INFLUENCE OF FILTER THICKNESS ON RESPONSE. DF EARTH. AND ROCKFILL DAM DURING EARTHQUAKE

Abstract

Static as well dynamic response of Earth and Rockfill dams are influenced by the zoning and fill material characteristic apart from the topography of the site. Various researches have studied the effect of the different components. The prime objective of this qualitative study is to know the influence of filter. (also known as transition zone) on the static as well as dynamic response of earth and rockfill. dam. For purpose of the present study, five cases of varying thickness of filter of earth and rockfill dam with vertical central core have been considered. These cases are of filter thickness 5 m, 10 m, 15 m, 20 m and 25 in respectively with 100 m high darn in each case. Finite. Element Analysis has been carried out-using four noded quadrilateral isoparametric elements and treating the material -to be linearly elastic. In static analysis the effect of filter thickness has been studied on both empty and full reservoir conditions. The stresses and displacements have been determined. The dynamic analysis has been based on the spectral response analysis conducted for the average acceleration spectra as specified in IS:1893-1984 for a constant damping 10% in all the modes. - Ftee vibration characteristic, viz, mode shapes and frequencies have been computed along with dynamic stresses and displacements, for only empty reservoir condition. The SRSS values up to first five modes of displacements/stresses have been combined with static -d.isplacernents/stresses. The acceleration variation along the height has also been determined. The results of static and dynamic analysis clearly indicate. that . thicker filter will prove to be superior to the dam under normal and seismic conditions. (