annex 2.8 - 0005-8491_description of standard gravity anchor foundation

Vestas Wind Systems A/S Alsvej 21 8940 Randers SV Denmark www.vestas.com

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Class 1 Document no.: 0005-8491.V04

2011-06-22

Description of Standard Gravity Anchor Foundation

V80-V90-V100-V112

VESTAS PROPRIETARY NOTICE: This document contains valuable confidential information of Vestas Wind Systems A/S. It is protected by copyright law as an unpublished work. Vestas reserves all patent, copyright, trade secret, and other proprietary rights to it. The information in this document may not be used, reproduced, or disclosed except if and to the extent rights are expressly granted by Vestas in writing and subject to applicable conditions. Vestas disclaims all warranties except as expressly granted by written agreement and is not responsible for unauthorized uses, for which it may pursue legal remedies against responsible parties.

Document no.: 0005-8491.V04 Description of Standard Gravity Anchor Foundation

V80-V90-V100-V112

History of this Document

Date: 2011-08-18 Issued by: Technology R&D Class: 1 Type: T05 General Description Page 2 of 40


History of this Document

Version

no.

Date Description of changes Technical

approver

02 2010-11-24 New template. Minor grammatical and formatting changes.

TIRIC

03 2011-06-22 Grout cast in one sequence, grout data included. Inclination of upper foundation surface. C-bars inside anchor cage.

SPJ

04 2011-08-18 Mesh under anchor cage. Densit added to list of suppliers.

SPJ

Table of Contents

1 Preconditions ....................................................................................................................... 3 2 Parties Involved ................................................................................................................... 4 2.1 Vestas Wind Systems A/S ..................................................................................................... 4 2.2 Required Documentation ....................................................................................................... 4 2.3 The Engineer ......................................................................................................................... 4 2.4 The Contractor ....................................................................................................................... 5 3 The Geotechnical Project Report ........................................................................................ 5 4 Inspection ............................................................................................................................. 5 5 General Guideline ................................................................................................................ 5 5.1 Excavation ............................................................................................................................. 5 5.2 Reinforcement ....................................................................................................................... 9 5.2.1 Installation of Anchor Cage .................................................................................................... 9 5.2.2 Installation of Lower Radial Reinforcement .......................................................................... 12 5.2.3 Installation of Lower Concentric Reinforcement: .................................................................. 15 5.2.4 Installation of Vertical Reinforcement: .................................................................................. 18 5.2.5 Installation of Upper Radial Reinforcement: ......................................................................... 20 5.2.6 Installation of Upper Concentric Reinforcement: .................................................................. 22 5.2.7 Hooking of Shear Locks in Upper Layer ............................................................................... 25 5.2.8 Installation of Reinforcement in Pedestal: ............................................................................ 26 5.3 Concrete .............................................................................................................................. 27 5.4 Grouting and Installation of Tower ....................................................................................... 28 5.5 Post Tensioning ................................................................................................................... 38 6 Enclosure 1 ........................................................................................................................ 39


V80-V90-V100-V112 Preconditions



1 Preconditions

The design of a gravity-flat foundation is based on two model soil types defined below and with a ground water level assumed to be either level with the terrain or at foundation level. The design can be used as standard design when the basic assumptions are fulfilled and verified for the actual location.

Calculations, drawings and descriptions apply to a standard circular gravity anchor foundation for a Vestas V80, V90, V100 or V112 wind turbine. The circular foundation can be implemented as a polygon with a minimum of eight sides (octagonal).

The design is based on the following European Standards:

EN 61400-1:2005 Wind turbines Part 1: Design requirements

EN 1992-1-1:2004 Design of concrete structures Part 1-1 General rules

EN 1997-1:2004 Geotechnical design Part 1 General rules

EN 206-1:2000 Concrete: Specification, performance, production and conformity

ENV 13670-1:2000 Execution of concrete structures Part 1: Common.

EN 10080:2005 Steel for the reinforcement of concrete

The design is according to IEC 61400-1. The safety factors on material properties are according to EN 1992 and EN 1997. Load factors are according IEC 61400-1.

The stability of the standard gravity foundation is designed for two soil types:

Sand: Friction angle: 30 (normal assumption)

Cohesion: 0

Density 18 KN/m3

Clay: Friction angle 0

Cohesion Cu KN/m (undrained) *)

Density 18 KN/m3

The level of the ground water is assumed to be either equal to the foundation level or equal to ground level. The design is valid for a ground water level equal to or less than the assumed value.

*) The undrained shear strength with the equivalent bearing capacity to the chosen friction angle is stated on the drawing.


V80-V90-V100-V112 Parties Involved



2 Parties Involved

2.1 Vestas Wind Systems A/S

Vestas Wind Systems A/S offers an approved foundation design for a circular gravity anchor foundation of a tubular steel tower with ground water level at terrain or at foundation level. The design consists of a:

Foundation Load Report where loads, geometry and stiffness requirements are stated for the interface between tower and foundation

Assembly drawing of the Vestas anchor cage Drawing of the gravity foundation Cut and Bending List for reinforcement Calculation based on Eurocodes and EN 61400-1 Foundation earthing work instruction, including quality control.

2.2 Required Documentation

Document no. Title

0017-5653 Switch gear foundation guideline

0019-4493 Installation of Switchgear

0018-0743 Assembling and Installation Anchor Cage

0016-7148 SIF for assembling and installation of Anchor cage

0018-0710 Grouting of Anchor Cage

0014-6511 Earthing system on Anchor Cage Foundation

0019-2575 Work Description of Foundation, Earthing on Anchor Cage Foundation

0019-2576 Quality Earthing Anchor Cage Foundation

2.3 The Engineer

If the standard circular gravity foundation design is used as basis for the design, the engineer must verify that all assumptions made by Vestas Wind Systems A/S, such as soil data, ground water table, material used, local regulations, etc. are valid for the actual project.

If a site-specific design is used, the engineer must verify that all requirements to the interface between anchor cage and foundation are fulfilled (geometry and rotational stiffness).

A Geotechnical Project Report must be issued and all assumptions made by Vestas Wind Systems A/S must be verified as valid for the project. The engineer must instruct the contractor, organize, report and verify Quality Assurance (QA) measurements in a scope that is, at a minimum, equal to the content listed in this description. The engineer shall releases the foundation for the erection of the tower. If in doubt, the engineer must consult Vestas Wind Systems A/S.


V80-V90-V100-V112 The Geotechnical Project Report



2.4 The Contractor

The contractor is responsible for preparation of the working site, excavation, scaffolding, reinforcement and concreting of the foundation according to drawings, descriptions and engineer advise. It is the contractors responsibility to install and adjust the anchor cage. It is the contractors responsibility to install all earthing parts and electrical conduits prior to any concreting.

3 The Geotechnical Project Report

A template for a Geotechnical Project Report is enclosed in this description as Enclosure 1 (see 6 Enclosure 1, p. 39). This template contains the minimum requirements.

4 Inspection

At a minimum, the following soil parameters must be verified before the foundation works can start:

Friction angle or cohesion Density Ground water level, actual and estimated highest level Stratification of soil.

During execution of work the following items must be verified or reported:

Quality of material Sequence of work Vital dimensions (main geometry, reinforcement, minimum concrete cover

etc.) Discrepancies of materials and dimensions Unforeseen events (settlements, influence on neighbouring constructions,

etc.) Temporary works, interruptions and commencement of work

5 General Guideline

5.1 Excavation

Precautions against any negative effects from ground water must be established before the excavation work can start. In case of high ground water level, a well point system must be established and a stable level of ground water must be achieved before the excavation work starts.


V80-V90-V100-V112 General Guideline



Figure 5-1: Excavation.

During excavation the composition of the soil must be observed visually and special attention must be paid to organic remains or signs of previous excavations. When the final level of excavation is reached, special caution must be taken to protect the upper layers of the soil from mechanical digging equipment, rain or surface water. Immediately after the final level of excavation is reached, it is recommended to concrete the blinding layer with a minimum of 100 mm low class concrete C12/15. For some soft or weak soil types, it may be necessary to arrange a reinforcement net in the cleaning layer locally below the anchor cage adjustment feet to prevent punching and differential settlements.

If, by error, the level of excavation is below the expected level, or if a layer of poor soil has to be removed, a layer of compacted sand or low class concrete must be added to replace the soil.





The top level of the blinding layer at the centre of the excavation must be lower than the surrounding parts. This form can be achieved in two different ways:

1. Excavating to a constant level and using increased thickness of blinding layer outside the centre part or

2. Excavating to two different levels

The second possibility is preferable due to less material consumption (see Figure 5-1, p. 6. Consider to arrange a drainage hole at the low parts when having friction soil to avoid water to be accumulated at the centre part.

Figure 5-2: PVC pipes.

The guiding PVC-pipes for the cabling are located below the blinding layer in an excavated trench. See Figure 5-2, p. 7.

The number and sizes of PVC guiding pipes is stated on the site specific cable layout. The figure above shows only the principles for the installation. Further general information can be found in the Installation of Switchgear.

The clearance between the pipes must be a minimum of 40 mm.

The pipes can be secured against floating in the wet blinding layer by hammering U-shaped bars 2 m in the ground next to each pipe.

All horizontal PVC guiding pipes including the 90 elbows shall be installed before the blinding layer is cast but avoid installing the vertical PVC pipes until the anchor cage is installed.

In case of high ground water level install a 45 bend outside the foundation edge and a straight pipe long enough to be above the level which the water will reach when the pumps are stopped. This makes the installation of the cables much more convenient!





The switchgear will be placed directly on the pedestal and therefore it is important to pay attention to how the pipes for respective grid cables, communication cables and earthing cables are arranged. Manual for installation of Switchgear 0019-4493 shows how the pipes have to be installed for different types of switchgear. See below example Figure 5-3.

Figure 5-3:

pipe arrangement for switchgear installation shown on completed foundation.

Different possible arrangements of guidance for both HV cables and communication cables are shown in 0017-5653. Location and distances are specified with respect to foundation centre but in general the HV cables are located between the diagonal stiffeners of the template, which also defines the location of the door. The HV cables are entering the switchgear directly but the communication cables are located outside the switchgear.

Guiding PVC Pipes and Blinding Layer C12/15

Figure 5-4: Guiding PVC pipes and blinding layer C12/15.





5.2 Reinforcement

It is recommended to arrange scaffolds along the perimeter of the foundation. The installation of permanent scaffolds of for example chipboard is acceptable and often advantageous if backfilling of soil is performed to balance the horizontal pressure from the wet concrete. If the soil allows direct concreting, the concrete cover must be increased to 100 mm and the global dimensions of the foundation have to be adopted accordingly.

The reinforcement steel must be checked in regard to correct dimension, location, number, material grade and certification. The certification must be preserved as part of the Quality Assurance. Only correct materials must be installed.

5.2.1 Installation of Anchor Cage

The assembled anchor cage consists of two halves, each 180. The assembly can take place in a workshop or onsite depending on local agreement.

For information concerning on site assembling of anchor cage please consult the work instruction Assembling and Installation of Anchor Cage.

Prior to the installation of the anchor cage install the lower mesh pos 13.2 directly on the blinding layer. The mesh is cut to a circular shape and openings are cut for cable guidance and adjustment feet of the anchor cage. In most cases a number of concentric rings pos 5 have to be installed underneath the coming radial bars. Place these rings loose on top of the mesh together with the 2 rings pos 12.2 and 12.3 and the Z-bars pos 12.1:

Figure 5-5: Reinforcement under anchor cage.

As an alternative to cutting holes for the adjustment feet of the anchor cage consider to place the feet in advance in the correct position before the mesh, rings and Z-bars are installed.





Place the halves of the anchor cage in the correct final position on the blinding layer and then join the two halves by brackets at the template and the base flange. The brackets are attached to the cage flanges.

The anchor cage halves must be handled using only the lifting hooks of the cage.

Figure 5-6: Anchor cage placed with future door located along the main axis.

With the anchor cage in correct position spacers are placed underneath the lower mesh to lift it to the correct position. Check that all lower nuts and washers are in full contact with the base.





Anchor Cage Placed at Centre of Foundation on Adjustment Feet

Figure 5-7: Anchor cage with lower concentric rings in place.

Figure 5-8: Anchor cage at centre of foundation.





The anchor cage is placed with the future door located along the main axis, which contains the guiding PVC pipes as shown in Figure 5-, p. 8, Figure 5-5, p.9 and Figure 5-7, p.10. The anchor cage is adjusted vertically by adjusting the support feet so that upper side of the lower base flange is level with the top of blinding layer outside the centre part and within +/- 4 mm from a horizontal plane at upper template flange. See Figure 5-6, p. 10 and Figure 5-7, p. 11.

Before reinforcement work can commence Vestas Service Inspection Form 0016-7148, SIF for Assembling and Installation of Anchor Cage, must be completed.

5.2.2 Installation of Lower Radial Reinforcement

The bottom radial reinforcement layer is installed on spacers located the correct distance from the blinding layer. It is allowed to install a few numbers of concentric rings below the radial bars to form a continuous support. The reinforcement bars are installed in a radial pattern using the anchor cage as a template:

Figure 5-9: Lower radial reinforcement, horizontal view.

Pos 1.1 spans from centre core to edge and is installed in every 4th anchor space, check cord distance on the foundation drawing. Pos 1.2 is placed between pos 1.1 and pos 1.3 in the remaining spaces. Pos 1.4 is located outside the anchor and for larger diameters pos 1.5 is placed between each radial bar. See Figure 5-9, p. 12.





In some cases the radial bars are anchored in concentric rings above and below the radial bars. The concentric rings pos 5 already placed on top of the lower mesh are installed underneath the radial bars. See Figure 5.9, p. 12, Figure 5.10, p. 13, Figure 5.11, p. 13 and Figure 5.12, p. 14:

Figure 5-10: Lower radial reinforcement, vertical view.

Every 4th Main Radial Reinforcement Passing the Anchors Installed

Figure 5-11: Every 4th radial reinforcement installed.





All Main Radial Reinforcements Installed

Figure 5-12: All main radial reinforcements installed.

Detail of Centre Part Showing All Bars Installed:

Figure 5-13: Detail of centre part.





Please note the concentric rings below the radial bars mentioned also shown in Figure 5-13, p. 14.

5.2.3 Installation of Lower Concentric Reinforcement:

Figure 5-14: Bottom concentric reinforcement layer installed on top of radial

layer

The bottom concentric reinforcement layer is installed on top of the radial layer inside and outside the anchor cage. See Figure 5-14, p. 15.

Reinforcement bars are held in correct position by an adequate number of steel wire bindings at reinforcement crossings. Welding is NOT allowed!

Additional radial bars pos 1.6 are in some cases required above the main radial bars where they pass the anchors. If required, they are specified on the foundation drawing.

Note that concentric bars inside the anchor cage in some cases are both below and above the radial bars. Bars below are lifted and fastened to the radial bars.





Concentric Rings Installed

Figure 5-15: Concentric rings installed.

Detail of Centre Part

Figure 5-16: Detail of centre part.





For the concentric rings inside the cage the rings below the radial bars are lifted and joined to the matching rings above the radial bars. Continue this until the ring which defines the location of the outer row of C-bar pos 8.1.2. The start of the bend of the horizontal leg of the C-bars is to match the concentric ring. Attach the outer row of C-bars to radial bars pos 1.2. The C-bars are held in position by installing some of the upper concentric rings pos 6.1 under the horizontal legs of the C-bars. Install the remaining rings and the inner row of C-bars as described for the outer row. Attach the inner row of C-bars pos. 8.1.1 to radial bar pos 1.1.

In some cases there are extra bars pos 1.6 between the anchors. Install these bars and pay attention not to damage the plastic shrink hose of the anchors. Check further more if the position 2.6, which is a radial bar similar to pos 1.6 but placed underneath the upper main radial bars, is required for the actual site. If so place the pos 2.6 between the bars together with pos 1.6 ready to be installed on a later stage. See Figure 5-16, p. 16 and Figure 5-17, p. 17:

Figure 5-17: C-bars and pos 1.6, vertical view.

Fasten the pos 12.1 already placed on the lower mesh to the radial bars, lower mesh and concentric rings pos 12.2 and 12.3:





5.2.4 Installation of Vertical Reinforcement:

Figure 5-3: Shear locks in the anchor cage.

The vertical reinforcement consists of shear locks equally distributed inside the anchor cage (pos 8.1) and outside the anchor cage (pos 8.2 and 8.3), as specified on the foundation drawing, and edge bars (pos 7.1) installed at the edge. See Figure 5-3, p. 18 and Figure 5-27, p. 24. Inside the cage and at the edge the bars are C-shaped but the rest, pos 8.2 and 8.3, are U-shaped with horizontal legs at the bottom. The horizontal legs of the U-shaped shear locks are installed with the legs pointing away from the centre close to the cage and against the centre at the edge to avoid conflicts with edge bars.

The shear locks (pos 8.2 to 8.3) are designed to be located below the upper main reinforcement and serve as support in the installation phase. The shear locks are properly locked in the lower layer by hooking them under the lower concentric reinforcement. For the upper reinforcement, additional hair pin reinforcement will be placed at a later stage. Shear locks inside the cage are anchored in the upper main reinforcement without hair pins.





Shear Locks Installed

Figure 5-19: Shear locks installed.

Detail at Centre, Locks Equally Distributed

Figure 5-20: Detail at centre.





5.2.5 Installation of Upper Radial Reinforcement:

Figure 5-21: Upper radial reinforcement.

The upper radial and concentric reinforcement might differ in size but will have the same overall geometry. The radial bars are installed on top of the shear locks by using the anchor cage and lower reinforcement as a template. See Figure 5-21, p. 20 and Figure 5-23, p. 21.

In most cases the shear locks will offer sufficient support but in some cases it may be necessary to install 2-3 of the concentric rings pos 4 under the radial bars to support the radial bars that are located between shear locks. Additional bars pos 2.6 are in some cases required below the main radial bars where they pass the anchors. See Figure 5.21, p. 20, Figure 5.22, p. 21 and Figure 5-23, p.21.If required, they are specified on the foundation drawing.

Note that the radial bars have to be placed below the rings already present inside the cage to keep the vertical C-bars in position.





Concentric Rings to Support Radial Bars

Figure 5-22: Concentric rings to support radial bars.

Upper Radial Bars Passing Anchors Installed

Figure 5-23: Upper radial bars passing anchors installed.





All Upper Radial Reinforcement Placed on Shear Locks

Figure 5-24: All upper radial reinforcement placed on shear locks.

5.2.6 Installation of Upper Concentric Reinforcement:

Figure 5-25: Upper concentric reinforcement layer installed on top of radial layer

The upper concentric reinforcement layer is installed on top of the radial layer inside and outside the anchor cage. See Figure 5-24, p. 22.





Upper Concentric Reinforcement in Place

Figure 5-26: Upper concentric reinforcement in place.

The remaining radial bars are installed by attaching them to the concentric reinforcement. See Figure 5-26, p. 23.





Edge Bars Installed at Outer Edge

Figure 5-27: Edge bars installed at outer edge.

The number of edge bars will normally match the number of radial bars. In this case arrange the edge bars to overlap the lower and upper radial reinforcement.





5.2.7 Hooking of Shear Locks in Upper Layer

Figure 5-28: Hooking of shear locks in upper layer.

With all concentric upper bars installed, hair pin-shaped reinforcement (pos 8.4) are dropped from above for each shear lock. The hair pins are hooked in the radial bars. See Figure 5-28, p. 25.

The vertical legs of the hair pins overlap with the vertical part of the shear reinforcement and are held in correct position with steel wires.





5.2.8 Installation of Reinforcement in Pedestal:

Figure 5-30: Vertical bars in reinforcement of the pedestal.

The reinforcement of the pedestal consists of a number of vertical bars, pos 9.1 and 9.2, which are attached to the upper concentric reinforcement. Pos 9.1 is placed exactly outside each anchor whereas pos 9.1 typically is placed outside every 4th anchor, compare the actual numbers of bars on the drawing.

Place the rings pos 10.3 to 10.8 on top of the upper radial bars for a convenient later installation.

If the foundation is concreted with a cold joint, install the upper horizontal ring pos 10.1 and 10.2 to hold the vertical bars in the correct position. When concreting in one sequence continue as described.

Horizontal outer rings, pos 10.1, are installed on the vertical bars pos 9.1 in an equivalent distance. Similar to these 3 horizontal inner rings, pos 10.2, are installed on the vertical bars pos 9.2 to form support for the splitting bars pos 11.1 and fix the top of the vertical bar.

Install the splitting bars pos 11.1 shaped like a hook on every second horizontal rings in a radial direction. The splitting shall be hooked to the vertical bars pos 9.1 and placed in two levels with an offset of one anchor distance. In some cases where the mandrel diameter conflicts with the anchor distance it will necessary to





install the hooks some degrees out of horizontal plane. Lift the rings pos 10.3 to 10.8 above the hairpins to make the final installation possible.

Install the outer bows pos 9.3 on the horizontal rings pos 10.1 as close to the splitting bars as possible and the inner bows on the horizontal rings pos 10.2.

The concentric rings pos 10.3 to 10.8 are lifted and attached to the bows.

See Figure 5-30, p. 26 and Figure 5-31, p. 27.

Reinforcement of Pedestal

Figure 5-31: Reinforcement of pedestal.

5.3 Concrete

Before concreting can start, the engineer must inspect all reinforcement work and anchor cage according to the quality requirements.

It is important to treat the foam that creates the grout trench, with some slip agent such as formwork oil, to prevent the foam from sticking to the concrete.

Concerning installation of earthing parts, please refer to the Foundation Earthing work instruction for an optimal coordination of reinforcement work and the installation of the earthing parts. It can be advantageous to install earthing parts connected to lower reinforcement before installing upper reinforcement.

The concrete must comply with ENV 206-1 as specified on the drawings. In case of ready-mixed concrete, all materials must be delivered and certified according to ENV 206-1 and the quality requirements can be a part of the suppliers quality system. Certification includes density of concrete.





All parts of the concrete must be compacted according to the standards and show a closed structure without porosity. No entrapped air must be present above the steel base flange of the anchor cage.

The foam pad under the anchor case template has to be treated with a slip agent such as form oil to ease the later removal.

The concreting can be performed in two continuous working sequences:

1. Main plate

2. Pedestal

If concreting in two sequences, leave the surface of the main plate within the pedestal rough and make sure that the cold joint surface between the main plate and pedestal is clean and wet before the pedestal sequence is performed. Cold joints are only acceptable when shown on the drawing.

The concrete is pumped in place with a restricted fall height of normally 1 meter to ensure that no unacceptable separation of the concrete takes place. Access to the lower part can occur by leaving some of the upper bars loose until the concrete level is close to the upper reinforcement.

The concreting is continued until the top level of the template form work is reached and full concrete cover is established. At the pedestal the concreting is continued to the top of the steel template flange with an inclination against the edge.

The concrete must be protected to prevent its surface from drying out by covering the exposed surface with an impermeable covering or insulation mats adapted to local environmental conditions. It is recommended to execute all soil back fillings as early as possible. Note that the use of insulation mats even at higher temperature could enable a shorter curing period and ensure a uniform temperature distribution over foundation height.

The pedestal with all the anchors and cable guidance shall be protected with tarpaulins until the preparation for tower installation takes place. If there is a risk of frost damages it is recommended to leave the foam pad under the template until tower installation. In other cases it is recommended to remove the foam pad as early as possible.

5.4 Grouting and Installation of Tower

Before installation of the tower, the engineer must successfully perform a final inspection of the foundation. For normal concrete a minimum curing period of four weeks is required. A specific calculation that takes actual environmental conditions (temperature, variation of temperature, humidity, etc.) into account and/or the use of special concrete with additives can reduce the curing period. Grouting and adjustment feet will require a compression strength of the concrete of min 15 MPa at the day of installation.

The number of adjustment feet is designed to support the complete tower when exposed to a 12 m/sec wind speed. When the grout has reached a compression strength of 5 MPa the grout has the same bearing capacity as the adjustment feet and 10 MPa the grout alone is able to withstand a tower reaction from a one year IEC wind load of 34 m/sec on the complete tower. Please note that the grout in the first phase of the curing period will remain liquid but when the grout starts to cure the growth in strength and stiffness is rapid. It is therefore strongly





recommended to pump the grout into the trench to start the curing process as early as possible that is when the tower base section is installed. The curing periods for reaching 10 MPa is stated in figure 5-1 on page 35.





When planning the installation we recommend to study the figure below careful.

For most towers it is possible to install up to 2 sections without facing oscillation problems. With only 2 sections installed the adjustment feet are able to support the tower when loaded with an IEC one year wind (34 m/sec).

When installing more sections the risk of having oscillation problems increases and the acceptable max wind speed falls. With all section installed the risk of oscillation is the highest and the acceptable wind speed is 12 m/sec.

The curing curve for the grout material is shown on the figure as a dotted line. In the first hours the grout remains liquid but after this period the compression strength develops in the beginning very fast. When the compression strength reaches 5 MPa the bearing capacity of the grout exceeds the bearing capacity of the adjustment feet which means that they now have outplayed their role. When the grout reaches 10 MPa the grout is able to withstand the loads from a one year IEC wind.

The conclusion is therefore to pump in the grout as early as possible to start the curing process and the ideal situation is that the compression strength has reached 10 MPa before section 3 is installed.





If the wind speed within the time that the grout needs to reach 10 MPa is expected to exceed 12 m/sec multiply the number of adjustment feet stated on the anchor cage approval drawing with the factor in the table below:

12 m/sec 14 m/sec 16 m/sec 18 m/sec 20 m/sec

1.00 1.36 1.78 2.25 2.78

Anchors shall not be post tensioned before the grout and concrete have reached the required compression strength which is stated on the approval drawing for the anchor cage. Vestas will perform the post tension by using hydraulic pulling tools when the flange connection of the tower is torqued.

The trench for the grout is formed either by the anchor cage template flange alone or the anchor template flange together with a formwork of foam.

The illustrations shown are based on the use of the formwork of foam and adjustment feet consisting of a steel bar with a threaded hole and a full threaded bolt at the upper end and a layer of nylon attached to the lower surface. The adjustment feet of this type are used when the grout thickness is from 100 to 300 mm. (For smaller grout thicknesses a nut with a threaded bar is used and the grout thickness is then fixed to 40 mm.)

By using a combination of steel and nylon the adjustment feet will have the same deformation properties as the grout cylinder it is replacing. The feet can therefore be left in the grout without causing any deviation from the ideal uniform stress distribution along the circumference.





Figure 5-32: Foundations with form work of foam.

Before the tower erection can take place the template flange must be removed by removing all nuts and washers of the anchors. The flange is lifted off, leaving the foam formwork in the concrete. Use only crow bars, jackets, wedges, etc and avoid to lift using crane, forklift, etc as the template can have a strong attachment to the concrete and could cause injuries .

Loosen the foam formwork by using a spade and a crow bar and deposit the foam as waste material (see Assembling and installation anchor cage 0018-0743 and Figure 5-31, p. 36). The template flange will be picked up by Vestas, cleaned and used for another anchor cage, so handle the template flange with care, lifting only by using the lifting brackets or lifting holes. All nuts and washers must be stored and protected against dirt, soil, concrete, etc., and mechanical damages onsite repaired to the time of tower installation.





Situation before Lifting Off Template and Form Work

Figure 5-33: Situation before lifting off template and form work.

Situation after Lifting of Template and Removal of Form Work

Figure 5-34: Situation after lifting of template and removal of form work.





Grouting

Before installing the tower base section the trench shall be cleaned and loose particles removed by blasting, high-pressure water, vacuum cleaner, etc. If blasting, the threaded anchor ends must be protected against damages from blasting.

The adjustment feet are adjusted to the correct level and the use of a rotating laser device is recommended. The correct level is found by first checking the highest point of the concrete along the outer edge of the trench. Then, adjust the first foot to be the tower flange thickness minus 10 mm below this highest point. The remaining feet are adjusted to match this level. Doing so, the upper side of the tower flange is a minimum off 10 mm above the concrete allowing for a simple grouting process and allowing water to flow off the tower flange.

Figure 5-35: Situation showing tower base installed on adjustment feet.

Situation after Installation of Adjustment Feet

Figure 5-36: Situation after installation of adjustment feet.





Check that the lowest anchor is a minimum of 180 mm above the highest point of the concrete surface at the edge of the trench and the highest anchor has the end of the thread equal to or under the concrete surface.

The concrete surface has to be fully damped with water. Before watering check if the points where the anchors come out of the concrete are watertight and apply sealing material if necessary. Note that app. 10 anchor pairs are installed in steel pipes to keep base and template flange apart during installation and foundation works and there is a gap between this pipe and the anchor. This gap shall be sealed with tape or mastic.

The grout is stored, handled, mixed and treated according to the suppliers specification using suitable equipment with adequate capacity. The excellent flow properties of the grout will not be present unless the specifications from the supplier concerning mixing devise, water content, mixing time and intensity, etc. are fulfilled. It is of outmost importance that the grout is placed in one continuous working sequence. Pay special attention to keep the material dry and reject to use sacks with damages.

Depending on the local regulations a number of test items have to be cast. As a minimum Vestas recommend performing 3 test items at the start of the grouting and 6 and the end. The last 3 is intended to verify that the grout has 10 MPa which allows tower installation to continue and the remaining 6 is intended to verify the final 28 days strength. The required minimum compression strength for post tension is stated on the foundation drawing and on the anchor cage approval drawing. When this strength is reached and the anchors are post tensioned the turbine can be taken into production and note that it is not required to wait 28 days to verify this strength. If an earlier result is required 3 of the 6 test items can be tested before 28 days.

The water in the trench from pre-dampening the concrete must be removed and no free water must be present when grouting begins unless the grout and pumping equipment is suitable for under water grouting. Start the pumping process against a temporary plate installed radial in the trench for preventing the grout to flow in two directions. Pump in the grout at the bottom of the trench, continue until the top level is in level with the concrete and has formed as much over height as possible. Move the inlet place of injection and keep focus on maintaining the over height of the grout already pumped in place.

At the end grout some litres of grout in a bucket. When the grout in the bucket is beginning to cure remove the over height of the grout and give the exposed surface its final finish having a slight inclination outwards.

After grouting the exposed surface will start to settle and form a skin. To prevent early dry out of the grout material, take the necessary curing precautions such as cover with wet cloths, spray with water, curing agents, etc.

To prevent dry-out through the surface, the grout must be protected by spraying water gently 60-90 minutes after grouting. While adding the water, ensure that the skin layer of the grout is not destroyed.

The grout is left to cure and, during this period, must be protected against mechanical disturbance, etc., by adding a tarpaulin, sheet or similar cover. During cold periods special precaution, such as adding insulation mats with electrical tracing, must be taken to ensure that the temperature of concrete and grout





before and during the curing period is above the specified minimum temperature which is specific for the product but typical 5 C.

Note that some installation schedules will require using insulation mats with electrical tracing for temperatures above 5 C.

Figure 5-37: Grout and sealing work completed.





Grout materials:

BASF Masterflow 9500 (9200)

Cylindrical compression strength 150 x 300 / 150 x 150 x 150 EN 1992-1-1

C110/135

MPa

Conversion factor prism - cylindrical 40 x 40 x 60 150 x 300

0.90

Shrinkage rate when curing under water

< 0

Curing time for 10 MPa 20 C 8 hours 15 C 12 hours 10 C 18hours 5 C 24 hours

DENSIT Ducorit S5


C100/115

MPa


0.89


< 0

Curing time for 10 MPa 20 C 20 hours 15 C 25 hours 10 C 35 hours 5 C 40 hours

Pagel v1/30HF or v1/60HF


v1/60: C100/115 v1/30: C110/130

MPa


0.85


< 0

Curing time for 10 MPa 20 C 8 hours 15 C 12 hours 10 C 18 hours 5 C 24 hours

Table 5-1: Grout material.





Treatment after Grouting

The grout must be protected against drying out caused by temperature and wind according to manufacturer recommendations.

At least the upper surface of the grout and concrete shall be sealed. Due to the post tension design no movement will take place between tower steel flange and grout or concrete under normal characteristic loads. However both concrete and the grout close to the surface will form shrinkage cracking and these cracks shall be sealed by adding a micro filler sealing. Add the sealing to the vertical edge of the tower flange to make sure that the micro crack at the flange is filled.

Sealing materials:

BASF

Masterseal 550

Pagel

Pagelastic

Tower installation:

Before installation of the tower, the engineer must successfully perform a final inspection of the foundation and the related documents such as quality schemes, delivery notes, material certificates, etc. and sign for its release for tower installation. For normal concrete a minimum curing period of four weeks is required.

A specific calculation that takes actual environmental conditions (temperature, variation of temperature, humidity, etc.) into account and/or the use of special concrete with additives can reduce the curing period.

The adjustment feet are designed to support the complete tower.

Anchors shall not be post tensioned before the grout and concrete have reached sufficient compression strength. Vestas will complete post tension.

Required compression strengths and post-tension sequences are specified on the anchor cage approval drawing and in the installation manuals.

The gap between flange and concrete is sealed with a water tight sealant supplied by Vestas.

5.5 Post Tensioning

Vestas performs post tensioning of the anchors according to the specification on the anchor cage approval drawing.


V80-V90-V100-V112 Enclosure 1



6 Enclosure 1

1. Geotechnical Project Report (Example)

1.1 Construction Site

Location: __________________________________________________________

Engineer: __________________________________________________________

Contractor: __________________________________________________________

1.2 Description of Soil

The required design bearing capacity of the soil is _________ KN/m.

Conclusions from the Geotechnical Report no ____________________

Classification of soil: _________________________________________________________

Bearing capacity: _________________________________________________________

Friction angle: ______________

Cohesion: ______________ KN/m

Density: ______________ kN/m3

Ground water level: ______________ m below terrain

1.3 Description of Construction

The actual construction is a circular, concrete foundation plate designed for direct bearing.

The loads from the tower are transferred to the sub soil through post tension anchors, high strength grout and reinforced concrete.

Concrete is classified according to the cylindrical 150 x 300 mm compression strength.

Reinforcement is classified according to the yield strength and the ductility class.


V80-V90-V100-V112 Enclosure 1



1.4 Parameters to be verified by their actual values:

Classification of concrete: C_______________(pedestal)

Classification of concrete: C_______________(main plate)

Min. density of concrete: _______________ kg/m3

Certification of concrete: _______________

Classification of steel: S_________Class ______

Certification of steel: _______________

Diameter of foundation: D = __________ m Tolerance: - 0.00 m

Diameter of pedestal: D = __________ m Tolerance: - 0.00 m

Height at anchor cage H = __________ m Tolerance: - 0.00 m

Height at outer edge: H = __________ m Tolerance: - 0.00 m

Height of pedestal: H = __________ m Tolerance: - 0.00 m

(Only minus tolerances are relevant to verify min. weight of foundation)

Levelling of anchor ________ mm Tolerance < 4.0 mm.

1.5 Release for tower installation

The foundation has sufficient compression strength and is released for erection of tower by:

_______________ _________________________

Date Signature

Before the turbine is taken into production Vestas shall perform post tension of the foundation anchors.

1.6 Enclosures

1 Preconditions2 Parties Involved2.1 Vestas Wind Systems A/S2.2 Required Documentation2.3 The Engineer2.4 The Contractor

3 The Geotechnical Project Report4 Inspection5 General Guideline5.1 Excavation5.2 Reinforcement5.2.1 Installation of Anchor CageAnchor Cage Placed at Centre of Foundation on Adjustment Feet

5.2.2 Installation of Lower Radial ReinforcementEvery 4th Main Radial Reinforcement Passing the Anchors InstalledAll Main Radial Reinforcements InstalledDetail of Centre Part Showing All Bars Installed:

5.2.3 Installation of Lower Concentric Reinforcement:Concentric Rings InstalledDetail of Centre Part

5.2.4 Installation of Vertical Reinforcement:Shear Locks InstalledDetail at Centre, Locks Equally Distributed

5.2.5 Installation of Upper Radial Reinforcement:Concentric Rings to Support Radial BarsUpper Radial Bars Passing Anchors InstalledAll Upper Radial Reinforcement Placed on Shear Locks

5.2.6 Installation of Upper Concentric Reinforcement:Upper Concentric Reinforcement in PlaceEdge Bars Installed at Outer Edge

5.2.7 Hooking of Shear Locks in Upper Layer5.2.8 Installation of Reinforcement in Pedestal:Reinforcement of Pedestal

5.3 Concrete5.4 Grouting and Installation of TowerSituation before Lifting Off Template and Form WorkSituation after Lifting of Template and Removal of Form WorkGroutingSituation after Installation of Adjustment FeetGrout materials:Treatment after GroutingSealing materials:Tower installation:

5.5 Post Tensioning

6 Enclosure 1

annex 2.8 - 0005-8491_description of standard gravity anchor foundation

Documents

document date

document version

installation of anchor

v100v112 history

randers sv denmark

t05 general description

proprietary rights

responsible parties