Investigating mechanical properties of hydrate-bearing sediments during hydrate dissociation using multiscale approach

This paper investigates the impact of hydrate dissociation on the mechanical behavior of hydrate-bearing sediments (HBSs) using a hierarchical multiscale approach. First, a hydrate contact model considering temperature effects is developed, and representative volume elements (RVEs) that characterize the mechanical properties of HBSs are established. Discrete element method (DEM) simulation is conducted to estimate the effective mechanical properties of HBSs. The simulation results are compared with experimental data obtained from the literature, which validates the feasibility of the hydrate contact model and the suitability of the RVE. Next, a hierarchical multiscale approach is constructed to simulate biaxial compression tests under different hydrate saturation conditions. The failure mechanisms are analyzed from the microscopic to the macroscopic. The results indicate that hydrate dissociation leads to a reduction in the load-bearing capacity of HBSs, with failure closely related to factors such as shear band formation, particle rotation, and changes in porosity. Additionally, biaxial compression simulations are performed for the hydrate dissociation in different regions. The results indicate that with an increase in the layered angle α, the peak load under triaxial compression decreases, accompanied by a reduction in the axial strain required to reach peak strength. Finally, the impact of hydrate dissociation and temperature changes on the deformation and stability of submarine slope is analyzed, demonstrating that the progression of hydrate dissociation and the increase in temperature lead to the development of horizontal displacements and the emergence of shear strain. Moreover, the maximum shear strain exhibits an arc-shaped distribution beneath the submarine slope, increasing the risk of submarine landslides and compromising slope stability.