Abstract: On the basis of triaxial and direct shear tests, modified Mohr-Coulomb strength criterion and the modified Lade-Duncan strength criterion in which the effect of methane hydrate saturation is considered are used to describe the strength of micro-elements for methane hydrate-bearing sediments. Based on the results, statistic damage constitutive models for methane hydrate-bearing sediments are put forward using the theory of continuous damage mechanics together with statistical theory. Then, by comparing the results obtained from theoretical models to those from laboratory tests, the validity of statistical damage models based on different strength criteria are verified. The results show that the damage constitutive model based on the modified Lade-Duncan strength criterion can accurately simulate the stress-strain curves of hydrate-bearing sediments before reaching the peak stress, while the damage constitutive model based on the modified Mohr-Coulomb strength criterion can capture the strain-softening characteristics after the peak stress observed in the experiments. For the experiments with different hydrate saturations and lower effective confining pressure, the simulation accuracy of the damage constitutive model based on the modified Mohr-Coulomb strength criterion is better than that based on the modified Lade-Duncan criterion. On the contrary, under the same hydrate saturation and different effective confining pressures, the simulation results of the damage constitutive model based on the modified Lade-Duncan strength criterion are better than those based on the modified Mohr-Coulomb strength criterion.

Key words: hydrate-bearing sediments, modified Lade-Duncan strength criterion, modified Mohr-Coulomb strength criterion, statistical damage models, hydrate saturation