Variable-section concrete pile, pile mold, and method for manufacturing variable-section concrete pile

Abstract

The present invention provides a variable-section concrete pile, a pile mold and a method for manufacturing a variable-section concrete pile, wherein the variable-section concrete pile is manufactured and formed in the pile mold, the variable-section concrete pile comprises a pile body and two or more prefabricated rings arranged at intervals along the length direction of the pile body, the prefabricated ring is provided with a center hole, the pile body is solidified and formed by passing concrete slurry through the center hole, and the solidified pile body and the prefabricated ring form an integrated structure, the prefabricated ring is prefabricated first, that is, the rib part on the variable-section concrete pile is manufactured first, and then the concrete slurry is passed through the center hole of the prefabricated ring to solidify to form the pile body, and the solidified pile body and the prefabricated ring form an integrated structure, and the pile is not manufactured by a special one-piece pile mold, thereby reducing the structural requirements for the pile mold and reducing the difficulty of manufacturing the pile mold.

Description

Technical Field

[0001] The invention relates to the technical field of precast concrete piles, and in particular to a variable-section concrete pile, a pile mould and a method for manufacturing the variable-section concrete pile. Background Art

[0002] The superiority of precast concrete ribbed piles over other pile types has been recognized by the industry. There is great room for development in the field of soft soil foundation treatment, and it has a certain positive effect on the field of engineering construction.

[0003] At present, common concrete ribbed piles on the market include various types of bamboo piles. Bamboo piles are prestressed concrete piles with bamboo-like protrusions arranged at equal intervals along the axial direction of the pile body. They have strong pressure bearing capacity and pull-out resistance. Generally, this type of ribbed pile is formed in one piece through a special pile mold. However, since the cross-section of the pile body of the ribbed pile varies along the axial direction, the one-piece production method has special requirements for the pile mold. The traditional pile mold used for processing equal-section concrete piles cannot be promoted and applied to the production of concrete ribbed piles. The pile mold structure dedicated to concrete ribbed piles is relatively complex and has poor applicability. When the shape and size of the ribs of the pile body change, they need to be processed separately to form corresponding pile molds. The manufacture of the pile mold is complicated and the economic efficiency of the production method is poor. Summary of the invention

[0004] In order to solve the technical problems that the existing concrete ribbed piles have high requirements on the pile mold and complex pile mold structure when they are integrally formed by a special pile mold, the present invention provides a variable-section concrete pile, a pile mold and a method for manufacturing a variable-section concrete pile.

[0005] A variable-section concrete pile, which is formed in a pile mold, comprises a pile body and two or more prefabricated rings arranged at intervals along the length direction of the pile body, and the cross-sectional dimension of the thickest section of the pile body is smaller than the cross-sectional dimension of the thickest section of the prefabricated ring;

[0006] The prefabricated ring is provided with a central hole, the pile body is solidified and formed in the pile mold by passing concrete slurry through the central hole, and the solidified pile body and the prefabricated ring form an integrated structure.

[0007] The beneficial effect of the variable-section concrete pile of the present invention is as follows: a prefabricated ring is first prefabricated, that is, the rib part on the variable-section concrete pile is first manufactured, and then the concrete slurry is passed through the center hole of the prefabricated ring to be solidified to form a pile body, and the solidified pile body and the prefabricated ring form an integrated structure, and are not manufactured through a special integrated pile mold, which reduces the structural requirements for the pile mold and reduces the difficulty of manufacturing the pile mold.

[0008] In addition, the present invention also provides a pile mold for preparing the aforementioned variable-section concrete pile, comprising a pile mold body, the pile mold body being provided with a molding cavity and an installation groove located between adjacent molding cavities, the prefabricated ring being detachably embedded in the installation groove, the molding cavity of the pile mold body being connected to the center hole of the prefabricated ring, and the concrete slurry being solidified in the molding cavity and the center hole to form a pile body.

[0009] The beneficial effects of the pile mold of the present invention are: by providing a forming cavity and an installation groove on the pile mold, the prefabricated ring is embedded in the installation groove, and by first arranging the prefabricated ring on the pile mold, the structural requirements of the pile mold for the ribs of the pile body are reduced, the manufacturing requirements of the pile mold are reduced, and the manufacturing process difficulty of the pile mold is reduced.

[0010] In addition, the present invention also provides a pile mold for preparing the aforementioned variable-section concrete pile, including a pile mold body, the pile mold body including a base and a plurality of forming molds arranged at intervals on the base, the forming molds are provided with forming cavities, prefabricated rings are embedded in the gaps between adjacent forming molds, the forming cavities are connected to the center holes of the prefabricated rings, and the concrete slurry is solidified in the forming cavities and the center holes to form a pile body.

[0011] The beneficial effects of the pile mold of the present invention are: the pile mold body is split into multiple forming molds, and prefabricated rings are embedded between adjacent forming molds. The pile mold of the present invention has strong applicability, and forming molds of different lengths can be replaced as needed, and the gap width between adjacent forming molds can be limited as needed. The prefabricated rings are equivalent to the ribs of the pile body. Compared with the existing one-piece pile mold, the pile mold of the present invention has low structural requirements for the ribs of the pile body, and the prefabricated rings can be embedded, thereby reducing the production requirements of the pile mold and reducing the difficulty of the pile mold production process.

[0012] In addition, the present invention also provides a method for manufacturing a variable-section concrete pile, which is used to prepare the aforementioned variable-section concrete pile, comprising the following steps:

[0013] S1, making a prefabricated ring;

[0014] S2, embedding and positioning the prefabricated ring on any of the above pile forms;

[0015] S3, concrete spreading, making the pile body which is solidified into an integrated structure with the prefabricated ring;

[0016] S4, demoulding to obtain a variable-section concrete pile.

[0017] The method for making a variable-section concrete pile of the present invention uses the above-mentioned pile mold of the concrete pile to first make a prefabricated ring, and then reduce the requirements for the pile mold structure by cooperating the prefabricated ring with the pile mold, thereby reducing the difficulty of making the variable-section concrete pile, and has the advantages of convenient construction and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a variable cross-section concrete pile of the present invention;

[0019] Figure 2 It is a structural schematic diagram of a pile mold of the present invention;

[0020] Figure 3 It is another structural schematic diagram of the pile mold of the present invention;

[0021] Figure 4 It is a schematic diagram of the structure of the prefabricated ring;

[0022] Figure 5 It is a structural schematic diagram of the forming die;

[0023] Figure 6 It is the longitudinal section of the variable cross-section concrete pile;

[0024] Figure 7 It is a structural schematic diagram of the buckle assembly.

[0025] Figure numerals: 10, variable-section concrete pile; 11, pile body; 111, outer section; 112, embedded section; 12, prefabricated ring; 121, center hole; 122, draft surface; 123, prefabricated block; 20, pile mold; 21, pile mold body; 22, base; 221, support rail; 222, limiting frame; 23, forming mold; 232, bottom plate; 233, side plate; 24, forming cavity; 25, mounting groove; 30, connecting assembly; 31, connecting pin; 32, connecting rod; 33, connecting buckle; 50, buckle assembly; 51, first nut sleeve; 52, second nut sleeve; 53, backstop; 54, plug rod; 541, reducing plug joint; 55, steel bar heading clamp. DETAILED DESCRIPTION

[0026] In order to facilitate the understanding of the technical solution of the present invention, a detailed description is given below in conjunction with the accompanying drawings and specific embodiments.

[0027] See also Figure 1-7 The present invention provides a variable-section concrete pile, which is manufactured and formed in a pile mold 20. The variable-section concrete pile 10 comprises a pile body 11 and two or more prefabricated rings 12 arranged at intervals along the length direction of the pile body 11. The cross-sectional dimension of the thickest section of the pile body 11 is smaller than the cross-sectional dimension of the thickest section of the prefabricated ring 12. The prefabricated ring 12 is provided with a central hole 121. The pile body 11 is solidified and formed in the pile mold 20 by concrete slurry passing through the central hole 121, and the solidified pile body 11 and the prefabricated ring 12 form an integrated structure.

[0028] First, the prefabricated ring 12 is prefabricated, that is, the rib part on the variable cross-section concrete pile 10 is first manufactured, and then the concrete slurry is passed through the central hole 121 of the prefabricated ring 12 to solidify to form the pile body 11, and the solidified pile body 11 and the prefabricated ring 12 form an integrated structure, and are not manufactured by a special integrated pile mold 20, which reduces the structural requirements for the pile mold 20 and reduces the difficulty of manufacturing the pile mold 20. The variable cross-section concrete pile 10 increases the contact area between the concrete pile and the soil, and enhances the bite between the concrete pile and the soil, thereby effectively enhancing the interaction force between the concrete pile and the soil, and making the connection between the concrete pile and the soil tighter.

[0029] The difference from the above embodiment is that, see Figure 1 , 6 The pile body 11 includes a peripheral section 111 and an embedded section 112. The cross-sectional dimension of the peripheral section 111 of the pile body 11 is larger than the cross-sectional dimension of the wall of the central hole 121, so that part of the structure of the prefabricated ring 12 is embedded in the pile body 11, so that the pile body 11 can be firmly connected with the prefabricated ring 12. Figure 2 , 3 6. The outer section 111 of the pile body 11 is formed by curing concrete in the forming cavity 24 of the pile form body 21 described below, and the embedded section 112 of the pile body 11 is formed by curing concrete in the central hole 121 of the prefabricated ring 12. The difference from the above embodiment is that, see Figure 4 The outer wall surface of the prefabricated ring 12 is formed with a draft surface 122 along the length direction of the pile body 11, and the draft surface 122 extends toward the outer section 111 of the pile body 11, which facilitates demoulding of the prefabricated ring 12 when manufacturing the prefabricated ring 12, and facilitates demoulding of the variable-section concrete pile 10 when manufacturing the variable-section concrete pile 10.

[0030] The difference from the above embodiment is that, see Figure 4 The prefabricated ring 12 is an integrated structure, which is easy to manufacture, has high strength and is not easy to split.

[0031] The difference from the above embodiment is that, see Figure 3 , 7 The prefabricated ring 12 is a split structure, and the prefabricated ring 12 includes at least two prefabricated blocks 123, each prefabricated block 123 is connected end to end in sequence, and the ends of two adjacent prefabricated blocks 123 are assembled and fixed by at least one snap assembly 50. The prefabricated ring 12 is formed by setting the prefabricated blocks 123, and the ends of two adjacent prefabricated blocks 123 are assembled and fixed by at least one snap assembly 50. The prefabricated ring 12 has strong applicability and can be replaced when one of the prefabricated blocks 123 is damaged.

[0032] The difference from the above embodiment is that, see Figure 7The buckle assembly 50 includes a first nut sleeve 51 and a second nut sleeve 52. The first nut sleeve 51 is fixed to one end of a prefabricated block 123, and the second nut sleeve 52 is fixed to one end of an adjacent prefabricated block 123. The second nut sleeve 52 is installed with an insert rod 54. The insert rod 54 is formed with a reducer plug joint 541 at the end away from the second nut sleeve 52, which can be inserted into the first nut sleeve 51. The first nut sleeve 51 is provided with a backstop 53 which can reversibly stop the reducer plug joint 541. The docking operation of adjacent prefabricated blocks 123 is simple, and the docking speed is improved.

[0033] The difference from the above embodiment is that the prefabricated block 123 is a reinforced concrete component with a stable structure.

[0034] The difference from the above embodiment is that the steel bars in the prefabricated block 123 are connected and fixed to the first nut sleeve 51 and / or the second nut sleeve 52 , so that the prefabricated block 123 is firmly connected to the first nut sleeve 51 and / or the second nut sleeve 52 .

[0035] The difference from the above embodiment is that, see Figure 7 The first nut sleeve 51 and the second nut sleeve 52 are both provided with a steel bar upsetting head clamp 55, and the steel bars in the prefabricated block 123 are clamped on the steel bar upsetting head clamp 55, which has a simple structure and a stable connection; or, the first nut sleeve 51 and / or the second nut sleeve 52 are respectively screwed and fixed to the steel bars, which has a simple structure and is easy to operate.

[0036] See also Figure 1-2 4. The present invention further provides a pile mold for preparing the above-mentioned variable-section concrete pile 10, comprising a pile mold body 21, the pile mold body 21 is provided with a forming cavity 24 and a mounting groove 25 located between adjacent forming cavities 24, a prefabricated ring 12 is detachably embedded in the mounting groove 25, the forming cavity 24 of the pile mold body 21 is connected with the center hole 121 of the prefabricated ring 12, and the concrete slurry is solidified in the forming cavity 24 and the center hole 121 to form a pile body 11. By providing the forming cavity 24 and the mounting groove 25 on the pile mold 20, the prefabricated ring 12 is embedded in the mounting groove 25, and the prefabricated ring 12 is first arranged on the pile mold 20, the structural requirements of the pile mold for the ribs of the pile body are reduced, the production requirements of the pile mold are reduced, and the difficulty of the production process of the pile mold is reduced.

[0037] The difference from the above embodiment is that the shape of the installation groove 25 is matched with the shape of the prefabricated ring 12 so that the prefabricated ring 12 can be detachably embedded in the installation groove 25 .

[0038] See also Figure 3-5The present invention also provides a pile mold for preparing the aforementioned variable-section concrete pile 10, including a pile mold body 21, the pile mold body 21 including a base 22 and a plurality of forming molds 23 spaced apart on the base 22, a forming cavity 24 is provided on the forming mold 23, a prefabricated ring 12 is embedded in the gap between adjacent forming molds 23, the forming cavity 24 is connected to the center hole 121 of the prefabricated ring 12, and the concrete slurry is solidified in the forming cavity 24 and the center hole 121 to form the pile body 11.

[0039] The pile mold body 21 is divided into multiple forming molds 23, and the prefabricated rings 12 are embedded in the gaps between adjacent forming molds 23. The pile mold of the present invention has strong applicability, and the forming molds 23 of different lengths can be replaced as needed, and the gap width between adjacent forming molds 23 can be limited as needed. The prefabricated rings 12 are equivalent to the ribs of the pile body. Compared with the existing one-piece pile mold, the pile mold of the present invention has low structural requirements for the ribs of the pile body 11, and the prefabricated rings 12 can be embedded, thereby reducing the production requirements of the pile mold and reducing the difficulty of the production process of the pile mold.

[0040] The difference from the above embodiment is that the cross-sectional dimension of the wall of the forming cavity 24 is larger than the cross-sectional dimension of the wall of the central hole 121 of the prefabricated ring 12, and smaller than the cross-sectional dimension of the thickest section of the prefabricated ring 12. When pouring concrete, part of the structure of the prefabricated ring 12 is embedded with the pile body 11 formed in the forming cavity 24 and the central hole 121, thereby enhancing the stability of the connection between the prefabricated ring 12 and the pile body 11.

[0041] The difference from the above embodiment is that the cross-sectional dimension of the thinnest section of the prefabricated ring 12 is smaller than the cross-sectional dimension of the cavity wall of the forming cavity 24, so that part of the structure of the prefabricated ring 12 is inserted into the forming cavity 24, so that when pouring concrete, part of the structure of the prefabricated ring 12 is embedded with the forming cavity 24 and the pile body 11 formed in the center hole 121, thereby enhancing the stability of the connection between the prefabricated ring 12 and the pile body 11.

[0042] The difference from the above embodiment is that, see Figure 5 The molding die 23 includes a bottom plate 232 and two side plates 233 respectively arranged on both sides of the bottom plate 232. A molding cavity 24 is formed between the bottom plate 232 and the two side plates 233. A connecting assembly 30 that matches and connects with each other is arranged between adjacent templates. The structure is simple. The adjacent templates are connected by the connecting assembly 30, so that the adjacent molding dies 23 can be stably and tightly embedded with the prefabricated rings 12.

[0043] The difference from the above embodiment is that, see Figure 3The connecting assembly 30 includes a connecting pin 31, a connecting rod 32 and a connecting buckle 33. The two ends of the outer side of each side plate 233 are respectively provided with a connecting pin 31 and a connecting buckle 33. The connecting rod 32 is rotatably connected to the connecting pin 31 and is detachably connected to the connecting buckle 33 on the side plate 233 on the same side of the adjacent molding die 23. The structure is simple and the assembly is easy. Preferably, the length from the rotatable connection on the connecting rod 32 to the connection with the connecting buckle 33 is just enough to make the two adjacent molding dies 23 fit tightly against the prefabricated ring 12.

[0044] The difference from the above embodiment is that, see Figure 3 The base 22 includes a support rail 221 and a plurality of limiting frames 222 arranged at intervals on the support rail 221, and the limiting frames 222 are movably arranged on the support rail 221, and the forming mold 23 is installed on the limiting frames 222, and the prefabricated rings 12 are embedded between adjacent limiting frames 222. The structure is simple, and the setting of the limiting frames 222 is convenient for the installation of the forming mold 23 and the movement of the forming mold 23. Therefore, the width of the limiting frames 222 can be set according to actual needs to match the selected forming mold 23, and the distance between adjacent limiting frames 222 can also be set according to actual needs to match the selected prefabricated ring 12, and the prefabricated ring 12 is tightly attached to the limiting frames 222 on both sides.

[0045] The present invention also provides a method for manufacturing a variable-section concrete pile, which is used to prepare the aforementioned variable-section concrete pile 10, comprising the following steps:

[0046] S1, making a prefabricated ring 12;

[0047] S2, embedding and positioning the prefabricated ring 12 on the pile form 20;

[0048] S3, concrete spreading, making the pile body 11 which is solidified into an integral structure with the prefabricated ring 12;

[0049] S4, demoulding, and obtaining a variable-section concrete pile 10.

[0050] In step S2, if the prefabricated ring 12 is an integrated structure, the prefabricated ring 12 is first mounted on the steel cage; then the steel cage with the prefabricated ring 12 is placed in the pile mold 20, and the prefabricated ring 12 is embedded and positioned in the installation groove 25 or between adjacent forming molds 23; if the prefabricated ring 12 is a split structure, then the prefabricated blocks 123 embedded in the bottom and sides of the pile mold 20 are first embedded in the pile mold 20, and then the steel cage is placed in the pile mold 20, and then the remaining prefabricated blocks 123 are matched and docked with the prefabricated blocks 123 in the pile mold 20.

[0051] First, the prefabricated ring 12 is manufactured by making a mold for the prefabricated ring 12. Since the mold for making the prefabricated ring 12 is smaller than the pile mold 20, the weight of the prefabricated ring 12 is smaller than the weight of the pile. Even if the mold for making the prefabricated ring 12 has high precision, it is much simpler than making the pile mold 20 integrally formed with the pile.

[0052] Specifically, after the manufactured prefabricated ring 12 and the steel cage are installed in the pile mold 20, tensioning plates are installed at both ends of the steel cage and tensioned. When the prefabricated ring 12 is embedded and positioned in the installation groove 25 or between adjacent forming molds 23, the prefabricated ring 12 is closely attached to the cavity wall of the forming cavity 24 to avoid the concrete poured when the pile body 11 is manufactured to affect the prefabricated ring 12; concrete is poured to manufacture the pile body 11 fixedly connected to the prefabricated ring 12; and then demolding is performed. Since the prefabricated ring 12 is made in advance, only the pile body 11 and the pile mold 20 are demolded during demolding, so that the variable-section concrete pile 10 of the present invention is easier to demold than the one-piece pile.

[0053] Preferably, the prefabricated ring 12 has steel bars connected to the steel cage, so that the connection between the prefabricated ring 12 and the pile body 11 is more stable.

[0054] The method for manufacturing the variable-section concrete pile 10 of the present invention first manufactures a prefabricated ring 12 , and then reduces the requirements on the structure of the pile mold 20 by matching the prefabricated ring 12 with the pile mold 20 , thereby reducing the difficulty of manufacturing the variable-section concrete pile 10 .

[0055] The size in this specification refers to the circumference. For example, the circumference of the outer cross section of the thickest section of the pile body 11 is smaller than the circumference of the outer cross section of the thickest section of the prefabricated ring 12 .

[0056] The above are only preferred embodiments of the present invention. The protection scope of the present invention shall be based on the scope defined by the claims. Several improvements and modifications made by those skilled in the art without departing from the spirit and scope of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A pile mold for preparing variable-section concrete piles, characterized in that: The variable-section concrete pile comprises a pile body and two or more prefabricated rings arranged at intervals along the length direction of the pile body, wherein the cross-sectional dimension of the thickest section of the pile body is smaller than the cross-sectional dimension of the thickest section of the prefabricated ring; wherein the prefabricated ring is provided with a central hole, the pile body is solidified and formed in a pile mold by passing concrete slurry through the central hole, and the solidified pile body and the prefabricated ring form an integral structure; The pile mold comprises a pile mold body, which is provided with a forming cavity and a mounting groove located between adjacent forming cavities. The prefabricated ring is detachably embedded in the mounting groove. The forming cavity of the pile mold body is communicated with the center hole of the prefabricated ring. Concrete slurry is cured in the forming cavity and the center hole to form a pile body.

2. A pile mold for preparing variable-section concrete piles, characterized in that: The variable-section concrete pile comprises a pile body and two or more prefabricated rings arranged at intervals along the length direction of the pile body, wherein the cross-sectional dimension of the thickest section of the pile body is smaller than the cross-sectional dimension of the thickest section of the prefabricated ring; wherein the prefabricated ring is provided with a central hole, the pile body is solidified and formed in a pile mold by passing concrete slurry through the central hole, and the solidified pile body and the prefabricated ring form an integral structure; The pile mold includes a pile mold body, which includes a base and a plurality of forming molds arranged on the base at intervals. The forming molds are formed with forming cavities, and prefabricated rings are embedded in the gaps between adjacent forming molds. The forming cavities are connected to the center holes of the prefabricated rings, and concrete slurry is cured in the forming cavities and the center holes to form a pile body.

3. The pile mold according to claim 1 or 2, characterized in that: The cross-sectional dimension of the wall of the forming cavity is larger than the cross-sectional dimension of the wall of the central hole of the prefabricated ring, and smaller than the cross-sectional dimension of the thickest section of the prefabricated ring.

4. The pile mold according to claim 1 or 2, characterized in that: The cross-sectional dimension of the thinnest section of the prefabricated ring is smaller than the cross-sectional dimension of the wall of the molding cavity, so that a part of the structure of the prefabricated ring is inserted into the molding cavity.

5. The pile mold according to claim 2, characterized in that: The forming mold comprises a bottom plate and two side plates respectively arranged on both sides of the bottom plate, a forming cavity is formed between the bottom plate and the two side plates, and connecting components matched and connected are arranged between adjacent templates.

6. The pile mold according to claim 2, characterized in that: The connecting assembly includes a connecting pin, a connecting rod and a connecting buckle. The outer ends of each side plate are respectively provided with a connecting pin and a connecting buckle. The connecting rod can be rotatably connected to the connecting pin and can be detachably connected to the connecting buckle on the side plate on the same side of the adjacent molding mold.

7. The pile mold according to claim 2, characterized in that: The base comprises a support rail and a plurality of limiting frames which are arranged on the support rail at intervals, and the limiting frames are movably arranged on the support rail, the forming mold is installed on the limiting frames, and prefabricated rings are embedded between adjacent limiting frames.

8. The pile mold according to any one of claims 1, 2, 5-7, characterized in that: The pile body comprises a peripheral section and an embedded section, wherein the cross-sectional dimension of the peripheral section of the pile body is larger than the cross-sectional dimension of the wall of the central hole.

9. The pile mold according to any one of claims 1, 2, 5-7, characterized in that: The outer wall surface of the prefabricated ring is formed with a draft surface along the length direction of the pile body.

10. The pile mold according to any one of claims 1, 2, 5-7, characterized in that: The prefabricated ring is a one-piece structure; Alternatively, the prefabricated ring comprises at least two prefabricated blocks, each of the prefabricated blocks is sequentially connected end to end, and ends of two adjacent prefabricated blocks are assembled and fixed by at least one buckle assembly.

11. The pile formwork according to claim 10, characterized in that: The snap-fit ​​assembly includes a first nut sleeve and a second nut sleeve. The first nut sleeve is fixed to one end of a prefabricated block, and the second nut sleeve is fixed to one end of an adjacent prefabricated block. The second nut sleeve is installed with an insert rod, and the insert rod is formed with a reducing joint at the end away from the second nut sleeve, which can be extended into the first nut sleeve. A back-off device that can reversibly stop the reducing joint is provided in the first nut sleeve.

12. The pile formwork according to claim 10, characterized in that: The prefabricated blocks are reinforced concrete components.

13. The pile formwork according to claim 10, characterized in that: The steel bars in the prefabricated block are connected and fixed to the first nut sleeve and / or the second nut sleeve.

14. The pile formwork according to claim 10, characterized in that: A steel bar upsetting clamp is provided in both the first nut sleeve and the second nut sleeve, and the steel bars in the prefabricated block are clamped on the steel bar upsetting clamp; or, the first nut sleeve and / or the second nut sleeve are respectively screwed and fixed to the steel bars.

15. A method for preparing a variable cross-section concrete pile, for preparing a variable cross-section concrete pile, characterized in that: The variable-section concrete pile comprises a pile body and two or more prefabricated rings arranged at intervals along the length direction of the pile body, wherein the cross-sectional dimension of the thickest section of the pile body is smaller than the cross-sectional dimension of the thickest section of the prefabricated ring; wherein the prefabricated ring is provided with a central hole, the pile body is solidified and formed in a pile mold by passing concrete slurry through the central hole, and the solidified pile body and the prefabricated ring form an integral structure; The production method comprises the following steps: S1, making a prefabricated ring; S2, embedding and positioning the prefabricated ring on the pile formwork according to any one of claims 1 to 14; S3, concrete spreading, making the pile body which is solidified into an integrated structure with the prefabricated ring; S4, demoulding to obtain a variable-section concrete pile.

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