Long-term creep damage analysis of deep-buried hydraulic tunnels with lining scour pits based on an improved CVISC model

Deep-buried hydraulic tunnels are susceptible to long-term creep damage under hydro-mechanical coupling, particularly in the presence of lining defects such as scour pits. To address the limitations of conventional creep models, this study develops an extended CVISC model incorporating nonlinear accelerated creep and moisture-dependent damage. A three-dimensional numerical model of a hydraulic tunnel with typical scour pits is established using FLAC3D to investigate the evolution of surrounding rock deformation, plastic zones, and lining internal forces. The results indicate that scour pits markedly accelerate damage evolution and stress redistribution, leading to rapid expansion of butterfly-shaped plastic zones and substantial increases in lining internal forces. Critical regions, including the arch springings, shoulders, and crown, exhibit pronounced stress concentration and progressive failure characteristics. The coupling effect of seepage-induced moisture variation and creep deformation plays a key role in the deterioration process. This study provides an effective framework for analyzing defect-induced creep mechanisms and offers practical insights into the long-term stability assessment of deep-buried hydraulic tunnels.