西部麓山帶砂岩潛變特性研究

In the western Taiwan most rocks
are sedimentary rocks of tertiary period.
These rocks are often not well cemented,
and sometimes full of geological
structure, such as joint, faults, fracture.
Besides, rainfalls in Taiwan often
exceeds thousands of millimeter, rock in
this situation may weathered very
quickly, and may cause many
engineering problems.
In order to reduce the problems
encountered during engineering, we
must research the mechanical behavior
of these rock.
In this study, we research the creep
behavior of sandstone, included three
rock strata. Uniaxial and triaxial creep
2
tests are used to study the creep behavior
sandstone. The effective of stress path
and level of shear stress and confining
pressure were investigated.
The uniaxial creep test results
indicate that sandstone has the following
creeping behavior: In Mushan sandstone,
the primary axial creep behavior is
significant at low level of shear stress. In
Mushan, creep strain is large at the
initial step and reduces rapidly at the
second step. Nevertheless, in overall
situation greater degree of shear stress
will induce greater creep strain.
According to the conventional
triaxial creep test results, the creep strain
and creep strain rate increase with
deviatoric stress. And if we normalize
the deviatoric stress to SSR (Stress -
Strength Ratio), we found that in the
SSR ε− diagram, every curve has the
same trend, and falls in a very narrow
region, in spite of confining pressure. In
this study, we also found that in the
same SSR the strain of wet specimens
always greater than dry specimens. In
the volume strain of wet specimens, the
volume always dilates at every SSR. the
strength of sandstones decreased with
water.
In the hydrostatic creep test, when
cell pressure is higher than 10 MPa, the
axial creep behavior and laterial creep
behavior are similar. the amount of
lateral and volumetric creep during the
pure shear stress path creep test is higher
than during the tradition triaxial test at
the same stress level.