A 110kV booster station outgoing line construction method

Abstract

This invention discloses a construction method for a 110kV substation power transmission line, comprising four core steps: 1. Line and tower foundation re-survey, using professional measuring tools and methods to control the accuracy of parameters such as line straightness and turning angle; 2. Tower foundation construction, encompassing foundation pit preparation, pit excavation, rebar tying, formwork installation, concrete pouring and curing, strictly controlling pit opening dimensions, rebar welding quality, and concrete strength; 3. Tower erection, using cranes for segmented hoisting, standardizing lifting point settings, bolt tightening, and accessory installation to ensure tower structural stability; 4. Overhead line erection, employing tension-based conductor laying technology for graded conductor deployment, combined with sag adjustment, tension tower stringing, and accessory installation to ensure line erection quality. This invention, through standardized and refined process design, improves construction accuracy and efficiency, enhances the safety and stability of line operation, and is suitable for large-scale construction of 110kV substation power transmission lines.

Description

Technical Field

[0001] This invention relates to the field of substation construction technology, specifically a construction method for a 110kV substation power transmission line. Background Technology

[0002] The 110kV step-up substation transmission line is a crucial channel connecting the substation to the main power grid in the power system, and its construction quality directly affects the safety, stability, and economy of power transmission. In existing technologies, the construction of transmission lines involves multiple complex stages, including line re-survey, foundation construction, tower erection, and overhead line installation. The construction accuracy, process control, and safety management at each stage are critical to the overall project quality. However, traditional construction methods have the following shortcomings:

[0003] During line resurveying, inconsistent measurement methods and lax precision control can easily lead to deviations in line alignment and tower location shifts, affecting subsequent construction.

[0004] In the foundation construction, unreasonable calculation of pit dimensions, improper control of pit excavation slope, and non-standard reinforcement binding and concrete pouring processes may lead to insufficient stability of the foundation structure.

[0005] During the erection of iron towers, improper selection of cranes, unscientific setting of lifting points, and failure to meet the requirements for bolt tightening torque can easily lead to safety hazards or deformation of the iron tower structure.

[0006] Outdated stringing methods, low sag control accuracy, and non-standard accessory installation during overhead line installation may lead to risks such as wear and breakage during line operation.

[0007] The connections between different processes are loose, quality control standards are unclear, overall construction efficiency is low, and project quality is difficult to guarantee.

[0008] Therefore, given the complexity and high requirements of the construction of the 110kV substation transmission line, there is an urgent need for a systematic, standardized, and high-precision construction method to solve the above-mentioned technical problems and ensure project quality and construction safety. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of the existing methods and provide a construction method for a 110kV substation power transmission line.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a construction method for a 110kV substation transmission line, comprising the following steps:

[0011] S1, Line and Tower Foundation Re-survey: Using professional surveying equipment, a comprehensive survey of the line route, tower location parameters and terrain features is conducted, protective stakes are set up and data is recorded;

[0012] S2, Tower foundation construction: The foundation pit is constructed in sequence, including foundation pit preparation, pit excavation, steel bar processing and binding, formwork installation, anchor bolt fixing, concrete pouring, curing, formwork removal and pit backfilling.

[0013] S3 uses a crane to lift the iron tower components in sections to complete the tower body assembly, bolt tightening and accessory installation;

[0014] S4, Overhead line installation: The conductors and ground wires are laid out using tension laying, and the wires are tightened, sag adjusted, tension towers are hung, and accessories are installed to finally complete the grounding system construction.

[0015] Preferably, the specific steps for the S1 re-survey of the line and tower base are as follows:

[0016] S11, the measurement content covers the straightness of the line, the horizontal turning angle of the corner tower, the span, the elevation difference, the crossing position, the micro-section of the tower base, the foundation slope and the location of the drainage ditch;

[0017] S12 uses the forward and reverse mirror centering method to measure straightness, the repetition method to measure the turning angle, the stadia method to measure the span and height difference, and the stadia method of bisecting the intersection angle to measure the crossing.

[0018] S13, after re-measurement, auxiliary piles were set in the direction along and across the line of the center pile of the tower location, and protected with 300mm×300mm concrete. The line direction, pile number and tower leg number were marked, and the abandoned piles were removed.

[0019] Preferably, the specific steps for the basic pit division in step S2 are as follows:

[0020] Before excavation, prepare an excavation diagram including foundation dimensions and control parameters. Use a theodolite with an accuracy of ≥2″ and a 30m steel tape measure. For straight towers, use the theodolite to rotate 45° to locate the center of the foundation plate and the center of the column. For corner towers, first determine the second bisector stakes and then locate the control points.

[0021] After the pit is divided, check the foundation root opening and diagonal error, the torsion of the whole foundation and the displacement of the central pile;

[0022] The pit opening size is calculated using the formula: Pit opening size = Pit bottom slab cross-sectional size + 2 × soil slope coefficient × foundation depth. A 200mm working surface is reserved at the bottom of the pit, and the slope gradient is determined according to the soil quality.

[0023] Preferably, the specific steps for the foundation pit excavation in step S2 are as follows:

[0024] Mechanical excavation was the primary method, supplemented by manual cleaning. During the excavation process, the central pile and auxiliary piles of the tower site were protected. The pit depth deviation was controlled at +100mm / -0. For the excessively deep parts, stone paving and grouting were used.

[0025] Drainage ditches were constructed around the foundation pit. During excavation, the geological conditions were checked to ensure they were consistent with the design. Any abnormalities were reported immediately.

[0026] After excavation, two leveling operations are carried out: the first leveling operation before the foundation layer is poured, and the second leveling operation after the foundation layer is poured, to ensure that the foundation depth and exposed height meet the design requirements.

[0027] Preferably, the specific steps for processing and binding the reinforcing bars in step S2 are as follows:

[0028] The main reinforcement bars are made of HRB400 threaded steel, the stirrups are made of HPB300 round steel, the main reinforcement bar joints are made of double-sided lap welding, the distance of the weld joint from the bend is ≥10d, and the number of joints in the same section is ≤50% of the total number of main reinforcement bars.

[0029] Before binding the reinforcing bars, remove surface rust and oil stains. Use the figure-eight binding method. Use No. 22 iron wire for reinforcing bars less than 12mm, No. 20 iron wire for reinforcing bars between 12-25mm, and No. 18 iron wire for reinforcing bars more than 25mm.

[0030] The spacing error of the main reinforcement bars is ±5mm, the spacing error of the stirrups is ±20mm, and the bottom is set with concrete spacers of the same grade to ensure the thickness of the protective layer. The center position of the reinforcement cage is checked before it is put into the formwork.

[0031] Preferably, the specific steps for template installation and anchor bolt fixing in step S2 are as follows:

[0032] Use wood formwork with a thickness of ≥15mm. For columns that are more than 1m deep into the ground, use seamless whole formwork and apply release agent to the surface.

[0033] The base plate formwork is aligned using horizontal and vertical lines, while the column formwork is controlled by two theodolites to ensure that the inclination is ≤8‰ and the displacement is ≤10mm.

[0034] The formwork is reinforced with steel pipes. Angle steel supports are installed at the four corners of the base plate formwork, and a support is installed every 500mm for the column formwork. Wooden boards are placed at the ends of the supports.

[0035] Preferably, the specific steps for concrete pouring, curing, formwork removal, and foundation pit backfilling in step S2 are as follows:

[0036] When using ready-mixed concrete, chutes are used when the discharge height exceeds 2m, and immersion vibrators are used for compaction.

[0037] For each foundation, one set of 150mm×150mm×150mm test blocks (labeled with tower number, leg number, and date) were made, and both standard curing and curing under the same conditions were carried out respectively.

[0038] Cover with straw mats and water for curing within 12 hours after pouring. The curing period is ≥5 days and nights. When removing the formwork, the concrete strength is ≥25% of the design strength. After removing the formwork, wrap with plastic film to keep it moist.

[0039] Preferably, step S3, which involves using a crane to hoist the tower components in sections to complete the tower assembly, bolt tightening, and accessory installation, comprises the following specific steps:

[0040] Before assembly, check that the foundation root opening, diagonal and height difference meet the requirements, the foundation strength is ≥ 70% of the design strength, use a 25-70 ton crane for hoisting, set the hoisting points at the main material nodes, and the included angle between the hoisting point ropes is ≤ 120°.

[0041] When assembling tower components on the ground, assemble the tower legs first, then the tower body, and finally the tower head. Ensure that all bolts are tightened to 100%. When hoisting, pause the inspection when the hoisting component is 0.1m off the ground, and continue only after confirming that everything is correct.

[0042] Bolts are inserted in accordance with specifications. For three-dimensional structures, bolts are inserted from the inside out horizontally and from the bottom up vertically. For two-dimensional structures, bolts are inserted from the smaller side along the route. Anti-theft bolts are used for bolts under 8 meters. All other single-cap bolts are fitted with anti-loosening nuts. The tightening torque is in accordance with specifications. Bolts are tightened again after the line is laid.

[0043] Preferably, step S4, which involves tensioning and laying out the conductor and ground wire, tightening the wire, adjusting the sag, installing the tension tower wire and accessories, and finally completing the grounding system construction, comprises the following specific steps:

[0044] Laying sequence: φ6 nylon rope → φ14 nylon rope → φ13 guide wire rope → φ18 guide wire rope → φ24 traction wire rope → conductor. For complex terrain, drones are used to lay out the nylon rope.

[0045] Tensioners and conductor frames are set up in the tensioning field, temporary guy wires are installed on the tension tower, and the stringing pulleys are suspended in accordance with the connection requirements of "crossarm hanging point - insulator string - pulley";

[0046] When tightening the line, first adjust the sag of the furthest observation span, then adjust the nearest spans in turn. After the sag is qualified, mark it on the straight tower. Before hanging the line on the tension tower, set up an aerial temporary anchor. Complete the conductor connection through the pulley block and crimp the tension clamp.

[0047] The suspension clamp is installed using a chain hoist with a line lifter, the spacer bar is used to fix the clamp head rubber pad in place, and the jumper wire is installed in accordance with the design curvature.

[0048] After the tower is erected, a C15 protective cap is poured, and the grounding down conductor is bent with a special tool to ensure tight bonding with the main material and foundation surface.

[0049] Each tower leg is connected to the grounding electrode via a grounding down conductor. The grounding electrode is buried in accordance with the design requirements, and the overall grounding resistance meets the specifications.

[0050] Preferably, this also includes full-process quality control.

[0051] If the retest data does not match the design, report it to the supervisor and design unit in a timely manner for handling.

[0052] Before materials such as steel bars, concrete, and bolts are brought to the site, their certificates of conformity and inspection reports shall be checked, and samples shall be taken and sent for testing in accordance with regulations.

[0053] After the foundation and tower construction is completed, the acceptance shall be carried out in accordance with the construction quality inspection and evaluation procedures for 110kV~750kV overhead transmission lines, and a complete construction record shall be formed and archived.

[0054] Compared with the prior art, the beneficial effects of the present invention are:

[0055] Improve construction accuracy: The re-survey of the line and tower base adopts professional measurement methods such as the forward and reverse mirror centering method and the repetition method, and strictly controls the error range of parameters such as straightness, rotation angle, and span (e.g., straightness ≤ 50mm, rotation angle ± 1′30″) to ensure the accuracy of the line route, tower position and foundation positioning, and avoid subsequent rework.

[0056] Ensuring foundation quality: During foundation construction, precise pit calculations (such as pit opening dimensions combined with slope coefficients and burial depth), standardized steel bar welding (double-sided lap welding, staggered joint arrangement), formwork reinforcement (seamless formwork, verticality controlled by theodolite), and concrete curing (regular watering, curing period ≥ 5 days and nights) significantly improve the stability and durability of the foundation structure.

[0057] To improve the safety and efficiency of tower erection: 25-70 ton cranes are used for segmented lifting, with clear lifting point settings (at the main material nodes, the angle between the lifting ropes is ≤120°), bolt tightening standards (combining anti-theft bolts and anti-loosening measures), and foundation strength verification before lifting (≥70% of design strength), thereby reducing the risk of tower deformation and ensuring the quality of erection and construction safety.

[0058] To ensure the quality of overhead line installation: tensioning is carried out in stages in the order of "nylon rope → guide rope → traction rope → conductor", with the help of drones to cross complex terrain. Combined with precise sag adjustment (calibrating from the farthest span to the nearest span) and tension tower hanging technology (aerial anchoring + pulley block traction), the conductor is prevented from being worn or twisted, thus ensuring the safety of line operation.

[0059] Achieve standardized construction: By clearly defining the personnel allocation, tool requirements, quality inspection standards (such as concrete test block curing and bolt torque testing) and safety control measures (temporary guy wires and cross-crossing monitoring) for each process, we can achieve standardized management of the entire construction process, improve overall construction efficiency, and reduce project costs. Attached Figure Description Figure 1 Test block identification diagram Detailed Implementation

[0060] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0061] This invention provides the following technical solution: a construction method for a 110kV substation power transmission line, comprising the following steps:

[0062] S1, Line and Tower Foundation Re-survey: Using professional surveying equipment, a comprehensive survey of the line route, tower location parameters and terrain features is conducted, protective stakes are set up and data is recorded;

[0063] S2, Tower foundation construction: The foundation pit is constructed in sequence, including foundation pit preparation, pit excavation, steel bar processing and binding, formwork installation, anchor bolt fixing, concrete pouring, curing, formwork removal and pit backfilling.

[0064] S3 uses a crane to lift the iron tower components in sections to complete the tower body assembly, bolt tightening and accessory installation;

[0065] S4, Overhead line installation: The conductors and ground wires are laid out using tension laying, and the wires are tightened, sag adjusted, tension towers are hung, and accessories are installed to finally complete the grounding system construction.

[0066] Specifically, the steps for the S1 line and tower base re-survey are as follows:

[0067] S11, the measurement content covers the straightness of the line, the horizontal turning angle of the corner tower, the span, the elevation difference, the crossing position, the micro-section of the tower base, the foundation slope and the location of the drainage ditch;

[0068] S12 uses the forward and reverse mirror centering method to measure straightness (error ≤ 50 mm), the repetition method to measure the turning angle (error ± 1′30″), the stadia method to measure the span (error ≤ ± 1%) and height difference (error ≤ 0.5 m), and the stadia method of the bisecting line of the intersection to measure the crossing.

[0069] S13, after re-measurement, auxiliary piles were set in the direction along and across the line of the center pile of the tower location, and protected with 300mm×300mm concrete. The line direction, pile number and tower leg number were marked, and the abandoned piles were removed.

[0070] 1. Contents of Line Retest

[0071] The resurvey of the line includes: straightness of the line, horizontal turning angle of the corner towers, horizontal span and height difference between the center piles of the towers, measurement of crossovers, measurement of the line's protruding points and wind deflection, replacement of lost piles, measurement of the micro-section of the tower base, and location survey of the foundation slope and drainage ditch.

[0072] 2. Methods for retesting the line

[0073] For straight-line routes: the centering method using both forward and reverse mirrors is employed for measurement;

[0074] The horizontal rotation angle of the angle tower was measured using the repetition method.

[0075] Span, elevation difference, wind deflection, and micro-section of tower base: measured using the stadia method;

[0076] Crossing: Measurement using the angle bisecting line stadia method.

[0077] Construction Precautions

[0078] 1) The locations of all poles and towers in this project are marked by the installation of wooden stakes.

[0079] 2) Before construction, construction personnel must be familiar with the route map, plan and section drawings, tower and foundation details, tower location details and other relevant information provided by the design; be familiar with the traffic and terrain conditions along the route; determine the re-survey sequence, make good personnel assignments, and prepare re-survey tools, relevant technical data and record forms.

[0080] 3) The theodolite must be kept by a designated person and must be in its valid use period. It must be calibrated by the surveyor before and after get off work every day. If any abnormality is found, it should be checked or replaced immediately.

[0081] 4) During the retest, it is necessary to check whether the center stake of the tower is stable and whether there is any looseness; if it is loose, it should be stabilized before retesting.

[0082] 5) For any lost or damaged pole posts, the mileage and elevation shown on the longitudinal profile map of the route shall be used as the reference when replacing them. Replacement should be based on the design data, and the measurement accuracy should comply with the current regulations and design requirements for overhead line measurement technology.

[0083] 6) During the re-measurement, auxiliary stakes should be driven into the pole center stake along the longitudinal and transverse directions of the line, and protective measures should be taken. These stakes should be retained until the foundation acceptance is completed. The tower center stake, the corner tower bisector stakes, and the direction stakes must be protected with concrete and marked with the line direction, circuit, stake number, and tower leg number. Any useless stakes that are deemed unusable on-site during the re-measurement should be removed.

[0084] 7) When there are significant changes in the terrain along the line, or when there are obstacles crossing between towers, or when the design requires excavation of protruding earth and rock, the elevations of the tower center stake, the protruding points in the terrain, and the objects being crossed should be re-measured. The distance and elevation of areas where wind deflection may be insufficient should also be re-measured to verify against the design specifications.

[0085] 8) Original records must be kept for route re-surveys. After completion, a route re-survey report should be prepared and archived. If there are any discrepancies between the re-survey results and the design drawings, the project department must be notified and the issue should be addressed in conjunction with the supervisor and designer.

[0086] 9) Retesting should be suspended during heavy rain, strong winds, or dense fog.

[0087] 10) When re-measuring highways and railways, attention should be paid to oncoming vehicles, and a dedicated person should be assigned to supervise the measurement.

[0088] 11) When retesting live lines crossing each other, care should be taken to avoid electric shock caused by induced current, and a dedicated person should be assigned to supervise the measurement.

[0089] Specifically, the basic pit division steps in step S2 are as follows:

[0090] Before excavation, a pit-exploration diagram containing foundation dimensions and control parameters is prepared. A theodolite with an accuracy of ≥2″ is used in conjunction with a 30m steel tape measure. For straight towers, the center of the foundation plate (A″, B″, C″, D″) and the center of the column (A, B, C, D) are located by rotating the theodolite 45°. For corner towers, the bisecting stakes (FE1, FE2) are determined first, and then the control points are located.

[0091] Pit-digging steps (1) Corner tower pit-digging steps

[0092] ① Level the theodolite on the center pile O of the foundation, and check the distance between the front and rear spans and the rotation angle of the corner tower by aligning it with the foresight and back sights.

[0093] ② After ensuring that the measured angle of rotation of the angle tower is within 1′30″, calculate the degree of the bisection of the angle of rotation of the angle tower based on the measured angle of rotation.

[0094] ③ Rotate the theodolite according to the degrees calculated in ②, and drive out the bisection line stakes respectively.

[0095] ④ Align with FE1 and FE2, rotate 45°, and mark the center A of the foundation slab using the trigonometric leveling method according to the corresponding values ​​given in the foundation pit data table for this project. 〃 B 〃 C 〃 D 〃 And the center control points A, B, C, and D of the foundation top surface.

[0096] ⑤ Move the instruments to A respectively 〃 B 〃 C 〃 D 〃 Along with A, B, C, and D, respectively drive out the corresponding control stakes F1 to F8.

[0097] (2) Foundation pit for straight tower:

[0098] ① Place the theodolite on the center pile O of the foundation and level it. Align it with the foresight and backsight to check the straightness of the straight tower.

[0099] ② After ensuring that the straightness of the center pile of the tower foundation meets the specifications, rotate the theodolite 45° for both front and back views, and use the theodolite orientation and trigonometric leveling to mark the center A of the foundation slab. 〃 B 〃 C 〃 D 〃 And the center control points A, B, C, and D of the foundation top surface.

[0100] ③Then move the instruments to A respectively. 〃 B 〃 C 〃 D 〃 Align points A, B, C, and D with the foundation center pile O point and rotate 45° to drive out the corresponding control piles or alignment piles F1 to F8.

[0101] 3) Precautions for basic pit division

[0102] (1) Before the pit is divided, the construction technicians must carefully check the relevant data in the foundation construction drawings and the pit division diagram data list.

[0103] (2) The theodolite used in the pit-digging process should be an accuracy of not less than 2″ and be a qualified theodolite; the steel ruler should have a certificate of production qualification and an MC quality mark.

[0104] (3) After the pits are completed, the root opening, diagonal and the torsion of the entire foundation should be checked immediately. If the data after the check exceeds the requirements in (foundation pit quality requirements), the pits should be re-pitted.

[0105] (4) After the corner tower foundation pits are completed, another surveyor should check them and fill in the corner tower pit record.

[0106] (5) After all the foundation pits are completed, all auxiliary piles (for corner towers, displacement piles and second-order dividing piles should also be protected) should be properly protected as a basis for foundation inspection and acceptance.

[0107] (6) Generally, the bisecting line stakes should be set at a characteristic landform that is not easily damaged by human activity, more than 20m away from the center stake. The bisecting line stakes should be measured and checked by another person. If the site does not meet the conditions, the person should measure twice, at large and small angles, and check them separately.

[0108] Basic pit quality standards Basic root opening and diagonal (%) Anchor bolt type ±0.16, high tower ±0.08 whole foundation torsion 8′ Displacement of the center pile of the entire foundation (mm) Horizontal Line 24 Vertical Line 24 After the pit is divided, check the foundation root opening and diagonal error (anchor bolt type ±0.16%, high tower ±0.08%), the overall foundation torsion (≤8′) and the center pile displacement (horizontal / longitudinal ≤24mm); 5) Inspection of foundation pits (1) For the foundation pit inspection in flat areas (with four foundation legs at the same height), the relevant data can be directly measured with a steel ruler for verification.

[0117] 6) Pithead layout

[0118] (1) Calculation of the dimensions of the foundation pit layout (opening):

[0119] Before setting out the foundation pit, the dimensions of the pit opening should be calculated. Under the premise of ensuring construction safety, the amount of excavation should be reduced to save construction costs and speed up the construction progress.

[0120] 2) The working face at the bottom of the foundation pit is generally considered to be 200 mm. The slope of the excavation side is determined based on the actual conditions such as the soil quality, excavation depth, ground load, and soil stability.

[0121] The pit opening size is calculated using the formula: Pit opening size = Pit bottom slab cross-sectional size + 2 × Soil slope coefficient × Foundation depth. A 200mm working surface is reserved at the bottom of the pit. The slope gradient is determined according to the soil type (sand 1:0.75, sandy clay 1:0.5, clay 1:0.3, hard clay 1:0.15).

[0122] 1. Basic Pit Preparation

[0123] 1) This project requires that all center piles, bisecting piles, and direction piles be protected with concrete. The protection area for the center pile should be a square of 300mm x 300mm (length x width), and the height can be determined according to the actual terrain. However, formwork must be used for pouring; haphazard masonry is not permitted. The protective piles must be smooth and secure. If any damage or cracks occur to the protective piles, they should be repaired promptly.

[0124] 2) Basic pit preparation technology

[0125] (1) Before the excavation, the construction technicians should carefully study the drawings to become familiar with each construction drawing and understand the relationship between them.

[0126] (2) Before the foundation pit is dug, a foundation pit drawing should be prepared. The drawing should include all information and data related to the foundation pit to improve the efficiency and quality of the foundation pit.

[0127] (3) Before the foundation pits are dug, the line re-measurement must be confirmed to be correct before the foundation pits can be dug.

[0128] 3) Preparation of personnel for basic pit division

[0129] (1) Foundation pit excavation should be carried out by qualified surveyors who have received training. Unlicensed personnel are not allowed to engage in foundation pit excavation work.

[0130] (2) Before the foundation pit is divided, training and instructions on pit division techniques and methods should be given to technical personnel at all levels to ensure that construction technical personnel are proficient in the calculation and inspection methods of foundation pit division, thereby improving the technical level of technical personnel at all levels and the quality of pit division.

[0131] Specifically, the specific steps for the foundation pit excavation in step S2 are as follows:

[0132] Mechanical excavation was the primary method, supplemented by manual cleaning. During the excavation process, the central pile and auxiliary piles of the tower site were protected. The pit depth deviation was controlled at +100mm / -0. For the excessively deep parts, stone paving and grouting were used.

[0133] Drainage ditches were constructed around the foundation pit. During excavation, the geological conditions were checked to ensure they were consistent with the design. Any abnormalities were reported immediately.

[0134] After excavation, two leveling operations are carried out: the first leveling operation before the foundation layer is poured, and the second leveling operation after the foundation layer is poured, to ensure that the foundation depth and exposed height meet the design requirements.

[0135] 1. General requirements for foundation pit excavation

[0136] 1) The foundation excavation for this project will be mainly carried out by mechanical excavation, with manual cleaning as an auxiliary method.

[0137] 2) Before the excavation of the foundation pit, the on-site technical personnel should conduct on-site briefings for the person in charge of the excavation and the construction personnel to clarify the construction tasks and methods.

[0138] 3) Construction personnel should be familiar with the construction drawings and foundation construction card specifications for the foundation excavation, clearly understand the dimensions of the construction base surface, foundation pit depth, and height above ground, and frequently check and measure to prevent the foundation pit from being excavated too deep or not deep enough, and ensure the correct pit location to avoid rework.

[0139] 4) The depth of the foundation pit should be based on the designed construction base surface. If the design does not require a construction base surface, the ground surface of the center pile of the tower should be used as the reference.

[0140] 5) During the excavation of the foundation pit, the central pile of the tower and the auxiliary piles driven during the pit measurement should be protected as reference marks for verifying the top height of the column and the depth of the foundation. If they cannot be retained, the central pile of the tower position should be led out, and the height difference between the original central pile and the led-out pile should be recorded.

[0141] 6) When excavating foundation pits for corner towers, terminal towers, and leg foundations of unequal heights, the orientation must be carefully checked to prevent incorrect excavation.

[0142] 7) When excavating the foundation pit, drainage ditches should be built around the pit to prevent irrigation water or rainwater from flowing into the pit and causing the pit wall to collapse.

[0143] 8) While excavating the foundation pit, check whether the geology of the foundation pit is the same as the design geology. If the geology of the foundation pit is inconsistent with the design, or if ancient tombs, pipelines, faults, etc. are found, the project department should be notified in time.

[0144] 9) The deviation of the excavation depth of the foundation pit is +100mm to -0mm. Within the allowable range, the deepest pit shall be leveled. When the excavation depth exceeds the specified limit, the excess portion shall be treated with paving stone and grouting. For foundations with pre-extra-high deviations, the pre-extra-high deviation shall be taken into account within the pit depth.

[0145] 10) The first leveling is carried out before the foundation pad is poured, and the second leveling is carried out after the foundation pad is poured.

[0146] 11) During the excavation process, there should be a supervisor on the pit to observe the changes in the pit shape at any time to prevent collapse and injury.

[0147] 12) The soil excavated from the pit should be piled up at least 1.0 meter away from the pit opening to prevent the edge of the pit from collapsing under pressure.

[0148] 13) If the pit wall collapses partially during the excavation of the foundation pit, protective measures should be taken. When excavating the foundation pit at the tower site, the exposure time of the foundation pit should be minimized.

[0149] 14) Construction workers must wear safety helmets correctly and should pay attention to checking for changes in soil conditions, cracks or other abnormalities during construction.

[0150] 15) The excavation pit should be cleaned from top to bottom. After cleaning, the cross-sectional dimensions and pit depth should be measured and recorded.

[0151] 16) When excavating foundation pits mechanically, the following regulations shall be met.

[0152] (1) Select appropriate excavation machinery to prevent the excavation arm from being too short, which would make excavation difficult.

[0153] (2) Operators of excavating machinery should have a driver's license and are not allowed to operate the machine without a license. The machine should be carefully inspected before use to ensure that it is in good condition.

[0154] (3) There should be one person directing the excavation from the ground.

[0155] (4) After excavating to the designed depth, the bottom of the pit is trimmed manually and the loose soil is removed to prevent mechanical disturbance of the bottom soil.

[0156] 17) The excavation, pouring, and backfilling of the foundation must completely protect the central pile and auxiliary piles.

[0157] Specifically, the specific steps for processing and binding the reinforcing bars in step S2 are as follows:

[0158] The main reinforcement uses HRB400 threaded steel, the stirrups use HPB300 round steel, the main reinforcement joints use double-sided lap welding (lap length ≥ 5d, where d is the diameter of the steel bar), the distance of the weld joint from the bend is ≥ 10d, and the number of joints in the same section is ≤ 50% of the total number of main reinforcements.

[0159] Before binding the reinforcing bars, remove surface rust and oil stains. Use the figure-eight binding method. Use No. 22 iron wire for reinforcing bars less than 12mm, No. 20 iron wire for reinforcing bars between 12-25mm, and No. 18 iron wire for reinforcing bars more than 25mm.

[0160] The spacing error of the main reinforcement bars is ±5mm, the spacing error of the stirrups is ±20mm, and the bottom is set with concrete spacers of the same grade to ensure the thickness of the protective layer. The center position of the reinforcement cage is checked before it is put into the formwork.

[0161] Reinforcing bar binding

[0162] (1) When the foundation of this project has bottom slab reinforcement, attention should be paid to the binding sequence. After determining the center of the bottom slab and the four corners of the bottom slab reinforcement with a theodolite, the bottom reinforcement of the bottom slab should be bound first, then the column reinforcement cage should be bound, and finally the bottom reinforcement of the bottom slab should be bound.

[0163] (2) Before binding, the specifications and quantity of the steel bars should be checked, and their quality should be checked to ensure they meet the requirements and that the surface is clean. Any rust, oil stains, etc. should be removed.

[0164] (3) The main reinforcement joints should be staggered. The area of ​​the joints of the stressed reinforcement in the same section should not be greater than 50% of the total cross-sectional area of ​​the stressed reinforcement. When they are staggered, the distance between the two joints (based on the end of the nearest joint) should not be less than 35 times the diameter of the reinforcement and not less than 500mm.

[0165] (4) At the intersection of reinforcing bars, use wire to tie them. Use No. 22 wire for tying reinforcing bars with a diameter of less than 12mm, No. 20 wire for tying reinforcing bars with a diameter of 12mm to 25mm, and No. 18 wire for tying reinforcing bars with a diameter of more than 25mm. To prevent the reinforcing cage from tilting or deforming, tie the reinforcing bars in a figure-eight pattern, alternating between left and right sides. The openings of the column stirrups should be spaced apart and placed on the four corner main bars. The column stirrups should be perpendicular to the longitudinal direction of the reinforcing cage, and the ends of the stirrups should be bent inward.

[0166] (5) All foundation reinforcement bindings for this project must be completed in the pit. When binding, the positional offset between the center of the column and the center of the bottom slab reinforcement should be calculated to prevent the situation where the thickness of the protective layer of the main reinforcement of the column and the bottom slab reinforcement cannot be consistent after the formwork is erected.

[0167] (6) Before the foundation reinforcement is put into the pit, a sufficient number of concrete pads should be placed at the bottom of the pit according to the size of the reinforcement cage. The position of the pads should be able to ensure that the thickness of the bottom protective layer of the reinforcement cage meets the design requirements.

[0168] (7) Error requirements during binding: the spacing of main bars and the spacing of each row of main bars shall be ±5mm; the spacing of stirrups shall be ±20mm.

[0169] Specifically, the steps for template installation and anchor bolt fixing in step S2 are as follows:

[0170] Use wood formwork with a thickness of ≥15mm. For columns that are more than 1m deep into the ground, use seamless whole formwork and apply release agent to the surface.

[0171] The base plate formwork is aligned using horizontal and vertical lines, while the column formwork is controlled by two theodolites to ensure that the inclination is ≤8‰ and the displacement is ≤10mm.

[0172] The formwork is reinforced with steel pipes. Angle steel supports are installed at the four corners of the base plate formwork, and a support is installed every 500mm for the column formwork (each support has ≥2 points). Wooden boards are placed at the ends of the supports.

[0173] Basic template installation

[0174] 1) To ensure a smooth surface after demolding, use wood-covered formwork with a thickness of not less than 15mm. For square foundation columns embedded more than 1 meter into the ground, the formwork must be seamless and should be a single piece, not bamboo plywood, as this can easily result in a mosaic-like appearance. The formwork surface must be flat, the joints tight, and the strength reliable.

[0175] 2) The splicing and fixing of the plywood formwork for the columns shall use 100mm×50mm wooden strips. The wooden strips shall be arranged longitudinally, with one strip at each corner and two to eight strips evenly distributed in the middle on each side of the formwork. Horizontal reinforcing wooden strips flush with the formwork shall be provided on the top surface of the column and the ground. The formwork joints shall be tight, and there shall be no joints within 1 meter below the top surface of the column. A single piece of formwork shall be used.

[0176] 3) A layer of release agent should be applied to the contact surface between the formwork and the concrete. The release agent should be applied to the pit before it is lowered into the pit.

[0177] 4) For the base slab alignment, a rope can be stretched along both the horizontal and vertical lines, using a suspension method for centering and alignment. For the columns, two theodolites can be used to control the horizontal and vertical directions respectively; alternatively, a theodolite can be set up at the center stake, and the oblique distance at the corner of the formwork can be converted into a horizontal distance (trigonometric leveling method) for control. Finally, the center of the top surface of the formwork is found using the crosshair centering method and checked using trigonometric leveling. Each surface of the aligned base slab formwork should be level, with an inclination not exceeding 8‰ and a horizontal and vertical displacement not exceeding 10mm. The slope, height, cross-section, and root opening of the aligned column formwork must meet the design requirements.

[0178] 5) The base formwork is supported by angle steel at the four corners of the lower formwork. Horizontal supports are secured from all four sides using top bracing devices. Each step formwork layer is reinforced horizontally with steel pipes, with two reinforcements per step. Column formwork is supported every 500mm, with each support having at least two points, and each support is padded with wooden planks against the pit wall.

[0179] 6) The foundation column formwork should be secured with two extended support poles, and the support poles or scaffolding should be fixed after the formwork is aligned. When using scaffolding for fixation, it must be erected stably, and anti-sinking measures should be set at the bottom of the uprights.

[0180] 7) After all the formwork is erected, the dimensions of each part should be checked again. At the same time, attention should be paid to ensuring that the column formwork does not have a prismatic shape.

[0181] 8) To ensure the thickness of the protective layer for the main reinforcement bars, precast pads with the same grade as the foundation concrete and the same size as the protective layer thickness must be used to support the main reinforcement bars. The protective layer thickness of the column main reinforcement bars can be supported by square timber strips with the same thickness as the protective layer and a length not less than 2 / 3 of the column height. Two strips are inserted on each side, and they are pulled upwards while pouring the concrete.

[0182] 9) When erecting the column formwork, care should be taken to ensure that the supporting angle steel at the bottom does not enter the column cross-section.

[0183] 10) After each foundation formwork is erected, the project department's quality inspectors and supervising engineers must be notified to come to the site for inspection and approval before pouring can begin.

[0184] 11) For straight-line tower foundation columns, one clamping rod can be used for securing the formwork. For tension tower foundation columns, two clamping rods must be used for securing the formwork, and the clamping rods should be fixed after the formwork is aligned. When the foundation pit is wide, multiple sections of clamping rods can be extended, and several vertical supports should be added in the middle to prevent the clamping rods from bending. If scaffolding is used for fixing, it must be erected stably, and anti-sinking measures should be set at the bottom of the uprights.

[0185] Anchor bolt installation and fixing

[0186] 1) Anchor bolts can be fixed after the formwork is installed and fixed, or they can be fixed when the foundation column is poured up to the root of the anchor bolts. The choice depends on the size of the foundation column cross-section and the difficulty of concrete pouring.

[0187] 2) Before installation, the diameter, length, specifications, and welding dimensions of the anchor bolts must be checked. Welding dimensions include the bolt root opening, diagonal, and height difference between bolts. Installation is only permitted after everything meets design requirements. To facilitate anchor bolt installation, stirrups can be spot-welded to the anchor bolts. Spot welding should be done to ensure the anchor bolts remain in place without deformation, and the strength of the anchor bolts must not be compromised during the process. During transportation, handle with care to prevent deformation.

[0188] 3) Prepare anchor bolt clamps in advance according to the specifications, root opening, diagonal and column cross-sectional dimensions of the anchor bolts.

[0189] 4) The installation of anchor bolts usually involves first inserting the threaded part into the template hole of the anchor bolt clamp on the ground and fixing it with a nut. Then, the anchor bolt clamp and anchor bolt are installed into the column reinforcement cage. The foundation root opening and diagonal are adjusted to meet the design requirements, and then the clamp is fixed to the column formwork.

[0190] 5) After the anchor bolts are installed, the theodolite should be used to inspect the entire foundation. If any changes or errors are found, they should be corrected.

[0191] 6) The height of the anchor bolt threads protruding from the clamps should meet the requirements specified in the design drawings after the formwork is leveled. After the foundation is poured, the bolt threads should be coated with grease and protected with PVC sleeves or heat shrink tubing of similar diameter to prevent rust.

[0192] Specifically, the concrete pouring, curing, formwork removal, and foundation pit backfilling steps in step S2 are as follows:

[0193] When using ready-mixed concrete, use chutes when the discharge height exceeds 2m, and use immersion vibrators for compaction (compaction time 20-30s, moving distance ≤ 1.5 times the radius of action, insertion depth into the lower layer of concrete ≥ 50mm);

[0194] For each foundation, one set of 150mm×150mm×150mm test blocks (labeled with tower number, leg number, and date) were made, and both standard curing and curing under the same conditions were carried out respectively.

[0195] Cover with straw mats and water for curing within 12 hours after pouring (3 hours in hot weather). The curing period is ≥5 days and nights. When removing the formwork, the concrete strength is ≥25% of the design strength. After removing the formwork, wrap with plastic film to keep it moist.

[0196] Foundation casting

[0197] 1. Erection of the pouring platform:

[0198] 1) Before pouring, a pouring platform should be erected as required. Steel pipes should be used to set up crossbars on the pouring platform to prevent vehicles from moving. The pouring platform should be erected firmly and reliably. The material transport channel should be set up independently to ensure that the position of the formwork is not affected by the transport of materials during the pouring process, thus ensuring the correct position of the foundation.

[0199] 2) The area of ​​the pouring platform should be large enough to meet the requirements for concrete pouring.

[0200] 3) The surface of the casting platform should be flat and free of excessively high edges or other obstacles to prevent workers from accidentally falling into the pit.

[0201] 4) For foundation pits with a wide opening, steel pipes should be used to support the scaffolding at the platform every 2 meters to prevent the scaffolding from breaking under stress, and the bolts at the joints of the scaffolding must be fully connected and tightened.

[0202] 2. Concrete pouring

[0203] 1) Before pouring concrete, remove silt, debris and water from the pit, and check whether the anchor bolts, reinforcing bars and formwork meet the requirements of the design drawings.

[0204] 2) Before pouring concrete, dirt, soil and oil stains on the reinforcing bars inside the formwork should be cleaned.

[0205] 3) When the discharge height exceeds 2m, a chute should be used for discharge.

[0206] 4) When pouring concrete, start from one corner or one side and gradually extend to the surrounding area. When pouring concrete around the steel cage, pour the material evenly to prevent squeezing the steel cage.

[0207] 5) During the material feeding process, attention should be paid at all times to whether the formwork and supports are deformed, sinking, moving, or leaking grout, and whether the protective layer of the steel cage meets the requirements.

[0208] 6) The concrete pouring for one tower leg should be carried out continuously, and the interval should not exceed 2.5 hours.

[0209] 7) It is not advisable to pour concrete in the open air when it is raining.

[0210] 8) Quality inspection shall be carried out at the concrete pouring site in accordance with the following provisions:

[0211] (1) Slump: Check at least twice a day or for each foundation.

[0212] (2) Mixing ratio: Check at least twice per shift or per base, and control the weight error within the allowable range.

[0213] 9) Concrete test blocks are the basis for checking whether the concrete strength has reached the design strength, and their fabrication should comply with the following regulations:

[0214] Test blocks should be sampled and prepared during the pouring process at the pouring site. Concrete test blocks should be cured using both standard curing and same-condition curing methods. (Standard curing test blocks are collected by the team's quality inspector and sent to the standard curing room for unified curing, and then collected by the project department and sent to the laboratory for pressure testing.) When there is a special need, additional test blocks cured under the same conditions should be made. The strength testing of concrete test blocks should be conducted by a qualified testing unit.

[0215] The number of test blocks prepared should meet the following requirements: (1) Generally, one set of foundations should be taken for each iron tower foundation. When a single leg exceeds 100m... 3 One set should also be selected at that time; (2) For cast-in-place pile foundations, one set should be taken for each pile.

[0216] (3) When raw materials or mix proportions change, a separate preparation should be made; Specifications: 150×150×150 (mm) test block boxes are used uniformly.

[0217] Marking: Mark the surface of the test block with red paint after initial setting. Tower number, leg number, date.

[0223] 10) Concrete vibration:

[0224] Concrete vibration must be carried out mechanically. There must be two immersion vibrators on the construction site for interchange and backup. If the immersion vibrator cannot vibrate in certain construction areas, manual tamping should be used as a supplement, and a dedicated person should be in charge. The casing of the electric vibrator should be properly grounded and equipped with a leakage protection device.

[0225] When vibrating, proceed sequentially point by point, with a moving distance not exceeding 1.5 times the effective radius; start from the corners and edges, then move to the center. The distance between the vibrator and the formwork should not exceed half the effective radius of the vibrator (generally 400mm). The vibration time at each point must be carefully controlled, generally 20-30 seconds. Too short a time will hinder compaction and air bubble removal, while too long a time may cause concrete segregation, resulting in inconsistent concrete surface color. If the vibrator is placed too close to the formwork, it may push air bubbles to the edge, hindering their removal. Therefore, the vibrator should maintain a gap of approximately 150-200mm from the formwork to facilitate air bubble removal.

[0226] The vibrator should be inserted to a depth of no more than 500mm each time, and the depth into the lower layer of concrete should be no less than 50mm. During vibration, it should be inserted quickly and withdrawn slowly until the concrete is dense and uniform, the surface shows a layer of slurry, and there is no settling.

[0227] During the pouring and vibration of concrete, phenomena such as the rebar cage tilting may occur. Therefore, it is necessary to constantly measure and monitor the position, root spacing, and height difference of the rebar cage, formwork, and anchor bolts, and correct any deviations promptly. Special attention should be paid to ensuring that the height difference of the foundation top surface is within the allowable error range and formed in one go.

[0228] Concrete pouring should begin from the center of the column and gradually extend to the surrounding area to avoid squeezing and deforming the reinforcing bars to one side.

[0229] 11) Ground assembly of anchor bolts

[0230] The anchor bolts for this project are made of Q235 steel, and the anchor bolt stirrups are made of HPB300 steel. The anchor bolts are assembled using round steel welding. Before welding, the specifications, root opening, and diagonal dimensions of the anchor bolts should be carefully checked and strictly followed according to the design drawings, specifically the "Anchor Bolt Assembly Drawing." The welded anchor bolts should ensure sufficient stability to prevent deformation during transportation and alignment.

[0231] 12) Anchor bolt installation and alignment

[0232] (1) After the anchor bolts are installed on the column formwork, they should be aligned. Due to their large weight, additional reinforcement measures should be added to the column formwork, support frame, scaffolding or scaffolding to prevent the column formwork from sinking or deforming after the anchor bolts are installed.

[0233] (2) The exposed portion of the anchor bolts should meet the design requirements. During construction, all anchor bolts in each group should be adjusted to have the same slope and exposed height.

[0234] 3. Basic finishing (smoothing)

[0235] After the foundation is poured, a designated person should be responsible for finishing the top surface and the upper surface of the base plate. This finishing work must be done carefully and responsibly, ensuring the finished surface is flat, smooth, and aesthetically pleasing. Secondary finishing is strictly prohibited. During the finishing process, the height difference at the four corners of the foundation and the exposed height of the anchor bolts should be measured to ensure the flatness of the foundation surface and that the height difference between foundation sections meets the requirements. The height difference of the top surface of the foundation should be controlled by the exposed height of the anchor bolts.

[0236] Watering should begin within 12 hours of pouring the foundation. In hot, dry, and windy weather, watering should begin within 3 hours. During curing, straw mats or other coverings should be placed on the outside of the foundation formwork. The frequency of watering should be sufficient to keep the concrete surface constantly moist. The concrete should be watered for no less than 5 days and nights.

[0237] Basic demolding and backfilling 1. Basic demolding requirements 1) The concrete strength at the time of formwork removal should not be less than 25% of the design strength. Before formwork removal, the construction team must notify the supervising engineer and the project quality inspector in advance. The formwork can only be removed after the supervising engineer and the project quality inspector agree. At the same time, the concealed works acceptance should be carried out and the construction record should be made.

[0240] 2) When dismantling the mold, care must be taken to protect the base surface and edges from damage.

[0241] 3) After demolding, the concrete on the threaded part of the anchor bolts should be cleaned in time, and grease should be applied and then heat shrink tubing should be wrapped around it for protection.

[0242] 4) After demolding, wrap the column with plastic film and immediately pour water from the top of the column to reduce the evaporation of water from the foundation.

[0243] 5) Requirements for backfilling the foundation pit and burying dust-proof soil:

[0244] ① Before backfilling, plastic film should be wrapped around the outside of the column. After wrapping, water should be poured from the top of the column immediately to reduce the evaporation of water from the foundation.

[0245] ② Before backfilling, tree roots, weeds and other debris, as well as any water accumulation in the pit, should be removed. During backfilling, the soil should be compacted every 300mm of backfill, and water should be sprinkled while backfilling to maintain an appropriate moisture content in the soil to facilitate compaction. The compaction coefficient should be no less than 0.95.

[0246] During backfilling, secondary damage to the surrounding vegetation should be avoided.

[0247] ③ When backfilling the foundation, the ground surface should be restored according to the natural slope.

[0248] ④ After the foundation is backfilled, the technicians of each team should check the dimensions of each part of the foundation again and compare them with the data and design values ​​before backfilling, summarize the construction experience in a timely manner, and improve the construction methods.

[0249] ⑤ In areas where there is sufficient earthwork:

[0250] 1) If the four legs are in a plane, the four legs (including the middle part) are buried as a whole, taking the outer edge of the pit opening as the reference.

[0251] 2) If the two legs are in the same plane, the two legs (including the middle part) are buried as a whole, taking the outer edge of the pit opening as the reference.

[0252] 3) If the four legs are not in the same plane, they should be buried separately with the size of the pit opening of each leg extending 1m outward.

[0253] 2. Protective cap size

[0254] 1) After the tower is erected, the base plate of the tower foot should have good contact with the foundation surface. Steel plates should be placed in any gaps, and cement mortar should be poured in. For straight-line towers, the protective cap can be poured after inspection and approval. For tension towers, the protective cap should be poured after the lines are strung. The concrete grade for the protective cap is C15, and the mix proportions should be strictly followed during construction.

[0255] Specifically, step S3 involves using a crane to lift the tower components in sections, completing the tower assembly, bolt tightening, and accessory installation. The specific steps are as follows:

[0256] Before assembly, check that the foundation root opening, diagonal and height difference meet the requirements, the foundation strength is ≥ 70% of the design strength, use a 25-70 ton crane for hoisting, set the hoisting points at the main material nodes, and the included angle between the hoisting point ropes is ≤ 120°.

[0257] When assembling tower components on the ground, assemble the tower legs first, then the tower body, and finally the tower head. Ensure that all bolts are tightened to 100%. When hoisting, pause the inspection when the hoisting component is 0.1m off the ground, and continue only after confirming that everything is correct.

[0258] Bolt insertion direction conforms to specifications (for three-dimensional structures, horizontal direction from inside to outside and vertical direction from bottom to top; for planar structures, insertion is from the smaller side along the route). Anti-theft bolts are used for the section below 8m, and anti-loosening nuts are added to the remaining single-cap bolts. Tightening torque conforms to specifications, and the bolts are retightened after the line is laid.

[0259] Tower assembly

[0260] Construction preparation

[0261] The preparation work for crane tower assembly includes technical preparation, access roads, site leveling, anchor pile arrangement, and ground assembly of tower sections or tower frames.

[0262] Technical preparation

[0263] (1) Before erecting the iron tower, the foundation type, root opening, diagonal, relative height difference, corner tower angle and pre-offset value data should be carefully checked. Only after confirming that there are no errors can the iron tower be erected.

[0264] (2) Construction personnel participating in the tower erection must pass a physical examination at a county-level or higher hospital and purchase accident insurance. Special operation personnel must hold a certificate to work. All on-site construction personnel should receive safety technical training and briefing before tower erection and can only enter the construction site after passing the examination.

[0265] (3) Before erecting the tower, the technician and crane operator must investigate the access road and the on-site construction environment, conduct on-site measurements, and make written records. They must also repair the road and arrange the site in accordance with the requirements of the tower erection operation manual.

[0266] (4) Before the tower is erected, the certificates of conformity and factory quality certificates of the tower materials should be collected and sorted out, and the material issuance tracking record should be filled out in a timely manner. The tower bolts should be counted according to specifications and quantity, and should be classified and placed before use to facilitate use and prevent misuse, and confirmed to be consistent with the construction drawings.

[0267] (5) Large cranes must pass the annual safety inspection for special equipment and be insured in accordance with relevant regulations. Operators must hold driver's licenses and special equipment operation certificates. Safety status must be confirmed on site and a record must be made. The project department should improve the crane management working group and management system, identify risks throughout the entire lifting operation process, and formulate pre-control measures.

[0268] Access Road

[0269] Select a properly designed and convenient access route for the crane. Repair and reinforce any access routes that do not meet the requirements.

[0270] level ground

[0271] Based on the plan layout design of the crane tower, the assembly site and the crane placement site were leveled.

[0272] (1) Before leveling the site, remove or move any obstacles that may affect the hoisting of the iron tower.

[0273] (2) To ensure that the crane can operate continuously, the component assembly site must be able to accommodate all components to be assembled on the ground at once.

[0274] (3) The crane placement site meets the needs of the crane relocation operation.

[0275] (4) For firm ground, level the ground so that components or cranes can be placed securely on the firm ground. For soft ground such as mud or sandy soil, take measures such as laying gravel or steel plates to prevent components or cranes from sinking.

[0276] Equipment preparation

[0277] (1) Tools used for tower erection construction shall be inspected and marked by the project department's safety supervision department and engineering department. Only those that pass the inspection may be used in the construction of this project.

[0278] (2) The measuring instruments (vernier calipers, theodolites, torque wrenches, steel rulers) used in this project shall be inspected by a qualified testing unit and may only be used if they pass the inspection.

[0279] (3) Wire ropes shall be scrapped or cut if any of the following conditions are met:

[0280] a. For interlaced wire ropes, the number of broken wires within one lay (the axial distance of any one wire rope strand around the other) reaches 10% of the total number of wires in the rope.

[0281] b. Corrosion or wear of the steel wires on the surface of the wire rope reaches 40% of the original wire diameter.

[0282] The diameter of the steel wire rope was reduced by up to 7%.

[0283] The steel wire rope has obvious internal corrosion.

[0284] The surface of the steel wire rope is worn or corroded, and there is a certain number of broken wires. The number of broken wires should be determined by multiplying the reduction factor by the provisions of (1) and (2): when the wear or corrosion rate is 10, 15, 20, 25, 30-40% respectively, the reduction factor is 85, 75, 70, 60, 50%.

[0285] f The entire strand broke or burned.

[0286] g. In some areas, the outer layer of the steel wire rope elongates into a "cage" shape, or the diameter of the steel wire rope fiber core increases significantly.

[0287] The steel wire rope suffered severe deformation, including kinking, dead angles, hard bends, plastic deformation, and core detachment.

[0288] (4) When splicing wire rope sleeves, the length of the splice section shall not be less than 15 times the diameter of the wire rope and shall not be less than 300mm.

[0289] (5) The pulley must be inspected and lubricated frequently. Those with cracks or severe wear on the edges, deformed bearings, or cracks or obvious deformation in the hook must not be used.

[0290] Material preparation

[0291] (1) Before erecting the iron tower, the quantity and quality of the tower materials transported to the site must be counted and inspected. Those that do not meet the quality standards shall not be used, and those that lack main materials and steel casing shall not be erected.

[0292] (2) All bolts, washers and foot nails used for assembly must be complete, and attention should be paid to the different types of bolts.

[0293] (3) Tower sections that have been assembled on the ground are allowed to be hoisted only after they have passed inspection.

[0294] On-site setup

[0295] (1) Based on the tower structure and the erection site, level the site and remove obstacles that may affect the tower erection.

[0296] (2) Construction signs and safety warning signs are set up at the construction site, and materials are stacked neatly, which meets the requirements of civilized construction.

[0297] (3) Set up a safe working area at the construction site near the highway and village, and put up colorful flags and safety slogans on site.

[0298] Ground assembly of the integrated tower

[0299] The assembly orientation of the tower is determined based on the site terrain and crane location, and the centerline of the tower structure is established. The arrangement of the tower feet meets the requirements of the boom amplitude and lifting weight after the tower is lifted off the ground.

[0300] (1) The assembly sequence is first the tower legs, then the tower body, and finally the tower head, connecting them in sections from bottom to top.

[0301] (2) Each section of the assembled components has no less than four support points, and the support is stable and firm.

[0302] (3) The assembly method combines lifting components with manual installation of bolts.

[0303] (4) After the tower is assembled, it will be reinforced and strengthened according to the hoisting plan. The main reinforcement points are as follows:

[0304] For the tower legs, round logs or steel pipes are tied between the upper and lower tower legs to prevent deformation.

[0305] b. The weak points in the structure at the suspension point are reinforced with steel pipes or angle steel.

[0306] After the tower is assembled, all bolts are tightened to ensure they are within acceptable limits, preventing tower deformation during hoisting.

[0307] After the tower bolts are tightened, check the curvature of the main materials of each structural section and the dimensions of each part (especially the tower foot opening) to ensure they meet the design and acceptance specifications.

[0308] Ground assembly of decomposition tower

[0309] (1) The assembly site should be flat and clean, and obstacles should be removed. The tower sections should be arranged strictly according to the planned layout. The tower materials should be leveled with wooden supports between them and the ground. The position and number of supports should be such that the tower materials do not bend. Except for the temporary diagonal bolts, all other bolts, washers and shims should be connected according to the drawings and tightened on the ground. The bolt tightening rate and torque should meet the specifications.

[0310] (2) Before assembling the components, a comprehensive inspection of the component dimensions and appearance quality (including galvanizing quality) shall be carried out to confirm that they meet the design and relevant technical standards before assembly.

[0311] (3) When assembling in sections, the connecting plate is hoisted along with the main material or auxiliary material at one time, but the iron strip should be able to move freely and the nuts should be out of the thread.

[0312] (4) The orientation of components and the specifications and direction of bolts must be consistent with the design drawings to avoid rework at high points on the tower.

[0313] (5) Analyze the tower structure and list the position and weight of each lifting component of the decomposed tower.

[0314] All components that need to be assembled must be assembled before hoisting to facilitate continuous crane operation and improve construction efficiency.

[0315] (6) Calculate the boom length and boom working radius for each hoisting operation, and check whether the crane performance parameters meet the requirements.

[0316] (7) When components need to be stacked in three dimensions, the components that are hoisted later are assembled first, and the components that are hoisted first are assembled later. Square timber is placed between the layers of components to maintain stability.

[0317] (8) Based on the weight of each component, make sure that the heavier components are as close to the foundation as possible, and the lighter components are further away from the heavier components.

[0318] (9) Component assembly is carried out using a truck crane for lifting, while bolts are inserted manually. Key points for crane operation are as follows:

[0319] Crane operation must comply with the operating procedures and traffic rules related to automobiles. Before operation, place the boom on the support and hook it with a special steel wire rope; place the two support rods at the rear of the frame into the two supports below the rear (ensuring only slight stress on the support rods) and lock them with the locking nuts to improve the stress distribution when the turntable is moving; insert the locking brake into the pin hole to prevent rotation.

[0320] b. The work site must be firm and level. If the ground is soft or uneven, the support legs must be level and firm, and suitable pads should be laid on them. Work can only begin after safety has been confirmed.

[0321] During operation, it is strictly forbidden for anyone to stand under the crane boom; no one may sit in the driver's cab of the lower vehicle; heavy objects must not extend above the driver's cab, and lifting is prohibited in front of the vehicle.

[0322] When extending or retracting a telescopic crane boom, follow the prescribed sequence; lower the hook accordingly while extending the boom, and stop extending the boom immediately when the limit switch issues an alarm; the angle should not be too small when retracting the boom.

[0323] If the length of the front section is greater than the length of the rear section after the boom is extended, it must be adjusted to be normal before operation.

[0324] When operating at full load, carefully check the deflection of the crane boom. When operating laterally, pay attention to the condition of the outriggers. If any abnormalities are found, immediately lower the load and check and adjust it before continuing operation.

[0325] After the crane stops, the tilt angle of the entire machine should generally not exceed 1.5°, and the handbrake of the chassis vehicle must be locked.

[0326] When lifting heavy loads, the outrigger control valve handle must not be operated. If it is necessary to adjust the outriggers, the load must be placed on the ground and the boom must be positioned directly in front or behind before adjustment can be made.

[0327] For critical components of the crane, such as the boom, regular inspections should be conducted to check for cracks, deformation, and the tightness of connecting bolts. Any crane exhibiting any defects should not be used.

[0328] hoisting:

[0329] The hoisting plan will be determined based on the tower's weight. The tower can be erected either piecemeal or as a single unit.

[0330] Before hoisting, the hoisting sequence, weight, hoisting point location, and reinforcement method of the tower sections should be clearly defined. The principle of "hoisting the heaviest sections first and the lightest sections later" and "hoisting sections closer to the foundation first and assembling sections further away from the foundation later" should be followed, and on-site planning should be done in advance.

[0331] The main materials and tower sections assembled on the ground are only allowed to be lifted after the installation quality has been inspected and approved. The total weight of the assembled components must not exceed the maximum allowable lifting weight of the crane under the current working conditions.

[0332] When the base of a tower section is more than 5m or the lifting weight exceeds the crane's current operating weight, the same segmented lifting method as for the tower legs should be used.

[0333] The lifting point rope should consist of two steel wire ropes of equal length connected by a shackle, and the angle between the two lifting point ropes should not exceed 120°. The tying point of the lifting point rope should be at the node of the main material above the center of gravity of the lifting object. When the crane height is sufficient, it can also be set at the top node of the entire section.

[0334] During the lifting process, maintain a certain distance from the already installed tower body to prevent scratches and collisions. When the tower section is lifted to the installation height, slowly adjust the boom's elevation angle and direction until the tower section is in place. When lifting the entire unit, all four nodes need to be moved simultaneously. Workers at height need to cooperate with each other, moving the lower nodes first and then the higher nodes.

[0335] To prevent increased deformation of the root gap between the lower main materials caused by lifting from the top, a guide chain or double hook can be used to tighten the root gap before lifting from the ground to facilitate high-altitude positioning.

[0336] Depending on the tower type, the positions of the ground wire crossarm and conductor crossarm vary, requiring 3-6 hoisting operations per tower. The following are precautions to take during tower hoisting:

[0337] (1) Check whether the weight and height of the lifting parts meet the lifting performance of the crane, and overloading is strictly prohibited.

[0338] (2) During the lifting process, the lifting speed should be uniform, the lifting and lowering should be slow, and the lifting situation should be paid attention to at all times.

[0339] (3) When hoisting in sections, after the upper and lower sections are connected, it is strictly forbidden to use the method of rotating the crane arm to shift and align. Control ropes must be used for adjustment.

[0340] (4) When disassembling and assembling a steel tower, the arrangement of lifting points should refer to the requirements for tower assembly by crane. The lifting points of the steel tower assembled as a whole should preferably be selected at the node position above the center of gravity of the tower.

[0341] (5) When erecting towers near power lines, the crane must be properly grounded. The minimum safe distance from live parts must comply with the safety regulations.

[0342] (6) When the lifting part is about 0.1m off the ground, the lifting should be suspended and an inspection should be carried out. The lifting can only be carried out after it is confirmed that it is normal.

[0343] (7) If the crane malfunctions during operation, take measures to lower the tower components, stop operation and carry out maintenance. It is strictly forbidden to make adjustments or maintenance during operation.

[0344] (8) Lifting shall not be carried out when the commanding personnel cannot see the work site or the operators cannot see the command signals.

[0345] (9) The selection of the specifications of the suspension rope must be based on stress calculation.

[0346] Key points for crane tower erection operation:

[0347] (1) The crane station must be located on a flat and solid ground, and the crane outriggers must be firm and stable.

[0348] (2) After the tower legs are erected, two reverse guy lines with a 90° angle must be installed. The guy lines are φ13 steel wire ropes, and a 3t hand lever hoist is installed at the end of the guy lines for adjustment.

[0349] (3) When hoisting components or assemblies with a weight greater than 2t, the load condition table of the crane must be checked to confirm that it is within the safe load range.

[0350] (4) Before hoisting the tower head (crossarm), the tower height, crossarm weight and crane limit conditions should be checked to prevent and eliminate crane overload hoisting.

[0351] (5) Lifting weight control:

[0352] Before commencing operations, the on-site construction supervisor must confirm the crane's location and, once the working radius is determined, strictly control the lifting weight according to the crane's performance parameter table.

[0353] (6) Control during component lifting process:

[0354] a. When the component begins to be lifted, a dedicated person should be assigned to guard the end of the component that is touching the ground to prevent the tower material from deforming under stress.

[0355] After component b is lifted off the ground, hoisting should be suspended for a comprehensive inspection. Hoisting can only continue if no abnormalities are found.

[0356] A safety officer should be stationed on tower C to liaise with the ground commander, coordinate the work of personnel on the tower, and ensure close cooperation and unified action.

[0357] When the lower end of component d is hoisted above the upper end of the assembled tower section, the crane operator shall, according to the instructions of the operator on the tower, direct the crane to align the main material of the component with the main material of the assembled tower section and slowly position it for installation.

[0358] Crane use safety measures

[0359] (1) Lifting operations and high-altitude operations personnel should cooperate closely. Operators should stand to the side of the component being lifted, and non-construction personnel are prohibited from entering the crane's operating area. Pedestrians are strictly prohibited from passing within the boom's slewing range, and assembly work is strictly forbidden under the tower sections. During lifting, the lifted component must not pass over the crane head. Construction personnel are strictly prohibited from accompanying the lifted component during the lifting process.

[0360] (2) Before using the crane, its performance should be checked to ensure that all parts are in good working order before it is put into operation. The crane outriggers must not be directly supported on the ground. The crane outriggers must be supported on sleepers, and the area of ​​the sleepers must not be less than three times the area of ​​the outrigger base. A test lift must be conducted to prove that the outriggers will not sink. The crane should be parked on a level surface for operation, and the allowable tilt angle after parking must not exceed 3°.

[0361] (3) Before the hoisting operation, the crane operators, technicians and construction supervisors who participate in the hoisting of the iron tower should be familiar with the performance of the crane and the technical parameters of the tower piece to be hoisted, such as the lifting weight, height and center of gravity height.

[0362] (4) When directing crane operations, signals must be uniform, clear, correct, and timely. During the lifting process, the lifting situation must be closely monitored to prevent deformation of the main material and displacement of the lifting point. The lifting speed of the heavy object must be uniform and stable, and sudden changes in speed or height are not allowed to prevent the component from swaying in the air. The component should be lowered into place slowly, and the operator's instructions should be closely observed.

[0363] (5) The angle between the crane boom and the ground plane should be within the range specified by the crane's technical performance. Blindly extending the boom is prohibited. The crane must not be pulled at an angle to prevent the wire rope from getting caught or crushed outside the pulley groove. Overloading of the crane is strictly prohibited. The load on a single crane must not exceed 80% of its rated load, and the maximum elevation angle must not exceed 78 degrees. When the boom is fully extended and the jib is used, the elevation angle must not be less than 45 degrees.

[0364] (6) When hoisting heavy objects, the lifting platform should be 10cm off the ground for an impact test. Simultaneously, check the mechanical performance, whether the outriggers have sunk, and whether the binding is reliable before lifting smoothly, ensuring the hook reaches the top. When lowering the lifting platform, it must be lowered gently and at a uniform speed. Rotation should not be too fast, and sudden braking and changes in direction are prohibited. Lifted objects must not remain suspended in the air for extended periods. During lunch breaks or overnight stays, the lifting tower plates must be placed on the ground, and the (lifting) hook should be fixed to a sturdy object.

[0365] Installation of foot spikes and installation requirements

[0366] (1) The foot spikes are designed to be non-slip, and the hooks of the foot spikes are set at 135°. When foot spikes are used to replace bolts on joints or node plates, the diameter and strength grade of the foot spikes should be the same as those of the bolts being replaced, and the thread length should be sufficient to connect the connected rods.

[0367] (2) The anchor bolts should be installed approximately 1.5m above the top surface of the foundation, with a spacing of 400-450mm. For straight-type towers, the anchor bolts should be arranged on the main member on the right rear side (D leg) in the direction of line movement. The ground wire brackets should be installed symmetrically on the left and right sides of the main member in the front (A and D legs, rear side in the direction of line movement). For tension-type towers, the anchor bolts should be set on the B or D leg inside the corner. That is: when the line turns left, it is on the left front side (B leg); when the line turns right (including 0°), it is on the right rear side (D leg).

[0368] (3) The installation height of the anti-theft foot nails is consistent with the height of the anti-theft bolts on the tower legs.

[0369] (4) During installation, all the bends of the foot nails should be vertically upward to ensure uniformity.

[0370] (5) Straight-line towers (including straight-line towers with angles): The tower body and tower leg anchors are arranged on the right main member of the front (i.e., leg D, the right rear side in the direction of line travel). The ground wire brackets are installed symmetrically on the left and right sides, i.e., on the left and right main members of the front (legs A and D, the rear side in the direction of line travel). For double-circuit and multi-circuit towers, double-sided anchors are arranged on legs B and D.

[0371] (6) Straight-line angle towers and tension angle towers: The tension tower foot bolts are set on the B or D leg inside the angle. That is: when the line turns left, it is the left front side (B leg); when the line turns right (including 0° angle), it is the right rear side (D leg).

[0372] (7) All iron towers, except for anti-theft bolts and double-cap bolts, shall be equipped with anti-loosening devices.

[0373] (8) Grounding down conductor of the tower: When installing the grounding down conductor, special tools should be used for bending to avoid damaging the surface galvanized and concrete surfaces and edges. After installation, it should be tightly bonded to the main material, protective cap and foundation surface, and be straight and aesthetically pleasing.

[0374] Anti-theft and anti-loosening treatment for foot spikes

[0375] Anti-theft measures

[0376] All bolts and foot nails within 8m above the foundation of all tower types are made of anti-theft bolts. If there is a joint plate or joint at 8m, all bolts on it are made of anti-theft bolts.

[0377] Anti-loosening treatment

[0378] For single-nut bolts that were not fitted with anti-theft bolts, after the bolts have been tightened to the required standard after the tower installation is completed, all bolts should be fitted with anti-corrosion fastening nuts to prevent loosening.

[0379] Note the construction drawing instructions. If the construction drawing requires bolts with double caps, the double caps must be fully installed and at least flush with the head.

[0380] When installing tension towers, long and short crossarms should be distinguished. Long crossarms should be installed on the outer corner side. At the same time, the installation direction of the foot spikes should be checked.

[0381] Tower erection can only proceed after the foundation concrete strength reaches more than 70% of the design strength and passes intermediate inspection and acceptance.

[0382] Bolt and washer installation instructions

[0383] Where the tower assembly drawing requires the installation of double caps, the double caps must be fully installed and properly fastened. At the intersections of tower materials or the connections between plates and materials, shims or blocks should be used for leveling. The thickness of the shims and the number of shims should be based on the construction drawings during installation.

[0384] After the tower materials arrive, the bolts should be counted against the bolt delivery list in a timely manner. If the quantity does not match the list, the construction team or project department must be notified immediately.

[0385] All single-nut bolts use a combination of one washer, one nut, and one tightening nut; double-nut bolts use two nuts and one washer. The washer is installed on the nut side (i.e., the threaded side).

[0386] Regulations for bolted connections

[0387] For three-dimensional structures:

[0388] (1) Horizontally from inside to outside;

[0389] (2) The vertical direction should be from bottom to top;

[0390] (3) For those going at an angle, it is advisable to go from the bottom of the angle to the top of the angle. If this is inconvenient, they should take the same direction within the same angle.

[0391] For planar structures:

[0392] (1) Follow the direction of the route, enter from the smaller side or enter in the same direction;

[0393] (2) The horizontal line direction is from the inside to the outside on both sides, and from the left to the right in the middle or in a uniform direction.

[0394] (3) Those perpendicular to the ground direction are from bottom to top;

[0395] (4) For those going diagonally, it is advisable to go from the bottom of the slope to the top of the slope. If this is inconvenient, a unified direction should be taken within the same slope.

[0396] (5) For cross-shaped cross section composite angle steel main body connecting bolts, they should be installed clockwise.

[0397] Additional information on bolts:

[0398] (1) If individual bolts are difficult to install in the specified direction, their insertion direction may be changed.

[0399] (2) The crossbeam is divided by the center of the structure and is inserted from the center outwards; when the center is a single row of bolts, it is inserted from left to right (facing the larger side).

[0400] (3) The single row of bolts along the line is inserted from the smaller side to the larger side.

[0401] (4) The bolts at the conductor and ground wire suspension points should have double caps. Tension bolts must use double caps; when using double caps, the bolt thread must be either flush or protruding. See the tower installation diagram for details.

[0402] (5) When the unthreaded portion of the bolt is long, a washer should be added to the nut side before tightening to prevent the bolt from still rotating after tightening. However, the number of washers should not exceed two.

[0403] (6) The shims and small shims with steel grades indicated in the tower structure drawings are generally used for leveling the connecting components. During construction and installation, they must be placed between the two components that should be leveled, and are not allowed to be placed on the nut side. The quantity and specifications should meet the requirements of the structure drawings.

[0404] (7) The threaded portion must not enter the shear surface; otherwise, the bolt should be replaced.

[0405] (8) The wrench opening for tightening bolts should match the nut to prevent the wrench from damaging the edges and zinc layer of the nut.

[0406] (9) All tower connection bolts must be tightened once when the tower is assembled, and tightened again after the line is strung.

[0407] (10) Strictly follow the bolt specifications and bolt grades specified in the design drawings;

[0408] Bolt tightening requirements

[0409] Bolt configuration requirements

[0410] All tower bolts are fitted with thin lock nuts. Bolt symbols, weights, etc., shall be in accordance with the bolt table provided by the design unit.

[0411] (1) Single nut bolt: with 1 washer, 1 ordinary nut, and 1 thin anti-loosening and anti-disassembly nut;

[0412] (2) Double nut bolt: with 1 washer and 2 nuts;

[0413] (3) Anti-theft bolts: equipped with 1 washer, 1 ordinary nut, and 1 anti-theft nut;

[0414] (4) Foot nails: equipped with 1 washer, 2 ordinary nuts, and 1 thin anti-loosening and anti-disassembly nut.

[0415] (5) All bolts are hot-dip galvanized. The strength grades of ordinary bolts, anti-theft bolts, and foot nails meet the design requirements and are marked on the ends.

[0416] Bolt tightening torque requirements

[0417] (1) The components of the iron tower should be assembled tightly. Where there are gaps at the cross irons, shims of appropriate thickness should be installed. For bolts with a thread length greater than or equal to the thickness, shims should be added to the threaded end. When the required shim thickness exceeds 3 washers, shims of appropriate thickness should be used.

[0418] (2) Each bolt and foot nail is equipped with a flat washer, which is installed on the side of the stress-bearing fastening nut.

[0419] Gasket installation and bolt tightening requirements

[0420] (1) All tower bolts in this project must have a washer installed on the nut side, and the bolts should be tightened on the washer side; the washer of the foot nail is uniformly installed on the side close to the thread end, the thread on the hook side should be flush with the nut, and the foot nail is tightened on the side close to the thread end.

[0421] (2) The tightening quality of the tower bolts meets the requirements of the "Construction and Acceptance Specifications for 110-750kV Overhead Transmission Lines". The exposed length of the bolts after tightening meets the requirements of the acceptance specifications, and the exposed length of bolts of the same specification should be consistent.

[0422] (3) The gaskets and pads at the intersections shall be installed according to the construction drawings.

[0423] (4) For each section of the tower, all bolts must be tightened one by one. After the tower is assembled and the line is strung, they should be tightened again. The bolt tightening rate should reach 100%.

[0424] Post-construction work after tower erection

[0425] Protective hat

[0426] After the tower is erected, the base plate should be in good contact with the top surface of the foundation. If there are gaps, iron plates should be used as shims, and cement mortar should be poured in. After the tower is inspected, the protective cap can be poured immediately. During the construction of the protective cap, the top of the base in contact with the tower should be roughened and thoroughly cleaned before pouring the cap. The protective cap should be made of C20 grade fine aggregate concrete and vibrated to ensure compaction. The construction quality should be the same as the foundation, and its surface should be free of defects such as cracks and peeling. After demolding, the surface should be smooth.

[0427] The dimensions of the protective cap are based on the foundation construction drawings. Considering aesthetics, the surface is a smooth square pyramid. The top of the protective cap is smoothed into a 3%-5% micro-slope to meet the requirements of the drainage system.

[0428] Tower grounding down conductor

[0429] After installation, the grounding down conductor should be tightly bonded to the main material, protective cap, and foundation surface, straight, aesthetically pleasing, and with intact galvanized coating. Use specialized tools for bending during installation, taking care not to damage the galvanized coating, concrete surface, or edges of the down conductor.

[0430] Grounding connection

[0431] Tower hoisting should be carried out after grounding construction is completed. For this project, each leg of the self-erected tower must be connected to a grounding conductor (the grounding conductor should be driven into the tower's protective cap). Before tower erection, the location of the grounding holes should be checked to ensure they match the tower drawings. Towers that do not meet the requirements must not be erected, and the project management team should be notified immediately for handling. After the tower legs are erected, the grounding conductors should be connected immediately, and lightning protection measures should be implemented before the tower can be further erected.

[0432] Overhead line installation

[0433] Construction preparation

[0434] (1) Preparation of technical materials

[0435] Inventory the equipment and materials to ensure they meet design and construction requirements;

[0436] The construction drawings, towers, overhead lines, and construction instructions were checked and found to be consistent.

[0437] Select the tensioning section, and draw the entire line layout diagram based on the selection, clearly marking the section length, tower number, tower type, span, turning direction and angle, conductor layout code, excess wire length, joint position, crossing and other details of the laying section;

[0438] Clear the route;

[0439] Insulator withstand voltage test;

[0440] Tension clamp and splice gripping force test;

[0441] The construction tools and equipment have been inspected and tested to meet the construction requirements.

[0442] (2) Suspension of insulator strings and wire-laying pulleys for straight-line towers

[0443] 1) String shears suspension

[0444] The suspension system for a straight tower consists of, from top to bottom: crossarm hanging point, hanging plate, ball head hanging ring, insulator, cup head hanging plate, UB hanging plate, and three-wheeled wire-laying pulley.

[0445] Tension angle tower stringing pulley suspension: Two pulleys are suspended for each phase along the line direction, connected to the construction holes on the stringing plate; along the line direction, the stringing plate construction holes are connected to the pulleys via U-rings, tie rods, U-rings, and three-wheel stringing pulleys. The two pulleys are connected by angle steel connecting frames along the line direction, and a steel wire rope is used for safety between the U-ring and the main crossarm.

[0446] 2) Temporary tension wire installation

[0447] Temporary guy wires are installed at both ends of the tensioning section, with a tension steel anchor at one end and a UT clamp at the other end for adjustment.

[0448] 3) Suspension of the tensioning machine at the entrance and exit of the first tower for laying the line

[0449] The suspension of the stringing pulley at the first tower position of the tensioning machine's inlet and outlet adopts a low-hanging method.

[0450] Specifically, step S4 involves laying out the conductor and ground wire under tension, tightening the wire, adjusting the sag, hanging the tension tower wire, and installing accessories to finally complete the grounding system construction.

[0451] Laying sequence: φ6 nylon rope → φ14 nylon rope → φ13 guide wire rope → φ18 guide wire rope → φ24 traction wire rope → conductor. For complex terrain, drones are used to lay out the nylon rope.

[0452] Tensioners and conductor frames are set up in the tensioning field, and temporary guy wires (φ13 steel wire rope with 3t hand lever hoist) are installed on the tension tower. The suspension of the wire laying pulley meets the connection requirements of "crossarm hanging point - insulator string - pulley".

[0453] When tightening the line, first adjust the sag of the furthest observation span, then adjust the nearest spans in turn. After the sag is qualified, mark it on the straight tower. Before hanging the line on the tension tower, set up an aerial temporary anchor. Complete the conductor connection through the pulley block and crimp the tension clamp.

[0454] The suspension clamp is installed using a chain hoist with a line lifter, the spacer bar is used to fix the clamp head rubber pad in place, and the jumper wire is installed in accordance with the design curvature.

[0455] After the tower is erected, a C15 protective cap is poured (with a 3%-5% drainage slope on top). The grounding down conductor is bent using a special tool and tightly bonded to the main material and foundation surface.

[0456] Each tower leg is connected to the grounding electrode via a grounding down conductor. The grounding electrode is buried in accordance with the design requirements, and the overall grounding resistance meets the specifications.

[0457] Tension setting out construction

[0458] (1) Tension setting out construction method

[0459] The conductor and ground wire are laid using a straight-through tensioning method at the tension tower, followed by tensioning and balanced stringing at the tension tower. The optical cable is tensioned using a small-pull, small-tensioning method, with the tension section length matching the cable reel length. The conductors are erected using a one-pull, two-line-stretching method, with one large pulling machine at the traction site and one two-line tensioning machine at the tension field, pulling two conductors simultaneously. The conductors and ground wire are hydraulically connected.

[0460] 1) Layout of the tensioning field

[0461] The tensioning machine is arranged on the center line of the line in the direction of line laying. The large, medium and small tensioning machines are fixed with ground anchors. Four conductor frames are arranged behind the large tensioning machine, and the conductors emerge from the center axis of the reel.

[0462] Laying sequence: First lay the outer phase of the crossarm, then lay the inner phase of the crossarm, and finally lay the outer phase of the middle crossarm, with the left and right circuits laid in a crisscross pattern.

[0463] 2) Deployment of guide rope and traction rope

[0464] Lay the conductor and ground wire in the following order: φ6 nylon rope → φ14 nylon rope → φ13 guide wire rope → φ18 guide wire rope → φ24 traction wire rope → conductor.

[0465] In areas with complex terrain, thin nylon ropes are deployed using drones.

[0466] 3) Fiber optic cable laying

[0467] The optical cable is laid using the tension laying method, with a small traction machine and a small tension machine. The optical cable laying pulleys are special pulleys.

[0468] 4) Laying out the conductor

[0469] Tension release traction rope

[0470] φ13 guide wire rope → φ18 guide wire rope → φ24 traction wire rope → conductor

[0471] Tension wire laying

[0472] Place the traction rope on the traction wheel, start the traction machine to tighten the traction rope, release the temporary anchor, install and fix the traction rope on the tail car, tighten the traction rope, and when the conductor is pulled to the traction field, anchor it in time. After the conductor is laid out, if it needs to be turned around, leave a certain distance to facilitate the tightening operation and the placement of the remaining conductor.

[0473] If the spool runs out, stop traction, set a temporary anchor, remove the wire end for crimping, and after inspection and approval, use the tensioner to retrieve the remaining wire, release the temporary anchor, and continue laying the wire. Once the traction is in place, attach a temporary anchor and secure it to the conductor with a wire clamp. After the clamp is secured, release the conductor with the tensioner until the temporary anchor rope is under tension, cut the conductor, and lay the second conductor. To prevent conductor tangling, install conductor separators in long spans.

[0474] 5) Anchorage

[0475] Guide ropes and traction ropes: If the next process cannot be carried out in time after deployment, both ends of the ropes should be temporarily anchored.

[0476] After the conductors and ground wires are laid out, both ends should be temporarily anchored.

[0477] The conductor guide wheel anchor and end anchor consist of a wire clamp, plastic-coated steel stranded wire for the temporary anchor, a right-angle hanging plate, a chain hoist, and a ground anchor.

[0478] Balanced hanging line high-altitude temporary anchor: When hydraulically operated in the air, the temporary anchor clamp should be 10m away from the crossarm, and the temporary anchor should be softly hung; when hydraulically operated on the ground, the temporary anchor clamp should be 10m away from the crossarm at the hanging point height; when the temporary anchor line is tightened, the over-traction of the isolated span should be controlled within 100mm, and the over-traction of the continuous span should be controlled at around 200mm.

[0479] 6) Grounding

[0480] All mechanical equipment is grounded, and the grounding wire is a braided copper wire with a diameter of not less than 16mm2.

[0481] (2) Tight line marking

[0482] Before tightening the wires, inspect the direction and quality of the conductors and ground wires laid on the ground within the tightening section, the connection of the straight-line splicing pipes, the treatment of damage to the conductors and ground wires, and the obstruction facilities, and deal with any problems found in a timely manner.

[0483] (3) Remove the non-tension tower pulleys and suspend the tension insulator string and wire.

[0484] 1) Anchoring in the air

[0485] Install a tensioner on the outgoing line, cover it with a protective tube, make anchor holes on the crossarm hanging plate, and tighten the stranded wire to make the tensioner bear the force.

[0486] 2) Broken or loose wire

[0487] Use a 50KN pulley block to simultaneously tighten one side of the conductor until the other side is fully anchored. Tie on the slack rope, disconnect the conductor, and use the slack rope to loosen the conductor to the ground. At the same time, release the pulley block. Repeat the same method until all conductors of the same phase are disconnected.

[0488] 3) Dismantle the tension pulleys

[0489] Use a φ13 steel wire rope to loosen the pulley and assemble the tension insulator string.

[0490] 4) Suspend tension insulator strings

[0491] The tension insulator string was lifted into position and installed using a φ13 steel wire rope and a winch.

[0492] 5) Crimping

[0493] The conductor placed on the ground is crimped with a tension clamp for hanging.

[0494] 6) Hanging wire A 60KN two-way tensioning pulley is connected to the tensioning pulley via a special connecting plate. The pulley is tightened, and a 30KN steering pulley is installed near the crossarm hanging point to lead the wire to the ground winch, so that all the wires are hung in place.

[0496] (3) Tension tower hanging line

[0497] For anchoring in mid-air, broken or loose lines, and for tightly securing lines at high altitudes, the methods are the same as before.

[0498] After tightening the wire and marking it, observe the sag after the conductor is in place. Once the conductor is stable, use the crossarm hanging hole of the tension tower as a reference and measure from the sub-conductor to the hardware hanging hole with a rope ruler. Wrap tape around the rope ruler to make a mark.

[0499] Hanging the wire: Mark the guide wire according to the rope ruler, remove the relevant clamps and hardware, mark the guide wire again, cut the wire and crimp the corresponding clamps. Use the pulley block used for tightening the wire to hang the wire. Connect the equalizing ring, remove the workbench, and contact the temporary anchor.

[0500] (4) Release anchor and lift into the air

[0501] (5) Sag observation and straight-line tower marking

[0502] 1) Sag observation and adjustment

[0503] Measure the sag and compare it with the sag converted to the observation range. Adjust the sag plate to meet the design requirements.

[0504] Sag adjustment sequence: Tighten the conductor first to make the sag of the observation span farthest from the tensioning tower acceptable, loosen the conductor to make the sag of the observation span farthest from the tensioning tower acceptable, then tighten the conductor again to make the sag of the observation span closer to the tensioning tower acceptable, until all meet the requirements.

[0505] 2) Straight-line tower printing

[0506] Once the tensioning stress reaches the standard, keep the tensioning stress constant and simultaneously mark all straight towers within this tensioning segment.

[0507] (6) Installation of accessories

[0508] Accessory installation is the final step in overhead line construction, and this step should eliminate any problems that arose in the previous step. After the wires are tightened, the conductors and ground wires have reached their design stress, and accessory installation should be completed as soon as possible.

[0509] 1) Installation of suspension clamps: Generally, a chain hoist with a lifting device is used to install the suspension pre-twisted wire on both sides of the external lifting attachment.

[0510] 2) Spacer installation

[0511] Use a special tool to grip the movable clamp, insert the fixing pin, and assemble the spacer bar, clamping rubber post, and rubber pad into place. It must be clamped tightly when connected to the wire.

[0512] 3) Jumper installation

[0513] Specifically, this also includes full-process quality control.

[0514] If the retest data does not match the design, report it to the supervisor and design unit in a timely manner for handling.

[0515] Before materials such as steel bars, concrete, and bolts are brought to the site, their certificates of conformity and inspection reports shall be checked, and samples shall be taken and sent for testing in accordance with regulations.

[0516] After the foundation and tower construction is completed, the acceptance shall be carried out in accordance with the construction quality inspection and evaluation procedures for 110kV~750kV overhead transmission lines, and a complete construction record shall be formed and archived.

[0517] Improve construction accuracy: The re-survey of the line and tower base adopts professional measurement methods such as the forward and reverse mirror centering method and the repetition method, and strictly controls the error range of parameters such as straightness, rotation angle, and span (e.g., straightness ≤ 50mm, rotation angle ± 1′30″) to ensure the accuracy of the line route, tower position and foundation positioning, and avoid subsequent rework.

[0518] Ensuring foundation quality: During foundation construction, precise pit calculations (such as pit opening dimensions combined with slope coefficients and burial depth), standardized steel bar welding (double-sided lap welding, staggered joint arrangement), formwork reinforcement (seamless formwork, verticality controlled by theodolite), and concrete curing (regular watering, curing period ≥ 5 days and nights) significantly improve the stability and durability of the foundation structure.

[0519] To improve the safety and efficiency of tower erection: 25-70 ton cranes are used for segmented lifting, with clear lifting point settings (at the main material nodes, the angle between the lifting ropes is ≤120°), bolt tightening standards (combining anti-theft bolts and anti-loosening measures), and foundation strength verification before lifting (≥70% of design strength), thereby reducing the risk of tower deformation and ensuring the quality of erection and construction safety.

[0520] To ensure the quality of overhead line installation: tensioning is carried out in stages in the order of "nylon rope → guide rope → traction rope → conductor", with the help of drones to cross complex terrain. Combined with precise sag adjustment (calibrating from the farthest span to the nearest span) and tension tower hanging technology (aerial anchoring + pulley block traction), the conductor is prevented from being worn or twisted, thus ensuring the safety of line operation.

[0521] Achieve standardized construction: By clearly defining the personnel allocation, tool requirements, quality inspection standards (such as concrete test block curing and bolt torque testing) and safety control measures (temporary guy wires and cross-crossing monitoring) for each process, we can achieve standardized management of the entire construction process, improve overall construction efficiency, and reduce project costs.

[0522] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A construction method for a 110kV substation power transmission line, characterized in that, Includes the following steps: S1, Line and Tower Foundation Re-survey: Using professional surveying equipment, a comprehensive survey of the line route, tower location parameters and terrain features is conducted, protective stakes are set up and data is recorded; S2, Tower foundation construction: The foundation pit is constructed in sequence, including foundation pit preparation, pit excavation, steel bar processing and binding, formwork installation, anchor bolt fixing, concrete pouring, curing, formwork removal and pit backfilling. S3 uses a crane to lift the iron tower components in sections to complete the tower body assembly, bolt tightening and accessory installation; S4, Overhead line installation: The conductors and ground wires are laid out using tension laying, and the wires are tightened, sag adjusted, tension towers are hung, and accessories are installed to finally complete the grounding system construction.

2. The construction method for a 110kV substation transmission line according to claim 1, characterized in that: The specific steps for the re-survey of the line and tower base in S1 are as follows: S11, the measurement content covers the straightness of the line, the horizontal turning angle of the corner tower, the span, the elevation difference, the crossing position, the micro-section of the tower base, the foundation slope and the location of the drainage ditch; S12 uses the forward and reverse mirror centering method to measure straightness, the repetition method to measure the turning angle, the stadia method to measure the span and height difference, and the stadia method of bisecting the intersection angle to measure the crossing. S13, after re-measurement, auxiliary piles were set in the direction along and across the line of the center pile of the tower location, and protected with 300mm×300mm concrete. The line direction, pile number and tower leg number were marked, and the abandoned piles were removed.

3. The construction method for a 110kV substation transmission line according to claim 1, characterized in that: The specific steps for the basic pit division in step S2 are as follows: Before excavation, prepare an excavation diagram including foundation dimensions and control parameters. Use a theodolite with an accuracy of ≥2″ and a 30m steel tape measure. For straight towers, use the theodolite to rotate 45° to locate the center of the foundation plate and the center of the column. For corner towers, first determine the second bisector stakes and then locate the control points. After the pit is divided, check the foundation root opening and diagonal error, the torsion of the whole foundation and the displacement of the central pile; The pit opening size is calculated using the formula: Pit opening size = Pit bottom slab cross-sectional size + 2 × soil slope coefficient × foundation depth. A 200mm working surface is reserved at the bottom of the pit, and the slope gradient is determined according to the soil quality.

4. The construction method for a 110kV substation transmission line according to claim 1, characterized in that: The specific steps for the foundation pit excavation in step S2 are as follows: Mechanical excavation was the primary method, supplemented by manual cleaning. During the excavation process, the central pile and auxiliary piles of the tower site were protected. The pit depth deviation was controlled at +100mm / -0. For the excessively deep parts, stone paving and grouting were used. Drainage ditches were constructed around the foundation pit. During excavation, the geological conditions were checked to ensure they were consistent with the design. Any abnormalities were reported immediately. After excavation, two leveling operations are carried out: the first leveling operation before the foundation layer is poured, and the second leveling operation after the foundation layer is poured, to ensure that the foundation depth and exposed height meet the design requirements.

5. The construction method for a 110kV step-up substation transmission line according to claim 1, characterized in that: The specific steps for processing and binding the reinforcing bars in step S2 are as follows: The main reinforcement bars are made of HRB400 threaded steel, the stirrups are made of HPB300 round steel, the main reinforcement bar joints are made of double-sided lap welding, the distance of the weld joint from the bend is ≥10d, and the number of joints in the same section is ≤50% of the total number of main reinforcement bars. Before binding the reinforcing bars, remove surface rust and oil stains. Use the figure-eight binding method. Use No. 22 iron wire for reinforcing bars less than 12mm, No. 20 iron wire for reinforcing bars between 12-25mm, and No. 18 iron wire for reinforcing bars more than 25mm. The spacing error of the main reinforcement bars is ±5mm, the spacing error of the stirrups is ±20mm, and the bottom is set with concrete spacers of the same grade to ensure the thickness of the protective layer. The center position of the reinforcement cage is checked before it is put into the formwork.

6. The construction method for a 110kV substation transmission line according to claim 1, characterized in that: The specific steps for template installation and anchor bolt fixing in step S2 are as follows: Use wood formwork with a thickness of ≥15mm. For columns buried more than 1m into the ground, use seamless whole formwork and apply release agent to the surface. The base plate formwork is aligned using horizontal and vertical lines, while the column formwork is controlled by two theodolites to ensure that the inclination is ≤8‰ and the displacement is ≤10mm. The formwork is reinforced with steel pipes. Angle steel supports are installed at the four corners of the base plate formwork, and a support is installed every 500mm for the column formwork. Wooden boards are placed at the ends of the supports.

7. The construction method for a 110kV substation transmission line according to claim 1, characterized in that: The specific steps for concrete pouring, curing, formwork removal, and foundation pit backfilling in step S2 are as follows: When using ready-mixed concrete, chutes are used when the discharge height exceeds 2m, and immersion vibrators are used for compaction. For each foundation, one set of 150mm×150mm×150mm test blocks was made, and both standard curing and curing under the same conditions were carried out respectively. Cover with straw mats and water for curing within 12 hours after pouring. The curing period is ≥5 days and nights. When removing the formwork, the concrete strength is ≥25% of the design strength. After removing the formwork, wrap with plastic film to keep it moist.

8. The construction method for a 110kV substation transmission line according to claim 1, characterized in that: The specific steps in step S3, which involves using a crane to hoist the tower components in sections to complete the tower assembly, bolt tightening, and accessory installation, are as follows: Before assembly, check that the foundation root opening, diagonal and height difference meet the requirements, the foundation strength is ≥ 70% of the design strength, use a 25-70 ton crane for hoisting, set the hoisting points at the main material nodes, and the included angle between the hoisting point ropes is ≤ 120°. When assembling tower components on the ground, assemble the tower legs first, then the tower body, and finally the tower head. Ensure that all bolts are tightened to 100%. When hoisting, pause the inspection when the hoisting component is 0.1m off the ground, and continue only after confirming that everything is correct. Bolts are inserted in accordance with specifications. For three-dimensional structures, bolts are inserted from the inside out horizontally and from the bottom up vertically. For two-dimensional structures, bolts are inserted from the smaller side along the route. Anti-theft bolts are used for bolts under 8 meters. All other single-cap bolts are fitted with anti-loosening nuts. The tightening torque is in accordance with specifications. Bolts are tightened again after the line is laid.

9. The construction method for a 110kV substation transmission line according to claim 1, characterized in that: Step S4, which involves tensioning and laying out the conductor and ground wire, tightening the wire, adjusting the sag, hanging the tension tower wire, and installing accessories, ultimately completes the grounding system construction. Laying sequence: φ6 nylon rope → φ14 nylon rope → φ13 guide wire rope → φ18 guide wire rope → φ24 traction wire rope → conductor. For complex terrain, drones are used to lay out the nylon rope. Tensioners and conductor frames are set up in the tensioning field, temporary guy wires are installed on the tension tower, and the stringing pulleys are suspended in accordance with the connection requirements of "crossarm hanging point - insulator string - pulley"; When tightening the line, first adjust the sag of the furthest observation span, then adjust the nearest spans in turn. After the sag is qualified, mark it on the straight tower. Before hanging the line on the tension tower, set up an aerial temporary anchor. Complete the conductor connection through the pulley block and crimp the tension clamp. The suspension clamp is installed using a chain hoist with a line lifter, the spacer bar is used to fix the clamp head rubber pad in place, and the jumper wire is installed in accordance with the design curvature. After the tower is erected, a C15 protective cap is poured, and the grounding down conductor is bent with a special tool to ensure tight bonding with the main material and foundation surface. Each tower leg is connected to the grounding electrode via a grounding down conductor. The grounding electrode is buried in accordance with the design requirements, and the overall grounding resistance meets the specifications.

10. A construction method for a 110kV substation transmission line according to claim 1, characterized in that: It also includes full-process quality control. If the retest data does not match the design, report it to the supervisor and design unit in a timely manner for handling. Before materials such as steel bars, concrete, and bolts are brought to the site, their certificates of conformity and inspection reports shall be checked, and samples shall be taken and sent for testing in accordance with regulations. After the foundation and tower construction is completed, the acceptance shall be carried out in accordance with the construction quality inspection and evaluation procedures for 110kV~750kV overhead transmission lines, and a complete construction record shall be formed and archived.

Images