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# Re:RE: Rockery Retaining Walls

• To: <seaint(--nospam--at)seaint.org>, <seaint(--nospam--at)seaint.org>
• Subject: Re:RE: Rockery Retaining Walls
• From: tbenson(--nospam--at)lowney.com
• Date: Wed, 13 Jan 1999 10:14:29 -0800

```Is there such a thing as a "one man rock"?  As a Geotechnical Engineer, I
suppose I should know the answer.  But I don't (not in ASTM D 653-97).  I hope
the original author will define this, and describe the origin of their
definition.  My hypothesis is that it is a boulder which requires 2 to 3 workers
to move.  How powerful are the "men" and how far do they have to move it remains
a mystery.  Can we convert that to Newtons or Joules, or should it be a unit of
mass?  A boulder is precisely defined as "a rock fragment, usually rounded by
weathering or abrasion, with an average dimension of 12 inches (305 mm) or more"
(ASTM D 653-97).

On the more serious side, I agree that this "retaining wall" probably should be
designed as a gravity wall, and will require a sloping face.  The slope face
will be a function of the interlocking ability of the boulders (or angle of
repose).  Although the previously mentioned 0.25:1 (horizontal:vertical) face is
common for crib walls and the like, this may not be very stable for well rounded
boulders, depending upon the composition and geometry of the boulders.  What is
the consequence of failure of this wall?  Not to overanalyze or over-engineer
the problem, but if you must carefully engineer this wall, the most formidable
problem is to define the strength and interlocking characteristics of your
boulders, including durability.  I will say this, a boulder wall probably drains
well, and if the boulders are durable, will work well on shorelines.  You may
also contain the boulders in cribs (reinforced concrete or metal), or in
gabions. (Gabion is not in ASTM D 653-97, but is in my 1973 Webster's New
Collegiate Dictionary.)

Tom Benson at Lowney Associates
tbenson(--nospam--at)lowney.com

Subject:    RE: Rockery Retaining Walls
Author: <seaint(--nospam--at)seaint.org>
Date:       1/13/99 9:33 AM

I sure hope someone answers this so that I don't have to show my ignorance too.
JDC

-----Original Message-----
From:        Charley Hamilton [SMTP:chamilto(--nospam--at)eng.uci.edu]
Sent:        Tuesday, January 12, 1999 4:05 PM
To:        seaint(--nospam--at)seaint.org
Subject:        Re: Rockery Retaining Walls

I must admit ignorance (no surprise to anyone out there, I'm sure).
What exactly is a 2 to 3 man rock rockery wall?  Perhaps the question I really
want answered is "What is a 2 to 3 man rock?"

Charley

---------
Charles Hamilton, EIT                                Phone:        949.824.8257
(office)
Department of Civil and                         FAX:        949.824.8694
Environmental Engineering                        Email:
chamilto(--nospam--at)eng.uci.edu
University of California, Irvine

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