Mechanical behavior of gas‐saturated methane hydrate‐bearing sediments

Abstract

[1] A series of triaxial compression tests were conducted in order to investigate the mechanical behavior of gas-saturated methane hydrate-bearing sediments, and a comparison was made between gas-saturated and water-saturated specimens. Measurements on gas-saturated specimens indicate that (1) the larger the methane hydrate saturation, the larger the failure strength and the more apparent the shear dilation behavior; (2) failure strength and stiffness increase with increasing effective confining stress and pore pressure applied during compression, though the specimen becomes less dilative under higher effective confining stress; (3) lower temperatures lead to an increase of the stiffness and failure strength; (4) stiffness of specimens formed under lower pore pressure is higher than that of specimens formed under higher pore pressure but at the same effective stress; (5) stiffness and failure strength of gas-saturated specimens are higher than those of watersaturated specimens; (6) gas-saturated specimens show more apparent strain-softening behavior and larger volumetric strain than that of water-saturated specimens.

Mechanical behaviors of permafrost-associated methane hydrate-bearing sediments under different mining methods

“…3 shows the relationship between the failure strength and confining pressure for the hydrate-bearing sediments containing ice, which dissociated by depressurization or heating method under different exhaust conditions. The results indicate that the failure strength clearly increases with increasing confining pressure, which is accordant with our previous study [26][27][28]. The reason for this behavior is that pore fissure being closed under higher confining pressures, which prevents crack propagation in the sediments.…”

“…The reason is that the pore spaces are filled with dissociated methane gas and ice. The existence of methane gas will increase the pore pressure, which induce a reduction of effective confining pressure and then decreases the failure strength as a result [26,27].…”

Numerical simulations for analyzing deformation characteristics of hydrate-bearing sediments during depressurization

“…Solid NGHs are decomposed into liquid water and natural gas during depressurization. This, in turn, may result in a loss of cementation and a corresponding effective stress decrease of hydrate-bearing sediments (HBS) (Hyodo et al, 2013;Song et al, 2014;Yoneda et al, 2015;Kajiyama et al, 2017;Zhang et al, 2017). NGHs have been treated as a potential trigger in submarine geohazards such as wellbore failures, seabed settlements, and submarine landslides (Nixon and Grozic, 2007;Lee et al, 2010b;Maslin et al, 2010;Ning et al, 2012).…”

“…A vast variety of triaxial shear tests have been performed on HBS to understand the stress-strain behavior under different hydrate saturations (Yun et al, 2007;Miyazaki et al, 2011;Zhang et al, 2012;Ghiassian and Grozic, 2013;Hyodo et al, 2013;Hyodo et al, 2014;Li et al, 2016). Based on these experimental data, various constitutive models of HBS have been proposed and improved (Pinkert and Grozic, 2014;Lin et al, 2015;Pinkert et al, 2015;Sun et al, 2015;Shen et al, 2016;Uchida et al, 2016).…”

A Model for the Elastic Modulus of Hydrate-Bearing Sediments

“…Many studies have been conducted in the laboratory by triaxial compression tests to obtain the mechanical data of HBS (Masui et al, 2008;Hyodo et al, 2007;Hyodo, 2013;Miyazaki et al, 2010;Miyazaki and Masui, 2011;Waite et al, 2008Waite et al, , 2009Winters, 1999;Winters et al, 2004;Yun et al, 2007;Zhang et al, 2012a;Song et al, 2010). Different methodologies for sampling methane hydrate (dissolved gas method, partial water saturation method, ice-seeding method, hydrate premixing method) resulted in different hydrate occurrence modes in the pores of sediment (Ecker et al, 2000;Winters et al, 2004).…”