Triaxial tests on the overconsolidated methane hydrate-bearing clayey-silty sediments

Significant experimental efforts have been made to understand the mechanical behaviors of hydrate-bearing sediment; however, studies on the influence of over consolidation conditions on hydrate-bearing sediment are quite rare, while a series of exploratory drilling surveys for hydrate in hydrate-bearing sediment has reported that the phenomenon of over consolidation or apparent over consolidation is widespread. In this study, we present triaxial test results of influence of the over consolidation on hydrate-bearing clayey-silty sediment. The results reveal that both the tested normally consolidated and overconsolidated hydrate-bearing sediment appear to undergo strain-hardening and volumetric contraction, although the increasing over consolidation ratio would weaken the strain-hardening phenomenon and enhance the initial elastic modulus and failure strength. In addition, the increasing hydrate saturation would also increase the initial elastic modulus and failure strength and decrease the volumetric strain of the overconsolidated hydrate-bearing sediment. The mechanism controlling the influence of over consolidation on the hydrate-bearing sediment has been further investigated and discussed by scanning electron microscopy, and it is found that the over consolidation could damage a certain proportion of the cementation structure formed by the hydrate, while increasing the particle occlusion and strengthening the sediment. Under low over consolidation condition, these two mechanisms may almost counteract each other, while under high over consolidation condition, the strengthening mechanism caused by over consolidation is dominant.

Automated summary

The study investigates the influence of over consolidation on hydrate-bearing sediment, revealing that increasing over consolidation ratio weakens strain-hardening phenomenon and enhances initial elastic modulus and failure strength. Furthermore, increasing hydrate saturation also affects the sediment's properties.