Rock mass classification calculation

Developed by Bieniawski in 1973, and updated in 1979 and 1989, this is a rock mass classification system that relates quality indexes with rock mass geotechnical parameters and with excavation and support parameters in tunnels. This classification takes the following geomechanical parameters into account:
— Uniaxial compressive strength of intact rock.
— Degree of fracturing (RQD).
— Spacing of discontinuities.
— Condition of discontinuities.
— Groundwater conditions.
— Orientation of discontinuities.
The influence of these parameters in the geomechanical behaviour of a rock mass is expressed using the RMR (Rock Mass Rating) quality index, which varies from 0 to 100.

To apply the RMR classification, the rock mass is divided into areas or sections with similar geological characteristics according to field observations, where data and measurements are taken relating to the properties and characteristics of the intact rock and its discontinuities.

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