軟弱砂岩力學行為與其岩象分析研究

Owing to the high porosity, low strength,
and large deformability of weak sandstone,
tunnel construction in western Taiwan
encounters lots of excess deformation. This
research first explores this problem from
experimental data. A series of triaxial tests
have been carried out to investigate the
deformational characteristics of weak
sandstone. The experimental results indicate
that: (1)significant plastic volumetric strain
comes up at low levels of confining stress,
and locks at higher levels of confining stress;
(2)apparent coupling behavior exists between
shear stress and elastic volumetric strain; (3)a
set of elliptical plastic potential surface is
proposed according to the distribution of
plastic flow. An elasto -plastic model is
then proposed to characterize the behaviors
of the sandstones. Through the simulations of
different stress paths for various sandstones,
it is found that good agreements arise
between the predictions and the experimental
results.