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EagleLandscape
01-28-2008, 03:02 PM
Hey guys. I'm building about to build a home for myself right now on a lot that I can get for a steal of a price. I have a soil report that is about 3 years old (ordered a new one that will come in next week), but based off the last report the PVR (potential vertical rise) is 6". The P.I. is about 34-38. It seems the soil is not very compacted on this site. What should I be looking at for someone to come in and compact this site in well. The size of the slab is a little under 4000 sq ft. Thanks,

bobcat_ron
01-28-2008, 03:40 PM
Can you do a pre-load and wait for 3 months?

EagleLandscape
01-28-2008, 04:16 PM
Say what now?

Dirt Digger2
01-28-2008, 04:25 PM
a pre-load is where you load the soil well above what the soil will ever carry and leave it set for a few months, then come back and take the pre-load off and build your pad...this is typically done by putting anywhere from 2'-...well the sky is literally the limit for how much stone you can pile for a pre-load. Pre loading gets very expensive...

have an engineer design you up something...chances are you will be ok with a pad footing, or even micro-piles would be cheaper then a pre-load


micro-piles are where a drill rig will come in and drill 4" holes straight down to bed rock, the holes are then filled with mortar and you build your pad on top of the micro-piles. This method is very common and used on virtually all sports stadiums and open floor warehouses that have an open center with no roof supports and require the outside walls to support all the weight

bobcat_ron
01-28-2008, 04:27 PM
You can also get cheap building fill hauled in that some excavation contractor wants to get rid of for cheap and use it for fill or sell it out by the load to someone else.

BIGBEN2004
01-28-2008, 07:48 PM
Are you digging a basement? If so you might be able to dig out of the bad soil and into some good clay. Also you can have a engineer design a layer set up with layers of stone and then putting down geo grid matting, then stone then geo grid, and so on and so on until grade has been met.. I have done this on a job site near Leesburg VA where we kept having sink hole problems. The most popular way we handle things like that around here is to excavate the bad soil out until stable ground is found and then refill in lifts and compact with a stable clay material. We always have it certified by having a soil engineer company on site while the lifts are installed so they can do certified compaction testing. If anything fails due to the ground moving under the foundation in the future they are held responsible and must pay for damages.

BIGBEN2004
01-28-2008, 07:53 PM
Can you do a pre-load and wait for 3 months?
Just curious, what do you do with all the stone when you take it back out? I have never seen that done around here. Sounds too expensive for anyone to do.

bobcat_ron
01-28-2008, 08:21 PM
Just curious, what do you do with all the stone when you take it back out? I have never seen that done around here. Sounds too expensive for anyone to do.

The pre-load I got pics of, all of the gravel (19 feet high by 180x180 square and some 34,000 tons of gravel) will be shoved over and used up for the parking lots, in jwingfield2k's case, if there needs to be a driveway made or any other fill needed to bring a lower elevation back up, the fill can be used there, it doesn't always have to be rock, even sand or heavy soil like clay, as long as the structural engineer approves of it.

RockSet N' Grade
01-28-2008, 09:11 PM
I thought I heard that Bob_Cat_Ron sold all that pre-load material for Pet Rocks? Maybe that was another thread.....

bobcat_ron
01-28-2008, 09:13 PM
Yeah, I made Ka-jillions of dollars!!!!!

ksss
01-28-2008, 09:37 PM
It sounds like your home will be slab on grade. I would talk to your soil engineer for recommendations as these issues tend to be very regional. Some suggestions would be a footing wall around the perimeter of the house extending down to firm soil. The other option is excavate down to solid material and build back up to grade using structural fill and of course density testing.

EagleLandscape
01-28-2008, 10:20 PM
Yes it will be slab on grade. No one has basements here because of the plasticity of the soil. I guess I was looking at a dollar figure estimate on what it would cost to get a guy out there on site with a roller for a few hours and compact out a 4000sq ft base. I mean, am I looking at 2k, 5k, 15k to spend? That number will be the deciding factor on if this site is a feasible building site or not.

My soils engineer will obviously give me a recommendation, but until then, I am curious about what dollar figure I could be expecting.

RockSet N' Grade
01-28-2008, 11:03 PM
Jw.....you are putting the cart before the horse. With out reccomendations and a plan from a soils engineer........no one knows what to do and you will get all sorts of ideas, prices, etc. You could throw a dart at a dartboard and get a number. From process to product, get an engineer that has dealt with building in that area, dig test holes at various locations on the site to determine what you have to deal with and after that get bids from locals in the area. That is the way it is done. Also, remember, there are unknowns that you can start to eliminate by doing some research on your own.....talk with surrounding land owners, realtors and people they would refer you to: was the site ever used as a dump? have people filled in the site with truck loads of dirt? find out the history of the gound. I have done 50 plus projects with site layouts on the short side of 12,000 sq. ft. upwards of a couple hundred thousand sq. ft......each one is different. Ask alot of questions from the locals if at all possible, there is always a kernal of truth to be found by asking and it is alot cheaper asking and finding out than finding out in the process of the job.

EagleLandscape
01-29-2008, 12:02 AM
There was a house on the lot until a few years ago when it was burned down. I know I will need to wait until the final word, but I know many civil engrs that work for the larger cities around here and with loose soil, thats what needs to happen. the site still has the old slab on it, I might get the demo company to redo the lot while they are out there. im sure they will have a 320 ex out there or something along those lines. I'll keep yall posted with what I find out.

Dirt Digger2
01-29-2008, 12:52 AM
you can't just run a roller over it a bunch of times...rollers are really only good for a maximum of 12" compaction and even that has a lot to do with moisture contents, and blah, blah, blah

if there was already a house there and you plan on building at the same site then there has already been a pre-load and you should be fine...unless the house you are building dwarfs the past house...but like mentioned above, soil is the largest unknown in all of engineering so it is hard for us to say what will work when we have never been to the site or seen the dirt you are working with...your local engineer will have good advice

bigboy24
01-29-2008, 01:11 AM
Down here the norm for your situation is to dig 2' to 4' down past top of proposed slab and bring in redfill. it gets compacted by the dozer or loader doing the dirt work( we used a cat 963 where i used to work ) per truck load. Always ended up above spec. Also the use piers quite alot here. But as mentioned earlier, there are too many variations untill you get it looked at to get a right on estimate.:weightlifter:

Good luck!

ksss
01-29-2008, 01:13 AM
you can't just run a roller over it a bunch of times...rollers are really only good for a maximum of 12" compaction and even that has a lot to do with moisture contents, and blah, blah, blah

if there was already a house there and you plan on building at the same site then there has already been a pre-load and you should be fine...unless the house you are building dwarfs the past house...but like mentioned above, soil is the largest unknown in all of engineering so it is hard for us to say what will work when we have never been to the site or seen the dirt you are working with...your local engineer will have good advice

You and Rock beat me to it.

Scag48
01-29-2008, 02:38 AM
I encountered a slab on grade job that ran into the same problem. Soil didn't test right, we knew it going into the project and had prepared for it. Proposed slab sat on fill from a cut roadway that was estabilished only a few years before. We ended up going way deep, removing the unsuitable soil, hauling it out, dug down to suitable soil, threw some 8-10" rock in the bottom for good measure, hammered it down good with a hoe pac, filled about half way with 5/8" compacting every 6-8" and threw some some fabric in there to bridge the load as it was a gnarly deep fill, then continued to fill with 5/8" until finish grade. I'm proud to say we hit 98-99% on that job compacting with a reversible plate and used the hoe pac here and there.

BIGBEN2004
01-29-2008, 10:30 AM
Another way that I have seen done on a basement I dug once that had no bottom to it was some sort of augers drilled in the ground. It was a series of large augers that looked like post hole diggers but they kept drilling them in the ground until they hit solid ground then they would cut them off at the surface and poured the slab over top of them. It cost allot of money but that was the only way.

Dirt Digger2
01-29-2008, 11:51 AM
Another way that I have seen done on a basement I dug once that had no bottom to it was some sort of augers drilled in the ground. It was a series of large augers that looked like post hole diggers but they kept drilling them in the ground until they hit solid ground then they would cut them off at the surface and poured the slab over top of them. It cost allot of money but that was the only way.

those are called deep foundations...along the same premise of a micro-pile ecept they are larger diameter and take more time to drill. but its a really neat thing to see. Drill the holes down to bedrock, drop steel in there, fill them with mortar and you have a building that is essentially resting on the bedrock

ksss
01-29-2008, 12:23 PM
One of the houses we dug in Mt had to be micro piled. Very expensive, I had pondered getting into that business.

Dirt Digger2
01-29-2008, 01:10 PM
it really wouldn't be a bad business to get into...once you have the drill rig you are pretty much set. The only problem is with larger buildings you may need to have 4 or 5 drill rigs on one location to get done on time, and those crawler rigs aren't cheap.

and you would need a larger dozer or trackloader to pull out all the concrete trucks that get stuck on those jobs

ksss
01-29-2008, 04:48 PM
My plan was using the type of drill rig that pin on the stick of an excavator. The company I was talking to shows them on on small excavators (mini excavators). I figured the only additional equipment that I would need would be a grout pump.