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Herein is the problem with the soil reports that causes grief
to many builders using deep foundations when they end up much
deeper (and more expensive) than expected.
The soil reports often do not clearly identify that a further
and deeper investigation is needed.
We can torque up a screw pile in a dense layer until it meets
its torque requirement and appears to satisfy the SWL requirement.
This is meaningless if it is sitting 200mm above a soft layer
as it can punch through and building settlement occurs. Only an
expensive static load test will identify that potential problem.
Conversely if the layer is several metres thick then it may be
possible to found the piles in that layer if we have confidence
that the Geotechnical capacity of the soils below that.
In order to design screw piles for your project, we need some
definitive results from your Geotech report.
Actual DCP, SPT or CPT results are required to accurately
design your piling system.
If your soil report recommends piles and does not identify the
soil capabilities for 2 plus metres beneath their base; then you
probably need to commission a deeper examination. Your Geotechnical
Engineer or Structural Engineer will advise the appropriate methods,
such as a continuous CPT probe with Pore Pressure and Sleeve Friction
readings or deep Borelogs with SPT density sampling every metre,
taken with a heavier drill truck. If the Engineer is not sure
of our requirements, he can contact us to discuss further.
Don't waste your money on foundations that could potentially
fail. Find out what is beneath your foundations and be sure that
they will support your building.
By spending a small amount of money up front and obtaining a
quality Geotech Report, we can actually save you money in the
long run.
A recent example - Broadwater
Sugar Mill NSW:
By having SPT results, at the building location, which went
some 8m deeper than the final founding depth, we were able
to confidently design the piles. The installation process
involved torque measurements of all piles every 500mm to correlate
the installation with the design.
This resulted in a 35% saving on piling costs on a major project
by using a quality report which enabled the pile design to
be completed with a high level of confidence. |
Here at Russell Heale, we are dependent on the accuracy of
the soil report which is supplied, as it is impossible to go out
on every site to make our own personal observations. Our Screw Piling
quotes are always based on this report. Variations are extra, however
we prefer to have it right and know what we would be up against
before going on-site. We are always concerned about the 'confidence'
level with your pile.
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Should you or your engineer need further
advise, please give us a call on:
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(07) 5593 7755
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