关键词: 灰岩, 酸性环境, 干湿循环, 损伤本构, 损伤演化

Abstract:

[Objectives] This study focuses on the damage patterns of limestone in karst regions under acidic dry-wet cycles, aiming to explore the effects of the coupled action of acidic environment and dry-wet cycles on the mechanical properties and damage mechanisms of limestone. [Methods] Limestone from the Guilin karst region was selected as the research subject. Dry-wet cycle tests were conducted in acidic solutions with pH values of 3, 5, and 7 to simulate acid rain erosion. The number of cycles was set at 10, 20, and 30. Conventional triaxial compression tests were carried out to obtain stress-strain data and analyze the strength and deformation characteristics of the limestone. By integrating the Weibull distribution function with a composite damage variable, a geometric damage model was established. A statistical damage constitutive model for limestone was derived and its validity was verified using experimental data. [Results] (1)Mechanical degradation behavior: peak stress and elastic modulus exhibited exponential decay with increasing cycle count. The most significant degradation occurred at pH 3, where the elastic modulus decreased by 29.6% after 30 cycles. Notably, at higher cycle counts, the degradation rate in elastic modulus exceeded that of peak strength. (2)Model validation: The theoretical curves of the newly developed constitutive model showed strong agreement with the experimental data, accurately capturing the full stress-strain response of limestone under triaxial compression, including the residual strength phase. (3)Damage evolution mechanism: The total damage curve followed an “S”-shaped four-stage evolution (initial damage, rapid development, slowed development, and complete damage). Lower pH values led to an earlier onset of critical strain. After 10 cycles, the strain at the peak damage rate was significantly reduced, indicating that acidic environments induce increased brittleness in limestone. [Conclusions] The damage constitutive model developed in this study effectively reflects the mechanical behavior and damage evolution of limestone under acidic dry-wet cycles. The research reveals the complex mechanisms of acid-induced damage in limestone, offering new theoretical insights and methods for geotechnical design and slope stability analysis in karst regions, and provides an important reference for evaluating and predicting the performance of limestone materials in practical engineering applications in karst regions.

Key words: limestone, acidic environment, dry-wet cycle, damage constitutive model, damage evolution