ABSTRACT
There are various geo-mechanical classifications for characterization and classification of rock mass. But Slope Mass Rating (SMR) index is best suited for slopes. It is computed by adding some correction factors to basic Rock Mass Rating (RMRb) values which will depend upon the parallelism of discontinuity and slope (F1), the dip of discontinuity(F2), the relative dip between discontinuity and slope (F3). There is an additional factor (F4) which is fixed empirically according to the excavation method employed. The RMRb in our case is taken from literature from well-established empirical relationships. SMR tool, which is basically an open source software developed in MATLAB is being implemented for rock mass classification in our study area which is located in East Sikkim. Sikkim is chosen for our study as the terrain in the state is highly undulated in nature and the slopes are highly vulnerable to landslides. The lithology in the terrain mostly consists of schists and gneisses (high grade metamorphic rocks) of central crystalline complex of Higher Himalayas. In this study, graphical methods are being employed to compare our results from SMR tool and the kinematic analysis is being done with the help of DIPS (v8.0.3) for slope stability analysis and for finding out the mode of failure viz. planar, wedge and toppling. Kinematic slope instability is generally caused due to geometric orientations of dip of slope and discontinuity planes (bedding planes, joint etc.) and relationship among them. Also, the correction factors for SMR index is computed from stereo net plotting and employed to calculate the SMR index. Based upon the value of SMR index we are able to predict the stability of the rock slope and also suggest measures to control slope failure at a preliminary level.
