Soluble limestone in karst areas has experienced long-term hydrochemical corrosion, leading to significant deterioration of its internal microstructure and physical–mechanical properties. During tunnel excavation, the surrounding rock is subjected to a true three-dimensional (3D) stress state. Limestone, a common rock in karst regions, effectively simulates the geological conditions encountered during tunnel excavation in such areas. Therefore, investigating the deformation and damage mechanisms of limestone under true 3D stress after hydrochemical corrosion offers valuable theoretical support for tunnel excavation. To address this issue, true triaxial compression tests were conducted on karst limestone under various pH levels, acid corrosion durations, and intermediate principal stress conditions. This study analyzed the effects of these factors on the macro/mesostructure, deformation, failure, and strength of limestone. The results indicated that as pH decreased and acid corrosion time increased, the reaction between carbonate and acid at the limestone surface intensified, increasing the surface roughness and enhancing the shear failure characteristics, while the crack stable propagation initiation stress (σci), the crack unstable propagation initiation stress (σcd), peak strength (σp), residual strength (σr), and elastic modulus (E) declined significantly. Specifically, when the pH decreased from 7 to 3, the stress parameters decreased by 39.6, 24.53, 16.56, 24.36 and 40.41%, respectively. In comparison, 90 d of acid corrosion led to reductions of 34.05, 22.23, 7.65, 10.3 and 20.66%, respectively. Additionally, with an increase in the intermediate principal stress (σ2), the tensile failure characteristics of limestone became more pronounced. As σ2 increased from 5 to 50 MPa, σci and E remained nearly unchanged, whereas σcd, σp, and σr increased by 84.95, 43.01 and 173.25%, respectively. A quantitative characterization method for macroscopic mechanical response to pH and corrosion time was proposed. Based on the true triaxial test results and the Mogi-Coulomb three-dimensional strength criterion, a three-dimensional statistical damage constitutive model was developed, which effectively simulated the deformation characteristics of limestone across the compaction, elastic, pre-peak plastic strengthening, post-peak strain softening, and residual stages under hydrochemical corrosion and true triaxial conditions, demonstrating agreement with the experimental results.

Mechanical Characterization and Deterioration Mechanism of Karst Tunnel Limestone under Hydrochemistry and Three-Dimensional Stress

期刊论文
发表日期：

2025年10月28日

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Zhi Zheng,
ZhengYu Chen,
ZhiJia Luo,
GaoMing Lu,
Wei Wang,
DingPing Xu

摘要

Soluble limestone in karst areas has experienced long-term hydrochemical corrosion, leading to significant deterioration of its internal microstructure and physical–mechanical properties. During tunnel excavation, the surrounding rock is subjected to a true three-dimensional (3D) stress state. Limestone, a common rock in karst regions, effectively simulates the geological conditions encountered during tunnel excavation in such areas. Therefore, investigating the deformation and damage mechanisms of limestone under true 3D stress after hydrochemical corrosion offers valuable theoretical support for tunnel excavation. To address this issue, true triaxial compression tests were conducted on karst limestone under various pH levels, acid corrosion durations, and intermediate principal stress conditions. This study analyzed the effects of these factors on the macro/mesostructure, deformation, failure, and strength of limestone. The results indicated that as pH decreased and acid corrosion time increased, the reaction between carbonate and acid at the limestone surface intensified, increasing the surface roughness and enhancing the shear failure characteristics, while the crack stable propagation initiation stress (σ_ci), the crack unstable propagation initiation stress (σ_cd), peak strength (σ_p), residual strength (σ_r), and elastic modulus (E) declined significantly. Specifically, when the pH decreased from 7 to 3, the stress parameters decreased by 39.6, 24.53, 16.56, 24.36 and 40.41%, respectively. In comparison, 90 d of acid corrosion led to reductions of 34.05, 22.23, 7.65, 10.3 and 20.66%, respectively. Additionally, with an increase in the intermediate principal stress (σ₂), the tensile failure characteristics of limestone became more pronounced. As σ₂ increased from 5 to 50 MPa, σ_ci and E remained nearly unchanged, whereas σ_cd, σ_p, and σ_r increased by 84.95, 43.01 and 173.25%, respectively. A quantitative characterization method for macroscopic mechanical response to pH and corrosion time was proposed. Based on the true triaxial test results and the Mogi-Coulomb three-dimensional strength criterion, a three-dimensional statistical damage constitutive model was developed, which effectively simulated the deformation characteristics of limestone across the compaction, elastic, pre-peak plastic strengthening, post-peak strain softening, and residual stages under hydrochemical corrosion and true triaxial conditions, demonstrating agreement with the experimental results.