Mechanical behaviors of natural gas hydrate-bearing clayey-silty sediments: Experiments and constitutive modeling

It is of great importance to investigate the mechanical properties and constitutive models of hydrate -bearing sediments (HBS) for the safe extraction of hydrate. However, there are few experiments and constitutive models for fine-grained HBS to date. In this work, a range of triaxial tests were first performed to reveal the mechanical properties of hydrate -bearing clayey -silty sediments (HBCSS). Subsequently, the compression properties and shear behaviors of HBS were summarized in depth. Finally, a constitutive model that could describe the mechanical behaviors of clayey sediments and sandy sediments uniformly was established by proposing the compressibility parameter (reflecting compression characteristics), cementation factor (reflecting cementation effect), and dilatancy factor (reflecting filling effect). The results show that increasing saturation can significantly improve the stiffness and strength of HBCSS. While strain softening can be induced by high hydrate saturation. Strain hardening often produces volume contraction, and strain softening produces volume dilatation. The established constitutive model can not only effectively reflect strain softening and hardening, volume dilatation and contraction, but also describe the characteristics of isotropic compression and one-dimensional consolidation. Meanwhile, it has a good prediction on the effects of confining pressure and hydrate saturation. The model is suitable for both coarse -grained sandy HBS and fine-grained clayey HBS.