Construction method of high wall reinforced anti-overturning support system on upper part of nuclear island raft foundation

Abstract

This invention discloses a construction method for an anti-overturning support system for the upper high wall of a nuclear island raft foundation, relating to the field of nuclear island construction technology. The method utilizes steel bars welded to pre-installed H-shaped steel supports within the raft foundation, steel pipes used as diagonal braces, and swivel fasteners to form a support system. During construction, a pre-tightening torque is first applied to establish active constraint. After binding the root reference skeleton, transverse steel bars are bound layer by layer, and slippage is monitored for torque compensation and re-tightening. Flexible tie rods are arranged above the construction joint to form a gradual stiffness transition zone, which is removed after the upper support is erected. Cross-cable pretensioning is applied to the complete steel skeleton. After concrete pouring, the supports are dismantled from top to bottom in sections according to both age and strength conditions. This invention achieves full-process anti-overturning control through active constraint, dynamic compensation, gradual stiffness transition, and zoned and sequential release, without occupying internal wall space, ensuring the verticality of the high wall reinforcement and the quality of concrete forming.

Description

Technical Field

[0001] This invention relates to the field of nuclear island construction technology, and in particular to a construction method for a steel reinforcement anti-overturning support system for the upper high wall of a nuclear island raft foundation. Background Technology

[0002] As the last physical barrier in the nuclear power plant's defense-in-depth system, the nuclear island building has thick reinforced concrete walls, dense reinforcement, and extraordinary height. The steel reinforcement engineering during construction is the core link that determines the structural safety and construction period.

[0003] Currently, to ensure temporary stability during the reinforcement binding stage of high walls, it is common practice to erect steel pipe scaffolding inside the reinforcement cage as a temporary support system.

[0004] However, existing steel pipe scaffolding support methods have the following prominent problems: the scaffolding occupies the internal space of the wall, interferes with the dense steel mesh, and affects the operation surface for steel bar binding and subsequent formwork installation; the connection between the support and the steel mesh is a passive constraint, which cannot actively eliminate node slippage, causing the steel skeleton to gradually tilt under the cumulative effect of construction load, making it difficult to maintain the initial verticality; the dismantling process after concrete pouring lacks precise matching with the development of concrete strength. Too early dismantling can easily lead to early concrete cracking, while too late dismantling will affect the turnover efficiency of formwork. Summary of the Invention

[0005] The main objective of this invention is to propose a construction method for a steel reinforcement anti-overturning support system for the upper high wall of a nuclear island raft foundation. This method aims to solve the technical problems of existing steel pipe scaffolding support methods occupying internal wall space, passive constraints leading to cumulative node slippage, and the mismatch between the dismantling process and the development of concrete strength.

[0006] To achieve the above objectives, the present invention proposes a construction method for a reinforced concrete anti-overturning support system for the upper high wall of a nuclear island raft foundation. The support system includes reinforcing steel bars welded to pre-installed H-shaped steel supports within the raft foundation, steel pipes used as diagonal braces, and swivel fasteners that lock the ends of the steel pipes to the reinforcing steel bars. The wall reinforcement is installed on the raft foundation. The construction method for the reinforced concrete anti-overturning support system for the upper high wall of the nuclear island raft foundation includes: The steel pipe and the rebar head are connected by the swivel coupler, and a preset pre-tightening torque is applied to the swivel coupler to establish initial active constraint; Vertical steel bars of a predetermined height are tied above the top surface of the raft foundation to form a root reference skeleton; Starting from the root reference skeleton, horizontal steel bars are tied layer by layer upwards. After each preset number of horizontal steel bars are tied, the slippage of the steel pipe end relative to the steel bar head is measured. When the measured slippage reaches a preset threshold, the corresponding swivel fastener is torque compensated and re-tightened until the slippage is eliminated and the locking torque is restored to the pre-tightening torque. The measurement and compensation re-tightening steps are repeated until all the steel bars of this section of the wall are tied. Within a preset height range above the top surface of the concrete construction joint, flexible tie members with an acute angle are installed. The flexible tie members are used to temporarily connect the upper section of vertical steel bars to be tied to the lower section of the poured wall, forming a gradual stiffness transition zone. After the upper section of the steel pipe is erected and the pre-tightening torque is applied, the flexible tie members are released. For the completed steel reinforcement cage, cross cables are installed diagonally at the top. Tensioning equipment is used to apply pretension to the cross cables, so that stress redistribution occurs inside the complete steel reinforcement cage. After the concrete is poured, the wall is divided into multiple areas along its height, and the dismantling and support process is carried out in a zoned and timed manner. The dismantling and support activation conditions for each area include at least the following: the concrete age corresponding to the area reaches the age threshold and the concrete strength corresponding to the area reaches the strength threshold, and the dismantling and support release is carried out from top to bottom zone by zone.

[0007] The technical solution of this invention establishes initial active constraints by using inclined steel pipes and steel bars on the pre-embedded H-shaped steel supports of the raft foundation through rotating fasteners. Starting from the root reference skeleton, the steel bars are tied layer by layer upwards, and dynamic monitoring and compensation are carried out to eliminate node slippage. Flexible tie members with acute angles are arranged above the construction joint to form a gradual stiffness transition zone. Cross cable pretension is applied to the top of the complete steel skeleton to achieve stress redistribution. The invention also implements a zoned and timed dismantling process based on age and strength dual control. This ensures that the wall steel bars are always under effective constraints that can be actively adjusted throughout the entire construction cycle, without occupying the internal space of the wall. This avoids the tilting and verticality deviation of the steel skeleton caused by the accumulation of construction loads. At the same time, the dismantling and release are synchronized with the increase of concrete strength, thereby ensuring the overturning safety and structural forming quality of the high wall steel bar binding and concrete pouring process. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0009] Figure 1This is a schematic flowchart of an embodiment of the construction method for the anti-overturning support system of the upper high wall of the nuclear island raft foundation provided by the present invention.

[0010] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0012] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0013] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0014] As the last physical barrier in a nuclear power plant's defense-in-depth system, the nuclear island building features thick, densely reinforced, and unusually tall reinforced concrete walls. Reinforcement engineering during construction is a crucial factor determining structural safety and construction timeline. With the continuous increase in the capacity of individual nuclear power units, the height of the upper walls of the nuclear island raft foundation has generally exceeded 20 meters, and the arrangement of double-layer, bi-directional, or even triple-layer bi-directional steel reinforcement mesh has become commonplace. Before concrete pouring, the towering vertical steel reinforcement mesh, due to its insufficient rigidity, is highly susceptible to out-of-plane tilting or even complete overturning under wind loads, construction disturbances, and lateral pressure from the concrete.

[0015] Currently, to ensure temporary stability during the reinforcement binding phase of high walls, it is common practice to erect steel pipe scaffolding inside the reinforcement cage as a temporary support system. The bottom of the scaffolding uprights is supported on the raft foundation concrete surface, and the top is connected to the reinforcement mesh using couplers or steel wire, relying on the spatial rigidity of the scaffolding itself to resist the lateral deformation of the reinforcement mesh. In terms of construction segmentation, the conventional practice is to erect scaffolding and bind reinforcement layer by layer as the wall height increases, and after the concrete pouring reaches the design strength, the support is removed from top to bottom in one go or in sections.

[0016] However, existing steel pipe scaffolding support methods have the following prominent problems: the scaffolding occupies internal wall space, interferes with the dense steel mesh, affecting the steel reinforcement binding operation surface and subsequent formwork installation; the connection between the support and the steel mesh is a passive constraint, unable to actively eliminate node slippage, causing the steel reinforcement cage to gradually tilt under the cumulative construction load, making it difficult to maintain initial verticality; the dismantling process after concrete pouring lacks precise matching with the concrete strength development, premature dismantling easily leads to early concrete cracking, while delayed dismantling affects formwork turnover efficiency. Therefore, how to establish an active, controllable, and adjustable steel reinforcement anti-overturning support system without occupying internal wall space, and achieve dynamic coordination between support constraints and construction progress and concrete strength development, has become an urgent technical problem to be solved in the construction of high wall reinforcement engineering in nuclear islands.

[0017] To address this technical problem, this invention proposes a construction method for a reinforced concrete anti-overturning support system for the upper high wall of a nuclear island raft foundation.

[0018] Please see Figure 1 In one embodiment of the present invention, the support system includes steel bar ends welded to a pre-set H-shaped steel bracket within the raft foundation, steel pipes used as diagonal braces, and swivel fasteners for locking the ends of the steel pipes to the steel bar ends; wall reinforcement is installed on the raft foundation, and the construction method of the anti-overturning support system for the upper high wall reinforcement of the nuclear island raft foundation includes: Step S10: Connect the steel pipe and the rebar head through the swivel coupler, and apply a preset pre-tightening torque to the swivel coupler to establish initial active constraint; Step S20: Tie vertical steel bars of a predetermined height above the top surface of the raft foundation to form a root reference skeleton; Step S30: Starting from the root reference skeleton, tie the horizontal reinforcing bars layer by layer upwards. After completing the tying of each preset number of horizontal reinforcing bars, measure the slippage of the end of the steel pipe relative to the head of the reinforcing bar. When the measured slippage reaches a preset threshold, perform torque compensation re-tightening on the corresponding swivel fastener until the slippage is eliminated and the locking torque is restored to the pre-tightening torque. Repeat the measurement and compensation re-tightening steps until all the reinforcing bars of this section of the wall are tied. Step S40: Within a preset height range above the top surface of the concrete construction joint, a flexible tie member with an acute angle is installed. The flexible tie member is used to temporarily connect the upper section of the vertical steel bar to be tied to the lower section of the poured wall, forming a gradual stiffness transition zone. After the upper section of the steel pipe is erected and the pre-tightening torque is applied, the flexible tie member is released. Step S50: For the completed steel reinforcement cage, cross cables are set at the top diagonal direction, and pretension is applied to the cross cables using a tensioning device to cause stress redistribution inside the complete steel reinforcement cage. Step S60: After the concrete is poured, the wall is divided into multiple areas along its height, and the dismantling and support removal process is carried out in a zoned and timed manner. The dismantling and support removal start conditions for each area include at least the following: the concrete age corresponding to the area reaches the age threshold and the concrete strength corresponding to the area reaches the strength threshold, and the dismantling and support removal sequence is from top to bottom, releasing area by area.

[0019] It should be noted that in this embodiment, "H-beam steel support" refers to hot-rolled H-beam steel components pre-embedded in the reinforcing steel skeleton of the raft foundation before the concrete pouring, with vertical or diagonal reinforcing bar ends welded to the top surface of its flanges or webs. The reinforcing bar ends are made of HRB400 steel, with a diameter of not less than 20 mm, and the welding adopts double-sided fillet welds with a weld leg size of not less than 8 mm. "Swivel coupler" refers to a right-angle coupler for steel pipe scaffolding that conforms to current national standards, which achieves a fixed connection between the steel pipe and the reinforcing bar ends through the frictional resistance generated by bolt tightening. "Initial active constraint" refers to applying a quantitative pre-tightening torque to the swivel coupler before the wall reinforcement binding begins, so that a force transmission node with a preset frictional resistance is established between the diagonal bracing steel pipe and the pre-embedded reinforcing bar ends in the raft foundation, eliminating the initial void of the node from the source, which is different from the passive constraint formed by the self-weight of the steel pipe scaffolding and passive overlapping. "Root reference skeleton" refers to the steel mesh formed by the first section of vertical and horizontal steel bars tied above the top surface of the raft foundation. Its top elevation serves as the reference plane for subsequent upward tying and also as the reaction force basis for the diagonal bracing steel pipe to transfer loads. "Slippage" refers to the relative linear displacement between the swivel coupler and the steel bar head under external load, reflecting the inelastic deformation of the node under cumulative load. "Torque compensation re-tightening" refers to using a torque wrench to retighten the bolts of the corresponding swivel coupler to the preset pre-tightening torque when the slippage reaches a preset threshold, in order to eliminate the slippage and restore the initial frictional resistance of the node. "Flexible tie" refers to a temporary connector with flexible and tensionable characteristics arranged above the construction joint, used to create elastic constraints between the upper steel skeleton and the lower cast-in-place wall. The "gradual stiffness transition zone" refers to a mechanical transition zone between the lower rigid wall section and the upper flexible steel reinforcement cage, formed by flexible tie members. This zone's constraint stiffness falls between unconstrained and rigid constraints, preventing stress concentration at construction joints caused by abrupt stiffness changes. "Cross cables" refer to tension members arranged diagonally across the top plane of the steel reinforcement cage. "Pretension" refers to the quantitative initial tension applied to the cross cables using tensioning equipment, taut the cables and establishing a self-balancing stress field within the cage. "Zoned and time-sequential support removal process" refers to dividing the wall into several zones along its height. The start time for support removal in each zone is independently determined based on its concrete age and measured strength, with the removal of supports in different zones staggered in time.

[0020] Specifically, this technical solution solves the problem of skeleton tilting and verticality deviation caused by support constraint failure during the reinforcement binding and concrete pouring process of the high wall of the nuclear island by constructing a full-process anti-overturning control path of "active constraint establishment - dynamic slip compensation - gradual stiffness transition - pretension adjustment - zoned time-sequential release". First, H-shaped steel supports are pre-embedded and steel bar ends are welded before the raft foundation concrete is poured, so that the reaction foundation of the support system is integrated with the raft foundation. After the raft foundation concrete reaches the strength, the diagonal bracing steel pipes and steel bar ends are connected with swivel couplers and a preset pre-tightening torque is applied. At this time, the support system is transformed from a geometrically variable mechanism into a prestressed structure with preset stiffness. Active constraint is established before the self-weight of the steel bars and construction load. When each subsequent steel bar is added to the skeleton, the support system already has the ability to resist lateral deformation immediately. Secondly, during the process of binding transverse reinforcement layer by layer starting from the root reference skeleton, the slippage of nodes is measured and compensated re-tightening is performed after each preset number of layers is completed, forming a dynamic closed-loop control of "monitoring-compensation-re-monitoring-re-compensation" to ensure that the active constraint state of the support system does not degrade due to the gradual increase of construction load. Thirdly, flexible tie rods are installed above the construction joint of the lower wall section, giving the root of the upper reinforcement skeleton an elastic constraint boundary. After the upper diagonal bracing steel pipe is erected and the pre-tightening torque is applied, the load path shifts from the flexible tie rods to the diagonal bracing steel pipe, achieving a smooth switch in constraint form. Then, cross-cable pretension is applied to the complete reinforcement skeleton. The diagonal pressure component generated by the pretension in the top plane of the skeleton causes a compressive tendency between the skeleton members, forming a self-balancing stress system internally, significantly enhancing the spatial integrity and resistance to out-of-plane deformation of the skeleton. Finally, after the concrete is poured, the dismantling of the supports is carried out in zones and in sequence. The dismantling of each zone is controlled by both the concrete age and the measured strength. The dismantling sequence is from top to bottom, releasing the supports zone by zone, to ensure that each layer of concrete has sufficient strength to bear the corresponding upper load, and to avoid structural cracking due to premature dismantling or affecting the turnover efficiency of the formwork due to late dismantling.

[0021] More specifically, the construction steps of this technical solution are as follows: S10: During the raft foundation reinforcement cage binding stage, H-shaped steel supports are pre-embedded at the designed locations. The bottom of the H-shaped steel supports is welded and fixed to the raft foundation base reinforcement. Vertical or diagonal steel bar heads are welded to the top surface of the flanges or webs of the H-shaped steel supports, with the steel bar heads protruding from the top surface of the raft foundation concrete by no less than 150 mm. After the raft foundation concrete is poured and cured to more than 75% of its design strength, the positioning and layout of the vertical reinforcement of the wall are carried out. One end of the steel pipe used as diagonal bracing is connected to the pre-embedded steel bar head on the raft foundation using a swivel coupler, and the other end of the steel pipe is fixed to the vertical or horizontal reinforcement of the wall reinforcement cage using a swivel coupler. A calibrated torque wrench is used to apply a preset pre-tightening torque to the bolts of each swivel coupler. Each bolt is tightened twice. The torque value is considered qualified if it is stable within the preset range during the second tightening, thus completing the establishment of the initial active constraint.

[0022] S20: Tie vertical steel bars at a set height above the top surface of the raft foundation. The lower end of the vertical steel bars is fixed to the pre-reserved reinforcing bars of the raft foundation by tying or mechanical connection to form the root reference skeleton.

[0023] S30: Starting from the top elevation of the root reference frame, tie the horizontal reinforcing bars layer by layer upwards. After completing the tying of each preset number of layers of horizontal reinforcing bars, measure the slippage of the swivel coupler at the end of each diagonal brace relative to the corresponding reinforcing bar head. When the slippage measured at any node reaches the preset threshold, use a torque wrench to perform torque compensation re-tightening on the corresponding swivel coupler. The target torque value for re-tightening is the preset pre-tightening torque. During the re-tightening process, continuously monitor the change in slippage until the slippage is eliminated to zero. Repeat the above steps until all reinforcing bars within the design elevation range of this wall section are tied.

[0024] S40: After the lower section of the wall concrete is poured and reaches 75% of its design strength, flexible tie rods are installed within a preset height range above the top surface of the concrete construction joint. One end of the flexible tie rod is fixed to the pre-reserved vertical reinforcing bar in the upper section, and the other end is fixed to the anchor point at the top of the lower section of the poured wall. The inclination angle of the flexible tie rod is acute, that is, the angle between the flexible tie rod and the wall plane is less than 90°. After the upper section of the diagonal bracing steel pipe is erected, and the locking torque of the swivel coupler connecting the upper section of the steel pipe and the corresponding reinforcing bar head has been verified to reach the preset pre-tightening torque, all flexible tie rods are removed.

[0025] S50: For the completed steel reinforcement cage, two cables are arranged diagonally in the top plane, with the ends of the cables anchored to the roots of the vertical reinforcement bars at the top corners of the cage. Pretensioning is applied symmetrically and synchronously to the two cables using tensioning equipment, and the anchorages are locked after the pretensioning is completed.

[0026] S60: After the concrete pouring is completed, the wall is divided into multiple zones along its height. An age threshold and a strength threshold are set for each zone. Support removal for a zone can only begin when the concrete age for that zone reaches the age threshold and the compressive strength of concrete test blocks cured under the same conditions for that zone reaches the strength threshold. The support removal sequence strictly follows a top-down, zone-by-zone release approach: first remove the supports in the upper zone, then the supports in the middle zone, and finally the supports in the lower zone.

[0027] In an embodiment of the present invention, the preset preload torque is between 40 N·m and 50 N·m.

[0028] It should be noted that the torque range of "40 N·m to 50 N·m" refers to the optimal torque range determined through repeated testing for conventional swivel couplers used in the anti-overturning support system of the high wall reinforcement in the upper part of the nuclear island raft foundation. This range simultaneously meets the requirements for joint anti-slipping and avoids overload damage to the coupler bolts. When the torque value is below 40 N·m, the frictional resistance between the swivel coupler and the rebar head is insufficient, making slippage prone to occur under construction loads. When the torque value is above 50 N·m, the coupler bolts may enter a yielding state, leading to thread damage or bolt breakage.

[0029] Specifically, this technical solution limits the preset pre-tightening torque to 40 N·m to 50 N·m. On the one hand, it ensures that the frictional resistance generated between the swivel coupler and the rebar head can reliably resist the construction load accumulated during the rebar binding process, so that the node maintains its initial constraint state throughout the construction cycle without harmful slippage. On the other hand, it avoids plastic deformation or stress corrosion cracking of the coupler bolts due to over-tightening, ensuring the reusability of the coupler and the long-term reliability of the node.

[0030] More specifically, when implementing step S10, select a calibrated torque wrench with a range of 0 to 100 N·m, and set the preset torque value of the torque wrench to a specific value within the range of 40 N·m to 50 N·m, for example, 45 N·m. When tightening the swivel bolt, rotate the torque wrench at a constant speed. When you hear a "click" sound from the wrench or feel a noticeable bending motion in the wrench joint, stop applying force. At this point, the bolt has reached the preset torque value. Repeat the tightening twice for each bolt. If the wrench emits an indicator signal during the second tightening without rotating or with a very small rotation angle, it indicates that the torque value is stable and the joint is properly tightened.

[0031] In an embodiment of the present invention, the step of measuring the slippage of the end of the steel pipe relative to the end of the reinforcing bar includes: Step S301: Using a mechanical dial indicator or vernier caliper installed at the connection node between the steel pipe and the rebar head, measure the displacement between the reference lines preset on the steel pipe and the rebar head; Step S302: The preset number of layers is 2, and the preset threshold is 2.0 mm.

[0032] It should be noted that: "Mechanical dial indicator" refers to a mechanical precision measuring instrument that uses gear transmission to convert the linear displacement of the measuring rod into the angular displacement of the pointer, with a resolution of 0.001 mm to 0.01 mm. "Vernier caliper" refers to a length measuring tool that uses the vernier principle for reading, with a resolution of 0.02 mm or 0.05 mm. "Reference line" refers to the alignment marking lines drawn on the outer wall of the steel pipe and the outer wall of the rebar head using a steel needle or electric marking pen after the swivel fastener is tightened. The two marking lines are initially flush and serve as the zero reference for measuring slippage. "Preset number of layers is 2 layers" means that a slippage measurement is performed after every 2 layers of transverse rebar binding is completed. This frequency matches the spacing of the transverse rebar in the nuclear island wall and the step characteristics of the construction load. "Preset threshold is 2.0 mm" means that torque compensation re-tightening is triggered when the node slippage reaches 2.0 mm. This value is less than the allowable deviation of the wall rebar verticality, ensuring that compensation is initiated before the deviation exceeds the limit.

[0033] Specifically, this technical solution sets a monitoring cycle of every two layers of transverse steel reinforcement binding, synchronizing the slippage detection frequency with the step increase in construction load. This avoids excessively frequent detection affecting construction efficiency or excessively long detection intervals leading to slippage exceeding limits. Setting the slippage threshold to 2.0 mm provides a controllable small margin for node slippage, preventing excessively frequent re-tightening that could disrupt construction continuity. Furthermore, a slippage of 2.0 mm represents a very small proportion of the overall wall verticality deviation, far below the allowable deviation value for wall verticality in relevant construction acceptance specifications, ensuring that node slippage is eliminated before it has a noticeable impact on the overall posture of the framework.

[0034] More specifically, the operation method for implementing step S30 is as follows: After the swivel fastener is tightened and the torque is confirmed to be qualified, immediately use a steel needle to draw aligned reference lines on adjacent positions on the outer wall of the steel pipe and the outer wall of the rebar head. The width of both lines should not exceed 0.2 mm, and the two lines should be flush and aligned in the initial state. Fix the mechanical dial indicator to the steel pipe by magnetic adsorption, with the dial indicator probe perpendicularly against the preset measuring surface on the end face or side wall of the rebar head. After completing the binding of every two layers of transverse rebar, read the dial indicator value; the change in the reading is the slippage. In the absence of a mechanical dial indicator, a vernier caliper can be used to measure the misalignment distance between the two reference lines as a substitute. When the measured slippage reaches 2.0 mm, immediately perform torque compensation re-tightening, continuously observing the change in the dial indicator or vernier caliper reading during the re-tightening process until the slippage is eliminated to zero.

[0035] In an embodiment of the present invention, the step of arranging flexible tie members with acute angles within a preset height range above the top surface of the concrete construction joint, and using the flexible tie members to temporarily connect the upper section of vertical reinforcing bars to be tied to the lower section of the poured wall, includes: Step S401: Within a height range of 300 mm to 600 mm above the top surface of the construction joint, steel wire ropes at an angle of 30° to 45° to the wall are laid out as the flexible tie members. One end of the steel wire rope is fixed to the vertical steel bar reserved in the upper section, and the other end is fixed to the anchor point at the top of the lower section of the poured wall.

[0036] It should be noted that: "Height range of 300 mm to 600 mm" refers to the arrangement height range of the flexible tie member above the top surface of the construction joint of the lower wall section. This range covers the section where the constraint requirements at the root of the upper vertical reinforcement are most concentrated. "Angle range of 30° to 45°" refers to the angle between the wire rope and the wall plane. This angle range can control the magnitude of the vertical component while providing horizontal constraint force, so that the wire rope mainly functions to limit the lateral displacement of the upper reinforcement skeleton. In this embodiment, the "wire rope" is a galvanized wire rope with a diameter of not less than 8 mm, and its breaking tensile strength meets the safety requirements of temporary ties. "Anchor point" refers to a reliable connection point set on the concrete surface or embedded part at the top of the lower poured wall section for fixing the end of the wire rope. It can be a pre-embedded steel ring, expansion bolt, or chemical anchor.

[0037] Specifically, this technical solution limits the placement height of the flexible tie members to 300 mm to 600 mm above the top surface of the construction joint. This height range is precisely located in the area where the bending moment at the root of the upper section of the reinforcing steel skeleton is the largest and the lateral restraint requirement is the most concentrated. The flexible tie members provide restraint within this range, limiting the lateral displacement of the root of the upper section of the reinforcing steel skeleton with the shortest force transmission path. The steel wire rope is arranged at an angle of 30° to 45° with the wall, so that the tension of the steel wire rope is decomposed into a horizontal component perpendicular to the wall and a vertical component parallel to the wall. The horizontal component directly resists the lateral overturning moment of the reinforcing steel skeleton, while the vertical component applies a downward force, which helps to press the root of the upper vertical reinforcing steel against the top surface of the lower wall, enhancing the force transmission reliability at the construction joint. Under the combined action of a height range of 300 mm to 600 mm and an included angle range of 30° to 45°, the flexible tie member forms an elastic constraint on the upper section of the steel reinforcement skeleton, which has both lateral limiting and vertical clamping functions, realizing a gradual transition in stiffness from the lower rigid wall to the upper flexible skeleton.

[0038] More specifically, the procedure for implementing step S40 is as follows: S401: After the lower section of the wall concrete has been poured and cured to 75% of its design strength, remove the laitance and debris from the top surface of the construction joint. Within a height range of 300 mm to 600 mm above the top surface of the construction joint, select the pre-reserved vertical reinforcing bars from the upper section as the upper fixing points for the flexible tie rods. Drill holes at the corresponding horizontal positions at the top of the lower section of the poured wall and insert expansion bolts as anchor points, or utilize the pre-embedded reinforcing rings at the top of the lower section of the wall as anchor points. The spacing between anchor points along the horizontal direction of the wall should not exceed 2 m.

[0039] S402: Cut galvanized steel wire ropes of appropriate length with a diameter of not less than 8 mm. Secure one end of the wire rope to the pre-reserved vertical reinforcing bar in the upper section with no less than 3 rope clips, and secure the other end to the anchor point at the top of the lower section of the wall with no less than 3 rope clips. Adjust the length and fixing position of the wire rope to control the angle between the wire rope and the wall plane within the range of 30° to 45°. Tension the wire ropes one by one to make them taut and have a certain initial tension, but do not over-tension to avoid pulling the upper section of the reinforcing bar skeleton off-center.

[0040] S403: The diagonal bracing steel pipes of the upper section of the wall are all erected and positioned according to the design. One end of the steel pipe is connected to the pre-embedded steel bar of the raft foundation via a swivel coupler, and the other end is fixed to the steel bar skeleton of the upper section of the wall via a swivel coupler. Use a torque wrench to check the torque of each swivel coupler at both ends of the upper section of the steel pipe. The preset torque value is the same as the preset pre-tightening torque value applied in step S10. Tighten any nodes with insufficient torque values ​​during the test until the locking torque of all nodes reaches the preset pre-tightening torque value after verification. After confirming that the torque of all upper section swivel couplers is qualified, remove the flexible tie members. During removal, first loosen the rope clamp nut at the end of the wire rope, remove the rope clamp, and then disconnect the wire rope from the upper section of the vertical steel bar and the lower section of the wall anchor point. Retrieve all the wire rope and rope clamp. The removal sequence can be carried out one by one along the horizontal direction of the wall until all flexible tie members are removed.

[0041] In an embodiment of the present invention, after setting cross cables diagonally at the top of the completed steel reinforcement cage and applying pretension to the cross cables using a tensioning device to cause stress redistribution within the complete steel reinforcement cage, the construction method of the steel reinforcement anti-overturning support system for the upper high wall of the nuclear island raft foundation further includes: Step S51: Apply a predetermined horizontal thrust to the center of the top of the wall and release it instantaneously. Use a mechanical displacement measuring device installed on the top of the wall to record the number of swing cycles of the free decay of the top horizontal displacement. Step S52: When the number of recorded oscillation cycles does not exceed 3, it is determined that the overall stiffness of the complete steel reinforcement cage meets the predetermined anti-overturning requirements.

[0042] It should be noted that: "Predetermined horizontal thrust" in this embodiment is 500 N, which is slowly applied horizontally at the center of the top of the wall using a spring tension gauge. "Instant release" refers to quickly cutting off the force transmission path between the force application device and the wall after reaching the predetermined thrust value, allowing the wall to begin freely decaying vibrations without continuous external force. "Mechanical displacement measuring device" in this embodiment is a dial gauge or a large-range displacement gauge, installed on the opposite side of the top of the wall from the force application point, used to record the decay process of the top horizontal displacement over time. "Number of oscillation cycles" refers to the number of complete reciprocating oscillations from the moment the horizontal thrust is released until the top horizontal displacement amplitude decays to less than 5% of the initial displacement amplitude. "3 times" is the judgment threshold; a number of cycles not exceeding 3 times indicates that the internal connection of the frame is tight, the damping is large, and the overall stiffness is sufficient.

[0043] Specifically, this technical solution is based on the mechanical principle of structural free vibration decay. By instantaneously releasing the external force applied to the center of the top of the wall, the steel reinforcement cage generates free decaying vibration at its natural frequency. The higher the overall stiffness of the system, the tighter the connection between the internal members, and the greater the frictional damping at the nodes, the faster the vibration energy is dissipated, resulting in fewer cycles of free decaying vibration. Using three cycles as the judgment threshold, if the number of oscillation cycles does not exceed three, it indicates that the internal structure of the cage has formed an effective spatial overall force-bearing system through the combined effect of the pre-tightening torque of the swivel fasteners and the pre-tension of the cross cables, possessing the stiffness reserve to withstand the impact loads and fluid lateral pressure generated during concrete pouring without causing harmful deformation. If the number of cycles exceeds three, it indicates that the overall stiffness of the cage is insufficient or that there are loose local nodes, requiring investigation and reinforcement before further verification.

[0044] More specifically, after implementing step S50 and before pouring concrete, perform the following stiffness check steps: S501: Install a spring tension gauge at the center of the top of the wall. One end of the spring tension gauge is reliably connected to the vertical or horizontal reinforcing bar at the center of the top of the wall via a wire rope or clamp, and the other end is held by the operator or fixed to a fixed support.

[0045] S502: Install a dial indicator on the opposite side of the top of the wall from the point of force application. The dial indicator is attached to an independent reference bracket that does not contact the steel reinforcement frame by magnetic base. The probe of the dial indicator is horizontally pressed against the vertical steel reinforcement on the side of the top of the wall.

[0046] S503: The operator slowly and uniformly pulls the spring tension gauge to read the tension value. When the tension reaches 500 N, it is held stably for 3 to 5 seconds, and then the tension is released instantly. The instantaneous release can be achieved by quickly loosening the clamp or cutting the connecting rope.

[0047] S504: Start from the moment of release, observe and count the number of complete reciprocating swing cycles of the dial indicator pointer, continue to observe until the pointer swing amplitude is less than 5% of the initial amplitude, then stop counting.

[0048] S505: When the recorded number of oscillation cycles does not exceed 3, the overall stiffness of the complete steel reinforcement cage is determined to meet the predetermined anti-overturning requirements, and the process can proceed to the next step. When the number of cycles exceeds 3, a torque wrench is used to perform a comprehensive re-tightening check on all swivel fasteners, the cross cables are re-tensioned, and the stiffness verification steps from S501 to S505 are executed again until the number of cycles meets the requirements.

[0049] In an embodiment of the present invention, after the concrete is poured, the wall is divided into multiple areas along its height, and a zoned and timed dismantling process is performed. The dismantling initiation conditions for each area include at least: the concrete age corresponding to the area reaches an age threshold and the concrete strength corresponding to the area reaches a strength threshold. The dismantling sequence is a top-down, zone-by-zone release step, including: Step S601: Divide the wall into a top section, a middle section and a bottom section along its height, each accounting for one-third of the total height of the wall; Step S602, the conditions for initiating the dismantling of the support in the bottom area are: the concrete pouring is completed and the static curing time is not less than 48 hours, and the compressive strength of the concrete test block cured under the same conditions as the bottom area reaches at least 50% of the design value; Step S603, the conditions for initiating the dismantling of the supports in the central area are: the concrete pouring is completed and the static curing time is not less than 72 hours, and the compressive strength of the concrete test block cured under the same conditions as the central area reaches at least 75% of the design value; Step S604, the conditions for starting the dismantling of the top area are: the concrete pouring is completed and the static curing time is not less than 7 days, and the compressive strength of the concrete test block cured under the same conditions as the top area reaches at least 100% of the design value.

[0050] It should be noted that: "Top zone, middle zone, and bottom zone" refers to dividing the wall into three equal zones along its height, each zone occupying one-third of the total wall height. "Concrete test blocks cured under the same conditions" refers to concrete cube test blocks prepared simultaneously with the wall concrete pouring and cured in the same temperature and humidity environment as the wall, used to represent the actual strength development state of the concrete in that zone. "Age threshold" is expressed as static curing time, and "strength threshold" is expressed as the percentage of the concrete test block's compressive strength reaching the design value. Both constitute the dual control conditions for initiating support removal; if either condition is not met, the support removal in that zone cannot be initiated. "48 hours" and "50%" are the dual control parameters for the bottom zone, "72 hours" and "75%" for the middle zone, and "7 days" and "100%" for the top zone.

[0051] Specifically, this technical solution establishes differentiated dismantling initiation conditions for each section of the wall based on the load magnitude and concrete strength development patterns after dismantling the supports. The bottom section bears the entire self-weight of the upper wall after dismantling, thus requiring the highest concrete strength. However, due to the compaction effect of the upper concrete's weight, the bottom section has high density and sufficient hydration, resulting in relatively rapid strength gain. Therefore, a static rest period of at least 48 hours is set until the strength reaches 50% of the design value. This strength is sufficient to bear the early loads transmitted from the bottom section and above after dismantling. The middle section bears part of the upper wall's self-weight after dismantling, with a moderate load. A static rest period of at least 72 hours is set until the strength reaches 75% of the design value. This considers both the faster water evaporation rate of the middle section compared to the bottom section and ensures sufficient strength margin when bearing the corresponding loads. After the top area is dismantled, it only bears a small portion of its own weight. However, since the concrete in the top area evaporates moisture the fastest and develops early strength the slowest, and the cross cables also need to be removed at the same time as the top area is dismantled, it is set to remain static for no less than 7 days and reach 100% of the design strength. The most stringent strength requirements are used to ensure that the top area will not crack due to early shrinkage or temperature stress after the support is completely removed.

[0052] More specifically, the procedure for implementing step S60 is as follows: S6001: Before pouring concrete, the wall shall be evenly divided into a top zone, a middle zone, and a bottom zone according to its height, with each zone accounting for one-third of the total wall height. At the concrete pouring layer corresponding to each zone, no less than three sets of concrete test blocks cured under the same conditions shall be prepared simultaneously. The test blocks shall be placed near the wall of the corresponding section and covered with the same curing film or insulation material.

[0053] S6002: Timing begins after concrete pouring is completed. The resting time for the bottom zone is calculated from the moment concrete pouring is completed. When the resting time reaches 48 hours and the compressive strength of the bottom zone test blocks cured under the same conditions reaches 50% or more of the design value, the bottom zone is ready for support removal. The resting time for the middle zone is calculated from the moment concrete pouring is completed. When the resting time reaches 72 hours and the compressive strength of the middle zone test blocks cured under the same conditions reaches 75% or more of the design value, the middle zone is ready for support removal. The resting time for the top zone is calculated from the moment concrete pouring is completed. When the resting time reaches 7 days and the compressive strength of the top zone test blocks cured under the same conditions reaches 100% or more of the design value, the top zone is ready for support removal.

[0054] S6003: Of the two conditions in the same area, the time when the later condition is met shall be taken as the actual permitted time for the dismantling of the support in that area.

[0055] In an embodiment of the present invention, the step of releasing the supports in a top-down, zone-by-zone manner includes: Step S61: First, remove the support in the top area and the cross cable, then remove the support in the middle area, and finally remove the support in the bottom area.

[0056] It should be noted that: "Remove the top area first" means that after the top area simultaneously meets both the age and strength thresholds, all diagonal bracing pipes, swivel couplers, and cross cables corresponding to the top area should be removed first. "Remove the middle area next" means that after the top area supports are removed, and the middle area simultaneously meets both the age and strength thresholds, the diagonal bracing pipes and swivel couplers corresponding to the middle area should be removed. "Remove the bottom area last" means that after the middle area supports are removed, and the bottom area simultaneously meets both the age and strength thresholds, the diagonal bracing pipes and swivel couplers corresponding to the bottom area should be removed. The entire dismantling process must strictly follow the spatial sequence from top to bottom; skipping areas or reversing the dismantling process is prohibited.

[0057] Specifically, this technical solution specifies that the supports should be removed sequentially: top section, middle section, and bottom section. This order aligns with the concrete strength development pattern and structural load requirements. The top section exhibits the slowest concrete strength growth but bears the smallest upper load. Once the top section reaches 100% of its design strength, the supports are removed, ensuring the top section structure has full load-bearing capacity and will not experience any adverse deformation due to support removal. After the top section supports are removed, the load boundary conditions in the middle section change, shifting from bearing the support reaction force transmitted from the top section to bearing its own weight. The middle section's strength, reaching 75% of its design value, is sufficient to withstand this change. The bottom section is removed last, as it has had the longest curing time and the most abundant strength reserve, enabling it to safely bear the entire self-weight of the wall section and subsequent construction loads. If the bottom section is removed first, contrary to the top-to-bottom order, the bottom section concrete will be forced to bear the full upper weight without sufficient strength, easily leading to cracking of the bottom section concrete or even overall wall subsidence, causing serious structural quality accidents.

[0058] More specifically, the dismantling operations should be performed in the following order: When the age and strength control conditions of the top zone are simultaneously met, first remove the swivel couplers connecting the diagonal bracing steel pipes and rebar heads in the top zone, and then remove the steel pipes. Next, release the anchorages of the top cross cables and dismantle the cross cables. When the age and strength control conditions of the middle zone are simultaneously met, remove the swivel couplers connecting the diagonal bracing steel pipes and rebar heads in the middle zone, and then remove the steel pipes. When the age and strength control conditions of the bottom zone are simultaneously met, remove the swivel couplers connecting the diagonal bracing steel pipes and rebar heads in the bottom zone, and then remove the steel pipes. After all supports are removed, check the wall surface for cracks or other abnormal deformations to confirm that the structure is intact.

[0059] In an embodiment of the present invention, during the process of binding vertical steel bars above the top surface of the raft foundation to form a root reference skeleton, the binding height of the vertical steel bars is 1.5 m. Step S21: After the root reference frame is formed, immediately perform a supplementary tightening on the swivel fasteners connected to all the diagonal bracing steel pipes constituting the root reference frame. The tightening torque value is equal to the preset pre-tightening torque to ensure that the locking torque of each swivel fastener is restored to the preset pre-tightening torque.

[0060] It should be noted that "1.5 m" refers to the vertical reinforcement binding height of the root reference skeleton. This height corresponds to the arrangement range of the horizontal reinforcement of approximately two standard floors, and is also the height of the main stress section connecting the diagonal bracing steel pipe and the wall reinforcement skeleton. "Supplementary tightening" refers to an additional torque check and tightening operation specifically performed on all swivel couplers within the skeleton area after the root reference skeleton is formed and before the layer-by-layer horizontal reinforcement binding process begins. This is different from the compensation tightening triggered when the slippage reaches a threshold. "Immediately" means that the supplementary tightening must be completed within 30 minutes after the last vertical reinforcement of the root reference skeleton is bound and fixed.

[0061] Specifically, this technical solution specifies the binding height of the root reference skeleton as 1.5 m. This height comprehensively considers the standard length of the nuclear island wall reinforcement, the effective constraint range of the diagonal bracing steel pipes, and the convenience of construction operations. A root skeleton height of 1.5 m provides a sufficient effective connection section for the diagonal bracing steel pipes, allowing the active constraint force to be evenly transmitted to each vertical reinforcement of the skeleton. The reason for immediately performing supplementary tightening after the root reference skeleton is that during the binding process, the vibration and additional load generated by the hoisting, positioning, and binding of a large number of vertical reinforcements can cause some rotating fastener bolts to become slightly loose, resulting in a decrease in torque values. If supplementary tightening is not performed and the horizontal reinforcement binding stage proceeds directly, the slippage speed of these loosened nodes will significantly increase with subsequent load increases, potentially leading to premature triggering of the preset slippage threshold or monitoring failure. Supplementary tightening restores the torque of all nodes to the initial preset value, establishing an accurate torque benchmark for subsequent slippage monitoring.

[0062] More specifically, the operation is as follows: Tie the vertical reinforcing bars above the top surface of the raft foundation. Measure 1.5 m upwards from the top of the pre-reserved reinforcing bars in the raft foundation. Set temporary horizontal positioning bars at this 1.5 m height to ensure that the tops of all tied vertical reinforcing bars are at the same horizontal elevation. Align all vertical reinforcing bars within the 1.5 m height range with the pre-reserved reinforcing bars in the raft foundation one by one, using tying wire or mechanical connection sleeves for reliable connection. After the vertical reinforcing bars are tied, confirm that the root reference skeleton has been formed. Within 30 minutes, use a torque wrench to check the torque of each swivel coupler connected to all the diagonal bracing steel pipes forming the root reference skeleton and perform supplementary tightening. The target torque value for tightening is equal to the preset pre-tightening torque value applied in the previous steps. For nodes where the torque value is found to be lower than the preset value during the check, tighten to the preset value; for nodes where the torque value remains at the preset value, a verification tightening action should also be performed to confirm that the torque value is stable.

[0063] In an embodiment of the present invention, before setting cross cables diagonally at the top of the completed steel reinforcement cage and applying pretension to the cross cables using a tensioning device, the construction method of the steel reinforcement anti-overturning support system for the upper high wall of the nuclear island raft foundation further includes: Step S41: Use a torque wrench to perform a final comprehensive check on all swivel fasteners to ensure that the locking torque of all connection nodes reaches the pre-tightening torque.

[0064] It should be noted that "final comprehensive verification" refers to the last quality control point before applying the pretension of the cross cables, where the locking torque of each swivel coupler in the support system is checked and confirmed one by one. "All swivel couplers" covers all swivel couplers from the rebar head connection nodes at the base of the raft foundation to all connection nodes of the diagonal bracing steel pipes in each section of the wall. "All connection nodes" includes the connection nodes between the diagonal bracing steel pipes and the rebar heads of the raft foundation, as well as the connection nodes between the diagonal bracing steel pipes and the wall rebar skeleton.

[0065] Specifically, this technical solution adds a final comprehensive verification step before applying the pretension of the cross cables. The purpose is to ensure that the boundary constraints of the steel reinforcement cage are consistent with the design assumptions when the pretension is applied. The self-balancing stress field established by the pretension of the cross cables within the cage relies on the stable constraints provided by the supporting nodes around the cage. If the locking torque of any individual node is insufficient, that node will slip during the pretension application process, causing the pretension to be unable to be effectively transferred to the cage, significantly reducing the stress redistribution effect, and potentially even causing torsional deformation of the cage due to constraint asymmetry. Through the final comprehensive verification, it is confirmed that the locking torque of all nodes reaches the preset value, ensuring that the boundary conditions for pretension application are complete and reliable, enabling the pretension of the cross cables to establish a uniform stress field within the cage according to the expected path.

[0066] More specifically, the operation is as follows: Prepare a calibrated torque wrench and preset the torque value to the preset pre-tightening torque value applied in the aforementioned steps. Check the tightening torque of all swivel fasteners one by one, from bottom to top and from one side to the other. During the check, insert the torque wrench into the hexagonal head of the fastener bolt and rotate the wrench at a constant speed. If the wrench indicates torque arrival before the bolt rotates, it indicates that the tightening torque of that node is not lower than the preset value, and this is recorded as qualified. If the wrench only indicates torque arrival after the bolt has visibly rotated, it indicates that there is torque attenuation at that node; continue tightening until the wrench indicates torque arrival, and this is recorded as re-tightening qualified. Only after all nodes have passed the check can the tensioning operation of the cross cables proceed.

[0067] In an embodiment of the present invention, the step of releasing the flexible tie includes: Step S4021: After the upper section of the steel pipe is erected and the locking torque of the swivel fastener connecting the upper section of the steel pipe and the corresponding rebar head is verified to reach the pre-tightening torque, the flexible tie is released.

[0068] It should be noted that: "Upper section steel pipe" refers to the newly erected diagonal bracing steel pipe during the construction of the upper section of the wall. "Verifying that the pre-tightening torque has been achieved" means using a torque wrench to test the torque of the swivel coupler connecting the upper section steel pipe to the corresponding rebar head, confirming that the tightening torque is equal to or greater than the preset pre-tightening torque value. "Release" means removing the rope clips and wire ropes of the flexible tie members, restoring the unconnected state between the upper section of the rebar skeleton and the lower section of the poured wall.

[0069] Specifically, this technical solution strictly sets the timing for releasing the flexible tie members after the upper section of the steel pipe is erected and the locking torque of the swivel coupler has passed the verification. Its core logic is to ensure a seamless switch in constraint methods. The elastic constraint provided by the flexible tie members at the construction joint is temporary; its function is to provide a stiffness transition phase for the binding and support erection of the upper section of the reinforcing steel skeleton. Once the upper section of the diagonal bracing steel pipe is erected and the locking torque of the swivel coupler has been verified to reach the preset value, the upper support system has the ability to independently provide active constraint, and the load transfer path has been completely transferred from the flexible tie members to the diagonal bracing steel pipe. Releasing the flexible tie members at this time will not weaken the constraint state of the upper section of the reinforcing steel skeleton. If the flexible tie members are released prematurely before the diagonal bracing steel pipe is erected or the torque verification has failed, the upper section of the reinforcing steel skeleton will be in a state of no support or insufficient support after losing the constraint of the flexible tie members. This makes it extremely prone to lateral tilting under its own weight or wind loads, leading to excessive verticality deviations or even overturning of the already bound reinforcing steel skeleton.

[0070] More specifically, the operation is as follows: All the diagonal bracing steel pipes of the upper wall section are erected and positioned according to the design. One end of the steel pipe is connected to the pre-embedded reinforcing bar of the raft foundation via a swivel coupler, and the other end is fixed to the reinforcing bar skeleton of the upper wall section via a swivel coupler. A torque wrench is used to check the torque of each swivel coupler at both ends of the upper steel pipe section. The preset torque value is the same as the preset pre-tightening torque value applied in the previous step. Any nodes with insufficient torque values ​​are tightened until the locking torque of all nodes reaches the preset pre-tightening torque value after verification. Only after confirming that the torque of all upper swivel couplers has passed the torque check can the flexible tie members be removed. During removal, first loosen the rope clamp nut at the end of the wire rope, remove the rope clamp, and then disconnect the wire rope from the upper vertical reinforcing bar and the anchor point of the lower wall section. All wire ropes and rope clamps are then retrieved. The removal sequence can proceed horizontally along the wall section one by one until all flexible tie members are removed.

[0071] The above description is merely an exemplary embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural transformations made based on the technical concept of the present invention and the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A construction method for a reinforced concrete anti-overturning support system for the upper high wall of a nuclear island raft foundation, characterized in that, The support system includes steel bars welded to pre-installed H-shaped steel supports within the raft foundation, steel pipes used as diagonal braces, and swivel fasteners that lock the ends of the steel pipes to the steel bars; wall reinforcement is installed on the raft foundation; the construction method for the anti-overturning support system for the upper high wall reinforcement of the nuclear island raft foundation includes: The steel pipe and the rebar head are connected by the swivel coupler, and a preset pre-tightening torque is applied to the swivel coupler to establish initial active constraint; Vertical steel bars of a predetermined height are tied above the top surface of the raft foundation to form a root reference skeleton; Starting from the root reference skeleton, horizontal steel bars are tied layer by layer upwards. After each preset number of horizontal steel bars are tied, the slippage of the steel pipe end relative to the steel bar head is measured. When the measured slippage reaches a preset threshold, the corresponding swivel fastener is torque compensated and re-tightened until the slippage is eliminated and the locking torque is restored to the pre-tightening torque. The measurement and compensation re-tightening steps are repeated until all the steel bars of this section of the wall are tied. Within a preset height range above the top surface of the concrete construction joint, flexible tie members with an acute angle are installed. The flexible tie members are used to temporarily connect the upper section of vertical steel bars to be tied to the lower section of the poured wall, forming a gradual stiffness transition zone. After the upper section of the steel pipe is erected and the pre-tightening torque is applied, the flexible tie members are released. For the completed steel reinforcement cage, cross cables are installed diagonally at the top. Tensioning equipment is used to apply pretension to the cross cables, so that stress redistribution occurs inside the complete steel reinforcement cage. After the concrete is poured, the wall is divided into multiple areas along its height, and the dismantling and support process is carried out in a zoned and timed manner. The dismantling and support activation conditions for each area include at least the following: the concrete age corresponding to the area reaches the age threshold and the concrete strength corresponding to the area reaches the strength threshold, and the dismantling and support release is carried out from top to bottom zone by zone.

2. The construction method of the reinforced concrete anti-overturning support system for the upper high wall of the nuclear island raft foundation as described in claim 1, characterized in that, The preset preload torque is between 40 N·m and 50 N·m.

3. The construction method of the upper high wall body steel bar anti-overturning support system of the nuclear island raft foundation according to claim 2, characterized in that, The step of measuring the slippage of the end of the steel pipe relative to the end of the reinforcing bar includes: Using a mechanical dial indicator or vernier caliper installed at the connection node between the steel pipe and the rebar head, the displacement between the reference lines preset on the steel pipe and the rebar head is measured; The preset number of layers is 2, and the preset threshold is 2.0 mm.

4. The construction method of the upper high wall body steel bar anti-overturning support system of the nuclear island raft foundation according to claim 3, characterized in that, The step of arranging flexible tie members with acute angles within a preset height range above the top surface of the concrete construction joint, and using the flexible tie members to temporarily connect the upper section of vertical reinforcing bars to be tied to the lower section of the poured wall, includes: Within a height range of 300 mm to 600 mm above the top surface of the construction joint, steel wire ropes at an angle of 30° to 45° to the wall are laid out as the flexible tie members. One end of the steel wire rope is fixed to the vertical steel bar reserved in the upper section, and the other end is fixed to the anchor point at the top of the lower section of the poured wall.

5. The construction method of the upper high wall body steel bar anti-overturning support system of the nuclear island raft foundation according to claim 4, characterized in that, After the steps of installing cross cables diagonally at the top of the completed steel reinforcement cage and applying pretension to the cross cables using tensioning equipment to redistribute stress within the complete steel reinforcement cage, the construction method of the steel reinforcement anti-overturning support system for the upper high wall of the nuclear island raft foundation further includes: A predetermined horizontal thrust is applied to the center of the top of the wall and released instantaneously. The number of oscillation cycles of the free decay of the top horizontal displacement is recorded using a mechanical displacement measuring device installed on the top of the wall. When the number of recorded oscillation cycles does not exceed 3, the overall stiffness of the complete steel reinforcement cage is determined to meet the predetermined anti-overturning requirements.

6. The construction method of the upper high wall body steel bar anti-overturning support system of the nuclear island raft foundation according to claim 5, characterized in that, After the concrete is poured, the wall is divided into multiple zones along its height, and a zoned and timed dismantling process is performed. The dismantling initiation conditions for each zone include at least the following: the concrete age corresponding to the zone reaches the age threshold and the concrete strength corresponding to the zone reaches the strength threshold. The dismantling sequence is a top-down, zone-by-zone release step, including: The wall is divided into a top section, a middle section, and a bottom section along its height, each accounting for one-third of the total wall height; The conditions for initiating the removal of supports in the bottom area are: the concrete pouring is completed and the static curing time is not less than 48 hours, and the compressive strength of the concrete test block cured under the same conditions as the bottom area reaches at least 50% of the design value; The conditions for initiating the dismantling of the supports in the central area are: the concrete pouring is completed and the static curing time is not less than 72 hours, and the compressive strength of the concrete test blocks cured under the same conditions as those in the central area reaches at least 75% of the design value; The conditions for initiating the removal of supports in the top area are: the concrete pouring is completed and the static curing time is not less than 7 days, and the compressive strength of the concrete test block cured under the same conditions as the top area reaches at least 100% of the design value.

7. The construction method of the upper high wall body steel bar anti-overturning support system of the nuclear island raft foundation according to claim 6, characterized in that, The dismantling sequence, which involves releasing the supports section by section from top to bottom, includes the following steps: First, remove the supports in the top area and the cross cables, then remove the supports in the middle area, and finally remove the supports in the bottom area.

8. The construction method of the upper high wall body steel bar anti-overturning support system of the nuclear island raft foundation according to claim 7, characterized in that, During the process of tying vertical steel bars above the top surface of the raft foundation to form the root reference skeleton, the tying height of the vertical steel bars is 1.5 m. After the root reference frame is formed, the swivel fasteners connected to all the diagonal bracing steel pipes constituting the root reference frame are immediately re-tightened. The re-tightening torque value is equal to the preset pre-tightening torque to ensure that the locking torque of each swivel fastener is restored to the preset pre-tightening torque.

9. The construction method of the upper high wall body steel bar anti-overturning support system of the nuclear island raft foundation according to claim 8, characterized in that, Before installing cross cables diagonally at the top of the completed steel reinforcement cage and applying pretension to the cross cables using tensioning equipment, the construction method for the anti-overturning support system of the upper high wall of the nuclear island raft foundation further includes: Use a torque wrench to perform a final comprehensive check on all swivel fasteners to ensure that the locking torque of all connection nodes reaches the pre-tightening torque.

10. The construction method of the reinforced concrete anti-overturning support system for the upper high wall of the nuclear island raft foundation as described in any one of claims 1 to 9, characterized in that, The step of releasing the flexible tie includes: After the upper section of the steel pipe is erected and the locking torque of the swivel fastener connecting the upper section of the steel pipe and the corresponding rebar head is checked to reach the pre-tightening torque, the flexible tie is released.

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