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Characterization of the geotechnical properties of a carbonate clayey silt till for a
shallow wind turbine foundation
Caractérisation des propriétés géotechniques d'un silt argileux carbonaté glaciaires pour une
fondation su
perficielle d’éolienne
Tyldesley M., Newson T.
Geotechnical Research Centre, Department of Civil Engineering, University of Western Ontario, Ontario, Canada.
Boone S.
Golder Associates Ltd., London, Ontario, Canada.
Carriveau R.
Entelligence Research Group, Department of Civil Engineering, University of Windsor, Ontario, Canada.
ABSTRACT: Wind energy is a major source of renewable energy and is projected to capture 11% of the energy generation capacity
for Ontario by 2018. A number of problems that the energy industry currently faces stem from a lack of understanding of cyclic
loading of Ontario soils and a paucity of regional regulatory guidance for site investigation and design methods for wind turbine
foundations. A multi-disciplinary research project is underway to integrate laboratory testing, field monitoring and numerical
modeling of a commercial wind turbine on a shallow foundation. This paper describes an initial part of the study to characterize the
geotechnical properties of the clayey silt till soils on the site. Emphasis has been placed on comparison of different
in situ
and
laboratory methods, and correlations for determining key geotechnical parameters for wind turbine foundation design.
RÉSUMÉ : L'énergie éolienne est une source importante d'énergie renouvelable et doit permettre de satisfaire 11 % de la capacité de
production d'énergie de l'Ontario d'ici 2018. Un certain nombre de problèmes auxquels l'industrie de l'énergie est actuellement
confrontée provient d'un manque de
connaissances des sols de l’Ontario sous
charges cycliques et de directives réglementaires
régionales pour les méthodes d'investigation et de conception des fondations
d’éoliennes
. Un projet de recherche multidisciplinaire est
en cours pour intégrer les tests en laboratoire,
l’instrumentation
et la modélisation numérique d'une éolienne commerciale sur
fondation superficielle. Cet article décrit la partie initiale de l'étude pour caractériser les propriétés géotechniques du silt argileux
glaciaire du site. L'accent a été mis sur la comparaison de différentes méthodes
in situ
et en laboratoire ainsi que les corrélations pour
déterminer les paramètres géotechniques clés pour la conception de fondation d
’éoliennes
.
KEYWORDS: wind turbine, clay, till, shallow foundation, soil-structure interaction, elastic, anisotropy,
in situ
, geophysical.
1 INTRODUCTION
1.1 Wind energy and turbine design in Canada
Wind is a major source of renewable energy and is projected to
capture 11% of the energy generation capacity for Ontario by
2018 (CANWEA, 2011). However, to achieve this expansion
some major technical and policy issues must be addressed by
the Canadian wind sector. Some of these issues are associated
with the construction and design of foundations for wind
turbines. Foundations for onshore wind turbines usually consist
of large gravity bases and monopiles (e.g. DNV/Risø, 2002).
The geometry and foundation type depends on the wind climate,
power regulation philosophy, physical characteristics of the
machine, uplift criteria, required foundation stiffness and
geotechnical characteristics of the site (Bonnett, 2005). The
critical analyses for design include bearing capacity and
overturning resistance, horizontal and rotational displacements,
and dynamic soil-structure interaction (Harte et al., 2012).
Although there has been much recent research associated
with foundations for offshore wind turbines (e.g. Byrne and
Houlsby, 2003), the literature on onshore systems is still
relatively sparse. Consequently, despite similar issues for wind
turbine foundations across the industry, there is often diverse
interpretation of design codes and understanding of the behavior
of foundations (Morgan and Ntambakwa, 2008). This can lead
to quite different foundation designs on different wind farms
with the same turbines and comparable geotechnical profiles.
This issue is exacerbated in Canada, since there is currently no
regional regulatory guidance for site investigation and design
methods for wind turbine foundations. Hence it is not surprising
that rather generic approaches have developed for site
investigation and design, which are relatively crude and can
lead to quite conservative designs. To capture more wind
energy, the industry is continuing to develop larger turbines and
is considering more marginal sites in terms of geotechnical
characteristics, which will only complicate the current situation.
1.2 Project overview and objectives
A number of the above issues are being addressed as part of a
multi-disciplinary research project that includes an integrated
laboratory testing, field monitoring and numerical modeling
program investigating the behaviour of a fully operational
Canadian commercial wind turbine throughout its service life.
The equipment installed on the turbine will enable an integrated,
life cycle assessment of the wind turbine and its foundation.
This paper describes the portion of the study that involves
preliminary characterization of the geotechnical properties of
the wind farm site. In particular, a comparison between the
in
situ
testing, laboratory testing and commonly used correlations
are presented. It is anticipated this process will guide future
projects on clayey silt tills in Ontario and provide cost effective
site investigation and design methods for turbine foundations.
2 SOIL PROFILES & MATERIAL CHARACTERISATION
2.1 Wind farm and geological environment
The wind farm is located in a simple geographical and
environmental area in the Great Lakes region of Southern
Ontario. The farm has horizontal axis 2.3 MW turbines with an
Characterization of the geotechnical properties of a carbonate clayey silt till
for a shallow wind turbine foundation
Caractérisation des propriétés géotechniques d'un silt argileux carbonaté glaciaires
pour une fondation superficielle d’éolienne
Tyldesley M., Newson T.
Geotechnical Research Centre, Department of Civil Engineering, University of Western Ontario, Ontario, Canada
Boone S.
Golder Associates Ltd., London, Ontario, Canada
Carriveau R.
Entelligence Research Group, Department of Civil Engineering, University of Windsor, Ontario, Canada
