Numerical study of the hydromechanical behavior of Itaipu's left bank earth dam

• Main Author: Silveira, Isabela Augusto [UNESP]
• Publication Date: 2025
• Format: Doctoral thesis
• Language: eng
• Source: Repositório Institucional da UNESP
• Download full: https://hdl.handle.net/11449/314960
• topic: Unsaturated soil; Saturated soil; Earth dam; Numerical simulation; SI curve; Solo não saturado; Solo saturado; Barragem de terra; Simulação numérica; Curva SI

The analysis of the hydro-mechanical conditions of both saturated and unsaturated soils is essential for understanding the geotechnical behavior of earth dams. Constitutive models and numerical simulations that consider hydro-mechanical coupling provide consistent framework for understanding and predicting the behavior of these soils. This research aims to numerically analyze the geotechnical behavior of the Itaipu dam throughout its construction, reservoir filling, and years of operation, with particular emphasis on understanding the settlement case observed during operation, taking into account the saturated and unsaturated conditions of the massif. The stress–strain and flow responses of the dam were simulated using the finite element method and a coupled hydro-mechanical approach. The finite element program CODE_BRIGHT, together with the Barcelona Basic Model (BBM) as the constitutive law, was employed to reproduce the dam’s construction, reservoir filling, and operational phases. Furthermore, in order to incorporate drying-induced hardening effects in the analyses, the BBM was extended within CODE_BRIGHT by implementing the suction-increase (SI) curve. The results of the numerical simulations were compared with field instrumentation data, showing good agreement during construction and reservoir filling. However, during the operational phase, simulations using the original BBM formulation failed to reproduce the observed settlements, likely due to a series of water level drawdowns that maintained the reservoir below the full operational level. The implementation of the SI curve successfully captured the volumetric shrinkage tests under drying conditions, accounting for plastic hardening caused by suction increase. Nonetheless, even with the SI curve, the numerical analyses of the dam could not reproduce the settlements, as the reservoir drawdowns during operation were insufficient to reduce suction and activate drying-induced plasticity as defined by the SI boundary introduced in this work.