An Elastoplastic Constitutive Model Considering Bonding Effects for Methane Hydrate-Bearing Sand

Methane hydrates exist in solid form within the pores of sand and have a significant impact on its mechanical and deformation properties. Therefore, it is essential to simulate the mechanical behavior of methane hydrate-bearing sand (MHBS) and evaluate its stability prior to commercial methane gas extraction. In this article, an elastoplastic constitutive model for MHBS is proposed. The yield surface function, which accounts for the bonding strength due to the hydrate cementation effect, is discussed, and the critical state line equation as a function of hydrate saturation is presented. Additionally, a simple debonding law is incorporated as a function of the plastic damage strain. Furthermore, an expression for the dilatancy is established based on the nonassociated flow rule. The hardening rule of the proposed model aligns with that of the Cam-Clay model. Model parameters are calibrated based on drained triaxial compression test data on MHBS. The simulation results closely match the test data, demonstrating the model’s effectiveness in predicting the stress–strain and volume change behavior of MHBS across a broad spectrum of initial densities, hydrate saturation, and effective confining pressures.