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Re: Retaining wall of sawdust

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Hello Joe,

You say that the sawdust is protected so that it doesn't get wet, but
what is the moisture content of that sawdust in the pile?  There are
some species of wood that will hold more that their dry unit weight in
water. The amount of water that a wood can hold is also dependent on
where in the log the wood is located, or what type of wood it is.

For instance, Western Red Cedar, a commonly used wood for fences,
has an average green moisture content of 58% for the heartwood and
249% for the sapwood.  The sapwood will hold quite a bit more water
than the heartwood.  Also the amount of heartwood or sapwood as a
percentage of the volume of the log varies quite a bit by species.

You need to find what the maximum moisture content is in the pile. Then
you will need to know the friction angle of the material in that pile.  I 
would expect the friction angle to go up with an increasing moisture content. 
 That is to say that the sawdust will be more prone to caking or adhering
to itself with more moisture in the pile.  That will help with the lateral
bearing pressure.  It may be that as the moisture goes up the friction
angle goes up to offset the increase in weight and thereby the affect
of that weight on the lateral bearing of the sawdust.

I just might have to write a spreadsheet to look at this, thanks for the

I'd be happy to help you look at this further if you'd like, and can get
more information.

Take Care,

On 13 May 2015 at 17:34, Joseph Goldbronn wrote:

> I have a project where we are repairing a building that is storing
> sawdust for a fire log manufacturer and I am wondering if anyone would
> have any information what the equivalent fluid active pressure would
> be of sawdust on a retaining wall.  I assume it is less than soil but
> just how much less?
> I should note that the sawdust is protected from the outside elements
> and
> does not get wet.
> Thank you to anyone who may have any insight on this one.
> Joe>

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