Design, Installation and Testing of Belled Pile Foundations
Authors: Burt Nicholas J. , Halcrow William , Harris Richard P. 
Published: October 2008

Preliminary design for the Jubail Tanker Terminal in Saudi Arabia included consideration of three alternative pile types. Following further site investigation, steel piles with grouted underreamed bases founded in a layer of variable weak rocks, were chosen as most suitable to support the structures. The design of the belled piles is described and the installation activities are reviewed. Six full-scale piles were test loaded offshore to confirm the design. The testing procedures and instrumentation are described and selected test results analysed and discussed.

INTRODUCTION

The Jubail Open Sea Tanker Terminal forms part of a new industrial and commercial harbour complex constructed on the eastern coast of Saudi Arabia, for the Saudi Ports Authority.

Design of the terminal commenced in mid 1975. The installation of some 100,000 tonnes of steelwork in piles, jackets and deck structures was substantially completed in early'1979 by the Contractor, Hyundai Construction Co. Ltd. The installation and testing of the pile foundations described below took place between May 1977 and December 1978.

The general layout of the tanker terminal is shown in Fig. 1. Water depth varies over the terminal length from 3m at the seaward limit of the approach causeway to an approximate constant 29m in the line of the berths. The water depth of 15m was selected as being the design division between deep and shallow water.

The terminal is located and designed to accommodate tankers in the range of 100,000 to 300,000 D.W.T. Four berths are provided, each serviced by a loading platform, two breasting dolphins and four mooring dolphins. A 10m wide access road runs the entire length of the terminal. To the side of the roadway run two levels of pipe track. The roadway and pipe track link the inshore industrial complex to the loading berths via a reclaimed approach causeway 9km long.

At each of the four berths a two level deck structure, 60m × 40m in plan, is supported by three identical, six-legged, jacket structures. The eighteen 8l3mm diameter piles supporting each loading platform deck are all vertical through jacket piles.

Breasting dolphins have been installed, as groups of three raking 2m diameter piles held together at their heads by collars and supporting the berthing fender and deck structure.

Mooring dolphins are simple four-legged jacket structures with an 864mm diameter pile through each leg at rake of 1:5.

Typical sections through the access roadway are given in Fig. 2. The 3.3 km long roadway consists of pre-cast composite reinforced concrete/ I-beam units spanning 20m between braced box beams. The export pipe lines similarly freely span the box beams.

The typical box beam is supported at two points. In water depths less than 25m the supports are exclusively free standing piles which are either single vertical piles or raking pairs. In deep water maximum use has been made of simple four-legged jacket structures. The box beams are supported on the heads of the 9l4mm diameter through jacket piles or on free standing 1067mm diameter vertical piles forming a portal.