Design Aspects of an LNG Loadout Jetty in Yemen

Abstract

SummaryThis paper discusses the design problems associated with the site and how they were overcome in consultation with the construction contractor to best suit their expertise and equipment. The facility consists of an 800 m long approach trestle giving vehicular access to the loading platform and carrying the product pipelines, six mooring dolphins, four berthing dolphins, and a multi-level loading platform with four LNG loading arms. Conventional piled headstocks were chosen for the approach trestle, but deeper water along the berthing face led to jacket structures for each of the berthing and mooring dolphins, and the loading platform. The site geology generally consists of sandy sediments overlying Basaltic rock, with the depth of overburden varying from around 15 m at the berth to exposed rock onshore. Low tension capacity of driven piles required a significant number of tension anchors to be drilled into rock. The 7.8 m design wave at the site was a breaking wave over about one-third of the length of the trestle, and the headstock level was chosen to clear the wave crest by 1.5 m. The design of the topworks was being carried out by the main contractor at the same time, which resulted in uncertain pipe loads during the preliminary design phase. Prefabrication was carried out in Malaysia and transported to Yemen by barge, along with all equipment and construction materials. Provisions for sea transport of the fabricated jacket structures and the mechanics of their handling and installation were important parts of the design process.