INFLUENCE OF INCLINATION OF CORE ON DYNAMIC RESPONSE OF EARTH & ROCKFILL -DAM

Abstract

Till recent times, the design of the earth & rockf.iil dam was mainly carried out by rule of thumb, i t was more of an art than a science. However, the art and science of designing earth r ock.f ill dams- has undergone rapid development in the past few decades Apart from var i ou, other components, static and dynamic response of earth & r ockf i .i i dams are influenced by the po i t i ors of the core in the darn. The prime objective of this study is to know the influence of inclination of core on the static as well as dynamic response of the dam. A 1 3Om high ear t.h & r ock f.i l..1 dam with five different types of core geometries viz. , Ci3 central core. Cii) moderately inclined core, Ciii) combination of -central core & moderately Inclined core, C i v) steeply inclined core. and C v) combination of central core & steeply inclined core have been considered for- this study. Static and dynamic analyses have been carried out by a 2-D finite element program using four noded quadrilateral isotropic elements and assuming the fill materials in the dam to be linearly elastic. The static analysis has been carried out under both empt.y and full reservoir conditions. The statt c.:- displacements and stresses have been computed. The dynamic analysis has been carried out only in f ul I reservoir condition since most of the time the reservoir shall be iIi full of water. The IS: 181-213-11-084 average acceleration-n spectra for 1O damping has been used as the seismic input. Assuming ng that the damping shall remain constant in all the modes, the first five modes have been computed and drawn. The modal displacements and stresses in these five modes are combined by S ;SS method and added to the corresponding static displacements and stresses respectively to have the most critical values of these parameters. The accelerat ons and time periods of the structure it all the five modes have al so been computed. The stress contours for both i major and minor principal stresses In static as well as dynamic conditions have been drawn. It. is seen that under both the .loading conditicans arching takes place from the core to the shell.. However, the amount of arching Is comparatively less in case of steeply inclined core wherein the core rests on the cl/s shell. Considering the static stresses, static + dynamic SR 33 stresses, horizontal and vertical displacements. ti* peri od and acceleration, a dam with moderately inclined core seems to behave better during earthquake condition.