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  • Acoustical Society of America (ASA)  (3)
  • 1
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2021
    In:  The Journal of the Acoustical Society of America Vol. 150, No. 4_Supplement ( 2021-10-01), p. A350-A350
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 150, No. 4_Supplement ( 2021-10-01), p. A350-A350
    Abstract: Nearshore and estuarine sediments experience varying sediment inputs that create sharp gradients in sediment properties over fairly small vertical and horizontal distances. In this study, we explored the sand-mud transition in sediment cores collected from Mobile Bay, AL, with acoustic and geotechnical approaches. A custom built instrument was used to measure depth profiles of tensile strength at cm-scale resolution. These measurements were compared to acoustic sound speed and attenuation across a range of frequencies. Cores collected exhibited a horizontal gradient from sand to mud across the study area with a sandy layer on top of muddier sediment in most cores. This study explicitly examines the relationship between acoustic sound speed and attenuation and strength-related properties of sediments such as cohesion that can be measured in situ more easily than textural properties (e.g., porosity and grain size). We compare our data to in situ normal incidence measurements and portable free fall penetrometer data as well as infaunal community composition to better relate acoustic, geotechnical, and biological properties across a gradient of sediments.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2021
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2021
    In:  The Journal of the Acoustical Society of America Vol. 150, No. 4_Supplement ( 2021-10-01), p. A350-A351
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 150, No. 4_Supplement ( 2021-10-01), p. A350-A351
    Abstract: Seabed variability introduced by physical or biogenic processes contributes to multi-scale horizontal and vertical variability in seabed acoustic and geotechnical properties. An experiment was conducted near the mouth of Mobile Bay to investigate such spatial variability over a mud-sand gradient. A normal-incidence bottom loss survey was conducted on a 750 × 1500 m2 grid with 50-m track-line spacing, in which a broadband acoustic source transmitted frequency-modulated chirps (1–100 kHz) every second, resulting in dense sampling of the seabed reflection coefficient over a wide frequency band. Diver cores were collected in the survey area for direct analysis of near-surface seabed properties. Cores were acoustically logged to obtain vertical profiles of sound speed and attenuation (10–1000 kHz) and then analyzed for physical properties (porosity, grain size, carbon content), infauna community composition, and sediment strength properties. Additionally, in situ portable free fall penetrometer measurements were conducted within the survey area to characterize geotechnical properties within the upper 50 cm of the sediment. Spatial distributions of properties estimated from bottom loss measurements (e.g. porosity and sound speed) will be compared with vertical profiles from the cores and from the penetrometer to examine potential connections between seabed acoustic, geotechnical, and biological parameters. [Sponsored by ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2021
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2022
    In:  The Journal of the Acoustical Society of America Vol. 151, No. 4_Supplement ( 2022-04-01), p. A150-A150
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 151, No. 4_Supplement ( 2022-04-01), p. A150-A150
    Abstract: The process of fine-grained seabed sediment consolidation is governed by a variety of factors including grain size distributions, organics, sediment dynamics, and anthropogenic activities (e.g., marine traffic and dredging). Poorly consolidated sediments are typically softer and more susceptible to mobility from shear, while over consolidated sediments are typically stiffer with a higher threshold for mobility from shear. Knowledge of the state of consolidation of seabed sediments is important to assess and maintain navigable depth, predict length scales of seafloor roughness, and assess seabed-object interaction (e.g., anchors, unexploded ordnance). For example, the porosity varies significantly for the same type of sediment for different states of consolidation. Variability is expected and has been qualitatively demonstrated in acoustic seabed surveying including high- and low-frequency techniques. In this study, seabed sediments were characterized using a portable free fall penetrometer along with geotechnical and sedimentological laboratory testing of fine-grained seabed sediments. Testing results quantified both sediment textural (e.g., bulk density, water content, void ratio, and porosity) and strength properties (e.g., undrained shear strength and consolidation state and behavior) and were related to the backscatter intensity observed with different high- and low-frequency off-the-shelf acoustic surveying devices.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2022
    detail.hit.zdb_id: 1461063-2
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
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