Foundation system protects from liquefaction

00:33, Feb 15 2013
liquefaction foundation
NEW TECHNOLOGY: Jon Hambling, Firth technical manager, demonstrates the foundation design.

A new foundation system created in New Zealand to protect Christchurch home owners from earthquake liquefaction is being unveiled today.

Canterbury Earthquake Recovery Minister Gerry Brownlee launched Firth's latest RibRaft technology which allows floor construction to sit on the ground, not in it.

The product has been developed to provide solutions for residential housing and light commercial buildings in post-earthquake Canterbury.

Previously the product has been available for use only on land labelled TC1 and TC2 but Firth has created a solution which can be used widely in TC3 areas, where there are around 28,000 homes.

Around 12,500 of these homes have major foundation and pile damage that will require more investigation of the ground around them.

This means engineers need to look at TC3 land more closely and decide what foundations are needed so the property will perform well and be safe in future earthquakes.


"On TC3 land moderate to significant damage from liquefaction is possible in future significant earthquakes," Firth general manager Andrew Moss said.

"After eight months in development, we have now created a viable, cost effective TC3 foundation option which will help give home owners and builders more peace of mind."

Moss said the city council approved the first set of plans using RibRaft TC3 - for a new home in Hoon Hay.

Firth's RibRaft is seismically strong, energy efficient and cost effective due to reduced time and labour required. It is also less disruptive on the land as it lessens excavation.

The TC3 system comprises of upper and lower slabs that can be jacked apart following an earthquake that causes settlement, allowing the house to be re-levelled quickly and easily with reoccupation inside four weeks.

In the event of another earthquake, the foundation can be re-levelled by a builder rather than requiring specialist personnel.

"There's been extraordinary demand for the Ribraft EQ version which now accounts for a third of all new building foundations in Christchurch. We now expect strong demand for RibRaft TC3 which may well be the answer to the prayers of many," Moss said.

The Press