Atterberg limits measured on powdered samples indicate that
the fine fraction can be classified as low plasticity clay (Fig. 5).
These results are similar to those shown for sheared shales to the
Alicurá dam.
Laboratory tests included a large number of triaxial tests on
samples of clayey sandstone of El Chocón formation and cemented
siltstones Cerros Colorados formation. The triaxial tests were performed
step-wise type, drained and measuring the volume change.
Were also conducted direct shear test in a specially designed
device for testing clay weak rocks, with measurement of volume
changes and pore pressure.
The results of the tests are shown in Table 14 as modified by
Vardé apud Bolognesi and Moretto [1].
Vardéalso analyzed the geomechanical characteristics of
sandstones and claystones of the Monte León formation (tertiary)
at the site of the future site of the hydroelectric Project N [1].
The stratigraphic sequence consists of a layered sedimentary rock
substrate corresponding to the Monte León Formation of Miocene
age. Its lithology consists of tuffs, tuffaceous mudstones,
sandstones and interbedded tuffaceous sandstones with thicknesses
of several meters in the upper parts of the profiles surveyed.
This unit lays well stratified, subhorizontal, in beds of several decimeters
to 2–3 m thick. The contacts between different lithologies
are predominantly transitional. Monte León Formation crops out
poorly in the area of dams and is generally covered by most
modern sedimentary deposits and basalt flows of Pliocene age.
The results of laboratory tests indicate that the rocks exhibit low
compressive