Highly productive and reliable, the
Vietnamese ground engineering and foundations specialist contractor, Dua Fat Foundation Joint Stock Company has been using the Liebherr LB 36-410 rotary drilling rig to complete the lions’ share of bored piling in the tricky conditions onsite. The machine has been working on the western approaches to a new road bridge, which is spanning the River Cam in Haiphong.
The new Hoang Van Thu Bridge will provide an important link for the area as it will connect the centre of Haiphong to Thuy Nguyen, a north-west suburb, through an expressway and will provide better access to a new riverside township, Thuong Ly.
Construction of the 200m-span bridge also includes a 1km elevated western approach through cleared former mangroves. However, the poor underfoot conditions presented contractor Dua Fat with considerable problems relating to the high water table, virtually on the surface and resulting in almost constant quagmire conditions.
The LB 36-410 rotary drilling rig is one of five rigs employed by Dua Fat on the Western Approach two-month contract, which involves sinking 100 piles. The Liebherr machine has completed more than 80% of the bored piles due to its power, flexibility and stability.
Drilling through 50m of waterlogged soil and soft sedimentary conditions and 10m of soft rock, Dua Fat is drilling to depths of up to 62m, socketing into very hard granite-type rock. This includes 35 piles, with diameters of 1.6m, beneath the main column.
According to the contractor, the Liebherr LB 36-410 is taking just 20 hours to drill each pile. The other rigs the firm has been using have taken 28 hours to bore each pile in these highly waterlogged conditions.
The heavy-duty drilling rig LB 36-410 is versatile and can be used for bored piling using a variety of techniques such as Kelly drilling, continuous flight auger drilling, partial and full displacement drilling or double rotary drilling.
The rig has been designed for easy transportation and fast set-up at the jobsite. Despite its large machine class, the upper carriage is compact and designed for small working radii. Featuring an operating weight of 115tonnes, the LB 36-410 offers a maximum torque of 410kNm. Using Kelly bar drilling techniques, the drilling rig can be used to drill up to 80m and a maximum drilling diameter of 3m.
Dua Fat Foundation has recently completed modifications to one of its fleet of Liebherr drilling rigs, supervised by the Ha Noi representative office of Liebherr-Werk Nenzing. Although only purchased in 2015, the company decided to upgrade an LB 36 with an extended Kelly bar, permitting increased drilling depths from 68m to 72m. The company also has a top-of-the-range LB 44 rig.
