356
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
6 CONCLUSIONS
This paper studied thoroughly the mechanical behavior of thirty
rockfill materials subjected to triaxial compression shearing
with three different confining stresses. The Hyperbolic Model
(Duncan and Chang 1970) was employed as the behavioral
model for this study. Features of the mechanical behavior of
rockfill materials, as compared with soils, were highlighted
through the exponent parameter (n) of the Hyperbolic Model.
Unlike for soils, n is not constant for rockfill materials, and
depends on confining stress levels; n can even takes a negative
value, which is a sign of particle breakage in the materials.
The main focus in this paper was on the effect of confining
pressure on the stiffness (initial deformation modulus and
tangential deformation modulus) of the materials. It was shown
that rockfill materials undergo particle breakage to some extents
and therefore, they may behave comparatively softer under
higher confining stresses. The extent of particle breakage
depends on gradation characteristics, (especially coefficient of
uniformity), particle shape (angular or rounded), wetting
condition, and confining stress.
Two correlations for estimating initial elasticity modulus (E
i
)
and internal friction angle (
φ
) of the studied rockfill materials,
based on particles shape, confining pressure (
σ
3
), and
coefficient of uniformity (C
u
) were suggested. Investigations on
the variations of internal friction angle (
φ
) with confining stress
(
σ
3
) also showed that
φ
decreases with increasing of
σ
3
in all
types of rockfill materials. The extent of reduction in
φ
depends
on the extent of particle breakage.
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