Steel cofferdam for water-bearing platform and construction method

Abstract

The present invention provides an underwater foundation steel cofferdam and construction method, comprising the following steps: setting a modular telescopic bracket; adopting a "reverse construction method" for steel sheet pile cofferdam; setting a steel casing positioning device; adopting a steel casing lead hole synchronous backfilling technology; adopting a lock-type connection water-stopping system for steel sheet piles; setting a steel sheet pile rapid leakage prevention system; and setting a hopper positioning device. The main construction steps include: (1) construction preparation, (2) installation of modular telescopic bracket, (3) assembly and lowering of purlins, (4) installation of steel casing positioning device, (5) construction of steel sheet pile lead holes, (6) driving of steel sheet piles, (7) desilting the cofferdam to the bottom elevation of the bottom concrete, (8) installation of the hopper positioning device, (9) pouring the bottom concrete, (10) pumping and foundation construction, and (11) removal of the steel sheet pile cofferdam. The present invention has a large applicable depth for foundation pits, good leakage prevention effect, and fast construction speed. It can achieve good technical and economic benefits when applied to actual projects.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cofferdam construction system, in particular to a steel cofferdam for water-bearing platform and a construction method thereof. BACKGROUND

[0002] The river-crossing bridge engineering is limited by location, and many procedures need to be carried out in water. However, due to the complex terrain in water, the water flow will greatly affect the efficiency and safety of the construction of the steel cofferdam for water-bearing platform, and the construction is very difficult. The traditional construction of the steel cofferdam for water-bearing platform usually adopts the form of “piling first and supporting later”, which leads to small applicable depth of the foundation pit of the steel sheet pile cofferdam. During the construction, the local lock of the adjacent steel sheet pile is prone to water leakage, and the traditional leakage stopping method is time-consuming and money-consuming, and has high re-leakage rate in the later period. In addition, there are problems of low efficiency of steel sheet pile insertion and driving and low quality of bottom sealing concrete pouring, and the construction process of the steel cofferdam for water-bearing platform needs to be strictly controlled and improved. SUMMARY

[0003] The purpose of the present application is to provide a steel cofferdam for water-bearing platform and a construction method thereof, which have large applicable depth of foundation pit, good leakage stopping effect, fast construction speed, and can achieve good technical and economic benefits in practical engineering.

[0004] To solve the above technical problems, the present application provides a construction method of a steel cofferdam for water-bearing platform, comprising the following steps:

[0005] Step one, construction preparation;

[0006] Step two, installation of assembly type telescopic corbel support: the end of the horizontal fixing member is connected with the beginning of the vertical fixing member, and an adjustable inclined brace is arranged between the horizontal fixing member and the vertical fixing member;

[0007] Step three, assembly of coffering and lowering: the assembly type telescopic corbel support is arranged on the steel casing, the assembled steel coffering is arranged above the assembly type telescopic corbel support, and the coffering is formed by surrounding the steel casings through the steel cofferings; a plurality of fixed bases are arranged on the coffering, and the inclined braces and straight braces are connected by the fixed bases to form the first coffering; the assembly type telescopic corbel support is arranged at the specified position of the steel casing, and the second coffering is arranged in the same way; the hanger rods are arranged on the bearing beam to connect the first and second cofferings, the assembly type telescopic corbel support is folded, and the coffering is integrally lifted or lowered to the specified position by the jack; after the steel sheet pile is inserted and driven, the force transmission plates are connected between the coffering and the steel sheet pile;

[0008] Step four, steel casing positioning device installation: the first limiting rod and the second limiting rod are connected to form the first layer horizontal support; the positioning sleeve is symmetrically connected with the fixed wing plate on both sides; the fixed screw rod is connected with the second limiting rod through the reserved hole of the fixed wing plate; the second limiting rod is connected with the horizontal fixed plate through the vertical fixed plate, forming the second layer horizontal support, and the second layer horizontal support also fixes the positioning sleeve through the fixed screw rod; thus, the two-layer steel casing positioning device is formed and arranged on the construction platform, and the lower end of the construction platform is connected with the vertical support;

[0009] Step five, steel sheet pile hole construction: a reserved through hole is arranged on each positioning sleeve as a sand backfill pipe outlet, the backfill pipe is connected with the pump to transport backfill sand, and a valve is arranged on the main pipe of the backfill pipe to control the transportation of sand, so that the steel sheet pile is simultaneously guided and backfilled before being inserted;

[0010] Step six, steel sheet pile insertion: the steel sheet pile is inserted by using a vibration hammer, and the same steel sheet pile wall body is fixed through a lap joint groove; the connection between different prefabricated steel sheet piles adopts a lock type connection, one side of the steel sheet pile is connected with an edge groove steel, a fixed plate is arranged between the edge groove steel and the steel sheet pile; a plurality of fixed supports are connected with the edge groove steel away from the steel sheet pile, and a lock steel pipe is laid along the fixed supports, a positioning groove is arranged on the lock steel pipe, and a lock steel is inserted into the positioning groove; thus, a lock type water stop system is formed;

[0011] Step seven, cofferdam dredging to bottom concrete bottom elevation: after the steel sheet pile is set to be closed, the secondary foundation pit is excavated and sucked to the design elevation, and the outer wall of the steel casing, the web plate and the root of the steel sheet pile within the thickness of the bottom sealing concrete are cleaned;

[0012] Step eight, installation of hopper positioning device: a hopper through hole is reserved on the pressure plate, and hopper positioning devices are symmetrically arranged on both sides of the through hole, wherein the front side of the arc-shaped positioning block is arranged above the through hole and overlaps with the circular arc of the through hole, the rear side is fixedly connected with the connecting block, the connecting block is connected with the fixed block, and the fixed block is connected with the pressure plate, so as to realize accurate positioning of the hopper;

[0013] Step nine, bottom sealing concrete pouring: each steel casing is connected to the specified design elevation by flanges, the top of the steel casing is connected with a combined telescopic corbel support, and the combined telescopic corbel support is connected with a pressure plate above, so as to form a concrete pouring platform;

[0014] Step 10: Pumping out water and foundation pile construction: After the concrete strength reaches the standard, pump out water, cut off the steel casing, break the pile head, and carry out foundation pile construction; if the steel sheet pile is found to be leaking during the bottom sealing, pumping out water and other construction processes, take quick measures to stop the leakage; set strips of waterproof film on both sides of the steel sheet pile, tie knots at both ends of the waterproof film to form film knots, and fix them to the ends of the two telescopic rods respectively, and the film knots wrap the fall-off blocks set at the ends of the telescopic rods; at the same time, insert the two telescopic rods into the riverbed. When the telescopic rods become difficult to insert, press the button on the top of the telescopic rods to lower the fall-off blocks, pull out the telescopic rods, leave the waterproof film in the riverbed, and tighten and straighten the film at the lock mouth of the steel sheet piles;

[0015] Step 11. Dismantling of the steel sheet pile cofferdam: After the underwater foundation and related construction procedures are completed, the internal support dismantling work is completed in a bottom-up order; after the internal support system of the cofferdam is completely dismantled, use a crane to pull out the locking steel to unlock the wall and remove the steel sheet piles.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention is provided with a modular telescopic corbel bracket, which increases the speed of installing the purlin.

[0018] 2. The present invention adopts the "reverse construction method" of steel sheet pile cofferdam, which increases the applicable depth of the foundation pit of the steel sheet pile cofferdam.

[0019] 3. The present invention adopts the steel casing boring and synchronous backfilling technology, which improves the efficiency of steel casing insertion.

[0020] 4. The present invention adopts a lock-type connection water-stopping system, which improves the water-stopping effect of the cofferdam.

[0021] 5. The present invention provides a steel sheet pile rapid leakage prevention system, which is easy to operate and saves construction costs.

[0022] 6. The present invention is provided with a hopper positioning device, which increases the pouring speed of the bottom sealing concrete.

[0023] 7. The present invention is provided with a steel casing positioning device, which improves the layout accuracy and construction speed of the steel casing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the underwater cap steel cofferdam structure;

[0025] Figure 2 This is a schematic diagram of the "reverse construction method" of the steel sheet pile cofferdam;

[0026] Figure 3 This is a schematic diagram of the installation of the steel casing positioning device;

[0027] Figure 4 It is a structural diagram of the steel casing positioning device;

[0028] Figure 5 is a schematic diagram of a lock type connection water stop system structure;

[0029] Figure 6 is a schematic diagram of a lock type steel pipe installation;

[0030] Figure 7 is Figure 1 is an enlarged schematic diagram of part A in

[0031] Figure 8 is a schematic diagram of a steel sheet pile layout;

[0032] Figure 9 is a schematic diagram of a steel cofferdam cast-in-place concrete bottom sealing structure;

[0033] Figure 10 is a cross-sectional view of a hopper;

[0034] Figure 11 is a schematic diagram of a hopper positioning device structure;

[0035] Figure 12 is a schematic diagram of a modular telescopic corbel support structure;

[0036] Figure 13 is a schematic diagram of a modular telescopic corbel support structure after folding.

[0037] In the drawings: 1 - steel sheet pile, 2 - overlapping groove, 3 - fixed base, 4 - reinforcing rib plate, 5 - pressure bearing base, 6 - bearing beam, 7 - suspender, 8 - connecting rod, 9 - jack, 10 - modular telescopic corbel support, 11 - enclosing purlin, 12 - steel casing, 13 - diagonal brace, 14 - straight brace, 15 - water-tight filler, 16 - lock type steel pipe, 17 - mortar, 18 - edge sealing steel plate, 19 - lock type steel, 20 - edge sealing channel steel, 21 - connecting plate, 22 - button, 23 - waterproof film, 24 - telescopic rod, 25 - falling block, 26 - film knot, 27 - fixed screw, 28 - fixed wing plate, 29 - through hole, 30 - first limiting rod, 31 - construction platform, 32 - second limiting rod, 33 - vertical support, 34 - transverse fixing plate, 35 - positioning sleeve, 36 - backfill pipe, 37 - vertical fixing plate, 38 - connecting column, 39 - fixed support, 40 - positioning groove, 41 - force transmission plate, 42 - arc-shaped positioning block, 43 - upper support, 44 - positioning cylinder, 45 - connecting column, 46 - concrete, 47 - outer support, 48 - rope, 49 - pressure bearing plate, 50 - hopper, 51 - discharge pipe, 52 - cast-in-place concrete bottom plate, 53 - flange, 54 - vertical fixing member, 55 - adjustable diagonal brace, 56 - adjusting groove, 57 - transverse fixing member, 58 - connecting block, 59 - fixed block, 60 - water-blocking ball. DETAILED DESCRIPTION

[0038] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

[0039] Those skilled in the art should understand that, in the disclosure of the present application, the orientations or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the above terms cannot be understood as a limitation on the present application.

[0040] It can be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of one element can be one, and in another embodiment, the number of the element can be multiple, and the term "one" cannot be understood as a limitation on the number.

[0041] As Figures 1-13 The present application provides a water bearing platform steel cofferdam and a construction method, comprising the following steps:

[0042] Step one, construction preparation: before construction, materials are transported to the site in time according to the construction plan and site conditions, and relevant construction personnel are arranged to familiarize themselves with the site construction in advance.

[0043] Step two, installation of the assembled telescopic corbel support (10): the vertical fixing member (54) is arranged on the center line of each steel casing (12), the end of the transverse fixing member (57) is connected to the beginning of the vertical fixing member (54) through a bolt, and an adjustable diagonal brace (55) is arranged between the transverse fixing member (57) and the vertical fixing member (54) to strengthen the connection; the beginning of the transverse fixing member (57) is provided with an adjusting groove (56), one end of the adjustable diagonal brace (55) is fixed in the adjusting groove (56), and the entire assembled telescopic corbel support (10) is folded by changing the fixed position of one end of the adjustable diagonal brace (55) in the adjusting groove (56).

[0044] Step three, the surrounding purlin (11) group assembly and down: a number of steel casing (12) upper end is respectively set pressure base (5), through the connection position welding connecting reinforcing rib plate (4) to enhance the connection of pressure base (5) and steel casing (12);At least two bearing beams (6) are arranged above the pressure base (5), and the bearing beams (6) are arranged on the steel casings (12) at the same time, the connecting rods (8) are evenly arranged between the adjacent two bearing beams (6), and are connected by bolt anchoring;The assembly type telescopic bracket (10) is arranged on the steel casing (12), and the assembled steel fence is arranged above the assembly type telescopic bracket (10), and the steel fence is surrounded by the steel casing (12) to form the surrounding purlin (11);A plurality of fixed bases (3) are arranged on the surrounding purlin (11), the diagonal bracing (13) and the straight bracing (14) are connected by the fixed bases (3), the strength of the steel fence (11) is enhanced, and the first surrounding purlin (11) is formed;According to the construction requirement, the assembly type telescopic bracket (10) is also arranged at the specified position of the steel casing (12), and the second surrounding purlin (11) is arranged in the same way, the connecting column (38) is welded and connected between the first surrounding purlin (11) and the second surrounding purlin (11), so that a structural whole is formed;The hanger (7) is arranged on the bearing beam (6) to connect the first and second surrounding purlins (11) assembled, the folding assembly type telescopic bracket (10) is folded, the surrounding purlin (11) is integrally lifted or lowered to the specified position through the jack (9), and the force transmission plate (41) is welded and connected between the surrounding purlin (11) and the steel sheet pile (1) in time after the steel sheet pile (1) is inserted and driven.

[0045] Step four, the steel casing (12) positioning device installation: the first limiting rod (30) and the second limiting rod (32) are connected by welding to form the first layer horizontal support;The fixed wing plate (28) is symmetrically welded and connected on both sides of the positioning sleeve (35), and the whole is formed by splicing the same two parts;The fixed screw (27) passes through the reserved hole of the fixed wing plate (28) and is connected with the second limiting rod (32);The second limiting rod (32) is connected with the horizontal fixing plate (34) through a plurality of vertical fixing plates (37), forming the second layer horizontal support, the second layer horizontal support is also fixed with the positioning sleeve (35) through the fixed screw (27), and the center of the positioning sleeve (35) at the first layer horizontal support and the center of the positioning sleeve (35) at the second layer horizontal support are on the same vertical axis;The two-layer steel casing (12) positioning device is assembled to form a two-layer steel casing (12) positioning device, which is arranged on the construction platform (31) according to the construction requirement, and the vertical support (33) is welded and connected at the lower end of the construction platform (31) for fixation.

[0046] Among them, the steel casing positioning step of step four and the surrounding purlin (11) assembly and down step in step three, the before and after relationship of the two can be determined by the site construction requirement.

[0047] Step five, steel sheet pile (1) hole construction: each positioning sleeve (35) reserved through hole (29), as the sand backfill pipe (36) outlet, backfill pipe (36) connected with the pump, delivery backfill sand, backfill pipe (36) on the main pipe set valve control sand delivery, so as to realize the steel sheet pile (1) in the plug before the synchronous hole and backfill.

[0048] Step six, steel sheet pile (1) plug: the vibration hammer is used to plug the steel sheet pile, and butter must be uniformly brushed on the lock position before plugging to improve the lubrication degree and facilitate the insertion and extraction; the same steel sheet pile (1) wall body is fixed through the lap joint groove (2); the connection of different prefabricated steel sheet piles (1) adopts the lock type connection, the steel sheet pile (1) side is welded with the connecting edge groove steel (20), the edge groove steel (20) is welded with the fixed connecting plate (21) to strengthen the fixed connection; the edge groove steel (20) away from the steel sheet pile (1) side is welded with a plurality of fixed supports (39), and the lock steel pipe (16) is laid along the plurality of fixed supports (39), the lock steel pipe (16) is provided with the positioning groove (40), the lock steel pipe (16) is inserted into the lock steel (19) through the positioning groove (40), the gap between the lock steel pipe (16) and the lock steel (19) is provided with the water sealing filler (15); the adjacent lock steel pipe (16) bottom is welded with the edge steel plate (18), the lock steel (19) and the edge steel plate (18) are provided with the mortar (17), so as to form the lock type water stop system.

[0049] Step seven, cofferdam dredging to bottom concrete bottom elevation: after the steel sheet pile is folded, the secondary foundation pit is excavated and sucked to the design elevation, the steel casing (12) underwater cleaner and high pressure water gun are used to clean the outer wall of the steel casing (12) within the thickness of the bottom concrete, the web plate and the root of the steel sheet pile (1).

[0050] Step eight, installation of hopper (50) positioning device: the through hole of the hopper (50) is reserved on the pressure bearing plate (49), the hopper (50) positioning device is symmetrically arranged on both sides of the through hole, the arc-shaped positioning block (42) is arranged above the through hole and overlaps with the arc of the through hole, the rear side is welded with the connecting block (58), the connecting block (58) is welded with the fixed block (59), the bolt is arranged on the fixed block (59) and connected with the pressure bearing plate (49), so as to realize the accurate positioning of the hopper (50).

[0051] Step nine, bottom concrete pouring: each steel casing (12) is connected to the specified design elevation by flange (53), the top of steel casing (12) is welded to connect the assembled telescopic knee bracket (10), the pressure plate (49) is welded on the assembled telescopic knee bracket (10), thus forming the concrete pouring platform; the hopper (50) is arranged above the pressure plate (49), the outer support (47) is welded around the hopper (50), the upper support (43) is welded on the top of the hopper (50), the positioning cylinder (44) is arranged on the upper support (43), the connecting column (45) is provided with a thread at the upper end and is screwed with the positioning cylinder (44), and the lower end is provided with the rope (48) connected with the water stop ball (60); the water stop ball (60) is hung at the end of the discharge pipe (51), when the amount of concrete (46) meets the bottom sealing requirement, the connecting column (45) is unscrewed, the water stop ball (60) extrudes the water in the discharge pipe (51) under the pressure of the concrete (46), so that the concrete (46) is not mixed with the water in the pipe, and the diameter of the water stop ball (60) is slightly smaller than that of the discharge pipe (51), so that the water stop ball (60) can smoothly pass through the discharge pipe (51), thus completing the construction of the cast-in-place concrete bottom plate (52).

[0052] Step ten, pumping and pile cap construction: after the strength of the concrete reaches the standard, pumping, cutting off the steel casing (12), breaking the pile head, and carrying out the pile cap operation; if it is found that the steel sheet pile (1) leaks during the bottom sealing and pumping construction process, quick leak stopping measures are taken; the strip-shaped waterproof film (23) with a width of about 300mm is arranged on both sides of the steel sheet pile (1), the waterproof film (23) is knotted at both ends to form the film knot (26) which is fixed at the end of the two telescopic rods (24), and the film knot (26) wraps the falling block (25) arranged at the end of the telescopic rod (24); the operator inserts the two telescopic rods (24) into the riverbed at the same time, when the telescopic rod (24) is difficult to insert, the falling block (25) is lowered by pressing the button (22) at the top of the telescopic rod (24), the telescopic rod (24) is pulled out, the waterproof film (23) is left in the riverbed, and the film at the lock opening of the steel sheet pile (1) is pulled tight and straight, so that the leakage is prevented.

[0053] Step eleven, steel sheet pile (1) cofferdam removal: after the water in the pile cap and the related construction process are completed, the inner support removal work is completed in the order from bottom to top; after the internal support system of the cofferdam is completely removed, the wall body is unlocked by pulling out the lock buckle steel (19) with a crane, and the steel sheet pile (1) is quickly removed; before the steel sheet pile is actually pulled out, the pulling time and sequence are comprehensively analyzed according to the actual situation on site.

[0054] The application further discloses a water-bearing platform steel cofferdam, which is obtained according to the construction method of the water-bearing platform steel cofferdam, and comprises a set-puzzle type telescopic bracket support, adopts a steel sheet pile (1) cofferdam reverse construction method, sets a steel casing (12) positioning device, adopts a steel casing (12) hole guiding and synchronous backfilling technology, adopts a lock type connecting water stop system for the steel sheet pile (1), sets a steel sheet pile (1) quick leak stopping system, sets a hopper (50) positioning device and adopts a steel cofferdam cast-in-situ concrete bottom sealing technology.

[0055] The application is not limited to the above-mentioned best mode, and anyone can derive other various forms of products under the inspiration of the application, but regardless of any change in shape or structure, any technical solution with the same or similar technical solution as the application falls within the protection scope of the application.

Claims

1. A construction method for an underwater platform steel cofferdam, characterized in that: The following steps are involved: Step 1: Construction preparation; Step 2: Install the assembled telescopic bracket (10): connect the end of the horizontal fixing member (57) to the beginning of the vertical fixing member (54), and set an adjustable diagonal brace (55) between the horizontal fixing member (57) and the vertical fixing member (54); Step 3, assembling and lowering the purlin (11): arranging an assembled telescopic bracket (10) on the steel casing (12), and arranging the assembled steel enclosure on the top of the assembled telescopic bracket (10), and enclosing a plurality of steel casings (12) by a plurality of steel enclosures to form a purlin (11); arranging a plurality of fixed bases (3) on the purlin (11), and using the plurality of fixed bases (3) to connect the diagonal braces (13) and the straight braces (14) in pairs, thereby forming the first purlin (11); A modular telescopic bracket (10) is provided at a designated position of the steel casing (12), and a second purlin (11) is arranged in the same manner; a suspender (7) is provided on the load-bearing beam (6) to connect the assembled first and second purlins (11), the modular telescopic bracket (10) is folded, and the purlin (11) is hoisted or lowered as a whole to a designated position by a jack (9); after the steel sheet pile (1) is inserted and driven, a force transmission plate (41) is connected between the purlin (11) and the steel sheet pile (1); Step 4, installation of the steel casing (12) positioning device: the first limiting rod (30) and the second limiting rod (32) are connected to form a first-layer horizontal bracket; the positioning sleeve (35) is symmetrically connected to the fixed wing plate (28) on both sides; the fixing screw (27) passes through the reserved hole of the fixed wing plate (28) and is connected to the second limiting rod (32); the second limiting rod (32) is connected to the horizontal fixing plate (34) through a plurality of vertical fixing plates (37) to form a second-layer horizontal bracket, and the second-layer horizontal bracket is also fixed to the positioning sleeve (35) through the fixing screw (27); the two-layer steel casing (12) positioning device is assembled in this way and arranged on the construction platform (31), and the lower end of the construction platform (31) is connected to the vertical support (33) for fixation; Step 5, construction of steel sheet pile (1) lead hole: a through hole (29) is reserved on each positioning sleeve (35) as the outlet of the sand backfill pipe (36), the backfill pipe (36) is connected to a pump to transport the backfill sand, and a valve is set on the main pipe of the backfill pipe (36) to control the transportation of the sand, so as to achieve the simultaneous lead hole and backfill of the steel sheet pile (1) before driving; Step 6, steel sheet pile (1) insertion: a vibrating hammer is used to insert the steel sheet pile, and the prefabricated same steel sheet pile (1) is fixed between the wall body through the overlapping groove (2); the connection of different prefabricated steel sheet piles (1) adopts a lock-type connection, one side of the steel sheet pile (1) is connected to the edge sealing channel steel (20), and the edge sealing channel steel (20) and the steel sheet pile are fixed with a connecting plate (21); the side of the edge sealing channel steel (20) away from the steel sheet pile (1) is connected to a plurality of fixed brackets (39), and a lock-type steel pipe (16) is laid along the plurality of fixed brackets (39), and a positioning groove (40) is provided on the lock-type steel pipe (16), and the lock-type steel (19) is inserted through the positioning groove (40); thereby forming a lock-type water-stop system; Step 7: Desilting the cofferdam to the bottom elevation of the bottom concrete: After the steel sheet piles (1) are driven and closed, the secondary foundation pit is excavated and the sludge is sucked to the design elevation, and the outer wall of the steel casing (12), the web and the root of the steel sheet piles (1) within the thickness of the bottom concrete are cleaned; Step eight, installation of the hopper (50) positioning device: a through hole for the hopper (50) is reserved on the pressure plate (49), and the hopper (50) positioning device is symmetrically arranged on both sides of the through hole, wherein the front side of the arc-shaped positioning block (42) is arranged above the through hole and overlaps with the arc of the through hole, and the rear side is fixed with the connecting block (58), and the connecting block (58) is connected to the fixing block (59), and the fixing block (59) is connected to the pressure plate (49), thereby achieving accurate positioning of the hopper (50); Step 9, bottom sealing concrete pouring: each steel casing (12) is extended to the specified design elevation through the flange (53), the top of the steel casing (12) is connected to the assembled telescopic bracket (10), and the upper part of the assembled telescopic bracket (10) is connected to the pressure plate (49), thereby forming a concrete pouring platform; Step 10, pumping and foundation construction: After the concrete strength reaches the standard, pump out the water, cut off the steel casing (12), break the pile head, and carry out foundation operation; if the steel sheet pile (1) is found to be leaking during the bottom sealing and pumping construction process, take quick leakage prevention measures; set strip waterproof film (23) on both sides of the steel sheet pile (1), tie knots at both ends of the waterproof film (23) to form film knots (26) and fix them on the ends of the two telescopic rods (24), and the film knots (26) wrap around the falling blocks (25) set at the ends of the telescopic rods (24); insert the two telescopic rods (24) into the riverbed at the same time, and when the telescopic rods (24) are difficult to insert, press the button (22) on the top of the telescopic rod (24) to lower the falling block (25), pull out the telescopic rod (24), leave the waterproof film (23) in the riverbed, and tighten and straighten the film at the lock mouth of the steel sheet pile (1); Step 11, steel sheet pile (1) cofferdam removal: After the underwater foundation and related construction procedures are completed, the internal support removal work is completed in a bottom-up order; after the internal support system of the cofferdam is completely removed, the locking steel (19) is pulled out by a crane to unlock the wall and remove the steel sheet pile (1).

2. The construction method of the underwater platform steel cofferdam according to claim 1 is characterized in that: A vertical fixing member (54) is provided on the center line of each steel casing (12), an adjustment groove (56) is provided at the beginning of the horizontal fixing member (57), and one end of the adjustable diagonal brace (55) is fixed in the adjustment groove (56).

3. The construction method of the underwater platform steel cofferdam according to claim 1 is characterized in that: Pressure bases (5) are respectively provided at the upper ends of the plurality of steel casings (12), and reinforcing ribs (4) are connected at the connection positions of the pressure bases (5) and the steel casings (12); at least two load-bearing beams (6) are provided above the pressure bases (5), and the load-bearing beams (6) are simultaneously placed on the plurality of steel casings (12), and a connecting rod (8) is arranged between two adjacent load-bearing beams (6).

4. The construction method of the underwater platform steel cofferdam according to claim 1 is characterized in that: A connecting column (38) is connected between the first purlin (11) and the second purlin (11) to form a structural whole.

5. The construction method of underwater platform steel cofferdam according to claim 1, characterized in that: The center of the positioning sleeve (35) at the first-layer horizontal support and the center of the positioning sleeve (35) at the second-layer horizontal support are located on the same vertical axis.

6. The construction method of underwater platform steel cofferdam according to claim 1, characterized in that: A watertight filler (15) is provided in the gap between the locking steel pipe (16) and the locking steel (19).

7. The construction method of underwater platform steel cofferdam according to claim 1, characterized in that: The bottoms of adjacent locking steel pipes (16) are connected to edge-sealing steel plates (18), and mortar (17) is provided between the locking steel (19) and the edge-sealing steel plates (18).

8. The construction method of underwater platform steel cofferdam according to claim 1, characterized in that: The hopper (50) is arranged above the pressure plate (49), and the hopper (50) is connected to the outer bracket (47) on all sides. The top of the hopper (50) is connected to the upper bracket (43), and a positioning cylinder (44) is arranged on the upper bracket (43). The upper end of the connecting column (45) is connected to the positioning cylinder (44), and the lower end is provided with a rope (48) connected to the water-blocking ball (60); the water-blocking ball (60) is hung at the end of the discharge pipe (51). When the amount of concrete (46) prepared meets the bottom sealing requirement, the connecting column (45) is unscrewed, and the water-blocking ball (60) squeezes out the water in the discharge pipe (51) under the pressure of the concrete (46), and the diameter of the water-blocking ball (60) is slightly smaller than that of the discharge pipe (51).

9. An underwater platform steel cofferdam, characterized by: The invention is obtained by the construction method of the underwater foundation steel cofferdam according to any one of claims 1 to 8.

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