By Annabelle Tukia
Simulated earthquake testing in Christchurch is angering some residents whose homes are being shaken.
Building foundations on liquefaction prone land have been put through a simulated 7.5 magnitude quake at Christchurch’s QEII stadium.
One of the tests lasted ten seconds and was not unlike what the city has been experiencing for the last 18 months.
Nearly 300kg of explosives were used to simulate earthquake forces for the purpose of testing building foundations.
Tonkin and Taylor geotechnical engineer Peter Millar has been involved in the tests.
“In the test panels there the magnitude would have been close to 7.5. This is what we've designed this to, but what happens is the energy dissipates with distance away and so by the time it’s got to the nearest residence it's at a very low level.”
But after enduring months of earthquakes and aftershocks some residents say this second round of testing at the stadium is the last straw.
Keith Mackay is not happy.
“It was much greater than I expected, in short it was frightening.
“Actually this house raised. I was on the telephone looking out the window at the time of the explosion and visibly noticed the house lifted.”
In a round of testing last November four different foundation systems were tested and Mr Millar says that revealed one in particular that coped well with liquefaction processes.
Today's testing was about refining those results.
“By stabilising a layer about 2m deep with cement, and what that does is it confines the material underneath and reduces the levels of settlement.”
Although the testing is in its early stages, it is already generating interest with nearly 10,000 homes in Christchurch sitting on liquefaction prone land.
EQC Canterbury events manager Reid Stiven says it is necessary.
“EQC are trying to establish whether we’re able to effect repairs to land in tc3 categories [blue zones] that are cost-effective and durable and may allow us not to have to go down the track of a site specific foundation development.”
Tonkin and Taylor say today's testing is likely to be their last at the site, which should be good news for the QEII residents who say they have had enough.
3 News