Rock mass classification systems for rock engineering have gained widespread acceptance since their introduction in the mid-60''s. Their widespread use can be attributed to the ease with which they employ simple measurements and observations to provide a quantitative index of rock mass quality. It is then possible to link this index to specific engineering objectives such as predicted stand-up time, maximum size of stable excavation, choice of support etc. Improvements in rock mass classification systems and their application have been based on more quantitative field measuring techniques, improvements to the weightings assigned to the different parameters, and better links to design. The widespread use of classification systems for design has resulted in a significant increase in case histories linking classification to rock mass behaviour, under a wide variety of conditions. Consequently this has contributed to the statistical validity of design recommendations. More recently there has been a trend to link different classification systems to avoid collecting the required field data to quantify the additional classification values.
Rock mass characterization is an integral part of any design process in mining, even though most classification systems now in use have their origin in underground civil engineering applications. Project duration, scale, access, even tolerance of risk, can contribute to developing different engineering strategies for civil and mining applications.
The results of rock mass classification are routinely used to estimate rock mass behaviour as well as provide guidelines for underground mine design. Documented case studies can provide an extraordinary amount of knowledge and experience that can be used for design purposes. There has been a tendency to also use the resulting empirical ratings to determine the constitutive laws as well as failure criteria now employed with the majority of numerical models.
