Method for detecting, evaluating and reinforcing foundation anchor bolt assembly after tower collapse of wind turbine generator

Abstract

The invention relates to the technical field of wind power engineering, in particular to a method for detecting, evaluating and reinforcing a foundation anchor bolt assembly after tower falling of a wind turbine generator set, and the method comprises the steps: obtaining tower falling characteristic information which comprises residual pre-tension force; the exposed length of the anchor bolt is detected, and an area with the exposed length exceeding the limit is obtained; pre-tension detection is conducted on anchor bolts in the tension area and the compression area, the residual pre-tension value is obtained, and a pre-tension loss area is obtained; evaluating the plastic damage degree of the anchor bolt based on the pre-tension loss value under the working condition of reverse pushing of the residual pre-tension and the maximum axial force actually borne by the anchor bolt in the tower falling process; comprehensively evaluating the grade of the foundation state by combining the exposed length, the pre-tension force loss value and the maximum axial force of the anchor bolt on the tension side; and providing reinforcement measures according to the comprehensive evaluation grade of the basic state. Millimeter-level damage which is difficult to find by a conventional method can be effectively identified, and positioning is more accurate; therefore, the plastic damage degree and the residual safety of the anchor bolt are scientifically judged.

Description

Technical Field

[0001] This invention relates to the field of wind power engineering technology, and in particular to a method for detecting, evaluating and reinforcing foundation anchor bolt components after a wind turbine tower collapses. Background Technology

[0002] In common tower collapse scenarios, preload loss in foundation anchor bolts is prevalent, becoming a key factor in post-accident handling and safety assessment. Accurately assessing the damage to anchor bolts and the foundation is fundamental to determining repair plans and ensuring the safe operation of the unit. Existing detection methods mainly include the following: (1) Radar detection (according to JGJ / T456-2019 standard): detects internal defects in concrete by reflecting radar waves. However, its main drawback is that it can only identify larger volume voids or delaminations. It is difficult to accurately identify local crushing, loosening and other damages around the lower anchor plate at the millimeter level, and cannot meet the requirements of fine evaluation.

[0003] (2) Ultrasonic testing method: This method uses the propagation characteristics of ultrasonic waves in concrete to assess internal quality. However, this method is not sensitive enough to deep-buried or small-scale local damage, and the test results are easily affected by the distribution of reinforcing bars, making interpretation difficult.

[0004] (3) Anchor bolt tension-deformation field testing method (ZL202410396262.8): The mechanical response of the anchor bolt is measured by directly tensioning it. This method is effective for severely damaged tower collapse modes (such as the tower being completely pulled out of the foundation), but it is not suitable for the more common and less damaged tower collapse modes in engineering (such as the tower bending but not completely detaching). In addition, the operation is complicated and costly, and it is not suitable for scenarios where a large number of anchor bolts need to be quickly screened after an accident.

[0005] (4) Long-term prestress monitoring technologies: such as vibration monitoring combined with deep learning, PZT piezoelectric sensing, etc. These technologies are mainly used for monitoring the prestress evolution of structures during normal operation or under environmental degradation, and are not suitable for rapid emergency assessment after sudden, strong impact events such as tower collapse.

[0006] Furthermore, the above-mentioned testing methods lack computational models that correlate on-site testing data (such as preload loss) with the extreme load of tower collapse. This makes it impossible to quantitatively assess the maximum stress state of the anchor bolts at the moment of collapse, and consequently, to scientifically determine the degree of plastic damage and remaining safety of the anchor bolts. Because of this inability to accurately assess the situation, engineering practice often tends to adopt conservative strategies, such as replacing all anchor bolts, resulting in high repair costs and extended construction periods. Summary of the Invention

[0007] The main objective of this invention is to provide a method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after a wind turbine tower collapses. This method aims to solve the technical problem that existing methods cannot scientifically determine the degree of plastic damage and remaining safety of the anchor bolts, resulting in long tower repair and reinforcement periods and high costs.

[0008] To achieve the above objectives, this invention proposes a method for detecting, evaluating, and reinforcing foundation anchor bolt assemblies after a wind turbine tower collapses, comprising the following steps: S1. Obtain the collapse characteristic information, determine the collapse direction and mode, and divide the tension zone and compression zone of the collapse foundation. The collapse characteristic information includes residual preload. S2. Detect the exposed length of the anchor bolts to identify areas where the exposed length exceeds the limit; S3. Perform pre-tension testing on anchor bolts in tension and compression zones to obtain residual pre-tension values ​​and identify areas of pre-tension loss. S4. Compare the area of ​​prestress loss with the area of ​​exposed length exceeding the limit to verify their consistency and find out the cause of prestress loss. S5. Based on the preload loss value under the residual preload reverse push tower collapse condition and the maximum axial force actually subjected to the anchor bolt during the tower collapse process, assess the degree of plastic damage to the anchor bolt. S6. The foundation condition level is comprehensively assessed by combining the exposed length, preload loss value, and maximum axial force of the anchor bolts on the tension side. S7. Based on the basic condition level, propose reinforcement measures.

[0009] A further improvement of the present invention regarding the detection, evaluation, and reinforcement method for the foundation anchor bolt assembly after wind turbine tower collapse is that S2 includes the following steps: Measured exposed length of anchor bolts on the foundation ring ; Theoretical limits for calculating the exposed length of anchor bolts Actual measured exposed length of anchor bolt It consists of three parts: the design exposed length Elastic elongation of anchor bolts during initial tensioning and the deformation of the lower anchor plate during initial tensioning. ,Right now: ; The construction and installation error should be controlled within ±1.5mm. If the deviation of the exposed length of the anchor bolt exceeds this range, it is determined that the foundation concrete has initial crushing or insufficient compaction defects. Therefore, the theoretical limit of the exposed length of the anchor bolt before tower removal is... for: ; The actual exposed length of the anchor bolt Theoretical limit of exposed length of anchor bolt Perform a comparison, if > If the concrete around the lower anchor plate corresponding to the anchor bolt is found to be non-compacted or has crushing defects, it is marked as a suspicious area; if ≤ If the anchor bolt is in the initial tensioning stage, it is determined that the concrete around the lower anchor plate did not show any abnormal additional displacement caused by insufficient pouring or initial crushing. ; in: Design preload for anchor bolts, L The length of the anchor bolt between the upper and lower nuts. E For the elastic modulus of the anchor bolt, This represents the effective cross-sectional area of ​​the anchor bolt.

[0010] A further improvement of the present invention regarding the detection, evaluation, and reinforcement method for foundation anchor bolt assemblies after wind turbine tower collapse lies in the reduction of anchor bolt preload loss value. The range is arrive between: ; ; in: This represents the residual preload of the anchor bolts after the tower collapses. relative design preload Preload loss, The relative over-tensioning preload is 1.15. The loss of preload.

[0011] A further improvement of the present invention regarding the detection, evaluation, and reinforcement method for the foundation anchor bolt assembly after wind turbine tower collapse lies in the fact that the maximum axial force actually experienced by the anchor bolt during the tower collapse process... The calculation formula is as follows: ; in: The axial force at which the anchor bolt reaches its yield strength. ; The effective cross-sectional area of ​​the anchor bolt; The conditional yield strength of the anchor bolt steel; This refers to the elastic modulus of the anchor bolt.

[0012] A further improvement of the present invention regarding the detection, evaluation, and reinforcement method for the foundation anchor bolt assembly after wind turbine tower collapse is that, at S5, the maximum axial force actually experienced by the anchor bolt during the tower collapse process is measured. Axial force when the anchor bolt steel reaches the conditional yield strength If a comparison is made, < If the anchor bolt has not undergone significant plastic deformation and is within its elastic working range, it can continue to be used; if ≥ If the anchor bolt deformation has entered the plastic stage, it needs to be replaced.

[0013] A further improvement to the method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after a wind turbine tower collapse is that, when the foundation condition level is localized damage, the reinforcement measures are as follows: For localized damage caused by non-dense concrete around the anchor plate in the tension zone, drilling and grouting techniques were used to drill holes in the suspected areas and fill voids and cracks by injecting high-strength epoxy resin. For damage to the upper anchor plate area on the pressure side, a local replacement repair method is adopted, which involves removing the damaged grouting layer and concrete, and then re-grouting with high-strength grout.

[0014] The technical solution of the present invention has the following beneficial effects: The present invention provides a method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after wind turbine tower collapse. Compared to radar and ultrasonic methods, the exposed length detection method of the present invention is simpler and faster to operate, effectively identifying millimeter-level damage that is difficult to detect by conventional methods, and providing more precise positioning. This allows for a scientific assessment of the degree of plastic damage and remaining safety of the anchor bolts. Compared to relying solely on experience or conservative assumptions, the maximum axial force calculation method of the present invention is based on measured data and mechanical models, enabling a quantitative assessment of anchor bolt safety, avoiding unnecessary anchor bolt replacement, and saving costs. The core repair solution of the present invention is grouting reinforcement of the concrete, rather than replacing the anchor bolts, which can save approximately 60-70% of repair costs and shorten the construction period by more than 50%, solving the technical problems of long construction period and high cost of tower repair and reinforcement. The present invention provides a one-stop technical solution from rapid on-site detection and mechanical condition assessment to economical repair solutions. The logic is clear, the steps are well-defined, and it is easy for engineering technicians to master and implement. It is particularly suitable for the most common tower collapse modes in engineering, where the damage is relatively minor. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a flowchart of the method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after the wind turbine tower collapses according to the present invention; Figure 2The flowchart for obtaining the simplified bilinear stress-strain model of steel without obvious yield point in this invention is shown below (a is the constitutive model, b is the simplified bilinear stress model, and c is the simplified bilinear axial force model). Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0019] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0020] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0022] like Figure 1 As shown, this invention proposes a method for detecting, evaluating, and reinforcing foundation anchor bolt assemblies after a wind turbine tower collapses, comprising the following steps: S1. First, collect unit design drawings, construction records, etc., obtain tower collapse characteristic information, determine the tower collapse direction and mode, divide the tension zone and compression zone of the tower collapse foundation, and the tower collapse characteristic information includes residual preload. S2. Inspect the exposed length of the anchor bolts to identify areas where the exposed length exceeds the limit. This step is used to assess whether there are initial defects or crushing caused by tower collapse in the concrete around the lower anchor plate. Its core function is to detect abnormal values ​​in the exposed length of the anchor bolts. This establishes a correlation between an easily measurable geometric dimension (exposed length) and a difficult-to-detect internal condition (concrete density), solving the problem of rapid screening for deeply buried defects.

[0023] After the tower collapses but before the tower casing is dismantled (i.e., before the anchor bolt preload is removed), use a high-precision measuring tool (such as a depth caliper) to measure the actual exposed length of all anchor bolts on the foundation ring. ; Based on design parameters and material properties, calculate the theoretical limit for the exposed length of the anchor bolt. Actual measured exposed length of anchor bolt It consists of three parts: the design exposed length Elastic elongation of anchor bolts during initial tensioning and the deformation of the lower anchor plate during initial tensioning. ,Right now: ; According to the "Technical Specification for Anchor Cage Assembly of Prestressed Foundation for Wind Turbine Generators," the construction and installation error should be controlled within ±1.5mm. If the deviation of the exposed length of the anchor bolt exceeds this range, it is determined that the foundation concrete has initial crushing or incomplete compaction defects. Therefore, the theoretical limit of the exposed length of the anchor bolt before tower removal is... for: ; ; in: Design preload for anchor bolts, L The length of the anchor bolt between the upper and lower nuts. E For the elastic modulus of the anchor bolt, This represents the effective cross-sectional area of ​​the anchor bolt.

[0024] It should be noted that this invention does not solely rely on permissible deviations in construction and installation to determine the qualification of the exposed length of the anchor bolts. Instead, it treats the exposed length of the anchor bolts as an external characteristic of the overall deformation response of the anchor bolt-lower anchor plate-concrete system under the condition of tower collapse. When there are initial defects in the compaction of the concrete around the lower anchor plate, the lower anchor plate will undergo additional displacement under the preload, resulting in a significant increase in the exposed length of the anchor bolts. When this increase exceeds the limit determined by design parameters and material elastic properties, simple construction and installation errors can be ruled out, thus indicating a structural defect in the concrete in that area.

[0025] The actual exposed length of the anchor bolt Theoretical limit of exposed length of anchor bolt Perform a comparison, if > If the concrete around the lower anchor plate corresponding to the anchor bolt is found to be non-compacted or has crushing defects, it is marked as a suspicious area; if ≤ If the anchor bolt does not show obvious signs of insufficient concrete pouring or additional displacement caused by initial crushing during the initial tensioning stage, it is determined that the concrete around the lower anchor plate did not show obvious signs of insufficient concrete pouring or additional displacement caused by initial crushing. However, further evaluation is still needed by combining the residual preload test in S3 with the consistency analysis in S4, because the additional crushing deformation of the concrete around the lower anchor plate caused by the tower collapse load may lead to preload loss and will not affect the exposed length.

[0026] This step is simple to operate, fast to detect, and low in cost. It can quickly survey all anchors at the accident site, accurately locate potential damaged areas, and provide clear targets for subsequent detailed testing and evaluation.

[0027] S3. Perform pre-tension testing on the anchors in the tension and compression zones to obtain the residual pre-tension values ​​of the anchors after tower collapse. The preload loss area is obtained; S4. Compare the area of ​​preload loss with the area of ​​excessive exposed length to verify their consistency and determine the cause of preload loss: If the two areas are consistent, it indicates that the prestress loss is strongly correlated with the additional displacement of the lower anchor plate caused by local crushing of the concrete around the lower anchor plate or insufficient compaction of the concrete. The mechanism of prestress loss is likely mainly due to local damage to the foundation.

[0028] If the two areas are inconsistent, it indicates that the preload loss mechanism is more likely caused by the elongation of the anchor bolt itself.

[0029] S5. Based on the preload loss value under the residual preload reverse push tower collapse condition and the maximum axial force actually subjected to the anchor bolt during the tower collapse process, assess the degree of plastic damage to the anchor bolt. Due to the frequent use of over-tensioning during construction, the preload loss of anchor bolts is significant. The range is arrive between: ; ; in: This represents the residual preload of the anchor bolts after the tower collapses. relative design preload Preload loss, Relative over-tensioning preload 1.15 The loss of preload.

[0030] A simplified bilinear stress-strain model is used for steel without a clear yield point, assuming the anchor bolt design preload. Corresponding to the elastic limit point, such as Figure 2 As shown, the maximum axial force actually experienced by the anchor bolts during the tower collapse process is derived. The calculation formula is as follows: ; ; in: This refers to the axial force required for the anchor bolt to reach its yield strength. The effective cross-sectional area of ​​the anchor bolt; The conditional yield strength of the anchor bolt steel; This refers to the elastic modulus of the anchor bolt.

[0031] Figure 2 middle: and The anchor bolts are respectively under the design preload. The strain and stress at that time are also set as the elastic limit point; The conditional yield strength of the anchor bolt steel; The plastic strain at which the anchor bolt reaches its conditional yield strength; This represents the total strain when the anchor bolt reaches its conditional yield strength. Design preload for anchor bolts; This represents the maximum axial force actually experienced by the anchor bolts during the tower collapse process; The value of the residual preload of the anchor bolts after the tower collapses can be determined based on on-site measurements. This refers to the axial force required for the anchor bolt to reach its yield strength. This represents the preload loss value of the anchor bolts; This represents the total strain generated by the anchor bolts during the tower collapse process; This refers to the plastic strain generated by the anchor bolts during the tower collapse process; This refers to the elastic strain generated by the anchor bolts during the tower collapse process; This refers to the plastic strain at which the anchor bolt reaches its conditional yield strength. This represents the plastic elastic strain at which the anchor bolt reaches its conditional yield strength.

[0032] The maximum axial force actually experienced by the anchor bolts during the tower collapse process. Axial force when the anchor bolt steel reaches the conditional yield strength If a comparison is made, < If the anchor bolt has not undergone significant plastic deformation and is within its elastic working range, it can continue to be used; if ≥ ( Approaching or exceeding If the anchor bolt deformation has entered the plastic stage, it means that it needs to be replaced directly.

[0033] S6. Combining the exposed length, preload loss, and maximum axial force of the anchor bolts on the tension side, the foundation condition level is comprehensively assessed. The foundation condition is comprehensively assessed into three levels: "intact," "locally damaged," or "severely damaged" (assessment as shown in Table 1). This step provides a quantifiable mechanical assessment tool, solving the problem of how to scientifically determine whether anchor bolts have undergone plastic damage after extreme loads. By cross-comparing and analyzing the consistency of abnormal exposed length areas, significant preload loss areas, and back-calculated maximum axial force results, different damage modes caused by concrete crushing, anchor bolt plastic deformation, or local construction defects can be effectively distinguished, thereby improving the reliability of the assessment conclusions and avoiding misjudgments caused by a single detection method.

[0034] Table 1. Comprehensive Assessment Method for Basic Status Level

[0035] In Table 1: Design preload for anchor bolts; This represents the theoretical limit for the exposed length. This is the axial force required for the anchor bolt to reach its yield strength.

[0036] S7. Based on the comprehensive assessment of the foundation condition, propose reinforcement measures. This step standardizes the on-site operation procedures after a tower collapse accident, realizing a closed loop from rapid initial judgment to accurate assessment, and improving assessment efficiency and accuracy.

[0037] The reinforcement and repair scheme of this invention is not proposed independently, but is determined comprehensively based on the aforementioned anchor bolt exposed length test results, residual preload test results, and maximum axial force back-calculation evaluation conclusions. When the evaluation results indicate that the anchor bolt is still in an elastic working state but there is local damage to the concrete around the lower anchor plate, reinforcement and repair measures targeting the concrete are preferred to avoid unnecessary anchor bolt replacement.

[0038] When the overall assessment of the basic condition is localized damage, the reinforcement measures are as follows: For localized damage caused by non-dense concrete around the lower anchor plate in the tension zone, drilling and grouting techniques are used to drill holes in the suspected area and inject high-strength epoxy resin (compressive strength greater than 50MPa, grouting pressure 3~4MPa) to fill voids and cracks, restoring the density of the concrete around the lower anchor plate. For damage to the upper anchor plate area on the pressure side, a local replacement repair method is adopted. The damaged grouting layer and concrete are removed, and high-strength grout (with a strength 5MPa higher than the original design requirement) is used for re-grouting.

[0039] The aforementioned reinforcement measures advocate drilling and grouting to repair the concrete around the lower anchor plate, rather than replacing the anchor bolts. This significantly reduces repair costs and construction time, and has important engineering economic value.

[0040] Through precise assessment, it has been demonstrated that in most cases, the safety of the foundation can be restored simply by repairing the concrete, without the need to replace expensive and complex anchor bolts, thus achieving an economical, efficient, and reliable repair.

[0041] Figure 1 This is a flowchart of the method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after a wind turbine tower collapse, according to the present invention. The specific process includes: collecting data, including the design, construction, and historical operation of the collapsed tower unit, as well as the cause of the collapse, its location, and the height of the tower's bending point; calculating the collapse bending moment and the anchor bolt axial force, using the following formula: ; ; in, For the inverted tower bending moment; Theoretical calculation of axial force for any anchor bolt under the action of tower collapse; The value for severe damage to steel is the coefficient, ranging from 1.0 to 1.32 (strength-to-yield ratio of steel). / ,in, (where is the ultimate tensile strength of the steel), and in this embodiment, it is taken as 1.32; The thickness of the steel tower; Where is the tower radius; This is the distance from the anchor bolt to the neutral axis; For the tower's own weight; This refers to the number of anchor bolts. This refers to the bending range of the steel tower.

[0042] Further on-site testing and data collection were conducted, including testing the condition of the upper anchor plate and foundation surface, measuring the exposed length of the anchor bolts, and testing the anchor bolt preload. The calculation formula is the theoretical limit of the exposed length before the upper tower is removed. Formula and the maximum axial force actually experienced by the anchor bolts during the tower collapse process Formula; then conduct a comprehensive assessment, assessing the deformation of the upper anchor plate and the crushing of the grouting layer and concrete, and assessing the deformation of the anchor bolts and the defects in the concrete around the lower anchor plate; obtain reinforcement measures, including corresponding material conversion or drilling and grouting reinforcement at corresponding locations.

[0043] (1) Validation of the exposed length detection method: At a turbine tower collapse site, this method detected multiple anchor bolts exceeding the permitted exposed length. Subsequent drilling and video evidence of the excess locations clearly showed voids and looseness in the concrete surrounding the lower anchor plate, perfectly matching the detection results. This method has been validated in multiple turbine units at various locations.

[0044] (2) Verification of the maximum axial force calculation method: Calculations were performed on the test data of multiple tower collapse units (results are shown in Table 2). It was found that the maximum axial force actually experienced by the anchor bolts during the tower collapse process was derived by back-calculation using this method. The calculated value of the theoretical inverted tower bending moment is only. The results show that the anchor bolts did not break in the field even when the theoretically calculated values ​​far exceeded their bearing capacity. This demonstrates the plastic energy dissipation effect of concrete and verifies that the calculation method can more realistically reflect the actual stress level of the anchor bolts, avoiding over-evaluation.

[0045] Table 2 Calculation of maximum axial force on foundation anchor bolts for multiple tower collapse units

[0046] In the table, For P s1 The calculated maximum axial force of the anchor bolts during the tower collapse process; For P s2 The calculated maximum axial force of the anchor bolts during the tower collapse process; This is the maximum axial force actually experienced by the anchor bolts during the tower collapse process, and also... and The larger value in the range.

[0047] (3) Reinforcement Case Verification: The drilling and grouting reinforcement scheme proposed in this invention has been used to repair the foundations of several collapsed power tower units in China. Subsequent monitoring after the repair showed that the foundation bearing capacity was well restored, the anchor bolt preload remained stable, and no further abnormal losses occurred, proving the reliability and economy of the repair scheme.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the scope of the present invention. All equivalent structural transformations made under the inventive concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the protection scope of the present invention.

Claims

1. A method for detecting, evaluating, and reinforcing foundation anchor bolt assemblies after a wind turbine tower collapses, characterized in that, Includes the following steps: S1. Obtain the collapse characteristic information, determine the collapse direction and mode, and divide the tension zone and compression zone of the collapse foundation. The collapse characteristic information includes residual preload. S2. Detect the exposed length of the anchor bolts to identify areas where the exposed length exceeds the limit; Measured exposed length of anchor bolts on the foundation ring ; Theoretical limits for calculating the exposed length of anchor bolts Actual measured exposed length of anchor bolt It consists of three parts: the design exposed length Elastic elongation of anchor bolts during initial tensioning and the deformation of the lower anchor plate during initial tensioning. ,Right now: ； The construction and installation error should be controlled within ±1.5mm. If the deviation of the exposed length of the anchor bolt exceeds this range, it is determined that the foundation concrete has initial crushing or insufficient compaction defects. Therefore, the theoretical limit of the exposed length of the anchor bolt before tower removal is... for: ； The actual exposed length of the anchor bolt Theoretical limit of exposed length of anchor bolt Perform a comparison, if > If the concrete around the lower anchor plate corresponding to the anchor bolt is found to be non-compacted or has crushing defects, it is marked as a suspicious area; if ≤ If the anchor bolt is in the initial tensioning stage, it is determined that the concrete around the lower anchor plate did not show any abnormal additional displacement caused by insufficient pouring or initial crushing. ； in: Design preload for anchor bolts, L The length of the anchor bolt between the upper and lower nuts. E For the elastic modulus of the anchor bolt, The effective cross-sectional area of ​​the anchor bolt; S3. Perform pre-tension testing on anchor bolts in tension and compression zones to obtain residual pre-tension values ​​and identify areas of pre-tension loss. S4. Compare the area of ​​prestress loss with the area of ​​exposed length exceeding the limit to verify their consistency and find out the cause of prestress loss. S5. Based on the preload loss value under the residual preload reverse push tower collapse condition and the maximum axial force actually subjected to the anchor bolt during the tower collapse process, assess the degree of plastic damage to the anchor bolt. S6. The foundation condition level is comprehensively assessed by combining the exposed length, preload loss value, and maximum axial force of the anchor bolts on the tension side. S7. Based on the basic condition level, propose reinforcement measures.

2. The method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after wind turbine tower collapse according to claim 1, characterized in that, Anchor bolt preload loss value The range is arrive between: ； ； in: This represents the residual preload of the anchor bolts after the tower collapses. relative design preload Preload loss, The relative over-tensioning preload is 1.

15. The loss of preload.

3. The method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after wind turbine tower collapse according to claim 2, characterized in that, The maximum axial force actually experienced by the anchor bolts during the tower collapse process The calculation formula is as follows: ； in: The axial force at which the anchor bolt reaches its yield strength. ; This represents the conditional yield strength of the anchor bolt steel.

4. The method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after wind turbine tower collapse according to claim 3, characterized in that, At S5, the maximum axial force actually experienced by the anchor bolts during the tower collapse process will be calculated. Axial force when the anchor bolt steel reaches the conditional yield strength If a comparison is made, < If the anchor bolt has not undergone significant plastic deformation and is within its elastic working range, it can continue to be used; if ≥ If the anchor bolt deformation has entered the plastic stage, it should be replaced.

5. The method for detecting, evaluating, and reinforcing the foundation anchor bolt assembly after wind turbine tower collapse according to claim 1, characterized in that, When the basic condition level is localized damage, the reinforcement measures are as follows: For localized damage caused by non-dense concrete around the anchor plate in the tension zone, drilling and grouting techniques were used to drill holes in the suspected areas and fill voids and cracks by injecting high-strength epoxy resin. For damage to the upper anchor plate area on the pressure side, a local replacement repair method is adopted, which involves removing the damaged grouting layer and concrete, and then re-grouting with high-strength grout.

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