SEISMIC STABILITY ANALYSIS OF ROCK SLOPES USING UDEC

Abstract

Surbhi Landslide is located near Surbhi Resort on Mussoorie-Kempty Fall road. The initial failure of this slide had occurred during the Uttarkashi Earthquake in 1991. It had again occurred during the heavy rains in July,2003. This slide is one of the biggest slides in the Mussoorie hills. It caused huge losses to human livings and agricultural fields of villages located immediately downslope of this hill due to the debris and big rock boulders that were caned away along the slope during failure. In the present study the stability analysis of the landslide has been carried out. As the slope was highly jointed distinct element method is the best method which can simulate the jointed rock mass under static, dynamic and under the effect of water. Numerical modeling of the landslide has been done by using UDEC (Universal Distinct Element Code) under static and dynamic conditions. Usually a thin layer of the slope gets weathered due to degradation of the rock material beacause of rainfall, erosion etc. The same was the situation at Surbhi landslide also, therefore a rockfall analysis is done to see whether the heavy boulders can reach the toe of the slope. For this the top layer of the slope is kept heavily jointed and also the blocks were taken cohesionless. The analysis is then followed by the parametric study in which the effects of parameters like Jkn, Joint friction. Joint spacing, Jks and water depth have been studied.