A constitutive mechanical model for gas hydrate bearing sediments incorporating inelastic mechanisms

Sánchez, Marcelo; Gai, Xuerui; Santamarina, J. Carlos

doi:10.1016/j.compgeo.2016.11.012

Cited by 101 publications

(49 citation statements)

References 52 publications

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“…The set of critical state parameters characterizing the behavior of pure Toyoura sand (ie, hydrate‐free sediment) (Table ) has been calibrated here using the stress‐strain curve and the volumetric response of the host specimen used for the synthetic formation of cementing hydrate ( S h = 0% in Figure C). For the calibration process, values adopted in previous publications that also model the mechanical response of Toyoura sand have been used as a reference . In addition, the different void ratios of 0.6 and 0.75 reported for the cementing and pore‐filling specimens, respectively, have also been considered in the simulations (Table ).…”

Section: Hydrate‐casm Performancementioning

confidence: 99%

“…Previous mechanical models for MHBS that also modeled Masui's et al experimental data assume that the differences in strength and dilatancy observed between cementing and pore‐filling specimens for a given hydrate saturation are controlled by hydrate morphology. However, Masui et al state that if the pore hydrate saturation is the same in both types of specimens (eg, S h ≈ 40% in Figures C and D), shear strength becomes higher for the specimen with lower void ratio.…”

Section: Hydrate‐casm Performancementioning

confidence: 99%

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

Fuente

Vaunat

Marín‐Moreno

2020

Num Anal Meth Geomechanics

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SUMMARY 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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Section: Hydrate‐casm Performancementioning

confidence: 99%

Section: Hydrate‐casm Performancementioning

confidence: 99%

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

Fuente

Vaunat

Marín‐Moreno

2020

Num Anal Meth Geomechanics

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“…Experimental studies have evaluated effects of varying S h (e.g., Masui et al, ; Santamarina & Ruppel, ), temperatures (Jia et al, ; Song et al, ), pore pressures ( u , Jiang, Zhu, et al, ), and effective stresses ( σ 3 ′, Lee, Francisca, et al, ; Miyazaki, Tenma, et al, ) to identify relevant parameters and initial conditions in the geotechnical analysis of GHBS. In particular with the perspective on sand production issues during natural gas production and potential slope failure of fine‐grained sediments, the effects of fines content (Hyodo et al, ; Jung et al, ; Kajiyama, Hyodo, et al, ; Lee, Santamarina, et al, ; Yun et al, ), lithology and consolidation history (Fujii et al, ; Ito et al, ; Santamarina et al, ; Suzuki et al, ; Yoneda et al, ), and thermo‐hydro‐chemo‐mechanical process coupling (Gupta et al, ; Klar et al, ; Sánchez et al, ; Uchida et al, ) have received attention.…”

Section: Introductionmentioning

confidence: 99%

Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments

Deusner

Gupta

Xie

et al. 2019

Geochem Geophys Geosyst

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The presence of gas hydrates (GHs) increases the stiffness and strength of marine sediments. In elasto‐plastic constitutive models, it is common to consider GH saturation (Sh) as key internal variable for defining the contribution of GHs to composite soil mechanical behavior. However, the stress‐strain behavior of GH‐bearing sediments (GHBS) also depends on the microscale distribution of GH and on GH‐sediment fabrics. A thorough analysis of GHBS is difficult, because there is no unique relation between Sh and GH morphology. To improve the understanding of stress‐strain behavior of GHBS in terms of established soil models, this study summarizes results from triaxial compression tests with different Sh, pore fluids, effective confining stresses, and strain histories. Our data indicate that the mechanical behavior of GHBS strongly depends on Sh and GH morphology, and also on the strain‐induced alteration of GH‐sediment fabrics. Hardening‐softening characteristics of GHBS are strain rate‐dependent, which suggests that GH‐sediment fabrics dynamically rearrange during plastic yielding events. We hypothesize that rearrangement of GH‐sediment fabrics, through viscous deformation or transient dissociation and reformation of GHs, results in kinematic hardening, suppressed softening, and secondary strength recovery, which could potentially mitigate or counteract large‐strain failure events. For constitutive modeling approaches, we suggest that strain rate‐dependent micromechanical effects from alterations of the GH‐sediment fabrics can be lumped into a nonconstant residual friction parameter. We propose simple empirical evolution functions for the mechanical properties and calibrate the model parameters against the experimental data.

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“…In addition, some constitutive models have been proposed to predict the stress‐strain relationship of methane hydrate‐bearing sediments in the recent decade (Lin et al, ; Pinkert et al, ; Sánchez et al, ; Shen et al, ; Uchida et al, ). The simulated strengths of the pore‐filling and cementing types of hydrate‐bearing sediments classified by Dai et al () and Waite et al () were obtained using different values of fitting parameters to interpret the influence of hydrate morphology on the mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Influence of Fines Content on the Mechanical Behavior of Methane Hydrate‐Bearing Sediments

et al. 2017

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Methane hydrate‐bearing sediments with different amounts of fines content and at three densities were artificially prepared under controlled temperature and pressure conditions. The void ratios of specimens after isotropic consolidation tend to decrease with a rise in fines content. The fines particles enter into the pore space between sand grains and densify the specimens. A series of triaxial compression tests were performed to systematically investigate the influences of fines content and density on the shear properties of hydrate‐free sediments and methane hydrate‐bearing sediments. The test results demonstrate that a rise in fines content within methane hydrate‐bearing sediments significantly enhances peak shear strength and promotes dilation behavior. These influences are particularly prominent for specimens at loose packing state. A decrease in void ratio increases the shear strength and stiffness of hydrate‐free sediments and methane hydrate‐bearing sediments containing fines content of 0% and 8.9%. It is noted that the formation of methane hydrate in samples with varying amounts of fines content increases the stress ratios at the critical state. The addition of fines particles into coarse‐grained sand grains alters the internal microstructure of sand matrix and the hydrate formation pattern in the pore space between sand grains and fines particles.

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A constitutive mechanical model for gas hydrate bearing sediments incorporating inelastic mechanisms

Cited by 101 publications

References 52 publications

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

Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments

Influence of Fines Content on the Mechanical Behavior of Methane Hydrate‐Bearing Sediments

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