Influence of layered hydrate accumulation on mechanical behavior of marine silty clay in South China Sea: Experimental study and constitutive modeling

Layered hydrates are widely distributed in marine sediments and it has a significant effect on the mechanical properties of hydrate-bearing sediment (HBS) strata. Nevertheless, the mechanical properties of layered HBS remain poorly understood, which is related to the safety and stability of mining. In this paper, triaxial tests were conducted to investigate the influence of layered hydrates on mechanical behavior of marine sediments. Subsequently, a modified Duncan-Chang model was proposed, in which a quadratic term was introduced, thus rendering it applicable to HBS. Finally, the parameters of the HBS modified model are predicted from the mechanical parameters of hydrate-free sediments by a homogenization theory. The results show that as the hydrate volume fraction increased from 0 to 11%, the cohesion and the tangent of the internal friction angle of the specimen increase by 30% and 49% respectively. As the confining pressure increases, the hydrate content has a more obvious effect on the strength and stiffness of the specimens. The average errors between the predicted mechanical parameters derived from the homogenization theory and the experimental results is within the range of 10%. The modified model was more suitable for the layered HBS than the traditional Duncan-Chang model.