To: <seaint(--nospam--at)seaint.org>, <seaint(--nospam--at)seaint.org>
Subject: Re:Retaining wall at property line?
Date: Tue, 01 Jun 1999 15:40:53 -0700
This is a common problem that generally can be solved with, what has recently
(in the last decade or two) been referred to as "top-down construction", and by
other more conventional methods. There are numerous solutions with different
pro's and con's depending upon parameters you have not yet disclosed such as (1)
depth of excavation, (2) earth material type, (3) groundwater level, (4)
construction sequencing requirements, etc. You mentioned "a" below grade floor,
therefore I will assume a 15-foot deep excavation.
When the excavation is only 15 feet deep or less, slot cutting (segmented
excavations) or cantilever cast-in-place reinforced concrete soldier piles could
be used. Permanent soldier piles could also be used to support the vertical
structural loads. Slot cut dimensions or soldier pile spacing is a function of
the retained earth material strength. A 15-foot excavation in sound quartz
monzonite may not require segmented excavations or shoring at all, depending
upon weathering, joints and foliations. But don't try this in Bay Mud or fill.
Therefore, you need to consult your qualified and licensed geotechnical
engineer, experienced with local construction practices. Pre-documentation of
off-site facilities is essential to reducing your risk.
Typically, gunite or shotcrete reinforced walls over drainage geocomposits are
constructed in slot cuts or between the soldier piles, in height increments
dictated by the earth material strength. Cast-in-place walls should also work,
but probably due to the construction sequencing and schedule, I have rarely seen
this used with top-down construction.
For deeper excavations in caving soils below groundwater, a slurry wall can be
used. This is definitely an expensive and complex alternative, but may be the
only viable alternative for deeper excavations in poor soils with shallow
It sounds like you did not want to use temporary soldier piles or sheet piles.
But these can also be used beyond conventional cantilever depths using internal
bracing (i. e. rakers, cross braced tubular steel, etc.). Of course, where you
have room to spare, a temporary cut slope is the most economical alternative.
None of these alternatives require off site intrusions. There are many more
Tom Benson at Lowney Associates, Pasadena (626) 396-1490
(don't talk to me about the Red Wings)
Subject: Retaining wall at property line?
Date: 6/1/99 4:49 PM
I am trying to find information on systems that will allow us to build a 5 story
building with a below grade floor adjacent to a property line. The adjacent
properties consist basically of homeowners with some light structures or a
We are currently trying to examine alternatives to build a retaining system
that does not trespass for anchorage or involve temporary structures on the
adjacent property holders land. The floor loads will come down on columns and
therefore the retaining wall is not currently intended to be load bearing.
we see that the shoring see that the shoring system will become part of the
structural system. Appreciate any advice...
Richard Lindenberg, EIT
Davis, Bowen & Friedel, Inc.