on classification
The rock mass is a complex material involving several parameters, all showing wide variations. In addition, the constructions in rock involve large volumes in this material. Caused by this, testing of relevant samples is generally impossible or so costly that the specifications of the material largely have to be based on descriptions/characterizations of the various rock mass parameters of importance. A main item in engineering geology and rock engineering is, therefore, to find and use methods or systems to describe and characterize rock masses so that appropriate ratings or values can be estimated and used in engineering and design. For this, classification systems often serve as a main tool.
Due to the difficulties in retrieving relevant strength parameters of rock masses, classification systems are frequently applied to serve several applications. You will find an overview of the probably most known classification systems.
As it is often confusion about the differences between description, identification, characterization and classification, see explanations presented at the end of this page.
It is a continuous discussion on the use and limitations of these systems, among others on
= how the input parameters to the systems are collected/measured, given values and used;
= what the limits of the actual system are; and
= the experience requirements of the user.
The following papers give information and comments on these topics:
A short introduction to classification presented at the GeoEng2000 workshop on reliability of classification systems in Melbourne.
On classification systems presented at the GeoEng2000 workshop on reliability of classification systems.
GeoEng2000 workshop summary on reliability of classification systems.
Comments by Dr. Nick Barton on workshop summary with Reply to Dr. Barton.
Comments by Dr. Nick Barton on the paper Deformation modulus with Respons to Dr. Barton.
The paper “The Q system – possibilities and limitations” (see www.rockmass.no/page.php?3) was first presented in Norwegian at the annual Norwegian tunnelling conference, 2002. Later, in 2006, an English version was presented in Tunnels and Underground Space (see "Published papers").
A list of references on Rock engineering classification.
The paper Classification as a tool in rock engineering, published in Tunnels and Underground Space Technology 2003.
Table showing the Terzaghi rock mass classification of 1946 with adjustments by Sinha 1990.
Goodman’s technical classification of rocks.
The following explanations may clarify some confusion about description, identification, characterization and classification of rocks and rock masses:
Classification is the result of putting objects into different classes. The purpose of such classification is to get a better overview of a phenomenon or set of data, to try to gain an improved understanding of them. By contrast, characterisation is the procedure of describing the condition of, for example, a substance or material, and defining or giving value to the various features it displays. In practical rock engineering, the task is to:
1. Identify the features or parameters of importance or relevance to a project and the assessments to be performed.
2. Measure and/or describe the properties of these parameters, giving them values or ratings according to their structure, composition and properties.
Thus, the process of rock mass characterisation consists of describing and quantifying the parameters that govern or influence the rock mass properties and behaviour. These parameters can be expressed as intact rock characteristics, discontinuity (joint) characteristics, and the density and pattern of discontinuities.
The characterization can be simplified by putting the different properties into classes - in other words, by classifying them. There are many examples of this process in engineering geology, such as describing the strength of the rock material or the joint spacing and density, and placing them into pre-defined and general accepted categories.
Due to the difficulties in retrieving relevant strength parameters of rock masses, classification systems are frequently applied to serve several applications. You will find an overview of the probably most known classification systems.
As it is often confusion about the differences between description, identification, characterization and classification, see explanations presented at the end of this page.
It is a continuous discussion on the use and limitations of these systems, among others on
= how the input parameters to the systems are collected/measured, given values and used;
= what the limits of the actual system are; and
= the experience requirements of the user.
The following papers give information and comments on these topics:
A short introduction to classification presented at the GeoEng2000 workshop on reliability of classification systems in Melbourne.
On classification systems presented at the GeoEng2000 workshop on reliability of classification systems.
GeoEng2000 workshop summary on reliability of classification systems.
Comments by Dr. Nick Barton on workshop summary with Reply to Dr. Barton.
Comments by Dr. Nick Barton on the paper Deformation modulus with Respons to Dr. Barton.
The paper “The Q system – possibilities and limitations” (see www.rockmass.no/page.php?3) was first presented in Norwegian at the annual Norwegian tunnelling conference, 2002. Later, in 2006, an English version was presented in Tunnels and Underground Space (see "Published papers").
A list of references on Rock engineering classification.
The paper Classification as a tool in rock engineering, published in Tunnels and Underground Space Technology 2003.
Table showing the Terzaghi rock mass classification of 1946 with adjustments by Sinha 1990.
Goodman’s technical classification of rocks.
The following explanations may clarify some confusion about description, identification, characterization and classification of rocks and rock masses:
Classification is the result of putting objects into different classes. The purpose of such classification is to get a better overview of a phenomenon or set of data, to try to gain an improved understanding of them. By contrast, characterisation is the procedure of describing the condition of, for example, a substance or material, and defining or giving value to the various features it displays. In practical rock engineering, the task is to:
1. Identify the features or parameters of importance or relevance to a project and the assessments to be performed.
2. Measure and/or describe the properties of these parameters, giving them values or ratings according to their structure, composition and properties.
Thus, the process of rock mass characterisation consists of describing and quantifying the parameters that govern or influence the rock mass properties and behaviour. These parameters can be expressed as intact rock characteristics, discontinuity (joint) characteristics, and the density and pattern of discontinuities.
The characterization can be simplified by putting the different properties into classes - in other words, by classifying them. There are many examples of this process in engineering geology, such as describing the strength of the rock material or the joint spacing and density, and placing them into pre-defined and general accepted categories.
