Parametric Seismic Stability Assessment of RCC Gravity Dams: Impact of Ground Motion Intensity and Foundation Flexibility

Abstract

Ensuring the seismic resilience of high-head hydropower projects is critical, yet conventional design often oversimplifies the dam-foundation interface. By simulating the non-linear dynamic response of the Longtan RCC Dam (non-overflow section) under extreme ground motion, this study challenges that assumption. In contrast to conventional static evaluations, this study fully couples the hydrodynamic pressure of the reservoir, the compliance of the underlying limestone foundation, and the dam structure using the GeoStudio finite element framework. The analysis measures precisely when and how the system transitions from stable to critical by exposing the model to the Northridge earthquake record, which is scaled parametrically from 0.1g to 0.9g. The findings are clear: the safety factor against sliding decreases nonlinearly, exceeding the failure threshold (F.S. < 1.0) at a Peak Ground Acceleration of 0.65g, even though the dam remains stable during moderate shaking. Furthermore, the rock foundation’s rigidity produces a “double-edged” effect; it successfully limits lateral displacement but forces a sharp spike in tensile stress at the heel (exceeding 3.0 MPa), posing a cracking risk well before global failure occurs. These findings highlight the need for foundation-specific retrofitting in high-seismicity zones.