Key Takeaways & Executive Findings
- •• Liquid water is a critical factor in reducing the brittleness of schist under cyclic environmental actions. • The attenuation function model accurately predicts peak stress and elastic modulus degradation (R2 > 0.97). • Freeze-thaw cycles in water (FTW) cause the most severe deterioration, with the shortest half-life for strength (28 cycles) and wave velocity (208 cycles). • Damage variables for compressive strength and elastic modulus increase with cycle number, with FTW showing the highest damage after 40 cycles.
Abstract
In cold regions, slope rocks are inevitably impacted by freeze-thaw, dry-wet cycles and their alternating actions, leading to strength weakening and pore degradation. In this study, the mechanical and microstructural properties of schist subjected to four conditions were investigated: freeze-thaw cycles in air (FTA), freeze-thaw cycles in water (FTW), dry-wet cycles (DW), and dry-wet-freeze-thaw cycles (DWFT). Uniaxial compressive strength (UCS), water absorption, ultrasonication, low-field nuclear magnetic resonance, and scanning electron microscopy analyses were conducted. The integrity attenuation characteristics of the longitudinal wave velocity, UCS, and elastic modulus were analyzed. The results showed that liquid water emerged as a critical factor in reducing the brittleness of schist. The attenuation function model accurately described the peak stress and static elastic modulus of schist in various media (R2>0.97). Different media affected the schist deterioration and half-life, with the FTW-immersed samples having a half-life of 28 cycles. Furthermore, the longitudinal wave velocity decreased as the number of cycles increased, with the FTW showing the most significant reduction and having the shortest half-life of 208 cycles. Moreover, the damage variables of compressive strength and elastic modulus increased with the number of cycles. After 40 cycles, the schist exposed to FTW exhibited the highest damage variables and saturated water content.
1. Introduction
With the increasing demand for mineral resources, many mines have been constructed and laid out in cold regions, particularly open-pit mines, which have high and steep rock slopes [1]. Most mines are located in cold regions with complex and unpredictable climatic conditions. Recently, China has established several large-scale open-pit mining operations in cold regions, including the Huolinhe and Baorixile open-pit coal mines, mines in the Daxing’anling region, and lithium mines in the western Sichuan high-cold area. It is important to highlight that mining operations in these cold regions encounter distinct challenges such as extreme weather, limited construction seasons, and potential ecological impacts. Consequently, mines in these areas are typically adopted rigorous environmental protection measures to ensure sustainable development.
Generally, the seasonal temperature fluctuations and temperature between day and night are significant, heavy rainfall is observed, and intense freeze-thaw actions and evaporation frequently occur. Consequently, the slope rocks exposed at the surface are highly vulnerable to the effects of freeze-thaw, dry-wet cycles and their alternating actions, which leads to structural weakening and mechanical strength reduction. This poses a serious threat to mining engineering safety [2].
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Jiajia Gao, Jiajian Jin, Daguo Wang, Shaogang Lei, Jianguo Lu, Huan Xiao, Jinhe Li, Huadong Li (2025). Mechanical and microstructural properties of schist exposed to freeze-thaw cycles, dry-wet cycles, and alternating actions. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.04.003
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Frequently Asked Questions
What are the main environmental actions studied on schist?
The study investigates freeze-thaw cycles in air (FTA), freeze-thaw cycles in water (FTW), dry-wet cycles (DW), and dry-wet-freeze-thaw cycles (DWFT) on schist.
How does liquid water affect schist under cyclic actions?
Liquid water is identified as a critical factor in reducing the brittleness of schist, leading to more pronounced strength and stiffness degradation.
Which condition causes the most severe deterioration of schist?
Freeze-thaw cycles in water (FTW) cause the most significant deterioration, with the shortest half-life for strength (28 cycles) and longitudinal wave velocity (208 cycles).
What model was used to describe the degradation of schist?
An attenuation function model accurately described the peak stress and static elastic modulus degradation with R2 values greater than 0.97.
What methods were used to analyze the microstructural properties?
The study employed uniaxial compressive strength (UCS), water absorption, ultrasonication, low-field nuclear magnetic resonance, and scanning electron microscopy analyses.
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