North Morecambe Terminal, Barrow: pile design for seismic conditions

Very poor ground conditions and soils that were susceptible to liquefaction to depths of up to 20 m beneath the site were major problems for the construction of the largest natural gas processing terminal in Europe. Foundations were required to cater for liquefaction and the need to design for defined magnitudes of earthquake. An innovative foundation solution combining deep vibrocompaction with short cast-in-place piles driven into the treated soils was adopted as both cost- and programme-effective. The design and build project included preliminary site preparation and civils work comprising earthworks, drainage and road construction. The contract started in September 1991 and was completed by October 1992, with the process plant programmed to be on stream by October 1994. This paper presents details of the unusual pile design and foundation solution proposed to overcome the earthquake risk.