A double-wall steel cofferdam system assembled with steel sheet piles and an assembly method

Abstract

The present invention is a double-walled steel cofferdam system and an assembly method assembled with steel sheet piles. The double-walled steel cofferdam system includes a double-walled steel cofferdam, and the cavity of the double-walled steel cofferdam is filled with a reinforcement body; the double-walled steel cofferdam is assembled and combined by a plurality of Z1-type steel sheet piles, Z2-type steel sheet piles, L1-type steel sheet piles and L2-type steel sheet piles through a locking structure, the Z1-type steel sheet piles are assembled at the four side walls of the double-walled steel cofferdam, and the Z2-type steel sheet piles, L1-type steel sheet piles and L2-type steel sheet piles are assembled at the four corners of the double-walled steel cofferdam. The present invention divides the double-walled steel cofferdam plane into discrete steel sheet pile units, and forms the overall structure of the double-walled steel cofferdam system by inserting and assembling them one by one, thereby reducing the dependence of the construction of the double-walled steel cofferdam system on large-scale lifting equipment, and can be constructed on multiple working surfaces, reducing the construction difficulty; through the locking bite between the steel sheet piles and the reinforcement of the reinforcement bodies between the piles, the water-stopping performance and lateral stiffness of the double-walled steel cofferdam system are improved.

Description

Technical Field

[0001] The invention relates to the technical field of temporary water retaining structures, and in particular to a double-wall steel cofferdam system assembled with steel sheet piles and an assembling method. Background Art

[0002] When dry construction is carried out in a high groundwater level environment or near-shore shallows environment, steel cofferdams, as a temporary water retaining structure, play an extremely important role. Steel cofferdams can be single-walled steel cofferdams or double-walled steel cofferdams. Compared with single-walled steel cofferdams, double-walled steel cofferdams have the characteristics of high rigidity, good stability, and good water-stopping effect, and have been widely used in bridge foundations and other projects.

[0003] At present, the construction of double-walled steel cofferdam is mainly divided into two construction methods. One is the overall hoisting method. After all the components of the double-walled steel cofferdam are processed and assembled into an overall structure in the factory, they are transported by land or floating to the vicinity of the proposed location, and are located at the foundation trench or designated shoal by large-tonnage lifting equipment. This construction method has a long construction period, high requirements for lifting equipment, and poor economy. The other is to layer the double-walled steel cofferdam in height and block it in plane. After all the components are processed in the factory, they are transported to the construction site, set up an assembly platform, and assemble them piece by piece and layer by layer. After the assembly is completed, welding is performed at the horizontal and vertical joints between the cofferdam blocks. This construction method requires the cooperation of multiple lifting equipment, the on-site welding workload is large, and the installation efficiency is low. Therefore, there is an urgent need for a double-walled steel cofferdam structure with low lifting equipment requirements and high construction efficiency, which can also ensure the water-stopping effect and construction quality of the steel cofferdam. Summary of the invention

[0004] The present invention aims to solve the deficiencies of the prior art and provide a double-wall steel cofferdam system and assembly method assembled with steel sheet piles, which reduces the requirements for lifting equipment, improves construction efficiency, saves costs and construction period, ensures the water-stopping effect and construction quality of the steel cofferdam, and is suitable for high groundwater level environments or nearshore shallow environments in non-rock and pebble formations.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A double-wall steel cofferdam system assembled with steel sheet piles, comprising a double-wall steel cofferdam, the double-wall steel cofferdam comprising an inner wall and an outer wall, the space formed between the inner wall and the outer wall is divided into a plurality of partitioned cavities and the partitioned cavities are filled with reinforcement bodies;

[0007] The double-walled steel cofferdam is composed of a number of Z1 steel sheet piles, Z2 steel sheet piles, L1 steel sheet piles and L2 steel sheet piles assembled through a lock structure. The Z1 steel sheet piles are assembled at the four side walls of the double-walled steel cofferdam, and the Z2 steel sheet piles, L1 steel sheet piles and L2 steel sheet piles are assembled at the four corners of the double-walled steel cofferdam.

[0008] The Z1 type steel sheet pile includes a first web, first flange plates are arranged at both ends of the first web, the two first flange plates and the first web form a Z-shaped structure, a first main locking port is arranged at the end of the first flange plate, each first flange plate is collinearly provided with a first extension plate, the corresponding collinear first flange plates and first extension plates are arranged on both sides of the first web, a first auxiliary locking port is arranged at the end of the first extension plate, the two first main locking ports are symmetrical about the center of the first web, and the two first auxiliary locking ports are symmetrical about the center of the first web.

[0009] The included angles of the first flange plate, the first extension plate and the first web plate are 45-135 degrees.

[0010] The length of the first extension plate is not less than 100 mm.

[0011] The Z2 steel sheet pile includes a second web, second flange plates are arranged at both ends of the second web, the two second flange plates and the second web form a Z-shaped structure, a second main locking port is arranged at the end of the second flange plate, each second flange plate is collinearly provided with a second extension plate, the corresponding collinear second flange plates and second extension plates are arranged on both sides of the second web, a second auxiliary locking port is arranged at the end of the second extension plate, an auxiliary extension plate is collinearly provided at one end of the second web, a supplementary locking port is arranged at the end of the auxiliary extension plate, the two second main locking ports are symmetrical about the center of the second web, and the two second auxiliary locking ports are symmetrical about the center of the second web.

[0012] The included angles of the second flange plate, the second extension plate and the second web plate are 45-135°.

[0013] The length of the second extension plate is not less than 100 mm.

[0014] The L1 type steel sheet pile includes a first long flange plate and a first short flange plate. The angle between the first long flange plate and the first short flange plate is 45-135°. A first connecting lock is provided at the end of the first long flange plate, and a first docking lock is provided at the end of the first short flange plate. The length of the first short flange plate is not less than 300mm.

[0015] The L2 steel sheet pile includes a second long flange plate and a second short flange plate, the angle between the second long flange plate and the second short flange plate is 45-135°, a second connecting lock is provided at the end of the second long flange plate, a second butt lock is provided at the end of the second short flange plate, an extended connecting plate is provided in the same line as the second short flange plate, the second short flange plate and the extended connecting plate are located on both sides of the second long flange plate, a connecting plate lock is provided at the end of the extended connecting plate, the length of the second short flange plate is not less than 300 mm, and the length of the extended connecting plate is not less than 100 mm.

[0016] The above-mentioned method for assembling a double-wall steel cofferdam system assembled with steel sheet piles comprises the following specific steps:

[0017] S1. Guide pile construction:

[0018] Clear the debris on the construction site and draw lines and stake out according to the design drawings. Arrange several guide piles along the circumference of the double-walled steel cofferdam and drive them to a certain depth using a hammering machine. The guide piles are made of H-shaped steel or steel pipes, and the verticality meets the requirements when driven. The driving depth of the guide piles meets the lateral stability requirements of the double-walled steel cofferdam pre-assembly and the steel sheet piles adjacent to the guide piles when hammered and driven.

[0019] S2. Pre-assembly and calibration of double-wall steel cofferdam:

[0020] Use guide piles to assemble steel sheet piles in sequence, and use hammering machinery to hammer into the soil layer to a certain depth. The depth of steel sheet pile penetration into the soil layer should meet the requirements of its own stability and the lateral stability of the subsequent pre-assembled steel sheet piles, which is 1 / 5 of the design depth of the double-walled steel cofferdam. Use water-stopping materials to caulk the steel sheet pile lock structure. Water-stopping materials include tape, sealant, and waterproof coating. During the pre-assembly process of the double-walled steel cofferdam, check the assembly deviation in time and make corrections;

[0021] The pre-assembly sequence of the double-wall steel cofferdam is as follows: first assemble the Z2 steel sheet piles, then assemble the L2 steel sheet piles, then assemble the L1 steel sheet piles, and finally assemble the Z1 steel sheet piles;

[0022] S3, Steel Sheet Pile Hammering:

[0023] After the pre-assembly of the double-wall steel cofferdam is completed, the steel sheet piles are hammered in sequence using a vibrating hammer. The hammering is repeated multiple times, and the penetration of each hammering is set to 1 / 5 of the design depth of the double-wall steel cofferdam. When the steel sheet piles are hammered into place, the hammering is stopped.

[0024] S4. Steel sheet pile reinforcement:

[0025] After the double-wall steel cofferdam is hammered, the sleeve valve pipe is used to grout the separated cavity formed between the inner wall and the outer wall of the double-wall steel cofferdam to form a reinforcement body. The grouting materials include water glass and cement slurry.

[0026] S5. Excavation of foundation pit:

[0027] After the double-wall steel cofferdam is reinforced, a long-arm excavator is used to excavate the foundation pit and complete the dry operation construction;

[0028] When the foundation pit is excavated, the groundwater in the foundation pit is lowered by using pumping equipment; when the foundation pit is excavated, the foundation pit support system is set up in the double-walled steel cofferdam; after the foundation pit is completed, the bottom sealing concrete is poured in the double-walled steel cofferdam;

[0029] S6. Sheet pile removal:

[0030] After the dry construction is completed, the steel sheet piles of the double-walled steel cofferdam are removed and recovered using vibrating lifting equipment.

[0031] The beneficial effects of the present invention are as follows: the present invention divides the double-wall steel cofferdam into discrete steel sheet pile units on the plane, and forms the overall structure of the double-wall steel cofferdam system by inserting and assembling them one by one, thereby reducing the dependence of the construction of the double-wall steel cofferdam system on large-scale lifting equipment, and can be constructed on multiple working surfaces, reducing the construction difficulty; through the locking and biting between the steel sheet piles and the reinforcement of the reinforcement bodies between the piles, the water-stopping performance and lateral stiffness of the double-wall steel cofferdam system are improved, and construction in a high groundwater level environment or near-shore shallow environment in non-rock and pebble formations can improve construction efficiency, save costs and construction period, and can ensure the water-stopping effect and construction quality of the steel cofferdam, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A top view of the present invention;

[0033] Figure 2 It is a three-dimensional diagram of the double-wall steel cofferdam in the present invention;

[0034] Figure 3 It is a schematic diagram of the assembly of the corner of the double-wall steel cofferdam in the present invention;

[0035] Figure 4 It is a schematic diagram of a Z1 type steel sheet pile in the present invention;

[0036] Figure 5 Schematic diagram of Z2 type steel sheet pile in the present invention;

[0037] Figure 6 Schematic diagram of L1 type steel sheet pile in the present invention;

[0038] Figure 7 Schematic diagram of L2 type steel sheet pile in the present invention;

[0039] Figure 8 This is a distribution diagram of guide piles when assembling the double-wall steel cofferdam of the present invention;

[0040] In the figure: 1- double-walled steel cofferdam; 2- reinforcement body; 3- guide pile;

[0041] 11-Z1 steel sheet pile; 12-Z2 steel sheet pile; 13-L1 steel sheet pile; 14-L2 steel sheet pile;

[0042] 111-first web plate; 112-first flange plate; 113-first main lock; 114-first extension plate; 115-first auxiliary lock;

[0043] 121 - second web plate; 122 - second flange plate; 123 - second main lock; 124 - second extension plate; 125 - second auxiliary lock; 126 - auxiliary extension plate; 127 - supplementary lock;

[0044] 131-first long flange plate; 132-first short flange plate; 133-first connecting lock; 134-first docking lock;

[0045] 141-second long flange plate; 142-second short flange plate; 143-second connection lock; 144-second docking lock; 145-extended connection plate; 146-connection plate lock;

[0046] The following is a detailed description of the embodiments of the present invention with reference to the accompanying drawings. DETAILED DESCRIPTION

[0047] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The embodiments are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the accompanying drawings in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0048] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0050] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0051] A double-walled steel cofferdam system assembled with steel sheet piles, such as Figure 1 As shown, it includes a double-walled steel cofferdam 1, which includes an inner wall and an outer wall. The space formed between the inner wall and the outer wall is divided into a number of partitioned cavities and the partitioned cavities are filled with reinforcement bodies 2; the double-walled steel cofferdam 1 and the reinforcement bodies 2 together form the lateral force resistance system of the side walls of the double-walled steel cofferdam system.

[0052] The reinforcement body 2 can be reinforced by sleeve valve pipe grouting, but not limited to. The grouting materials include but are not limited to water glass, cement slurry, etc. The purpose is to increase the stiffness between the steel sheet piles, restrain the lateral deformation of the steel sheet pile web and improve the water-stopping performance of the double-wall steel cofferdam 1.

[0053] The double-walled steel cofferdam 1 is composed of various types of steel sheet piles, such as Figure 2 , Figure 3 As shown, specifically:

[0054] The double-walled steel cofferdam 1 is composed of a plurality of Z1-type steel sheet piles 11, Z2-type steel sheet piles 12, L1-type steel sheet piles 13 and L2-type steel sheet piles 14 assembled and combined through a locking structure. The Z1-type steel sheet piles 11 are assembled at the four side walls of the double-walled steel cofferdam 1, and the Z2-type steel sheet piles 12, L1-type steel sheet piles 13 and L2-type steel sheet piles 14 are assembled at the four corners of the double-walled steel cofferdam 1.

[0055] like Figure 4 As shown, the Z1 type steel sheet pile 11 includes a first web 111, and first flange plates 112 are arranged at both ends of the first web 111. The two first flange plates 112 and the first web 111 form a Z-shaped structure, and a first main locking opening 113 is arranged at the end of the first flange plate 112. Each first flange plate 112 is collinearly provided with a first extension plate 114, and the corresponding collinear first flange plates 112 and first extension plates 114 are arranged on both sides of the first web 111. A first auxiliary locking opening 115 is arranged at the end of the first extension plate 114, and the two first main locking openings 113 are symmetrical about the center of the first web 111, and the two first auxiliary locking openings 115 are symmetrical about the center of the first web 111.

[0056] The included angles of the first flange plate 112 , the first extension plate 114 and the first web plate 111 are 45-135°.

[0057] The length of the first extension plate 114 is not less than 100 mm.

[0058] like Figure 5 As shown, the Z2 type steel sheet pile 12 includes a second web 121, and second flange plates 122 are arranged at both ends of the second web 121. The two second flange plates 122 and the second web 121 form a Z-shaped structure, and a second main locking port 123 is arranged at the end of the second flange plate 122. Each second flange plate 122 is colinearly provided with a second extension plate 124, and the corresponding colinear second flange plates 122 and second extension plates 124 are arranged on both sides of the second web 121. A second auxiliary locking port 125 is arranged at the end of the second extension plate 124, and an auxiliary extension plate 126 is colinearly provided at one end of the second web 121. A supplementary locking port 127 is arranged at the end of the auxiliary extension plate 126. The two second main locking ports 123 are symmetrical about the center of the second web 121, and the two second auxiliary locking ports 125 are symmetrical about the center of the second web 121.

[0059] The included angles between the second flange plate 122 , the second extension plate 124 and the second web plate 121 are 45-135°.

[0060] The length of the second extension plate 124 is not less than 100 mm.

[0061] like Figure 6 As shown, the L1 type steel sheet pile 13 includes a first long flange plate 131 and a first short flange plate 132, the angle between the first long flange plate 131 and the first short flange plate 132 is 45-135°, a first connecting lock 133 is provided at the end of the first long flange plate 131, and a first docking lock 134 is provided at the end of the first short flange plate 132; the length of the first short flange plate 132 is not less than 300 mm.

[0062] like Figure 7 As shown, the L2 type steel sheet pile 14 includes a second long flange plate 141 and a second short flange plate 142, the angle between the second long flange plate 141 and the second short flange plate 142 is 45-135°, a second connecting lock 143 is provided at the end of the second long flange plate 141, a second docking lock 144 is provided at the end of the second short flange plate 142, and an extended connecting plate 145 is provided in a colinear manner on the second short flange plate 142. The second short flange plate 142 and the extended connecting plate 145 are located on both sides of the second long flange plate 141, and a connecting plate lock 146 is provided at the end of the extended connecting plate 145. The length of the second short flange plate 142 is not less than 300 mm, and the length of the extended connecting plate 145 is not less than 100 mm.

[0063] The above-mentioned method for assembling a double-wall steel cofferdam system assembled with steel sheet piles comprises the following specific steps:

[0064] S1. Construction of guide pile 3:

[0065] Clear the debris on the construction site and draw lines and stake out according to the design drawings. Arrange several guide piles 3 along the circumference of the double-walled steel cofferdam 1, such as Figure 8 As shown, a hammer is used to mechanically insert the hammer to a certain depth;

[0066] The guide pile 3 can be selected from but not limited to H-shaped steel, steel pipe and other pile types, and its verticality should meet the requirements when inserted;

[0067] The driving depth of the guide pile 3 meets the lateral stability requirements during the pre-assembly of the double-walled steel cofferdam 1 and the hammering of the steel sheet piles adjacent to the guide pile 3;

[0068] S2. Pre-assembly and calibration of double-wall steel cofferdam 1:

[0069] The steel sheet piles are assembled in sequence using the guide piles 3, and are hammered into the soil layer to a certain depth using a hammering machine. The depth of the steel sheet piles into the soil layer should meet the requirements of their own stability and the lateral stability of the subsequent pre-assembled steel sheet piles, which can be set to but not limited to 1 / 5 of the design depth of the double-walled steel cofferdam 1. The steel sheet pile lock structure is caulked with water-stopping materials, which include but are not limited to tapes, sealants, waterproof coatings, etc. During the pre-assembly process of the double-walled steel cofferdam 1, the assembly deviation is checked in time and corrected;

[0070] The pre-assembly sequence of the double-walled steel cofferdam 1 is not fixed, and the following sequence may be adopted: first assemble the Z2 type steel sheet piles 12, then assemble the L2 type steel sheet piles 14, then assemble the L1 type steel sheet piles 13, and finally assemble the Z1 type steel sheet piles 11;

[0071] S3, Steel Sheet Pile Hammering:

[0072] After the pre-assembly of the double-walled steel cofferdam 1 is completed, the steel sheet piles are hammered in sequence using a vibrating hammer device, and the hammering is performed in multiple rounds and multiple passes. The penetration of each hammering can be set to, but not limited to, 1 / 5 of the design depth of the double-walled steel cofferdam 1. When the steel sheet piles are hammered into place, the hammering is stopped;

[0073] S4. Steel sheet pile reinforcement:

[0074] After the double-walled steel cofferdam 1 is hammered, a sleeve valve pipe is used to grout the separated cavity formed between the inner wall and the outer wall of the double-walled steel cofferdam 1 to form a reinforcement body 2, and the grouting material includes but is not limited to water glass, cement slurry, etc.;

[0075] S5. Excavation of foundation pit:

[0076] After the double-wall steel cofferdam 1 is reinforced, a long-arm excavator is used to excavate the foundation pit and complete the dry operation construction;

[0077] When the foundation pit is excavated, the groundwater in the foundation pit is lowered by using pumping equipment; when the foundation pit is excavated, a foundation pit support system is set in the double-walled steel cofferdam 1; after the foundation pit is completed, the bottom sealing concrete is poured in the double-walled steel cofferdam 1;

[0078] S6. Sheet pile removal:

[0079] After the dry construction is completed, the steel sheet piles of the double-walled steel cofferdam 1 are removed and recovered using a vibrating lifting device.

[0080] The present invention divides the double-walled steel cofferdam 1 into discrete plane steel sheet pile units, and forms the overall structure of the double-walled steel cofferdam system by inserting and assembling them one by one, thereby reducing the dependence of the construction of the double-walled steel cofferdam system on large-scale lifting equipment, and can be constructed on multiple working surfaces, reducing the construction difficulty; through the locking and biting between the steel sheet piles and the reinforcement of the reinforcement bodies 2 between the piles, the water-stopping performance and lateral stiffness of the double-walled steel cofferdam system are improved, and construction in a high groundwater level environment or near-shore shallow environment in non-rock and pebble formations can improve construction efficiency, save costs and construction period, and can ensure the water-stopping effect and construction quality of the steel cofferdam, and has good application prospects.

[0081] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A double-walled steel cofferdam system assembled with steel sheet piles, characterized in that: The double-walled steel cofferdam (1) comprises an inner cofferdam wall and an outer cofferdam wall, wherein the space formed between the inner cofferdam wall and the outer cofferdam wall is divided into a plurality of partitioned cavities, and the partitioned cavities are filled with reinforcement bodies (2); The double-walled steel cofferdam (1) is composed of a plurality of Z1-type steel sheet piles (11), Z2-type steel sheet piles (12), L1-type steel sheet piles (13) and L2-type steel sheet piles (14) assembled and combined by means of a locking structure, wherein the Z1-type steel sheet piles (11) are assembled at the four side walls of the double-walled steel cofferdam (1), and the Z2-type steel sheet piles (12), L1-type steel sheet piles (13) and L2-type steel sheet piles (14) are assembled at the four corners of the double-walled steel cofferdam (1); The Z1-type steel sheet pile (11) comprises a first web (111), first flange plates (112) are arranged at both ends of the first web (111), the two first flange plates (112) and the first web (111) form a Z-shaped structure, the ends of the first flange plates (112) are provided with first main locking openings (113), each first flange plate (112) is collinearly provided with a first extension plate (114), and the corresponding collinear first flange plates (112) and the first extension plates (114) are arranged in the first On both sides of a web (111), first auxiliary locking openings (115) are provided at the ends of a first extension plate (114); the two first main locking openings (113) are symmetrical about the center of the first web (111); the two first auxiliary locking openings (115) are symmetrical about the center of the first web (111); the angle between the first flange plate (112), the first extension plate (114) and the first web (111) is 45-135°; and the length of the first extension plate (114) is not less than 100 mm; The Z2-type steel sheet pile (12) comprises a second web (121), second flange plates (122) are arranged at both ends of the second web (121), the two second flange plates (122) and the second web (121) form a Z-shaped structure, a second main locking opening (123) is arranged at the end of the second flange plate (122), each second flange plate (122) is colinearly provided with a second extension plate (124), corresponding colinear second flange plates (122) and second extension plates (124) are arranged on both sides of the second web (121), a second auxiliary locking opening (125) is arranged at the end of the second extension plate (124), an auxiliary extension plate (126) is colinearly arranged at one end of the second web (121), a supplementary locking opening (127) is arranged at the end of the auxiliary extension plate (126), the two second main locking openings (123) are symmetrical about the center of the second web (121), and the two second auxiliary locking openings (125) are symmetrical about the center of the second web (121).

2. A double-walled steel cofferdam system assembled with steel sheet piles according to claim 1, characterized in that: The included angle between the second flange plate (122), the second extension plate (124) and the second web plate (121) is 45-135°.

3. A double-walled steel cofferdam system assembled with steel sheet piles according to claim 2, characterized in that: The length of the second extension plate (124) is not less than 100 mm.

4. A double-walled steel cofferdam system assembled with steel sheet piles according to claim 3, characterized in that: The L1-type steel sheet pile (13) comprises a first long flange plate (131) and a first short flange plate (132); the angle between the first long flange plate (131) and the first short flange plate (132) is 45-135 degrees; a first connecting lock (133) is provided at the end of the first long flange plate (131); and a first docking lock (134) is provided at the end of the first short flange plate (132); and the length of the first short flange plate (132) is not less than 300 mm.

5. A double-walled steel cofferdam system assembled with steel sheet piles according to claim 4, characterized in that: The L2-type steel sheet pile (14) comprises a second long flange plate (141) and a second short flange plate (142), wherein the angle between the second long flange plate (141) and the second short flange plate (142) is 45-135 degrees, a second connection lock opening (143) is provided at the end of the second long flange plate (141), a second docking lock opening (144) is provided at the end of the second short flange plate (142), an extended connection plate (145) is provided colinearly with the second short flange plate (142), the second short flange plate (142) and the extended connection plate (145) are located on both sides of the second long flange plate (141), a connection plate lock opening (146) is provided at the end of the extended connection plate (145), the length of the second short flange plate (142) is not less than 300 mm, and the length of the extended connection plate (145) is not less than 100 mm.

6. A method for assembling a double-walled steel cofferdam system assembled with steel sheet piles as claimed in claim 5, characterized in that: The specific steps are: S1. Guide pile (3) construction: The debris on the construction site is cleared and the layout is drawn according to the design drawings. A number of guide piles (3) are arranged along the circumference of the double-walled steel cofferdam (1) and driven to a certain depth by a hammering machine. The guide piles (3) are made of H-shaped steel or steel pipes, and the verticality meets the requirements when driven. The driving depth of the guide piles (3) meets the lateral stability requirements of the pre-assembly of the double-walled steel cofferdam (1) and the steel sheet piles adjacent to the guide piles (3) when driven by hammering. S2. Double-wall steel cofferdam (1) Pre-assembly and calibration: The steel sheet piles are assembled in sequence using the guide piles (3) and driven into the soil layer to a certain depth using a hammering machine. The depth of the steel sheet piles driven into the soil layer should meet the requirements of their own stability and the lateral stability of the subsequently pre-assembled steel sheet piles, and should be 1 / 5 of the design depth of the double-walled steel cofferdam (1). The steel sheet pile locking structure is caulked using water-stopping materials, which include adhesive tape, sealant, and waterproof coating. During the pre-assembly process of the double-walled steel cofferdam (1), the assembly deviation is promptly checked and corrected. The pre-assembly sequence of the double-walled steel cofferdam (1) is as follows: first assemble the Z2 type steel sheet piles (12), then assemble the L2 type steel sheet piles (14), then assemble the L1 type steel sheet piles (13), and finally assemble the Z1 type steel sheet piles (11); S3, Steel Sheet Pile Hammering: After the pre-assembly of the double-walled steel cofferdam (1) is completed, the steel sheet piles are hammered in sequence using a vibrating hammer device, and the hammering is performed in multiple rounds and multiple passes, with the hammering depth of each pass set to 1 / 5 of the design depth of the double-walled steel cofferdam (1). When the steel sheet piles are hammered into place, the hammering is stopped; S4. Steel sheet pile reinforcement: After the double-walled steel cofferdam (1) is hammered, a sleeve valve pipe is used to inject grout into the separated cavity formed between the inner wall and the outer wall of the double-walled steel cofferdam (1) to form a reinforcement body (2), and the injection material includes water glass and cement slurry; S5. Excavation of foundation pit: After the double-wall steel cofferdam (1) is reinforced, a long-arm excavator is used to excavate the foundation pit to complete the dry operation; When the foundation pit is excavated, the groundwater in the foundation pit is lowered by using pumping equipment; when the foundation pit is excavated, a foundation pit support system is set in the double-walled steel cofferdam (1); after the foundation pit is completed, the bottom sealing concrete is poured in the double-walled steel cofferdam (1); S6. Sheet pile removal: After the dry construction is completed, the steel sheet piles of the double-walled steel cofferdam (1) are removed and recovered using a vibrating lifting device.

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