Construction method for precise positioning of gravity anchor prestressed pipeline

Abstract

The present application belongs to the field of bridge construction technology, and relates to a precise positioning construction method for gravity anchor prestressed pipe. The method comprises the following steps: construction preparation; anchor block foundation pouring and positioning frame manufacturing (including rear anchor chamber support frame and positioning frame); setting out the rear anchor chamber and installing the rear anchor chamber support frame; positioning frame manufacturing and installation; setting out the rear anchor surface slot and installation; positioning the special point in the frame body; installation of the prestressed pipe; precise adjustment of the position of the prestressed pipe; concrete pouring; and concrete curing (with the increase of the layer number, the steps from the third step are repeated until the pouring is completed. The present application ensures the balanced stress of the main cable of the suspension bridge, and the stable distribution and overall stability of the internal stress of the gravity anchor anchorage.

Description

Technical Field

[0001] This invention belongs to the field of bridge construction technology, specifically relating to a construction method for precise positioning of gravity anchor prestressed ducts. Background Technology

[0002] Gravity anchorages for suspension bridges are the end anchorage structures for the main cables of the suspension bridge. Relying on their own enormous weight and the frictional resistance and pull-out force between themselves and the foundation, they balance the enormous horizontal tension of the main cables. They are a key load-bearing foundation ensuring the overall stability of the bridge and belong to the category of gravity anchorage. Figure 1 As shown, the gravity anchor body consists of five parts: foundation, anchor block, cable saddle support, front anchor chamber, and rear anchor chamber. The gravity anchor can also be divided into an anchorage system and an anchoring system. The anchoring system comprises a cable strand anchoring connection structure and a prestressed anchoring structure. The cable strand anchoring connection structure consists of tie rods and their components, connecting plates, support cylinders, and support plates. The prestressed anchoring structure consists of ducts, extruded precast cables and anchorages, and anchor head protective caps. At the front anchor face, one end of the tie rod is connected to the cable strand anchor head, and the other end is connected to the connecting plate anchored to the front anchor face by the prestressed steel strands. To position and fix the prestressed ducts of the anchoring system, a prestressed duct positioning frame is required.

[0003] Positioning the prestressed duct in the anchorage main cable anchoring system is a crucial step in anchorage construction. Research has shown that steel supports are used for positioning, and bolts are installed on the positioning beams to achieve precise positioning of the prestressed duct. Therefore, the processing and installation accuracy of the steel supports, especially the installation accuracy of the positioning beams, directly affects the positioning accuracy of the steel duct.

[0004] Therefore, in the construction of gravity anchorages for suspension bridges, solving the problem of precise positioning of prestressed ducts is of paramount importance, especially since the processing and installation accuracy of steel supports and the installation accuracy of positioning beams directly affect the positioning accuracy of steel pipes. This is to ensure the balanced stress on the main cable of the suspension bridge and the stable distribution of stress within the gravity anchorage and the overall stability. Summary of the Invention

[0005] The purpose of this invention is to propose a construction method for precise positioning of gravity-anchored prestressed ducts, which enables precise positioning of prestressed ducts while achieving a high safety factor and high operational efficiency.

[0006] Before installing gravity anchor prestressed ducts, a three-dimensional coordinate system is first established for rapid positioning: the center line of the main cable of the anchoring system is taken as the X-axis, the center position of the rear anchor surface is taken as the origin of the coordinate system, and the Y-axis and Z-axis are established perpendicular to the X-axis to form an independent coordinate system; under this coordinate system, the three-dimensional spatial positioning of the positioning frame can be carried out quickly, reducing the probability of errors and facilitating verification; the rear anchor surface is located on the top surface of the rear anchor chamber and is the rear fixed surface of the cable strand anchoring connection structure; the front anchor chamber provides a conversion space for the cable strand anchoring connection structure after the cable is spread out. At the position of the front anchor surface, one end of the tie rod is connected to the cable strand anchor head, and the other end is connected to the connection plane of the prestressed steel strand anchored to the front anchor surface.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A construction method for precise positioning of gravity-anchored prestressed ducts involves establishing a three-dimensional coordinate system for preliminary positioning, followed by precise positioning of the gravity-anchored prestressed duct installation. A prestressed duct positioning frame is used for precise positioning and support of the prestressed duct. The specific steps are as follows: Construction preparation: Anchor block foundation pouring and prestressed duct positioning frame fabrication: The prestressed duct positioning frame consists of a positioning frame and a rear anchor chamber support; a) Fabrication of the rear anchor chamber support: The rear anchor chamber support is a frame structure composed of horizontal bars, vertical bars and diagonal bars, and the rear anchor chamber support contains multiple modules; b) Fabrication of the positioning frame: The positioning frame is made of welded steel sections and is set up in layers and blocks; each layer has at least two blocks; a positioning frame fabrication platform is built in a suitable site. When building the platform, the height of the four corners must be measured with a level to ensure that the platform is level; I-beams are welded on the platform in units according to the drawings; after the frame is welded, the frame is spatially checked on site, mainly measuring the length of the I-beams and the welding angles. 2) Lay out the anchor chamber and install the anchor chamber support frame: Weld the bottommost module anchor chamber support frame to the embedded parts in the anchor chamber step; 3) Installation of the positioning frame: The positioning frame is installed in layers and sections: Installation of the positioning frames in the first layer: Each positioning frame in the first layer has a vertical frame with an inclined surface perpendicular to the rear anchor chamber support; the upper part of the vertical frame away from the rear anchor chamber support has an upwardly protruding frame for welding connection to the positioning frame in the previous layer; the vertical frames of multiple positioning frames in the first layer are welded to embedded parts pre-embedded in the anchor block foundation through multiple vertical frames. The anchor block foundation is poured in layers, and the embedded parts are also installed in layers: in the positioning frames in the first layer, the vertical frame of the first positioning frame that is attached to the rear anchor chamber support is welded to the rear anchor chamber support; the vertical frames of other pipe positioning frames are respectively welded to the vertical frame of the positioning frame before them. 4) Layout and installation of the rear anchor groove: The aforementioned rear anchor support frame serves as the rear anchor support. It is precisely positioned using three-dimensional coordinate measurement with a total station to form the rear anchor reference surface. On this reference surface, the longitudinal and transverse axes of each anchor cup and the center of each anchor cup are precisely located using a total station, and painted markings are made as the reference lines for installing the anchor cups. The grooves for installing the anchor cups are processed into different sizes according to their spatial location, forming their respective spatial angles after installation. The corresponding anchor cups are anchored to the grooves, serving as guide tubes. The coordinates of the positioning disk are measured with a total station to ensure they match the design coordinates, thus achieving spatial positioning of the pipeline. 5) Location of special points in the middle of the frame: The special points in the middle of the frame refer to the starting control points of each stage and the spatial change points of the prestressed ducts, since the frame is installed in three stages and the prestressed ducts are spatially linear. During the layered pouring process, the slot opening and the position of the prestressed ducts should be laid out in a timely manner according to the pouring height. When laying out the slot opening and the position of the prestressed ducts, the main cable of the anchoring system is used as the X-axis, and the Y-axis and Z-axis are set in the other two directions of the vertical axis to establish a separate coordinate system. This allows for layout and verification based on the position coordinates, reducing the process of back-calculating construction coordinates and reducing calculation errors. 6) Installation of prestressed ducts: The guide device for prestressed ducts is made of steel plate. The guide device is disc-shaped, and the diameter of the disc is machined based on the inner diameter of the duct. A small hole is drilled in the center of the disc as a measurement mirror point. One disc must be machined for each specification of duct. When installing the duct, the disc is placed on the duct opening, and the center coordinates of the disc are directly measured and aligned with the design coordinates of the duct. Since the prestressed duct is long, it is difficult to install and position it in one go. Therefore, the duct is installed in two sections. 7) Precise adjustment of the prestressed duct position: A semi-circular positioning beam is welded to the prestressed pipe position on the positioning frame; positioning fine adjustment bolts are respectively set on both sides and the lower end of the semi-circular positioning beam. The positioning fine adjustment bolts accurately position the prestressed pipe from both sides and the lower end to achieve precise positioning of the prestressed pipe; after the center coordinates of the front pipe are adjusted to be qualified by the positioning fine adjustment bolts, the pipe end is sealed and the bolts are welded to the prestressed pipe for fixation. Layered concrete pouring and concrete curing are carried out. As the number of layers increases, repeat steps 3 through 8 until all pouring is completed.

[0008] This invention proposes a construction method for precise positioning of prestressed ducts in gravity anchors. The method employs steel supports for positioning and bolts on the positioning beams to achieve precise positioning of the prestressed ducts. The positioning frame consists of a positioning frame and a rear anchor chamber support. The positioning frame is supported on the already poured anchor concrete and the rear anchor chamber support. The positioning frame is firmly welded to the embedded parts of the layered concrete of the anchorage and the template on the rear anchor chamber support. Using the centerline of the main cable of the anchoring system as the X-axis and the center position of the rear anchor surface as the origin, Y-axis and Z-axis are established perpendicular to the X-axis, thus creating a separate coordinate system. Rapid positioning based on these three-dimensional coordinates ensures balanced stress on the main cable of the suspension bridge, stable stress distribution within the gravity anchorage, and overall stability. Attached Figure Description

[0009] Figure 1 A schematic diagram showing the division of the anchor body.

[0010] Figure 2 This is a schematic diagram of cable anchorage.

[0011] Figure 3-1 , 3-2 This is a schematic diagram of a gravity anchor.

[0012] Figure 4 This is a schematic diagram of the segmented structure of the rear anchor chamber support frame.

[0013] Figure 5 This is a schematic diagram of the segmented structure of the positioning frame.

[0014] Figure 6 Structural diagram of the first positioning frame and the rear anchor chamber support. Figure 7 This is a schematic diagram of the slot structure.

[0015] Figure 8 This is a schematic diagram of the prestressed steel strand designation on the front anchor face.

[0016] Figure 9 This is a schematic diagram of the front anchor surface, rear anchor surface, and steel strands.

[0017] Figure 10 Positioning diagram of special points in the middle of the positioning frame.

[0018] Figure 11 A plan view showing how prestressed ducts are precisely positioned using positioning plates and bolts.

[0019] Figure 12 This is a schematic diagram of the structure after the prestressed duct positioning frame is installed.

[0020] In the diagram: 1. Anchor block, 2. Support pier, 3. Front anchor chamber, 4. Anchor block foundation, 5. Support pier foundation, 6. Rear anchor surface, 7. Transverse post-cast strip, 8. Rear anchor chamber, 9. Front anchor chamber top cover, 10. Positioning frame, 11. Front anchor surface, 12. Main cable strand, 13. Cable strand anchoring reference surface, 14. Rear anchor chamber support frame, 15. Embedded parts, 16. Prestressed duct, 17. Semi-circular positioning beam, 18. Positioning fine-tuning bolt. Detailed Implementation

[0021] The present invention will be described in detail with reference to the accompanying drawings and specific embodiments; like Figure 2 As shown, and with reference Figure 3-1 , 3-2 Before installing the gravity anchor prestressed duct, a three-dimensional coordinate system is first established for rapid positioning: the center line of the main cable of the anchoring system is taken as the X-axis, the center position of the rear anchor surface is taken as the origin of the coordinate system, and the Y-axis and Z-axis are established perpendicular to the X-axis to form an independent coordinate system; under this coordinate system, the three-dimensional spatial positioning of the positioning frame can be carried out quickly, reducing the probability of error and facilitating verification; the rear anchor surface is located on the top surface of the rear anchor chamber and is the rear fixed surface of the cable strand anchoring connection structure; the front anchor chamber provides a conversion space for the cable strand anchoring connection structure after the cable is spread out. At the position of the front anchor surface, one end of the tie rod is connected to the cable strand anchor head, and the other end is connected to the connecting plate that is anchored to the front anchor surface by the prestressed steel strand.

[0022] A construction method for precise positioning of gravity-anchored prestressed ducts involves establishing a three-dimensional coordinate system for preliminary positioning, followed by precise positioning of the gravity-anchored prestressed duct installation. A prestressed duct positioning frame is used for precise positioning and support of the prestressed duct. The specific steps are as follows: Construction preparation: Anchor block foundation pouring and prestressed duct positioning frame fabrication: The prestressed duct positioning frame consists of a positioning frame and a rear anchor chamber support; the anchor foundation is also poured in layers; during layered pouring, the embedded parts are poured in layers, and the embedded parts are embedded at the corresponding positions at the lower end of the support frame; as the anchor foundation is poured in layers, the positioning frame can be installed simply by splicing the various units according to the elevation, thus improving work efficiency; a) Fabrication of the rear anchor chamber support: combined with Figure 4 The rear anchor chamber support is a frame structure composed of horizontal bars, vertical bars, and diagonal bars. The rear anchor chamber support includes five modules. The horizontal bars and vertical bars are made of I16 I-beams, and the diagonal bars are made of I10 I-beams. It is divided into 5 modules for assembly and construction. A total of 8 modules are set up, with a spacing of 1.25m between them, and connected by I10 connecting systems. b) Fabrication of the positioning frame: combined with Figure 5The positioning frame is made of welded steel sections and is arranged in layers and blocks. In this embodiment, the positioning frame is divided into three layers, with each layer having at least two blocks. A positioning frame fabrication platform is built in a suitable location. When building the platform, a level instrument is used to measure the height of the four corners to ensure that the platform is level. I-beams are welded on the platform in units according to the drawings. After the frame is welded, the frame is spatially checked on site, mainly by measuring the length of the I-beams and the welding angle. 2) Laying out the anchor chamber and installing the anchor chamber support frame: The operation steps and methods for laying out the anchor chamber are existing technologies and will not be explained in detail here; weld the bottommost module anchor chamber support frame to the embedded parts in the anchor chamber step; 3) Installation of the positioning frame: The positioning frame is installed in layers and sections: Combination Figure 6 The installation of the positioning frames in the first layer: Each positioning frame in the first layer has a vertical frame with an inclined surface perpendicular to the rear anchor chamber support; the upper part of the vertical frame away from the rear anchor chamber support has an upwardly protruding frame for welding connection to the positioning frame in the previous layer; the vertical frames of multiple positioning frames in the first layer are welded to the embedded parts 15 pre-embedded in the anchor block foundation through multiple vertical frames. The anchor block foundation is poured in layers, and the embedded parts are also installed in layers: In the positioning frames in the first layer, the vertical frame of the first positioning frame that is attached to the rear anchor chamber support is welded to the rear anchor chamber support; the vertical frames of other pipe positioning frames are respectively welded to the vertical frame of the positioning frame before them. 4) Layout and installation of the rear anchor groove: The aforementioned rear anchor support frame serves as the support for the rear anchor surface 6. It is precisely positioned using three-dimensional coordinate measurement with a total station to form the rear anchor reference surface. On this reference surface, the longitudinal and transverse axes of each anchor cup and the center of each anchor cup are precisely located using a total station, and painted markings are made as the reference lines for installing the anchor cups. The grooves for installing the anchor cups are processed into different sizes according to their spatial location, forming their respective spatial angles after installation. The corresponding anchor cups are anchored to the grooves, serving as guide tubes. The coordinates of the positioning disc are measured with a total station to ensure they match the design coordinates, thus achieving spatial positioning of the pipeline. The structure of the groove is as follows: Figure 7 As shown; 5) Combining Figure 10The positioning of special points in the middle of the frame: Because the frame is installed in three stages and the prestressed ducts are spatially linear, the special points in the middle of the frame refer to the starting control points of each stage and the spatial change points of the prestressed ducts. During the layered pouring process, the slot opening and the position of the prestressed ducts should be laid out in a timely manner according to the pouring height. When laying out the slot opening and the position of the prestressed ducts, the main cable of the anchoring system is used as the X-axis, and the Y-axis and Z-axis are set in the other two directions of the vertical axis to establish a separate coordinate system. This allows for layout and verification based on the position coordinates, reducing the process of back-calculating construction coordinates and reducing calculation errors. 6) Installation of prestressed ducts: The guide device for prestressed ducts is made of steel plate. The guide device is disc-shaped, and the diameter of the disc is machined based on the inner diameter of the duct. A small hole is drilled in the center of the disc as a measurement mirror point. One disc must be machined for each specification of duct. When installing the duct, the disc is placed on the duct opening, and the center coordinates of the disc are directly measured and aligned with the design coordinates of the duct. Since the prestressed duct is long, it is difficult to install and position it in one go. Therefore, the duct is installed in two sections. 7) Precise adjustment of the prestressed duct position: Combination Figure 11 A semi-circular positioning beam 17 is welded to the prestressed duct 16 on the positioning frame; positioning fine-tuning bolts 18 are respectively provided on both sides and the lower end of the semi-circular positioning beam 17. The positioning fine-tuning bolts accurately position the prestressed duct from both sides and the lower end to achieve accurate positioning of the prestressed duct; after the center coordinates of the front end duct are adjusted to be qualified by the positioning fine-tuning bolts, the duct end is sealed and the bolts are welded to the prestressed duct for fixation. Layered concrete pouring and concrete curing are carried out. As the number of layers increases, repeat steps 3 through 8 until all pouring is complete; the completed structure is as follows: Figure 12 As shown.

[0023] During the installation of the groove, the coordinate error between the front and rear anchor grooves and the center of the pipe is controlled within ±0.5cm, and the angle error is controlled within ±0.1°. The installation accuracy of the anchoring system is high, and the installation accuracy of the corresponding positioning frame is also high. The rear anchor chamber support with sufficient rigidity is used as the support for the rear anchor surface. The rear anchor reference surface is accurately positioned by three-dimensional coordinate measurement of the total station. On the reference surface, the longitudinal and transverse axes of each anchor cup and the center of each anchor cup are accurately positioned by the total station, and the paint marks are made as the reference line for installing the anchor cups. Before installing the first layer of positioning frames for the rear anchor chamber, the position of the bottom embedded steel plate must be accurately laid out and controlled. The position and elevation of the embedded steel plate are calculated according to the three-dimensional coordinates based on the gravity anchor structure diagram, and laid out at an appropriate floor height using a total station. After the concrete is correctly poured at the position of the embedded steel plate, the first section of the positioning frame is installed using a tower crane. During this process, measurements should be taken to check the installation position of the outriggers and the slope angle of the rear anchor chamber support frame. When verifying the slope of the rear anchor support frame, a total station is used to measure two points at the same offset on different positions of the slope, calculate the vertical and horizontal distances between the two points, and then calculate the horizontal angle of the slope using inverse trigonometric functions. The slope of the positioning frame can be controlled by adjusting the thickness of the steel plate below the outriggers based on the measurement results. After the bottom positioning frame is installed, the remaining parts can be installed according to the geometric relationship in the drawings. Before layered pouring, only the position of the special points at the top needs to be checked to avoid displacement of the positioning frame before final setting, which cannot be adjusted.

[0024] The prestressed duct positioning process using this method saves on the investment in positioning frame materials, reduces the investment in measuring instruments and personnel, and allows for step-by-step and segmented construction, reasonable organization, strict quality control, and shortens the construction cycle. It effectively saves resources, resulting in a total saving of 800,000 yuan and achieving good economic benefits.

[0025] The application of this construction method has improved the efficiency, accuracy, and safety of prestressed duct positioning. It provides a strong technical guarantee for the positioning of similar gravity-anchored prestressed ducts and similar embedded parts in the future, and has important guiding significance for promoting suspension bridge construction. The adoption of this prestressed duct positioning method has improved construction efficiency, shortened the construction period, ensured accurate positioning, produced excellent quality, and resulted in no safety accidents during construction. It has been commended by the supervisor and the owner, and has achieved good social benefits.

Claims

1. A construction method for precise positioning of gravity-anchored prestressed ducts, comprising establishing a three-dimensional coordinate system for preliminary positioning and then precisely positioning the installation of the gravity-anchored prestressed ducts, characterized in that: The prestressed duct positioning frame is used to accurately position and support the prestressed duct. The specific steps are as follows: Construction preparation: Anchor block foundation pouring and prestressed duct positioning frame fabrication: The prestressed duct positioning frame consists of a positioning frame and a rear anchor chamber support; a) Fabrication of the rear anchor chamber support: The rear anchor chamber support is a frame structure composed of horizontal bars, vertical bars and diagonal bars, and the rear anchor chamber support contains multiple modules; b) Fabrication of the positioning frame: The positioning frame is made of welded steel profiles and is arranged in layers and blocks; each layer has at least two blocks; 2) Lay out the anchor chamber and install the anchor chamber support frame: Weld the bottommost module anchor chamber support frame to the embedded parts in the anchor chamber step; 3) Installation of the positioning frame: The positioning frame is installed in layers and sections: Installation of the positioning frames in the first layer: Each positioning frame in the first layer has a vertical frame with an inclined surface perpendicular to the rear anchor chamber support; the upper part of the vertical frame away from the rear anchor chamber support has an upwardly protruding frame for welding connection to the positioning frame in the previous layer; the vertical frames of multiple positioning frames in the first layer are welded to embedded parts pre-embedded in the anchor block foundation through multiple vertical frames. The anchor block foundation is poured in layers, and the embedded parts are also installed in layers: in the positioning frames in the first layer, the vertical frame of the first positioning frame that is attached to the rear anchor chamber support is welded to the rear anchor chamber support; the vertical frames of other pipe positioning frames are respectively welded to the vertical frame of the positioning frame before them. 4) Layout and installation of the rear anchor groove: The aforementioned rear anchor support frame serves as the rear anchor support. It is precisely positioned using three-dimensional coordinate measurement with a total station to form the rear anchor reference surface. On this reference surface, the longitudinal and transverse axes of each anchor cup and the center of each anchor cup are precisely located using a total station, and painted markings are made as the reference lines for installing the anchor cups. The grooves for installing the anchor cups are processed into different sizes according to their spatial location, forming their respective spatial angles after installation. The corresponding anchor cups are anchored to the grooves, serving as guide tubes. The coordinates of the positioning disk are measured with a total station to ensure they match the design coordinates, thus achieving spatial positioning of the pipeline. 5) Location of special points in the middle of the frame: The special points in the middle of the frame refer to the starting control points of each stage and the spatial change points of the prestressed ducts, since the frame is installed in three stages and the prestressed ducts are spatially linear. During the layered pouring process, the slot opening and the position of the prestressed ducts should be laid out in a timely manner according to the pouring height. When laying out the slot opening and the position of the prestressed ducts, the main cable of the anchoring system is used as the X-axis, and the Y-axis and Z-axis are set in the other two directions of the vertical axis to establish a separate coordinate system. This allows for layout and verification based on the position coordinates, reducing the process of back-calculating construction coordinates and reducing calculation errors. 6) Installation of prestressed ducts: The guide device for prestressed ducts is made of steel plate. The guide device is disc-shaped, and the diameter of the disc is machined based on the inner diameter of the duct. A small hole is drilled in the center of the disc as a measurement mirror point. One disc must be machined for each specification of duct. When installing the duct, the disc is placed on the duct opening, and the center coordinates of the disc are directly measured and aligned with the design coordinates of the duct. Since the prestressed duct is long, it is difficult to install and position it in one go. Therefore, the duct is installed in two sections. 7) Precise adjustment of the prestressed duct position: A semi-circular positioning beam is welded to the prestressed pipe position on the positioning frame; positioning fine adjustment bolts are respectively set on both sides and the lower end of the semi-circular positioning beam. The positioning fine adjustment bolts accurately position the prestressed pipe from both sides and the lower end to achieve precise positioning of the prestressed pipe; after the center coordinates of the front pipe are adjusted to be qualified by the positioning fine adjustment bolts, the pipe end is sealed and the bolts are welded to the prestressed pipe for fixation. Layered concrete pouring and concrete curing are carried out. As the number of layers increases, repeat steps 3 through 8 until all pouring is completed.

2. The construction method for precise positioning of gravity-anchored prestressed ducts as described in claim 1, characterized in that: Step b specifically involves: setting up a positioning frame fabrication platform in a suitable location. When setting up the platform, a level instrument is needed to measure the height of the four corners to ensure that the platform is level; welding I-beams in units according to the drawings on the platform; after the frame is welded, the frame needs to be spatially checked on site, mainly measuring the length of the I-beams and the welding angles.

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