STATIC AND DYNAMIC STRESS ANALYSIS OF A LARGE SIZE ROCKFILL DAM

Abstract

The dams to be located in an active seismic region must be designed to withstand safely the expected earthquake motion for that region. The frequent occurrence of destructive earthquakes during the past few decades has caused great damages to life and property, therefore, it is extremely important that the safety of the dams be maintained during a major earthquake. Further, the failure of a dam is far more disastrous to a community than any other structures. In India many projects are located in active seismic areas and may be subjected to strong shaking. In such type of areas rock fill dams are very usefull, because they provide a high resistance to seismic force due to their flexible character. It is therefore essential that dams should be designed taking into account its effects. With this objective in mind "Static and dynamic stress analysis of a large size rockfill dam" is taken up. The static, free vibration characteristics and earthquake response of a high rockfill dam are investigated with particular reference to linear and nonlinear finite element analysis. The static stress analyses are carried out by (1) single lift linear analysis, (ii) single lift nonlinear analysis and (iii) multilift nonlinear analysis. The dam stability analysis is carried out using the conventional slice method and the finite element analysis. The natural period of vibration and mode shapes of the dam are studied. In dynamic analysis linear and nonlinear earthquake response of dam due to Uttarkashi Earthquake are worked out. The study indicate in static response as for as stresses are concern. There are some difference between linear and nonlinear analysis. But there is hardly any difference between the stress distribution due to single lift and multilift nonlinear analysis. The single lift deformation and multi lift deformation are significantly different. It is observed that the nonlinear power variation of Young modulus E computed from the initial stress obtained either by linear or nonlinear analysis yield almost same natural time periods of vibrations and the mode shapes. Dynamic study indicates that the nonlinear response is significantly different than the linear response