Abstract: Local scour depth of bridge pier is an important parameter in bridge design. The empirical calculation formula of local scour depth for large-sized piers is prone to generate big errors. In view of this, we established an empirical formula of local scour depth of bridge pier in sandy river under the principle of unified dimension, and further modified the formula considering the influence of abutment exposed on bed surface on the scour. Comparison with Chinese and American calculation specifications verified that the formula proposed in this paper is of higher precision, uniform dimension and comprehensive consideration of factors. It is suitable for calculating local scour depth of large piers.

Key words: pier scour, scour mechanism, local scour depth, empirical formula, formula improvement, near-flow velocity