PARAMETERS FOR STRESS AND DEFORMATION ANALYSIS OF ROCKFILL DAMS

Stress-strain parameters for modelling the response of rockfill dams t o construction and reservoir filling are examined. Parameters from bot h laboratory tests and back analysis of existing dams are considered. The influence of physical properties of the material, such as mineral composition, grading curves, grain shape, and grain size, is also exam ined. The results of the study were applied to Foz do Areia dam in Bra zil. Finite element analyses were carried out using selected material parameters to predict the response of the dam for both construction an d reservoir-filling stages. The predicted and observed results were fo und to be in good agreement during the construction stage. During rese rvoir filling, measurements indicated that the dam initially behaved i n a much stiffer manner than during construction. The stiffer response results from an initial unloading of stress ratio caused by the water load on the face. Under increased reservoir loading, the stress ratio increases again, activating the softer normal loading modulus, leadin g to substantially larger movements. The predicted results for both co nstruction and reservoir filling are in good agreement with the measur ements, provided a stress ratio criterion is used to specify the appro priate tangent moduli.