A Classification System for the Slope Stability Assessment of Opencast Coal Mines in Central India

Excerpt

There are many empirical methods of rock mass classification, which are directly or indirectly used for the purpose of slope designs in opencast mines. Most of these empirical methods are basically derived from the rock mass rating (RMR) system (Bieniawski 1973) either by extending or by modifying the existing system. Duran and Douglas (2000) also observed that most of the RMR techniques have been based upon or are similar to Bieniawski’s RMR system. The latest version of RMR system (Bieniawski 1989) has a total rating of 100 of which only 15 is contributed from the intact rock strength (IRS). The rock quality designation (RQD), discontinuities and ground water, which account for a maximum rating of 20, 50 and 15, respectively, are one-fifth, half and about one-sixth part, respectively, of the total rating in RMR system. The RQD indirectly includes the effect of discontinuity spacing, and thus discontinuity effects grossly override the influence of intact rock in the assessment of RMR. This appears to be more logical in cases, where rock mass behavior in slopes is controlled more by structures than by IRS. Furthermore, the effect of water is reflected in the ratings of IRS and discontinuity condition. The effect of water can be better accounted for during the stability analysis. …