Construction method for capacity increasing transformation of original fan foundation

Abstract

The construction method comprises the following steps that a horizontal anchor rod, a bottom plate vertical anchor rod, a stand vertical anchor rod and a new anchor bolt assembly are constructed on an original fan foundation bottom plate and an original fan foundation stand correspondingly; new pile foundations are constructed at the bottom of the new foundation bottom plate; newly-added foundation slabs are constructed on the periphery and the top of the original fan foundation slab, and newly-added foundation pillars are constructed on the periphery and the top of the original fan foundation pillars; and the original wind turbine foundation bottom plate, the original wind turbine foundation stand, the newly-added foundation bottom plate and the newly-added foundation stand are reinforced through the horizontal anchor rods, the bottom plate vertical anchor rods, the stand vertical anchor rods and the new anchor bolt assemblies, and construction is completed. The method has the beneficial effects that the workload of breaking and removing an original fan foundation is avoided, the original fan foundation is utilized to the maximum extent, energy conservation and environmental protection are better achieved, the use amount and transportation difficulty of fan foundation concrete are reduced, the construction period is shortened, and the construction cost is saved.

Description

Technical Field

[0001] This invention belongs to the field of wind turbine foundation technology, specifically relating to a construction method for upgrading and modifying an existing wind turbine foundation. Background Technology

[0002] Wind power, with its clean and renewable core advantages, has become the fastest-growing and most promising sector in the new energy industry. However, with technological advancements in wind power equipment, larger single-unit capacity wind turbines are constantly being developed, leaving older, smaller-capacity turbines at a significant disadvantage in power generation efficiency. Furthermore, due to the rapid development of wind power in its early stages, older, smaller-capacity turbines have consumed a large amount of high-quality wind resources with relatively low utilization efficiency, and as wind power continues to grow, the availability of high-quality wind resources for wind farm construction is decreasing. Therefore, longer blades, higher hub heights, and larger tower diameters meet the optimization direction of wind power development. However, longer blades, higher hub heights, and larger tower diameters mean that the foundation needs to bear a greater load.

[0003] In order to optimize the original wind turbine foundation, the traditional solution of demolishing the original foundation by blasting and then rebuilding it not only requires bearing the high costs of foundation demolition, construction waste removal and new foundation pouring, but also extends the construction period by at least 60 days due to blasting construction, concrete curing and other processes. In addition, blasting operations may disturb the geological environment of the surrounding site and cause ecological protection risks.

[0004] Therefore, it is very necessary to provide a construction method for new dikes and existing bridges, as well as a new dike structure, to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a construction method for upgrading and modifying the original wind turbine foundation, aiming to solve the problems of high demolition costs and long reconstruction time associated with the existing technology that involves demolishing the original foundation by blasting and then rebuilding.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a construction method for upgrading and modifying the original wind turbine foundation, comprising the following steps: Horizontal anchor bolts, vertical anchor bolts on the base plate, vertical anchor bolts on the column, and new anchor bolt assemblies were installed on the original wind turbine foundation slab and the original wind turbine foundation column, respectively. New pile foundations will be constructed at the bottom of the new foundation slab. A new foundation slab will be constructed around and on top of the original wind turbine foundation base slab, and new foundation columns will be constructed around and on top of the original wind turbine foundation columns. The original wind turbine foundation slab, the original wind turbine foundation columns, the newly added foundation slab, and the newly added foundation columns are reinforced using horizontal anchor bolts, vertical anchor bolts on the base plate, vertical anchor bolts on the columns, and new anchor bolt assemblies, thus completing the construction.

[0007] Preferably, by installing horizontal anchors, vertical anchors on the foundation slab and columns, vertical anchors on the columns, and new anchor bolt assemblies, combined with the synergistic effect of the newly added pile foundation and the new foundation structure, a multi-dimensional and comprehensive reinforcement system is constructed. The newly added pile foundation effectively expands the force transmission path of the foundation, evenly transferring the load after the wind turbine capacity increase to deeper stable soil, avoiding local stress concentration; various anchor bolt assemblies can firmly connect the original foundation and the new foundation, ensuring that the two form a stable overall load-bearing unit, significantly improving the foundation's pull-out resistance, overturning resistance, and overall stiffness.

[0008] Furthermore, the construction of horizontal anchor bolts, vertical anchor bolts on the original wind turbine foundation slab and the original wind turbine foundation columns, respectively, also includes the following steps: Drill holes at the rock anchor positions of the original wind turbine foundation slab on the top and sides of the original wind turbine foundation pier to meet the construction depth requirements for horizontal anchors, vertical anchors of the slab and vertical anchors of the pier. At the same time, enlarge the holes at the bottom. After completing the drilling of horizontal anchor bolts, vertical anchor bolts for the base plate, and vertical anchor bolts for the pedestal column, horizontal anchor bolts, vertical anchor bolts for the base plate, and vertical anchor bolts for the pedestal column are placed in the corresponding drill holes, and grouting is carried out in the holes.

[0009] Preferably, the determination of the construction depth should be based on design calculations, geological conditions, and regulatory requirements. The method is as follows: Values ​​are obtained from preliminary design calculations. Based on the actual load parameters after the wind turbine capacity expansion (such as vertical pressure, horizontal thrust, and pull-out force), combined with the original foundation structure strength test report, and in accordance with the relevant requirements of the "Code for Construction and Acceptance of Wind Power Engineering" (GB / T51121-2015) and the "Code for Design of Building Foundations," the minimum lengths of the anchorage section and free section of the anchor bolts are calculated and determined. Specifically, the anchorage section length of rock anchor bolts should not be less than 3.0m, the anchorage section length of soil anchor bolts should not be less than 4.0m, and the free section of prestressed anchor bolts should extend at least 1.5m beyond the potential slip surface and not less than 5.0m. The total construction depth is the anchorage depth. The first step is to measure the total length of the anchored section, the free section, and the external anchor head embedded in the foundation. Secondly, the on-site geological conditions are verified. Before construction, the geological survey report is consulted to clarify the stratification of the soil and rock mass in the drilling area (such as residual slope deposits and moderately weathered rock layers), the distribution of groundwater, and adverse geological conditions. If there are discrepancies between the actual geology and the survey data, the depth needs to be adjusted through supplementary surveys to ensure that the anchored section is embedded in stable rock or dense soil layers, avoiding weak areas such as fractured zones and quicksand layers. Thirdly, the construction process is precisely controlled. Drilling depth is measured in real time using drill rods or measuring ropes with length scales. A 0.5~1.0m over-drilling allowance is reserved during drilling. After drilling is completed, the measuring rope is used again to verify that the hole depth is not less than the design calculation value, and the deviation is controlled within the range of +50mm~0mm. Simultaneously, the bottom of the hole is enlarged, and the enlargement depth must match the design requirements of the anchor bolt enlargement structure to ensure anchorage bearing capacity. After drilling, the corresponding horizontal anchor bolts, base plate vertical anchor bolts, and column vertical anchor bolts are placed into the hole, and grouting is completed to ensure a stable bond between the anchor bolts and the foundation structure. The enlargement depth is determined to meet the anchorage bearing capacity requirements of the anchor bolts, while also adapting to the anchor bolt structure design and geological conditions. Based on the anchorage force principle, the core purpose of enlargement is to increase the contact area between the anchor bolt anchorage section and the grouting body and soil / rock mass, improving the interface bonding strength and thus enhancing the anchor bolt's pull-out and shear bearing capacity. Therefore, the enlargement depth needs to be calculated and determined based on the required bearing capacity. The higher the bearing capacity requirement, the larger the contact area is needed to offset the load, and the enlargement depth increases accordingly. Furthermore, the enlargement structure must match the anchor bolt type and structural design. Different types of anchor bolts (such as enlarged-bottom anchor bolts and end-enlarged-hole anchor bolts) have different enlargement structures. The depth must be compatible with the prefabricated structure of the anchor head and anchoring section. For example, the enlargement depth of the bottom-enlarged anchor must ensure that the anchor head is fully embedded in the enlarged section and leave sufficient space for grouting and compaction, generally not less than 1.5 to 2 times the diameter of the anchor head. It must also be compatible with geological conditions and specifications. For different geological conditions such as rock, dense soil, and soft soil, the bonding strength of the soil and rock is different, and the enlargement depth needs to be adjusted according to geological parameters (for example, the enlargement depth needs to be appropriately increased in soft soil to compensate for insufficient bonding strength). At the same time, it must comply with relevant standards such as the "Technical Specification for Building Slope Engineering" (GB50330-2013) to ensure the stability of the anchoring section after enlargement and avoid insufficient bearing capacity due to shallow enlargement or disturbance of the soil and rock due to excessive depth. Therefore, after determining the enlargement depth, the bottom enlargement treatment should be carried out to ensure the anchor bearing capacity.

[0010] Furthermore, it also includes the following steps: Based on the center of the original wind turbine foundation plate, horizontal anchor rods are installed in a circumferential manner, and at least one layer of horizontal anchor rods is installed. Based on the center of the original wind turbine foundation slab, vertical anchor bolts are installed in a circumferential manner on the foundation slab, with at least one ring of vertical anchor bolts.

[0011] Preferably, by setting multiple sets of horizontal anchors and vertical anchors on the base plate, the bearing capacity is evenly transferred to the deep soil, thereby enhancing the overall pull-out stability of the foundation.

[0012] Furthermore, it also includes the following steps: Based on the center of the original wind turbine foundation column, vertical anchor rods are constructed in a circumferential manner, with at least one ring of vertical anchor rods on the column.

[0013] Preferably, by setting multiple sets of vertical anchor rods for the columns, the vertical reinforcement force on the columns is evenly distributed, thereby improving the connection stability between the columns and the foundation slab and the newly added structure.

[0014] Furthermore, the construction of new anchor bolt assemblies on the original wind turbine foundation slab and the original wind turbine foundation columns specifically includes the following steps: Remove the original anchor bolt assembly from the original wind turbine foundation column; Embed iron on the top surface of the original wind turbine foundation column; Connect the new anchor bolt assembly to the top embedded iron.

[0015] Preferably, the original anchor bolt assembly on the original wind turbine foundation column is removed. During the removal process, damage to the main structure of the column must be avoided, and the installation base surface after removal must be cleaned. A top-mounted embedded iron is pre-embedded on the original wind turbine foundation column. During pre-embedding, the level and elevation of the embedded iron must be precisely controlled to ensure that the embedded iron is tightly bonded to the column concrete without gaps. The new anchor bolt assembly is connected to the top-mounted embedded iron. The connection method can be welding or bolt fastening to ensure that the connection node is firm and reliable and meets the load transfer requirements after the wind turbine capacity is increased.

[0016] Furthermore, the construction of a new foundation slab around and on top of the original wind turbine foundation base slab, and the construction of a new foundation column around and on top of the original wind turbine foundation column, also includes the following steps: Before pouring, steel bars are placed on the top surface of the new foundation slab and inside the new foundation columns. The steel bars are distributed in a ring shape and multiple rings are distributed radially. Then, the concrete for the new foundation slab and the new foundation columns is poured.

[0017] Preferably, the layout design of multiple rings and radial rings ensures the uniformity of stress and the overall stiffness of the new structure; after the reinforcement is configured and accepted, the concrete of the new foundation slab and the new foundation column is poured to ensure that the new structure forms a stable whole with the original foundation, anchor rods and anchor bolts.

[0018] Furthermore, the step of constructing new pile foundations at the bottom of the new foundation slab also includes the following steps: The new pile foundations are distributed radially outward from the center of the original wind turbine foundation slab, and the spacing of the new pile foundations is adjusted adaptively according to geological conditions.

[0019] Preferably, the spacing can be reduced in areas with weak soil layers to improve bearing stability, while the spacing can be appropriately increased in areas with dense rock layers to reduce construction costs. For example, in areas with soft soil layers, where the soil particles are loose and the bearing capacity is low, uneven settlement is likely to occur. Therefore, the pile spacing needs to be reduced to 3-5m. Increasing the number of piles improves the bearing density per unit area, allowing the increased load from the wind turbine to be evenly distributed across more piles, preventing settlement or damage caused by excessive load on a single pile. A ring-shaped arrangement with equal spacing can also be used to ensure balanced load transfer. In areas with dense rock layers, where the geological integrity is good and the bearing capacity is high, the vertical bearing capacity of a single pile meets the requirements. The pile spacing can be appropriately increased to 6-8m to reduce the number of piles and material consumption, thus lowering construction costs. During adjustments, it is necessary to ensure that the piles still evenly cover the area of ​​the newly added foundation slab to avoid bearing blind spots. In areas with general soil layers (such as silty clay and sand), which are between soft soil layers and dense rock layers, the spacing can be controlled at 4-6m, with adjustments made based on soil density. The denser the soil, the larger the spacing can be, and vice versa.

[0020] Furthermore, the newly added foundation slab specifically comprises a portion that is horizontally widened in the radial direction of the original wind turbine foundation slab and a portion that is vertically thickened in the vertical direction of the original wind turbine foundation slab. The newly added foundation slab, which is horizontally widened in the radial direction of the original wind turbine foundation slab, meets the construction requirements for the new pile foundation; the thickness of the newly added foundation slab, which is vertically thickened in the vertical direction of the original wind turbine foundation slab, meets the structural bearing capacity requirements.

[0021] Preferably, during construction, firstly, the widening dimension needs to be determined based on the number and spacing of the new anchor bolt components and the available installation space. Sufficient construction clearance must be reserved between adjacent new anchor bolt components and between the anchor bolt components and the edge of the support column, generally not less than 150mm, to meet the operational requirements of anchor bolt installation, welding, or bolt tightening, and to avoid inadequate construction due to space constraints. Secondly, the concrete strength grade of the widened section must be no lower than the original support column's concrete strength grade, and no less than C30, to ensure it can bear the increased wind turbine load transmitted by the new anchor bolt components. Simultaneously, the widened section must form a stable whole with the original support column. The mating surface must be roughened, coated with an interface agent, and shear reinforcement bars must be embedded. The spacing of the shear reinforcement bars should be ≤300mm to ensure that the old and new structures share the load collaboratively and to avoid relative slippage. Furthermore, precise layout is required before widening the section to ensure that the installation positioning deviation of the new anchor bolt components is ≤5mm, the radial distribution uniformity deviation is ≤10mm, and that they precisely match the mounting holes of the increased-capacity wind turbine base, avoiding anchor bolt connection failures due to positioning deviations. Finally, the widened section needs to reserve space for the anti-corrosion treatment of the new anchor bolt assembly to ensure that the exposed part of the anchor bolt can be smoothly subjected to anti-corrosion construction such as rust removal, painting or hot-dip galvanizing, while avoiding interference with the surrounding structure after the anchor bolt is installed, and ensuring long-term operational stability. The load-bearing capacity mainly includes the ability to effectively bear and transmit the weight of the upgraded wind turbine, the vertical vibration load during operation, and the weight of the new foundation itself, ensuring that it does not exceed the allowable compression deformation or structural damage under long-term vertical loads; the ability to withstand the horizontal thrust, gust impact loads, and seismic horizontal forces generated by the wind turbine during operation, preventing lateral displacement or shear failure of the foundation; the uplift resistance capacity to withstand the upward pull of the wind turbine under extreme operating conditions, preventing structural instability caused by the foundation being pulled upwards; and the ability to withstand the upward pull of the foundation under extreme operating conditions. The foundation slab, newly added piles, and various anchors form a collaborative load-bearing system. Through the firm bond between the thickened concrete and the original foundation, various loads are evenly transferred to the new piles and deep soil, avoiding local stress concentration and ensuring collaborative bearing capacity. The strength grade of the thickened concrete must be no lower than that of the original foundation slab concrete and no lower than C30. With the reinforcement design of ring and radial multi-ring steel bars, the concrete and steel bars are ensured to share the load, meeting the material strength matching requirements corresponding to the bearing capacity. Based on the known bearing capacity, the thickened new foundation slab can be better obtained.

[0022] Furthermore, the newly added foundation column specifically comprises a portion that is horizontally widened radially along the original wind turbine foundation column and a portion that is vertically heightened along the original wind turbine foundation column. The newly added foundation column that is horizontally widened radially along the original wind turbine foundation column meets the construction requirements for the new anchor bolt assembly for the upgraded wind turbine unit. The newly added foundation column that is vertically heightened along the original wind turbine foundation column is determined based on the length and structure of the new anchor bolt assembly.

[0023] Furthermore, the reinforcement of the original wind turbine foundation base plate, the original wind turbine foundation column, the newly added foundation base plate, and the newly added foundation column using horizontal anchor bolts, vertical anchor bolts on the base plate, vertical anchor bolts on the column, and new anchor bolt assemblies also includes the following steps: After the concrete strength of the newly added foundation slab and the newly added foundation columns meets the construction standards, the corresponding anchors will be installed on the horizontal anchors, the vertical anchors of the foundation slab, and the vertical anchors of the columns. The horizontal anchor bolts, the vertical anchor bolts of the base plate, and the vertical anchor bolts of the pedestal are tensioned in batches and stages in a symmetrical direction. After the prestress value reaches the required level, the anchor head is locked and protected.

[0024] The advantages of this invention compared to the prior art are: 1. Rock anchors can provide high tensile stress, which makes the connection between the original wind turbine foundation and the new foundation structure more stable, so that the structure can meet the punching shear requirements of the new outer ring pile foundation and meet the greater load requirements of the new wind turbine for the foundation. 2. It eliminates the need to demolish the original wind turbine foundation, makes the most of the original foundation, is more energy-efficient and environmentally friendly, reduces the amount of concrete used for the wind turbine foundation and the difficulty of transportation, saves construction time and reduces project costs. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of a construction method for upgrading and modifying an existing wind turbine foundation, as provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the upper plan layout of a construction method for upgrading and modifying an existing wind turbine foundation, provided as an example. Figure 3 This is a schematic diagram of the lower plan layout of a construction method for upgrading and modifying an existing wind turbine foundation, provided as an example.

[0026] Explanation of reference numerals in the attached figures: 1. Original wind turbine foundation base plate; 2. Original wind turbine foundation pedestal; 3. Horizontal anchor bolts; 4. Vertical anchor bolts for the base plate; 5. Vertical anchor bolts for the pedestal; 6. New anchor bolt assembly; 7. New foundation base plate; 8. New pile foundation; 9. New foundation pedestal; 10. Embedded iron on the top surface. Detailed Implementation

[0027] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0028] See Figure 1 , Figure 2 and Figure 3 As shown, this invention discloses a construction method for upgrading and modifying an existing wind turbine foundation, comprising the following steps: Horizontal anchor bolts 3, vertical anchor bolts 4, vertical anchor bolts 5, and new anchor bolt assemblies 6 are installed on the original wind turbine foundation base plate 1 and the original wind turbine foundation column 2, respectively. New pile foundations 8 will be constructed at the bottom of the newly added foundation slab 7; A new foundation slab 7 is constructed around and on top of the original wind turbine foundation slab 1, and a new foundation column 9 is constructed around and on top of the original wind turbine foundation column 2. The original wind turbine foundation base plate 1, the original wind turbine foundation column 2, the newly added foundation base plate 7, and the newly added foundation column 9 are reinforced using horizontal anchor bolts 3, vertical anchor bolts 4 on the base plate, vertical anchor bolts 5 on the column, and new anchor bolt assembly 6, thus completing the construction.

[0029] In this embodiment, horizontal anchor rods 3 are installed on the original wind turbine foundation plate 1 and the newly added foundation plate 7. The horizontal anchor rods 3 can reinforce the original wind turbine foundation plate 1 and the newly added foundation plate 7 in a horizontal direction. Meanwhile, the horizontal anchor bolts 3 effectively resist the horizontal forces generated by external forces such as wind and earthquakes during wind turbine operation, preventing foundation overturning. Vertical anchor bolts 4 for the original wind turbine foundation slab 1 and vertical anchor bolts 5 for the new foundation slab 7 and new foundation columns 9 are installed on the slab and columns, respectively, reinforcing them vertically. Vertical anchor bolts 5 for the original wind turbine foundation columns 2 and new foundation columns 9, along with new anchor bolt assemblies 6, further reinforce these structures. Thus, the original wind turbine foundation slab 1, original wind turbine foundation columns 2, new foundation slab 7, and new foundation columns 9 form a complete whole, better transmitting and distributing loads and avoiding structural damage caused by localized stress concentration. During wind turbine operation, they work together to bear various loads, improving the durability and reliability of the foundation structure.

[0030] In some embodiments, the construction of horizontal anchor bolts 3, vertical anchor bolts 4 on the original wind turbine foundation base plate 1, and vertical anchor bolts 5 on the original wind turbine foundation column 2, respectively, further includes the following steps: On the top and side surfaces of the original wind turbine foundation base plate 1, and at the rock anchor positions of the original wind turbine foundation column 2, holes are drilled to meet the construction depth requirements of the horizontal anchor 3, the vertical anchor 4 of the base plate, and the vertical anchor 5 of the column. At the same time, the bottom of the holes is enlarged. After completing the drilling of horizontal anchor bolts 3, vertical anchor bolts 4 for the base plate, and vertical anchor bolts 5 for the pedestal, horizontal anchor bolts 3, vertical anchor bolts 4 for the base plate, and vertical anchor bolts 5 for the pedestal are placed in the corresponding drill holes, and grouting is carried out in the holes.

[0031] In this embodiment, by enlarging the hole at the bottom, the horizontal anchor 3, the vertical anchor 4 of the base plate, and the vertical anchor 5 of the column can be more firmly anchored to the original wind turbine foundation base plate 1 and the original wind turbine foundation column 2, so that the horizontal anchor 3, the vertical anchor 4 of the base plate, and the vertical anchor 5 of the column can obtain a greater tensile force. Meanwhile, when constructing the horizontal anchor bolts 3, the vertical anchor bolts 4 of the base plate, and the vertical anchor bolts 5 of the column, it is also necessary to roughen the surface of the original wind turbine foundation base plate 1 and the original wind turbine foundation column 2 and apply an interface agent to obtain greater adhesion and durability.

[0032] In some embodiments, the following steps are also included: Based on the center of the original wind turbine foundation plate 1, horizontal anchor rods 3 are constructed in a circumferential manner, and the horizontal anchor rods 3 are provided with at least one layer; Based on the center of the original wind turbine foundation plate 1, vertical anchor rods 4 are constructed in a circumferential manner, and the vertical anchor rods 4 are set in at least one ring.

[0033] In this embodiment, during the operation of the wind turbine, it will be subjected to horizontal forces such as wind force. The multi-layered circumferentially arranged horizontal anchor rods 3 are like strong hoops that tightly bind the original wind turbine foundation plate 1 to resist horizontal deformation and prevent the newly added foundation plate 7 from displacing or tilting due to horizontal forces, thereby improving the stability of the foundation in the horizontal direction.

[0034] In some embodiments, the following steps are also included: Based on the center of the original wind turbine foundation column 2, vertical anchor rods 5 are constructed in a circumferential manner, and the vertical anchor rods 5 have at least one ring.

[0035] In this embodiment, the circumferentially arranged vertical anchor rods 5 form a support frame, which can evenly transfer the upper load to the original wind turbine foundation column 2 and the newly added foundation column 9 below, enhance the vertical bearing capacity of the column, prevent the column from being compressed or damaged due to excessive local stress, and improve its anti-overturning stability to ensure the safe operation of the wind turbine.

[0036] In some embodiments, the construction of the new anchor bolt assembly 6 on the original wind turbine foundation base plate 1 and the original wind turbine foundation column 2 specifically includes the following steps: Remove the original anchor bolt assembly on the original wind turbine foundation column 2; Embed iron 10 on the top surface of the original wind turbine foundation column 2; Connect the new anchor bolt assembly 6 to the top embedded iron 10.

[0037] In this embodiment, removing the original anchor bolt assemblies on the original wind turbine foundation column 2 that have degraded in performance or are incompatible eliminates potential hazards such as loosening and corrosion of the original anchor bolts. The pre-embedded top surface iron 10 provides a more stable connection foundation for the new anchor bolt assembly 6. The top surface iron 10 has a large contact area and good mechanical properties, which can better distribute the load transmitted from the new anchor bolt assembly 6. After the new anchor bolt assembly 6 is connected to the top surface iron 10, the connection between the original wind turbine foundation column 2 and the superstructure is more stable, greatly improving the shear, tensile, and torsional resistance of this application under complex loads, ensuring that the foundation structure will not be endangered due to loose connections during wind turbine operation.

[0038] In some embodiments, the construction of a new foundation slab 7 around and on top of the original wind turbine foundation base slab 1, and the construction of a new foundation column 9 around and on top of the original wind turbine foundation column 2, further includes the following steps: Before pouring, steel bars are placed on the top surface of the new foundation slab 7 and inside the new foundation column 9. The steel bars are distributed in a ring shape and multiple rings are distributed radially. Then, the concrete of the new foundation slab 7 and the new foundation column 9 is poured.

[0039] In this embodiment, the ring-shaped steel bars can effectively resist the circumferential stress generated during wind turbine operation, such as torque caused by wind; the radially distributed multi-ring steel bars can enhance the structure's ability to resist radial pressure and tension. This improves the load-bearing capacity of the newly added foundation slab 7 and the newly added foundation columns 9, enabling them to better withstand the enormous loads transmitted from the wind turbine's upper structure, including the wind turbine's own weight, wind force, and seismic forces, ensuring the wind turbine foundation remains stable under various operating conditions.

[0040] In some embodiments, the step of constructing new pile foundations 8 at the bottom of the new foundation slab 7 further includes the following steps: The newly added pile foundations 8 are distributed radially outward from the center of the original wind turbine foundation base plate 1, and the spacing of the newly added pile foundations 8 is adjusted adaptively according to the geological conditions.

[0041] In this embodiment, in areas with better geological conditions, the spacing between the new piles 8 is appropriately increased, and the number of new piles 8 is reduced while ensuring bearing capacity. In areas with poor geological conditions and low soil bearing capacity, the spacing between piles is reduced and the pile density is increased, so that the new piles 8 can penetrate the weak soil layer more deeply and reach the soil or rock layer with higher bearing capacity, thereby improving the vertical bearing capacity of the wind turbine foundation and meeting the wind turbine's requirements for foundation bearing capacity.

[0042] In some embodiments, the newly added foundation slab 7 specifically comprises a portion that is horizontally widened in the radial direction of the original wind turbine foundation slab 1 and a portion that is vertically thickened in the vertical direction of the original wind turbine foundation slab 1. The newly added foundation slab 7, which is horizontally widened in the radial direction of the original wind turbine foundation slab 1, meets the construction requirements of the newly added pile foundation 8. The thickness of the newly added foundation slab 7, which is vertically thickened in the vertical direction of the original wind turbine foundation slab 1, meets the structural bearing capacity requirements.

[0043] In this embodiment, the structural bearing capacity includes static load, dynamic load, and environmental load. Static load includes the self-weight of the newly added foundation slab, the self-weight of the newly added foundation columns, the self-weight of the wind turbine main unit and tower, and the pre-tightening force of the new anchor bolt assembly. Dynamic load includes tower vibration load during wind turbine operation, alternating load generated by blade rotation, and gust impact load. Environmental load includes wind load, seismic action, and additional stress generated by uneven foundation settlement. Therefore, it is necessary to meet the following requirements: strength bearing capacity (concrete does not crush and steel bars do not yield); stiffness bearing capacity (foundation deformation does not exceed the specified limits to avoid tower misalignment affecting unit operation); and crack resistance bearing capacity (concrete does not develop harmful cracks to prevent groundwater erosion of the steel bars). In addition, the thickened foundation slab increases the contact area with the soil. Therefore, it is necessary to verify whether the base pressure is less than the allowable bearing capacity of the foundation soil, taking into account the bearing capacity of the newly added pile 8. The formula is: ; In the formula: This represents the standard value of the base average pressure. This represents the standard value of the vertical force transmitted from the superstructure to the top surface of the foundation; The weight of the foundation itself and the weight of the soil on the foundation; This is the total area of ​​the thickened foundation slab; This is the corrected characteristic value of the foundation bearing capacity; Finally, the concrete strength grade of the thickened section must be no lower than that of the original foundation slab concrete, and no lower than C30. At the same time, a micro-expansion agent must be added to reduce shrinkage cracks at the interface between the old and new concrete. Before the thickening construction, the top surface of the original foundation slab must be roughened and cleaned, and shear nails or connecting steel bars must be inserted to ensure that the old and new concrete form an integral load-bearing structure. The thickness value must be determined in conjunction with the load increase after the wind turbine capacity is increased, and verified by modeling and calculation using finite element software such as ANSYS or MIDAS / GTS. Generally, the thickening thickness should not be less than 300mm, and the specific thickness should be determined based on the load calculation results.

[0044] In some embodiments, the newly added foundation column 9 specifically comprises a portion that is horizontally widened in the radial direction of the original wind turbine foundation column 2 and a portion that is vertically heightened in the vertical direction of the original wind turbine foundation column 2. The newly added foundation column 9, which is horizontally widened in the radial direction of the original wind turbine foundation column 2, meets the construction requirements of the new anchor bolt assembly 6 for the upgraded wind turbine unit. The newly added foundation column 9, which is vertically heightened in the vertical direction of the original wind turbine foundation column 2, is determined according to the length and structure of the new anchor bolt assembly 6.

[0045] In this embodiment, the new anchor bolt assembly needs to be embedded deep enough into the newly added foundation column to provide stable pull-out and shear bearing capacity. The embedment depth needs to meet the specifications and is generally not less than 25 times the anchor bolt diameter. Therefore, the height of the column needs to cover the embedded section length of the anchor bolt. The new anchor bolt assembly needs to be exposed for a certain length to connect to the flange of the wind turbine tower base. The exposed length needs to match the flange thickness, nut height, and gasket thickness, and reserve sufficient tensioning space. Therefore, the height of the column needs to reserve the size of the exposed section of the anchor bolt. The height increase of the newly added foundation column 9 must meet the following formula: ; In the formula, Increase the height of the pillars; This refers to the length of the anchor bolt embedment section; The length of the exposed section of the anchor bolt; To allow for construction allowance, a margin of 50 to 100 mm is generally taken; In addition, the size of the flange of the wind turbine tower base may increase after the capacity expansion. The top surface of the newly added foundation column must match the size of the flange. The top surface of the heightened column must be flat and the elevation must be accurate. Therefore, the height increase must be determined in conjunction with the flange installation elevation. The heightened column must verify its compressive bearing capacity and overturning stability to avoid lateral deformation due to excessive height. At the same time, circumferential and longitudinal reinforcement bars must be installed to enhance the crack resistance and rigidity of the column. The heightened part must form an integral part with the original foundation column. During construction, the top surface of the original column must be roughened and rebar must be installed. The length of the rebar extension must meet the anchorage requirements. Therefore, the height increase must be determined in conjunction with the rebar length and the number of rebar layers. The wind turbine foundation column needs to reserve cable holes, maintenance ladder installation holes, etc. The height increase must take into account the installation position of auxiliary facilities to avoid conflicts with anchor bolt components and rebar layout. Finally, the concrete strength grade of the heightened section must be no lower than that of the original column concrete, and high-flowability concrete must be used to ensure dense pouring; a formwork support system must be set up during the heightening construction of the column to control the verticality deviation to no more than one-thousandth; after the heightening is completed, the top surface of the column must be leveled, with a flatness deviation of no more than 5mm / m, to meet the installation accuracy requirements of the tower flange.

[0046] In some embodiments, the reinforcement of the original wind turbine foundation base plate 1, the original wind turbine foundation column 2, the newly added foundation base plate 7, and the newly added foundation column 9 using horizontal anchor bolts 3, vertical anchor bolts 4 of the base plate, vertical anchor bolts 5 of the column, and new anchor bolt assembly 6 further includes the following steps: After the concrete strength of the newly added foundation slab 7 and the newly added foundation column 9 meets the construction standards, the corresponding anchors will be installed on the horizontal anchor 3, the vertical anchor 4 of the foundation slab, and the vertical anchor 5 of the column. The horizontal anchor bolts 3, the vertical anchor bolts 4 of the base plate, and the vertical anchor bolts 5 of the pedestal are tensioned in batches and stages in a symmetrical direction. After the prestress value reaches the required level, the anchor heads are locked and protected.

[0047] In this embodiment, prestress is applied by tensioning the horizontal anchor rods 3, the vertical anchor rods 4 of the base plate, and the vertical anchor rods 5 of the column, thereby generating compressive stress reserves within the structure. When the wind turbine foundation is subjected to external loads, these prestresses can partially or completely offset the tensile stress generated by the external loads, thus reducing the stress level within the structure and improving its load-bearing capacity. For example, applying prestress to the horizontal anchor rods 3 can enhance the foundation's ability to resist horizontal loads and prevent excessive displacement of the foundation under horizontal forces; the prestress of the vertical anchor rods 4 of the base plate and the vertical anchor rods 5 of the column can enhance the foundation's ability to resist vertical loads and bending moments, ensuring that the foundation can safely and stably support the upper structure of the wind turbine under various working conditions.

[0048] Phased and staged tensioning in a symmetrical direction allows for more uniform and rational application of prestress. This tensioning method avoids excessive local stress in the structure due to prestress concentration, reducing the possibility of cracks and deformation. Simultaneously, symmetrical tensioning ensures the balance and stability of the structure during the tensioning process, resulting in better load-bearing capacity and deformation coordination after reinforcement, further improving the service life and reliability of the wind turbine foundation.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method for upgrading and modifying an existing wind turbine foundation, characterized in that, Includes the following steps: Horizontal anchor bolts (3), vertical anchor bolts (4), vertical anchor bolts (5) and new anchor bolt assemblies (6) are installed on the original wind turbine foundation base plate (1) and the original wind turbine foundation column (2). New pile foundations (8) are constructed at the bottom of the newly added foundation slab (7); A new foundation slab (7) is constructed on the periphery and top of the original wind turbine foundation slab (1), and a new foundation column (9) is constructed on the periphery and top of the original wind turbine foundation column (2). The original wind turbine foundation base plate (1), the original wind turbine foundation column (2), the newly added foundation base plate (7), and the newly added foundation column (9) are reinforced by using horizontal anchor bolts (3), vertical anchor bolts (4) of the base plate, vertical anchor bolts (5) of the column, and new anchor bolt assembly (6), thus completing the construction.

2. The construction method for upgrading and modifying the original wind turbine foundation as described in claim 1, characterized in that, The construction of horizontal anchor bolts (3), vertical anchor bolts (4) on the original wind turbine foundation base plate (1) and vertical anchor bolts (5) on the original wind turbine foundation column (2) also includes the following steps: Drill holes at the rock anchor positions of the original wind turbine foundation base plate (1) and the original wind turbine foundation column (2) to meet the construction depth of the horizontal anchor (3), the vertical anchor (4) of the base plate and the vertical anchor (5) of the column. At the same time, enlarge the hole bottom. After completing the drilling of the horizontal anchor (3), the vertical anchor (4) of the base plate and the vertical anchor (5) of the pedestal, the horizontal anchor (3), the vertical anchor (4) of the base plate and the vertical anchor (5) of the pedestal are placed in the corresponding holes and grouting is carried out in the holes.

3. The construction method for upgrading and modifying the original wind turbine foundation as described in claim 1, characterized in that, It also includes the following steps: Based on the center of the original wind turbine foundation plate (1), horizontal anchor rods (3) are constructed in a circumferential manner, and the horizontal anchor rods (3) are provided with at least one layer; Based on the center of the original wind turbine foundation plate (1), vertical anchor rods (4) are constructed in a circumferential manner, and the vertical anchor rods (4) of the foundation plate are set with at least one ring.

4. The construction method for upgrading and modifying the original wind turbine foundation as described in claim 1, characterized in that, It also includes the following steps: Based on the center of the original wind turbine foundation column (2), vertical anchor rods (5) are constructed in a circumferential manner, and the vertical anchor rods (5) of the column are arranged in at least one ring.

5. A construction method for upgrading and modifying an existing wind turbine foundation as described in claim 1, characterized in that, The construction of new anchor bolt assemblies (6) on the original wind turbine foundation base plate (1) and the original wind turbine foundation column (2) specifically includes the following steps: Remove the original anchor bolt assembly on the original wind turbine foundation column (2); Embed iron (10) on the top surface of the original wind turbine foundation column (2); Connect the new anchor bolt assembly (6) to the top embedded iron (10).

6. A construction method for upgrading and modifying an existing wind turbine foundation as described in claim 1, characterized in that, The construction of a new foundation slab (7) around and on top of the original wind turbine foundation slab (1), and the construction of a new foundation column (9) around and on top of the original wind turbine foundation column (2), also includes the following steps: Before pouring, steel bars are placed on the top surface of the new foundation slab (7) and inside the new foundation column (9). The steel bars are distributed in a ring shape and are distributed in multiple rings along the radial direction. Then, the concrete of the new foundation slab (7) and the new foundation column (9) is poured.

7. A construction method for upgrading and modifying an existing wind turbine foundation as described in claim 1, characterized in that, The step of constructing new pile foundations (8) at the bottom of the newly added foundation slab (7) also includes the following steps: The new pile foundations (8) are distributed radially around the center of the original wind turbine foundation plate (1), and the spacing of the new pile foundations (8) is adjusted according to the geological conditions.

8. A construction method for upgrading and modifying an existing wind turbine foundation as described in claim 1, characterized in that, The newly added foundation slab (7) is specifically a part that is horizontally widened in the radial direction of the original wind turbine foundation slab (1) and a part that is vertically thickened in the vertical direction of the original wind turbine foundation slab (1). The newly added foundation slab (7) which is horizontally widened in the radial direction of the original wind turbine foundation slab (1) meets the construction requirements of the newly added pile foundation (8); the thickness of the newly added foundation slab (7) which is vertically thickened in the vertical direction of the original wind turbine foundation slab (1) meets the structural bearing capacity.

9. A construction method for upgrading and modifying an existing wind turbine foundation as described in claim 1, characterized in that, The newly added foundation column (9) is specifically the part that is horizontally widened in the radial direction of the original wind turbine foundation column (2) and the part that is vertically increased in the vertical direction of the original wind turbine foundation column (2). The newly added foundation column (9) that is horizontally widened in the radial direction of the original wind turbine foundation column (2) meets the construction requirements of the new anchor bolt assembly (6) for the wind turbine with increased capacity. The newly added foundation column (9) that is vertically increased in the vertical direction of the original wind turbine foundation column (2) is determined according to the length and structure of the new anchor bolt assembly (6).

10. A construction method for upgrading and modifying an existing wind turbine foundation as described in claim 1, characterized in that, The reinforcement of the original wind turbine foundation base plate (1), the original wind turbine foundation column (2), the newly added foundation base plate (7), and the newly added foundation column (9) using horizontal anchor bolts (3), vertical anchor bolts (4) of the base plate, vertical anchor bolts (5) of the column, and new anchor bolt assembly (6) also includes the following steps: After the concrete strength of the newly added foundation slab (7) and the newly added foundation column (9) meets the construction standards, the corresponding anchors are installed on the horizontal anchor (3), the vertical anchor (4) of the foundation slab and the vertical anchor (5) of the column; The horizontal anchor bolts (3), the vertical anchor bolts (4) of the base plate and the vertical anchor bolts (5) of the pedestal are tensioned in batches and stages in the symmetrical direction. After the prestress value reaches the requirement, the anchor head is locked and protected.

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