Seepage through Mira Dam embankments

Abstract

The Mira dam was buildt with a clayey central core and shells of weathered schist. As coarse materiais with plate shaped grains were used and the compaction was made with smooth track vibrating rollers, a great effort was dane during construction to measure the perrneability of the fills.

The objective was attained by making hundreds ofmeasurements: in situ tests on recently compacted fill and laboratory tests on undisturbed samples. From the results it was concluded of larger horizontal permeabilities and that this anisotropy was particulary marked on the shells.

By the measurement of the embankments pore pressures it has been possible to follow the evolution of the seepage during construction and operation of the dam.

The available results as well as theoretical calculations by the finite element method shows that the steady-state flow for full reservoir was not attained and allows the deterrnination of the directional permeability relationships.