Research Papers: Offshore Geotechnics

Experimental Investigation of Pile Installation by Vertical Jet Fluidization in Sand

[+] Author and Article Information
Larissa de Brum Passini

Department of Civil Engineering,
Federal University of Rio Grande do Sul,
Porto Alegre,
Rio Grande do Sul 90035-190, Brazil
e-mail: larissapassini@hotmail.com

Fernando Schnaid

Department of Civil Engineering,
Federal University of Rio Grande do Sul,
Porto Alegre,
Rio Grande do Sul 90035-190, Brazil
e-mail: fschanid@gmail.com

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received December 19, 2014; final manuscript received May 25, 2015; published online June 16, 2015. Assoc. Editor: Solomon Yim.

J. Offshore Mech. Arct. Eng 137(4), 042002 (Aug 01, 2015) (10 pages) Paper No: OMAE-14-1151; doi: 10.1115/1.4030707 History: Received December 19, 2014; Revised May 25, 2015; Online June 16, 2015

The paper examines the mechanism of pile installation by vertical jet fluidization in saturated sand in order to define the constitutive parameters that control installation geometry and pile depth of embedment. A series of laboratory model tests representative of offshore torpedo piles was carried out using downwardly directed vertical water jets in both medium and dense sands. Measurements from model tests at three different scales indicate that the geometry of fluidized cavities is not influenced by the initial density of the sand and that the perturbed zone is constrained to a distance of about two pile diameters from the pile centerline during pile installation. Following the laws of dimensional analysis, an expression for the embedment of fluidized piles is derived and shows that penetration depth is a function of pile weight and geometry, fluidized water jet flow rate and velocity, as well as the soil and fluid properties. Penetration is shown to increase with increasing flow rate and pile weight and decreasing soil relative density. Although the results have to be validated by tests at larger scales to prove compatibility with the full-scale behavior, model tests indicate maximum embedment depth of the order of 50 times the pile diameter.

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Fig. 1

Grain-size distribution

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Fig. 2

Experimental setup

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Fig. 3

Schematic representation of fluidization geometry in (a) suspended tubes STs and (b) free-fall tubes FTs

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Fig. 4

Schematic representations from lateral tests for (a) the installation process during penetration and (b) the enlargement of the fluidized zone (after penetration)

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Fig. 5

Fluidized zone (dh/de) versus pile penetration (L) from lateral tests in FTs and STs at Dr = 50% and 90%

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Fig. 6

Pile fluidization in fine sand: (a) de = 14.0 mm; dj = 9.7 mm; mB = 275 g; Qo = 1.0 × 10−3 m3/min; Dr = 50%, (b) de = 16.2 mm; dj = 11.6 mm; mB = 400 g; Qo = 1.0 × 10−3 m3/min; Dr = 90%, and (c) de = 21.3 mm; dj = 16.2 mm; mB = 960 g; Qo = 1.6 × 10−3 m3/min; Dr = 50%

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Fig. 7

Parameters controlling (a) constant and (b) discontinuous penetration

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Fig. 8

Model test results expressed as (a) tip displacement and versus time and (b) tip velocity versus time

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Fig. 9

Pile load–penetration curves without fluidization: (a) dimension and (b) dimensionless results for Dr = 50% and 90%

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Fig. 10

Pile penetration expressed as a function of (a) flow rate and (b) jet velocity for Dr = 50%

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Fig. 11

Pile penetration plotted against (a) flow rate and (b) jet velocity for Dr = 50% and 90%

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Fig. 12

Dimensionless groups Π1 versus Π2 and Π3

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Fig. 13

Comparison between measured and predicted normalized penetration depth Π1




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