Gravity type caisson special-shaped cantilever parapet prefabricated assembly integral forming structure and method

Abstract

This invention belongs to the field of coastal engineering construction technology, specifically relating to the prefabricated assembly and integral molding structure and method of gravity caisson irregular cantilever breast walls. It includes: S1. Structural layering and segmentation optimization; S2. Cast-in-place support surface unit construction; S3. Prefabrication of prefabricated irregular cantilever components; S4. Transportation and placement of prefabricated components; S5. Offshore installation of prefabricated components; and S6. Post-cast wet connection construction. This invention controls the installation accuracy of a single prefabricated component to within 20mm, shortens the offshore construction period by 40% compared to traditional cast-in-place processes, and reduces overall construction costs by 17%. It ensures the overall stability of large-volume breast walls, with a minimum anti-slip safety factor of over 2.13 and a foundation grounding rate of 77.6%, meeting the nuclear-grade seismic resistance and durability requirements of nuclear power plants. Offshore construction is safe, controllable, economical, and reasonable, filling the technological gap in the prefabricated seismic design of irregular breast walls in the water transport field of nuclear power plants. It is particularly suitable for offshore engineering scenarios with stringent requirements for structural seismic resistance and durability, such as nuclear power plant intakes, and is easy to promote and apply.

Description

Technical Field

[0001] This invention belongs to the field of coastal engineering construction technology, specifically relating to the prefabricated assembly and integral molding structure and method of gravity caisson irregular cantilever breast wall, which is particularly suitable for marine irregular concrete structure projects with strict requirements for structural seismic resistance, durability and construction accuracy, such as nuclear power plant water intake, coastal wharf, breakwater. Background Technology

[0002] With the rapid development of marine engineering construction, the construction of large-volume concrete structures at sea faces multiple challenges, including complex marine environments, stringent technical standards, and tight construction windows. The irregularly shaped cantilevered breast wall on top of gravity caissons is a core load-bearing component of marine structures such as wharves and intake debris net platforms. These components are generally characterized by large volume, large cantilever, and irregular cross-sections. Traditional construction techniques primarily rely on monolithic cast-in-place casting at sea, which has revealed the following unresolved technical difficulties in engineering practice:

[0003] 1. Offshore construction is extremely difficult and carries high operational risks. Cast-in-place construction of irregular cantilever structures requires the erection of large-area offshore formwork and operating platforms. Under the influence of wind, waves, and tides at sea, the safety risks of formwork erection and high-altitude operations are extremely high. Especially for components with cantilever sections of more than 4 meters, the difficulty of erecting and reinforcing the formwork support system increases exponentially, and quality problems such as formwork deformation and bulging are very likely to occur.

[0004] 2. Long construction period and low utilization rate of working window. Traditional cast-in-place construction requires multiple processes to be completed at sea, including rebar tying, formwork erection, concrete pouring, and curing. The effective working days at sea are limited by factors such as monsoons, cold waves, and the closure of the nuclear power plant's cold source grid. Taking the Hongyanhe Nuclear Power Plant intake project as an example, the effective working days at sea decrease sharply after September each year, and offshore construction must be stopped from June to August. The construction period for a single breast wall using cast-in-place construction is more than 25 days, and the overall construction period is 5 months, which is difficult to meet the project's milestone requirements.

[0005] 3. Structural quality and durability are difficult to guarantee. In the harsh marine environment, temperature control, vibration and curing of large-volume cast-in-place concrete are difficult, and quality defects such as temperature cracks and honeycomb pitting are prone to occur. At the same time, cast-in-place structures have many construction joints, and under the action of seawater erosion and repeated loads, the structural durability and impermeability are difficult to meet the 100-year design service life requirements of projects such as nuclear power plant water intakes.

[0006] 4. The seismic performance and overall stability control are challenging. For projects with extremely high seismic fortification requirements, such as nuclear power plant water intakes, under the SL-2 seismic condition, although the integrity of cast-in-place structures is guaranteed, the dispersion of construction quality can easily lead to substandard seismic performance. On the other hand, conventional fully prefabricated assembly processes have weak load-bearing capacity at component splicing nodes, making it difficult to meet the seismic and overall stability requirements of large cantilever structures.

[0007] Among the existing technologies related to prefabricated cantilevered breast walls, the invention patent with publication number CN119571762A discloses a cantilevered breast wall structure, forming method, and wharf berth system. This technology divides the cantilevered breast wall into a prefabricated support structure and a post-cast wall structure. The prefabricated support structure is connected to the side wall of the wharf caisson through a reverse hanging bracket hook, and the post-cast wall structure is cast in place on the top surface of the prefabricated support structure, thereby solving problems such as formwork deformation and component root rot caused by tidal erosion. However, this technology has significant limitations: First, the structural connection is limited to a single type, using side-mounted hooks without a through-type rigid connection, resulting in weak joint stress and an inability to meet the overall stability requirements of large-volume, irregularly shaped cantilevered structures. Second, it lacks nuclear-grade seismic design and has not conducted calculations and structural optimizations for the extreme SL-2 earthquake condition, making it unsuitable for high seismic fortification projects such as nuclear power plant water intakes. Third, it suffers from poor construction precision and adaptability, lacking modular disassembly, precise positioning and installation, and specialized hoisting equipment, making it only suitable for small cantilevered breast walls in conventional wharves and unsuitable for large-volume, large-cantilever, irregularly shaped marine structures. Fourth, the stress system is unreasonable, lacking a cast-in-place support structure, resulting in low vertical load transfer efficiency and significant difficulty in controlling stability during construction.

[0008] Significant gaps exist in existing technologies and research both domestically and internationally: Domestic research on prefabricated hydraulic breast walls currently focuses primarily on standard cross-section components, with almost no research on the seismic design of prefabricated irregular breast walls; existing relevant standards and research findings only provide macroscopic design principles for cast-in-place irregular breast wall structures, without establishing design calculation methods, node construction schemes, and verification systems for prefabricated irregular breast walls under the SL-2 seismic condition of nuclear power plants; there is a lack of mature technical solutions and engineering practices for key issues such as modular disassembly, hoisting punching shear design, and stress verification during construction of large cantilever and multi-cantilever irregular breast walls, making them unsuitable for the nuclear safety design requirements of nuclear power plant projects. Foreign studies have focused on the seismic performance of the overall caisson structure, with limited research on the prefabricated seismic design of the superstructure irregular breast wall. A combined seismic design method for irregular breast walls consisting of "cast-in-place support surface plus precast blocks" has not been developed. Furthermore, the relevant seismic design codes for nuclear power hydraulic structures and the standards for selecting ground motion parameters differ significantly from the domestic code system, making it impossible to directly adapt to the design compliance requirements of domestic nuclear power projects.

[0009] Existing research has not yet filled the industry gap in the prefabricated seismic design of irregularly shaped breast walls under the special operating conditions of nuclear power plants, and cannot simultaneously resolve the dual contradictions of "high difficulty in offshore construction" and "high requirements for overall structural stress and nuclear-grade seismic performance." Therefore, there is an urgent need to develop an innovative technical solution that combines ease of construction, structural safety, and controllable quality to address the industry pain points of constructing irregularly shaped cantilevered breast walls at sea. Summary of the Invention

[0010] The core objective of this invention is to overcome the aforementioned deficiencies of the prior art. On the one hand, it addresses the problems of difficult formwork installation, long construction period, high safety risks, and difficult quality control in the on-site construction of large-volume, irregularly shaped cantilevered components at sea. On the other hand, it solves the problems of weak stress at conventional prefabricated process nodes, insufficient overall structural stability and seismic performance, and inability to meet the requirements of extreme seismic conditions in nuclear power plants like SL-2. The invention provides a prefabricated installation and integral molding structure and method for irregularly shaped cantilevered breast walls at sea, achieving the core objectives of "standardized prefabrication on land to reduce risks, rapid installation at sea to improve efficiency, post-cast wet connection to ensure overall stress resistance, and full-process design to control nuclear-grade seismic resistance."

[0011] To achieve the aforementioned objectives, this invention employs a combined system of partially cast-in-place, partially precast, and post-cast integral molding. It innovatively adopts a modular design method guided by functional requirements and verifying load-bearing performance. It pioneers a combined structural system of cast-in-place support surfaces, precast blocks, and through-core structures. It establishes a nuclear-grade seismic design method involving multi-mechanical model coupling, multi-condition verification, and multi-index control. It also develops a complete set of construction technologies, including full-process precision control, specialized hoisting equipment, and intelligent monitoring and management. The specific technical solutions are as follows:

[0012] The gravity caisson irregular cantilever breast wall prefabricated assembly integral molding structure includes four core parts: caisson foundation, cast-in-place support surface unit, prefabricated irregular cantilever component unit, and post-cast wet connection unit.

[0013] 1. Caisson foundation: It is a gravity-type circular or rectangular caisson, which serves as the load-bearing foundation for the breast wall structure. After the caisson is installed, the filling material and concrete sealing layer inside the caisson are completed, and the top is reserved with frustum nuts and outward reinforcing bars.

[0014] 2. Cast-in-place support surface unit: This is the extension section cast in place on top of the caisson at sea. Its external dimensions are completely consistent with the cross-section of the top of the caisson. The height is determined according to the installation height difference of the caisson and the length of the extended steel bars, preferably 2.25m. Its top surface is a mechanically smoothed precast component installation reference surface. The interior is reserved with a through cavity corresponding to the post-cast wet connection unit. The inner wall of the cavity adopts a non-removable template system, which does not need to be removed later. The top surface is pre-embedded with limiting devices for guiding the installation of precast components, and anchoring points for pre-embedded reinforcing bars are reserved along the perimeter of the cavity.

[0015] 3. Precast Irregular Cantilever Component Unit: This is a large-volume irregular cantilever concrete component precast on land, with the same architectural shape as the original breast wall design. The complex cantilever beam design of the original design is optimized into a rectangular section, reducing the difficulty of prefabrication and hoisting. The internal core block cavity is reserved and coaxially connected with the cavity of the cast-in-place support surface unit, forming a core-locking structure that runs through the upper and lower parts. The upper and lower layers of steel mesh inside the component are continuously connected at the core block cavity without being cut off. Multiple lifting rings are symmetrically embedded at the top of the component according to the hoisting calculation. Post-cast areas are set on both sides of the component to reduce weight. The weight of a single piece is controlled within 85% of the rated lifting capacity of the crane vessel, preferably within 600t.

[0016] 4. Post-cast wet connection unit: This is the core component for achieving overall structural load-bearing and seismic performance. It includes a post-cast core block running through the coaxial cavity, reserved post-cast blocks on both sides of the precast component, and two rows of embedded reinforcing bars arranged around the cavity. The midpoint of the embedded reinforcing bars is located at the interface between the cast-in-place surface and the precast component, and the upper and lower ends extend into the precast component and the cast-in-place surface to the designed depth, preferably not less than 960mm. The post-cast core block and the reserved post-cast blocks are integrally cast using a higher grade of micro-expansion concrete, filling all cavities and post-cast areas, so that the cast-in-place surface and the precast irregular cantilever component form a rigidly connected overall load-bearing structure.

[0017] This structural system follows a collaborative load-bearing mechanism, relying on supports for vertical load transfer and interlocking for horizontal load transfer. The bottom of each precast block has a roughened support surface, which, during installation, is leveled with mortar and adheres to the top surface of the cast-in-place section, primarily bearing the vertical load transfer. A 1.0m diameter through-hole is pre-reserved at the corresponding position of the precast block and the cast-in-place section. After the precast block is installed, steel sections or precision-rolled threaded steel bars are inserted into the hole, followed by the pouring of non-shrinkage high-strength concrete, forming a through-hole interlocking shear resistance system. This transforms the most critical horizontal shear force transfer path in seismic design from contact surface friction to interlocking shear resistance, significantly improving the shear bearing capacity and deformation capacity of the connection nodes. The 600mm wide post-cast strip between two precast blocks is achieved through pre-reserved steel bar lap splices or mechanical connections, enabling lateral collaborative load-bearing between the blocks and ensuring the integrity of the superstructure.

[0018] The limiting device embedded in the top surface of the cast-in-place support surface is a trapezoidal steel limiter welded from I-beams. One limiter is arranged every 2m along the installation edge of the precast component. The distance between the limiting device and the installation edge is 20mm. Its sloping surface faces the installation side of the precast component. During installation, the component can slide down the sloping surface into place, achieving millimeter-level precision control.

[0019] At the interface between the cast-in-place support surface and the precast irregular cantilever component, a 10-20mm thick layer of high-grade cement mortar is provided to eliminate gaps at the interface and ensure smooth vertical force transmission. Two rows of reinforcing bars are installed around the core block cavity between the two, and micro-expansion concrete is poured to fill the gaps and improve the horizontal shear resistance under seismic conditions.

[0020] The construction method for a prefabricated and assembled monolithic structure with an irregular cantilevered breast wall in a gravity caisson includes the following steps:

[0021] S1. Structural layering and block optimization

[0022] A functional requirements-oriented design approach combined with stress performance verification was adopted, dividing the irregularly shaped, large-volume cantilevered breast wall above the caisson into three major construction modules: a lower cast-in-place support surface unit, an upper precast irregularly shaped cantilever component unit, and a middle post-cast wet connection unit. The modular design adhered to the principles of clear functional zoning, reasonable structural stress, standardized interfaces, and balanced weight distribution. The modular design avoided high-stress areas, prioritizing sections with lower structural stress. The maximum weight of a single component was determined based on the capabilities of the construction equipment, serving as the fundamental constraint for modularization. Simultaneously, the formwork for the cast-in-place structure, the reinforcement and lifting point details for the precast components, and the seismic design of the post-cast joints were completed. Stress analyses were performed on the modularized components under various conditions, including lifting, support, and seismic events, verifying their structural safety under different stress states. Provisions were made for future connections at the modular interfaces to ensure that the overall structural performance was not compromised by the modularization process.

[0023] Simultaneously, mechanical protection design for key working conditions during the construction period was carried out, high-risk working conditions were systematically identified throughout the entire prefabricated construction process, and hoisting and placement of uncast post-pouring strips were selected as control working conditions:

[0024] Lifting condition calculation: The maximum weight of a single breast wall is calculated as 6280kN. There are 8 lifting points. After considering the partial factor of 1.2, the unevenness factor of 1.3, and the dynamic factor of 1.3, the force on a single lifting point is 1591.98kN. The punching shear bearing capacity of the concrete is calculated in accordance with the "Code for Design of Concrete Structures of Water Transport Engineering" to ensure that the design value of the punching shear bearing capacity is greater than the maximum force on a single lifting point.

[0025] Calculation of the suspended condition: For the stage where the precast blocks are hoisted and installed on the top of the caisson but the post-cast strip has not yet been poured, the structural strength and stability of the precast body in the suspended condition are calculated to ensure that the reinforcement scheme under the design bending moment and shear force meets the structural bending, shear and crack control requirements. At the same time, the overall stability of the structure in the suspended condition is calculated to ensure that overturning or slippage will not occur.

[0026] S2. Construction of cast-in-place supporting surface unit

[0027] After the caisson installation and the filling and concrete sealing layer construction are completed, the offshore cast-in-place extension section construction will commence: Reinforcing bars will be fabricated in the background, transported to the site by flat barge, and manually tied. Reinforcing bar joints will be mechanically connected, with the joint rate at the same cross-section not exceeding 50%. Precast steel formwork will be used for the caisson's outer panels, reinforced at the bottom with pre-reserved frustum nuts on the top of the caisson, and reinforced at the top with tie rods. Adjacent formwork will be fixed with bolts. Removable formwork will be installed at the reserved core block cavity positions, and trapezoidal limiting devices will be embedded in the top surface. Concrete will be mixed at an onshore mixing plant and poured using a ground pump, with each layer not exceeding 50cm in thickness, and compacted using an immersion vibrator. After pouring, curing liquid will be used for curing, with the top surface flatness controlled within 10mm and the elevation deviation controlled within ±10mm. Curing will continue until the design strength is reached, forming an installation reference surface.

[0028] S3. Precast irregular cantilever components

[0029] Components are prefabricated in a land-based prefabrication yard near the dock. The prefabrication yard is hardened with a 20cm thick C30 concrete surface layer and a 15cm thick crushed stone cushion layer, and the flatness of the bottom surface is controlled within 10mm. Universal reusable prefabricated steel bar binding tools and truss-type prefabricated steel bar hoisting tools are used to achieve overall binding, overall hoisting and precise positioning of the steel bars for the outer wall and inner partition wall of the caisson, thereby improving the quality and efficiency of steel bar construction from the source.

[0030] After the formwork is erected, the reinforcing bars are tied, and the core cavity and the weight-reducing post-cast area on both sides are reserved. The upper and lower layers of reinforcing mesh are continuously connected in the cavity. According to the hoisting calculation results, eight Q355B round steel lifting rings are symmetrically embedded in the top of the component. The formwork adopts a steel-wood combination formwork, which is reinforced with flange plates and tie bolts. The concrete is mixed at a batching plant and poured in layers by a boom pump, with a layer thickness of no more than 50cm. The concrete is vibrated with an immersion vibrator. After the pouring is completed, the concrete is immediately covered with geotextile and plastic sheeting. After the final setting, it is cured with fresh water for no less than 14 days. The component can only be shipped after its strength reaches 100% of the design strength.

[0031] S4. Precast component shipping and placement

[0032] A 1000t crane vessel, equipped with a specialized steel gantry, was used for loading precast components. The main chord of the gantry was constructed from Ф1020×16mm Q235 seamless steel pipe, internally filled with C40 micro-expansion concrete; the vertical web members were constructed from Ф480×16mm Q235 seamless steel pipe. A 20m long, 100t high-strength ring-type sling was used to connect the gantry to the precast component, coupled with a 120t bow-shaped shackle. A 42m long, 350mm... The components are connected by polymer ring slings. When lifting, the components are lifted 20cm off the ground and left to stand for 10 minutes. After checking for any abnormalities, they are then lifted onto a 6000t transport barge. The components are loaded onto a double-layer barge, with 800mm×150mm×220mm wooden supports between the layers. The components are reinforced by anchors on the ship's deck and cables. The transport barge is transported to the construction site along the pre-designated channel. The crane ship and the transport barge are then positioned on-site, with the bow of the crane ship facing the installation position and the transport barge positioned perpendicular to the crane ship.

[0033] S5. Offshore installation of prefabricated components

[0034] One hour before installation, the mating surfaces of the cast-in-place support surface and the bottom surface of the precast component are roughened, moistened with fresh water, and coated with a 10-20mm thick layer of high-grade cement mortar. Four GPS receiving antennas are installed on the top surface of the precast component, and the three-dimensional position of the component is fed back in real time through the receiving device on the ship. The crane ship lifts the component above the installation position, and the component position is adjusted by the guide action of the trapezoidal limit device and the GPS automatic positioning system. The component is then slowly lowered into place, and the deviation of the installation plane position is controlled within 20mm. During the lifting process, the stress state of the lifting is monitored throughout the process by a multi-point lifting stress real-time monitoring system. A combination of long gauge length overall stress monitoring and short gauge length local stress capture sensor network is used, along with wireless data transmission, real-time intelligent analysis and dual-level dynamic early warning modules, to keep the stress deviation of the lifting points stable within 5% throughout the lifting process. Temporary fixed steel supports are installed immediately after the lifting is completed to ensure the stability of the component.

[0035] S6. Post-pouring wet connection construction

[0036] The concrete bonding surfaces of the core block cavity and the reserved post-cast area are thoroughly roughened to expose fresh coarse aggregate. A 1m x 1m operating hole is made in the steel mesh at the core block cavity of the precast component. Construction personnel enter the cavity and install two rows of pre-embedded reinforcing bars around the perimeter. After the reinforcing bars are installed, the steel mesh is welded to restore its integrity. The old concrete bonding surface is cleaned with high-pressure water. The formwork for the post-cast area is erected and, after acceptance, micro-expansion concrete of a grade one higher than that of the main structure is used. The post-cast core blocks and reserved post-cast blocks are poured in layers, with a layer thickness not exceeding 50cm, and continuous pouring without construction joints. After pouring, the entire structure is covered with geotextile and continuously sprayed with fresh water for moisturizing and curing for no less than 14 days. After curing, the entire breast wall structure is formed, and construction is completed.

[0037] For the extreme seismic conditions of the SL-2 nuclear power plant, this method forms a complete nuclear-grade seismic design and verification system: The Duncan-Chang EB static model is used to simulate the nonlinear stress-strain relationship of the soil during construction, and the incremental analysis method is used to simulate the layered filling construction process to obtain the initial stress field before the earthquake; an equivalent linear viscoelastic dynamic model is used to simulate the nonlinear and hysteretic characteristics of the soil under seismic action, the Newmark method is used to solve the motion equations, and the damping matrix is ​​determined by combining Rayleigh damping theory; the radiation damping effect of the infinite domain of the foundation is simulated through a viscoelastic artificial boundary; the US RG1.60 spectrum is selected as the seismic motion input, with horizontal and vertical acceleration time history amplitudes of 0.18g and 0.12g, respectively. Multi-dimensional verification is performed on structural strength, anti-sliding and anti-tilting stability, foundation bearing capacity, foundation grounding ratio, and seismic performance of connection nodes to ensure that the structure meets the nuclear-grade seismic requirements.

[0038] This invention overcomes the shortcomings of conventional prefabricated construction technology compared to existing technologies, and combines construction safety, structural seismic resistance, quality control, and economic efficiency. Specific beneficial effects are as follows:

[0039] 1. Improved Structural Performance. Addressing the weak points of existing side-mounted hook connections, this invention pioneers a combined structural system of cast-in-place support surfaces, precast blocks, and through-core fasteners. Combined with pre-embedded reinforcing bars and post-cast wet connections using micro-expansion concrete, it achieves rigid integration of the upper and lower structures. Calculations under extreme seismic conditions (SL-2) show an anti-slip safety factor ≥2.13 and a foundation grounding rate of 77.6%, far exceeding nuclear power specifications. This fills the gap in seismic design for prefabricated breast walls in the nuclear power and water transport sector, completely resolving the shortcomings of conventional prefabricated structures in terms of seismic resistance.

[0040] 2. Optimized load-bearing system. Abandoning the existing side-hanging load-bearing mode, the cast-in-place surface on the top of the caisson is used as the exclusive support reference surface for prefabricated components. Vertical loads are directly transferred to the caisson foundation, and the load-bearing path is clear and reasonable. The split interface avoids high-stress areas. With the support of hoisting and placement multi-condition mechanical calculations, there is no risk of overturning or slippage during construction. It is suitable for the construction of large-volume irregular components of 600t class, and its stability far exceeds that of conventional side-hanging prefabricated structures.

[0041] 3. Intelligent construction. We have developed a dual-control installation process combining physical limiting and GPS automatic positioning, as well as specialized hoisting equipment and a real-time stress monitoring system. The installation accuracy of precast components is ≤20mm. High-altitude operations at sea are reduced by more than 60%, and the installation of a single component takes only 2 hours. The overall construction period is shortened by 40% compared to traditional cast-in-place construction, and the efficiency is improved by 30% compared to the existing tidal-adaptive process. The overall construction cost is reduced by 17%.

[0042] 4. Expanding the scope of engineering applications. Unlike existing technologies that are only suitable for small cantilevered breast walls at conventional wharves, this invention can be adapted to demanding marine engineering scenarios such as nuclear power plant intakes, breakwaters, and cross-sea piers, involving large volumes, large cantilever sections, high seismic resistance, and high durability. Standardized prefabrication on land avoids the impact of harsh marine environments, ensuring a 100% component acceptance rate, a frost resistance rating ≥F400, and meeting a 100-year design service life. Its industrialization and scalability are significantly superior to existing technologies.

[0043] 5. Simplify offshore construction procedures. More than 90% of offshore high-altitude formwork and rebar tying operations are converted to onshore factory construction, eliminating the need to erect offshore cantilever formwork scaffolds, completely avoiding the risks of high-altitude operations caused by wind, waves and tides, and eliminating common quality problems such as formwork deformation, bulging, and component root decay. The construction safety and controllability are comprehensively superior to traditional cast-in-place processes. Attached Figure Description

[0044] Figure 1 This is a top view of the overall structure of the present invention;

[0045] Figure 2 For the present invention Figure 1 Schematic diagram of the overall structure of section AA;

[0046] Figure 3 For the present invention Figure 1 Schematic diagram of the overall structure of the BB section;

[0047] Figure 4 This is a detailed structural drawing of the limiting device of the present invention;

[0048] Figure 5 This is a schematic diagram of the arrangement of lifting points for the prefabricated components of the present invention;

[0049] Figure 6 This is a schematic diagram of the special steel hanger structure of the present invention;

[0050] In the figure: 1-caisson; 2-cast-in-place support surface unit; 3-precast irregular cantilever component unit; 4-post-cast core block; 5-limiting device; 6-lifting ring; 7-embedded reinforcing bar; 8-reserved post-cast block; 9-removable formwork system; 10-grouting layer; 11-GPS receiving antenna. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to the accompanying drawings and specific engineering embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the technical solutions 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.

[0052] Example 1

[0053] This embodiment relies on the Liaoning Hongyanhe Nuclear Power Plant intake debris barrier renovation project. The second debris barrier adopts a circular caisson-type independent pier structure, consisting of 10 circular caissons, each with a diameter of 14.4m, a height of 16.5m, and a net distance of 10.6m between caissons. The original design for the upper part of the caissons was a monolithic cast-in-place irregular concrete breast wall, divided into three models: A, B, and C. The bottom elevation of the breast wall is +1.5m, the top elevation is +5.75m, the maximum cantilever reaches 4.2m, and the cantilever end has a 4.23m cantilever, which is a typical offshore irregular large-volume cantilevered breast wall. This project is a key project for the cold source guarantee of the nuclear power plant and must meet the nuclear-grade seismic resistance requirements of the SL-2 extreme seismic condition. The corresponding zero-cycle site bedrock ultimate safety horizontal seismic acceleration is taken as 0.18g, and the vertical peak value is taken as 0.12g, which places extremely high requirements on the structural seismic performance, durability, and construction precision.

[0054] This embodiment employs the prefabricated and assembled integral molding structure construction method of the gravity caisson irregular cantilevered breast wall of the present invention, and the specific implementation is as follows:

[0055] I. Gravity-type caisson irregular cantilevered breast wall prefabricated assembly integral molding structure

[0056] 1. Layered and segmented division: The original 4.25m high monolithic cast-in-place breast wall was divided into a lower 2.25m high cast-in-place support surface unit, an upper 2.0m high precast irregular cantilever component unit, and a middle post-cast wet connection unit. The cast-in-place support surface unit has a bottom elevation of +1.5m and a top elevation of +3.75m, consistent with the caisson diameter of 14.4m, perfectly covering the caisson's top protruding reinforcing bars (protruding height 1.43m), thus resolving the issue of installation height differences between the caisson and the protruding reinforcing bars affecting installation.

[0057] 2. Cavity and core design: Inside the cast-in-place support unit and the precast irregular cantilever component unit, a coaxial core cavity with a size of 6.34m×11.8m is reserved to form a core structure that runs through the top and bottom; the upper and lower layers of steel mesh in the precast component are continuously connected in the cavity without being cut off, ensuring the integrity of the structure.

[0058] 3. Weight reduction and optimization of precast components: The original complex cantilever slab beam design was optimized into a rectangular section. At the same time, 800mm wide precast blocks were set on both sides of the precast components to reduce weight. The final weight of a single A-type breast wall precast block is 575t, a single B-type breast wall block is 550t, and the C-type is split into 3 blocks (595t+543t+543t). All of these weights are controlled within the rated lifting capacity of 600t of the 1000t crane vessel on site, which is 75% of the rated lifting capacity of the crane vessel, thus meeting the safety requirements.

[0059] 4. Lifting point design: Each type of precast block is symmetrically equipped with 8 lifting points. The lifting rings are made of Q355B round steel with a diameter of 100mm. The pre-embedded position and depth are determined by punching shear test. The design value of the punching shear bearing capacity of a single lifting point is 2897.66kN, which is much greater than the maximum force of 1591.98kN of a single lifting point, thus meeting the lifting safety requirements.

[0060] 5. Limiting and shear resistance design: Trapezoidal limiting devices are pre-embedded on the top surface of the cast-in-place support surface. They are made of I25b I-beams and are arranged at 2m intervals, with a distance of 20mm from the installation edge. Two rows of reinforcing bars are set around the perimeter of the core block cavity to improve the horizontal shear resistance.

[0061] 6. Wet connection design: Two rows of 32mm diameter HRB400 pre-embedded reinforcing bars are set around the perimeter of the core block cavity. The midpoint of the reinforcing bars is located at the joint surface, and the upper and lower ends extend into the cast-in-place section and the precast section by 960mm respectively. The post-cast core block and the reserved post-cast block are made of C50 micro-expansion concrete (one grade higher than the main C45 concrete), with a frost resistance grade of F400, which meets the durability requirements of nuclear power engineering.

[0062] 7. Nuclear-grade seismic resistance verification was performed using GEODYNA software developed by Dalian University of Technology. A three-dimensional finite element model was established with a total of 280,000 elements and approximately 720,000 degrees of freedom. The seismic input used the American RG1.60 spectrum, with horizontal and vertical acceleration time history amplitudes of 0.18g and 0.12g, respectively. The verification results are as follows:

[0063] Structural strength: Under seismic loading, the maximum principal stress of the sump is 4.03 MPa and the minimum principal stress is -1.42 MPa, both of which are far below the design strength of C45 concrete for compressive (21.1 MPa) and tensile (1.8 MPa).

[0064] Overall stability: The minimum anti-slip safety factor of caissons A1 and B1 is 2.13-2.33, and the minimum anti-tipping safety factor is 1.93-3.06, both of which meet the requirement of greater than 1.2 in the specification;

[0065] Foundation bearing capacity: The maximum average vertical stress on the top surface of the rubble foundation bed is 350-950 kPa, and the vertical stress at the edge is about 1200 kPa, both of which are less than the corresponding limits;

[0066] Foundation grounding ratio: Under seismic loading, the grounding ratio of the sump foundation of SL-2 is 77.6%, which is higher than the standard requirement of 50%.

[0067] Seismic performance of nodes: The maximum combined shear force borne by a single shear key in caisson A1 is 314kN, and in caisson B1 it is 368kN. The design bearing capacity of the shear keys fully meets the requirements.

[0068] II. Construction Method of Gravity-Type Caisson Irregular Cantilevered Breast Wall Prefabricated Assembly Integral Forming Structure

[0069] S1. Structural layering and block optimization

[0070] A functional requirements-oriented design approach combined with stress performance verification was adopted, dividing the irregularly shaped, large-volume cantilevered breast wall above the caisson into three major construction modules: a lower cast-in-place support surface unit, an upper precast irregularly shaped cantilever component unit, and a middle post-cast wet connection unit. The modular design adhered to the principles of clear functional zoning, reasonable structural stress, standardized interfaces, and balanced weight distribution. The modular design avoided high-stress areas, prioritizing sections with lower structural stress. The maximum weight of a single component was determined based on the capabilities of the construction equipment, serving as the fundamental constraint for modularization. Simultaneously, the formwork for the cast-in-place structure, the reinforcement and lifting point details for the precast components, and the seismic design of the post-cast joints were completed. Stress analyses were performed on the modularized components under various conditions, including lifting, support, and seismic events, verifying their structural safety under different stress states. Provisions were made for future connections at the modular interfaces to ensure that the overall structural performance was not compromised by the modularization process.

[0071] Simultaneously, mechanical protection design for key working conditions during the construction period was carried out, high-risk working conditions were systematically identified throughout the entire prefabricated construction process, and hoisting and placement of uncast post-pouring strips were selected as control working conditions:

[0072] Lifting condition calculation: The maximum weight of a single breast wall is calculated as 6280kN. There are 8 lifting points. After considering the partial factor of 1.2, the unevenness factor of 1.3, and the dynamic factor of 1.3, the force on a single lifting point is 1591.98kN. The punching shear bearing capacity of the concrete is calculated in accordance with the "Code for Design of Concrete Structures of Water Transport Engineering" to ensure that the design value of the punching shear bearing capacity is greater than the maximum force on a single lifting point.

[0073] Calculation of the suspended condition: For the stage where the precast blocks are hoisted and installed on the top of the caisson but the post-cast strip has not yet been poured, the structural strength and stability of the precast body in the suspended condition are calculated to ensure that the reinforcement scheme under the design bending moment and shear force meets the structural bending, shear and crack control requirements. At the same time, the overall stability of the structure in the suspended condition is calculated to ensure that overturning or slippage will not occur.

[0074] S2. Construction of cast-in-place supporting surface unit

[0075] After the caisson installation and the filling and concrete sealing layer construction are completed, the offshore cast-in-place extension section construction will commence: Reinforcing bars will be fabricated in the background, transported to the site by flat barge, and manually tied. Reinforcing bar joints will be mechanically connected, with the joint rate at the same cross-section not exceeding 50%. Precast steel formwork will be used for the caisson's outer panels, reinforced at the bottom with pre-reserved frustum nuts on the top of the caisson, and reinforced at the top with tie rods. Adjacent formwork will be fixed with bolts. Removable formwork will be installed at the reserved core block cavity positions, and trapezoidal limiting devices will be embedded in the top surface. Concrete will be mixed at an onshore mixing plant and poured using a ground pump, with each layer not exceeding 50cm in thickness, and compacted using an immersion vibrator. After pouring, curing liquid will be used for curing, with the top surface flatness controlled within 10mm and the elevation deviation controlled within ±10mm. Curing will continue until the design strength is reached, forming an installation reference surface.

[0076] After the caisson installation, internal filling, and C15 concrete sealing layer construction are completed, offshore cast-in-place construction will commence.

[0077] Rebar processing: Rebar is processed on land and transported to the site by flatbed barge. It is then hoisted by a 150t crawler crane and manually tied. Rebar joints are made using straight thread mechanical connections, with the joint rate at the same cross section not exceeding 50%. Protective layer spacers are arranged in a staggered pattern at 1 piece / m², and upper and lower layers of rebar are supported by stirrups.

[0078] Template erection: Four prefabricated outer arc steel templates are used for the caisson, each covering 1 / 4 of the circumference; the bottom of the template is reinforced on the pre-reserved frustum nut on the top of the caisson, and the top is reinforced with Φ25 round steel tie rods, and adjacent templates are fixed with bolts; a channel steel walkway is pre-welded to the outside of the top of the caisson as an operating platform; a non-removable template is installed at the core block cavity position and firmly fixed with Φ22 threaded steel.

[0079] Concrete pouring: C45F400 concrete produced by an onshore mixing plant is used, transported to the site by tanker truck, and poured by ground pump; the thickness of each layer is no more than 50cm, and immersion vibrators are used for compaction, with the vibration spacing no more than 1.5 times the effective radius of the vibrator; after pouring, the top surface is mechanically smoothed, and the flatness is controlled within 10mm. Curing liquid is used for curing, and the curing period is no less than 7 days. After the strength reaches 100% of the design strength, the next process can be carried out.

[0080] S3. Precast irregular cantilever components

[0081] The prefabrication site was selected at the wharf in front of the Xinde caisson prefabrication yard on Changxing Island. The site was hardened in advance. The prefabrication yard was hardened with a 20cm thick C30 concrete surface layer and a 15cm thick crushed stone cushion layer. The flatness of the bottom surface was controlled within 10mm. A general-purpose, reusable prefabricated steel bar binding tool was used. The steel bars were cut and processed in the prefabrication yard's processing workshop. An 80t truck crane lifted and transported the steel bars to the prefabrication station, where the overall steel bar skeleton was manually bound. Before binding, wood pulp cardboard was fully laid on the bottom surface to reduce the adhesion between the steel bar skeleton and the bottom surface and to prevent steel bar contamination and corrosion. During the operation, the spacing of the steel bars and the thickness of the protective layer were strictly controlled to ensure the forming accuracy and overall stability of the steel bar skeleton.

[0082] Formwork erection: Considering the unique structural features of the breast wall, the side formwork utilizes a combination of customized steel formwork of various models. For special irregular sections, a steel-wood composite formwork is used, balancing structural forming accuracy with adaptability to the irregular structure. After the formwork passes inspection upon arrival, the surface is ground to remove rust and a release agent is evenly applied. M25 tie rods are used for reinforcement, with the spacing between tie rods at 30cm from the ground strictly controlled at 80cm. The tie rods are fitted with PVC sleeves to prevent them from contaminating the concrete and affecting the component's appearance. For the sides penetrating the core area, non-removable formwork is used for erection, ensuring the forming quality of irregularly shaped openings.

[0083] Concrete pouring and curing: C45F400 antifreeze concrete is poured using a super pump. The pouring process adopts a layered continuous pouring process, with the thickness of each layer strictly controlled to ≤50cm, ensuring that the upper layer is poured before the lower layer of concrete sets, and eliminating construction cold joints. The vibration operation follows the principle of "quick insertion and slow withdrawal", with special attention paid to vibrating irregular corners and areas with dense reinforcement to avoid missed vibration or over-vibration. After the concrete strength reaches the design demolding requirements, the formwork is removed, and then the concrete is fully covered with geotextile and continuously sprayed with fresh water for moisturizing and curing. The curing period is not less than 14 days, and the components can only be shipped after the strength reaches 100% of the design strength.

[0084] S4. Precast component shipping and placement

[0085] A 1000t crane vessel, equipped with a specialized steel gantry, was used for loading precast components. The main chord of the gantry consisted of Ф1020×16mm Q235 seamless steel pipe filled with C40 micro-expansion concrete; the vertical web members were made of Ф480×16mm Q235 seamless steel pipe. A 20m long, 100t high-strength ring-type sling was used to connect the gantry to the precast component, along with a 120t bow-shaped shackle. A 42m long, 350t polymer ring-type sling was used to connect the gantry to the main hook of the crane vessel. After the components were lifted 20cm off the ground, they were left to stand for 10 minutes. Once no abnormalities were found, they were then hoisted onto a 6000t transport barge. The components were loaded onto a double-layer barge, with 800mm×150mm×220mm wooden supports between the layers. The barge was reinforced with anchors on the ship's deck and cables. The transport barge traveled along the Hulushan Bay waterway of Changxing Island to the Hongyanhe construction area, a distance of approximately 33 nautical miles. Before transport, the stability of the components was calculated, and the transport was carried out only after approval from the traffic management department. The status of the components and the ship was monitored in real time throughout the entire process using a caisson floating remote monitoring system.

[0086] S5. Offshore installation of prefabricated components

[0087] On-site positioning: When the 1000t crane vessel is positioned, its bow faces the installation location, and the transport barge is perpendicular to the crane vessel. The water depth in the installation area is -6.5m, which meets the draft requirements of both the crane vessel and the transport barge. The furthest installation distance is 37m. At this distance, the crane vessel's rated lifting capacity is 800t, and the total weight of the components and lifting gear is 600t, which is 75% of the rated lifting capacity, meeting the safety requirements.

[0088] Preparations before installation: One hour in advance, roughen the top surface of the cast-in-place support surface, moisten it with fresh water, and apply a 15mm thick C50 cement mortar bedding layer; manually roughen the bonding surface of the post-cast strip area to expose fresh coarse aggregate; install one GPS receiving antenna at each of the four corners of the top surface of the precast component, connect it to the ship's automatic positioning system, and provide real-time feedback on the component's position; install stress monitoring sensors on the inclined surface of the hook and connect them to the real-time hoisting stress monitoring system.

[0089] Lifting and positioning: The crane vessel lifts the component to 10cm above the installation position, adjusts the component's planar position using the GPS system, and slowly lowers the component along the slope of the trapezoidal limit device for positioning, guided by the trapezoidal limit device. During installation, the stress monitoring system monitors the stress on the lifting points in real time, keeping the stress deviation within 5%. After installation, temporary steel supports are immediately installed to ensure the stability of the component. After installation, measurements are taken and verified, with the planar position deviation controlled within 20mm and the top elevation deviation controlled within ±10mm.

[0090] S6. Post-pouring wet connection construction

[0091] Surface treatment and reinforcement bar installation: All surfaces of the core block cavity and the reserved post-cast area are thoroughly roughened, laitance and loose stones are removed, and the surface is cleaned with high-pressure water; 1m×1m working holes are made in the steel mesh at the core block cavity of the precast component, and construction personnel enter the cavity to install two rows of Φ32 pre-embedded reinforcement bars around the perimeter. The anchorage length of the upper and lower ends of the reinforcement bars is 960mm. After installation, the reinforcement mesh is welded to restore the integrity.

[0092] Shear key construction: Insert steel sections into the reserved shear key ducts and fill them with micro-expansion concrete to make them dense.

[0093] Formwork erection: Steel formwork is used to erect the reserved post-cast block area, which is reinforced and secure, with tight joints to prevent grout leakage.

[0094] Concrete pouring and curing: C50 micro-expansion concrete is used, poured by ground pump, with each layer not exceeding 50cm in thickness, poured continuously, and vibrated to ensure that the concrete in the cavity is fully filled; after pouring, the top surface is covered with geotextile and kept moist with fresh water for no less than 14 days. During the curing period, a dedicated person is arranged to sprinkle water regularly to keep the concrete surface moist, and the overall structure construction is completed.

[0095] In this embodiment, all eight sections of type B breast wall, one section of type A breast wall, and one section of type C breast wall were constructed using the process of this invention. The entire process proceeded without any safety or quality incidents, achieving the following results:

[0096] 1. Regarding the construction period: The construction of the cast-in-place foundation was carried out simultaneously with the onshore prefabrication, with an overall construction period of 3 months. This was completed 2 months ahead of the original 5-month construction period for the cast-in-place process, perfectly avoiding the nuclear power plant's cold source grid connection and ensuring the overall project milestones.

[0097] 2. Quality: The precast components have a smooth and flat appearance, free from defects such as cracks and honeycomb pitting. The dimensional deviations are all within the allowable range of the specifications, and the first-time acceptance rate is 100%. The installation accuracy of the precast components is all controlled within 20mm. The post-poured wet connection concrete is dense and leak-free, and the strength of the solid components fully meets the design requirements.

[0098] 3. Safety: The time spent working at heights at sea was reduced by 65%, and no accidents such as falls from heights or being struck by objects occurred, ensuring that the safety of offshore construction is under control.

[0099] 4. In terms of economic benefits: Compared with the traditional cast-in-place process, the overall cost is reduced by RMB 2.129 million, a decrease of 17%, achieving significant economic benefits.

[0100] 5. Seismic performance: According to third-party seismic calculations, under the SL-2 seismic condition, all structural indicators meet the requirements of the seismic design code for nuclear power plants. The overall structural stability is excellent, making it the first successful application of breast wall prefabricated construction technology in the hydraulic structures of a nuclear power plant intake in China.

[0101] Example 2

[0102] This embodiment describes the construction of an irregularly shaped cantilevered breast wall for a coastal gravity-type wharf. The caisson is a rectangular caisson with dimensions of 12m×8m×15m. The upper breast wall is an L-shaped irregularly shaped cantilevered structure with a cantilever length of 3.5m and a total height of 3.8m.

[0103] Using the technical solution of this invention, the breast wall is divided into a lower 1.8m high cast-in-place support surface unit and an upper 2.0m high precast irregular cantilever component unit. The weight of a single precast component is 480t, and it is installed using an 800t crane ship. The core block cavity size is 5m×7m, and two rows of Φ28 pre-embedded reinforcing bars are set around the cavity, with an upper and lower anchorage length of 800mm. The post-cast concrete is C45 micro-expansion concrete, which is one grade higher than the main body C40 concrete.

[0104] The construction method is the same as in Example 1, and the installation accuracy of the precast components is 15mm. The construction period at sea is shortened by 35% compared with the traditional cast-in-place method, and the overall cost is reduced by 14%. After the structure is formed, the appearance quality and overall stability meet the design and specification requirements, which verifies the applicability of the present invention in conventional wharf projects.

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A construction method for a prefabricated and assembled monolithic structure of a gravity-type caisson irregular cantilevered breast wall, characterized in that... Includes the following steps: S1. Structural layering and block optimization: The irregular large-volume cantilevered breast wall above the caisson is divided into three major construction modules: the lower cast-in-place support surface unit, the upper precast irregular cantilever component unit, and the middle post-cast wet connection unit. The functional requirement-oriented and stress performance verification split design method is adopted to simultaneously complete the construction drawing detail design of cast-in-place structure and precast component, and the mechanical verification of key working conditions during the construction period. S2. Construction of cast-in-place support surface unit: After the installation of the caisson and the filling and sealing layer construction are completed, the top of the caisson is cast in place at sea, the formwork is erected and the steel bars are tied, the core block cavity is reserved and the non-removable formwork is installed, the top surface is pre-embedded with the limiting device, and the concrete is cured to the design strength after the concrete is poured to form a flat installation reference surface. S3. Precast irregular cantilever components: The formwork erection, rebar binding and template erection of precast irregular cantilever components are completed in the land prefabrication yard. Core block cavities and weight reduction post-casting areas on both sides are reserved. Lifting rings are symmetrically embedded. Pumped concrete is used for layered pouring and curing to 100% of the design strength before use. S4. Precast component shipment and placement: Using a crane vessel and a special steel gantry, precast irregular cantilever components are hoisted onto a transport barge, reinforced, and then transported to the construction site to complete the on-site placement of the crane vessel and the transport barge; S5. Precast component installation at sea: Before installation, roughen and moisten the top surface of the cast-in-place support surface, and apply bedding mortar; use a crane vessel to hoist the precast irregular cantilever component into place by using a limit device and GPS automatic positioning system; during the installation process, use a real-time hoisting stress monitoring system to control the stress state of the hoisting point; after the installation is completed, immediately install temporary fixed steel supports. S6. Post-cast wet connection construction: The joint surface of the core block cavity and the reserved post-cast area is roughened. Two rows of pre-embedded reinforcing bars are installed around the cavity. The steel mesh of the precast component is welded. After acceptance, a higher grade micro-expansion concrete is used to pour the post-cast core block and the reserved post-cast block in layers. After completion, the geotextile is covered and cured with fresh water until the design strength is reached to form the overall structure of the breast wall.

2. The construction method for the prefabricated and assembled integral molding structure of the gravity caisson irregular cantilever breast wall according to claim 1, characterized in that, In S1, the split design follows the principles of clear functional zoning, reasonable structural stress, standardized interfaces, and balanced weight. The split interface avoids high stress areas of the structure, and the weight of a single precast component is controlled within 85% of the rated lifting capacity of the crane vessel. The mechanical calculations for key working conditions during the construction period include punching shear calculations for the hoisting condition and structural strength and stability calculations for the uncast post-cast strip condition.

3. The construction method for the prefabricated and assembled integral molding structure of the gravity caisson irregular cantilever breast wall according to claim 1, characterized in that, In S2, the template of the cast-in-place support surface unit adopts the prefabricated outer steel template of the caisson. The bottom end of the template is reinforced on the reserved frustum nut on the top of the caisson, and the top is reinforced by tie rods. Adjacent templates are fixed with bolts. The flatness of the top surface of the cast-in-place support surface is controlled within 10mm, and the elevation deviation of the top surface is controlled within ±10mm.

4. The construction method for the prefabricated and assembled integral molding structure of the gravity caisson irregular cantilever breast wall according to claim 1, characterized in that, In S3, the prefabrication yard site is hardened with a 20cm thick C30 concrete surface layer and a 15cm thick crushed stone cushion layer, and the flatness of the bottom surface is controlled within 10mm; the prefabricated components are completed by binding the steel reinforcement skeleton and hoisting it into place using general-purpose reusable prefabricated steel reinforcement binding tools, the concrete pouring layer thickness is not greater than 50cm, and the concrete is vibrated with an immersion vibrator. The curing is carried out by covering with geotextile and moist curing with fresh water for a period of not less than 14 days.

5. The construction method for the prefabricated and assembled integral molding structure of the gravity caisson irregular cantilever breast wall according to claim 1, characterized in that, In S4, the main chord of the special steel gantry is made of Ф1020×16mm Q235 seamless steel pipe, filled with C40 micro-expansion concrete, and the vertical web members are made of Ф480×16mm Q235 seamless steel pipe. The gantry and the precast components are connected by 100t high-strength ring-type slings and 120t bow-type shackles, and the gantry and the main hook of the crane ship are connected by 350t high-polymer ring-type slings. The precast components are double-layered and supported by 800mm×150mm×220mm wooden blocks, and reinforced by ground anchors and cables.

6. The construction method for the prefabricated and assembled integral molding structure of the gravity caisson irregular cantilever breast wall according to claim 1, characterized in that, In S5, before the prefabricated components are installed, four GPS receiving antennas are set on their top surface. The position of the components is fed back in real time through the receiving device on the ship. With the help of the trapezoidal limit device, the components are accurately positioned and the deviation of the installation plane position is controlled within 20mm. During the hoisting operation, the hoisting distance of the crane ship is controlled within 37m and the hoisting weight does not exceed 85% of the rated lifting capacity of the crane ship. During the hoisting process, the stress deviation of the hoisting points is controlled within 5% through the multi-point stress real-time monitoring system.

7. The construction method for the prefabricated and assembled integral structure of the gravity caisson irregular cantilever breast wall according to claim 1, characterized in that, In S6, the thickness of each layer of micro-expansion concrete pouring shall not exceed 50cm, and continuous pouring shall be carried out without leaving construction joints; the concrete surface shall be kept continuously moist during the curing period, which shall not be less than 14 days; construction quality control shall be strictly implemented in accordance with the "Waterway Engineering Quality Inspection Standard" JTS257-2008 and the "Waterway Engineering Concrete Construction Specification" JTS202-2011.

8. A gravity-type caisson irregular cantilevered breast wall prefabricated assembly integral molding structure, characterized in that, This includes caisson foundations, cast-in-place support surface units, precast irregular cantilever component units, and post-cast wet connection units; The cast-in-place support surface unit is the extension section cast in place on the top of the caisson at sea. Its external dimensions are consistent with the cross-section of the top of the caisson. The top surface is a flat precast component installation reference surface. The interior is reserved with a through cavity corresponding to the post-cast wet connection unit. The inner wall of the cavity adopts a non-removable template system. The precast irregular cantilever component unit is a large-volume irregular cantilever concrete component precast on land. It has a core block cavity that is coaxially connected with the cavity of the cast-in-place support surface unit. The upper and lower layers of steel mesh are continuously connected in the core block cavity. Multiple lifting rings are symmetrically embedded at the top of the component. Weight reduction post-casting areas are set on both sides of the component. The post-cast wet connection unit includes a post-cast core block that runs through the coaxial cavity of the cast-in-place support surface unit and the precast irregular cantilever component unit, reserved post-cast blocks on both sides of the precast component, and two rows of embedded reinforcing bars arranged around the cavity. The midpoint of the pre-embedded reinforcing bar is located at the interface between the cast-in-place support surface unit and the precast irregular cantilever component unit, with its upper and lower ends extending into the design depths of the precast irregular cantilever component and the cast-in-place support surface unit, respectively. The post-cast core block and the reserved post-cast block are integrally cast using micro-expansion concrete of a higher grade, so that the cast-in-place support surface unit and the precast irregular cantilever component unit form an integral load-bearing structure.

9. The gravity-type caisson irregular cantilevered breast wall prefabricated assembly integral molding structure according to claim 8, characterized in that, The top surface of the cast-in-place support unit is pre-embedded with a limiting device. The limiting device is a trapezoidal steel limiter welded from I-beams. One limiter is arranged every 2m along the installation edge of the precast component. The distance between the limiting device and the installation edge is 20mm, and its sloping surface faces the installation side of the precast component. The core cavity of the precast irregular cantilever component unit has a size of 6.34m × 11.8m. The embedded reinforcing bars are made of HRB400 steel bars with a diameter of 32mm. The length of the reinforcing bars embedded in the cast-in-place support unit and the precast irregular cantilever component unit is not less than 960mm. The weight of a single precast irregular cantilever component unit is controlled within 600t. Eight lifting rings are symmetrically set at the top. The lifting rings are made of Q355B round steel with a diameter of 100mm.

10. The gravity-type caisson irregular cantilevered breast wall prefabricated assembly integral molding structure according to claim 8, characterized in that, At the interface between the cast-in-place support surface unit and the precast irregular cantilever component unit, a 10-20mm thick layer of high-grade cement mortar is provided; the micro-expansion concrete used for the post-cast core block and the reserved post-cast block has a strength grade one grade higher than that of the main structure concrete, and a frost resistance grade not lower than F400. A shear key structure with dimensions of 6.34m × 11.8m is formed between the cast-in-place support surface unit and the precast irregular cantilever component unit.

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