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Posted by on September 6, 2006, 2:16 am
Michael Daly wrote:
> tim@wetfoot.net wrote:
>
> > My questions are how does this plan sound overall, is there anything
> > you would do differently or add? Should I add any sort of landscape
> > cloth behind the rocks or plastic to keep the water from seeping out or
> > would that create too much pressure? On a wall of this height should I
> > place any rocks perpendicular that would sit back to the ground
> > formation and backfill over them? I guess this should add more strength
> > to the wall..
>
> What you need to do depends on the slope and the type of soil. It can also
> depend on the water table depth and rainfall.
This is the pacific NW so plenty of rain falls in winter, though now
it's dry 2 feet below the surface. Last winter it seemed water was
coming out of the toe about a foot lower then grade.
>
> If you build a retaining wall to hold up flat-topped soil, you are only holding
> up the soil closest to the wall. If the surface is sloped enough, however, you
> are holding up a potentially big chunk of the hill.
makes sense, my property has a natural slope coming down from the hill
above
> If the soil is prone to loosen up a lot when wet, then it could come down. At
> one extreme, soils can liquify in an earth tremor and your wall has to be a
dam.
> I doubt you have that situation, but you have to consider that.
not sure how loose it gets but it can rain quite alot late fall, winter
and early spring. ;-)
> Removing the toe of a slope can cause the water to drain and wash out the base
> behind your wall. This is especially true if the water table is usually high.
> Another worst case scenario, but a vertical filter fabric can avoid some of
that.
is a vertical fabric something like whats shown in the last picture on
this page? - http://www.millerengrs.com/rock_walls.htm
> Buttressing the wall into the hill is always a good idea IMNSHO. That or some
> kind of crib arrangement makes for a more solid wall. It can be cheap
insurance.
I'm guessing buttressing is laying a few of the rocks perpendicular to
the run of the wall and into the hill. how would you crib the rocks?
> A phone call to a local foundations engineer could tell you if there are
problem
> soils in your area. If not, you plan seems relatively sound. If the hill is
> quite steep, though, you might want a pro to look at it.
was considering this as well, will have one come out and give me an
assesment.
Thanks!
> Mike
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