Experimental Study of Local Scour Around Four Piles Under Different Attack Angles and Gap Ratios.

In an effort to investigate and quantify the patterns of local scour, researchers embarked on an in-depth study using a systematic experimental approach. The research focused on the effects of local scour around a set of four piles, each subjected to different hydromechanical conditions. In particular, this study aimed to determine how different attack angles—the angles at which the water flow impinges on the piles, and gap ratios—the ratios of the spacing between the piles to their diameters, influence the extent and nature of scour. A comprehensive series of 35 carefully designed experiments were orchestrated, each designed to dissect the nuances in how the gap ratio and attack angle might contribute to changes in the local scour observed at the base of pile groups. During these experimental trials, a wealth of local scour data were collected to support the analysis. These data included precise topographic profiles of the sediment bed around the pile groups, as well as detailed scour time histories showing the evolution of scour at strategic feature points throughout the test procedure. The analysis of the experimental data provided interesting insights. The study revealed that the interplay between the gap ratio and the attack angle had a pronounced influence on the scouring dynamics of the pile groups. One of the key observations was that the initial phases of scour, particularly within the first hour of water flow exposure, were characterized by a sharp increase in the scour depth occurring immediately in front of the piles. After this initial rapid development, the scour depth transitioned to a more gradual change rate. In contrast, the scour topography around the piles continuously evolved. This suggests that sediment displacement and the associated sculpting of the seabed around pile foundations are sustained and progressive processes, altering the underwater landscape over time. The results of this empirical investigation have significant implications for the design and construction of offshore multi-pile foundations, providing a critical reference for engineers and designers to estimate the expected scour depth around such structures, which is an integral part of decisions regarding foundation design, selection of structural materials, and implementation of scour protection measures. [ABSTRACT FROM AUTHOR]