Olympic extension

Uk-Based amec is using two E-Z Drill Model 210B drilling rigs to remove redundant concrete from bored piles during the UK£ 180 million (€ 267 million) expansion of London’s Docklands Light Railway (DLR).

Hired from the Castellan Group, the two rigs were chosen, according to Castellan managing director Colin Jailler, because they comply with the Control of Vibration at Work Regulations 2005, which aims to help prevent Hand Arm Vibration Syndrome.

To do this the rig uses a compressed air powered Chicago Pneumatic CP32 rock drill, mounted in a frame supported on two jockey wheels at the front and spigot legs at the rear. This not only allows the operator to move, reposition and accurately align the drill for each hole, but means once it is set up the rig can be monitored from a safe distance, if desired. A single tool compressor powers the rig, which can be adjusted for rate of feed and retraction to suit the material being drilled.

At the DLR site the rigs drilled horizontal holes into the tops of concrete bored piles to assist the removal of concrete to a specified level, exposing the piles’ internal reinforcing. The two parallel rows of piles - 700 mm to 1,05 m diameter - will act as retaining walls for the new Woolwich Arsenal station’s cut and cover box. The exposed reinforcement is then tied into the cast insitu station roof slab, prior to excavating material from inside the box.

During operation a single 45 mm diameter hole was drilled to a depth of up to 750 mm into the piles. Afterwards a Darda hydraulic burster was inserted in the hole to break the concrete away from the reinforcing. Depending on their location the piles were cut down by 1,5 to 4 m, which was done in 1 m sections.

Construction of the 2,5 km extension, started in June 2005 and scheduled to finish in 2008, will provide rail access from Woolwich and southeast London to the Olympic Park in 2012.