Hardcore for retaining wall

[richard7761]

Normally you would build on undisturbed soil. But I've disturbed the soil. Anyway, I'm going to fill in a trench with hardcore and compress it with a tool I've made. My tool is a large piece of wood with a 1/2" thick plate on the end. I'll put a layer of hardcore down, compress, then put another layer down, etc. On top of the hardcore will be a layer of concrete. Then wall built on that.

But, just focusing on the hardcore, I've got broken brick and also lots of stones out of the ground (sandstone). How large should the hardcore be? Do I put any soil in with the hardcore? (sort of replicating the original undisturbed soil conditions). Should I put in the stones?

 

[richard7761]

I think good hardcore contains both fine particles and not so fine crushed brick or concrete. What I'm doing is just taking from this pile of stones and broken bricks, but I'm not throwing in any fine particles that would have been created when I broke some of the stones and the bricks up. The stones (especially) do crush somewhat when I use my compressor tool. I really bang down on the stone and brick chippings. But, in an effort to make it look better settled I'm throwing in dirt and not any fine stone or brick particles. And I'm wondering whether that is a mistake, and that what I should be doing is keeping the fine dirt out, and making sure that fine stone and brick particles is put in with the stones and brick chippings. What say? Thanks.

 

[digdilem]

Not enough info. What you describe is fine for a small retaining wall, but a hand-tamper is not going to be able to consolidate well enough for a sizeable retaining wall.

 

[noseall]

If it means anything to you Richard 7761, i think your idea of making up ground with manually consolidated material, then building a retaining wall on top is bonkers.

 

[Static]

Agreed would never do it, would fill the disturbed area in with lean mix concrete.. your never going to get it fully compacted manually and it will sink or cause rotation in the wall..

 

[richard7761]

Yep, I've put some stone in the trench, and tampered it down -but it just doesn't look good. There was going to be a 100mm concrete foundation on top, but it's just not going to stop rotation. Best to put some cement in and produce a concrete. It's only a small brick wall (1.1m high), so no real downward pressure, might not settle much, but it's the rotation that is the key thing. What is a lean mix? Lots of stone, minimal cemement?

 

[Static]

Yer basically, something like urm 1:3:6 cement:sand:agg.. or can go leaner if its not critical.. 1:4:8 maybe

Anyways you need something thats stable or your wall will move and crack and in 2 years you'll be repairing it and in 5 rebuilding..