I live in an area which is pretty sandy especially when they dug the house foundations and drainage and filled the gaps around the brickwork with sand dune sand!
I've excavated the extended area of my drive and it is now full of MOT.
I dug down about 500 mm in places to remove all the sand until I reached what I'd call fairly solid soil/clay. Hence the reason it has so far swallowed 15 tonnes of MOT!
Now I'm digging out the main run of my drive and I reckon the same depth of sand will be there too.
My question is am I going OTT in digging down to this depth or is simply digging down 300mm with 200mm of sub base enough?
You can see the depth of my excavations of this picture.
Some natural sands, and especially the sandy gravels, are actually excellent sub-grades for construction purposes. If you look at the table used to give guidance on typical CBRs for British/Irish soils, the sand/gravels are rated at 40-60%ish, while even firm clay is only rated at 6-8%.
So: if the sand is natural (ie: not backfill), and is well compacted, leave it be. Just use a standard 100-150mm sub-base, and that will be more than adequate. However, any backfilled areas should be excavated to make sure you have a firm substrate.
we did work in leighton buzzard (built on sand deposits) and the BCO are happy for us to pour foundations on virgin sand
just the back fill they dont like
cheers LLL
it was basically building sand,we could have sieved it and used it but it was just skipped
nice lumps of sandstone but nothing like the injun stuff
cheers LLL
p.s. we named the job "sands of iwo jima" as for every 1 foot done the trench was 2 wide,has to shutter it to crete it
Thanks for the responses fellas.
There is an area of concrete on the driveway that is just 3 inches deep (Which has cracked and dropped as the sand is so soft) so I cut a hole in it to see what was beneath and again it's soft sand.
It's definately back filled sand even though it has been there 70 years. When its wet it just crumbles. The gravelly part in the picture is an where the driveway has been extended sideways and filled with gravel instead of concrete.
Now I just need to work out how I'm going to organise such a big summer project with so much material involved.
i would of thought after 70 years the sand has sank as much as its going to. i would think as long as you dig out as you would any spoil to the required depth ( maybe cover in terran) 100ml of type one etc you should have a sound finish. personally i would leave it in. the fact that the existing concrete hasnt sunk too much is testimony to its strength.
