Abstract
In this study, effect of confining pressure on mechanical properties of artificial methane hydrate sediment was experimentally investigated and discussed. Two kinds of drained triaxial compression tests were conducted for artificial sediment specimens containing Toyoura sand and synthetic methane hydrate under a pore water pressure of 8 MPa and a temperature of 278 K; “constant confining pressure test” and “two-stage confining pressure test”. In the former test, confining pressure was kept constant at 8.5 MPa, 9 MPa, 10 MPa or 11 MPa during axial loading process. In the latter test, confining pressure was altered from 8.5 MPa to 11 MPa during axial loading process. The findings can be summarized as follows.
(1) A specimen was restrained from deforming laterally by confining pressure.
(2) Strength and stiffness of a specimen were enhanced by confining pressure.
(3) Two strengths under different confining pressures could be obtained from a single specimen by two-stage confining pressure test.
(4) Strength was formulated as a function of confining pressure and methane hydrate saturation based upon earlier findings.
These findings concerning the effect of confining pressure seem to be of considerable help for a proposal of constitutive equation and numerical simulation in the future.
