Determining the final soil type group from Borehole log

[Hasady]

Hi Folks,

I need help in knowing how is the final soil type chosen for design of foundations from a borehole log which gives you different soil types for each 0.75m of the hole. So, if it is a 10m bore hole it may give you three to four different types of soil, which one do designers take for designing the foundation?

Thanks.
HA

 

[EireChch]

A designer should consider the layering as encountered in the BH. Each layer has different properties, such as friction angle and Youngs Modulus etc

For an elastic settlement calculation you need to consider the modulus of each layer. A consolidation calculation would also need to be undertaken as you have lean CLAY.

For a bearing capacity (i.e. shear failure), you may consider a layered method such as that from Meyerhoff and Hanna, or conservatively adopt the most conservative parameters and do a traditional bearing capacity calc.