28 ft retaining wall 3

[LBengineer]

Im attempting to design a segmented retaining wall approximately 28 ft tall. my initial design included geogrid, but the problem that I had encountered is that i only have 15 ft of clearance to install geogrid and that isn't enough support. if anyone has any precast systems in the northeast (USA) that are large enough to potentially be sound for a gravity wall, of if you have any other ideas for a solution please let me know

 

[MTNClimber]

15 feet clearance to what? Property line, structure, ect.?

 

[bridgebuster]

Have you considered an inverted T-Wall (Reinforced Earth Company). I've used T wall but not inverted. However, there's a design build project in Queens NY that will be using them. I know a number of walls are taller than 28'.

 

[JedClampett]

Have you called a segmental wall supplier (Belgard just had a seminar, so they're fresh in my mind) about this? Maybe there's a solution they commonly use, or maybe you'll have to try another wall design.
These guys are happy to answer questions, especially to get a hot lead.

 

[PEinc]

Another thing to consider: Is the wall going to be a fill wall (bottom-up) or a cut wall (top-down)? If a cut wall, you will also need temporary sheeting which should require tieback anchors and, therefore, temporary easements from the neighbor or require internal raker braces which will interfere with setting precast wall segments.

http://www.PeirceEngineering.com

 

[SlideRuleEra]

...design a segmented retaining wall approximately 28 ft tall.
... precast systems... that are large enough to potentially be sound for a gravity wall...

Redi Rock may be able to do that. Look at the larger size blocks.

 

[EireChch]

Concrete crib wall?

 

[Milliontown]

Hilfiker Retaining Wall may have something. They have a few different wall types, mostly variations on MSE and Gabion walls (or combination). There's loads of example projects (with plans) that may be helpful for finding an appropriate wall type. They may be able to work with you on a solution.

https://www.hilfiker.com

 

[MTNClimber]

Depending on where in the northeast, its common to see Redi-Rock or Recon big blocks for tall gravity retaining walls. There may be other types. Look into which concrete suppliers are closest to your project to see what makes sense. Some precast plants only make one type of block system, some don't make any.

28ft is tall for a gravity block system. I'm not sure what type of surcharge loading you have at the top of the wall (slope, traffic, landscape, ect.) or the strength properties of your retained and foundation soils but you'll probably need somewhere in the ballpark of 0.4H - 0.5H to make it work. 15/28=0.54 x H which might work depending on the soils. Usually my global controls with big blocks at taller heights. You definitely need to double stack the blocks. You might also need a concrete footing instead of a crushed stone leveling pad.

Keep in mind that you need room to excavate behind the wall alignment to make it safe to install the blocks and properly backfill. So if the 15' clearance is the distance from the wall face to the property line you might be out of luck and will have to consider another type of system.

 

[PEinc]

LBengineer, it is hard and imprudent to recommend a retaining wall type without sufficient information - such as cut wall, fill wall, gravity wall, non-gravity wall, required wall embedment below finished grade, property line, nearby utilities, nearby structures, soil and rock conditions, ground water, availability of permanent or temporary underground easements for ground anchors, possible surcharge loads, etc. In any case, a 15' maximum width for a 28' high wall sounds very "iffy." 15'/28' = 0.53 which is a very low ratio for gravity walls.

http://www.PeirceEngineering.com

 

[LBengineer]

For more information, its a cut wall with a 20 ft clearance to property line, but we can only work with 15 ft because we cant do any excavation within 5 ft of that property line. I was panning on putting in a temp solider pile wall with tie backs and asking for a easement into the neighboring properties. I think were going to try to cut some off the hill top and slope down the soil level to hopefully only have a 24 ft wall and we've worked with Doublewal blocks before that can handle that height. I appreciate the recommendations, if anyone else has any more ideas or possible solutions I am always interested.

 

[MTNClimber]

Doublewal has the largest blocks I've seen for a gravity system. I can't believe they make blocks that are up to 24 feet deep. Recon's depth max out at 84" and Redi-Rock's max out at 96". You can double stack them to increase their depth but you need to run the analysis by hand as their software does not support double stacking. Sounds like doublewal is good option if you can make it work with your space limitations. Good luck. Sounds like something might have to give though such as moving the wall alignment, switching to a really expensive rigid cantilever system or getting a permanent easement for some permanent anchors.

 

[BridgeSmith]

With that limited space, you should consider a drilled shaft retaining wall.

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

 

[PEinc]

I was at a jobsite yesterday that is building a T-Wall that will be up to 45' high. A 38' high section used T's that are 34' long. I don't see any type of 24' or 28' high wall (other than a drilled shaft wall or a very heavy, cantilevered, soldier beam wall) fitting within a 15' space.

EDIT:
I just used the Redi-Rock design program for a 28' high wall, slightly battered wall with geogrids in every other block course. I kept the total width of the blocks and grids to 15 feet. I used good granular soil for the retained and foundation soils. Surprisingly, the program gave me good results - internally, externally, and globally. You may want to get the Redi-Rock program, play around with it, and talk to Redi-Rock. This may be doable. However, you will still need temporary, tiedback sheeting to support the adjacent property while the MSE wall is being built.

Please re-read the above first response from MTNClimber. He makes good comments.

http://www.PeirceEngineering.com

 

[MTNClimber]

Thanks PEinc.

I think the min. stem length to wall height ratio may be higher for T-walls than the depth to height ratio for concrete blocks so it may not be an apples to apples comparison.

We have gotten creative on smaller gravity walls that have less room than 0.4-0.5H by using no fines concrete backfill but I'm not 100% sold on doing that on a 28' tall wall.

 

[JohnTerry4]

This might be a late response but you should use no-fines concrete which you would only need to go back approximately 11 feet. I use it all the time with property line constraints.

 

[dik]

With only 15' behind, you may have great difficulty.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[MTNClimber]

JohnTerry4 - Have you used it on walls with a similar height?

 

[LBengineer]

JohnTerry4
If you could elaborate a little more on the advantages such wall that would make is stable enough to be designed in such small clearances. I haven't seen any designs with lightweight concrete before.

And thank you everyone for the help. The project got delayed till Spring, so I am still open to anyone's ideas.

PEinc/MTNClimber
I looked into Redirock and their software is extremely intuitive and also gave me great results, the only problem is I am located in southwestern Connecticut and the closest distributor is up near Boston. I am still keeping my options open with them and did get a quote for the blocks I would need but the delivery was pretty outrageous. keeping my options open for when I take another look at this project come springtime.

 

[LBengineer]

Another option that I was proposed by a mentor of mine was to install some soil nails at the top 10 ft of excavation to increase the acceptable slope behind the wall and hopefully not penetrating into the neighbor's property then being able to decrease the size of wall to approx. 14-16 ft which would be easier to fit a segmented wall with geogrid. Does anyone have an experience with anything like that?