Building a garage on a bank, now to back fill under

[Doing it for the kids]

so looking to build a traditional style oak framed garage about 10m wide by 7 deep.

Access is from the top of the bank which falls away about 2m over the 7 m depth.

I therefore need to build a retaining structure to hold back 2 m worth of retaining back fill, concrete pad then garage and contents off.

My initial thought was to sink some big steels in the ground and slot some grain walling in the slots to act as a wall.

Since been advised that this will not be strong enough so now looking at digging a trench and concreting in said grain walls to anchor full length in.

I’ll probably make the pad a metre bigger than garage so corner posts don’t sit right on the corner. The sub base is decent malmestone.

How does one work out how much thrust is exerted on the walls and thus what thickness etc is required?

Structural engineers have been confused and un committed so Far!

 

[Case290]

put the steel posts closer together and use stronger posts. And go deeper. I’ve see them 20ft panels used as retaining walls and there far to long. 10ft would be much better.

 

[pycoed]

Why not use concrete blocks laid flat? Double row i.e 18" wide for first 4 feet then 9" wide with piers up to slab. Golden opportunity to incorporate an inspection pit, too with guaranteed dry floor & fire escape door

 

[bobk]

The footings have to be at the lowest point , so at the front the footings will be 2.5 m deep , basically you flatten the land .

 

[upnortheast]

The footings have to be at the lowest point , so at the front the footings will be 2.5 m deep ,

Could step the footings ?

 

[bobk]

Could step the footings ?

Possibly , down to building control

 

[tomlad]

If there's a retaining wall , good plan to put a French drain behind it, try to keep the wall dryer

 

[How much]

so this is holding back the backfill rather than existing earth embankment ?

I don't think a structural engineer would probably do you any calculations or spec based on grain panels , they are not designed to hold back earth walls and as such the spec for them assuming there is one probably won't cover that application so he probably won't specify it even if it would work as they are all pretty risk averse for obvious reasons as if it failed you would sue him ! and he would therefore only specify a product designed for that type of application.

if your space not limited , could you have an embankment rather than a retaining wall , as if you layered and rolled in the fill putting geogrid in the layers you could end up with nice embankment rather than a massive concrete wall , you could perhaps put some gabion baskets or some large rocks at the toe of the slope sloping back up it to make it look better also and that would ultimately look better , after all there is no point in having a smart oak garage propped up on some ropey looking concrete the above

another alternative would be using some concrete lego blocks or a combination

 

[Pennine Ploughing]

Earth takes more holding back than most think, it get wet, it gets dry, it's gets wet and moves, years ago we had a silage pit, and back filled the walls, it was a wet spring, soil was wet, and it pushed the sides in, and it was only 2 meters deep, so don't do a half job on it

 

[Bongodog]

Steel frame, concrete panel floor, void underneath garage.