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Re: soils pressure

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If i understand your question correctly, the purpose of free draining fill, which usually wrapped around by mirafi filter fabric is only to release hydrostatic pressure. It will not counteract  full lateral soil pressure against the wall.

In the past, I have designed many retaining wall as a basement wall by assuming additional support at the top of the wall. To determine if the top support (floor diaphragm) is sufficient, it really depends on the condition of the other end of the room. Keep in mind that the pressure at the top of wall is less than on the bottom of wall due to triangular soil loading.

I would be skeptical if the soil would be able to stand almost straight up for 12? (+ footing thickness) without any means of shoring during the duration of the construction.

I hope this help.

Hadi Djohan, P.E.
Brooker Engineering, NY

Joe Grill <jgrill(--nospam--at)> wrote:
I have been asked to design a basement wall with a 12' retained height of
soil. There has been no geotechnical review of the residence, but the
architect, who has done other work in the area, tells me the cut will
probably stand almost vertical. If this near vertical face is just a couple
of feet away from the wall and the backfill is a free draining fill, will
the fill be able to achieve full lateral soil pressure against the wall.
The architect/contractor/owner wants to use the floor diaphragm to restrain
the top of the wall. If the full lateral soil pressure is achieved then the
diaphragm doesn't have the capacity to restrain the wall. I have suggested
a geotech be brought in to look at the excavation and make recommendations
at that point, but of course that hasn't been received very well. If the
full soil pressure is not activated will there be any pressure at all and
how is it calculated.

Any ideas?

Joseph R. Grill

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