Parametric Evaluation of the Stability of Natural Slopes

Abstract

A new geotechnical criterion called the Slope Stability Index, SSI, is proposed to be used for the assessment of the relative stability of natural slopes. This criterion involves the calculation of 11 factors in addition to the Rock Mass Rating (RMR). The author has added to the RMR of Bieniawski (1979) two new parameters; namely: the geodurability of the slope material and the geologic setting of the slope. The relative weights of the parameters in the RMR have been adjusted based on experience and judgement. The parameters F1, F2 and F3 related to the joint – slope relationship as well as F4 related to the method of excavation that were introduced by Romana (1996) in his SMR were also adjusted. The new parameters introduced by the author are related to the slope geometry (steepness and shape) and to the environmental factors (rainfall, drainage, climatic and seismic conditions). Zuyu factor E (1995) related to slope height was also introduced with suggested upper and lower values. The new index is believed to give a fair assessment of the relative stability of the slopes under consideration. This would help planners and engineers in their selection of the sites of their engineering projects and in the treatment of slopes that exist in a critical state of stability.