Raft foundation or potentially something else?

[^woody^]

Trust me on this it's a shocking build.

And yet the foundations have performed OK for 40 years, despite the "desperate miners" lack of building skills?

BTW, if miners built this I'd suspect deep foundations.

You'll need a engineer's input in terms of what to look for and how to look for it for all this proposed extra weight, not a forum, and not DIY random digging,

 

[asnoop20]

And yet the foundations have performed OK for 40 years, despite the "desperate miners" lack of building skills?

BTW, if miners built this I'd suspect deep foundations.

You'll need a engineer's input in terms of what to look for and how to look for it for all this proposed extra weight, not a forum, and not DIY random digging,

You've jumped the gun. I am feeding this to a SE. Knowing it isn't a raft, i.e the floor is not structural, progresses the next decision.

 

[martygturner]

If that was the case, more likely a raft to deal with any poor load bearing, or piles.

No not really, its all about the soil profile, closer to a river channel you tend to get a structured soil profile eg layers of material as its prone to flooding and therefore deposition but away from a the channel you get chaotic soil profiles laid down by large events, eg the end of an ice age which was not a single event but large floods over thousands over years, which in England is generally clay soils intersperse with gravel and sands see https://mapapps2.bgs.ac.uk/ukso/home.html?layer=NSRISoilscapes if you look at the rivers you can see that the soil types are pretty uniformed.

In a structured profile that can be saturated you would look for a layer that is compressed, if you build a raft then you could easily end up with failures due to liquefaction in saturated soils. Rafts tend to be used to get over problems with non uniformed chaotic soil profiles across the site.

But piles are a really good choice to.

 

[noseall]

Knowing it isn't a raft, i.e the floor is not structural, progresses the next decision.

Why the emphasis on the floor, in particular?

 

[asnoop20]

Why the emphasis on the floor, in particular?

For an RSJ opening the SE wants a new wall, I was happy to build it but only if I didn't have to start digging a new foundation for it. I drilled a hole and had about 23cm of solid material and with it being closish to a river suspected I could have a raft. With a raft the floor is structural so was a solution to the wall.

No raft means the solution has to not involve building the wall, or I abort. This I relayed to the SE.

 

[stevie888]

Has your SE done any investigative work?

The edge detail doesn't look like a raft but if you have 230mm of concrete in your floor, even allowing for screed that seems rather thick.

FWIW raft foundations are often used in soft ground where there is no decent material within sensible reach for piles. Canvey Island is a prime example.

 

[asnoop20]

I think they didn't bother with hardpack just poured the concrete straight in. It might be 18 or 20cm, it was difficult to tell. As thick as it is it's not re-enforced unless it's a raft.