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• Turbine Foundation Product Design Guide

Turbine Foundation Product Design Guide

This section provides you with operation suggestions of turbine foundation design in Greenwich and related references. Read this section to get acquainted with the design procedures and regulations.

Greenwich turbine foundation product V2.0 is a tool to design the turbine foundation scheme based on conditions as turbine load and geological material and optimize LCOE. Currently, the optimization and design of natural subgrade and pile foundation are supported.

Design References

This guide is formulated based on the following standards and regulations:

• Wind farm engineering level classification and design security criteria FD002-2007
• Design regulations on subgrade and foundation for WTGS of wind power station FD003-2007
• Code for building structure load GB50009-2012
• Uniform standard for design of building structure reliability GB50068-2001
• Code for design of concrete structures GB50010-2010
• Code for design of building foundation GB50007-2011
• Code for design of anti-seismic buildings GB50011-2010
• Code for design of high-rise structures GB50135-2006
• Code for design of chimney GB50051 - 2013
• Regulation for building steel structure welding technology JGJ81-2002
• Code for design of steel structure GB50017-2003
• Code for design of dynamic machine foundation GB50040-96
• Technical Code for Building Pile Foundations JGJ94-2008

Operation Procedure and Related Suggestions

This section introduces the main operations in turbine foundation design and related parameter setup guidelines.

Basic Operation

For main operation steps in Greenwich turbine foundation product V2.0, refer to the user guide in Greenwich documents.

Load Data

• Earthquake load is excluded in the standard foundation load data. If it is impossible to get the precise earthquake load, set the default value of frequently and rarely occurred earthquake in the template as 1. In the Greenwich user interface, input seismic oscillation parameters of the project and select base shear method to calculate the earthquake load.
• For fatigue load, input Inverse SN Slope as load data for 3-12.
• It is not needed to input Mxy for average load under normal working condition at rated wind speed.
• Adopt default values for Markov matrix.
• Under normal condition and extreme condition, maximum bending moment Mxy is located at the second row from the bottom. If the maximum Mxy is not at the second row from the bottom, copy the row with the maximum values to that row manually.

Geological Data

Geological material may be obtained from geological exploration report, the third chapter in feasibility study report, or other ways. During the feasibility or bidding phase, when it is not possible to obtain geological exploration material, refer to the counterpart of adjacent projects or material from big data library.

Table 1: Source and Directory of Main Geological Parameters

Parameter	Source	Note
Layer No.	Bare log and geological layer description
Earth type	Bare log, geological parameter table, and geological layer description
Earthwork/stonework	Judged by earth type
Layer thickness	Bare log, geological parameter table, and geological layer description
Volume weight	Rock soil physical mechanics parameter table, or check table 3-1-24 and 3-1-43 in Project Geological Manual
Characteristic value of bearing capacity	Rock soil physical mechanics parameter table, or check the third section in Chapter 5 of Project Geological Manual
Compression/deformation modulus	Rock soil physical mechanics parameter table, or check table 3-1-24 and 3-1-43 in Project Geological Manual and table C.0.1 in Standard for engineering classification of rock mass	Compression modulus is not equal to 0 theoretically
Internal friction angle	Rock soil physical mechanics parameter table, or check table 3-1-24 in Project Geological Manual and table D.0.1 in Standard for engineering classification of rock mass
Standard value of ultimate lateral friction	Pile foundation design parameter table, or check table 5.3.5-1 in Technical Code for Building Pile Foundations	It is mandatory for pile foundation. For expanded foundation, adopt the default value 0.
Ultimate-end resistance standard value	Pile foundation design parameter table, or check table 5.3.5-2 in Technical Code for Building Pile Foundations	It is mandatory for pile foundation. For spread foundation, adopt the default value 0.
Tension coefficient	Pile foundation design parameter table, or check table 5.4.6-2 in Technical Code for Building Pile Foundations	It is mandatory for pile foundation. For spread foundation, adopt the default value 0.
Proportional coefficient of horizontal resistance	Pile foundation design parameter table, or check table 5.7.5 in Technical Code for Building Pile Foundations	It is mandatory for pile foundation. For spread foundation, adopt the default value 0. Note: The unit is KN/m4.
Groundwater depth	Geological exploration report or the hydrology section in feasibility study report	Depth in mountain region is generally deep, such as -10m, and shallow in plain region, such as -3m.
High level of groundwater	Geological exploration report or the hydrological geology section in feasibility study report	Depth in mountain region is generally deep, such as -5m, and shallow in plain region, such as 0m.
Earthquake parameter	Geological exploration report or the regional geology section in feasibility study report, or check Seismic ground motion parameters zonation map of China	It is only needed in earthquake load calculation by base shear method.

Check related specification documents for foundation design through the following link:

https://greenwich.ai/%E8%A7%84%E8%8C%83%E6%A0%87%E5%87%86/%E8%A7%84%E8%8C%83%E6%A0%87%E5%87%86%E5%BA%93.

Foundation Cost and Grouping

• Under general conditions, adopt the default values of cost. If necessary, adjust the unit price according to the local price level of the project. For rock subgrade, increase the price of earth-rock excavation by an appropriate scale.
• Select infield landform with reference to materials as satellite map of wind farm, geology section in feasibility study report, geological exploration report, etc.
• Select environment class with reference to item 3.5.2 in Code for Design of Concrete Structures GB50010-2010. For turbine foundation onshore, environment class is generally Class II b.

Foundation Parameter Setting (FDGroup Page)

• Calculation type

  Foundation optimization: Through automatic iteration, optimization, and verification, Greenwich output the most economical and reasonable foundation scheme based on geological and load data, boundary parameter and optimizing region set by user.

  Foundation check: If you have a validated foundation scheme, select Base Checking to define foundation size and file foundation placement parameters. Greenwich calculates and outputs various verification results for the specific scheme.

• Connection type

  Generally, select anchor as the connection between turbine foundation and tower (for Envision self-built projects). If wind farm owner has specific need, select the connection type he need. The material specifications of base ring and anchor should be defined according to turbine type parameters as power production, hub height, maximum bending moment, etc.

• Platform type

  Only extended platform is supported in Greenwich foundation design. The lattice platform is not supported.

• Subgrade type

  The design and optimization of natural subgrade (extended foundation) and pile foundation are supported in Greenwich foundation design. Pile foundation consists of precast pile and caisson pile. Select subgrade type according to the following conditions:

  • Select subgrade type recommended by existing feasibility study report or geological exploration unit.
  • Select extended foundation when the load characteristic value is beyond 300kPa at the depth of 5m or when there is bed rock.
  • For turbines located around water area as pond or river or for foundation located on relatively thick soft soil layer (such as mucky soil) at the depth of 10m, select pile foundation.
  • Select extended foundation when the load characteristic value is below 200kPa at the depth of 5m and hub height is above 100m.
  • Under common conditions, pile foundation is recommended for plain region and extended foundation for mountainous region.
  • Pile type selection: select precast pile in most cases When the powder sand layer is thick or standard penetration test blow count of clay is larger than 20 and that of sand is larger than 40 at the depth of 20m of subgrade, caisson pile is recommended because of difficulties in pile sinking.

• Pile foundation parameter

  • Precast pile: Select tubular pile with the external diameter of 500 or 600 mm in common situations. The most commonly used model is PHC-II600B110.
  • Caisson pile: The pile diameter is 600 - 1000 mm in common situations. The most commonly used size is 800 mm.
  • Pile length: Optimize the length of caisson pile within the default range. The construction of precast pile might encounter pile sinking. It is recommended to optimize the upper and lower limit of pile length according to the bearing layer buried depth or pile length specified in the geological exploration material.

• Foundation size

  • For foundation size, adopt the default values of upper and lower limit in common situations.
  • Adjust lower limit of the bottom board edge height according to the owner’s regulation when requested.
  • If some margin is needed in the foundation design, adjust the bottom board edge height as 0.9 m, 0.95 m, or 1.0 m according to the actual situation.
  • If there is rock subgrade, reduce the upper limit of foundation buried depth in a proper proportion to minimize the excavation difficulty in construction.

• Other commonly-used parameters

  • Adopt the default values for commonly-used parameters in common situations. For some of them, edit the values according to actual situation.
  • If some margin is needed in the foundation design, for extended foundation, set the upper limit of zero stress zone at foundation bottom under frequent earthquake condition as 0%.
  • If some margin is needed in the foundation design, the upper limit of ratio of bottom board width and height should be set as 2.5.
  • The value of slope excavation ratio should be set according to that recommended in geological exploration material or Table 6.7.2 in Code for Design of Building Foundation. Generally, adopt the default value 1:0.75 (1.33333).
  • If it is requested to design a foundation radically, for extended foundation, excavate the bottom board to reduce the concrete construction quantity. Set the bottom board hollow radius as 1.7 m.
  • Generally, select line outer type as tower line outer.

Foundation Output Result

• Foundation calculation sheet

  After the calculation is completed, export the calculation sheet to view the various verification results of foundation design.

• Foundation design report

  After the calculation is completed, export the design report to view the foundation scheme overview, main project quantities, and main verification results.

• Foundation PBOM and budget estimation

  After the calculation is completed, check the PBOM of each turbine foundation in the PBOM page.

  For the regenerated foundation design scheme, click the Generate button in the PBOM page to show new PBOM details.

  In the feasibility study phase, expand the land area for turbine foundation in a proper proportion. Adjust the land area for turbine foundation under the forest and land levy structure according to Electric Power Project Construction Land Indexes (Wind Power Farms).

  Figure: Single WTG Group Land Indexes

• Foundation CAD drawings

  After the calculation is completed, export and view the foundation CAD drawings.