Experimental investigation of the effect of geometrical parameters on the equilibrium time of scour around the complex pier group

Scour around the bridge piers is a kind of erosion that occurs due to complex vortex flows and finally creates a hole around the bridge piers (Yang et al., 2019). The maximum scour depth, which called Equilibrium scour depth, can take a very long time to reach. Although many researches have been carried out to determine the equilibrium scour time, there is still no suitable criteria for determining the equilibrium scour time for the complex piers which consist of the pile group, pile cap and piers. In the present study, considering the importance of this fact that the local scour process is dependent on time, the effect of the complex pier geometrical parameters on the equilibrium scour time around the complex pier is investigated. In addition, a regression equation for the estimation of equilibrium scour time was presented which has suitable performance to estimate desired output in the range of the experimental data of the present study.