A kind of variable cross-section cast-in-place pile and construction method thereof

Abstract

The present invention belongs to the technical field of cast-in-place pile construction, and specifically provides a new type of variable-section cast-in-place pile and a construction method thereof. The present invention partially expands the diameter of the foundation pit on the side wall of the cast-in-place pile foundation pit to form an annular outer expansion hole. The position and number of the annular outer expansion hole can be flexibly arranged according to the actual engineering situation. An expansion steel cage connected to the vertical pile body steel cage is arranged in the annular outer expansion hole through an extension device, thereby casting a variable-section cast-in-place foundation pile with high compressive and tensile bearing capacity. The variable-section cast-in-place pile of the present invention is simple to construct, and better solves the problem of insufficient compressive and tensile bearing capacity of the pile, and has strong engineering practicality.

Description

Technical Field

[0001] The invention belongs to the technical field of cast-in-place pile construction, and in particular relates to a cast-in-place pile with a variable cross-section and a construction method thereof. Background Art

[0002] Ordinary bored piles have average compression and tensile resistance. Compared with piles with equal cross-section, the bearing capacity of variable cross-section bored piles is greatly improved and the settlement is reduced. However, the current variable cross-section bored piles are difficult to construct and the construction cost is also high.

[0003] In response to this series of defects, the variable-section cast-in-place piles of the present invention can set the variable section at different positions of the pile body according to the different bearing capacities required for the pile foundation. The size, position and number of the variable sections can be flexibly set. The device is simple and easy to use and the manufacturing process is simple. It is easy to process and tie. It is low in cost, easy to implement, and has strong versatility. It makes up for the defects of equal-section piles and current variable-section piles and has good application prospects. Summary of the invention

[0004] The object of the present invention is to provide a variable cross-section cast-in-place pile and a construction method thereof, so as to at least solve the problems of weakened compressive and tensile bearing capacity of current equal cross-section piles during use and the difficulty and high cost of construction of current variable cross-section piles.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A variable cross-section cast-in-place pile, the cast-in-place pile is located in a foundation pit, the cast-in-place pile comprises a vertical pile body and a transversely extended and expanded steel cage, the extended and expanded steel cage is arranged in an annular external expansion hole, and the foundation pit is radially expanded outward at the elevation where the extended and expanded steel cage is located to form an annular external expansion hole;

[0007] The outwardly extending hole-expanding steel cage comprises an inner hole-expanding steel cage and an outer hole-expanding steel cage. The diameter of the outer hole-expanding steel cage is the same as the diameter of the vertical pile body and is arranged in the foundation pit. The outer hole-expanding steel cage is connected to the vertical steel cage in the vertical pile body. A guide rail is arranged on the outer hole-expanding steel cage. The inner hole-expanding steel cage extends along the guide rail into the annular outer hole.

[0008] For the variable cross-section cast-in-place piles as described above, preferably, the outer layer expanded hole steel cage comprises guide main bars, vertical connecting bars and transverse connecting bars, the guide main bars are cross-connected with the transverse connecting bars to form a transverse outer layer steel mesh; the guide main bars are cross-connected with the vertical connecting bars to form a vertical outer layer steel mesh, and the two transverse outer layer steel meshes and the two vertical outer layer steel meshes are enclosed to form a cylindrical outer layer expanded hole steel cage.

[0009] For the variable cross-section cast-in-place pile as described above, preferably, the outer layer expanded hole steel cage is connected to the vertical steel cage by binding or welding.

[0010] In the variable cross-section cast-in-place pile as described above, preferably, the inner layer hole-expanding steel cage comprises an inner layer steel mesh and connecting transverse bars, a plurality of inner layer steel meshes are arranged at intervals, and the plurality of inner layer steel meshes are connected together by connecting transverse bars to form an inner layer hole-expanding steel cage;

[0011] The inner layer steel mesh includes guide transverse bars and connecting vertical bars, a plurality of the guide transverse bars are cross-connected with the connecting vertical bars to form a grid-like inner layer steel mesh, the guide transverse bars at the top of the inner layer steel mesh and the guide transverse bars at the bottom are arranged in parallel, and the connecting vertical bars are arranged between the guide transverse bars at the top and bottom of the inner layer steel mesh;

[0012] The guide transverse reinforcements at the top and bottom of the inner layer hole-expanding steel cage are arranged in the guide rails;

[0013] More preferably, the guide rail is a guide rail with a rectangular groove.

[0014] For the variable-section cast-in-place pile as described above, preferably, the outer expanded hole steel cage is a rectangular frame structure, and the two inner expanded hole steel cages are respectively arranged at the two ends of the outer expanded hole steel cage, extending from the inside of the outer expanded hole steel cage to the annular outer expanded hole; preferably, there are two outer expanded hole steel cages, the two outer expanded hole steel cages are cross-arranged, and the two outer expanded hole steel cages are both arranged along the radial direction of the vertical pile body.

[0015] For the variable cross-section cast-in-place pile as described above, preferably, the transverse outer steel mesh is a fan-shaped ring structure, and two adjacent inner steel meshes are connected by a plurality of connecting transverse bars, and the connecting transverse bars are telescopic structures, and the connecting transverse bars include A sliding bars, B sliding bars and sliding sleeves, and the fixed ends of the A sliding bars and the B sliding bars are respectively connected to the inner steel mesh, and the free ends of the A sliding bars and the B sliding bars are respectively inserted into the sliding sleeve from both ends of the sliding sleeve, and the A sliding bars and the B sliding bars slide freely along the sliding sleeve to achieve the elongation and shortening of the connecting transverse bars;

[0016] More preferably, the connecting transverse reinforcement is arranged at the connection between the guiding transverse reinforcement and the connecting vertical reinforcement in two adjacent inner layer steel meshes.

[0017] For the variable cross-section cast-in-place pile as described above, preferably, the inner layer expanded hole steel cage extends out to the annular outer expanded hole and partially overlaps with the outer layer expanded hole steel cage.

[0018] For the variable cross-section cast-in-place pile as described above, preferably, the outwardly extended and expanded hole steel cage also includes a steel cage displacement rod, and the steel cage displacement rod includes a main rod and a secondary rod, the main rod is arranged in the steel cage displacement rod protective tube and slides freely along the steel cage displacement rod protective tube, both ends of the main rod extend out of the steel cage displacement rod protective tube, the bottom end of the main rod is located at the elevation of the annular outer expanded hole, one end of the secondary rod is hinged to the bottom end of the main rod, and the other end is hinged to the inner layer expanded hole steel cage.

[0019] The construction method of the variable cross-section cast-in-place pile as described above, preferably, comprises the following steps:

[0020] Step S1, drilling an annular outer expansion hole, expanding the hole at the connection elevation of the outer expansion steel cage and the vertical steel cage to form an annular outer expansion hole;

[0021] Step S2, lowering the vertical steel cage in the vertical pile body into the foundation pit, and extending the outwardly extending expanded steel cage into the annular outwardly expanded hole in step S1;

[0022] Step S3, integrally casting the vertical steel cage in the vertical pile body of the variable-section cast-in-place pile and the outwardly extended hole-expanded steel cage to obtain the variable-section cast-in-place pile.

[0023] Compared with the closest prior art, the technical solution provided by the present invention has the following excellent effects:

[0024] The variable cross-section cast-in-place pile and its construction method provided by the present invention expand the hole diameter of the side wall of the foundation pit at the elevation where the extended hole expansion steel cage is located to form an annular external hole expansion, and the hole expansion steel cage is tied or welded to the variable cross-section cast-in-place pile vertical pile body and the same diameter steel cage, and the connection position and number are flexibly arranged according to the actual project situation. The extended hole expansion steel cage includes an outer hole expansion steel cage and an inner hole expansion steel cage, and the inner hole expansion steel cage slides relative to the outer hole expansion steel cage and extends into the annular external hole expansion. A steel cage displacement tie rod is set to connect with the inner hole expansion steel cage, so as to realize the remote control of the sliding of the inner steel cage (controlling the inner steel cage in the deep pile hole from the ground), and the steel cage displacement tie rod has a simple structure and low cost. After the concrete pouring is completed, the extended hole expansion steel cage and the concrete of the same diameter steel cage of the variable cross-section cast-in-place pile vertical pile body are connected to form a whole, which greatly enhances the compressive and tensile bearing capacity of the foundation pile. The outer layer expanded hole steel cage and the inner layer expanded hole steel cage are used as the extended expanded hole steel cage, which is simple to install, easy to process and tie, simple in overall structure and low in construction cost. The outer layer expanded hole steel cage is tied or welded together with the equal diameter steel cage of the vertical pile body of the variable cross-section cast-in-place pile, so that the pile hole where the equal diameter steel cage of the vertical pile body of the variable cross-section cast-in-place pile is located is cast into one with the annular outer expanded hole structure, which significantly improves the compression and pull-out capacity of ordinary equal cross-section piles and improves the bearing capacity of cast-in-place piles. Compared with the current variable cross-section piles, the variable cross-section position, quantity and cross-section size of the pile can be flexibly set according to the actual situation of the project, which is simple and easy to operate and simple to make, making up for the defects of ordinary equal cross-section piles and significantly improving the current application level of variable cross-section piles, so it has a good application prospect in engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings in the specification, which constitute a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] in:

[0027] Figure 1 It is a structural schematic diagram of a cast-in-place pile when the annular outer expansion hole is located at the upper part of the pile body and the inner expansion steel cage does not extend to the annular outer expansion hole according to an embodiment of the present invention;

[0028] Figure 2 It is a structural schematic diagram of a cast-in-place pile in which an annular outer expansion hole is located at the upper part of the pile body and an inner expansion steel cage extends out to the annular outer expansion hole according to an embodiment of the present invention;

[0029] Figure 3 It is a structural schematic diagram of a cast-in-place pile when the annular outer expansion hole is located at the bottom of the pile body and the inner expansion steel cage does not extend to the annular outer expansion hole according to an embodiment of the present invention;

[0030] Figure 4It is a schematic structural diagram of a cast-in-place pile in which an annular outer expansion hole is located at the bottom of the pile body and an inner-layer expansion steel cage extends out of the annular outer expansion hole according to an embodiment of the present invention;

[0031] Figure 5 In Example 1 of the present invention Figure 1 AA view;

[0032] Figure 6 In Example 1 of the present invention Figure 2 AA view;

[0033] Figure 7 In Example 2 of the present invention Figure 1 AA view;

[0034] Figure 8 In Example 2 of the present invention Figure 2 AA view;

[0035] Fig. 9 It is a structural schematic diagram of the inner layer hole-expanding steel reinforcement cage in the embodiment of the present invention when it is not extended;

[0036] Fig.10 It is a structural schematic diagram of the inner layer hole-expanding steel reinforcement cage in an embodiment of the present invention when it is extended;

[0037] Fig.11 for Figure 6 CC section view in;

[0038] Fig.12 Schematic diagram of the guide rail structure in an embodiment of the present invention;

[0039] Fig.13 This is a schematic diagram of the structure of the inner layer hole-expanding steel cage in Example 2 of the present invention when it is not extended;

[0040] Fig.14 This is a schematic diagram of the structure of the inner-layer expanded hole steel cage in the extended state in Example 2 of the present invention.

[0041] In the figure: 1. vertical steel cage; 4. outwardly extended expanded steel cage; 16. steel cage displacement tie rod; 17. steel cage displacement tie rod protective tube; 21. annular outer expanded hole; 22. guide rail; 23. outer expanded steel cage; 24. inner expanded steel cage; 25. concrete grouting pipe; 26. grouting system; 27. vertical connecting ribs; 28. sliding sleeve; 29. ​​guide main ribs; 30. transverse connecting ribs; 31. connecting transverse ribs; 32. guiding transverse ribs; 33. connecting vertical ribs; 34. main rod; 35. auxiliary rod. DETAILED DESCRIPTION

[0042] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0043] In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention. The terms "connected" and "connected" used in the present invention should be understood in a broad sense. For example, they can be fixed connections or detachable connections; they can be directly connected or indirectly connected through intermediate components. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] Example 1

[0045] According to a specific embodiment of the present invention, Figure 1 to Figure 6 and Figures 9 to 12 As shown, the present invention provides a variable cross-section cast-in-place pile and a construction method thereof. Figure 1 It is a structural schematic diagram of a cast-in-place pile when the annular outer expansion hole 21 is located at the upper part of the vertical pile body and the inner expansion steel cage 24 does not extend to the annular outer expansion hole 21; Figure 2 The schematic diagram of the structure of the cast-in-place pile is that the annular outer expansion hole 21 is located at the upper part of the vertical pile body and the inner expansion hole steel cage 24 extends out to the annular outer expansion hole 21. The cast-in-place pile of the present invention is located in a foundation pit, and a vertical steel cage 1 with the same diameter as the vertical pile body is arranged in the foundation pit. The cast-in-place pile includes a vertical pile body and an outward expansion hole steel cage 4 arranged at the upper part of the vertical pile body. The outward expansion hole steel cage 4 is arranged in the annular outer expansion hole 21. The outward expansion hole steel cage 4 can be connected to the vertical steel cage 1 in the vertical pile body of the variable-section cast-in-place pile by binding or welding. The position of the annular outer expansion hole 21 can be located at any position of the vertical pile body. The specific position, number and cross-sectional size can be flexibly set according to the actual engineering situation. The side wall of the foundation pit at the elevation where the outward expansion hole steel cage 4 is located expands radially outward to form an annular outer expansion hole 21. Figures 1 to 4 At the same time, a grouting system 26 is arranged on the ground, and a concrete grouting pipe 25 is connected to the grouting system 26, and the concrete grouting pipe 25 penetrates the vertical pile body and is used to pour concrete into the vertical pile body.

[0046] The grouting system 26 is used for grouting into the foundation pit where the vertical reinforcement cage 1 is located in the vertical pile body of the variable-section cast-in-place pile and into the annular outer expansion hole 21 where the outwardly extending expanded reinforcement cage 4 is located.

[0047] One end of the outwardly extended hole-expanded steel cage 4 extends from the upper and lower elevations of the connection between the outer layer of the outwardly extended hole-expanded steel cage 4 and the vertical steel cage 1 in the vertical pile body of the variable-section cast-in-place pile to the annular outwardly expanded hole 21. After pouring concrete, the reinforced concrete of the vertical pile body of the variable-section cast-in-place pile and the concrete of the outwardly extended hole-expanded steel bars 4 in the annular outwardly expanded hole 21 are connected as a whole to form an annular convex structure. When the cast-in-place pile is subjected to tensile force and compressive force, the annular convex structure can be firmly stuck in the annular outwardly expanded hole 21, thereby increasing the pull-out bearing capacity and compressive bearing capacity of the foundation pile during subsequent use.

[0048] Furthermore, the outwardly extending hole-expanding steel cage 4 includes an inner-layer hole-expanding steel cage 24, and a guide rail 22 is arranged on the outer-layer hole-expanding steel cage 23. The inner-layer hole-expanding steel cage 24 runs along the guide rail 22, and one end of the inner-layer hole-expanding steel cage 24 extends out of the outer-layer hole-expanding steel cage 23 to the annular outer hole 21. The inner-layer hole-expanding steel cage 24 is arranged to be deep in the annular outer hole 21, and after the subsequent pouring of concrete, it can be ensured that the vertical pile body reinforced concrete of the variable-section cast-in-place pile and the concrete of the outwardly extending hole-expanding steel bars 4 in the annular outer hole 21 can be well combined, which greatly improves the tensile bearing capacity of the variable-section cast-in-place pile, and the inner-layer hole-expanding steel cage 24 is freely extended and retracted relative to the outer-layer hole-expanding steel cage 23, which overcomes the defect that it is difficult to directly arrange steel bars in the annular outer hole 21.

[0049] Further, the outwardly extending hole-expanding steel cage 4 also includes an outer hole-expanding steel cage 23, which includes a guide main bar 29, a vertical connecting bar 27 and a transverse connecting bar 30. The guide main bar 29 and the transverse connecting bar 30 are cross-connected to form a transverse outer steel mesh; the guide main bar 29 and the vertical connecting bar 27 are cross-connected to form a vertical outer steel mesh, and two transverse outer steel meshes and two vertical outer steel meshes are enclosed to form a cylindrical outer hole-expanding steel cage 23. The guide rail 22 is arranged in the outer hole-expanding steel cage 23, and the outer hole-expanding steel cage 23 is tied or welded to the vertical steel cage in the vertical pile body of the variable-section cast-in-place pile. Further, the inner hole-expanding steel cage 24 includes an inner layer steel mesh and a connecting transverse bar 31, and multiple inner layer steel meshes are arranged at intervals, and multiple inner layer steel meshes are connected together by connecting transverse bars 31 to form an inner layer hole-expanding steel cage 24.

[0050] The inner layer steel mesh includes a guide transverse rib 32 and a connecting vertical rib 33. A plurality of guide transverse ribs 32 and connecting vertical ribs 33 are cross-connected to form a grid-like inner layer steel mesh. The guide transverse ribs 32 at the top and the guide transverse ribs 32 at the bottom of the inner layer steel mesh are arranged in parallel. The connecting vertical ribs 33 are arranged between the guide transverse ribs 32 at the top and the bottom of the inner layer steel mesh. In an embodiment of the present invention, the inner layer steel mesh includes a plurality of parallel guide transverse ribs 32 and a plurality of parallel connecting vertical ribs 33. The plurality of guide transverse ribs 32 and the plurality of connecting vertical ribs 33 are cross-connected at a vertical angle to form the inner layer steel mesh. The guide transverse ribs 32 circumferentially of the inner layer hole expansion steel cage 24 are arranged in the guide rail 22. In an embodiment of the present invention, the guide transverse ribs 32 circumferentially of the inner layer hole expansion steel cage 24 refer to the guide transverse ribs 32 that can be directly contacted from the outside of the inner layer hole expansion steel cage 24. These guide steel bars are located at the outermost layer of the inner layer hole expansion steel cage 24.

[0051] In the embodiment of the present invention, in order to further increase the connection strength between the extended hole-expanding steel bar 4 concrete in the annular outer hole 21 and the variable cross-section cast-in-place pile vertical pile body reinforced concrete, the inner hole-expanding steel bar cage 24 extends to the annular outer hole 21 and partially overlaps with the outer hole-expanding steel bar cage 23. This arrangement can form a high-strength connection between the variable cross-section cast-in-place pile vertical pile body reinforced concrete and the extended hole-expanding steel bar 4 concrete in the annular outer hole 21 after the subsequent pouring of concrete.

[0052] Furthermore, the variable cross-section cast-in-place pile body is provided with a steel cage displacement tie rod protective tube 17 along the axial direction, and the outwardly extended hole-expanding steel cage 4 also includes a steel cage displacement tie rod 16, and the steel cage displacement tie rod 16 includes a main rod 34 and a secondary rod 35, the main rod 34 is arranged in the steel cage displacement tie rod protective tube 17 and slides freely along the steel cage displacement tie rod protective tube 17, and both ends of the main rod 34 extend out of the steel cage displacement tie rod protective tube 17, and the bottom end of the main rod 34 is located within a certain range of upper and lower elevations of the connection between the outer hole-expanding steel cage and the variable cross-section cast-in-place pile vertical pile body equal diameter steel cage, and one end of the secondary rod 35 is hinged to the bottom end of the main rod 34, and the other end is hinged to the inner hole-expanding steel cage 24. The steel cage displacement tie rod protective tube 17 not only protects the steel cage displacement tie rod 16, but also ensures the free sliding of the tie rod in the vertical direction.

[0053] Furthermore, the guide rail 22 is a guide rail with a rectangular groove. The guide rail 22 is arranged (preferably welded) on the upper and lower end surfaces inside the outer steel cage 23. It is a plurality of pairs of upper and lower guide rails 22 that are relatively arranged and arranged in pairs symmetrically along the center line of the cross section of the outer steel cage 23. The guide rail 22 protects and guides the inner hole-expanding steel cage 24, and the friction coefficient of the sliding guide rail 22 surface in contact with the guide cross rib 32 is low, which is conducive to the sliding of the inner hole-expanding steel cage 24.

[0054] The top of the main rod 34 is exposed from the top of the vertical pile body. The main rod 34 is connected to the lifting and stretching device, and the lifting device is started. The lifting device drives the main rod 34 to move upward, and the main rod 34 drives the auxiliary rod 35 hinged to it to move upward at the same time. The auxiliary rod 35 drives the inner layer expanded hole steel cage 24 hinged to it to unfold along the guide rail and extend into the annular outer expanded hole 21.

[0055] The present invention also provides a construction method for a variable-section cast-in-place pile, which comprises the following steps:

[0056] Step S1, using a drilling machine to drill the pile hole, expand the foundation pit side wall locally within a certain range of the upper and lower elevations where the outer layer expanded hole steel cage 4 is connected to the variable cross-section cast-in-place pile vertical pile body and equal diameter steel cage, to form a circular outer expanded hole 21, and the expansion process is high-pressure rotary spray expansion and mechanical expansion. After the pile hole is drilled to the design elevation, replace the drill bit, and expand the hole with high-pressure rotary spray or mechanical expansion. High-pressure jet expansion can use water or cement slurry. When using the cement slurry expansion process, the hole should be expanded up and down at least twice; when using the water expansion process, cement slurry should be used to expand the hole once, and finally the hole should be cleaned and the pile hole should be inspected.

[0057] Step S2, lower the variable cross-section cast-in-place pile vertical pile body equal diameter steel cage into the foundation pit, and extend the extended hole steel cage 4 into the annular outer hole 21; specifically: mechanically stretch the main rod 34 of the steel cage displacement rod 16 in the vertical direction, and obtain Figure 6 The state of the inner layer hole-expanding steel cage 24 and the steel cage displacement rod 16 after sliding is shown. Fig. 9 and Fig.10 It reflects the state of the inner layer hole-expanding steel cage 24 and the steel cage displacement rod 16 before and after the inner layer hole-expanding steel cage 24 is extended. Fig.10 for Fig. 9 The state of the inner hole-expanding steel cage 24 after mechanical stretching. After the steel cage displacement pull rod 16 is stretched, due to the pushing effect of the auxiliary rod 35 on the inner hole-expanding steel cage 24, the inner hole-expanding steel cage 24 slides along the guide rail 22 to the annular outer hole 21, and the outer hole-expanding steel cage 23 is constrained by the steel cage of the vertical pile body of the variable-section cast-in-place pile due to the vertical connecting ribs 27, and always remains stationary. After the sliding is completed, the outer hole-expanding steel cage 23 and the inner hole-expanding steel cage 24 maintain a certain length of overlap to ensure the integrity of the steel cage. The present invention immediately opens the outward hole-expanding steel cage 4 after the steel cage of the equal diameter of the vertical pile body of the variable-section cast-in-place pile is lowered, so as to prevent dirt and other debris from entering the annular outer hole 21 during subsequent construction, thereby affecting the normal opening of the inner hole-expanding steel cage 24.

[0058] Step S3, pouring concrete into the foundation pit where the vertical pile body steel cage of the variable-section cast-in-place pile is located and the annular external expansion hole 21 where the externally extended expanded hole steel cage 4 is located through the grouting system 26 and the concrete grouting pipe 25, the vertical pile body steel cage of the variable-section cast-in-place pile and the externally extended expanded hole steel cage 4 are integrally cast to form a variable-section cast-in-place pile, which jointly bears the upward pull force and the downward pressure bearing capacity, and significantly improves the compressive pull capacity of the cast-in-place pile.

[0059] In order to facilitate the inner layer hole-expanding steel cage 24 to extend through the guide rail 22 more quickly than the outer layer hole-expanding steel cage 23, as shown in FIG. Figure 5 and Figure 6 As shown, in a specific implementation, the outer hole-expanding steel cage 23 can be a rectangular parallelepiped frame structure, the outer hole-expanding steel cage 23 is arranged along the radial direction of the pile hole, and two inner hole-expanding steel cages 24 are respectively arranged at both ends of the outer hole-expanding steel cage 23, extending from the inside of the outer hole-expanding steel cage 23 to the inside of the annular outer hole 21. There are two outer hole-expanding steel cages 23, and the two outer hole-expanding steel cages 23 are arranged crosswise to form a cross-shaped transverse steel cage sliding system, and the two outer hole-expanding steel cages 23 are both arranged along the radial direction of the pile hole.

[0060] Example 2

[0061] In order to increase the overall coverage area of ​​the extended hole-expanding steel cage 4 after extension, as shown in FIG. Figure 7 , Figure 8 , Fig.13 and Fig.14 As shown, in the specific implementation, the transverse outer steel mesh can also be fan-shaped, and the two adjacent inner steel meshes are connected by connecting transverse bars 31. The connecting transverse bars 31 are telescopic structures. The connecting transverse bars 31 include A sliding bars, B sliding bars and sliding sleeves 28. The fixed ends of the A sliding bars and the B sliding bars are respectively connected to the inner steel meshes, and the free ends of the A sliding bars and the B sliding bars are respectively inserted into the sliding sleeves 28 from both ends of the sliding sleeves 28. The A sliding bars and the B sliding bars slide along the sliding sleeves 28 to achieve the elongation and shortening of the connecting transverse bars 31; the connecting transverse bars 31 are arranged at the connection between the guide transverse bars 32 and the connecting vertical bars 33 in the two adjacent inner steel meshes.

[0062] When in use, under the guidance of the guide rail 22, the inner layer hole-expanding steel cage 24 extends from the outer layer hole-expanding steel cage 23 to the annular outer hole 21, and the connecting transverse bars 31 between the multiple inner layer steel meshes are extended, specifically, the A sliding bar and the B sliding bar are extended relative to the sliding sleeve. In order to prevent the A sliding bar and / or the B sliding bar from detaching from the sliding sleeve, a guide groove can be set on the side wall of the sliding sleeve, and a guide pin is set at the free end of the A sliding bar and the B sliding bar. The guide pin is set in the guide groove, so as to prevent the A sliding bar and / or the B sliding bar from detaching from the sliding sleeve. Of course, other schemes that can achieve the above purpose are also possible. The A sliding bar and the B sliding bar can be mechanically bent by a steel bar bending machine first. Of course, the A sliding bar and the B sliding bar can also be made into a straight line. Other structures and construction methods are the same as those in Example 1 and will not be repeated here.

[0063] In summary, the variable cross-section cast-in-place pile and its construction method provided by the present invention are to expand the side wall of the foundation pit within a certain range of upper and lower elevations at the connection between the outwardly extended hole-expanded steel cage 4 and the vertical steel cage 1 in the vertical pile body of the variable cross-section cast-in-place pile to form a circular outwardly expanded hole 21, and the outwardly extended hole-expanded steel cage 4 is connected to the vertical steel cage 1 in the vertical pile body of the variable cross-section cast-in-place pile. The connection position is flexibly arranged according to the actual situation of the project, such as Figures 1 to 4 As shown. The outward-extending hole-expanding steel cage 4 includes an outer-layer hole-expanding steel cage 23 and an inner-layer hole-expanding steel cage 24, and the inner-layer hole-expanding steel cage 24 slides and extends into the annular outer hole 21 relative to the outer-layer hole-expanding steel cage 23. A steel cage displacement rod 16 is provided to be connected to the inner-layer hole-expanding steel cage 24, thereby realizing the remote control of the sliding of the inner-layer steel cage (controlling the inner-layer steel cage in the deep pile hole from the ground), and the steel cage displacement rod 16 has a simple structure and low cost. After the concrete is poured, the outward-extending hole-expanding steel bar 4 concrete in the annular outer hole 21 is connected to the variable-section cast-in-place pile vertical pile body reinforced concrete to form a whole, which greatly enhances the compressive and tensile bearing capacity of the cast-in-place pile in the subsequent use process. The outer-layer hole-expanding steel cage 23 and the inner-layer hole-expanding steel cage 24 are used as the outward-extending device, which is simple and easy to operate, easy to process and tie, simple in overall structure, and low in construction cost. And the reinforced concrete formed after the subsequent concrete pouring has strong integrity and high strength. The outer expanded hole steel cage 23 is connected with the variable cross-section cast-in-place pile vertical pile steel cage, so that the foundation pit where the variable cross-section cast-in-place pile vertical pile steel cage is located and the annular outer expanded hole structure are cast into one, which significantly improves the compressive and tensile strength of the cast-in-place pile and increases the bearing capacity of the cast-in-place pile, which has a good application prospect in engineering applications.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A variable cross-section cast-in-place pile, characterized in that: The cast-in-place pile is located in the foundation pit, and the cast-in-place pile includes a vertical pile body and a transversely extended and expanded steel cage, the extended and expanded steel cage is arranged in the annular external expansion hole, and the foundation pit is radially expanded outward at the elevation where the extended and expanded steel cage is located to form an annular external expansion hole; The outwardly extended hole-expanding steel cage comprises an inner hole-expanding steel cage and an outer hole-expanding steel cage, the diameter of the outer hole-expanding steel cage is the same as the diameter of the vertical pile body and is arranged in the foundation pit, the outer hole-expanding steel cage is connected to the vertical steel cage in the vertical pile body, a guide rail is arranged on the outer hole-expanding steel cage, the inner hole-expanding steel cage extends along the guide rail into the annular outer hole, the outer hole-expanding steel cage comprises a guide main bar, a vertical connecting bar and a transverse connecting bar, the guide main bar is cross-connected with the transverse connecting bar to form a transverse outer steel mesh; the guide main bar is cross-connected with the vertical connecting bar to form a vertical outer steel mesh, and the two transverse outer steel meshes and the two vertical outer steel meshes are enclosed to form a cylindrical outer hole-expanding steel cage; The inner layer hole-expanding steel cage comprises an inner layer steel mesh and connecting transverse bars, a plurality of inner layer steel meshes are arranged at intervals, and the plurality of inner layer steel meshes are connected together by connecting transverse bars to form an inner layer hole-expanding steel cage; The inner layer steel mesh includes guide transverse bars and connecting vertical bars, a plurality of the guide transverse bars are cross-connected with the connecting vertical bars to form a grid-like inner layer steel mesh, the guide transverse bars at the top of the inner layer steel mesh and the guide transverse bars at the bottom are arranged in parallel, and the connecting vertical bars are arranged between the guide transverse bars at the top and bottom of the inner layer steel mesh; The guide transverse reinforcements at the top and bottom of the inner layer hole-expanding steel cage are arranged in the guide rails; The guide rail is a guide rail with a rectangular groove; The transverse outer steel mesh is a fan-shaped structure, and two adjacent inner steel meshes are connected by a plurality of connecting transverse bars, and the connecting transverse bars are telescopic structures. The connecting transverse bars include A sliding bars, B sliding bars and sliding sleeves. The fixed ends of the A sliding bars and the B sliding bars are respectively connected to the inner steel mesh, and the free ends of the A sliding bars and the B sliding bars are respectively inserted into the sliding sleeve from both ends of the sliding sleeve. The A sliding bars and the B sliding bars slide freely along the sliding sleeve to achieve the extension and shortening of the connecting transverse bars. The connecting transverse reinforcement is arranged at the connection between the guiding transverse reinforcement and the connecting vertical reinforcement in two adjacent inner layer steel meshes; The inner layer hole-expanding steel cage extends to the annular outer hole and partially overlaps with the outer layer hole-expanding steel cage; The outwardly extended hole-expanding steel cage also includes a steel cage displacement rod, which includes a main rod and a secondary rod. The main rod is arranged in the steel cage displacement rod protective tube and slides freely along the steel cage displacement rod protective tube. Both ends of the main rod extend out of the steel cage displacement rod protective tube. The bottom end of the main rod is located at the elevation of the annular outer hole. One end of the secondary rod is hinged to the bottom end of the main rod, and the other end is hinged to the inner layer hole-expanding steel cage.

2. The variable cross-section cast-in-place pile according to claim 1, characterized in that: The outer hole-expanding steel cage is connected to the vertical steel cage by binding or welding.

3. The construction method of variable cross-section cast-in-place pile according to any one of claims 1 to 2, characterized in that: The construction method comprises the following steps: Step S1, drilling an annular outer expansion hole, expanding the hole at the connection elevation of the outer expansion steel cage and the vertical steel cage to form an annular outer expansion hole; Step S2, lowering the vertical steel cage in the vertical pile body into the foundation pit, and extending the outwardly extended hole steel cage into the annular outwardly expanded hole in step S1; Step S3, integrally casting the vertical steel cage in the vertical pile body of the variable-section cast-in-place pile and the outwardly extended hole-expanded steel cage to obtain the variable-section cast-in-place pile.

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