Modified wall backfill

Discussion in 'Hardscaping' started by D Felix, Jul 11, 2006.

  1. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    Anyone see any problem with using clean, angular stone (8's around here) as backfill behind a wall?

    I'm looking at a side job right now, grid pulls need to be 15' or more. There probably won't be enough excavation spoils to fill the entire backfill area, so backfill material will need to be brought in.

    My initial thought was to use dusty limestone (53's around here), but those would need to be compacted much more than clean stone. I'd feel comfortable with 6"+ lifts of the clean stone, versus 3" lifts of the dusty stuff. Obviously I'd have a foot or more of the clean stone behind the wall for drainage purposes no matter what. What I'm thinking is using most of the excavation spoils as backfill, when that runs out, put down fabric, then the clean gravel on top of the fabric, pulling grid as necessary. At the top, put down some more fabric, and soil on top of that as a final layer....

    This wall will take a while to build, so it'll be a while before I need to get backfill brought in. In other words, you all have a fair amount of time to discuss it!

    Thanks guys!


    Dan
     
  2. Mike33

    Mike33 LawnSite Bronze Member
    Posts: 1,649

    What is the dimensions in plain english? Srw total purpose is drainage, i will over kill a wall for drainage. Most of the time you are replacing one because of im proper drainage. On a wall 3' i will fill 2' behind with clean stone. Walls 7-8' in height i have 3-4' of clean stone then balance of backfill with a shale or slate material that will still drain and compact. The more stone behind a wall allowing it to drain you are taking pressure off of it. Yes my stone bills are high but it is figured in the cost and i still make good money on building walls. Im not sure about your sizes we use a 57 which is aroud 3/4 to an inch. These numbers vary from state to state. I would not use dust.
    Mike
     
  3. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    I'm not worried about drainage, I'll make sure there's plenty of it!:)

    I've used dusty limestone as backfill before (with adequate free-draining stone behind the wall) without problems. I'm just not sure about the lack of available compaction behind the wall when using the free-draining stone. I guess my question is whether the free-draining stone will "hold" the grid well enough to hold the wall.

    Total length of the wall at the base will be between 90-110 feet, possibly a few more. The wall will turn into the hill at both ends. After 8-10 feet of hieght, the wall will shorten in length and will again turn into the hillside. Total wall hieght will be 15-20 feet. Final size will be determined once the project starts. I've recommended that they contact an engineer, but ultimately that decision lies with the homeowner.

    I'm not worried about cost, they are getting it cheaply on the labor end and are paying for everything else. It's a side job for me.

    I've attached a couple of pics to give an idea of the site.

    IMG_4482resize.jpg

    IMG_4483resize.jpg
     
  4. Mike33

    Mike33 LawnSite Bronze Member
    Posts: 1,649

    Our 57's are 99% went dumped in. Yes clean stone will compact well with gridding ive have over 150 out there. I would want the clean stone at least the first 3' behind the wall. An eng. drawing shoud be done for one this height but if not build it right. Go down solid footings, bury 1.5 block and grid properly.
    Mike
     
  5. tylermckee

    tylermckee LawnSite Member
    from wa
    Posts: 248

    What are you compacting with that you can only 2 3" lifts? time to rent a bigger jumping jack if you ask me.
     
  6. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    I don't know if they've contacted an engineer yet. I'll probably be talking to them in the next few days. I told them I would feel more comfortable with an engineered plan, but if they didn't want to spend the $2-5k I would understand. $2-5k buys a LOT of grid!

    Forgot to mention this will be a Keystone Century wall.... All 8" blocks.

    Plans are (at this point) to bury at least 2 courses of block, possibly 3, though 2 courses plus a 6" base gets close to below frost line as it is... Grid no less than every 3 courses, with pull length being as much as possible- at least 15', using the strongest grid available. Backfill with the soil spoils until they run out, then use clean stone as backfill. Drainage won't be an issue; it'll get daylighted out each end most likely. Logistics will be somewhat of an issue since this will be primarily a weekend and evening job, working by myself and with the homeowner... Nothing that can't be overcome though. :)
     
  7. D Felix

    D Felix LawnSite Bronze Member
    Posts: 1,898

    The massive area behind the wall calls for the biggest plate compactor we can find. Possibly two. Which around here isn't very big. Probably in the 3,000 lb centrifical force range. Meaning not very big lifts....

    I/we will be spending a lot more time compacting than we will actually building. I'll have to discuss it with them, but if it means the wall will get built faster and just as strong, we might go with all clean angular stone behind the wall.... It's possible that the added cost of the stone could/would be offset by the reduction in labor.
     
  8. Mike33

    Mike33 LawnSite Bronze Member
    Posts: 1,649

    your on the right tract, looking at your pic is there any way you could excavate different to elimante such a big wall? Like i said just looking at the pic you know the job where i dont.
    Mike
     
  9. tylermckee

    tylermckee LawnSite Member
    from wa
    Posts: 248

    Yeah, is that hill on their property? if it were my place i would cut the hill down, spread out what material i could and haul off the rest. eliminate the wall completely
     
  10. DreamscapeDesigns

    DreamscapeDesigns LawnSite Member
    Posts: 10

    Keystone will spin an engineered plan for free if you commit to using that block for the job call the main office, not your ditributor..
     

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