Increasing the height of silage pit wall

foxy farmer

Anybody raise the height of a silo wall. Looking at raising one here from 6ft to about 7ft6. Existing Wall is 12" thick and parallel sided ( not tapered ). Ground level is almost level with top of existing wall and settled with yrs. Was thinking of drilling existing wall hammering in plenty rebar erecting the shuttering and pouring concrete. Then afterwards I am thinking of digging 2x2 ft footings every 10ft outside the new wall and then pouring a pillar or buttress on the footings against the wall.
Any opinions on this or alternative suggestions welcome.

Sam Kade

I did it to a slurry tank to raise it 4'. I drilled holes a foot apart and 6" deep into existing wall. The holes would want to be almost the same diameter as the rebar so that it will stay in position. I put every second bar to inside edge and outside edge of the wall. The height you are raising your wall there should be no need for piers IMO.

Cavanjack

Sam Kade wrote: »

I did it to a slurry tank to raise it 4'. I drilled holes a foot apart and 6" deep into existing wall. The holes would want to be almost the same diameter as the rebar so that it will stay in position. I put every second bar to inside edge and outside edge of the wall. The height you are raising your wall there should be no need for piers IMO.

There is a chemical anchor used in this situation. Drill the hole a couple of mm bigger than the bar and pump in the chemical then insert the rebar, let set then install shuttering. One would really want to consult with a structural engineering before undertaking this work as regards distance between rebar etc.

Sam Kade

Cavanjack wrote: »

There is a chemical anchor used in this situation. Drill the hole a couple of mm bigger than the bar and pump in the chemical then insert the rebar, let set then install shuttering. One would really want to consult with a structural engineering before undertaking this work as regards distance between rebar etc.

The man I had doing it is a qualified builder and is doing tanks with years, I have plenty confidence in him. Employing an engineer to raise a tank a few feet would end up costing more than the ready mix.

Miname

Rebar and the chemical anchor as said. I wouldn't be pulling the rebar far off centre . Keep it 4" minimum from the outsides lines. You could cut a track into the wall and set a flat steel into it the whole way round to form a real good seal.

raypallas

Sam Kade wrote:

The man I had doing it is a qualified builder and is doing tanks with years, I have plenty confidence in him. Employing an engineer to raise a tank a few feet would end up costing more than the ready mix.

Yes but would anybody stand over it afterwards if it collapsed?

Bullocks

Sam Kade wrote: »

The man I had doing it is a qualified builder and is doing tanks with years, I have plenty confidence in him. Employing an engineer to raise a tank a few feet would end up costing more than the ready mix.

An engineer wouldn't rob you for a simple drawing like that and I would prefer to pay it for peace of mind

Cavanjack

raypallas wrote: »

Yes but would anybody stand over it afterwards if it collapsed?

My point exactly. If you've a man putting up silage and the wall falls and the tractor with it and somebody gets hurt you'll be thinking to yourself the engineer would have been good value. Shouldmt cost a fortune either.

Water John

Mimame, putting rebars in the centre is totally ineffective.
The bars must be close to the outside and/or inside.
Think of the pressures on the wall.
Why is a steel pipe as strong as a steel bar, when you try to bend it? Because the steel in the centre doesn't contribute to the strength.

rangler1

Water John wrote: »

Mimame, putting rebars in the centre is totally ineffective.
The bars must be close to the outside and/or inside.
Think of the pressures on the wall.
Why is a steel pipe as strong as a steel bar, when you try to bend it? Because the steel in the centre doesn't contribute to the strength.

and the rebar would have to be fixed in the bottom wall too or it wouldn't be worth putting in, probably those in the business would be better to ask

Miname

Water John wrote: »

Mimame, putting rebars in the centre is totally ineffective.
The bars must be close to the outside and/or inside.
Think of the pressures on the wall.
Why is a steel pipe as strong as a steel bar, when you try to bend it? Because the steel in the centre doesn't contribute to the strength.

It does but if it's too close to the edge it can start to rot. It's why there's a minimum spacing from the edge. On a twelve inch wall you will have a four inch line up the middle to work with any more and your waiting from rust. At ranger the chemical anchor fixes it into the bottom wall. You'd use a 16mm sds bit for half inch rebar then clean the holes out with a compressor and the chemical anchor is pumped in, you'd never move them bars without tearing the wall apart. It's an 18" raise not the Berlin Wall. If the bottom wall is sound I wouldn't worry about it.

Bullocks

Miname wrote: »

It does but if it's too close to the edge it can start to rot. It's why there's a minimum spacing from the edge. On a twelve inch wall you will have a four inch line up the middle to work with any more and your waiting from rust. At ranger the chemical anchor fixes it into the bottom wall. You'd use a 16mm sds bit for half inch rebar then clean the holes out with a compressor and the chemical anchor is pumped in, you'd never move them bars without tearing the wall apart. It's an 18" raise not the Berlin Wall. If the bottom wall is sound I wouldn't worry about it.

I bought the hilti gun for the the chemical anchor last year , it gets a savage grip alright

Miname

Bullocks wrote: »

I bought the hilti gun for the the chemical anchor last year , it gets a savage grip alright

I hate seeing those Hilti reps. I'm usually a few quid lighter when they leave. Serious equipment but.

Water John

50mm in from each side of 300mm wall.
Just cut through a slat and see where the bars are.

Sam Kade

raypallas wrote: »

Yes but would anybody stand over it afterwards if it collapsed?

There's no fear of it collapsing, I've seen tanks built with 6" blocks 8' deep nearly 40 years ago that have held up slats and cattle every year since so 35n concrete and rebar will have no trouble and it's also an open tank.

foxy farmer

To pull the rebar out of the wall bearing in mind its only18" high and 1ft wide youd want to apply some serious force to the upper inner edge of the wall. A loader tyre rubbing off it while filling the pit isnt going to rip it off like velcro. Id like to put in a few pillars just for peace of mind. Not a major job and wouldn't take much concrete. 4-5cuft per pier maybe.

keep going

foxy farmer wrote: »

To pull the rebar out of the wall bearing in mind its only18" high and 1ft wide youd want to apply some serious force to the upper inner edge of the wall. A loader tyre rubbing off it while filling the pit isnt going to rip it off like velcro. Id like to put in a few pillars just for peace of mind. Not a major job and wouldn't take much concrete. 4-5cuft per pier maybe.

Surprised nobody has asked how old the wall is and its condition. 12 inchs isnt massive thick for silage pit wall, ours are 18 inchs and how well speced was the reinforcement in it.ive done putting 18 inchs on slurry tank wall and it was no problem but as part of the job we had to put a bank against the bottom of the original wall which gives it support

darragh_haven

Cavanjack wrote: »

There is a chemical anchor used in this situation. Drill the hole a couple of mm bigger than the bar and pump in the chemical then insert the rebar, let set then install shuttering. One would really want to consult with a structural engineering before undertaking this work as regards distance between rebar etc.

An engineer wont stand over this work even if he does do a design for it..... unless he designed the original wall AND signed off on it.

PS. I wouldn't bother my hole with an engineer anyway for what the OP wants to do