Understanding the Structural Stability of the Tehri Dam: A Comprehensive Analysis

Abstract

The Tehri dam is the highest dam in India. The height of dam is 260 m. It is situated on the Himalayan region which is in earthquake prone region. A Sengupta in 2006 found that the predicted deformation due to an M=7.0 earthquake are not large enough to compromise the safety of the dam. However the deformation predicted by Seed and Makdisi’s method, and Bureau’s method for an M=8.5 earthquake are large enough to compromise the safety of dam. The Seed and Makdisi’s procedure predicted the maximum deformations, while the minimum deformations are computed by Jansen’s method. In the present work, the stability analysis four type of analysis such as structural stability analysis, Centre of slip circle by genetic algorithm, stability of dam under sudden draw down condition and dynamic analysis are considered Structural stability analysis have done by Fellenius method and radial slice method. In Fellenius method three number of slip circles are taken which cuts the slope at two third distances from top of slope. By finding the resisting moment and driving moment the factor of safety is found that for first slip circle, second slip circle and third slip circle are 1.997, 2.103 and 2.045 respectively. In the radial slice method the failure wages are divided into number of slice radially by joining the line from the center of slip circle to the arch. The factor of safety is found as 1.15. The coordinate of centre of slip circle has found by genetic algorithm. In order to validate the genetic algorithm method, the input data has been imported from the results of graphical method. The centre coordinate of slip circle is obtained as (210,485) which was found to be very close the value of centre of slip circle by graphical method. Numerical analysis has been made by using commercially available software PLAXIS under sudden draw down condition. The deformation in X-direction was 16.99 m. Dynamic analysis has been used by PLAXIS software and the total deformation is obtained as 0.4150 m.