Displacements of the Xingó Concrete Face Rockfill Dam-Brazil

摘要

The Xingo Hydroelectric Project is located on the Sao Francisco River,between the states of Alagoas and sergipe in the Northeast region of Brazil. The main dam is a concrete face rockfill embankment type (CFRD),with maximum height of 150 m. The upstream slab thickness varies between 0.30 and 0.70 m and it was built with vertical contraction joints,16 m apart,in two construction stages. The rockfill embankment was entirely built with gneissic and granitic rock made available by excavation for the foundation of the concrete structures. The performance of the dam during construction and operation was accompanied through monitoring instruments installed in three main sections. The reservoir impound began June 10,1994 and reached its maximum normal water level on Nov.15,1994. To monitor the vertical and horizontal displacements of the rockfill embankment three sections were chosen,representing the right abutment,the highest section in the riverbed and the left abutment.Fifteen years after the reservoir impound The largest vertical displacement of the superficial marks occurred in the central section of the dam,having reached at the crest about 615 mm.Inspections detected a crack 20 m deep close to the plinth,a set of transversal fissures 26 m deep at the slab L6 with opening of up to 35 mm and crushing of the concrete in the upper portion at the joint L12/L13. This paper presents the dam performance during construction,reservoir impounding and operation stages.