Rock mass rating

The rock mass rating (RMR) system is a geomechanical classification system for rocks, developed by Z. T. Bieniawski between 1972 and 1973.^[1]

Definition

The following six parameters are used to classify a rock mass using the RMR system

1. Uniaxial compressive strength of rock material
2. Rock quality designation (RQD)
3. Spacing of discontinuities
4. Condition of discontinuities
5. Groundwater conditions
6. Orientation of discontinuities

Each of the six parameters is assigned a value corresponding to the characteristics of the rock. These values are derived from field surveys. The sum of the six parameters is the "RMR value", which lies between 0 and 100.

Classification table

Below is the classification table for the RMR system.

Applications

Rock Mass Rating has found wide application in various types of engineering projects such as tunnels, slopes, foundations, and mines. It is also adaptable for knowledge-based expert systems. A joke among engineers is that rock structure can be commonly broken into two general classifications; 'CHILE' — Continuous Homogenous Isotropic Linear Elastic (what most geotechinical engineers would like to see) and 'DIANE' — Discontinuous Inhomogenous Anisotropic Non-Elastic (what most in-situ rock masses actually are). A RMR system provides a method of incorporating some of the complex mechanics of DIANE rocks into engineering design.

See also

• Core recovery parameters
• Hoek-Brown failure criterion

References

1. ^ Bieniawski, Z. T. (1989). Engineering rock mass classifications : a complete manual for engineers and geologists in mining, civil, and petroleum engineering. Wiley-Interscience. pp. 40–47. ISBN 0-471-60172-1. 

Further reading

• Hack, H.R.G.K. (25-28 November 2002). "An evaluation of slope stability classification. Keynote Lecture.". In Dinis da Gama, C.; Ribeira e Sousa, L.. Proc. ISRM EUROCK’2002. Funchal, Madeira, Portugal: Sociedade Portuguesa de Geotecnia, Lisboa, Portugal. pp. 3–32. ISBN 972-98781-2-9. 
• Pantelidis L. (2009) "Rock slope stability assessment through rock mass classification systems" International Journal of Rock Mechanics and Mining Sciences, 46(2):315–325.