Post-wall filling construction method for integral box culvert of super-large-diameter shield tunnel

Abstract

The invention relates to a super-large-diameter shield tunnel integral box culvert wall back filling construction method which comprises the following steps: S1, cleaning the bottom of a box culvert, namely removing soil, mortar and accumulated water deposited in the bottom area of the box culvert; s2, the steel formwork is treated, impurities on the surface of the steel formwork are removed, and polishing is conducted; s3, steel formworks are installed, specifically, a bottom steel formwork and a side steel formwork are installed at the bottom delimited position and the side hole of the box culvert correspondingly; s4, the steel formworks are supported and reinforced, supporting structures are arranged between the bottom steel formwork and the top plate of the box culvert and between the side steel formworks and the top plate of the box culvert, and no gap is reserved between the steel formworks and the outline of the to-be-poured area; s5, self-compacting concrete pouring is conducted, and symmetrical pouring is conducted from the positions, not constructed, of the cable grooves in the two sides of the box culvert as preset pouring openings; s6, the steel formworks are dismantled, and after the self-compacting concrete is initially set, the bottom steel formwork and the side steel formworks are dismantled; and S7, concrete curing. According to the construction method, the shield construction period can be shortened, and the compactness of backfilling behind the integral box culvert wall is ensured.

Description

Technical Field

[0001] This application relates to the technical field of shield tunnel box culvert construction, and in particular to a method for backfilling construction of an integral box culvert wall for ultra-large diameter shield tunnels. Background Technology

[0002] With the development of prefabricated tunnel construction and supporting equipment technology, the substructure of shield tunnels for ultra-large diameter shield tunnels mainly takes four forms: "prefabricated box culvert in the middle + cast-in-place box culverts on both sides", "prefabricated box culvert in the middle + backfill on both sides", "prefabricated box culvert in the middle + prefabricated box culverts on both sides" and "integral prefabricated box culvert". It often also serves as an evacuation passage, equipment space, ventilation and smoke exhaust and operation drainage passage.

[0003] Using an integral precast box culvert offers better structural stability than "intermediate precast box culvert + other forms". After the integral precast box culvert under the track is assembled, concrete is needed to fill the gap between the precast box culvert and the segments. The quality of the concrete filling affects the stability and safety of the integral box culvert under the track.

[0004] Therefore, how to improve the quality of the backfill behind the concrete wall and reduce the construction risks of integral box culverts have become urgent issues to be considered in shield tunneling construction. Summary of the Invention

[0005] To improve the quality of backfilling behind concrete walls and reduce the construction risks of monolithic box culverts, this application provides a construction method for backfilling behind monolithic box culvert walls in ultra-large diameter shield tunnels.

[0006] The construction method for backfilling the wall of an integral box culvert for ultra-large diameter shield tunnels provided in this application adopts the following technical solution: A method for backfilling the wall of an integral box culvert in an ultra-large diameter shield tunnel includes the following steps: S1. Clean the bottom of the box culvert, removing accumulated soil, mortar, and water from the bottom area of ​​the box culvert; S2. Steel formwork treatment: remove debris from the surface of the steel formwork and grind it. S3. Steel formwork installation: Install bottom steel formwork and side steel formwork at the designated positions at the bottom of the box culvert and at the side openings, respectively; S4. Steel formwork support and reinforcement: A support structure is set between the bottom steel formwork and the side steel formwork and the top plate of the box culvert, and the steel formwork is made without gaps between the outline of the area to be poured. S5. For self-compacting concrete pouring, the cable trenches on both sides of the box culvert that have not yet been constructed are used as pre-set pouring ports, and symmetrical pouring is carried out respectively. S6. Steel formwork removal: After the self-compacting concrete has initially set, remove the bottom steel formwork and the side steel formwork. S7. Concrete curing.

[0007] Furthermore, after the steel template surface is polished in step S2, template cloth is then pasted onto the steel template surface.

[0008] Furthermore, in step S4, after the side steel formwork is accurately positioned, side pressure strips and side support mechanisms are installed along its length. One end of the side support mechanism is pressed against the side pressure strip, and the other end is pressed against the top plate of the box culvert. A bottom pressure strip and a bottom support mechanism are provided on the bottom steel template along its length. One end of the bottom support mechanism is pressed against the bottom pressure strip, and the other end is pressed against the top plate of the box culvert.

[0009] Furthermore, both the side support mechanism and the bottom support mechanism include disc-type steel pipes and adjustable bottom support bolts. Angle adjustment platforms are provided at intervals on both the side pressure strip and the bottom pressure strip. Positioning columns are fixedly connected to the angle adjustment platforms, and the adjustable bottom support bolts are inserted into the positioning columns.

[0010] Furthermore, both the side steel template and the bottom steel template include multiple splicing templates, which are bolted together and fixed to each other, and a handle is provided on the back of the splicing template; The splicing template on the side steel template is fixedly connected to an L-shaped positioning steel plate. When the edge of the L-shaped positioning steel plate is in contact with the inner wall of the side hole of the box culvert, the front of the splicing template is flush with the outer wall of the box culvert.

[0011] Furthermore, in step S1, high-pressure water jets, pneumatic picks, or manual chiseling are used to ensure that the soil and mortar debris attached to the pipe segments and in various corners are completely removed and transported away from the site; and the soil and water in the bolt holes are cleaned to ensure that the bolt holes are clean and dry.

[0012] Furthermore, in step S2, tools such as scrapers and wire brushes are used in conjunction with high-pressure air to clean the loose and easily removable attachments on the surface of the steel template. Then, an electric grinder equipped with a suitable grinding wheel or sanding belt is used to grind the surface of the steel template evenly and meticulously along the surface texture or a certain direction, so that the surface of the steel template is free of obvious sharp edges and burrs, and the overall feel is smooth.

[0013] Furthermore, in step S5, when symmetrically pouring self-compacting concrete into the cable trenches on both sides of the box culvert, the pouring speed is controlled to ensure that the concrete, under its own weight, can flow naturally and smoothly along the arc contour of the box culvert wall and gradually fill every corner.

[0014] Furthermore, the pouring height on both sides needs to be kept uniform at all times. This can be achieved by observing the rise of the concrete at the pouring ports on both sides, or by using a measuring tape to make measurements and comparisons. By adjusting the pouring speed on both sides, it is ensured that the concrete on both sides is always at approximately the same height.

[0015] Furthermore, after the backfilling is completed, an ultrasonic detector is used to probe the upper surface of the arc-shaped section at the bottom of the box culvert ring by ring to evaluate the overall quality of the filling effect and identify any areas that are not compacted. Then, grouting is performed using the pre-reserved grouting holes at the bottom of the box culvert.

[0016] In summary, the beneficial technical effects of this application are as follows: 1. High reusability: The integrated box culvert backfill steel formwork of this application adopts a modular design, which is convenient to assemble and disassemble, and can promote the recycling of steel formwork, reduce the loss of wooden formwork, and improve construction safety, economy and work efficiency. 2. High safety: Traditional wooden formwork construction has many potential risks, which may cause accidents and result in significant losses and disasters. The construction method of this application is guaranteed during the construction process, which can avoid safety accidents and fully ensure the smooth progress of the project. It provides a reference for similar construction of backfilling behind integral box culvert walls and has promotion and guidance significance. 3. High applicability: For different integral box culvert cross-sections, standardized modular steel formwork is used for backfilling behind the box culvert wall. The width and height can be flexibly adjusted through bolt connections and adjustable supports, enabling rapid reinforcement of the steel formwork. For the lower arc-shaped structure, a composite structure of segmented prefabricated formwork + locally customized arc-shaped panels is used to complete the backfilling task behind the integral box culvert wall. It has strong scalability and is suitable for various integral box culvert structures. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of an embodiment of this application; Figure 2 This is a schematic diagram of the bottom steel template according to an embodiment of this application; Figure 3 This is a structural schematic diagram of the side steel template according to an embodiment of this application.

[0018] Explanation of reference numerals in the attached figures: 1. Bottom steel formwork; 11. Handles; 2. Side steel formwork; 21. L-shaped positioning steel plate; 211. Edge fastener; 3. Side pressure strips; 4. Bottom pressure strip; 51. Angle adjustment platform; 52. Positioning post. Detailed Implementation

[0019] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] This application discloses a method for backfilling the wall of an integral box culvert in an ultra-large diameter shield tunnel. (Refer to...) Figure 1 It includes the following steps: S1. Cleaning the bottom of the box culvert: Remove accumulated soil, mortar, and water from the bottom area of ​​the box culvert. Specifically, use high-pressure water jets, pneumatic picks, or manual chiseling to ensure that all soil and mortar debris adhering to the segments and corners are completely removed and transported away from the site. Also, clean the bolt holes thoroughly to ensure they are clean and dry. This is to prevent these loose or semi-solidified materials from occupying valuable structural space behind the wall infill, affecting the effective compaction of the self-compacting concrete, and becoming a potential source of voids and settlement in the future. Meticulous bottom cleaning provides a clean, flat, and solid working surface for subsequent wall infill, ensuring that the self-compacting concrete adheres tightly to the box culvert structure and achieves the expected compaction and stability requirements.

[0021] S2. Steel formwork treatment: Remove debris from the surface of the steel formwork and grind it. After grinding, apply formwork fabric to the surface of the steel formwork. Specifically, use tools such as scrapers and wire brushes, along with high-pressure air blowing, to clean loose and easily removable attachments such as laitance, oil stains, dust, and other debris generated during construction from the surface of the steel formwork. Then, use an electric grinder equipped with appropriate grinding wheels or belts to evenly and meticulously grind along the surface texture or in a certain direction, so that the surface of the steel formwork has no obvious sharp edges or burrs, and the overall feel is smooth. The grinding process is not only to remove stubborn stains, rust, and minor unevenness remaining on the surface of the steel formwork, but more importantly, to make the surface of the steel formwork reach the standard of "smoothness" to ensure that it can fit tightly against the box culvert structure and reduce interference with the subsequent application of formwork fabric.

[0022] Furthermore, applying this specially designed formwork fabric not only further isolates the steel formwork from the concrete, preventing adhesion and ensuring smooth demolding, but also effectively absorbs excess moisture from the concrete, resulting in a more uniform, smooth, and aesthetically pleasing concrete surface after demolding, reducing air bubbles and color differences. During application, ensure the formwork fabric is flat and wrinkle-free, with firmly adhered edges, providing a perfect interface for the upcoming backfilling construction of the box culvert wall.

[0023] S3. Steel formwork installation: Bottom steel formwork 1 and side steel formwork 2 are installed at designated locations at the bottom of the box culvert and at the side openings, respectively. The steel formwork used is custom-made to fit the prefabricated arc-shaped structure of the box culvert. The steel formwork consists of side steel formwork 2 on the left and right sides and bottom steel formwork 1 on the bottom. Both side steel formwork 2 and bottom steel formwork 1 include multiple splicing templates, which are bolted together. Handles 11 are provided on the back of the splicing templates. In this embodiment, the splicing templates are divided into four equal sections.

[0024] Furthermore, by setting precise positioning holes at the joints of the splicing templates, the four splicing templates can be quickly and securely connected using only standard bolts, forming a seamless, integrated bottom structure. Considering the actual conditions of on-site construction, the difficulty of transporting the templates is greatly reduced, allowing workers to easily operate and assemble them flexibly even in confined work spaces. The main body of each splicing template uses high-quality curved steel plates, which not only ensures a perfect fit with the inner wall of the box culvert but also provides a smooth forming surface for concrete pouring. In addition, multiple stiffening plates and end plates are set on the inner curved surface of the splicing template to enhance its structural stability, and the stress and deformation values ​​under uniformly distributed loads during concrete pouring have been verified through finite element data analysis.

[0025] During installation, the bottom steel formwork 1 is installed in the designated position at the bottom of the integral box culvert without leaving gaps. After the bottom steel formwork 1 is stable, the side steel formwork 2 is assembled and installed. The components of the side steel formwork 2 are pre-assembled on the ground, and the firmness of the connection is checked. Then, it is divided into upper and lower parts and transported to the side hole of the integral box culvert. The lower edge of the lower side splicing formwork is tightly attached to the side hole of the integral box culvert, and the upper side splicing formwork is installed in sequence. The two parts of the side splicing formwork are connected with bolts to ensure that the outline of the side steel formwork 2 and the side hole of the box culvert are consistent.

[0026] Specifically, based on the cross-sectional dimensions and design requirements of the box culvert, pre-fabricated standardized template units (such as the four-part arc-shaped blocks at the bottom and the four-part blocks on both sides) are transported to the installation location. During assembly, the pre-set positioning pin holes or marking points on the splicing templates are used for rough positioning to ensure that the splicing edges of adjacent template units are roughly aligned. High-strength bolts are then inserted into the corresponding holes and initially tightened using manual or small power tools to form a preliminary connection. The pre-connected template system is then fine-tuned, adjusting its centerline and gaps to maintain the designed spacing and angle with the box culvert wall, ensuring uniform filling thickness. Finally, all bolts are tightened symmetrically in stages to ensure that each splicing template unit is tightly interlocked, forming a unified, stable, and dimensionally accurate template cavity, providing reliable constraint and support for subsequent concrete pouring. The entire process emphasizes standardization, tooling, and measurement feedback, aiming to efficiently and accurately construct a temporary structure that meets design requirements.

[0027] S4. Steel formwork support and reinforcement: A support structure is installed between the bottom steel formwork 1 and the side steel formwork 2 and the top slab of the box culvert, ensuring no gaps between the steel formwork and the outline of the area to be poured. Specifically, after the side steel formwork 2 is accurately positioned, side pressure strips 3 and side support mechanisms are installed along its length. One end of the side support mechanism is pressed against the side pressure strip 3, and the other end is pressed against the top slab of the box culvert. A bottom pressure strip 4 and a bottom support mechanism are installed along the length of the bottom steel formwork 1. One end of the bottom support mechanism is pressed against the bottom pressure strip 4, and the other end is pressed against the top slab of the box culvert. The installation of side pressure strips 3 and bottom pressure strips 4 not only reinforces the formwork structure but, more importantly, provides a reliable point of contact for the subsequent support system.

[0028] The splicing template on the side steel formwork 2 is fixedly connected to an L-shaped positioning steel plate 21. When the snap edge 211 of the L-shaped positioning steel plate 21 is flush with the inner wall of the side hole of the box culvert, the front of the splicing template is flush with the outer wall of the box culvert. Furthermore, both the side support mechanism and the bottom support mechanism include disc-type steel pipes and adjustable bottom support bolts. Angle adjustment platforms 51 are spaced apart on both the side pressure strip 3 and the bottom pressure strip 4. Positioning columns 52 are fixedly connected to the angle adjustment platforms 51, and the adjustable bottom support bolts are inserted into the positioning columns 52. Thus, the side support mechanism forms a stable triangular support structure, effectively resisting the lateral pressure generated during concrete pouring; the bottom support mechanism ensures that the entire bottom formwork system will not shift or deform during subsequent construction. Thus, by precisely adjusting the tightness of the adjustable base bolts in each support structure, the steel formwork is evenly and appropriately compressed, making the entire formwork system a rigid, well-integrated, and precisely dimensional enclosed space, laying a solid foundation for the upcoming backfilling operation.

[0029] While steel formwork can form a pouring chamber, its structural strength alone is often insufficient to resist deformation and maintain precise positioning when subjected to the lateral pressure of highly fluid concrete, especially in cases of large spans or high filling heights. Therefore, external supports and reinforcement systems are needed to provide additional constraints and support. Through these support structures, part of the load borne by the formwork is effectively transferred to the more rigid box culvert main body, forming a cohesive force system of "formwork-support structure-box culvert structure." Simultaneously, the reinforcement system, through its internal members and curved structures, restricts the local and overall displacement of the steel formwork, ensuring sufficient rigidity and stability under the dynamic pressure of concrete pouring, preventing formwork displacement and bulging, and thus guaranteeing the uniform thickness and accurate shape of the backfill layer. In short, the support structure is a "tailor-made" external "skeleton" for flexible or medium-rigidity formwork, achieving internal and external coordination and a balance of rigidity and flexibility to ensure structural safety and forming quality.

[0030] S5. Self-compacting concrete pouring: Starting from the unconstructed cable trenches on both sides of the box culvert, symmetrical pouring is carried out. Specifically, in step S5, when symmetrically pouring self-compacting concrete into the cable trenches on both sides of the box culvert, the pouring speed is controlled to ensure that the concrete, under its own weight, can flow naturally and smoothly along the arc contour of the box culvert wall and gradually fill every corner. Furthermore, the pouring height on both sides needs to be kept uniform at all times. This is achieved by observing the rise in concrete elevation at the pouring ports on both sides, or by measuring and comparing with a tape measure. By adjusting the pouring speed on both sides, it is ensured that the concrete on both sides is always at approximately the same height.

[0031] Furthermore, it is important to note that self-compacting concrete should be transported using specialized concrete transport vehicles. The transportation process should be quick and convenient, minimizing the number of transfers and transport time. Maintaining the homogeneity of the self-compacting concrete mix during transportation is crucial for ensuring the final filling quality. Strict measures must be taken to prevent performance degradation of the concrete during transport. Transport vehicles are typically equipped with mixer trucks, which maintain low-speed mixing during transport to prevent the settling of coarse and fine aggregates and the floating of cement paste, thereby avoiding the separation of internal components of the mix.

[0032] After the transport truck stops at the designated location on the pouring site, it does not unload immediately. Instead, the truck's mixing drum is started and rotated at a high speed (usually set at 8-12 rpm) for 20 to 30 seconds. The purpose of this crucial step is to thoroughly remix the concrete before unloading, further evenly distributing any components that may have slightly separated within the mixture, restoring its ideal rheological properties, and ensuring that the unloaded concrete maintains excellent homogeneity and stability, without exhibiting adverse phenomena such as segregation, stratification, or surface bleeding of cement paste.

[0033] In addition, special chutes or conduits are used during the pouring process to slowly and evenly guide the concrete into the voids behind the box culvert wall. Controlling the pouring speed is crucial; too fast a speed may result in excessive impact on the concrete, causing localized air bubbles; too slow a speed may prolong construction time and affect efficiency. Therefore, the entire pouring process must maintain a stable and continuous rhythm to ensure that the concrete, under its own weight, flows naturally and smoothly along the curved contour of the box culvert wall, like water, gradually filling every corner, especially those complex gaps and dead angles, thus achieving a completely dense effect.

[0034] Meanwhile, the pouring height on both sides needs to be kept uniform at all times. This is achieved by observing the rise in concrete elevation at the pouring ports on both sides, or by measuring and comparing with a tape measure. If necessary, the pouring speed on both sides can be adjusted to ensure that the concrete on both sides is always at approximately the same height. This symmetrical and balanced pouring method not only helps the concrete to be stressed more evenly, preventing structural displacement or stress concentration caused by excessively rapid filling on one side, but also ensures the consistency of the overall performance of the final backfill material, providing a reliable guarantee for the long-term stability of the box culvert structure.

[0035] Therefore, the monolithic box culvert wall backfill uses C40 self-compacting fine aggregate concrete. Steel formwork is installed at the bottom and sides of the box culvert, and a supporting structure tightly connects the steel formwork to the box culvert wall, forming a highly rigid monolithic structure. This effectively resists the lateral pressure of the concrete on the steel formwork during concrete pouring, preventing deformation and displacement of the steel formwork. Furthermore, this technology utilizes finite element analysis to accurately calculate and verify the stress and deformation of the steel formwork during concrete pouring, ensuring the safety and reliability of the steel formwork during construction. Through these measures, the monolithic box culvert wall backfill technology effectively guarantees the construction quality and safety of the box culvert structure.

[0036] S6. Steel formwork removal: After the self-compacting concrete has initially set, remove the bottom steel formwork 1 and the side steel formwork 2. Specifically, prioritize removing the bottom steel formwork 1. This step is done ahead of schedule because removing the bottom steel formwork 1 is relatively simple and will not disturb the not-yet-fully-hardened concrete sidewalls. Since the side steel formwork 2 directly contacts the wall before being filled with concrete, its removal requires more care; following a pre-set sequence, symmetrically and evenly loosen the steel pipe supports of the side steel formwork 2 to ensure that the side steel formwork 2 can smoothly and controllably detach from the concrete surface after losing its support.

[0037] Furthermore, after dismantling, these steel formworks were thoroughly cleaned and tidied up; the cleaning work included using tools such as scrapers to remove concrete residue, laitance, and other debris adhering to the surface of the formwork.

[0038] S7. Concrete curing.

[0039] The type, specifications, and performance of the steel used in the steel formwork should comply with current national product standards and design requirements. If the steel is bent, it should be straightened before use. The straightened steel surface should not have obvious concavities or damage, and the depth of scratches should not exceed 0.5mm, nor should it exceed half of the negative allowable deviation of the steel thickness. During welding, there should be no incomplete welds or missed welds, and no defects affecting quality or appearance should exist.

[0040] In addition, after the backfilling is completed, an ultrasonic detector is used to detect the upper surface of the arc-shaped part at the bottom of the box culvert ring by ring to evaluate the overall quality of the filling effect and to identify the locations that are not compacted. Then, grouting is performed using the grouting holes reserved at the bottom of the box culvert.

[0041] In specific examples, such as the Guangnan Link Line Section 2 tunnel, which is 2990m long, the minimum curve radius of the shield tunnel section is 605m, the maximum longitudinal slope is 28‰, and the overburden thickness ranges from 9.6 to 48.5m. The shield tunnel has an inner diameter of 11.3m and an outer diameter of 12.4m, adopting a single-bore, double-track cross-section without partition walls. It includes two 1m wide rescue passages on both sides. The lower evacuation corridor has a clear height of 2.0m and a clear width of 3.5m. An evacuation staircase connects the track area to the evacuation corridor every 150m.

[0042] The box culvert is designed with an average width of 2m, a length of 9.329m, and a height of 2.81m per block, with a wedge shape of 40mm (60mm for turning radii <600m). It is a double-sided wedge shape, with four M36 leveling bolts at the bottom of each precast arc-shaped block. A 50mm gap is left between the precast box culvert and the lining segments, filled with C40 self-compacting fine aggregate concrete. By adopting this technology, the backfilling of the integral box culvert wall can be carried out smoothly and orderly inside the shield tunnel while ensuring safety, quality, and schedule. This avoids the impact of delayed integral box culvert filling on shield tunneling, facilitating overall construction and significantly shortening the construction period.

[0043] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," "third," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, and do not exclude other elements or objects. "Above," "below," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0044] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for backfilling construction of an integral box culvert wall in an ultra-large diameter shield tunnel, characterized in that, Includes the following steps: S1. Clean the bottom of the box culvert, removing accumulated soil, mortar, and water from the bottom area of ​​the box culvert; S2. Steel formwork treatment: remove debris from the surface of the steel formwork and grind it. S3. Steel formwork installation: Install bottom steel formwork and side steel formwork at the designated positions at the bottom of the box culvert and at the side openings, respectively; S4. Steel formwork support and reinforcement: A support structure is set between the bottom steel formwork and the side steel formwork and the top plate of the box culvert, and the steel formwork is made without gaps between the outline of the area to be poured. S5. For self-compacting concrete pouring, the cable trenches on both sides of the box culvert that have not yet been constructed are used as pre-set pouring ports, and symmetrical pouring is carried out respectively. S6. Steel formwork removal: After the self-compacting concrete has initially set, remove the bottom steel formwork and the side steel formwork. S7. Concrete curing.

2. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 1, characterized in that, After the steel template surface is polished in step S2, template cloth is then pasted onto the steel template surface.

3. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 2, characterized in that, In step S4, after the side steel formwork is accurately positioned, the side pressure strip and side support mechanism are installed along its length. One end of the side support mechanism is pressed against the side pressure strip, and the other end is pressed against the top plate of the box culvert. A bottom pressure strip and a bottom support mechanism are provided on the bottom steel template along its length. One end of the bottom support mechanism is pressed against the bottom pressure strip, and the other end is pressed against the top plate of the box culvert.

4. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 3, characterized in that, Both the side support mechanism and the bottom support mechanism include disc-type steel pipes and adjustable bottom support bolts. Angle adjustment platforms are provided at intervals on both the side pressure strip and the bottom pressure strip. Positioning columns are fixedly connected to the angle adjustment platforms, and the adjustable bottom support bolts are inserted into the positioning columns.

5. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 4, characterized in that, Both the side steel template and the bottom steel template include multiple splicing templates, and adjacent splicing templates are bolted together and fixed. A handle is provided on the back of the splicing template. The splicing template on the side steel template is fixedly connected to an L-shaped positioning steel plate. When the edge of the L-shaped positioning steel plate is in contact with the inner wall of the side hole of the box culvert, the front of the splicing template is flush with the outer wall of the box culvert.

6. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 1, characterized in that, In step S1, high-pressure water jets, pneumatic picks, or manual chiseling are used to ensure that the soil and mortar debris attached to the pipe segments and in various corners are completely removed and transported away from the site; and the soil and water in the bolt holes are cleaned to ensure that the bolt holes are clean and dry.

7. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 1, characterized in that, In step S2, tools such as scrapers and wire brushes are used in conjunction with high-pressure air to clean the loose and easily removable attachments on the surface of the steel template. Then, an electric grinder equipped with a suitable grinding wheel or sanding belt is used to grind the surface of the steel template evenly and meticulously along the surface texture or a certain direction, so that the surface of the steel template is free of obvious sharp edges and burrs, and the overall feel is smooth.

8. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 7, characterized in that, In step S5, when symmetrically pouring self-compacting concrete into the cable trenches on both sides of the box culvert, the pouring speed is controlled to ensure that the concrete, under its own weight, can flow naturally and smoothly along the arc contour of the box culvert wall and gradually fill every corner.

9. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 8, characterized in that, The pouring height on both sides needs to be kept uniform at all times. This can be achieved by observing the rise of the concrete at the pouring openings on both sides, or by using a measuring tape to measure and compare. By adjusting the pouring speed on both sides, it is ensured that the concrete on both sides is always at approximately the same height.

10. The method for backfilling the integral box culvert wall of an ultra-large diameter shield tunnel according to claim 1, characterized in that, After backfilling is completed, an ultrasonic detector is used to probe the upper surface of the arc-shaped part at the bottom of the box culvert ring by ring to evaluate the overall quality of the filling effect and identify the locations that are not compacted. Then, grouting is performed using the grouting holes reserved at the bottom of the box culvert.

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