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D Felix
07-11-2006, 03:34 PM
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

Mike33
07-11-2006, 05:19 PM
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

D Felix
07-11-2006, 06:39 PM
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.

Mike33
07-11-2006, 09:08 PM
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

tylermckee
07-11-2006, 09:24 PM
What are you compacting with that you can only 2 3" lifts? time to rent a bigger jumping jack if you ask me.

D Felix
07-11-2006, 09:29 PM
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. :)

D Felix
07-11-2006, 09:33 PM
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.

Mike33
07-11-2006, 10:06 PM
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. :)
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

tylermckee
07-11-2006, 10:59 PM
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

DreamscapeDesigns
07-11-2006, 11:10 PM
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..

D Felix
07-12-2006, 04:30 PM
There is a possibility that some of the hill can be cut down. They've already cut a lot of it out to build the house, and it goes WAY back there. To cut it down to a managable slope would take probably as much work as building a wall, to to mention it would mostly need to be hauled away. There's already been as much spread as can be spread.

Calling the manufacturer was something that I mentioned to them. Gave them the rep's name from OldCastle, don't know if something came out of that or not... I've got a call into the owners, just waiting to hear back.

Is there any problem with lack of friction putting the grid into clean stone versus compacted soil? There's a better phi angle with the stone than with soil so that could help with the lack of friction, but is it enough to make up for it?

Depending on how much the top gets cut down, there may or may not be a need for more fill....

orionkf
07-12-2006, 09:12 PM
I talked to a geotech/wall designer over the winter, and he mentioned that on large wall installs around here, some people are using clean drainage rock to speed up the backfilling process, just as you are thinking about. If the labor savings pencil out, I would go for it.

mrusk
07-12-2006, 09:58 PM
By the pics, i can't see why you couldn't level it out. If your going to make a 15ft cut for the grid, you mind as well just load it all into a triaxle and make get it down to a minor wall. It sure is cheaper to haul dirt off instead of compacting a 15ft cut.

Matt

D Felix
07-13-2006, 04:50 PM
The pics are decieving. All the material that is sluffed off at the base of the hil is approximately 15-16 deep.

Keep in mind that where the hill is cut is 90+ feet long.... From backyard grade to top of the hill is ~20 feet...

neversatisfiedj
07-13-2006, 10:17 PM
You need to spike your grid into soil.