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Re:Drilled Pier Question

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Pier diameters can be a function of the earth materials.  For example, in
southwestern river channels with gravel and cobbles, small diameter piers are
difficult to auger.  To answer your question, though, in clays and silts, a
12-inch diameter bucket auger can be used.  Nevertheless, this is unusual in
Southern California (at least).  Typically specified minimum diameter in soils
is 18-inches.  Size increments typically are 6 inches (e.g. 24, 30, and 36
inches).  I suppose you could auger a smaller diameter hole (4 to 8 inches), but
plumbness, reinforcement spacing and cover, concrete placement, and bending
strength for the retaining wall can all become problems.

Tom Benson, GE, at Lowney Associates

____________________Reply Separator____________________
Subject:    Drilled Pier Question 
Author: <seaint(--nospam--at)>
Date:       11/21/98 6:15 PM

What is the minimum shaft diameter possible and what is the increment in
diameters?  I am currently investigating the possibility using a single row of
drilled piers to laterally support a retaining wall for a flood control
channel and would like to keep the pier diameter as small as possible.

Bob Conley, P.E.