A replaceable prestressed anchor bolt fan foundation structure and method

Abstract

This invention discloses a replaceable prestressed anchor bolt wind turbine foundation structure and method, belonging to the technical field of wind power foundation structure. The structure includes a foundation base, a sleeve installed within the foundation base, anchor bolts inserted through the sleeve, a lower anchor plate connecting the lower part of the sleeve, an upper anchor plate connecting the upper part of the sleeve, and an anchoring assembly connecting the upper anchor plate. This invention, through the pre-embedded sleeve structure, eliminates the need for a bottom channel within the foundation base, providing a replaceable operating space for the anchor bolts. The anchor bolts are positioned by a threaded connection at the lower end and locked by prestressing tension at the upper end. Replacement of the anchor bolts only requires dismantling the upper anchoring structure, without needing to break the foundation base serving as the wind turbine's concrete foundation. This significantly reduces maintenance costs and construction time after anchor bolt damage, solving the technical problem of difficulty in replacing damaged anchor bolts in traditional integrated anchor bolt wind turbine foundations. It is applicable to various onshore and offshore wind farms.

Description

Technical Field

[0001] This invention belongs to the technical field of wind power generation foundation structure, and particularly relates to a replaceable prestressed anchor bolt wind turbine foundation structure and method. Background Technology

[0002] During the 20-30 year design life of wind turbine foundations, they need to withstand the combined effects of millions of wind-induced fatigue loads and marine corrosion. The corrosion, breakage, or prestress relaxation of a single anchor bolt can cause the load to transfer to adjacent anchor bolts, resulting in the risk of cascading failures.

[0003] Patent applications CN105155571A and CN213014351U employ a through-hole nut locking anchor bolt structure. A steel pipe or corrugated pipe is pre-embedded in the foundation concrete. The anchor bolt passes through the pipe, with its lower end extending out of the through-hole of the lower anchor plate. It is locked to the bottom surface of the lower anchor plate by a nut, leaving the lower end of the anchor bolt exposed. The upper end of the anchor bolt extends through the upper anchor plate and is locked by the upper nut. To prevent corrosion, a nut box is often installed on the outside of the lower nut and filled with grease. The annular gap between the anchor bolt and the sleeve is usually filled with cement grout or epoxy grout to bond the anchor bolt to the foundation.

[0004] The patent applications with application numbers CN105297766A and CN217998155U adopt a replaceable anchor bolt foundation with an operating channel at the bottom. A vertical manhole or operating well is set in the foundation body, and a hollow operating space is formed below. Personnel go down to the bottom of the well to remove and install the lower end nut of the anchor bolt or cut off the failed anchor bolt, and then pull it out from the top section by section for replacement.

[0005] The aforementioned existing solutions have revealed the following shortcomings in engineering practice, which have a particularly significant impact on the operation and maintenance of offshore wind farms: 1. The through-hole nut method cannot achieve non-destructive replacement of individual anchor bolts: Because the upper end of the anchor bolt is fixed in the grout layer below the upper anchor plate by grouting material, the entire length of the anchor bolt is bonded to the foundation as a whole. Even if the lower nut is removed, it cannot be replaced from the top. Once the anchor bolt fails, traditional repair methods can only remove a large amount of foundation concrete, which is time-consuming, costly, and difficult to restore the overall load-bearing performance of the original structure after repair.

[0006] 2. The lower end of the anchor bolt penetrates the lower anchor plate and is exposed on the bottom surface of the anchor plate. Although it is protected by the nut box, the threaded connection is still a weak point for corrosion under long-term immersion in groundwater or seawater, which can easily lead to stress corrosion cracking and cannot be inspected in daily life.

[0007] 3. The bottom operating space design carries significant construction risks and extremely high costs: For offshore wind turbine foundations, access to the bottom operating well requires specialized vessels and diving equipment, and is strictly limited by tides and weather windows. Based on actual data from a certain offshore wind farm, the cost of replacing a single anchor bolt, involving vessels and diving operations, can exceed 100,000 yuan, with significant personnel safety risks. Furthermore, the reserved space at the bottom weakens the overall rigidity and overturning resistance of the foundation base.

[0008] 4. Existing solutions, such as grouting or leaving the annular space between the anchor bolt and the casing, cannot simultaneously provide long-term corrosion protection and ensure that the anchor bolt can be freely replaced. Grouting makes it impossible to remove the anchor bolt, while leaving it empty accelerates corrosion. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a replaceable prestressed anchor bolt fan foundation structure and method.

[0010] The present invention is achieved through the following technical solutions.

[0011] The present invention provides a replaceable prestressed anchor bolt fan foundation structure, including a foundation base, a sleeve, an anchor bolt inserted in the sleeve, a lower anchor plate connected to the lower part of the sleeve, an upper anchor plate connected to the upper part of the sleeve, and an anchoring assembly connected to the upper anchor plate.

[0012] Preferably, the bottom surface of the lower anchor plate is provided with a connecting sleeve and a through hole for the anchor bolt to pass through at the position corresponding to the anchor bolt, and the connecting sleeve is provided with an internal thread blind hole.

[0013] Preferably, the lower end of the anchor bolt is provided with an external thread section that mates with the internal thread blind hole, and the lower end of the anchor bolt is provided with a tapered guide head without threads.

[0014] Preferably, the bottom surface of the lower anchor plate is provided with an internally threaded blind hole.

[0015] Preferably, a boss is provided on the bottom surface of the lower anchor plate corresponding to the internal thread blind hole.

[0016] Preferably, the opening of the internally threaded blind hole is provided with a tapered guide chamfer.

[0017] Preferably, the casing is provided with a grease injection nozzle, and there is a gap between the inner wall of the casing and the anchor bolt.

[0018] Preferably, a leveling nut is provided on the sleeve, the leveling nut is located below the upper anchor plate, and the leveling nut is placed in a placement groove on the foundation base.

[0019] A construction method for a replaceable prestressed anchor bolt fan foundation structure includes the following steps: S1: Weld the lower anchor plate and sleeve into a pre-embedded component, hoist the pre-embedded component and fix it in the foundation reinforcement cage, and install the leveling nut above the sleeve; S2: Place the upper anchor plate on the leveling nut and rotate the leveling nut to adjust the upper anchor plate to be horizontal; S3: Concrete is used to pour the foundation base, and a placement groove is set on the foundation base. Grouting material that wraps the leveling nut is poured into the placement groove to form a grouting material layer. S4: After the foundation base reaches the design strength, insert the anchor bolt from the top of the sleeve, let the anchor bolt slide into the internal thread blind hole, rotate the anchor bolt, and tighten the anchor bolt with the internal thread blind hole under the action of the thread connection. S5: Pump anti-corrosion lubricating grease into the gap through the grease injection nozzle until the sleeve is full; S6: Install the anchoring components, then perform prestressing tensioning and locking.

[0020] A maintenance method for a replaceable prestressed anchor bolt fan foundation structure includes the following steps: S7: Place the jack on the upper end of the anchor bolt, press the base of the jack on the upper anchor plate, clamp the tool anchor at the front end of the jack with the upper end of the anchor bolt, apply pressure and lift, and transfer the preload of the anchor bolt to the jack. S8: Remove the anchoring components at the upper end of the anchor bolt; S9: Unload the jack to zero and rotate the upper end of the anchor bolt in the opposite direction so that the external thread section at its lower end is completely unscrewed from the internal thread blind hole and loosened. S10: Pull the anchor bolt vertically upward along the sleeve; S11: Insert the new anchor bolt into the sleeve along the original path, and rotate the anchor bolt to tighten the external thread section at its lower end and the internal thread blind hole to the design torque. S12: Replenish the worn anti-corrosion grease into the sleeve through the grease injection nozzle; S13: Reinstall the anchoring components, tension them to the design prestress, and lock the anchoring components.

[0021] The beneficial effects of this invention are as follows: 1. Single anchor bolt replacement completely eliminates underwater operations: The scenario for replacing offshore wind turbine anchor bolts has been changed from ship and diving construction to routine operation on the top surface of the foundation base. The overall cost of anchor bolt replacement has been reduced from more than 100,000 yuan per bolt to several thousand yuan per bolt, a reduction of more than 90%. The replacement time can be reduced from several days (waiting for weather windows) to within 4 hours, which greatly improves the availability and life-cycle economy of offshore wind farms.

[0022] 2. The integrity of the foundation base is not weakened: Since there is no need to set up any bottom operating well or hollow space, the foundation base is still a complete solid body. Its overturning resistance and durability are consistent with traditional foundations, and the weak links in the structure are reduced.

[0023] 3. Eliminate corrosion channels in anchor bolts: By connecting the anchor bolt to the internal thread blind hole, the exposed thread corrosion points caused by traditional through holes are eliminated at the source. With the addition of a sealed annular gap filled with grease, the anchor bolt is protected by an oil film throughout its entire life cycle, which greatly reduces the risk of corrosion and breakage and is expected to meet the life requirement of more than 30 years.

[0024] 4. Precise and convenient leveling during construction: The leveling nut on the sleeve can precisely adjust the height and level of the upper anchor plate. It is simple to operate, highly accurate, and the leveling nut does not affect the replacement of the anchor bolt.

[0025] 5. High reliability and easy maintenance: The connecting sleeve and the lower anchor plate are welded into a whole, and the force transmission is direct; the anti-corrosion lubricating grease is stable for a long time; the grease injection nozzle supports regular grease replenishment; all operations are compatible with mature tools, and the on-site promotion threshold is low. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 2 yes Figure 1 A magnified view of a portion of the image; Figure 3 yes Figure 1 Schematic diagram of the structure of region A; Figure 4 This is a structural schematic diagram of the connecting sleeve and anchor bolt of the present invention; Figure 5 yes Figure 1 Schematic diagram of the structure of region B; Figure 6 This is a schematic diagram of the lower anchor plate in Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the structure of the lower anchor plate and anchor bolt in Embodiment 2 of the present invention; In the diagram: 1-base base, 11-placement groove, 12-conical guide chamfer, 2-sleeve, 21-leveling nut, 22-grease nozzle, 3-anchor bolt, 31-external thread section, 32-conical guide head, 4-anchoring assembly, 41-locking element, 42-locking bolt, 5-lower anchor plate, 51-bore, 6-connecting sleeve, 7-internal thread blind hole, 8-gap, 10-upper anchor plate. Detailed Implementation

[0027] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0028] Example 1: like Figure 1-5As shown, a replaceable prestressed anchor bolt fan foundation structure includes a foundation base 1. The foundation base 1 is provided with several sleeves 2, anchor bolts 3 passing through each sleeve 2, a lower anchor plate 5 connecting the lower part of the sleeve 2, an upper anchor plate 10 connecting the upper part of the sleeve 2, and an anchoring component 4 connecting the upper anchor plate 10. The anchoring component 4 is used to lock the upper end of the anchor bolt 3 to the top surface of the upper anchor plate 10.

[0029] The number of sleeves 2 is determined according to actual needs. Two sleeves 2 can be set on each lower anchor plate 5. The number of internal thread blind holes 7 corresponds to the number of sleeves 2.

[0030] The bottom surface of the lower anchor plate 5 is provided with a connecting sleeve 6 and a through hole for the anchor bolt 3 to pass through. The connecting sleeve 6 is provided with a non-permeable internal thread blind hole 7. The connecting sleeve 6 is welded to the lower anchor plate 5. The sleeve 6 is designed to have sufficient axial load-bearing thickness, so there is no need to thicken the bottom surface of the lower anchor plate 5. The non-permeable internal thread blind hole 7 can isolate the lower end of the anchor bolt 3 from contact with the external environment and protect the lower end of the anchor bolt 3.

[0031] The lower end of the anchor bolt 3 is provided with an external thread section 31 that mates with the internal thread blind hole 7. The lower end of the anchor bolt 3 is provided with a non-threaded tapered guide head 32. The lower end of the anchor bolt 3 is screwed into the internal thread blind hole 7 through the external thread section 31 to achieve detachable fixed connection. The threaded connection part is completely hidden in the internal thread blind hole 7.

[0032] The opening of the internal thread blind hole 7 is provided with a tapered guide chamfer 12, and the external thread section 31 is guided into the interior of the internal thread blind hole 7 through the tapered surface of the tapered guide chamfer 12.

[0033] The anchoring assembly 4 includes a locking member 41 and two locking bolts 42, the locking bolts 42 passing through the locking member 41 and the upper anchor plate 10; the sleeve 2 is provided with a grease nipple 22, and there is an annular gap 8 between the inner wall of the sleeve 2 and the anchor bolt 3. The upper and lower ends of the annular gap 8 are sealed by a sealing ring or a sealing grease nipple assembly to form a closed anti-corrosion medium receiving cavity.

[0034] A leveling nut 21 is provided on the sleeve 2. The leveling nut 21 is located below the upper anchor plate 10 and is placed in the placement groove 11 on the foundation base 1. The leveling nut 21, which is fixed to the outer wall of the upper end of the sleeve 2, is used to support and finely adjust the elevation of the upper anchor plate 10 during the construction stage, and also ensures that the leveling nut 21 is not connected to the internal anchor bolt 3, thus ensuring that the anchor bolt 3 can be replaced.

[0035] A construction method for a replaceable prestressed anchor bolt fan foundation structure includes the following steps: S1: Weld the lower anchor plate 5 and the sleeve 2 into a pre-embedded assembly, hoist the pre-embedded assembly and fix it in the foundation steel cage, and install the leveling nut 21 above the sleeve 2; S2: Place the upper anchor plate 10 on the leveling nut 21, rotate the leveling nut 21 to adjust the upper anchor plate 10 to be horizontal, with an adjustment accuracy of millimeters; S3: Concrete is used to pour the foundation base 1, and a placement groove 11 is set on the foundation base 1. Grouting material that wraps the leveling nut 21 is poured into the placement groove 11 to form a grouting material layer. S4: After the base 1 reaches the design strength, the anchor bolt 3 is inserted from the top of the sleeve 2. With the help of the tapered guide head 32, the anchor bolt 3 is automatically slid into the internal thread blind hole 7. The anchor bolt 3 is rotated and tightened with the internal thread blind hole 7 under the action of the threaded connection to form a detachable strong anchor. S5: Pump anti-corrosion lubricating grease into the gap 8 through the grease injection nozzle 22 until the sleeve 2 is full; S6: Install anchoring component 4, then perform prestressing tensioning and locking, and install a protective sleeve on anchor bolt 3 to protect the upper end of anchor bolt 3, upper anchor plate 10 and anchoring component 4.

[0036] A maintenance method for a replaceable prestressed anchor bolt fan foundation structure includes the following steps: S7: Place the jack on the upper end of the anchor bolt 3, press the base of the jack on the upper anchor plate 10, clamp the tool anchor at the front end of the jack to the upper end of the anchor bolt 3, apply pressure and lift, and transfer the preload of the anchor bolt 3 to the jack. S8: Remove the anchoring component 4 at the upper end of the anchor bolt 3; S9: Slowly unload the jack to zero by returning oil, and rotate the upper end of the anchor bolt 3 in the opposite direction so that the external thread section 31 at its lower end is completely unscrewed from the internal thread blind hole 7 and loosened. S10: Use a winch or manual labor to pull the anchor bolt 3 vertically upward along the sleeve 2. If the anchor bolt 3 is broken, first pull out the upper half of the broken anchor bolt 3, and then use an extended rotating tool to unscrew the lower half of the broken anchor bolt 3 and pull it out. S11: Insert the new anchor bolt 3 into the sleeve 2 along the original path, and rotate the anchor bolt 3 to tighten the external thread section 31 at its lower end and the internal thread blind hole 7 to the designed torque. S12: Replenish the worn anti-corrosion grease into the sleeve 2 through the grease injection nozzle 22; S13: Reinstall anchoring component 4, tension to the design prestress and lock anchoring component 4; the whole process only applies to a single anchor bolt 3, the upper anchor plate 10 and the surrounding anchor bolts 3 remain under constant stress, and the foundation structure is not damaged in any way.

[0037] The jack is a perforated jack; The aforementioned sealing rings, sealing grease nipple assemblies, and jacks are all existing technologies.

[0038] Anti-corrosion grease has the functions of anti-corrosion and lubrication. Commercially available anti-corrosion greases include: Mobilux EP2, Shell Gadus S2 V220 2 or equivalent lithium-based extreme pressure grease, with a dropping point ≥180℃, working cone penetration 265-295, and temperature range -20℃~120℃.

[0039] Example 2: like Figure 6-7 As shown, a replaceable prestressed anchor bolt fan foundation structure is based on Embodiment 1, with the only difference being: no connecting sleeve 6 is provided, and an impenetrable internal thread blind hole 7 is provided on the bottom surface of the lower anchor plate 5. The opening of the internal thread blind hole 7 is provided with a tapered guide chamfer 12, and a boss 51 is provided on the bottom surface of the lower anchor plate 5 corresponding to the internal thread blind hole 7 to increase the punching shear thickness of the bottom surface of the thread blind hole 7 and ensure stress safety.

Claims

1. A replaceable prestressed anchor bolt fan foundation structure, characterized in that: It includes a base base (1), a sleeve (2) is provided inside the base base (1), an anchor bolt (3) passing through the sleeve (2), a lower anchor plate (5) connecting the lower part of the sleeve (2), an upper anchor plate (10) connecting the upper part of the sleeve (2), and an anchoring assembly (4) connecting the upper anchor plate (10).

2. The replaceable prestressed anchor bolt fan foundation structure as described in claim 1, characterized in that: The bottom surface of the lower anchor plate (5) is provided with a connecting sleeve (6) and a through hole for the anchor bolt (3) to pass through. The connecting sleeve (6) is provided with an internal thread blind hole (7).

3. The replaceable prestressed anchor bolt fan foundation structure as described in claim 2, characterized in that: The lower end of the anchor bolt (3) is provided with an external thread section (31) that mates with the internal thread blind hole (7), and the lower end of the anchor bolt (3) is provided with a non-threaded tapered guide head (32).

4. The replaceable prestressed anchor bolt fan foundation structure as described in claim 1, characterized in that: The bottom surface of the lower anchor plate (5) is provided with an internal thread blind hole (7).

5. The replaceable prestressed anchor bolt fan foundation structure as described in claim 4, characterized in that: A boss (51) is provided on the bottom surface of the lower anchor plate (5) corresponding to the internal thread blind hole (7).

6. A replaceable prestressed anchor bolt fan foundation structure as described in claim 2 or 4, characterized in that: The opening of the internal thread blind hole (7) is provided with a tapered guide chamfer (12).

7. The replaceable prestressed anchor bolt fan foundation structure as described in claim 1, characterized in that: A grease injection nozzle (22) is provided on the sleeve (2), and there is a gap (8) between the inner wall of the sleeve (2) and the anchor bolt (3).

8. The replaceable prestressed anchor bolt fan foundation structure as described in claim 7, characterized in that: The sleeve (2) is provided with a leveling nut (21), which is located below the upper anchor plate (10) and is placed in the placement groove (11) on the foundation base (1).

9. A construction method for a replaceable prestressed anchor bolt fan foundation structure as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Weld the lower anchor plate (5) and sleeve (2) into a pre-embedded component, hoist the pre-embedded component and fix it in the foundation steel cage, and install the leveling nut (21) above the sleeve (2). S2: Place the upper anchor plate (10) on the leveling nut (21) and rotate the leveling nut (21) to adjust the upper anchor plate (10) to be horizontal; S3: Concrete is used to pour the foundation base (1), and a placement groove (11) is set on the foundation base (1). Grouting material that wraps the leveling nut (21) is poured into the placement groove (11) to form a grouting material layer; S4: After the base (1) reaches the design strength, insert the anchor bolt (3) from the top of the sleeve (2) so that the anchor bolt (3) slides into the internal thread blind hole (7), rotate the anchor bolt (3), and tighten the anchor bolt (3) with the internal thread blind hole (7) under the action of the thread connection. S5: Pump anti-corrosion lubricating grease into the gap (8) through the grease injection nozzle (22) until the sleeve (2) is full; S6: Install the anchoring components (4), and then perform prestressing tensioning and locking.

10. A maintenance method for a replaceable prestressed anchor bolt wind turbine foundation structure as described in any one of claims 1-8, characterized in that, Includes the following steps: S7: Place the jack on the upper end of the anchor bolt (3), press the base of the jack on the upper anchor plate (10), clamp the tool anchor at the front end of the jack to the upper end of the anchor bolt (3), apply pressure and lift, and transfer the preload of the anchor bolt (3) to the jack. S8: Remove the anchoring assembly (4) at the upper end of the anchor bolt (3); S9: Unload the jack to zero and rotate the upper end of the anchor bolt (3) in the opposite direction so that the external thread section (31) at its lower end is completely unscrewed from the internal thread blind hole (7) and loosened; S10: Pull the anchor bolt (3) vertically upward along the sleeve (2); S11: Insert the new anchor bolt (3) into the sleeve (2) along the original path, and rotate the anchor bolt (3) to tighten the external thread section (31) at its lower end to the internal thread blind hole (7) to the designed torque; S12: Replenish the lost anti-corrosion grease into the sleeve (2) through the grease injection nozzle (22); S13: Reinstall the anchoring assembly (4), tension it to the design prestress, and lock the anchoring assembly (4).

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