Submarine slope failures due to pipe structure formation

Elger, Judith; Berndt, Christian; Rüpke, Lars; Krastel, Sebastian; Groß, Felix; Geissler, Wolfram

doi:10.1038/s41467-018-03176-1

Cited by 91 publications

(53 citation statements)

References 46 publications

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“…Moreover, hydrates can trigger large‐scale underwater landslides due to climate change (Paull et al, ; Elger et al, ), while hydrate dissociation in the course of gas production by human activity may not significantly affect slope stability (Moridis et al, ; Rutqvist et al, ; Rutqvist & Moridis, ). Additionally, the release of gas bubbles is hypothesized to be responsible for the sinking of ships (Deming, ).…”

Section: Introductionmentioning

confidence: 99%

In Situ Mechanical Properties of Shallow Gas Hydrate Deposits in the Deep Seabed

Yoneda

Kida

Konno

et al. 2019

Geophysical Research Letters

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Natural gas hydrates (or methane hydrates) could become a major energy source but could also exacerbate global warming, because as the climate warms, hydrate deposits deep under the oceans or in permafrost may release methane into the atmosphere. There are many shallow deposits of gas hydrates in fine-grained muddy sediments on the seafloor. However, the mechanical properties of these sediments have not yet been investigated because of the engineering challenges in coring and testing at in situ temperatures and pressures. Here we present the first uniaxial and triaxial strength and stiffness measurements of pure massive natural gas hydrates and muddy sediments containing hydrate nodules obtained by pressure coring. As a result, we were able to observe the hydrate undergoing a catastrophic brittle failure. Its strength and deformation moduli were 3 and 300 MPa, respectively. Muddy sediments containing hydrate nodules had the same strength as that of hydrate-free sediments.

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Section: Introductionmentioning

confidence: 99%

In Situ Mechanical Properties of Shallow Gas Hydrate Deposits in the Deep Seabed

Yoneda

Kida

Konno

et al. 2019

Geophysical Research Letters

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“…For this reason, it is crucial to know the pathways where methane-rich fluids could migrate. The release of this methane stored in the forearc wedge could have consequences for the ocean and atmosphere systems, and the destabilized gas hydrate-bearing sediments are a formidable geohazard, in the form of submarine slumps, induced earthquakes, and tsunamis (e.g., [2,6,[50][51][52][53][54]).…”

Section: Introductionmentioning

confidence: 99%

Gas Hydrate Estimate in an Area of Deformation and High Heat Flow at the Chile Triple Junction

et al. 2019

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Large amounts of gas hydrate are present in marine sediments offshore Taitao Peninsula, near the Chile Triple Junction. Here, marine sediments on the forearc contain carbon that is converted to methane in a regime of very high heat flow and intense rock deformation above the downgoing oceanic spreading ridge separating the Nazca and Antarctic plates. This regime enables vigorous fluid migration. Here, we present an analysis of the spatial distribution, concentration, estimate of gas-phases (gas hydrate and free gas) and geothermal gradients in the accretionary prism, and forearc sediments offshore Taitao (45.5°–47° S). Velocity analysis of Seismic Profile RC2901-751 indicates gas hydrate concentration values <10% of the total rock volume and extremely high geothermal gradients (<190 °C·km−1). Gas hydrates are located in shallow sediments (90–280 m below the seafloor). The large amount of hydrate and free gas estimated (7.21 × 1011 m3 and 4.1 × 1010 m3; respectively), the high seismicity, the mechanically unstable nature of the sediments, and the anomalous conditions of the geothermal gradient set the stage for potentially massive releases of methane to the ocean, mainly through hydrate dissociation and/or migration directly to the seabed through faults. We conclude that the Chile Triple Junction is an important methane seepage area and should be the focus of novel geological, oceanographic, and ecological research.

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“…The presence of GH changes the mechanical properties of these sediments or soils, with increased GH saturations (S h ) often being related to higher shear strength, increased stiffness, and stronger dilatancy (e.g., Waite et al, 2009;Yun et al, 2007). The mechanical and hydraulic properties of GH-bearing sediments (GHBS) are considered to influence the stability of marine sediments and slopes (Bugge et al, 1988;Elger et al, 2018;Kvalstad et al, 2005;Mountjoy et al, 2014), and they are crucial factors for drilling operations (McConnell et al, 2012) and natural gas production scenarios (Boswell et al, 2017;Collett, 2002;Konno et al, 2017;Schoderbek et al, 2012;Yamamoto et al, 2014). Thus, considerable effort is invested in geotechnical testing of GHBS to better understand geomechanical properties and stress-strain behavior in slope failure events or GH production scenarios.…”

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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Submarine slope failures due to pipe structure formation

Cited by 91 publications

References 46 publications

In Situ Mechanical Properties of Shallow Gas Hydrate Deposits in the Deep Seabed

In Situ Mechanical Properties of Shallow Gas Hydrate Deposits in the Deep Seabed

Gas Hydrate Estimate in an Area of Deformation and High Heat Flow at the Chile Triple Junction

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

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