LDD has delivered robust solutions to a series of technical and geographical challenges in a major pile installation programme deep in the jungle of Papua New Guinea.
Specialist marine construction and drilling services company LDD has secured a major contract with the Clough Curtain joint venture to install about 150 marine foundation steel piles for the PNG LNG upstream infrastructure project. This work supports Esso Highlands’ (an ExxonMobil subsidiary) plans for a world-class operation to commercialise Papua New Guinea’s undeveloped petroleum and gas resources in the Southern Highlands and Western provinces.
Along with fellow Acteon company CIS , LDD is providing a complete pile installation service. It developed the bespoke pile installation methodology and is operating all the drilling and piling equipment, which includes two pile-top, reverse circulation, large-diameter drilling rigs; a specially adapted Diamec® 262 geotechnical coring rig with a twin Cat mud mix and pump unit; two large-diameter underreaming units; two hydraulic hammers with data loggers, handling and lifting equipment; and a vibratory hammer.
Some sixty 48-in. and ninety 18-in. steel foundation piles are being installed for two wharfs and three river crossings. The country’s geography, which is mostly mountains with coastal lowlands and foothills, and its tropical climate, fast-flowing rivers and lack of infrastructure have placed special demands on the crews delivering the project. All had to undergo extensive medical checks.
The project’s remote location presented some of the toughest challenges, though. For instance, because the sites are deep in the jungle, the client could not perform geotechnical investigations ahead of the project. Nevertheless, LDD adjusted its procedures and custom built a pile-top platform so that a rock coring drill could be mounted on top of the piles to proof-core the rock socket before piling. From this geotechnical coring, LDD and its client can determine the best sequence and energy requirements for driving and drilling to safely install a pile to the required depth.
“This analysis is performed in real time and provides appreciable cost and schedule savings compared with the drilled and grouted installations originally planned,” says Jason Clark, managing director, LDD. “Instead, we use our specialist drive–drill–drive (3D) installation technique. Material inside and ahead of the pile is drilled out, and an under-reamer removes more material below the toe of the pile. As well as facilitating on-the-fly geotechnical analysis, this enables standard piles to be driven into harder rock than would otherwise be possible.”
The LDD-designed under-reaming bit offers infinite variation on drill bit diameter, which, coupled with up-to-date pile driving information from the CIS data loggers, enables the piling system to be further evaluated and refined.
Moreover, the 3D approach is up to three times quicker than the conventional drill-and-grout approach. This saves time and incurs fewer costs for materials such as grout and temporary casing. Flexibility such as this is essential, according to Clark. “We are working out in the jungle where there is no infrastructure support whatsoever, so the ability to adapt procedures to the current conditions is key to a successful project.”