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Letters

01 Jul 2003

Piling problems

Sir - We regret that your Product News report 'Drains become piles' (RG 5.03 p325) has mixed up two of Cofra's range of soil consolidation and foundation technologies. MebraDrain has nothing to do with our new AuGeo system.

Cofra's AuGeo system consists of concrete piles formed in the ground to provide a foundation that is free of settlement. It is being used on a large scale for upgrading the 180 km line between Kuala Lumpur and Ipoh in Malaysia, where the single track is being doubled between Rawang and Ipoh. Cofra is installing AuGeo to support about 50 km of this second track. AuGeo provides a low maintenance infrastructure which can be achieved rapidly in an economical way wherever highly compressible soil is present, needing immediate stabilisation.

Piled embankments are often used where the construction needs to be delivered free of settlement to tight time schedules. AuGeo consists of a large number of small piles set out in a square or rectangular pattern. The piles have an enlarged foot bearing on the deeper sand layer, and a load-spreading construction consisting of a layer of aggregate packed between two layers of geogrid with very low elasticity is put on top of the pile heads. This spreader mattress ensures an even distribution of forces over the piles.

A complex part of the track in Malaysia is the application of AuGeo on a stepped alignment. In order to install this line correctly, the choice was made to apply the system in phases. Cofra has set up its own production line in Malaysia in order to have the concrete pile heads and reinforcement baskets at its disposal on time. Despite benefiting from the local expertise and contacts, Cofra retains final responsibility for correct implementation.

AuGeo can be used at depths down to 25m, and installation is rapid, vibration-free and low-noise, without any environmental effects. It is relatively inexpensive as compared to traditional systems.

Aside from the high production rate, raising the embankment immediately to the full height is possible, without risking instability. There is no settling period, which makes AuGeo highly suitable for embankments for new roads and railways.

Adeline de Vries

Cofra BV

Netherlands