Study on the Dynamic Damage Mechanism and Kinetic Evolution Law of the Hydrate Deposit Layer under Stress in Deep-Water Pipelines

Natural gas hydrate deposition poses a significant threat to pipeline transportation safety. Due to the high-pressure, sealed environment in which hydrates form, it is challenging to analyze the microdamage characteristics of hydrate layers under dynamic conditions using conventional equipment. This limitation hinders our understanding of the damage evolution patterns and mechanisms within deposited layers under stress loading. This study combines experimental and numerical simulation methods to clarify the mechanical evolution of hydrate deposits. A predictive model was established for consolidation forces as a function of the consolidation time and subcooling degree. For the first time, a discrete element simulation was used to model deposits with structural strength gradients, analyzing damage mechanisms and evolution patterns under stress loading. The consolidation strength of the hydrate deposit layer exhibits a trend of initially increasing significantly with the consolidation time before gradually stabilizing. Under stress loading, tensile damage dominates the failure mechanism. Consolidation time has little effect on the crack ratio; however, as stress loading intensifies, the ratio of tensile cracks to shear cracks decreases from 7:1 to 4:1. Furthermore, the codirectional nature of gravitational and contact forces results in a greater tendency for damage along the deposit layer's longitudinal direction. The failure patterns of these deposits are influenced by stress concentration paths and the direction of aging consolidation gradients, which lead to differences in the degree of destruction. This study establishes the first research framework for examining damage evolution in deep-water pipeline hydrate deposits, providing a theoretical foundation for the study of hydrate deposit stability.