Influence of matrix composition on the mechanical behavior of methane hydrate-bearing clayey-sandy sediments: Insights from fine and clay contents.

It is extremely necessary to fully understand the mechanical properties of hydrate-bearing sediments before the commercialization of hydrate. However, few studies have explored the effect of matrix composition on mechanical behavior. In this paper, seabed clay recovered from the Shenhu Sea in the hydrate deposit area of the South China Sea and quartz sand were used as the matrix skeleton to remold hydrate-bearing clayey-sandy sediments (HBCSS). A series of triaxial tests were then carried out to investigate the effect of matrix composition (clay and fine contents) on the strength behavior of HBCSS. The results show that the fine can fill the pores and thus increase the density, which in turn enhances the strength and stiffness of HBCSS and makes the stress-strain relationship more easily softened. The lubrication of clay can significantly change the contact relationship between particles, induce strain hardening and reduce stiffness. Cohesion and internal friction angle are positively and negatively correlated with clay content, respectively. A new concept of the hardening index was proposed, which has a better quantitative description of the hardening or softening of the stress-strain relationship. The strength behavior of HBCSS is the result of the coupling of various factors. • The effects of fine and clay on the strength behavior of HBCSS are illustrated. • The influence essences of fine and clay are the filling and lubricating effects respectively. • Particle-scale shearing mechanisms are revealed. • A new hardening index is proposed to quantitatively analyze hardening or softening. [ABSTRACT FROM AUTHOR]