A structure of a soft soil foundation assembled soil core steel sheet pile cofferdam and a construction method thereof

Abstract

This invention relates to the field of water conservancy engineering construction technology, specifically to a structure and construction method of a prefabricated soil-core steel sheet pile cofferdam for soft soil foundations. The structure of this application includes: steel sheet piles, integrated tension-compression transverse members, drainage boards, geogrids, and spoil heap cores; the integrated tension-compression transverse members include: transverse members, locking ends, ribbed channel steel, nuts, and double-ended threaded rods; the transverse members include: small-diameter steel pipes, first blind flanges, second blind flanges, grouting bodies, and grouting holes; the locking ends include: locking end steel pipes, third blind flanges, internal threaded sleeves, end plates, grouting bodies, and grouting holes. This application creates dry ground conditions by establishing a prefabricated retaining structure on water, quickly inserting drainage boards at the bottom of the heap to form drainage channels, utilizing spoil as the heap core material, and forming a permanent and temporary integrated structure with the retaining structure during filling, achieving a green, low-carbon, convenient, efficient, and cost-effective structural system.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering construction technology, and more specifically to a structure and construction method of a prefabricated soil-core steel sheet pile cofferdam for soft soil foundation. Background Technology

[0002] In water conservancy engineering construction, temporary cofferdams are often used when constructing pump houses, sluices, tunnels, and other structures in shallow water areas to withstand the effects of external water flow erosion, wave impact, and soil erosion, providing dry conditions for construction. Double-row steel sheet pile cofferdams have certain advantages in terms of load-bearing performance, water-stopping effect, and construction efficiency, and have been applied in ports, water conservancy, municipal engineering, and other fields. However, the geological conditions of water sites are often poor, with deep soft silt and, especially, shallow surfaces with flowing mud and other unfavorable conditions. Improper treatment of steel sheet pile cofferdams can easily lead to excessive deformation and collapse risks.

[0003] Traditional cofferdams use sand and gravel as the core material, which consumes a lot of resources and is expensive. With sand resources becoming increasingly scarce, some projects in recent years have used backfill soil as an alternative. Currently, during project implementation, cohesive soil is directly dumped into the water area of ​​the cofferdam core to form a soil core cofferdam. However, its integrity is poor, and the foundation is prone to instability. In multiple cases, the steel sheet piles on both sides tilted and bulged outward, and the kicker became unstable. With the displacement of the outer side of the piles, the middle tie rod could not withstand the tension, resulting in the tie rod breaking. At the same time, the cohesive soil in the cofferdam core forms silt after being soaked in water. The disposal of waste silt is difficult, costly, and environmentally damaging.

[0004] Chinese invention patent CN217811134U (publication date: November 15, 2022) provides a cofferdam structure, including: two sets of sheet pile assemblies, each set of sheet pile assemblies being composed of multiple vertically arranged sheet piles spliced ​​together, the bottom of the sheet pile assembly being inserted below the riverbed, the two sets of sheet pile assemblies being arranged in parallel, a filling area being formed between the inner sides of the two sets of sheet pile assemblies, and a filler material being placed in the filling area; multiple tie rods, horizontally arranged on the upper part of the sheet pile assemblies and perpendicular to the sheet pile assemblies, the two ends of the tie rods extending out of the outer sides of the two sets of sheet pile assemblies respectively, the multiple tie rods being arranged along the extension direction of the sheet pile assemblies, and fixing members being provided at both ends of the tie rods, the fixing members being located on the outer side of the sheet pile assemblies, the fixing members being configured to limit the distance between the upper parts of the two sets of sheet pile assemblies. The cofferdam structure in this utility model is stable and reliable, and can be applied to narrow construction spaces.

[0005] Chinese invention patent application CN118686125A (publication date: September 24, 2024) provides a prefabricated longitudinal water-passing earth-rock cofferdam structure and its construction method. It employs H-shaped steel columns and connecting steel plates to form a lattice-type skeleton structure, filling with on-site waste soil and rock to form the cofferdam body. The components are bolted together using equilateral angle steel connectors. The steel structure is reusable, and the lack of internal support design improves construction convenience. This invention effectively utilizes on-site excavated soil and rock, saving costs; no slope is required inside or outside the cofferdam, saving land; there is no internal support, facilitating construction; the steel structure is reusable and environmentally friendly; the cofferdam structure has good seepage prevention performance; and the amount of drainage work in the foundation pit is small.

[0006] Existing cofferdam structures utilize double-layer sheet piles and tie rods for added stability; they also employ H-shaped steel columns and connecting steel plates to create a lattice-like framework structure, further enhancing overall stability. However, current technologies have not fully resolved issues such as the weak compressive strength of tie rod structures during traditional sheet pile cofferdam construction, soil softening due to traditional cohesive backfilling, increased waste silt, weak overall stiffness and susceptibility to instability in the cofferdam structure, and poor soil quality, low bearing capacity, and high compressibility beneath the cofferdam. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a prefabricated soil-core steel sheet pile cofferdam structure and its construction method for soft soil foundations. It utilizes waste soil as the cofferdam core material, employs dry compaction backfilling, and features a novel combined structure integrating compression bracing and anchoring. This prefabricated steel structure is designed for use on water, eliminating the need for prior foundation treatment. Furthermore, it can withstand external forces during cofferdam core backfilling and site operations within the cofferdam.

[0008] A prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation includes: steel sheet piles, tension-compression integrated transverse members, drainage board, geogrid, and spoil dike core; The sheet piles are arranged in parallel and fixedly connected by integrated tension and compression transverse members. A geomembrane is laid on the inner side of the sheet piles on the water-facing side, and a geotextile is laid on the inner side of the sheet piles on the back side. The drainage board is located within the base mud surface of the steel sheet pile enclosure area, and the geogrid is laid on top of the drainage board. The tension-compression integrated transverse member includes: a transverse member, a locking end, a ribbed channel steel, a nut, and a double-ended screw; The transverse member is located inside the area enclosed by the sheet pile and is connected to the locking end flange; The ribbed channel steels are symmetrically arranged on both sides of the sheet pile; The double-ended screw passes sequentially through the ribbed channel steel on the outside of the sheet pile, the sheet pile itself, and the ribbed channel steel on the inside, and is threadedly connected to the locking end. The nut is threaded onto the outside of the double-ended screw, adjacent to the channel steel on the outside of the ribbed sheet pile.

[0009] Furthermore, the transverse member includes: a small-diameter steel pipe, a first blind flange, a second blind flange, a grouting body, and a grouting hole; The first blind flange and the second blind flange are symmetrically welded to both sides of the small-diameter steel pipe. The first blind flange is equipped with grouting holes, while the second blind flange has no through-hole structure. The grout is filled inside a small-diameter steel pipe.

[0010] Furthermore, the locking end includes: a locking end steel pipe, a third blind flange, an internal threaded sleeve, a head plate, a grouting body, and a grouting hole; The internal threaded sleeve is embedded inside the locking end steel pipe and is threadedly connected to the double-ended screw. The end cap plate is provided with grouting holes, which cover the end face of the locking end steel pipe; The grout is filled inside the locking end steel pipe; The third blind flange is connected to the second blind flange.

[0011] A construction method for a prefabricated soil-core steel sheet pile cofferdam structure on soft soil foundation, characterized by the following steps: Step S1: Select the cofferdam structure type, determine the type and length of the sheet piles, and determine the cross-sectional dimensions of the transverse members; Step S2: Set up a prefabrication yard on the shore, assemble and process steel sheet piles, and manufacture transverse members and locking ends; Step S3: Fabricate the ribbed channel steel, nut, and double-ended threaded rod; Step S4: Construct steel sheet piles and tension-compression integrated transverse members to form a composite structure; Step S5: Drain the water within the weir body to create dry conditions. At the same time, lay geogrid and drainage sand cushion on the natural mud surface, and use a handheld inserter to install drainage boards. Step S6: Lay geogrid as a cushion layer at the bottom of the dam body, lay geomembrane on the inside of the steel sheet piles on the water-facing side, lay geotextile on the inside of the backwater side, then backfill the spoil dam core in layers with compaction, and seal the top with clay. Step S7: Repeat steps S4, S5, and S6 until the entire section of the project is completed.

[0012] Furthermore, in step S1, the cofferdam structure type is selected based on hydrological and geological conditions and cofferdam design standards; the internal forces, deformations, and structural stability of the sheet piles and transverse members are calculated under two working conditions: dry backfilling and backfill completion, to determine the type, length, and cross-sectional dimensions of the transverse members.

[0013] Furthermore, the method for manufacturing the transverse member in step S2 is as follows: by welding the first blind flange and the second blind flange at both ends of the small-diameter steel pipe, grout is injected into the small-diameter steel pipe and cured to complete the manufacturing of the transverse member.

[0014] Furthermore, the method for manufacturing the locking end in step S2 is as follows: by processing and manufacturing the locking end steel pipe, welding the third blind flange and end plate to its end, processing and manufacturing the internal thread sleeve, and then grouting and curing the locking end steel pipe to complete the manufacturing of the locking end.

[0015] Furthermore, in step S4, steel sheet piles are driven into the water, followed by the installation of double-ended bolts, ribbed channel steel, and locking ends. After initial locking with nuts, a reliable base is formed.

[0016] Furthermore, in step S4, after the reliable base is formed and the transverse members are installed, they are connected to the locking end through a flange. Finally, the nuts on the outside of the sheet pile are locked again to form a combined structure.

[0017] Compared with existing technologies, the advantages and effects of this application are as follows: 1. This invention provides a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundations, proposing a green backfilling technology that uses excavated soil as cofferdam core filling material. This solves the problems of scarce sand and gravel resources and high construction costs, achieving resource utilization, local material sourcing, and low-carbon environmental protection. It overcomes the drawbacks of traditional cohesive soil backfilling on water, such as soil softening, increased waste silt, and weak overall stiffness and instability of the cofferdam structure. It proposes a dry compaction backfilling technology, reducing the design width requirement of the cofferdam body, reducing the lateral retaining pressure of the sheet piles, and allowing the excavated soil to be recycled, achieving ecological environmental protection, cost reduction and efficiency improvement.

[0018] 2. The present invention provides a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation, proposing a novel combined structure of compression bracing and anchoring, overcoming the shortcomings of weak compressive strength of traditional steel tie rod structures for cofferdams, and proposing a tension-compression integrated transverse member with grouting inside a small-diameter steel pipe. Furthermore, the novel combined structure serves as both the water-retaining structure on both sides during dry filling and the cofferdam structure after the dam body is filled, achieving a combination of permanent and temporary structures, rapid construction, recycling, and low-carbon environmental protection.

[0019] 3. This invention provides a prefabricated steel sheet pile cofferdam structure for soft soil foundations. It proposes a fully prefabricated steel cofferdam structure for water, overcoming the pain points of welding, pouring, and curing on water, and giving full play to the advantages of simple construction and significant efficiency. It proposes a drainage board surcharge reinforcement technology for the bottom of the cofferdam, which does not require pre-loading consolidation. The backfilling of the cofferdam core soil is the loading process, which solves the difficulties of poor soil quality, low bearing capacity, and high compressibility of the foundation soil below the cofferdam, especially the shallow muddy layer. It also avoids the risk of a significant increase in lateral deformation of the sheet piles and instability after the cofferdam is backfilled.

[0020] 4. The present invention provides a construction method for a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation. By creating a prefabricated retaining structure on the water to form dry ground conditions, drainage boards are quickly driven into the bottom of the cofferdam to form a drainage channel. The excavated soil is used as the core material of the cofferdam, which is also the foundation loading material. It forms a permanent and temporary combination with the retaining structure during the filling period, realizing a green and low-carbon, convenient construction, high efficiency and cost advantage structural system.

[0021] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0022] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0024] in: Figure 1 This is a plan view of the prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation in this application; Figure 2 This is a cross-sectional view of the prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation in this application; Figure 3 This is a schematic diagram of the integrated bracing and anchoring structure of this application (before pumping). Figure 4 This is a schematic diagram of the integrated bracing and anchoring structure of this application (after pumping out water). Figure 5 This is a detailed drawing of the tension-compression integrated transverse member of this application; Figure 6 This is a detailed drawing of the transverse members in this application; Figure 7 This is a detailed drawing of the locking end of this application.

[0025] Reference numerals: 100-Sheet pile; 200-Integrated tension and compression transverse member; 300-Drainage board; 400-Geogrid; 500-Spoil weir core; 110-Geomembrane; 120-Geotextile; 210-Transverse member; 220-Locking end; 230-Ribped channel steel; 240-Nut; 250-Double-ended threaded rod; 211-Small diameter steel pipe; 212-First blind flange; 213-Second blind flange; 214-Grouting body; 215-Grouting hole; 221-Locking end steel pipe; 222-Third blind flange; 223-Internal threaded sleeve; 224-End plate. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0027] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0028] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0029] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it have an "or" relationship.

[0030] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0031] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0032] Example 1 This embodiment describes the structure of a prefabricated soil-core steel sheet pile cofferdam for soft soil foundation. Please refer to the structural plan view for details. Figure 1 Please refer to the structural cross-sectional diagram. Figure 2 Please refer to the detailed drawing of the tension / compression integrated transverse member. Figure 5 Please refer to the detailed drawing of the transverse members. Figure 6 Please refer to the detailed drawing of the locking end. Figure 7 .

[0033] A prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation includes: steel sheet piles 100, tension-compression integrated transverse members 200, drainage board 300, geogrid 400, and spoil dam core 500. The sheet piles 100 are arranged in parallel and fixedly connected by an integrated tension and compression transverse member 200. A geomembrane 110 is laid on the inner side of the sheet piles 100 on the water-facing side and a geotextile 120 is laid on the inner side of the back water-facing side. The drainage board 300 is located within the base mud surface of the area enclosed by the steel sheet pile 100, and the geogrid 400 is laid on top of the drainage board 300. The tension-compression integrated transverse member 200 includes: a transverse member 210, a locking end 220, a ribbed channel steel 230, a nut 240, and a double-ended screw 250; The transverse member 210 is located inside the area enclosed by the sheet pile 100 and is connected to the flange of the locking end 220. The ribbed channel steel 230 is symmetrically arranged on both sides of the sheet pile 100; The double-headed screw 250 passes through the ribbed channel steel 230 on the outside of the sheet pile 100, the sheet pile 100, and the ribbed channel steel 230 on the inside, and is threadedly connected to the locking end 220. The nut 240 is threaded onto the outside of the double-ended screw 250, adjacent to the channel steel 230 on the outside of the ribbed sheet pile 100.

[0034] Furthermore, the transverse member 210 includes: a small-diameter steel pipe 211, a first blind flange 212, a second blind flange 213, a grouting body 214, and a grouting hole 215; The first blind flange 212 and the second blind flange 213 are symmetrically welded to both sides of the small-diameter steel pipe 211. The first blind flange 212 is equipped with a grouting hole 215, and the second blind flange 213 has no through hole structure. The grout 214 is filled inside the small-diameter steel pipe 211.

[0035] Furthermore, the locking end 220 includes: a locking end steel pipe 221, a third blind flange 222, an internal threaded sleeve 223, a head plate 224, a grouting body 214, and a grouting hole 215; The internal threaded sleeve 223 is embedded inside the locking end steel pipe 221 and is threadedly connected to the double-ended screw 250. The end plate 224 is provided with grouting holes 215, which cover the end face of the locking end steel pipe 221; The grouting body 214 fills the interior of the locking end steel pipe 221; The third blind flange 222 is connected to the second blind flange 213.

[0036] The technical effects achieved in this embodiment are as follows: This application provides a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundations, proposing a fully prefabricated steel cofferdam structure for water, overcoming the pain points of welding, pouring, and curing on water, and giving full play to the advantages of simple construction and significant efficiency; it proposes a drainage board surcharge reinforcement technology for the bottom of the cofferdam, which does not require pre-loading consolidation, and the backfilling of the cofferdam core soil is the loading process, which solves the difficulties of poor soil quality, low bearing capacity, and high compressibility of the foundation soil below the cofferdam, especially the shallow surface mud layer, and also avoids the risk of a significant increase in lateral deformation of the sheet piles and instability after the cofferdam is backfilled.

[0037] Example 2 Based on Example 1, this example introduces a construction method for a prefabricated soil-core steel sheet pile cofferdam structure on soft soil foundation. For the assembly structure in step S4, please refer to [link to example]. Figure 3 Please refer to the structural diagram of step S5. Figure 4 .

[0038] A construction method for a prefabricated soil-core steel sheet pile cofferdam structure on soft soil foundation includes the following steps: Step S1: Select the cofferdam structure type, determine the model and length of the sheet pile 100, and determine the cross-sectional dimensions of the transverse member 210; Step S2: Build a prefabrication yard on the shore, splice and process steel sheet piles 100, and make transverse members 210 and locking ends 220; Step S3: Fabricate ribbed channel steel 230, nut 240, and double-ended screw 250; Step S4: Construct the sheet piles 100 and the tension-compression integrated transverse members 200 to form a combined structure; Step S5: Drain the water within the weir body to create dry conditions. At the same time, lay geogrid 400 and drainage sand cushion on the natural mud surface, and use a handheld inserter to install drainage board 300. Step S6: Lay a geogrid 400 as a cushion layer at the bottom of the dam body, lay a geomembrane 110 inside the steel sheet piles 100 on the water-facing side, lay a geotextile 120 inside the backwater side, and then backfill the spoil dam core 500 in layers with compacted soil, and seal the top with clay. Step S7: Repeat steps S4, S5, and S6 until the entire section of the project is completed.

[0039] The technical effect achieved by this embodiment is as follows: by creating a prefabricated retaining structure on the water to form dry ground conditions, drainage boards are quickly inserted at the bottom of the weir to form a drainage channel, and the excavated soil is used as the core material of the weir, which is also the foundation loading material. It forms a permanent and temporary combination with the retaining structure during the filling period, thus realizing a green, low-carbon, convenient, efficient and cost-effective structural system.

[0040] Example 3 Based on the above embodiments 1 and 2, this embodiment further introduces a construction method for a prefabricated soil-core steel sheet pile cofferdam structure on soft soil foundation.

[0041] Furthermore, in step S1, the cofferdam structure type is selected based on hydrological and geological conditions and cofferdam design standards; the internal forces, deformations, and structural stability of the sheet piles 100 and transverse members 210 are calculated under two working conditions: dry backfilling and backfill completion, to determine the type, length, and cross-sectional dimensions of the sheet piles 100 and transverse members 210.

[0042] Furthermore, the method for manufacturing the transverse member 210 in step S2 is as follows: by welding the first blind flange 212 and the second blind flange 213 at both ends of the small-diameter steel pipe 211, and then grouting and curing are performed inside the small-diameter steel pipe 211 to complete the manufacturing of the transverse member 210.

[0043] Furthermore, the specific method for manufacturing the locking end 220 in step S2 is as follows: by processing and manufacturing the locking end steel pipe 221, welding the third blind flange 222 and the end plate 224 to its end, processing and manufacturing the internal thread sleeve 223, and then grouting and curing the locking end steel pipe 221 to complete the manufacturing of the locking end 220.

[0044] Furthermore, in step S4, steel sheet piles 100 are driven into the water, followed by the installation of double-headed screws 250, ribbed channel steel 230 and locking end (220), and a reliable base is formed after the first locking by nuts (240).

[0045] Furthermore, in step S4, after the horizontal member 210 is installed after forming a reliable base, it is connected to the locking end 220 through a flange. Finally, the nut (240) on the outside of the sheet pile 100 is locked again to form a combined structure.

[0046] The technical effects achieved in this embodiment are: to propose a new type of combined structure integrating compression bracing and anchoring, overcoming the shortcomings of weak compressive strength of traditional cofferdam steel tie rod structures, and to propose a lateral member integrating tension and compression with grouting inside a small-diameter steel pipe. Furthermore, the new combined structure serves as both the water-retaining structure on both sides during dry land filling and the cofferdam structure after the dam body is filled, achieving a combination of permanent and temporary structures, rapid construction, recycling, and low-carbon environmental protection.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Any equivalent substitutions, parameter adjustments, or reasonable changes to the functional implementation methods made by those skilled in the art under the guidance of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A structure for a prefabricated soil-core steel sheet pile cofferdam on soft soil foundation, characterized in that, include: Sheet piles (100), tension-compression integrated transverse members (200), drainage boards (300), geogrids (400), and spoil heap cores (500). The sheet piles (100) are arranged in parallel and fixedly connected by a tension-compression integrated transverse member (200). A geomembrane (110) is laid on the inner side of the sheet piles (100) on the water-facing side, and a geotextile (120) is laid on the inner side of the back water-facing side. The drainage board (300) is located within the base mud surface of the area enclosed by the sheet piles (100), and the geogrid (400) is laid on top of the drainage board (300); The tension-compression integrated transverse member (200) includes: a transverse member (210), a locking end (220), a ribbed channel steel (230), a nut (240), and a double-ended screw (250). The transverse member (210) is located inside the area enclosed by the sheet pile (100) and is connected to the flange of the locking end (220); The ribbed channel steel (230) is symmetrically arranged on both sides of the sheet pile (100); The double-headed screw (250) passes through the ribbed channel steel (230) on the outside of the sheet pile (100), the sheet pile (100), and the ribbed channel steel (230) on the inside, and is threaded to the locking end (220); The nut (240) is threaded onto the outside of the double-ended screw (250), adjacent to the channel steel (230) on the outside of the ribbed sheet pile (100).

2. The structure of a prefabricated soil-core steel sheet pile cofferdam for soft soil foundation according to claim 1, characterized in that, The transverse member (210) includes: a small-diameter steel pipe (211), a first blind flange (212), a second blind flange (213), a grouting body (214), and a grouting hole (215). The first blind flange (212) and the second blind flange (213) are symmetrically welded on both sides of the small-diameter steel pipe (211). The first blind flange (212) is equipped with a grouting hole (215), while the second blind flange (213) has no through hole structure. The grout (214) is filled inside the small-diameter steel pipe (211).

3. The structure of a prefabricated soil-core steel sheet pile cofferdam for soft soil foundation according to claim 1 or 2, characterized in that, The locking end (220) includes: a locking end steel pipe (221), a third blind flange (222), an internal threaded sleeve (223), a head plate (224), a grouting body (214), and a grouting hole (215). The internal threaded sleeve (223) is embedded inside the locking end steel pipe (221) and is threadedly connected to the double-ended screw (250); The end plate (224) is provided with grouting holes (215) that cover the end face of the locking end steel pipe (221); The grout (214) is filled inside the locking end steel pipe (221); The third blind flange (222) is flanged and connected to the second blind flange (213).

4. A construction method for a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation according to any one of claims 1-3, characterized in that, Includes the following steps: Step S1: Select the cofferdam structure type, determine the type and length of the sheet piles (100), and determine the cross-sectional dimensions of the transverse members (210); Step S2: Build a prefabrication yard on the shore, splice and process steel sheet piles (100), and make transverse members (210) and locking ends (220). Step S3: Fabricate the ribbed channel steel (230), nut (240), and double-ended screw (250); Step S4: Construct steel sheet piles (100) and tension-compression integrated transverse members (200) to form a combined structure; Step S5: Drain the water within the weir body to create dry conditions. At the same time, lay geogrid (400) and drainage sand cushion on the natural mud surface, and use a handheld inserter to install drainage boards (300). Step S6: Lay a geogrid (400) as a cushion layer at the bottom of the dam body, lay a geomembrane (110) on the inner side of the steel sheet piles (100) on the water-facing side, lay a geotextile (120) on the inner side of the backwater side, and then backfill the spoil dam core (500) in layers with compaction, and seal the top with clay. Step S7: Repeat steps S4, S5, and S6 until the entire section of the project is completed.

5. The construction method of a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation according to claim 4, characterized in that, The specific method for manufacturing the transverse member (210) in step S2 is as follows: by welding the first blind flange (212) and the second blind flange (213) at both ends of the small diameter steel pipe (211), grout is injected into the small diameter steel pipe (211) and cured to complete the manufacturing of the transverse member (210).

6. A construction method for a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation according to claim 4 or 5, characterized in that, The specific method for manufacturing the locking end (220) in step S2 is as follows: by processing and manufacturing the locking end steel pipe (221), welding the third blind flange (222) and end plate (224) to its end, processing and manufacturing the internal thread sleeve (223), and then grouting and curing the locking end steel pipe (221) to complete the manufacturing of the locking end (220).

7. The construction method of a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation according to claim 4, characterized in that, In step S4, steel sheet piles (100) are driven into the water, followed by the installation of double-ended screws (250), ribbed channel steel (230), and locking end (220). After initial locking with nuts (240), a reliable base is formed.

8. The construction method of a prefabricated soil-core steel sheet pile cofferdam structure for soft soil foundation according to claim 7, characterized in that, In step S4, after a reliable base is formed, a transverse member (210) is installed and connected to the locking end (220) via a flange. Finally, the nut (240) on the outside of the sheet pile (100) is locked again to form a combined structure.

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