) proposed a predictive model for uniaxial compressive strength of expansive soft rock that integrates F-T cycles, based on the elastic-plastic theory, and fatigue damage mechanics [18].…”