Offshore Pile Testing Campaign Wikinger

(1)

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

(2)

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

Slide 2 Offshore Pile Testing Campaign Wikinger l Jan Fischer & Rob van Dorp l Geotechniekdag 2015

(3)

Location

(4)

Pile testing campaign

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

(5)

Fichtner / Allnamics

 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.

(6)

Phase I

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

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:

(7)

Phase I - Equipment

Triplex Template (Pile guiding frame)

Pile Hammer

(MENCK MHU 800S)

(8)

Phase I - Video

(9)

Instrumentation

• 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

(10)

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

Reference frame (SLT-T) Displacement measurement

Loading beam (SLT-T) Force application

Hammer (DLT)

(11)

Phase II - Video

(12)

page 12

Locking Tool Loading Beam and Reference Frame

Phase II – SLT-T

(13)

page 13

Phase II – SLT-T

(14)

Phase II – Results

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

normalized displacement [-]

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

normalized force [-]

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

normalized force [-]

time [ms]

DLT restrike

Strain transducer 1 Strain transducer 2

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

Restrike dynamic load test

(15)

Summary

• 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

(16)

Thank you for your attention

Fichtner Water & Wind GmbH Hammerbrookstrasse 47b D-20097 Hamburg

Tel. +49 40 300673 – 0

[email protected] www.fww.fichtner.de

Allnamics BV Waterpas 98 NL-2495 Den Haag Tel. +31 (0)882556264 [email protected] www.allnamics.eu

FICHTNER

WATER & WIND

FICHTNER

WATER & WIND