Case Study: Experimental Investigation into the Feasibility of Pier Nose Extensions to Reduce Local Scour around Bridge Piers

Abstract

The feasibility of pier nose extensions as an environmentally acceptable alternative to reduce local pier scour for a nontypical pier geometry was investigated using a 1:30 Froude-scaled movable-bed model. The movable-bed characteristics were investigated using Shields scaling to the D90 grain. The study was conducted for a site-specific location, the Burlington Northern Santa Fe (BNSF) Railway crossing on the Santa Ana River near Corona, California. Local scour behavior was evaluated in the model for the estimated worst-case hydrodynamic conditions with and without the pier nose extensions. When aligned with the approach flow, the pier extensions reduced the local pier scour. They produce a reduction of 53% compared with the existing pier configuration without extensions. Historically, pier nose extensions have been used for the passage of debris and to increase the conveyance in lined channels. This study extends the possible engineering applicability of pier nose extensions as a countermeasure for local scour.