We have a lot of engineers here right?

Discussion in 'Hangar Talk' started by Timbeck2, Jul 8, 2019.

  1. Timbeck2

    Timbeck2 Final Approach

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    Looking for opinions of structural engineering strength differences between a poured solid reinforced concrete retaining wall vs stacked cinder blocks filled with concrete and reinforced with rebar. More or less I'm looking to see if I can build a 5' retaining wall using cinder blocks as the mold versus using a mold I'd have to remove.
     
  2. murphey

    murphey Final Approach PoA Supporter

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    Gonna need rebar either way. Or is the reinforced poured wall including the rebar?
     
  3. SoonerAviator

    SoonerAviator En-Route PoA Supporter

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    Not an engineer, but I wouldn't think there'd be much (if any) savings in buying/stacking the cinder blocks, then adding rebar and filling with concrete vs just constructing a reinforced concrete wall. The joints of the cinder blocks would obviously be the failure points and result in a wall of inferior strength vs a poured concrete wall. Make sure you have proper drains installed either way, as you don't want the wall to trap the water behind it.
     
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  4. luvflyin

    luvflyin Final Approach

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    Let me be the first non engineer to jump with an opinion. It's about the steel, how many cores in the blocks you fill and how many bond beams you run.. More rebar and cores filled the better and more than just one bond beam at the top also. Filling cores can be tedious. The strength of the mud itself isn't going to be that much of an issue because a retaining wall isn't going to have a lot of compression.
     
  5. overdrive148

    overdrive148 En-Route

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  6. Fiveslide

    Fiveslide Pre-takeoff checklist

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    Are you going through proper channels to get a permit, it may be required. I haven't much experience with retaining walls outside of my former home county in NC or walls that aren't part of new development plans reviewed by appropriate county departments.

    That said, in my county, something that tall would have to be designed by a PE, built to plans and inspected by that PE to be entirely compliant with code. IIRC, anything over 4 feet has to go through all that.

    Your world may vary, but sometimes asking questions and getting permission is better than doing it and asking forgiveness.
     
  7. luvflyin

    luvflyin Final Approach

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    Oh yeah. Do you have some use for the forming lumber afterwards?
     
  8. Timbeck2

    Timbeck2 Final Approach

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    Yes, in my mind "reinforced" means reinforced with rebar.
     
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  9. Grum.Man

    Grum.Man Pattern Altitude

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    I'm no civil engineer but I do know the most important part of a retaining wall is the drainage behind it. I would think either method would be acceptable assuming you are putting mortar between the joints of the cinder blocks.
     
  10. Fiveslide

    Fiveslide Pre-takeoff checklist

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    Are you going through the proper channels to get a permit? Just some thoughts...

    I'm not experienced in walls beyond my home county in NC or walls not part of new development that have been approved by appropriate city or county departments.

    That said, in my county, anything that tall would have to be designed by a PE, built to plans and inspected by that PE to be entirely compliant with code. I think anything over 4 feet would have to go through all that where I'm from. There might have been some exemption from that on a private wall on private property, but I never had to find that out.

    Your world may vary, but sometimes it is better to ask questions and get permission than do it and ask forgiveness.

    Taking off my work hat now.
     
  11. Timbeck2

    Timbeck2 Final Approach

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    I thought about that and was planning on staggering the joints rather than just stacking them up. They would have rebar embedded in the footing and them up through the holes in the blocks essentially making it solid. Don't know if my words convey what is in my head.
     
  12. Timbeck2

    Timbeck2 Final Approach

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    Not really
     
  13. Timbeck2

    Timbeck2 Final Approach

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    I've done this before pouring a solid wall using home made plywood forms spaced apart with 8" pieces of pvc pipe then connected with a threaded rod which can be reused on the next pour. The pvc stays in the wall as drains.
     
  14. Sac Arrow

    Sac Arrow Touchdown! Greaser!

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    You might look in to Keystone retaining walls. https://www.keystonewalls.com

    One key thing with retaining walls is how well you compact the soil behind them, and the type of soil you are retaining. Loose, unconsolidated soil will create pressure on the wall. Five feet is getting in to an engineered solution, so if it were me, I'd split in to two sections, and place the upper section two and a half feet behind the lower. Both a poured or CMU wall will be strong enough they won't break, but tipping is a bigger problem.
     
  15. Timbeck2

    Timbeck2 Final Approach

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    I actually have keystone retaining walls in front of my house that are only 3' tall at the highest point. I'm planning to build a smaller retaining wall in front of the one in question with fill in between. Since the one in question won't be visible, I was going to a less expensive route.
     
  16. Kenny Phillips

    Kenny Phillips Pattern Altitude

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    Any way of peeling back the hill a bit and using some form of geo grid? That will make the wall less critical.
     
  17. Checkout_my_Six

    Checkout_my_Six Final Approach

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    that and drainage....keeping it dry is key. If it won't drain....the wall will blow out. Hydro-pressure will blow out any wall...block or reinforced concrete.

    but....I'm not a dirt engineer. ;)
     
    Last edited: Jul 8, 2019
  18. SkyDog58

    SkyDog58 Touchdown! Greaser! PoA Supporter

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    Canis Non Grata
    So then, you’re an uncivil engineer?

    :cool:
     
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  19. Grum.Man

    Grum.Man Pattern Altitude

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    Just a little rowdy
     
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  20. MIFlyer

    MIFlyer Line Up and Wait PoA Supporter

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    how about eco blocks? I don't know if they have them down there, or if they catch fire in your heat.

    [​IMG]
     
  21. Timbeck2

    Timbeck2 Final Approach

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    I was looking at something I could do by myself without cranes and heavy equipment.
     
  22. Zeldman

    Zeldman Touchdown! Greaser!

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    Real men will use cranes and heavy equipment even if it is not needed....:lol::lol:
     
  23. Checkout_my_Six

    Checkout_my_Six Final Approach

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    Yup.....
     

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  24. Timbeck2

    Timbeck2 Final Approach

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    Not following what you mean by geo grid.
     
  25. Pilawt

    Pilawt Final Approach PoA Supporter

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    Looking for an engineer?

    disneystulla.jpg
     
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  26. cgrab

    cgrab Pattern Altitude

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    I'll start by saying I'm a PE. That said there are keys to any wall that need to be considered: 1 footing-dig below the frost line and pour a reinforced footing that is wider than the wall to be built on it; wall height will factor into width difference. 2 ends-or in the case of a retaining wall, dead men; there has to be something to hold the wall from falling over. 3 drainage and root control-whatever is behind the wall will push it over eventually and must be controlled; perforated pipe in gravel with agricultural felt will help. Back to the question...either solid or block wall will work if the above is taken into account.
     
  27. flyingron

    flyingron Touchdown! Greaser!

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    Rebar and concrete block with filled voids is going to be a formidable wall.

    When I built my house, I had poured concrete foundation walls (with rebar). Except for one place which was planned to be the archway into the expansion of the house. I had a steel I-beam put in and told the guys to just make a concrete block wall there so it would be easy to bust out when the time came.

    Well, that time came a couple of years ago. The crew came in with sledgehammers and a start wailing away at the wall. Eight hours later I go down to check on the progress, and they've only managed a hole the size of my fist. Apparently, the masons decided to use rebar and fill the voids with concrete. That wall was tougher than my poured walls. It took nearly a week with concrete saws and jackhammers to get that "temporary" wall out.
     
  28. SoonerAviator

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    GeoGrid refers to using a wire or plastic mesh to act as the first line in soil erosion control. You usually use it in conjunction with a retaining wall in order to help keep the soil behind the wall from shifting and putting extra pressure on the wall.
     
  29. MIFlyer

    MIFlyer Line Up and Wait PoA Supporter

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  30. Sac Arrow

    Sac Arrow Touchdown! Greaser!

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    I don't design retaining walls and I don't like playing structural, but if were to design one it would look a whole lot like a concrete hydraulic structure. 12" thick walls with a double mat of #5's, keyed in to the ground with four sides. It would probably withstand a nucular blast.
     
  31. coach

    coach Pre-Flight

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    The strength between the two materials doesn't really matter, concrete is a bit stronger so CMU would have a little more reinforcing steel, either way the same earth pressure is resisted. If you want I can send you my typical CMU retaining wall detail, you are welcome to use it but I don't have an Arizona stamp. You might find that a Keystone type wall is cheaper. PS: I am a Structural Engineer
     
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  32. Timbeck2

    Timbeck2 Final Approach

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    Sure Coach...your offer is appreciated and thank you.
     
  33. Checkout_my_Six

    Checkout_my_Six Final Approach

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    build that wall.....;)
     
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  34. GRG55

    GRG55 Final Approach

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    Hollow concrete block structures are intended for vertical compressive loads. They are a poor choice for retaining walls of any material height. Five feet is material.

    Stick with one of the numerous pre-cast products specifically designed for retaining walls. Run perforated drain tile imbedded in 1 1/4" drain rock at the base on the back side of the wall.
     
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  35. Kenny Phillips

    Kenny Phillips Pattern Altitude

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    Far more than erosion control! It creates an engineered soil that will hold just about anything without collapsing. I found this:
     
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  36. overdrive148

    overdrive148 En-Route

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    Stack them horizontally :stirpot:
     
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  37. X3 Skier

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    Just another brick in the wall.

    Cheers
     
  38. Checkout_my_Six

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    yup....stack em high...watch em fly....o_O
     
  39. Timbeck2

    Timbeck2 Final Approach

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    The 5' height is the maximum and will decrease to around 1' at the other end of the back yard. I plan on a couple of T shaped dead men on the tallest sections and then a smaller retaining wall with dirt and planters between it and the main retaining wall on most of it. I will account for drainage with probably more than I need. My concern here was to verify if my planning was going to work and based on all the information I've read, I think it will be over-engineered and work just fine. Thanks to everyone for your input.
     
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