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Ashby’s is on the cutting edge of liquefaction resistant ground remediation

The Christchurch earthquakes have spurred new research into how to provide cost effective ground improvements to minimize liquefaction for residents and businesses rebuilding on the area’s sand and gravel soils. Many traditional methods are complicated by the very high ground water levels, layers of liquifiable sands and gravels and lack of a solid subsoil founding layer in many parts of the city.

The Canterbury Earthquake Recovery Authority (CERA) has been sponsoring actual in-ground testing of various liquefaction remediation options including the use of “Short Pile Rafts” to limit liquefaction. The latest testing took place in November and December of 2013 in known bad ground within the Red Zone of the city. The test set up a number of different remediation options along with monitoring equipment within a circle of explosive charges which were detonated in a timed sequence to exert similar effects on the ground as an earthquake. The explosions were severe enough to liquefy the ground throughout the test zone for a depth of up to four metres however the ground within the short piled raft did not liquefy.

While the formal results of this testing are still being published the results have been released in public geotechnical meetings and while this method is not as yet within the MBIE Guidance Document we predict that within the next 12 months it will become the preeminent method for dealing with, and building on TC3 land both because of its effectiveness and cost savings relative to other options.

Based on the results of these tests, as well as other similar design work Ashby’s has reviewed both within the country and internationally, Ashby’s has developed a Short Pile Raft design methodology along with foundation designs to limit potential liquefaction and settlement for residential and light commercial construction on TC3 sites. To learn more about Ashby’s Short Pile Raft remediation and foundation design contact the Ashby’s Christchurch office.

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