River foundation pit box culvert diversion staged cofferdam system and river foundation pit staged construction method

Abstract

The invention discloses a river branch foundation pit box culvert diversion staged cofferdam system and a river branch foundation pit staged construction method, and relates to the technical field of constructional engineering. The system comprises a flow guide box culvert which is arranged in a foundation pit to guide flow of a river, a foundation pit supporting system which is used for supporting the foundation pit, and a cofferdam system which is used for blocking the river and is arranged on the outer side of the foundation pit supporting system; the foundation pit supporting system comprises a supporting wall arranged on the periphery of a foundation pit, an inner support arranged in the foundation pit, stand columns and stand column piles, wherein the stand columns and the stand column piles are arranged below the inner support. The cofferdam system comprises Larsen steel sheet piles, plain fill, a reverse support, a retention wall and a water stop system. The construction period can be greatly shortened, and the manufacturing cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building engineering, in particular to a river trench foundation box culvert diversion staged cofferdam system and a river trench foundation staged construction method. BACKGROUND

[0002] With the continuous development of urbanization and the expansion of urban subway line network, more and more foundation pit projects are adjacent to existing buildings and structures, so the environmental impact of foundation pit excavation is increasingly prominent, and the influence of foundation pit engineering on the surrounding environment cannot be ignored. The distance between deep foundation pit engineering and ground rivers is becoming smaller and smaller, and the mutual influence of foundation pit engineering on the surrounding environment is also increasing.

[0003] At present, subway station river foundation is relatively common, and the protection research of adjacent river is relatively mature, but the setting of foundation pit through the entire river is relatively rare, and relevant research and design documents are rarely seen. For the foundation pit located in the full river range, if the river flood control and drainage function is not high, or the river flow area is small, the full-section closure + pumping scheme is usually used to solve this problem. This scheme is the most common, but if the river flow area is large, its applicability will be greatly reduced. Another traditional scheme is to set a partition wall to stage the cofferdam of the foundation pit, which can ensure the flow function and meet the construction requirements of the foundation pit, but the disadvantages are long construction period, multiple process connections, small construction site and high engineering cost. Therefore, how to design a new river foundation construction scheme to meet the flow requirements, optimize the construction period and process, and save the cost, so as to better serve the needs of urban development, has become a problem that needs to be solved at present. SUMMARY

[0004] The present application provides a river trench foundation box culvert diversion staged cofferdam system and a river trench foundation staged construction method, which can greatly shorten the construction period and reduce the cost.

[0005] In a first aspect, the present application provides a river trench foundation box culvert diversion staged cofferdam system, which comprises: a diversion box culvert for setting in the foundation pit to guide the river; a foundation pit support system for providing support to the foundation pit, the foundation pit support system comprising a support wall for being arranged on the outer periphery of the foundation pit, an inner support for being arranged inside the foundation pit, and a column and a column pile arranged below the inner support; a cofferdam system for blocking the river and being arranged outside the foundation pit support system, the cofferdam system comprising a Larsen steel sheet pile, plain fill, a reverse support, a water retaining wall, and a water stop system.

[0006] In combination with the first aspect, in an implementation, the inner support is a grid structure, wherein each intersection of the grid structure is provided with a column or the columns are provided at intervals below the intersections of the grid structure, and each column is provided with a column pile below.

[0007] In combination with the first aspect, in an implementation, the axes of the columns and the column piles are on the same line and perpendicular to the inner support.

[0008] In combination with the first aspect, in an implementation, the water stop system is located on the outer side of the support wall or on both sides of the support wall.

[0009] In combination with the first aspect, in an implementation, the Larsen steel sheet piles are used to enclose to form a cofferdam or the Larsen steel sheet piles and the water retaining walls are used to enclose to form a cofferdam, and the water stop system is provided at the interface position when the Larsen steel sheet piles and the water retaining walls enclose to form a cofferdam.

[0010] In combination with the first aspect, in an implementation, the reverse support is located on the side of the Larsen steel sheet piles close to water.

[0011] The second aspect provides a river trench foundation pit staged construction method, which is based on the river trench box culvert diversion staged cofferdam system described above. The river is divided into two sides along the flow direction, which are the first side river and the second side river. The river trench foundation pit staged construction method comprises: The cofferdam system and foundation pit support system at the first side river are constructed, the inner support and the diversion box culvert are integrally poured and constructed, and the cofferdam system is removed after the diversion box culvert has the flow-through condition, and the flow-through of the first side river is conducted by using the diversion box culvert; The cofferdam system, foundation pit support system at the second side river, and all foundation pit structures are constructed, and the cofferdam system and the inner support within the cofferdam range are removed after the construction of the foundation pit structure is completed, and the flow of the second side river is restored; The cofferdam system at the first side river is constructed again, and the diversion box culvert and the inner support within the cofferdam range are removed after the construction of the cofferdam system is completed, and then the cofferdam system is removed to restore the flow of the first side river.

[0012] In combination with the second aspect, in an implementation, the cofferdam system and foundation pit support system at the first side river are constructed, the inner support and the diversion box culvert are integrally poured and constructed, and the cofferdam system is removed after the diversion box culvert has the flow-through condition, and the flow-through of the first side river is conducted by using the diversion box culvert, which specifically comprises: The vacant land beside the first side river is used as a construction site, and the soil is backfilled to the site level; The cofferdam system at the first side river is constructed, the Larsen steel sheet piles and the reverse support are installed, and the soil is backfilled to form a cofferdam; The support wall, column and column pile of the foundation pit at the first side river are buried, the foundation pit is excavated to the bottom elevation of the diversion box culvert, the erection of the foundation pit support system is completed, and the internal support and the whole pouring construction of the diversion box culvert are completed; After the diversion box culvert has the flow-through condition, the Larsen steel sheet pile and the reverse support at the first side river are removed, the plain fill in the cofferdam at the first side river is removed, and the flow-through of the first side river is performed by using the diversion box culvert.

[0013] In combination with the second aspect, in an implementation, the cofferdam system at the second side river is constructed, the foundation pit support system is constructed, and the whole foundation pit structure is constructed, and after the construction of the foundation pit structure is completed, the internal support in the cofferdam range is removed, and the flow of the second side river is restored, and specifically includes: The empty land beside the second side river is used as a construction site, and the plain fill is backfilled to the site flat elevation; The cofferdam system at the second side river is constructed, the Larsen steel sheet pile and the reverse support are installed, and the plain fill is backfilled, and the cofferdam is formed by the side edges of the Larsen steel sheet pile and the diversion box culvert; The support wall, column and column pile of the foundation pit at the second side river are buried, the erection of the foundation pit support system is performed while the foundation pit is excavated, and after the foundation pit is excavated to the bottom elevation of the foundation pit, the whole foundation pit structure is constructed; The protection plate is installed at the bottom of the river and the top of the foundation pit structure, and the water retaining wall is installed on the protection plate of the foundation pit structure at the boundary between the second side river and the first side river; The foundation pit support system in the range of the second side river is removed, the Larsen steel sheet pile and the reverse support are pulled out, and the flow of the second side river is restored.

[0014] In combination with the second aspect, in an implementation, the cofferdam system at the first side river is constructed again, and after the construction of the cofferdam system is completed, the internal support in the cofferdam range and the diversion box culvert are removed, and then the cofferdam system is removed to restore the flow of the first side river, and specifically includes: The empty land beside the first side river is used as a construction site, and the plain fill is backfilled to the site flat elevation; The cofferdam system at the first side river is constructed, the Larsen steel sheet pile and the reverse support are installed, and the cofferdam is formed by the Larsen steel sheet pile and the water retaining wall of the foundation pit structure at the second side river; The diversion box culvert at the first side river is removed; The internal support, the diversion box culvert and the water retaining wall are removed, and then the cofferdam system is removed to restore the flow of the first side river.

[0015] The technical scheme provided by the embodiments of the present application has the following beneficial effects: The construction gap is utilized to advance the foundation pit structure construction, saves the process joint period, simplifies the process, saves the period, greatly speeds up the construction progress under the premise of not sacrificing the safety performance, improves the work efficiency, and the application does not need to additionally set a strong drainage pump station, compared with the conventional cofferdam mode, a middle partition wall is not needed, the site and investment are saved, the influence on the surrounding environment is minimized, meanwhile, the diversion box culvert and the foundation pit inner support system are integrally poured, the stress is good, the stability is high, and the flow section is large. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 It is a plan distribution example diagram of the river ditch foundation pit box culvert diversion staged cofferdam system of the present application. Figure 2 It is a section view of the river ditch foundation pit box culvert diversion staged cofferdam system of the present application. Figure 3 It is a first-stage construction schematic diagram. Figure 4 It is a second-stage construction schematic diagram. Figure 5 It is a third-stage construction schematic diagram. In the figure: 1-diversion box culvert; 2-supporting wall; 3-inner support; 4-Larsen steel sheet pile; 5-reverse support; 6-water retaining wall; 7-water stop system; 8-river ditch; 8A-first side river ditch; 8B-second side river ditch; 9-stand column; 10-stand column pile. DETAILED DESCRIPTION

[0018] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0019] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail in combination with the drawings.

[0020] In a first aspect, the embodiments of the present application provide a river trench box culvert diversion staged cofferdam system, which can realize staged implementation of the trench, ensure normal water flow of the river 8 during trench implementation, and does not need to additionally set a strong drainage pump station. Compared with a conventional cofferdam, the river trench box culvert diversion staged cofferdam system has small construction site requirements, does not need to set a trench partition wall, and can implement the main structure at one time, thereby greatly shortening the construction period and reducing the cost.

[0021] In an embodiment, referring to Figure 1 , Figure 1 FIG. 1 is a structural schematic diagram of a river trench box culvert diversion staged cofferdam system according to the present application. As shown in Figure 1 , the river trench box culvert diversion staged cofferdam system includes a diversion box culvert 1 for being arranged in a trench to guide a river 8, a trench support system for providing support to the trench, and a cofferdam system for blocking the river 8 and being arranged outside the trench support system.

[0022] For the diversion box culvert 1 of the present application, it is arranged along the water flow direction of the river 8, so that the water flow of the river 8 can be realized, the normal flow of part of the water flow of the river 8 can be realized, and the river 8 is not completely blocked.

[0023] In the present application, the trench support system includes a support wall 2 for being arranged outside the trench, an inner support 3 for being arranged inside the trench, and a column 9 and a column pile 10 arranged below the inner support 3. The support wall 2 is arranged around the trench to be excavated to support the excavated trench, and the inner support 3, the column 9, and the column pile 10 are arranged inside the trench. The inner support 3 is a grid structure formed by pouring a plurality of cross-arranged longitudinal and transverse beams, or a non-parallel distribution.

[0024] For the specific arrangement form of the trench support system of the present application, refer to Figure 2 , each intersection of the grid structure of the inner support 3 is provided with a column 9 or the columns 9 are arranged at intervals below the intersections of the grid structure, and each column 9 is provided with a column pile 10 below. The axes of the interconnected column 9 and column pile 10 are located on the same straight line and are perpendicular to the inner support 3. The support wall 2, the inner support 3, the column 9, and the column pile 10 jointly form a support action. The diversion box culvert 1 of the present application is integrally poured with the inner support 3 when arranged, and the inner support 3 provides support to the diversion box culvert 1.

[0025] In the present application, the cofferdam system includes the Larsen steel sheet pile 4, the plain fill, the reverse support 5, the water retaining wall 6, and the water stop system 7. The Larsen steel sheet pile 4 is used to be arranged at the periphery of the foundation pit to form a cofferdam to achieve water blocking to facilitate the excavation of the foundation pit. The reverse support 5 is located at the water side of the Larsen steel sheet pile 4 to achieve water retaining to increase the stability of the Larsen steel sheet pile 4. The reverse support 5 can be a sand and stone bag. The plain fill is used to be arranged in the cofferdam or other positions as needed. The water stop system 7 is used to be arranged at the outer side of the support wall 2 or at both sides of the support wall 2 to achieve water stopping effect.

[0026] The Larsen steel sheet pile 4 is used to form a cofferdam or the Larsen steel sheet pile 4 and the water retaining wall 6 are used to form a cofferdam in cooperation. When the Larsen steel sheet pile 4 and the water retaining wall form a cofferdam, the water stop system 7 is arranged at the interface position to improve the water stopping effect of the cofferdam. Specifically, the water retaining wall 6 is used in the third stage of the staged construction of the foundation pit. Since the river 8 has completed the construction of the foundation pit structure at this time, the Larsen steel sheet pile 4 cannot be inserted on the foundation pit structure. At this time, the water retaining wall 6 can be arranged on the foundation pit structure to form a cofferdam in cooperation with the Larsen steel sheet pile 4 inserted at other positions. Further, when forming a cofferdam, if the cofferdam contains the river 8 bank, the water retaining wall 6 can be arranged on the river 8 bank as the edge of the cofferdam.

[0027] In the second aspect, the embodiments of the present application also provide a river foundation pit staged construction method based on the above-mentioned river foundation pit box culvert diversion staged cofferdam system. For the convenience of description, the river 8 is divided into two sides along the water flow direction, i.e. the river 8 at the position of the construction foundation pit is divided into two sides, which are the first side river 8A and the second side river 8B. The river foundation pit staged construction method of the present application includes: S1: constructing the cofferdam system and the foundation pit support system at the first side river 8A, integrally pouring and constructing the inner support 3 and the diversion box culvert 1, and removing the cofferdam system after the diversion box culvert 1 has the flow-through condition, and using the diversion box culvert 1 to flow through the first side river 8A; this is the first stage construction of the foundation pit construction; S2: constructing the cofferdam system and the foundation pit support system at the second side river 8B, and constructing the entire foundation pit structure, and removing the cofferdam system and the inner support 3 within the cofferdam range after the construction of the foundation pit structure is completed, and restoring the flow of the second side river 8B; this is the second stage construction of the foundation pit construction; S3: again constructing the cofferdam system at the first side river 8A, removing the diversion box culvert 1 and the inner support 3 within the cofferdam range after the construction of the cofferdam system is completed, and then removing the cofferdam system to restore the flow of the first side river 8A; this is the third stage construction of the foundation pit construction.

[0028] Reference is made to Figure 3As shown, further, in an embodiment, the cofferdam system and foundation pit support system at the first side river creek 8A are constructed, the inner support 3 and the diversion box culvert 1 are integrally poured and constructed, and after the diversion box culvert 1 has the flow-through condition, the cofferdam system is removed, the first side river creek 8A is flow-through by using the diversion box culvert 1, and specifically includes: S101: The empty land beside the first side river creek 8A is taken as the construction site, and the plain fill is backfilled to the site level elevation; S102: The cofferdam system at the first side river creek 8A is constructed, the Larsen steel sheet pile 4 and the reverse support 5 are installed, and the plain fill is backfilled to form the cofferdam; at this time, the Larsen steel sheet pile 4 and the bank of the first side river creek 8A are combined to form the cofferdam, as shown in FIG. 2A, and the cofferdam range formed at this time is shown by the middle label A; Figure 3 S103: The support wall 2, the column 9 and the column pile 10 of the foundation pit at the first side river creek 8A are buried, the foundation pit depth is excavated to the bottom elevation of the diversion box culvert 1, the erection of the foundation pit support system is completed, and the inner support 3 and the diversion box culvert 1 are integrally poured and constructed; Specifically, the support wall 2, the column 9 and the column pile 10 are buried in the cofferdam first, then the foundation pit depth is excavated to the bottom elevation of the diversion box culvert 1, the erection of the foundation pit support system is completed, and the inner support 3 and the diversion box culvert 1 are integrally poured and constructed; S104: After the diversion box culvert 1 has the flow-through condition, the Larsen steel sheet pile 4 and the reverse support 5 at the first side river creek 8A are removed, the plain fill in the cofferdam at the first side river creek 8A is removed, and the first side river creek 8A is flow-through by using the diversion box culvert 1. Specifically, after the diversion box culvert 1 is installed, the foundation pit structure is not constructed, then the Larsen steel sheet pile 4 and the reverse support 5 at the first side river creek 8A are removed, the plain fill in the cofferdam at the first side river creek 8A is removed, the diversion box culvert 1 is flow-through, and the flow of the first side river creek 8A is restored.

[0029] Referring to FIG. 2B, Figure 4 As shown, further, in an embodiment, the cofferdam system, the foundation pit support system and the foundation pit structure at the second side river creek 8B are constructed, all the foundation pit structures are constructed, and after the construction of the foundation pit structure is completed, the cofferdam system and the inner support 3 in the cofferdam range are removed, and the flow of the second side river creek 8B is restored, and specifically includes: S201: The empty land beside the second side river creek 8B is taken as the construction site, and the plain fill is backfilled to the site level elevation; S202: The cofferdam system at the second side river creek 8B is constructed, the Larsen steel sheet pile 4 and the reverse support 5 are installed, and the plain fill is backfilled, and the Larsen steel sheet pile 4 and the side of the diversion box culvert 1 are combined to form the cofferdam; at this time, the Larsen steel sheet pile 4, the diversion box culvert 1 close to the side of the second side river creek 8B, and the bank of the second side river creek 8B are combined to form the cofferdam, as shown in FIG. 3A, and the cofferdam range formed at this time is shown by the middle label B; Figure 4 ​​S203: embed the supporting wall 2, the column 9 and the column pile 10 of the foundation pit at the second side river 8B, carry out the erection of the foundation pit supporting system while excavating the foundation pit, and carry out the construction of the whole foundation pit structure after excavating to the bottom elevation of the foundation pit; Specifically, the embedding of the supporting wall 2, the column 9 and the column pile 10 is first carried out in the cofferdam, then the erection of the foundation pit supporting system is carried out while excavating the foundation pit, and the construction of the whole foundation pit structure is carried out after excavating to the bottom elevation of the foundation pit; S204: install protection plates at the bottom of the river and the top of the foundation pit structure, and install a water retaining wall 6 on the protection plate of the foundation pit structure at the boundary between the second side river 8B and the first side river 8A; it should be noted that the installation of the protection plate can also not be carried out; Specifically, after the construction of the foundation pit structure at the second side river 8B is completed, protection plates are installed at the bottom of the second side river 8B and the top of the foundation pit structure at the second side river 8B, and a water retaining wall 6 is installed on the protection plate of the foundation pit structure at the second side river 8B, and the water retaining wall 6 is located on the side of the foundation pit structure close to the first side river 8A; S205: remove the foundation pit supporting system within the range of the second side river 8B, pull out the Larsen steel sheet pile 4 and the reverse support 5, and restore the flow of the second side river 8B. Specifically, the foundation pit supporting system within the range of the second side river 8B is removed, that is, the inner support 3, the column 9 and the column pile 10 within the range of the second side river 8B are removed, and the supporting wall 2 is chiseled out, then the Larsen steel sheet pile 4 and the reverse support 5 at the second side river 8B are pulled out, and the flow of the second side river 8B is restored.

[0030] Referring to Figure 5 Further, in an embodiment, the cofferdam system at the first side river 8A is constructed again, and after the construction of the cofferdam system is completed, the diversion box culvert 1 and the inner support 3 within the range of the cofferdam are removed, and then the cofferdam system is removed to restore the flow of the first side river 8A, which specifically includes: S301: use the empty land beside the first side river 8A as a construction site, and backfill the plain fill to the site level; S302: construct the cofferdam system at the first side river 8A, install the Larsen steel sheet pile 4 and the reverse support 5, so that the Larsen steel sheet pile 4 and the water retaining wall 6 on the foundation pit structure at the second side river 8B form a cofferdam; at this time, the Larsen steel sheet pile 4, the water retaining wall 6 on the foundation pit structure at the second side river 8B, and the bank of the first side river 8A form a cofferdam, see Figure 5 The cofferdam range formed at this time is indicated by reference character C; S303: remove the diversion box culvert 1 at the first side river 8A; S304: remove the inner support 3, the diversion box culvert 1 and the water retaining wall 6, and then remove the cofferdam system, and restore the flow of the first side creek 8A. Specifically, the foundation pit support system at the first side creek 8A is removed, that is, the diversion box culvert 1, the inner support 3, the column 9 and the column pile 10 within the range of the first side creek 8A are removed, and the support wall 2 is chiseled out, then the Larsen steel sheet pile 4 and the reverse support 5 at the first side creek 8A are pulled out, the flow of the first side creek 8A is restored, and thus the foundation pit construction is completed.

[0031] The present application adopts cross construction, utilizes construction gaps, and proceeds with the foundation pit structure construction in advance, thereby saving the process joint construction period, simplifying the process, saving the construction period, greatly accelerating the construction progress and improving the work efficiency without sacrificing the safety performance. The present application does not need to additionally set a strong drainage pump station, does not need to set a partition wall compared with the conventional cofferdam mode, saves the site and investment, and can minimize the influence on the surrounding environment. Meanwhile, the diversion box culvert 1 and the foundation pit inner support 3 system are integrally poured, the stress is good, the stability is high, and the flow section is large.

[0032] In the description of the present application, it should be noted that the positions or position relationships indicated by the terms "upper", "lower" and the like are based on the positions or position relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular position, be constructed and operated in a particular position, and therefore cannot be understood as a limitation on the present application. Unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of additional identical elements in the process, method, article or equipment including the element.

[0034] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A phased cofferdam system for diverting river channel foundation pit box culverts, characterized in that, The phased cofferdam system for diverting the river channel foundation pit box culvert includes: A diversion box culvert (1) is installed in the foundation pit to divert the river (8). The foundation pit support system is used to provide support for the foundation pit. The foundation pit support system includes a support wall (2) for the outer perimeter of the foundation pit, an inner support (3) for the inside of the foundation pit, and columns (9) and column piles (10) located below the inner support (3). A cofferdam system for blocking river channels (8) and located outside the foundation pit support system, the cofferdam system including Larssen sheet piles (4), plain fill, reverse support (5), water retaining wall (6), and water-stopping system (7).

2. The phased cofferdam system for diverting river channel foundation pits and box culverts as described in claim 1, characterized in that: The inner support (3) is a grid structure, wherein a column (9) is provided below each intersection of the grid structure or the columns (9) are spaced apart below the intersection of the grid structure, and a column pile (10) is provided below each column (9).

3. The phased cofferdam system for diverting river channel foundation pit box culverts as described in claim 2, characterized in that: The axes of the interconnected columns (9) and column piles (10) are on the same straight line and perpendicular to the inner support (3).

4. The phased cofferdam system for diverting river channel foundation pit box culverts as described in claim 1, characterized in that: The water-stopping system (7) is located on the outside of the retaining wall (2) or on both sides of the retaining wall (2).

5. A phased cofferdam system for diverting river channel foundation pit box culverts as described in claim 1, characterized in that: The Larssen sheet piles (4) are used to enclose and form a cofferdam, or the Larssen sheet piles (4) and the retaining wall (6) are used to enclose and form a cofferdam. When the Larssen sheet piles (4) and the retaining wall enclose and form a cofferdam, a water-stopping system (7) is set at the interface.

6. A phased cofferdam system for diverting river channel foundation pit box culverts as described in claim 5, characterized in that: The reverse support (5) is located on the water-facing side of the Larsen sheet pile (4).

7. A method for phased construction of a river channel foundation pit, based on the phased cofferdam system for diversion of the river channel foundation pit box culvert as described in any one of claims 1 to 6, wherein the river channel (8) is divided into two sides along the water flow direction, namely a first side river channel (8A) and a second side river channel (8B), characterized in that, The phased construction method for the river channel foundation pit includes: The cofferdam system and foundation pit support system at the first side river channel (8A) were constructed as a whole, with the internal support (3) and the diversion box culvert (1) being poured and constructed. After the diversion box culvert (1) was ready for flow, the cofferdam system was removed and the first side river channel (8A) was opened for flow using the diversion box culvert (1). Construct the cofferdam system and foundation pit support system at the second side river channel (8B), and construct the entire foundation pit structure. After the foundation pit structure is completed, remove the cofferdam system and the internal support within the cofferdam area (3) to restore the flow of the second side river channel (8B). The cofferdam system at the first side channel (8A) was reconstructed, and the diversion culvert (1) and the inner support (3) within the cofferdam area were removed after the cofferdam system was completed. Then the cofferdam system was removed to restore the flow of the first side channel (8A).

8. The method for phased construction of a river channel foundation pit as described in claim 7, characterized in that, The cofferdam system and foundation pit support system at the first side river channel (8A) of the construction site, the internal support (3) and the diversion box culvert (1) are integrally cast and constructed. After the diversion box culvert (1) is ready for flow, the cofferdam system is removed and the first side river channel (8A) is opened for flow using the diversion box culvert (1). Specifically, this includes: The open space next to the first side river channel (8A) will be used as the construction site, and plain fill soil will be backfilled to the site level. The construction of the cofferdam system at the first side river channel (8A) involves installing Larssen sheet piles (4) and reverse retaining walls (5) and backfilling with plain fill to form a cofferdam; The retaining wall (2), column (9) and column pile (10) of the foundation pit at the first side river channel (8A) are buried. The foundation pit is excavated to the bottom elevation of the diversion box culvert (1). The foundation pit support system is erected, and the internal support (3) and diversion box culvert (1) are poured as a whole. After the diversion box culvert (1) is ready for flow, the Larsen sheet piles (4) and reverse retaining (5) at the first side river channel (8A) are removed, the plain fill soil in the cofferdam at the first side river channel (8A) is cleared, and the diversion box culvert (1) is used to allow flow in the first side river channel (8A).

9. A method for phased construction of a river channel foundation pit as described in claim 8, characterized in that, The construction includes the construction of the cofferdam system and foundation pit support system at the second side river channel (8B), and the construction of the entire foundation pit structure. After the foundation pit structure construction is completed, the cofferdam system and the internal support (3) within the cofferdam area are removed to restore the flow of the second side river channel (8B), specifically including: The open space next to the second side river channel (8B) will be used as the construction site, and plain fill soil will be backfilled to the site level. The construction of the cofferdam system at the second side river channel (8B) involves installing Larssen sheet piles (4) and reverse retaining walls (5) and backfilling with plain fill soil. The Larssen sheet piles (4) and the side of the diversion box culvert (1) together form a cofferdam. The retaining wall (2), column (9) and column pile (10) of the foundation pit at the second side river channel (8B) are buried. The foundation pit support system is erected while the foundation pit is being excavated. After the foundation pit is excavated to the bottom elevation of the foundation pit, the construction of the entire foundation pit structure is carried out. Protective plates are installed at the bottom of the river channel and the top of the foundation pit structure, and a retaining wall (6) is installed on the protective plate of the foundation pit structure at the boundary between the second side river channel (8B) and the first side river channel (8A). Remove the foundation pit support system within the area of ​​the second side channel (8B), pull out the Larsen sheet piles (4) and the reverse retaining (5), and restore the flow of the second side channel (8B).

10. A method for phased construction of a river channel foundation pit as described in claim 9, characterized in that, The construction of the cofferdam system at the first side channel (8A) is carried out again, and the diversion culvert (1) and the internal support (3) within the cofferdam area are removed after the cofferdam system is completed. Then the cofferdam system is removed to restore the flow of the first side channel (8A), specifically including: The open space next to the first side river channel (8A) will be used as the construction site, and plain fill soil will be backfilled to the site level. The construction of the cofferdam system at the first side river channel (8A) involves installing Larssen sheet piles (4) and reverse supports (5) so that the Larssen sheet piles (4) and the water retaining wall (6) on the foundation pit structure at the second side river channel (8B) can be combined to form a cofferdam; Demolish the diversion box culvert (1) at the first side river channel (8A); Remove the internal support (3), the diversion box culvert (1) and the retaining wall (6), then remove the cofferdam system and restore the flow of the first side channel (8A).

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