Lateral pressure
Lateral pressure
(OP)
I am just wondering, what test do you guys use to get the active and at rest lateral pressure? Everytime we get a soil report from this company, we always get high numbers. We are starting to think it is the company, not the soil. We just want to do a little research before we question her numbers. Everytime we get a soil report from them, we get 60-70 pcf lateral pressure. I've done soil tests before when I was an intern but I dont remember having to calculate lateral pressue.





RE: Lateral pressure
RE: Lateral pressure
RE: Lateral pressure
Complete Text Online (Free)
See Chapter 8
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RE: Lateral pressure
It is therefore important to discuss with the geotech about the project and design concepts to get a more refined value.
Very often referrals are "drill some holes and provide a soils report".
I would consider the numbers given to be preliminary which could be refined when details of project re structural design concepts are provided. This assumes that such has not been done before.
SlideRuleEra has provided info on how the pressures are determined generally. However, note that other factors that may be dictated by construction, site conditions after construction etc may have an influence on the numbers.
I would recommend speaking to the Geotech about the information provided after reading the info re SideRule Era.
Testing to determine phi values would require knowledge of material to be used as backfill and is normally not done for routine projects. Codes tend to provide lateral pressures that are applicable for certain structures etc, but here again be sure that these do not have to be modified for site conditions.
RE: Lateral pressure
RE: Lateral pressure
RE: Lateral pressure
I had the opportunity once to measure wall pressures on a wall 40 feet tall at least, backfilled with bank run sand. The wall was part of a building with no opportunity to deflect under load. We asked the designer to use an equivalent fluid of 35 p/cf. As compactors worked on this sand, in layers, the pressure sensors showed pressures going up much higher than this 35.
I also noted that when a heavy duty hand guided plate compactor was working next to the wall, the sensor some 12 feet lower showed a slight increase with each pass of that compactor.
So, what should we do?
It was obious the compaction effect was causing a wedging of that soil next to the wall.
First we changed the compaction location to outside an 18 inch limit, then going to 24 inches as the closest compaction work. Then,the design pressure came out on subsequent wall backfills. Keep the compactors away from the wall face by a distance sufficient to allow some looser zones next to the wall.
No problem with settlement, since that vertical uncompacted zone acts as a cushion and soil hangs up on both the wall and the compacted earth, the "silo effect".
Maybe your "high numbered guy" did some measuring as I did and the backfill was compacted right next to walls and that is his reasoning. Remember, to achieve active pressure, that wall has to move or the soil has to compress some.
The final result depends on YOUR SPECIFICATION.
Many a wall has deflected excessively due to heavy backfill compaction.
RE: Lateral pressure
RE: Lateral pressure
RE: Lateral pressure