Grade beam soil pressures
Grade beam soil pressures
(OP)
I am design multiple grade beams running between spreadfooters. The spreadfooters are for building columns which are isolated from the mat foundation that I am also design. So the spreadfooters and grade beams are the perimeter of the mat.
The spreadfooters go below the frost depth (2m) and the grade beams are just in place for the mat foundation, obvioulsy I can't make the mat 2m thick for the frost depth.
My question is should I apply the at-rest pressure to both sides of the grade beam, or apply at-rest pressure on one side and active or passive on the other side??
Thank you
The spreadfooters go below the frost depth (2m) and the grade beams are just in place for the mat foundation, obvioulsy I can't make the mat 2m thick for the frost depth.
My question is should I apply the at-rest pressure to both sides of the grade beam, or apply at-rest pressure on one side and active or passive on the other side??
Thank you





RE: Grade beam soil pressures
RE: Grade beam soil pressures
RE: Grade beam soil pressures
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RE: Grade beam soil pressures
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Grade beam soil pressures
PEinc & paddingtongreen: There shall be equal back fill on each side of the grade beam but as paddingtongreen has said the inside will be backfilled first during the construction process.
Ron: I have heard the use of both "footings" and "footers". Also, the lateral earth pressure is not negligible compared to other loads. The only other loads acting on the grade beams is the surcharge load. I might not have explained the grade beam properly.
I have a 2m heigh pier with a 0.6m spreadfooting. Say, the top of the pier is @ EL. 300mm, than grade is @ EL. 0mm. The grade beam will extend from grade to the bottom of the spreadfooting. So, it is not between just the spreadfooting itself but between the piers also.
RE: Grade beam soil pressures
RE: Grade beam soil pressures
I've attached a sketch to clarify what I'm doing.
RE: Grade beam soil pressures
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RE: Grade beam soil pressures
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RE: Grade beam soil pressures
My answer; apply active pressure on the inside only.
Why would you use lateral loads on both sides when designing for the temporary case with backfill on one side only?
RE: Grade beam soil pressures
Thank you apsix for answering my question.
I was applying lateral loads on both sides (at-rest pressure on the outside and active pressure on the inside) for a worst-case design.
RE: Grade beam soil pressures
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RE: Grade beam soil pressures
Only use active if you expect the grade beam to deflect due to the loading. At rest will result in more force, and designing for it should decrease the potential for wall deflection.
And as Ron said (first thing I thought when I read the OP) is that they are footings. Footers are at the bottom of the page. Just because people use the wrong term does not make it right.
RE: Grade beam soil pressures