In recent years there has been an increasing interest in production of methane gas from hydrate-bearing sediments, located below the permafrost in arctic regions and offshore within the continental margins. In order to simulate the geomechanical response of the hydrate accumulation during gas production, comprehensive evaluation of the sediments' properties is imperative. This paper presents an analysis of the mechanical properties of methane-hydrate-bearing sediments determined through numerical simulation of drained triaxial compression tests on three different sand types. The adjustment of the numerical to the experimental results was performed for the entire stress-strain curves and therefore enables a good understanding of the material constitutive relations. New constitutive relations are suggested for the hydrate-related properties. An optimization process was used, finding separately the soil skeleton-related coefficients and the hydrate-related coefficients. The values of the obtained coefficients associated with the hydrate were found to have minor deviations from each other, for the three examined sand types. By separating the soil skeleton and the hydrate-related response, this paper suggests a prediction method for the mechanical response of hydrate-bearing sands.

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A significant portion of our knowledge on gas hydrate-bearing sands comes from experimental results on laboratory-synthesized specimens. The failure mechanics are often interpreted using components of the stress–strain curves, which capture the specimen’s global (large-scale) response to shear. In this paper, we postulate on the microscale mechanics, which lead to a variety of interesting global behaviors. Two mechanisms of failure during shear are postulated: one involves debonding of the hydrate particle from the soil solid, and the other involves crushing or breakage through the hydrate itself. Both modes of failure lead to similar peak strengths, which arise from both friction and apparent cohesion induced by the hydrate bonding; however, the differences observed in postpeak softening may be attributed to the different failure mechanisms. Global specimen responses such as sudden strength loss, occurrence of double shear banding, and differences in postpeak behavior are manifestations of the microscale hydrate sand interactions.

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This paper presents an experimental verification of a prediction model for the mechanical properties of hydrate‐bearing sand. The model is examined using experimental drained triaxial test results of three independent data sets, which are associated with different hydrate formations and testing conditions. For each data set, an optimization process is applied based on numerical modeling of the testing conditions in order to evaluate the pure sand properties. Based on these properties, the model forecasts the stress‐stain curves for different hydrate saturations, based on an advanced hydrate simulator. Although the model does not show a fair forecast with “ice‐seeding” hydrate formation samples and for specimens tested under gas saturation, it predicts the mechanical behavior of samples with “partly saturated” hydrate formation tested under water saturation.