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A densification mechanism to model the mechanical effect of methane hydrates in sandy sediments

A densification mechanism to model the mechanical effect of methane hydrates in sandy sediments
A densification mechanism to model the mechanical effect of methane hydrates in sandy sediments
Recent pore‐scale observations and geomechanical investigations suggest the lack of true cohesion in methane hydrate‐bearing sediments (MHBSs) and propose that their mechanical behavior is governed by kinematic constrictions at pore‐scale. This paper presents a constitutive model for MHBS, which does not rely on physical bonding between hydrate crystals and sediment grains but on the densification effect that pore invasion with hydrate has on the sediment mechanical properties. The Hydrate‐CASM extends the critical state model Clay and Sand Model (CASM) by implementing the subloading surface model and introducing the densification mechanism. The model suggests that the decrease of the sediment available void volume during hydrate formation stiffens its structure and has a similar mechanical effect as the increase of sediment density. In particular, the model attributes stress‐strain changes observed in MHBS to the variations in sediment available void volume with hydrate saturation and its consequent effect on isotropic yield stress and swelling line slope. The model performance is examined against published experimental data from drained triaxial tests performed at different confining stress and with distinct hydrate saturation and morphology. Overall, the simulations capture the influence of hydrate saturation in both the magnitude and trend of the stiffness, shear strength, and volumetric response of synthetic MHBS. The results are validated against those obtained from previous mechanical models for MHBS that examine the same experimental data. The Hydrate‐CASM performs similarly to previous models, but its formulation only requires one hydrate‐related empirical parameter to express changes in the sediment elastic stiffness with hydrate saturation.
Hydrate-CASM, constitutive modeling, densification mechanism, mechanical behavior, methane hydrate-bearing sediments
0363-9061
1-21
De La Fuente, Maria
327351b7-cd3e-4e19-85a4-1b92a60c1971
Vaunat, Jean
c8939ecb-3c86-4cf1-9286-cd97acdee002
Marín‐moreno, Héctor
f8b611ad-3be4-44da-989a-274e2dd2ca66
De La Fuente, Maria
327351b7-cd3e-4e19-85a4-1b92a60c1971
Vaunat, Jean
c8939ecb-3c86-4cf1-9286-cd97acdee002
Marín‐moreno, Héctor
f8b611ad-3be4-44da-989a-274e2dd2ca66

De La Fuente, Maria, Vaunat, Jean and Marín‐moreno, Héctor (2020) A densification mechanism to model the mechanical effect of methane hydrates in sandy sediments. International Journal for Numerical and Analytical Methods in Geomechanics, 44 (6), 1-21. (doi:10.1002/nag.3038).

Record type: Article

Abstract

Recent pore‐scale observations and geomechanical investigations suggest the lack of true cohesion in methane hydrate‐bearing sediments (MHBSs) and propose that their mechanical behavior is governed by kinematic constrictions at pore‐scale. This paper presents a constitutive model for MHBS, which does not rely on physical bonding between hydrate crystals and sediment grains but on the densification effect that pore invasion with hydrate has on the sediment mechanical properties. The Hydrate‐CASM extends the critical state model Clay and Sand Model (CASM) by implementing the subloading surface model and introducing the densification mechanism. The model suggests that the decrease of the sediment available void volume during hydrate formation stiffens its structure and has a similar mechanical effect as the increase of sediment density. In particular, the model attributes stress‐strain changes observed in MHBS to the variations in sediment available void volume with hydrate saturation and its consequent effect on isotropic yield stress and swelling line slope. The model performance is examined against published experimental data from drained triaxial tests performed at different confining stress and with distinct hydrate saturation and morphology. Overall, the simulations capture the influence of hydrate saturation in both the magnitude and trend of the stiffness, shear strength, and volumetric response of synthetic MHBS. The results are validated against those obtained from previous mechanical models for MHBS that examine the same experimental data. The Hydrate‐CASM performs similarly to previous models, but its formulation only requires one hydrate‐related empirical parameter to express changes in the sediment elastic stiffness with hydrate saturation.

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More information

Accepted/In Press date: 3 December 2019
e-pub ahead of print date: 9 January 2020
Keywords: Hydrate-CASM, constitutive modeling, densification mechanism, mechanical behavior, methane hydrate-bearing sediments

Identifiers

Local EPrints ID: 439512
URI: http://eprints.soton.ac.uk/id/eprint/439512
ISSN: 0363-9061
PURE UUID: 0302e206-9da1-4140-81f2-3f9a1b1e35ce

Catalogue record

Date deposited: 24 Apr 2020 16:44
Last modified: 25 Mar 2021 18:20

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Contributors

Author: Maria De La Fuente
Author: Jean Vaunat
Author: Héctor Marín‐moreno

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