Buoyant or saturated weight to stabilize cantilever ret. wall?
Buoyant or saturated weight to stabilize cantilever ret. wall?
(OP)
I have a bridge abutment providing also as an open hydraulic channel wall. The geotechnical report mentions to take hydrostatic forces into account wrt applied loads to the wall. All this being done, my question is what do I use for my stabilizing weights on the heel? Buoyant or saturated weight of concrete and soil?
Thanks
VOD
Thanks
VOD





RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
good luck
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
Could you give us some idea of what you mean by using the bouyant unit weight of the concrete? Are you refering to accounting for the uplift force from the water that would act on the bottom of the wall? I agree with RWF7437, you need to look at combinations of backfill water conditions and channel water conditions and select the most critical. The most critical for sliding or overturning might be a rapid lowering of the channel water level with a saturated backfill.
Could you give us some idea of what design cases you are considering so that we can comment on what forces you may be using in the analysis?
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
By the way gandersen, I am using typical combinations found in bridge codes such as Dead + Earth + Water + Live, etc.
I will be using special draining material behind the wall.
Regards
VOD
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
What kind of special drain are you using? I've seen some good specs where the drainage layer against the wall is given, then you place necessary filters to the embankment - still, I have also seen the embankment soil be the "base" and you put filters against the wall - haven't figured this out yet! If you have weepholes, make sure that you have the hole "plugged" to prevent loss of fines/gravel. Try placing the weepholes going "up" to the outside rather than "down". Aggregate, even under water pressure, don't roll up hill well!! Make sure outlet for base drain - sometimes, I've seen it put too deep - it needs to be just above, in my view, normal water level.
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
To me, there are only one circumstance where buoyant weights matter: for all soils (and concrete) below the level of the flow in the channel, or the groundwater level - whichever is highest.
I don't see another circumstance where buoyant weights would apply. Anyone else have an idea?
Please see FAQ731-376 by VPL for tips on how to make the best use of Eng-Tips Fora.
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
The special drain I refer to is 600mm thk of graded stones, no less than 3/8" diameter, from the interior of the wall for the entire height of the wall and wingwalls with filter fabric between the backfill and 600mm thk drain.
I cannot see the build up of hydrostatic pressure with this setup as the water will drain as the water level drops in the channel. The abutment sits on sandy soil.
Regards
VOD
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
Of course for submerged situations, only the buoyant weight is standing and is the one than must be used.
RE: Buoyant or saturated weight to stabilize cantilever ret. wall?
VOD