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Preparing driveway base problems.

Redbear

LawnSite Member
Just started a job, 700 sqft driveway. In a heavy clay soil. Driveway was previously asphalt so we removed that along with 15 inches of previous base and clay to provide a 12 inch gravel base. Put in 2 loads now up to about 8" of compacted base, the water seems to be moving up into the gravel. The base is spongy under foot and only another 4" of base remaining to put in. Suggestions. I'm thinking I have to go down another 12 inches or perhaps more, but how far do I take it and is there anything else that needs to be done.
 

Drafto

LawnSite Senior Member
Location
Wilmington, DE
This might be a stupid question but did you compact your subsoil at all before putting in your base? Sometimes you can force the water out by compaction, or you can let the soil dry out a little then compact. These are obvious things to some, but I just figured I would ask.

Dan
 
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Redbear

LawnSite Member
Tested a few areas in the driveway and no I don't see that all will have to come up again but about 1/3. Test holes showed that I would have to go down about another 15 inches. Does that seem practical.

Subsoil was compacted before hand with diesel plate compactor, being clay should I have used a rammer instead or does it matter much?
 

Drafto

LawnSite Senior Member
Location
Wilmington, DE
With clay a rammer is recommended. Did you use textile fabric? I had an experience once on a patio that had "pumping soil", you would step on it and it would still sink, even after the modified was in place. I ended up re-excavating it until I found suitable soil. Keep this thread at the top and I am sure one of the experts on here will help you, also try searching a little on the subject.

Dan
 

DVS Hardscaper

LawnSite Fanatic
Location
County Jail
Remove the clay and replace with proper soil, such as a silt/sand type.

Compaction shall be done with a ride on roller.

If all that extra excavating is not possible...then they need a poured concrete driveway.
 

cgland

LawnSite Bronze Member
Location
Reading, PA
Redbear - You need to excavate to suitable subsoil. DO NOT add any other types of soil to the excavation. The only thing goig into that hole is the base aggregate. You can try a couple of things. You could excavate another 12" and use portland cement to stabilize the soil or try rolling (vibratory roller)3A or larger riprap into the soil to firm it up. Definately use a geo separation fabric. It will help with stone migration and settlement if properly installed. You just have to explain to the homeowner that the soilis not suitable to build on and it will require some additional materials and labor. Doing it right the first time is alot cheaper than having to go back and tear it up. Hope this helps.

Chris
 

mbella

LawnSite Bronze Member
DVS Hardscaper said:
Remove the clay and replace with proper soil, such as a silt/sand type.

Compaction shall be done with a ride on roller.

If all that extra excavating is not possible...then they need a poured concrete driveway.
DVS, why would you add soil and not stone?
 
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Redbear

LawnSite Member
I've returned to the driveway to see how things are now( 20 hrs later), all the water is out of the base and it is actually quite solid now. Guess all the tamping with 9000 lbs brought the water level up through the clay into base. What are your thoughts now, should I still excavate further or am I OK to carry on since it seems that the water level won't come up without the tamping? Thanks in advance.
 
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