Underwater construction system and method for highway bridge

Abstract

The invention discloses a highway bridge underwater construction system and method, and belongs to the technical field of highway bridge underwater construction. The invention aims to solve the problems that the existing underwater bottom sealing construction concrete is easy to have the defects of insufficient compactness, poor integrity and the like, the bearing capacity and the impermeability of a base soil body are weak, and construction potential safety hazards such as water burst, piping and the like are easy to cause. The construction system comprises a double-layer cofferdam, an inner supporting support, a concrete conveying assembly, a portal frame with an impact assembly and a drainage unit. During construction, a water stop enclosure structure is constructed through the double-layer cofferdam, after bottom sealing concrete is poured, under the plastic state before initial setting, a concrete bottom sealing layer, the bottom of the cofferdam and surrounding soil are synchronously compacted and reinforced through low-frequency vertical impact, and dynamic drainage and impact position regulation and control are matched. The compactness and the water stopping effect of the bottom sealing structure can be improved, the performance of a base soil body is enhanced, the construction safety risk is reduced, and the underwater construction quality of a bridge is guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of underwater construction technology for highway bridges, and specifically relates to an underwater construction system and method for highway bridges. Background Technology

[0002] With the continuous improvement of my country's highway transportation infrastructure network, the number of long-span highway bridge projects spanning rivers, seas, and lakes continues to grow. Underwater construction of bridge piers and abutment foundations is a core and critical aspect of such projects. The core technical challenge of underwater construction lies in constructing a closed retaining structure with reliable water-stopping performance and strong structural stability, while ensuring the compactness and impermeability of the base sealing structure. This provides a safe and dry working environment for subsequent bridge foundation construction, preventing quality and safety accidents such as cofferdam instability, base water inrush, piping, and settlement deformation during construction.

[0003] Currently, underwater construction of highway bridges generally adopts the cofferdam method. The mainstream cofferdam types include steel sheet pile cofferdams, steel caisson cofferdams, and concrete cofferdams. The conventional construction process is as follows: a cofferdam is driven or sunk in the target construction water area to form a closed retaining structure. The water inside the cofferdam is pumped out through the drainage system to lower the internal water level. The foundation is then cleaned. Underwater sealing concrete is then poured using the tremie method. After the sealing concrete reaches the design strength, the subsequent construction of the bridge piers and abutments is carried out.

[0004] Existing technologies commonly employ the tremie method for underwater bottom sealing concrete pouring. However, due to the complex underwater pouring environment, the concrete is prone to defects such as segregation, bleeding, honeycomb surface defects, and broken piles. This makes it difficult to meet the design requirements for the integrity, compactness, and water-stopping effect of the bottom sealing structure. Furthermore, conventional bottom sealing construction relies solely on the self-weight of the concrete to achieve adhesion with the foundation soil, which cannot compact and reinforce the riverbed soil at the bottom and around the cofferdam. The original soil at the foundation has insufficient bearing capacity and poor impermeability. During subsequent dewatering and superstructure construction, problems such as foundation heave, seepage channel penetration, and piping are highly likely to occur, threatening construction safety. Summary of the Invention

[0005] To address the problems existing in the prior art, a system and method for underwater construction of highway bridges are proposed.

[0006] The technical solution to the technical problem solved by the present invention is as follows: On the one hand, an underwater construction system for highway bridges is proposed, comprising: a cofferdam, which encloses and forms a construction space; a support frame, which is supported inside the cofferdam, with its sidewalls attached to the inner wall of the cofferdam to support it; a conveying assembly, which is mounted on the support frame and used to convey concrete to the construction surface to form a concrete sealing layer; a gantry frame, which is supported outside the cofferdam, with an impact assembly connected to the gantry frame, the impact end of which is connected to an impact plate for compacting the concrete sealing layer; and a drainage pipe for emptying the construction space, which is connected to a drainage pump.

[0007] Preferably, the cofferdam includes an outer dam body, an inner dam body is provided inside the outer dam body, and a support is provided inside the inner dam body; a filling cavity is formed between the outer dam body and the inner dam body, and the filling cavity is filled with graded sand and gravel.

[0008] Preferably, the conveying assembly includes a conveying pipe, and a connecting pulley frame is fitted over the conveying pipe, with the pulley frame connected to the inner wall of the support.

[0009] Preferably, the impact assembly includes a vertical slide rail disposed in the middle of the gantry, a movable frame connected to the vertical slide rail, a vertical impact hammer connected to the movable frame, and an impact plate connected to the bottom of the vertical impact hammer.

[0010] Preferably, a laser rangefinder is installed on the mobile frame to detect the distance between the mobile frame and the concrete sealing layer, and the operation of the winch is adjusted through the control module on the gantry.

[0011] On the other hand, an underwater construction method using the aforementioned underwater construction system for highway bridges is proposed, comprising the following steps: S1. Cofferdam Construction: Locate and lay out the target construction water area, and install the outer and inner cofferdam bodies in sequence to form a filling cavity by enclosing the two cofferdam bodies. Fill the filling cavity with graded sand and gravel in layers and compact it to form a water-stopping cofferdam structure. Install a support frame in the construction space so that the side walls of the support frame are attached to the inner wall of the inner cofferdam to form internal support. Erect a gantry frame on the stable foundation outside the cofferdam to complete the main construction system. S2. Initial Dewatering and Construction Surface Pretreatment: Start the drainage pump on the gantry and pump the water in the construction space to the outside through the drainage pipe until the water level drops below the preset level. Clean the silt, loose soil and debris at the bottom of the construction space and level the foundation soil. S3. Sealing Concrete Pouring Construction: The conveying pipeline is laid along the inner wall of the support, and the conveying pipeline is guided and limited by the pulley frame. Underwater concrete is continuously poured into the surface of the base soil through the conveying pipeline to form a complete concrete sealing layer at the bottom of the construction space. S4. Impact assembly installation: Install and adjust the impact assembly on the gantry, aligning the vertical impact hammer with the bottom impact plate in the center of the construction space, and adjust the stroke and initial impact distance of the impact hammer to complete the pre-impact preparation work. S5. Impact compaction: When the concrete sealing layer is in a plastic state before initial setting, start the vertical impact hammer and drive the impact plate to periodically impact the upper surface of the concrete sealing layer, so that the impact force spreads downward and around the concrete sealing layer, and simultaneously compacts and reinforces the soil at the bottom of the cofferdam and the soil around the side wall of the cofferdam. S6. Impact position adjustment and drainage: During the impact process, the moving frame is driven to rise and fall along the vertical slide rail by the winch, and the distance between the moving frame and the upper surface of the concrete sealing layer is detected in real time by the laser rangefinder, and the impact height and impact spacing of the impact plate are dynamically adjusted; at the same time, the drainage pump and drainage pipe continuously pump out the seepage water and concrete bleeding water in the construction space, so that the input end of the drainage pipe is always kept at the preset water level above the concrete sealing layer. S7. Compaction and Molding Acceptance: After the concrete sealing layer has solidified to the design strength, stop the dewatering and impact operations, and test the flatness, compactness and reinforcement effect of the concrete sealing layer and the base soil. After the acceptance is qualified, the sealing construction is completed and the subsequent bridge foundation construction process begins.

[0012] Preferably, both the outer and inner weirs are corrugated steel plate structures, which are inserted into the riverbed down to the bedrock layer using a vibrating device.

[0013] Preferably, the lower surface of the impact plate has an arc-shaped structure with a high center and low edges, so as to form a pressure wave that spreads outward when impacting the concrete sealing layer.

[0014] Preferably, the impact hammer drives the impact plate to impact the concrete sealing layer at an impact frequency of 0.02Hz-0.2Hz.

[0015] Preferably, the inlet end of the drainage pipe is located inside the inner weir, and the middle part of the drainage pipe is fixedly connected to the moving frame, so that the drainage pipe moves synchronously with the lifting and lowering of the moving frame, and its lower end is always located above the concrete sealing layer.

[0016] Compared with existing technologies, the above technical solution has the following advantages or beneficial effects: 1. By installing a hydraulic impact hammer and impact plate, low-frequency impact can be applied to the uncured concrete sealing layer, so that the impact force is evenly transmitted to the bottom and side walls of the cofferdam through the concrete, thereby compacting the bottom soil and reducing the pore seepage channels and reducing the amount of seepage.

[0017] 2. By setting up a movable frame and track, and cooperating with a winch and laser rangefinder, the impact plate can be continuously raised and lowered with the thickness of the concrete, ensuring that the impact covers the entire bottom sealing area and maintains the optimal impact position, thereby improving the uniformity of compaction and construction efficiency.

[0018] 3. By installing drainage pipes and drainage pumps, water above the sealing concrete can be continuously pumped out, preventing water accumulation from interfering with impact compaction, allowing the concrete to directly contact the impact plate, thereby enhancing the impact force transmission effect and improving the compaction and seepage resistance of the bottom of the cofferdam.

[0019] 4. By setting up a double-layer cofferdam and graded sand and gravel filling, a reverse filter structure can be formed at the side wall of the cofferdam, thereby reducing the groundwater seepage rate and improving the stability of the cofferdam, ensuring the safety and reliability of the construction space. By setting up supports and pulley frames, the concrete conveying pipeline can be supported and the concrete pouring process can be stabilized, so that the concrete sealing layer is formed continuously and evenly, effectively sealing the bottom of the cofferdam and ensuring the structural integrity of the bottom of the bridge pier or abutment foundation. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a schematic diagram of the front structure of the present invention; Figure 2 This is a schematic diagram of the structure at the rear side of the present invention; Figure 3 This is a schematic diagram of the outer weir structure of the present invention; Figure 4 This is a schematic diagram of the internal structure of the inner dam body of the present invention; Figure 5 This is a schematic diagram of the impact component structure of the present invention; Figure 6 This is a schematic diagram of the rear structure of the impact assembly of the present invention; Explanation of reference numerals in the attached figures: In the diagram: 1. Outer weir; 2. Inner weir; 3. Filling cavity; 4. Support; 5. Conveying pipe; 6. Pulley frame; 7. Concrete sealing layer; 8. Impact assembly; 801. Gantry frame; 802. Vertical slide rail; 803. Moving frame; 804. Vertical impact hammer; 805. Connecting flange; 806. Impact plate; 807. Winch; 808. Traveling trolley; 9. Laser rangefinder; 10. Drainage pump; 11. Drainage pipe. Detailed Implementation

[0022] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. The following disclosure provides many different embodiments or examples for implementing different structures of the invention. To simplify the disclosure of the invention, components and arrangements of specific examples are described below. Furthermore, reference numerals and / or letters may be repeated in different examples. This repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. It should be noted that the components illustrated in the drawings are not necessarily drawn to scale. Descriptions of well-known components and processing techniques and processes are omitted to avoid unnecessarily limiting the invention. Terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Please see Figures 1-6 This embodiment proposes an underwater construction system for highway bridges, applicable to the underwater construction of conventional highway bridge pier caps in inland waterways with riverbeds consisting of silty clay and gravel layers. It is suitable for the construction requirements of single pier caps and includes the following structure: The cofferdam consists of an outer cofferdam 1 and an inner cofferdam 2, both constructed using SP-IV type corrugated Larssen sheet piles. The outer cofferdam 1 has a designed outer diameter of 14m, and the inner cofferdam 2 has a designed inner diameter of 12m. A 1m wide annular filling cavity 3 is formed between the outer cofferdam 1 and the inner cofferdam 2. The filling cavity 3 is filled with continuously graded sand and gravel in layers. The graded sand and gravel is a mixture of 5-25mm crushed stone and medium-coarse sand at a mass ratio of 3:2, with a compaction degree of not less than 96%. EPDM water-stopping rubber strips are embedded at the interlocking joints of the outer cofferdam 1 and the interlocking cavities are filled with a butter-talcum powder water-stopping mixture. The sheet piles are driven to 8m below the riverbed using a vibratory hammer, which can be a hydraulic vibratory hammer. The bottom of the sheet piles is embedded at least 0.5m into the moderately weathered bedrock layer, forming a closed and water-stopping retaining structure.

[0024] Support 4: It adopts a ring-shaped cage truss structure, which matches the inner diameter of the inner dam 2; Support 4 includes vertical I-beam columns evenly distributed along the circumference. Adjacent columns are welded together with transverse circumferential connecting rods and diagonal support rods to form an integral truss. The bottom end extends to the riverbed base soil, and the top end is flush with the top elevation of the inner dam 2; Each column of Support 4 is welded with a steel plate-rubber composite bonding plate on its outer side. The outer surface of the bonding plate is completely bonded to the inner wall of the inner dam 2, forming a continuous circumferential support for the inner dam 2; Conveying components are installed on the inner side of the columns of Support 4.

[0025] Conveying assembly: includes conveying pipe 5 and pulley frame 6; conveying pipe 5 is made of DN150 seamless steel pipe, with a single section length of 3m, and is connected by flanges. The bottom end of conveying pipe 5 is flared outward to form an underwater casting guide flare, and the top end is connected to the discharge port of concrete conveying pump; conveying pipe 5 is fixed to support 4 by pulley frame 6. Pulley frame 6 includes clamps, which are bolted to the outer wall of conveying pipe 5 and are snapped onto support 4. Conveying pipe 5 can slide vertically within clamps to adjust its position. After tightening the clamp bolts, the conveying pipe 5 is fixed.

[0026] Gantry 801: Supported on a stable foundation in the riverbed outside the cofferdam, the top beam of gantry 801 is equipped with a transverse moving track, on which an electric traveling trolley 808 is installed. A vertical slide rail 802 is fixed to the side of the electric traveling trolley 808, which can move laterally along the beam with the traveling trolley 808 to cover the entire area of ​​the circular construction space. A winch 807 is fixed on the top beam of gantry 801. The wire rope of the winch 807 is fixedly connected to the top of the moving frame 803 through a fixed pulley block, which is used to drive the moving frame 803 to rise and fall along the vertical slide rail 802.

[0027] Impact assembly 8 includes a movable frame 803, a hydraulic vertical impact hammer 804, and an impact plate 806, fixed to the bottom of the electric traveling trolley 808. The movable frame 803 is a welded steel plate frame structure, with its sides slidably connected to the vertical slide rail 802 via sliders. The vertical impact hammer 804 is a double-acting hydraulic impact hammer, fixedly installed at the bottom center of the movable frame 803. The bottom end of the impact rod of the vertical impact hammer 804 is fixedly connected to the impact plate 806 via a connecting flange 805. The lower surface of the impact plate 806 has an arc-shaped structure with a high center and low edges. With a height of 200mm, it can generate a circumferential pressure wave that spreads evenly to the surrounding area upon impact. A laser rangefinder 9 is installed at the bottom of the mobile frame 803, with the detection end of the laser rangefinder 9 facing vertically downwards towards the construction surface. It can detect the vertical distance between the mobile frame 803 and the upper surface of the concrete sealing layer 7 in real time. The signal output end of the laser rangefinder 9 is electrically connected to the control module fixed on the gantry 801. The signal output end of the control module is electrically connected to the winch 807, the vertical impact hammer 804, and the electric traveling trolley 808, respectively, to realize closed-loop automatic control of impact parameters.

[0028] Drainage components include a drainage pipe 11 and a submersible drainage pump 10. The drainage pipe 11 is made of DN200 high-strength steel wire reinforced hose. The inlet end of the drainage pipe 11 is equipped with a suction head with a filter screen to prevent debris and concrete aggregate from being sucked into the pipe. The middle part of the drainage pipe 11 is fixedly connected to the side of the mobile frame 803 through a pipe clamp, and can be raised and lowered synchronously with the mobile frame 803 in the vertical direction to ensure that the suction head is always at the preset water level above the concrete sealing layer 7. The top of the drainage pipe 11 passes through the crossbeam of the gantry frame 801 and is connected to the inlet of the drainage pump 10. The outlet of the drainage pump 10 is connected to the external sedimentation tank through a pipeline. The control module is electrically connected to the drainage pump 10 and can adjust the drainage power in real time according to the water level in the construction space.

[0029] In addition to the system proposed in the above embodiments, an underwater construction method is also proposed, specifically including: S1. Cofferdam Construction: Using GPS-RTK positioning and layout in the target construction area, the outline of the cofferdam is determined. A hydraulic vibratory hammer, in conjunction with an underwater piling platform, is used to drive sheet piles for the outer cofferdam body 1 one by one along the outer outline. The sheet piles interlock, and the verticality deviation is controlled to be no more than 0.5% throughout the driving process, until the outer cofferdam body 1 is driven to 10m below the riverbed, with the bottom embedded at least 0.5m into the moderately weathered silty mudstone bedrock. After the outer cofferdam body 1 is driven, sheet piles for the inner cofferdam body 2 are driven along the inner outline using the same process, forming a closed annular filling cavity 3 between the two cofferdam bodies. Graded sand and gravel are filled into the filling cavity 3 in layers. Each layer is fully compacted using an immersion vibrator. After the compaction degree reaches 96% or higher, the next layer is filled, continuing until the top of the cofferdam is reached, forming a water-stopping and structurally reinforced cofferdam structure, enclosing a closed underwater construction space. The prefabricated cage-type support 4 is hoisted as a whole within the construction space. The planar position and verticality of the support 4 are adjusted so that the outer bonding plate of the support 4 column is completely attached to the inner wall of the inner dam 2. The bottom of the support 4 rests stably on the riverbed base soil, and the top is flush with the top of the inner dam 2. The support 4 and the inner dam 2 are fixedly connected by pre-embedded connectors to form a continuous circumferential support for the inner dam 2. A strip concrete foundation of the gantry frame 801 is poured on the stable foundation outside the cofferdam, and anchor bolts are pre-embedded. After the foundation reaches the design strength, the gantry frame 801 is hoisted as a whole and fixed with anchor bolts. The traveling trolley 808, winch 807 and fixed pulley block are installed on the top crossbeam of the gantry frame 801. The vertical slide rail 802 and moving frame 803 are installed on the traveling trolley 808. The installation and wiring of the conveying component, impact component 8 and drainage component are completed. The linkage function of the control module is debugged, and the main body of the construction system is completed. S2. Initial Dewatering and Construction Surface Pretreatment: Start the drainage pump 10 on the gantry 801 and pump the water in the construction space to the outside through the drainage pipe 11 until the water level drops below the preset water level. Clean the silt, loose soil and debris at the bottom of the construction space and level the foundation soil. S3. Construction of bottom sealing concrete pouring: The conveying pipe 5 is laid along the inner wall of the support 4. The conveying pipe 5 is guided and limited by the pulley frame 6. Underwater concrete is continuously poured onto the surface of the base soil through the conveying pipe 5 to form a complete concrete sealing layer 7 at the bottom of the construction space. S4. Installation of Impact Assembly 8: Install and adjust the impact assembly 8 on the gantry 801 so that the vertical impact hammer 804 and the bottom impact plate 806 are aligned with the center area of ​​the construction space. Adjust the stroke of the impact hammer and the initial impact distance to complete the pre-impact preparation work. S5. Impact Compaction: Five hours after the concrete sealing layer 7 is poured, when the concrete is in a plastic state before initial setting, the vertical impact hammer 804 is activated, and the impact plate 806 is driven to periodically impact the upper surface of the concrete sealing layer 7 at a set impact frequency in the range of 0.02Hz-0.2Hz. During the impact, the vertical impact force is transmitted downward through the plastic concrete sealing layer 7 to the base soil. At the same time, a circumferential pressure wave is formed through the arc-shaped lower surface of the impact plate 806, which spreads evenly to the surrounding area. This allows the impact force to spread to the bottom and sidewalls of the cofferdam, and simultaneously compacts and reinforces the concrete sealing layer 7, the soil at the bottom of the cofferdam, and the soil around the sidewalls of the cofferdam. This eliminates internal pore defects in the concrete, improves the bearing capacity and impermeability of the base soil, and avoids the risks of piping and heave in subsequent construction. The impact operation continues, and the impact component 8 is driven to move laterally by the traveling trolley 808, and the entire area within the construction space is fully covered by impact compaction along the preset path to ensure uniform density throughout the concrete sealing layer 7.

[0030] S6. Impact position adjustment and drainage: During the impact process, the moving frame 803 is driven to rise and fall along the vertical slide rail 802 by the winch 807. The distance between the moving frame 803 and the upper surface of the concrete sealing layer 7 is detected in real time by the laser rangefinder 9, and the impact height and impact spacing of the impact plate 806 are dynamically adjusted. At the same time, the drainage pump 10 and the drainage pipe 11 continuously pump out the seepage water and concrete bleeding water in the construction space, so that the input end of the drainage pipe 11 is always kept at the preset water level above the concrete sealing layer 7. S7. Compaction and Acceptance: After the concrete sealing layer 7 has solidified to the design strength, stop the dewatering and impact operations, and test the flatness, density and reinforcement effect of the concrete sealing layer 7 and the base soil. After the acceptance is qualified, the sealing construction is completed and the subsequent bridge foundation construction process begins.

[0031] By using the above construction method, low-frequency impact is used to compact the upper surface of the concrete during the bottom sealing concrete pouring process. This allows the impact pressure to be transmitted through the concrete to the bottom and side walls of the cofferdam, thereby increasing the density of the bottom soil and reducing seepage channels. This effectively solves the problem of continuous seepage at the bottom during cofferdam construction and improves the stability and efficiency of bridge foundation construction.

[0032] Although the specific embodiments of the invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the invention. Based on the technical solutions of the invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the invention.

Claims

1. An underwater construction system for highway bridges, characterized in that, include: A cofferdam is used to enclose and create construction space. The support (4) is placed inside the cofferdam. The side wall of the support (4) is attached to the inner wall of the cofferdam to support the cofferdam. Conveying assembly; mounted on a support (4) for conveying concrete to the construction surface to form a concrete sealing layer (7). A gantry frame (801) is erected outside the cofferdam. An impact assembly (8) is connected to the gantry frame (801). The impact end of the impact assembly (8) is connected to an impact plate (806) for compacting the concrete sealing layer (7). A drainage pipe (11) for emptying the construction space is also provided on the gantry frame (801). The drainage pipe (11) is connected to a drainage pump (10).

2. The underwater construction system for highway bridges according to claim 1, characterized in that: The cofferdam includes an outer dam body (1), an inner dam body (2) is set inside the outer dam body (1), and a support (4) is supported inside the inner dam body (2); a filling cavity (3) is formed between the outer dam body (1) and the inner dam body (2), and the filling cavity (3) is filled with graded sand and gravel.

3. The underwater construction system for highway bridges according to claim 1, characterized in that: The conveying assembly includes a conveying pipe (5), and a connecting pulley frame (6) is installed outside the conveying pipe (5). The pulley frame (6) is connected to the inner wall of the support (4).

4. The underwater construction system for highway bridges according to claim 1, characterized in that: The impact assembly (8) includes a vertical slide rail (802) located in the middle of the gantry (801), a movable frame (803) connected to the vertical slide rail (802), a vertical impact hammer (804) connected to the movable frame (803), and an impact plate (806) connected to the bottom of the vertical impact hammer (804).

5. The underwater construction system for highway bridges according to claim 1, characterized in that: A laser rangefinder (9) is installed on the mobile frame (803) to detect the distance between the mobile frame (803) and the concrete sealing layer (7), and to adjust the operation of the winch (807) through the control module on the gantry frame (801).

6. An underwater construction method using the underwater construction system for highway bridges according to any one of claims 1-5, comprising the following steps: S1. Cofferdam Construction: Locate and lay out the target construction water area, and install the outer cofferdam (1) and the inner cofferdam (2) in sequence, so that the two cofferdams enclose the filling cavity (3), fill the filling cavity (3) with graded sand and gravel in layers and compact it to form a water-stopping cofferdam structure; install the support (4) in the construction space, so that the side wall of the support (4) is attached to the inner wall of the inner cofferdam (2) to form internal support; set up the gantry frame (801) on the stable foundation outside the cofferdam to complete the main construction of the construction system; S2. Initial precipitation and construction surface pretreatment: Start the drainage pump (10) on the gantry (801) and pump the water in the construction space to the outside through the drainage pipe (11) until the water level drops below the preset water level. Clean the silt, loose soil and debris at the bottom of the construction space and level the foundation soil. S3. Construction of bottom sealing concrete: The conveying pipe (5) is laid out along the inner wall of the support (4). The conveying pipe (5) is guided and fixed by the pulley frame (6). Underwater concrete is continuously poured into the surface of the base soil through the conveying pipe (5) to form a complete concrete sealing layer (7) at the bottom of the construction space. S4. Impact assembly (8) installation: Install and adjust the impact assembly (8) on the gantry (801) so that the vertical impact hammer (804) and the bottom impact plate (806) are aligned with the center area of ​​the construction space. Adjust the stroke of the impact hammer and the initial impact distance to complete the pre-impact preparation work. S5. Impact compaction: When the concrete sealing layer (7) is in a plastic state before initial setting, start the vertical impact hammer (804) and drive the impact plate (806) to periodically impact the upper surface of the concrete sealing layer (7), so that the impact force spreads downward and around the concrete sealing layer (7), and simultaneously compacts and reinforces the soil at the bottom of the cofferdam and the soil around the side wall of the cofferdam. S6. Impact position adjustment and drainage: During the impact process, the moving frame (803) is driven to rise and fall along the vertical slide rail (802) by the winch (807). The distance between the moving frame (803) and the upper surface of the concrete sealing layer (7) is detected in real time by the laser rangefinder (9), and the impact height and impact spacing of the impact plate (806) are dynamically adjusted. At the same time, the seepage water and concrete bleeding water in the construction space are continuously pumped out by the drainage pump (10) and the drainage pipe (11), so that the input end of the drainage pipe (11) is always kept at the preset water level above the concrete sealing layer (7). S7. Compaction and Acceptance: After the concrete sealing layer (7) has solidified to the design strength, stop the dewatering and impact operations, test the flatness, density and reinforcement effect of the concrete sealing layer (7) and the base soil. After the acceptance is qualified, the sealing construction is completed and the subsequent bridge foundation construction process begins.

7. The underwater construction method according to claim 6, characterized in that: Both the outer weir (1) and the inner weir (2) are corrugated steel plate structures, which are inserted into the riverbed through a vibrating device until they reach the bedrock layer.

8. The underwater construction method according to claim 6, characterized in that: The lower surface of the impact plate (806) has an arc-shaped structure with a high center and low edges, so as to form a pressure wave that spreads to the periphery when impacting the concrete sealing layer (7).

9. The underwater construction method according to claim 6, characterized in that: The impact hammer drives the impact plate (806) to impact the concrete sealing layer (7) at an impact frequency of 0.02Hz-0.2Hz.

10. The underwater construction method according to claim 6, characterized in that: The inlet end of the drainage pipe (11) is located inside the inner dam body (2). The middle part of the drainage pipe (11) is fixedly connected to the moving frame (803), so that the drainage pipe (11) moves synchronously with the lifting and lowering of the moving frame (803), and its lower end is always located above the concrete sealing layer (7).

Images