Driveway connected or separated from retaining wall? 1

[AaronMcD]

I am designing a small 3 ft retaining wall that will retain a residential driveway. The owner plans to have heavy equipment driving over the driveway for future work. There is no geotech. The main failure concern is sliding force from equipment. Which sound better to you?

1) Design the wall to resist the forces via friction (0.3 assumed) and passive pressure (250 assumed, below top 8"). Keep the driveway separated from the wall.
2) Tie the driveway into the top of the wall to resist sliding.

The only concern I have with (2) is that I don't know the soil properties and I'm worried the driveway could settle or heave or crack under equipment, held in place at the edge. I would still need the wall to support itself and construction loads behind it. I was leaning towards (1). Typically I have a geotechnical engineer to tell me where he wants slabs tied to foundations and where he wants them to float.

http://www.hellodwell.design

 

[phamENG]

Sounds like the best bet is to not only keep them separated, but build the wall, do sub base and base for the driveway with an extra layer of stone, use the heavy equipment, then come back and scrape the excess stone and pour the driveway.

 

[AaronMcD]

Yeah, that's probably best, but homeowners can tend to be slow with their projects. Do one project, wait a year or three, do another, wait, etc.

I guess I'm wondering if it's really bad practice to tie it into the wall. The architect prefers them tied together for aesthetics and I don't like to be that guy that says "no" unless it really is likely to be a problem.

The driveway is not in my scope, nor are the future projects.

http://www.hellodwell.design

 

[phamENG]

Given the rather murky nature of the conditions under which this wall will be used in the coming years, I'd design it ignoring any benefits of attaching it but accounting for any negative influences.

Phasing projects makes it easier to pay for them, it doesn't make them cheaper. Building bigger to account for undecided future variables is one of the associated costs.

 

[BAretired]

Provide a ledge at the wall for the slab to rest on. Do not tie slab to wall. It can heave, but can't settle at the wall. Add bottom reinforcement for a length of five or six feet from the wall to enable the slab to span a short distance from wall to grade. If the ground settles, the slope is gentle. If the ground heaves, the slab is free to rise.





BA

 

[BridgeSmith]

I like the approach proposed by BAretired.

There's also the option to cantilever the retaining wall from the slab as a cutoff wall. It might require reinforcing more of the driveway slab than you would otherwise, but it simplifies the retaining wall design to providing a slab to wall connection that can resist the soil pressure moment - no foundation design, no overturning, and sliding resistance should be be easily adequate, unless the driveway is very narrow.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[EdStainless]

If he really wants the slab now then he will be buying more concrete and steel that he really needs in long run.
That might be enough to persuade him to go with the wall and gravel for now.
And that would make the ledge a good way to go.

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P.E. Metallurgy, consulting work welcomed

 

[BridgeSmith]

If the wall is built first, the cleanest way IMO is to extend the slab over the wall a little. Laying galvanized sheet metal on top of the wall that extends 6-8 inches off the back provides a good bond breaker so the slab and wall don't push and pull on each other.

Rod Smith, P.E., The artist formerly known as HotRod10