Geotechnical Services – Good ground for wind turbines
Interview with Ana Bielza, Senior Engineer CTE Wind Iberica Head of Geotech Serv...
Find out more
Geotechnical Services – Good ground for wind turbines×
Interview with Ana Bielza, Senior Engineer CTE Wind Iberica Head of Geotech Services CTE Wind International
Since 2019 CTE Wind provides geotechnical engineering services to their clients. Over the last six months, Ana Bielza, Senior Engineer at CTE Wind Iberica has taken part in over 45 projects. We have asked her what she actually does and why her role is crucial for the foundation design of wind turbine generators (WTG).
Can you briefly explain to us what a specialist in geotechnical engineering like you does? Ana Bielza: Geotechnicians apply scientific methods and engineering principles to predict the response of the ground to the foundation requirements. They then deliver this information to the civil engineers so they can design foundations accordingly.
What is the difference between common geotechnical engineering for bridges or building compared to the WTG-geotechnics? Ana Bielza: There are not many differences. The ground has to be investigated with similar methods (drillings, geophysics, lab tests, etc.) and the same kind of parameters are needed. But the ground capacity is usually not what determines the foundation size, because most of the time the soil strength transmitted by a turbine foundation is not high. Besides, settlements in general are not important in this type of structures. But rotational stiffness can rather be the main ground parameter to manage and sometimes it can even set the foundation size.
Ana Bielza, lives in Madrid. She holds a Bachelor in Geology and a Master’s degree as Geology Engineer. In 2019 she has joined CTE Wind Iberica where she can draw on her stong expertise of more than 18 years as senior engineer.
CTE Wind offers his services worldwide
You worked on over 45 projects in six months, which is quite a lot. In which countries did you take a look at the ground? Ana Bielza: Yes, there were many. It looks like our services are very appreciated by the customers (She smiles delighted). I worked for projects in Argentina, Australia, Belgium, Brazil, Chile, India, Indonesia, Israel, Lithuania, Mexico, Netherlands, Peru, Russia, Spain, Tanzania, Tonga, Turkey, and Ukraine. Of course, every country has its peculiarities. And I not only mean the different ground types you can find but also how the different investigations that are conducted and how the results are delivered.
Looking back on these last months, what were the challenges? Can you maybe share one or two projects with us? Ana Bielza: Challenging projects are usually the ones located on recent soils in seismic areas and near to the shore (high water table). For example, we have done several basic designs for a huge project in India with 1000 wind turbines, located on a saline desertic zone most of the year. But during the monsoon season the landscape becomes a swamp, with water at ground level. It is a region with an extreme seismic risks, on a recent granular soil (potentially liquefiable) and very aggressive to the concrete. We had to analyze the ground with just four boreholes in an area for 1000 turbines!
Sounds like fun. As far as we know, there are no known cases of significant damage from liquefaction in wind farms. So, how did you solve this problem? Ana Bielza: Well, with only four drillings for such a huge area, it was mandatory to be conservative, therefore, and according to the client, we worked with two possible scenarios. We hope they were representative for the situation in most of the future turbine positions. The civil engineer then follows our specifications and designs the foundations accordingly with piles.
Trust is an important key factor
Could you tell us about another project? Ana Bielza: Another challenging project has been the one in a country in South America, a wind farm with over 40 turbines. This was a constructive design where we had also drafted the geotechnical study from a factual report given by the customer, with 45 boreholes, 80 trial pits and 46 geophysical tests as well as an important amount of laboratory tests. The ground was good, a consolidated gravely soil -a conglomerate-, but seemed to be prone to suffer some dissolution because it had salt in its matrix.
What does it mean exactly? Ana Bielza: The matrix describes the different layers a soil can have. The salt in the matrix can be dissolved by heavy rain or ground water. But even if the ground suffers an hypothetical dissolution, the remaining gravely soil would show enough strength and rigidity to carry the WTG. Besides, there was no water at all in the area, it was in a desert area.
Good conditions. What was the problem then? Ana Bielza: Yes, but the client was pressuring us to set down categorically that there was no risk of dissolution, and there was no possibility at all for buoyancy. The geotechnics of the project showed good conditions for our SOFT-SPOT® foundation, but the wind farm owner seemed to have unfounded fears and wanted us to affirm that there was zero risk in this area. But zero risk does not exist. It was tricky to explain why there are no risk but we had to write about an hypothetical dissolution. Luckily, we finally came to an understanding. (ctewind)
Foundation Design Helps To Save Resources
Coöperatie Zuidenwind has poured the concrete for the foundation in Heibloem in...
Find out more
Foundation Design Helps To Save Resources×
Coöperatie Zuidenwind has poured the concrete for the foundation in Heibloem in the Netherlands and created the basis for the installation of their wind turbines. The foundation design and calculation for this project was done by CTE Wind Civil Engineering. The expert in foundation design WTG suggested their Soft-Spot® instead of a typical pile foundation.
«To work with CTE Wind as designer was nice. The speed of response and reliability of the planning has been a winning experience for us.»
Arjan Louwerse from H4a Windenergie B.V.
(NL) / La Richardais (FR) – The Netherlands soil consistsof
unconsolidated, very young sediments. Due to the proximity of the low-lying
part of the European continent, the basin of the North Sea, the bottom rarely
rises higher than 30 m above sea level. In the areas along the coast (provinces
of Groningen, Friesland, Noord-Holland, Zuid-Holland, Zeeland) the surface soil
layers consist mainly of clay deposits. In the west of the Netherlands the
clays are replaced by lowland moors (peat). To sum up: in the Netherlands, pile
foundations are mandatory for wind turbines because of the concentrated forces
occurring on little surface area. Except in Heibloem, where the ground is
exceptionally stable. So good, in fact, that CTE Wind offered its
resource-saving Soft-Spot® instead of the usual foundation.
Soft-Spot® in the Netherlands
The Soft-Spot® was developed by CTE Wind’s engineering team and is implemented in various countries around the world. «It was simply the most economical foundation we could choose », Arjan Louwerse from H4a Windenergie B.V. says. He is the project manager for Coöperatie Zuidenwind wind turbines. This foundation design optimizes the use of resources and helps to save up to 15 % of concrete and 2 to 5 % of reinforcement steel. In some cases what is even more important than the costs is the available space : with Soft-Spot® you need less surface for the foundation. This reduces the time and excavation costs. «The philosophy to reduce the costs of the Soft-Spot® was also a good point of discussion with our client. From the beginning we had a good feeling with the design», he explains.
In fact thanks to the new design the outer diameter of the foundation was 1.1m smaller compared to a typical foundation design. This resulted in a reduction of 11 % of concrete and 3 % of steel – or more precisely about 100m3 of reinforced concrete. «To work with CTE Wind as designer was nice. The speed of response and reliability of the planning has been a winning experience for us», Louwerse added. In spring 2020 the wind turbine will arrive together with the largest blades ever installed onshore in the Netherlands. (ctewind)
The SOFT-SPOT® was developed by CTE Wind’s engineering team and is implemente...
Find out more
The SOFT-SPOT® was developed by CTE Wind’s engineering team and is implemented in various countries around the world. This foundation design optimizes the use of resources and helps to save concrete, reinforcement bars and less surface for the foundation. This reduces the time and costs.
La Richardais (FRA) – CTE Wind has already developed and implemented some projects since the launch of the SOFT-SPOT®. Several hundreds of the new foundation design are built around the world : Brazil, France, Lithuania, Indonesia, Mexico, Netherland, Russia, Serbia, Sweden and Thailand to name a few. As a result of his astonishing design the projects allow savings in concrete volume up to 15%, reduction of foundation diameter and total weight of reinforcement bars of 2-5%. In some cases what is even more important than the material costs is the available space : with SOFT-SPOT® you need less surface for the foundation. This reduces the time and excavation costs.
Layer of soft material
CTE WIND Civil Engineering presents to the market a new foundation system for wind turbines, a WTG shallow gravity foundation with SOFT-SPOT®. Through placing a layer of soft material below the central part of the foundation, the slab will effectively act as a ring foundation with respect to the soil-structure interaction. The bearing pressure of the WTG is concentrated at the annular contact surface closer to the edge of the slab. This increases the lever arm of the stabilizing moment. Therefore, the foundation diameter can be reduced in comparison to a standard foundation solution.
Simply the most economical foundation
Thanks to SOFT-SPOT® intelligent design less excavation work is needed. This reduces the machine costs. A major point is that no additional training of site workers is required for the construction of the soft layer. The construction is very easy and the material for the soft layer can be purchased cheaply all over the world. Or as one of CTE Wind’s client pointed out: It is simply the most economical foundation you can choose. (ctewind)
Please contact us if you are interested in knowing more about CTE Wind’s SOFT-SPOT®
Nearshore foundation – New platform design allows up to 30 percent savings
A new design of a nearshore foundation for wind turbine generator has been final...
Find out more
Nearshore foundation – New platform design allows up to 30 percent savings×
Hanoi (VNM) /La Richardais (FRA) – A new design of a nearshore foundation for wind turbine generator has been finalized by CTV, a branch of CTE WIND group at the end of September 2019. The project is located in the East Vietnam sea and allows to save 30 percent of the construction costs compared to similar projects due to the astonishing design of the foundation.
For a 4 MW wind turbine above the platform, CTE Wind has designed a foundation with 520m3 of concrete, 120 tons of steel and 46 piles. The piles have an average length of 70 meters and are hammered into the muddy nearshore underground. In fact, the geotechnics were very challenging and the piles were also designed in-house to withstand tides, waves and ship movements close to the platforms.
CTP – foundation design for the biggest wind park in Poland
Poland biggest wind park with an estimated power output of 220 MW is actually in...
Find out more
CTP – foundation design for the biggest wind park in Poland×
Waraw (POL) /La Richardais (FRA) – Poland biggest wind park with an estimated power output of 220 MW is currently in the assembly phase. The project is a complex of parcs on the Middle Seashore close to the Baltic sea and will have 81 wind turbines. It is scheduled for completion next year. CTE Wind made the foundation design for all WTGs trough his local office in Warsaw.
Since 2011 CTP – part of CTE Wind International – designed 777 WTG foundations for onshore power plants in Poland. CTPs office in Warsaw is responsible not only for Poland but also for all Baltic countries up to Kazakhstan. Commenting on the largest Polish project, Dariusz Krasowski, CEO and engineer of CTP, said: « We are delighted to have played an important role in this project. This shows the confidence of our customers in our designs and is also an encouragement for us to continue to perform well. »
About CTE Wind International
CTE Wind is an international engineering consulting firm specialized in the analysis and design of onshore wind turbine foundations. The company is active in the wind energy sector since 2003. Over the last 16 years CTE Wind calculated foundations for 15’000 turbines in 61 countries. CTE Wind has offices in France (HQ), Brazil, Vietnam, Poland, Portugal, Ireland and in Spain.
The company is a subsidiary of the CTE Group, a consulting firm, specialized in building and civil engineering (www.cte-sa.com). The CTE Group was founded in 1965 and is today one of the leaders in the structural engineering sector.
Vietnam Wind 2019 Energy Summit
We are happy to announce our participation at the upcoming wind event in Hanoi. ...
Find out more
Vietnam Wind 2019 Energy Summit×
We are happy to announce our participation at the upcoming wind event in Hanoi. The CEO, Alexander Martin, and the head of our Vietnamese office will be giving a presentation regarding international foundation design experience and near-shore solutions. We are looking forward to seeing you there!
WindEurope Conference & Exhibition 2019
We are happy to announce our participation at this event which will take place i...
Find out more
WindEurope Conference & Exhibition 2019×
We are happy to announce our participation at this event which will take place in Bilbao 2 – 4 April. There are over 8,000 companies and 400+ exhibitors that have confirmed their presence. Please come and visit us at our stand n° 3-B42
En poursuivant votre navigation sur ce site, vous acceptez nos CGV et l’utilisation de cookies pour vous proposer des contenus et services adaptés à vos centres d’intérêts et vous permettre l'utilisation de boutons de partages sociaux.