Influence of Effective Confinement Pressure on Geomechanical Characteristics of Hydrate-Bearing Sediments

Methane gas hydrates are a promising unconventional energy resource. However, the gas extraction can lead to destabilization of hydrate-bearing sediments (HBS). Therefore, it is crucial to understand the mechanical behaviour of HBS to ensure safe extraction practices. This study experimentally investigates the influence of hydrate saturation (Sh) and effective confinement pressure (σ3′) on the mechanical behavior of methane hydrate-bearing specimens (MHBS) with cemented hydrate morphology. Results indicate that with increasing Sh, there is a notable enhancement in strength and stiffness due to hydrate-induced bonding. It is also observed that, under higher σ3′, MHBS exhibits a transition in post-peak behavior from strain-softening and dilation to strain-hardening and contraction. Based on the experimental results, an advanced hypoplastic constitutive model for HBS is calibrated. The model captured the peak strength and the dilation to contraction transition, but did not fully reproduce the post-peak softening to hardening transition with increasing σ3′ in MHBS.