SRICOS: Prediction of Scour Rate in Cohesive Soils at Bridge Piers

A new method called SRICOS is proposed to predict the scour depth z versus time t around a cylindrical bridge pier of diameter D founded in clay. The steps involved are: (1) taking samples at the bridge pier site; (2) testing them in an erosion function apparatus to obtain the scour rate ? versus the hydraulic shear stress applied τ; (3) predicting the maximum shear stress τmax, which will be induced around the pier by the water flowing at vo before the scour hole starts to develop; (4) using the measured ? versus τ curve to obtain the initial scour rate ?i corresponding to τmax; (5) predicting the maximum depth of scour zmax for the pier; (6) using ?i and zmax to develop the hyperbolic function describing the scour depth z versus time t curve; and (7) reading the z versus t curve at a time corresponding to the duration of the flood to find the scour depth that will develop around that pier. A new apparatus is developed to measure the ? versus t curve of step 2, a series of advanced numerical simulations are performed to develop an equation for the τmax value of step 3, and a series of flume tests are performed to develop an equation for the zmax value of step 5. The method is evaluated by comparing predictions and measurements in 42 flume experiments.