Depth of influence for raft foundations

[jg11]

Hello

I am advising on the founding depth for a raft foundation for a warehouse on soft clay. I want to calculate the depth of influence as there is a hard layer near to surface, if I treat the raft as a slab (so this would 35m x 20m) I am being too conservative?

Would it be more realistic to calculate the depth of influence treating the raft as a collection of strip foundations?

Thanks

 

[fattdad]

A collection of strip foundations would generate overlap effects that would result in the same stress influence. Just use your loaded area and the Boussinesq equations to solve the problem. It's easy.

f-d

¡papá gordo ain’t no madre flaca!

 

[jg11]

Thanks for the reply.

 

[BigH]

Depth of influence - for multi-layer soils of significantly differing stiffness - see Poulos and Davis' Elastic Solutions for Soil and Rock Mechanics for multilayer system. (you can get the book in electronic form from a number of web sites - google it).

 

[fattdad]

I like the P&D charts too.

f-d

¡papá gordo ain’t no madre flaca!