INTRODUCTION
Rock mass classification is one of an engineers most widely used tools for predicting the response of a large scale rock mass to an engineering structure. Classification schemes have two main aims. The first deals with quantifying the actual properties of the rock mass. The second looks at design by considering the loading condition, or environment, acting on the rock mass and predicting its resulting behaviour. This paper only considers the quantifying of rock mass properties.
Advances have been made towards improving the measurement of individual properties of a rock mass such as joint strength. Sophisticated computer modelling techniques can take advantage of our improving knowledge in these areas. In general, empirical classification schemes cannot take advantage of improved data because of the subjective nature of rock classification. The surface characteristics of joints are a major component in rock classification and improvements which have been made over purely subjective descriptions should be applied. A method is suggested for removing some of the subjectivity in the area of joint condition and applying similar input parameters to both empirical and computer modelling techniques.
A method is looked at to assess joint condition in three of the most widely used rock classification systems. The NGI Q system (Barton et al. 1974), the Rock Mass Rating (RMR) (Bieniawski 1974) and the Mining Rock Mass Rating (MRMR) (Laubscher 1984) are all considered. The following sections discuss a method for assessing the joint condition for these classification systems.
