Bowles rock bearing capacity

[ramihabchi]

Joseph Bowles in his book "foundation analysis and design fifth edition",in bearing capacity of rock,he multiplies bearing capacity obtained from terzaghi'equation by RQD^2 to obtain ultimate bearing capacity.
1)is this multiplication applicable for all modes of failure?or only for global shear failure?for e.g compressive failure and splitting failure.
2)doesn't global shear failure depends on orientation of jointing?if this is true is it taken into consideration through the use of RQD?

 

[oldestguy]

Bowles used a lot of the publications and writings of others in his publications. I suspect his text has notations as to publications that he used and that may be enough for you to resolve the questions..

 

[RGKVI]

2. Adverse jointing would only be applicable if the structure was founded on a rock slope / cutting where the dip angle and dip direction of the rock joint were in the same plane as the cutting.

 

[ramihabchi]

thank you.
When jointing is vertical and opened,compressive failure(like buckling)is likely to be the mode of failure.what I want is to determine bearing capacity of this failure mode,using cohesion and friction angle obtained from high pressure triaxial test and RQD.

 

[Okiryu]

What type of structure is planned? High-rise? Light-weight structure? dams foundation? For buildings, you may not need to report the "real" rock capacity, rather, you may just need to give an allowable bearing pressure so the structural engineer will be very confortable to work with...which the rock will be able to provide...

Anyway, check with your local engineering offices....you can verify your numbers against the typical used numbers for rocks in your area...