I. Terms of reference
The Geological Society Engineering Group Working Party on the Description of Rock Masses for Engineering Purposes was established to produce a report which would provide a format for the collection of descriptive data from the rock mass to permit assessment and hence rational design and construction of structures or excavations, on, or within, that mass. It was further intended that the report should facilitate communication in the description of rock masses betweent the various branches of geology concerned with mining and civil engineering.
It is very necessary that standardisation should be achieved in the description and assessment of rock masses to facilitate the communication of facts between interested parties. It is thus essential that any system recommended should find wide acceptance.
Only the description of rock masses is considered in this report; assessment of the engineering properties and behaviour of rock masses is beyond the terms of reference. These aspects are specifically excluded both because of their wide range and because the type and scale of the engineering operation has considerable bearing on the way the mass should be assessed. As description forms the first step in the process of assessment it is essential that uniformity and consistency of description should be introduced into the subsequent process of rock mass assessment. It is recognised, however, that it may be possible to reduce this process of description by considering fewer parameters in an endeavour to produce a rock mass ‘rating’ as a quick guide to