The shear characterization of hydrate-bearing clayey-silty sediments with layered hydrate distributions: Insights from different hydrate saturations and effective confining pressures

Abstract

The mechanical behavior of hydrate-bearing sediments (HBS) is influenced by the layered hydrate distribution, and comprehensively understanding the mechanical properties of layered HBS is a precondition for achieving safe and efficient hydrate exploration. In this paper, a series of consolidation-drained triaxial tests of layered hydrate-bearing clayey-silty sediments (LHBCSS) were carried out with the clayey-silty reservoir in the South China Sea as the investigation background. The evolution rules of cohesion c and internal friction angle φ of LHBCSS under different impact factors were investigated. The shear dilatation characteristics of LHBCSS were clarified. The shear mechanism of the LHBCSS was revealed. The results show that the strain hardening dominates the stress-strain curves of LHBCSS, and the effective confining pressure σ′ promotes the strain hardening. The failure strength σ_f and stiffness increased with the increment of the upper layer saturation. The c rises exponentially with the upper layer saturation, while the impact of upper layer saturation on the φ is insignificant. With the increase of σ′, the LHBCSS transforms from shear dilatation to shear contraction. The shear dilatation characteristics of the LHBCSS are influenced by the coupled impacts from multiple influencing factors.