CONE PENETRATION TEST AND ITS INTERPRETATION FOR MEDIUM-DENSE HYDRATE-BEARING SAND

The exploitation of deep-sea hydrates may induce significant geological hazards, making it essential to determine the physical and mechanical parameters of hydrate reservoirs in advance. In this study, CO₂ hydrate-bearing sand samples were prepared using a self-developed high-pressure low-temperature calibration chamber, and cone penetration tests were conducted. The penetration process was simulated using the Arbitrary Lagrangian-Eulerian(ALE)large deformation finite element method. The hydrate-bearing sand was modeled as a modified Mohr-Coulomb material in the numerical simulations. Consolidated drained triaxial tests on hydrate-bearing sand and bending element tests on pure sand were performed to determine the constitutive parameters. The results show that the net cone tip resistance of hydrate-bearing sand increases with rising hydrate saturation and effective confining pressure. The cone tip resistances obtained from numerical simulations are in good agreement with the calibration chamber experiments. Based on extensive parametric analysis, an empirical relationship for predicting hydrate saturation from net cone tip resistance is proposed.