Makatote Viaduct
ONTRACK

The North Island main trunk line is a vital link in New Zealand’s economic activities. The line crosses the Makatote River on the high and slender Makatote Viaduct, but river erosion threatened the foundations of one of the viaduct’s piers, creating an unacceptably high risk of catastrophic failure. The chosen remedial design solution involved transferring the pier load to two deep piles via a post-tensioned concrete cross beam.

The existing pier foundations were built into a mix of volcanic boulders and pumiceous material. The material was sensitive and could be destabilised by construction vibrations, so a more delicate oscillating pile driving system was used. A telescopic casing design was applied to deal with a troublesome aquifer.

The project team’s solution used world best practice to drive the piles and displayed considerable ingenuity in overcoming problems. The project makes a significant contribution to the reputation of New Zealand engineering.

The judges considered this outstanding piece of structural engineering to be world best practice in retrofitting. They unanimously agreed that this innovative project demonstrating both technical and contractual skill resulted in a fine example of engineering excellence.

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