Experimental study of the effect of non-structural materials on scouring of bridge piers with removal of river material: cationic polyacrylamide (PAM)

Abstract

Scouring damage to piers is a major risk factor for hydraulic structures. In this research, a new eco-friendly method has been proposed to reduce both the length and depth of scouring near bridges and the volume of pits created by the removal of river-bed materials. Since clay and cationic polyacrylamide (PAM) have good compatibility with river systems and their ecology, the mobile bed has two different granulations, and clay with a weight percentage of 10% and PAM material with a weight percentage of 0.5 and 1% have been added to the bed materials. Their effects on scouring reduction for four different discharge rates and three different pit depths were investigated. The results indicate the enhancement of the effects of adding clay and PAM for reducing scouring. The best performance of mixture in the present study is related to the mixture of clay and 1% cationic polyacrylamide, which reduces the scouring depth compared to the simple bed materials by 24.27% and 46.78% for mixture of just clay and mix of clay and PAM, respectively for 0.6 mm granulation. Also, these quantities are reduced by 26.9% and 45.18% for 0.15 mm granulation. The scouring length for both grains decreased by 17.73% and 31.22%, respectively. This investigation shows that the utilization of clay and PAM has a positive effect on reducing scouring and using of this material in rivers is typically compatible with the ecology of the system.