Parameters for stress and deformation analysis of rockfill dams

Abstract

Stress–strain parameters for modelling the response of rockfill dams to construction and reservoir filling are examined. Parameters from both 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 examined. The results of the study were applied to Foz do Areia dam in Brazil. Finite element analyses were carried out using selected material parameters to predict the response of the dam for both construction and reservoir-filling stages. The predicted and observed results were found to be in good agreement during the construction stage. During reservoir filling, measurements indicated that the dam initially behaved in a much suffer 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, leading to substantially larger movements. The predicted results for both construction and reservoir filling are in good agreement with the measurements, provided a stress ratio criterion is used to specify the appropriate tangent moduli. Key words : rockfill, dams, deformations, finite element analysis, field measurements.