Assessment of Safety Monitoring Indexes of High RCC Gravity Dams Considering Hydraulic Fracture

High concrete gravity dams, particularly Roller-Compacted Concrete (RCC) types, face long-term safety challenges due to weak interlayer formation and crack propagation. This study presents a comprehensive evaluation of safety monitoring indexes for the Guxian high RCC dam (currently under construction in China) using both numerical and theoretical models. A Finite Element Method (FEM) was applied with two approaches: the strength reduction method, which considers weak layers, and the overloading method, which simulates extreme loading without accounting for material degradation. A comparative analysis between these two methods was conducted to determine which more effectively evaluates dam safety under varying conditions. Additionally, a fracture mechanics model was employed to assess the impact of crack propagation on dam integrity, using the Failure Assessment Diagram (FAD) to calculate safety factors and the residual strength curve to determine critical crack depths. Two crack types (single-edge and centre-through) were analysed to understand the effect of crack location on structural stability during hydraulic fracture. Results indicated that weak layers reduce the safety index by approximately 20%, particularly in lower sections with extensive interlayer interfaces. The overloading method produced more conservative and realistic safety index values than the strength reduction method when weak layers were not considered. Furthermore, single-edge cracks pose a significantly higher risk, decreasing the safety factor by 10% and reducing the critical crack depth by 40% compared to center-through cracks. These findings emphasize the need to incorporate RCC dam weak layer behavior and crack propagation into the safety monitoring and design standards of high RCC gravity dams.