A construction method for pre-burying and positioning foundation bolts of a large vertical tower body

Abstract

This invention discloses a construction method for pre-embedding and positioning anchor bolts for large vertical tower foundations. It employs a combined positioning and reinforcement system integrating "reference center positioning, dual-control positioning using fixed radius and fixed chord length, and a double-constraint support system," effectively solving common technical challenges in the industry such as the large number, large diameter, deep embedment, easy displacement during casting, difficulty in controlling pre-embedding accuracy, high rework rate, and low construction efficiency of anchor bolts in large industrial towers. This method achieves high-precision positioning, high-stability fixing, and one-time pre-embedding of anchor bolts, ensuring that the spacing between adjacent bolts, circumferential coaxiality, concentricity, and verticality meet high-precision installation requirements. The measured accuracy indicators in engineering projects are: axis deviation ≤ 2mm, adjacent bolt spacing deviation ≤ 2mm, elevation deviation 0~+3mm, verticality deviation ≤ L / 450, and coaxiality and concentricity deviation ≤ 2mm.

Description

Technical Field

[0001] This invention belongs to the field of building engineering and industrial equipment installation and construction technology, and relates to a method for pre-embedding and positioning anchor bolts for the foundations of large vertical towers such as pulp and paper towers, thermal power desulfurization towers, wastewater anaerobic towers, emergency towers, absorption towers, and reaction towers. Background Technology

[0002] In pulp and paper making, thermal power, and environmental water treatment systems, pulp towers, desulfurization towers, anaerobic towers, emergency towers, absorption towers, and reaction towers are all large-diameter, high-tonnage, high-height-to-diameter ratio, and demanding vertical core equipment with stringent operational stability requirements. Their full-load weight can reach thousands of tons, placing extremely high demands on foundation settlement and bolt stress uniformity. Structural stability under extreme conditions must be guaranteed, and the quality of foundation bolt pre-embedding is mandatory. The accuracy of anchor bolt pre-embedding directly determines the tower installation quality and structural safety, characterized by a large number of anchors, large nominal diameters, deep embedment depths, and high precision requirements for ring-shaped group control.

[0003] Existing conventional pre-embedded processes have the following unavoidable technical defects: First, precision control is difficult and adjustment efficiency is low: the number of anchor bolts is large and the arrangement is dense. Traditional line-laying and positioning are prone to cumulative errors, and concentricity is difficult to guarantee. If deviation occurs, the positioning frame needs to be cut and welded repeatedly. Not only can the accuracy not meet the design requirements, but it will also seriously affect the construction period and cannot meet the high-precision control requirements of large vertical tower anchor groups.

[0004] Secondly, the positioning stiffness is insufficient, which easily leads to irreversible deviation: the bolt diameter is large and the embedment is deep, and the lateral pressure during concrete pouring is large, which easily causes deviation, tilting and floating; traditional processes mostly use single-layer positioning plates + steel reinforcement cages for positioning, which can only constrain the position of the upper part of the bolt, and cannot control the verticality of the middle and lower sections of the bolt with large embedment, which is very easy to cause the problem of "the upper part is straight and the lower part is deviated"; positioning relies on simple supports, which have insufficient stiffness, no independent anti-deviation system, poor overall stability, and are easily disturbed during the pouring process; Third, it has poor versatility and serious material waste: traditional positioning molds are mostly custom-made whole steel plates for single tower bodies, which cannot be adapted to tower body construction with different diameters and hole spacings, and cannot be reused. They are scrapped directly after the project is completed, resulting in serious material waste and failing to meet the requirements of green construction.

[0005] Fourth, the difficulty in adjusting the elevation and axis, the low rate of qualified pre-embedded parts, and the high rate of rework seriously affect the efficiency of equipment installation and the cost of construction period.

[0006] Therefore, developing a construction method for pre-embedded anchor bolts of large vertical towers that features high positioning accuracy, strong anti-disturbance capability, convenient construction, high versatility, and one-time molding has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the present invention aims to propose a construction method for pre-embedding and positioning anchor bolts for the foundation of large vertical towers in pulp and paper making, thermal power and environmental water treatment, so as to achieve overall rigid fixation of the anchor bolt group and effectively solve the technical pain points of pre-embedding misalignment, insufficient accuracy and high rework rate that are common in construction.

[0008] The technical solution of the present invention: A method for pre-embedding and positioning anchor bolts for the foundation of a large vertical tower is disclosed. The anchor bolts are fixedly installed inside the concrete of the tower foundation, arranged in a circular array with the central axis of the foundation as the geometric center. The positioning accuracy is such that the diameter error of the center circle is no greater than ±15mm, and the circumferential positioning error of the bolts is no greater than ±0.1°. The method includes the following steps: 1) Precise positioning of the reference center: A fixed positioning steel bracket is set on the periphery of the foundation. The cross positioning axis is tensioned with steel wire and the tension is corrected and tightened. A positioning steel plate is set at the intersection of the axes and welded to the surface steel mesh. The center control point is precisely positioned and marked by a total station. A short positioning steel bar is welded at the center point as the reference center. 2) Calculation of positioning parameters: Taking the center of the tower foundation as the reference, calculate the fixed radius of the bolt and the fixed chord length of the adjacent bolt. The fixed radius is the bolt center circle radius minus the bolt radius, and the fixed chord length is the center distance between adjacent bolts minus the bolt diameter. 3) Dual-control positioning and verticality and elevation correction: Dual-control positioning is adopted, which is "base circle center positioning + fixed radius + fixed chord length". The position of anchor bolts is determined one by one by combining top and bottom limiting methods. The bolt positioning is completed in sequence with the center reference steel bar as the rotation center. The verticality of the bolts is corrected in two directions by using a magnetic plumb bob, and the top elevation of the bolts is controlled by a level. After the positioning is qualified, the upper and lower ends of the bolts are spot welded to the surface layer and bottom layer steel mesh respectively to form multi-point constraints. 4) Double constraint support system: Limiting steel bars and diagonal supports are set at the top and bottom of the anchor bolts respectively, and welded with the foundation steel mesh to form a double rigid constraint system to resist the lateral pressure of concrete and vibration disturbance, and prevent bolt deviation and tilting. 5) Pre-pouring verification and acceptance: The center position, radius, chord length, elevation, verticality, and coaxiality of the bolts are fully verified. After all deviations meet the specifications, the bolt threads are wrapped with plastic film for protection before they can be concealed. 6) Concrete pouring and finished product protection: Layered, symmetrical and uniform pouring method is adopted to avoid unilateral stress; the bolts and support system must not be touched during the vibration process; a dedicated person is responsible for real-time monitoring and correction throughout the pouring process and before the initial setting of the concrete. After the initial setting, the final calibration is completed, and heat preservation, moisture retention and finished product protection measures are taken.

[0009] Further, in step 2) above, the positioning parameters are calculated as follows: the fixed-length radius and fixed-length chord length are calculated, and the center distance between adjacent anchor bolts is calculated using the formula: L = 2R1sin(θ / 2), where: L—center distance between adjacent anchor bolts, R1—radius of the bolt distribution circle, θ—corresponding central angle in radians. The corresponding central angle θ (radians) = θ (degrees) × π / 180, θ1 = 6.5°, θ2 = 7.0°, θ3 = 7.5°, θ4 = 8.5°, which is the bolt distribution angle along the circumference. The center distances of the bolts L1, L2, L3, and L4 are calculated respectively using L = 2R1sin(θ / 2); the anchor bolt diameter d is calculated, then: fixed-length radius r = R1 - d / 2; fixed-length chord length l = Ld, and the net distances between adjacent bolts l1, l2, l3, and l4 are calculated respectively.

[0010] The key innovations and beneficial effects of this invention are as follows: First, the single-point benchmark positioning method achieved accuracy indicators exceeding expectations. By using a single benchmark as the measurement reference for the entire system, and eliminating the cumulative errors caused by multi-level transmission through the principle of benchmark unification, the absolute accuracy of the basic positioning benchmark is guaranteed. Empirical studies have shown that this method's key accuracy indicators all surpass the design standards.

[0011] Secondly, an innovative dual-control positioning mechanism of "reference center positioning + fixed radius + fixed chord length" was constructed to double-check the circumferentially distributed bolt group, effectively ensuring the uniformity of bolt spacing and circumferential position accuracy. This system effectively overcomes common technical pain points in the industry, such as easy deviation during casting, difficulty in controlling positioning accuracy, cumbersome procedures, and high rework rate caused by the large number, large diameter, and deep embedment of anchor bolts in large industrial towers.

[0012] Third, a combined anchoring system with upper and lower double constraint support is constructed. The upper steel mesh, support frame and lower steel mesh are welded into an integral rigid structure. Limiting steel bars are added to the upper and lower ends of the pre-embedded bolts and welded to the steel mesh to form a spatial anchoring structure of "upper and lower clamping and overall constraint". This significantly improves the system's anti-disturbance ability and realizes the in-situ stability of the anchor bolts and one-time pre-embedding during the concrete pouring stage.

[0013] Fourth, the construction method improves both efficiency and economy. It avoids the high costs associated with rework, cutting, reinforcement, and secondary positioning in one step. Achieving "excellence from the first attempt" significantly reduces subsequent maintenance and rectification costs, resulting in substantial economic benefits.

[0014] Fifth, technical performance and application prospects. This construction method fundamentally solves the existing technical defects of low installation accuracy and poor displacement resistance of anchor bolts, and ensures the requirements of adjacent bolt spacing, circumferential coaxiality and perpendicularity. Attached Figure Description

[0015] Figure 1 This is a diagram showing the positioning of the foundation bolts for an anaerobic reactor.

[0016] Figure 2 Pre-embed a dual-control positioning diagram of "fixed radius + fixed chord length" for the anchor bolts.

[0017] Figure 3 for Figure 1 Section 1-1.

[0018] Figure 4 Detailed diagram of node A.

[0019] Figure 5 Detailed diagram of node B.

[0020] Figure 6 Detailed diagram of node C.

[0021] In the diagram: 1-M56 anchor bolt, length 1950mm; 2-200X200X8 thick steel plate; 3-Φ12 short steel bar as positioning mandrel; 4-M14 nut; 5-Φ16 steel bar fixed-length radius member; 6-Φ16 steel bar fixed-length chord member; 7-Φ12 steel bar support member. Detailed Implementation

[0022] The following description, in conjunction with the accompanying drawings, illustrates the embodiments.

[0023] A method for pre-embedding and positioning anchor bolts for the foundation of large vertical towers used in pulp and paper making, thermal power, and environmental water treatment is proposed. The method includes: 1. 48 M56 anchor bolts; 2. One 200x200x8mm thick steel plate; 3. A Φ12 short steel bar as a positioning mandrel; 4. M14 nuts; 5. Φ16 steel bar members with fixed length and radius; 6. Φ16 steel bar members with fixed length and chord length (4 different lengths); 7. Several Φ12 steel bars (approximately 1.10 meters long). The process is as follows: construction preparation → benchmark establishment and axis measurement → precise positioning of the benchmark center → component processing and cutting → dual-control positioning and adjustment → reinforcement of the upper and lower double-constraint support system → process verification and acceptance → symmetrical layered concrete pouring → real-time monitoring of the entire construction process → formwork removal and finished product curing → final acceptance and handover. The method includes the following steps: 1) Precise positioning of the reference center: Figure 1 , Figure 2 As shown, after the foundation reinforcement mesh is tied, a steel reinforcement support frame is used to weld the surface layer and the bottom layer reinforcement mesh to form an integral rigid skeleton. Fixed positioning steel supports are installed around the foundation, with the top surface of the supports extending 100mm above the foundation surface reinforcement mesh. 1.0mm diameter steel wires are tensioned on the supports to form a cross-shaped positioning axis for the tower foundation in both longitudinal and transverse directions. After calibration with a total station, approximately 1400N of tension is applied using turnbuckles. Colored warning signs are placed on the steel wires at 1.0m intervals to improve visibility and prevent workers from tripping.

[0024] Figure 3 , Figure 4 , Figure 6 As shown, a 200mm×200mm×8mm steel plate is welded to the surface steel reinforcement mesh at the center of the tower. The center point of the foundation and the "+" positioning axis are measured and laid out using a total station or high-precision theodolite, with a center point positioning error ≤0.5mm. A Φ12 short steel bar with a length of 60-80mm is welded at the center point as a reference positioning mandrel, serving as the measurement reference for the pre-embedded positioning of the anchor bolts.

[0025] 2) Calculation of Fixed-Length Radius and Chord Length Parameters: Taking the foundation of the anaerobic reactor tank with the largest diameter, highest height, and heaviest weight as an example, the fixed-length radius and chord length parameters are calculated as follows: The formula for calculating the center distance between adjacent anchor bolts is: L = 2R1sin(θ / 2), where: L is the center distance between adjacent anchor bolts, R1 is the radius of the bolt distribution circle, and θ is the corresponding central angle in radians. The corresponding central angle θ (radians) = θ (degrees) × π / 180, θ1 = 6.5°, θ2 = 7.0°, θ3 = 7.5°, and θ4 = 8.5° are the bolt distribution angles along the circumference. The bolt center distances L1, L2, L3, and L4 are calculated using L = 2R1sin(θ / 2).

[0026] If the anchor bolt diameter is d, then the fixed length radius r = R1 - d / 2, and the fixed length chord length l = Ld. Calculate the net distances l1, l2, l3, and l4 between adjacent bolts respectively.

[0027] 3) Dual-control positioning of fixed radius and fixed chord length: Figures 2-6 As shown, M14 nuts and Φ16 steel bars are welded together to form a fixed-length radius member. The length from the center of the nut to the end of the steel bar is the fixed-length radius r. The fixed-length chord member uses Φ16 steel bars. The cutting length is controlled according to the calculated lengths l1, l2, l3, and l4 above. The cutting length deviation is ±0.2mm. The ends are ground flat.

[0028] Positioning of the first anchor bolt: Figure 2 As shown, with the central positioning mandrel as the reference, the nut of the fixed-radius rod is sleeved on the mandrel. The midpoint of the fixed-length chord rod l3 is aligned with the positioning axis Y. The position of the first anchor bolt is determined by the fixed-radius + fixed-length chord double control. If there is a conflict with the surface layer and the middle layer steel mesh, the steel bar is moved appropriately by a pry bar and welded to fix it. It is strictly forbidden to cut the stressed steel bar at will.

[0029] After the bolt position is determined, a magnetic plumb bob is used to check the verticality in both directions. The allowable deviation of verticality is ≤L / 450 and ≤5mm (L is the effective length of the bolt). A level is used to control the elevation of the top surface of the bolt. The elevation error is controlled to be 0 to +3mm. Negative deviation is not allowed. The thread length of the double nut is ensured.

[0030] Figure 2 , Figure 5 , Figure 6As shown, using the central mandrel as a reference, each bolt is positioned, corrected, and fixed sequentially along the circumference clockwise or counterclockwise using a "double control + top-mounted combination" method. An error check is performed each time the bolt is installed to the X position of the positioning axis. The deviation from the bolt center to the axis is ≤2mm to eliminate cumulative errors and ensure that the circumferential coaxiality, concentricity, spacing, and perpendicularity all meet the design and specification requirements.

[0031] 4) Dual constraint support system: Figure 3 As shown, the surface and bottom steel meshes are connected into a rigid skeleton by a steel support frame; limiting steel bars are set at both ends of the anchor bolts and welded to the steel mesh to form a double constraint system to resist the lateral pressure of concrete and vibration disturbance, and prevent deviation and tilting. After the bolt elevation and verticality are checked and approved, the upper part is fixed to the surface steel mesh by spot welding with Φ12 short steel bars.

[0032] Figure 3 As shown, the lower anchoring end is fixed by welding three Φ12 steel bars to the bottom steel mesh; the angle of the inclined support should be greater than 45° to ensure the rigidity and stability of the support system and avoid bolt displacement caused by pouring disturbance.

[0033] 5) Pre-embedded accuracy verification and acceptance: Before concrete pouring, the center point, radius, chord length, elevation, and verticality shall be fully verified. The control indicators are as follows: axis deviation ≤ 2mm; adjacent bolt spacing deviation ≤ 2mm; elevation deviation 0~+3mm; verticality deviation ≤ L / 450 and ≤ 5mm; circumferential coaxiality and concentricity deviation ≤ 2mm. After the verification is qualified, the bolt threads shall be wrapped with plastic film for protection before concealment and concrete pouring.

[0034] 6) Concrete Pouring and Finished Product Protection: The tank foundation is made of large-volume concrete, which is poured in layers, symmetrically, and uniformly, with symmetrical vibration to avoid concentrated loads on one side; the vibrator must not directly touch the anchor bolts and support system. A dedicated person monitors the pouring process in real time, and any deviations are corrected immediately; the final accuracy calibration is completed before the concrete initially sets, and after final setting, it is promptly covered and moisturized for curing. A film covering + water-retaining insulation curing method is adopted to control temperature difference cracks and protect the embedded finished products.

Claims

1. A method for pre-embedding and positioning anchor bolts for the foundation of a large vertical tower, wherein the anchor bolts are fixedly installed inside the concrete of the tower foundation, arranged in a circular array vertically in a circumferential manner with the central axis of the tower foundation as the geometric center. The positioning accuracy is such that the diameter error of the center circle is no greater than ±15mm, and the circumferential positioning error of the bolts is no greater than ±0.1°. The method is characterized by... Includes the following steps: 1) Precise positioning of the reference center: A fixed positioning steel bracket is set on the periphery of the foundation. The cross positioning axis is tensioned with steel wire and the tension is corrected and tightened. A positioning steel plate is set at the intersection of the axes and welded to the surface steel mesh. The center control point is precisely positioned and marked by a total station. A short positioning steel bar is welded at the center point as the reference center. 2) Calculation of positioning parameters: Taking the center of the tower foundation as the reference, calculate the fixed radius of the bolt and the fixed chord length of the adjacent bolt. The fixed radius is the bolt center circle radius minus the bolt radius, and the fixed chord length is the center distance between adjacent bolts minus the bolt diameter. 3) Dual-control positioning and verticality and elevation correction: The "base circle center positioning + fixed radius + fixed chord length" dual-control positioning is adopted to determine the position of each anchor bolt; the bolt positioning is completed in sequence with the center reference steel bar as the rotation center; the verticality of the bolt is corrected in two directions with a magnetic plumb bob, and the bolt top elevation is controlled with a level; after the positioning is qualified, the upper and lower ends of the bolt are spot welded to the surface layer and the bottom layer steel mesh respectively to form multi-point constraints; 4) Double constraint support system: Limiting steel bars and diagonal supports are set at the top and bottom of the anchor bolts respectively, and welded with the foundation steel mesh to form a double rigid constraint system to resist the lateral pressure of concrete and vibration disturbance, and prevent bolt deviation and tilting. 5) Pre-pouring verification and acceptance: Conduct a comprehensive verification of the bolt center position, radius, chord length, elevation, verticality, and coaxiality. After all deviations meet the specifications, wrap the bolt threads with plastic film for protection. 6) Concrete pouring and finished product protection: Layered, symmetrical and uniform pouring method is adopted to avoid unilateral stress; the bolts and support system must not be touched during the vibration process; a dedicated person is responsible for real-time monitoring and correction throughout the pouring process and before the initial setting of the concrete. After the initial setting, the final calibration is completed, and heat preservation, moisture retention and finished product protection measures are taken.

2. The construction method for pre-embedding and positioning anchor bolts for a large vertical tower foundation according to claim 1, characterized in that... Step 2) Calculation of positioning parameters: Calculate the fixed-length radius and fixed-length chord length parameters. The formula for calculating the center distance between adjacent anchor bolts is L=2R1sin(θ / 2), where L is the center distance between adjacent anchor bolts, R1 is the radius of the bolt distribution circle, and θ is the corresponding central angle in radians; the corresponding central angle θ in radians = θ degrees × π / 180, θ1=6.5°, θ2=7.0°, θ3=7.5°, θ4=8.5° is the bolt distribution angle along the circumference; calculate the bolt center distances L1, L2, L3, and L4 respectively according to L=2R1sin(θ / 2); for the anchor bolt diameter d, the fixed-length radius r=R1-d / 2, and the fixed-length chord length l=L-d, calculate the net distances l1, l2, l3, and l4 between adjacent bolts respectively.

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