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Liebherr ploughs ahead in Hanoi

Liebherr ploughs

During competitive comparison trials held in Hanoi, between a Liebherr LB28 XL rotary drilling rig and a similarly rated European competitor’s rig, foundations specialist Thiên An said the Liebherr was superior in terms of speed, fuel efficiency and drilling deeper holes.

Vietnamese foundations specialist contractor Thiên An is using the rotary rig to complete a diaphragm wall and piling contract on the Eurowindow Multicomplex tower in Hanoi.

With a 92.5m frontage along Tran Duy Hung Street, some 7km from the centre of Hanoi, the complex will include a department store, shops, residential apartments and offices.

Work began in April 2010, on a 240-day contract. The project consultant is Raymond Woo & Henry Sng. Featuring a footprint of 3,600m², the site includes a 216m diaphragm wall along three sides to a depth of 21m. Thiên An’s contract also includes the installation of four rectangular, 6.2m x 1.2m piles along the 31m-long side wall to a depth of 45.7m.

Specified to accept the loadings of the high-rise tower, the piles will be bored alongside the diaphragm wall, with Thiên An transferring its Liebherr HS855 HD crawler crane from another city centre foundations contract to bore the rectangular piles.

Each pile is expected to take up to 14 hours to excavate, and six hours to remove the soil and waste before pouring concrete.

Soil conditions are typical of those away from the rivers of Hanoi, with a 3m layer of soil above a 22m layer of clay and a ‘sticky’, soil layer down to 42m, resting on a bed of pebbles and soil.

With nearly 75% of the diaphragm wall completed by mid-June, construction is dependent on one of two recently delivered Liebherr LB28 rotary rigs. According to project manager Ngo Minh Trinh, the Liebherr rig “is allowing us to stay on schedule despite the rainy season creating many stoppages”.

The Liebherr LB28 XL has been designed for operations using Kelly drilling equipment, continuous flight augers (CFA) and double-rotary heads. The machine’s operating weight of about 105t, together with a compact build, ensures ease of transport as a single piece of equipment, minimising assembly work on-site and saving time before operations begin.

The LB28 XL offers a maximum torque of 286kNm and maximum drilling diameter of 2,500mm, and can drill to depths of 70m. Its rope crowd system with a 40t retraction force is a key advantage. The rig is powered by a Liebherr six-cylinder, in-line diesel engine, rated at 350kW at 1,900rpm.

Thiên An specified a 72m Kelly bar, which necessitated an additional 5.2t counterweight, and a 30t Kelly winch, ensuring increased drilling depths.

Excavating 6.2m segments to a final depth of 21m, the LB 28 takes six hours to excavate and four hours to pour the concrete.

With so much of the wall completed, the contractor has begun to bore 177 piles across the site. Of these, 168 are up to a depth of 45.7m and 1.2m in diameter, and nine are 45.7m deep with a 1m diameter.

According to Ngo Minh Trinh, “even though the ground condition is relatively soft, this number of wide-diameter, bored piles is sufficient to meet the specified load bearing”.
Courtesy Geo Drilling

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