At-rest earth pressure?

Question

At-rest earth pressure?

cepe01 (Civil/Environmental)

(OP)

3 Oct 17 12:45

Please see sketch below. Is this a case where at-rest lateral earth pressure should be considered? The area between two existing walls is to be infilled to allow for some equipment to be driven over. I'm sure this question has been asked before but I've done a bit research and still am not clear which pressure to consider, and if passive is used the lateral load will be much greater. As I understood because the walls are restrained from movement, at rest should be used with a surcharge load for the equipment. Thanks.

fattdad (Geotechnical) · Answer 1 · 2017-10-03 12:56:43

use at-rest earth pressures.

f-d

ípapß gordo ainÆt no madre flaca!

Okiryu (Civil/Environmental) · Answer 2 · 2017-10-03 13:30:33

Same as f-d, I would use at rest pressures. Also, I would at rest pressures at both sides of the wall if you have soils under the slabs.

oldestguy (Geotechnical) · Answer 3 · 2017-10-03 14:56:25

OK on the at rest comment, but take the case of running compactors on backfill. Will any of the traffic be within 3 feet of the walls? Then you will get a higher pressure, possibly exceeding the vertical pressures. I've measured this situation and see the effect as far down the wall as 8 feet. How may times have the commentators seen walls tipped due to compactors going too close? I have.
The safer way is take the pressure at least the same as vertical.

PEinc (Geotechnical) · Answer 4 · 2017-10-03 16:04:23

How can anyone answer this when it is not clear, at least to me, what you are trying to do? Is there soil under the two upper slabs? Are you worried about pushing the two wall outward? Are the two upper slabs attached to the tops of the walls? Are the walls attached to a slab at the bottom of the walls?

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cepe01 (Civil/Environmental) · Answer 5 · 2017-10-03 16:14:31

Thanks for the replies! Okiryu and PEinc, there is no soil under the two upper slabs/other side of wall. The walls are attached at top and bottom. It is a small area which will have a dirt ramp to run a small excavator on. Not sure what the height of the soil will be at the moment.

oldestguy (Geotechnical) · Answer 6 · 2017-10-03 16:47:27

I'd double check those attachments of wall top and bottom and if not significant strength do some reinforcing of them.

EireChch (Geotechnical) · Answer 7 · 2017-10-03 19:37:52

what wall type are you using? I assume it would be some L shaped cantilever wall, however as there is no soil beneath the slabs, the L will have to extend into the fill which would be beneficial. Depending on the size of fill and span of track you may be able to join the two base slabs together.

You could may do a piled strip footing to support the wall either.

Id be interested to know the topography of the cross section as it extends into the page. Is it all at the same level?

PEinc (Geotechnical) · Answer 8 · 2017-10-03 19:58:33

If there was no soil on either side of the 2 walls, they aren't retaining walls. There may be insufficient steel in the 2 walls and bottom slab to let the walls act as retaining walls.

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EireChch (Geotechnical) · Answer 9 · 2017-10-04 07:20:26

PEinc - were missing a good description and more information from the OP, but isnt there soil between the walls as shown in the diagram. I would also be concerned with connections but they may be ok and just not shown by the OP in his post. I would envisage that a thickened base slab will be need (to replicate an L shaped wall). Again were all guessing without sufficient information.

PEinc (Geotechnical) · Answer 10 · 2017-10-04 17:41:18

EireChch, I agree with you. I am assuming that the brown soil shown between the 2 walls is the (temporary?) fill to be placed and no other soil is shown on either side of each wall. Therefore, they are not necessarily retaining walls. Therefore, I have concern for the wall reinforcing and connections and the footing (slab?) below the 2 walls. As usual, not enough information, too many answers.

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oldestguy (Geotechnical) · Answer 11 · 2017-10-04 19:17:21

So guys, what should he do in case, say they are merely masonry block walls? Maybe a temporary wood platform instead of fill? Add tension reinforcing rods on the other sides? Fill with weak concrete instead of earth?

PEinc (Geotechnical) · Answer 12 · 2017-10-04 20:02:27

It really depends on the width between the 2 walls and the height of fill needed. You could install some type of MSE or gabion walls to hold the fill without loading the 2 walls. You could make a temporary ramp out of timber deck mats. You could place large rip rap (high angle of repose) that does not touch the 2 walls and then fill over top of it with better graded material. You could possibly ramp up using street plates and cribbing.

www.PeirceEngineering.com

aeoliantexan (Geotechnical) · Answer 13 · 2017-11-03 18:04:26

There is a procedure on pages 7.2-76 and 7.2-77 of the Navy Manual, DM-7.2, for estimating the lateral pressure from compaction, knowing the roller characteristics and the distance of the roller from the wall. You can find DM-7.2 online for no cost.

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At-rest earth pressure?