MEMBRA vertical pipes normally used to drain surface water through a clay layer to permeable material below have been adapted by Cobra to form piles supporting 28 km of track in Malaysia. The company is hoping for an order covering a further 50 km on KTM’s Kuala Lumpur - Padang Besar main line.
In the AuGeo system, 150mm diameter perforated pipes up to 25m long are forced into the soft ground by a vertical piling rig. The bottom end of the pipe is capped by a steel mandrel that is withdrawn up the centre when a firm layer of sand is reached. A reinforcing cage is lowered down the pipe, and a liquid cement and sand grout is forced in. This forms the pile when set, and a 300mm square cap is cast on top.
Four rows of piles are drilled, forming a grid at 1m spacing. Once the caps are cast, a geotextile grid is placed across the top of the piles, and a shallow embankment is formed above that. Each pile is designed to carry a load of 30 tonnes.
Cobra BV, Netherlands
Reader Enquiry Number 144
