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Hello All,
. I am constructing a g+2 house. As a result of soil testing , i was asked to go in for a raft foundation as the soil is loose.The engineer has suggested a 8 ft excavation on which a 2ft boulder, 6 inch pcc and a 2feet raft will be put. The columns will be raised on the raft. I would like to know if this is ok and the steel inforcement details for the same.

Thanks
BM

@BM,

Just like when doctor suggests a big procedure you take second opinion, you should do the same for this problem too.

My Structural Engineer is doing Ph.D in con-conventional structures. He studied our soil testing reports and suggested foundation depth. PM me know if you need his contact.

how much was the sbc ?

The report is as below:

bore no values. Sbc T/m2
bh01 5. 5.0
. 40. 20.0
bh02. 6. 6.0
. 31. 20.0

bh03. 5. 5.0
. 40. 20.0

Pls read it as boreno. nvalues. Sbc (T/m2)
. 1. 5. 5
. 40. 20
. 2. 6. 6
. 31. 20
. 3. 5. 5
. 40. 20

you did a very good thing going for the SBC test , in fact it should be a safe practice when buying the site as well.
5T/M2 is low Bearing Capacity , your site could be a marsh with low water table or Unmanaged landfill , you might have to go with raft as suggested by your engineer. If you carefully read your remarks on the test report \ inference,it might have suggested kind of foundation or at least mentioned not suitable for Shallow foundation. Or you can call the test agency and get their opinion free of cost.

Is this 5T/M2 or 20?

regards

The table has 2 n values for each bore point. For a n value 5 it is 5t/m2 and for a n value 40 the sbc is 20t/m2.

Also the first set is for a depth of 1.5 m from ogl and the second set if for 4.5 from ogl.