A small area of my yard has a bounce to it.... stepping on this area the ground will sink and come back up to it's resting place.. standing with feet about 3 feet apart and push down with one foot the other will be pushed up with the ground movement...
this was under my patio slabs. I dug down and found a very large construction tape along with bricks buried under the ground. about 3 feet down.
I removed the debris and re-filled the hole. The ground still has a bonce to it, but continues to sink.
The soil is heavy clay. I thought the tarp was protecting voids in the soil from filling in during settling and have removed the tarp would have corrected the problem.
Any idea's of what the problem is.

smearcase

In roadbuilding, when the ground moves as you have described, it is called pumping and it is an indication that special attention is needed at that area before attempting to build the roadway on top of the bad spot.
It sounds as if someone tried to correct the problem by removing some of the clay and refilling with old bricks or someone may have tried to create a "french drain" by using the bricks to create voids for storage and slow release of water.
If there is no constant supply of water (from downspout ug drains, septic fields etc) you may be able to remove the clay down to level of the bricks and refill with crushed stone (about 2" in dia. stones, no dust) and top off with topsoil.
If there is constant supply of water draining to the area, it maybe necessary to pipe the water to a better area to drain to. Clay is almost always a problem and clay with a water supply is a big problem.
Since the area is small, a reinforced concrete slab might "bridge" the pumping area but dont put the clay on top of the slab when backfilling. Find some good fill material.
Many of these areas we would find building roads were found to be old dump areas. That could be the origin of the bricks also. if that were a possibility. I would go to the concrete slab and skip the other steps.
These are just some ideas and I have never seen the area in question, just my best educated guesses.

kenfarrell

thanks smearcase.. Type O in my original.... Very large Tarp... like the kind used to wrap a house when working in cold weather to lay bricks.. etc...

The house is 10 years old.. just bought it in Nov 07. I'm the third owner.

Water is not running into this space..(used as a drain) I believe the builder was just lazy and dumped garbage here... The neighbor tells me my house was one of the last to be built.. Fire Break I guess. and the 2 other owners didn't do much. Laid a patio... with 1.5' x 1.5 patio stones... I took them up because they were leaning into the house and water would pool at the wall... have to fix this.


Should I remove the clay to fix the pumping.... would a tamper fix it or cause more problems as it's only 2-3 feet from he basement wall.... I want to relay some kind of inter lock patio and not fixing the pumping would would be trouble for the new patio.

smearcase

I'm just guessing having not seen the lay of the land etc. But possibly the tarp was placed in an attempt to keep water from going down into the basement(?) But the tarp prob. kept the clay from drying out. Tamping the clay isnt a good option unless it can be kept dry and it sounds like it can't. I didnt realize the pumping area was close to the house.
I had a similar problem with a concrete (topped with loose laid brick) patio that was built level. Water seeped into the crawl space and rotted seven joists. I had to put drains under the patio to solve the problem.
I originally suggested (in my first reponse) removing the clay and placing coarse stone but that would not be good if it close to the house. It might allow water to seep down to the basement.
If you could place a 6" perforated drain pipe (holes oriented down at about 5 and 7 o'clock) surrounded with small (1") gravel or crushed stone at a decent slope (min 1/2" per foot) you could keep that area drained and replace the clay with stone up to the bottom of the patio. The perforated pipe and stone trench it is in will carry away rain seeping down from above or water level rising with water table).
It is most likely the wet clay that is moving. But there could be more trash and voids deeper down (similar to a sink hole) and if there is a void it will keep settling especially after heavy rains.
I think I would rent a small backhoe and dig a little deeper to see if there are more voids because if there are, anything you do up top could end up being a waste of time and money. As I said earlier, if the area is relatively small, a reinforced concrete slab ( 8" depth with rebar 3 in from bottom) might last for a long time but only if at least 2 opposite ends are resting on firm stable material. This would be a gamble without knowing about voids lower down.
I think your biggest enemy is the clay and voids in debris, but your biggest threat of all is water going to your basement.