Corporate Office, NHPC, Faridabad
For design of Civil Structures of Chamera Hydroelectric Project, Stage-II, the Design Earthquake Parameters were evaluated during feasibility stage by Deptt. of Earthquake Engineering, IIT, Roorkee. As a matter of practice the parameters of ground motion for project structures are evaluated in all seismic terrains. This requires an understanding of seismic scenario and geological setting with regard to the site. Initially, the maximum credible earthquake that can be generated with in a given seismotectonic framework is defined. Thereafter, the design based earthquake, taken as half of the maximum credible earthquake in terms of the acceleration intensity is formulated using probabilistic or deterministic approach. Subsequently, through empirical relationship, peak ground acceleration is worked out on the basis of earthquake magnitude and its epicentral distance and focal depth. In case of Chamera Project the background acceleration from 3 prominent earthquakes are estimated as 0.17g, 0.2g, and 0.22g. Corresponding design acceleration response spectra and time history of ground motion have been recommended for two levels of earthquakes for maximum credible earthquake and operating basis earthquake. A concrete gravity dam of 39 m height and its appurtenant structures are found feasible for the recommended earthquake loads.
