QUASI PLANE STRAIN ANALYSIS OF GRAVITY DAMS

Abstract

A number of situations arise in practical problems where either the material anisotropy or the orientations of in-situ stresses make the assumptions of plane strain analysis invalid and an expensive fully three dimensional analysis has to be carried out. For tunnels, retaining walls and dams where the length is very large in comparison to the dimensions of its cross sections, a comprehensive three dimensional analysis including the total structure is neither necessary nor very useful but involves a solution of a large size problem with many elements and cumbersome data. input and difficult interpretation of output. An economical alternative formulation named as quasi-plane strain (cPs) analysis is presented in this thesis. The increase in computational costs in QPS analysis with respect to a two-dimensional analysis is marginal. Thus, it can be stated that there will be considerable economy in terms of computational costs and time as compared to a three-dimensional analysis. General formulation of quasi plane strain analysis has been presented and compared with 2D and 3D formulation. General purpose computer program has also been developed and the results of some of the typical problems have been presented. iv The BPS formulation has been further modified for the analysis of dams with straight or curved axis in plan for trapezoidal valley shapes. The results of a 200 m high dam have been compared with 3D analysis for different valley shapes. The results obtained from BPS an modified CjPS analysis are very close to results from 3-D .analysis. It may this be stated that the future for the new fozmuiation presented in this thesis is very promising and further development is in progress to account for the effects of sequence of construction and non,linear material behaviour etc •