Tensile strength anisotropy of Barre Granite

Rock Engineering 2009 - Rock Engineering in Difficult Conditions
Feng Dai,
Abstract Granitic rocks usually exhibit strongly
anisotropy due to pre-existing microcracks
induced by geologic loadings. The understanding
of the rock anisotropy in mechanical properties
is critical to quarrying and stabilization of
underground structures. In this paper, Brazilian
Disc (BD) specimens are used in combination with
MTS material testing machine and split Hopkinson
pressure bar (SHPB) system to measure both static
and dynamic tensile strength of Barre Granite
(BG). Samples are cored and labelled using the
three principle anisotropic directions of BG.
These directions are also chosen as the loading
directions for the BD tests. For dynamic tests,
pulse shaping technique is used to achieve
dynamic equilibrium in the samples during the
test. Finite Element Method is implemented to
formulate equations that relate the failure load
to the material tensile strength. For samples in
the same orientation group, the tensile strength
shows clear loading rate sensitivity. Under a
given loading rate, the tensile strengths exhibit
clear anisotropy. This tensile strength
anisotropy is interpreted as the interactions of
the pre-existing micro-cracks.
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