Seismic Slope Stability of the Tipaimukh Dam of North-Eastern India: A Numerical Modelling Approach

Abstract

This article represents the seismic slope stability analysis of earth core rock-fill Tipaimukh Dam under static and dynamic loading conditions. The Tipaimukh area is located at the triple junction of the three continental plates- Indian, Eurasian and Burmese tectonic plate. The area is frequently interrupted by unanticipated geological discontinuities, such as regional and local-scale faults and fractures that behave as a strike-slip and extensional movements. Two kinds of numerical models (A and B) are presented here. Both models consist of five zones and each zone has individual rock mechanical characteristics. Model A assumes safety factor of dam slope associated with impervious core including clay material. Model B assumes also safety factor associated with masonry wall as an impervious core. The present numerical modeling results reveal that under static condition of the dam the safety factor ranges from 2.56 to 2.69. On the contrary, under seismic/dynamic loading conditions associated with earthquake M6.0 to M8.5, the safety factor ranges from 1.60 to 0.98 for model A, and from 1.66 to 0.98 for model B. The past records of the historical earthquakes in north-eastern India reveal that the recurrence period of intensive magnitude earthquakes, as experienced in Assam, Shillong plateau and Manipur area, is 38 to 53 years. The calculated safety factor of the Tipaimukh Dam implies that the dam would be destroyed if it would be affected by earthquakes magnitude over 7.0 throughout its operational life, which is usually extent from 50 to 100 years.