Soil Bearing Capcity From Cone Penetration Test Data???

[TekEngr]

Any one can tell me how i can calculate soil bearing capacity at 2m level from below provided data however in soil test report soil bearing capacity is recommended 0.75kg/cm^2 at 1m depth for shallow foundations but i want to construct my footing below the underground water table level at 2m. (underground water table level is below 1m from natural level).
I guess the bearing capacity will be more at 2m level for footing (footing might be isolated or might be raft).

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3. SUBGRADE CONDITIONS
Soil conditions on the basis of existing ground elevation investigation by Boring and cone penetration data is as follows :

0.00 - 2.00 m : A clay, a medium stiff consistency
to stiff, brown color with cone penetration resistance, qc = 10-20 kg / cm2.
While the borlog NSPT value = 7-9 blows / 30 cm penetration,

2.00 - 6.00 m : Is sand, dense medium brown color
with the value NSPT = 18-32 blows / 30 cm penetration and qc = 80-250 kg / cm

6.00 - 16.00 m : A layer of sand, dense brown color with a value NSPT
= 34-47 blows / 30 cm penetration

16.00 – drill end : A layer of coarse sand, very dense brown
with the value NSPT> 60 blows / 30 cm
penetration From the cone penetration work, hard layer (quite hard layer), the layer with value (qc) cone penetration ≥ 250 kg / cm² encountered at depth as follows:
S1 in depth - 3.40 m from the existing ground surface elevation
S2 in depth - 3.20 m from the existing ground surface elevation
S3 in depth - 2.80 m from the existing ground surface elevation
S4 in depth - 2.40 m from the existing ground surface elevation

 

[HENRYZAU]

What's the footing size?

 

[TekEngr]

Below is the roughly estimated footing sizes.
Raft footing size 18m x 46m (bottom level of footing is below 2m from NSL)
Isolated Footing 3m x 3m (bottom level of footing is below 2m from NSL)

 

[EireChch]

Google CONE PENETRATION TESTING (CPT) "Simplified Description of the Use and Design Methods for CPTs in Ground Engineering' from Fugro. This document contains information on how to assess bearing capacity. Its a starting point.

If you have a raft as big as you have said bearing capacity failure may not be an issue (depending on your loads) and you will likely need information on your modulus of Subgrade reaction to design the raft.

 

[HENRYZAU]

I expect that settlement governs for both footings.

 

[TekEngr]

How we can control settlement ???

 

[oldestguy]

On the subject of controlling settlement there are a few methods: Make the structure so rigid that settlements do not affect its use; undercut weaker materials and replace with better materials; drive piles for better support; set the base of the slab or footing deeper where you by pass the weaker material and also the ratio of new pressure to existing is less; revise the building details to make it lighter such as not so many floors.