A critical review of rock mass classification systems for assessing the stability condition of rock slopes

In the last few decades, several rock mass classification systems have been proposed to identify rock slope stability conditions, having high probability of failure and accordingly prioritize preventive measures. This paper reviews the various classification systems, highlighting their differences and similarities with regard to the factors involved and the mode of their failures. The advantages and limitations of each classification have also been compared. However, many of these existing systems fail to classify slope cuttings according to their actual vulnerability of failure, as they ignore important triggering factors such as earthquakes or precipitation. For example groundwater is considered as an instability causing factor with limited effect, rather than a triggering factor for failure. It is observed that rock slope should be classified according to their potential of failure, taking into account both their condition and the influence of triggering factors upon stability. It is also observed that it is important to analyse each type of failure separately, since each one is influenced by unique factors of instability. Finally, it provides suggestion for the improvement of existing classifications through incorporation of all the critical factors like slope aspect, mode of excavation, earthquake, and rainfall that would have caused slope instability.