Wave load formulae for prediction of wave-induced forces on a slender pile within pile groups

In this study, new wave load formulae for the prediction of wave-induced force on a slender pile in pile groups with different arrangements are developed using a series of laboratory data obtained from systematic model tests conducted in the 2 m-wide wave flume of Leichtweiss-Institute for Hydraulic Engineering and Water Resources (LWI) in Braunschweig, Germany. For the analysis of the laboratory data and the development of the new prediction formulae, an artificial intelligence (AI)-based computational tool, named “hybrid M5MT-GP model”, is implemented. The new hybrid model and the new wave load formulae allow us to systematically assess the pile group effect (KG) as a function of the flow regime (KC number) and the relative spacing (SG/D) for each tested pile group arrangement. The results show that the pile group effect needs to be considered in calculating wave loads on the slender piles in pile groups, unless KG = 1 where there is no interference effect between neighbouring piles and piles in the group can be treated as a single isolated pile. The accuracy of the new formulae in predicting pile group effect KG is confirmed by the statistical indicators using agreement index Ia, correlation coefficient CC and scatter index SI.