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difference between hard rock & soft rock

difference between hard rock & soft rock

(OP)
Hi

we are argumenting with the contractor about the soil, which he needs to excavat. He says this should be paid as hard rock but I think this is still soft rock.

how or where is the diference between this two? How can we classifie it on the site?

Regards

TomTOm

RE: difference between hard rock & soft rock

Looks pretty soft to me... what is the norm in your jurisdiction? and is there any local definition?  I would normally onsider sedimentary rock as 'soft' and igneous and metamorphic as 'hard'.  Can you check with a local geotekkie to see if there is any 'formal' stipulation.

Dik

RE: difference between hard rock & soft rock

The way I have seen it defined in most specifications is by reference to being rippaple by a given size tracked machine, say a D9.

RE: difference between hard rock & soft rock

Looks soft to me but I am not a geotechnical engineer. I would not be giving advice as a structural engineer on what the material which is to be found on is. Rather, I would give a footing size with a minimum required allowable bearing capacity and then would get the contractor to pay for a geotechnical engineer prior to placing concrete.

I have seen in the past a hard rock (alloable bearing capacity of 600kPa) and the rock was white in appearance and the contractor mentioned that it was very hard rock to try an drill through.

RE: difference between hard rock & soft rock

(OP)
we work here according to the SABS south african standards or even BS british standards.

Is there not like a test with a pick or a pole which you hit into the ground?

The only part in the SABS which classifies it refers to heave machines and the afford to remove it. This does not help me since we don't have any of such machines on the site

Tom

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