Complex geological underwater pier local movable type inner supporting steel sheet pile cofferdam and construction method

Abstract

The invention relates to a local movable type inner support steel sheet pile cofferdam and a construction method, and the construction method comprises the steps of inner support splicing, inner support lowering, steel sheet pile inserting and driving, layered water pumping and support mounting, outer ring beam mounting, pile head breaking and removing, bearing platform and pier body construction and the like. The transverse connector and the inclined connector release bending moment to profile steel to be dismantled through hydraulic jacks in the transverse connector and the inclined connector, the dismantling difficulty of the inner support is reduced, a positioning and lowering device used for bearing the inner support is installed on a steel casing and an auxiliary steel casing, and the outer ring beam and the inner ring beam form an opposite-pulling state. And the water level regulator is mounted on the steel sheet pile through the connection of the flexible joint and the flange plate. The method has the advantages of being high in construction efficiency, low in steel sheet pile deformation, fast in inner support installation and convenient in inner support system conversion, and good technical and economic benefits can be obtained when the method is applied to actual engineering.

Description

Technical Field

[0001] The invention relates to the field of bridges, and in particular to a locally movable internally supported steel sheet pile cofferdam for underwater piers in complex geology and a construction method thereof. Background Art

[0002] As the steel sheet pile cofferdam develops towards complex geological conditions, frequent water level changes and other environmental conditions, many problems in the construction of steel sheet pile cofferdams are gradually exposed. The conventional sequential construction method for steel sheet pile cofferdam construction is prone to deformation of the steel sheet piles, especially when pumping water layer by layer for internal support installation, the deformation of the steel sheet piles will gradually accumulate. In order to control the deformation of the steel sheet piles, the internal support design is too complicated, and the encrypted internal support is also prone to narrow construction work surface, which will cause the internal support to undergo multiple transformation systems, increase construction steps, and thus extend the construction period. Obviously, the conventional steel sheet pile construction method is not applicable to construction under complex environmental conditions, and in order to ensure the safety of the steel sheet pile cofferdam during construction, the design of the internal support is very important.

[0003] In summary, in view of the above existing problems, a partially movable internally supported steel sheet pile cofferdam and its construction method are proposed from the aspects of internal support system, construction sequence and reducing water head difference. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned problems existing in the prior art and to provide a locally movable internally supported steel sheet pile cofferdam for underwater piers in complex geology and a construction method thereof.

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme: a construction method of a partially movable internally supported steel sheet pile cofferdam of a complex geological underwater pier, comprising the following steps:

[0006] Step 1, splicing inner support: the inner support includes an inner ring beam, and the transverse support is welded to the inner ring beam, the transverse support is located inside the inner ring beam, and the transverse support divides the inner ring beam into two areas of unequal area; the transverse joint and the diagonal joint are welded on the inner side of the inner ring beam and the transverse support; the first section steel, the third section steel and the fixed diagonal brace are welded in the area with a smaller area, and the fifth section steel is welded in the area with a larger area, and the two ends of the fifth section steel are respectively connected to the transverse joints welded on the inner ring beam and the transverse support; the movable diagonal brace and the fixed diagonal brace are installed at the same time, and the two ends of the movable diagonal brace are respectively connected to the diagonal joints welded on the inner ring beam and the transverse support; after the first inner support is installed, the second inner support is made according to the same operation; the two inner supports are connected by a temporary connection system;

[0007] Step 2: Lowering the inner support: First, insert auxiliary steel casing in a smaller area of ​​the inner ring beam in advance to assist in lowering the inner support. Install the positioning and lowering device on the steel casing and the auxiliary steel casing that need to support the inner support in advance. Use a crane to place the spliced ​​inner support on the positioning and lowering device.

[0008] Step 3: Steel sheet pile driving: first insert positioning piles around, weld I-beams on the positioning piles as the outer guide frame; then use the inner ring beam as the inner guide frame to form a positioning guide frame for the steel sheet piles, and then drive the steel sheet piles; the steel sheet piles pass through the area between the outer guide frame and the inner guide frame; one of the steel sheet piles is installed with a water level regulator before driving, and after the steel sheet pile is driven, the water level regulator is submerged in water;

[0009] Step 4: Pumping out water in layers and installing supports: After the steel sheet piles are inserted and driven, start pumping out water layer by layer. When the water is pumped to a position 50 cm below the bottom of the inner ring beam of each layer, install supports on the steel sheet piles at the bottom of the inner ring beam. After the support installation is completed, remove the positioning and lowering devices from the steel casing and the auxiliary steel casing one by one, and then further remove the auxiliary steel casing. Then install the second steel between the inner ring beam and the transverse support, install the two ends of the second steel on the transverse joints of the inner ring beam and the transverse support, and cut off some fixed diagonal braces.

[0010] Step 5: Installation of outer ring beam: an outer ring beam is arranged at the same height as the first inner ring beam, the outer ring beam is arranged outside the inner ring beam, and a screw is installed between the inner ring beam and the outer ring beam; the screw passes through the outer ring beam, and then passes through the steel sheet pile and the inner ring beam in turn, forming a tension with the first inner ring beam;

[0011] Step 6: Pile head removal: After the bottom concrete construction is completed, the pile head removal operation is carried out, and the pile heads are lifted out one by one by a crane; after the pile heads are lifted out, the sixth and fourth steels are lifted and fixed to the transverse joints at the transverse support and the inner ring beam, and the movable diagonal brace is removed;

[0012] Step 7: Construction of foundation and pier body.

[0013] Preferably, in step one, steel plates with bolt holes are provided at the tops of the transverse joints and the diagonal joints, the transverse joints and the diagonal joints are installed on the transverse supports and the inner ring beam, and then steel plates with bolt holes are installed on both ends of the fifth steel section and the movable diagonal brace, the steel plates on the fifth steel section and the movable diagonal brace are connected to the steel plates on the transverse joints and the diagonal joints, and connected with high-strength bolts.

[0014] Preferably, the transverse joint and the oblique joint are composed of steel plates, ribs, supports, bases and hydraulic jacks, and the hydraulic jacks are arranged between the supports and the bases; the steel plates are arranged on one end of the supports away from the bases, and ribs are arranged between the steel plates and the supports.

[0015] Preferably, in step two, the positioning and lowering device includes a crossbeam, a vertical I-beam and a corbel; when installing the positioning and lowering device, first weld one side of the crossbeam to the steel casing or the auxiliary steel casing, and weld the other side to the vertical I-beam, and then weld the corbel to the vertical I-beam according to the designed position for the installation of the inner support; when hanging the inner support, the lower end of the inner support is placed on the corbel of the positioning and lowering device.

[0016] Preferably, in step three, the water level regulator consists of a steel pipe, a flexible joint and a valve; when installing the water level regulator, first install two flexible joints with flanges on both sides of the prefabricated holes on the steel sheet piles, insert the flexible joints into the holes, and then pass the steel pipe through the flexible joints on both sides, install the flange on the steel pipe, connect the flange on the steel pipe with the flange on the flexible joint, use the flange to connect and fix the flexible joint and the steel pipe, and finally install the valve on the steel pipe.

[0017] Preferably, the specific method of step seven is as follows: before the construction of the foundation and the pier body, the fifth type steel is first removed; then the foundation is constructed; after the foundation construction is completed, a sand and soil mixture is filled between the foundation and the steel sheet piles and compacted, and concrete is poured on the top, and finally the pier body is constructed.

[0018] The invention discloses a partially movable internally supported steel sheet pile cofferdam for a pier in water with complex geology, which is constructed by a construction method of a partially movable internally supported steel sheet pile cofferdam for a pier in water with complex geology.

[0019] Working principle and beneficial effects:

[0020] 1. The present invention adopts the technology of high-efficiency system conversion prefabricated internal support and the technology of surrounding purlin steel sheet piles first and then construction. Some internal supports are designed to be movable, and the internal supports are installed and removed by using the assembled connection method of bolting with transverse joints and oblique joints and steel sections to provide sufficient construction working surface. At the same time, the internal supports placed on the steel casing are used as positioning guide frames for steel sheet piles, thereby improving the construction quality of steel sheet piles.

[0021] 2. The present invention adopts the technology of quickly reducing the double ring beam cofferdam by using the difference of internal and external water heads. By setting the outer ring beam at the same height as the outer side of the inner ring beam of the first floor and setting the water level regulator under the inner support of the bottom floor, the water level difference between the inside and outside is adjusted, thereby eliminating the adverse effects of the water level difference.

[0022] 3. The present invention adopts the technology of accurately controlling verticality by auxiliary positioning of steel casing, and utilizes the positioning and lowering device as the supporting device of the inner support, thereby improving the installation accuracy of the inner support. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the plan view of the internal support installation;

[0024] Figure 2 It is the positioning elevation drawing below the inner support;

[0025] Figure 3 It is the AA section view;

[0026] Figure 4 It is a three-dimensional diagram of a water level regulator;

[0027] Figure 5 It is a BB cross-section;

[0028] Figure 6 It is the plan view of the internal support arrangement during the construction of the cap and pier body;

[0029] Figure 7 This is a detailed structural drawing of the transverse joint.

[0030] In the figure, 1, inner ring beam; 2, lateral support; 3, fixed diagonal brace; 4, movable diagonal brace; 5, lateral joint; 6, diagonal joint; 7, first section steel; 8, second section steel; 9, third section steel; 10, fourth section steel; 11, fifth section steel; 12, sixth section steel; 15, steel casing; 16, auxiliary steel casing; 17, steel sheet pile; 18, positioning and lowering device; 19, cross beam; 20, vertical I-beam; 21, corbel; 22, temporary connection system; 23, outer ring beam; 24, steel pipe; 25, flange; 26, flexible joint; 27, valve; 28, water level regulator; 29, screw; 30, steel plate; 31, rib plate; 32, support; 33, base; 34, hydraulic jack; 35, high-strength bolt. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0032] Those skilled in the art should understand that, in the disclosure of the present invention, the orientation or position relationship indicated by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0033] like Figure 1-7 As shown, the construction method of the local movable internal support steel sheet pile cofferdam includes the following steps:

[0034] Step 1: Splice the inner support:

[0035] The inner support comprises an inner ring beam 1, which is made of double-piece steel. A transverse support 2 is welded to the inner ring beam 1, and the transverse support 2 is located inside the inner ring beam 1. The transverse support 2 divides the inner ring beam 1 into two areas of unequal area. A transverse joint 5 and an oblique joint 6 are welded on the inner side of the inner ring beam 1 and the transverse support 2. A first steel section 7, a third steel section 9 and a fixed oblique brace 3 are welded in the area with a smaller area, and a fifth steel section 11 is welded in the area with a larger area. The two ends of the fifth steel section 11 are respectively welded to the inner The ring beam 1 is connected to the transverse joint 5 on the transverse support 2, and the transverse support 5 and the inner ring beam 1 are connected together through the fifth steel section 11 and the movable diagonal brace 4; the movable diagonal brace 4 and the fixed diagonal brace 3 are installed at the same time, and the two ends of the movable diagonal brace 4 are respectively connected to the diagonal joints 6 welded on the inner ring beam 1 and the transverse support 2, and the fixed diagonal brace 3 is installed at the corner of the inner ring beam 1; after the first inner support is installed, the second inner support is completed according to the same operation; the two inner supports are connected by a temporary connection system 22.

[0036] Among them, transverse joints 5 and oblique joints 6 are arranged in the larger area of ​​the inner ring beam 1, which are used to connect the fifth steel section 11 and the movable diagonal brace 4. The fifth steel section 11 and the movable diagonal brace 4 constitute a movable support structure. The transverse joints 5 and the oblique joints 6 realize the assembled installation of the movable support structure, which facilitates the installation, disassembly and conversion of the movable support structure, improves the installation flexibility of the movable support structure, and at the same time plays a role in facilitating the conversion of the movable support structure in the subsequent pile foundation breaking and pier construction.

[0037] Specifically, steel plates 30 with bolt holes are provided at the tops of the transverse joints 5 and the diagonal joints 6. Several transverse joints 5 and diagonal joints 6 are installed at designated positions of the transverse supports 2 and the inner ring beam 1. Then, steel plates 30 with bolt holes are installed at both ends of the fifth steel section 11 and the movable diagonal brace 4. The steel plates 30 on the fifth steel section 11 and the movable diagonal brace 4 are connected to the steel plates 30 on the transverse joints 5 and the diagonal joints 6, and connected with high-strength bolts 35.

[0038] Furthermore, the transverse joint 5 and the diagonal joint 6 are composed of a steel plate 30, a rib plate 31, a support 32, a base 33 and a hydraulic jack 34, wherein the hydraulic jack 34 is arranged between the support 32 and the base 33; the steel plate 30 is arranged on the support 32 at one end away from the base 33, and a rib plate 31 is arranged between the steel plate 30 and the support 32. When replacing the movable support structure (taking the replacement of the fifth steel 11 and the movable diagonal brace 4 as an example), the hydraulic jack 34 applies pressure to the fifth steel 11 and the movable diagonal brace 4, so that the fifth steel 11 and the movable diagonal brace 4 release part of the bending moment, thereby reducing the difficulty of dismantling the movable support structure.

[0039] It is worth mentioning that when the remaining supports of the transverse joint 5 and the oblique joint 6 are replaced, they are all replaced in the above-mentioned manner.

[0040] Step 2: Lower the inner support:

[0041] First, insert the auxiliary steel casing 16 in a smaller area of ​​the inner ring beam 1 in advance to assist in the lowering of the inner support. Install the positioning and lowering device 18 in advance on the steel casing 15 that needs to support the inner support and the auxiliary steel casing 16, and use a crane to place the spliced ​​inner support on the positioning and lowering device 18.

[0042] Among them, the steel casing 15 is completed before the inner support is installed.

[0043] Specifically, the positioning and lowering device 18 includes a crossbeam 19, a vertical I-beam 20 and a bracket 21. When installing the positioning and lowering device 18, firstly weld one side of a plurality of crossbeams 19 to the steel casing 15 or the auxiliary steel casing 16, and weld the other side to the vertical I-beam 20, and then weld the bracket 21 to the vertical I-beam 20 according to the designed position of the inner support installation; when the inner support is suspended, the lower end of the inner support is placed on the bracket 21 of the positioning and lowering device 18.

[0044] Step 3: Inserting and driving the steel sheet pile 17:

[0045] First, insert positioning piles on all sides, and weld I-beams on the positioning piles to serve as an outer guide frame; then use the inner ring beam 1 as an inner guide frame to form a positioning guide frame for the steel sheet piles, with the inner ring beam 1 located on the inner side of the outer guide frame, and then drive the steel sheet piles 17; the steel sheet piles 17 pass through the area between the outer guide frame and the inner guide frame; a water level regulator 28 is installed on one of the steel sheet piles 17 before driving, and after the steel sheet pile 17 is driven, the water level regulator 28 is submerged in water.

[0046] Specifically, the water level regulator 28 is composed of a steel pipe 24, a flexible joint 26 and a valve 27; when installing the water level regulator 28, first install two flexible joints 26 with flanges 25 on both sides of the prefabricated holes on the steel sheet piles 17, insert the flexible joints 26 into the holes, and then pass the steel pipe 24 through the flexible joints 26 on both sides, install the flanges 25 on the steel pipe 24, connect the flanges 25 on the steel pipe 24 with the flanges 25 on the flexible joints 26, use the flanges 25 to connect and fix the flexible joints 26 and the steel pipe 24, and finally install the valve 27 on the steel pipe 24.

[0047] Step 4: Pump out water in layers and install supports:

[0048] After the steel sheet piles 17 are driven in, water is pumped out layer by layer. When the water is pumped to a position 50 cm below the bottom of the inner ring beam 1 of each layer, supports are installed on the steel sheet piles 17 at the bottom of the inner ring beam 1. After the support is fixed, the positioning and lowering devices 18 are removed one by one from the steel casing 15 and the auxiliary steel casing 16, and then the auxiliary steel casing 16 is further removed. Then, the second steel section 8 is installed between the inner ring beam 1 and the transverse support 2, and the two ends of the second steel section 8 are installed on the transverse joints 5 between the inner ring beam 1 and the transverse support 2, and part of the fixed diagonal braces 3 are cut off.

[0049] Step 5: Installation of outer ring beam:

[0050] An outer ring beam 23 is arranged at the same height as the first inner ring beam 1. The outer ring beam 23 is arranged on the periphery of the inner ring beam 1. A screw rod 29 is installed between the inner ring beam 1 and the outer ring beam 23. The screw rod 29 passes through the outer ring beam 23, and then passes through the steel sheet piles 17 and the inner ring beam 1 in sequence, forming a counter-tension with the first inner ring beam 1.

[0051] It is worth noting that an outer ring beam 23 is arranged outside the first inner support and forms a tensioning state with the inner ring beam 1, which effectively avoids the deformation of the steel sheet pile 17 caused by the excessive difference in internal and external water heads.

[0052] Step 6: Pile head removal:

[0053] After the bottom concrete construction is completed, the pile head is broken and the pile heads are lifted out in sequence by a crane. After the pile heads are lifted out, the sixth steel 12 and the fourth steel 10 are lifted and fixed to the transverse joint 5 at the transverse support 2 and the inner ring beam 1, and the movable diagonal support 4 is removed.

[0054] Step 7: Construction of the cap and pier:

[0055] Before the construction of the cap and pier body, the fifth steel 11 is first removed to increase the working surface; then the cap is constructed. After the cap construction is completed, a sand and soil mixture is filled and compacted between the cap and the steel sheet piles 17, and concrete is poured on the top, and finally the pier body is constructed.

[0056] The invention also discloses a partially movable internally supported steel sheet pile cofferdam, which is obtained by a partially movable internally supported steel sheet pile cofferdam construction method.

[0057] The parts not described in detail in the present invention are prior art, so the present invention does not describe them in detail.

[0058] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. The construction method of the partially movable internally supported steel sheet pile cofferdam in the water with complex geology is characterized by: The following steps are involved: Step 1: splicing the inner support: the inner support comprises an inner ring beam (1), a transverse support (2) is welded to the inner ring beam (1), the transverse support (2) is located inside the inner ring beam (1), and the transverse support (2) divides the inner ring beam (1) into two areas of unequal area; a transverse joint (5) and an oblique joint (6) are welded on the inner side of the inner ring beam (1) and the transverse support (2); wherein the first section steel (7), the third section steel (9) and the fixed oblique brace (3) are welded in the area with a smaller area, and the area with a larger area is welded in the area with a smaller area. The fifth section steel (11) is welded inside, and the two ends of the fifth section steel (11) are respectively connected to the transverse joints (5) welded on the inner ring beam (1) and the transverse support (2); at the same time, the movable diagonal brace (4) and the fixed diagonal brace (3) are installed, and the two ends of the movable diagonal brace (4) are respectively connected to the oblique joints (6) welded on the inner ring beam (1) and the transverse support (2); after the first inner support is installed, the second inner support is manufactured according to the same operation; the two inner supports are connected by a temporary connection system (22); Step 2: Lowering the inner support: first, insert an auxiliary steel casing (16) in a smaller area of ​​the inner ring beam (1) in advance to assist in lowering the inner support, install a positioning and lowering device (18) in advance on the steel casing (15) and the auxiliary steel casing (16) that need to support the inner support, and use a crane to place the spliced ​​inner support on the positioning and lowering device (18); Step 3, driving the steel sheet piles (17): first insert positioning piles around, weld I-beams on the positioning piles to serve as outer guide frames; then use the inner ring beam (1) as the inner guide frame to form a positioning guide frame for the steel sheet piles, and then drive the steel sheet piles (17); the steel sheet piles (17) pass through the area between the outer guide frame and the inner guide frame; before driving one of the steel sheet piles (17), a water level regulator (28) is installed, and after the steel sheet pile (17) is driven, the water level regulator (28) is submerged in water; Step 4, layered pumping and support installation: After the steel sheet piles (17) are inserted and driven, start pumping layer by layer. When the water is pumped to a position 50 cm below the bottom of the inner ring beam (1) of each layer, install the support on the steel sheet pile (17) at the bottom of the inner ring beam (1); after the support installation is completed, remove the positioning and lowering device (18) from the steel casing (15) and the auxiliary steel casing (16) one by one, and then further remove the auxiliary steel casing (16); then install the second steel (8) between the inner ring beam (1) and the transverse support (2), install the two ends of the second steel (8) on the transverse joint (5) between the inner ring beam (1) and the transverse support (2), and cut off part of the fixed diagonal brace (3); Step 5, outer ring beam installation: an outer ring beam (23) is arranged at a position equal to the height of the first inner ring beam (1), the outer ring beam (23) is arranged on the periphery of the inner ring beam (1), and a screw rod (29) is installed between the inner ring beam (1) and the outer ring beam (23); the screw rod (29) passes through the outer ring beam (23), and then passes through the steel sheet pile (17) and the inner ring beam (1) in sequence, forming a tension with the first inner ring beam (1); Step 6: Pile head removal: After the bottom concrete construction is completed, the pile head removal operation is carried out, and the pile heads are lifted out in sequence by a crane; after the pile heads are lifted out, the sixth steel (12) and the fourth steel (10) are lifted and fixed to the transverse joints (5) at the transverse support (2) and the inner ring beam (1), and the movable diagonal brace (4) is removed; Step 7: Construction of foundation and pier body.

2. The construction method of the partially movable internally supported steel sheet pile cofferdam in the water with complex geological conditions according to claim 1 is characterized in that: In step 1, a steel plate (30) with bolt holes is provided at the top of each of the transverse joint (5) and the oblique joint (6), and the transverse joint (5) and the oblique joint (6) are installed on the transverse support (2) and the inner ring beam (1), and then the steel plates (30) with bolt holes are installed at both ends of the fifth steel section (11) and the movable diagonal brace (4), and the steel plates (30) on the fifth steel section (11) and the movable diagonal brace (4) are butt-jointed with the steel plates (30) on the transverse joint (5) and the oblique joint (6), and connected with high-strength bolts (35).

3. The construction method of the partially movable internally supported steel sheet pile cofferdam in the water with complex geological conditions according to claim 1 is characterized in that: The transverse joint (5) and the oblique joint (6) are both composed of a steel plate (30), a rib plate (31), a support (32), a base (33) and a hydraulic jack (34), wherein the hydraulic jack (34) is arranged between the support (32) and the base (33); the steel plate (30) is arranged on one end of the support (32) away from the base (33), and a rib plate (31) is arranged between the steel plate (30) and the support (32).

4. The construction method of the partially movable internally supported steel sheet pile cofferdam in the water with complex geological conditions according to claim 1 is characterized in that: In step 2, the positioning and lowering device (18) includes a crossbeam (19), a vertical I-beam (20) and a bracket (21); when installing the positioning and lowering device (18), one side of the crossbeam (19) is first welded to the steel casing (15) or the auxiliary steel casing (16), and the other side is welded to the vertical I-beam (20), and then the bracket (21) is welded to the vertical I-beam (20) according to the designed position of the inner support installation; when the inner support is suspended, the lower end of the inner support is placed on the bracket (21) of the positioning and lowering device (18).

5. The construction method of the partially movable internally supported steel sheet pile cofferdam in complex geological water according to claim 1 is characterized in that: In step three, the water level regulator (28) is composed of a steel pipe (24), a flexible joint (26) and a valve (27); when installing the water level regulator (28), firstly, two flexible joints (26) with flanges (25) are installed on both sides of the prefabricated hole on the steel sheet pile (17), the flexible joints (26) are inserted into the holes, and then the steel pipe (24) is passed through the flexible joints (26) on both sides, the flanges (25) are installed on the steel pipe (24), the flanges (25) on the steel pipe (24) are connected to the flanges (25) on the flexible joints (26), the flexible joints (26) and the steel pipe (24) are connected and fixed by using the flanges (25), and finally the valve (27) is installed on the steel pipe (24).

6. The construction method of the partially movable internally supported steel sheet pile cofferdam in complex geological water according to claim 1 is characterized in that: The specific method of step seven is as follows: before the construction of the foundation and the pier body, the fifth type steel (11) is first removed; then the foundation is constructed; after the foundation is constructed, a sand and soil mixture is filled between the foundation and the steel sheet pile (17) and compacted, and concrete is poured on the top, and finally the pier body is constructed.

7. A partially movable internally supported steel sheet pile cofferdam in a complex geological underwater environment, characterized in that: The cofferdam is obtained by the construction method of the partially movable internally supported steel sheet pile cofferdam for underwater piers in complex geology as described in any one of claims 1 to 6.

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