• Cyclic water intrusion progressively deteriorates all critical shear mechanical parameters of rock joints, including peak shear strength, shear stiffness, basic friction angle, and joint compressive strength.
• A novel shear damage constitutive model coupling cyclic water intrusion and loading accurately predicts joint behavior, validated by experimental curve comparisons.
• The model reveals a brittle-to-ductile transition in joint surface deformation with increasing water intrusion cycles, consistent with experimental observations.
• Damage evolution under coupled water intrusion and loading follows an S-shaped trend with three stages: stabilization (water-dominated), development (load-dominated), and completion.