Allowable Bearing Pressure For Backfill
Allowable Bearing Pressure For Backfill
(OP)
Due to a metre of soft ground below the proposed basement, we've been advised in the geotech report to dig it out and replace with compacted material. Although the report gives allowable bearing pressures for the clay (that will be below the backfill) I guess we really need bearing pressures for the granular soil, as this is what the basement sits on. Is it possible to work on a typical bearing pressure for say medium/dense granular material and then state this is what we require on the drawings? Settlement must also be an important consideration in backfill and I'm presuming this can be calcuated and a geotech engineer is best suited to do this. Is that correct?





RE: Allowable Bearing Pressure For Backfill
RE: Allowable Bearing Pressure For Backfill
Compacting the first few lifts could pump the clay right into the fill. You might consider putting down a geotextile to keep the clay from pumping through, before you start backfilling.
RE: Allowable Bearing Pressure For Backfill
If you have questions I recommend you go back to the geotech and ask why. For all we know there could still be relatively soft soils that are governing bearing capacity.
Hope this helps.
RE: Allowable Bearing Pressure For Backfill
It is often tempting to relate this directly to the strength of the soil layer. However, bearing pressure "failure" is rarely the governing mechanism for foundation design. Much more often, foundation design is based on performance (i.e., to limit settlement). As long as there is increased stress in the soft soil layer, you need to remain concerned about compression of this layer.
I just point out the obvious: You have a geotechnical engineer working on your project and are receiving feedback from civil/environmental and structural engineers. Two professions that I respect, but this is a geotechnical engineering issue.
f-d
¡papá gordo ain't no madre flaca!
RE: Allowable Bearing Pressure For Backfill
RE: Allowable Bearing Pressure For Backfill
RE: Allowable Bearing Pressure For Backfill
RE: Allowable Bearing Pressure For Backfill
RE: Allowable Bearing Pressure For Backfill
Now you need to figure out if the sample for the undrained shear strength represents the entire soil in the "increased stress zone." You also have to determine whether the foundation performance will be governed by consolidation (i.e., saturated conditions - 1-D consolidation) or compression (i.e., soil modulus). Typically the settlement derived from the empirical bearing formula is too great for servicability (i.e., the footing will settle too much).
Hope this helps.
f-d
¡papá gordo ain't no madre flaca!