Fan foundation secant pile construction method

Abstract

The invention relates to a fan foundation secant pile construction method, and relates to the field of fan foundation secant pile construction. Comprising the steps of construction preparation; the secant piles are constructed, plain concrete piles are constructed firstly, and a reinforced concrete pile between the two plain concrete piles is constructed after initial setting and before final setting of the two adjacent plain concrete piles which are completed later; secant pile hole forming comprises a plain concrete pile hole forming construction method, a reinforced concrete pile hole forming construction method and hole forming monitoring; hole cleaning is conducted, specifically, the drilling bucket is converted into a double-bottom and flat-bottom slag salvaging bucket, the drilling bucket is placed at the bottom of the hole and then rotated forwards, slag is contained in the slag bucket through a straight blade at the bottom of the drilling bucket, and the slag salvaging bucket is lifted out of the pile hole by closing a bucket door in a reverse rotation mode; construction of a reinforcement cage: manufacturing and mounting the reinforcement cage and hoisting the reinforcement cage; concrete is poured, and the steel sleeve is pulled out. According to the construction method, the plain concrete piles are firstly constructed, then the reinforced concrete pile between the two plain concrete piles is constructed, and the occlusive pile holes are emptied, so that the construction quality of the occlusive piles is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind turbine foundation interlocking pile construction, in particular to a wind turbine foundation interlocking pile construction method. BACKGROUND

[0002] The interlocking pile is characterized by facilitating the interlocking construction between piles. The interlocking pile is designed to be arranged alternately between plain concrete piles and reinforced concrete piles, and the plain concrete piles are not provided with steel cages. During construction, the plain concrete piles on both sides are constructed first, and then the reinforced concrete piles are constructed. The reinforced concrete piles are completed before the initial setting of the overlying concrete of the plain concrete piles, thereby realizing the interlocking between the piles.

[0003] The interlocking pile is constructed by using a full casing drill. The interlocking pile is constructed by using the shaking device of the full casing drill to reduce the friction between the steel casing and the soil layer. The casing is pressed into the soil while being shaken, and a drop hammer type grab is used to excavate and take out the soil or sand in the steel casing until the steel casing is sunk to the designed depth. After the hole is formed, the concrete is poured, and the steel casing is gradually pulled out for repeated use. The full casing drilling method has high degree of mechanization and fast hole forming speed. It has no noise and vibration, has little impact on the stratum and the surrounding environment, and can control the verticality of the pile to 3‰ (1 / 300 is required in the design of the interlocking pile). The full casing drilling method can adapt to various complex strata, effectively prevent accidents such as quicksand, hole collapse, shrinkage, expansion, exposed reinforcement, and broken pile, and has high pile quality. The interlocking effect between the piles is good, and the waterproof effect is good.

[0004] At present, some wind turbine sites are located near the coast, and the groundwater level is high. After the pile foundation is formed, the quicksand and floating sludge rapidly flow up due to the hydrostatic pressure. The space in the full casing is limited, and the steel cage has mud slurry buoyancy at the bottom of the limited space. When the first concrete is poured, the concrete, steel cage, and casing are integrated as a whole. When the casing is pulled out, the mud slurry buoyancy and the tension of the inner wall of the casing make the steel cage float together, thereby affecting the construction quality of the interlocking pile. SUMMARY

[0005] To solve at least one of the technical problems in the background art, the present application provides a wind turbine foundation interlocking pile construction method. The construction method is to first construct the plain concrete piles and then construct the reinforced concrete piles between the two adjacent completed plain concrete piles before the initial setting and before the final setting of the overlying concrete of the plain concrete piles. The construction method is beneficial to improve the construction quality of the interlocking pile.

[0006] To achieve the above-mentioned purpose, the present application provides a wind turbine foundation interlocking pile construction method, which comprises the following steps: Step S1, construction preparation; Step S2, interlocking pile construction, first construct the plain concrete piles, and then construct the reinforced concrete piles between the two adjacent completed plain concrete piles before the initial setting and before the final setting of the overlying concrete of the plain concrete piles; Step S3, interlocking pile drilling, including plain concrete pile drilling construction, reinforced concrete pile drilling construction and drilling monitoring; Step S4: hole cleaning: convert the drill bucket into a double-bottom flat-bottom slag bucket. Place the drill bucket at the bottom of the hole and rotate it forward to collect the slag in the slag bucket using the straight blade at the bottom of the drill bucket. Then, rotate it backward to close the bucket door and lift the slag bucket out of the pile hole. Step S5, steel cage construction, including the production and installation of the steel cage and the hoisting of the steel cage; Step S6: pouring concrete and pulling out the steel casing.

[0007] Furthermore, in step S1, construction preparation includes: leveling the site and clearing overhead, ground, and underground obstacles within the pile foundation range; overhead high-voltage lines must be no less than 10m away from the rotary drilling rig frame, and drainage measures must be taken; the foundation must be strong enough to ensure the stability of the drilling rig; thick steel plates are placed under the parking position for weak foundations; if sinking or tilting is found during the drilling operation, the rig should be stopped and handled immediately; Ensure the equipment is brought in for assembly and commissioning, as well as the supply of materials and the inspection of raw materials.

[0008] Furthermore, the plain concrete pile hole construction method includes: After the machine is in place, adjust the verticality of the fuselage and mast, align the center of the rotary drill rod with the crosshairs, and lock the azimuth of the rotary drill body; install the bucket-type drill bucket on the rotary drill body, align it with the crosshairs, and then carefully observe the gap around the hole mouth, and use the verticality control instrument of the rotary drill rig to control the verticality, start the rotation and sink the drill bucket to take soil; bury the thin-walled short steel casing, inject stabilizing liquid into the thin-walled short steel, continue drilling to take soil and replenish stabilizing liquid in the hole in time, so that the elevation stabilizing liquid level in the hole is more than 1m higher than the pile hole bearing water level.

[0009] Furthermore, the reinforced concrete pile drilling construction method includes: the reinforced concrete pile drilling is carried out after the concrete of the plain concrete pile is poured, the bottom section steel casing is connected with a rotary drilling rig, the cross line is aligned, the gap around the hole mouth is observed, and the verticality controller is observed to see whether it is within the allowable range; the rotary drilling function is turned on to sink the bottom section into the soil, the drilling and soil extraction function of the rotary drilling rig is turned on to drill into the soil with a bucket-type drill bucket and extract the soil outside the pile hole; the second and Nth sections of the steel casing are connected, the casing joint anti-slip pad is installed, and drilling and soil extraction are continued to the designed elevation.

[0010] Furthermore, the method of hole monitoring includes: during the hole-forming process, the verticality of the drill rod or steel casing of the rotary drilling rig must be monitored at any time, especially when the first and second sections of the casing are drilled. During monitoring, the equipment's built-in manual and automatic vertical adjustment functions or two plumb bobs are used for two-way control to ensure that the verticality is less than 1 / 300.

[0011] Furthermore, the method for making and installing the steel cage includes: The diameter of the steel cage is 600mm. The reinforced area has 8 main bars, 8 stirrups at 100mm, and a length of 9.25 meters. The non-reinforced area has 4 main bars, 8 stirrups at 200mm, and a length of 9.25 meters. The main bars are connected by arc lap welding. During welding, the assembly and positioning of the steel bars should meet the following requirements: the axes of the two steel bars are aligned after pre-bending and installation; the side bars and main bars are fixed with four-point tack welding; when overlapping, they are fixed with two points, and the tack weld should be at least 20mm away from the overlap end. When welding, the arc should be started at one end of the overlapping steel bar, and the arc should be closed at the end of the overlapping steel bar. The arc crater should be filled. When welding multiple layers, the first layer of weld should have sufficient penetration. The main weld and the positioning weld, especially at the beginning and end of the positioning weld, should be well fused. When lap welding is used for steel bar joints, the weld length should not be less than the lap length, the weld height h≥0.3d and shall not be less than 4mm; the weld width b>0.7d and shall not be less than 10mm; when lap welding is used for steel bar and steel plate joints, the weld height h>0.35d and shall not be less than 6mm; the weld width b≥0.5d and shall not be less than 8mm; where d is the diameter of the steel bar.

[0012] Furthermore, the method of lifting the steel cage includes: the steel cage should be inspected before lifting, and the inspection contents include length, diameter, and whether the welding points are deformed. After the inspection is completed, the lifting begins. The lifting is carried out by a 25-ton truck crane with double hooks and multiple points for slow lifting to prevent the steel cage from deformation; the length of the steel cage in the design drawing is 19.86m, and the steel cage consists of two sections, the first section is 10 meters and the second section is 9.86 meters. During the lifting, there must be a dedicated person to command to ensure safety. The protective block of the steel cage adopts a roller-type high-strength cement mortar protective block to prevent the steel cage from being brought up when the steel casing is pulled out. At the same time, a 3~5mm anti-floating steel plate is set at the bottom of the steel cage. When pulling out the steel casing, a measuring rope is tied to the top of the steel cage to monitor the condition of the steel cage in real time during pouring concrete and pulling out the steel casing.

[0013] Furthermore, the method of pouring concrete and pulling out the steel casing includes: According to the design drawings, the length of a single pile needs to be 20.86 meters, the concrete volume of a single pile is 10.48m³, and the filling coefficient of the interlocking pile is 1.1 to 1.3, so the concrete volume each time should be no less than 13.624m³; 1) Install concrete conduit The concrete conduit adopts Φ220~250mm threaded steel casing. Each section of the concrete conduit should be fastened to prevent leakage and blockage. The bottom of the concrete conduit should be 300~500mm away from the bottom of the hole. 2) Pouring concrete After the concrete pipe is installed, a pipe pulling inspection should be carried out. The purpose of the inspection is to check whether the steel casing is pulled out smoothly, whether the steel cage follows the pipe or rotates during the pulling process, and the pulling amount is controlled within 0-200mm; 3) Preparations before pouring include wetting the loading and storage hoppers with water, conducting on-site concrete slump tests, and preparing concrete test blocks. The plug in the storage hopper should be a round steel plate suspended by a thin steel wire rope. The first loading should ensure that it is not less than the initial pouring volume. After the first pouring is completed, the concrete conduit should be at a depth of more than 2 meters. After the first bucket of material has been lowered, the steel casing should be pulled out to check whether the steel cage floats up with the pipe. After each bucket of concrete or truck is completed, a pull-out inspection should be carried out, and the pull-out amount should not exceed 100mm. This process continues until the first section of the outer casing is removed. 4) When the concrete pouring height in the steel casing exceeds 3m of the first section of steel casing, the first section of steel casing should be removed for the first time. After removing the first section of steel casing, the steel casing should be buried in the concrete at a depth of not less than 2m, and the concrete guide tube should be buried at a depth of 2.5m; 5) Repeat the above process and enter the second pipe pulling cycle. When the last section of the steel casing is pulled out at one time, the concrete conduit should remain in the hole. After the steel casing is completely pulled out and removed, measure the concrete surface elevation in the hole and re-pour concrete as needed; remove the concrete conduit after pouring; the concrete pouring process takes 2 to 3 hours; each time the concrete conduit and steel casing are removed, they should be immediately rinsed with clean water to prepare for the next concrete pouring.

[0014] The beneficial effects of the present invention are: The present invention provides a method for constructing interlocking piles of a wind turbine foundation. The method comprises the following steps: first constructing plain concrete piles, then constructing reinforced concrete piles between the two plain concrete piles, and emptying the interlocking pile holes, thereby improving the construction quality of the interlocking piles. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a process flow chart of the present invention; Figure 2 It is the construction drawing of the interlocking pile of the present invention. DETAILED DESCRIPTION

[0016] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0017] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0018] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "center," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe this application and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0019] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0020] Furthermore, the terms "installed," "disposed," "provided with," "connected," "connected," and "socketed" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral structures; mechanical connections or electrical connections; direct connections, indirect connections through an intermediary, or internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0021] like Figure 1 As shown, the present invention provides a method for constructing wind turbine foundation interlocking piles, comprising the following steps: Step S1, construction preparation; Construction preparation includes: leveling the site and clearing the high-altitude, ground and underground obstacles within the scope of the pile foundation, overhead high-voltage wire distance from the rotary drilling rig frame (outer dimensions 11m long 4.8m wide 7m, turning radius The distance between the drilling rig and the nearest building shall not be less than 10 m (for a drilling rig 25 m high) and drainage measures shall be taken; the foundation shall have sufficient strength (ground resistance ≥ 110 Kpa) to ensure the stability of the drilling rig, and thick steel plates shall be laid under the drilling rig in soft ground; if sinking or tilting is found during drilling, the drilling rig shall be stopped for treatment; The equipment shall be assembled and debugged, and the supply of materials and the inspection of raw materials shall be implemented.

[0022] Step S2: construction of the interlocking pile, first, the plain concrete pile is constructed, and then the reinforced concrete pile between the two adjacent plain concrete piles is constructed after the completion of the two adjacent plain concrete piles, and the construction sequence is shown in Figure 2 ; Step S3: hole forming of the interlocking pile, including hole forming construction of the plain concrete pile, hole forming construction of the reinforced concrete pile and hole forming monitoring; The top elevation of the interlocking pile is designed to be -4.1 m, the design pile length is 18.5 m, the construction platform elevation of the rotary drilling rig is ±0.00 m, the construction depth of the rotary drilling rig is 22.6 m, the steel casing pipe with a diameter of 800 mm is used for wall protection, and the rotary bucket drill is used for drilling and soil taking.

[0023] The hole forming construction method of the plain concrete pile includes: after the machine is positioned, the machine body and the verticality of the mast are adjusted, the rotary drill rod center is centered with the cross line, and the azimuth angle of the rotary drilling rig body is locked; the rotary drill rod is installed with the bucket drill, which is aligned with the cross line, and the clearance around the hole is observed, and the verticality is controlled by using the verticality control instrument of the rotary drilling rig, and the rotary sinking drill is started to take soil; the short steel casing pipe is buried, the stable liquid is injected into the short steel casing pipe, the soil is continuously taken by drilling, and the stable liquid is supplied to the hole in time, so that the liquid level of the stable liquid in the hole is higher than the pile hole pressure water level by more than 1 m.

[0024] The hole forming construction method of the reinforced concrete pile includes: the hole forming of the reinforced concrete pile is performed after the concrete of the plain concrete pile, the bottom section (with a cutting blade) steel casing pipe is connected to the rotary drilling rig, the cross line is aligned, the clearance around the hole is observed, and whether the verticality control instrument is within the allowable range is observed; the bottom section is sunk into the soil by starting the rotary drilling function, the soil in the soil body is taken out of the pile hole by using the bucket drill to drill into the soil body, the second section to the N section steel casing pipe is connected, the casing pipe joint is installed, the anti-loose pad is installed, and the soil is continuously taken by drilling to the design elevation.

[0025] The soil taking construction in the steel casing pipe is generally constructed by using the full casing pipe method in the soft soil layer, and 1-3 m of soil is always left in the casing pipe to prevent piping.

[0026] The hole forming monitoring method includes: during the hole forming process, the verticality of the rotary drill rod or the steel casing pipe must be monitored at any time, especially when the first section and the second section of the casing pipe are drilled, the manual and automatic verticality adjustment functions of the equipment are used or two line hammers are used for bidirectional control to ensure that the verticality is less than 1 / 300.

[0027] The measures to ensure hole formation are as follows: Steel casing positioning: After the steel casing is pressed into the soil, turn on the drill rig and rotate it one circle to observe whether the surrounding gap is uniform. If it is inconsistent, adjust it in time. After the steel casing is installed, the verticality should be re-measured. The re-measurement uses the machine's own instruments and theodolite to re-measure in both directions. Only when the requirements are met can the hole be drilled.

[0028] Controlling Hole Verticality: The verticality of the steel casing of a rotary drilling rig depends crucially on the first and second sections. This is because there's only a 10mm gap between the outer cutting edge and the outer wall of the casing. Once the casing has penetrated a certain depth into the soil, its outer wall is nearly in contact with the soil. If it tilts to one side, the resulting lateral resistance cannot be adjusted by the rotary drilling rig alone. Therefore, the verticality of the first and second sections must be kept within the allowable deviation. During drilling, the rig should be stopped regularly or irregularly for observation. If any deviations are exceeded, use the adjustment cylinder to adjust the verticality promptly. If adjustment is impossible, backfill the pile hole with clay, lift the steel casing, and re-drill.

[0029] The rotary drill must rotate smoothly while sinking the casing to prevent damage to the carbide cutting edge. Once inside the rock formation, slow down the rotation to prevent the bottom cutting edge from wearing out before the hole is drilled, preventing the hole from being completed. If this occurs, backfill the pile hole with clay, remove the steel casing, replace the new cutting edge, and then drill again to complete the hole.

[0030] When drilling with a rotary drilling rig, determine whether to inject water into the hole and reserve soil thickness for the steel casing based on the geological conditions to prevent accidents such as pipe bursts. Generally, for clayey soils, a 3-5m depth of soil can be reserved inside the pipe. For silty soils and sandy soils, 5-10m of soil should be reserved. Alternatively, water should be promptly injected into the hole to maintain a bearing pressure approximately 1-2m higher than that outside the hole. When lifting the drill, do not increase the speed too quickly to prevent a vacuum from forming below, which could cause fluid soil outside the pipe to flow in from the bottom.

[0031] When a pipe burst occurs, use an excavator to backfill the hole with clay in time. After the complete drilling rig has sunk the steel casing into the stable soil layer, use the rotary drilling rig bucket to remove the soil in the hole.

[0032] Step S4: hole cleaning: convert the drill bucket into a double-bottom flat-bottom slag bucket. Place the drill bucket at the bottom of the hole and rotate it forward to collect the slag in the slag bucket using the straight blade at the bottom of the drill bucket. Then, rotate it backward to close the bucket door and lift the slag bucket out of the pile hole. Because the wind turbine is located near the coast and the groundwater is high, after the pile foundation is bored, the quicksand and slag rise rapidly due to the hydrostatic pressure. The space inside the entire casing is limited, and the steel cage has mud buoyancy at the bottom of the limited space. When pouring the first batch of concrete, the concrete, steel cage and casing are connected as a whole. When the casing is pulled out, the buoyancy of the mud and the tension of the inner wall of the casing carry the steel cage up, thus affecting the construction quality of the interlocking pile. When the drilling rig cannot achieve the purpose of clearing the hole, the mud wall protection method can be used.

[0033] During bored pile construction, a stabilizing fluid, such as bentonite, is added to the hole. Bentonite allows the slurry to penetrate and gradually fill the voids in the soil layer of the hole wall, thereby blocking waterways and forming a water barrier on the hole wall, effectively preventing hole wall collapse. Bentonite slurry also serves as a slag carrier and lubricant for tools. A slurry with a certain viscosity not only carries away drilling cuttings but also acts as a lubricant and coolant for the drill tool, cooling and lubricating the casing while flushing the drill tool and removing the casing. The hydrostatic pressure of the slurry counteracts the earth and water pressures acting on the hole wall and prevents groundwater infiltration. Although drilling disrupts the equilibrium of the original soil, reducing the static earth pressure on the hole wall and causing the pore water pressure to become negative, exerting a tensile force on the soil, once the hole is filled with bentonite slurry, the hydrostatic pressure on the hole wall balances the earth pressure. At the same time, the penetration of fine soil particles in the bentonite slurry into the soil layer also enhances the strength of the soil layer, thereby maintaining the stability of the hole wall.

[0034] According to the requirements of the construction unit, in order to prevent the upwelling of quicksand at the bottom of the hole, prevent the bottom of the hole from being blocked and the mud from having excessive buoyancy, and at the same time reduce the friction of the inner wall of the casing on the concrete and steel bars, bentonite was added when the original reinforced concrete piles were drilled, and bentonite mud was used to protect the walls. 6 tons of clay was added to a single pile foundation, and the mud was prepared to fill the pile body. The specific addition ratio was adjusted according to the on-site conditions. A circulation process was used to clean the sediment at the bottom of the hole and balance the hydrostatic pressure to reduce the buoyancy of groundwater on the steel cage.

[0035] Step S5, steel cage construction, including the production and installation of the steel cage and the hoisting of the steel cage; The fabrication and installation methods of the steel cage include: According to the design drawings, the main reinforcement of the occlusal pile reinforcement cage uses 28mm threaded steel, the stirrups use 8mm round steel, and the anchor ring reinforcement uses 20mm threaded steel. The reinforcement arrangement is shown in Table 1:

[0036] Table 1

[0037] The diameter of the steel cage is 600mm. The reinforced area has 8 main bars, 8 stirrups at 100mm, and a length of 9.25 meters. The non-reinforced area has 4 main bars, 8 stirrups at 200mm, and a length of 9.25 meters. The main bars are connected by arc lap welding. During welding, the assembly and positioning of the steel bars should meet the following requirements: the axes of the two steel bars are aligned after pre-bending and installation; the side bars and main bars are fixed with four-point tack welding; when overlapping, they are fixed with two points, and the tack weld should be at least 20mm away from the overlap end. When welding, the arc should be started at one end of the overlapping steel bar, and the arc should be closed at the end of the overlapping steel bar. The arc crater should be filled. When welding multiple layers, the first layer of weld should have sufficient penetration. The main weld and the positioning weld, especially at the beginning and end of the positioning weld, should be well fused. When lap welding is used for steel bar joints, the weld length should not be less than the lap length, the weld height h≥0.3d and shall not be less than 4mm; the weld width b>0.7d and shall not be less than 10mm; when lap welding is used for steel bar and steel plate joints, the weld height h>0.35d and shall not be less than 6mm; the weld width b≥0.5d and shall not be less than 8mm; where d is the diameter of the steel bar.

[0038] Arc welding precautions: (1) The size of the reinforcement bars, the angle of the groove, the gap between the ends of the reinforcement bars and the axis of the reinforcement bars shall all comply with the relevant regulations; (2) The welding ground wire should be in good contact with the steel bar to prevent the steel bar from being burned due to arcing; (3) For joints with backing plates or bars, arc striking should be carried out on the steel plate or bar. For joints without steel plates or bars, arc striking should be carried out at the weld seam to prevent burning of the main reinforcement. (4) According to the steel bar grade, diameter, joint form and welding position, select the appropriate welding rod diameter and welding current to ensure good fusion between the weld and the steel bar: (5) Clean slag in time during welding, make the weld surface smooth and flat, strengthen the weld with a smooth transition, and fill the arc pit.

[0039] The method of lifting the steel cage includes: the steel cage should be inspected before lifting, and the inspection contents include length, diameter, whether the welding points are deformed, etc. The lifting can be started after the inspection is completed. The lifting is carried out by a 25-ton truck crane with double hooks and multiple points for slow lifting to prevent the steel cage from deformation; the length of the steel cage in the design drawing is 19.86m, and the steel cage consists of two sections, the first section is 10 meters and the second section is 9.86 meters. During lifting, there must be a dedicated person to direct to ensure safety. The protective block of the steel cage adopts a roller-type high-strength cement mortar protective block to prevent the steel cage from being brought up when the steel casing is pulled out. At the same time, a 3~5mm anti-floating steel plate (or anti-floating concrete block) can be set at the bottom of the steel cage. When pulling out the steel casing, a measuring rope is tied to the top of the steel cage to monitor the condition of the steel cage in real time during pouring concrete and pulling out the steel casing.

[0040] When hoisting the rebar cage, use two or more lifting points to prevent the cage bottom from dragging on the ground and the cage reinforcement from bending, deforming, or becoming unwelded. Lower the cage slowly. After entering the hole, secure the cage securely to the lifting bars. After alignment, the joints should be staggered by 50%, with the overlap length meeting design requirements. Connect and seal the acoustic testing pipes as required. Once the cage has reached its designed elevation, secure it to the steel casing. Ensure a secure fit to prevent the cage from falling or floating during concrete pouring.

[0041] Step S6: pouring concrete and pulling out the steel casing.

[0042] Methods for pouring concrete and pulling out steel casing include: According to the design drawing requirements, the single pile length needs to pour concrete 20.86 meters, the single pile concrete volume is 10.48 m³, the occlusion pile filling coefficient is 1.1-1.3, so the concrete volume is not less than 13.624 m³ each time; 1) Install the concrete conduit The concrete conduit adopts Φ220-250mm threaded coupling steel casing pipe, each section of the concrete conduit should be buckled tightly to prevent air leakage and pipe blockage, and the bottom of the concrete conduit is 300-500mm away from the hole bottom; 2) Pour concrete After the concrete conduit is installed, it should be pulled out for inspection, the purpose of the inspection is to check whether the steel casing pipe is smoothly pulled out, whether the reinforcement cage is stuck or rotated during the pulling process, and the pulling amount is generally controlled within 0-200mm; 3) The preparation before pouring includes loading and water wetting of the storage hopper, on-site concrete slump test and making concrete test blocks; if the concrete workability is found to be poor and the slump cannot meet the design requirements, water should not be directly injected into the concrete tank truck, the concrete in the truck should be returned, and after the inspection is completed and everything is normal, the first loading is carried out. The plug in the storage hopper is suspended by a fine steel wire rope; the first loading should ensure that the initial pouring amount is not less than 2 meters, and the concrete conduit should be at a buried depth of more than 2 meters after the first pouring is completed. After the first batch of material is dropped, the steel casing pipe should be pulled out (the pulling amount should not exceed 100mm), and whether the reinforcement cage is stuck or floated should be checked; if it is found that the casing pipe is stuck, it should be immediately treated with counter pressure, and if everything is normal, the loading operation should continue. After each batch of concrete or truck is completed, the pulling inspection should be carried out, the pulling amount should not exceed 100mm, and the process should continue until the first section of the outer casing pipe is removed; 4) When the concrete pouring height in the steel casing pipe exceeds 3m of the first section of the steel casing pipe, the first pulling of the first section of the steel casing pipe should be started at this time, and after the first section of the steel casing pipe is removed, the steel casing pipe should be buried in the concrete for not less than 2m, and the concrete conduit should be buried for 2.5m; 5) Repeat the above process to enter the second pulling cycle, when the last section of the steel casing pipe is pulled out at one time, the concrete conduit should remain in the hole, and after the steel casing pipe is completely pulled out and removed, the concrete surface elevation in the hole is measured, and the concrete is supplemented according to the needs; after pouring, the concrete conduit is removed; the concrete pouring process takes 2-3 hours; the concrete conduit and steel casing pipe removed each time should be immediately cleaned with water for the next concrete pouring preparation.

[0043] The above pouring concrete and pulling pipe scheme should be determined through on-site tests to prevent the outer casing pipe from being buried too deep and the pulling pipe being difficult to pull out.

[0044] After the pile foundation construction is completed, the integrity of all occlusion piles should be detected according to the design drawing requirements.

[0045] The distance between the concrete conduit and the bottom of the hole should be 300-500mm. If the distance is too small, it will easily cause blockage. To avoid water seepage in the concrete conduit, the quality of the welds should be emphasized when making the concrete conduit. Strict requirements must be met for the welds in all parts of the concrete conduit. The threaded joints of the concrete conduit must be installed with elastic and uniform sealing rings and tightened. A water pressure test should be conducted before the first use. Only qualified ones can be used. Before construction, both new and old concrete conduits must undergo a water pressure test. If leaks are found, they must be repaired in time. Unqualified ones should be resolutely eliminated. After pouring, the concrete conduit should be cleaned promptly. No concrete, sand, or soil should remain at the two ports or on the inner wall of the conduit. A mesh made of steel bars that is 1.5 times larger than the maximum particle size of the gravel should be placed on the top of the hopper to prevent large-sized debris in the commercial concrete from falling into the conduit and causing blockage.

[0046] If pipe blockage occurs during initial pouring, immediately remove the pipe reinforcement cage and clean the concrete inside the hole. Continue pouring after it meets requirements. If the concrete pipe becomes clogged at mid-depth, consider raising the pipe appropriately to reduce water pressure, taking into account its burial depth. Installing a high-frequency oscillator on the concrete pipe at the orifice will generally allow the concrete inside to continue pouring. Never remove the concrete pipe from the underwater concrete surface.

[0047] Sediment, excessive wall slurry, concrete workability, slump, pipe lifting from the underwater concrete surface, and inability to pour concrete continuously are the main factors contributing to broken piles. Therefore, concrete slump should be strictly controlled according to design or specification requirements. Before pouring, check the workability and fluidity of commercial concrete. Ensure continuous, seamless pouring. During pouring, frequently measure the rise of the concrete top surface and monitor the pipe burial depth to avoid overburdening or lifting the pipe from the concrete surface.

[0048] The reasons and solutions for the floating of the steel cage during the construction of this application are as follows: Cause 1: The steel casing is being pulled up too quickly or mud and concrete residue are deposited on the inner wall of the steel casing. This causes the concrete debris to squeeze the steel cage during extraction, causing the cage and the steel casing to rise together, resulting in floating. Preventive Measure 1: Before each casing installation, carefully observe and remove mud and concrete residue from the inner wall of the casing. If necessary, apply mold release agent to the inner wall. Before pulling out the steel casing, fix a measuring rope to the main reinforcement at the top of the cage and hang the other end on the outside of the casing. As the outer casing is pulled out, observe whether the measuring rope is lowered into the pipe accordingly. If it does not or is not synchronized, it indicates that the steel cage is rising with it. Stop pulling out the casing, identify the cause, and then continue after counter-pressure.

[0049] Reason 2: The concrete is taken out of the tank for too long, resulting in initial setting and other phenomena. The concrete slump is too small, causing the concrete to stick to the inner wall of the casing, and workability problems. Preventive measure 2: Track the slump of the concrete at the discharge port and on-site, adjust the slump of the concrete to 200-220mm at the site, and use the nearest commercial concrete station to reduce the time it takes for the concrete to arrive at the site.

[0050] Reason 3: The verticality problem of the steel cage. Poor verticality will increase the friction resistance of the steel cage. Preventive measure 3: Ensure the verticality of the steel cage when lowering the cage and welding.

[0051] The present invention provides a method for constructing interlocking piles of a wind turbine foundation. The method comprises the following steps: first constructing plain concrete piles, then constructing reinforced concrete piles between the two plain concrete piles, and emptying the interlocking pile holes, thereby improving the construction quality of the interlocking piles.

[0052] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A wind turbine foundation interlocking pile construction method, characterized in that: The steps include: Step S1, construction preparation; Step S2, interlocking pile construction, first constructing the plain concrete pile, and then constructing the reinforced concrete pile between the two adjacent plain concrete piles after the initial setting and before the final setting of the two adjacent plain concrete piles; Step S3, interlocking pile drilling, including plain concrete pile drilling construction, reinforced concrete pile drilling construction and drilling monitoring; Step S4: hole cleaning: convert the drill bucket into a double-bottom flat-bottom slag bucket. Place the drill bucket at the bottom of the hole and rotate it forward to collect the slag in the slag bucket using the straight blade at the bottom of the drill bucket. Then, rotate it backward to close the bucket door and lift the slag bucket out of the pile hole. Step S5, steel cage construction, including the production and installation of the steel cage and the hoisting of the steel cage; Step S6: pouring concrete and pulling out the steel casing.

2. A wind turbine foundation interlocking pile construction method according to claim 1, characterized in that: In step S1, construction preparation includes: leveling the site and clearing overhead, ground, and underground obstacles within the pile foundation range; overhead high-voltage lines must be no less than 10 meters away from the rotary drilling rig frame, and drainage measures must be taken; the foundation must be strong enough to ensure the stability of the drilling rig; thick steel plates are placed under the parking position for weak foundations; if sinking or tilting is found during drilling operations, the rig should be stopped immediately for processing; Ensure the equipment is brought in for assembly and commissioning, as well as the supply of materials and the inspection of raw materials.

3. A wind turbine foundation interlocking pile construction method according to claim 1 or 2, characterized in that: The construction methods of plain concrete pile holes include: After the machine is in place, adjust the verticality of the fuselage and mast, align the center of the rotary drill rod with the crosshairs, and lock the azimuth of the rotary drill body; install the bucket-type drill bucket on the rotary drill body, align it with the crosshairs, and then carefully observe the gap around the hole mouth, and use the verticality control instrument of the rotary drill rig to control the verticality, start the rotation and sink the drill bucket to take soil; bury the thin-walled short steel casing, inject stabilizing liquid into the thin-walled short steel, continue drilling to take soil and replenish stabilizing liquid in the hole in time, so that the elevation stabilizing liquid level in the hole is more than 1m higher than the pile hole bearing water level.

4. A wind turbine foundation interlocking pile construction method according to claim 3, characterized in that: The construction method of reinforced concrete pile drilling includes: the reinforced concrete pile drilling is carried out after the concrete of the plain concrete pile is concreted, the bottom section steel casing is connected with a rotary drilling rig, the cross line is aligned, the gap around the hole mouth is observed, and the verticality controller is observed to see if it is within the allowable range; the rotary drilling function is turned on to sink the bottom section into the soil, the drilling and soil extraction function of the rotary drilling rig is turned on to drill into the soil with a bucket drill bucket and extract the soil out of the pile hole; the second and Nth sections of the steel casing are connected, the casing joint anti-slip pad is installed, and drilling and soil extraction are continued to the designed elevation.

5. A wind turbine foundation interlocking pile construction method according to claim 4, characterized in that: The methods of hole formation monitoring include: During the hole formation process, the verticality of the drill rod or steel casing of the rotary drilling rig must be monitored at any time, especially when the first and second sections of the casing are drilled. During monitoring, the equipment's built-in manual and automatic vertical adjustment functions or two plumb bobs are used for two-way control to ensure that the verticality is less than 1 / 300.

6. A wind turbine foundation interlocking pile construction method according to claim 5, characterized in that: The fabrication and installation methods of steel cages include: The diameter of the steel cage is 600mm. The reinforced area has 8 main bars, 8 stirrups at 100mm, and a length of 9.25 meters. The non-reinforced area has 4 main bars, 8 stirrups at 200mm, and a length of 9.25 meters. The main bars are connected by arc lap welding. During welding, the assembly and positioning of the steel bars should meet the following requirements: the axes of the two steel bars are aligned after pre-bending and installation; the side bars and main bars are fixed with four-point tack welding; when overlapping, they are fixed with two points, and the tack weld should be at least 20mm away from the overlap end. When welding, the arc should be started at one end of the overlapping steel bar, and the arc should be closed at the end of the overlapping steel bar. The arc crater should be filled. When welding multiple layers, the first layer of weld should have sufficient penetration. The main weld and the positioning weld, especially at the beginning and end of the positioning weld, should be well fused. When lap welding is used for steel bar joints, the weld length should not be less than the lap length, the weld height h≥0.3d and shall not be less than 4mm; the weld width b>0.7d and shall not be less than 10mm; when lap welding is used for steel bar and steel plate joints, the weld height h>0.35d and shall not be less than 6mm; the weld width b≥0.5d and shall not be less than 8mm; where d is the diameter of the steel bar.

7. A wind turbine foundation interlocking pile construction method according to claim 6, characterized in that: The method of lifting the steel cage includes: the steel cage should be inspected before lifting, including the length, diameter, and whether the welding points are deformed. After the inspection is completed, the lifting begins. The lifting is carried out by a 25-ton truck crane with double hooks and multiple points for slow lifting to prevent the steel cage from deformation. The design drawing shows that the steel cage is 19.86m long. The steel cage consists of two sections, the first section is 10 meters and the second section is 9.86 meters. During the lifting, there must be a dedicated person to direct to ensure safety. The protective block of the steel cage adopts a roller-type high-strength cement mortar protective block to prevent the steel cage from being brought up when the steel casing is pulled out. At the same time, a 3~5mm anti-floating steel plate is set at the bottom of the steel cage. When pulling out the steel casing, a measuring rope is tied to the top of the steel cage to monitor the condition of the steel cage in real time during pouring concrete and pulling out the steel casing.

8. A wind turbine foundation interlocking pile construction method according to claim 1, characterized in that: Methods for pouring concrete and pulling out steel casing include: According to the design drawings, the length of a single pile needs to be 20.86 meters, the concrete volume of a single pile is 10.48m³, and the filling coefficient of the interlocking pile is 1.1 to 1.3, so the concrete volume each time should be no less than 13.624m³; 1) Install concrete conduit The concrete conduit adopts Φ220~250mm threaded steel casing. Each section of the concrete conduit should be fastened to prevent leakage and blockage. The bottom of the concrete conduit should be 300~500mm away from the bottom of the hole. 2) Pouring concrete After the concrete pipe is installed, a pipe pulling inspection should be carried out. The purpose of the inspection is to check whether the steel casing is pulled out smoothly, whether the steel cage follows the pipe or rotates during the pulling process, and the pulling amount is controlled within 0-200mm; 3) Preparations before pouring include wetting the loading and storage hoppers with water, conducting on-site concrete slump tests, and preparing concrete test blocks. The plug in the storage hopper should be a round steel plate suspended by a thin steel wire rope. The first loading should ensure that it is not less than the initial pouring volume. After the first pouring is completed, the concrete conduit should be at a depth of more than 2 meters. After the first bucket of material has been lowered, the steel casing should be pulled out to check whether the steel cage floats up with the pipe. After each bucket of concrete or truck is completed, a pull-out inspection should be carried out, and the pull-out amount should not exceed 100mm. This process continues until the first section of the outer casing is removed. 4) When the concrete pouring height in the steel casing exceeds 3m of the first section of steel casing, the first section of steel casing should be removed for the first time. After removing the first section of steel casing, the steel casing should be buried in the concrete at a depth of not less than 2m, and the concrete guide tube should be buried at a depth of 2.5m; 5) Repeat the above process and enter the second pipe pulling cycle. When the last section of the steel casing is pulled out at one time, the concrete conduit should remain in the hole. After the steel casing is completely pulled out and removed, measure the concrete surface elevation in the hole and re-pour concrete as needed; remove the concrete conduit after pouring; the concrete pouring process takes 2 to 3 hours; each time the concrete conduit and steel casing are removed, they should be immediately rinsed with clean water to prepare for the next concrete pouring.

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