This paper describes an investigation carried out to establish the trends of correlation between rock mass classification methods with data derived from rock mass in Korea. The parameters for rock mass classification were obtained from several regions in widely differing geological environments. Both the rock mass rating RMR of Bieniawski (1973) and the rock mass quality Q of Barton et al.(1974) were employed in determining the quality of rock masses. The concept of determining the engineering qualities of rock masses by means of their classification has been used for a number of years. The linear regression analyses were undertaken in order to assess a possible correlation between each classification system with rock types. The analyses showed a good correlation between rock classification methods. A correlation between seismic P-wave velocity and Rock mass rating classification system was also determined from several borehole logging measurements. RMR and P-wave velocity also showed a good correlation. We will be able to assess the rock mass quality with measuring P-wave velocity alone in borehole.
The rock mass classification systems are used as the semi quantitative tool of empirical design approaches which relate experience encountered at previous projects to the conditions anticipated at proposed site. The rock mass classifications have been recently widely employed in the rock engineering and being used in feasibility design. In fact, on many projects. the rock classification approach serves as the practical basis for the design of complex rock structures. In the Rock Mass Rating classification system of Bieniawski (1973) the following five basic parameters are determined: uniaxial compressive strength of intact rock, rock quality designation RQD, discontinuity spacing, discontinuity condition and ground water condition. The ratings for each parameter are summed and then corrected by a rating adjustment for discontinuity orientation to give a parameter called the RMR Which has a range from 0 to 100. From study of about 200 case histories of tunnels and caverns, Barton et al.(1974) proposed a very detailed rock classification system based on six parameters combined in the following way to give the rock mass quality Q.
The investigations were carried out to establish the correlation trends between rock mass classification methods with data derived from many projects in Korea. The data were obtained from several regions in widely different geological environments. If the numerical values of rock classification system actually are parameters indicating the quality of the rock, then a correlation would be expected between different system. For these cases the plots were made of RQD versus RMR, Q versus RMR, and RMR versus P-velocity. Bieniawski(1976), Abad et al.(l984), Moreno(1980), Rutledge and Prestone(I978), Cameron Clarke and Budavari(1981) have proposed the different correlations between RMR and Q. Fig. 1 shows RQD versus RMR of all type rocks and Fig. 2 shows RQD versus RMR classified by the rock type. These correlations have good reliability in the results. From regression analysis the following relationship were obtained. The equation (I).
