Bionic Root Foundation for Onshore Wind Turbine Generators

Abstract

Embodiments of the present foundation for wind turbine generators comprise four structural members: one short central hollow pier, one continued grade beam, several solid piles built below the continued grade beam, and several arm grade beams linking the structural members. All structural members are constructed of cast-in-place concrete reinforced with rebars, and all connections are fixed and rigid. The short central hollow pier positions in the center of the system, functions as a hub to take the loadings and continuously to transfer and distribute the loadings further to the continued grade beam, arranged circumferentially in outer periphery of the system, and deeper to the solid piles, through the arm grade beams, which have a varied section and embed into ground in the far end. The present foundation utilizes the ground to shape and form the structural members, no formworks, backfilling and compaction is needed.

Claims

1. The present foundation comprises the following structural members: a short central hollow pier 1, a continued grade beam 2, several arm grade beams 3 and several solid piles 4 arranged circumferentially in outer periphery of the present foundation. The short central hollow pier 1 positions in the center of the foundation, the continued grade beam 2 positions in outer periphery of the system, solid piles 4 are built below the continued grade beam 2, and arm grade beams 3 connect the central hollow pier 1 to continued grade beam 2 and solid piles 4. Solid piles 4 and the arm grade beams 3 have the same quantity.

2. The outer and inner diameters of the central hollow pier 1, typically matching the configuration of superstructure, are larger than the diameter of solid piles 4 arranged circumferentially in outer periphery.

3. The inner and outer diameters of the continued grade beam 2 are much larger than the diameters of the short central hollow pier 1 to enable the present foundation functions as invented.

4. The short central hollow pier 1 in the present foundation is a short hollow structure in round or regular polygonal shape, solid piles 4 are solid structure in round or square shape, and the continued grade beam 2 and arm grade beam 3 are solid structures in rectangular or square shape.

5. The arm grade beams 3 extend from the wall of the short central hollow pier 1 to continued grade beam 2 as well as solid piles 4 and have a varied section with the height increasing from connection to solid piles 4 to the central hollow pier 1.

6. Diameter of solid piles 4 may not necessarily equals the width of the continued grade beam 2.

7. All structural members of the present foundation are constructed of cast-in-place concrete reinforced with rebars, and all connections for the structural members are fixed and rigid.

8. The short central hollow pier 1 works as a hub to take the loadings from superstructures by utilizing the anchoring system embedded within the wall concrete, and transfers and distributes the loadings to continued grade beam 2 arranged in further location as well as solid piles 4 embedded in deep ground through the arm grade beams 3.

9. The quantity and dimensions for the structural members, as well as the shapes, sizes and grades of the reinforcements, of the present foundation may vary in accordance with the site and loading conditions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a 3-D illustration of the invented foundation. The foundation is completed constructed in accordance with the preferred embodiments of the present invention. The surrounding soil and rock masses are omitted in the sketch so the forms and features comprised in the present foundation can be seen clearly, and the invented foundation is skewed in order to show the foundation embodiment clearly. Four structural members, short central hollow pier, continued grade beam, solid piles and arm grade beams are clearly shown in FIG. 1. Reinforcements for the structural members are also partially shown in FIG. 1.

[0039] FIG. 2 is a 3-D illustration for the short central hollow pier and reinforcement arrangements. The short central hollow pier functions as a hub of taking, transferring and distributing loadings to other forms and features comprised in the present foundation. Concrete, anchoring system including base flange, embedment ring, washers and nuts as well as reinforcements are also shown in FIG. 2.

[0040] FIG. 3 is a top plan view of the invented foundation. Four major structural members and their geometry relationship are illustrated in FIG. 3.

[0041] FIG. 4 is a vertical sectional view of the invented foundation, illustrating the arrangements for the four major structural members constructed in accordance with preferred embodiments. Since the length of the arm grade beams and solid piles, break symbols are used, and only part of the labeling numerals are shown in FIG. 4.

[0042] FIG. 5 is a vertical sectional view for the short central hollow pier, reinforcements and anchoring system. The concrete shape, the anchoring system and reinforcements arranged in accordance with the invented foundation during construction are illustrated.

[0043] FIG. 6 shows the detail for vertical sectional view of anchor bolts and the base flange. Anchor bolts, PVC wrap, base flange as well as washers and nuts assembled in accordance with the present foundation are illustrated.

[0044] FIG. 7 shows the detail for vertical sectional view of anchor bolts and embedment ring. Anchor bolts, PVC wrap, Embedment Ring as well as washers and nuts assembled in accordance with the present foundation are illustrated.

[0045] FIG. 8 shows the detail for cross-sectional view of continued grade beam and reinforcements. The reinforcements arrangements during construction in accordance with the present foundation are mainly illustrated.

[0046] FIG. 9 shows the details for 3-D illustration and sectional view for connection of arm grade beam to central hollow pier with reinforcements. How these structural members connect to each other and how to arrange the reinforcements during construction in accordance with the present foundation are mainly illustrated.

[0047] FIG. 10 shows the details for 3-D illustration and sectional view for connection of continued grade beam, solid pile and arm grade beam with reinforcements. How these structural members connect to each other and how to arrange the reinforcements during construction in accordance with the present foundation are mainly illustrated.

[0048] FIG. 11 is a 3-D illustration and sectional view of solid piles with reinforcements, illustrating the reinforcement arrangements during construction in accordance with the present foundation.

[0049] Designations for numerals in FIGS. 4,5, 6,7,8,9,10 and 11 are as follows:

[0050] 1Short Central Hollow Pier; 2Continued Grade Beam; 3Arm Grade Beams; 4Solid Piles in Outer Periphery of the System; 5Tower Flange; 6Grouting Trough; 7Anchor Bolts; 8PVC Wrap; 9Embedment Ring; 10Washers; 11Nuts; 12Concrete; 13Longitudinal reinforcements of Central Hollow Pier; 14Hooping of Central Hollow Pier; 15Longitudinal Reinforcements of Arm Grade Beams; 16Hooping of Arm Grade Beams; 17Longitudinal Reinforcements of Solid Piles; 18Hooping of Continued Grade Beam; 19Longitudinal Reinforcements of Continued Grade Beam; 20Preserved Holes in Flange; 21Predrilled Holes in Embedment Rings; 22Hooping of Solid Piles

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Referring specifically to the drawings, FIG. 1 and FIG. 2 are 3-D illustration for the present foundation, and FIG. 3 designates the top plan view of the invention. FIGS. 4 to 11 show the details for the foundation. FIG. 4 designates a vertical sectional view of the foundation, the numerals in FIG. 4 show that the foundation comprises four major structural members, central hollow pier 1, continued grade beam 2, arm grade beams 3 and solid piles 4. The configuration of the central hollow pier 1 matches the tower base flange 5, which is also shown on FIG. 1. The inner and outer diameters of the central hollow pier 1 typically range from 10 feet to 18 feet for wind turbine generator foundation to accommodate the base flange 5 which sits in the grouting trough 6 shown in FIG. 5. The grouting trough 6 is constructed on the top of the central hollow pier 1. The depth of the grouting trough 6 typically ranges 2 to 5 inches, and its width and diameters are wider than the tower base flange 5. The length of central hollow pier 1 is typically set as 6 feet and functions as a hub to take the loadings as well as to transfer and distribute the loadings further and deeper to continued grade beam 2 and solid piles 4 built below the continued grade beam 2 through arm grade beams 3.

[0052] As shown in FIG. 5 and FIG. 9, the central hollow pier 1 contains a series of reinforcements, including 13 designating the longitudinal reinforcements of central hollow pier 1 and 14 designating the hooping of central hollow pier 1. Arm grade beams 3 connect to the central hollow pier 1, thus the longitudinal reinforcements designated by numeral 15 for arm grade beams 3 are extended into the central hollow pier 1. The longitudinal reinforcements 13 are curved inwardly at the top and the bottom of the central hollow pier 1 to provide more pull-out resistance capacity for the anchoring system, whereas the hooping for central hollow pier 1 designated by numeral 14 uses curved steel bars, arranged with 4 or 5 layers and placed next to the longitudinal reinforcements 13. The anchoring system is also shown in FIG. 5, while more details are shown in FIGS. 6 and 7. The anchoring system comprises of tower base flange 5, embedment ring 9, anchor bolts 7, PVC wrap 8, washers 10, and nuts 11. The tower base flange 5 positions on the top of grouting trough 6, the embedment ring 9 is placed on the bottom of the central hollow pier 1 and embedded in concrete 12. The anchor bolts 7 are assembled through and within the reinforcements, and the PVC wrap 8 is used to separate the anchor bolts 7 from concrete 12. Washers 10 and nuts 11 are placed above the base flange 5 and below the embedment ring 9, respectively. Anchor bolt 7 extrudes through the preserved holes 20 in base flange 5, and predrilled holes 21 in embedment ring 9. Post-tension on anchor bolts 7 can be applied by fastening the nuts 11 after concrete 12 hardens and reaches a designed strength.

[0053] FIG. 8 and FIG. 10 show the reinforcements in continued grade beam 2, details of connection for continued grade beam 2, solid piles 4 and arm grade beams 3. The width of the continued grade beam 2 usually uses the same as the diameter of solid piles 4, a diameter of 3 feet is typically used but sometimes varies with the subsurface conditions and the loadings distributed to the solid piles 3. The height of the continued grade beam 2 is determined by the distributed loadings too, but typically 4 feet. The length of arm grade beams 3 typically adopts 15 to 25 feet. With this length, the dimensions of the solid piles 4, including its diameter and the embedment depth, which typically uses 50 to 70 feet below the continued grade beam 2, can be optimized. The top of the arm grade beams 3 levels with ground surface at the end with approximately 3 feet offset from the wall of the central hollow pier 1, and then slopes down to embed in ground and matches the top of the continued grade beam 2. The height of arm grade beams 3 at connection with central hollow pier 1 is approximately 5 feet shown in FIG. 4 and FIG. 5, principally it equals the length of the central hollow pier 1 reduced by the stickup and the part for embedment ring 9. The width typically uses 3 to 4 feet to fully utilize the mechanical properties of the reinforced concrete beam to resist the moment transferred and distributed from the central hollow pier 1. Numerals 18 and 19 designate hooping and longitudinal reinforcements for continued grade beam 2, respectively. Reinforcements 19 are curved, arranged circumferentially within the continued grade beam 2 in two layers, while hooping 18 hoop the reinforcements 19 with a spacing say 3 feet. Numeral 15 designates longitudinal reinforcements for arm grade beams 3, and the longitudinal reinforcements 15 extend into the connections of continued grade beam 2, arm grade beams 3 and solid piles 4, as well as the central hollow pier 1. Two layers are typically used for reinforcements 15, each layer contains 3 steel bars. Numeral 16 designates the hooping for arm grade beams 3. Similarly the hooping 16 hoop the reinforcements 15 with a spacing say 3 feet.

[0054] FIG. 11 shows the solid piles 4 and the reinforcements. Numeral 17 designates the longitudinal reinforcements for piles 4. Reinforcements 17 typically use 8 vertical steel bars, arranged circumferentially along the perimeter of the solid piles 3. Reinforcements 17 may be staggered to save the steel, and extend into the connections with continued grade beam 2 and arm grade beams 3. Reinforcements 17 are curved inwardly at the top. Hooping 22 hoops the vertical reinforcements 17 with a spacing 3 feet, sometimes spiral-like reinforcements can be used for hooping 22.

[0055] The following construction steps are for illustrative purpose only, and may be adjusted in accordance with project conditions: [0056] 1. Level the construction site. Delineate the locations for the above mentioned four major structural members 1, 2, 3 and 4. [0057] 2. Fabricate reinforcement for central hollow pier 1, continued grade beam 2, solid piles 4 and arm grade beams 3 per design drawings. [0058] 3. Assembled embedment ring 9 and anchor bolts 7. A template ring may be needed to ensure the anchor bolts 7 positioning accurate and vertical. [0059] 4. It is ideal to assemble the embedment ring 9 and anchor bolts 7 within reinforcements for short central hollow pier 1 prior to place reinforcements for central hollow pier 1 to the trench described below. [0060] 5. Drill the holes for solid piles 4 to the designed depth. Bentonite slurry may be needed during hole drilling to prevent caving when subsurface geomaterial are sands. [0061] 6. Excavate trenches for the central hollow pier 1, continued grade beam 2 and arm grade beams 3 using backhoe or other trenching equipment. Bentonite slurry may be needed during trenching to prevent caving when subsurface geomaterial are sands. [0062] 7. Set up auxiliary equipment such as pullies/cranes. The equipment will be used to stabilize the embedment ring 9 and anchor bolts 7 in central hollow pier 1, and will be used to place reinforcements to the excavated trenches. [0063] 8. Place reinforcements fabricated per design drawing to the drilled holes for solid piles 4. Prior to reinforcement placement, proceed with QA/QC checking for deposits at the bottom of the holes per industry standards. [0064] 9. Holes may need to use recycled tap water to replace the slurry to ensure no mud bond to the reinforcement if slurry is used to prevent caving per industry standards. [0065] 10. Using the auxiliary equipment such as pullies/cranes to place reinforcements in the trench for continued grade beam 2, arm grade beams 3, short central hollow pier 1. [0066] 11. Place embedment ring 9 and anchor bolts 7 within the reinforcements for central hollow pier 1. If the embedment ring 9 and anchor bolts 7 are assembled within reinforcements for short central hollow pier 1, skip this step. [0067] 12. Use recycling water to bring the slurry out if slurry is used during trenching and ensure reinforcements clean from slurry per industry standards in relation to pier/pile/wall foundation. [0068] 13. Using tremie pipe to place concrete 12 from the bottom of the solid piles 4. [0069] 14. Place concrete 12 to the trenches for continued grade beam 2 and arm grade beams 3, when the concrete 12 is placed to the level matches the bottoms of continued grade beam 2 and arm grade beams 3. [0070] 15. Step 14 can be proceeded one by one, not necessary to proceed together, but the time for concrete placement shall comply with industry standards to avoid cold joints in concrete. [0071] 16. Continue to place concrete 12, to the trench for central hollow pier 1. Prior to placement for concrete 12, ensure all reinforcements, embedment ring 9 and anchor bolts 7, as well as apparatus and/or preserved conduits for electrical cables/wires, are in right position. [0072] 17. Place two concentric steel cases to the concrete surface, which to be used to shape the foundation stickup in central hollow pier 1. The outer steel case should have a door which is used to pass though the possible steel strings being used to hang the template ring and anchor bolts 7, as well as reinforcements for short central hollow pier 1. [0073] 18. Place concrete to the two concentric steel cases to form stickup for foundation. [0074] 19. Restore on-site soils above the structural members per design; move the steel cases out and clean them to prepare for using with the next foundation. [0075] 20. Cure placed concrete 12 by keeping the restored fill moistured or using other measures to cure the poured concrete 12. [0076] 21. When concrete at the top of the pier 1 are hardened, install the flange of superstructure to the grout trough 6, level the base flange 5 and ensure the anchor bolts 7 vertical. [0077] 22. Grout the grout trough 6. [0078] 23. When foundation concrete and the grout reach the designed strength, apply tensions to anchor bolts 7 by fastening the nuts 11. [0079] 24. Move the auxiliary equipment to the next foundation and repeat the steps for next foundation.

[0080] The above description uses examples to disclose the invention, and to enable any person skilled in the art to practice the invention, including making and using any forms and features and performing any incorporated methods. All the dimensions for the four major structural members and the reinforcement shape, size and grade shall be detailed in design phase. The construction steps described above are duly for further clarification for construction of the invented foundation, the construction steps may be adjusted and optimized per project conditions. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.