Construction method of steel sheet pile cofferdam in tidal zone with large water level difference

Abstract

The present invention relates to a method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference, comprising the following steps: installing longitudinal and transverse guide frames; constructing a casing clamp system; installing an inner upper steel support; constructing Larsen steel sheet piles; setting up a central construction platform; installing an inner lower steel support; and excavating and clearing the foundation within the cofferdam and pouring concrete. The present invention has the following beneficial effects: the stability of the longitudinal guide frame is effectively improved by using rigid pull rods and flexible pull ropes, thereby improving the stability of the entire guide frame system; the I-shaped pre-set holes enable rapid installation of the longitudinal and transverse guide frames; high-precision construction of Larsen steel sheet piles is achieved by pre-setting tracks and installing fine-tuning jacking equipment; the central construction platform provides a safe and convenient working space for excavating and clearing the foundation within the cofferdam and for concrete bottom sealing; and the provision of a water level monitor and axial force gauge enables dynamic monitoring of the supports and water level within the cofferdam.

Description

Technical Field

[0001] The present invention belongs to the field of bridge engineering, and in particular relates to a method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference. The method is applicable to bridge pedestal cofferdam projects, and in particular to bridge pedestal construction in a tidal zone with a large water level difference. Background Art

[0002] Larsen steel sheet pile cofferdam construction technology is widely used in the construction of cross-sea bridges. In recent years, with the rapid development of my country's transportation network, the construction of cross-sea bridges has increased significantly, leading to a surge in deepwater foundation construction. A key factor influencing the success and safety of deepwater foundation projects is the design and construction of temporary protective structures to isolate the seawater. Larsen steel sheet piles, due to their unique advantages, are the preferred choice for cofferdam construction. However, construction of Larsen steel sheet pile cofferdams in tidal coastal areas is more challenging than in general sea areas or inland rivers, as the impact of periodic tides on construction must be considered.

[0003] Cofferdam construction in coastal tidal areas is subject to cyclical fluctuations in the position of tidal surges, with the highest and lowest water levels fluctuating constantly with the ebb and flow of the tide. This places high demands on the cofferdam's overall structural stability, anti-seepage, anti-uplift, and anti-overturning capabilities. Conventional steel sheet pile cofferdam construction processes are unable to meet the construction requirements of tidal zones with large water level differences. There is considerable room for improvement in the Larsen steel sheet pile construction speed, overall structural system, construction safety, and tidal scour monitoring.

[0004] In view of this, there is an urgent need to invent a steel sheet pile cofferdam construction method in a large water level difference tidal zone with fast construction speed, high structural stability, controllable construction safety, and outstanding economic and technical benefits. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference.

[0006] This method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference comprises the following steps:

[0007] S1. Installation of longitudinal and transverse guide frames: Fix the longitudinal guide frame to the platform steel columns and connect it to the trestle platform through rigid tie rods and flexible tie ropes. Insert the transverse guide frame into the I-shaped reserved hole of the longitudinal guide frame.

[0008] S2. Construction of casing hoop system: Install casing hoop on the outer wall of pile foundation steel casing;

[0009] S3. Installation of inner upper steel support: Install the inner upper steel support, and reserve space for Larsen steel sheet pile operation between the inner upper steel support and the longitudinal and transverse guide frames;

[0010] S4, Larsen steel sheet pile construction: deploy pile drivers on the trestle platform, start driving Larsen steel sheet piles from the center of the upstream cofferdam, and finally close them at the center of the downstream cofferdam;

[0011] S5. Central area construction platform erection: Install the central area construction platform and the lap plate on the wing plate, and install the lower hanging construction platform. Set a water level monitor on the outside of the Larsen steel sheet pile;

[0012] S6. Installation of inner lower steel support: Install the inner lower steel support directly below the inner upper steel support, and set a monitoring axial force meter between the inner lower steel support and the Larsen steel sheet pile;

[0013] S7. Excavation and foundation clearing and concrete pouring within the cofferdam: A slurry pump is placed on the central construction platform, and a high-pressure water gun is used in conjunction with the slurry pump to flush the slurry and clear the foundation; when the tide recedes, concrete is poured on the dry beach to seal the bottom.

[0014] Preferably, in step S1, the symmetrically arranged longitudinal guide frames on both sides are preliminarily fixed to the platform steel columns of the trestle platform by using frame beam clamps. The main body of the longitudinal guide frame is an I-beam structure. Frame beam clamps are set at the ends of the longitudinal guide frame. Lifting rings are set at the ends and the middle of the top surface of the longitudinal guide frame. The lifting rings on the longitudinal guide frame are connected to the platform steel longitudinal beams of the trestle platform by rigid pull rods and flexible pull ropes. Tracks are set between the lifting rings and between the lifting rings and the frame beam clamps. At the same time, I-shaped reserved holes are also set at both ends of the web of the longitudinal guide frame; the transverse guide frame is welded to the web of the longitudinal guide frame through the I-shaped reserved holes, and a full-length track is also set on the top surface of the transverse guide frame.

[0015] Preferably, in step S2, casing hoops are installed on the outer wall of the pile foundation steel casing using anchor bolts, all casing hoops are installed at the same elevation, and the outer wall of the casing hoops is provided with wing plates parallel to the longitudinal guide frame and the transverse guide frame respectively.

[0016] Preferably, in step S3, the inner upper steel support is installed on the casing clamp wing plate by welding. The inner upper steel support is a double-layer H-shaped steel structure, wherein a full-length track is provided on the top surface of the upper H-shaped steel web, and a fine-tuning jacking device is provided in the track, and inner reinforcing angle braces are welded between adjacent and mutually perpendicular inner upper steel supports.

[0017] Preferably, in step S4, the inner upper steel support is a double-layer H-shaped steel structure, and the top surface of the upper H-shaped steel web of the inner upper steel support is also provided with a track; and a fine-tuning jacking device is provided on the track;

[0018] When driving Larsen steel sheet piles, the longitudinal and transverse guide frames and the fine-tuning jacking equipment installed on the inner upper steel support surface are used to perform simultaneous measurement and correction to ensure that the steel sheet piles are in the same straight line. When the resistance of local special terrain is too large, the prefabricated pile caps and the symmetrical high-pressure water guns on both sides of the steel sheet piles can be used to assist in pile sinking. After each steel sheet pile is driven, it is firmly welded to the channel steel. The high-pressure water gun is installed and fixed through the preset connector on the side of the Larsen steel sheet pile, and a water pipe is connected to the tail of the high-pressure water gun.

[0019] Preferably, in step S4, the Larsen steel sheet piles use auxiliary closure steel to ensure closing accuracy, and the auxiliary closure steel is arranged on both sides of the Larsen steel sheet piles. The auxiliary closure steels on both sides are fixed to each other by setting tension anchor cables between the anchor ends of the Larsen steel sheet piles.

[0020] Preferably, in step S5, the wing plates of the casing clamp are provided with reserved bolt holes, and the central area construction platform is installed through the reserved bolt holes of each wing plate, and the platform guardrail is installed, and a water level monitor is set on the outer side of the top of the Larsen steel sheet pile using a mounting bracket; the central area construction platform is set in the area enclosed by the pile foundation, and the end of the central area construction platform is connected to the end of the lap plate by an anchor bolt, and the end of the lap plate is connected to the inner upper steel support wing plate by an anchor bolt.

[0021] Preferably, in step S6, the time when the water level drops after the tide recedes is used to install the inner lower steel support 3m below the inner upper steel support, and the inner lower steel support is welded to the wing plate of the casing clamp.

[0022] The steel sheet pile cofferdam in the tidal zone with large water level difference is obtained by any of the above methods.

[0023] The beneficial effects of the present invention are:

[0024] 1) The present invention makes full use of the trestle platform structural system, effectively improves the stability of the longitudinal guide frame through rigid pull rods and flexible pull ropes, thereby improving the stability of the entire guide frame system. In addition, the quick installation of the longitudinal and transverse guide frames is achieved by cleverly setting I-shaped reserved holes.

[0025] 2) Based on the installed guide structure system, the present invention achieves high-precision construction of Larsen steel sheet piles by pre-setting tracks and installing fine-tuning jacking equipment. The adjustment time of the closing section is greatly reduced by providing auxiliary closure steel in the closing section. At the same time, the combination of prefabricated pile caps and high-pressure water guns solves the problem of excessive resistance in local special terrain and difficulty in pile sinking.

[0026] 3) The present invention provides a safe and convenient working space for dredging and clearing the foundation and concrete bottom sealing inside the cofferdam by setting up a central construction platform, and realizes dynamic monitoring of the support and water level inside the cofferdam by reasonably setting up water level monitors and axial force gauges to ensure safe and controllable construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a top view of the steel sheet pile cofferdam in the tidal zone with large water level difference in the present invention;

[0028] Figure 2 This is a schematic diagram of the connection between the guide frame and the construction platform in the present invention;

[0029] Figure 3 This is a working diagram of the fine-tuning jacking device of the present invention;

[0030] Figure 4 This is a schematic diagram of the installation of the auxiliary closure steel in the present invention;

[0031] Figure 5 This is a schematic diagram of symmetrical high-pressure water-jet-assisted pile sinking in the present invention;

[0032] Figure 6 This is a top view of the central construction platform in the present invention;

[0033] Figure 7 It is a cross-sectional view of the central area construction platform in the present invention.

[0034] In the figure: 1- trestle platform; 2- platform steel crossbeam; 3- platform steel column; 4- platform steel longitudinal beam; 5- pile foundation steel casing; 6- casing clamp; 7- pile foundation; 8- transverse guide frame; 9- inner upper steel support; 10- wing plate; 11- reserved bolt hole; 12- inner reinforced angle brace; 13- longitudinal guide frame; 14- Larsen steel sheet pile; 15- rigid tie rod; 16- anchor bolt; 17- track; 18- lifting ring; 19- I-shaped reserved hole; 20- flexible pull rope; 21- frame beam clamp Hoop; 22-column diagonal brace; 23-fine-tuning jacking equipment; 24-tension anchor cable; 25-anchor end; 26-auxiliary closure steel; 27-water pipe; 28-high-pressure water gun; 29-connector; 30-anchor nut; 31-mud pump; 32-lap plate; 33-central area construction platform; 34-water level monitor; 35-mounting bracket; 36-platform guardrail; 37-axial force gauge; 38-concrete bottom seal; 39-suspended construction platform; 40-inner lower steel support; 41-precast pile cap. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the following examples. The following examples are provided only to facilitate understanding of the present invention. It should be noted that, without departing from the principles of the present invention, it is possible for a person skilled in the art to make various modifications to the present invention, and such improvements and modifications fall within the scope of the claims of the present invention.

[0036] Example 1

[0037] As an embodiment, this embodiment provides a method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference, comprising the following steps:

[0038] S1. Installation of longitudinal and transverse guide frames: Use frame beam clamps 21 to preliminarily fix the symmetrically arranged longitudinal guide frames 13 on both sides to the platform steel columns 3 of the trestle platform 1, and use rigid pull rods 15 and flexible pull ropes 20 to connect the lifting rings 18 on the longitudinal guide frames 13 to the platform steel longitudinal beams 4 of the trestle platform 1, and then vertically insert the transverse guide frames 8 into the I-shaped reserved holes 19 on the webs of the longitudinal guide frames 13 to complete the installation of the longitudinal and transverse guide frames 8; the main body of the longitudinal guide frame 13 is an I-steel structure, and a frame beam clamp 21 is provided at the end. A lifting ring 18 is provided at the end and in the middle of the top surface of the longitudinal guide frame 13, and rails 17 are provided between the lifting rings 18 and the lifting rings 18, and between the lifting rings 18 and the frame beam clamps 21. At the same time, I-shaped reserved holes 19 are also provided at both ends of the web of the longitudinal guide frame 13; the transverse guide frame 8 is welded to the web of the longitudinal guide frame 13 through the I-shaped reserved holes 19, and a full-length rail 17 is also provided on the top surface of the transverse guide frame 8.

[0039] S2. Construction of casing clamp system: Casing clamp 6 is installed on the outer wall of pile foundation steel casing 5 using anchor bolts 16. All casing clamps 6 must be installed at the same elevation, and the longitudinal (transverse) wing plates 10 on the outer wall of casing clamp 6 must be parallel to the longitudinal (transverse) guide frame.

[0040] S3. Installation of inner upper steel supports: Install the inner upper steel supports 9 on the wing plates 10 of the casing clamp 6 by welding. Reserve operating space for Larsen steel sheet piles 14 between the inner upper steel supports 9 and the longitudinal and transverse guide frames 8. Simultaneously, weld inner reinforcing angle braces 12 between adjacent and mutually perpendicular inner upper steel supports 9. The inner upper steel supports 9 are double-layer H-shaped steel structures, wherein a full-length track 17 is provided on the top surface of the upper H-shaped steel web, and a fine-tuning jacking device 23 can be installed in the track 17.

[0041] S4. Larsen Steel Sheet Pile Construction: A pile driver is deployed on the trestle platform 1 and begins driving the steel sheet piles from the center of the upstream cofferdam. During driving, the longitudinal and transverse guide frames 8 and the fine-tuning jacking equipment 23 mounted on the inner upper steel support 9 are used for simultaneous measurement and calibration to ensure the steel sheet piles are aligned. If local terrain resistance is excessive, prefabricated pile caps 41 and symmetrical high-pressure water guns 28 on either side of the steel sheet piles can be used to assist in sinking the piles. After each steel sheet pile is driven, it is welded securely to the channel steel and finally closed at the center of the downstream cofferdam. Auxiliary closure steel 26 is used to ensure closure accuracy. The high-pressure water guns 28 are mounted and secured via connectors 29 pre-set on the side of the Larsen steel sheet piles 14. A water pipe 27 is connected to the tail of the high-pressure water guns 28. The auxiliary closure steel 26 is placed on both sides of the Larsen steel sheet piles 14 and secured to each other by tensioning anchor cables 24 installed between the anchor ends 25.

[0042] S5. Erection of the central construction platform: After the Larsen steel sheet piles 14 are successfully closed, the central construction platform 33 and its overlap plate 32 are installed through the reserved bolt holes 11 on each wing plate 10. The platform guardrail 36 and the lower hanging construction platform 39 are also installed. Simultaneously, a water level monitor 34 is installed on the outside of the top of the Larsen steel sheet pile 14 using the mounting bracket 35; the central construction platform 33 is set in the area enclosed by the pile foundation 7. The end of the central construction platform 33 is connected to the end of the overlap plate 32 by the anchor bolt 16, and the end of the overlap plate 32 is connected to the inner upper steel support 9 wing plate 10 by the anchor bolt 16.

[0043] S6. Installation of the inner lower steel support: After the construction of the central area construction platform 33 is completed, the inner lower steel support 40 is installed 3 meters below the inner upper steel support 9 by taking advantage of the time when the water level drops after the tide. The inner lower steel support 40 is also installed on the wing plate 10 of the lower casing clamp 6 by welding, and a monitoring axial force meter 37 is installed between the inner lower steel support 40 and the Larsen steel sheet pile 14.

[0044] S7. Excavation and clearing of the cofferdam: A slurry pump 31 is pre-placed on the central construction platform 33. After the tide recedes, on-site technicians measure and record the clearing area within the cofferdam, mark the depth around the cofferdam, and then begin to use a high-pressure water gun 28 in conjunction with the slurry pump 31 to flush the slurry and clear the base until the required depth is reached.

[0045] Concrete bottom seal pouring: After the foundation inside the cofferdam is cleared, C30 marine concrete is used for bottom seal. The concrete bottom seal 38 is poured on the dry beach during low tide. After the concrete bottom seal 38 reaches the designed strength, the next step of foundation and pier construction is carried out.

[0046] Example 2

[0047] As another embodiment, the steel sheet pile cofferdam with large water level difference in tidal zone obtained by the construction method of the steel sheet pile cofferdam with large water level difference in tidal zone proposed in the first embodiment is as follows: Figures 1 to 7 As shown, it includes: a trestle platform 1, a pile foundation steel casing 5, a longitudinal guide frame 13 and Larsen steel sheet piles 14;

[0048] like Figure 2As shown, platform steel columns 3 are provided below the trestle platform 1. These columns are connected by column braces 22. Two longitudinal guide frames 13 are symmetrically fixed to the platform steel columns 3 of the trestle platform 1 via frame beam clamps 21. The longitudinal guide frames 13 are I-beams, with frame beam clamps 21 at their ends. Lifting rings 18 are provided at the top and middle of the longitudinal guide frames 13, and I-shaped pre-set holes 19 are provided at both ends of the web of the longitudinal guide frames 13. The trestle platform 1 is provided with platform steel longitudinal beams 4. The lifting rings 18 on the longitudinal guide frames 13 are connected to the platform steel longitudinal beams 4 of the trestle platform 1 via rigid pull rods 15 and flexible pull ropes 20. This improves the stability of the longitudinal guide frames 13, and thereby the stability of the entire guide frame system. The transverse guide frame 8 is provided between the longitudinal guide frames 13 via the I-shaped pre-set holes 19.

[0049] like Figure 1 As shown, Larsen steel sheet piles 14 are installed inside the longitudinal guide frame 13 and the transverse guide frame 8. Inside the Larsen steel sheet piles 14, inner upper steel supports 9 are installed. The inner upper steel supports 9 are double-layer H-shaped steel structures. The outer wall of the pile foundation steel casing 5 is fixed with casing clamps 6 using anchor bolts 16. All casing clamps 6 have the same elevation. The outer wall of the casing clamps 6 is equipped with wing plates 10 parallel to the longitudinal guide frame 13 and the transverse guide frame 8. The wing plates 10 are divided into two groups, upper and lower, respectively, for connecting the inner upper steel supports 9 and the inner lower steel supports 40. The casing clamps 6 are connected to the inner upper steel supports 9 through the wing plates 10. Inner reinforcing angle braces 12 are welded between adjacent and mutually perpendicular inner upper steel supports 9.

[0050] like Figure 1 and Figure 3 As shown, rails 17 are provided between the lifting rings 18 and the lifting rings 18, and between the lifting rings 18 and the frame beam clamps 21. The top surface of the upper H-shaped steel web of the inner upper steel support 9 is also provided with a rail 17; the top surface of the transverse guide frame 8 is also provided with a rail 17 along its entire length; the rails 17 on the surface of the longitudinal guide frame 13, the transverse guide frame 8 and the inner upper steel support 9 are all provided with fine-tuning jacking devices 23, and the fine-tuning jacking devices 23 are used to accurately position and adjust the Larsen steel sheet piles 14.

[0051] like Figure 4 and Figure 5 As shown, a prefabricated pile cap 41 is provided at the bottom of the Larsen steel sheet pile 14, and high-pressure water guns 28 are symmetrically provided on both sides of the Larsen steel sheet pile 14. The high-pressure water guns 28 are fixed to the sides of the Larsen steel sheet pile 14 through connectors 29, and a water pipe 27 is connected to the tail of the high-pressure water gun 28; the Larsen steel sheet pile 14 is connected at the center of the downstream cofferdam, and auxiliary connection steel sections 26 are provided on both sides of the Larsen steel sheet pile 14. The auxiliary connection steel sections 26 are fixed to each other by tension anchor cables 24 to ensure the connection accuracy of the Larsen steel sheet pile 14.

[0052] like Figure 6 As shown, the wing plate 10 of the casing clamp 6 is provided with a reserved bolt hole 11, and the central area construction platform 33 is connected to the reserved bolt holes 11 on each wing plate 10; the central area construction platform 33 is arranged in the area enclosed by the pile foundation 7, and the end of the central area construction platform 33 is connected to the end of the lap plate 32 through the anchor bolt 16, and the end of the lap plate 32 is connected to the wing plate 10 of the inner upper steel support 9 through the anchor bolt 16; the central area construction platform 33 also includes a platform guardrail 36.

[0053] like Figure 7 As shown, a mud pump 31 is provided on the central construction platform 33, and a hanging construction platform 39 is provided at the lower part of the central construction platform 33; a water level monitor 34 is provided on the outer side of the top of the Larsen steel sheet pile 14 through a mounting bracket 35; an inner lower steel support 40 is installed 3 m below the inner upper steel support 9, and the inner lower steel support 40 is also connected to the wing plate 10 of the casing clamp 6. A monitoring axial force meter 37 is provided between the inner lower steel support 40 and the Larsen steel sheet pile 14. The water level monitor 34 and the monitoring axial force meter 37 can realize dynamic monitoring of the support and water level inside the cofferdam.

Claims

1. A method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference, characterized in that: The following steps are involved: S1. Installation of longitudinal and transverse guide frames: Fix the longitudinal guide frame (13) on the platform steel column (3) and connect it to the trestle platform (1) through the rigid pull rod (15) and the flexible pull rope (20). Insert the transverse guide frame (8) into the I-shaped reserved hole (19) of the longitudinal guide frame (13); S2. Construction of casing hoop system: installing casing hoop (6) on the outer wall of the pile foundation steel casing (5); installing casing hoop (6) on the outer wall of the pile foundation steel casing (5) using anchor bolts (16), all casing hoop (6) are installed at the same elevation, and the outer wall of the casing hoop (6) is provided with wing plates (10) parallel to the longitudinal guide frame (13) and the transverse guide frame (8); S3. Installation of the inner upper steel support: Install the inner upper steel support (9), and reserve a Larsen steel sheet pile (14) operation space between the inner upper steel support (9) and the longitudinal and transverse guide frames (8); install the inner upper steel support (9) on the wing plate (10) of the casing hoop (6) by welding. The inner upper steel support (9) is a double-layer H-shaped steel structure, wherein a full-length track (17) is set on the top surface of the upper H-shaped steel web, and a fine-tuning jacking device (23) is set in the track (17). The inner reinforcing angle brace (12) is welded between adjacent and mutually perpendicular inner upper steel supports (9); S4, Larsen steel sheet pile construction: a pile driver is arranged on the trestle platform (1), and the Larsen steel sheet piles (14) are driven from the center of the upstream cofferdam, and finally closed at the center of the downstream cofferdam; S5. Installation of the central construction platform: Install the central construction platform (33) and the lap plate (32) on the wing plate (10), and install the lower hanging construction platform (39). Set a water level monitor (34) outside the Larsen steel sheet pile (14); S6. Installation of the inner lower steel support: Install the inner lower steel support (40) directly below the inner upper steel support (9), and set a monitoring axial force meter (37) between the inner lower steel support (40) and the Larsen steel sheet pile (14); take advantage of the time when the water level drops after the tide, install the inner lower steel support (40) 3m directly below the inner upper steel support (9), and weld the inner lower steel support (40) to the wing plate (10) of the casing hoop (6); S7. Excavation and clearing of the cofferdam foundation and pouring of concrete: a slurry pump (31) is arranged on the central construction platform (33), and a high-pressure water gun (28) is used in conjunction with the slurry pump (31) to flush the slurry and clear the foundation; when the tide recedes, a concrete bottom seal (38) is poured on the dry beach.

2. The method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference according to claim 1, characterized in that: In step S1, the longitudinal guide frames (13) on both sides of the symmetrical arrangement are initially fixed to the platform steel columns (3) of the trestle platform (1) by using the frame beam clamps (21). The main body of the longitudinal guide frame (13) is an I-steel structure. The frame beam clamps (21) are provided at the ends of the longitudinal guide frame (13). The top ends and the middle of the longitudinal guide frame (13) are provided with lifting rings (18). The lifting rings on the longitudinal guide frame (13) are fixed by the rigid pull rods (15) and the flexible pull ropes (20). (18) is connected to the platform steel longitudinal beam (4) of the trestle platform (1), and rails (17) are provided between the lifting rings (18) and between the lifting rings (18) and the frame beam hoop (21). At the same time, I-shaped reserved holes (19) are provided at both ends of the web of the longitudinal guide frame (13); the transverse guide frame (8) is welded to the web of the longitudinal guide frame (13) through the I-shaped reserved holes (19), and a full-length rail (17) is also provided on the top surface of the transverse guide frame (8).

3. The method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference according to claim 1, wherein: In step S4, when the Larsen steel sheet pile (14) is driven, the longitudinal and transverse guide frames and the fine-tuning jacking equipment (23) provided on the surface of the inner upper steel support (9) are used to perform measurement and correction synchronously to ensure that the steel sheet piles are in the same straight line. When the resistance of the local special terrain is too large, the prefabricated pile cap (41) and the high-pressure water guns (28) symmetrical on both sides of the steel sheet pile are used to flush and assist the pile sinking. After each steel sheet pile is driven, it is firmly welded to the channel steel. The high-pressure water gun (28) is installed and fixed through the connector (29) preset on the side of the Larsen steel sheet pile (14). The tail of the high-pressure water gun (28) is connected to a water pipe (27).

4. The method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference according to claim 1, wherein: In step S4, the Larsen steel sheet pile (14) uses auxiliary closure steel (26) to ensure the closing accuracy. The auxiliary closure steel (26) is arranged on both sides of the Larsen steel sheet pile (14). The auxiliary closure steel (26) on both sides are fixed to each other by arranging a tension anchor cable (24) between the anchor ends (25) of the Larsen steel sheet pile (14).

5. The method for constructing a steel sheet pile cofferdam in a tidal zone with a large water level difference according to claim 1, wherein: In step S5, the wing plate (10) of the casing hoop (6) is provided with a reserved bolt hole (11), and the central area construction platform (33) is installed through the reserved bolt hole (11) of each wing plate (10), and the platform guardrail (36) is installed, and a water level monitor (34) is installed on the outer side of the top of the Larsen steel sheet pile (14) using a mounting bracket (35); the central area construction platform (33) is set in the area enclosed by the pile foundation (7), and the end of the central area construction platform (33) is connected to the end of the lap plate (32) through the anchor bolt (16), and the end of the lap plate (32) is connected to the inner upper steel support (9) wing plate (10) through the anchor bolt (16).

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