SEACORE USED large diameter reverse circulation drilling to install rock socketed tubular steel raking piles into the bed of the Arabian Sea on the west coast of India.
The piles are for a 15,000t capacity ship lift and ship transfer facility for the Indian Navy's vast new Seabird naval base at Karwar in Karnataka State. When complete the $7.5bn (£4.1bn) base will stretch 28km along the coast and be the biggest in Asia.
Skanska Cementation India was installing 30 open-ended 23m long marine piles at a rake of 1 in 5 under a £27M contract.
Ground conditions and low vibration requirements dictated that Skanska use reverse circulation drilling for the piles' rock sockets rather than down-the-hole hammer techniques.
'Skanska was keen to have an experienced drilling contractor on site.We had previously installed even bigger rock sockets for the Jamnagar jetty further up the west coast of India, ' says Seacore divisional manager Jason Clark. For the earlier contract Seacore installed 200 sockets up to 3m in diameter.
At Karwar, working in about 13m to 17m of water, each 860mm diameter tubular steel pile was pitched on its 1 in 5 rake and initially driven by a hammer through overburden to toe into the underlying bedrock.
The hammer was then removed and the reverse circulation drill mounted on top of the pile. Seacore drilled out the overburden from inside the tube and continued past the pile toe to create an open blind socket into the broken basalt bedrock beneath. Sockets were typically between 5m and 13m deep but in one pile the socket was 24m.
Skanska's contract also covers the construction of two buildings, piping works, mechanical and electrical services and fabricating and driving 740 vertical close-ended steel tubular marine piles.