Probabilistic and Sensitivity Investigation for the Hill Slopes in Uttarakhand, Lesser Himalaya, India

Abstract

Himalayas is one of most seismically active mountain chain in the world. Landsides and the mass wasting are a prevalent phenomenon in this region. There are a considerable number of human populations living in the hilly regions which are under a constant threat of hill slope collapse. The stability assessment of these hills is one of the vital steps to mitigate the danger to this natural calamity. The deterministic factor of safety calculations have been traditionally used for the hazard evaluation of the hill slopes. For the present study, two hill slopes, Chandaak and Chhera, have been selected for probabilistic and sensitivity analysis. These areas were analyzed using limit equilibrium method for calculation of factor of safety and probability of failure. The factors of safety were calculated using Bishop's method of slice. The analysis was done for both dry and saturated conditions. At the same time the sensitivity of each parameter on the factor of safety was analyzed. The probability analysis of these areas was done using Monte-Carlo simulation which uses randomly selected discrete values of each variable from their probability distribution. In both the hill slopes the rock mass has varied weathering grade, ranging from highly weathered to moderately weathered. Seasonal variation in the rock mass strength was accounted for in the study. Chhera hill were quantified to have high FOS in both cases (dry and saturated) as compared to the Chahdaak hill, making than more vulnerable.