Shear damage constitutive model of rock-like joint surface considering the coupling effect of cyclic water intrusion and loading

Abstract

Prolonged cyclic water intrusion has progressively developed joints in the hydro-fluctuation belt, elevating the instability risk of reservoir bank slopes. To investigate its impact on joint shear damage evolution, joint samples were prepared using three representative roughness curves and subjected to direct shear testing following cyclic water intrusion. A shear damage constitutive model considering the coupling effect of cyclic water intrusion and load was developed based on macroscopic phenomenological damage mechanics and micro-statistical theory. Results indicate: (1) All critical shear mechanical parameters (including peak shear strength, shear stiffness, basic friction angle, and joint compressive strength) exhibit progressive deterioration with increasing water intrusion cycles; (2) Model validation through experimental curve comparisons confirms its reliability. The model demonstrates that intensified water intrusion cycles reduce key mechanical indices, inducing a brittle-to-ductile transition in joint surface deformation — a behavior consistent with experimental observations; (3) Damage under cyclic water intrusion and load coupling follows an S-shaped trend, divided into stabilization (water-dominated stage), development (load-dominated stage), and completion stages. The research provides valuable insights for stability studies, such as similar model experiments for reservoir bank slopes and other water-related projects.

1. Introduction

To meet multifunctional operational requirements such as flood control, power generation, and water supply, reservoir water levels typically undergo periodic fluctuations. These recurrent hydrological changes induce progressive erosion of rock masses in the hydro-fluctuation zone [1,2]. During prolonged cyclic water intrusion, existing fractures propagate while new joints and cracks form, leading to deterioration of the rock mass's physical and mechanical properties in the hydro-fluctuation belt, potentially resulting in slope instability [3–5]. Given these effects, a systematic investigation of how cyclic water intrusion influences the shear damage evolution of joint surfaces becomes imperative for advancing the stability assessment and engineering design of reservoir slopes.

Current research extensively investigates rock damage evolution under water-load coupling effects, given its critical implications for geotechnical engineering. Scholars employ experimental and theoretical approaches to analyze hydro-mechanical interactions, damage accumulation mechanisms, and constitutive modelling, aiming to predict long-term stability in water-bearing rock masses [6,7]. Li et al. [8] performed uniaxial compression tests and constant-load creep tests on sandstone subjected to different wet-dry cycles, proposing a fractal derivative creep constitutive model. Based on energy theory, Jiang et al. [9] developed a damage constitutive model for sandstone accounting for water–rock interaction using microscopic testing under coupled water–rock conditions. Bian et al. [10] proposed a uniaxial load and water-weakening damage constitutive model by integrating the generalized strain equivalence principle and statistical microscopic damage mechanics theory. Fu et al. [11] identified the damage mechanisms of silty [text truncated]