Raft VS Piles

[engvin]

I looked at some trial holes for a house (2 storey). The ground make-up was generally loose sand (3ft) over soft blue cobbly clay (10") over running sand.

I am assuming a raft foundation would suit this situation, are there any specific issues relating to the ground conditions I should be looking at?

What would be a practical bearing pressure to assume for this type of ground. I think the house will impose a pressure of approx. 20kN/m2.

If I build up existing foundation excavations with hardcore compacted in layers to the underside of the raft would this be reasonable?

 

[garrettk]

Perhaps a call to your local geotech firm would be a good start. It sounds like a fairly nasty subsurface set up.