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Posted: Wed Nov 23, 2005 7:22 pm
by Nik
Hello,
I'm just in the proccess of planning and quoting for Block Paving with Brett Omega Charcoal paving about 210sq mtrs in the corner of a commercial yard used for parking and as an occasional (once a week) truck turning area (40-foot artic stuff!!).
I'm working on the lines of 300mm sub-base (DTp1) with 100mm thick blocks (as in 2005 catalogue), is this excessive and would you sttle for 250mm and 80mm blocks? Heavy commercial is not my usual remit!
An area adjacent to this has been done (not by myself I may add) within the last year but has sunk about 90mm hence my overkill approach. I know the sub-soil is good sandy ballast at the depth this would require (450mm), but with the site being 80mm above finish level I'm making a lot of muck to take away!!
Experienced advice very welcome.
Posted: Wed Nov 23, 2005 11:26 pm
by Tony McC
80mm blocks should be fine. The 100mm blocks are really only necessary for exceptional loads, such as at ports. We used 80mm blocks on dozens of freight yards and never had a problem.
The key to successful design is knowing the CBR of the sub-grade. if you have sandy-gravel, or gravelly-sand, that should give a CBR in excess of 10, so there should be no major problem.
I would probably go with summat along the lines of a capping layer of 100-150mm, then a geo-grid with equal longitudinal and transverse strength. On top of that, two sub-base layers - the lower one being 150-225 deep type 1 compacted to refusal with a bloody decent double drum vib roller and then a top layer of 100-150mm type 1, again compacted with the roller.
Keep the laying curse down to 30mm and make sure you use a Zone 1 sand, nothing less. Although a zone 2 should be ok, with all those shearing forces from the artics, I'd be worried about the crushing effect.
Other than that, make sure falls are ample and that the drainage is adequate and functional. If your client is really concerned about settlement, then it might be worth talking them into using a CBM sub-base to replace that top sub-base I mentioned earlier
Posted: Thu Nov 24, 2005 6:25 am
by Nik
many, many thanks........and 3 further questions 
What would you recommend for the Capping Layer?
& if you recommend CBM rather than mass concrete what spec?
My local BM's go vague and confused at the mention of zone1 / Cat1 sand, so if you know of local supplier for that too........
p.s. i see a similarity between a picture in your concreting section and that of a beam screed from 'hopefully sometime soon'
Posted: Sun Nov 27, 2005 6:57 pm
by Tony McC
Capping layer - Type 2 or 50mm crusher run, whatever is available locally at the right price.
CBM is mass concrete, so you need at least 100mm, preferably 150mm
Local BMs? Sorry, but I'm not familiar with that part of the country. I know Meakins in Basingstoke, and Crescent at...at.....at Uxbridge (I think), but that's about it. Anyone else familiar with this Maidenhead place?
Posted: Mon Nov 28, 2005 8:56 am
by Nik
Thanks again for reply, but more confused now,
your original post;
'I would probably go with summat along the lines of a capping layer of 100-150mm, then a geo-grid with equal longitudinal and transverse strength. On top of that, two sub-base layers - the lower one being 150-225 deep type 1 compacted to refusal with a bloody decent double drum vib roller and then a top layer of 100-150mm type 1, again compacted with the roller.'
=
Capping layer + grid + 2 layers Type 1
Later post =
Capping layer (Type 1) + grid + Type 1 + Type 2
if i'm reading your posts correctly (prolly not)
so where is CBM? and would C20 be close to what you had in mind for CBM?
Sorry if I'm being stupid here!
Nik..
Posted: Mon Nov 28, 2005 4:53 pm
by Tony McC
No, you've confused yerself!
The capping layer material was unspecified in my original post; you asked for a spec; I suggested Type 2 or 50mm C.run
The geo-grid remains, then two layers of Type 1 granular sub-base.
Then you asked about the possibility of using CBM and I suggested 100-150mm. CBM is a mass concrete and the specs for the various types are given on the sub-bases page. C20 is not really a CBM - it's more correctly described as a concrete hardstanding or a slab, although it is occasionally used as a CBM sub-base. The thinking tends to be that, if the site warrants use of a 20 Newton concrete as a sub-base, there's summat seriously wrong with the sub-grade.
Posted: Mon Nov 28, 2005 5:18 pm
by Nik
Doh!
thanks.