Retaining Wall System without Demolition of Road 5

[elinwood]

I have a project "retrofitting" a "retaining wall" and I'm having trouble selecting the type of retaining wall. You'll see why I put those two words in quotation marks below:

A brick wall was erected between our property and the neighbor's property. There's initially no need of a "retaining wall" because originally, the ground level between our property and the neighbor's property was relatively level. On our side of the brick wall, there's a concrete gutter 80 cm wide and 80 cm deep. Further into the property is a 12 meter wide road designated for very heavy loads (the property is a warehouse) The neighbor decided to excavate their property resulting in a 2 to 7 meters of elevation difference.

Due to the difference of elevation, the earth (w/ the brick wall and the foundation) has now collapsed. I'm in a country where lawsuits aren't exactly useful so there's no use in finding out whose fault it is. Since the road is already built - and is not damaged, is there any hope of salvaging the road ? The owner is pretty insistent on salvaging the road. I've thought about using MSE walls and RCC Walls with counterforts but all these methods involve demolishing at least 3 meters of the 12 meter wide road for construction of the retaining wall.

The other issue is, if we did end up salvaging the road, the contractor evidently didn't do a very good job on it. The road was only 13 cm thick and there was no subbase whatsoever - which probably contributed to the wall collapsing. I'm concerned that if the old road was re-used, there will be major settlement issues (the current "sub-base" is clay).

 

[elinwood]

I thought pictures would be useful to it's attached

 

[dcarr82775]

Tangent pier walls or soil nail walls come to mind. I am not a believer in the 'A-frame' micropier walls I see built at times.

 

[dcarr82775]

I should have looked at the picture first.

I think a tangent pier wall could work although you will loose a little bit of the road to put it in. You could drill soil nails or anchors into the face of the existing wall (from above so a bit more difficult drilling) and then shotcrete the wall for new structural facing.

Somehow have to address the 'loose' soils under the road. Not sure what would work best for clay.

 

[DDBPE]

Can you get a drill rig in on the lower side? If so, how about a soldier pile wall with lagging.

 

[oldestguy]

Consider removing the wall. Then drive heavy sectioned sheet piles at that aligment, sufficiently deep to cantilever except for the greatest height to be retained. It would be there where diagonal anchors should be driven down at an angle into your property.

All of this should be designed first. A boring would help a lot also.

I suspect the 7 meter elevation difference is some distance away from the property line, or a lot more would have collapsed.

The paved ditch may need sealing of joints.

 

[msquared48]

Any way of saving the wall by using tiebacks drilled through the wall and under the existing roadway?
Removing the wall will undermine the road.



Mike McCann
MMC Engineering

 

[cvg]

why would you "save" a non-structural brick wall? the brick wall is not helping your roadway much, if any. maybe you can't sue the neighbor, but you could certainly impose on him to allow you access to the bottom of the slope to bring in your rig or other construction equipment. then install sheet pile, soil nails or whatever your geotechnical engineer recommends. without geotechnical investigation and analysis, you cant get much further in the weeds than that.

 

[msquared48]

Got it. I thought the wall was more extensive.

Well, then soil nailing, possibly combined with shotcrete.

Mike McCann
MMC Engineering

 

[elinwood]

I don't think my post was very clear. We're supposed to demolish the wall and re-construct everything underneath the wall (drains etc.). The wall isn't structural. The only thing that we're trying to save is the road. Another engineer proposed a counterfort RCC wall, but there's just no way to install the RCC wall's footing without demolishing the road. Then again, if I can convince the owner that demolishing the road and re-building it is a cheaper solution, the owner might go for it.

We can't get a drill rig on the lower side. The clear distance available was only 1.5m from the wall to a building on the neighbor's side of the fence. We can get it through our property's side though, but I'm not sure how we'd install the soldier pile from our side.

We thought about soil nails but we're not sure how to address the consolidation issue that will emerge from that - there's no way to compact it with the road already constructed. Shotcrete is a good idea to save the road, but it sounds expensive. We've checked into sheet piling and the cost was too high here.

I'll look into either soldier piles or soil nailing with shotcrete and compare it with a simple MSE-wall with road demolition and see which one is cheaper.

 

[oldestguy]

If the road can be removed, and with all that room, you can consider other types of walls. If your concrete plant saves the reject and returned concrete, saved in forms, those concrete blocks make a great MSE wall at lowest cost I have found.

 

[elinwood]

My boss (who isn't an engineer) and I have been discussing. We've looked into using concrete sheet piling and it was too expensive. We've also looked into soldier walls and it was still relatively expensive. A senior engineer and I have been talking and we've agreed that there's just no way that we can construct an RCC Wall on the 7 m high section with that little space. The angle of the soil would be too great without destroying a portion of the pavement. Regardless, the boss is insisting that I do a calculation up til I know how much it will cost with all the variables and then - and only then - will he consider the other alternatives.

Thanks for the suggestions and I'll try to remember to update this thread with what we ended up using

 

[cvg]

concrete sheet piles? should that be steel?

 

[oldestguy]

For more thought from the forum, could you provide a few cross sections reasonably to scale? A few more photos also may help with ideas.

For instance, maybe the 7M wall area would have a different design than elsewhere. I can't believe there is a free standing earth cut 7M high next to the property line without a whole lot more failure than you show. Isn't there some sloping earth between that lower level and the property line old wall? If so, maybe the wall height can be less, depending.

 

[RFreund]

remove the road and replace with a segmental wall. Depending on your area this maybe the most economical solution. Crush the demoed wall and use it as reinforced backfill (if you can).

EIT

http://www.HowToEngineer.com

 

[tempeng]

concrete sheet piles? should that be steel?

I think the OP means steel sheet piles with a RC facing.

 

[FixedEarth]

You may consider cantilever wood poles (electric poles) @ 2 m on center(driven or drilled )and pressure treated timber lagging.

 

[elinwood]

I wasn't a typo. It's a concrete sheet pile, maybe similar to this -

http://xmt.vn/web/en/precast-prestressed-concrete-sheet-pile-384/

It would've been pretty effective, but the owner deemed it too expensive.

Here's another image looking along the wall:

http://imgur.com/GOTpyCh

Another looking up the wall:

http://imgur.com/aDPpgXb

Another closer to the high wall :

http://imgur.com/2RFzw1S

There's currently maybe a 7m to 1m slope on the taller side. Even the collapsed wall didn't collapse right away. The "cut" contractor didn't cut it at a 90 degree angle. He left a little bit of slope, but definitely not enough for its load.

I discussed this with the boss again and he told me that he's going to talk to the neighbor to buy 3m of his space. If you look on the image looking along the wall, there's a house. The roof is about 1.5m from the wall. The wall is about 2.5m - but the boss is saying that he can convince the guy and to assume that the design has 3m clear space.

The first thing I thought about was MSE wall again, but we'll need 6 m of space to prevent sliding (I calculated it based on the Coherent Gravity method) which is a no-go. He's telling me to go back to an RCC wall design w/ a counterfort and add a tie beam on top of the counterfort that will tie onto a pile on the inside of the road. Any thoughts on this design ? I'll post a sketch of it in a few mins.

 

[elinwood]

Here is a sketch of the owner's request (this is based on a previous design that is currently being constructed) :

http://imgur.com/xLx8tpF

I don't think it's a very effective design considering the cost of bored pile and the number of piles per linear meter. The concrete sheet pile I was thinking of maybe designing maybe a counterfort RCC wall with an MSE hybrid in that I'll anchor the geotextiles on to the RCC wall but I'm not sure how I'd calculate this type of design.

Regarding the cantilever wood poles - would the design be similar to a crib wall ? Or similar to a soldier pile wall like so:

http://www.irvinegeotech.com/picture_library/shot2.jpg

?

 

[oldestguy]

Elin:

You have a number of us thinking. However, before any final design is done, I certainly would want to know what the soil-rock situation is. At least one boring in a representative location would help a lot, especially with any form of pile supported wall or those concrete sheet piles considered.

What's the purpose of that extra pile in your boss's sketch plan, the one with a tie beam on top?