Life-Cycle Safety Evaluation of Arch Dam Abutments: A Comprehensive Framework Considering Spatiotemporal Variation in Fault Mechanical Parameters

Abstract

Through-going faults represent critical geological hazards that threaten the long-term operational safety of arch dams. Conventional studies predominantly rely on homogeneous material assumptions and static analysis, neglecting two essential characteristics of natural faults: (1) the discrete, localized distribution of intact rock blocks within fractured zones, and (2) degradation of the mechanical properties of faults with time during the service life of arch dams. These limitations will unavoidably introduce systematic errors into the safety state judgment of operating arch dams. To address these limitations, this paper develops an enhanced constitutive model that couples three key mechanisms: confining pressure strengthening with burial depth, local reinforcement from discrete random rock blocks, and fatigue damage accumulation under cyclic water level fluctuations. The model is implemented via ABAQUS UMAT subroutine development, enabling three-dimensional spatiotemporal evolution simulation of fault mechanical parameters. Furthermore, a multi-index comprehensive evaluation framework is established by integrating normalized dam stress state and abutment strength reduction stability, providing a holistic assessment of arch dam performance throughout its service life. Applied to a practical pumped storage arch dam project, the results demonstrate that: (1) Fault damage evolution is characterized by prominent spatial heterogeneity. The results reveal that the fault damage coefficient at a burial depth of 0 m after 40,000 days of service is nearly twice that of the fault at a burial depth of 270 m. (2) The abutment safety factor decreases from 2.36 to 1.17 after 40,000 days of cyclic operation, entering a critical warning state at approximately 28,000 days. This study provides refined characterization methods and quantitative assessment tools for the long-term safety evaluation of fault-controlled arch dams, with direct implications for engineering risk prevention and reinforcement design.