A new instrument for high-resolution in situ assessment of Young’s modulus in shallow cohesive sediments

Barry, Mark A.; Johnson, Bruce D.; Boudreau, Bernard P.

doi:10.1007/s00367-012-0277-z

Cited by 18 publications

(11 citation statements)

References 20 publications

(23 reference statements)

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“…Another important control on the development of a gassy layer is related to sediment elastic properties. In situ profiling of tensile fracture toughness and measurements of Young's modulus in cohesive sediments has shown relatively smaller values in the surface layers than at increasing depth and could be related to compactness and grain size distribution [ Barry et al ., ; Johnson et al ., ]. With our homogenized sediment columns, the presence of the gassy layer could not be due to grain size stratification but was related to the development of bulk density stratification, i.e., sediment compaction and the gas‐charging process in the upper sediment layers.…”

Section: Discussionmentioning

confidence: 97%

The role of sediment structure in gas bubble storage and release

et al. 2016

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Ebullition is an important pathway for methane emission from inland waters. However, the mechanisms controlling methane bubble formation and release in aquatic sediments remain unclear. A laboratory incubation experiment was conducted to investigate the dynamics of methane bubble formation, storage, and release in response to hydrostatic head drops in three different types of natural sediment. Homogenized clayey, silty, and sandy sediments (initially quasi‐uniform through the depth of the columns) were incubated in chambers for 3 weeks. We observed three distinct stages of methane bubble formation and release: stage I—microbubble formation‐displacing mobile water from sediment pores with negligible ebullition; stage II—formation of large bubbles, displacing the surrounding sediment with concurrent increase in ebullition; and stage III—formation of conduits with relatively steady ebullition. The maximum depth‐averaged volumetric gas content at steady state varied from 18.8% in clayey to 12.0% in silty and 13.2% in sandy sediment. Gas storage in the sediment columns showed strong vertical stratification: most of the free gas was stored in an upper layer, whose thickness varied with sediment grain size. The magnitude of individual ebullition episodes was linearly correlated to hydrostatic head drop and decreased from clayey to sandy to silty sediment and was in excess of that estimated from gas expansion alone, indicating the release of pore water methane. These findings combined with a hydrodynamic model capable of determining dominant sediment type and depositional zones could help resolve spatial heterogeneities in methane ebullition at medium to larger scales in inland waters.

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Section: Discussionmentioning

confidence: 97%

The role of sediment structure in gas bubble storage and release

et al. 2016

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“…In natural muds, fracture toughness and stiffness are low in the top approximately 2-3 cm of sediments [24,25], corresponding to the depth distribution of A. brevis [16]. At the surface, fracture toughness approaches zero, indicating that surface muds are non-cohesive, high-porosity aggregates and that linear elastic fracture occurs only below the surface layer.…”

Section: Results and Discussion (A) Armandia Brevis Does Not Extend Bmentioning

confidence: 99%

“…Based on LEFM, lateral fracture resistance is only barely sufficient for A. brevis to overcome anterior resistance, but dorsoventral plastic deformation of sediments could increase resistance to lateral slipping (figure 2c). In natural muds, fracture toughness and stiffness are low in the top approximately 2-3 cm of sediments [24,25], corresponding to the depth distribution of A. brevis [16]. At the surface, fracture toughness approaches zero, indicating that surface muds are non-cohesive, high-porosity aggregates and that linear elastic fracture occurs only below the surface layer.…”

Section: (B) Non-cohesive Granular Media Exhibits Solid Response To Undulatory Burrowingmentioning

confidence: 99%

Meandering worms: mechanics of undulatory burrowing in muds

2013

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Recent work has shown that muddy sediments are elastic solids through which animals extend burrows by fracture, whereas non-cohesive granular sands fluidize around some burrowers. These different mechanical responses are reflected in the morphologies and behaviours of their respective inhabitants. However, Armandia brevis, a mud-burrowing opheliid polychaete, lacks an expansible anterior consistent with fracturing mud, and instead uses undulatory movements similar to those of sandfish lizards that fluidize desert sands. Here, we show that A. brevis neither fractures nor fluidizes sediments, but instead uses a third mechanism, plastically rearranging sediment grains to create a burrow. The curvature of the undulating body fits meander geometry used to describe rivers, and changes in curvature driven by muscle contraction are similar for swimming and burrowing worms, indicating that the same gait is used in both sediments and water. Large calculated friction forces for undulatory burrowers suggest that sediment mechanics affect undulatory and peristaltic burrowers differently; undulatory burrowing may be more effective for small worms that live in sediments not compacted or cohesive enough to extend burrows by fracture.

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“…In situ measurements of E for soft, cohesive, coastal sediments are reported in Barry et al (2012a). As an example, if one inserts the parameter values in Boudreau et al (2005), the predicted b/ a (inverse aspect ratio) is of the order of 0.03, which is a very thin, eccentric bubble indeed.…”

mentioning

confidence: 97%