2319
Geotechnical Exploration for Wind Energy Projects
Compagnes géotechniques destinées aux parcs éoliens
Ben-Hassine J.
Renewable Energy Systems Americas Inc., Broomfield, Colorado, USA
Griffiths D.V.
Colorado School of Mines, Golden, Colorado, USA
ABSTRACT: Wind energy projects are often fast-paced and cover large terrains. Such conditions result in increased geotechnical
risks and require specially adapted geotechnical exploration and data analysis techniques that are designed to manage risks at different
stages of project development. Use of geophysical methods, in addition to the traditional subsurface exploration methods, is generally
required to collect design critical data. During the early stages of project development, using quick qualitative geophysical methods
can prove advantageous for finalization of wind farm layout and preliminary foundation design. However, as project plans progress, a
more thorough geotechnical investigation is required. At all stages of a project, an understanding of the available geotechnical tools,
along with their associated risks and cost implications is essential to minimize the likelihood of design changes that result in cost over
runs. This paper presents geotechnical exploration methods used at different stages of project development and discusses key
geotechnical parameters for wind turbine foundation design, available geotechnical tools, and the degree of confidence associated
with these tools. The paper makes an attempt to present an exploration approach that is optimized for efficiency and risk.
RÉSUMÉ : Les projets d'énergie éolienne sont souvent réalisés dans un contexte d'exécution rapide et couvrent des terrains de
grandes envergures. Ces conditions présentent des risques géotechniques accrus et nécessitent des compagnes d'exploration
géotechnique et des techniques d'analyse de données spécialement bien adaptées pour gérer les risques à différentes étapes du projet.
Le recours à des techniques géophysiques en plus des méthodes d'exploration traditionnelle est généralement requis pour obtenir les
données critiques. Durant les premières étapes du projet, le recours à des méthodes géophysiques qualitatives et rapides peut s'avérer
plus avantageux pour établir '' la faisabilité du projet, '' le plan d'implantation du projet et la conception préliminaire des fondations.
Toutefois, dans les étapes plus avancées, une étude géotechnique plus poussée doit être réalisée. A toute étape, une connaissance
adéquate des méthodes géotechniques disponibles, des risques et coûts qui leurs sont associés est essentielle pour minimiser
l’éventualité de changements à la conception résultant en dépassement de coûts. Cet article est un essai de présenter une approche
d'exploration optimisant l'efficacité et le risque.
KEYWORDS: geotechnical exploration, risk management, wind energy, efficiency.
1 INTRODUCTION
The period leading up to an operational wind energy plant
starts several years before construction and can be divided into
three overlapping phases: project development, engineering
design, and project construction (Figure 1). During the
development phase, various risk types and sources are evaluated
and decisions are made to maintain, modify, or abandon the
project. During the engineering design phase, decisions are
made to refine the design while maintaining acceptable levels of
risk. Any subsequent changes to the design typically result in
additional cost. This paper focuses on geotechnical risks,
particularly how such risks are being addressed currently and
how this process may be improved. The objective is to assess
risks and catch flaws as early as possible in the project
development phase while there are still opportunities to make
changes before significant development funds are spent. As in
all large expenditure projects, early decisions have the greatest
impact on financial performance. The motivation of this paper is
to minimize the cost of civil infrastructure related to wind
energy projects (turbine foundations, access roads and facilities
such as the substation and the operation and maintenance
building) through a rational redistribution of the geotechnical
exploration effort. It has been estimated that civil infrastructure
accounts for 4 to 10% of the total wind energy project cost.
Given the thin profit margins of wind energy projects, a 2%
saving can make the difference between whether a project goes
ahead or is shelved.
Figure 1. Overlapping phases leading up to a wind energy plant.
1 PROJECT REALISATION PHASES
All three project phases (development, design, and
construction) involve some level of geotechnical risk
assessment and management, with most of this effort currently
focused at the engineering design phase. Current and proposed
activities related to geotechnical risk assessment for each phase
are described below.
