Experimental Investigation of the Influence of Grain Size Distribution and Sediment Disposition on Local Scour Around Bridge Pier

Scour around bridge piers due to flooding is the leading cause of bridge failure. Numerous numerical and experimental studies have investigated local scour under various sediment properties, pier geometries, and hydraulic conditions. In this paper, we present the results of an experimental study on the influence of sediment grain-size distribution and disposition on local scour around a circular bridge pier. The study aims to qualitatively evaluate how various factors, particularly grain size distribution and sediment disposition, affect local scour in open-channel flow. Four factors were tested: flow rate, channel slope, grain size distribution, and sediment disposition. Results show that both sediment properties and their arrangement significantly impact the maximum scour depth. While channel slope also affects local scour, its influence is less pronounced than that of flow rate. The most significant changes in scour volume are attributed to sediment disposition in the channel. These findings highlight the critical role of sediment composition and arrangement in bridge pier scour mitigation and provide valuable insights for riverbed protection and hydraulic structure design.