A method for fixing construction of a wind farm mixed tower foundation

Abstract

The present application relates to the technical field of wind farm foundation, in particular to a fixing construction method of wind farm mixed tower foundation.The fixing construction method of wind farm mixed tower foundation comprises the following steps: digging a foundation pit on a construction surface;installing a tension chamber pouring formwork in the foundation pit and pouring the tension chamber;removing the tension chamber pouring formwork;backfilling the first fat groove between the tension chamber and the foundation pit with soil to form a first backfill layer;pouring a foundation pile cap on the upper part of the tension chamber;backfilling the second fat groove between the foundation pile cap and the foundation pit with soil to form a second backfill layer.The present application saves the time required for the erection and support process of the fat groove formwork, and saves the time for waiting for the solidification of the concrete after pouring the concrete into the space between the fat groove formwork and the foundation pit, simplifies the construction process, shortens the construction period, and saves the construction period and labor cost under the premise of ensuring the reliable fixation of the mixed tower foundation.

Description

Technical Field

[0001] This invention relates to the field of wind farm foundation technology, specifically to a method for fixing and constructing a hybrid tower foundation for a wind farm. Background Technology

[0002] Currently, hybrid tower foundations equipped with tension chamber structures are increasingly widely used in wind farm construction. The hybrid tower foundation is connected to the upper tower via high-strength prestressed anchor cables. Given the significant weight of the tower, the stability, durability, and construction precision of the hybrid tower foundation are crucial for the safe and stable operation of the wind farm.

[0003] The current method for fixing the foundation of a hybrid wind farm tower requires first excavating a foundation pit, installing sheet piles for the tension chamber sidewalls within the pit, then pouring a tension chamber cushion layer at the bottom of the pit, followed by erecting a formwork template and a support system to support it. Concrete is then poured into the space between the template and the pit, and after solidification, the tension chamber sidewalls are formed. The templates are then removed, and the tension chamber itself is poured inside the sidewalls. Finally, the foundation cap is poured. This method is cumbersome, resulting in long construction periods, significant delays, and high project costs, failing to meet the demands of modern wind farm projects for efficient, economical, and green construction. Summary of the Invention

[0004] The purpose of this invention is to provide a fixed construction method for hybrid tower foundations in wind farms, so as to solve the problem that existing construction methods are complicated and have long construction cycles.

[0005] The present invention provides a method for fixing a hybrid tower foundation in a wind farm, comprising the following steps: Excavate a foundation pit at the construction site; Install the tension chamber casting template in the foundation pit, and then pour the tension chamber. Remove the formwork for the tensioning chamber; Plain soil is backfilled into the first trench between the tensioning chamber and the foundation pit to form a first backfill layer; A foundation platform is poured on the upper part of the tensioning chamber; Plain soil is backfilled into the second trench between the foundation cap and the foundation pit to form a second backfill layer.

[0006] Furthermore, in the steps of backfilling plain soil into the first fertilizer tank to form the first backfill layer and backfilling plain soil into the second fertilizer tank to form the second backfill layer, the plain soil is backfilled in layers by compaction.

[0007] Furthermore, during the backfilling of the subgrade using a layered compaction method, the compaction degree of each layer of subgrade is tested using a ring cutter method.

[0008] Furthermore, after backfilling plain soil into the first fertilizer tank to form a first backfill layer, a light dynamic penetration test is used to detect the bearing capacity of the first backfill layer; after backfilling plain soil into the second fertilizer tank to form a second backfill layer, a light dynamic penetration test is used to detect the bearing capacity of the second backfill layer.

[0009] Furthermore, the subgrade soil includes the excavated soil generated during the excavation of the foundation pit.

[0010] Furthermore, during the excavation of the foundation pit at the construction surface, the foundation pit is excavated using a natural slope method, and the slope of the pit wall is not less than 45°.

[0011] Furthermore, the foundation pit is a stepped foundation pit, including a primary foundation pit at the bottom and a secondary foundation pit at the top. The primary foundation pit and the secondary foundation pit are arranged concentrically, and the planar dimensions of the primary foundation pit are smaller than those of the secondary foundation pit. The tensioning chamber is arranged in the primary foundation pit, and the foundation cap is poured in the secondary foundation pit.

[0012] Furthermore, before the step of backfilling the first fertilizer trench with plain soil to form the first backfill layer, the method further includes: A circular drainage ditch is provided at the bottom of the first fertilizer tank; Water collection wells are installed at intervals along the drainage ditch of the fertilizer trough; Install a water pump in the water collection well.

[0013] Furthermore, after setting up water collection wells at intervals along the drainage ditch of the fertilizer tank, a sand and gravel filter layer is laid at the bottom of the first fertilizer tank, and the sand and gravel filter layer is connected to the water collection wells.

[0014] Furthermore, before backfilling plain soil into the first fertilizer trench to form the first backfill layer, a water-retaining sill is installed on the construction surface near the foundation pit.

[0015] After the foundation pit construction is completed, the tensioning chamber is poured first, followed by backfilling with plain soil into the first trench between the tensioning chamber and the foundation pit. Then, the foundation cap is poured, and plain soil is backfilled into the second trench between the foundation cap and the foundation pit. This invention employs a standardized process of "simultaneous pouring of the tensioning chamber and backfilling with plain soil," eliminating the time required for the erection and support of the trench formwork. It also saves the time spent waiting for the concrete to solidify after pouring it into the space between the trench formwork and the foundation pit. While ensuring the reliable fixation of the concrete tower foundation, this simplifies the construction process, shortens the construction cycle, and saves on construction time and labor costs. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a hybrid tower foundation fixed using the fixed construction method of a hybrid tower foundation for wind farms according to the present invention.

[0017] In the diagram, 1 is the tensioning chamber; 2 is the foundation cap; 3 is the foundation pit; 31 is the primary foundation pit; 32 is the secondary foundation pit; 4 is the first trench; 5 is the first backfill layer; 6 is the second backfill layer; and 7 is the second trench. Detailed Implementation

[0018] The core concept of this invention is as follows: After the foundation pit construction is completed, the tensioning chamber is poured first, followed by backfilling plain soil directly into the first trench between the tensioning chamber and the foundation pit. Then, the foundation cap is poured, and plain soil is backfilled into the second trench between the foundation cap and the foundation pit. This invention adopts a standardized process of "simultaneous pouring of the tensioning chamber and backfilling of plain soil," eliminating the time required for the erection and support of the trench formwork, and also saving the time spent waiting for the concrete to solidify after pouring it into the space between the trench formwork and the foundation pit. While ensuring the reliable fixation of the concrete tower foundation, this simplifies the construction process, shortens the construction cycle, and saves on construction time and labor costs.

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0021] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0022] The present invention provides a method for fixing a hybrid tower foundation in a wind farm, comprising the following steps: excavating a foundation pit 3 on the construction surface; installing a casting template for a tension chamber 1 in the foundation pit 3 and pouring the tension chamber 1; removing the casting template for the tension chamber 1; backfilling plain soil into the first trench 4 (a trench is a technical term referring to the extra space excavated between the building's exterior wall and the edge of the foundation pit to provide a working surface) between the tension chamber 1 and the foundation pit 3 to form a first backfill layer 5; the plain soil is clean, free of impurities and admixtures, natural undisturbed soil, with stable chemical composition, free of corrosive substances, and will not corrode the hybrid tower foundation, ensuring high reliability for long-term use. Then, pouring the following on top of the tension chamber 1... Figure 1 The foundation cap 2 is shown, and plain soil is backfilled into the second trench 7 between the foundation cap 2 and the foundation pit 3 to form the second backfill layer 6. In this invention, the tension chamber 1 is poured first, achieving simultaneous pouring of the bottom plate and side walls of the tension chamber 1. Then, plain soil is directly backfilled into the first trench 4 between the tension chamber 1 and the foundation pit 3. Subsequently, the foundation cap 2 is poured, and plain soil is backfilled into the second trench 7 between the foundation cap 2 and the foundation pit 3. This eliminates the time required for the erection and support of the trench formwork, and also saves the time required for waiting for the concrete to solidify after pouring concrete into the space between the trench formwork and the foundation pit 3. Under the premise of ensuring the reliable fixation of the concrete tower foundation, the construction process is simplified, the construction cycle is shortened, and the construction period and labor costs are saved. At the same time, the cost of plain soil backfilling is much lower than the cost of concrete pouring. Therefore, this invention can also save material costs.

[0023] In steps 5 (backfilling plain soil into the first fertilizer trench 4 to form the first backfill layer) and 6 (backfilling plain soil into the second fertilizer trench 7 to form the second backfill layer), the plain soil is backfilled in layers and compacted in layers. When backfilling the plain soil in layers, the backfilling proceeds from the lowest point upwards, and is symmetrical, with a height difference ≤ 50cm, to avoid displacement of the mixed tower foundation caused by unilateral backfilling. This method is suitable for the process requirements of casting the tension chamber 1 and the foundation cap 2 in two stages. Simultaneously, it is necessary to use string lines and stakes (5m spacing) to mark the height, ensuring uniform thickness. Stepped joints are left during layered backfilling, with a step height of 30cm and a step width of 50cm. The joints between upper and lower layers are staggered by ≥ 1m to avoid continuous joints.

[0024] In case of layered compaction, if manual compaction is adopted, the loose paving thickness of each layer shall be ≤ 250 mm; if mechanical compaction is adopted, the loose paving thickness of each layer shall be ≤ 300 mm. For mechanical compaction: in open areas, a small vibratory road roller (≤ 3t) shall be adopted, with a road roller traveling speed of 2-3 km / h, 4-5 rolling passes, and an overlapping width of ≥ 1 / 3 of the roller width; in narrow areas, a frog-type rammer (power ≥ 3kW) shall be adopted, with 3-4 compaction passes, a 20 cm spacing between ramming points arranged in a quincunx pattern. After compaction, it is required to ensure that the surface of the backfill layer has no obvious wheel tracks, no subsidence, and no obvious depression when stepped on (subsidence ≤ 5mm). If spring soil occurs, it shall be immediately excavated and replaced with dry plain soil for backfilling, and then re-compacted. The layered compaction method can enable the first backfill layer 5 and the second backfill layer 6 to have uniform compactness and stable structure, effectively avoid post-settlement, loosening and deformation of each backfill layer, provide uniform and reliable lateral support for the hybrid tower foundation, improve the overall anti-lateral displacement and anti-overturning capabilities of the hybrid tower foundation, and meet the requirements for long-term stable operation of wind farms. In practical application, quality inspection is also required for the first backfill layer 5 and the second backfill layer 6 constructed by the "symmetrical layered backfilling + plain soil compaction" method. After inspection, the compaction coefficient of the first backfill layer 5 and the second backfill layer 6 is ≥ 0.94, the foundation settlement is ≤ 3mm, and the qualified rate of quality reaches 100%.

[0025] In the process of backfilling plain soil by means of layered compaction, the cutting ring method is adopted to detect the compactness of each layer of plain soil. The cutting ring method uses a cutting ring with known mass and volume to cut a soil sample, the mass of the soil is obtained by subtracting the mass of the cutting ring after weighing, the volume of the cutting ring is the volume of the soil, and then the density of the soil can be calculated. The cutting ring method shall be carried out within 48h after the compaction of each layer of plain soil is completed. During inspection, 1 testing point is set per 100 square meters of each layer of plain soil, and the layer is qualified when the compaction coefficient is ≥ 0.94; when the detection result is unqualified, the detection scope shall be expanded to investigate the defective area, the loose plain soil in the defective area shall be excavated, and then construction shall be carried out again and re-inspection shall be conducted.

[0026] After the step of backfilling plain soil into the first working gap 4 to form the first backfill layer 5, light dynamic penetration test is adopted to detect the bearing capacity of the first backfill layer 5; after the step of backfilling plain soil into the second working gap 7 to form the second backfill layer 6, light dynamic penetration test is adopted to detect the bearing capacity of the second backfill layer 6. The light dynamic penetration test method is an in-situ testing technology in the field of engineering mechanics. A 10kg穿心锤 is adopted to drive a conical probe with a 60° cone angle and a bottom area of 12.6 cm² into the soil layer with a 50cm free falling distance, and the engineering property of the foundation soil is evaluated through the number of hammer blows N10 required for penetrating 30cm. During inspection, 1 hole is set every 20m to ensure the quality meets the standard.

[0027] The subgrade soil includes the excavated soil generated during the excavation of foundation pit 3. The excavated soil is screened to obtain the subgrade soil, which has a particle size ≤50mm, an overall organic matter content <2%, and a moisture content controlled between 12-18%. Of course, the subgrade soil needs to be tested at this stage, with particle size distribution and moisture content checked every 500m³. Substandard soil (such as soil containing humus or construction waste) is strictly prohibited from use. In practical applications, the utilization rate of the excavated soil from foundation pit 3 is ≥85%. Using subgrade soil as the main backfill material can reduce the amount of excavated soil transported by approximately 1300 cubic meters, saving approximately 5.3 acres of land for the excavation site. At this time, there is no need to purchase concrete, reducing the input of concrete transportation, pouring, and labor, thus lowering construction costs and environmental disturbance. In this way, both material costs and energy consumption and pollution from concrete production and transportation are reduced.

[0028] When excavating the foundation pit (step 3) at the construction site, the foundation pit 3 is excavated using a natural slope method, with the slope of the pit wall not less than 45°. This invention eliminates the traditional sheet pile support, employing a large-angle (50°) natural slope layered excavation method (each layer depth ≤1m) to avoid pit wall collapse. This invention eliminates the construction period delays and cost increases caused by the sheet pile support process. This invention is particularly suitable for similar terrain and geological conditions such as plains, lake areas, and ponds, where the groundwater level is 0.5-1.2m higher than the bottom of the foundation pit, the bearing layer is silty clay or soft soil, and the pit wall is self-supporting and non-formable (bearing capacity ≤80kPa). When excavating the foundation pit 3, the soil's own stability can be used to form lateral confinement. After eliminating the sheet pile support, the displacement of the pit wall of foundation pit 3 is monitored once a day. If the displacement exceeds 5mm, emergency measures such as sandbag loading are taken in time to ensure construction safety. Of course, before excavating the foundation pit 3, the construction, supervision, design and construction units need to jointly inspect the pit, focusing on verifying whether the soil quality of the bearing layer is consistent with the survey report, whether there are weak underlying layers and underground buried objects. The main method is to use light dynamic penetration test to conduct general testing, with one hole every 20m, and the number of hammer blows for a penetration of 30cm ≥ 15 blows to confirm the uniformity of the bearing layer. In key areas (such as near the pit wall and the undulating part at the bottom of the foundation pit), the density is increased to one hole every 10m. After the pit inspection is qualified, the "Record of Pit Bottom Inspection" is filled out, clearly stating the rationality of canceling the steel sheet pile support based on the geological survey data. After signing and confirming, the next process can be carried out.

[0029] The foundation pit 3 is a stepped foundation pit 3, including as follows Figure 1 The diagram shows a primary foundation pit 31 at the bottom and a secondary foundation pit 32 at the top. The primary and secondary foundation pits 31 and 32 are concentrically arranged, with the planar dimensions of the primary pit 31 being smaller than those of the secondary pit 32. The tensioning chamber 1 is located within the primary foundation pit 31, and the foundation cap 2 is poured within the secondary foundation pit 32. After the tensioning chamber and foundation cap are poured, concrete strength is tested using test blocks. The compressive strength of the concrete must be ≥20 MPa after 28 days of pouring.

[0030] Before the step of backfilling plain soil into the first trench 4 between the tensioning chamber 1 and the foundation pit 3 to form the first backfill layer 5, the method further includes: The first fertilizer trench 4 was cleaned using a combination of a small excavator and manual labor. The excavator (0.3m³ bucket capacity) removed floating mud and large debris from the bottom of the pit, while manual labor cleaned up any remaining debris, ensuring that the bottom of the first fertilizer trench 4 was free of hard objects larger than 10cm and water accumulation. Given the geology of the pit surface in the plain lake area, if the bottom of the pit was submerged in water, a 30-50cm layer of disturbed soil was excavated and allowed to dry to an optimal moisture content of ±2%. After cleaning, a 300mm×300mm circular drainage ditch was constructed at the bottom of the first fertilizer trench 4, with a slope of 3‰. 800mm×800mm×800mm collection wells were installed at 20m intervals along the drainage ditch. A Φ100mm submersible pump was installed in each collection well to drain any remaining water. The drainage ditch, collection wells, and pumps ensured that the first fertilizer trench remained free of water during construction, preventing the backfill soil from being soaked.

[0031] Before the step of backfilling plain soil into the second trench 7 between the foundation cap 2 and the foundation pit 3 to form the second backfill layer 6, the following steps are also included: A second fertilizer tank drainage ditch is set up in the second fertilizer tank. The slope of the second fertilizer tank drainage ditch is 3‰. 800mm×800mm×800mm water collection wells are set up at 20m intervals along the second fertilizer tank drainage ditch. Water pumps are installed in the water collection wells.

[0032] When the groundwater level is 1m higher than the bottom of the foundation pit, a 10cm thick sand and gravel filter layer is laid at the bottom of the first trench 4. The sand and gravel filter layer is connected to the water collection well to prevent the bottom of the foundation pit from being soaked by the subsequent rise in groundwater level.

[0033] Before backfilling plain soil into the first trench 4 between the tensioning chamber 1 and the foundation pit 3 to form the first backfill layer 5, a 50cm high water-retaining sill is set up on the construction surface near the foundation pit 3. The water-retaining sill is set around the foundation pit 3 to prevent rainwater from flowing into the first trench 4 and the second trench 7 and affecting the compaction quality of the plain soil.

[0034] This invention is applied to a wind farm that has installed 16 Goldwind GWH221-6.25-H160 hybrid tower wind turbines, each with a capacity of 6.25MW and a hub height of 160m. The tensioning chamber 1 is 2.3m deep, and the foundation platform 2 is 2.55m deep. The tensioning chamber 1 and foundation platform 2 are poured in two stages. The wind turbine foundation is a circular extended foundation, with the first trench width 1.5-2.2m and a depth 1.0-2.5m, and a total backfill volume of approximately 4200 cubic meters. The project has a high groundwater level (1.0m above the bottom of the foundation pit), and the geology is silty clay (bearing capacity of 120kPa). It is located near farmland and water sources, with strict environmental protection requirements. This invention establishes a standardized process of "natural slope + simultaneous pouring of tensioning chambers + backfilling with plain soil" during construction, solving the industry pain points of redundant procedures and high costs associated with traditional processes. The application effects are as follows: Construction parameters: The backfilling period for the fertilizer trench is 5 days, shortening it by 7 days compared to traditional methods; the concrete pouring period reduces labor by 40 man-days and machine shifts by 5, resulting in a cumulative reduction of 640 man-days and 80 machine shifts for the 16 generating units, lowering the overall cost of labor, materials, and equipment by more than 35%. This avoids hidden costs such as management fees and equipment idleness caused by construction delays. It effectively ensures the project's early grid connection, which can increase power generation revenue, help alleviate regional power supply and demand imbalances, and provide support for the high-quality development of the new energy industry.

[0035] Replacing concrete pouring with plain soil avoids potential wastewater pollution from concrete pouring, achieving coordinated development between engineering construction and ecological protection. Plain soil backfilling saves 80 cubic meters of concrete per foundation, totaling 1300 cubic meters saved across 16 units. Based on a comprehensive concrete purchase and pouring unit price of 400 yuan / cubic meter, this translates to material cost savings of 520,000 yuan. Assuming a carbon emission of 0.25 tons per cubic meter of concrete, this reduces carbon emissions by approximately 325 tons. It also reduces the frequency of construction machinery use, lowers fuel consumption by 15%, and reduces exhaust emissions (CO, NOx, etc.) by approximately 20 tons, meeting green construction requirements. Furthermore, it saves on machinery rental and fuel costs. Using locally sourced plain soil eliminates the need for additional procurement, reducing the amount of excavated soil transported by approximately 1300 cubic meters, lowering material costs by over 90%, reducing the amount of natural sand and gravel mining, and minimizing disturbance to the ecological environment of ponds and lakes in the plains, thus protecting the ecological environment.

[0036] Within one year of project commissioning, the stability of the concrete tower foundation was monitored. The settlement of the concrete tower foundation was ≤2.5mm, and there was no leakage. The compaction coefficient of the plain soil backfill was ≥0.94, and the quality qualification rate was 100%.

[0037] During construction, a 1.2m high guardrail must be installed around the perimeter of the first pit 4, painted with alternating red and white warning paint, and "Caution: Falling" signs must be hung. Warning lights (spaced 10m apart) must be installed at night, and 30cm high toe boards must be installed on the outside of the guardrail to prevent personnel from falling. Excavators and road rollers must be operated by designated personnel, and personnel are prohibited from staying within the operating radius. Construction electricity will adopt a "three-level power distribution, two-level protection" system. Submersible pumps, vibrators, and other equipment will be equipped with leakage protection devices (operating current ≤30mA). Cables will be laid overhead or underground (buried depth ≥0.7m), and rolling or soaking is strictly prohibited. Simultaneously, emergency plans for pit wall collapse and electric shock must be developed, and emergency supplies (shovels, stretchers, first aid kits) must be provided. An emergency drill will be organized quarterly to improve response capabilities. During the rainy season, the frequency of pit wall displacement monitoring will be increased (once every 4 hours), and outdoor work will be suspended during heavy rain. Heatstroke prevention and cooling supplies will be provided during high temperatures to prevent heatstroke among construction personnel.

[0038] Dust control nets are used to cover the soil piles, and tarpaulins are used to cover transport vehicles. The construction site is regularly watered to reduce dust (2-3 times a day), and the water used for watering is recycled from the sedimentation tank to save water. Wastewater treatment: Construction wastewater (washing machinery and watering to reduce dust) is reused after sedimentation in the sedimentation tank and is strictly prohibited from being discharged directly into the surface of pits and ponds. The oil storage area is equipped with anti-seepage trays to prevent oil leakage from polluting the soil and water. Noise control: The construction time is arranged reasonably to avoid construction at night (22:00-6:00). Noise reduction devices are installed on machinery to control the noise below 75dB(A) to reduce the impact on the surrounding farmland ecology.

[0039] During construction, a dedicated quality inspector must regularly check the moisture content of the subgrade, the thickness of the loose layer, the number of compaction passes, and the fixing of the formwork to avoid substandard compaction due to excessive moisture content or insufficient compaction. Hidden procedures such as bottom treatment of the foundation pit, layout of the drainage system, and layered testing of the subgrade must be inspected and signed off by the supervision unit before the next procedure can be carried out.

[0040] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. The scope of protection of this application should be determined by the scope of the claims. Although this application has disclosed the preferred embodiment above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solution of this application shall fall within the scope of the technical solution of this application.

Claims

1. A method for fixing the foundation of a hybrid tower in a wind farm, characterized in that, Includes the following steps: Excavate a foundation pit at the construction site (3); Install the tension chamber casting template in the foundation pit (3) and pour the tension chamber (1); Remove the formwork for the tensioning chamber; Plain soil is backfilled into the first trench (4) between the tensioning chamber (1) and the foundation pit (3) to form a first backfill layer (5); A foundation pier (2) is poured on the upper part of the tensioning chamber (1); Plain soil is backfilled into the second trench (7) between the foundation cap (2) and the foundation pit (3) to form a second backfill layer (6).

2. The method for fixing a hybrid tower foundation in a wind farm according to claim 1, characterized in that, In the steps of backfilling plain soil into the first fertilizer tank (4) to form the first backfill layer (5) and backfilling plain soil into the second fertilizer tank (7) to form the second backfill layer (6), the plain soil is backfilled in a layered compaction manner.

3. The method for fixing a hybrid tower foundation in a wind farm according to claim 2, characterized in that, During the backfilling process using a layered compaction method, the compaction degree of each layer of the soil is tested using a ring cutter method.

4. The method for fixing a hybrid tower foundation in a wind farm according to claim 3, characterized in that, After backfilling plain soil into the first fertilizer tank (4) to form the first backfill layer (5), the bearing capacity of the first backfill layer (5) is tested by a light dynamic penetration test; after backfilling plain soil into the second fertilizer tank (7) to form the second backfill layer (6), the bearing capacity of the second backfill layer (6) is tested by a light dynamic penetration test.

5. A method for fixing a hybrid tower foundation in a wind farm according to any one of claims 1-4, characterized in that, The soil includes the excavated soil generated during the excavation of the foundation pit (3).

6. A method for fixing a hybrid tower foundation in a wind farm according to any one of claims 1-4, characterized in that, When excavating the foundation pit (3) at the construction surface, the foundation pit (3) is excavated by natural slope method, and the slope of the pit wall of the foundation pit (3) is not less than 45°.

7. A method for fixing a hybrid tower foundation in a wind farm according to any one of claims 1-4, characterized in that, The foundation pit (3) is a stepped foundation pit, including a primary foundation pit (31) at the bottom and a secondary foundation pit (32) at the top. The primary foundation pit (31) and the secondary foundation pit (32) are arranged concentrically, and the planar dimensions of the primary foundation pit (31) are smaller than those of the secondary foundation pit (32). The tensioning chamber (1) is arranged in the primary foundation pit (31), and the foundation cap (2) is poured in the secondary foundation pit (32).

8. A method for fixing a hybrid tower foundation in a wind farm according to any one of claims 1-4, characterized in that: Before the step of backfilling plain soil into the first fertilizer tank (4) to form the first backfill layer (5), the following steps are also included: A circular drainage ditch is provided at the bottom of the first fertilizer tank (4); Water collection wells are installed at intervals along the drainage ditch of the fertilizer trough; Install a water pump in the water collection well.

9. The method for fixing a hybrid tower foundation in a wind farm according to claim 8, characterized in that, After setting up water collection wells at intervals along the drainage ditch of the fertilizer trough, a sand and gravel filter layer is laid at the bottom of the first fertilizer trough (4), and the sand and gravel filter layer is connected to the water collection well.

10. A method for fixing a hybrid tower foundation in a wind farm according to any one of claims 1-4, characterized in that, Before the step of backfilling plain soil into the first fertilizer trench (4) to form the first backfill layer (5), a water-retaining sill is set at the position of the construction surface near the foundation pit (3).

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