ORIGINAL PAPER On the Use of Random Material in Dam Cores: Case of the Manso Dam, Brazil Breno S. Ferreira . Marcio S. S. Almeida . Francisco R. Lopes . Maria do Carmo Reis Cavalcanti . Celso Jose ´ Pires Filho Received: 20 March 2021 / Accepted: 3 October 2021 / Published online: 10 November 2021 Ó The Author(s), under exclusive licence to Springer Nature Switzerland AG 2021 Abstract The Manso Dam, in the Brazilian State of Mato Grosso, intended for flood control and electricity generation, was built by a state-owned energy com- pany in partnership with the private sector. In order to reduce costs and minimize the environmental impact of the project, the private consortium proposed changes to the preliminary design, which were reassessed with the participation of the Federal University of Rio de Janeiro. The design and the behavior of the dam are discussed in this paper. The main section of the Manso Dam, 73 m high, has rockfill shells and a core of compacted soil. For the core, colluvial and residual soils derived from the necessary excavations for the concrete structures and dam foundation were chosen in order to reduce both the cost and environmental damage that would result from borrow/disposal. Such composite clay, gravel and cobbles of different sizes and degrees of weath- ering is generally referred to in the literature as random fill, and because is not typically used in dam cores, laboratory and field tests were then performed. Parameter evaluation and Finite Element (FEM) analyses of seepage and deformation were carried out. The seepage analysis was carried out for the maximum normal reservoir level, and the results were confirmed by the field monitoring data, enabling the establishment of safety levels (alert and emergency conditions). Embankment construction and first reser- voir filling were simulated with the FEM, yielding, as expected, stress concentrations in the more rigid materials, such as the filters and transitions. During reservoir filling, seepage forces induced horizontal displacements in the downstream direction and reduc- tion in effective stresses in the upstream region due to submersion. The predicted settlement distribution was compatible with field monitoring data. Construction was completed in 2010 and the dam has been operating normally ever since. Keywords Dam cores Á Random fill Á Seepage analysis Á Deformation analysis Abbreviations c Cohesion u Angle of shearing resistance B. S. Ferreira ENEL, Rio de Janeiro, Brazil e-mail: breno.ferreira@enel.com M. S. S. Almeida Á F. R. Lopes (&) Á Maria do Carmo Reis Cavalcanti Federal University of Rio de Janeiro, Rio de Janeiro, Brazil e-mail: flopes@coc.ufrj.br M. S. S. Almeida e-mail: marciossal@gmail.com Maria do CarmoReis Cavalcanti e-mail: carminhacavalcanti@poli.ufrj.br C. J. Pires Filho Furnas Centrais Ele ´tricas, Rio de Janeiro, Brazil e-mail: celsos@furnas.com.br 123 Geotech Geol Eng (2022) 40:1973–1987 https://doi.org/10.1007/s10706-021-02003-7