Gunns Contractors Ltd

[T whiting]

I'd be bloody amazed .....

Wouldn't be the first tank I've seen pop a d they go all of a sudden when they do go.

It'll be fine once the slabs on its the interim that you have to be careful with even if you fill it in temporally

 

[V8Druid]

Wouldn't be the first tank I've seen pop a d they go all of a sudden when they do go.

It'll be fine once the slabs on its the interim that you have to be careful with even if you fill it in temporally

tanks yes ...... this is a looong way from being a tank ... the buoyancy in that is probably negative for its weight as such a small volume in comparison

 

[DaveDCB]

tanks yes ...... this is a looong way from being a tank ... the buoyancy in that is probably negative for its weight as such a small volume in comparison

I have seen slabs of concrete cast in the bottom of holes split in half (pushed up!) from water!
I think Paul’s fine, I’m sure his Penny jar craned in will squash it back down

 

[T whiting]

tanks yes ...... this is a looong way from being a tank ... the buoyancy in that is probably negative for its weight as such a small volume in comparison

I don't believe that they make boats from steel I say STEEL

come on @Mogman furnish us with some measurements so we can do some maths

 

[Mogman]

I don't believe that they make boats from steel I say STEEL

come on @Mogman furnish us with some measurements so we can do some maths

Ok 6 cube of concrete @ 2.4 tonne per cube 14.4 tonnes
pannels 1.2 high 100mm thick 10m long 1.1 wide so 22.2m X 1.2 X 0.1 6.39 cube 15.3 tonnes

the hole was 10.5m x 1.5m x 1.4 but the top 400mm is made up hardcore so only 1 meter in the virgin ground so
10.5 X 1.5 X 1 = 15.75

therefore I have nearly 30 tonnes of concrete keeping 16 tonnes of water back does that sound right to you

 

[T whiting]

Sounds good to me

Always good to see maths put to practical use

 

[V8Druid]

Ok 6 cube of concrete @ 2.4 tonne per cube 14.4 tonnes
pannels 1.2 high 100mm thick 10m long 1.1 wide so 22.2m X 1.2 X 0.1 6.39 cube 15.3 tonnes

the hole was 10.5m x 1.5m x 1.4 but the top 400mm is made up hardcore so only 1 meter in the virgin ground so
10.5 X 1.5 X 1 = 15.75

therefore I have nearly 30 tonnes of concrete keeping 16 tonnes of water back does that sound right to you

yup .... sink like a brick .......
would need to be well over twice as deep to float in water (and have some freeboard) but then it would be a lot heavier .

 

[V8Druid]

I don't believe that they make boats from steel I say STEEL

come on @Mogman furnish us with some measurements so we can do some maths

and floated in 10" of water empty -- circa 6t

 

[Gunners]

Genuine question here guys. I find this all quite interesting. How did you arrive at the figure for the water? And does the water just have a static value or any pressure behind it?

 

[V8Druid]

Genuine question here guys. I find this all quite interesting. How did you arrive at the figure for the water? And does the water just have a static value or any pressure behind it?

water weighs 10lbs a gallon / 1kg a litre roughly ... cube of water is circa a tonne .. simple displacement maths if you place a metre cube in water as long as it weighs less than the water it displaces (pushes it out the way by being in the space it once occupied) it'll float ... fill your cube with summat heavier by the cubic metre and down it goes

 

[diggerjones]

water weighs 10lbs a gallon / 1kg a litre roughly ... cube of water is circa a tonne .. simple displacement maths if you place a metre cube in water as long as it weighs less than the water it displaces (pushes it out the way by being in the space it once occupied) it'll float ... fill your cube with summat heavier by the cubic metre and down it goes

Another question. Is concrete lighter when cured, as the water has evaporated

 

[Mogman]

Another question. Is concrete lighter when cured, as the water has evaporated

Thought it was more of a chemical reaction then water evaporated maybe the top bit

 

[Furniss]

Surprising though what can happen I have only had one come out of the ground .......we got the tank in the ground late in the day and hadn't got the IBC's with us so I set the hose running into it while we packed up etc
It was a 3000l concrete tank weighing 1.9t and the hole was only overdug by say 15cms all round - usually I leave the hose running and come back later that night to turn it off but this day I had a new bloke working for me who did all the maths and insisted that no way could it come out of the hole with the tank weight plus the maybe 1000l of water we had got into it, he was leaning on an open door because I didnt fancy the run back later, so like a numpty I listened, sure enough next morning it was bobbing about like a boat with about 60cms of water under it
Next day I put a decompression drain across the paddock to a ditch.

 

[diggerjones]

Thought it was more of a chemical reaction then water evaporated maybe the top bit

i ait got a clue

 

[TiltyShaun]

So the simply rule when putting in tanks is to make sure you fill it with more water than the ground water level. Don’t fill it faster than you have backfilled.

Basically, if putting a tank in. Follow the instructions!!

 

[Furniss]

Yeah common sense stuff really - and dont get your inverts too tight to minimums - even with a good bed they can settle and go slightly one way or the other, some tanks we put in have 4cm of fall through them and if they have less they can be failed on inspection but if they have more then they only get a remark on the report, so I try to leave some tolerance.

 

[T whiting]

So the simply rule when putting in tanks is to make sure you fill it with more water than the ground water level. Don’t fill it faster than you have backfilled.

Basically, if putting a tank in. Follow the instructions!!

Yes any tank that can be ballasted I chuck a hose in as soon as it's in the ground and by the time it's backfilled it's normally full for domestic stuff

It's when your on gas/petrol tanks that it's easy to come a cropper

The calculations for working out wether something will float are fairly simple once you've got your head round it measure the length /width/hight of the hole not the tank (the concrete needs to be inside the area calculated) that will give you a m³ volume if you worked in meters. Then for the weight take the amount of concrete used and times it by 2 to get it's weight in tons (yes I know it can be a bit heavier but it's better to be on the light side with the maths). If the volume is grater than the weight in tons it'll float like a boat if the hole fills with water if the weight is grater it'll sink like a submarine.

I can't see why concrete would get lighter as it cures but as it dries out over the next month/years I could easily see it getting lighter

 

[muckyman]

Strong pit it came up in one piece

 

[DaveDCB]

I had one idiot builder have me put the bucket over the treatment tank as he backfilled with s4 concrete... needless to say it destroyed the tank! He didn't listen to anything I had to say to him

 

[diggerjones]

So i just watched 1 of ollies videos, and when hes directing chap on telehandler, ollie is doing the swirly finger motion pointing down. Got me thinking, why not just point down. I've seen it done loads and no doubt done it myself .