Esitmating Rock Mass Shear Strength

[twg7]

I am tring to figure out how to estimate rock mass shear strength. I have some unconfined compressive strength test result and I can't remeber if there is a way to relate compressive strength to shear strength.

 

[jdonville]

twg7,

This subject is hard slogging with no easy relations.

AASHTO HB-17 and the new LRFD spec have some rough correlations between UCS, RQD, Recovery / RMR values and Hoek-Brown coefficients. Use at your own risk, as AASHTO reportedly advises against using them, even though they are reproduced in AASHTO's own publication.

I suggest that you try and develop some synthetic Rock Mass Rating (RMR) values and work with existing RMR correlations to characterize your situation. Google "Rock Mass Rating" if you need some background. USBR and USACOE have some published information on RMR and its uses. Check out

http://www.rocscience.com

for background on rock mechanics and some papers by Hoek.

Jeff

 

[csd72]

Rock shear strength is dictated by the prescence of fracture planes in the rock and is not necessarily related to compressive strength.

 

[fattdad]

Here's some interesting reading! My thesis:

http://home.comcast.net/~fatt-dad/thesis.pdf

Enjoy!

f-d

¡papá gordo ain’t no madre flaca!