Hydratesare often filled in the pores of sediment soil particles or bonded betweengrain contacts

which have filling or bonding effects on sediments. Theseformation patterns of hydrate change the original void ratio and density of soil

which significantly affect the physical and mechanical properties of sediments

so it is necessary to consider the effects of hydrate filling and bonding to describethe mechanical properties of hydrate-bearing sediments. In this paper

theequivalent hydrate ratio was proposed to reflect the filling effect of hydratebased on the unified critical state constitutive model for both clay and sand (clayand sand model

referred to as CASM) and combined with the densificationcharacteristics of hydrate intrusion pores. The cohesive strength was introducedto reflect the cementation of hydrates on sediments. Furthermore

anelastoplastic constitutive model for hydrate-bearing sediments was establishedto describe the hydrate filling and bonding effect by using the stateparameters to reflect the stress state and the dilatancy of the soil andadopting the non-associated flow rule. The comparison between laboratory testresults and presented constitutive models shows that this model can effectivelysimulate the stress-strain relationship of hydrate-bearing sediments

andreasonably describe the influence of hydrate content and effective confiningpressure on the mechanical properties of sediments

such as strength

stiffness

dilatancy

and so on.