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A Timber Pole Ground Improvement solution was installed to provide the foundation for a concrete waffle slab for a new residential dwelling in earthquake-affected Christchurch.
MultiPole Uglie poles, 4.8m x 300mm, 160 pieces, were identified as being able to satisfy the stringent design specifications.
MultiPoles are incredibly versatile timber poles with a unique hollow core.
MultiPole Uglie poles are similar to SED poles but are debarked rather than peeled. They offer greater skin friction when used as piles and are stronger than SED poles.
The unique hollow core of the MultiPole allowed for fast installation via high-frequency vibration. This method of installation resulted in minimal disturbance to the neighbouring properties and no pre-drilling was required.
The dwelling needed to be able to withstand any future earthquakes.
It required a foundation solution that could support a concrete waffle slab.
The ground conditions were very soft, silty, liquefiable ground.
Site access was very restricted.
Piles had to be installed close to adjacent dwellings, but installation was not allowed to impact on these neighbouring properties.
Installation needed to be rapid.
Unloading and handling needed to be easy.
H5 treated Radiata Pine timber piles were determined as the best solution.
The piles were installed at 1.4m centres, and all 160 pieces were installed in one day.
The design was in accordance with MBIE guidelines with a replacement ratio of 5%.
A 200mm thick gravel raft was placed on top of the piles. Then a standard TC2 waffle slab was installed.
Piles were designed to mitigate liquefaction and transfer loads to a deeper layer.
TGI01 – Ground Improvement tech sheet
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