Underwater Concrete Casting Method for Large-Section Steel Cofferdams

Abstract

This invention discloses a method for underwater concrete pouring of large-section steel cofferdams, belonging to the field of underwater construction technology for hydraulic engineering. This method is for large-section steel cofferdams constructed by sequentially connecting multiple steel cofferdam segments via interlocking joints. The method includes the following steps: First, based on the internal truss positions of the steel cofferdam segments, each segment is divided into multiple independently pourable sections; then, partition plates are installed between adjacent sections, with the partition plates mounted on the internal truss of the steel cofferdam segments; finally, concrete is poured into each section, wherein the section containing the interlocking joint is the last section to be poured. The underwater concrete pouring method for large-section steel cofferdams provided by this invention can significantly improve the concrete density and water-stopping reliability of underwater pouring of large-section steel cofferdams, ensuring the structural stability of the steel cofferdam.

Description

Technical Field

[0001] This invention belongs to the field of underwater construction technology for water conservancy projects, and particularly relates to a method for underwater concrete pouring of large-section steel cofferdams. Background Technology

[0002] After the installation of the immersed tunnel sections is completed, the prefabricated dry dock needs to be dewatered a second time to carry out the subsequent construction of the buried section. Before dewatering, a secondary water-stopping structure needs to be constructed through the dock entrance steel cofferdam. This steel cofferdam usually has a large cross-sectional feature (such as 1.0m wide and 39.5m long), and its core function is to achieve reliable water stopping through internal concrete filling.

[0003] In existing technologies, underwater concrete pouring for large-section steel cofferdams has the following defects: some processes adopt integral one-time pouring, which is limited by the large cross-section space, and the concrete is prone to pouring blind spots, resulting in uneven internal density and difficulty in achieving the water-stopping effect; some segmented pouring processes lack targeted segmentation methods, and the segment partitions are prone to displacement due to the lateral pressure of the concrete during the pouring process, causing segment forming deviations; the pouring sequence is not planned, and the density of key areas is insufficient, becoming weak points in water-stopping.

[0004] Traditional underwater concrete pouring techniques are not suitable for the structural characteristics of large-section steel cofferdams, and it is difficult to balance construction quality and water-stopping reliability. There is an urgent need for a targeted compartmentalized pouring method. Summary of the Invention

[0005] In view of the shortcomings of the related technologies, the purpose of this invention is to provide a method for underwater concrete pouring of large-section steel cofferdams, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for underwater concrete pouring of a large-section steel cofferdam, wherein the large-section steel cofferdam is constructed by sequentially connecting multiple steel cofferdam segments through interlocking joints, the method includes the following steps:

[0008] S1. Based on the internal truss position of the steel cofferdam segment, each steel cofferdam segment is divided into multiple independently cast sections; each steel cofferdam segment includes a middle area and an end locking area. The middle area of ​​each steel cofferdam segment is divided into multiple middle sections through internal trusses. The end locking areas of two adjacent steel cofferdam segments are jointly designated as one middle interface section. The single-sided end locking area of ​​the end steel cofferdam segment is designated as one end interface section. The end steel cofferdam segments are the steel cofferdam segments at both ends of the large-section steel cofferdam.

[0009] S2. Install compartment partitions between adjacent compartment sections. The compartment partitions are installed on the internal trusses of the steel cofferdam sections.

[0010] S3. Concrete is poured for each section, with the section containing the lock being the last section to be poured.

[0011] Specifically, step S2 includes:

[0012] S21. First, install the first compartment partition between the end interface section of the large-section steel cofferdam and the adjacent first intermediate section. The first compartment partition abuts against and is fixed to the side of the corresponding internal truss near the first intermediate section.

[0013] S22. Then install the second compartment partition between the first intermediate compartment section and the adjacent second intermediate compartment section. The second compartment partition abuts against and is fixed to the side of the corresponding internal truss closest to the first intermediate compartment section so that the second compartment partition and the first compartment partition are set opposite to each other.

[0014] S23. Then install the third compartment partition between the second intermediate compartment section and the adjacent third intermediate compartment section. The third compartment partition abuts against and is fixed to the side of the corresponding internal truss near the third intermediate compartment section so that the third compartment partition and the second compartment partition are set opposite to each other.

[0015] S24. The partition plates are installed alternately and opposite to each other until the installation of the partition plates between the end interface section and the adjacent intermediate section of the large-section steel cofferdam is completed.

[0016] In some embodiments, step S3 specifically includes:

[0017] S31. First batch of pouring: First pour the middle section with the two side partitions set opposite each other;

[0018] S32, Second Batch Pouring: Pouring the middle section with the partition plates on both sides facing away from each other;

[0019] S33, Third Batch of Pouring: The final pouring of the intermediate interface section and the end interface section.

[0020] In some embodiments, for the intermediate interface compartment section, the corresponding compartment partitions on both sides are arranged opposite to each other; for the end interface compartment section, the compartment partition on the side closer to the adjacent intermediate compartment section is arranged opposite to the compartment partition on the side of the adjacent intermediate compartment section away from the end interface compartment section.

[0021] In some embodiments, during the pouring of each batch of compartment sections in step S3, the lateral support method of the corresponding compartment partition is as follows:

[0022] When the first batch of concrete is poured into the middle section with the two side partitions set opposite each other, the internal truss of the steel cofferdam segment is used as the lateral support for the corresponding partition of the section in this batch.

[0023] After the concrete in the first batch of poured sections reaches more than 30% of the design strength, the second batch and the third batch of pouring will be carried out in sequence. At this time, the concrete in the first batch of poured sections will serve as the lateral support for the partition plates of each section in the second and third batches of pouring.

[0024] In some embodiments, the compartment partition is composed of a non-removable template, a steel mesh, and reinforcing bars; the steel mesh is fixed to both sides of the non-removable template, with one side of the steel mesh abutting against and fixed to the internal truss of the steel cofferdam segment, and the reinforcing bars are fixed to the other side of the steel mesh away from the non-removable template.

[0025] In some embodiments, in step S3, concrete is poured using a conduit with a diameter of Φ300mm and a wall thickness of not less than 4mm. Before use, the conduit needs to be assembled section by section and subjected to a watertight pressure test. The water pressure of the watertight pressure test must simultaneously meet the following requirements: not less than 1.5 times the water pressure corresponding to the maximum water depth in the pouring area, and not less than 1.5 times the maximum internal pressure that the conduit wall and welds bear when pouring concrete.

[0026] In some embodiments, in step S3, the concrete used for pouring is CL15 lightweight concrete, and flocculants are added to the concrete.

[0027] In some embodiments, the length of each intermediate section is 3-4m, and the number of intermediate sections divided within each steel cofferdam segment is 3-5.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The underwater concrete pouring method for large-section steel cofferdams provided by this invention can significantly improve the overall density of underwater concrete, strengthen the water-stopping ability of key parts such as segmental interlocking joints, effectively avoid leakage risks, ensure the structural stability of large-section steel cofferdams under complex working conditions in water conservancy projects, provide reliable guarantees for the long-term service of the project, and meet the construction quality requirements of large-section structures.

[0030] 2. The underwater concrete pouring method for large-section steel cofferdams provided by this invention simplifies the construction process of underwater pouring of large-section steel cofferdams. It eliminates the need to add temporary support structures for the compartment partitions, reducing construction difficulty and cost. At the same time, it reduces the risk of section forming deviation, improves the consistency of pouring quality and construction error tolerance, helps the project to proceed efficiently, and provides stable and efficient technical support for the construction of large-section steel cofferdams. Attached Figure Description

[0031] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0032] Figure 1 This is a flowchart illustrating an embodiment of the underwater concrete pouring method for large-section steel cofferdams according to the present invention.

[0033] Figure 2 This is a flowchart illustrating the installation process of compartment partitions in one embodiment of the underwater concrete pouring method for large-section steel cofferdams according to the present invention.

[0034] Figure 3 This is a flowchart illustrating the batch pouring process of an embodiment of the underwater concrete pouring method for large-section steel cofferdams of the present invention.

[0035] Figure 4 This is a schematic diagram of the segmented and batched pouring and construction equipment layout of an embodiment of the underwater concrete pouring method for large-section steel cofferdams of the present invention.

[0036] Figure 5 This is a schematic diagram of a steel cofferdam segment and its internal truss structure, representing an embodiment of the underwater concrete pouring method for large-section steel cofferdams of the present invention.

[0037] Figure 6 for Figure 5 Enlarged structural diagram at point A in the middle;

[0038] Figure 7 This is a schematic diagram of another steel cofferdam segment and its internal truss structure, representing an embodiment of the underwater concrete pouring method for large-section steel cofferdams of the present invention.

[0039] Figure 8 for Figure 7 Enlarged structural diagram at point B;

[0040] Figure 9 This is a schematic diagram of the compartment partition structure of an embodiment of the underwater concrete pouring method for large-section steel cofferdams of the present invention;

[0041] Figure 10 This is a schematic diagram of the compartment division and compartment partition arrangement of an embodiment of the underwater concrete pouring method for large-section steel cofferdams of the present invention.

[0042] Figure 11 This is a schematic diagram of the interlocking connection of adjacent steel cofferdam segments in an embodiment of the underwater concrete pouring method for large-section steel cofferdams of the present invention.

[0043] In the picture:

[0044] 1. Large-section steel cofferdam; 11. Steel cofferdam segment; 12. Lock joint; 13. Internal truss; 2. Compartment partition; 21. Removable formwork; 22. Steel mesh; 23. Reinforcing steel; 201. First compartment partition; 202. Second compartment partition; 203. Third compartment partition; 3. Compartment segment; 31. Intermediate compartment segment; 32. Intermediate interface compartment segment; 33. End interface compartment segment; 301. First intermediate compartment segment; 302. Second intermediate compartment segment; 303. Third intermediate compartment segment; 4. Pipeline; 5. Tanker truck; 6. Top pump. Detailed Implementation

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] Example 1:

[0049] See appendix Figures 1 to 11 This paper presents an illustrative embodiment of the underwater concrete pouring method for a large-section steel cofferdam proposed in this invention. The large-section steel cofferdam 1 is composed of multiple steel cofferdam segments 11 connected sequentially by interlocking joints 12. The underwater concrete pouring method for the large-section steel cofferdam includes the following steps:

[0050] S1. Based on the position of the internal truss 13 of the steel cofferdam segment 11, each steel cofferdam segment 11 is divided into multiple independently cast sections 3.

[0051] S2. Install compartment partitions 2 between adjacent compartment sections 3. The compartment partitions 2 are installed on the internal truss 13 of the steel cofferdam section 11.

[0052] S3. Concrete is poured for each section 3, of which the section 3 where the lock 12 is located is the last section 3 to be poured.

[0053] In step S2, the compartment partition 2 is installed on the internal truss 13 of the steel cofferdam segment 11, specifically fixed to the vertical angle steel members that make up the internal truss 13.

[0054] The division of the compartment into independent pouring sections 3 based on the position of the internal truss 13 allows the compartment partitions 2 to be directly fixed to the internal truss 13, providing reliable initial lateral support for the compartment structure and improving the overall stability of the compartment. Placing the section 3 containing the locking joint 12 in the last pour ensures the concrete density of this critical connection area, enhancing the water-stopping and sealing performance of the large-section steel cofferdam 1. Simultaneously, the clear compartment design simplifies the underwater pouring construction process, contributing to improved overall construction efficiency.

[0055] See appendix Figure 10 and Figure 11 Step S1 specifically includes: each steel cofferdam segment 11 includes a middle area and an end locking area; the middle area of ​​each steel cofferdam segment 11 is divided into multiple intermediate compartments 31; the end locking areas of two adjacent steel cofferdam segments 11 are jointly designated as an intermediate interface compartment 32; the single-sided end locking area of ​​the end steel cofferdam segment 11 is designated as an end interface compartment 33; the end steel cofferdam segment 11 is the steel cofferdam segment 11 at both ends of the large cross-section steel cofferdam 1.

[0056] The steel cofferdam segment 11 is precisely divided into intermediate section 31, intermediate interface section 32, and end interface section 33. This can adapt to the structural characteristics of multi-segment splicing of large-section steel cofferdam 1, and achieve precise matching between the segment division and the stress distribution and lock layout of the steel cofferdam. The intermediate interface section 32 integrates the end lock areas of adjacent segments, and the end interface section 33 separately delineates the first and last end lock areas. This provides a clear basis for the implementation of the subsequent batch pouring process. At the same time, it can specifically strengthen the construction quality control of the lock area and improve the sealing reliability of the connection of the steel cofferdam segment 11.

[0057] See appendix Figure 2 and Figure 10 Step S2 specifically includes:

[0058] S21. First, install the first compartment partition 201 between the end interface section 33 at the head of the large section steel cofferdam 1 and the adjacent first intermediate section 301. The first compartment partition 201 abuts against and is fixed to the side of the corresponding internal truss 13 near the first intermediate section 301.

[0059] S22. Install the second compartment partition 202 between the first intermediate compartment section 301 and the adjacent second intermediate compartment section 302. The second compartment partition 202 abuts against and is fixed to the side of the corresponding internal truss 13 closest to the first intermediate compartment section 301, so that the second compartment partition 202 and the first compartment partition 201 are arranged opposite to each other; see appendix. Figure 6 This is a schematic diagram showing that adjacent compartment partitions 2 are arranged opposite each other in this embodiment.

[0060] S23. Install the third compartment partition 203 between the second intermediate compartment section 302 and the adjacent third intermediate compartment section 303. The third compartment partition 203 abuts against and is fixed to the side of the corresponding internal truss 13 closest to the third intermediate compartment section 303, so that the third compartment partition 203 and the second compartment partition 202 are arranged opposite to each other; see appendix. Figure 8 This is a schematic diagram showing that adjacent compartment partitions 2 are arranged in opposite directions in this embodiment.

[0061] S24. The partition plates 2 are alternately set opposite each other and back to back until the installation of the partition plates 2 between the end interface section 33 at the tail end of the large section steel cofferdam 1 and the adjacent intermediate section 31 is completed.

[0062] The installation method of alternating and back-to-back arrangement of adjacent compartment partitions 2 ensures that the installation state of the compartment partitions 2 is precisely adapted to the support requirements of subsequent pouring construction. The opposing compartment partitions 2 can form a bidirectional stable constraint with the help of the internal truss 13. Combined with the alternating back-to-back arrangement, the overall compartment structure is more in line with the construction process. This installation method does not require additional temporary support components, reduces construction interference, and ensures clear boundaries of each compartment 3, effectively preventing concrete cross-contamination between adjacent compartments 3 during pouring and improving the forming accuracy of the compartments.

[0063] See appendix Figure 10 and Figure 11 To address the structural differences between the intermediate interface section 32 and the end interface section 33, corresponding compartment partition 2 configurations are defined. For the intermediate interface section 32, the corresponding compartment partitions 2 on both sides are arranged opposite to each other, ensuring lateral pressure balance during pouring in the interlocking area. For the end interface section 33, the compartment partition 2 on the side closest to the adjacent intermediate section 31 is arranged opposite to the compartment partition 2 on the side of the adjacent intermediate section 31 furthest from the end interface section 33, achieving double fixation through the internal truss 13 support of the intermediate section 31 and the already poured concrete. Both configurations precisely match the water-stopping requirements of the interface sections, significantly improving the water-stopping reliability at the joints of the steel cofferdam segments 11.

[0064] In this embodiment, the length of each intermediate section 31 is 3~4m, and the number of intermediate sections 31 divided within each steel cofferdam segment 11 is 3~5, so as to balance construction efficiency and structural stability. The reasonable length can avoid the concrete pouring being not dense due to the intermediate section 31 being too large. At the same time, reducing the number of sections reduces the complexity of the construction process. It is adapted to the length of the steel cofferdam segment 11, ensuring that each section is subjected to uniform stress and avoiding local stress concentration. It provides a clear basis for construction organization planning and material allocation, and improves the level of construction standardization.

[0065] See appendix Figure 4 In this embodiment, the large-section steel cofferdam 1 is composed of three steel cofferdam segments 11 connected in sequence by interlocking joints 12; the end steel cofferdam segments 11 are connected to the post-welded components of the box-shaped steel beam by interlocking joints 12.

[0066] See appendix Figure 5 This is a structural schematic diagram of the end steel cofferdam segment 11 in this embodiment. The end steel cofferdam segment 11 is divided into three intermediate compartments 31, with the adjacent compartment partitions 2 arranged in the following order: facing each other, back to back, and facing each other again. For the left-hand end interface compartment 33, the compartment partition 2 on the side closest to the adjacent intermediate compartment 31 is arranged opposite to the compartment partition 2 on the side of the intermediate compartment 31 furthest from the end interface compartment 33; that is, the two compartment partitions 2 on both sides of the first left-hand intermediate compartment 31 are arranged opposite each other. For the right-hand intermediate interface compartment 32, the corresponding compartment partitions 2 on both sides are arranged back to back (this figure only shows the side of the intermediate interface compartment 32 closest to the steel cofferdam segment 11).

[0067] See appendix Figure 7 This is a schematic diagram of the non-end steel cofferdam segment 11 in this embodiment, which is divided into four intermediate sections 31. When the number of intermediate sections 31 is even, simply arranging adjacent compartment partitions 2 alternately facing each other and back to back will not meet the installation layout requirements of the compartment partitions on both sides of the intermediate interface section 32. Therefore, in this embodiment, the rule of alternating facing and back to back arrangement of adjacent compartment partitions 2 is still followed. By adjusting the length of some intermediate sections 31, the arrangement of each compartment partition 2 is ensured to meet the requirements; then, the longer intermediate section 31 is divided into two sections to ensure the quality of concrete pouring.

[0068] Here, the intermediate section 31 with adjusted length is preferably placed in the middle of the steel cofferdam segment 11 to ensure structural stability during concrete pouring. When splitting the longer intermediate section 31, a partition plate 2 needs to be added to the internal truss 13 corresponding to the middle of the section. The partition plate 2 can be fixed on any side of the vertical angle steel member of the internal truss 13 according to the layout requirements. When pouring the split section, the side with the newly added partition plate 2 is poured first, so as to use the vertical angle steel member of the internal truss 13 to help fix the partition plate.

[0069] See appendix Figure 3 Step S3 specifically includes:

[0070] S31, First batch of pouring: First pour the middle section 31 with the two side partitions 2 being set opposite each other;

[0071] S32, Second batch of pouring: The middle section 31 with the two side partitions 2 set back from each other is poured again;

[0072] S33, Third batch of pouring: The final pouring of the intermediate interface section 32 and the end interface section 33.

[0073] See appendix Figure 4 The gray section 3 is the first batch of pouring area, the blue section 3 is the third batch of pouring area, and the green section 3 is the second batch of pouring area.

[0074] The three-batch pouring sequence is clearly defined. After the first batch of pouring is completed, a stable supporting foundation can be quickly formed, providing reliable lateral fixation for subsequent batches of pouring and preventing displacement of the opposing compartment partitions 2. In addition, the delayed pouring of the intermediate interface section 32 and the end interface section 33 allows for flexible adjustment of pouring parameters based on the actual forming condition of the previous sections, ensuring the fit between the concrete in the interlocking area and the steel cofferdam structure, and improving the overall stability of construction quality.

[0075] In this embodiment, concrete pouring is carried out by a combination of a concrete mixer truck 5 and a boom pump 6. The concrete mixer truck 5 is responsible for transporting the properly mixed CL15 lightweight concrete (with flocculant added) to the pouring surface to ensure a continuous and uninterrupted supply of concrete and avoid cold joints in the pouring sections due to untimely material supply. The boom pump 6 is flexibly deployed according to the location, height and pouring requirements of each pouring batch of sections 3. Its delivery pipe is precisely connected to the underwater pouring pipe 4, which can realize fixed-point and uniform speed pouring of each section 3. It can adapt to different pouring conditions of intermediate sections 31, intermediate interface sections 32 and end interface sections 33, and effectively control the concrete pouring speed and pouring height, reduce underwater concrete segregation and leakage, further coordinate with the pouring sequence to ensure construction quality and work efficiency, and at the same time facilitate the flexible adjustment of the pouring flow rate to match the parameter adjustment requirements based on on-site pouring feedback.

[0076] During the pouring of each batch of compartments in step S3, the lateral support method for the corresponding compartment partition 2 is as follows:

[0077] When the first batch of concrete is poured into the middle section 31 with the two side partitions 2 set opposite each other, the internal truss 13 of the steel cofferdam section 11 is used as the lateral support for the corresponding partition 2 of the section in this batch.

[0078] After the concrete of the first batch of poured sections reaches more than 30% of the design strength, the second batch and the third batch of pouring will be carried out in sequence. At this time, the concrete of the first batch of poured sections will serve as the lateral support for the partition plates 2 of each section in the second and third batches of pouring.

[0079] The lateral support method for the compartment partitions 2 during each batch of pouring was clearly defined. The first batch relied on the internal truss 13 for support, while subsequent batches relied on the concrete already poured in the first batch. This effectively solved the displacement problem of compartment partitions 2, which are set up opposite to each other, without independent truss support. Subsequent pouring was limited to the first batch of concrete reaching at least 30% of its design strength. This ensured that the support strength could withstand the lateral pressure during pouring without affecting the construction progress due to excessive curing time. No additional temporary supports were required, reducing construction costs, while also ensuring the regularity of the boundaries of each compartment 3 and improving the quality of concrete forming.

[0080] See appendix Figure 9 The compartment partition 2 is composed of a non-removable template 21, a steel mesh 22 and a reinforcing steel bar 23. The steel mesh 22 is fixed on both sides of the non-removable template 21. One side of the steel mesh 22 is abutted against and fixed to the internal truss 13 of the steel cofferdam segment 11, and the reinforcing steel bar 23 is fixed to the side of the other side of the steel mesh 22 away from the non-removable template 21.

[0081] The compartment partition 2 adopts a combined structure of non-removable formwork 21, steel mesh 22, and reinforcing steel bars 23. The non-removable formwork 21 can be directly used as the concrete forming surface, eliminating the need for subsequent formwork removal and significantly improving construction efficiency. The steel mesh 22 is fixed to both sides of the non-removable formwork 21, forming a three-dimensional force-bearing system with the reinforcing steel bars 23 on the side away from the non-removable formwork 21. This effectively improves the structural strength and impact resistance of the compartment partition 2 during pouring, preventing deformation or damage during the pouring process. One side of the steel mesh 22 is directly fixed to the internal truss 13, ensuring installation stability. The overall structure can adapt to the complex conditions of underwater pouring, balancing permeability and compartment stability. It allows water to seep out during pouring while preventing concrete aggregate from flowing across, ensuring the independent forming quality of each compartment 3.

[0082] In step S3, concrete is poured using a conduit 4 with a diameter of Φ300mm and a wall thickness of not less than 4mm. Before use, the conduit 4 needs to be assembled section by section and subjected to a watertight pressure test. The water pressure of the watertight pressure test must simultaneously meet the following requirements: not less than 1.5 times the water pressure corresponding to the maximum water depth in the pouring area, and not less than 1.5 times the maximum internal pressure that the conduit wall and welds bear when pouring concrete.

[0083] By limiting the diameter and wall thickness of the guide pipe 4, the efficiency of concrete delivery can be guaranteed while ensuring that the guide pipe 4 has sufficient structural strength. Before use, the guide pipe 4 is assembled section by section and subjected to a watertight pressure test. This can thoroughly eliminate potential sealing hazards in the joints and welds of the guide pipe 4, effectively avoiding concrete contamination or pouring failure caused by grout leakage and weld cracking during underwater pouring, and significantly improving the reliability and construction safety of underwater concrete pouring.

[0084] In step S3, the concrete used for pouring is CL15 lightweight concrete, and flocculant is added to the concrete. Lightweight concrete can effectively reduce the overall stress load on the steel cofferdam, preventing settlement of the steel cofferdam due to excessive self-weight during the pouring process. The flocculant can significantly improve the underwater anti-dispersion and workability of the concrete (workability refers to the comprehensive performance of fresh concrete in terms of ease of operation and ability to form a dense and homogeneous body during construction), effectively solving the common problems of aggregate segregation and cement paste loss during underwater pouring, and ensuring that the concrete has uniform strength and meets the density standards after pouring.

[0085] In the above illustrative embodiments, the underwater concrete pouring method for large-section steel cofferdams can significantly improve the overall density of underwater concrete, strengthen the water-stopping ability of key parts such as segmental interlocks, effectively avoid leakage risks, ensure the structural stability of large-section steel cofferdams under complex working conditions in water conservancy projects, provide reliable guarantees for the long-term service of the project, and meet the construction quality requirements of large-section structures.

[0086] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0087] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for underwater concrete pouring of a large-section steel cofferdam, characterized in that, The large-section steel cofferdam (1) is composed of multiple steel cofferdam segments (11) connected sequentially through interlocking joints (12). The method includes the following steps: S1. Based on the position of the internal truss (13) of the steel cofferdam segment (11), each steel cofferdam segment (11) is divided into multiple independently cast sections (3); each steel cofferdam segment (11) includes a middle area and an end lock (12) area. The middle area of ​​each steel cofferdam segment (11) is divided into multiple middle sections (31) through the internal truss (13). The end lock (12) areas of two adjacent steel cofferdam segments (11) are jointly designated as a middle interface section (32). The end lock (12) area of ​​one side of the end steel cofferdam segment (11) is designated as an end interface section (33). The end steel cofferdam segment (11) is the steel cofferdam segment (11) at both ends of the large cross-section steel cofferdam (1). S2. Install partition plates (2) between adjacent compartment sections (3), the partition plates (2) being installed on the internal truss (13) of the steel cofferdam section (11); S3. Concrete is poured for each section (3), of which the section (3) where the lock (12) is located is the last section (3) to be poured. Specifically, step S2 includes: S21. First, install the first compartment partition (201) between the end interface section (33) at the head end of the large section steel cofferdam (1) and the adjacent first intermediate section (301). The first compartment partition (201) abuts against and is fixed to the side of the corresponding internal truss (13) near the first intermediate section (301). S22. Then install the second compartment partition (202) between the first intermediate compartment section (301) and the adjacent second intermediate compartment section (302). The second compartment partition (202) abuts against and is fixed to the side of the corresponding internal truss (13) near the first intermediate compartment section (301) so that the second compartment partition (202) and the first compartment partition (201) are arranged opposite to each other. S23. Then install the third compartment partition (203) between the second intermediate compartment section (302) and the adjacent third intermediate compartment section (303). The third compartment partition (203) abuts against and is fixed to the side of the corresponding internal truss (13) near the third intermediate compartment section (303) so that the third compartment partition (203) and the second compartment partition (202) are arranged opposite to each other. S24. The partition plates (2) of the adjacent compartments (2) are alternately set in opposite directions until the installation of the partition plates (2) between the end interface compartment section (33) of the tail end of the large section steel cofferdam (1) and the adjacent intermediate compartment section (31) is completed.

2. The method for underwater concrete pouring of large-section steel cofferdams according to claim 1, characterized in that, Step S3 specifically includes: S31, First batch of pouring: First pour the middle section (31) with the two side partitions (2) set opposite each other. S32, Second batch of pouring: The two side compartment partitions (2) are poured again as the middle compartment (31) set opposite to each other; S33, Third batch of pouring: The final pouring of the intermediate interface section (32) and the end interface section (33).

3. The method for underwater concrete pouring of large-section steel cofferdams according to claim 1, characterized in that, For the intermediate interface section (32), the corresponding compartment partitions (2) on both sides are arranged opposite to each other; for the end interface section (33), the compartment partition (2) on the side closer to the adjacent intermediate section (31) is arranged opposite to the compartment partition (2) on the side of the adjacent intermediate section (31) away from the end interface section (33).

4. The method for underwater concrete pouring of large-section steel cofferdams according to claim 2, characterized in that, During the pouring of each batch of compartment (3) in step S3, the lateral support method of the corresponding compartment partition (2) is as follows: When the first batch of pouring is the middle section (31) with the two side partitions (2) set opposite each other, the internal truss (13) of the steel cofferdam section (11) is used as the lateral support of the partition (2) corresponding to the section (3) of this batch; After the concrete of the first batch of poured section (3) reaches more than 30% of the design strength, the second batch of pouring and the third batch of pouring will be carried out in sequence. At this time, the concrete of the first batch of poured section (3) will serve as the lateral support for the partition plates (2) of each section (3) in the second and third batches of pouring.

5. The method for underwater concrete pouring of large-section steel cofferdams according to claim 1, characterized in that, The compartment partition (2) is composed of a non-removable template (21), a steel mesh (22) and a reinforcing steel bar (23); the steel mesh (22) is fixed on both sides of the non-removable template (21), one side of the steel mesh (22) abuts against and is fixed on the internal truss (13) of the steel cofferdam segment (11), and the reinforcing steel bar (23) is fixed on the other side of the steel mesh (22) away from the non-removable template (21).

6. The method for underwater concrete pouring of large-section steel cofferdams according to claim 1, characterized in that, In step S3, concrete is poured using a conduit (4) for delivery. The conduit (4) has a diameter of Φ300mm and a wall thickness of not less than 4mm. Before use, the conduit (4) needs to be assembled section by section and subjected to a watertight pressure test. The water pressure of the watertight pressure test must simultaneously meet the following requirements: not less than 1.5 times the water pressure corresponding to the maximum water depth in the pouring area, and not less than 1.5 times the maximum internal pressure that the conduit wall and welds bear when pouring concrete.

7. The method for underwater concrete pouring of large-section steel cofferdams according to claim 1, characterized in that, In step S3, the concrete used for pouring is CL15 lightweight concrete, and flocculant is added to the concrete.

8. The method for underwater concrete pouring of large-section steel cofferdams according to any one of claims 1-7, characterized in that, The length of each intermediate section (31) is 3~4m, and the number of intermediate sections (31) divided within each steel cofferdam segment (11) is 3~5.

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