Offshore Pile Testing Campaign Wikinger

Pile driving analysis, static and dynamic load tests in 40m water depth

Jan Fischer, Fichtner Water & Wind GmbH, Hamburg, Germany

Rob van Dorp, Allnamics BV, Den Haag, The Netherlands

Wikinger OWF

Developer Iberdrola Renewables Deutschland GmbH

The Windfarm Turbine: 70 Adwen AD 5-135 (5 MW, Rotor-, 135 m) Project Capacity: 350MW Foundation: Jackets Water depth: 36 m to 42 m

Pile testing campaign Execution: Bilfinger Marine & Offshore Systems GmbH Date: 2014/2015

Installation Company: Boskalis and Volker Stevin Start: spring 2016

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Location

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Pile testing campaign

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General Only very little information exists about the skin friction and toe resistance behavior of typical Baltic Sea soils as glacial till and chalk.

Why Gain soil data information for driveability studies and for bearing capacity calculations

How Extensive offshore pile testing campaign including pile driving analysis (PDA), dynamic load tests (DLT) and pull out static load tests (SLT-T)

Source: ECSMGE 2015, Barbosa et al.

Special Task: Testing underwater, in depths of approx. 40 m

Fichtner / Allnamics

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Drivability predictions / hammer selection

Producing the deep sea operation sensors, cables etc. (for PDA and DLT)

Development of method statements for the different investigation phases

Pile driving analysis / dynamic load tests (at altogether six piles)

Signal matching (using AllWave-DLT)

Back calculation (simulation) of the pile driving using the results from the pile driving protocols and the dynamic load tests

Execution of the static tension pull out test (SLT-T) in terms of correct application of the different load steps

Interpretation of the static tension pull out test

Restrike dynamic load tests including signal matching

Interpretation of the soil setup on the basis of the results from the different phases

etc.

Phase I

Installation of nine piles at three different locations, including pile driving analysis (PDA) and dynamic load testing (DLT)

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Location Water depth

[m MSL]

Diameter

[m]

Pile

length

[m]

Penetration

depth at the end

of driving

[m BSF]

WK-a 40.0 1.37 21.8 16.8

WK-b 38.2 1.37 35.7 30.7

WK-c 36.6 1.37 36.0 31.0 MV Lone: DP2 Vessel by SAL

Test piles:

Phase I - Equipment

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Triplex Template (Pile guiding frame)

Pile Hammer (MENCK MHU 800S)

Phase I - Video

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Instrumentation

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• Two equipped test piles per location (for SLT and DLT)

• Two separate sets per pile

• Each set consisting of two strain transducers and two acceleration transducers

• Each 'pair' (strain and acceleration) placed diametrically opposed on the pile shaft

• Special deep sea sensors and cables

Data recorder (PDR)

Instrumentation

and testing

Phase II: Execution of one static tension pull out test (SLT-T) and one dynamic re-strike test (DLT) per test location. More than ten weeks after pile installation as part of Phase I

Phase II - Equipment

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Reference frame (SLT-T) Displacement measurement

Loading beam (SLT-T) Force application

Hammer (DLT)

Phase II - Video

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page 12

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Locking Tool

Loading Beam and Reference Frame

Phase II – SLT-T

page 13

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Phase II – SLT-T

Phase II – Results

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0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 0.2 0.4 0.6 0.8 1 1.2

norm

aliz

ed d

ispla

cem

ent [-

]

normalized Force [-]

Statische Probebelastung

Load-Displacement

Static tension pull out test (SLT-T)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.2 0.4 0.6 0.8 1.0 1.2

no

rma

lize

d fo

rce

[-]

normalized time [-]

Allnamics strain gauges (mean value)

Load cells (cumulative value)

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 10 20 30 40 50 60

norm

aliz

ed forc

e [-]

time [ms]

DLT restrike

Strain transducer 1Strain transducer 2Acceleration trancducer 1 (v*Z)Accerleration trancducer 2 (v*Z)

Restrike dynamic load test

Summary

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• The entire offshore testing campaign can be considered a huge success, especially since tests of this nature had not been performed before

• During the execution of the work in Phase I and Phase II, all tests could be carried out with high accuracy and high quality data

• The obtained test results led to a detailed understanding of the skin friction and toe resistance values for large diameter offshore pipe piles in typical Baltic Sea soils, i.e. glacial till and chalk

What is next • On the basis of the obtained test results, the installation of the wind turbine

piles was predicted by us

• The results were used e.g. for pile driving fatigue calculations, as an important value for the pile design

Thank you for your attention

Fichtner Water & Wind GmbH

Hammerbrookstrasse 47b D-20097 Hamburg Tel. +49 40 300673 – 0

jan.fischer@fww.fichtner.de www.fww.fichtner.de

Allnamics BV

Waterpas 98 NL-2495 Den Haag

Tel. +31 (0)882556264

vandorp@allnamics.eu www.allnamics.eu

FICHTNER WATER & WIND

FICHTNER WATER & WIND