Water conservancy cofferdam anti-seepage structure and anti-seepage method

Abstract

This invention belongs to the field of cofferdam engineering technology, and particularly relates to a seepage prevention structure and method for water conservancy cofferdams. It solves the problem that existing steel sheet pile cofferdams are prone to extensive damage to the geomembrane under external fluctuation pressure during use. The invention includes multiple steel plates connected end-to-end. One side of each steel plate has a retaining strip with a sealing strip, and the other side has a groove. A sinkhole is located on the side of the retaining strip away from the steel plate, and a pusher plate is located within the sinkhole. A top plate is located within the sinkhole inside the pusher plate. When the top plate moves upward, it causes the pusher plate to move outward from the sinkhole, causing the sealing strip to press against the inner wall of the groove. A sinkhole is opened at the top of each steel plate, and a float is installed within the sinkhole. The float is sealed to the inner wall of the sinkhole. An inlet is opened on the inner wall of the sinkhole below the float, extending to the outer wall of the steel plate. When liquid columns of different heights are injected into the sinkhole above the float, the float can exert different magnitudes of thrust on the top plate under the action of the hydraulic pressure difference between the upper and lower end faces.

Description

Technical Field

[0001] This invention belongs to the field of cofferdam construction technology, and particularly relates to a seepage prevention structure and method for cofferdams in water conservancy projects. Background Technology

[0002] In water conservancy construction, cofferdams are often used to create a favorable construction environment. Currently, steel sheet pile cofferdams are the most commonly used type. During construction, grease is first applied to the interlocking parts of the steel sheet piles, and then the steel sheet piles are driven into the riverbed one by one using a pile driver. An internal support structure and geomembrane are also added. However, whether constructing on the sea surface, in a river, or in soil, it is impossible to avoid the pressure of fluctuating changes on the steel sheet piles, such as the impact of ocean waves, the impact of upstream river water, and the vibration of passing vehicles. Even if the cofferdam has internal support, it will still undergo slight deformation under fluctuating pressure changes, which will lead to damage to the geomembrane. Moreover, as the project progresses, the geomembrane damage rate continues to increase, and the workload of seepage prevention and maintenance becomes increasingly large. Therefore, improving the seepage prevention structure of cofferdams remains an ongoing research and development process. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a cofferdam seepage prevention structure and method that can maintain a seal for a long time under fluctuating pressure.

[0004] The technical solution comprises multiple steel plates connected end-to-end to form a circular cofferdam. Each steel plate has a baffle bar on one side with a sealing strip, and a groove on the other side. The baffle bar on each steel plate can only be inserted vertically into the groove on the adjacent steel plate. A sinkhole is provided on the side of the baffle bar away from the steel plate, extending into the interior of the steel plate. A pusher plate is provided in the sinkhole, and a top plate is provided in the sinkhole inside the pusher plate. When the top plate moves upward, it can move the pusher plate out of the sinkhole, causing the sealing strip to be squeezed against the inner wall of the groove. A countersunk hole is opened at the top of the steel plate, and a float is provided in the countersunk hole. The float is sealed against the inner wall of the countersunk hole. An inlet is opened on the inner wall of the countersunk hole below the float, extending to the outer wall of the steel plate. When liquid columns of different heights are injected into the countersunk hole above the float, the float can provide different magnitudes of thrust to the top plate under the action of the hydraulic pressure difference between the upper and lower end faces.

[0005] In the above or some embodiments, the stop bar is a round rod, which is welded and fixed to the steel plate. The sealing strip is wrapped around the outside of the round rod. The cross-sectional shape of the groove is circular, and the inner diameter of the groove is equal to the outer diameter of the sealing strip, so that the stop bar with the sealing strip can be smoothly inserted into the groove. The circular limiting structure can allow angular rotation between two adjacent steel plates to form a circular cofferdam.

[0006] In the above or some embodiments, the top surface of the push plate is trapezoidal, and wedge blocks are fixed to both sides of the sink groove opening by bolts. The two inclined surfaces of the push plate are respectively attached to the inclined surfaces on the two wedge blocks. When the push plate moves outward from the sink groove, the wedge blocks cause the baffle to expand outward, thereby causing the sealing strip to be squeezed against the inner wall of the groove to achieve a sealing effect.

[0007] In the above or some embodiments, a pressure plate is provided in the groove inside the push plate. The two sides of the pressure plate are respectively attached to the push plate and the top plate, and the contact surface between the pressure plate and the push plate forms an acute angle with the contact surface between the pressure plate and the top plate. A pressing module is provided between the pressure plate and the steel plate. When the pressure plate moves downward in the groove, the pressure plate can make the push plate slide out of the groove. Then, when the top plate does not move upward, the pressing module generates a pre-tightening force between the sealing strip and the groove on the adjacent steel plate, providing a manual seal between the two adjacent steel plates.

[0008] In the above or some embodiments, the pressing module includes a pad block located in the settling groove and in contact with the top of the pressure plate. The pad block can slide on the top surface of the pressure plate. A through hole extending to the top surface of the steel plate is opened at the top of the settling groove. A lead screw is installed in the through hole and welded to the top of the pad block. A through groove is opened on the side wall of the steel plate, which is connected to the middle of the through hole. A lead screw nut coaxial with the lead screw is installed in the through groove. Since the pad block cannot rotate in the settling groove, when the lead screw nut is rotated, the lead screw will drive the pad block to move up and down, thereby causing the pressure plate to move downward, so that a pre-tightening force is generated between the sealing strip and the groove on the adjacent steel plate.

[0009] In the above or some embodiments, a rectangular groove is opened on the side wall of the steel plate opposite the water inlet. The sinking groove and the sinking hole are both connected to the rectangular groove. The length and width of the rectangular groove are greater than the length and width of the push plate, the pressure plate and the top plate. A cover plate is provided in the sinking groove. The cover plate is fixed to the steel plate by bolts, and a sealing gasket is provided between the cover plate and the steel plate. After the cover plate is removed, it is convenient to install and maintain in the sinking groove and the sinking hole, while avoiding water leakage in the sinking hole.

[0010] In the above or some embodiments, the outer wall of the float has multiple annular limiting grooves, and a sealing ring is fitted on the limiting grooves to achieve a sealing effect between the float and the inner wall of the sinkhole, preventing liquid below the float from entering above the float; and a clearance groove is provided between the sinkhole and the sinking tank, and a connecting plate is provided in the clearance groove. The two ends of the connecting plate are fixed to the float and the top plate respectively by bolts, so that when the float moves upward, it can drive the top plate to move upward.

[0011] In the above or some embodiments, the inner wall of the countersunk hole above the float has a liquid inlet that extends to the outside of the steel plate. The liquid inlet and the water inlet are located on the same side of the steel plate. A rubber plug is installed in the countersunk hole. The height of the rubber plug is greater than the diameter of the liquid inlet. A pull rod is fixed to the top of the rubber plug by bolts. When the rubber plug is at the same height as the liquid inlet by the pull rod, the rubber plug can close the liquid inlet. The rubber plug has multiple open circular holes. When the rubber plug is at different heights from the liquid inlet, the circular holes can allow the liquid below the rubber plug to flow to the top of the rubber plug. Multiple overflow ports are opened on the other side of the steel plate. The multiple overflow ports are all connected to the countersunk hole above the float and are at different heights. Each overflow port is equipped with a plunger. By removing the plungers in the overflow ports at different heights, the height of the liquid column above the float can be controlled.

[0012] In the above or some embodiments, a method for preventing seepage in a cofferdam for a water conservancy project is as follows: S1: Seal all overflow ports with the plunger, and at the same time lift the lever so that the rubber stopper is above the inlet.

[0013] S2: Rotate the lead screw nut on each steel plate to ensure that there is no squeezing between the pad and the pressure plate in each steel plate, and apply grease to the groove to reduce the insertion resistance; S3: Steel plates are driven symmetrically from upstream to downstream using a pile driver, and finally closed at the downstream end. The retaining strip of each steel plate is inserted into the groove of the adjacent steel plate. After the closure is completed, internal supports are erected inside the cofferdam. S4: Rotate the lead screw nut to expand and deform the baffle outward through the push plate, achieving initial manual sealing. Then press down the pull rod to seal the inlet with the rubber stopper. S5: Pump out the water inside the cofferdam and observe whether there is any seepage. If there is seepage, pull out the plunger on the overflow outlet in the seepage area from top to bottom until there is no more seepage. S6: If the sealing strip ages during use and causes leakage again, continue to pull out the rubber plug from top to bottom in the leakage area until leakage stops. S7: When dismantling the cofferdam, first seal all overflow ports with plungers, then pull the lever upwards to allow the liquid outside the cofferdam to flow through the round holes to the sinkhole above the float until the liquid level in the sinkhole is the same as the liquid level outside the cofferdam. S8: Rotate the lead screw nut to remove the pressure between the pad and the pressure plate, then pull out the steel plates one by one from the downstream side to complete the disassembly.

[0014] This technical solution has the following technical effects: 1. This solution sets a sealing strip on the retaining strip. After the retaining strip is inserted into the groove, rotating the screw nut will cause the push plate and wedge block to squeeze the retaining strip outward and deform it, achieving a preliminary sealing effect. There is no need to attach a large area of ​​geomembrane inside the cofferdam. The operation is convenient and the construction period is short.

[0015] 2. If leakage occurs due to external pressure fluctuations during the long-term use of the cofferdam, this solution can quickly improve the compression between the sealing strip and the inner wall of the groove by pulling out the plungers in the leakage area from top to bottom, thus restoring the sealing effect of the cofferdam. Compared with the situation where geomembranes crack extensively in the later stages, this solution can greatly reduce the subsequent seepage prevention work, which is conducive to saving costs and maintaining the construction environment inside the cofferdam.

[0016] 3. In this solution, the compression between the sealing strip and the groove is provided manually only during the initial sealing. The compression force required for subsequent sealing is provided by the pressure difference between the upper and lower parts of the float, which avoids the situation where the manpower is insufficient. At the same time, the contact surfaces between the pressure plate and the push plate and the contact surfaces between the pressure plate and the top plate are all force-saving levers, which helps to reduce the shear strength requirements of the connecting plate.

[0017] 4. In this scheme, two adjacent steel plates are connected by a circular retaining strip and a groove. Within the allowable range of the groove opening, the included angle between the two adjacent steel plates can be adjusted independently to realize the construction of circular cofferdams with different diameters.

[0018] Figure 1 This is a perspective view of a single steel plate of the present invention.

[0019] Figure 2 This is a perspective view of the two steel plates after they are joined together according to the present invention.

[0020] Figure 3 This is an exploded view of a single steel plate of the present invention.

[0021] Figure 4 This is a diagram showing the internal structure of the steel plate after the cover plate has been removed according to the present invention.

[0022] Figure 5 For the present invention Figure 2 Enlarged view of point A in the middle.

[0023] Figure 6 For the present invention Figure 4 Enlarged view of section B in the middle.

[0024] Figure 7 This is a part drawing of the steel plate after the cover plate is removed according to the present invention.

[0025] Figure descriptions: 1. Steel plate; 2. Baffle strip; 3. Sealing strip; 4. Groove; 5. Settling groove; 6. Push plate; 7. Top plate; 8. Countersunk hole; 9. Float; 10. Inlet; 11. Wedge block; 12. Pressure plate; 13. Pad block; 14. Through hole; 15. Lead screw; 16. Through groove; 17. Lead screw nut; 18. Rectangular groove; 19. Cover plate; 20. Sealing ring; 21. Relief groove; 22. Connecting plate; 23. Liquid inlet; 24. Rubber plug; 25. Pull rod; 26. Round hole; 27. Overflow port. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] A seepage prevention structure for a water conservancy project includes multiple steel plates 1 connected end to end to form a circular cofferdam. Each steel plate 1 has a baffle 2 on one side. The baffle 2 is a round rod and is welded and fixed to the steel plate 1. A sealing strip 3 is provided on the baffle 2. A groove 4 is provided on the other side. The cross-sectional shape of the groove 4 is circular, and the inner diameter of the groove 4 is equal to the outer diameter of the sealing strip 3, so that the baffle 2 with the sealing strip 3 can be smoothly inserted into the groove 4. The circular limiting structure allows for angular rotation between two adjacent steel plates 1 to form a circular cofferdam. A groove 5 is provided on the side of the baffle 2 away from the steel plate 1. The groove 5 extends into the interior of the steel plate 1. A push plate 6 is provided inside the groove 5. The top surface of the push plate 6 is trapezoidal. Wedge blocks 11 are fixed to both sides of the groove opening of the groove 5 by bolts. The two inclined surfaces on the push plate 6 are respectively attached to the inclined surfaces on the two wedge blocks 11. When the push plate 6 moves outward from the groove 5, the baffle 2 is deformed outward through the wedge blocks 11, which in turn causes the sealing strip 3 to be squeezed against the inner wall of the groove 4, thus achieving a sealing effect. A pressure plate 12 is provided in the recessed groove 5 inside the push plate 6, and a top plate 7 is provided in the recessed groove 5 inside the pressure plate 12. The two sides of the pressure plate 12 are respectively attached to the push plate 6 and the top plate 7, and the contact surface between the pressure plate 12 and the push plate 6 and the contact surface between the pressure plate 12 and the top plate 7 form an acute angle with the opening facing upward. A pad 13 is provided above the pressure plate 12. The pad 13 is located in the recessed groove 5 and contacts the top of the pressure plate 12. A through hole 14 is opened at the top of the recessed groove 5, extending to the top surface of the steel plate 1. A lead screw 15 is provided in the through hole 14 and is welded to the top of the pad 13. A through groove is opened on the side wall of the steel plate 1. 16. The through groove 16 is connected to the middle of the through hole 14. The through groove 16 is provided with a screw nut 17 coaxial with the screw 15. Since the pad 13 cannot rotate in the recess 5, when the screw nut 17 is rotated, the screw 15 will drive the pad 13 to move up and down. When the pad 13 moves down, the pressure plate 12 and the push plate 6 will generate a pre-tightening force between the sealing strip 3 and the groove 4 on the adjacent steel plate 1, providing a manual seal between the two adjacent steel plates 1. When the top plate 7 moves up, the pressure plate 12 can move the push plate 6 out of the recess 5, so that the sealing strip 3 and the inner wall of the groove 4 are further squeezed. A countersunk hole 8 is formed at the top of the steel plate 1, and a float 9 is installed inside the countersunk hole 8. The float 9 is fitted and sealed to the inner wall of the countersunk hole 8. An inlet 10 is formed on the inner wall of the countersunk hole 8 below the float 9, extending to the outer wall of the steel plate 1. A rectangular groove 18 is formed on the side wall of the steel plate 1 opposite to the inlet 10. The countersunk groove 5 and the countersunk hole 8 are both connected to the rectangular groove 18. The length and width of the rectangular groove 18 are greater than the length and width of the push plate 6, the pressure plate 12, and the top plate 7. A cover plate 19 is provided inside the countersunk groove 5. The cover plate 19 is fixed to the steel plate 1 by bolts, and a sealing gasket is provided between the cover plate 19 and the steel plate 1. This allows for easy installation and maintenance in the countersunk groove 5 and the countersunk hole 8 after the cover plate 19 is removed, while preventing leakage in the countersunk hole 8. Multiple annular limiting grooves are opened on the outer wall of the float 9, and sealing rings 20 are fitted on the limiting grooves to achieve a sealing effect between the float 9 and the inner wall of the counterbore 8, preventing liquid below the float 9 from entering above the float 9; and a clearance groove 21 is opened between the counterbore 8 and the countersink 5, and a connecting plate 22 is provided in the clearance groove 21. The two ends of the connecting plate 22 are fixed to the float 9 and the top plate 7 respectively by bolts, so that when the float 9 moves upward, it can drive the top plate 7 to move upward. A liquid inlet 23 extending through to the outside of the steel plate 1 is opened on the inner wall of the countersunk hole 8 above the float 9. The liquid inlet 23 and the water inlet 10 are located on the same side of the steel plate 1. A rubber plug 24 is installed inside the countersunk hole 8. The height of the rubber plug 24 is greater than the diameter of the liquid inlet 23. A pull rod 25 is fixed to the top of the rubber plug 24 by bolts. When the rubber plug 24 is at the same height as the liquid inlet 23 by the pull rod 25, the rubber plug 24 can close the liquid inlet 23. The rubber plug 24 has multiple through-holes 26. When the rubber stopper 24 and the liquid inlet 23 are at different heights, the round hole 26 allows the liquid below the rubber stopper 24 to flow to the top of the rubber stopper 24. Multiple overflow ports 27 are opened on the other side of the steel plate 1. The multiple overflow ports 27 are all connected to the sinkhole 8 above the float 9 and are at different heights. Each overflow port 27 is equipped with a plunger. By removing the plungers in the overflow ports 27 at different heights, the height of the liquid column above the float 9 can be controlled, and the pressure difference between the upper and lower parts of the float 9 can be used to provide an upward thrust for the top plate 7.

[0029] One method for preventing seepage in cofferdams used in water conservancy projects is as follows: S1: Seal all overflow ports 27 with the plunger, and at the same time lift the lever 25 so that the rubber stopper 24 is above the liquid inlet 23.

[0030] S2: Rotate the lead screw nut 17 on each steel plate 1 to ensure that there is no squeezing between the pad 13 and the pressure plate 12 in each steel plate 1, and apply grease to the groove 4 to reduce the insertion resistance; S3: Steel plates 1 are driven symmetrically from upstream to downstream using a pile driver, and finally closed at the downstream end. The retaining strips 2 of each steel plate 1 are inserted into the grooves 4 of the adjacent steel plate 1. After the closure is completed, internal supports are erected inside the cofferdam. S4: Rotate the lead screw nut 17 to expand and deform the baffle 2 outward through the push plate 6 to achieve initial manual sealing. Then press down the pull rod 25 to seal the inlet 23 with the rubber plug 24. S5: Pump out the water inside the cofferdam and observe whether there is any seepage. If there is seepage, pull out the plunger on the overflow outlet 27 in the seepage area from top to bottom until there is no more seepage. S6: If the sealing strip 3 ages during use and causes leakage again, continue to pull out the rubber plug 24 from top to bottom in the leakage area until leakage stops. S7: When dismantling the cofferdam, first seal all overflow ports 27 with plungers, then pull up the tie rod 25 so that the liquid outside the cofferdam can flow through the round hole 26 to the sinkhole 8 above the float 9 until the liquid level in the sinkhole 8 is the same as the liquid level outside the cofferdam. S8: Rotate the lead screw nut 17 to remove the pressure between the pad 13 and the pressure plate 12, and then pull out the steel plate 1 from the downstream side to complete the disassembly.

[0031] When using this technical solution, first, all overflow ports 27 are sealed by the plunger, then the pull rod 25 is pulled upwards. The pull rod 25 drives the rubber plug 24 to move above the liquid inlet 23, so that the liquid inlet 23 is connected to the countersunk hole 8. Then, the screw nut 17 on each steel plate 1 is rotated to ensure that there is no squeezing between the pad block 13 and the pressure plate 12 in each steel plate 1. Under the weight of the pressure plate 12, the pressure between the push plate 6 and the wedge block 11 is not enough to deform the baffle 2, so as to avoid the baffle 2 expanding outwards and causing the baffle 2 to be unable to be smoothly inserted into the groove 4 on the adjacent steel plate 1. Finally, grease is applied to the groove 4 on each steel plate 1 to reduce the resistance when driving the steel plate 1 downwards. The driving process is the same as the existing steel plate 1 pile driving method, driving symmetrically from upstream to downstream and closing at the downstream, adding an internal support structure. It should be noted that after multiple steel plates 1 are combined into a circular cofferdam, because the rubber plug 24 has a circular hole 26, the liquid level in the sinkhole 8 is the same as the liquid level outside the circular cofferdam. The buoyancy of the float 9 is equal to the weight of the same volume of water. At this time, the buoyancy of the float 9 is insufficient to move the top plate 7. Therefore, in order to avoid the sealing strip 3 and the side wall of the groove 4 not being sealed properly, a preliminary manual sealing is required. The screw nut 17 on each steel plate 1 is rotated one by one to make the pad 13 move downward to press the pressure plate 12. Since the top plate 7 cannot move, the pressure plate 12 can only press the push plate 6 to move outward to the side of the sinkhole 5, and then the baffle 2 is initially deformed by the wedge block 11 to complete the preliminary sealing. The pressure rod is then pressed down, causing the side wall of the rubber stopper 24 to seal the inlet 23. At this point, the liquid on the upper and lower sides of the float 9 has been separated, and the water pump begins to pump out the accumulated water in the cofferdam. During the pumping process, the cofferdam is observed for any leakage. If there is no leakage, no action is needed. If there is leakage, the baffle 2 corresponding to the leakage gap will continue to expand and deform outward. At this point, the deformation of the baffle 2 only occurs within the groove 4 and has no effect on the size of the cofferdam. The baffle 2 is then expanded by pulling out the plunger in the overflow port 27 from top to bottom, causing the liquid column height in the countersunk hole 8 above the float 9 to continuously decrease. The pressure on the upper end of the float 9 continuously decreases, while the pressure on the lower end of the float 9 remains unchanged. Therefore, the float 9 will be subjected to an upward thrust. As the thrust increases, it causes the top plate 7 to move upward, while the pressure plate 12 cannot move upward due to the self-locking action of the screw 15 and the obstruction of the pad 13. The top plate 7 can only push the pressure plate 12 towards the opening of the sink 5, which in turn causes the push plate 6 to continue moving outward from the sink 5, thereby further expanding the baffle 2 until no more leakage occurs. During this process, no manual force is required; it can be achieved simply by changing the height of the liquid column in the sink hole 8. At the same time, since the contact surface between the pressure plate 12 and the push plate 6 forms an acute angle with the contact surface between the pressure plate 12 and the top plate 7, the force of the push plate 6 moving outward from the sink 5 is greater than the buoyancy applied by the float 9, which helps to reduce the shear strength requirement of the connecting plate 22. During use, the external pressure is constantly fluctuating, so the cofferdam itself will inevitably undergo slight deformation. The sealing strip 3 is repeatedly squeezed and stretched. Under long-term action, the sealing strip 3 ages and its elasticity weakens, which may cause leakage again. At this time, the plungers in the leakage area are pulled out from top to bottom in sequence, so that the upward thrust on the float 9 is further increased, which in turn pushes the push plate 6 to further squeeze the baffle 2 outward to compensate for the insufficient pressure caused by the aging of the sealing strip 3, and continue to maintain the sealing state, thereby reducing the later maintenance cost of the cofferdam. When the cofferdam needs to be dismantled after construction is completed, the pull rod 25 is lifted again, so that the liquid outside the cofferdam passes through the inlet 23 and the round hole 26 into the sinkhole 8. The liquid in the sinkhole 8 is connected with the outside liquid again, and the buoyancy of the float 9 is equal to the weight of the displaced water. The top plate 7 moves downward under the action of internal compression and gravity. Then the screw nut 17 is turned to release the pressure applied to the push plate 6 during the initial sealing. The baffle 2 is restored to its state before use, which makes it convenient to pull out the steel plate 1 in sequence. When maintenance is required, unscrew the bolts, remove the cover plate 19 and wedge block 11, first remove the pressure plate 12 from the rectangular groove 18, then remove the push plate 6, then remove the bolts on the connecting plate 22, remove the top plate 7 and connecting plate 22, remove the pull rod 25 and rubber plug 24, then remove the float 9 from the opening of the countersunk hole 8, then turn the screw nut 17 to move the screw 15 into the countersunk groove 5, and then remove the screw 15 and screw nut 17 to complete the disassembly of all parts on the steel plate 1, replace and maintain them, and then reassemble them. Even if the baffle 2 undergoes plastic deformation, causing the baffle 2 to be unable to be smoothly inserted into the groove 4 during installation, the baffle 2 can be restored by tapping it. In subsequent use, it can still expand and deform outward by the extrusion of the push plate 6 to achieve a sealing effect. It is worth noting that a wrench or a lever can be used to rotate the lead screw nut 17. For example, the lead screw nut 17 can be shaped as a hexagonal prism and rotated with the help of a wrench, or a relief hole can be made on the lead screw nut 17 and the lever can be inserted into the relief hole to reduce the rotation resistance of the lead screw nut 17.

Claims

1. A seepage prevention structure for a cofferdam in a water conservancy project, characterized in that, It includes multiple steel plates (1) connected end to end. Each steel plate (1) has a baffle (2) on one side, a sealing strip (3) on the baffle (2), and a groove (4) on the other side. The baffle (2) on each steel plate (1) can and can only be inserted into the groove (4) on the adjacent steel plate (1) in a vertical direction. A groove (5) is provided on the side of the baffle (2) away from the steel plate (1). The groove (5) penetrates into the interior of the steel plate (1). A push plate (6) is provided in the groove (5). A top plate (7) is provided in the groove (5) inside the push plate (6). (7) When moving upward, the push plate (6) can move out of the sink (5) and squeeze the sealing strip (3) against the inner wall of the groove (4); the top of the steel plate (1) has a sink hole (8), and a float (9) is provided in the sink hole (8). The float (9) is sealed against the inner wall of the sink hole (8). The inner wall of the sink hole (8) below the float (9) has an inlet (10) that penetrates to the outer wall of the steel plate (1). When liquid columns of different heights are injected into the sink hole (8) above the float (9), the float (9) can give the top plate (7) different thrusts under the action of the hydraulic pressure difference between the upper and lower end faces.

2. The seepage-proof structure according to claim 1, characterized in that, The baffle (2) is a round rod, which is welded and fixed to the steel plate (1). The sealing strip (3) is wrapped around the outside of the round rod. The cross-sectional shape of the groove (4) is circular, and the inner diameter of the groove (4) is equal to the outer diameter of the sealing strip (3).

3. The seepage-proof structure according to claim 1, characterized in that, The top surface of the push plate (6) is trapezoidal, and wedge blocks (11) are fixed on both sides of the groove opening of the sink (5) by bolts. The two inclined surfaces on the push plate (6) are respectively attached to the inclined surfaces on the two wedge blocks (11).

4. The seepage-proof structure according to claim 1, characterized in that, A pressure plate (12) is provided in the sink trough (5) inside the push plate (6). The two sides of the pressure plate (12) are respectively attached to the push plate (6) and the top plate (7). The contact surface between the pressure plate (12) and the push plate (6) and the contact surface between the pressure plate (12) and the top plate (7) form an acute angle with the opening facing upward. A pressing module is provided between the pressure plate (12) and the steel plate (1). When the pressing module causes the pressure plate (12) to move downward in the sink trough (5), the pressure plate (12) can make the push plate (6) slide out of the sink trough (5).

5. The seepage-proof structure according to claim 4, characterized in that, The pressing module includes a pad (13), which is located in the sink (5) and contacts the top of the pressure plate (12). The pad (13) can slide on the top surface of the pressure plate (12). The top of the sink (5) has a through hole (14) that extends to the top surface of the steel plate (1). A lead screw (15) is provided in the through hole (14). The lead screw (15) is welded to the top of the pad (13). A through groove (16) is provided on the side wall of the steel plate (1). The through groove (16) is connected to the middle of the through hole (14). A lead screw nut (17) coaxial with the lead screw (15) is provided in the through groove (16).

6. The seepage-proof structure according to claim 4, characterized in that, A rectangular groove (18) is opened on the side wall of the steel plate (1) opposite the water inlet (10). The sinking trough (5) and the sinking hole (8) are connected to the rectangular groove (18). The length and width of the rectangular groove (18) are greater than the length and width of the push plate (6), the pressure plate (12) and the top plate (7). A cover plate (19) is provided in the sinking trough (5). The cover plate (19) is fixed to the steel plate (1) by bolts, and a sealing gasket is provided between the cover plate (19) and the steel plate (1).

7. The seepage-proof structure according to claim 1, characterized in that, The outer wall of the float (9) has multiple annular limiting grooves, and a sealing ring (20) is fitted on the limiting groove; and a relief groove (21) is opened between the countersunk hole (8) and the countersunk groove (5), and a connecting plate (22) is provided in the relief groove (21). The two ends of the connecting plate (22) are fixed to the float (9) and the top plate (7) respectively by bolts.

8. The seepage-proof structure according to claim 1, characterized in that, The inner wall of the countersunk hole (8) above the float (9) has a liquid inlet (23) that extends to the outside of the steel plate (1). The liquid inlet (23) and the water inlet (10) are located on the same side of the steel plate (1). A rubber plug (24) is provided inside the countersunk hole (8). The height of the rubber plug (24) is greater than the diameter of the liquid inlet (23). A pull rod (25) is fixed to the top of the rubber plug (24) by bolts. When the rubber plug (24) is made to be at the same height as the liquid inlet (23) by the pull rod (25), the rubber plug (24) 24) It can seal the inlet (23). The rubber stopper (24) has multiple open holes (26) that are open from top to bottom. When the rubber stopper (24) and the inlet (23) are at different heights, the holes (26) can allow the liquid below the rubber stopper (24) to flow to the top of the rubber stopper (24). The other side of the steel plate (1) has multiple overflow ports (27). The multiple overflow ports (27) are all connected to the sinkhole (8) above the float (9) and are at different heights. Each overflow port (27) is equipped with a plunger.

9. According to any one of claims 1-8, the seepage prevention method of the scheme is as follows: S1: Seal all overflow ports (27) with the plunger, and at the same time lift the lever (25) so that the rubber stopper (24) is above the liquid inlet (23); S2: Rotate the screw nut (17) on each steel plate (1) to ensure that there is no squeezing between the pad (13) and the pressure plate (12) in each steel plate (1), and apply grease in the groove (4) to reduce the insertion resistance; S3: Steel plates (1) are driven symmetrically from upstream to downstream using a pile driver, and finally closed at the downstream end. The retaining strip (2) of each steel plate (1) is inserted into the groove (4) of the adjacent steel plate (1). After the closure is completed, an internal support is erected inside the cofferdam. S4: Rotate the screw nut (17) to expand and deform the baffle (2) outward through the push plate (6) to achieve initial manual sealing, and then press down the pull rod (25) to seal the inlet (23) with the rubber plug (24). S5: Drain the water inside the cofferdam and observe whether there is any seepage. If there is seepage, pull out the plunger on the overflow port (27) in the seepage area from top to bottom until there is no more seepage. S6: If the sealing strip (3) ages during use and causes leakage again, continue to pull out the rubber plug (24) from top to bottom in the leakage area until leakage stops; S7: When dismantling the cofferdam, first seal all the overflow ports (27) with the plunger, then pull up the pull rod (25) so that the liquid outside the cofferdam can flow through the round hole (26) to the sinkhole (8) above the float (9) until the liquid height in the sinkhole (8) is the same as the liquid height outside the cofferdam. S8: Rotate the lead screw nut (17) to remove the pressure between the pad (13) and the pressure plate (12), and then pull out the steel plate (1) from the downstream side to complete the disassembly.

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