lmpervious elements in rockfill dams, and slope protection considerations

Abstract

The report comprises a review of the papers presented at the Technical Sessions on the theme, at the International Congress on Large Dams, Madrid 1973, and the Brazilian Seminar on Large Dams, Novembro, 1973.

Among the upstream impervious membranes, the one that merits principal attention is the reinforced concrete slab resting on compacted rockfill.

Regarding the earth-core rockfill dam, the case of the Salto Osório inclined-core dam is used as a basis for discussion of the principal problems of design and construction, because of use of about the most clayey material, anticipated to be very compressible and subject to cracking because of deformations significantly different from those of the rock shells. For the clay core, construction equipament and specifications are discussed, along with inspection testing and interpretation. Regarding the design of the dam section the use of finite element analyses is discussed, demonstrating the significant advantage of the inclined core to avoid hang-up on the less compressible rock shells and potential hydraulic cracking. Properties of tensile resistance and flexibility of compacted clay fill are discussed, it being emphasized that clays of high Plasticity Index are not plastic at compaction water contents. Finally, modem criteria of filter and transition materials are discussed with respect to "washing­ through" and "self-healing". Moreover, modem criteria of wind wave calculation and rip-rap design are summarized. ln conclusion a summary is drawn up of topics for discussion.