Compacted or non-compacted fill under ramp?
Compacted or non-compacted fill under ramp?
(OP)
Please see the attached detail/section for an exterior concrete ramp which is somewhat of a standard starting detail I came across. We are in the midwest, so frost & snow are common.
Looking at this detail it appears that the slab is not spanning between the walls on each side since its only doweled into the walls and not bearing on them. So I am guessing that the slab itself sits on grade. Which raises the question of why this detail shows non-compacted granular fill? If the slab is bearing I would want the sub-grade to be compacted. Is it possible that compacted base heaves more in frost then non-compacted fill? That is the only reason I can think of why the fill could be non-compacted.
Amount and location or rebar in the walls is also an issue I have with this detail but my question is focused more on the fill.
Thank you.
Looking at this detail it appears that the slab is not spanning between the walls on each side since its only doweled into the walls and not bearing on them. So I am guessing that the slab itself sits on grade. Which raises the question of why this detail shows non-compacted granular fill? If the slab is bearing I would want the sub-grade to be compacted. Is it possible that compacted base heaves more in frost then non-compacted fill? That is the only reason I can think of why the fill could be non-compacted.
Amount and location or rebar in the walls is also an issue I have with this detail but my question is focused more on the fill.
Thank you.






RE: Compacted or non-compacted fill under ramp?
RE: Compacted or non-compacted fill under ramp?
RE: Compacted or non-compacted fill under ramp?
Seriously, I have never seen somebody not compact subgrade for frost protection, but I can understand the logic. I wouldn't do it, but it is difficult to frost protect a ramp. In any event, if you want to span the slab with dowels, there's no reason you can't use shear friction principles. It's done all the time. If you check the numbers, #4 @ 18" o.c. probably works just fine, as long as they're developed on both sides of the joint.
RE: Compacted or non-compacted fill under ramp?
RE: Compacted or non-compacted fill under ramp?
If frost heave is a concern, there are a variety of voidformers available. It is better to compact the fill, although granular fill may not need much compaction.
BA
RE: Compacted or non-compacted fill under ramp?
1) doesnt look like it provides minimum cover for concrete in direct contact with ground per ACI.
2) The embedded post base detail is not good and not allowed in many jurisdictions. Plate with Anchor bolts has been standard for a few years now.
And obviously the retaining wall vertical rebar placement is a fail.
RareBugRA
RE: Compacted or non-compacted fill under ramp?
I'm shocked that you don't "believe" in shear friction. I guess it's been in ACI 318 all these years without merit. Shear friction is a clamping mechanism due to tension in the reinforcing, not bearing on dowels. I've personally used it in several serious situations where dowel bearing strength alone wouldn't even come close to cutting it. The most serious one has been there for about 20 years now.
RE: Compacted or non-compacted fill under ramp?
Two other quick points... agree with BA, shear friction needs to be on the tension side of the joint.
Regarding hokie's comment about corrosion, my serious use of shear friction was in a cast-in-place parking garage.
RE: Compacted or non-compacted fill under ramp?
Sorry, I'll stop. I realize shear friction was not the original question in this thread.
RE: Compacted or non-compacted fill under ramp?
I think the thought behind the use of the dowels is to brace the walls so that they are not pure cantilevers.