2-D FINITE ELEMENT SEISMIC ANALYSIS OF EARTHEN ROCK-FILL DAM

Abstract

Earthen-rock fill dams are economical in construction if feasible from design consideration as these can utilize locally - available materials and less skilled labour. Further, modem developments in earth hauling equipments have considerably reduced the cost of carriage and laying of dam materials. This dissertation presents the results of 2D finite element seismic analysis of an earthen rock fill dam. The rock fill dams are highly resistant to seismic loads due to their large flexibility and capacity to absorb large seismic energy therefore less vulnerable to earthquake damage. The behavior of an earthen dam under earthquake loading was studied. The seismic analysis of the dam consists of static and dynamic 2D finite element analysis. First, the in-situ stress state conditions that exist before the earthquake are established, and then its results are used for the dynamic part of analysis. Plots of the variations of the displacements at the core with dam height are shown. The dam section is analyzed modeling the vertical boundaries of the dam foundation using dampers. The parametric study of an earthen rock fill dam is also carried with varying shear wave velocity of the shell material of the dam. The analysis permitted evaluation of the overall patterns of the dam behavior in terms of contours of displacements and stresses. The use of dampers in the modeling considerably reduced the horizontal displacements and amplification of accelerations at the dam top. Performance of the dam was satisfactory in terms of the computed maximum settlements at dam crest, which were considerably smaller than the permissible values. Developed methodology is applied to a real case study where Tehri dam, Uttarakhand is considered for two-dimensional dynamic analysis. The dam is analyzed for three different shear wave velocities of shell material. Thus effect of shear strength of shell material on dynamic response is investigated.