In this study, triaxial compression tests were conducted for Toyoura sand containing synthetic methane hydrate at conditions of confining pressure 9 MPa, pore water pressure 8 MPa and temperature 278 K. In the test, strain rate was switched between
C1 and
C2 (
C1 <
C2) at every predetermined strain interval, and two stress-strain curves at strain rates of
C1 and
C2 were estimated from a single specimen.
As a result, the peak strength at the faster strain rate
C2 was higher than that at the slower strain rate
C1. It was also found that strain-rate dependency of peak strength increased with methane hydrate saturation. It can be said that methane hydrate saturation significantly affected to the strain-rate dependency and then failure mechanism of the methane hydrate sediments.
Strain-rate dependency of residual strength (stress in the post failure region) was discussed. The ratio, (stress at the strain rate
C2 / stress at the strain rate
C1), was almost constant in the region. This finding may suggest that the mechanism of strain-rate dependency or time-dependent behavior of methane hydrate sediments does not change in the post-failure region.
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