Alicurá Dam on the Rio Limay (Neuquen and Rio Negro province),
was built between 1979 and 1984 for the state company
Hidronor. The particularity of this dam is the presence of the
interbedded mylonitized pelitic levels in the sequence of sandstones
to Las Coloradas Formation of Jurassic age. These sheared
pelitic layers have received special attention in the study of
foundation conditions of concrete structures because of their low
frictional strength [9–11]. The lithology of the formation is a result
of succession polycyclic of conglomerates, conglomeratic
sandstone, sandstone, clayey sandstone, sandy micaceous shales,
mudstones and siltstones silty clay. Folding processes have
produced interbedding slides located in some of the pelitic layers.
The rock mass is mechanically inhomogeneous and this is particularly
critical on the left bank of the valley where the layers dip into
the valley creating a clear instability.
Geotechnical properties of the sandstone are highly variable
and the average values obtained from tests on samples of rock
NX diameter are presented in Table 11.
The shale sheared layers were classified as clay as low to
medium plasticity (IP between 5 and 20), liquid limit between 20
and 40. More plastic samples show about 40% clay and 25% of
the particles through the sieve 200.
The drained strength parameters were determined by direct
shear tests, simple shear tests and triaxial tests on remolded