A gravity type prestressed anchor bolt fan foundation and a preparation method thereof and the fan foundation

Abstract

The application belongs to the field of mixed tower foundation, and provides a gravity type prestressed anchor bolt fan foundation, a preparation method thereof and the fan foundation. The preparation method of the gravity type prestressed anchor bolt fan foundation comprises the following steps: pouring a construction cushion; installing a foundation prestressed anchor bolt cage assembly and binding a steel bar of the fan foundation on the poured cushion; building a prefabricated concrete formwork with a cavity in a convex shape on a bottom plane of the fan foundation; pouring the fan foundation in an integral continuity; after the pouring of the fan foundation is completed and moisture curing is performed, performing secondary grouting and prestressed tensioning treatment on the fan foundation; and finally, removing the formwork to form the gravity type prestressed anchor bolt fan foundation.

Description

Technical Field

[0001] This invention belongs to the field of anchor bolt fan foundations, and particularly relates to a gravity-type prestressed anchor bolt fan foundation, its preparation method, and the fan foundation itself. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] The future development trend of wind turbine units is characterized by large capacity, large rotors, and high hubs. Therefore, the design and safety assessment of the support system structure of wind turbine generator units, which consists of towers and foundations, are becoming increasingly important. The frequency of accidents in traditional ring-type wind turbine foundations is increasing. The stress level in the ring beam of the ring-type wind turbine foundation is high, making the concrete prone to cracking and easily generating cracks under external cyclic loads. In addition, the foundation ring has few openings, making it difficult to thread reinforcement, and the integration of the foundation ring and the foundation is poor.

[0004] In the reinforced concrete foundation of prestressed anchored wind turbines, the connection system composed of prestressed anchors and upper and lower anchor plates can transfer the wind turbine load to the entire foundation column area, ensuring structural continuity, no abrupt changes in stiffness, and good overall foundation integrity. Due to the presence of prestress, the concrete in the core area of ​​the foundation column is under compression under external loads, preventing cracking and improving durability. As the single-unit capacity of wind turbines increases, the load transferred to the top of the foundation also increases, leading to a larger workload for wind turbine foundations, especially gravity foundations. While the traditional prestressed circular gravity abutment design, which runs through the entire foundation, has a relatively simple structural form, the longer the anchors, the more material is consumed, the greater the probability of anchor damage, and the larger the consumption of reinforced concrete. Furthermore, the bottom of the wind turbine foundation slab is subjected to significant tensile stress, making it prone to cracking. Summary of the Invention

[0005] To address the technical problems mentioned above, this invention provides a method for preparing a gravity-type prestressed anchor bolt wind turbine foundation and the foundation itself. By applying prestress to the radial reinforcement of the bottom plate of the ring foundation, the foundation's overturning resistance and durability are improved, enabling more efficient synergistic stress distribution between the reinforcement and concrete, optimizing the foundation's engineering volume, significantly reducing the overall cost of the foundation, and simultaneously fulfilling the need for replacing prestressed anchor bolts.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for preparing a gravity-type prestressed anchor bolt fan foundation.

[0008] A method for preparing a gravity-type prestressed anchor bolt fan foundation, comprising:

[0009] Pouring the foundation layer;

[0010] Install the foundation prestressed anchor cage assembly and tie the steel bars for the wind turbine foundation on the poured foundation layer;

[0011] Construct a precast concrete formwork with a convex-shaped cavity on the bottom plane of the wind turbine foundation;

[0012] The fan foundation was constructed using a continuous, integral pouring method.

[0013] After the wind turbine foundation is poured and moisturized, secondary grouting and prestressing treatment are carried out on the wind turbine foundation. Finally, the formwork is removed to form a gravity-type prestressed anchor bolt wind turbine foundation.

[0014] As one implementation method, the prestressed foundation anchor cage assembly is checked and installed according to the drawings of the prestressed foundation anchor cage assembly.

[0015] As one implementation method, the steel bars of the wind turbine foundation are tied from bottom to top and from the inside to the outside.

[0016] As one implementation method, in the process of tying the reinforcing bars of the wind turbine foundation, the radial ordinary reinforcing bars at the bottom of the foundation slab are tied first, followed by the circumferential reinforcing bars at the bottom of the foundation slab. Corrugated pipes are then placed radially according to the construction drawings for threading steel strands, and spiral reinforcement and anchor plates are installed.

[0017] As one implementation method, steel pipe columns are used for formwork support during the construction of precast concrete formwork, ensuring no grout leakage at the formwork joints.

[0018] As one implementation method, in the process of using continuous pouring for the wind turbine foundation, pouring begins from one end of the bottom layer. Before the lower layer of concrete has set, the second layer is poured, and so on, layer by layer, until the pouring is completed.

[0019] In one implementation method, when the concrete strength reaches the design strength, prestressed steel strands are threaded through, and working anchors, working clamps, and limiting plates are inserted. Then, jacks are used to perform prestressing tensioning. Once the specified tension is reached, the tensioning equipment is removed in sequence.

[0020] As one implementation method, the secondary grouting of the wind turbine foundation is carried out by positive air grouting method for duct grouting.

[0021] As one implementation method, the load-bearing side formwork can only be removed when the concrete reaches a predetermined proportion of the design strength.

[0022] A second aspect of the present invention provides a gravity-type prestressed anchor bolt fan foundation.

[0023] A gravity-type prestressed anchor bolt fan foundation is prepared using the preparation method for gravity-type prestressed anchor bolt fan foundations described above.

[0024] The beneficial effects of this invention are:

[0025] This invention offers advantages such as low engineering workload and replaceable anchors while ensuring structural safety. Firstly, by replacing the foundation ring with high-strength prestressed anchors to connect the tower and foundation, it solves the shortcomings of abrupt changes in strength and stiffness, and easy cracking, inherent in ring foundations. Secondly, by modifying the traditional prestressed anchor foundation from a circular extended foundation to a ring foundation, it improves the overall overturning resistance of the foundation, while reducing concrete usage, shortening anchor length, and saving project investment costs. Furthermore, the bottom cavity provides operational space for replacing prestressed anchors.

[0026] This invention, through analysis of mechanical properties and practical experience, reveals that the bottom plate of the wind turbine foundation is subject to significant tensile stress and is prone to cracking. Therefore, by applying prestress to the radial reinforcement of the bottom plate of the ring foundation, more efficient synergistic stress distribution between the reinforcement and concrete is achieved, improving the strength and crack resistance of the wind turbine foundation itself, thereby optimizing the amount of foundation reinforcement. Given the current trend of wind turbine units towards large capacity, large impellers, and high hubs, the novel prestressed anchor bolt foundation provided by this invention has a certain competitive advantage in the future market for ultra-large wind turbine units.

[0027] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 The traditional basic front view;

[0030] Figure 2 A front view of a gravity-type prestressed anchor bolt fan foundation provided in an embodiment of the present invention;

[0031] Figure 3 The shape of the cavity in the gravity-type prestressed anchor bolt fan foundation provided in the embodiments of the present invention;

[0032] Figure 4 The reinforcement diagrams for the prestressed steel bars and ordinary radial steel bars on the foundation bottom surface are provided for embodiments of the present invention.

[0033] Figure 5 A diagram of prestressed anchors provided for an embodiment of the present invention.

[0034] Figure 6 is a detailed construction drawing of radial prestressed steel bars at the bottom of a foundation base slab provided by an embodiment of the present invention.

[0035] In the figure: 1, fan cylinder wall; 2, anchor bolt; 3, high-strength cement-based grouting material; 4, cavity; 5, vertical steel bars of foundation base slab; 6, circumferential steel bars at the bottom of foundation base slab; 7, radial steel bars at the top of foundation base slab; 8, circumferential steel bars at the top of foundation base slab; 9, radial prestressed steel bars at the bottom of foundation base slab; 10, common radial steel bars at the bottom of foundation base slab; 11, radial steel bars in core area; 12, vertical steel bars in core area; 13, circumferential steel bars in core area; 14, lower anchor plate; 15, embedded part; 16, upper anchor plate; 17, corrugated pipe; 18, anchorage; 19, spiral reinforcement; 20, grouting pipeline. Detailed Description of Embodiments

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] It should be noted that all the following detailed descriptions are exemplary and intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the technical field to which the present invention pertains.

[0038] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] Compared with the gravity prestressed anchor bolt wind turbine foundation of the present invention, such as Figure 1 the conventional prestressed anchor bolt wind turbine foundation shown in the drawings, the gravity prestressed anchor bolt wind turbine foundation of the present invention has a cavity with a cross-section similar to a Chinese character "convex".

[0040] as Figure 2 shown, the embodiment provides a preparation method of a gravity prestressed anchor bolt wind turbine foundation, comprising:

[0041] Step 1: pouring construction cushion course.

[0042] The foundation layer is poured in two stages. During the first pour, the embedded parts 15 and anchor bolt supports are installed according to the prestressed anchor bolt foundation drawing. The foundation layer uses C20 sulfate-resistant concrete. The concrete is transported by mixer truck, pumped into the formwork, and poured using a chute. The surface is leveled manually. After pouring, the surface is finished, but care should be taken not to smooth it; a flatness of no more than 2mm is sufficient. Water is sprinkled immediately after pouring, and the surface is kept warm and cured with plastic film.

[0043] Step 2: Install the foundation prestressed anchor cage assembly and tie the reinforcing steel bars for the wind turbine foundation on the poured foundation layer.

[0044] Specifically, the installation of the prestressed foundation anchor cage assembly is verified according to the drawings. This includes checking the quantity, dimensions, and positions of the connecting plates, connecting bolts, connecting nuts, support components, and embedded parts 15 of the lower anchor plate 14.

[0045] Using a suitable crane, lift the lower anchor plate 14 and slowly move it directly above the embedded part 15. First, insert the support bolts of the lower anchor plate 14 into the corresponding bolt holes on the lower anchor plate 14. Place a nut on the top and bottom of the lower anchor plate 14, and add a washer to the nut below the lower anchor plate 14. The support nuts should be screwed to the same height. After aligning the support bolts with the embedded part 15, place the lower anchor plate 14 on the embedded part 15 using the crane.

[0046] The installation steps for the upper anchor plate 16 are the same as those for the lower anchor plate.

[0047] Use a crane to lift the upper anchor plate 16 to a certain height and slowly move it directly above the lower anchor plate 14, ensuring the marked lines on the upper and lower anchor plates are aligned. First, evenly insert the upper end of the positioning anchor bolt (with nylon nuts installed) into the anchor bolt holes of the upper anchor plate. Then, insert the lower end of the positioning anchor bolt (with thin nuts installed) into the corresponding anchor bolt holes of the lower anchor plate 14. After the thin nuts are tightly fitted to the lower anchor plate, place a washer under the lower anchor plate 14 and manually tighten the nut. The upper end of the positioning anchor bolt should protrude 2-3 threads from the upper surface of the upper anchor plate 16, and manually tighten the nut at the top of the anchor bolt.

[0048] The installer inserts the upper end of the ordinary anchor bolt into the anchor plate hole of the upper anchor plate 16, tilts it at a certain angle, lifts the ordinary anchor bolt (with the thin nut already installed), rotates it a certain angle, and then inserts the lower end of the anchor bolt into the lower anchor plate 14. After the bottom surface of the thin nut is in close contact with the lower anchor plate 14, a washer is placed under the lower anchor plate 14 and the nut is manually tightened. During the installation of ordinary anchor bolts, considering the overall uniformity of force distribution within the anchor cage, the inner and outer rings of the ordinary anchor bolts are installed using clockwise and counterclockwise methods.

[0049] Adjust and secure the anchor cage.

[0050] After acceptance, six reinforcing bars are welded to reinforce the anchor cage. The upper end of the reinforcing bars is welded to the lower surface of the upper anchor plate 16, and the lower end is welded to the inner circle of the lower anchor plate 14 and the foundation embedded part 15, with the intersection points welded to enhance the overall stability of the anchor cage. In addition, the nut at the lower end of the connecting plate of the upper anchor plate 16 should be spot welded to the bottom of the upper anchor plate 16 to prevent the bolts from being stuck when disassembling the connecting plate.

[0051] Specifically, the installation of reinforcing steel bars in the wind turbine foundation should follow a specific sequence, proceeding from bottom to top and from inside to outside. The surface of the reinforcing steel bars should be clean and undamaged; paint contamination and rust should be removed before use. Reinforcing steel bars with granular or flaky rust should not be used. The foundation layer must be cleaned before installing the reinforcing steel bars to ensure its surface is spotless.

[0052] The mechanical connection of the reinforcing bars adopts the rolled rib stripping straight thread connection.

[0053] First, tie the radial ordinary steel bars 10 at the bottom of the foundation slab, then tie the circumferential steel bars 5 at the bottom of the foundation slab, and according to the construction drawings, place the corrugated pipes 17 in the radial direction for threading the steel strands, and install the spiral bars 19 and anchor plates.

[0054] Reinforcing bars that are difficult to pass through the anchor cage should be bent or cut in advance without affecting the design load. Considering that the anchorage space of the prestressed tendons should not collide with that of ordinary reinforcing bars, the ratio of prestressed tendons to non-prestressed tendons is 1:5. Therefore, the ratio of the number of corrugated pipes 17 to the number of ordinary radial reinforcing bars 10 tied to the bottom of the foundation is 1:5.

[0055] The vertical reinforcing bars 12 and the circumferential reinforcing bars 13 in the core area are tied around the anchor bolt cage.

[0056] Tie the vertical reinforcement 5 and the radial reinforcement 7 at the top of the foundation slab, and then tie the circumferential reinforcement 8 at the top of the foundation slab onto the radial reinforcement 7 at the top of the foundation slab.

[0057] The installed steel bars are firmly reinforced, and during the concrete pouring process, a dedicated person is assigned to monitor and inspect them frequently to prevent the steel bars from shifting or deforming.

[0058] Step 3: Construct a precast concrete formwork with a U-shaped cross-section, forming a hollow cavity, on the bottom plane of the wind turbine foundation, such as... Figure 3 As shown, cavity 4 is formed.

[0059] During the construction of precast concrete formwork, steel pipe columns were used for formwork support, and there was no leakage of grout at the formwork joints.

[0060] Specifically, the gaps can be pre-treated with cement mortar, and the contact surface between the formwork and the concrete should be cleaned and coated with a release agent, but release agents that affect the structural performance should not be used.

[0061] The formwork is reinforced by tie bolts and scaffold pipe walers. The tie bolts are welded to the trestles and must be firmly welded. The tie bolts should be blocked on the inside of the pad blocks.

[0062] Install formwork around the foundation, apply sponge strips to the formwork joints to prevent grout leakage, and reinforce the formwork with chain hoists.

[0063] Step 4: Construct the fan foundation using a continuous pouring method.

[0064] When using a continuous pouring method for wind turbine foundations, pouring begins from one end of the bottom layer. The second layer is poured before the first layer has set, and this process continues layer by layer until completion. The time interval between pouring two layers of concrete should not exceed one hour before the initial setting of the lower layer. Generally, pouring starts from the shorter side and proceeds along the longer side; alternatively, pouring can be done simultaneously from the middle towards both ends or from both ends towards the middle. The wind turbine foundation concrete should be poured continuously without construction joints, ensuring completion in one continuous pour.

[0065] When vibrating concrete, use a vibrator and follow the principle of "quick insertion and slow withdrawal". The vibration time for each point should generally be 10-30 seconds, and should be determined when the concrete surface is level, no longer sinks significantly, no longer has air bubbles, and mortar appears on the surface. Pay attention to the bonding between layers, strengthen vibration, ensure continuous pouring, and prevent cold joints.

[0066] After the concrete is poured, it should be covered and kept moist within 12 hours, and the curing time should not be less than 14 days. During the moist curing process, the integrity of the plastic film or curing agent should be checked frequently, and the concrete surface should be kept moist.

[0067] Step 5: After the wind turbine foundation is poured and cured, high-strength cement-based grouting material 3 is used for secondary grouting and prestressing tensioning of the wind turbine foundation. Finally, the formwork is removed, forming a gravity-type prestressed anchored wind turbine foundation. Figures 4-6 As shown.

[0068] Specifically, to ensure the quality of secondary grouting, the grouting surface of the wind turbine foundation must be treated before grouting. Use a chisel to remove the weak parts of the foundation concrete, and the roughness of the surface should be 10-20mm. 24 hours before the grouting operation, water should be sprinkled on the foundation concrete to keep it moist, allowing the concrete to fully absorb the water. Before construction begins, ensure the base surface is moist, but there should be no visible water.

[0069] Before the grout is poured, the upper anchor plate 16 can be leveled a second time.

[0070] When the concrete reaches its design strength, thread the prestressed steel strands 9. After inserting the working anchor 18, working clamps, and limiting plates, use jacks to perform prestressing tensioning. Once the specified tension is reached, dismantle the tensioning equipment in sequence.

[0071] Remove excess steel strands and cut the wires using an abrasive wheel saw.

[0072] Secondary grouting of the wind turbine foundation is performed using the positive air grouting method for duct grouting. For example, grouting of the 20mm grouting pipe is carried out immediately using the positive air grouting method to ensure tensioning accuracy and grout fullness. When thick grout emerges from the seepage holes, the valve is closed and pressure is maintained for two minutes. After grouting is completed, all anchor heads are sealed with concrete, followed by continued curing.

[0073] Specifically, in addition to complying with the provisions of the construction drawings, the following regulations must also be observed regarding the time limit for formwork removal: the formwork on non-load-bearing sides shall be removed only when the concrete strength reaches a point where its surface and edges will not be damaged during formwork removal.

[0074] The load-bearing side formwork can only be removed when the concrete reaches a predetermined proportion of the design strength (e.g., 70%).

[0075] In one or more embodiments, a gravity-type prestressed anchored fan foundation is provided, which is prepared using the preparation method for gravity-type prestressed anchored fan foundations as described above. Figure 2 1 represents the fan casing wall, and 2 represents the anchor bolt.

[0076] This invention provides a novel prestressed anchor bolt foundation that offers advantages such as low engineering workload and replaceable anchor bolts while ensuring structural safety. Firstly, by replacing the foundation ring with high-strength prestressed anchor bolts to connect the tower and foundation, it solves the shortcomings of abrupt changes in strength and stiffness, and susceptibility to cracking, inherent in ring foundations. Secondly, by modifying traditional prestressed anchor bolt foundations, it reduces concrete usage and shortens anchor bolt length, saving project investment costs. Furthermore, through mechanical performance and practical experience analysis, it is found that the bottom plate of the wind turbine foundation experiences significant tensile stress and is prone to cracking. Therefore, by applying prestress to the radial reinforcement of the bottom plate of the ring foundation, more efficient synergistic stress distribution between the reinforcement and concrete is achieved, improving the strength and crack resistance of the wind turbine foundation itself, thereby optimizing the amount of foundation reinforcement. This invention is suitable for today's large-capacity, large-impeller, and high-hub wind turbine units.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a gravity-type prestressed anchor bolt fan foundation, characterized in that, include: Pouring the foundation layer; Install the foundation prestressed anchor cage assembly and tie the reinforcing steel bars for the wind turbine foundation on the poured foundation layer; verify the installation of the prestressed foundation anchor cage assembly according to the drawings. The upper end of the anchor bolt is inserted into the anchor plate hole of the upper anchor plate and tilted at a certain angle. After the anchor bolt with the thin nut installed is rotated at a certain angle, the lower end of the anchor bolt is inserted into the lower anchor plate. During the installation of ordinary anchor bolts, the inner and outer rings are installed using clockwise and counterclockwise methods. The reinforcing bars of the wind turbine foundation are tied from bottom to top and from the inside to the outside; During the process of tying the reinforcing bars of the wind turbine foundation, first tie the radial ordinary reinforcing bars at the bottom of the foundation slab, then tie the circumferential reinforcing bars at the bottom of the foundation slab, and according to the construction drawings, place corrugated pipes in the radial direction for threading steel strands, and install spiral reinforcement and anchor plates. The ratio of prestressed tendons to non-prestressed tendons is 1:5; Construct a precast concrete formwork with a convex-shaped cavity on the bottom plane of the wind turbine foundation; The fan foundation was constructed using a continuous, integral pouring method. In the process of using continuous pouring for the wind turbine foundation, pouring begins from one end of the bottom layer. Before the lower layer of concrete has set, the second layer is poured, and so on, layer by layer, until the pouring is completed. After the wind turbine foundation is poured and moisturized, secondary grouting and prestressing tensioning are carried out on the wind turbine foundation. When the concrete strength reaches the design strength, prestressed steel strands are threaded through, and working anchors, working clamps and limiting plates are placed in. Then, jacks are used to perform prestressing tensioning. When the specified tension is reached, the tensioning equipment is removed in sequence. Secondary grouting of the wind turbine foundation was carried out using the positive air grouting method for duct grouting; By applying prestress to the radial reinforcement of the bottom plate of the ring foundation, the overturning resistance and durability of the foundation are improved, the reinforcement and concrete are more efficiently synergistically stressed, the foundation engineering volume is optimized, and the replacement of prestressed anchor bolts is achieved. The load-bearing side formwork can only be removed when the concrete reaches a predetermined proportion of the design strength. Finally, the formwork is removed to form a gravity-type prestressed anchor bolt wind turbine foundation.

2. The method for preparing a gravity-type prestressed anchor bolt fan foundation as described in claim 1, characterized in that, During the construction of precast concrete formwork, steel pipe columns were used for formwork support, and there was no leakage of grout at the formwork joints.

3. A gravity-type prestressed anchor bolt fan foundation, characterized in that, It is prepared using the preparation method of gravity-type prestressed anchor bolt wind turbine foundation as described in any one of claims 1-2.

Images