Diversion structure for cofferdam of narrow river channel and construction method of diversion structure

Abstract

The invention discloses a narrow riverway cofferdam diversion structure and a construction method thereof, and relates to the technical field of hydraulic engineering construction.The narrow riverway cofferdam diversion structure comprises riverway protection walls arranged on the two sides of a riverway and comprising a plurality of steel sheet piles which are sequentially spliced; the supporting frame is installed in a river channel, and fixing structures used for fixing a river channel protection wall are arranged on the two sides of the supporting frame; the water retaining cofferdam is installed on the supporting frame, the water retaining cofferdam comprises a front retaining wall, a rear retaining wall and a sandbag interlayer arranged between the front retaining wall and the rear retaining wall, each of the front retaining wall and the rear retaining wall comprises a plurality of water baffles which are spliced in sequence, and an installation structure used for installing the front retaining wall and the rear retaining wall is arranged on the supporting frame; and the diversion channel is mounted on the side of the river channel and used for guiding water flow in the river channel to the downstream of the river channel construction position. The cofferdam diversion structure for the narrow river channel has the advantages of being convenient to construct and install, high in stability and good in adaptability.

Description

Technical Field

[0001] The present application relates to the technical field of water conservancy project construction, and in particular to a narrow river channel cofferdam diversion structure and a construction method thereof. Background Art

[0002] The cofferdam diversion technology of the river channel is of great significance in water conservancy projects. With the acceleration of urbanization, the demand for river management and reconstruction is increasing. As a key means to ensure construction safety and efficiency, the cofferdam diversion structure is widely used in river channel dredging, bridge construction and other scenarios. By rationally designing the cofferdam and diversion system, not only can the water flow be effectively controlled, but also a stable dry land working environment can be provided for construction, thereby improving the quality and safety of the project.

[0003] At present, the cofferdam diversion methods commonly used in river channel construction mainly include earth-rock cofferdam, steel sheet pile cofferdam and concrete cofferdam. Although the earth-rock cofferdam is simple to construct, it is only suitable for rivers with slow water flow; although the steel sheet pile cofferdam has good stability, it has high requirements for river channels and terrain, and is only suitable for wide river channels. It is difficult to form an effective supporting structure in narrow river channels; although the concrete cofferdam has high strength and stability, it has a long construction period. Therefore, how to design a cofferdam diversion structure that can be easily constructed in a narrow river environment and has both high stability and high adaptability has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of the problems existing in the prior art, the present application provides a narrow river channel cofferdam diversion structure and a construction method thereof.

[0005] In the first aspect, the present application provides a narrow river channel cofferdam diversion structure, which adopts the following technical solution: A narrow river channel cofferdam diversion structure, including a channel retaining wall: arranged on both sides of the river channel, including a plurality of steel sheet piles spliced ​​in sequence, each of the steel sheet piles is driven into the soil layer at the bottom of the river channel; a support frame: installed in the river channel, and both sides of the support frame are provided with a fixing structure for fixing the channel retaining wall; a water retaining cofferdam: installed on the support frame, the water retaining cofferdam includes a front retaining wall, a rear retaining wall and a sandbag interlayer arranged between the front retaining wall and the rear retaining wall, the front retaining wall and the rear retaining wall each include a plurality of water retaining plates spliced ​​in sequence, and the support frame is provided with a mounting structure for mounting the front retaining wall and the rear retaining wall; a diversion channel: installed on the side of the river channel, the channel retaining wall is provided with a diversion port connected to the diversion channel, and the diversion channel is used to guide the water flow in the river channel to the downstream of the river channel construction position.

[0006] Optionally, the support frame includes a top bracket and side brackets slidably arranged on both sides of the top bracket. Fixing members for fixing the two side brackets are respectively arranged on the top bracket, and the fixing structure is arranged on the side brackets.

[0007] Optionally, the fixing structure includes a clamping frame and a limiting member. The side bracket is provided with a clamping groove for inserting the river channel retaining wall. The clamping frame is slidably arranged on the side bracket and is used for clamping the steel sheet pile, and the limiting member is used to prevent the clamping frame from sliding.

[0008] Optionally, an insertion block is fixedly arranged on the clamping frame, and the steel sheet pile is provided with an insertion hole for inserting the insertion block.

[0009] Optionally, the installation structure includes a first installation groove and a second installation groove arranged on the top bracket. The front retaining wall is inserted into the first installation groove, and the rear retaining wall is inserted into the second installation groove, and the widths of the first installation groove and the second installation groove are both adapted to the thickness of the water baffle.

[0010] Optionally, an energy dissipation weir is arranged at the bottom of the diversion port in the river channel. The energy dissipation weir is fixed on the steel sheet pile. The top end of the energy dissipation weir is arc-shaped, and a gravel cushion layer is arranged on the soil layer below the energy dissipation weir.

[0011] Optionally, the diversion channel includes a plurality of precast concrete blocks spliced in sequence. Each precast concrete block is provided with a diversion groove. A telescopic joint is arranged between adjacent precast concrete blocks, and the telescopic joint is filled with a sealing material.

[0012] Optionally, the bottom of the diversion channel is provided with a slope, and the slope gradually slopes downward along the upstream to downstream direction of the river channel.

[0013] In a second aspect, the present application provides a construction method for a diversion structure of a narrow river channel cofferdam, adopting the following technical solution: A construction method for a diversion structure of a narrow river channel cofferdam includes the following steps: S1. Construction survey: Determine the positions of the cofferdam and the diversion channel according to the river channel width and water flow conditions, and mark the construction range on the river bed; S2. Construction of the river channel retaining wall: Drive steel sheet piles in sequence at the slope positions on both sides of the river channel to form the river channel retaining wall; S3. Installation of the support frame: Hoist the support frame into the river channel, and both sides of the support frame are fixed to the river channel retaining walls on both sides of the river channel through the fixing structure; S4. Construction of the diversion channel: Excavate beside the river channel and construct the diversion channel. The diversion channel is communicated with the diversion port on the river channel retaining wall to ensure that the water in the river channel can be smoothly guided to the downstream of the river channel construction position through the diversion channel; S5. Construction of the water retaining cofferdam: The front retaining wall and the rear retaining wall are respectively installed on the support frame through the installation structure. When installing the front retaining wall and the rear retaining wall, according to the width of the river channel, the corresponding number of water retaining plates is set. Then, sandbags are placed in the space between the front retaining wall and the rear retaining wall to form a sandbag interlayer, completing the construction of the water retaining cofferdam.

[0014] In summary, the present application includes at least one of the following beneficial technical effects: 1. The narrow river channel cofferdam diversion structure of the present application has the effects of convenient construction and installation, high stability, and good adaptability. Specifically, the river channel retaining wall, the support frame, the water retaining cofferdam, and the diversion channel adopt a modular installation method, effectively improving the convenience of construction. The river channel retaining wall is formed by sequentially splicing multiple steel sheet piles and driving them into the soil layer at the bottom of the river channel, which can effectively form a stable side wall support structure to prevent the collapse of the river channel slope. The support frame is installed in the river channel and connected to the river channel retaining wall through the fixing structure, further enhancing the stability of the overall structure and ensuring the safety during construction. The water retaining cofferdam is composed of a front retaining wall, a rear retaining wall, and a sandbag interlayer, and is fixed by the installation structure on the support frame to form a reliable water retaining barrier, effectively blocking the water flow from entering the construction area. Moreover, the front retaining wall and the rear retaining wall are spliced by multiple water retaining plates, and the width of the water retaining cofferdam can be adjusted according to the width of the river channel to meet the water retaining requirements of river channels with different widths. The diversion channel is arranged beside the river channel and connected to the river channel retaining wall through the diversion opening, which can smoothly guide the water flow in the river channel to the downstream of the construction position, ensuring that the construction area is in a dry land state.

[0015] 2. The support frame of the present application is composed of a top bracket and side brackets slidably arranged on both sides thereof. This design makes the support frame have good adaptability, can adjust the position of the side brackets according to the width of the river channel, and is locked by fixing parts, thereby ensuring the firm connection between the support frame and the river channel retaining wall and improving the stability and reliability of the overall structure.

[0016] 3. Through the design of the energy dissipation weir, the present application can effectively reduce the impact force of the water flow when passing through the diversion opening, avoid the erosion of the soil layer at the bottom of the river channel by the water flow, and thus improve the stability of the structure. Specifically, the energy dissipation weir is fixed on the steel sheet pile, and its top is set in an arc shape, which can smoothly guide the water flow direction, reduce the water flow velocity, and reduce the energy loss. A gravel cushion layer is arranged below the energy dissipation weir to further enhance the buffering effect on the water flow and prevent the soil layer from being eroded, ensuring the stability of the bottom structure of the river channel. Description of the Drawings

[0017] Figure 1 is the structural top view of the embodiment of the present application; Figure 2 is the overall structural cross-sectional view of the embodiment of the present application; Figure 3It is a structural sectional view for expressing an energy dissipation weir in an embodiment of the present application; Figure 4 It is a structural sectional view for expressing a diversion channel in an embodiment of the present application; Figure 5 It is a schematic structural diagram for expressing a support frame in an embodiment of the present application; Figure 6 It is a schematic structural diagram for expressing a fixing structure in an embodiment of the present application.

[0018] Explanation of reference numerals: 1, river channel retaining wall; 11, steel sheet pile; 111, insertion hole; 12, diversion opening; 13, energy dissipation weir; 14, gravel cushion layer; 2, support frame; 21, top bracket; 211, guide post; 212, fixing member; 22, side bracket; 221, clamping groove; 23, first installation groove; 24, second installation groove; 25, clamping frame; 251, insertion block; 26, limiting member; 3, water retaining cofferdam; 31, front retaining wall; 32, rear retaining wall; 33, sandbag interlayer; 34, water retaining plate; 4, diversion channel; 41, precast concrete block; 411, diversion groove; 42, expansion joint; 43, sealing material; 44, slope. Detailed implementation manners

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the attached Figure 1 - attached Figure 6 , and the described embodiments are only possible technical implementations of the present invention, not all possible implementations. Those skilled in the art can completely combine the embodiments of the present invention to obtain other embodiments without creative labor, and these embodiments are also within the protection scope of the present invention.

[0020] The inventors of the present application found that the common cofferdam diversion methods in river channel construction mainly include earth-rock cofferdams, steel sheet pile cofferdams, and concrete cofferdams. Although earth-rock cofferdams are simple to construct, they are only applicable to river channels with slow water flow; although steel sheet pile cofferdams have good stability, they have high requirements for the river channel and terrain and are only applicable to river channels with a wide river channel and are difficult to form an effective support structure in narrow river channels; although concrete cofferdams have high strength and stability, they have a long construction period. Therefore, the present application discloses a narrow river channel cofferdam diversion structure and its construction method, which can adapt to the construction of narrow river channels and has the effects of convenient construction and installation, high stability, and good adaptability. The main solutions are as follows: An embodiment of the present application discloses a narrow river channel cofferdam diversion structure. Refer to Figure 1 , 2, including a river channel retaining wall 1, a support frame 2, a water retaining cofferdam 3 and a diversion channel 4. Among them, the river channel retaining wall 1 is arranged on both sides of the river channel, including a plurality of sequentially spliced steel sheet piles 11, and each steel sheet pile 11 is driven into the soil layer at the bottom of the river channel to form a stable side wall support structure; the support frame 2 is installed in the river channel and fixedly connected to the river channel retaining walls 1 on both sides of the river channel; the water retaining cofferdam 3 is composed of a front retaining wall 31, a rear retaining wall 32 and a sandbag interlayer 33, and is installed and fixed on the support frame 2 through the installation structure on the support frame 2 to form a reliable water retaining barrier in the river channel, effectively blocking the water flow from entering the construction area; the diversion channel 4 is arranged beside the river channel, and a diversion opening 12 communicating with the diversion channel 4 is arranged on the river channel retaining wall 1. The diversion channel 4 is communicated with the river channel through the diversion opening 12, and can smoothly guide the water flow in the river channel to the downstream of the construction position to ensure that the construction area is in a dry land state.

[0021] Refer to Figure 1 , specifically, the steel sheet pile 11 adopts a Larssen steel sheet pile. During the construction of the river slope protection, the Larssen steel sheet pile is driven into the riverbed piece by piece through a vibratory hammer, and it is ensured that the lock joints are tightly connected to ensure firm and reliable connection and form a closed river channel retaining wall 1 structure.

[0022] Refer to Figure 2 、 3 , a dissipation sill 13 is arranged at the bottom of the river channel and at the diversion opening 12. The dissipation sill 13 is fixed to the steel sheet pile 11 by bolts. The top end of the dissipation sill 13 is set to be arc-shaped and arched upward, which can effectively guide the water flow direction, reduce the water flow velocity, reduce energy loss, and can effectively reduce the impact force of the water flow when passing through the diversion opening 12, avoid the scouring of the soil layer at the bottom of the river channel by the water flow, and thus improve the structural stability.

[0023] Refer to Figure 2 、 3 , further, a gravel cushion layer 14 is arranged in the soil layer below the dissipation sill 13. The gravel cushion layer 14 adopts hard gravel with a particle size of 25 mm to 45 mm. The gravel cushion layer 14 can enhance the buffering effect on the water flow and prevent the soil layer from being eroded, ensuring the stability of the river channel bottom structure.

[0024] Refer to Figure 4, Specifically, the diversion channel 4 includes a plurality of precast concrete blocks 41 spliced in sequence. Each precast concrete block 41 is provided with a diversion groove 411, and the width is adjusted according to the water flow condition. A expansion joint 42 is arranged between adjacent precast concrete blocks 41, and the expansion joint 42 is filled with a sealing material 43. Specifically, the sealing material 43 can adopt a high-performance sealing strip or an expansion rubber strip. The diversion channel 4 is formed by splicing a plurality of precast concrete blocks 41 in sequence. The diversion grooves 411 provided on each precast concrete block 41 can ensure the smooth passage of water flow. The expansion joint 42 between adjacent precast concrete blocks 41 is designed to effectively relieve the structural stress caused by thermal expansion and contraction or uneven settlement, enhancing the overall stability of the diversion channel 4. At the same time, the expansion joint 42 is filled with the sealing material 43, further improving the waterproof performance of the diversion channel 4, preventing water leakage, and ensuring that the water in the river channel can be smoothly guided to the downstream of the construction position.

[0025] Refer to Figure 4 , A slope 44 is arranged at the bottom of the diversion channel 4, and the slope 44 gradually slopes downward along the upstream to downstream direction of the river channel. The slope 44 arranged at the bottom of the diversion channel 4 can effectively guide the water flow to flow smoothly along the predetermined direction, avoiding the formation of eddies or stagnation phenomena of the water flow in the diversion channel 4, reducing the impact force of the water flow on the bottom and side walls of the diversion channel 4, thereby improving the service life and stability of the diversion channel 4.

[0026] Refer to Figure 5 , The support frame 2 includes a top bracket 21 and side brackets 22 slidably arranged on both sides of the top bracket 21. Guide columns 211 are fixedly arranged on both sides of the top bracket 21. The length directions of the guide columns 211 are parallel, and the side brackets 22 are slidably sleeved on the guide columns 211 on the corresponding side. Fixing structures for fixing the river channel retaining wall 1 are arranged on both side brackets 22. This design enables the support frame 2 to have good adaptability and can adjust the positions of the side brackets 22 on both sides according to the river channel width, increasing the adaptability.

[0027] Refer to Figure 3 , 5 , The installation structure includes a first installation groove 23 and a second installation groove 24 arranged on the top bracket 21. The front retaining wall 31 is inserted into the first installation groove 23, and the rear retaining wall 32 is inserted into the second installation groove 24. The front retaining wall 31 and the rear retaining wall 32 both include a plurality of water retaining plates 34 spliced in sequence. The water retaining plates 34 are made of steel plates or composite material plates, and the widths of the first installation groove 23 and the second installation groove 24 are both adapted to the thickness of the water retaining plates 34. When installing the front retaining wall 31 and the rear retaining wall 32, the bottom ends of the water retaining plates 34 are inserted into the bottom of the riverbed to ensure the installation stability of the front retaining wall and the rear retaining wall 32. Moreover, the front retaining wall 31 and the rear retaining wall 32 are formed by splicing a plurality of water retaining plates 34, and the width of the water retaining cofferdam 3 can be adjusted according to the width of the river channel to meet the water retaining requirements of river channels with different widths.

[0028] Reference Figure 5 , fixing members 212 for fixing the two side frames 22 are respectively arranged on the top bracket 21; specifically, the fixing member 212 includes a locking bolt, and the locking bolt is fitted with a locking nut. Waist-shaped holes are respectively formed in the two sides of the top bracket 21 along the length direction of the guide post 211, the locking bolt is arranged in the waist-shaped hole on the corresponding side, and first through holes for the locking bolt to pass through are respectively arranged on the two side frames 22. The side frame 22 is locked by the fixing member 212, so as to ensure the stable connection between the support frame 2 and the river channel retaining wall 1, and improve the stability and reliability of the overall structure.

[0029] Reference Figure 5 , 6 , specifically, the fixing structure includes a clamping frame 25 and a limiting member 26. The side frame 22 is provided with a clamping groove 221 for inserting the river channel retaining wall 1, and the width of the clamping groove 221 is adapted to the thickness of the river channel retaining wall 1; the clamping frame 25 is made of high-strength steel plate and is slidably arranged on the side frame 22. The limiting member 26 is an opposed tension screw, and the opposed tension screw is fitted with a limiting nut. Two opposed tension screws are provided and are both fixedly installed on the two sides of the side frame 22. Second through holes for the opposed tension screw to pass through are respectively formed on the two sides of the clamping frame 25. The side frame 22 is sleeved on the top of the river channel retaining wall 1 through the clamping groove 221, and then, the limiting nut on the opposed tension screw is tightened to lock, so that the clamping frame 25 abuts against the steel sheet pile 11 of the river channel retaining wall 1, thereby fixing the side frame 22 on the river channel retaining wall 1.

[0030] Reference Figure 6 , a plurality of insertion blocks 251 are fixedly arranged on the clamping frame 25. The insertion blocks 251 can be designed in a trapezoidal or circular shape and are made of high-strength alloy steel. Insertion holes 111 for the insertion blocks 251 to insert are arranged on the steel sheet pile 11; when the side frame 22 is sleeved on the top of the river channel retaining wall 1, the insertion blocks 251 on the clamping frame 25 are accurately aligned with the insertion holes 111 on the steel sheet pile 11. When the clamping frame 25 abuts against the steel sheet pile 11 of the river channel retaining wall 1, the insertion blocks 251 are inserted into the insertion holes 111 of the steel sheet pile 11, which increases the installation firmness of the side frame 22 and effectively prevents the support frame 2 from displacing or loosening when stressed.

[0031] The implementation principle of the cofferdam diversion structure for narrow river channels in the embodiments of this application is as follows: The river channel retaining wall 1, support framework 2, water retaining cofferdam 3, and diversion channel 4 are installed in a modular manner, effectively improving the construction convenience. The river channel retaining wall 1 is formed by sequentially splicing multiple steel sheet piles 11 and driving them into the soil layer at the bottom of the river channel, which can effectively form a stable side wall support structure to prevent the collapse of the river channel slope; the support framework 2 is installed in the river channel and connected to the river channel retaining wall 1 through a fixing structure, further enhancing the stability of the overall structure and ensuring safety during construction; the water retaining cofferdam 3 consists of a front retaining wall 31, a rear retaining wall 32, and a sandbag interlayer 33, and is fixed by means of the installation structure on the support framework 2 to form a reliable water retaining barrier, effectively blocking the water flow from entering the construction area; moreover, the front retaining wall 31 and the rear retaining wall 32 are spliced by multiple water retaining plates 34, and the width of the water retaining cofferdam 3 can be adjusted according to the width of the river channel to meet the water retaining requirements of river channels with different widths. The diversion channel 4 is arranged beside the river channel and connected to the river channel retaining wall 1 through a diversion port 12, which can smoothly guide the water flow in the river channel to the downstream of the construction position to ensure that the construction area is in a dry state.

[0032] The embodiments of this application also disclose a construction method for the cofferdam diversion structure for narrow river channels, including the following steps: S1. Construction survey: According to the width of the river channel and the water flow condition, determine the positions of the cofferdam and the diversion channel 4, and mark the construction scope on the riverbed; S2. Construction of the river channel retaining wall 1: Sequentially drive the steel sheet piles 11 at the slope positions on both sides of the river channel to form the river channel retaining wall 1; S3. Installation of the support framework 2: Hoist the support framework 2 into the river channel, and fix both sides of the support framework 2 to the river channel retaining walls 1 on both sides of the river channel through a fixing structure; S4. Construction of the diversion channel 4: Excavate beside the river channel and construct the diversion channel 4, and connect the diversion channel 4 to the diversion port 12 on the river channel retaining wall 1 to ensure that the water in the river channel can be smoothly guided to the downstream of the river channel construction position through the diversion channel 4; S5. Construction of the water retaining cofferdam 3: Install the front retaining wall 31 and the rear retaining wall 32 on the support framework 2 respectively through the installation structure. When installing the front retaining wall 31 and the rear retaining wall 32, set the corresponding number of water retaining plates 34 according to the width of the river channel, and then put sandbags in the space between the front retaining wall 31 and the rear retaining wall 32 to form the sandbag interlayer 33, completing the construction of the water retaining cofferdam 3.

[0033] The above are all the preferred embodiments of this application. Without restricting the protection scope of this application accordingly, therefore: All equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A diversion structure for cofferdams in narrow river channels, characterized in that, Comprising: River channel retaining wall (1): Arranged on both sides of the river channel, including a plurality of steel sheet piles (11) spliced in sequence, and each of the steel sheet piles (11) is driven into the soil layer at the bottom of the river channel; Support frame (2): Installed in the river channel, and fixing structures for fixing the river channel retaining wall (1) are arranged on both sides of the support frame (2); Water retaining cofferdam (3): Installed on the support frame (2), the water retaining cofferdam (3) includes a front retaining wall (31), a rear retaining wall (32) and a sandbag interlayer (33) arranged between the front retaining wall (31) and the rear retaining wall (32), the front retaining wall (31) and the rear retaining wall (32) each include a plurality of water retaining plates (34) spliced in sequence, and an installation structure for installing the front retaining wall (31) and the rear retaining wall (32) is arranged on the support frame (2); Diversion channel (4): Installed beside the river channel, a diversion port (12) communicated with the diversion channel (4) is arranged on the river channel retaining wall (1), and the diversion channel (4) is used for guiding the water flow in the river channel to the downstream of the river channel construction position.

2. The diversion structure of cofferdam in a narrow river channel according to claim 1, characterized in that: The support frame (2) includes a top support (21) and side frames (22) slidably arranged on both sides of the top support (21), fixing members (212) for fixing the two side frames (22) are respectively arranged on the top support (21), and the fixing structure is arranged on the side frames (22).

3. A diversion structure for cofferdams in narrow river channels according to claim 2, characterized in that: The fixing structure includes a clamping frame (25) and a limiting member (26), a clamping groove (221) for inserting the river channel retaining wall (1) is arranged on the side frame (22), the clamping frame (25) is slidably arranged on the side frame (22) and is used for clamping the steel sheet pile (11), and the limiting member (26) is used for preventing the clamping frame (25) from sliding.

4. A diversion structure for cofferdams in narrow river channels according to claim 3, characterized in that: An insertion block (251) is fixedly arranged on the clamping frame (25), and an insertion hole (111) for inserting the insertion block (251) is arranged on the steel sheet pile (11).

5. A diversion structure for cofferdams in narrow river channels according to claim 2, characterized in that: The installation structure includes a first installation groove (23) and a second installation groove (24) arranged on the top support (21), the front retaining wall (31) is inserted into the first installation groove (23), the rear retaining wall (32) is inserted into the second installation groove (24), and the widths of the first installation groove (23) and the second installation groove (24) are both adapted to the thickness of the water retaining plate (34).

6. The diversion structure of cofferdam in a narrow river channel according to claim 1, wherein: An energy dissipation weir (13) is arranged at the bottom of the river channel and located at the diversion port (12), the energy dissipation weir (13) is fixed on the steel sheet pile (11), the top end of the energy dissipation weir (13) is arc-shaped, and a crushed stone cushion layer (14) is arranged in the soil layer below the energy dissipation weir (13).

7. A diversion structure for cofferdams in narrow river channels according to claim 1, characterized in that: The diversion channel (4) includes a plurality of precast concrete blocks (41) spliced in sequence, diversion grooves (411) are arranged on each of the precast concrete blocks (41), expansion joints (42) are arranged between adjacent precast concrete blocks (41), and sealing materials (43) are filled in the expansion joints (42).

8. A diversion structure for cofferdams in narrow river channels according to claim 1, characterized in that: A slope (44) is arranged at the bottom of the diversion channel (4), and the slope (44) gradually slopes downward along the upstream to downstream direction of the river channel.

9. A construction method for the diversion structure of cofferdams in narrow river channels according to any one of claims 1-8, characterized in that, Comprising the following steps: S1. Construction survey: Determine the positions of the cofferdam and the diversion channel (4) according to the width of the river channel and the water flow conditions, and mark the construction scope on the riverbed; S2. Construction of the river channel retaining wall (1): Drive steel sheet piles (11) successively at the slope positions on both sides of the river channel to form the river channel retaining wall (1); S3. Installation of the support frame (2): Hoist the support frame (2) into the river channel, and both sides of the support frame (2) are fixed to the river channel retaining walls (1) on both sides of the river channel through fixing structures; S4. Construction of the diversion channel (4): Excavate beside the river channel and construct the diversion channel (4), and the diversion channel (4) is communicated with the diversion opening (12) on the river channel retaining wall (1) to ensure that the water in the river channel can be smoothly guided to the downstream of the river channel construction position through the diversion channel (4); S5. Construction of the water retaining cofferdam (3): Install the front retaining wall (31) and the rear retaining wall (32) on the support frame (2) respectively through the installation structure. When installing the front retaining wall (31) and the rear retaining wall (32), set the corresponding number of water retaining plates (34) according to the width of the river channel. Then, put sandbags in the space between the front retaining wall (31) and the rear retaining wall (32) to form a sandbag interlayer (33) to complete the construction of the water retaining cofferdam (3).

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