Sinkhole in driveway...

[spudcrazy]

I had a watermain problem that has been repair. The plumber had to dig part of my asphalt driveway, to reveal that a crumby coupling joint had gone bad. I now have copper all the way to the street valve and it has been run through the old plastic. Now to the matter at hand...when he dug up where the union was, he found quite a big sinkhole under the asphalt, were the water had washed the soil away as silt (I presume). Both, him and I tried to back fill the sink hole as best as possible, with a hydrolic tamper, but obviously we couldn't completely fill it to the point of complete "packness". So now as the freshly backfilled dirt has settled a bit, the driveway has sunk a bit and there are some small stress fractures around the sunken part of the asphalt. My question is: can I just throw some patch in the dug up hole (this is just rock dust now) and the surrounding area of asphalt that has sunk around the hole or do I have to cut up all the sunken asphalt as well and redo the entire hole? I had planned on waiting a few months for the ground to completely settle and all the ground water from the leak to disperse. Then thoroughly clean the sunken asphalt and dig up the stone dust to a depth of about 4" then backfill with cold patch. Does that sound sufficient?

Sorry for being long winded and thanks in advance for the advice...

RUSTY

[maradcliff]

Carefully look down into that hole and see if there are any other cars down there. You might luck out and get yourself an antique cadillac or something, :)

[trader4]

If you want it done right so that it will last, I'd suggest getting a contractor to hot patch it. It should be excavated back to a perimeter where the ground is solid, base material placed in the hole area, compacted, then FABC. You can do this yourself for a small hole with cold patch, but for a reasonable size one, without the right eqpt, etc, it's not worth it.

[Ross Mac]

I had a house with a gravel driveway that would develop large potholes every couple of years. I kept filling them with gravel until a contractor suggested blast rock. These are chunks of rock, irregularly shaped under an inch in size. What happened when using this rock was the pieces locked together rather than being forced into the dirt and sand. I know this only answers part of your question, but it might help someone else with potholes or sink holes.....Ross

[SJF]

There is a backfilling procedure called "puddling" that works very well in granular soils -- gravel, sand and silts. You partially fill the hole with water so that the backfilled soil is deposited under the pool. A puddling stick (piece of 2x4, etc.) can be used if needed to break up clods. As the water drains out of the replaced fill, the soil compacts to near its maximum density. This does not work well on soils that are very clayey since the clay gels up and takes forever to drain out.

If a hole has already been loosely backfilled, jetting to flood the soil and drive out the air can settle what is there. Then, in a day or so when the water is drained out and the soil settled, you can add the needed soil. For my little yard projects, I do this with a watering lance which has had the water orifices drilled out to pass more water. -- SJF

[SJF]

I should add that the water jet is probed around the backfill to wet all parts, rather than making one insertion and letting it run. In predominantly granular soils, you may observe the settlement while you are probing. -- SJF