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Re: Piling for a Marina w/ difficult soil conditions

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Gary,

I hope your client understands that free advice is usually worth every cent you pay for it. His best bet is to hire the specialist (or for you to hire him on a reimbursable basis) on a phased service basis.

Failing that I would suggest you consider driven steel piles (with driving tips if necessary) battered as much as practical with moment resisting top beams. Diaphragm bracing in the plane of the deck could be added to cantilever it out from shore for lateral stability.

To do without piling you could use floats together with diaphragm bracing.

Regards,

H. Daryl Richardson

----- Original Message ----- From: "Gary Hodgson & Associates" <ghodgson(--nospam--at)bellnet.ca>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, April 04, 2006 7:23 AM
Subject: Piling for a Marina w/ difficult soil conditions


List,

I have a tricky piling problem that I'm looking for some input on.
First of all, if anybody can think of a solution besides piling, that
would be fantastic.  The project is a building for a marina and the
developer has asked me to come up with piling (preferably for free,
of course) for the docking area.

The top of dock El. is 100', water is at 95', soil (gloop) is at 88'
thru 90' and then extremely hard glacial till at 82'.  The geotech
report gives hammer blow count for the till of 50 blows per 10 cm
(4").  The gloop is a mix of fill and native soil with an angle of
repose of 10 degrees or Ka = 1.0.

With my limited piling experience, I can't come up with an economical
proposal.  I have been told that piling will not penetrate very
deeply into the glacial till so I cannot rely on cantilever shaft
piling.  I can't put in horizontal tie-backs because the gloop
requires you to go back forever (approx. 70') to get some anchorage.
I can't put in sloped tie-backs into the till because of the
excavation and penetration into the till.

I've spoken to one engineer who does nothing but piling who stated
that this is an unusual problem but he wants to be hired before
offering any opinions.  However, the developer doesn't want to pay
him to come up with a solution he can't afford.  I'm looking for any
and all suggestions from the brains here on the list as I'm running
out of ideas.

TIA,
Gary

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