A variable cross-section pile connection device and method

Abstract

The present invention discloses a variable cross-section pile connection device and a construction method, which solves the problem that the existing variable cross-section connection device has a single structure and cannot be applied to different pile diameters, and has the beneficial effects of improving the shear and bending resistance of the pile connection and having a wide application range. The specific solution is as follows: A variable cross-section pile connection device includes a conversion body, which is hollow; a support member, one end of the support member is fixed to the end face of the conversion body, and the other end is connected to an end plate to connect with the pile body. At least three support members are fixed at one end of the conversion body, and a set distance is provided between adjacent two support members at each end. The angle of the support member is adjustable to increase or decrease the distance between the ends of two adjacent support members on the same side away from the conversion body, so that the support members on one side of the conversion body are connected to end plates of different sizes; an inner protective body, which is placed inside the conversion body, the inner protective body is telescopically arranged, and after the end side of the inner protective body extends beyond the corresponding end plate, it is inserted into the pile body.

Description

Technical Field

[0001] The present invention relates to the field of ground treatment and foundation engineering, and in particular to a variable cross-section pile connection device and method. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] With the rapid economic development and the continuous expansion of the scale of engineering construction, in these engineering construction projects, pile foundations, as the most common basic structural form, play a crucial role. In particular, concrete pipe piles, as a common type of precast engineering pile, have many advantages such as fast construction progress, high pile body strength, reliable quality, convenient detection, and low cost, and are widely used in the soft soil foundation treatment and underground foundation engineering in the field of civil engineering.

[0004] Existing pipe piles are divided into two categories: equal cross-section piles and variable cross-section piles according to whether the cross-sectional form changes. Among them, variable cross-section piles are a new type of pile foundation structure developed on the basis of traditional equal cross-section piles. Under the condition of the same amount of pile body material used, variable cross-section piles usually can provide greater vertical and horizontal bearing capacities and have relatively significant technical and cost advantages. Different variable cross-section forms can play different technical advantages: (1) For the nail-shaped pile with a thick upper part and a narrow lower part, the stress state of the pile body is more consistent with the actual bearing characteristics of the load (including horizontal load, vertical load, and moment load) decreasing downward along the pile body, that is, increasing the cross-sectional area of the upper part of the pile can mobilize more soil resistance, and thus bear more transmitted loads, avoiding damage caused by insufficient pile body strength; at the same time, the small cross-sectional area of the lower part of the pile is beneficial to penetrate the underlying dense sand layer, which is beneficial to solving a series of engineering problems such as difficult pile sinking and even pile breaking, and can improve the construction efficiency and application range of the pile foundation; (2) For the variable cross-section pile with a locally enlarged cross-section, the bearing potential of each layer of soil in the stratified foundation can be more fully mobilized. It can be seen that variable cross-section piles can better adapt to different geological environments and different structural design requirements, achieve the purpose of saving engineering materials and reducing project costs, and have better formation adaptability and a wider range of engineering applications.

[0005] For cast-in-situ piles or in-situ mixing piles, the cross-section of the pile body can be changed by varying the excavation or mixing radius. However, the inventor found that for how to achieve variable cross-section construction of pipe piles such as cement concrete pipe piles, the current still remains in the exploratory stage, mainly due to the lack of relevant variable cross-section connection devices and supporting construction methods. At present, the contact area of the pipe pile connection device in the related technology is relatively small, and the connection surface is relatively single, resulting in the inability of the joint to bear a large horizontal load, easy to produce stress concentration phenomenon, and it is difficult to guarantee the joint quality. At the same time, it also greatly limits the range of pile diameter changes of the upper and lower pipe piles, making the pipe diameter change range very small and unable to fully exert the advantages of variable cross-section piles. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a variable cross-section pile connection device, which can conveniently and quickly connect different forms of variable cross-section piles, significantly improve the shear and bending resistance of the concrete pile connection while increasing the range of pile diameter changes, save materials, and effectively improve the project quality.

[0007] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0008] A variable cross-section pile connection device, comprising:

[0009] A conversion body, which is hollow inside;

[0010] A support member, one end of the support member is fixed to the end face of the conversion body, and the other end is connected to an end plate to connect with the pile body. At least three support members are fixed to one end of the conversion body, and a set distance is set between adjacent two support members at each end. The angle of the support member is adjustable to increase or decrease the distance between the ends of the adjacent two support members on the same side away from the conversion body, so that the support members on one side of the conversion body can be connected to end plates of different sizes;

[0011] An inner protection body, which is placed inside the conversion body, the inner protection body is telescopically arranged, and the end side of the inner protection body extends beyond the corresponding end plate and then inserts into the pile body.

[0012] For the variable cross-section pile connection device as described above, the support member includes a first bracket, a second bracket and a third bracket. The third bracket is fixed to the end of the conversion body, the second bracket is movably connected to the first bracket and the third bracket respectively, and the third bracket is connected to the end plate.

[0013] For the variable cross-section pile connection device as described above, the third bracket includes two support plates, and a set distance is set between the two support plates. One end of the second bracket is hinged to the two support plates, and one end of the third bracket is hinged to the other end of the second bracket.

[0014] For the variable cross-section pile connection device as described above, the support member and the end plate are connected by fasteners.

[0015] For the variable cross-section pile connection device as described above, the inner protection body includes at least three barrel layers sleeved in sequence, and adjacent two barrel layers can be locked after one barrel layer extends relative to the other barrel layer, and the conversion body and the barrel layer in contact with it can be locked;

[0016] A convex block is provided at the end of each barrel layer to facilitate the extension of the corresponding barrel layer and facilitate the extraction of the corresponding barrel layer.

[0017] A variable cross-section pile connection device as described above, a threaded structure is circumferentially arranged on the end side of each cylinder layer, and a threaded structure is also circumferentially arranged on the end side of the inner hole of the conversion body. The threaded structure of the inner hole of the conversion body cooperates with the threaded structure of the cylinder layer in contact with it.

[0018] A variable cross-section pile connection device as described above, from the outside to the inside, the inner protection body includes a first cylinder layer, a second cylinder layer and a third cylinder layer sleeved in sequence. The first cylinder layer and the second cylinder layer, and the second cylinder layer and the third cylinder layer can slide relative to each other. The outer diameter of the first cylinder layer is the same as the inner diameter of the upper pile body, and the outer diameter of the third cylinder layer is the same as the inner diameter of the lower pile body.

[0019] A variable cross-section pile connection device as described above, the end plate is an annular member, so that while ensuring the connection between the end plate and the pile body, it is ensured that the corresponding cylinder layer can pass through the inner hole of the annular member and be inserted into the corresponding pile body;

[0020] The conversion body has a set length.

[0021] A variable cross-section pile connection device as described above, the end plate is connected to the pile body by welding or flange.

[0022] In the second aspect, the present invention also provides a construction method for a variable cross-section pile connection device, including the following contents:

[0023] Sink the lower pile body into the soil, and the top is higher than the soil surface by a set height;

[0024] According to the outer diameters of the upper and lower pile bodies, adjust the angles of the support components at both ends of the conversion body to adapt to the outer diameters of the upper and lower pile bodies, ensure that the end of the first bracket away from the second bracket in the support component is horizontal, and fixedly connect the end plate to the corresponding support component;

[0025] According to the inner diameter of the lower pile body, extend one side of the inner protection body, and insert the extended side of the inner protection body into the lower pile body;

[0026] Connect the lower pile body to the end plate in contact with it;

[0027] After hoisting the upper pile body into place, extend the other side of the inner protection body according to the inner diameter of the upper pile body, and insert the extended upper side of the inner protection body into the upper pile body;

[0028] Lower the upper pile body and connect the upper pile body to the end plate in contact with it.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1) In the present invention, a support member is provided at the end of the conversion body. The support member is connected to the end side of the pile body through an end plate, and the inner protection body can extend into the inner hole of the pile body. In this way, the two points cooperate with each other to effectively connect the pile body and the connecting device, ensuring the reliability of the connection and thus guaranteeing the quality of pile splicing; the adjustable angle of the support member enables the conversion body to connect pile bodies with different variable cross-section forms, improving the application range of the connecting device and enhancing the adaptability of variable cross-section piles to different geological environments and different structural design requirements.

[0031] 2) In the present invention, multiple brackets are provided for the support member, and two adjacent brackets are hinged together, facilitating the adjustment of the angle of the support member, thus facilitating the connection of the support member to pile bodies of different sizes, effectively increasing the range of pile diameter changes, and having a fast overall adjustment speed, which can better improve the construction efficiency of variable cross-section pile bodies.

[0032] 3) In the present invention, multiple cylindrical layers are provided for the inner protection body, facilitating the extension of the inner protection body. The extended cylindrical layers can be inserted into the interiors of the upper and lower pile bodies, further increasing the contact area between the connecting device and the pile body at the pile body interface, thus significantly enhancing the shear and bending resistance at the pile body interface. At the same time, it can also save materials, reduce costs, and effectively improve the reliability of the project quality, which is beneficial to giving full play to the advantages of variable cross-section piles.

[0033] 4) With the provided construction method of the connecting device of the present invention, the support member can adjust its angle according to the outer diameters of the upper and lower pile bodies and then be connected to the matching end plate. The size of the end plate is matched with the outer diameters of the upper and lower pile bodies, effectively ensuring the reliability of the connection between the connecting device and the ends of the upper and lower pile bodies. As a result, the connecting device can be adjusted at any angle to form a connecting device with different diameters at the upper and lower ends, thereby effectively increasing the range of changes in the diameter of variable cross-section pile bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0035] Figure 1 is the front view of a variable cross-section pile body connecting device according to one or more embodiments of the present invention.

[0036] Figure 2 is the perspective view of a variable cross-section pile body connecting device according to one or more embodiments of the present invention.

[0037] Figure 3 is the schematic cross-sectional structure view of a variable cross-section pile body connecting device in the use state according to one or more embodiments of the present invention.

[0038] Figure 4It is a top view of a variable cross-section pile connection device according to one or more embodiments of the present invention.

[0039] Figure 5 It is a schematic diagram of welding joint when connecting piles of a variable cross-section pile connection device according to one or more embodiments of the present invention.

[0040] Figure 6 It is a schematic diagram of a variable cross-section pile connection device according to one or more embodiments of the present invention.

[0041] In the figure: The distances or dimensions between each part are exaggerated for showing the positions of each part, and the schematic diagram is only for illustration.

[0042] Wherein: 1 - first end plate, 2 - first bracket, 3 - hinge member, 4 - second bracket, 5 - third bracket, 6 - rotary handle, 7 - threaded structure, 8 - conversion body, 9 - inner protection body, 10 - second end plate, 11 - threaded hole, 12 - upper pile body, 13 - lower pile body, 14 - third end plate, 15 - weld seam, 16 - flange, 17 - bolt. Specific embodiments

[0043] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the present invention clearly states otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof;

[0045] For the convenience of narration, if the words "upper", "lower", "left", and "right" appear in the present invention, they only represent the same directions as the upper, lower, left, and right of the attached drawings themselves, and do not limit the structure. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0046] Glossary: Terms such as "installation", "connection", "linkage", and "fixation" in the present invention should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection, it can be a direct connection or an indirect connection through an intermediate medium, it can be an internal connection between two components, or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] As introduced in the background art, there is a problem in the prior art that it is difficult to ensure the quality of pile connection for variable cross-section connection devices. To solve the above technical problems, the present invention proposes a variable cross-section pile body connection device.

[0048] Embodiment 1

[0049] In a typical implementation of the present invention, with reference to Figure 1 、 Figure 2 and Figure 3 shown, a variable cross-section pile body connection device includes:

[0050] A conversion body 8, which is hollow inside;

[0051] A support member, one end of the support member is fixed to the end face of the conversion body, and the other end is connected to an end plate to connect with the pile body. At least three support members are fixed at one end of the conversion body, and a set distance is provided between adjacent two support members at each end. The angle of the support member is adjustable to increase or decrease the distance between the ends of adjacent two support members on the same side away from the conversion body. After adjusting the angles of all the support members on one side of the conversion body, the length or diameter of the frame formed by the ends of all the support members away from the conversion body changes, so that the support members on one side of the conversion body can be connected to end plates of different sizes;

[0052] An inner protection body 9, which is placed inside the conversion body 8, and the inner protection body is telescopically arranged. The end side of the inner protection body extends beyond the corresponding end plate and then inserts into the pile body.

[0053] In this embodiment, the pile body is a pipe pile as an example. The conversion body has a set length. Therefore, the variable cross-section pile body connection device in this embodiment is mainly applied to pipe pile connection; the conversion body 8 is a cylindrical steel structure with a hollow inside, and its material is a material that is not easy to rust; the outer diameter of the conversion body 8 is the same as the outer diameter of the upper pile body 12, and its inner diameter is slightly larger than the inner diameter of the upper pile body 12, and thread structures 7 are provided circumferentially at both the upper and lower ends in the internal hollow part; the conversion body 8 is fixedly connected to the support member.

[0054] In other embodiments, if the cross-section of the pile body is a rectangular pile, correspondingly, the cross-section of the conversion body is also a rectangular pile.

[0055] The end plates include a first end plate 1 and a second end plate 10. The first end plate is connected to the upper pile body 12, and the second end plate is connected to the lower pile body 13. Both the first end plate 1 and the second end plate 10 are annular. While ensuring the connection between the end plate and the pile body, it is ensured that the corresponding cylinder layers can pass through the inner holes of the annular first end plate or second end plate and be inserted into the corresponding pile bodies. Both the first end plate and the second end plate are horizontally arranged, and their inner and outer diameters are the same as the inner and outer diameters of the piles they are matched with, and their materials are materials that are not prone to rust, such as stainless steel. Both the first end plate 1 and the second end plate 10 are fixedly connected to the support components and are provided with a plurality of bolt holes 11.

[0056] In this embodiment, the support components include a first bracket 2, a second bracket 4, and a third bracket 5. The third bracket is fixed to the end of the conversion body. The second bracket is connected to the first bracket and the third bracket respectively through hinge members 3 such as pin shafts, and the third bracket is connected to the end plate.

[0057] To facilitate the adjustment of the angle of the support components, each pin shaft is provided with angle scale lines to achieve precise scale adjustment and ensure the accuracy of the numerical change of the pile diameter.

[0058] Specifically, the third bracket 5 includes two support plates. The support plates are provided with openings for installing the hinge members 3. One end of the support plates is fixedly connected to the end face of the conversion body. The two support plates are arranged at a set distance from each other. One end of the second bracket is hingedly connected to the two support plates, and one end of the third bracket is hingedly connected to the other end of the second bracket.

[0059] The support components are connected to the first end plate or the second end plate through fasteners. Thus, the first end plate and the second end plate are provided with a plurality of bolt holes 11. When the connecting device is connected to the pile body through a flange, some bolt holes are used for the connection between the third bracket and the corresponding end plate, and some bolt holes are used for the connection between the end plate and the upper pile body or the lower pile body.

[0060] In this embodiment, four groups of support components are provided at one end of the conversion body. There is a set distance between adjacent two support components, enclosing a ring. Every two groups of support components are symmetrically arranged with respect to the axis of the pipe pile. In other examples, the number of support components can be determined according to the outer diameters of the upper and lower pile bodies. Six groups, eight groups, etc. can be set on one side. To ensure the support strength, at least four groups of support components should be set on one side of the conversion body.

[0061] It should be explained that the inner protection body includes at least three cylinder layers sleeved in sequence. Adjacent two cylinder layers can be locked after one cylinder layer extends relative to the other cylinder layer, and the conversion body can be locked with the cylinder layer in contact with it. In this embodiment, adjacent two cylinder layers are locked through a threaded structure, and the outermost cylinder layer and the hollow part in the conversion body are also locked through a threaded structure.

[0062] In addition, refer to Figure 4As shown, bumps are provided at the ends of each cylinder layer to facilitate the protrusion of the corresponding cylinder layer. The rotation handle 6 is formed by the bumps. A plurality of rotation handles 6 are provided on each cylinder layer, and a set distance is spaced between adjacent two rotation handles. The corresponding cylinder layer can be easily pulled out through the rotation handle 6.

[0063] In order to ensure the stability of the inner protective body after the cylinder layer protrudes, a threaded structure is circumferentially provided on the end side of each cylinder layer, and a threaded structure is also circumferentially provided on the end side of the inner hole of the conversion body. The threaded structure of the inner hole of the conversion body cooperates with the threaded structure of the cylinder layer in contact with it.

[0064] In this embodiment, from the outside to the inside, the inner protective body 9 includes a first cylinder layer, a second cylinder layer, and a third cylinder layer that are sequentially sleeved. The first cylinder layer, the second cylinder layer, and the third cylinder layer are all cylinder layers. The first cylinder layer and the second cylinder layer, and the second cylinder layer and the third cylinder layer can slide relative to each other. The outer diameter of the first cylinder layer is the same as the inner diameter of the upper pile body, and the outer diameter of the third cylinder layer is the same as the inner diameter of the lower pile body.

[0065] The outer diameter of the first cylinder layer is the same as the inner diameter of the upper pile body 12, the inner diameter is the same as the outer diameter of the second cylinder layer, and threaded structures 7 are provided circumferentially on the upper and lower parts of the inner and outer diameters; the inner diameter of the second cylinder layer is the same as the outer diameter of the third cylinder layer, and the outer diameter of the third cylinder layer is the same as the inner diameter of the lower pile body 13. Similarly, threaded structures are provided circumferentially on the upper and lower parts of the inner and outer diameters; the first cylinder layer is connected to the conversion body through a threaded structure, the second cylinder layer is connected to the inner diameter of the first cylinder layer through a threaded structure, and the third cylinder layer is also connected to the inside of the second cylinder layer through a threaded structure.

[0066] In other examples, the inner protective body may further include four, five, or six cylinder layers.

[0067] Considering that the first end plate and the second end plate need to be connected to the upper pile body and the lower pile body, third end plates 14 are respectively embedded at the connection ends of the corresponding pile bodies where they are connected to the connection device. The thickness of the third end plate is less than or equal to the thickness of the first end plate and the second end plate.

[0068] In addition, it should also be noted that referring to Figure 5 As shown, in some examples, the third end plate is connected to the first end plate or the second end plate of the pile body by welding;

[0069] Referring to Figure 6 As shown, in other examples, the third end plate is connected to the first end plate or the second end plate of the pile body by a flange. Flanges 16 are respectively embedded at the ends of the upper and lower pile bodies. The bolt holes of the flanges 16 and the first end plate 1 and the second end plate 10 are fastened by bolts and nuts.

[0070] Embodiment 2

[0071] This embodiment provides a construction method for a variable cross-section pile body connection device, including the following contents:

[0072] First, determine the use position and pile splicing method of the pipe pile connection device according to the geological conditions and construction environment;

[0073] When using the welding method for pile splicing:

[0074] Sink the lower pile body into the soil to a set depth, with the top 0.5 m - 1.0 m above the soil;

[0075] According to the outer diameters of the upper and lower pile bodies, adjust the angles of the support components at both ends of the converter to adapt to the outer diameters of the upper and lower pile bodies, ensuring that the end of the first bracket away from the second bracket in the support component is horizontal. The first end plate is fixedly connected to the upper support component, and the second end plate is fixedly connected to the lower support component;

[0076] Extend the third cylinder layer in the inner protection body downward according to the inner diameter of the lower pile body. The third cylinder layer is inserted into the lower pile body, and the upper end of the third cylinder layer is tightened and fixed to the lower end inside the second cylinder layer through a threaded structure. The central axis of the converter coincides with the central axis of the lower pile body 13;

[0077] Sink the lower pile body into the soil, with the top above the soil at a set height;

[0078] According to the outer diameters of the upper and lower pile bodies, adjust the angles of the support components at both ends of the converter to adapt to the outer diameters of the upper and lower pile bodies, ensuring that the end of the first bracket away from the second bracket in the support component is horizontal. The end plate is fixedly connected to the corresponding support component;

[0079] Grind the third end plate and the second end plate of the lower pile body, and weld them together. The weld 15 between them shall meet the relevant specifications, and it is necessary to cool for a set time after welding;

[0080] After hoisting the upper pile body into position, extend the first cylinder layer according to the inner diameter of the upper pile body. The first cylinder layer is inserted into the upper pile body, and the lower end inside the first cylinder layer is tightened to the upper end outside the second cylinder layer through a threaded structure, while ensuring that the central axis of the converter coincides with the central axis of the lower pile body;

[0081] Grind the third end plate and the first end plate of the upper pile body, and weld them together. The weld 15 shall meet the relevant specifications, and it is necessary to cool for a set time after welding before continuing to press the pile;

[0082] Drive the pile body and the connection device into the target soil layer through equipment such as a pile driver;

[0083] When using flange connection:

[0084] The difference from welding connection is that asbestos or gasket needs to be placed between the first end plate, the second end plate and the flange 16, and then the first end plate, the second end plate and the flange 16 are connected through bolts 17. It is also necessary to tighten and weld the bolts 17 again when applying pressure through a pile press.

[0085] In some examples, according to the diameters of the upper pile body and the lower pile body, the angle of the support component in the connecting device can be adjusted first, the first end plate and the second end plate can be directly fixed, extended out of the corresponding cylinder layer, and then the connecting device can be connected to the lower pile body and the upper pile body in sequence.

[0086] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A variable cross-section pile connection device, characterized in that Comprising: A conversion body, which is hollow inside; A support member, one end of the support member is fixed to the end face of the conversion body, and the other end is connected to an end plate to be connected to a pile body. At least three support members are fixed to one end of the conversion body, and a set distance is provided between adjacent two support members at each end. The angle of the support member is adjustable to increase or decrease the distance between the ends of two adjacent support members on the same side away from the conversion body, so that the support members on one side of the conversion body are connected to end plates of different sizes; An inner protection body, which is placed inside the conversion body, and the inner protection body is telescopically arranged. The end side of the inner protection body extends beyond the corresponding end plate and then inserts into the pile body; The support member includes a first bracket, a second bracket and a third bracket. The third bracket is fixed to the end of the conversion body. The second bracket is movably connected to the first bracket and the third bracket respectively. The third bracket is connected to the end plate; The inner protection body includes at least three nested cylinder layers in sequence. When one of the adjacent two cylinder layers extends relative to the other cylinder layer, they can be locked. The conversion body and the cylinder layer in contact with it can be locked; A convex block is provided at the end of each cylinder layer to facilitate the extension of the corresponding cylinder layer.

2. The variable cross-section pile connection device according to claim 1, characterized in that The third bracket includes two support plates, and a set distance is provided between the two support plates. One end of the second bracket is hinged to the two support plates, and one end of the third bracket is hinged to the other end of the second bracket.

3. The variable cross-section pile connection device according to claim 1, characterized in that, The support member and the end plate are connected by fasteners.

4. The variable cross-section pile connection device according to claim 1, characterized in that, A threaded structure is circumferentially arranged on the end side of each cylinder layer, and a threaded structure is also circumferentially arranged on the end side of the inner hole of the conversion body. The threaded structure of the inner hole of the conversion body cooperates with the threaded structure of the cylinder layer in contact with it.

5. The variable cross-section pile connection device according to claim 1, characterized in that, From outside to inside, the inner protection body includes a first cylinder layer, a second cylinder layer and a third cylinder layer nested in sequence. The outer diameter of the first cylinder layer is the same as the inner diameter of the upper pile body, and the outer diameter of the third cylinder layer is the same as the inner diameter of the lower pile body.

6. The variable cross-section pile body connection device according to claim 1, characterized in that, The end plate is an annular member; The conversion body has a set length.

7. The variable cross-section pile body connection device according to claim 1, characterized in that, The end plate and the pile body are connected by welding or flange.

8. The construction method of a variable cross-section pile connection device according to any one of claims 1-7, characterized in that Including the following content: Sink the lower pile body into the soil mass, and the top is higher than the soil mass by a set height; According to the outer diameters of the upper and lower pile bodies, adjust the angles of the support members at both ends of the conversion body to adapt to the outer diameters of the upper and lower pile bodies, ensure that the end of the first bracket away from the second bracket in the support member is horizontal, and fixedly connect the end plate to the corresponding support member; Extend one side of the inner protection body according to the inner diameter of the lower pile body, and insert the extended side of the inner protection body into the lower pile body; Connect the lower pile body to the end plate in contact with it; After hoisting the upper pile body into place, extend the other side of the inner protection body according to the inner diameter of the upper pile body, and insert the extended upper side of the inner protection body into the upper pile body; Lower the upper pile body and connect the upper pile body to the end plate in contact with it.

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