Bridge Pier Scour in Complex Environments: The Case of Chacao Channel in Chile

Abstract

Chacao channel bridge is located in a tidal channel with highly-energetic hydrodynamics conditions and significant erodibility potential. Once finished, this 2.5 km long cable-stayed bridge will be the largest in South-America. Here we report an integrated procedure to estimate scour around two of its three towers, both located on a relatively complex but different soil matrices. A high-resolution hydrodynamic model based on the Reynolds-averaged Navier–Stokes equations (RANS), physical tests of in situ soil samples in a Rotating Erosion Testing Apparatus (RETA) and empirical formulas for scour estimation are combined to provide a reliable estimation of scour depth under a periodic tidal ebb-flow regime. The relatively homogeneous soil material at the North Tower shows a high susceptibility to hydrodynamic erosion, which is estimated with SRICOS methodology. The Central Tower, in contrast, needs a combined approach based on the current state of the rock, information collected from underwater explorations and theoretical progress made about rock scour in order to reduce the uncertainty of the soils’ substrate. This study reveals that scour estimation for engineering design purposes in complex soils can be achieved with a joined vision of different disciplines and modelling tools for minimizing the uncertainty.

Keywords

• rock erosion
• bridge design
• CFD simulations
• RETA experiments
• tidal channel
• extreme tides