Briar Fleming - New Business Engineer
From the outside it might seem like screw
piling is reasonably straight forward.
Anyone who has tried it will attest to the fact that it is nowhere near
as simple as it looks, and one of the key influencing factors occurs before you
even arrive on site – the design of the piles needs to balance load carrying
capacity (make the piles bigger and stronger!) versus being able to actually
get them in the ground (make the piles smaller and more penetrable!). This skill is
something our specialist design engineers have honed over the many years we’ve
been operating in this one field – and are now at a point where they’ve almost
seen it all, having even installed screw piles into a coral reef in the
Maldives.
For clients we haven’t worked with before,
load testing is an area that can cause confusion and we have written a post on load testing helping to de-mystify the various reasons why we sometimes suggest doing a load test (as it allows a more
refined design meaning smaller or fewer piles on the project, thereby bringing
the cost of the main piling works down), and other times why the risk profile
dictates that a load test is highly recommended (the designer will want to
prove a bearing capacity of the ground and the corresponding deflection of the
pile).
However whether your project has load
testing or not, by working with Piletech you are benefiting from something no other screw pile design company in New
Zealand has. It’s a tech-y name but
it is an absolute golden nugget of our business and it is closely guarded. It is our 17 year old Load Test Database.
To put it very simply, when designing piles
you need to take into account the strength of the ground, the strength of the
pile, and a factor that correlates
the ground strength to the torque required to install the pile. This ensures the pile won’t break or refuse
prematurely whilst being installed to design ground strength. An example of this correlation is shown in the graph at the end of this post, taken from the upcoming IPENZ Practice Note on screw piles. This factor is variable and is dependent on
the screw pile configuration, depth, and soil characteristics. When Piletech was being established in New Zealand (coming from operating in Australia), one of
our five key mandates for best practice was to complete a load test for every
project to obtain this correlation factor.
Now, having been in this business for so long, this database of over
1000 load test results often means we can determine this factor without needing
to complete a load test. The years and years of experience installing piles
gives the designers and an additional nuance giving the piles the best ability to
penetrate through the ground.
Again, it’s the balance between making the
pile strong enough, whilst also able to penetrate that is one of the key areas
that takes screw piling from being pure science, into the area of art. This very valuable load test database cumulated
over 17 years sits behind every design we undertake and gives the client
confidence they are getting a cost effective and trustworthy foundation
solution for their project – we’re not called the screw pile specialists for
nothing.
