Wind power prestress foundation pile capable of avoiding stress concentration

Abstract

The utility model discloses a wind power prestress foundation pile capable of avoiding stress concentration, which relates to the field of wind power project foundations, and comprises a pile bottom plate and a plurality of engineering piles positioned at the bottom of the pile bottom plate, the engineering piles are arranged in an annular array by taking the center of the pile bottom plate as a circle center, and the engineering piles comprise at least two types with different lengths. The end, away from the pile bottom plate, of the engineering pile goes deep into the ground and forms an expanded end at the end, a pile end grouting pipe and a pile side grouting pipe are arranged in the engineering pile, and the pile end grouting pipe extends into the expanded end to form a pile end grouting pipe nipple with a valve. The pile side grouting pipes comprise at least two hole bottom grouting pipes arranged in the height direction of the pile bottom plate and at least one hole side annular grouting pipe arranged around the peripheral side of the pile bottom plate. Concentrated stress can be avoided, and the service life of a built structure is prolonged; the arrangement of engineering piles can be reduced under the condition of the same bearing capacity, or the pile length or the pile diameter can be reduced under the condition of the same pile number, materials are saved, and meanwhile the construction efficiency is improved.

Description

Technical Field

[0001] The utility model belongs to the field of wind power project foundation, and in particular relates to a wind power prestressed foundation pile for avoiding stress concentration. Background Art

[0002] At present, the national wind power foundation adopts the reinforced concrete pile bottom plate of the same bearing layer. Most of the wind turbines of wind power projects are selected in mountainous areas with relatively high altitudes and relatively strong winds. For example, the terrain of a certain wind power project slopes from northeast to southwest, and the landform is generally formed by four parts: ridges, gullies, river platforms, and river valleys. It is mainly mountainous, with an altitude of 1486m to 2659.4m. The northeastern Longshan is majestic and the mountains overlap; the southwestern mountains are undulating and the gullies are crisscrossed. The six mountain ridges originating from the Longshan Mountains that run through the entire territory are like fingers, stretching from northeast to southwest. The landforms in the territory are complex. The northeast is Longshan stone and soil and stone mountains, the central and eastern parts are red soil and red sandstone clay mountains, and the central and western parts are loess ridges and gully mountains. The hourly average wind speed ranges from 0m / s to 40m / s; the wind direction ranges from 0° to 360°. According to the wind field exploration data, the foundation soil is mainly Quaternary Upper Pleistocene aeolian loess (Q3 eol), and the thickness is relatively large. In some areas, Cretaceous sandy mudstone and muddy sandstone (K1) can be seen at the bottom of the valley.

[0003] Traditional engineering foundation piles use dry-hole expansion concrete cast-in-place piles. In principle, the foundation pile hole requires mechanical drilling and expansion. In actual operation, manual digging is still used. Manual digging in such a deep hole, especially expansion, is unsafe. Once a collapse and burial accident occurs, rescue is very difficult. Therefore, the relevant departments have clearly listed manual digging as an eliminated method. In addition, the forces on the wind turbine pile foundation are often extremely uneven, covering various forms such as tension, compression, shear, torsion, and bending. People often lack sufficient understanding and attention to the harsh stress environment of the wind turbine pile foundation. The foundation pile design uses the same bearing layer, and in most cases the pile length is the same. Everyone does not think there is anything wrong. However, in some cases, problems will arise, even serious problems. For example, when the wind turbine encounters sudden external loads such as typhoons or tornadoes, the foundation piles will be subjected to uneven pull-out loads. At this time, because the pile bottom is located in the same layer, or even a horizontal layer, it will be easily pulled out. What's worse is that the uplift force has not yet been transmitted to the lower part of the pile, and the concrete of the pile body breaks first, which greatly reduces or even loses the ability of the pile to withstand the uplift force.

[0004] In view of this, how to design a wind turbine pile foundation to solve the above technical problems, so as to ensure that the concrete does not break under a complex stress environment and the pile foundation will not be pulled out, has become a technical problem in this field. Utility Model Content

[0005] The utility model aims to solve the above technical problems to a certain extent. To this end, the utility model proposes a wind power prestressed foundation pile that avoids stress concentration. The foundation column adopts a pile foundation type with partial bonding prestressing of different lengths with a bottom hole and a side grouting pipe. Since the pile length has a height difference, the lower end of the pile is not on a bearing layer, thus avoiding the problem of stress concentration and achieving the purpose of extending the life of the structure thereon. At the same time, in the pile arrangement operation with the same bearing capacity, it can reduce the material consumption, save costs, and improve construction efficiency.

[0006] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a prestressed foundation pile for wind power that avoids stress concentration, comprising a pile bottom plate and a plurality of engineering piles located at the bottom of the pile bottom plate, the engineering piles being arranged in a circular array with the center of the pile bottom plate as the center of the circle, the engineering piles comprising at least two models with different lengths, the end of the engineering pile away from the pile bottom plate being deep into the ground and forming an enlarged end at the end, a pile end grouting pipe and a pile side grouting pipe being arranged in the engineering pile, the pile end grouting pipe extending into the enlarged end forming a pile end grouting short section with a valve, the pile side grouting pipe comprising at least two bottom hole grouting pipes arranged along the height direction of the pile bottom plate and at least one hole side annular grouting pipe arranged around the circumference of the pile bottom plate.

[0007] Preferably, the engineering piles have two circles of annular arrays around the pile bottom plate.

[0008] Preferably, the engineering piles include type I engineering piles and type II engineering piles, the type I engineering piles and type II engineering piles have the same pile diameter but different lengths, and the length difference between the type I engineering piles and type II engineering piles is at least 4 times the pile diameter.

[0009] Preferably, the type I engineering piles and type II engineering piles are arranged alternately.

[0010] Preferably, the hole bottom grouting pipe is a steel pipe, and the hole side annular grouting pipe is a steel pipe or a resin material pipe.

[0011] Preferably, the bottom hole grouting pipes are evenly arranged with the axis of the engineering pile as the center of the circle.

[0012] Preferably, the pile bottom plate includes a cap and backfilled cement soil located around the cap. The cap is cast on the top of the engineering pile and has a C20 cushion layer between the cap and the engineering pile.

[0013] Preferably, the engineering pile includes a pile core concrete, a protective layer of concrete located outside the pile core concrete, and a steel cage located inside the pile core concrete. At least one bearing body is provided in the middle portion of the steel cage. A plurality of steel strands penetrate the length direction of the steel cage. A plurality of steel strand bonding sections for locking are provided on the steel strands located at the upper end, the lower end of the steel cage and the lower end of the bearing body.

[0014] Preferably, the two symmetrical steel strands pass through the lower end of the steel cage and are connected in a U shape.

[0015] The utility model discloses the following technical effects:

[0016] The utility model avoids stress concentration of wind power prestressed foundation piles, which can avoid concentrated force and extend the life of the structures thereon; under the same bearing capacity conditions, the arrangement of engineering piles can be reduced, or under the same number of piles conditions, the pile length or pile diameter can be reduced, thereby saving concrete and other machine costs. The cost savings brought by the increase in bearing capacity alone can account for more than about 20% of the total cost; at the same time, it helps to improve construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 This is a process flow chart of the piling process of the wind power prestressed foundation piles to avoid stress concentration according to the utility model;

[0019] Figure 2 This is a plan view of the wind power prestressed foundation piles for avoiding stress concentration according to the utility model;

[0020] Figure 3 for Figure 2 Cross-section at AA in the middle;

[0021] Figure 4 This is a diagram of a steel strand cage for partially bonding prestressed foundation pile reinforcement bars in the utility model;

[0022] Figure 5 for Figure 4 Enlarged views of both ends of the steel strand cage diagram;

[0023] Figure 6 for Figure 4 Cross-section at the middle BB;

[0024] Figure 7 for Figure 4 Sectional view at CC;

[0025] Figure 8 The U-shaped steel strand partially bonded prestressed foundation pile reinforcement steel strand cage diagram in the utility model;

[0026] Fig. 9 for Figure 8Enlarged views of both ends of the steel strand cage diagram;

[0027] Fig.10 for Figure 8 Sectional view at EE in the middle;

[0028] Fig.11 for Figure 8 Cross-section at FF;

[0029] Fig.12 It is a layer structure diagram of the utility model;

[0030] Fig.13 for Fig.12 Sectional view at XX in the middle;

[0031] Fig.14 for Fig.12 Cross-sectional view at point YY in the figure.

[0032] Among them, 1. Pile bottom plate; 2. Type I engineering pile; 3. Type II engineering pile; 5. Backfill cement soil; 6. C15 concrete sluice; 7. C20 cushion layer; 10. Steel cage; 11. Cap; 12. Pile core concrete; 13. Protective layer concrete; 101. Main reinforcement; 102. Reinforcement; 103. Hoops; 104. Grouting pipe at pile end; 105. Grouting pipe at bottom of hole; 106. Annular grouting pipe at hole side; 107. Steel strand; 108. Anchor head; 110. Pile end grouting short section with valve; 111. Enlarged end; 112. Cap reinforcement; 113. Fire-burned wire; 114. Annular grouting connecting pipe at bottom of hole; 115. Steel strand bonding section; 116. U-shaped card. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0034] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0035] Reference Figures 2 to 13As shown, the utility model provides a prestressed foundation pile for wind power generation to avoid stress concentration, including a pile bottom plate 1 and a plurality of engineering piles located at the bottom of the pile bottom plate 1. The plurality of engineering piles are arranged in a circular array with the center of the pile bottom plate 1 as the center. The engineering piles include multiple models, each model has different lengths, and all have side grouting pipes at the bottom of the hole. In this embodiment, two engineering piles of different lengths are taken as examples, such as Figure 2 and Figure 3 As shown, the bottom of the pile base plate 1 has type I engineering piles 2 and type II engineering piles 3. The type I engineering piles 2 and type II engineering piles 3 have the same pile diameters but different lengths. The type I engineering piles 2 are long piles, and the type II engineering piles 3 are short piles. The length difference between the long piles and the short piles is at least 4 times the pile diameter. Taking the pile diameter of 0.8m as an example, the difference between the long piles and the short piles is at least 3.2m. When the compressive bearing capacity of the long piles and the short piles can meet the requirements, the bearing capacity of the long piles is sufficient, and the lower end of the piles is not on the same bearing layer, thus avoiding stress concentration. When subjected to special external pulling forces, such as a tornado, the piles will not be "broken" or pulled out.

[0036] To further optimize the solution, the planar arrangement of the engineering piles can be arranged in two circles according to the shape of the cap 11.

[0037] According to a further optimization scheme, an enlarged end 111 is provided at one end of the type I engineering pile 2 and the type II engineering pile 3 that penetrates deep into the ground, and the enlarged end 111 helps to improve the pull-out bearing capacity of the engineering pile.

[0038] In the above embodiment, in order to better eliminate the influence of loose soil on the side and bottom of the hole, especially for engineering piles more than 30 meters long, a pile end grouting pipe 104 and a pile side grouting pipe are designed, wherein the pile side grouting pipe includes a hole bottom grouting pipe 105 and a hole side annular grouting pipe 106, and a pile end grouting short section 110 with a valve is arranged at the bottom of the pile end grouting pipe 104; post-grouting is used to eliminate the adverse effects of loose soil, improve the bearing capacity, and improve the quality of the project.

[0039] Further optimization scheme, such as Figures 4 to 11 As shown, a hole-side annular grouting pipe 106 is arranged every 12m in the direction of the engineering pile body. The number of the hole-side annular grouting pipes 106 is reasonably set according to the length of the engineering pile. Generally, two or more holes are required to be designed; at least two hole bottom grouting pipes 105 are arranged, and are evenly arranged with the axis of the engineering pile. When two holes are set, the two hole bottom grouting pipes 105 are symmetrically arranged, and the bottom ends are connected through the hole bottom annular grouting connecting pipe 114; the hole bottom grouting pipe 105 has three functions. One is that it can be used as a grouting pipe for post-grouting; the second is that it can be used as an ultrasonic test pipe to measure the integrity of the pile; and the third is that it can replace two steel bars on the steel cage 10.

[0040] In the above embodiment, if Figure 3As shown, the main part of the pile bottom plate 1 is a cap 11 poured with C40 concrete, the engineering pile is supported at the bottom of the cap 11, and there is a C20 cushion layer 7 between the cap 11; backfill cement soil 5 is poured into the foundation pit around the cap 11, and a C15 concrete splash 6 with a width of m is set at the contact position between the backfill cement soil 5 and the cap 11.

[0041] In the above embodiment, if Figure 12 to Figure 14 As shown, the main body of the engineering pile is poured with a pile core concrete 12 , a steel cage 10 is provided inside the pile core concrete 12 , and a protective layer concrete 13 is provided on the periphery of the pile core concrete 12 .

[0042] According to a further optimization scheme, the thickness of the protective layer concrete 13 is 50 mm.

[0043] In the above embodiment, the structure of the steel cage 10 in the engineering pile is: the steel cage 10 mainly includes main bars 101, reinforcing bars 102 (the reinforcing bars 102 are at least Ф12 steel bars) and stirrups 103, steel strands 107, and anchor heads 108. At least one bearing body is arranged in the middle part of the steel cage 10. The steel strands 107 penetrate the steel cage 10, and steel strand bonding sections 115 are arranged at the upper end, the lower end of the steel cage 10 and the lower end of the bearing body. Specifically, the steel strands 107 of the steel strand bonding section 115 are peeled, degreased by a wire brush, washed and deoiled, and then bonded to the concrete.

[0044] To further optimize the solution, the steel strand 107 passes through the lower end of the steel cage 10 and is connected in a U shape. The lower end 1.5 to 4 m is peeled and degreased with a wire brush, and then washed and degreased with gasoline. The peeled part is the steel strand bonding section 115.

[0045] To further optimize the solution, the steel strands 107 located 1.5 to 4 m below the carrier are peeled and degreased with a wire brush, and are cleaned and degreased with gasoline. The peeled parts are locked in pairs with U-shaped clips 116 or the steel strands 107 are locked with the main reinforcement bars 101.

[0046] To further optimize the solution, the steel strand 107 is as straight as the main reinforcement 101, and the bottom 1.5 to 4 m is peeled and degreased with a wire brush, and then cleaned and degreased with gasoline. The peeled part is the bonding part, and the steel strand 107 and the main reinforcement 101 in this part are tied together with fire wire 113, or connected together with a U-shaped clip 116.

[0047] To further optimize the solution, the steel strand 107 at the upper end of the steel cage 10 is finally peeled, degreased and deoiled and locked at the top of the pile. The remaining length according to the design and specifications is tied together with the foundation steel bars 112 with fire-burned wire 113 and anchored into the foundation 11.

[0048] To further optimize the solution, the bottom hole grouting pipe 105 is located outside the stirrups 103 of the steel cage 10, with 3 pipes arranged at an angle of 120 degrees or 4 pipes arranged at an angle of 90 degrees. To avoid damage during the lowering of the steel cage 10, at least 3 vertical “<” shaped guide reinforcement bars 102 are arranged on each reinforcement ring, and the diameter of the reinforcement is the same as the diameter of the main reinforcement 101.

[0049] As a further optimization scheme, the hole bottom grouting pipes 105 can be two straight pipes directly inserted into the stratum, which can ensure targeted grouting and bonding of the loose soil at the hole bottom, and the assembly and construction are relatively simple.

[0050] According to a further optimization scheme, the hole bottom grouting pipe 105 is a steel pipe, which can replace the two steel bars on the steel cage 10.

[0051] To further optimize the solution, the annular portion of the hole side annular grouting pipe 106 acts as a reinforcing hoop to ensure that the entire steel strand cage 107 is centered, and is centered from top to bottom.

[0052] To further optimize the solution, the hole side annular grouting pipe 106 can be a steel pipe or a resin material pipe. The resin material pipe has a better anti-corrosion effect and can meet the use in areas with strict corrosion requirements.

[0053] To further optimize the plan, several grouting holes with one-way valves are set in the annular part of the grouting pipe on the side of the hole and wrapped with waterproof tape.

[0054] In some embodiments, Figure 2 As shown, the lower part of the cap 11 in the pile base plate 1 is a cylinder with a diameter H of 19.8m and a height P of 0.9m, the upper part is a cylinder with a top diameter M of 7.8m and a height R of 1.0m, and the middle is a truncated cone with a bottom diameter of 19.8m, a top diameter of 7.8m and a height Q of 1.6m.

[0055] In some embodiments, Figure 1 and Figure 2 As shown, the pile bottom plate 1 is made of dry concrete poured into an engineering pile, the pile body diameter is 800mm, the expanded end 111 has a diameter of 1.65m, and the engineering piles are arranged in two circles. The outer circle radius is 8.9m, 24 engineering piles are arranged, and type I engineering piles 2 and type II engineering piles 3 are arranged alternately. The inner circle radius is 6.2m, 8 engineering piles are arranged, and type I engineering piles 2 and type II engineering piles 3 are arranged alternately, with an average pile length of 32m.

[0056] Reference Figure 1 As shown, the preparation method of the wind power prestressed foundation pile for avoiding stress concentration of the utility model comprises the following steps:

[0057] Step S1, site layout and pile position layout;

[0058] Step S2, burying casing;

[0059] Step S3, drilling and hole cleaning;

[0060] Step S4, hanging the steel cage 10;

[0061] Step S5, installing the conduit and cleaning the hole for a second time;

[0062] Step S6, pouring concrete and lifting the casing;

[0063] Step S7: grouting at the pile side and pile bottom.

[0064] In the above preparation method, in step S1, the site layout includes leveling the site. The plane size of the pile foundation construction site should be determined according to the plane size of the pile foundation design, the number of drilling rigs and the plane size of the drilling rig base, the drilling rig shifting requirements and other coordinated construction machinery and facilities layout; the size of the site must be able to meet the requirements of coordinated work such as the placement of the drilling rig, the position of the crane and the transportation of the concrete mixer truck.

[0065] In the above preparation method, in step S1, the pile position arrangement includes measuring and laying out the pile positions according to the design drawings, and using a total station to determine the pile positions; driving 200-300 mm deep wooden piles at the pile positions, marking the pile positions' centers on the piles, and marking them using the "cross bolt method", and protecting them to prevent the pile positions from being deflected by people walking on the surrounding roads.

[0066] In the above preparation method, in step S2, the casing is made of steel casing, which is made of 4-6 mm thick steel plate; the inner diameter of the casing is preferably 100 mm larger than the designed diameter of the pile body; after the pile foundation is positioned, four control piles are placed according to the pile positioning points by pulling cross nails, and the steel casing is buried based on the four control piles, buried in the center of the drill hole, so that the center of the casing coincides with the center of the drill hole, the deviation between the center of the casing and the center of the pile position shall not be greater than 20 mm, and it shall be kept vertical; the positioning piles are driven into the soil with thick steel bars.

[0067] In some preparation methods, in order to protect the hole mouth from collapse, form the water head in the hole and position the guide, the casing is buried by manual and mechanical cooperation, and is statically pressed into the soil by the rotary bucket of the drilling rig. The top should be 400mm above the ground and kept horizontal. The burial depth should be appropriate to achieve a stable soil layer. The vertical line of the center of the casing should coincide with the center line of the pile. The allowable deviation of the plane position is 20mm, and the deviation of the inclination is not more than 1%.

[0068] In some preparation methods, when burying the casing, the excavation method is adopted; when burying the casing, attention should be paid to whether the position and verticality of the casing are accurate, and whether the surrounding area of ​​the casing and the bottom of the casing are tight and waterproof.

[0069] In the above preparation method, step S3 comprises:

[0070] Step S31, positioning the drilling rig using a cross method;

[0071] Step S32, wall protection mud preparation and mud treatment;

[0072] When necessary, mud wall protection is used in drilling to ensure the stability of the hole wall during the drilling process. Due to the long drilling time and deep hole depth, the thickness of the bottom sediment and the thickness of the mud skin are required to be small.

[0073] In order to ensure the quality of the wall protection, mud is prepared on site and stored in a mud pool. The amount of mud stored can meet the daily demand for hole construction. During rotary drilling, the mud liquid level should be maintained to form sufficient mud column pressure, and mud should be added to the hole at any time. When pouring concrete, it is advisable to recycle the mud in time for reuse and to prevent environmental pollution.

[0074] When mixing new slurry, the amount of soda ash is halved to ensure that the pH value of the slurry is 7-9;

[0075] The amount of CMC can be appropriately increased to ensure that the mud viscosity is between 20 and 22 seconds (CMC needs to be soaked in advance);

[0076] After the trial drilling is completed, the mud ratio can be finally determined based on the geological conditions of this project.

[0077] After the mud is prepared, it needs to be expanded for 24 hours before use.

[0078] Based on the determination of mud material properties, timely trial mixing is carried out to determine the optimal mix ratio of the mud.

[0079] After the hole is formed, take a sample below the mud surface once, and measure it once after the hole is cleaned. If the hole is cleaned twice, the mud index at the bottom of the hole should be measured to check the cleaning effect.

[0080] Newly prepared mud should be tested and qualified before use.

[0081] For mud maintenance, vortex desander is used to remove the silt in the return slurry, and the performance index of the wall protection mud is always in good working condition. Within a certain range and conditions, the greater the water inlet pressure of the desander, the higher the desander rate, and multiple desanders can be used in parallel.

[0082] Step S33, drilling a hole and forming the enlarged end 111;

[0083] Before drilling, use a level to measure the elevation of the top of the hole casing in order to control the drilling depth. When drilling, the drilling rig should be pressed lightly and rotated slowly to gradually enter normal construction, ensuring that the drill bucket is aligned with the pile position. After entering normal construction, if necessary, the hole should be filled with mud at any time to balance the pressure in the hole.

[0084] During the drilling process, the mud surface should not be lower than 400mm below the bottom of the casing. When lifting the drill, the mud should be added into the hole in time to keep the mud surface not lower than 400mm below the bottom of the casing. During the drilling process, the drill bucket size should be checked frequently. During the drilling process, the rotary drilling rig's full-process automatic double theodolite is used for intermediate review to adjust and control the verticality of the drill rod.

[0085] During the construction of the enlarged end 111, when the designed depth is reached, the drill bit is lifted out of the hole and replaced with an expansion drill bit to carry out expansion drilling and clean up the drill cuttings so that the thickness of the sediment at the bottom of the hole meets the design requirements; the rotary drilling rig adopts the skip digging method for hole formation, and the minimum distance between the soil poured out by the drill bucket and the pile hole mouth should be greater than 6m and should be cleared in time.

[0086] Step S34, cleaning the hole;

[0087] The first hole cleaning should be carried out after the hole is formed and before the steel cage 10 is hoisted. The first hole cleaning is carried out by slowing down the drilling speed of the drilling rig and using the double-bottom sand-removing drill bucket to bring out all the suspended sediments; after the hole cleaning is completed and the self-inspection is qualified, the supervisory engineer and the pile hole parameters are measured and accepted together. After the steel cage 10 and the guide tube are lowered and before the concrete is poured, the sediment thickness is measured. If it exceeds the standard, the second hole cleaning is required. If the hole is dry, it is only necessary to use the drill bucket to bring out the loose soil at the bottom of the hole.

[0088] In the above preparation method, step S4 comprises:

[0089] Step S41, manufacturing the steel cage 10;

[0090] Step S42: hoisting the steel cage 10.

[0091] Wherein, in the step S41, the steel strand 107 uses 1860-grade unbonded steel strand 107, is cut according to the designed length, and is peeled, degreased, and deoiled according to the designed position and length, and the clip or fire-burned wire 113 is prepared;

[0092] For the processing and production of the steel cage 10, a special steel processing and production platform is set up on site. The ground surface is temporarily paved with crushed stones. The spacing between the frames is 1.5-2.5m, and 14#b channel steel beams or steel horse stools are inlaid on them.

[0093] The connection of steel bars uses Grade I joints to ensure that the number of joints in the same section does not exceed 50% of the total number of steel bars, the spacing between adjacent joints is not less than 35d, the original steel bar material is 12m or 9m, and the main steel bar 101 connection in each section uses stripped rib straight thread connection, and other steel bar connections such as reinforcing hoops and spiral hoops are connected by lap welding.

[0094] In some preparation methods, the step S41 comprises:

[0095] Place the main reinforcement 101 of the steel cage 10 on the processing platform, first fix the main reinforcement 101 of the steel cage 10 with the reinforcing hoop, set a reinforcing hoop every 2m along the pile length and spot weld it firmly with the longitudinal reinforcement to form the skeleton of the steel cage 10. The main reinforcement 101 of the steel cage 10 is positioned with a special flange disc and then fixedly connected with the reinforcement ring.

[0096] After the steel cage 10 skeleton is processed, the spiral stirrups 103 are installed.

[0097] After the spiral stirrups 103 are installed, the steel cage 10 is reinforced as a whole.

[0098] When assembling the steel strand 107 with the steel cage 10, the steel strand 107 only needs to be inserted into the gap between the frame reinforcement and the stirrup 103 according to the design requirements, and the steel strands 107 can be clamped in pairs with clips, or the steel strands 107 can be tied to the main reinforcement 101 of the steel cage 10 with fire wire 113.

[0099] In some preparation methods, in step S42, the long steel cage 10 is hoisted in two sections, the main reinforcement 101 and the reinforcing stirrups 103 of the pile foundation steel cage 10 are HRB400 steel bars, and the stirrups 103 are HRB400 steel bars. The steel cage 10 is manufactured in two sections, upper and lower, and extrusion butt joint is used at the hole. The first section of the steel cage 10 is hoisted by a 100t crawler crane (main crane) and a 50t crawler crane (auxiliary crane), which is hoisted horizontally and rotated in the air to stand upright. Pads should be placed before the steel cage 10 is lowered. The thickness of the protective layer of the underwater poured concrete steel cage 10 is 50mm. During construction, protective layer steel bars are welded on the main reinforcement 101, and steel bars are passed through the middle and welded to the outside of the two main reinforcements 101. The number depends on the cage diameter, cage length and segmentation. The lifting point of the steel cage 10 needs to be determined after calculating the balance point based on the segment length and reinforcement conditions. Mark the lifting point according to the drawing before lifting. The lifting must be fixed with the clamping ring according to the previously determined lifting point position to reduce the deformation of the steel cage 10.

[0100] In the above preparation method, step S5 includes catheter installation and secondary hole cleaning.

[0101] The catheter installation includes: using a 300mm diameter catheter (the maximum diameter of the joint is about 380mm), the bottom pipe length is generally 4 to 6m, the standard section is generally 2 to 3m, and the joint is a double-threaded square buckle quick connector; when assembling the catheter, the joint must be tight and watertight (sealing rings and grease seals are required); a closed water pressure test should be carried out before the first use, the test water pressure is 0.75-1.0MPa, and no water leakage is qualified; the distance from the bottom of the catheter to the bottom of the hole is 300 to 500mm; the funnel is installed at the top of the catheter.

[0102] The secondary hole cleaning includes: after the first hole cleaning is completed, after placing the steel cage 10, lowering the conduit, etc., the thickness of the sediment is measured again. If the sediment thickness is greater than 100mm, the hole should be cleaned for the second time; before the second hole cleaning, a sealing cap is added to the upper end of the conduit, and the pump pipe is connected to the sealing cap. At the same time, a rod pump is placed at the mouth of the casing to prepare for extracting circulating mud; before pouring concrete, a 3PN large pump is used at the mouth of the pouring conduit to clean the slag in a positive circulation, and the newly made mud is pumped into the conduit with a 3PN pump, with a flow rate of 100-200m 3 / h; at the same time, a rod pump is arranged at the casing mouth to extract mud. The positive cycle can successfully remove the sediment. This method can blow up the bottom sediment, and the sediment flows out of the hole with the mud. At the same time, new mud is added in the hole to achieve a sediment thickness of no more than 50mm. If concrete is not poured for more than 30 minutes after the hole is cleaned, the sediment at the bottom of the hole should be measured again before pouring. If the sediment thickness exceeds the standard, the hole should be cleaned again. After the hole is cleaned, the mud meets the design requirements (the sediment thickness is no more than 50mm).

[0103] In the above preparation method, in step S6, a concrete tank truck is used to drive directly to the edge of the hole for continuous pouring. The actual pouring elevation of the concrete must be higher than the design elevation by more than 1.0 m to ensure the strength of the concrete at the top of the pile.

[0104] In the above preparation method, in step S6, the casing can be lifted by direct lifting or by vibrating hammer lifting.

[0105] In the above preparation method, step S7 includes post-grouting the pile ends and pile sides of the foundation piles of this project, and the reverse pressure resistance of the grouting valve is not less than 1.0 MPa.

[0106] In some preparation methods, two grouting pipes are provided for each pile end: Φ40x3.5 steel pipes, and the grouting pipes for the pile end are symmetrically arranged along the longitudinal direction of the steel cage 10. Two grouting pipes are provided for the pile side, and the pile side pipes are Φ25 seamless steel pipes. The bottom of the pile side grouting pipe is provided with a tee connected to the annular pile side grouting valve. The upper ends of all grouting pipes should be 200mm higher than the pile construction floor and sealed with a wire plug.

[0107] In some preparation methods, the upper end of the grouting conduit is provided with a pipe thread, a pipe clamp and a screw plug; the lower end of the pile end grouting conduit is provided with a G1" thread and a pipe clamp for screwing the pile end grouting valve; the lower end of the pile side grouting conduit is provided with a G3 / 4" thread and a tee for plugging the pile side grouting valve.

[0108] In some preparation methods, the connection of the grouting conduit is made by casing welding, and continuous closed welding is required to make the weld full and uniform without pores or sand holes.

[0109] In some preparation methods, the grouting conduit and the reinforcement hoop of the steel cage 10 are cross-tied and fixed with No. 14 lead wire (spot welding is not allowed). The tying should be firm. The pile end grouting pipe 104104 can be tied inside the reinforcement hoop; the pile side grouting pipe 105 is tied outside the spiral hoop 103, and the spacing between the tying points is 2m. The longitudinal reinforcement of the foundation pile reinforcement cage 10 extends 200-300mm from the pile bottom elevation and the bottom should be flush (the bottom end of the grouting conduit is 200-300mm away from the bottom end of the extended reinforcement).

[0110] In some preparation methods, the cement used for post-grouting is PO 42.5, with a water-cement ratio of 0.55 to 0.60; and the grouting flow rate is 75 L / min.

[0111] In some preparation methods, post-grouting quality control adopts a dual control method of grouting volume and grouting pressure, with cement injection volume control as the main method and pumping termination pressure control as the auxiliary method.

[0112] In some preparation methods, the grouting pump adopts a 3SNS type high-pressure grouting pump with a rated pressure of not less than 8MPa, a rated flow of not less than 75L / min, and a power of 18kW.

[0113] In some preparation methods, the grouting pump control monitoring pressure gauge is a 1.6 level 16MPa seismic resistant pressure gauge.

[0114] In some preparation methods, the slurry mixer is a YJ-340 type slurry mixer matched with a grouting pump, with a volume of 0.34m3 and a power of 4kW.

[0115] In some preparation methods, the grouting sequence is top to bottom, pile side to pile end; anchor piles are constructed first, then test piles.

[0116] In some preparation methods, the amount of cement used for pile end grouting is not less than 3.5 tons / double tube; the amount of cement used for pile side grouting is not less than 1.0 ton / tube.

[0117] In some preparation methods, grouting is terminated when the total grouting amount has reached 80% of the design requirement and the grouting pressure has exceeded the design value.

[0118] In some preparation methods, when the total amount of grouting has reached the design requirement, but the grouting pressure has not reached the design requirement, the grouting amount should be increased by 20% and then the grouting is terminated.

[0119] The parts not described in detail in the present invention are all conventional technical means known to those skilled in the art.

[0120] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0121] The embodiments described above are only descriptions of the preferred methods of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A wind power prestressed foundation pile for avoiding stress concentration, characterized in that: The invention comprises a pile bottom plate (1) and a plurality of engineering piles located at the bottom of the pile bottom plate (1), wherein the engineering piles are arranged in a circular array with the center of the pile bottom plate (1) as the center of the circle, and the engineering piles comprise at least two types of engineering piles of different lengths, wherein one end of the engineering pile away from the pile bottom plate (1) extends deep into the ground and forms an enlarged end (111) at the end, and wherein a pile end grouting pipe (104) and a pile side grouting pipe are arranged in the engineering pile, wherein the pile end grouting pipe (104) extends into the enlarged end (111) to form a pile end grouting valve short section (110), and the pile side grouting pipe comprises at least two bottom hole grouting pipes (105) arranged along the height direction of the pile bottom plate (1) and at least one hole side annular grouting pipe (106) arranged around the circumference of the pile bottom plate (1).

2. The wind power prestressed foundation pile for avoiding stress concentration according to claim 1 is characterized in that: The engineering piles are arranged in two circles in a circular array with the pile bottom plate (1) as the center.

3. The wind power prestressed foundation pile for avoiding stress concentration according to claim 2 is characterized in that: The engineering piles include type I engineering piles (2) and type II engineering piles (3). The type I engineering piles (2) and type II engineering piles (3) have the same pile diameter but different lengths. The length difference between the type I engineering piles (2) and type II engineering piles (3) is at least 4 times the pile diameter.

4. The wind power prestressed foundation pile for avoiding stress concentration according to claim 3 is characterized in that: The type I engineering piles (2) and type II engineering piles (3) are arranged alternately.

5. The wind power prestressed foundation pile for avoiding stress concentration according to claim 1, characterized in that: The hole bottom grouting pipe (105) is a steel pipe, and the hole side annular grouting pipe (106) is a steel pipe or a resin material pipe.

6. The wind power prestressed foundation pile for avoiding stress concentration according to claim 5, characterized in that: The hole bottom grouting pipes (105) are evenly arranged with the axis of the engineering pile as the center of the circle.

7. The wind power prestressed foundation pile for avoiding stress concentration according to claim 1, characterized in that: The pile bottom plate (1) comprises a cap (11) and backfilled cement soil (5) located around the cap (11); the cap (11) is cast on the top of the engineering pile and has a C20 cushion layer (7) between the cap and the engineering pile.

8. The wind power prestressed foundation pile for avoiding stress concentration according to claim 1, characterized in that: The engineering pile comprises a pile core concrete (12), a protective layer concrete (13) located outside the pile core concrete (12), and a steel cage (10) located inside the pile core concrete (12); at least one bearing body is arranged in the middle of the steel cage (10); a plurality of steel strands (107) are passed through the steel cage (10) in the length direction; and a plurality of steel strand bonding sections (115) for locking are arranged on the steel strands (107) located at the upper end and the lower end of the steel cage (10) and the lower end of the bearing body.

9. The wind power prestressed foundation pile for avoiding stress concentration according to claim 8, characterized in that: The two symmetrical steel strands (107) pass through the lower end of the steel cage (10) and are connected in a U shape.

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