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25 April 2016 SAFER, SMARTER, GREENER DNV GL © 2016

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25 April 2016 Liv Hamre

INSTALLATION OF MONOPILES

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Analyses models

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25 April 2016

INSTALLATION OF MONOPILES

DNV GL – This is us

Geotechnical Design Basis

Soil resistance to driving

Fatigue from driving

Vibro installation

2

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OFFSHORE WIND - COMBINING DNV GL COMPETENCES

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OUR GEOGRAPHICAL REACH IN RENEWABLES

More than 1,000 renewables staff in 50 locations across 27 countries

4

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FOUNDATIONS

5

Zhou

Jon

PhD students Other sections in marine structures

Erik

Dhruba

Jørn

Knut

Liv

Kristian

Robert

Siamak

Jens

Sébastien

David

Jan

Knut

Erik

Xavi

Michael Wagner Senior Engineer

Michael Hauschildt Sr. Principal Engineer

Per Madsen Senior Engineer

Henning Höffmann Senior Engineer

Jana Gehrmann-Vorbau Senior Engineer

Stefan Baars

Head of Section

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WIND FARM CERTIFICATION

6

According to DNV GL-SE-0073

Project Certificate

Site Conditions Assessement

Design Basis Evaluation

Integrated Load Analysis

Support Structure Design Evaluation

Support Structure Manuf. Surveillance

Commissioning Surveillance

Transportation & Install. Surveillance

Final Evaluation

Project Characteristics Measurements

Project Certificate

Wind Turbine / RNA Manuf. Surveillance

Wind Turbine / RNA Design Evaluation

Other Installations Manuf. Surveillance

Other Installations Design Evaluation

Operations & Maintenance Surveillance

Type Certificate

Design B

asisD

esignInstal-lation

Com

mis-

sioningM

anufac-turing

In-service

DNV GL © 2016

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GEOTECHNICAL DESIGN BASIS

The Geotechnical Design Basis usually consists of:

– Geological Studies

– Bathymetric Investigations

– Geophysical Investigations

– Geotechnical Investigations

2014-09-09

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A cautious estimate of the characteristic strength would be a high value for the driveability calculations

The calculation models should preferably only be used for pile dimensions and soil conditions that they are based on

DNV GL © 2016

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25 April 2016

8

PILE INSTALLATION

Soil Resistance to Driving, SRD, is calculated predict the installation challenges

High soil strength must be considered

Relevant soil models must be applied in the assessment of soil resistance to driving

Fatigue from driving shall be included in the pile fatigue evaluation

Noise assessments and mitigation measures may be required

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25 April 2016

SOIL RESISTANCE TO DRIVING

Relevant published models: 1977 - Toolan & Fox 1981 - Semple & Gemeinhardt 1982 - Stevens et al 2001 - Alm & Hamre

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25 April 2016

SOIL RESISTANCE TO DRIVING

1977 - Toolan & Fox Based on CPT Minimum of plugged and unplugged

resistance Remoulded shear strength

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25 April 2016

SOIL RESISTANCE TO DRIVING

1981 - Semple & Gemeinhardt Based on static pile capacity

calculations including a “pile capacity factor” Suggest that the unit friction at a

given penetration decreases with the length of pile driven past this depth OCR is an important parameter

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DNV GL © 2016

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25 April 2016

SOIL RESISTANCE TO DRIVING

1982 – Stevens et al Based on static soil capacity

applying a pile capacity factor established from back-analyses Using both plugging and coring Include recommendation for

driving in rock

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DNV GL © 2016

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25 April 2016

SOIL RESISTANCE TO DRIVING

2001 – Alm & Hamre Based the friction fatigue concept

recommended by Jardine et al for axial pile capacity assessment Assuming coring pile Based on back-analyses from

several North Sea sites Pile diameters in the database is

30” to 108 “

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DNV GL © 2016

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25 April 2016

FATIGUE FROM DRIVING

According to DNV OS J101,

– DFF = 3 for WTGs and

– DFF = 10 for substations

Normally, the characteristic shear strength is applied

Planned interruptions in the driving operations must be included in the predictions

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DNV GL © 2016

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25 April 2016

VIBRO INSTALLATIONS

Noise from driving can be harmful to the environment and several countries are introducing limitation on noise emission

Vibro-driving is potentially a cost-effective and low-noise alternative to impact driving

Limited available information on prediction of resistance to installation

Research is ongoing with respect to lateral pile capacity for vibro installed monopiles compared to impact driven and drilled piles

Less impact on fatigue than impact driving

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Quad Kong, 12 m diameter pile in China (apevibro.com)

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25 April 2016

SAFER, SMARTER, GREENER

www.dnvgl.com

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Thank you for your attention!