Experimental study on riprap stable size around wing-wall abutments

Many experiments were done over a relatively wide range of effective parameters to determine the stable size of riprap stones around wing-wall abutments. The experiments involved five sizes of riprap stones, three abutment lengths, and various flow depths and velocities. The results of this study indicate that in the range of tested parameters, the most important factors influencing riprap instability are the upstream Froude number, the ratio of abutment length to flow depth, and the ratio of abutment width (thickness) to flow depth. Based on the experimental results, a relation for designing the stable size of riprap around wing-wall abutments is presented and compared with previous equations developed for different shapes of bridge abutments.