Indentation of a free-falling lance penetrometer into a poroelastic seabed

Derek Elsworth, Dae Sung Lee

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

A solution is developed for the build-up, steady and post-arrest dissipative pore fluid pressure fields that develop around a blunt penetrometer that self-embeds from freefall into the seabed. Arrest from freefall considers deceleration under undrained conditions in a purely cohesive soil, with constant shear strength with depth. The resulting decelerating velocity field is controlled by soil strength, geometric bearing capacity factors, and inertial components. At low impact velocities the embedment process is controlled by soil strength, and at high velocities by inertia. With the deceleration defined, a solution is evaluated for a point normal dislocation penetrating in a poroelastic medium with a prescribed decelerating velocity. Dynamic steady pressures, PD, develop relative to the penetrating tip geometry with their distribution conditioned by the non-dimensional penetration rate, UD, incorporating impacting penetration rate, consolidation coefficient and penetrometer radius, and the non-dimensional strength, ND, additionally incorporating undrained shear strength of the sediment. Pore pressures develop to a steady peak magnitude at the penetrometer tip, and drop as PD = 1/xD With distance xD behind the tip and along the shaft. Peak induced pressure magnitudes may be correlated with sediment permeabilities, post-arrest dissipation rates may be correlated with consolidation coefficients, and depths of penetration may be correlated with shear strengths. Together, these records enable strength and transport parameters to be recovered from lance penetrometer data. Penetrometer data recorded off La Palma in the Canary Islands (J. Volcanol. Geotherm. Res. 2000; 101:253) are used to recover permeabilities and consolidation coefficients from peak pressure and dissipation response, respectively.

Original languageEnglish (US)
Pages (from-to)141-162
Number of pages22
JournalInternational Journal for Numerical and Analytical Methods in Geomechanics
Volume29
Issue number2
DOIs
StatePublished - Feb 1 2005

Fingerprint

penetrometer
indentation
Indentation
Shear strength
Consolidation
shear strength
Deceleration
consolidation
Soils
penetration
soil strength
Sediments
pore pressure
dissipation
permeability
Pore pressure
Bearing capacity
cohesive soil
pressure field
fluid pressure

All Science Journal Classification (ASJC) codes

  • Computational Mechanics
  • Materials Science(all)
  • Geotechnical Engineering and Engineering Geology
  • Mechanics of Materials

Cite this

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abstract = "A solution is developed for the build-up, steady and post-arrest dissipative pore fluid pressure fields that develop around a blunt penetrometer that self-embeds from freefall into the seabed. Arrest from freefall considers deceleration under undrained conditions in a purely cohesive soil, with constant shear strength with depth. The resulting decelerating velocity field is controlled by soil strength, geometric bearing capacity factors, and inertial components. At low impact velocities the embedment process is controlled by soil strength, and at high velocities by inertia. With the deceleration defined, a solution is evaluated for a point normal dislocation penetrating in a poroelastic medium with a prescribed decelerating velocity. Dynamic steady pressures, PD, develop relative to the penetrating tip geometry with their distribution conditioned by the non-dimensional penetration rate, UD, incorporating impacting penetration rate, consolidation coefficient and penetrometer radius, and the non-dimensional strength, ND, additionally incorporating undrained shear strength of the sediment. Pore pressures develop to a steady peak magnitude at the penetrometer tip, and drop as PD = 1/xD With distance xD behind the tip and along the shaft. Peak induced pressure magnitudes may be correlated with sediment permeabilities, post-arrest dissipation rates may be correlated with consolidation coefficients, and depths of penetration may be correlated with shear strengths. Together, these records enable strength and transport parameters to be recovered from lance penetrometer data. Penetrometer data recorded off La Palma in the Canary Islands (J. Volcanol. Geotherm. Res. 2000; 101:253) are used to recover permeabilities and consolidation coefficients from peak pressure and dissipation response, respectively.",
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Indentation of a free-falling lance penetrometer into a poroelastic seabed. / Elsworth, Derek; Lee, Dae Sung.

In: International Journal for Numerical and Analytical Methods in Geomechanics, Vol. 29, No. 2, 01.02.2005, p. 141-162.

Research output: Contribution to journalArticle

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