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[Cob] Coblist Digest, Earthquake test

Ian Marcuse dtebb at
Tue Apr 1 21:16:56 CDT 2008

There was alot of discussion after the Bam quake and reasons given 
for at least some of the damage, everything from differing qualities 
of construction between the older and newer, infestations of critters 
in the walls that weakend them.

Though only a model, our test preformed extremely well given the 
extent of the shake. Anyone inside would likely have survived as the 
roof did not collapse. Much can be attributed to the round shape and 
lack of joints. There was predictable failure at the top corners of 
the door where forces are exerted in different directions.

What probably would have helped would have been vertical rods, 
bamboo, or sticks to help prevent the lateral cracking. These could 
be integrated into both the foundation and top bond beam perhaps or 
even just built in randomly as the walls are being built up.

We also did not build a foundation. The model would have acted much 
different in that case, with possible significantly more damage had 
the walls slid off the foundation. It is very important to key in the 
foundation and walls as much as possible.


>Very interesting, it is great to have real technology applied to 
>earth and other traditional methods.
>I recall the destruction of Bam in Iran, that was earth buildings 
>that collapsed in dust with much loss of life.  How big was that 
>earthquake, anyone know ?
>  Is there anything in your construction that makes it more 
>earthquake proof? (Looks like the stucco helped) No doubt you have 
>researched other work in this area, there was a conference a year or 
>two ago.  There is a professor who has done work in Peru with 
>reinforcement, it is pretty convincing (I can find the name if 
>My guess is that the round design makes your structure much 
>stronger.  Most buildings are rectangular for several resons.  I 
>would think that in scaling, the 1/2 scale would make the circular 
>shape about 4 times as strong as full size but that is a total hunch 
>based on quite different model testing I have done.
>No doubt the engineering department boffs are on top of all that.
>Dean Sherwin
>    1. earthquake test video (Ian Marcuse)
>Message: 1
>Date: Tue, 1 Apr 2008 01:17:33 -0700
>From: Ian Marcuse <dtebb at>
>Subject: [Cob] earthquake test video
>To: coblist at
>Message-ID: <p0623098fc4179e7ec074@[]>
>Content-Type: text/plain; charset="us-ascii" ; format="flowed"
>Dear Cobbers,
>Finally after many years (we have been rather busy), we have some
>video footage up on our website showing our cob model undergoing
>siesmic testing at the University of British Columbia. It was an
>important test, the only such test done as far as we know on cob
>(though some testing on earthen structures was supposedly done in
>Iran, though we have no confirmation of this).
>The model was finally inflicted with a 2 g force shake, over 9 on the
>richter and did break apart, though much of the structure was still
>standing, which in a quake of this magnitude is very good as most
>buildings would collapse.
>Scroll down to cob siesmic test video
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>End of Coblist Digest, Vol 6, Issue 36
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