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Re: RR Tie retaining walls

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I was consulted on a failure of this type of retaining wall.  Quite often
there are sprinkler systems that water the greenery on the retained ground.
 The failure of the sprinkler system loaded the wall and it failed.  The
bearing load on the downhill side of the vertical tie is very high.  It
takes good embedment to achieve the acceptable soil bearing stresses. 
Typically the ties available are limited in length and the resulting
retaining wall height is quite low.  You might consider the addition of a
deadman with corrosion protected tiebacks.  
Mark A. Scott,  SE, Washington

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From: Bruno Côté <bocte(--nospam--at)ibm.net>
To: seaoc(--nospam--at)seaoc.org
Subject: Re: RR Tie retaining walls
Date: Wednesday, June 03, 1998 7:25 PM

Kathleen A. O'Brien wrote:
> 
> HI All:
> 
> I have an interesting problem.
> 
> A client wants to put in a wall consisting of Rail Road Ties spanning
> between columns. The columns will probably be fat telephone poles. The RR
> ties will of course be pressure-treated.
> 
> This particular developer did this a decade or so ago, and got it OK'd by
> the City (Thousand Oaks). I took a photo of the existing wall and it
looks
> really nice, and appears to have held up quite well. Of course the Code
has
> changed a few times since then.
> 
> Questions:
> 
> 1. Does anyone know how easy it would be to get RR ties and telephone
> poles?
> 2. Does anyone have any ideas on what allowable stresses would befor RR
> ties? I would probably assume stresses for redwood if I couldn't get any
> information.
> 
> Thanks for any input
> 
> Kate O'Brien, P.E.
> Simi Valley, CA
> 


This type of wall you are referring to is called soldier pile walls.

You really do not have to be to worried about the stresses in the
railroad ties as long as they are in decent shape. Actually, some
railroads would use these ties to support a 20 foot excavation and the
weight of the train with pile spacing at approximately 8 feet. I do not
have handy the allowable stresses for the ties, but could easily find
them if you want. 

Note that most people agree that not much pressure is applied to the
ties. Arching action transfers the load directly to the piles rather
than to the lagging. 

I would be more worried about the piles. In addition to having adequate
strength, make sure that you have enough embedment to resist overturning
and sliding. You can assume the passive pressure acting on three times
the diameter of the pile. The rule of thumb is that the embedment should
be twice the height of the wall. 

Bruno Côté
BOCTE(--nospam--at)ibm.net


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