A method for construction of a heat-shrinkable cage core bag enlarged head anchor rod

Abstract

The application provides a heat-shrinking cage core bag expanding head anchor rod construction method, and belongs to the technical field of anchor rod construction. The heat-shrinking cage core bag expanding head anchor rod construction method comprises the following steps: coating the anchor rod body with epoxy asphalt with a thickness of no less than 300 microns from the orifice to the bag opening, and wrapping and heating the heat-shrinking tube to shrink; installing the buckle carrier every 1500 millimeters, installing the cage core bag at the end of the anchor rod, and locking and fixing the cage core bag by means of bolts; after pouring the cushion layer, laying out and positioning according to the design drawing, the hole position error is no more than 100 millimeters; the anchor rod needs to be lowered with the assistance of manual labor, the distance between the end of the rod body and the hole bottom is no more than 100 millimeters; the grouting adopts ordinary Portland cement with a strength of no less than 35 megapascals, and the opening diameter of the bag is monitored; the grouting is supplemented after 2 hours; after the raft waterproof construction, the spiral rib, the positioning nut and other components are installed, the steel cushion plate is welded with steel bars as temporary support, the positioning nut is adjusted to keep the elevation, and the raft rib is welded and connected; and the application can improve the bearing capacity of the anchor rod.

Description

Technical Field

[0001] This invention belongs to the field of anchor bolt construction technology, and more specifically, relates to a method for constructing an anchor bolt with an enlarged head and a heat-shrinkable core bladder. Background Technology

[0002] In the field of architecture and civil engineering, anchor bolts are widely used as an important means of foundation reinforcement in various foundation engineering projects. Typically, anchor bolts penetrate soil or weak rock layers and form a reliable anchoring connection with hard bedrock or concrete layers, thereby enhancing the bearing capacity, anti-slip capacity, and anti-overturning capacity of the foundation. Currently, common types of anchor bolts include prestressed anchor bolts, chemical anchor bolts, and mechanically enlarged head anchor bolts. Among them, mechanically enlarged head anchor bolts are widely used due to their advantages such as simple construction and stable performance.

[0003] Prestressed anchors require high-strength steel bars or strands to be pre-placed inside the anchor and prestressed through tensioning to improve its pull-out resistance. Chemical anchors, on the other hand, involve injecting high-strength chemical resin into the borehole to form a reliable bond with the borehole wall. Both methods improve the load-bearing capacity of anchors to some extent, but require specialized equipment and complex processes, making them difficult to operate and resulting in high material costs. In contrast, mechanically enlarged head anchors increase the anchor volume and contact area by pre-enlarging the borehole diameter at the bottom, thereby improving the overall pull-out resistance. This method is simple to construct, requires no complex specialized equipment, and does not have the problem of excessively high material costs, therefore it is widely used in various foundation reinforcement projects.

[0004] However, existing mechanically enlarged head anchor bolts still have some problems that need to be solved in practical applications. In projects with large spans and heavy loads, the bearing capacity of a single anchor bolt is often insufficient, requiring the use of multiple anchor bolts in combination, which undoubtedly increases the construction difficulty and cost. Summary of the Invention

[0005] In view of this, the present invention provides a construction method for heat shrink cage core bladder enlarged head anchor bolts, which can improve the load-bearing capacity of anchor bolts, eliminate the need for multiple anchor bolts to meet load-bearing requirements, reduce construction difficulty, and reduce construction costs.

[0006] This invention is implemented as follows:

[0007] This invention provides a method for constructing an anchor bolt with an enlarged head and a heat-shrinkable core bladder, comprising the following steps:

[0008] S10. Anti-corrosion treatment of the anchor rod body: apply epoxy asphalt to the anchor rod body from the hole opening to the bag opening, with a coating thickness of not less than 300 micrometers, and wrap the rod body with heat shrink tubing. Heat the tube evenly with a hot air gun to shrink the tube and wrap it around the rod body.

[0009] S20. Assemble the anchor bolts. Install the buckle bearings at 1500 mm intervals on the bolt body. Install the cage core bag at the end of the anchor bolt. Use transverse bolts to lock the upper locking sleeve into the anchor bolt body. Use axial bolts to connect and fix the cage core bag to the upper locking sleeve.

[0010] S30. After the foundation layer is poured, the layout and positioning are carried out. The hole positions are marked according to the design drawings. The error of the hole spacing in the horizontal and vertical directions of the anchor rod is not greater than 100 mm.

[0011] S40. When performing hole-forming operations, the hole diameter shall not be less than 160 mm, the diameter of the enlarged head section shall not be less than 700 mm, and the length shall not be less than 3000 mm. The enlargement time with clean water shall be controlled between 35 and 60 minutes.

[0012] S50. Lower the anchor bolt by manually assisted drilling into the hole. The end of the bolt should be no more than 100 mm from the bottom of the hole. A clip-on bearing is installed on the bolt every 1500 mm.

[0013] S60. Perform grouting of the bag, using ordinary silicate cement grouting, with a cement grout density of not less than 1.82, and an anchor body strength of not less than 35 MPa after 28 days. Monitor the opening diameter of the bag to ensure it reaches the design value using a grouting monitoring instrument.

[0014] S70. Two hours after grouting is completed, additional grouting is performed by injecting cement grout into the borehole.

[0015] S80. After the raft foundation waterproofing construction is completed and before the raft foundation reinforcement is laid, install spiral reinforcement, positioning nuts, steel washers, and precision binding nuts.

[0016] S90. Weld steel bars onto the steel pad as temporary supports. Adjust the positioning nuts to keep the steel pad at the same elevation. Weld the horizontal bidirectional reinforcement of the raft slab to the temporary supports.

[0017] Based on the above technical solution, the construction method of the heat shrink cage core bladder enlarged head anchor bolt of the present invention can be further improved as follows:

[0018] Specifically, step S10 includes: selecting high-strength steel bars to make anchor rod bodies; using professional epoxy asphalt coating equipment to uniformly coat the surface of the anchor rod body with epoxy asphalt as an inner anti-corrosion layer, controlling the thickness of the inner anti-corrosion layer coating to be no less than 300 micrometers; after the epoxy asphalt surface reaches a surface dry state, fitting a heat shrink tube onto the outside of the inner epoxy asphalt coating as an outer anti-corrosion layer; using a professional hot air gun to reciprocate along the axial direction of the anchor rod body to heat the heat shrink tube uniformly and generate a hot-pressure shrinkage effect, ensuring that the heat shrink tube and the inner epoxy asphalt coating are tightly bonded to form a double anti-corrosion protection structure.

[0019] Furthermore, step S20 specifically includes: firstly, installing buckle bearing components every 1500 mm along the length of the anchor rod. The buckle bearing components are made of high-strength engineering plastic and have annular buckle bodies. The inner surface of the annular buckle body is provided with annular grooves with anti-slip textures, and the outer surface has radial positioning ribs distributed in a star-shaped array. The ends of the radial positioning ribs are all equipped with arc-shaped protective caps. Then, the buckle, sealing sleeve, bag body, cage core skeleton and bottom locking component are installed sequentially at the end of the anchor rod. The annular buckle body and sealing sleeve are locked to the anchor rod body by using transverse fixing bolts. The sealing sleeve is made of elastic material and forms an interference fit with the rod body. The cage core skeleton is welded from circumferential steel bars and longitudinal connecting bars and placed inside the bag body. The bag body is made of flexible waterproof material and is fixedly connected to the anchor rod body by the bottom locking component.

[0020] Furthermore, step S30 specifically includes: after the concrete cushion layer is poured and reaches the design strength requirements, the surveyor will lay out and locate the anchor bolt holes according to the design drawings. A total station will be used to accurately locate and measure the anchor bolt holes, and the hole positions will be marked with lime. The error of the hole spacing in the horizontal and vertical directions of the anchor bolts will be strictly controlled to be no more than 100 mm. After the measurement is completed, a self-inspection will be carried out and the results will be submitted to the supervisor for review. Subsequent construction work can only be carried out after the supervisor's approval.

[0021] Furthermore, step S40 specifically includes: using professional drilling equipment to perform hole-forming operations, controlling the hole diameter to be no less than 160 mm, using a special reaming drill bit to perform hole-reaming construction in the enlarged head section, with an enlarged hole diameter of no less than 700 mm and an enlarged section length of no less than 3000 mm, using a clean water flushing process to perform hole-reaming operations, strictly controlling the clean water hole-reaming time to be between 35 minutes and 60 minutes, continuously observing the return water situation until the color of the return water is the same as the color of the clean water, ensuring that the drilling quality meets the design requirements.

[0022] Furthermore, step S50 specifically includes: the construction personnel, in coordination with the drilling equipment, slowly insert the heat shrink cage core bladder enlarged head anchor rod along the borehole axis, strictly controlling the distance between the end of the anchor rod body and the bottom of the hole to not exceed 100 mm, focusing on observing the gap state between the radial positioning rib of the snap-on bearing assembly and the borehole wall during the lowering process, and ensuring that the radial positioning rib does not get stuck by adjusting the lowering speed and angle, while using the snap-on bearing assembly to achieve the centering positioning effect of the anchor rod body in the borehole.

[0023] Furthermore, step S60 specifically includes: selecting 42.5 grade ordinary Portland cement to prepare grouting slurry, strictly controlling the cement slurry density to be not less than 1.82, ensuring the 28-day compressive strength of the anchor body is not less than 35 MPa through test block experiments, installing professional grouting monitoring instruments on the grouting pipeline to monitor the grouting pressure and the opening status of the bladder in real time, and terminating the grouting operation only when the grouting monitoring instrument shows that the bladder opening diameter reaches the design value and the system prompts that the stop condition has been met.

[0024] Furthermore, step S70 specifically includes: 2 hours after the completion of the bag grouting operation, using cement grout with the same mix ratio as the bag grouting to supplement the grouting of the borehole. During the grouting process, closely observe the grout return at the borehole opening. When the color and concentration of the returned grout are basically consistent with the injected grout, stop the grouting to ensure that the grouting fullness meets the design requirements and effectively improves the strength of the anchor body.

[0025] Furthermore, step S80 specifically includes: before the raft foundation waterproofing construction is completed but before the raft foundation reinforcement is laid, installing the top fixing components, which sequentially include spiral reinforcement, steel pad, positioning nut and precision binding nut. The spiral reinforcement adopts a spiral steel bar structure with a pitch of 50 mm and a twisted anti-slip texture on the surface. The steel pad adopts a square steel plate structure with diagonal reinforcing ribs of triangular cross section on the upper surface and positioning bosses distributed in a circumferential array at the edge of the lower surface. By adjusting the positioning nut and precision binding nut, the components form a stable locking connection.

[0026] Furthermore, step S90 specifically includes: using a laser level to project a horizontal elevation control line, precisely adjusting the positioning nuts and tightening nuts to keep all steel pads in the same elevation plane, welding reinforcing bars on the steel pads as temporary support components, and welding and fixing the horizontal bidirectional reinforcing bars of the raft foundation to the temporary support after they are in place to form a stable support system. When the design thickness of the raft foundation exceeds 1500 mm, diagonal bracing components are added at the temporary support position of the anchor bolts to ensure the overall stability of the anchor bolt stirrups.

[0027] The heat-shrinkable core-filled enlarged-head anchor bolt proposed in this invention achieves significant results in solving key problems in existing technologies. Firstly, the double anti-corrosion layer design on the anchor bolt surface—an inner epoxy asphalt coating and an outer heat-shrinkable tube—significantly improves the anchor bolt's corrosion resistance in harsh underground environments, ensuring its long-term reliable use. Secondly, by setting an expandable core-filled assembly at the bottom of the borehole, not only is the contact area and volume of the anchor body increased, but the opening degree of the core-filled assembly can also be adjusted according to actual conditions, further improving the overall load-bearing capacity of the anchor bolt. Furthermore, an adjustable fixing mechanism, including spiral reinforcement, steel pads, and multi-stage nuts, is set at the top of the anchor bolt, adapting to different engineering environments and load conditions, improving overall stability. In addition, compared to the traditional approach of using multiple anchor bolts, the single anchor bolt proposed in this invention can meet the needs of large-span, high-load projects, greatly simplifying the construction process and reducing project costs.

[0028] To further improve the performance of the heat shrink cage core bladder enlarged head anchor bolt, the relationship between the components of the heat shrink cage core bladder enlarged head anchor bolt is defined by the following equations:

[0029] 1. Constraint equation regarding the relationship between the core bag assembly and the anchor bolt:

[0030]

[0031] In the formula: D e The effective diameter (mm) of the sac after it opens; d r α is the diameter of the anchor rod (mm); h is the distance along the length of the bag (mm); L is the total length of the bag (mm); α is the basic expansion coefficient, ranging from 4.2 to 4.8; β is the fluctuation correction coefficient, ranging from 0.1 to 0.15.

[0032] 2. Equation for the spatial distribution relationship between circumferential reinforcement and longitudinal connecting reinforcement:

[0033]

[0034] In the formula: S i Si is the spacing (mm) between the i-th circumferential reinforcement and the adjacent circumferential reinforcement; S0 is the reference spacing, with a value of 150mm; λ is the attenuation coefficient, with a value range of 0.2-0.3; i is the serial number of the circumferential reinforcement; n is the total number of circumferential reinforcements.

[0035] 3. Equation for the radial positioning reinforcement distribution of the snap-on bearing:

[0036]

[0037] In the formula: R jR0 is the length (mm) of the j-th radial positioning rib; R0 is the reference length, with a value of 40mm; γ is the length variation coefficient, with a value range of 0.05-0.1; j is the serial number of the radial positioning rib; m is the total number of radial positioning ribs.

[0038] 4. Strength distribution equation of the steel plate reinforcing ribs:

[0039]

[0040] In the formula: T(x) is the thickness of the reinforcing rib at a distance x from the center point (mm); T0 is the reference thickness at the center point, with a value of 12mm; l is the length of the reinforcing rib (mm); x is the distance along the direction of the reinforcing rib (mm); μ is the thickness attenuation coefficient, with a value range of 0.002-0.003.

[0041] 5. Equation for the contact stress distribution between the spiral reinforcement and the anchor rod:

[0042] P(θ)=P0·(1+η·cos(θ))·e -κθ ;

[0043] In the formula: P(θ) is the contact stress at the rotation angle θ (MPa); P0 is the initial contact stress, with a value of 20MPa; η is the stress fluctuation coefficient, with a value range of 0.1-0.15; κ is the stress attenuation coefficient, with a value range of 0.01-0.02; θ is the rotation angle (rad).

[0044] Parameter acquisition method:

[0045] 1.D e The pressure was obtained in real time through a grouting pressure monitoring instrument. The specific steps were as follows: a) Record the grouting pressure value every 30 seconds during the grouting process; b) Calculate the opening diameter of the bladder based on the pressure-diameter calibration curve; c) Take the maximum stable diameter value as D. e .

[0046] 2.S i The measurement was obtained through the following steps: a) Measure the spacing between adjacent circumferential reinforcing bars using a high-precision vernier caliper; b) Measure each spacing position three times and take the average value; c) Record the serial number i of each position.

[0047] 3.R j The following steps were used to measure and obtain the data: a) Scan the buckle support body using a 3D scanner; b) Extract the length data of each radial positioning rib from the 3D model; c) Record the serial number j of each positioning rib.

[0048] 4. T(x) is obtained by the following steps: a) Use an ultrasonic thickness gauge to measure the thickness every 10 mm along the direction of the reinforcing rib; b) Measure 3 times at each location and take the average value; c) Record the distance x from the center point.

[0049] 5. P(θ) is obtained by the following steps: a) attaching strain gauges to the surface of the spiral reinforcement; b) recording the strain values ​​at different angles during tightening; c) calculating the contact stress using the strain-stress conversion formula.

[0050] Explanation of the principle of the equation:

[0051] 1. The equation relating the core bag assembly and the anchor rod is a sinusoidal function describing the opening shape of the bag, taking into account: a) the non-uniform expansion characteristics of the bag during grouting; b) the change in opening degree caused by end constraint effect; and c) the nonlinear characteristics of material elastic deformation.

[0052] 2. The circumferential reinforcement distribution equation adopts an exponential decay function, taking into account: a) the need for denser reinforcement distribution in stress concentration areas; b) the principle of economical material use; and c) the requirements for ease of construction operation.

[0053] 3. The radial positioning rib distribution equation adopts a cosine function, taking into account: a) the requirement for symmetrical distribution of positioning ribs; b) the feasibility of processing and manufacturing; and c) the anti-jamming performance during installation.

[0054] 4. The strength distribution equation of the stiffener adopts a combination of power function and exponential function, taking into account: a) bending moment distribution law; b) material strength utilization rate; c) feasibility of processing technology.

[0055] 5. The contact stress distribution equation adopts a combination of cosine function and exponential decay function, taking into account: a) the geometric characteristics of the spiral rib; b) the friction characteristics of the contact surface; and c) the transmission law of preload.

[0056] Compared with the prior art, the heat shrink cage core bladder enlarged head anchor bolt of the present invention has achieved significant progress in the following aspects:

[0057] 1. The double anti-corrosion layer design significantly improves the corrosion resistance and service life of the anchor bolt in the underground environment, effectively solving the corrosion problem in the existing technology.

[0058] 2. Setting an expandable bladder at the bottom of the hole not only increases the contact area and volume of the anchor body, but also allows for precise control of the bladder's opening degree according to actual conditions, thereby improving the overall load-bearing capacity.

[0059] 3. An adjustable fixing mechanism is installed at the top, which can adapt to complex engineering environments and load conditions, greatly improving the stability of the overall structure.

[0060] 4. A single anchor bolt can meet the needs of large-span and heavy-load projects, greatly simplifying the construction process and reducing project costs.

[0061] In summary, the heat shrinkable core bladder enlarged head anchor proposed in this invention has achieved remarkable results in solving key problems in the prior art, and has significantly improved in terms of load-bearing capacity, service life, construction difficulty and economy, providing a superior solution for foundation reinforcement projects. Attached Figure Description

[0062] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 A flowchart of a construction method for an enlarged head anchor bolt with a heat shrink cage core;

[0064] Figure 2 This is a schematic diagram of an anchor bolt used in a construction method for a heat-shrinkable core bladder enlarged head anchor bolt.

[0065] Figure 3 This is a cross-sectional view of an anchor bolt used in a construction method for an expanded head anchor bolt with a heat shrink cage core.

[0066] Figure 4 This is a schematic diagram of the anchor bag used in a heat-shrinkable core bladder enlarged head anchor bolt construction method.

[0067] The attached diagram lists the components represented by each number as follows:

[0068] 1. Anchor bolt body; 2. Cage core and bladder assembly; 21. Upper locking buckle; 22. Sealing sleeve; 23. Bladder body; 24. Cage core skeleton; 25. Bottom locking component; 3. Anti-corrosion layer assembly; 4. Buckle bearing assembly; 41. Ring buckle body; 5. Top fixing assembly; 51. Spiral reinforcement; 52. Steel pad; 53. Positioning nut; 54. Precision binding nut. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0070] like Figures 1-4 The image shown is a first embodiment of a construction method for an enlarged head anchor bolt using a heat-shrinkable core bladder provided by the present invention. This embodiment includes the following steps:

[0071] S10. Anti-corrosion treatment of the anchor rod body: apply epoxy asphalt to the anchor rod body from the hole opening to the bag opening, with a coating thickness of not less than 300 micrometers, and wrap the rod body with heat shrink tubing. Heat the tube evenly with a hot air gun to shrink the tube and wrap it around the rod body.

[0072] S20. Assemble the anchor bolts. Install the buckle bearings at 1500 mm intervals on the bolt body. Install the cage core bag at the end of the anchor bolt. Use transverse bolts to lock the upper locking sleeve into the anchor bolt body. Use axial bolts to connect and fix the cage core bag to the upper locking sleeve.

[0073] S30. After the foundation layer is poured, the layout and positioning are carried out. The hole positions are marked according to the design drawings. The error of the hole spacing in the horizontal and vertical directions of the anchor rod is not greater than 100 mm.

[0074] S40. When performing hole-forming operations, the hole diameter shall not be less than 160 mm, the diameter of the enlarged head section shall not be less than 700 mm, and the length shall not be less than 3000 mm. The enlargement time with clean water shall be controlled between 35 and 60 minutes.

[0075] S50. Lower the anchor bolt by manually assisted drilling into the hole. The end of the bolt should be no more than 100 mm from the bottom of the hole. A clip-on bearing is installed on the bolt every 1500 mm.

[0076] S60. Perform grouting of the bag, using ordinary silicate cement grouting, with a cement grout density of not less than 1.82, and an anchor body strength of not less than 35 MPa after 28 days. Monitor the opening diameter of the bag to ensure it reaches the design value using a grouting monitoring instrument.

[0077] S70. Two hours after grouting is completed, additional grouting is performed by injecting cement grout into the borehole.

[0078] S80. After the raft foundation waterproofing construction is completed and before the raft foundation reinforcement is laid, install spiral reinforcement, positioning nuts, steel washers, and precision binding nuts.

[0079] S90. Weld steel bars onto the steel pad as temporary supports. Adjust the positioning nuts to keep the steel pad at the same elevation. Weld the horizontal bidirectional reinforcement of the raft slab to the temporary supports.

[0080] In the above technical solution, step S10 specifically includes: selecting high-strength steel bars to make anchor rod bodies; using professional epoxy asphalt coating equipment to uniformly coat the surface of the anchor rod body with epoxy asphalt as an inner anti-corrosion layer; controlling the thickness of the inner anti-corrosion layer coating to be no less than 300 micrometers; after the epoxy asphalt surface reaches a surface dry state, fitting a heat shrink tube onto the outside of the inner epoxy asphalt coating as an outer anti-corrosion layer; using a professional hot air gun to reciprocate and heat along the axial direction of the anchor rod body, so that the heat shrink tube is uniformly heated and produces a hot-pressure shrinkage effect, ensuring that the heat shrink tube and the inner epoxy asphalt coating are tightly bonded to form a double anti-corrosion protection structure.

[0081] The specific implementation method is as follows: First, high-strength steel bars are selected to make the anchor rod body. Professional epoxy asphalt coating equipment is used to evenly coat the surface of the anchor rod body as an inner anti-corrosion layer. The coating thickness of the inner anti-corrosion layer is controlled to be no less than 300 micrometers. After the epoxy asphalt surface reaches a surface dry state, a heat shrink tubing is fitted onto the outside of the inner epoxy asphalt coating as an outer anti-corrosion layer. A professional hot air gun is used to reciprocate along the axial direction of the anchor rod body to heat it, ensuring that the heat shrink tubing is evenly heated and produces a thermo-compression shrinkage effect, ensuring that the heat shrink tubing and the inner epoxy asphalt coating are tightly bonded to form a double anti-corrosion protection structure. The purpose of this step is to form a reliable double anti-corrosion layer on the anchor rod surface, effectively preventing corrosion of the anchor rod in the underground environment, and improving its corrosion resistance and service life.

[0082] Furthermore, in the above technical solution, step S20 specifically includes: First, installing the buckle bearing assembly every 1500 mm along the length of the anchor rod. The buckle bearing assembly is made of high-strength engineering plastic to form a ring buckle body. The inner surface of the ring buckle body is provided with an annular groove with anti-slip texture, and the outer surface is distributed with radial positioning ribs in a star-shaped array. The ends of the radial positioning ribs are all equipped with arc-shaped protective caps. Then, the buckle, sealing sleeve, bag body, cage core skeleton and bottom locking component are installed sequentially at the end of the anchor rod. The ring buckle body and sealing sleeve are locked to the anchor rod body by using transverse fixing bolts. The sealing sleeve is made of elastic material and forms an interference fit with the rod body. The cage core skeleton is welded from circumferential steel bars and longitudinal connecting bars and placed inside the bag body. The bag body is made of flexible waterproof material and is fixedly connected to the anchor rod body by the bottom locking component.

[0083] The specific implementation method is as follows: First, install the snap-on bearing assembly every 1500 mm along the length of the anchor rod. The snap-on bearing assembly is made of high-strength engineering plastic and has a ring-shaped snap-on body. The inner surface of the ring-shaped snap-on body is provided with an annular groove with anti-slip texture, and the outer surface has radial positioning ribs distributed in a star-shaped array. Each radial positioning rib is fitted with an arc-shaped protective cap at its end. Then, install the snap-on, sealing sleeve, bladder body, core cage, and bottom locking device in sequence at the end of the anchor rod. Use transverse fixing bolts to lock the ring-shaped snap-on body and the sealing sleeve to the anchor rod, and the sealing sleeve is made of elastic material to form an interference fit with the rod. The core cage is welded from circumferential steel bars and longitudinal connecting bars and placed inside the bladder body. The bladder body is made of flexible waterproof material and is fixedly connected to the anchor rod through the bottom locking device. The purpose of this step is to install the core cage bladder assembly on the anchor rod and use the snap-on bearing assembly to achieve the positioning of the anchor rod in the borehole.

[0084] Furthermore, in the above technical solution, step S30 specifically includes: after the concrete cushion layer is poured and reaches the design strength requirements, the surveyor shall lay out and locate the anchor bolt holes according to the design drawings. The total station shall be used to accurately locate and measure the anchor bolt holes, and the hole positions shall be marked with lime. The error of the hole spacing in the horizontal and vertical directions of the anchor bolts shall be strictly controlled to be no more than 100 mm. After the measurement is completed, a self-inspection shall be carried out and the results shall be submitted to the supervisor for review. Subsequent construction work can only be carried out after the supervisor's approval.

[0085] The specific implementation method is as follows: After the concrete foundation layer is poured and reaches the design strength requirements, surveyors will lay out and locate the anchor bolt holes according to the design drawings. A total station will be used to accurately measure the anchor bolt holes, and the hole positions will be marked with lime. The error in the horizontal and vertical distance between the anchor bolt holes will be strictly controlled to be no more than 100 mm. After the measurement is completed, a self-inspection will be conducted and submitted to the supervisor for review. Subsequent construction work can only proceed after the supervisor's approval. The purpose of this step is to accurately locate the anchor bolt holes according to the design requirements, providing a foundation for the subsequent installation of the anchor bolts.

[0086] Furthermore, in the above technical solution, step S40 specifically includes: using professional drilling equipment to perform hole-forming operations, controlling the hole diameter to be no less than 160 mm, using a special reaming drill bit to perform hole-reaming construction in the enlarged head section, with an enlarged hole diameter of no less than 700 mm and an enlarged section length of no less than 3000 mm, using a clean water flushing process to perform hole-reaming operations, strictly controlling the clean water hole-reaming time to be between 35 minutes and 60 minutes, continuously observing the return water situation until the color of the return water is the same as the color of the clean water, ensuring that the drilling quality meets the design requirements.

[0087] The specific implementation method is as follows: Professional drilling equipment is used for hole drilling, with the borehole diameter controlled to be no less than 160 mm. The enlarged section is constructed using a specially designed reaming drill bit, with an enlarged diameter of no less than 700 mm and an enlarged section length of no less than 3000 mm. A clean water flushing process is used for the enlargement operation, with the water flushing time strictly controlled between 35 and 60 minutes. The return water is continuously observed until its color matches that of the clean water, ensuring the borehole quality meets design requirements. The purpose of this step is to enlarge the pre-drilled hole, providing sufficient space for subsequent anchor bolt installation.

[0088] Furthermore, in the above technical solution, step S50 specifically includes: the construction personnel, in coordination with the drilling equipment, slowly insert the heat shrink cage core bladder enlarged head anchor rod along the borehole axis, strictly controlling the distance between the end of the anchor rod body and the bottom of the hole to not exceed 100 mm, focusing on observing the gap state between the radial positioning rib of the snap-on bearing assembly and the borehole wall during the lowering process, and ensuring that the radial positioning rib does not get stuck by adjusting the lowering speed and angle, while using the snap-on bearing assembly to achieve the centering positioning effect of the anchor rod body in the borehole.

[0089] The specific implementation method is as follows: Construction personnel, in coordination with the drilling rig, slowly insert the heat-shrinkable core-filled enlarged-head anchor rod along the borehole axis, strictly controlling the distance between the end of the anchor rod and the bottom of the hole to not exceed 100 mm. During the lowering process, the gap between the radial positioning ribs of the clamping support assembly and the borehole wall is closely observed. By adjusting the lowering speed and angle, it is ensured that the radial positioning ribs do not become stuck. Simultaneously, the clamping support assembly achieves the centered positioning effect of the anchor rod in the borehole. The purpose of this step is to slowly insert the pre-assembled heat-shrinkable core-filled enlarged-head anchor rod into the pre-enlarged borehole, and to ensure the stable positioning of the anchor rod within the hole using the clamping support assembly.

[0090] Furthermore, in the above technical solution, step S60 specifically includes: selecting 42.5 grade ordinary Portland cement to prepare grouting slurry, strictly controlling the cement slurry density to be not less than 1.82, ensuring the 28-day compressive strength of the anchor body is not less than 35 MPa through test block experiments, installing professional grouting monitoring instruments on the grouting pipeline to monitor the grouting pressure and the opening status of the bladder in real time, and terminating the grouting operation only when the grouting monitoring instrument shows that the bladder opening diameter reaches the design specified value and the system prompts that the stop condition has been met.

[0091] The specific implementation method is as follows: 42.5 grade ordinary Portland cement is used to prepare the grouting slurry, and the cement slurry density is strictly controlled to be no less than 1.82. Test block experiments are conducted to ensure that the 28-day compressive strength of the anchor body is no less than 35 MPa. Professional grouting monitoring instruments are installed on the grouting pipeline to monitor the grouting pressure and the opening status of the grout bag in real time. Grouting operations can only be terminated when the grouting monitoring instrument shows that the grout bag opening diameter reaches the design specified value and the system prompts that the stop condition has been met. The purpose of this step is to fully expand the grout bag using grouting technology, forming a reliable anchor body with the pre-drilled borehole wall, thereby improving the overall load-bearing capacity of the anchor bolt.

[0092] Furthermore, in the above technical solution, step S70 specifically includes: 2 hours after the completion of the bag grouting operation, the borehole is supplemented with cement grout with the same mix ratio as the bag grouting. During the grouting process, the grout return situation at the borehole opening is closely observed. When the color and concentration of the returned grout are basically consistent with the injected grout, the grouting is stopped to ensure that the grouting fullness meets the design requirements and effectively improves the anchor body strength.

[0093] The specific implementation method is as follows: Two hours after the completion of the bag grouting operation, supplementary grouting is performed on the borehole using cement grout with the same mix ratio as the bag grouting. During the supplementary grouting process, the grout return at the borehole opening is closely observed. When the color and concentration of the returned grout are basically consistent with the injected grout, the supplementary grouting is stopped to ensure that the grouting fullness meets the design requirements and effectively improves the strength of the anchor body. The purpose of this step is to fill any voids that may exist in the borehole through supplementary grouting, further improving the overall compactness of the anchor body.

[0094] Furthermore, in the above technical solution, step S80 specifically includes: before the raft slab waterproofing construction is completed but before the raft slab reinforcement is laid, installing the top fixing components, which in turn include spiral reinforcement, steel pad, positioning nut and precision binding nut. The spiral reinforcement adopts a spiral steel bar structure with a pitch of 50 mm and a twisted anti-slip texture on the surface. The steel pad adopts a square steel plate structure with diagonal reinforcing ribs of triangular cross section on the upper surface and positioning bosses distributed in a circumferential array at the edge of the lower surface. By adjusting the positioning nut and precision binding nut, the components form a stable locking connection.

[0095] The specific implementation method is as follows: Before the raft foundation reinforcement is laid after the raft waterproofing construction is completed, the top fixing component is installed. The top fixing component includes spiral reinforcement, steel pads, positioning nuts, and precision nuts. The spiral reinforcement adopts a spiral steel bar structure with a pitch of 50 mm and a twisted anti-slip texture on the surface. The steel pad adopts a square steel plate structure with a through hole in the center that matches the anchor rod body. The upper surface has triangular cross-section reinforcing ribs along the diagonal direction, and the lower surface has positioning bosses distributed in a circumferential array at the edge. By adjusting the positioning nuts and precision nuts, a stable locking connection is formed between the components. The purpose of this step is to install an adjustable top fixing component at the top of the anchor rod, providing a stable support foundation for subsequent raft foundation construction.

[0096] Furthermore, in the above technical solution, step S90 specifically includes: using a laser level to project a horizontal elevation control line, precisely adjusting the positioning nuts and tightening nuts to keep all steel pads in the same elevation plane, welding reinforcing bars on the steel pads as temporary support components, and welding and fixing the horizontal bidirectional reinforcing bars of the raft foundation to the temporary support after they are in place to form a stable support system. When the design thickness of the raft foundation exceeds 1500 mm, diagonal bracing components are added at the temporary support position of the anchor bolts to ensure the overall stability of the anchor bolt stirrups.

[0097] The specific implementation method is as follows: A laser level is used to project a horizontal elevation control line, and the positioning nuts and tightening nuts are precisely adjusted to ensure that all steel pads are kept in the same elevation plane. Reinforcing bars are welded onto the steel pads as temporary support components. After the horizontal bidirectional reinforcing bars of the raft foundation are in place, they are welded and fixed to the temporary supports to form a stable support system. When the design thickness of the raft foundation exceeds 1500 mm, diagonal bracing components are added at the temporary support locations of the anchor bolts to ensure the overall stability of the anchor bolt stirrups. The purpose of this step is to ensure the stability of the anchor bolts during raft foundation pouring and subsequent construction by setting up temporary support components, avoiding displacement or deformation.

[0098] like Figures 2-4 As shown, in the above technical solution, the heat shrink cage core bladder enlargement head includes an anchor rod body 1, which is columnar. The outer surface of the anchor rod body 1 is provided with an anti-corrosion layer assembly 3, which is used to protect the anchor rod body 1 from corrosion. A top fixing assembly 5 is provided above the anchor rod body 1 for fixing. A snap-on bearing assembly 4 is provided on the outer side wall of the anti-corrosion layer assembly 3, which is used to ensure the anchor rod body is centered in the borehole. A cage core bladder assembly 2 is provided at the bottom of the anchor rod body 1 to enhance the load-bearing capacity of the anchor rod body 1.

[0099] The cage core assembly 2 includes an upper locking buckle 21, a sealing sleeve 22, a bag body 23, a cage core frame 24, and a bottom locking member 25. The sealing sleeve 22 is located at the bottom of the outer side wall of the anchor rod body 1, and has an annular structure. It is interference-fitted with the anchor rod body 1. The sealing sleeve 22 is made of elastic material. The outer side wall of the sealing sleeve 22 is provided with an upper locking buckle 21. The upper locking buckle 21 has an annular structure, and its inner side wall is in close contact with the outer side wall of the sealing sleeve 22. The bottom of the sealing sleeve 22 is fixedly connected to the cage core frame 24. The cage core frame 24 includes several circumferential reinforcing bars and longitudinal connecting bars. The circumferential reinforcing bars are evenly arranged along the length direction of the bag body 23. Adjacent circumferential reinforcing bars are welded and fixed together by longitudinal connecting bars. The bag body 23 is made of flexible waterproof material. Its upper end is fixedly connected to the sealing sleeve 22 and is located outside the cage core frame 24. The lower end of the bag body 23 is fixedly connected to the anchor rod body through the bottom locking member.

[0100] The anti-corrosion layer component 3 is located on the outer side wall of the anchor rod body 1 and is in close contact with the anchor rod body 1. The anti-corrosion layer component 3 has two layers. The inner layer of the anti-corrosion layer component 3 is an epoxy asphalt coating, and the outer layer is a heat shrink tube. The inner epoxy asphalt coating is in close contact with the surface of the anchor rod body, and the outer heat shrink tube is wrapped around the outer surface of the inner epoxy asphalt coating by hot pressing.

[0101] The buckle bearing assembly 4 is located on the outer wall of the anti-corrosion layer assembly 3. One buckle bearing assembly 4 is set every 1500 mm along the length of the anchor rod body. The buckle bearing assembly 4 includes multiple annular buckle bodies. The annular buckle bodies are made of high-strength engineering plastic. Their inner surface is provided with an annular groove that matches the outer surface of the anchor rod body. The annular groove is provided with anti-slip texture.

[0102] Furthermore, the buckle bearing assembly 4 also includes radial positioning ribs, which are distributed in a star-shaped array on the outer surface of the annular buckle body. Each radial positioning rib has an arc-shaped protective cap at its end to prevent the radial positioning rib from getting stuck with the borehole wall during the lowering process.

[0103] The top fixing component 5 includes a spiral bar 51, a steel pad 52, a positioning nut 53, and a precision nut 54. The spiral bar 51 is a threaded steel bar that spirally wraps around the outer wall of the anchor rod body 1. The inner diameter of the spiral bar 51 matches the outer diameter of the anchor rod body. The pitch of the spiral bar is 50 mm. The surface of the spiral bar is provided with a twisted anti-slip texture to enhance the grip with concrete. The top of the spiral bar 51 is provided with a precision nut 54. Above the precision nut 54 is a steel pad 52. The steel pad 52 is a square steel plate structure with a through hole in the center that matches the anchor rod body. The upper surface of the steel pad is provided with reinforcing ribs along the diagonal direction. The reinforcing ribs adopt a triangular cross-section design, and their bottom edges are welded and fixed to the upper surface of the steel pad. The spiral reinforcement has a pitch of 50 mm and a spiral anti-slip texture on its surface to enhance its grip with concrete. The positioning nut 53 is located above the steel pad 52 and cooperates with the precision nut 54 to fix the steel pad 52.

[0104] In the design of the heat shrink cage core bladder enlarged head anchor bolt, the relationship equations between several key parameters are used to limit the coordination performance between the components:

[0105] 1. The defining equation for the relationship between the core bag assembly and the anchor rod is:

[0106]

[0107] Where, D e d is the effective diameter of the sac after it opens (mm). r Let be the diameter of the anchor rod (mm), h be the distance along the length of the grout (mm), L be the total length of the grout (mm), α be the basic expansion coefficient, ranging from 4.2 to 4.8, and β be the fluctuation correction coefficient, ranging from 0.1 to 0.15. This equation describes the non-uniform expansion characteristics of the grout during the grouting process and considers the end constraint effect and the nonlinear characteristics of the material's elastic deformation.

[0108] 2. The equation relating the spatial distribution of circumferential reinforcement and longitudinal connecting reinforcement is:

[0109]

[0110] Where, S i Let Si be the spacing (mm) between the i-th circumferential rebar and its adjacent circumferential rebar, S0 be the baseline spacing (150mm), λ be the attenuation coefficient (range 0.2-0.3), i be the serial number of the circumferential rebar, and n be the total number of circumferential rebars. This equation uses an exponential attenuation function, taking into account the need for denser rebar distribution in stress concentration areas, while also considering the economy of material use and the convenience of construction operations.

[0111] 3. The radial positioning reinforcement distribution equation of the clip-on bearing body is:

[0112]

[0113] Where, R j Let R0 be the length (mm) of the j-th radial positioning rib, γ be the reference length (40mm), γ be the length variation coefficient (range 0.05-0.1), j be the serial number of the radial positioning rib, and m be the total number of radial positioning ribs. This equation uses a cosine function and considers the symmetrical distribution requirements of the positioning ribs, the feasibility of manufacturing, and the anti-jamming performance during installation.

[0114] 4. The strength distribution equation for the steel plate reinforcing ribs is:

[0115]

[0116] Where T(x) is the thickness of the stiffener at a distance x from the center point (mm), T0 is the reference thickness at the center point (12mm), l is the length of the stiffener (mm), x is the distance along the direction of the stiffener (mm), and μ is the thickness attenuation coefficient, ranging from 0.002 to 0.003. This equation uses a combination of power and exponential functions, taking into account the bending moment distribution, material strength utilization, and the feasibility of the processing technology.

[0117] 5. The stress distribution equation between the spiral reinforcement and the anchor rod is:

[0118] P(θ)=P0·(1+η·cos(θ))·e -κθ ;

[0119] Where P(θ) is the contact stress (MPa) at the rotation angle θ, P0 is the initial contact stress (20MPa), η is the stress fluctuation coefficient (range 0.1-0.15), κ is the stress attenuation coefficient (range 0.01-0.02), and θ is the rotation angle (rad). This equation uses a combination of a cosine function and an exponential attenuation function, considering the geometric characteristics of the spiral reinforcement, the frictional properties of the contact surface, and the transmission law of the preload.

[0120] The values ​​of all the above key parameters need to be obtained through actual measurement or experimentation. For example, D e It can be obtained in real time through a grouting pressure monitoring instrument; S i The value can be obtained by measuring the spacing between adjacent circumferential reinforcing bars with vernier calipers and taking the average value; R jData can be obtained by scanning the buckle carrier with a 3D scanner and extracting it from the 3D model; T(x) can be obtained by measuring the thickness along the direction of the reinforcing rib with an ultrasonic thickness gauge and taking the average value; P(θ) can be obtained by attaching strain gauges to the surface of the spiral rib, recording the strain values ​​at different angles during tightening, and then calculating it using the strain-stress conversion formula.

[0121] The formula variables and constants used in this invention are shown in Table 1:

[0122] Table 1. Explanation of Formula Constants and Variables in the Invention

[0123]

[0124]

[0125] The present invention provides a second embodiment of a construction method for a heat-shrinkable core bladder enlarged head anchor bolt. In this embodiment, a construction method for a heat-shrinkable core bladder enlarged head anchor bolt is provided:

[0126] In a large-scale subway project, due to complex geological conditions, it was necessary to reinforce the foundation using heat-shrinkable core-filled enlarged-head anchor bolts. The project area had a high groundwater level and weak soil layers, posing significant challenges to the foundation construction. Therefore, the project adopted the heat-shrinkable core-filled enlarged-head anchor bolt construction method proposed in this invention.

[0127] First, the anchor bolt body undergoes anti-corrosion treatment. Using professional epoxy asphalt coating equipment, a 300-micron-thick layer of epoxy asphalt is evenly applied to the surface of the anchor bolt body as the inner anti-corrosion layer. After the epoxy asphalt surface reaches a surface dry state, heat shrink tubing is fitted onto the outside of the inner coating as the outer anti-corrosion layer. Construction personnel use a professional hot air gun to repeatedly heat the anchor bolt body along its axial direction, ensuring the heat shrink tubing is evenly heated and generates a thermo-shrink effect, ensuring a tight bond between the heat shrink tubing and the inner epoxy asphalt coating, forming a double anti-corrosion protection structure.

[0128] Next, the anchor bolts are assembled. First, snap-fit ​​bearing assemblies are installed every 1500 mm along the length of the anchor bolt. These snap-fit ​​bearing assemblies are made of high-strength engineering plastic and include components such as annular snap-fit ​​bodies and radial positioning ribs. The inner surface of the annular snap-fit ​​body has an annular groove matching the outer diameter of the anchor bolt, with anti-slip textures inside the groove. The radial positioning ribs are distributed in a star-shaped array on the outer surface of the annular snap-fit ​​body, with an arc-shaped protective cap at the end of each rib. Then, the upper locking buckle, sealing sleeve, bladder body, core cage, and bottom locking device are installed sequentially at the end of the anchor bolt. The upper locking buckle consists of an annular snap-fit ​​body and transverse fixing bolts, which are used to lock it to the sealing sleeve and fix it to the anchor bolt. The sealing sleeve is made of elastic material and forms an interference fit with the outer surface of the bolt. The bladder body is made of flexible waterproof material and has an internal core cage made of welded circumferential and longitudinal connecting ribs. Its lower end is fixedly connected to the anchor bolt through the bottom locking device.

[0129] Next, the anchor bolt hole positions are marked out. After the concrete foundation is poured and reaches the design strength, surveyors use a total station to accurately measure the anchor bolt hole positions according to the design drawings. The horizontal and vertical hole spacing errors must be strictly controlled to be no more than 100 mm, and the hole positions are marked with lime. After measurement, a self-inspection is conducted, and subsequent construction can only proceed after approval by the supervisor.

[0130] Following this, hole drilling is carried out. Drilling equipment is used to ensure the hole diameter is no less than 160 mm, and a specially designed reaming drill bit is used to enlarge the bottom of the hole. The enlarged diameter is no less than 700 mm, and the length of the enlarged section is no less than 3000 mm. The entire reaming operation employs a clean water flushing process, strictly controlling the clean water reaming time between 35 and 60 minutes, continuously observing the return water until its color matches that of clean water, ensuring the drilling quality meets design requirements.

[0131] Next, the anchor bolt is lowered. Construction personnel, in coordination with the drilling rig, slowly insert the pre-assembled heat-shrinkable core-filled enlarged-head anchor bolt along the borehole axis. The distance between the end of the anchor bolt and the bottom of the borehole is strictly controlled to not exceed 100 mm. During the lowering process, the gap between the radial positioning ribs of the clamping support assembly and the borehole wall is closely observed. The lowering speed and angle are adjusted to ensure the positioning ribs do not become stuck, while the clamping support assembly helps to center the anchor bolt within the borehole.

[0132] Next, the grouting of the anchor bag is carried out. 42.5 grade ordinary Portland cement is used to prepare the grout, and the cement grout density is strictly controlled to be no less than 1.82. Test block experiments are conducted to ensure that the 28-day compressive strength of the anchor body is no less than 35 MPa. Professional monitoring instruments are installed on the grouting pipeline to monitor the grouting pressure and the opening status of the anchor bag in real time. Grouting operations can only be terminated when the monitoring instrument shows that the opening diameter of the anchor bag has reached the design value and the system prompts that the stop condition has been met.

[0133] Two hours after the bag grouting is completed, supplementary grouting is performed on the borehole using cement grout with the same mix ratio as the bag grouting. Closely observe the grout return at the borehole opening; stop supplementary grouting when the color and concentration of the returned grout are basically consistent with the injected grout, ensuring that the grouting fullness meets the design requirements.

[0134] Finally, before the raft foundation waterproofing construction is completed but before the raft foundation reinforcement is laid, the top fixing components are installed. First, spiral reinforcement, steel pads, positioning nuts, and precision nuts are installed sequentially at the top of the anchor rods. The spiral reinforcement uses a spiral steel structure with a pitch of 50 mm and a twisted anti-slip texture on the surface. The steel pads are square steel plates with a through hole in the center matching the anchor rod. The upper surface has triangular cross-section reinforcing ribs along the diagonal direction, and the lower surface has positioning bosses arranged in a circumferential array along the edge. The positioning nuts and precision nuts are adjusted to ensure a stable locking connection between the components. Then, a laser level is used to control the elevation, precisely adjusting each steel pad to the same horizontal plane, and reinforcing bars are welded onto the steel pads as temporary supports. After the horizontal bidirectional reinforcement of the raft foundation is in place, it is welded and fixed to the temporary supports to form a stable support system. If the raft foundation design thickness exceeds 1500 mm, diagonal bracing components need to be added at the temporary anchor support locations to ensure the overall stability of the stirrup reinforcement.

[0135] In summary, this heat-shrinkable core-filled enlarged-head anchor bolt construction method fully leverages the advantages of various innovative technologies, effectively solving the problems of existing mechanically enlarged-head anchor bolts in terms of corrosion resistance, anchoring performance, and stability. It not only improves project quality and reliability but also simplifies the construction process and reduces project costs. This method has been successfully applied in large-scale subway projects under complex geological conditions, providing a superior solution for foundation reinforcement engineering.

[0136] The present invention provides a third embodiment of a construction method for a heat-shrinkable core bladder enlarged head anchor bolt. In this embodiment, the specific structure of the heat-shrinkable core bladder enlarged head anchor bolt is provided:

[0137] A large-scale highway project required foundation reinforcement and adopted the heat-shrinkable core-filled enlarged-head anchor bolt proposed in this invention. This anchor bolt consists of the following main components:

[0138] 1. Anchor bolt body:

[0139] The anchor rod is made of precision-rolled steel bars with a diameter of 32 mm. To improve corrosion resistance, a double anti-corrosion layer is applied to the outer surface of the rod, consisting of an inner epoxy asphalt coating and an outer heat-shrink tubing.

[0140] The inner epoxy asphalt coating is 300 micrometers thick and is evenly applied to the surface of the rod using specialized coating equipment. After the coating reaches surface dryness, heat shrink tubing is fitted onto the outside to form the outer anti-corrosion layer. A specialized hot air gun is used to heat the rod axially, causing the heat shrink tubing to shrink and adhere tightly to the inner epoxy coating, working together to provide corrosion protection. This dual anti-corrosion design effectively blocks corrosive media in the underground environment, significantly extending the service life of the anchor bolt.

[0141] 2. Cage core bag assembly:

[0142] The cage core bag assembly is located at the bottom of the anchor rod and consists of components such as the upper locking buckle, sealing sleeve, bag body, cage core frame and bottom locking component.

[0143] The upper locking buckle consists of a ring-shaped locking body and a transverse fixing bolt. The transverse bolt forms a locking fit with the sealing sleeve, fixing it to the upper end of the anchor rod. The sealing sleeve is made of elastic polyurethane material, and its inner surface is interference-fitted with the outer diameter of the anchor rod, effectively sealing the space inside the hole.

[0144] The grout bag body is made of a flexible waterproof polyamide material, with its upper end fixedly connected to a sealing sleeve. Internally, it features a cage-like skeleton welded from circumferential and longitudinal reinforcing bars. This cage-like skeleton not only enhances the rigidity of the grout bag body but also improves the uniformity of grout distribution during the grouting process. The lower end of the grout bag body is fixedly connected to the anchor rod via a bottom locking device.

[0145] During the grouting process, cement grout enters the inside of the bladder, causing it to gradually expand to a preset diameter, thus forming a reliable anchoring connection with the borehole wall. This expandable bladder assembly not only significantly increases the contact area and volume of the anchor body, but also allows for precise adjustment of its opening degree according to actual conditions, further enhancing the overall load-bearing capacity.

[0146] 3. Clip-on carrier assembly:

[0147] One snap-on bearing assembly is installed every 1500 mm along the length of the anchor rod to ensure the anchor rod is centered in the borehole.

[0148] This clip-on carrier is made of high-strength engineering plastic and includes an annular clip body and radial positioning ribs. The inner surface of the annular clip body has an annular groove that matches the outer diameter of the anchor rod, and the groove has annular protrusions with anti-slip texture. The radial positioning ribs are distributed in a star-shaped array on the outer surface of the annular clip body, and each positioning rib is equipped with an arc-shaped protective cap at its end to prevent jamming during lowering.

[0149] This snap-fit ​​support assembly can reliably fix the anchor rod body, and during the lowering process, the contact between the radial positioning ribs and the hole wall achieves the centered positioning of the anchor rod within the hole. This not only facilitates subsequent grouting operations but also ensures that the anchor rod maintains a stable stress state under load.

[0150] 4. Top fixing component:

[0151] The top fixing assembly is located at the top of the anchor rod and includes components such as spiral reinforcement, steel pad, positioning nut and precision binding nut.

[0152] The spiral reinforcement uses a spiral steel bar structure, with an inner diameter matching the outer diameter of the anchor rod, a pitch of 50 mm, and a twisted anti-slip texture on the surface. This special spiral reinforcement structure can form a reliable interlocking connection with the concrete, enhancing the overall stability between it and the superstructure.

[0153] The steel pad is a square steel plate structure with a through hole in the center to match the anchor bolt. The upper surface of the steel pad has reinforcing ribs with triangular cross-sections along its diagonal, and the lower surface has several positioning bosses arranged in a circumferential array along its edge. By adjusting the positioning nuts and the precision nuts, the steel pad can be kept at the same horizontal elevation, providing stable support for the upper raft foundation.

[0154] In large-span, high-load projects, diagonal bracing components can be added at the temporary anchor support locations. These diagonal bracing components can further improve the stability of the overall structure and ensure that key components such as stirrups do not shift or deform under stress.

[0155] The heat shrink cage core enlarged head anchor bolt of the present invention uses a number of innovative technical means to solve the key problems in the prior art.

[0156] Firstly, a double-layer anti-corrosion design is employed on the anchor bolt surface, consisting of an inner layer of epoxy asphalt coating and an outer layer of heat-shrink tubing. Epoxy asphalt, as a high-quality anti-corrosion coating, effectively blocks corrosive media such as moisture and salt from eroding the anchor bolt steel. The heat-shrink tubing, as the outer protective layer, further enhances the anti-corrosion performance by shrinking and wrapping around the epoxy asphalt coating, forming a double barrier. This design not only improves the anchor bolt's corrosion resistance in underground environments but also effectively extends its service life, thus providing a reliable reinforcement method for foundation engineering.

[0157] Secondly, an expandable bladder assembly is installed at the end of the anchor bolt. This bladder assembly consists of a locking buckle, a sealing sleeve, a flexible bladder body, and a core cage. During grouting, cement grout enters the bladder, causing it to gradually expand to a preset diameter, thus forming a reliable anchoring connection with the borehole wall. This not only significantly increases the contact area and volume of the anchor body but also allows for precise control of the bladder's opening degree according to actual conditions, further improving the overall load-bearing capacity. Simultaneously, the core cage enhances the rigidity of the bladder's internal structure, ensuring it does not deform or break under load.

[0158] Furthermore, an adjustable fixing mechanism is installed at the top of the anchor bolt. This mechanism includes components such as spiral reinforcement, steel pads, positioning nuts, and precision nuts. By adjusting the positioning nuts and precision nuts, the steel pads can be kept at the same horizontal elevation, thus providing stable support for the superstructure such as the raft slab. Simultaneously, in large-span, high-load projects, diagonal bracing members can be added to the top of the anchor bolt to further improve the overall structural stability. This adjustable fixing mechanism can adapt to different engineering environments and load conditions, significantly enhancing the applicability of the invention.

[0159] Furthermore, compared to traditional multi-anchor combinations, the single anchor bolt in this invention can meet the needs of large-span, high-load projects. This is because the invention incorporates an expandable bag assembly at the bottom of the borehole, which not only increases the contact area and volume of the anchor body but also allows for precise adjustment of the bag's opening degree according to actual conditions, thereby significantly improving the overall load-bearing capacity of a single anchor bolt. This design not only simplifies the construction process and reduces project costs but also improves construction efficiency.

Claims

1. A method for construction of a heat-shrinkable caged core balloon enlarged head anchor rod, characterized by, It comprises the following steps: S10, anticorrosion treatment is performed on the anchor rod body, epoxy asphalt is coated on the anchor rod body below the orifice to the bag mouth, the coating thickness is not less than 300 microns, and the rod body is wrapped with a heat shrinkable tube, the heat shrinkable tube is uniformly heated by a hot air gun to shrink and wrap the rod body; S20, anchor rod assembly is performed, buckle carriers are installed every 1500 mm on the rod body, a cage core bag is installed at the end of the anchor rod, horizontal bolts are used to lock the upper lock buckle sleeve and the compression sealing sleeve, and axial bolts are used to connect and fix the cage core bag and the upper lock buckle; S30, after the cushion layer is poured, positioning is performed according to the design drawing, and the hole distance error in the horizontal and vertical directions of the anchor rod is not more than 100 mm; S40, hole forming operation is performed, the drilling diameter is not less than 160 mm, the expansion head section hole diameter is not less than 700 mm, the length is not less than 3000 mm, and the clean water hole expansion time is controlled to be between 35 minutes and 60 minutes; S50, anchor rod lowering is performed, the anchor rod is inserted into the hole by artificial auxiliary drilling, the end of the rod body is not more than 100 mm from the hole bottom, and buckle carriers are arranged every 1500 mm on the rod body; S60, bag grouting is performed, ordinary Portland cement grouting is adopted, the cement slurry volume weight is not less than 1.82, the anchoring body 28-day strength is not less than 35 MPa, and the bag opening diameter reaches the design value through grouting monitoring; S70, supplementary grouting is performed 2 hours after grouting is completed, and cement slurry is injected into the hole; S80, after the raft waterproof construction is completed and before the raft steel bars are laid, the spiral bars, positioning nuts, steel pads and precision nuts are installed; S90, steel bars are welded on the steel pads as temporary supports, the positioning nuts are adjusted to make the steel pads keep the same elevation, and the raft horizontal bidirectional bars are welded and connected with the temporary supports; The relationship between the cage core bag assembly and the anchor rod body is defined by the following equation: ; In the formula, is the effective diameter of the bag after opening, unit: mm; is the diameter of the anchor rod body, unit: mm; is the distance along the length direction of the bag, unit: mm; is the total length of the bag, unit: mm; is the basic inflation coefficient, the value range is 4.2-4.8; is the fluctuation correction coefficient, the value range is 0.1-0.15; the equation uses a sine function to describe the opening shape of the bag, considering the non-uniform inflation characteristics of the bag during grouting, the opening degree change caused by the end constraint effect, and the nonlinear characteristics of material elastic deformation.

2. The method according to claim 1, wherein the method is characterized by, The step S10 specifically comprises the following steps: the anchor rod body is made of fine rolled steel bars, professional epoxy asphalt coating equipment is used to uniformly coat epoxy asphalt on the surface of the anchor rod body as an inner anticorrosion layer, the inner anticorrosion layer coating thickness is controlled to be not less than 300 microns, after the epoxy asphalt surface reaches the surface dry state, a heat shrinkable tube is sleeved outside the inner epoxy asphalt coating layer as an outer anticorrosion layer, a professional hot air gun is used to reciprocally move along the axial direction of the anchor rod body to heat, the heat shrinkable tube is uniformly heated and generates a thermal pressure shrinkage effect, and the heat shrinkable tube is tightly combined with the inner epoxy asphalt coating layer to form a double anticorrosion protection structure.

3. The method according to claim 2, wherein the method is characterized by, The step S20 specifically comprises: firstly, installing the buckle carrier along the length direction of the anchor rod body every 1500mm, the buckle carrier adopts a high-strength engineering plastic to make a ring-shaped buckle body, an annular groove with anti-skid lines is arranged on the inner surface of the ring-shaped buckle body, the outer surface is provided with star-shaped array distributed radial positioning ribs, and the end of the radial positioning rib is equipped with an arc-shaped protective cap; then, sequentially installing the lock buckle, the sealing sleeve, the bag body, the cage core framework and the bottom locking part on the end of the anchor rod, using the transverse fixed bolt to form the locking and cooperation of the ring-shaped lock buckle body and the sealing sleeve, and fixing them on the anchor rod body, the sealing sleeve adopts an elastic material to form an interference fit with the rod body, the cage core framework is welded by the annular steel bars and the longitudinal connecting ribs and is placed inside the bag body, and the bag body is made of a flexible waterproof material and is fixedly connected with the anchor rod body through the bottom locking part.

4. The method according to claim 3, wherein the method is characterized by, The step S30 specifically comprises: after the concrete cushion layer is poured and reaches the design strength requirement, the anchor rod hole position is positioned by the survey personnel according to the design drawing label requirements, the anchor rod hole position is accurately positioned and measured by using a total station, the hole position is labeled by using lime, the hole distance error in the horizontal direction and the vertical direction of the anchor rod is strictly controlled to be not more than 100mm, self-inspection is performed after the measurement is completed and is reported to the supervision for auditing, and the subsequent construction operation can be performed after the supervision approval is obtained.

5. The method according to claim 4, wherein the method is characterized by, The step S40 specifically comprises: performing the hole forming operation by using professional drilling equipment, controlling the drilling diameter to be not less than 160mm, expanding the head section by using a special expanding drill to perform the hole expansion construction, the hole expansion diameter is not less than 700mm, the hole expansion section length is not less than 3000mm, the hole expansion operation is performed by using the clean water flushing hole process, the clean water hole expansion time is strictly controlled to be between 35 minutes and 60 minutes, the returned water condition is continuously observed until the returned water color is the same as the clean water color, and the drilling quality is ensured to meet the design requirement.

6. The method according to claim 5, wherein the method is characterized by, The step S50 specifically comprises: slowly inserting the heat-shrinkable cage core bag expansion head anchor rod along the drilling axial direction by the construction personnel cooperating with the drilling equipment, strictly controlling the distance between the end of the anchor rod body and the hole bottom to be not more than 100mm, and mainly observing the gap state between the radial positioning rib of the buckle carrier and the drilling wall during the lowering process, adjusting the lowering speed and angle to ensure that the radial positioning rib does not occur blocking phenomenon, and meanwhile, the buckle carrier is used to realize the center positioning effect of the anchor rod body in the drilling.

7. The method according to claim 6, wherein the method is characterized by, The step S60 specifically comprises: selecting the 42.5 grade ordinary portland cement to prepare the grouting slurry, strictly controlling the cement slurry container weight to be not less than 1.82, ensuring the anchoring body 28-day compressive strength to be not less than 35MPa through the test block test, installing professional grouting monitoring instruments on the grouting pipeline, and real-time monitoring the grouting pressure and the bag opening state, when the grouting monitoring instrument shows that the bag opening diameter reaches the design specified value and the system prompts to reach the stopping condition, the grouting operation can be terminated.

8. The method according to claim 7, wherein the method is characterized by, Step S70 specifically includes: 2 hours after the completion of the bag grouting operation, the borehole is supplemented with cement grout with the same ratio as the bag grouting. During the grouting process, the grout return at the borehole opening is closely observed. When the color and concentration of the returned grout are basically the same as the injected grout, the grouting is stopped to ensure that the grouting fullness meets the design requirements and effectively improves the strength of the anchor body.

9. The method according to claim 8, characterized in that, characterized in that, Step S80 specifically includes: before the raft foundation waterproofing construction is completed but before the raft foundation reinforcement is laid, installing the top fixing components, which in turn include spiral reinforcement, steel pad, positioning nut and precision binding nut. The spiral reinforcement adopts a spiral steel bar structure with a pitch of 50 mm and a twisted anti-slip texture on the surface. The steel pad adopts a square steel plate structure with diagonal reinforcing ribs of triangular cross section on the upper surface and positioning bosses distributed in a circumferential array at the edge of the lower surface. By adjusting the positioning nut and precision binding nut, the components form a stable locking connection.

10. The method according to claim 9, wherein the method is characterized by, Step S90 specifically includes: using a laser level to project a horizontal elevation control line, precisely adjusting the positioning nuts and tightening nuts to keep all steel pads in the same elevation plane, welding reinforcing bars on the steel pads as temporary support components, and welding and fixing the horizontal bidirectional reinforcing bars of the raft foundation to the temporary support after they are in place to form a stable support system. When the design thickness of the raft foundation exceeds 1500 mm, diagonal bracing components are added at the temporary support position of the anchor bolts to ensure the overall stability of the anchor bolt stirrups.

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