Estimating Bearing Capacity on Highly Fractured Rock

[Nanyaro]

During my geotechnical carrier I am always having a problem of estimating an allowable bearing capacity on highly fractured, highly to moderately weathered rock where RQD is 0 and no sample for UCS or Point Load Test. Some times I dwell in British Standard BS8004:1986 to derive the bearing capacity emperically but I have never be confortable with the results which most of the time are conservative. Please if thre is anybody who can assist me in this area i will be very grateful.

 

[Mccoy]

Nanvaro, I'm wondering about the suggestions given in the BS you cite, which I don't know.

Anyway, I've had the same problem for years, until I recently came across a satisfactory operative solution which involves use of a specific published technique. Very good with drillcores with RQD=0.

You should have a previous knowledge of the Hoek & Brown, 2002 method though which is fully explained in the Rocscience site, along with a freeware and scientific handbook.

I'm going and give you the details about the relevant journal paper as soon as I can retrieve them.

 

[Mccoy]

The reference paper is this one:

Osgoui et al. 2010: An assistant tool for the geological strength index to better characterize poor and very poor rock masses, International Journal of Rock Mechanics & Mining sciences, 47, 2010

Using this 'assistant' method and the Hoek & brown procedure, you can get the Mohr-Coulomb parameters and use them in the usual bearing-capcity formulas.

Or you can get the Hoek-brown parameters and use them in more specific methods.

I'm going to attach one real life example of this procedure.

 

[Nanyaro]

Dear Mccoy,

Thank you for your valuable info. infact i was outdated as i know only Hoek and Bray book for Rock slope engineering but i dont know this other book by Hoek and Brown. I will look how to get it through Amazon.


Best regards,

 

[Mccoy]

Nanyaro,
if you download the free roclab software, you'll get a few reference papers on the HB method.

Somewhere in the web there is even a whole handbook available, whose link I have to retrieve though.

This is the link to the roclab software download:

http://download.rocscience.com/products/RocLab.asp

 

[Mccoy]

This is the link to Dr. Evert Hoek free e-book "Practical rock engineering":

http://www.rocscience.com/education/hoeks_corner