Timber Piles
Eastbourne Coastal Protection
Aarsleff Piling successfully drove forests of about 6000 greenheart piles along the beach at Eastborune.The timber piles were driven as replacements for about 100 timber groynes, which formed part of the major repairs to East Sussex town’s sea defences.
Our client was Eastbourne Borough Council who removed about 6.6 km of the seafront’s old and badly damaged oak groyne field, installed new ramps and rock revetments and replenished the beach with sea dredged shingle. The £21.5 million project was predominantly funded by the Ministry of Agriculture and Fisheries grant aid together with additional monies from the Environment Agency and Eastbourne Borough Council and was believed to be one of the UK’s largest coastal protection schemes employing timber piles.
The main contractor in this case was Mackley Construction who sub-let all the piling that formed the vast bulk of the sea defence works to Aarsleff Piling in two separate phased contracts that totalled about £600,000. Prior to winning the initial pile driving contract Aarsleff first had to prove that our Banut 500 piling rigs could operate on the shingle beach and accurately drive the 306mm square timber piles to line and level. Aarsleff successfully drove a line of 22 test piles which formed part of a groyne to the satisfaction of Mackley Construction and the scheme’s designer and project managing consulting engineers Postford Divivier.
The Banut piling rig was equipped with a 4t drop weight falling just 450mm to generate the required high impact energy with low impact velocity to the piles, which were topped and tailed with steel driving ring and cast iron shoe. Aarsleff Piling had to work between the tides to drive an average of 24 piles/day whilst maintaining tight tolerances of ± 20mm on level, ± 40mm on line within 75mm verticality over their length. On average 90 piles were driven ranging from 5m to 12m long on each groyne that were up to 110m long. Around 70 king piles at 1.5m centres form the main spine of each groyne, whilst the remainder acted as anchor piles and were driven in pairs at 6m centres between each pair alongside the top end of the western face of each groyne. The anchor piles were fixed to sloping oak tree trunk struts, which were connected to high level greenheart waling bolted onto the eastern side of the groyne piles. The groynes, spaced at about 65m intervals along the beach, were finished off with greenheart timber cladding and sheeting. All the hardwood for the project was supplied from mills in South America that operated full forestry management policies in accordance with Forest Stewardship Council’s principles and criteria.
