THE BEHAVIOR OF DRIVEN TUBULAR STEEL PILES IN THE LAMINATED MUDSTONESOF SOUTH-WEST IRELAND

This paper describes the experiences gained during the installation of tubular steel piles into laminated mudstones for two jetty projects i n south-west Ireland. A feature of the pile driving, for the Moneypoin t Jetty in County Glare, was the development of a 'false set' as shown by a reduction in resistance when the piles were redriven, Following three pile test failures an extensive programme of investigation, rese arch and testing was carried out which resulted in piling operations b eing held up for three months, Pile redriving was carried out and 142 of the piles were redriven by up to 3.1 m. As the results of rock cori ng at about 135 locations and the results of an extensive programme of laboratory tests were already available, the bedrock could be categor ized into four different zones depending on the rock type, its strengt h and fracture state, It was shown that the piles which required redri ving and which failed the load test were mostly confined to one of the four zones. The paper describes the geology of the site, the design a nd construction of the piles, the problems encountered and the subsequ ent remedial action, Some possible explanations are given to the reaso ns for the development of the 'false set' and for the load test failur es. The lessons learned at Moneypoint were applied to the design and c onstruction of the foundation for Keelbeg Pier at Union Hall in west C ork, The pile installation procedure specified was based on the experi ences from Moneypoint.