A method for reconstructing and reinforcing a fan expansion foundation

Abstract

This invention specifically discloses a method for modifying and reinforcing a wind turbine foundation, comprising the following steps: S1, breaking the concrete of the original central pier in the original wind turbine foundation, excavating to the foundation base slab, installing several inner ring bolts on the top of the original foundation ring, and installing strain sensors at the connection between the original foundation ring and the inner ring bolts; S2, embedding a new foundation ring on the outside of the original foundation ring, the diameter of the new foundation ring being larger than the diameter of the original foundation ring but smaller than the diameter of the original central pier; S3, horizontally chiseling several first and second slots along the original foundation rib ring of the original wind turbine foundation, the first slots extending to the sidewall of the new foundation ring, the first anchor rod passing through the first slot and fixedly connected to the original foundation ring, the second slots extending to the sidewall of the original foundation ring, the second anchor rod passing through the second slot and fixedly connected to the original foundation ring. This invention is beneficial for improving the overturning resistance and compressive strength of the wind turbine foundation, and the modified wind turbine foundation has remote monitoring capabilities.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and in particular to a method for upgrading and reinforcing the foundation of a wind turbine for capacity expansion. Background Technology

[0002] Wind energy, as a renewable energy source, has a wide range of applications, large reserves, and is readily available. It is a green and ideal energy source that meets the needs of sustainable development. With the progress of the times and the development of human science and technology, old small wind turbines are no longer suitable for the development of the times and cannot meet human needs due to their low power output, easy damage, and large land occupation. It is now necessary to expand and upgrade existing wind turbines. At the same time, the principle of minimizing land occupation should be adhered to during the expansion and upgrading of the foundation.

[0003] There are many outdated wind farms. In order to complete the renovation of the foundations of old wind farms efficiently and at low cost, the renovation can be carried out on the basis of the existing old wind turbines. This avoids the demolition of the original wind turbine foundations and reduces or avoids the acquisition of new land.

[0004] In the prior art, patent CN114775676A discloses a method for retrofitting existing wind turbine foundations in aging wind farms. This method involves installing inner and outer rings of anchor bolts on the existing structure of the wind turbine foundation. After installation, concrete is poured on the top and outside of the foundation's central pier to form an enlarged central pier, into which the inner and outer rings of anchor bolts are embedded. The pre-tensioning force of the anchor bolts ensures sufficient integrity and safety of the retrofitted wind turbine foundation. However, while this method enlarges the original central pier and installs a tower, it does not improve the foundation ribs on both sides or install new pile foundations at the bottom. Consequently, its overturning resistance and compressive strength are not significantly improved, and the retrofitted wind turbine foundation lacks remote monitoring capabilities.

[0005] The aforementioned technical issues need to be addressed. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for modifying and reinforcing the foundation of a wind turbine, which is beneficial to improving the overturning resistance and compressive strength of the wind turbine foundation, and the modified wind turbine foundation has remote monitoring function.

[0007] To achieve the above objectives, the present invention provides a method for reinforcing and upgrading the foundation of a wind turbine expansion project, comprising the following steps:

[0008] S1. Destroy the concrete of the original central pier in the original wind turbine foundation, excavate to the foundation bottom plate, install several inner ring bolts on the top of the original foundation ring, and install strain sensors at the connection between the original foundation ring and the inner ring bolts.

[0009] S2. A new foundation ring is embedded outside the original foundation ring. The diameter of the new foundation ring is larger than the diameter of the original foundation ring and smaller than the diameter of the original central pier.

[0010] S3. Several first and second slots are horizontally chiseled along the original foundation rib ring of the original wind turbine foundation. The first slot extends to the side wall of the new foundation ring. The first anchor rod passes through the first slot and is fixedly connected to the original foundation ring. The second slot extends to the side wall of the original foundation ring. The second anchor rod passes through the second slot and is fixedly connected to the original foundation ring. After installation, the first anchor rod is tensioned and the first slot is grouted with high strength.

[0011] S4. New concrete is poured on the outside and top of the original central pier to form an enlarged circular central pier. After curing, the top of the new foundation ring is connected to the top of the inner ring bolts by connecting steel bars.

[0012] S5. Excavate along the original foundation rib to open the original foundation reinforcement, excavate several first ducts circumferentially and vertically along the outer periphery of the original foundation rib, excavate several second ducts circumferentially and vertically along the middle of the original foundation rib, and several third anchor rods pass through the corresponding first ducts with their bottom ends fixed to the rock mass and their top ends fixed to the foundation slab. Several uniformly variable cross-section piles pass through the corresponding second ducts with their bottom ends fixed to the rock mass and their top ends fixed to the foundation slab.

[0013] S6. A third anchor rod and a uniform variable cross-section pile are fixedly connected to the bottom of a new foundation rib, and the upper part of the new foundation rib is fixedly connected to the first anchor rod and the second anchor rod.

[0014] S7. After the new foundation ring passes inspection, the foundation reinforcement is tied, and then concrete is poured.

[0015] S8. After the concrete curing is completed, a level is installed on the side wall of the enlarged circular pier. The lead wire i of the strain sensor and the lead wire ii of the level are both connected to the signal transmitter box.

[0016] As a further improvement to the above technical solution, in step S1, after the inner ring bolt is fitted with a pre-embedded sleeve, the bottom end is anchored to the top flange of the original foundation ring, and an upper anchor plate is installed on the top of each inner ring bolt, with a nylon nut on the bottom surface of the upper anchor plate.

[0017] As a further improvement to the above technical solution, step S2, embedding the new foundation ring includes the following steps: pre-embedding steel plates in the concrete cushion layer; connecting the lower end of the support frame of the new foundation ring to the foundation base plate; connecting the new foundation ring and the support frame with adjusting bolts; adjusting bolts can adjust the flatness of the foundation ring; detecting three points on the upper flange surface of the new foundation ring corresponding to the adjusting bolts; if the levelness of the detected points exceeds the set threshold, then using a jack in conjunction with the adjusting bolts and readjusting the level instrument, the levelness of the foundation ring is controlled within the set range.

[0018] As a further improvement to the above technical solution, in step S3, the first anchor rod is a prestressed anchor rod structure, and the first anchor rod is fitted with a pre-embedded sleeve and bound or welded to the new foundation ring to form an integral whole; the second anchor rod is a hollow anchor rod structure, and the second anchor rod is bound or welded to the original foundation ring to form an integral whole; the lead wire i of the strain sensor passes through the second anchor rod and extends to the outside.

[0019] As a further improvement to the above technical solution, in step S4, when the new concrete is poured, an annular cavity for installing strain sensors is formed at the original foundation ring top flange.

[0020] As a further improvement to the above technical solution, in step S5, after the third anchor rod is fitted with a pre-embedded sleeve, the bottom end passes through the first duct from top to bottom. After the third anchor rod is fixed to the rock mass, concrete is poured into the first duct. After completion, the third anchor rod is tensioned. After completion, the top of the third anchor rod is tied or welded to the reinforcing steel of the foundation plate.

[0021] As a further improvement to the above technical solution, in step S5, a first cylindrical cavity and a second cylindrical cavity with larger diameters are left at the middle and bottom ends of the second duct, respectively. The reinforcing cage is placed into the second duct from top to bottom, and then grouting is carried out. When the grouting reaches the first cylindrical cavity and the second cylindrical cavity, the concrete slump, spread and air content are checked to ensure that the first cylindrical cavity and the second cylindrical cavity are completely filled, thereby forming a uniform variable cross-section pile. The upper end of the uniform variable cross-section pile is tied or welded to the reinforcing steel of the foundation slab to form a whole.

[0022] As a further improvement to the above technical solution, in step S6, the bottom of the new foundation rib is tied or welded to the foundation base plate, and the upper part of the new foundation rib is tied or welded to the first anchor rod and the second anchor rod.

[0023] As a further improvement to the above technical solution, in step S7, when pouring concrete, the concrete is poured in one go without leaving a construction joint.

[0024] As a further improvement to the above technical solution, in step S8, the signal transmitting box is connected to a remotely set monitoring station for communication.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] This invention provides a method for upgrading and reinforcing a wind turbine foundation. By forming a new foundation ring and new foundation ribs, the new foundation ring has a larger diameter than the old foundation ring, and the new foundation ribs occupy less space. A third anchor rod and uniformly variable cross-section piles are also installed under the new foundation ribs, connecting the third anchor rod or uniformly variable cross-section piles to the foundation slab as a whole, and connecting the foundation slab to the new foundation ribs as a whole. The newly added anchor rods increase the wind turbine's anti-overturning capacity, and the newly added uniformly variable cross-section piles increase the wind turbine's overall bearing capacity, compressive strength, and anti-overturning capacity. Simultaneously, this invention connects both the old and new foundation rings with the new foundation ribs to form a whole, improving the overall integrity of the wind turbine. Furthermore, this invention adds an intelligent remote monitoring system, enabling real-time remote monitoring of the wind turbine foundation's safety and stability.

[0027] The method of this invention is simple and easy to implement. All procedures can be carried out using conventional construction methods, which effectively improves the construction efficiency of wind turbine foundation technical transformation, speeds up the construction progress, and shortens the construction period.

[0028] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute a limitation thereof.

[0030] Figure 1 This is a schematic diagram of the original fan foundation;

[0031] Figure 2 This is a schematic diagram of the new air ventilator foundation modified according to the present invention;

[0032] Figure 3 This is a cross-sectional view of the internal structure of the new air ventilator foundation after the modification by this invention;

[0033] Figure 4 for Figure 3 Cross-sectional view along the AA direction;

[0034] Figure 5 for Figure 3 Cross-sectional view along the BB direction;

[0035] Figure 6 This is a cross-sectional view of a uniformly variable cross-section pile.

[0036] Figure 7 This is a top view of the new air ventilator foundation after the modification by the present invention.

[0037] Explanation of reference numerals in the attached drawings: 1-Original central pier; 2-Inner ring bolt; 3-Enlarged circular central pier; 4-Original foundation ring; 5-Upper anchor plate; 6-New foundation ring; 7-Foundation base plate; 8-Original foundation rib; 9-First slot; 10-First anchor rod; 11-First duct; 12-Second duct; 13-Third anchor rod; 14-New foundation rib; 15-Second slot; 16-Second anchor rod; 17-First cylindrical cavity; 18-Second cylindrical cavity; 19-Uniform variable cross-section pile; 20-Strain sensor; 21-Level; 22-Connecting reinforcing bar; 24-Annular cavity; 25-Adjusting bolt. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] like Figures 1 to 7 As shown: This embodiment provides a method for upgrading and reinforcing the foundation of a wind turbine expansion project, including the following steps:

[0041] S1. Destroy the concrete of the original central pier 1 in the original wind turbine foundation, excavate to the foundation bottom plate 7, install several inner ring bolts 2 on the top of the original foundation ring 4, and install strain sensors 20 at the connection between the original foundation ring 4 and the inner ring bolts 2.

[0042] S2. A new foundation ring 6 is embedded outside the original foundation ring 4. The diameter of the new foundation ring 6 is larger than the diameter of the original foundation ring 4 and smaller than the diameter of the original central pier 1.

[0043] S3. Several first slots 9 and second slots 15 are horizontally chiseled around the original foundation rib 8 of the original wind turbine foundation. The first slots 9 extend to the side wall of the new foundation ring 6. The first anchor rod 10 passes through the first slot 9 and is fixedly connected to the original foundation ring 4. The second slot 15 extends to the side wall of the original foundation ring 4. The second anchor rod 16 passes through the second slot 15 and is fixedly connected to the original foundation ring 4. After installation, the first anchor rod 10 is tensioned and the first slot 9 is grouted with high strength to ensure compactness.

[0044] S4. Concrete is poured on the outside and top of the original central pier 1 to form an enlarged circular central pier 3. After curing, the top of the new foundation ring 6 is connected to the top of the inner ring bolt 2 by connecting steel bars 22.

[0045] S5. Excavate along the original foundation rib 8 to open the original foundation reinforcement, excavate several first ducts 11 in a circumferential vertical direction along the outer periphery of the original foundation rib 8, excavate several second ducts 12 in a circumferential vertical direction along the middle of the original foundation rib 8, several third anchor rods 13 pass through the corresponding first ducts 11 and their bottom ends are fixed to the rock mass and their top ends are fixed to the foundation base plate 7, and several uniformly variable cross-section piles pass through the corresponding second ducts 12 and their bottom ends are fixed to the rock mass and their top ends are fixed to the foundation base plate 7.

[0046] S6. A third anchor rod 13 and a uniform variable cross-section pile 19 are fixedly connected to the bottom of a new foundation rib 14, and the upper part of the new foundation rib 14 is fixedly connected to the first anchor rod 10 and the second anchor rod 16.

[0047] After the S7 and new foundation ring 6 pass the acceptance test, the foundation reinforcement is tied, and then concrete is poured.

[0048] S8. After the concrete curing is completed, a level 21 is installed on the side wall of the enlarged circular pier 3. The lead wire i of the strain sensor 20 and the lead wire ii of the level 21 are connected to the signal transmission box.

[0049] The original wind turbine foundation was circular or polygonal.

[0050] This reinforcement method involves installing a new foundation ring 6 on the original central pier 1 of the existing wind turbine foundation of the old wind farm, and installing an inner ring of anchor bolts inside. After installation, new concrete is poured on the top and outside of the original central pier 1 to form an enlarged circular central pier 3. The original structure of the wind turbine foundation of the old wind farm, the new foundation ring 6, the uniform variable cross-section pile 19, the pile anchor bolts and the newly poured concrete together constitute the modified wind turbine foundation.

[0051] Because a new foundation ring 6 and a new foundation rib 14 are formed, the new foundation ring 6 has a larger diameter than the old foundation ring, and the new foundation rib 14 occupies less space than the old foundation rib. A third anchor rod 13 and a uniformly variable cross-section pile 19 are also set under the new foundation rib 14, and the third anchor rod 13 or the uniformly variable cross-section pile 19 is connected to the foundation plate 7 into a whole, and the foundation plate 7 is connected to the new foundation rib 14 into a whole. The newly added anchor rod increases the wind turbine's anti-overturning capacity, and the newly added uniformly variable cross-section pile 19 increases the wind turbine's overall bearing capacity, compressive strength, and anti-overturning capacity. At the same time, this invention connects the old foundation ring and the new foundation ring 6 to the new foundation rib 14 to form a whole, improving the overall integrity of the wind turbine. In addition, this invention adds an intelligent remote monitoring system, which can realize real-time remote monitoring of the safety and stability of the wind turbine foundation.

[0052] Specifically, in step S1, after the inner ring bolt 2 is fitted with a pre-embedded sleeve, its bottom end is anchored to the top flange 4a of the original foundation ring 4. Each inner ring bolt 2 has an upper anchor plate 5 installed at its top, and a nylon nut is provided on the bottom surface of the upper anchor plate 5. The original foundation ring 4 is embedded inside the original middle pier 1; the pre-embedded sleeve ensures that the inner ring anchors are separated from the newly poured concrete. At this time, the number of inner ring anchors is the same as the number of holes on the top flange of the original foundation ring 4. The original foundation ring 4 is connected to a lower flange 4a, and the new foundation ring 6 is connected to an upper flange 6a and a lower flange 6b.

[0053] In step S2, embedding the new foundation ring 6 includes the following steps: pre-embedding steel plates in the concrete cushion layer; connecting the lower end of the support frame of the new foundation ring 6 to the foundation base plate 7; connecting the new foundation ring 6 to the support frame with adjusting bolts 25; adjusting bolts 25 can adjust the flatness of the foundation ring; detecting three points on the upper flange 6a of the new foundation ring 6 corresponding to the adjusting bolts 25; if the levelness of the detected points exceeds the set threshold, then using a jack in conjunction with the adjusting bolts 25 and readjusting the level instrument to control the levelness of the foundation ring within the set range.

[0054] In step S3, the first anchor rod 10 is a prestressed anchor rod structure, and the first anchor rod 10 is fitted with a pre-embedded sleeve and bound or welded to the new foundation ring 6 to form an integral whole; the second anchor rod 16 is a hollow anchor rod structure, and the second anchor rod 16 is bound or welded to the original foundation ring 4 to form an integral whole; the lead wire i of the strain sensor 20 passes through the second anchor rod 16 and extends to the outside.

[0055] In step S4, during the pouring of new concrete, an annular cavity 24 for installing the strain sensor 20 is formed at the top flange of the original foundation ring 4. The annular cavity ensures separation between the concrete and the connection point of the inner ring bolts 2 of the original foundation ring 4, as well as the strain sensor 20.

[0056] In step S5, after the third anchor rod 13 is fitted with a pre-embedded sleeve, the bottom end passes through the first duct 11 from top to bottom. After the third anchor rod 13 is fixed to the rock mass, concrete is poured into the first duct 11. After completion, the third anchor rod 13 is tensioned. After completion, the top end of the third anchor rod 13 is tied or welded to the reinforcing steel of the foundation plate 7.

[0057] In step S5, larger-diameter first cylindrical cavity 17 and second cylindrical cavity 18 are left at the middle and bottom ends of the second duct 12, respectively. The reinforcing cage is placed into the second duct 12 from top to bottom, and then grouting is performed. When the grouting reaches the first cylindrical cavity 17 and the second cylindrical cavity 18, the concrete slump, spread, and air content are checked to ensure that the first cylindrical cavity 17 and the second cylindrical cavity 18 are completely filled, thus forming a uniform variable cross-section pile 19. The upper end of the uniform variable cross-section pile 19 is tied or welded to the reinforcing steel of the foundation slab 7 to form a whole. The new foundation rib 14 is formed by tying reinforcing steel to the foundation slab 7. The uniform variable cross-section pile 19 is a bored cast-in-place pile, and the diameters of the first cylindrical cavity 17 and the second cylindrical cavity 18 are both larger than the diameter of the second duct 12.

[0058] In step S6, the bottom of the new foundation rib 14 is tied or welded to the foundation base plate 7, and the upper part of the new foundation rib 14 is tied or welded to the first anchor rod 10 and the second anchor rod 16 through the rib steel bars.

[0059] In step S7, the concrete is poured in one go without leaving a construction joint. After the concrete is poured and cured, the anchor bolts are tensioned and anchored inside the enlarged central pier and the new foundation rib 14. The tension force of the anchor bolts is transferred to the original foundation, achieving a tight bond between the old and new concrete and between the new rib and the original structure, ensuring the stability and integrity of the wind turbine foundation after the renovation.

[0060] In step S8, the signal transmitting box is communicatively connected to a remotely set monitoring station. The strain sensor 20 can measure the strain generated by the deformation of the object under stress in real time (specifically, the strain at the connection between the original foundation ring 4 and the inner ring bolt 2), and the level 21 can measure the levelness of the object in real time (specifically, the levelness of the enlarged circular pier 3). Lead wires i and ii are both wires that can transmit electrical energy and data. As an example, a 5G IoT transmitting box can be used to transmit the detection signals from the internal strain sensor 20 and level 21 of the foundation in real time; the 5G IoT transmitting box can be powered by a built-in lithium battery; and the signals are received at a remotely set monitoring station, facilitating real-time monitoring, intelligent early warning, and timely maintenance.

[0061] Example 2

[0062] This embodiment provides a reference calculation method for the overall bearing capacity, overturning resistance, and compressive strength of the modified foundation.

[0063] I. Calculation of foundation bearing capacity:

[0064] The characteristic value of foundation bearing capacity is determined by a combination of methods, including load tests or other in-situ tests, formula calculations, and practical experience.

[0065] When the width of the extended foundation is greater than 3m or the burial depth is greater than 0.5m, the characteristic value of the foundation bearing capacity determined by load tests or other in-situ tests, empirical values, etc., can be corrected according to formula (1):

[0066] f a =f ak +η b γ(b-3)+η d γ m (h m -0.5) (1)

[0067] In the formula: f a —The corrected characteristic value of the foundation bearing capacity of the soil;

[0068] f ak —Characteristic value of foundation bearing capacity; v b η d — Correction factor for foundation bearing capacity based on extended foundation width and depth;

[0069] γ—Unit weight of soil below the base of the extended foundation; buoyancy unit weight is taken below the groundwater level.

[0070] bs——The width of the spread foundation under the direction of the moment of force. When the width of the spread foundation under the compressive force is greater than 6m, the value is taken as 6m.

[0071] γ m —The weighted average unit weight of the soil above the foundation bottom surface is used, and the buoyant unit weight is used below the groundwater level.

[0072] h m — Increase the depth of foundation burial.

[0073] Table 1 Bearing Capacity Correction Coefficient Table

[0074]

[0075] Table 2 Characteristic values ​​of bearing capacity f of foundation rock mass ak

[0076]

[0077] II. Foundation compressive strength calculation:

[0078] (I) When subjected to axial load, the following requirements shall be met:

[0079] p k ≤f a (2)

[0080] p k p k - Average pressure at ground level of extended foundation under standard combination of load effects;

[0081] f a - Corrected characteristic value of foundation bearing capacity.

[0082] (ii) When subjected to eccentric load, in addition to meeting the requirements of equation (2) above, the requirements of equation (3) should also be met:

[0083] p kmax ≤1.2f a (3)

[0084] In the formula, p kmax - The maximum pressure value at the edge of the extended foundation bottom surface under the standard combination of load effects.

[0085] When the spread foundation bears axial loads and eccentric loads within the core zone (e≤b / 6), and the base surface does not detach from the foundation, the pressure on the ground surface of the spread foundation can be calculated using the following formula:

[0086] 1) When a circular foundation bears an axial load:

[0087]

[0088] In the formula, N k - Under the standard combination of load effects, the corrected standard value of the vertical force transmitted from the superstructure to the top surface of the extended foundation, N. k =k0F zk ;

[0089] k0 - Load correction safety factor considering factors such as wind turbine load uncertainty and load model deviation, taken as 1.35;

[0090] G k -Standard values ​​of the self-weight of the extended foundation and the weight of the soil covering the extended foundation under the standard combination of load effects;

[0091] Under the T1-load effect standard combination, the new foundation rib anchor rod bears the vertical force transmitted from the superstructure to the top surface;

[0092] Under the standard combination of T2 load effects, the uniformly variable cross-section piles of the new foundation ribs bear the vertical force transmitted to the top surface by the superstructure;

[0093] A - Area of ​​the extended foundation, A = πr 2 ;

[0094] 2) When a circular spread foundation is placed within the core area (e≤b / 6) and subjected to eccentric loads:

[0095]

[0096]

[0097]

[0098] In the formula, M k —The corrected standard value of the resultant moment transmitted from the superstructure to the top surface of the extended foundation under the standard combination of load effects, M k =k0M rk M rk For the horizontal resultant moment, calculated based on unidirectional eccentricity, M rk The resultant horizontal moment of the original foundation is calculated by subtracting the horizontal force borne by the anchor rod and uniformly variable cross-section pile under the bottom surface of the pile cap from the height of the centroid of the anchor rod and uniformly variable cross-section pile to the top elevation of the foundation ring.

[0099] H k —The corrected standard value of the horizontal resultant force transmitted from the superstructure to the top surface of the extended foundation under the standard combination of load effects, H k =k0F rk ,F rk The horizontal resultant force is the original horizontal resultant force of the foundation minus the horizontal force borne by the anchor rods and uniformly variable cross-section piles under the bottom surface of the pile cap.

[0100] P kmin —Minimum pressure value at the edge of the extended foundation bottom surface under the standard combination of load effects;

[0101] e—eccentricity of the point of application of the resultant force;

[0102] h d —The height from the top of the foundation ring to the bottom of the foundation.

[0103] III. Stability Calculation:

[0104] The stability of extended foundations and rock anchor foundations should be determined based on engineering geological and hydrogeological conditions, including anti-sliding, anti-overturning, or anti-buoyancy stability calculations. Anti-sliding stability calculations should be performed along the deep structural planes of the foundation, depending on the geological conditions.

[0105] For load conditions other than rare conditions, the anti-sliding and anti-overturning stability shall be verified according to the following formulas.

[0106] 1) The anti-slip force and sliding force on the most dangerous sliding surface of the anti-slip stability should meet the requirements of equation (8):

[0107]

[0108] In the formula, F R —Anti-slip force under the basic combination of load effects;

[0109] Fs—The correction value for sliding force under the basic combination of load effects.

[0110] 2) The overturning stability calculation along the foundation bottom surface, the most dangerous calculation condition should meet the requirements of equation (9):

[0111]

[0112] In the formula, M R —Under the basic combination of load effects, the anti-tilting moment;

[0113] Ms—Correction value of overturning moment under the basic combination of load effects.

[0114] According to the seismic fortification objectives of GB500011, the anti-sliding and anti-overturning stability under rare earthquake conditions should be verified according to the following formulas.

[0115] 1) The anti-slip force and sliding force on the most dangerous sliding surface should meet the requirements of equation (10):

[0116]

[0117] In the formula, F′ R —Anti-slip force under accidental combinations of load effects;

[0118] F′ S — Correction value for sliding force under accidental combinations of load effects.

[0119] 2) The overturning stability calculation along the foundation bottom surface, the most dangerous calculation condition should meet the requirements of equation (11):

[0120]

[0121] In the formula, M′ R —Anti-tilting moment under accidental combinations of load effects;

[0122] M′ S — Correction value for overturning moment under accidental combinations of load effects.

[0123] Finally, it should be noted that this article uses specific examples to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the core ideas of the present invention. Without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A method for reinforcing and upgrading the foundation of a wind turbine expansion project, characterized in that, Includes the following steps: S1. Destroy the concrete of the original central pier in the original wind turbine foundation, excavate to the foundation bottom plate, install several inner ring bolts on the top of the original foundation ring, and install strain sensors at the connection between the original foundation ring and the inner ring bolts. S2. A new foundation ring is embedded outside the original foundation ring. The diameter of the new foundation ring is larger than the diameter of the original foundation ring and smaller than the diameter of the original central pier. S3. Several first and second slots are horizontally chiseled along the original foundation rib ring of the original wind turbine foundation. The first slots extend to the side wall of the new foundation ring. The first anchor rod is fitted with a pre-embedded sleeve and tied or welded to the new foundation ring to form a whole. The second slots extend to the side wall of the original foundation ring. The second anchor rod passes through the second slots and is fixedly connected to the original foundation ring. After installation, the first anchor rod is tensioned and the first slots are grouted with high strength. S4. New concrete is poured on the outside and top of the original central pier to form an enlarged circular central pier. After curing, the top of the new foundation ring is connected to the top of the inner ring bolts by connecting steel bars. S5. Excavate along the original foundation rib to open the original foundation reinforcement, excavate several first ducts circumferentially and vertically along the outer periphery of the original foundation rib, excavate several second ducts circumferentially and vertically along the middle of the original foundation rib, and several third anchor rods pass through the corresponding first ducts with their bottom ends fixed to the rock mass and their top ends fixed to the foundation slab. Several uniformly variable cross-section piles pass through the corresponding second ducts with their bottom ends fixed to the rock mass and their top ends fixed to the foundation slab. S6. A third anchor rod and a uniform variable cross-section pile are fixedly connected to the bottom of a new foundation rib, and the upper part of the new foundation rib is fixedly connected to the first anchor rod and the second anchor rod. S7. After the new foundation ring passes inspection, the foundation reinforcement is tied, and then concrete is poured. S8. After the concrete curing is completed, a level is installed on the side wall of the enlarged circular pier. The lead wire i of the strain sensor and the lead wire ii of the level are both connected to the signal transmitter box.

2. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 1, characterized in that: In step S1, after the inner ring bolt is fitted with a pre-embedded sleeve, the bottom end is anchored to the top flange of the original foundation ring. Each inner ring bolt is fitted with an upper anchor plate at its top, and the bottom surface of the upper anchor plate is provided with a nylon nut.

3. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 1, characterized in that: In step S2, embedding the new foundation ring includes the following steps: pre-embedding steel plates in the concrete cushion layer; connecting the lower end of the support frame of the new foundation ring to the foundation base plate; connecting the new foundation ring and the support frame with adjusting bolts, which can adjust the flatness of the foundation ring; detecting three points on the upper flange surface of the new foundation ring corresponding to the adjusting bolts; if the levelness of the detected points exceeds the set threshold, then using a jack in conjunction with the adjusting bolts and readjusting the level instrument to control the levelness of the foundation ring within the set range.

4. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 1, characterized in that: In step S3, the first anchor rod is a prestressed anchor rod structure; the second anchor rod is a hollow anchor rod structure, and the second anchor rod is bound or welded to the original foundation ring to form an integral whole; the lead wire i of the strain sensor passes through the second anchor rod and extends to the outside.

5. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 4, characterized in that: In step S4, when the new concrete is poured, an annular cavity for installing strain sensors is formed at the original foundation ring top flange.

6. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 1, characterized in that: In step S5, after the third anchor rod is fitted with a pre-embedded sleeve, the bottom end of the sleeve passes through the first duct from top to bottom. After the third anchor rod is fixed to the rock mass, concrete is poured into the first duct. After completion, the third anchor rod is tensioned. After completion, the top of the third anchor rod is tied or welded to the reinforcing steel of the foundation slab.

7. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 1, characterized in that: In step S5, larger diameter first cylindrical cavities and second cylindrical cavities are left at the middle and bottom ends of the second duct, respectively. The reinforcing cage is placed into the second duct from top to bottom, and then grouting is carried out. When the grouting reaches the first cylindrical cavity and the second cylindrical cavity, the concrete slump, spread and air content are checked to ensure that the first cylindrical cavity and the second cylindrical cavity are completely filled, thereby forming a uniform variable cross-section pile. The upper end of the uniform variable cross-section pile is tied or welded to the reinforcing steel of the foundation slab to form a whole.

8. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 7, characterized in that: In step S6, the bottom of the new foundation rib is tied or welded to the foundation base plate, and the upper part of the new foundation rib is tied or welded to the first anchor rod and the second anchor rod.

9. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 1, characterized in that: In step S7, when pouring concrete, the concrete is poured in one go without leaving a construction joint.

10. The method for upgrading and reinforcing a wind turbine expansion foundation according to claim 1, characterized in that: In step S8, the signal transmitting box establishes a communication connection with a remotely set monitoring station.

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