Construction method of steel pipe pile and bearing platform anchoring system

Abstract

The invention discloses a construction method of a steel pipe pile and bearing platform anchoring system. The construction method comprises the following steps of early-stage preparation; and designing and calculating an anchoring system: designing an anchoring structure body structure to form the anchoring system after connecting the steel pipe pile and the bearing platform, and calculating. And an anchoring system is constructed, specifically, a set of anchoring structure bodies are constructed on the outer circle of each steel pipe pile, and anchoring ribs used for stretching into the upper bearing platform protrude out of the top ends of the anchoring structure bodies. And foundation pit bottom sealing and bearing platform construction, specifically, a second bottom sealing concrete layer is constructed on the first bottom sealing concrete layer outside the anchoring structure bodies, isolation seams exist between the second bottom sealing concrete layer and the anchoring structure bodies, and bearing platforms are constructed on the top face of the second bottom sealing concrete layer, the top faces of the isolation seams, the top faces of the anchoring structure bodies and the top faces of the steel pipe piles. According to the anchoring system constructed through the construction method, dense bonding between the steel pipe pile and concrete can be achieved, the anchoring quality reliability of the steel pipe pile and the bearing platform is good, the overall structure is stable, and the bearing capacity is good.

Description

Technical Field

[0001] The invention relates to the technical field of bridge cap construction, and in particular to a construction method of a steel pipe pile and cap anchoring system. Background Art

[0002] In recent years, cast-in-place piles have been used as common pile foundations in bridge construction. A certain A-shaped single-tower cable-stayed bridge in the Guangdong Delta Plain is located in a strong earthquake intensity area with a seismic fortification intensity of 8 degrees (0.20g). In order to resist strong earthquake forces, the pile foundation of the main bridge 7# pier is equipped with a permanent steel casing with a length of 25m and an outer diameter of 2.5m, which is tightly bonded to the pile foundation concrete to form a large-diameter steel pipe pile (that is, the steel pipe pile is composed of a steel casing and cast-in-place pile concrete), which is jointly subjected to force and participates in earthquake resistance, so that the pile foundation has a sufficiently large bearing capacity and good bending resistance.

[0003] During the construction of the 7# pier cap of the main bridge, the upper end of the large-diameter steel pipe pile is extended into the cap. The steel casing and the cap are required to be reliably anchored so that the steel casing can effectively bear the load and work together with the pile foundation concrete. The bridge cap serves as the force transmission body between the large-diameter steel pipe pile and the upper structure of the bridge. The common connection methods between the bridge cap and the steel casing are: (1) Cut the part of the steel casing extending into the cap into a strip to form a steel strip, weld reinforcing steel bars on the steel strip, and the cap load-bearing steel bars pass through the cut steel casing; (2) Weld anchor steel bars on the end plate on the top surface of the steel casing; (3) Place dowel bars in the steel casing and pour core-filling concrete; (4) As disclosed in patent application number CN201711023517.2, a steel pipe composite pile and cap are connected. The anchoring structure of the platform and its construction method are as follows: a horizontal annular pressure plate is arranged on the outer wall of the steel casing, and a stiffening rib is welded on the upper plate surface of the annular pressure plate. One end of the prestressed steel bar is anchored on the annular pressure plate, and the other end passes through the corrugated casing upward to the interface between the second casting layer and the third casting layer of the platform, and is anchored after prestressing; (5) a new type of winged pile disclosed in patent application No. CN201620844479.1, in which an annular plate is welded on the steel pipe pile, and the upper surface of the annular plate is connected to the steel pipe pile through triangular ribs The annular plate is connected, and a plurality of wings staggered with the ribs are welded below the annular plate; (6) As disclosed in patent application number CN202010065869.X, a newly added steel pipe pile and a later added cap are anchored in foundation reconstruction and an anchoring method thereof, wherein a pile ring is evenly arranged in the axial direction at the bottom of the steel pipe pile, an L-arm component and a reinforcing plate are evenly arranged in the axial and radial directions at the bottom of the steel pipe pile, and the steel pipe pile, pile ring, L-arm component and reinforcing plate are cast on the cap and anchored together with the cap; (7) As disclosed in patent application number CN202010065869.X, a newly added steel pipe pile and a later added cap are anchored in the foundation reconstruction and an anchoring method thereof, wherein a pile ring is evenly arranged in the axial direction at the bottom of the steel pipe pile, and an L-arm component and a reinforcing plate are evenly arranged in the axial and radial directions at the bottom of the steel pipe pile, and the steel pipe pile, pile ring, L-arm component and reinforcing plate are cast on the cap and anchored together with the cap; No. CN201320733682.8 discloses a connection structure between a concrete pipe pile and a cap, wherein the upper end of the pipe pile is connected to the foundation cap, the upper and lower ends of the anchor steel bar are respectively connected to the foundation cap and the pipe pile, the embedded steel bar is located in the pipe pile body, a pile end plate is provided on the end face of the pipe pile, a plurality of bolt holes are evenly distributed along the circumference on the end face of the pile end plate, a plurality of embedded sleeves corresponding to the bolt holes are evenly distributed along the circumference on the bottom of the pile end plate in the pipe pile body, and the bottom end of the anchor steel bar passes through the pile end plate and is located in the pipe pile and connected to the embedded sleeve.

[0004] The above anchoring connection method has the following defects:

[0005] (1) The first connection method: a large number of steel strips are cut off, making it difficult for the steel casing to fully play its role. The anchor connection construction volume is large and the construction efficiency is low, which causes the construction period of the bridge pedestal to be extended.

[0006] (2) The second connection method: The on-site welding workload is large, the quality reliability is poor, and the force is discontinuous. The weld of the ordinary steel bar anchored in the pedestal is perpendicular to the force direction of the steel bar, which easily leads to weld tearing and failure.

[0007] (3) The third connection method: It has strict technical requirements and is difficult to fully implement on site. In addition, pouring core-filling concrete requires a lot of manpower and machinery, and has very high requirements on the quality of construction personnel.

[0008] (4) In the fourth to seventh connection methods, an annular pressure plate, annular plate, pile ring, L-arm member, reinforcing plate and pile end plate are all provided in a horizontal direction with the steel pipe pile. When the bottom concrete and the pedestal concrete are poured together, there are the following problems on the bottom surfaces of the annular pressure plate, annular plate, pile ring, L-arm member, reinforcing plate and pile end plate: bubbles in the concrete cannot be discharged to the outside or gaps are formed due to plastic shrinkage of the concrete, resulting in separation and loose bonding between the annular pressure plate, annular plate, pile ring, L-arm member, reinforcing plate and pile end plate and the bottom concrete and the pedestal concrete, which poses a hidden danger to the project quality. Summary of the invention

[0009] The invention provides a construction method of a steel pipe pile and a cap anchoring system to solve the technical problems of loose bonding between the steel pipe pile and concrete, poor quality, reliability and bearing capacity of the anchoring connection between the steel pipe pile and the cap in the existing connection method.

[0010] The technical solution adopted by the present invention is as follows:

[0011] A method for constructing a steel pipe pile and a cap anchoring system comprises the following steps: preliminary preparation: cutting and breaking the steel pipe piles with excess parts on the top of the steel pipe piles in a deep foundation pit to expose the reserved main steel bars, and constructing a first bottom concrete layer on the bottom of the foundation pit; anchoring system design and calculation: designing an anchoring structure to form an anchoring system after connecting the steel pipe piles and the cap, and calculating the bearing capacity of important components in the anchoring structure; anchoring system construction: constructing a group of anchoring structures connecting the steel pipe piles and the first bottom concrete layer on the outer circle of each steel pipe pile, and the top of the anchoring structure protrudes with anchoring bars for extending into the cap above; foundation pit bottom and cap construction: constructing a second bottom concrete layer with isolation joints between each anchoring structure on the first bottom concrete layer outside the anchoring structure, and constructing a cap on the top surface of the second bottom concrete layer, the top surface of the isolation joint, the top surface of the anchoring structure and the top surface of the steel pipe pile.

[0012] Furthermore, the step "preliminary preparation" specifically includes the following steps: preliminary construction preparation: according to the construction design drawings, the steel pipe piles, the foundation pit cofferdam, the foundation pit support, and the excavation of the foundation pit to the bottom of the foundation pit are completed; cutting and breaking: the excess steel casing on the top of the steel pipe piles is cut to expose the cast-in-place piles, and the exposed cast-in-place piles are broken to expose the reserved main steel bars; first layer pouring: the first bottom sealing concrete layer is poured on the bottom surface of the foundation pit.

[0013] Furthermore, the step "anchoring system design and calculation" specifically includes the following steps: anchoring system design: designing the anchoring structure so that the anchoring structure forms a radial annular anchoring system and a vertical annular anchoring system after connecting the steel pipe piles and the pedestal; force transmission path analysis: analyzing the force transmission paths of the radial annular anchoring system and the vertical annular anchoring system; component bearing calculation: calculating the bearing of important components in the anchoring structure.

[0014] Furthermore, each group of anchoring structures includes an anti-slip steel bar ring group for fixedly fitting on the outer circle of the corresponding steel pipe pile, a hollow cage-shaped annular steel bar cage for fitting on the outer circle of the steel pipe pile, an anchor steel bar ring with a hollow ring-shaped lower end for inserting into the annular steel bar cage and an upper end for inserting into the pedestal, and an anchor concrete layer formed by casting the anti-slip steel bar ring group, the annular steel bar cage and the anchor steel bar ring and connecting the steel pipe pile and the first layer of bottom sealing concrete layer.

[0015] Furthermore, the step of "anchoring system construction" specifically includes the following steps: installation of anti-slip steel bar ring group; installation of annular steel bar cage; installation of anchoring steel bar ring; and construction of anchoring concrete layer.

[0016] Furthermore, the step "installation of anti-slip steel bar ring group" specifically includes the following steps: structure construction: constructing the components of the anti-slip steel bar ring group - multiple anti-slip steel bar rings; coating removal: removing the protective coating on the outer wall surface of the steel casing of the outer layer of the steel pipe pile; installation: installing multiple anti-slip steel bar rings on the outer circle of the steel casing to form an anti-slip steel bar ring group.

[0017] Furthermore, the step of "annular steel cage installation" specifically includes the following steps: structure construction: constructing an annular steel cage using multiple annular steel bars and stirrups; installation: putting the annular steel cage onto the outer circle of the steel casing and radially spaced from the anti-slip steel ring group.

[0018] Furthermore, the step of "anchor steel bar ring installation" specifically includes the following steps: structure construction: constructing the components of the anchor steel bar ring - multiple anchor steel bars; installation: arranging the multiple anchor steel bars in sequence along the outer side of the steel casing in a circumferential direction, and each anchor steel bar is vertically inserted in sequence into the concrete of the first anchor concrete layer formed by the first pouring in the annular steel cage.

[0019] Furthermore, the step of "construction of anchoring concrete layer" specifically includes the following steps: formwork installation: installing an annular formwork surrounding the annular steel cage on the first bottom concrete layer outside the annular steel cage; concrete pouring: pouring in the annular formwork to form an anchoring concrete layer.

[0020] Furthermore, the step of "foundation pit bottom sealing and pedestal construction" specifically includes the following steps: second layer pouring: an isolation plate is set outside the anchoring structure, and a second bottom sealing concrete layer is poured on the first bottom sealing concrete layer outside the isolation plate; pedestal construction: the pedestal is poured on the top surface of the second bottom sealing concrete layer, the top surface of the isolation joint, the top surface of the anchoring structure and the top surface of the steel pipe pile.

[0021] The present invention has the following beneficial effects:

[0022] By adopting the construction method of the present invention, (1) a radial and vertical annular anchoring system can be constructed: a group of anchoring structures are constructed on the outer circle of each steel pipe pile, and the anchoring structures are respectively fixed to the corresponding steel pipe pile and the first bottom concrete layer below, so as to be connected with the steel pipe pile in a radial annular anchoring manner, forming a "flat head rivet" type steel pipe pile and abutment radial annular anchoring system, so that the anchoring structure and the steel pipe pile are tightly bonded to generate radial friction force, resisting the vertical slip between the steel pipe pile and the anchoring structure, and when the concrete layer in the anchoring structure expands in volume, a radial reaction force can be formed under the constraint of the steel bars in the anchoring structure, and radial prestress is generated in the direction of the steel pipe pile and uniformly acts on the steel pipe pile, so that the anchoring structure and the steel pipe pile are tightly bonded to generate radial friction force, resisting the vertical slip between the steel pipe pile and the anchoring structure. vertical slip between the structures; at the same time, the reserved main steel bars in the steel pipe piles and the anchor steel bars protruding from the top of the anchor structure are anchored into the pedestal and connected with the vertical annular anchor of the pedestal, forming a "serial" type steel pipe pile and pedestal vertical annular anchor system, achieving a close bond between the steel pipe piles and the pedestal to generate vertical friction force, resisting the vertical slip between the steel pipe piles and the pedestal; (2) achieving good force transmission of the anchor structure: when the force transmitted from the bridge superstructure to the pedestal, in addition to a part passing through the pedestal → reserved main steel bars → pressure between the pedestal concrete and the top of the steel casing → steel pipe piles, another part also passes through the pedestal → anchor structure → steel casing, so that the anchor system constructed by the construction method of the present invention can achieve close bond between the steel pipe piles and concrete, good reliability of the anchoring quality of the steel pipe piles and the pedestal, stable overall structure, and good bearing capacity.

[0023] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0025] Figure 1 It is a flow chart of the construction method of the steel pipe pile and cap anchoring system of the preferred embodiment of the present invention;

[0026] Figure 2 It is a vertical view of the anchor connection structure of the steel pipe pile and the cap according to the preferred embodiment of the present invention;

[0027] Figure 3 yes Figure 2 Middle Ι-Ι cross-section.

[0028] Legend:

[0029] 1. Cast-in-place piles; 2. Reserved main reinforcement; 3. Steel casing;

[0030] 4. Anti-slip steel ring;

[0031] 501, the first bottom sealing concrete layer; 502, the second bottom sealing concrete layer;

[0032] 6. Annular reinforcement; 7. Anchor reinforcement; 8. Anchor concrete layer; 9. Isolation joint;

[0033] 10. Platform support. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0035] Reference Figure 1-3 The preferred embodiment of the present invention provides a method for constructing a steel pipe pile and cap anchor system, comprising the following steps:

[0036] Preliminary preparation: the excess steel pipe piles on the top of the steel pipe piles in the deep foundation pit are cut and broken to expose the reserved main steel bars 2, and the first bottom sealing concrete layer 501 is constructed on the bottom of the foundation pit.

[0037] Design and calculation of anchoring system: Design the anchoring structure so that it can form an anchoring system after connecting the steel pipe piles and the cap 10, and calculate the bearing capacity of important components in the anchoring structure.

[0038] Construction of anchoring system: A set of anchoring structures connecting the steel pipe piles and the first bottom sealing concrete layer 501 is constructed on the outer circle of each steel pipe pile, and the top of the anchoring structure protrudes with anchoring bars for extending into the upper cap 10.

[0039] Construction of foundation pit bottom sealing and pedestal 10: A second bottom sealing concrete layer 502 with isolation joints 9 between each anchoring structure is constructed on the first bottom sealing concrete layer 501 outside the anchoring structure, and the pedestal 10 is constructed on the top surface of the second bottom sealing concrete layer 502, the top surface of the isolation joint 9, the top surface of the anchoring structure and the top surface of the steel pipe piles.

[0040] By adopting the construction method of the present invention, (1) a radial and vertical annular anchoring system can be constructed: by constructing a group of anchoring structures on the outer circle of each steel pipe pile, and the anchoring structures are respectively fixed to the corresponding steel pipe pile and the first bottom concrete layer 501 below, so as to be connected with the steel pipe pile in a radial annular anchoring manner, a "flat head rivet" type radial annular anchoring system of the steel pipe pile and the cap 10 is formed, so that the anchoring structure and the steel pipe pile are bonded tightly to generate radial friction force, and the vertical slip between the steel pipe pile and the anchoring structure is resisted. When the concrete layer in the anchoring structure expands in volume, a radial reaction force can be formed under the constraint of the steel bars in the anchoring structure, and radial prestress is generated in the direction of the steel pipe pile and uniformly acts on the steel pipe pile, so that the anchoring structure and the steel pipe pile are bonded tightly to generate radial friction force, and the vertical slip between the steel pipe pile and the anchoring structure is resisted. At the same time, the reserved main steel bars 2 in the steel pipe pile and the anchor bars protruding from the top of the anchor structure are anchored into the pedestal 10 and connected with the pedestal 10 in a vertical annular anchoring manner, forming a "serial" type vertical annular anchoring system of the steel pipe pile and the pedestal 10, so as to achieve a dense bond between the steel pipe pile and the pedestal 10 and generate a vertical friction force to resist the vertical slip between the steel pipe pile and the pedestal 10; (2) to achieve good force transmission of the anchoring structure: when the force transmitted from the bridge superstructure to the pedestal 10, in addition to a part passing through the pedestal 10 → reserved main steel bars 2 → pressure between the concrete of the pedestal 10 and the top of the steel casing 3 → steel pipe pile, another part also passes through the pedestal 10 → anchor structure → steel casing 3, so that the anchoring system constructed by the construction method of the present invention can achieve a dense bond between the steel pipe pile and the concrete, good reliability of the anchoring quality of the steel pipe pile and the pedestal 10, a stable overall structure, and good load-bearing capacity.

[0041] Optionally, step “S1: preliminary preparation” specifically includes the following steps:

[0042] 1. Preliminary construction preparation: According to the construction design drawings, the steel pipe piles, foundation pit cofferdam of the cap 10, foundation pit support, and excavation of the foundation pit to the bottom of the foundation pit are completed. Specifically, the steel pipe piles include cast-in-place piles 1 and external steel casings 3; after the foundation pit is excavated to the design elevation of the foundation pit bottom, the foundation pit bottom quality inspection and acceptance are required.

[0043] 2. Cutting and breaking: Cut the steel casing 3 of the excess part on the top of the steel pipe pile to expose the cast-in-place pile 1, and break the exposed cast-in-place pile 1 to expose the reserved main steel bar 2. Specifically, cut the steel casing 3 of the excess part on the top of the steel pipe pile, break the concrete of this part of the cast-in-place pile 1, and remove the concrete slag on the top of the cast-in-place pile 1 and the dust on the reserved main steel bar 2 on the top of the cast-in-place pile 1.

[0044] 3. First layer pouring: pour the first bottom concrete layer 501 on the bottom surface of the foundation pit. Specifically, level the bottom of the foundation pit, and pour the first layer of bottom concrete with a thickness of 200mm and a compressive strength grade of C30 on its surface; the height of the exposed pile head 1 is 800mm, the height of the steel casing 3 is 800mm, and the height of the reserved main steel bar 2 is 2300mm (the anchorage length of the reserved main steel bar 2 is required to be ≥35d, d is the diameter of the reserved main steel bar 2, and the diameter of the reserved main steel bar 2 is 32mm) to ensure the firmness of the anchor connection between the steel pipe pile and the cap 10.

[0045] Optionally, step “S2: anchoring system design calculation” specifically includes the following steps:

[0046] 1. Anchorage system design: The anchorage structure is designed so that the anchorage structure connects the steel pipe pile and the cap 10 to form a radial annular anchorage system and a vertical annular anchorage system.

[0047] 2. Force transmission path analysis: Analyze the force transmission paths of the radial annular anchor system and the vertical annular anchor system.

[0048] 3. Component bearing calculation: Calculate the bearing capacity of important components in the anchor structure.

[0049] In this optional solution, each group of anchoring structures includes an anti-slip steel bar ring group for fixedly fitting on the outer circle of the corresponding steel pipe pile, a hollow cage-shaped annular steel bar cage for fitting on the outer circle of the steel pipe pile, an anchor steel bar ring whose lower end of the hollow ring is used to be inserted into the annular steel bar cage and whose upper end is used to be inserted into the base 10, and an anchoring concrete layer 8 formed by casting the anti-slip steel bar ring group, the annular steel bar cage and the anchor steel bar ring and connecting the steel pipe pile and the first bottom sealing concrete layer 501.

[0050] Specifically, step “1. Anchor system design” specifically includes:

[0051] (1) Radial annular anchoring system: By arranging radial anti-slip steel ring groups, anchor steel rings, annular steel cages and anchoring concrete layers 8 on the outside of the steel pipe piles, and connecting them with the radial annular anchoring of the steel pipe piles, a radial annular anchoring system of the steel pipe piles and the cap 10 in the shape of a "flat head rivet" is formed, thereby improving the anchoring quality reliability of the steel pipe piles and the cap 10. When vertical slip occurs between the steel pipe piles and the anchoring concrete layer 8, the anchoring concrete layer 8 will expand in volume, generating radial stress to the outside of the anchoring concrete layer 8, and forming a radial reaction force under the constraint of the annular steel cage, generating radial prestress to the inside of the anchoring concrete layer 8 (towards the steel pipe pile) and acting uniformly on the steel pipe piles, so that the anchoring concrete layer 8 and the steel casing 3 are tightly bonded to generate radial friction, thereby resisting the vertical slip between the steel pipe piles and the anchoring concrete layer 8.

[0052] (2) Vertical annular anchoring system: By anchoring the reserved main steel bar 2 and the upper end of the anchor steel bar ring at the top of the cast-in-place pile 1 into the cap 10, and connecting them with the cap 10 through a vertical annular anchoring, a "serial" type vertical annular anchoring system of the steel pipe pile and the cap 10 is formed, ensuring the effective connection between the steel pipe pile and the cap 10, and enhancing the overall stability and safety of the cap 10 structure through the vertical annular anchoring system, thereby improving the anchoring quality reliability of the steel pipe pile and the cap 10. When vertical slip occurs between the steel pipe pile and the cap 10, the reserved main steel bar 2 and the anchor steel bar ring will generate a vertical anti-slip force acting on the steel pipe pile, so that the steel pipe pile and the cap 10 are tightly bonded and generate vertical friction to resist the vertical slip between the steel pipe pile and the cap 10.

[0053] Specifically, step “2. Force transmission path analysis” is as follows: when the force transmitted from the bridge superstructure to the pedestal, in addition to a part passing through the pedestal 10 → reserved main steel bars 2 → pressure-bearing space between the pedestal concrete and the top of the steel casing 3 → steel pipe piles, the other part passes through the pedestal 10 → anchoring steel bar ring → anchoring concrete layer 8 → contact surface between the anchoring concrete layer 8 and the steel casing 3 and the raised anti-slip steel bar ring group on the contact surface → steel casing 3.

[0054] Specifically, step "3. Component bearing capacity calculation" is as follows:

[0055] The calculation of the axial pull-out force of the anchor steel ring generally only considers the bonding force between the surface of the anchor steel ring buried in the concrete foundation and the concrete, without considering the anchoring effect of the hook at the end of the anchor steel ring in the concrete foundation.

[0056] The anchor steel bar ring in this embodiment includes 40 anchor steel bars 7, each anchor steel bar 7 has an anchoring depth of h=0.70m (i.e., 35d, d is the diameter of the anchor steel bar 7, and the diameter of the anchor steel bar 7 is 20mm), and the concrete bonding strength E b =2.5N mm2 The axial pull-out force of the anchor steel bar 7 is calculated according to the calculation method of the anchor strength of the anchor bolt:

[0057] F=nπdh E b =4396kN

[0058] Where: F-axial pull-out force of anchor steel bar 7 (N);

[0059] n-the number of anchorages of the anchoring steel bar 7;

[0060] π-value is 3.14;

[0061] d-diameter of anchor steel bar 7 (mm);

[0062] h-anchorage depth of anchoring steel bar 7 in concrete foundation (mm);

[0063] E b -Concrete bond strength (N / mm 2 ).

[0064] Optionally, the step of "anchoring system construction" specifically includes the following steps:

[0065] S3: Installation of anti-slip steel ring group;

[0066] S4: Installation of ring reinforcement cage;

[0067] S5: Anchor steel ring installation;

[0068] S6: Construction of anchoring concrete layer 8.

[0069] In this optional solution, step “S3: installation of anti-slip steel bar ring group” specifically includes the following steps:

[0070] 1. Structural construction: construct the components of the anti-slip steel ring group - multiple anti-slip steel rings 4. Specifically, the anti-slip steel rings 4 are made of Φ8mm, HRB400 hot-rolled ribbed steel bars with a length of 7850mm (i.e.: the outer circumference of the steel casing 3); the anti-slip steel rings 4 are horizontally arranged in the axial and radial directions of the outer wall of the steel casing 3.

[0071] 2. Coating removal: Remove the protective coating on the outer wall of the steel casing 3 of the outer layer of the steel pipe pile. Specifically, high temperature baking and an electric wire brush are used to remove the protective coating on the outer wall of the steel casing 3 exposed on the top surface of the first bottom sealing concrete layer 501 until the steel base surface of the steel casing 3 is exposed.

[0072] 3. Installation: Install multiple anti-slip steel bar rings 4 on the outer circle of the steel casing 3 to form an anti-slip steel bar ring group. Specifically, on the steel base surface of the outer wall of the steel casing 3 within 750mm of the effective shear failure area of ​​the anchor concrete layer 8 at the top of the steel casing 3, at the positions 250mm and 500mm away from the top surface of the steel casing 3, respectively, a Φ8mm anti-slip steel bar ring 4 is horizontally welded; the anti-slip steel bar ring 4 and the steel casing 3 are fully connected by artificial arc welding to ensure that the anti-slip steel bar ring 4 and the steel casing 3 are firmly welded; after welding, clean up the welding slag; after installation, make the center of the anti-slip steel bar ring 4 and the center of the steel pipe pile overlap and coincide, and all welds must be full, flat, smooth, without slag inclusions, bubbles, and cracks.

[0073] The function of the anti-slip steel ring 4 is as follows: within the effective shear failure area of ​​750mm of the anchoring concrete layer 8 at the top of the steel casing 3, two anti-slip steel rings 4 are horizontally arranged along the axial and radial directions of the outer wall of the steel casing 3 to increase the surface roughness of the outer wall of the steel casing 3, thereby increasing the radial friction between the steel casing 3 and the anchoring concrete layer 8, and resisting the vertical slip between the steel pipe pile and the anchoring concrete layer 8.

[0074] In this optional solution, step "S4: installation of annular reinforcement cage" specifically includes the following steps:

[0075] 1. Structural construction: A circular steel cage is constructed using a plurality of circular steel bars 6 and stirrups. Specifically, the main steel bars of the circular steel bars 6 are Φ8mm, HRB400 hot-rolled ribbed steel bars with a length of 8040mm (inner main steel bars), 8830mm (middle main steel bars), and 9610mm (outer main steel bars); the circular steel bars 6 are radially and horizontally arranged outside the top of the steel casing 3.

[0076] 2. Installation: Put the annular steel cage onto the outer circle of the steel casing 3 and space it radially from the anti-slip steel ring group. Specifically, remove the dust on the top surface of the first bottom concrete layer 501 within 320mm from the outer wall of the steel casing 3; install an annular steel cage with a width of 250mm and a height of 700mm (i.e.: 35d, d is the diameter of the anchor steel bar 7) on the top surface of the first bottom concrete layer 501 along the radial horizontal direction of the outer side of the steel casing 3; during installation, make the main steel bars at both ends of the annular steel cage correspond to each other one by one, and use artificial arc welding to weld them firmly; evenly arrange 2 annular steel bars 6 in the middle of the height side of the annular steel cage, and the distance between adjacent annular steel bars 6 is 217mm; in the middle of the width side of the annular steel cage One annular steel bar 6 is evenly arranged, and the spacing between adjacent annular steel bars 6 is 105mm; the stirrups of the annular steel cage are Φ6mm, HRB400 hot-rolled ribbed steel bars, and 40 stirrups are evenly arranged along the radial direction of the steel casing 3; the spacing between adjacent stirrups on the outside of the annular steel cage is 234mm, and the spacing between adjacent stirrups on the inside is 195mm; the height of the annular steel cage has an outer steel bar protective layer thickness of 50mm and an inner steel bar protective layer thickness of 20mm; after installation, the center of the annular steel cage, the center of the anti-slip steel ring group, and the center of the steel pipe pile are overlapped, which is conducive to the uniform action of the radial prestress generated by the anchoring concrete layer 8 on the steel pipe pile.

[0077] The role of the annular steel cage is as follows: when vertical slip occurs between the steel pipe pile and the anchoring concrete layer 8, the anchoring concrete layer 8 will expand in volume, generating radial stress toward the outside of the anchoring concrete layer 8, and forming a radial reaction force under the constraint of the annular steel cage, which will generate radial prestress toward the inside of the anchoring concrete layer 8 (towards the steel pipe pile) and act evenly on the steel pipe pile, so that the anchoring concrete layer 8 and the steel casing 3 are tightly bonded and radial friction is generated to resist the vertical slip between the steel pipe pile and the anchoring concrete layer 8.

[0078] In this optional solution, step “S5: installation of anchor steel ring” specifically includes the following steps:

[0079] 1. Structural construction: construct the components of the anchor steel ring - multiple anchor steel bars 7. Specifically, the anchor steel bar 7 uses a Φ20mm, HRB400 hot-rolled ribbed steel bar with a length of 2400mm; one end of the anchor steel bar 7 is processed into a bent short side with a length of 100mm and an angle of 90° to form a lower bend section, and the other end of the anchor steel bar 7 is processed into a bent bevel with a length of 1400mm and an angle of 30° to form an upper bend section; after processing, the upper bend section at the top of the anchor steel bar 7 and the lower bend section at the bottom of the anchor steel bar 7 are bent in the same side direction, and the upper bend section, vertical section, and lower bend section are all on the same plane; the anchor steel bar 7 is arranged in the radial vertical direction of the outer side of the steel casing 3 in the annular steel cage.

[0080] 2. Installation: multiple anchoring steel bars 7 are arranged in sequence along the outer side of the steel casing 3 in an annular direction, and each anchoring steel bar 7 is inserted vertically in sequence into the concrete of the first anchoring concrete layer 8 formed by the first pouring in the annular steel cage. Specifically, in the annular steel cage, a row of 40 anchoring steel bars 7 are evenly installed vertically along the radial direction of the outer side of the steel casing 3, and the spacing between adjacent anchoring steel bars 7 is 184mm; during installation, the lower bent end of the anchoring steel bar 7 is inserted from top to bottom into the concrete of the first anchoring concrete layer 8 at a position 20mm away from the top surface of the first bottom concrete layer 501; the upper folded end of the anchoring steel bar 7 is installed upward away from the top surface of the first bottom concrete layer 501, and the upper folded section, vertical section and lower bent section of the anchoring steel bar 7 are all away from the steel casing 3; after installation, the distance between the anchoring steel bar 7 and the outer wall of the steel casing 3 is 50mm (that is: 2 times the anchor length). The maximum particle size of coarse aggregate used in the solid concrete layer 8 is 25mm); the length of the anchoring steel bar 7 anchored in the anchoring concrete layer 8 is 700mm, and the length of the anchoring steel bar 7 anchored in the cap 10 is 1550mm (the anchoring length of the anchoring steel bar 7 is required to be ≥35d, d is the diameter of the anchoring steel bar 7, and the diameter of the anchoring steel bar 7 is 20mm) to ensure the firmness of the anchoring connection between the steel pipe pile and the cap 10; the center of the anchoring steel bar ring, the center of the annular steel bar cage, the center of the annular anti-slip steel bar ring group and the center of the steel pipe pile are overlapped; when the anchoring steel bar ring is tested for pull-out resistance, the anchoring steel bar 7 is qualified if it breaks without damaging the annular anchoring concrete layer 8.

[0081] The functions of the anchor steel ring are as follows: (1) reduce the welding workload between the anchor steel bar 7 and the steel casing 3 at the construction site, and avoid the problem of poor welding quality of the anchor steel bar 7; (2) the installation of the anchor steel bar 7 is safe and reliable, and the operation is convenient and fast, which greatly improves the construction efficiency, shortens the construction period, and saves construction costs; (3) the anchor steel bar 7 and the reserved main steel bar 2 are anchored into the pedestal 10, and connected with the vertical annular anchor of the pedestal 10 to form a "series" type vertical annular anchor system of steel pipe piles and pedestal 10, ensuring the effective connection between the steel pipe piles and the pedestal 10, and enhancing the overall stability and safety of the pedestal 10 structure through the vertical annular anchor system, thereby improving the safety of the pedestal 10 structure. The reliability of the anchoring quality of the high steel pipe pile and the cap 10; when vertical slip occurs between the steel pipe pile and the cap 10, the anchor steel bar 7 and the reserved main steel bar 2 will generate vertical anti-slip force on the steel pipe pile, so that the steel pipe pile and the cap 10 are tightly bonded to generate vertical friction force to resist the vertical slip between the steel pipe pile and the cap 10; (4) When the force transmitted to the cap by the bridge superstructure, in addition to a part passing through the cap 10 → reserved main steel bar 2 → the pressure between the cap concrete and the top of the steel casing 3 → steel pipe pile, the other part can pass through the cap 10 → anchor steel bar ring → anchor concrete layer 8 → the contact surface between the anchor concrete layer 8 and the steel casing 3 and the raised anti-slip steel bar ring group on the contact surface → steel casing 3.

[0082] In this optional solution, step "S6: construction of anchoring concrete layer 8" specifically includes the following steps:

[0083] 1. Formwork installation: An annular formwork surrounding the annular steel cage is installed on the first bottom concrete layer 501 outside the annular steel cage. Specifically, an annular formwork is installed on the outside of the annular steel cage and on the top surface of the first bottom concrete layer 501; when installing the formwork, it is necessary to ensure that the thickness of the steel protection layer on the outside and top surface of the anchor concrete layer 8 is 50 mm.

[0084] 2. Concrete pouring: Concrete is poured in the annular formwork to form an anchoring concrete layer 8. Specifically, after the installation quality inspection and acceptance of the anchoring steel ring, annular steel cage, and anti-slip steel ring group, an anchoring concrete layer 8 with a width of 320mm and a height of 800mm is poured on the top surface of the first bottom concrete layer 501. The anchoring concrete layer 8 uses C40 slightly expansive concrete; when pouring, the anchoring concrete layer 8 is cast in three layers, and the pouring thickness of each layer is 250 to 300mm, so that the anchoring concrete layer 8 is poured until it is flush with the top surface of the steel casing 3; before the initial setting of the anchoring concrete layer 8, the anchoring concrete layer 8 must be vibrated twice to prevent the anchoring concrete layer 8 from sinking the aggregate in the concrete and separating from the anchoring steel ring, annular steel cage, anti-slip steel ring group and steel casing 3 to produce gaps during plastic shrinkage, thereby reducing the anchoring concrete layer 8 and the top surface of the steel casing 3. The bond strength between the anchoring steel bar ring, the annular steel bar cage and the anti-slip steel bar ring group or the bonding strength between the anchoring concrete layer 8 and the steel casing 3; after the anchoring concrete layer 8 is poured, the center of the annular anchoring concrete layer 8, the center of the anchoring steel bar ring, the center of the annular steel bar cage, the center of the anti-slip steel bar ring group and the center of the steel pipe pile are overlapped to ensure that after the volume expansion of the anchoring concrete layer 8, a radial reaction force is formed under the constraint of the annular steel bar cage, and radial prestress is generated toward the inner side of the anchoring concrete layer 8 (towards the steel pipe pile) and uniformly acts on the steel pipe pile, so that the anchoring concrete layer 8 and the steel casing 3 are tightly bonded to generate radial friction force to resist the vertical slip between the steel pipe pile and the anchoring concrete layer 8; after the anchoring concrete layer 8 is finally set, it is covered with geotextile and watered for maintenance, and the maintenance age is not less than 14d.

[0085] The role of the annular anchoring concrete layer 8 is as follows: when the volume of the anchoring concrete layer 8 expands, a radial reaction force is formed under the constraint of the annular steel cage, and radial prestress is generated inside the anchoring concrete layer 8 (towards the steel pipe pile) and uniformly acts on the steel pipe pile, so that the anchoring concrete layer 8 and the steel casing 3 are tightly bonded and radial friction is generated to resist the vertical slip between the steel pipe pile and the anchoring concrete layer 8. Shear failure form of the anchoring concrete layer 8: when vertical slip occurs between the steel pipe pile and the anchoring concrete layer 8, the anchoring steel ring in the anchoring concrete layer 8 will generate an upward anti-slip force acting on the anchoring concrete layer 8, causing the anchoring concrete layer 8 to produce shear failure, forming a shear failure crack failure surface, which intersects with the outer peripheral wall of the steel casing 3 and the top surface of the first bottom sealing concrete layer 501 at an angle of 45°. Among them: the anchoring concrete layer 8 above the shear damage crack failure surface is the anchoring concrete layer 8 in the effective shear damage area, which plays a shearing role to resist the vertical slip between the steel pipe pile and the anchoring concrete layer 8; the anchoring concrete layer 8 below the shear damage crack failure surface is the anchoring concrete layer 8 in the shear damage failure area, that is, the anchoring concrete layer 8 in the shear damage failure area is an annular triangular shape with a width and height that is twice the maximum particle size of the coarse aggregate used in the anchoring concrete layer 8. It loses its shearing effect and cannot resist the vertical slip between the steel pipe pile and the anchoring concrete layer 8.

[0086] Optionally, step "S7: construction of foundation pit bottom sealing and foundation 10" specifically includes the following steps: 1. Casting of the second layer: an isolation plate is arranged on the periphery of the anchoring structure, and a second bottom sealing concrete layer 502 is cast on the first bottom sealing concrete layer 501 outside the isolation plate. Specifically, after removing the annular formwork, a layer of 0.2 mm thick oil paper is arranged on the outside of the anchoring concrete layer 8 to fill and isolate the anchoring concrete layer 8 and the second bottom sealing concrete layer 502 to form an isolation joint 9, so as to prevent the second bottom sealing concrete layer 502 from damaging the anchoring concrete layer 8 when shrinking, and is more conducive to the expansion of the anchoring concrete layer 8; on the top surface of the first bottom sealing concrete layer 501 outside the anchoring concrete layer 8, a second layer of C30 bottom sealing concrete is cast until it is flush with the top surface of the anchoring concrete layer 8 and the top surface of the steel casing 3.

[0087] 2. Construction of cap 10: Cast cap 10 on the top surface of the second bottom concrete layer 502, the top surface of the isolation joint 9, the top surface of the anchor structure and the top surface of the steel pipe pile. Specifically, on the top surface of the second bottom concrete layer 502, the top surface of the isolation joint 9, the top surface of the anchor concrete layer 8, the top surface of the steel casing 3 and the top surface of the cast-in-place pile 1, the construction of anchoring the reserved main steel bars 2 and the anchor steel bars 7 into the cap 10, the lightning protection and grounding construction, the installation of the steel bars of the cap 10, the installation of the cooling pipes and the installation of the embedded components are completed in sequence. After the installation quality is accepted, the cap 10 template can be installed and the cap 10 concrete can be cast. After the construction of the cap 10, the reserved main steel bars 2 and the anchor steel bars 7 are anchored into the cap 10 and connected to the cap 10 by vertical annular anchoring to ensure the firmness of the anchoring connection between the steel pipe piles and the cap 10, forming a "serial" vertical annular anchoring system of the steel pipe piles and the cap 10, ensuring the effective connection between the steel pipe piles and the cap 10, and enhancing the overall stability and safety of the cap 10 structure through the vertical annular anchoring system, thereby improving the reliability of the anchoring quality of the steel pipe piles and the cap 10.

[0088] The steel pipe pile and pedestal anchoring system construction method of the present invention can be applied not only to the bridge pedestal construction field of the above-mentioned embodiment, but also to highway bridge pile foundations, industrial and civil building foundations, structures in areas with strong earthquake intensity, structures under strong scouring and deep-water structure engineering construction.

[0089] 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 construction method for a steel pipe pile and cap anchor system, characterized in that: The following steps are involved: Preliminary preparation: cutting and breaking the excess steel pipe piles at the top of the steel pipe piles in the deep foundation pit to expose the reserved main steel bars (2), and constructing the first bottom sealing concrete layer (501) on the bottom of the foundation pit; Anchorage system design and calculation: design the anchorage structure so that it can connect the steel pipe pile and the cap (10) to form an anchorage system, and calculate the bearing capacity of important components in the anchorage structure; Anchoring system construction: a set of anchoring structures connecting the steel pipe piles and the first bottom sealing concrete layer (501) is constructed on the outer circle of each steel pipe pile, and the top of the anchoring structure protrudes with anchoring bars for extending into the upper cap (10); Construction of foundation pit bottom sealing and capping platform (10): A second bottom sealing concrete layer (502) with isolation joints (9) between each anchoring structure is constructed on the first bottom sealing concrete layer (501) outside the anchoring structure, and a capping platform (10) is constructed on the top surface of the second bottom sealing concrete layer (502), the top surface of the isolation joint (9), the top surface of the anchoring structure and the top surface of the steel pipe pile.

2. The method for constructing a steel pipe pile and cap anchor system according to claim 1, characterized in that: The step "Preliminary preparation" specifically includes the following steps: Preliminary construction preparation: According to the construction design drawings, complete the construction of steel pipe piles, foundation foundation (10), foundation pit cofferdam, foundation pit support, and excavation of foundation pit to the bottom of the foundation pit; Cutting and breaking: cutting the excess steel casing (3) on the top of the steel pipe pile to expose the cast-in-place pile (1), and breaking the exposed cast-in-place pile (1) to expose the reserved main steel bars (2); First layer pouring: pour the first bottom sealing concrete layer (501) on the bottom surface of the foundation pit.

3. The method for constructing a steel pipe pile and cap anchor system according to claim 1, characterized in that: The steps of "anchor system design calculation" specifically include the following steps: Anchorage system design: designing the anchorage structure so that the anchorage structure connects the steel pipe pile and the cap (10) to form a radial annular anchorage system and a vertical annular anchorage system; Force transmission path analysis: Analyze the force transmission paths of radial annular anchor systems and vertical annular anchor systems; Component bearing calculation: Calculate the bearing capacity of important components in the anchor structure.

4. The method for constructing a steel pipe pile and cap anchoring system according to claim 3, characterized in that: Each group of anchoring structures comprises an anti-slip steel bar ring group for fixedly fitting on the outer circle of a corresponding steel pipe pile, a hollow cage-shaped annular steel bar cage for fitting on the outer circle of the steel pipe pile, an anchoring steel bar ring with a hollow ring-shaped lower end for inserting into the annular steel bar cage and an upper end for inserting into a cap (10), and an anchoring concrete layer (8) formed by casting the anti-slip steel bar ring group, the annular steel bar cage and the anchoring steel bar ring and connecting the steel pipe pile and the first bottom sealing concrete layer (501).

5. The method for constructing a steel pipe pile and cap anchoring system according to claim 4, characterized in that: The step "anchor system construction" specifically includes the following steps: Installation of anti-slip steel ring group; Ring reinforcement cage installation; Anchor reinforcement ring installation; Construction of anchoring concrete layer (8).

6. The method for constructing a steel pipe pile and cap anchor system according to claim 5, characterized in that: The step "Anti-slip steel bar ring assembly installation" specifically includes the following steps: Structural construction: constructing components of the anti-slip reinforcement ring group - a plurality of anti-slip reinforcement rings (4); Coating removal: removing the protective coating on the outer wall surface of the steel casing (3) of the outer layer of the steel pipe pile; Installation: A plurality of anti-slip steel bar rings (4) are installed on the outer circumference of the steel casing (3) to form an anti-slip steel bar ring group.

7. The method for constructing a steel pipe pile and cap anchor system according to claim 5, characterized in that: The step "annular reinforcement cage installation" specifically includes the following steps: Structural construction: constructing a circular reinforcement cage using a plurality of circular reinforcement bars (6) and stirrups; Installation: The annular steel cage is mounted on the outer circumference of the steel casing (3) and is radially spaced from the anti-slip steel ring group.

8. The method for constructing a steel pipe pile and cap anchor system according to claim 5, characterized in that: The step "Installation of anchor reinforcement ring" specifically includes the following steps: Structural construction: constructing the components of the anchor steel bar ring - multiple anchor steel bars (7); Installation: multiple anchoring steel bars (7) are arranged in sequence along the outer side of the steel casing (3), and each anchoring steel bar (7) is vertically inserted in sequence into the concrete of the first anchoring concrete layer (8) formed by the first pouring in the annular steel cage.

9. The method for constructing a steel pipe pile and cap anchor system according to claim 5, characterized in that: The step "construction of anchoring concrete layer (8)" specifically comprises the following steps: Formwork installation: installing a ring-shaped formwork surrounding the ring-shaped steel cage on the first bottom sealing concrete layer (501) outside the ring-shaped steel cage; Concrete pouring: Concrete is poured inside the ring formwork to form an anchoring concrete layer (8).

10. The method for constructing a steel pipe pile and cap anchor system according to claim 1, characterized in that: The step "foundation pit bottom sealing and foundation pile (10) construction" specifically includes the following steps: Casting of the second layer: an isolation plate is arranged outside the anchor structure, and a second bottom sealing concrete layer (502) is cast on the first bottom sealing concrete layer (501) outside the isolation plate; Construction of the cap (10): The cap (10) is cast on the top surface of the second bottom sealing concrete layer (502), the top surface of the isolation joint (9), the top surface of the anchoring structure and the top surface of the steel pipe pile.

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