Settlement of vertical piles exposed to waves

In recent years, several authors have conducted experimental studies on the scour around piles fixed in the wave flume. In addition, the settlement of structures has been studied for the case of pipelines, due either to steady currents [International Journal of Offshore and Polar Engineering 4 (1) (1994) 30] or to wave forcing [Coastal Engineering 42 (2001) 313]. However, the settlement of a pile due to scour in waves has so far not been investigated. This paper reports an experimental study on the settlement of vertical cylindrical piles, either surface-piercing or entirely submerged, exposed to waves. The primary objective of the study was to investigate: (i) the scour-settlement process with piles of differing heights and densities with their bases initially lying on the seabed and (ii) the influence of the piles height and weight on the hydrodynamics vertical settlement. A series of experiments was carried Out Using isolated vertical cylinders of a given diameter (30 mm), different materials (PVC, aluminium, brass, copper and bronze) and different heights (30, 6 and 3 cm). The characteristics of the waves remained constant in all tests (water height= 15 cm, wave period=2.1 s, local wave height=4.0 cm, Keulegan-Carpenter number = 12). The cylinders were set up over a sand bed, so that they could move vertically. Both the initial settlement of each cylinder (when it occurs), due to its weight, and the evolution of additional settlement caused by flow-induced scour were measured. The tests were conducted over a period of 4000 wave cycles. (C) 2002 Elsevier Science B.V. All rights reserved.