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

Abstract

The present application relates to the technical field of wind power engineering, and particularly relates to a detection, evaluation and reinforcement method for a foundation anchor bolt assembly of a wind turbine after tower overturning, which comprises obtaining tower overturning characteristic information, the tower overturning characteristic information comprising residual pre-tension; detecting the exposed length of the anchor bolt to obtain a region with an exposed length exceeding a limit; detecting the pre-tension of the anchor bolt in the tension area and the compression area to obtain a residual pre-tension value and a pre-tension loss area; evaluating the plastic damage degree of the anchor bolt based on the residual pre-tension, the pre-tension loss value under the tower overturning condition and the maximum axial force actually borne by the anchor bolt during the tower overturning process; comprehensively evaluating the foundation state and grading based on the exposed length, the pre-tension loss value and the maximum axial force of the anchor bolt on the tension side; and proposing reinforcement measures according to the comprehensive evaluation grade of the foundation state. The present application can effectively identify millimeter-level damage that cannot be found by conventional methods and is more accurate in positioning, so as to scientifically judge the plastic damage degree and the remaining safety of the anchor bolt.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind power engineering, and in particular to a detection, evaluation and reinforcement method for a foundation anchor bolt assembly of a wind turbine after tower overturning. BACKGROUND

[0002] In the common tower overturning mode, the pre-tension loss of the foundation anchor bolt is widespread, which becomes the key to post-accident disposal and safety evaluation. Accurate evaluation of the damage degree of the anchor bolt and the foundation is the basis for determining the repair scheme and ensuring the safe operation of the unit. The existing detection methods mainly include the following:

[0003] (1) Radar detection (according to the JGJ / T456-2019 standard): The internal defects of concrete are detected by radar wave reflection. However, its main disadvantage is that it can only identify large-volume cavities or layers, and it is difficult to accurately identify local crushing, loosening and other damage around the anchor plate, which cannot meet the requirements of detailed evaluation.

[0004] (2) Ultrasonic detection method: The internal quality is evaluated by using the propagation characteristics of ultrasonic waves in concrete. Similarly, this method has insufficient sensitivity to deep-buried and small-range local damage, and the detection results are easily affected by the distribution of steel bars, making interpretation difficult.

[0005] (3) Anchor bolt tension force-deformation field detection method (ZL202410396262.8): The mechanical response of the anchor bolt is measured by directly tensioning the anchor bolt. This method has certain effect on severely damaged tower overturning modes (such as the tower cylinder completely pulled out of the foundation), but it is not suitable for the more common and less damaged tower overturning modes (such as the tower cylinder bending but not completely separated), and it is complex and costly, which is not suitable for the scene where a large number of anchor bolts need to be quickly screened after an accident.

[0006] (4) Long-term prestress monitoring technology: 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 environmental degradation, and are not suitable for rapid emergency evaluation after sudden and strong impact events such as tower overturning.

[0007] And the above detection methods lack a calculation model that relates the field detection data (such as pre-tension loss) to the tower overturning extreme load, and cannot quantitatively evaluate the maximum stress state of the anchor bolt at the moment of tower overturning, so as to scientifically judge the plastic damage degree and remaining safety of the anchor bolt. And due to the inability to accurately evaluate, the engineering practice often tends to adopt a conservative strategy, such as replacing the anchor bolt as a whole, resulting in high repair cost and prolonged construction period. SUMMARY

[0008] The main purpose of the present application is to provide a detection, evaluation and reinforcement method for the foundation anchor bolt assembly of a wind turbine after tower inversion, aiming to solve the technical problems of long repair and reinforcement period and high cost caused by the inability of existing methods to scientifically judge the plastic damage degree and residual safety of the anchor bolt.

[0009] To achieve the above-mentioned purpose, the present application provides a detection, evaluation and reinforcement method for the foundation anchor bolt assembly of a wind turbine after tower inversion, comprising the following steps:

[0010] S1, obtaining tower inversion characteristic information, determining the tower inversion direction and mode, dividing the tower inversion foundation tension zone and compression zone, and the tower inversion characteristic information including residual pre-tension;

[0011] S2, detecting the exposed length of the anchor bolt to obtain the area with exposed length exceeding the limit;

[0012] S3, detecting the pre-tension of the anchor bolt in the tension zone and the compression zone to obtain the residual pre-tension value and the pre-tension loss area;

[0013] S4, comparing the pre-tension loss area with the area with exposed length exceeding the limit to verify the consistency of the two, and obtaining the cause of pre-tension loss;

[0014] S5, based on the residual pre-tension, inversely deducing the pre-tension loss value under the tower inversion working condition and the maximum axial force actually borne by the anchor bolt during the tower inversion process, and evaluating the plastic damage degree of the anchor bolt;

[0015] S6, comprehensively evaluating the foundation state grade based on the exposed length, the pre-tension loss value and the maximum axial force of the anchor bolt on the tension side;

[0016] S7, proposing reinforcement measures according to the foundation state grade.

[0017] The further improvement of the detection, evaluation and reinforcement method for the foundation anchor bolt assembly of a wind turbine after tower inversion lies in that S2 comprises the following steps:

[0018] measuring the measured exposed length of the anchor bolt on the foundation ring ;

[0019] calculating the theoretical limit value of the exposed length of the anchor bolt , the measured exposed length of the anchor bolt is composed of three parts: the designed exposed length , the elastic elongation of the anchor bolt at the initial tensioning and the deformation amount of the anchor plate at the initial tensioning , that is:

[0020] ;

[0021] The construction installation error is controlled within ±1.5mm, if the exposed length deviation of the anchor bolt exceeds the range, it is determined that the initial crushing or the pouring non-dense defect exists in the foundation concrete, and the theoretical limit value of the exposed length of the anchor bolt before the tower cylinder is removed is:

[0022] ;

[0023] The measured exposed length of the anchor bolt is compared with the theoretical limit value of the exposed length of the anchor bolt If , it is determined that the non-dense or crushing defect exists in the surrounding concrete of the lower anchor plate corresponding to the anchor bolt, and is marked as a suspicious area; if ≤ , it is determined that the surrounding concrete of the lower anchor plate does not appear additional displacement abnormality caused by pouring non-dense or initial crushing in the initial tension stage of the anchor bolt.

[0024] ;

[0025] Wherein: is the design pre-tension of the anchor bolt, L is the length of the anchor bolt between the upper and lower nuts, E is the elastic modulus of the anchor bolt, is the effective cross-sectional area of the anchor bolt.

[0026] The further improvement of the detection, evaluation and reinforcement method of the foundation anchor bolt assembly of the wind turbine after the tower is reversed in the application lies in that the anchor bolt pre-tension loss value ranges from to :

[0027] ;

[0028] ;

[0029] Wherein: is the residual pre-tension value of the anchor bolt after the tower is reversed, is the pre-tension loss relative to the design pre-tension , and is the pre-tension loss relative to the over-tension pre-tension 1.15 .

[0030] The further improvement of the detection, evaluation and reinforcement method of the foundation anchor bolt assembly of the wind turbine after the tower is reversed in the application lies in that the maximum axial force actually borne by the anchor bolt in the tower reversing process is calculated as follows:

[0031] ;

[0032] wherein: is the axial force of the anchor when reaching the yield strength, ; is the effective cross-sectional area of the anchor; is the conditional yield strength of the anchor steel material; is the elastic modulus of the anchor.

[0033] The further improvement of the detection, evaluation and reinforcement method of the foundation anchor assembly of the wind turbine after tower overturning is that, at S5, the maximum axial force actually borne by the anchor during the tower overturning is compared with the axial force of the anchor steel material when reaching the conditional yield strength If , , it is indicated that the anchor does not have obvious plastic deformation and is in the elastic working range, and continues to be used; if ≥ , it is indicated that the anchor deformation enters the plastic stage, and needs to be replaced.

[0034] The further improvement of the detection, evaluation and reinforcement method of the foundation anchor assembly of the wind turbine after tower overturning is that, when the foundation state level is local damage, the reinforcement measures are as follows:

[0035] For the local damage of the non-dense concrete around the lower anchor plate in the tension area, the drilling and grouting technology is used to drill holes in the suspicious area, and the high-strength epoxy resin is injected to fill the cavities and cracks;

[0036] For the local damage of the upper anchor plate area on the compression side, the local replacement repair method is used to remove the damaged grouting layer and concrete, and high-strength grouting material is used for regrouting.

[0037] The technical scheme of the present application has the following beneficial effects:

[0038] Compared with the radar method and the ultrasonic method, the exposed length detection method of the wind turbine tower overturning foundation anchor bolt assembly is more convenient and faster to operate, can effectively identify millimeter-level damage that is difficult to find by conventional methods, and is more accurate in positioning, so as to scientifically judge the shaping damage degree and the remaining safety of the anchor bolt; compared with experience or conservative assumptions, the maximum axial force calculation method is based on measured data and a mechanical model, can quantitatively evaluate the safety of the anchor bolt, and avoids unnecessary replacement of the anchor bolt, thereby saving costs; the core repair scheme of the present application is grouting reinforcement of the concrete, instead of replacing the anchor bolt, which can save about 60-70% of the repair cost, shorten the construction period by more than 50%, and solve the technical problems of long construction period and high cost of tower body repair and reinforcement. The present application provides a one-stop technical solution from field rapid detection, mechanical state evaluation to economic repair scheme, which is clear in logic, clear in steps, easy for engineering and technical personnel to master and implement, and is especially suitable for the most common and relatively light damage mode of tower overturning. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and all other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0040] Figure 1 The flowchart of the detection, evaluation and reinforcement method of the wind turbine tower overturning foundation anchor bolt assembly of the present application;

[0041] Figure 2 The flowchart for obtaining the stress-strain simplified double-line model of the steel material without obvious yield point (a is the constitutive model, b is the stress simplified double-line model, and c is the axial force simplified double-line model). DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort belong to the scope of protection of the present application.

[0043] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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:

[0048] 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.

[0049] 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.

[0050] 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. ;

[0051] Based on design parameters and material properties, calculate the theoretical limit for the exposed length of the anchor bolt. , measured exposed length of anchor bolt consists of three parts: designed exposed length of anchor bolt , elastic elongation of anchor bolt at initial tensioning and deformation of lower anchor plate at initial tensioning , that is:

[0052] ;

[0053] According to the Technical Code for Wind Turbine Generator System Prestressed Foundation Anchor Bolt Cage Assembly, the construction installation error is 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 pouring defects, and the theoretical limit value of the exposed length of the anchor bolt before the tower cylinder is removed is:

[0054] ;

[0055] ;

[0056] Among them: is the designed pre-tension of the anchor bolt, L is the length of the anchor bolt between the upper and lower nuts, E is the elastic modulus of the anchor bolt, is the effective cross-sectional area of the anchor bolt.

[0057] It should be noted that the present application does not only determine the qualifiedness of the exposed length of the anchor bolt according to the allowable deviation of construction installation, but also takes the exposed length of the anchor bolt as an external characterization of the overall deformation response of the anchor bolt-lower anchor plate-concrete system under the inverted tower condition. When there is an initial pouring defect in the surrounding concrete of the lower anchor plate, the lower anchor plate will produce additional displacement under the action of the pre-tension, thereby causing the exposed length of the anchor bolt to increase significantly. When this increment exceeds the limit value determined by the design parameters and the elastic properties of the material, the construction installation error factor can be excluded, and it is further determined that the concrete in this area has a structural defect.

[0058] The measured exposed length of anchor bolt is compared with the theoretical limit value of the exposed length of the anchor bolt , if > , it is determined that the surrounding concrete of the lower anchor plate corresponding to the anchor bolt has a defect of pouring or crushing, and is marked as a suspicious area; if ≤ , it is determined that the surrounding concrete of the lower anchor plate corresponding to the anchor bolt has no obvious additional displacement abnormality caused by pouring or initial crushing at the initial tensioning stage, but further evaluation is still needed in combination with the residual pre-tension detection of S3 and the consistency analysis of S4, because the additional crushing deformation of the surrounding concrete of the lower anchor plate caused by the inverted tower load may cause the loss of pre-tension and have no effect on the exposed length.

[0059] This step is simple, fast and low cost, which can be used for rapid survey of all anchor bolts on the accident site, accurate positioning of potential damage area, and providing clear target for subsequent detailed detection and evaluation.

[0060] S3, pre-tension detection of anchor bolts in tension area and compression area to obtain residual pre-tension value of anchor bolts after tower collapse , and obtain pre-tension loss area;

[0061] S4, comparing the pre-tension loss area with the area with exposed length exceeding the limit to verify the consistency of the two areas, and obtaining the reason for pre-tension loss:

[0062] If the two areas are consistent, it indicates that the pre-tension loss and the additional displacement of the lower anchor plate caused by local crushing or non-dense pouring of the surrounding concrete of the lower anchor plate have a strong corresponding relationship, and the pre-tension loss mechanism is more likely to be mainly caused by local damage of the foundation.

[0063] If the two areas are inconsistent, it indicates that the pre-tension loss mechanism is more likely to be caused by the elongation of the anchor bolt itself.

[0064] S5, based on the residual pre-tension, the pre-tension loss value under the tower collapse working condition and the maximum axial force actually borne by the anchor bolt during the tower collapse process, the plastic damage degree of the anchor bolt is evaluated;

[0065] Since over-tensioning is often used in construction, the pre-tension loss value of the anchor bolt ranges from to :

[0066] ;

[0067] ;

[0068] Among them: is the residual pre-tension value of the anchor bolt after the tower collapse, is the pre-tension loss relative to the design pre-tension , and is the pre-tension loss relative to the over-tensioning pre-tension 1.15 .

[0069] Based on the simplified double-fold line model of stress-strain of steel material without obvious yield point, and assuming that the design pre-tension of the anchor bolt corresponds to the elastic limit point, as shown in Figure 2 , the calculation formula of the maximum axial force actually borne by the anchor bolt during the tower collapse process is derived as follows:

[0070] ;

[0071] ;

[0072] wherein: is the axial force of the anchor when reaching the yield strength; is the effective cross-sectional area of the anchor; is the conditional yield strength of the anchor steel material; is the elastic modulus of the anchor.

[0073] Figure 2 wherein: and are the strain and stress of the anchor at the design pre-tension , respectively, also set as the elastic limit point; is the conditional yield strength of the anchor steel material; is the plastic strain of the anchor when reaching the conditional yield strength; is the total strain of the anchor when reaching the conditional yield strength; is the design pre-tension of the anchor; is the maximum axial force actually borne by the anchor during the tower-toppling process; is the residual pre-tension value of the anchor after the tower-toppling, which can be determined according to the actual measurement on site; is the axial force of the anchor when reaching the yield strength; is the pre-tension loss value of the anchor; is the total strain of the anchor generated during the tower-toppling process; is the plastic strain of the anchor generated during the tower-toppling process; is the elastic strain of the anchor generated during the tower-toppling process; is the plastic strain of the anchor when reaching the conditional yield strength, is the plastic-elastic strain of the anchor when reaching the conditional yield strength.

[0074] The maximum axial force actually borne by the anchor during the tower-toppling process is compared with the axial force of the anchor steel material when reaching the conditional yield strength If < , it is indicated that the anchor does not have obvious plastic deformation and is in the elastic working range, and can be continued to be used; if ≥ ( approaches or exceeds ), it is indicated that the deformation of the anchor has entered the plastic stage and needs to be directly replaced.

[0075] S6, in combination with the exposed length, the pre-tension loss value and the maximum axial force of the anchor bolt on the tension side, the foundation state is comprehensively evaluated as three levels of "intact", "local damage" or "serious damage" (evaluation as shown in Table 1); this step provides a quantifiable mechanical evaluation tool, and solves the problem of how to scientifically judge whether the anchor bolt is plastically damaged after extreme load. By cross comparison and consistency analysis of the abnormal area of the exposed length of the anchor bolt, the significant area of the pre-tension loss and the inverse calculation result of the maximum axial force, different damage modes caused by concrete crushing, anchor bolt plastic deformation or local construction defects can be effectively distinguished, so that the reliability of the evaluation conclusion is improved and misjudgment caused by a single detection means is avoided.

[0076] Table 1: Comprehensive evaluation method of foundation state level

[0077]

[0078] In Table 1: The pre-tension of the anchor bolt is designed; The theoretical limit value of the exposed length is; The axial force of the anchor bolt when reaching the yield strength is.

[0079] S7, according to the comprehensive evaluation level of the foundation state, reinforcement measures are proposed. This step standardizes the on-site operation steps after the tower collapse accident, realizes the closed loop from rapid preliminary judgment to accurate evaluation, and improves the evaluation efficiency and accuracy.

[0080] The reinforcement and repair scheme of the application is not independently proposed, but is determined comprehensively based on the foregoing anchor bolt exposed length detection result, residual pre-tension detection result and maximum axial force inverse calculation evaluation conclusion. When the evaluation result shows that the anchor bolt is still in an elastic working state and the surrounding concrete of the lower anchor plate has local damage, the reinforcement and repair measures for the concrete are preferred to avoid unnecessary replacement of the anchor bolt.

[0081] When the comprehensive evaluation level of the foundation state is local damage, the reinforcement measures are as follows:

[0082] For local damage of the surrounding concrete of the lower anchor plate in the tension area, drilling and grouting technology is used to drill holes in the suspicious area, high-strength epoxy resin (compressive strength greater than 50MPa, grouting pressure 3~4MPa) is injected to fill the voids and cracks, and the density of the surrounding concrete of the lower anchor plate is restored;

[0083] For local damage of the upper anchor plate area on the compression side, the local replacement repair method is used to remove the damaged grouting layer and concrete, and high-strength grouting material (strength selected to be 5MPa higher than the original design requirement) is used for regrouting.

[0084] The reinforcement measures drill and grout the concrete around the lower anchor plate for repairing instead of replacing the anchor bolt, significantly reduce the repair cost and construction period, and have important engineering economic value.

[0085] Through accurate evaluation, it is proved that in most cases, the safety of the foundation can be restored by only repairing the concrete, without replacing the expensive and complex anchor bolt, so that economic, efficient and reliable repair is realized.

[0086] Figure 1 The flow chart of the detection, evaluation and reinforcement method of the wind turbine tower-reversed foundation anchor bolt assembly of the wind turbine set, and the specific process includes: collecting data, including the design, construction and historical operation of the tower-reversed set, the reason, direction and tower cylinder bending point height of the tower reversal; calculating the tower-reversed bending moment and anchor bolt axial force, and the calculation formula is as follows:

[0087]

[0088]

[0089] is the tower-reversed bending moment; is the theoretical calculation axial force of any anchor bolt under the action of the tower reversal; is a steel serious damage value coefficient, and the value range is 1.0-1.32 (steel yield ratio / , wherein is the ultimate value of the tensile strength of the steel), and the value of the embodiment is 1.32; is the thickness of the steel tower cylinder; is the radius of the tower cylinder; is the distance from the anchor bolt to the neutral axis; is the self weight of the tower cylinder; is the number of anchor bolts; is the bending range of the steel tower cylinder.

[0090] Then, the on-site detection is carried out, the data is collected, including the state detection of the upper anchor plate and the foundation surface layer, the exposed length detection of the anchor bolt and the pre-tension detection of the anchor bolt, the calculation formula is as follows: the theoretical limit value of the exposed length of the tower cylinder before the tower is removed formula and the maximum axial force actually borne by the anchor bolt during the tower reversal formula; then, the comprehensive evaluation is carried out, the deformation of the upper anchor plate and the crushing condition of the grouting layer and the concrete are evaluated, the deformation of the anchor bolt and the defect condition of the concrete around the lower anchor plate are evaluated; the reinforcement measures are obtained, including the corresponding material conversion or the drilling and grouting reinforcement at the corresponding position.

[0091] (1) exposed length detection method verification:

[0092] ​​​In a certain tower crane set site, multiple anchor bolt exposed length overruns are detected by the method. Subsequently, the overrun position is drilled for video evidence, and the results clearly show that there are holes and loose concrete around the anchor plate, which is completely consistent with the test results. The method is applied to multiple tower crane sets in many places, and is verified.

[0093] (2) Maximum axial force calculation method verification:

[0094] The detection data of multiple tower crane sets are calculated (the results are shown in Table 2), and it is found that the maximum axial force actually borne by the anchor bolt in the tower overturning process derived by the method is 49%-60% of the theoretical tower overturning moment calculation value. This result explains why the anchor bolt has not been broken in the case where the theoretical calculation value far exceeds the bearing capacity of the anchor bolt, proves the plastic energy dissipation effect of the concrete, and verifies that the calculation method can more truly reflect the actual stress level of the anchor bolt and avoid overestimation.

[0095] Table 2 Maximum axial force calculation of foundation anchor bolts of multiple tower crane sets

[0096]

[0097] In the table, P s1 is the maximum axial force of the anchor bolt in the tower overturning process calculated by the method; P s2 is the maximum axial force of the anchor bolt in the tower overturning process calculated by the method; is the maximum axial force actually borne by the anchor bolt in the tower overturning process, which is also the larger value in and .

[0098] (3) Reinforcement case verification:

[0099] The drilling and grouting reinforcement scheme proposed by the present application is used to repair the foundations of multiple tower crane sets in China. The subsequent monitoring after the repair shows that the foundation bearing capacity is restored well, the anchor bolt pre-tensioning force remains stable, and no abnormal loss occurs again, proving the reliability and economy of the repair scheme.

[0100] The above only describes the preferred embodiments of the present application, and does not limit the scope of the present application, and any equivalent structural transformation made under the inventive concept of the present application, or direct / indirect application in other related technical fields is included in the protection scope of the present application.​​​

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 incomplete 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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