|
A series of experimental work were carried out previously in NCTU
(National Chiao - Tung University) to investigate the mechanical behavior of
brittle rocks under elevated pressures and temperatures. In this study, the
experimental data of triaxial compression tests is summarized and re-analyzed.
Furthermore , the study develops a constitutive model to describe the
mechanical behavior of brittle rocks.
The experimental results show that crack-closure siginificantly affect
the initial stress - strain relation of a brittle rock during triaxial
compression. The initial stress - strain curve reveals that the tangent
stiffness gradually increases and reaches an elastic stiffness at a crack-
closed strain. As the confining pressure increases, the elastic stiffness
raises while the crack-closed strain decreases. The effect of temperature on
the elastic stiffness and the crack - closed strain , however, is still not
concluded from the experimental data. For the post - peak behavior , the
class II behavior is obvious.
On the basis of the experimental results, a constitutive model is
proposed to d escribe the mechanical behavior of brittle rocks. The presented
constitutive model contains a pore/crack closure model and a continuum damage
mechanics model. The study also developes a computer program behavior optimiz
-ation procedure for calibrating the appropriate material parameters from a
set of experimental data. By comparing the simulated and experimental results
, it is demonstrated that the proposed model can closely simulate the stress-
strain relation of brittle rocks with very limited material parameters.
Parametric studies also demonstrate that, with proper combination of
parameters,the proposed model is capable of modeling (i) the class I as well
as the class II post-peak behavior,and (ii) the dilatancy during a compression
test.
|