[Raj Venugopal]

Has anyone ever laid down multiple layers of geotex in a driveway application?

I'd really appreciate some of your thoughts.

We did a driveway dig out for stone pavers.
Pulled a buried tree trunk out of the middle of the driveway. It was under 8" of crushed rock and 1.5" of asphalt.
Dug down over 36" of clay/decomposed matter where the tree was...wet and smelly.
Laid down geotex.
Tractor tire tore the fabric in the soft spot while spreading lift 1...wet stuff started oozing through.
Rough levelled, packed it, and it was still soft underfoot in one specific 4' by 4' area.

We're still about 18" below the finished grade, and I'd like to ensure the 0-3/4" stays clean.

Should another layer of geotex go down?

And...if I'm going to do cement stabilization, should I till it into the last lift before the screed bed?

Thanks for your thoughts...I'm kinda stumped on this one and I'm just not satisfied with some of the guys I've asked who say it'll harden up over time.

[Paul]

Spot excavate the wet spot 12" more place a woven fabric then add 3" crushed stone to your normal grade height. 3" crushed has more surface area so it won't give.

[mrusk]

I thought i was the only one that had bad luck. I just dug a 12x7 hole 6 foot deep in front of a front stoop for a walkway. Damn excavator burried big rocks there.

Matt

[Raj Venugopal]

Hi Paul,

Thanks for the feedback.

I did that last night before reading your post...I hand dug out those spots; 20 wheelbarrows of clay, but filled it with 3/4" minus, not the 3" as you suggested. I pulled as much of the larger clean rocks to provide that mass.

Cheers,
R

[Stonehenge]

Yup - that's the overwhelming opinion here (including mine) - pretty much keep digging until it's not soft anymore.

Hope it turns out well.

[letsgetstoned]

This is just a wild idea, but maybe you could use one of those 4' x 4' steel plates you see on road construction that cover a hole...not sure how well the base would pack over it, though, but it might work and save you a lot of digging. Like I said, just a thought

[Raj Venugopal]

Digging out the soft stuff was the only way to go. Issue resolved. Messy job, but normally the right thing to do is the biggest PITA.

I can't help but wonder, however, whether something like a plate (which could cause heaving problems if above the frost line?) or laying geogrid would work in areas needing additional support.

[Stonehenge]

I wouldn't try a plate for the freeze-thaw reasons you mention. But there was a study done in Miami for some pavers installed at loading docks for ships. Many layers of grid were used to add stability and the result turned out to be very durable.

[Paul]

Anyone know the cost of one of those plates? We had a couple of them, if I remember right they were in the couple hundred dollar range. Much cheaper to dig a bit more and add gravel and fabric. Grid works but you have to make sure you use the right one most grid you buy is unilateral but for soil stabilization you need bi lateral grid, much more $$. What might work better would be a power sheep's pad roller. this will achieve 95% compaction much faster than any plate compactor for sub soil compaction at less cost and labor.