Failure criteria for shallow foundations 1

[Geosubhtech]

Greetings to all.

Is there any reference for the failure criteria of shallow foundations?
I mean three criteria (general, Local, Intermediate) are available. So what are the criteria to categorize these three in cohesive as well as cohesionless soils. For cohesionless soils we use angle of internal friction 28 deg. to 36 deg. as intermediate shear failure.

Any reference for this and for cohesive soil any criteria if available please mention.

thank you.

 

[oldestguy]

You missed the most important one: "tolerable settlement".

 

[MotorCity]

Unless its a structural failure (concrete cracking/splitting, rebar breaking, etc.), "failure" is whatever you determine it to be since it is a serviceability issue.

Bearing failure = not OK

Slope stability failure = not OK

Overturning failure = not OK

Sliding failure = how much sliding can be tolerated?

Settlement failure = how much sliding can be tolerated?

 

[EireChch]

Failure criteria is not separated for cohesionless or cohesive soils. An you can have sand / gravel with friction angles of 40+.

Motorcity's response is on the money.

 

[Geosubhtech]

Sorry for not being clear on my question.

The bearing capacity equation given by Terzaghi is for strip footing, but the factors help us to change the capacity to our requirement.
He considered general shear failure and local shear failure.
So, while calculating the bearing capacity how to consider the failure criteria to consider the shear strength parameters ?
Till now i use undrained cohesion > 100 and Dense sand is in general shear failure.
for dense sand if i use relative density 70 percent, by Mayerhof (1959) corerelation [phi = 28 + 0.15 x Relative density] angle of friction i will get as 38 deg. as lower boundary for general shear failure.
same as for loose and very loose for relative density less than 35 or 0 will give 33 deg and 28 deg. respectively as upper boundary for local shear failure criteria.
For local shear failure criteria
undrained cohesion (local) = (2/3)x undrained cohesion
tan (phi)[local] = (2/3) x tan (phi)

So is the consideration of these criteria were correct or my interpretation is missing some where.
And for cohesion also any reference if available please provide.