Location and Extents of Scour Hole around an Erodible Spill-through Abutment under Clear Water Condition and the Abutment Classification

Bridge abutment scour is a complex phenomenon, which significantly affects bridge stability and is responsible for the damage and failures of many bridges over waterways across the world. Given the widespread and devastating human and societal costs, numerous experimental studies have been conducted to find the mechanisms of bridge abutment scour, and several empirical and mathematical prediction models are available. However, the location of the scour hole and its extents have not been investigated in detail, which is one of the important parameters, not only for the bridge stability itself, but also for the safety of structures around the bridge and their design. Thus, in this study, laboratory experiments were carried out using several different lengths of erodible abutment under different flow conditions to suggest a new mathematical criterion for abutment classification with respect to the location of scour holes. Furthermore, additional analysis was conducted to locate the point of the deepest scour depth and extent of the scour hole around the abutment. Both in transverse and flow direction, the location of the scour hole and the point of the deepest scour are governed by the geometric contraction ratio. This research will be useful in analyzing the bridge safety itself as well as safety of the river training works close to the bridge with respect to the location and extents of the scour hole.