Structural Analysis Framework for Concrete-Faced Rockfill Dams

Abstract

Concrete-faced rockfill dams (CFRDs) are commonly built around the world. As energy demands soar and construction methods evolve, the interest in the construction of CFRDs with larger heights has increased tremendously. However, because of the construction of higher CFRDs, some dams have experienced considerable fractures at the concrete faces. Well-known cases include Campos Novos (Brazil), Barra Grande (Brazil), and Mohale (South Africa), where in some instances these cracks have led to dewatering of the reservoirs to allow for the concrete slabs’ repairs. The development of these fractures may be attributed to the highly deformable rockfill body. In general, the state-of-the-art design of CFRDs is mostly based on common practice rather than rigorous analysis procedures. And as such, cracking problems because of deformability of the rockfill may not be properly predicted unless a detailed analysis is performed. In this work, a new framework for the analysis of CFRDs is developed that is capable of predicting the possible failure of a concrete facing. As part of this framework, a comprehensive nonlinear finite-element analysis scheme is developed to model the construction sequence, the contact interaction between the concrete facing and the rockfill body, and the impounding of the reservoir. As a case study, using the developed framework, the Kárahnjúkar CFRD (Iceland, 198 m in height) is analyzed, the results are validated by the field measurements, and suggestions for mitigation measures are provided. This methodology, based on the results of the investigation, provides guidelines and establishes a framework for analysis of CFRDs that can be used for design purposes.