At Battleship Wharf, Blyth, Northumberland, contractor Ritchies has just completed a £45,000 contract to drill underwater rock sockets for piles for a new wharf.
This wharf is being built by parent company Nuttall for Port of Blyth. Designer is Halcrow. Drilling was carried out using a track mounted top drive rotary drill rig with down-the-hole equipment and air/water flush. At each of the pile locations, a drill platform measuring 6.35m x 2.5m and weighing 2t was positioned using a crane. The drill rig was set up vertically using an angle finder. Two 1.85t counterbalance weights prevented the rig from overturning the platform.
A 305mm down-the-hole hammer with a 558mm diameter button bit was lowered down the 660mm diameter pile on screwed drill rod sections. To advance the drill string, large volumes of air and water were necessary to remove spoil from the borehole. The sockets were drilled 3.5m into bedrock and flushed clean. Next, Ritchies installed a 508mm diameter steel pile inside the rock socket and grouted it into place using a tremmie line.