A new method for analysis of concrete face rockfill dams considering particle breakage phenomenon using discrete element method

摘要

The aim of this study is to introduce a new numerical method for the analysis of concrete face rockfill dams (CFRDs), and precede a quantitative study on the breakage of rockfill blocks using the discrete element method. Due to the size of rockfill blocks, the reliability of FEM analysis is questioned, since continuum assumptions are no longer valid. Moreover, finite element methods are unable to consider some specific rockfill features which are not so critical for common geotechnical material, such as sand. One of these determinant features is particle breakage. Due to the fact that large particles contain a higher quantity of cracks than smaller ones, and are subject to greater contact forces in a structure of rockfill dam scale, particle breakage has a dominant effect on rockfill behaviour. The vast number of particles in such a structure leaves no choice but to use a 2D medium instead of a 3D one. The model uses the discrete element code PFC2D[13l, and considers breakable clumps of 2D balls. The breakage strength ofrockfill blocks is defined in a way that ID blocks would have the same probability of breakage as 3D material. The necessary parameters for analysis are extracted from various tests conducted on rockfill material which have been previously published. In order to validate the adopted model and analysis procedure, several numerical bi-axial tests were conducted, and the results compared to experimental ones. Eventually a discrete model of an actual rockfill dam, and its displacement behaviour under gravity and hydraulic forces, is presented. The use of a discrete element model results in the robust ability to consider the special behaviour of rockfill material, such as large strains and high contracting.