Local scour around bridge abutments protected by angled spur dikes under ice-covered flow conditions

Abstract

Scouring around bridge piers and abutments presents a critical threat to bridge stability, necessitating effective mitigation strategies. Based on laboratory experiments in a large-scale flume which is 2.0-m wide and 38.5-m long, this study investigates the impact of non-submerged spur dikes with varying alignment angles of 45°, 60°, and 90° under different ice cover conditions on reducing local scour around bridge abutments located downstream of spur dikes. Results of this study reveal that the spur dike with an alignment angle of 90° relative to the downstream direction positioned 25 cm upstream of the abutment can effectively prevent the local scour around bridge abutment by redirecting flow and reducing vortex-induced erosion. The maximum depth of scour holes around bridge abutments increases with the increase in flow Froude number, relative roughness of ice cover and the dike alignment angle. On the other hand, the maximum depth of the scour hole decreases with the increase in the particle size of the bed material and the effective length of the dike. An empirical formula has been developed to determine the maximum depth of scour holes around bridge abutments, which are protected by spur dikes located upstream of the abutments. Clearly, the effective mitigation of local scour around bridge abutments varied with flow condition, ice cover roughness, particle size of bed material, alignment angle and the distance from the abutment to the spur dike located upstream of the abutments.