Need a Conveyor

So, you're down into the water table. I would guess that the level doesn't fluctuate more than six inches between wet and dry seasons.
Do you really want to pump water for the rest of your life?
Pool liner or fiberglass shell tall enough to get above the water level?

 

Not so sure that would work. In a typical application, a liner is held in place by the weight of the water inside, in this application, you'd have the water trying to dislodge the liner so, you'd need to find a good way to secure it without any penetrating fasteners below the water line.

 

Scenario:
Prefabricate the rebar in manageable sections.
On the day of the concrete pour, pump down the water, line the hole, cover the liner with old carpet/padding, lower in the rebar, tie it together, add tall enough wood forms to get above the water level, pour concrete.

 

The only passive solution I can think of would be a fibrous material to wick the water down a PVC pipe to a point outside where it can evaporate. It would still need maintenance and the scale/length may not be practical, even so it works for large trees to transport water to the leaves. Imagine a synthetic tree that wicks the water to roof level to evaporate in the sun over some square feet of wick area, it would still work at night just not as fast and only high humidity/freezing would stop it working. The only disadvantage would be a 4-6" bore PVC pipe under the slab to take the water outside to the evaporation point. It would also act as a substrate to grow bugs on and need maintenance.

 

Yup, this water is an official pain in my ASS! I'm from florida and we build pools BELOW a very high water table all the time. Granted, the job is pumped 24/7 until the gunite is blown AND the pool is finally filled with water. The weight of the water keeps from floating the shell. We had one pool resurfaced (which really sucks btw) and again the pump was turned on to remove ground water under the shell while it was recoated. I know there has to be some way to figure out what kind of up pressure is exhibited on a slab of 107"x207" concrete with some heavy anchors in the wall. Add that weight of 7000 pounds of lift and a couple of cars and at what point could it actually float?

Bonz recommended basically how swimming pools are built. With shorty concrete walls up the side from the slab it could act like a tub. 5000psi concrete is water proof. I am considering 45mil EPDM rubber and plastic as a first line of defense from water. The expensive rubber doesn't have to envelope the entire hole, just give me a dry area to work and prevent water ingress in the future. The carpet idea is a pretty slick idea to protect the important membrane.

More ball scratching is certainly required in this instance.

Any of this mean anything to anyone? https://precast.org/2010/07/designing-bottom-slabs-for-water-pressure/

 

From my understanding of physics in ordercto calculate if your concrete shell lining the hole will be lifted by the amount of water it will be sitting in you need to compare their densities ie if the density of the shell is less than the water it will lift, if notvthen you will be ok.

 

To add
The drnsity of water is about 1
To work out the density of the shell equals its mass divided by its total volume including the space inside.
To accurately measure the density of your water you can do the same or use a hydrometer. I think the presence of dissolved salts will slightly increase the density.

 

Look at the big brain on you buddy! lol

I've been in contact with another WEMET lift owner and this guy is in Belgium. He hit me up for details about what I bought. Anyways, I dropped him a note about my water well and here was his reply. The photos below are of his construction. He is new construction and looks like it's no joke. I think he's got some good ideas how to fight this.



Damn, thats unfortunate. Here in belgium, when we build houses in wet soil, we have a very large pump, that has a large hose to it that runs around the basement. Than we connect smaller hoses to that big hose all arround the area. Those smaller hoses are put in the ground with a pipe on it with small holes drilled in it. It sucks all the water out of the soil, littarally lowering the waterlevel in the soil.
Then when you have finished the hole, be quick with you concrete and make sure to make it waterproof. Here we use 2 methodes. We put a thin stainless steel plate between the joints, or if you are pouring concrete with a joint to existing concrete, we use a rubber band that swells after some time when exposed to moisture, and then cures
In your case i would do it in a cheaper way
Take 4 pipes, say 1inch, make some teeth on one side, and drill those suckers in the ground by rotating them with some downwords pressure and pulling them back out to get the soil out of the pipe every couple of inches. When they are in on all four corners, put soms cheap harborfreight pumps on them, and let them run untill the are having trouble finding water.
In the meanwhile keep digging finish up, letting the pumps run as long as possible to only pull them out, right before you pour the concrete
I have added a picture of a professional pump to give you an idea.
Also added some pictures of my progress
Started digging around 2 months ago, had nothing but bad luck eversince. From day one, started raining, freezing, snowing, .... everthing at once, non stop for the past 2 months. Pushing me to the point of almost trowing in the towel and just sell the whole lot as is.
I dug the hole but dirt collapsd everyday, making its way into my rebars. Making me restart every single day, again and again. Finally had a dry 2 weeks now, that gave me the chance to hurry up, and pour some concrete.
Added a photo with the current status.

 

You could use a simpler method. For a small excavation like yours mayby dig a small pit at the side of the main pit big enough to take your pump and a couple of feet deeper than the bottom of the main pit. You can then extract the water from below your main pit keeping it dry for lining with membrane and pouring the concrete. Sorry if this has already been suggested

 

Concrete’s density is about 2.4g/cm^3. So, your hole has to be occupied by 1/2.4=.4 or 40% concrete to prevent full saturation floating!

Of greater concern is power failure. The sump stops working during a storm and the car is in the hole without power to lift it. Ooops. So, adding to the complexity is a needed backup genset and someone on site to run it.

Maybe buy one of those aluminum-coated fitted covers, park it outside and call it good?

Denis

 

He's almost to depth before hitting water.
Don't fret too much.
Line it and pour

 

I punched another big ass hole down. The resting water table level is at 101". Now my fully collapsed hydraulic double decker pecker wrecker lift is exactly 94 1/4"
Now if it sits on 6inches of concrete, I'm right there at the water table. I think Bonz and Mantrid have the right idea, over dig to a slope, pump the shit out of it, bring in in the rubber bag, plastic the hell out of the base and a few feet up the walls. When all is said and done, if the water comes up 6inches on the sides, would it really float the slab??? I really need to pitch this idea by my engineer dude, I think he's going to want raft construction for that slab or pillars. Wonder how hard would it be to drive 20 of these I beams into the ground? I can get them for a mere 2bucks a foot.

Kelly has a good question regarding future water height... Only one way to find that one out is take it through a rainy season. (if there is such a thing in dry ass west Tejas!)

 

I missed something.... Tonight, I dug out the sump pit probably another foot. Before the pump was removing around 8 gallons of water every 50mins. Now that I dropped it down a little more, it's cycling every 20mins the same amount! My guess is I've just exposed a little more of the water column and allowing more water to enter my pit. If I shut it off and allow the water to come up, it matches the 2nd hole at 101". So if nothing changes, the water will be just below my floor, but the footers will definitely be buried. That doesn't bother me except for the MESS digging them out. Which hopefully could be solved with creative digging. I do have a very large drainage ditch behind the back fence, so I won't have to flood the street for a few months while this takes place. Just hide the garden hose in the weeds and let the city have the water for free.

 

To clarify the photos above what Hans here is doing.... The pit on the lower left is where his lift is going. You are looking at the basement floor. He is using his lift to lower vehicles from the garage floor down into his basement. If you think this kind of work is expensive here, multiply it by 3 for a job like this in Europe. This shit is BIG BUCKS over there.

 

Will it float?
What you are building is a displacement hull boat.
If we reverse calculate the displacement you can determine how tall the water column needs to get before it floats.
Determine the mass, the floor + the walls + the lift.
Your area is fixed, L x W. The variable will be the Height. This is the displacement needed to float the pounds of weight.
I gotta go open a slow flowing floor drain so no time to calculate.
I'll leave it to the math guys.

 

I was thinking the same thing and put a sump pump in it. It's cheap insurance, maybe you'll never need it, but if you ever do, you'll be very glad it's there. And, if there's the slightest case that the concrete pit could become buoyant, put a perimeter drain and sump around the outside of the pit too.