Gravel Lateral Pressure for Small Backfill Space

Question

Gravel Lateral Pressure for Small Backfill Space

MtnManBob (Structural)

(OP)

27 Sep 11 17:09

Have a condition where the inside face of a handicap ramp wall is located just 4'-5" from the outside face of building fdn wall. The building fdn wall retains 12'-9". Handicap ramp goes from lower grade to top of building fdn wall (12'-9"). Filling space btwn walls w/ 3/4" clean gravel. Seems to me the distance btwn walls is too small to mobilize full soil wedge so the EFP should be reduced. What EFP should the ramp wall be designed for?

CarlB (Civil/Environmental) · Answer 1 · 2011-10-01 01:47:10

Yes the EFP can be reduced, below a certain depth.
Has been discussed in a few threads, here are a few:

thread255-232396: Retaining Wall - Active pressure with rock face within failure plane
thread255-280817: Reduced Lateral Pressure For Back to Back Walls

fattdad (Geotechnical) · Answer 2 · 2011-10-03 10:48:56

When the angle 45+phi/2 (measured from the horizontal) intersects with the opposing retaining wall, the horizontal stress is at the maximum value.

f-d

¡papá gordo ain't no madre flaca!

csd72 (Structural) · Answer 3 · 2011-10-10 08:28:36

Go back to first principles and calculate the size and shape of the soil wedge to give you the actual stress.

Taking the friction between the wall and the soil may also make a significant difference in this case.

FixedEarth (Geotechnical) · Answer 4 · 2011-10-10 15:37:54

EFP = ka x Gamma. Assume ka = 0.22 (phi = 40 Deg.) and gravel unit weight to be 90 pcf, then EFP = 20 psf/ft. The 4.5 ft backfill width is plenty.

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Gravel Lateral Pressure for Small Backfill Space