Classifications

Published on February 15 2015

The geologic classification of the rock material is based on origin, mineralogical composition, mineral size and petrologic characteristics.  The condition, i.e. classes of the various features to be used in rock engineering should be easily observed or measured in the field and/or laboratory.

The rockmass contains several features, each of them with properties.  They all play a role in its strength and modulus of deformation.  Many of these features are applied as input to classification systems.  A collection of classifications is presented below:

Classification should provide a common basis of communication, and to identify a rock mass into one of the groups having well defined characteristics and also yield basic input data for engineering design.

The terminology used should be widely accepted by engineers and geologists. Only the most significant properties of the rock should be considered, which will influence the engineering properties and behaviour.

The paper "Classification systems and use og geological data" presented at the Iranian conference "Tunnelling and Climate", gives an overview of the geological parameters applied in classification systems and how these can be combined to calculate the values (rockmass quality) in different classification systems. The latter is also shown in the spreadsheet file here.

 

Important quotations are presented below from time to time:

"…..there is still no acceptable substitute for the field mapping and core logging carried out by an experienced engineering geologist."
Evert Hoek, 1986.