Mechanisms for subcritical penetration into a sandy bottom: Experimental and modeling results

Maguer, Alain; Fox, Warren L. J.; Schmidt, Henrik; Pouliquen, E.; Bovio, Edoardo

doi:10.1121/1.428411

Cited by 76 publications

(55 citation statements)

References 12 publications

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“…However, other measured parameters, e.g., slow wave impedance and speed, slow wave effective This experiment supports the conclusions that subcritical penetration in sandy sediment is from scattering and not from the Biot slow waves [17,26,34]. This is true for two reasons.…”

Section: Discussionsupporting

confidence: 63%

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Experimental Study of Sound Waves in Sandy Sediment

Yargus¹

2003

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and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examining committee have been made. This dissertation describes experiments intended to help understand the physics of sound (compressional waves) propagating through sandy sediments (unconsolidated porous media). The theory (using a lumped parameter model) and measurements (using a reflection ratio technique) includes derivations and measurements of acoustic impedances, effective densities, wave speeds (phase velocities), effective pressures, mode shapes, pressure reflection coefficients, and material moduli. The results show the acoustic impedance divided by the phase velocity, rendering an "effective density," is less than the total density of the sediment (effective density = 89% + 3% of total). The results also show the fluid in the sediment oscillates back-and-forth 2.2 + 0.4 times farther than the sand in the sediment (mode shape) during the passing of a sound wave.These facts suggest the existence of Biot waves (two compressional waves) in watersaturated sand.

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Section: Discussionsupporting

confidence: 63%

“…Recent field measurements [17,26,34] have strongly supported the conclusion that subcritical penetration in sands is due to scattering, not Biot slow waves.…”

mentioning

confidence: 87%

Experimental Study of Sound Waves in Sandy Sediment

Yargus¹

2003

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“…Maguer et al (2000) present promising sub-bottom detection feasibility even beyond the critical angle in sand using a parametric system. The present study site is characterized by mud having slower sound velocity than the seawater (Richardson and Briggs 1996;Schneider von Deimling et al 2013).…”

Section: Ideal Incidence For Cable Detectionmentioning

confidence: 99%

“…Szender and Kosalos (1997) and Leighton and Evans (2008) presented bistatic (spatially separated acoustic source and receiver) approaches to track underwater cables. Maguer et al (2000) showed experimentally that incidence between of 15°and 30°can be useful for subbottom investigations. Especially for naval mine hunting, sophisticated techniques were developed for enhanced detection of buried targets by towed low-frequency arrays (Jans et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Effects of using inclined parametric echosounding on sub-bottom acoustic imaging and advances in buried object detection

et al. 2015

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This study reports an adaptation of a parametric echosounder system using 15 kHz as secondary frequency to investigate the angular response of sub-bottom backscatter strength of layered mud, providing a new method for enhanced acoustic detection of buried targets. Adaptions to achieve both vertical (0°) and non-vertical inclination (1-15°, 30°, 45°and 60°) comprise mechanical tilting of the acoustic transducer and electronic beam steering. Data were acquired at 18 m water depth at a study site characterized by a flat, muddy seafloor where a 0.1 m diameter power cable lies 1-2 m below the seafloor. Surveying the cable with vertical incidence revealed that the buried cable can hardly be discriminated against the backscatter strength of the layered mud. However, the backscatter strength of layered mud decreases strongly at >3±0.5°incidence and the layered mud echo pattern vanishes beyond 5°. As a consequence, the backscatter pattern of the buried cable is very pronounced in acoustic images gathered at 15°, 30°, 45°and 60°incidence. The size of the cable echo pattern increases linearly with incidence. These effects are attributed to reflection loss from layered mud at larger incidence and to the scattering of the 0.1 m diameter buried cable. Data analyses support the visual impression of superior detection of the cable with an up to 2.6-fold increase of the signal-to-noise ratio at 40°incidence compared to the vertical incidence case.

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“…Second, seafloor roughness diffracts energy into the sediment (Thorsos et al, 1997). Third, sediment volume heterogeneity scatters the evanescent wave energy that propagates along the seafloor interface into the sediment (Maguer et al, 2000). In order to compare the predictions of…”

Section: Approachmentioning

confidence: 99%

High-Frequency Sound Interaction in Ocean Sediments: Modeling Environmental Controls

Richardson¹,

Briggs²,

Lavoie³

et al. 2001

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Award Number: N00014 01WX40009 LONG-TERM GOALSOur long term goal is to develop accurate models for high-frequency acoustic penetration into, propagation within, and scattering from shallow water ocean sediments. This work should specifically improve the Navy's ability to detect buried mines and, in general, improve sonar performance in shallow water. Additional objectives of the NRL program are to understand and model the complex interactions among environmental processes, sediment structure, properties, and behavior. These models allow portability of high-frequency bottom interaction models to sites of naval interest. OBJECTIVESProvide statistical characterization of the environmental properties, especially the roughness and sediment volume properties, required to determine and model the dominant mechanisms controlling the penetration of high-frequency acoustic energy into the seafloor. Determine the effects of biological, geological, biogeochemical, and hydrodynamic processes on the spatial and temporal distribution of sediment physical, geotechnical and geoacoustic properties at the experimental site. Develop predictive empirical and physical models of the relationships among those properties. APPROACHThe "High-Frequency Sound Interaction in Ocean Sediments" DRI addresses high-frequency acoustic penetration into, propagation within, and scattering from the shallow-water seafloor. The primary goal of the proposed study is to understand the mechanisms for high-frequency acoustic energy penetration into sediments at low grazing angles. At present, three mechanisms are hypothesized to contribute to subcritical acoustic penetration. First, the porous nature of the sediment leads to a "slow" wave with a speed less than the speed of sound in water; thus no critical angle for that converted wave exists (Chotiros, 1995). Second, seafloor roughness diffracts energy into the sediment (Thorsos et al., 1997). Third, sediment volume heterogeneity scatters the evanescent wave energy that propagates along the seafloor interface into the sediment (Maguer et al., 2000). In order to compare the predictions of 1

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Mechanisms for subcritical penetration into a sandy bottom: Experimental and modeling results

Cited by 76 publications

References 12 publications

Experimental Study of Sound Waves in Sandy Sediment

Experimental Study of Sound Waves in Sandy Sediment

Effects of using inclined parametric echosounding on sub-bottom acoustic imaging and advances in buried object detection

High-Frequency Sound Interaction in Ocean Sediments: Modeling Environmental Controls

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