MALAYSIAN CONTRACTOR UCP Geotechnics recently completed foundations for a retail development at Petaling Jaya, near Kuala Lumpur, achieving an impressive production while rock drilling under demanding conditions.
In all, 1,239 bored piles were installed during the 11 month programme, providing load bearing and contiguous bored pile retaining wall for the eight storey retail development with two level basement for parking.
These included 118 piles with diameters between 900mm and 1,200mm, bored conventionally down to rockhead and then socketed into the granite bedrock, using Swedish tool manufacturer Sandvik's XL-24 down-the-hole hammer, fitted to a Soilmec 515 rig. The tool, designed to drill holes up to 1,100mm diameter in hard rock and consolidated overburden, achieved average drilling rates of 35 to 40 minutes per metre in grade two granite.
The contiguous bored pile wall was built along the northern and western site perimeters. Some 100, 1,050mm diameter piles were bored along the northern wall down to depths of between 20m and 30m. The western wall was formed with 900mm diameter piles to similar depths.
To eliminate bulging and allow easier casing retrieval, piles were bored 75mm apart, with the gap skinned with concrete to provide a permanent wall structure.