Undrained deformation of hydrate-bearing clayey silt could generate submarine landslides

As global energy exploration extends into deep-sea environments, infrastructure deployment increasingly intersects with hydrate-bearing strata. Submarine landslides represent a major geohazard, exhibiting scales and energies far exceeding most terrestrial slope failures. However, conventional theories struggle to explain the widespread presence of layered streaks and weak layers detected in apparently stable deep-sea shallow formations. Through cryogenic high-pressure in-situ CT triaxial testing, we demonstrate that under undrained conditions, localized strain can develop in low-permeability hydrate-bearing sediments (HBS), leading to progressive shear band formation. Within this process, stress concentrations around localized structural heterogeneities act as nuclei for micro-cracks, which subsequently evolve into macroscopic shear bands. These structures alter local hydrate dissociation behavior, generating pore pressure anomalies and facilitating weak layer propagation. We reveal that localized internal shearing precedes macroscopic yield, demonstrating an 'inside-out' failure propagation mechanism. This cascading geomechanical response links microscale sediment behavior to macroscale slope instability, hypothesizing a potential triggering mechanism for large-scale submarine landslides.