Stone fill of large cistern

[baterboy]

Our industrial client has a large cistern no longer in use that he wants filled with stone and a new concrete top constructed. The cistern is 18' in diameter and 40' deep with a steel beam and concrete top. The beams have deteriorated and the concrete is failing. The walls are brick and stone in reasonable condition. Ground water fills the cistern to a height of about 25'. The cistern is in line with a truck dock and the concrete top must sustain tractor trailer loads.

We are proposing to remove the existing concrete top and beams and pump out the cistern. We would then install 10' of #4 stone and 20' of 3/4" stone followed by tamping with a boom mounted vibratory compactor. From prior pumping of the cistern ground water refills to the 25' level in about one week. We would stop at the 30' level to construct two concrete walls about 6' wide by 6' high closing two vision holes from a tunnel adjacent to the cistern. Once the walls are completed we would continue with the 3/4 inch stone fill and boom compactor to the top. We would then anticipate constructing a concrete slab on grade over the cistern fill and walls.

We would appreciate any comments regarding the fill process and possible settlement due to our proposed stone filling technique.

 

[beej67]

Just curious.. ..if you're abandoning the cistern, why not just fill the whole thing with soil?

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[JedClampett]

Adding to beej76's response, what's your end goal? If it's just removing the fall hazard, dirt will be fine. If you want to keep it dry, you'll need some cementatious material.

 

[baterboy]

As originally stated, heavy trucks will cross or sit on the cistern top while going to the loading dock. The intent of the stone fill is to provide a suitable base that would support a reinforced concrete slab that would not settle under the truck loads. Ground water would continue to fill the stone voids to a height of about 25'. If settlement is to be expected, then we would have to consider additional support beams under the slab, either steel or concrete. The question is whether the proposed stone fill procedure will provide a stable base without settlement. Would appreciate any thoughts or other procedures.

 

[bimr]

It sounds like a reasonable plan as long as the aggregate material is compacted.

Was this some type of well in the past? If so, you should follow well abandonment procedures.

Filling the cistern with gravel will provide a conduit for surface water to enter the ground. Sealing the top of the shaft with 3' of clay or clay-rich soil will prevent this from occurring.

See the attachment for abandonment of wells.

 

[cvg]

with good quality control you can eliminate most of the settlement. however, if it was me I would use a flowable fill to keep the water out and eliminate the need for compaction. perhaps a 1/2 sack slurry with about 9 inches of slump. place in lifts, little to no vibration required. zero settlement and zero water intrusion.

 

[Ron]

My concern would be raveling of adjacent soils into the stone fill. Why not use a combination of stone and soil that will cut out the larger voids and provide an extremely competent base for pavement.

 

[dicksewerrat]

I would get some 4 inch minus rock. dump in 10 feet then pump in flowable fill till level. Repeat 3 more times. Last lift, only do 9 feet. Construct your new slab.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilman72]

So many divergent opinions in this thread.

I would drop in a pump and create a water feature.

 

[LittleInch]

Foamed concrete??

Used to fill lots of voids.

http://en.wikipedia.org/wiki/Foam_Concrete

http://www.foamedconcrete.co.uk/foamed-concrete-applications/

(look at the sinkhole!)

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cvg]

cellular foam concrete, not a bad idea and might be cost effective - just make sure no water gets in, or design the lid to handle the bouyancy.

 

[baterboy]

For dicksewerrat. Are you suggesting that the flowable fill would work its way down through the 10' of #4 stone and fill most of the voids. If so, what flowable mix would be required to obtain this possibility.

 

[dicksewerrat]

Not #4 stone, I have no idea what that is. 4 inch minus stone. Maybe graded 50% 4 inch stone, 15% 3 inch, 20% 2 inch and 115% 2 inch stone. this would be the stone retained on a 4 inch screen etc. the flowable fill should go into that. Or put in 5 feet of flowable fill, add rock till it shows at the surface of the fill. Repeat till you get to a foot below grade. then design build the top slab. To get a mix, contact your local supplier. they may have a better idea.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[cvg]

i think Dicks idea is for preplaced aggregate concrete (PAC). not sure that is the most cost effective option but it is feasible.

http://wri.usace.army.mil/remr/technical_notes/concrete/CS-MR-9-4.pdf

 

[bridgebuster]

dick - AASHTO No 4 stone is 1 1/2" to 3/4" gradation, with a trace of smaller material

 

[dicksewerrat]

That would be way to small. the voids would not fill up.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[baterboy]

Dick - I'm sure that I'm older than you and did not mean to confuse you. The old grade for 4" stone or ballast was 4. The new AASHTO grade is #1. Thanks for your input to date. We are trying to price out the project for different methods to see what the client wants to do. Will update as we proceed.

 

[dicksewerrat]

When I was doing trench work, we called out the sizes of the rock unless it had a DOT spec. And I bet we may be the same age. I have spent 48 years working in sewers.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[baterboy]

I was wondering where the sewerrat came from. Your getting close to me. University of Pennsylvania CE '55.