Chapter 18 - Slope Mass Rating

Abstract

For evaluating the stability of rock slopes, there is a proposed classification system called the “slope mass rating” (SMR) system. SMR is obtained from Bieniawski's rock mass rating (RMR) by subtracting adjustment factors of the joint–slope relationship and adding a factor depending on method of excavation. The effect of future weathering on the slope stability cannot be assessed with rock mass classification, because it is a process that depends mostly on the mineralogical conditions of rock and the climate. In certain rock masses (e.g., some marls, clays, and shales), slopes are stable when excavated but fail sometime afterward—usually one to two years later. In such conditions, the classification is applied twice: initially and afterward for weathered conditions. It is always prudent to check SMR against adjoining stable rock slopes before applying it to rock slopes in distress. The stability of slope also depends upon length of joints along the slope. SMR is successfully used for landslide zonation in rocky and hilly areas in the Himalayas in India. Along with this, this chapter also provides case study of stability analysis using modified SMR approach with geology and rock slope analysis.