On the critical state characteristics of methane hydrate-bearing sediments

Reasonable prediction of marine ground stability is vital for the safe exploitation of methane gas from the seabed and development of relevant technologies for gas production. Constitutive models based on a critical state soil mechanics framework for methane hydrate-bearing sediments have been proposed in recent decades. They required careful calibration of laboratory results to obtain accurate information on model parameters. This study presents a comprehensive analysis of triaxial shear test data to examine the effects of hydrate saturation on the geomechanical characteristics of methane hydrate-bearing sediments, particularly at the critical state. Multiple critical state lines are identified for methane hydrate-bearing sediments with different levels of hydrate saturation on the specific volume and logarithm of mean stress plane. A rise in hydrate saturation shifts the critical state line of methane hydrate-bearing sediments upward and slightly increases the gradient of critical state line in the v- lnp' plane. Non-unique critical state lines are observed for methane hydrate-bearing sediments under plane-strain loading conditions. Considering methane hydrate saturation as an extra dimension of critical states, the critical state line in the plane of specific volume and logarithm of mean stress, becomes a three-dimensional critical state surface.