Key Takeaways & Executive Findings
- •• Wet-dry cycles cause logarithmic declines in elastic modulus, cohesion, UCS, and internal friction angle of gypsum rocks. • Higher flow rates accelerate the mechanical deterioration induced by wet-dry cycles, as confirmed by NMR microstructural analysis. • A disturbed state concept (DSC)-based constitutive model accurately predicts nonlinear compaction, peak stress, and post-peak behavior. • The findings offer practical implications for stability assessment and design of underground structures in gypsum-rich strata under complex water conditions.
Abstract
Gypsum rocks are highly susceptible to mechanical deterioration under the coupled effects of wet-dry (W-D) cycles and flow rates, which significantly influence the stability of underground excavations. Despite extensive research on the effects of W-D cycles, the coupling influence of flow rates and W-D cycles on gypsum rocks remains poorly understood. This study investigates the mechanical behavior and deterioration mechanisms of gypsum rocks subjected to varying W-D cycles and flow rate conditions. Axial compression tests, along with nuclear magnetic resonance (NMR) techniques, were employed to analyze the stress−strain response and microstructural changes. Based on the disturbed state concept (DSC) theory, a W-D deterioration model and a DSC-based constitutive model were developed to describe the degradation trends and mechanical responses of gypsum rocks under different conditions. The results demonstrate that key mechanical indices, elastic modulus, cohesion, uniaxial compressive strength (UCS), and internal friction angle, exhibit logarithmic declines with increasing W-D cycles, with higher flow rates accelerating the deterioration process. The theoretical models accurately capture the nonlinear compaction behavior, peak stress, and post-peak response of gypsum specimens. This study provides valuable insights for predicting the mechanical behavior of gypsum rocks and improving the stability assessments of underground structures under complex environmental conditions.
1. Introduction
Wet-dry (W-D) cycles are among the most destructive natural phenomena affecting in-situ rocks in underground engineering, causing cumulative damage that leads to significant engineering challenges. In practical applications, additional factors, such as environmental conditions, exacerbate the adverse effects of W-D cycles on geomaterials. However, most published studies have focused on the influence of cyclic W-D processes on the mechanical properties of materials. While additional natural factors, such as salt weathering, variations in pH, and freeze-thaw cycles, have been extensively studied in relation to W-D processes, relatively little attention has been given to the influence of flow rates. Neglecting the impact of flow rates often underestimates the severity of engineering problems caused by W-D cycles in practical applications.
Gypsum rocks, primarily composed of gypsum (CaSO4·2H2O), are soft evaporite rocks that are widely distributed globally, occurring in geological formations ranging from the Cambrian to the Tertiary periods. In underground engineering, gypsum rocks are commonly encountered as surrounding rock formations in tunnels, mines, and storage caverns. These rocks are characterized by their complex water-rock interaction behavior, exhibiting expansion, dissolution, and softening in wet conditions, with dissolved minerals contributing to sulfate corrosion of surrounding concrete structures. The unique physical and chemical properties of gypsum have garnered increasing attention in recent years, as rapid engineering developments in gypsum-rich strata have led to recurring challenges. Due to their solubility and sensitivity to moisture, they pose significant challenges in terms of stability and durability under varying environmental conditions. For example, the interaction of gypsum rocks with water during W-D cycles and flow rates can lead to mechanical deterioration, dissolution, and structural weakening, which are critical concerns in the design and maintenance of underground excavations. Despite its significance, the precise role of flow rate in this process remains inadequately understood, presenting challenges for proactive engineering interventions. The Nanlvliangshan Tunnel, located in Shanxi Province, China, exemplifies the adverse effects of W-D cycles coupled with flowing water. Within five years of it
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Jiang Song, Huang Ming, Wang Gang, Xu Chao-shui, Xiong Jun (2025). Static compressive mechanical properties and disturbed state concept-based theoretical model of gypsum rocks with coupled influences of wet-dry cycles and flow rates. Journal of Central South University. https://doi.org/10.1007/s11771-025-5998-z
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Frequently Asked Questions
How do wet-dry cycles affect the mechanical properties of gypsum rocks?
Wet-dry cycles cause cumulative damage, leading to logarithmic declines in elastic modulus, cohesion, uniaxial compressive strength (UCS), and internal friction angle. Higher flow rates accelerate this deterioration process.
What is the role of flow rate in the deterioration of gypsum rocks?
Flow rate significantly influences the rate of mechanical degradation under wet-dry cycles. Higher flow rates accelerate the deterioration process by enhancing dissolution and erosion, as demonstrated in the study.
What experimental methods were used in this study?
Axial compression tests and nuclear magnetic resonance (NMR) techniques were employed to analyze the stress-strain response and microstructural changes in gypsum rocks subjected to varying wet-dry cycles and flow rates.
What is the disturbed state concept (DSC) model?
The DSC theory is used to develop a constitutive model that accurately captures the nonlinear compaction behavior, peak stress, and post-peak response of gypsum specimens, providing a framework for predicting mechanical behavior under environmental degradation.
How can these findings benefit underground engineering?
The findings provide valuable insights for predicting the mechanical behavior of gypsum rocks and improving stability assessments of underground structures, such as tunnels and caverns, under complex environmental conditions including wet-dry cycles and flow rates.
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