A modification to the Indian practice of scour depth prediction around bridge piers

Estimation of the expected maximum scour depth is very crucial at the design stage of a bridge. In India, for design of a bridge pier, the guidelines given by the Indian Road Congress (IRC) code is generally followed. The IRC equation is generally used to estimate the mean scour depth with a factor of safety of two to obtain the maximum design scour depth. The IRC equation comprises of two factors pertaining to the flow characteristics and bed material characteristics respectively. However, pier geometry is one crucial attribute which contributes to the local scour, and it is not considered in the IRC equation. Due to this, the computed mean scour depth will be much less. In the present study, a modification to the IRC equation is suggested based on detailed experimental studies using different shapes of piers. The scour pattern is obtained on a sand bed for various shapes at different flow conditions. Based on the study, an empirical constant is introduced in the IRC equation, which attributes to the pier geometry. The proposed modified IRC (M-IRC) equation gives better scour prediction for all the shapes. The effectiveness of the proposed equation is verified by comparing with other equations available in literature. The proposed M-IRC equation will be very useful for the design of bridge foundation in Indian conditions.