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  • GSA (Geological Society of America)  (1)
  • PANGAEA  (1)
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  • 1
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    PANGAEA
    In:  Supplement to: Deusner, Christian; Gupta, Shubhangi; Xie, X-G; Leung, Y F; Uchida, S; Kossel, Elke; Haeckel, Matthias (2019): Strain Rate‐Dependent Hardening‐Softening Characteristics of Gas Hydrate‐Bearing Sediments. Geochemistry, Geophysics, Geosystems, 20(11), 4885-4905, https://doi.org/10.1029/2019GC008458
    Publication Date: 2023-01-13
    Description: The overall data set contains experimental data sets (24) and numerical simulation data sets (9) referring to triaxial compression tests on gas hydrate-bearing sediments (see cited publication). The compression tests were carried out in the high-pressure apparatus NESSI (Natural Environment Simulator for Sub-seafloor Interactions) which was equipped with a triaxial cell mounted in a 40 L stainless steel vessel. Sediment samples were prepared from quartz sand (porosity 0.35, grain size 0.1 - 0.6 mm, G20TEAS, Schlingmeier, Schwülper, Germany), and mixed with defined amounts of deionized water. The partially water-saturated and thoroughly homogenized sediments were filled into the triaxial sample cell, which was equipped with a combination of a FKM sleeve and a latex rubber sleeve to obtain final sample dimensions of 160 mm in height and 80 mm in diameter. GH formation was carried out in normally consolidated samples at constant isotropic effective stress of 1 MPa using the excess-gas-method. Strain-controlled drained triaxial compression tests were performed after individual hold periods. The tests were carried out at axial strain rates 0.006, 0.06 and 0.6 %/min, and at constant minor principal stresses of 0.25, 0.5 and 1.0 MPa. Further details on experimental procedures can be found in the publication.
    Keywords: Gas hydrate-bearing sediments; Gas seeps; Geomechanics; High-pressure studies; Slope stability; THCM modelling
    Type: Dataset
    Format: application/zip, 506.5 kBytes
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  • 2
    Publication Date: 2024-02-07
    Description: Groundwater seepage leads to the formation of theater-headed valleys (THVs) in unconsolidated sediments. In bedrock, the role of groundwater in THV development remains disputed. Here, we integrate field and remote-sensing observations from Gnejna Valley (Maltese Islands) with numerical modeling to demonstrate that groundwater seepage can be the main driver of THV formation in jointed limestone overlying clays. The inferred erosion mechanisms entail (1) widening of joints and fractures by fluid pressure and dissolution and (2) creeping of an underlying clay layer, which lead to slope failure at the valley head and its upslope retreat. The latter is slower than the removal of the talus by creep and sliding on the valley bed. The location and width of THVs are controlled by the location of the master fault and the extent of the damage zone, respectively. The variability of seepage across the fault zone determines the shape of the valley head, with an exponential decrease in seepage away from the fault giving rise to a theater-shaped head that best matches that of Gnejna Valley. Our model may explain the formation of THVs by groundwater in jointed, strong-over-weak chemical sedimentary lithologies, particularly in arid terrestrial settings.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
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