Transition retaining wall of cofferdam support system for underwater tunnel construction

Abstract

This invention discloses a transition retaining wall for a cofferdam-type underwater foundation pit support system used in the construction of underwater channels. It includes a main wall located on the top slab of the left half of the underwater channel. Two concrete protrusions extending along the length of the channel are provided on the top slab of the left half of the underwater channel. The two concrete protrusions and the top slab together form an installation groove filled with fly ash clay mortar. The main wall includes a row of continuously interlocking Larssen sheet piles, which are inserted into the installation groove and embedded in the fly ash clay mortar. Each left-protruding Larssen sheet pile in this row has a steel bracket welded to its left surface. A steel waler rests on all the steel brackets, and the left flange of the steel waler is connected to each right-protruding Larssen sheet pile by a tie bolt. A row of diagonal bracing is provided between the top slab of the left half of the underwater channel and the steel waler. This retaining wall enhances the water-stopping effect and is simple and convenient to assemble and disassemble.

Description

Technical Field

[0001] This invention relates to the field of cofferdam-type foundation pit support construction technology in civil engineering, specifically a transition retaining wall for a cofferdam-type underwater foundation pit support system used in the construction of underwater channels. Background Technology

[0002] PC (precast concrete) pile construction is a mature existing technology. It utilizes tongue-and-groove joints to interlock alternating PC steel pipe piles and Larssen steel sheet piles to form a continuous composite steel wall. Due to its good water-stopping effect, ideal rigidity, and ability to resist lateral water and soil pressure, it is widely used in river cofferdam construction. This application pertains to the construction of a concrete underwater channel in a river. This project can connect the underground spaces on both sides of the river into a unified whole for easy use, while maintaining unobstructed water flow and keeping the river channel unobstructed. It has minimal environmental impact and conforms to the concept of green environmental protection, hence its increasingly widespread promotion and application.

[0003] Current technologies often employ a half-width construction method for underwater concrete channels. Taking the construction sequence of first the left half and then the right half as an example, the construction process is as follows: First, construct the left front retaining wall, the interface retaining wall, and the left rear retaining wall using precast concrete (PC) piles. These three PC pile retaining walls are connected end-to-end to form the left half of the river channel's cofferdam and underwater foundation pit support system, while simultaneously maintaining unobstructed water flow in the right half of the river channel. Next, pump out the water from the left half of the cofferdam and excavate the soil. Then, construct the left half of the underwater concrete channel, and build a temporary brick wall at the right end of the left half channel's interface. Next, construct a transition retaining wall on the left side of the left half channel interface. The purpose of this transition retaining wall is to abut against the left front and left rear retaining walls on both sides to prevent water seepage. Finally, remove the sections of the left front and left rear retaining walls located to the left of the transition retaining wall. Partially, the interface retaining wall was dismantled to restore water flow to the left half of the river channel, while the portions of the left front retaining wall and left rear retaining wall located to the right of the transition retaining wall were retained. Then, the right front retaining wall and right rear retaining wall of the PC method piles were constructed, so that the right front retaining wall, the retained portion of the left front retaining wall, the transition retaining wall, the retained portion of the left rear retaining wall, and the right rear retaining wall were connected end to end to form a continuous water-stopping right half cofferdam and underwater foundation pit support system. Finally, the right half cofferdam was dewatered and excavated, and the right half concrete underwater channel was constructed to connect with the left half underwater channel. Then, the temporary brick wall at the interface was removed, and the right half cofferdam structure was dismantled.

[0004] The subject of this application is the structure and construction method of the transition retaining wall of the cofferdam-type underwater foundation pit support system used for the construction of the aforementioned underwater tunnel. The existing transition retaining wall includes a main wall located on the top slab of the left half of the concrete underwater tunnel. The main wall consists of a triangular steel truss resting on the top slab and a large number of sandbags stacked inside the triangular steel truss. The triangular steel truss serves as a skeleton to constrain the sandbags to form an overall water-stopping structure, thereby resisting the lateral pressure of the water on the left. The gap between the side of the main wall and the left front retaining wall or left rear retaining wall is backfilled with a layer of clay mortar.

[0005] The existing transition retaining wall technology has the following drawbacks. First, the stacked sandbags of the main retaining wall cannot achieve complete water stoppage, and the clay mortar in the gap between the main wall and the left front or left rear retaining wall also has a limited water-stopping effect. Therefore, the right half of the cofferdam often leaks water during actual construction, causing inconvenience and safety hazards. Furthermore, due to the large number and weight of the sandbags in the main wall, the process of stacking or moving a large number of sandbags when building or dismantling the main wall is time-consuming and labor-intensive, increasing labor costs and slowing down the construction period. In addition, the weight of the main wall with its stacked sandbags increases the burden on the underwater channel structure below the retaining wall. To ensure support, after pouring the concrete for the top slab of the left half of the channel, all the vertical and transverse support steel pipes of the bottom formwork of the top slab must be retained and cannot be removed for reuse. In fact, even more and denser vertical support steel pipe frames are needed, which reduces the turnover rate of the support steel pipe frames and increases construction costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a transition retaining wall for a cofferdam-type underwater foundation pit support system for construction underwater channels that can enhance water-stopping effect, improve lateral pressure resistance, is simple and convenient to assemble and disassemble, is lightweight, and puts little burden on the underwater channel structure below the retaining wall.

[0007] The technical solution of this invention is to provide a transition retaining wall for a cofferdam-type underwater foundation pit support system used in the construction of underwater tunnels; it includes a main wall located on the top slab of the left half of the underwater tunnel.

[0008] The top plate of the left half of the underwater channel is provided with two concrete protrusions extending along the length of the river channel. The two concrete protrusions and the top plate together form an installation groove, which is filled with fly ash clay mortar.

[0009] The main wall consists of a row of continuously interlocking Larssen sheet piles, which are inserted into the installation groove and embedded in fly ash clay mortar. Each left-convex Larssen sheet pile in the row has a steel bracket welded to its left surface. A steel waler is placed on all the steel brackets. The left flange of the steel waler is connected to each right-convex Larssen sheet pile by a tie bolt.

[0010] A row of diagonal bracing is installed between the top plate of the left half of the underwater passage and the steel waler.

[0011] Compared with the prior art, the transition retaining wall of the cofferdam-type underwater foundation pit support system for constructing underwater tunnels using the method described in this application has the following advantages.

[0012] First, the Larssen sheet piles of the main wall of the transition retaining wall are tightly interlocked with each other through tongue and groove, forming a continuous steel water-stop structure. Therefore, compared with stacked sandbags, the water-stopping effect is significantly enhanced, greatly reducing the probability of water leakage in the right half of the cofferdam during actual construction, facilitating the construction process, and reducing safety hazards.

[0013] Furthermore, since the Larssen sheet piles are inserted into the installation groove and filled with fly ash clay mortar, the bottom of the main wall is firmly embedded. The upper part of the main wall, which is the upper part of the Larssen sheet piles, is also fixed with a steel waler. The waler is connected to the top plate of the left half of the underwater channel by diagonal bracing. In this way, the main wall is transformed from a cantilever structure that is only fixed at the bottom into an integral structure that is stressed from both the top and bottom, so as to jointly resist the lateral pressure of the water. Therefore, it has stronger rigidity, more solid support, and naturally better water-stopping effect.

[0014] Furthermore, since the process of assembling the main wall uses a vibratory hammer to insert each Larssen sheet pile into the fly ash mortar for fixation, and the process of dismantling the main wall uses a vibratory hammer to pull each Larssen sheet pile out of the fly ash mortar, the mechanical insertion and extraction process is significantly more convenient, faster and less labor-intensive than the process of moving a large number of sandbags, thus reducing labor costs and speeding up the construction period.

[0015] Furthermore, compared to sandbags, the Larssen sheet pile wall of the main wall is lighter in weight and has a smaller load on the underwater channel structure below the retaining wall. Therefore, after the concrete at the top of the underwater channel has hardened, all the vertical support steel pipe frame of the bottom formwork of the top slab can be removed, which reduces material consumption, speeds up the turnover rate of the support steel pipe, and further reduces construction costs.

[0016] Moreover, since the steel walers are set on the water-facing side of the main wall and connected to the top plate of the underwater channel, the main wall can withstand the water pressure on its own. Therefore, when constructing the right half of the cofferdam, the steel walers of the main wall do not need to be connected to the other steel walers of the right front retaining wall and the right rear retaining wall of the right half. Thus, the welding process with the other steel walers of the right half is omitted. During disassembly, it is not necessary to cut them with other steel walers. In other words, the steel walers of the main wall are firmly supported, can be disassembled and assembled independently, and are easy to operate.

[0017] Of course, when assembling the steel walers of the main wall, you only need to place them on each steel bracket and quickly tie them together with each tie bolt. This significantly reduces the amount of on-site welding work while ensuring the connection is firm. When disassembling, you only need to loosen the nuts of the tie bolts. The steel walers themselves are also very easy to assemble and disassemble.

[0018] Preferably, a uniquely shaped tie sheet pile is installed between the foremost Larssen sheet pile of the main wall of the transition retaining wall and the nearest PC pipe pile in the left front retaining wall, and a uniquely shaped tie sheet pile is also installed between the last Larssen sheet pile and the nearest PC pipe pile in the left rear retaining wall; each uniquely shaped tie sheet pile includes an outward rolled edge for hooking with the PC pipe pile and an inward rolled edge for hooking with the Larssen sheet pile, the outward rolled edge extending down to the riverbed and the inward rolled edge extending down to the top plate of the underwater channel, and the uniquely shaped tie... The lower end of the sheet piles also extends to the riverbed; each irregularly shaped tie sheet pile has a water-facing steel plate on its water-facing side, and the water-facing steel plate has an inner and outer flange made of elastic material on both sides, with both flanges rolled towards the water-facing side; the outer flange abuts against the arc wall of the adjacent PC steel pipe pile, and the inner flange abuts against the side wall of the underwater channel corresponding to it; the upper end of each water-facing steel plate is fixed to the left or right end of the steel waler by tie bolts; a clay mortar interlayer is backfilled between each irregularly shaped tie sheet pile and the corresponding water-facing steel plate.

[0019] The aforementioned structure forms a three-layered water-stopping structure between the main wall and the left front or left rear retaining wall. The irregularly shaped sheet piles in the rear layer interlock with the outer PC steel pipe piles and the inner Larssen sheet piles via inward and outward rolled edges, initially providing some water-stopping effect and support rigidity. However, because the inner Larssen sheet piles only extend to the top of the underwater channel rather than the riverbed, only the upper part of the irregularly shaped sheet piles interlocks with the Larssen sheet piles, leaving the lower part unsupported. Given the greater depth and water pressure at the bottom, the water-stopping effect of the lower rear layer is incomplete. Therefore, a water-facing steel plate is installed in front of the irregularly shaped sheet piles, and the steel waler is placed on the water-facing side of the main wall. This allows the upper part of the water-facing steel plate to be fixed to the protruding part of the steel waler, while the lower end relies on an elastic flange to abut against and engage with the arc surface of the PC steel pipe pile and the underwater surface. Between the side walls of the passage, the front structure makes full use of the front-mounted steel walers, which serve both to connect the diagonal braces and as a fixed foundation for the upper part of the water-facing steel plate. The lower part uses elastic flanges for snap-fitting. Compared with the conventional approach of building a retaining brick wall, this assembly process requires less work and is faster to construct. Moreover, after the upper part of the water-facing steel plate is tied, the lower part will be tightened more and more under water pressure, thus giving the front structure a better waterproof effect. Combined with the clay mortar interlayer backfilled between the water-facing steel plate and the irregularly shaped tie steel sheet piles, a three-layer integrated waterproof structure is constructed, which completely solves the drawback of the imperfect water-stopping effect between the main wall and the two side retaining walls, and further improves the overall seepage resistance and water-stopping performance of the transition retaining wall.

[0020] The above structural features combine and complement each other, jointly improving the waterproofing efficiency. Moreover, the disassembly and assembly process of the above structure is very convenient. Simply hook the rear irregular-shaped steel sheet piles onto the tongue and groove joints on both sides, then insert the water-facing steel plate into the PC steel pipe pile and the side wall of the channel, and tie the upper end of the water-facing steel plate to the outer protrusion of the steel waler. Then, backfill the space between the front and rear steel plates with clay mortar. Later, the lower end of the water-facing steel plate will automatically abut against the pipe pile wall or channel wall under water pressure and seal it, further compacting the clay mortar in the middle layer, further improving the water-stopping efficiency.

[0021] More importantly, this application breaks through conventional thinking. According to common sense, to fix the front and rear steel plates, double tongue and groove joints are welded to the outer wall of the PC steel pipe pile to hook the double steel plates. However, this would result in too dense welding positions, damaging the PC steel pipe pile. In this application, the outer steel plate is clamped by the combined action of water pressure and elastic resistance at the lower end, without damaging the PC steel pipe pile. Furthermore, the rear tie steel plate hooks with the tongue and groove joints on both sides, and together with the clay in the middle layer that is further compacted by water pressure, a perfect water-stopping effect and convenient disassembly and assembly are achieved.

[0022] As a further optimization of the water-stopping structure, each water-facing steel plate has wedge-shaped grooves on both sides, and wedge-shaped strips on both the inner and outer flanges. The inner and outer flanges are engaged in the wedge-shaped grooves on the corresponding sides of the water-facing steel plate by their respective wedge-shaped strips. In this way, the assembly between the flexible flanges and the rigid water-facing steel plate is more convenient and the connection effect is more secure.

[0023] As another preferred option, a row of hanging rings is pre-embedded in the top plate of the left half of the underwater passage. Anchor holes are provided on the left flange plate of the steel waler. The lower end of the diagonal tie rod is provided with a hook to hook onto the hanging rings. The upper end of the diagonal tie rod is a threaded section with an adjusting nut. The upper end of the diagonal tie rod passes through the corresponding anchor hole of the steel waler and is tensioned by the adjusting nut. In this way, the tensioning and assembly process of the diagonal tie rod is convenient. It is only necessary to hook the lower end of the diagonal tie rod and then tighten the adjusting nut at its upper end to quickly tension the diagonal tie rod, thereby achieving the connection and fixation between the steel waler and the top plate of the underwater passage. Moreover, the process of tensioning the diagonal tie rod can be carried out simultaneously with the process of using tie bolts to connect the steel waler and the main wall, further facilitating the operation. In addition, during disassembly, it is only necessary to simultaneously loosen the upper end of the diagonal tie rod and the tie bolts to simultaneously remove the steel waler and the diagonal tie rod, so disassembly is also convenient.

[0024] As a further optimization, the two concrete protrusions are cast integrally with the top slab of the left half of the underwater channel; the cross-section of the left concrete protrusion is a wedge shape with the left side lower and the right side higher, and the cross-section of the right concrete protrusion is a wedge shape with the right side lower and the left side higher; in this way, the integral casting of the protrusions with the top slab can ensure the strong connection between the concrete protrusions and the top slab, and the symmetrical structure of the two protrusions can provide stronger support for the bottom of each Larssen sheet pile in the center, thereby ensuring a more firm and reliable clamping and embedding effect of the entire row of Larssen sheet piles in the installation groove. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the left half of the transition retaining wall during the construction of the cofferdam-type underwater foundation pit support system for the construction of underwater channels according to the present invention.

[0026] Figure 2 This is a top view of the left half of the transition retaining wall of the cofferdam-type underwater foundation pit support system used in the construction of the underwater tunnel of this invention during construction.

[0027] Figure 3 This is a structural diagram of the right half of the transition retaining wall during the construction of the cofferdam-type underwater foundation pit support system for the construction of underwater channels according to the present invention.

[0028] Figure 4 yes Figure 2 An enlarged schematic diagram of part A in the middle.

[0029] Figure 5 yes Figure 3 Enlarged schematic diagram of part B.

[0030] Figure 6 yes Figure 3 An enlarged schematic diagram of section C.

[0031] Figure 7 yes Figure 3 A structural diagram showing the structure after deflecting at a certain angle and removing part of the right rear retaining wall.

[0032] The diagram shows: 1. Underwater passage; 1.1. Top plate; 2. Concrete protrusion; 3. Installation groove; 4. Main wall; 4.1. Right convex Larssen sheet pile; 4.2. Left convex Larssen sheet pile; 4.3. Steel bracket; 5. Steel waler; 6. Tie bolt; 7. Right front retaining wall; 8. Left front retaining wall; 9. Interface retaining wall; 10. Right rear retaining wall; 11. Left rear retaining wall; 12. Irregularly shaped tie sheet pile; 12.1. Inward rolled edge; 12.2. Outward rolled edge; 13. Larssen sheet pile tongue and groove; 14. PC steel pipe pile tongue and groove; 15. Water-facing steel plate; 16. Clay mortar interlayer; 17. Inward turned edge; 18. Outward turned edge; 19. Wedge-shaped groove; 20. Wedge-shaped strip; 21. Diagonal tie bar. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] like Figures 1-7 As shown, the transition retaining wall of the cofferdam-type underwater foundation pit support system for the construction of the underwater passage of the present invention includes a main wall 4 located on the top slab 1.1 of the left half of the reinforced concrete underwater passage 1.

[0035] The top plate 1.1 of the left half of the underwater passage 1 is provided with two concrete protrusions 2 extending along the length of the river channel. The two concrete protrusions 2 and the top plate 1.1 together form an installation groove 3, which is filled with fly ash clay mortar. The two concrete protrusions 2 are integrally cast with the top plate 1.1 of the left half of the underwater passage 1. The cross-sections of the two concrete protrusions 2 are symmetrical along the centerline of the installation groove 3, that is, the cross-section of the left concrete protrusion 2 is a wedge shape with the left side lower and the right side higher, and the cross-section of the right concrete protrusion 2 is a wedge shape with the right side lower and the left side higher.

[0036] The main wall 4 includes a row of continuously interlocking Larssen sheet piles. This row of Larssen sheet piles includes right-convex Larssen sheet piles 4.1 and left-convex Larssen sheet piles 4.2 arranged at intervals. Each Larssen sheet pile is interlocked with the adjacent Larssen sheet pile via a tongue and groove joint. The bottom end of this row of Larssen sheet piles is inserted into the installation groove 3 and is bonded and fixed to fly ash clay mortar.

[0037] Each of the left-convex Larssen sheet piles 4.2 in this row has a steel bracket 4.3 welded to the upper left surface. All the steel brackets 4.3 are supported by a steel waler 5 parallel to the mounting groove 3. The left flange of the steel waler 5 is connected and fixed to each right-convex Larssen sheet pile 4.1 by a tie bolt 6.

[0038] A row of diagonal bracing 21 is installed between the top plate 1.1 of the left half of the underwater passage 1 and the steel waler 5 located on the left side of the main wall 4. Specifically, a row of hanging rings 22 is pre-embedded in the top plate 1.1 of the left half of the underwater passage 1. Anchor holes are provided on the left flange plate of the steel waler. The lower end of the diagonal bracing 21 is provided with a hook to hook the hanging ring. The upper end of the diagonal bracing 21 is a threaded rod section with an adjusting nut. The upper end of the diagonal bracing 21 passes through the corresponding anchor hole of the steel waler and is tensioned by the adjusting nut.

[0039] The gap between the front side of the main wall 4 and the left front retaining wall 8, or the gap between the rear side of the main wall 4 and the left rear retaining wall 11, are all equipped with a three-layer water-stopping structure (front, middle, and rear). Specifically,

[0040] A special-shaped tie sheet pile 12 is installed between the frontmost Larssen sheet pile of the main wall 4 and the nearest PC steel pipe pile in the left front retaining wall 8. A special-shaped tie sheet pile 12 is also installed between the rearmost Larssen sheet pile of the main wall 4 and the nearest PC steel pipe pile in the left rear retaining wall 11. Each special-shaped tie sheet pile 12 includes a vertical inward rolled edge 12.1 and an outward rolled edge 12.2. The outward rolled edge 12.2 extends down to the riverbed, while the inward rolled edge 12.1 extends down to the top plate 1.1 of the underwater channel 1. The lower end of the special-shaped tie sheet pile 12 also extends down to the riverbed. The inward rolled edge 12.1 of each special-shaped tie sheet pile 12 is hooked with the corresponding Larssen sheet pile tongue and groove 13, and the outward rolled edge 12.2 of each special-shaped tie sheet pile 12 is hooked with the corresponding PC steel pipe pile tongue and groove 14.

[0041] Each irregularly shaped tie sheet pile has a water-facing steel plate 15 on its water-facing side. The water-facing steel plate 15 has an inner flange 17 and an outer flange 18 made of elastic material on both sides. Specifically, each water-facing steel plate 15 has a wedge-shaped groove 19 on both sides, and the inner flange 17 and the outer flange 18 are provided with wedge-shaped clips 20. The inner flange 17 and the outer flange 18 are engaged in the wedge-shaped groove 19 on the corresponding side of the water-facing steel plate 15 by their respective wedge-shaped clips 20.

[0042] Both flanges are rolled towards the water-facing side; the outer flange 18 abuts against the arc wall of the adjacent PC steel pipe pile, and the inner flange 17 abuts against the side wall corresponding to the underwater channel 1. The upper end of each water-facing steel plate 15 is connected and fixed to the left or right end of the steel waler 5 by tie bolts 6.

[0043] Each irregularly shaped tie sheet pile 12 is backfilled with a clay mortar interlayer 16 between itself and the corresponding water-facing steel plate 15.

[0044] After the left half is completed, the portions of the left front retaining wall 8 and the left rear retaining wall 11 located to the left of the transition retaining wall are removed, and the interface retaining wall 9 is also removed, so that the water flow in the left half of the river channel is restored, while the portions of the left front retaining wall 8 and the left rear retaining wall 11 located to the right of the transition retaining wall are retained; then the right front retaining wall 7 and the right rear retaining wall 10 of the PC method piles are constructed, so that the right front retaining wall 7, the retained portion of the left front retaining wall 8, the transition retaining wall, the retained portion of the left rear retaining wall 11 and the right rear retaining wall 10 are connected end to end to form a continuous water-stopping cofferdam and underwater foundation pit support system for the right half.

[0045] Of course, this application uses the construction sequence of left half first and then right half as an example to illustrate the various structures. The left and right mentioned above are only for the purpose of description and not a limitation. If the construction sequence is right first and then left, then the transition retaining wall is inserted into the top plate 1.1 of the right half of the underwater channel 1, and the concrete protrusion 2 is also integrally cast into the top plate 1.1 of the right half of the underwater channel 1.

Claims

1. A transition retaining wall for a cofferdam-type underwater foundation pit support system used in the construction of an underwater passage, comprising a main wall located on the top slab of the left half of the underwater passage, characterized in that: The top plate of the left half of the underwater channel is provided with two concrete protrusions extending along the length of the river channel. The two concrete protrusions and the top plate together form an installation groove, which is filled with fly ash clay mortar. The main wall consists of a row of continuously interlocking Larssen sheet piles, which are inserted into the installation groove and embedded in fly ash clay mortar. Each left-convex Larssen sheet pile in the row has a steel bracket welded to its left surface. A steel waler is placed on all the steel brackets. The left flange of the steel waler is connected to each right-convex Larssen sheet pile by a tie bolt. A row of diagonal bracing is installed between the top plate of the left half of the underwater passage and the steel waler; A special-shaped tie sheet pile is installed between the frontmost Larssen sheet pile of the main wall and the nearest PC steel pipe pile in the left front retaining wall, and a special-shaped tie sheet pile is also installed between the rearmost Larssen sheet pile and the nearest PC steel pipe pile in the left rear retaining wall; each special-shaped tie sheet pile includes an outer rolled edge for hooking with the PC steel pipe pile and an inner rolled edge for hooking with the Larssen sheet pile. The outer rolled edge extends down to the riverbed and the inner rolled edge extends down to the top plate of the underwater channel. The lower end of the special-shaped tie sheet pile also extends down to the riverbed; Each irregularly shaped tie sheet pile has a water-facing steel plate on its water-facing side. The water-facing steel plate has an inner and outer flange made of elastic material on both sides, and both flanges are rolled towards the water-facing side. The outer flange abuts against the arc wall of the adjacent PC steel pipe pile, and the inner flange abuts against the side wall of the underwater channel. The upper end of each water-facing steel plate is fixed to the left or right end of the steel waler by tie bolts. Each irregularly shaped tie sheet pile is backfilled with a clay mortar interlayer between itself and the corresponding water-facing steel plate.

2. The transition retaining wall of the cofferdam-type underwater foundation pit support system for constructing underwater passages according to claim 1, characterized in that: Each water-facing steel plate has wedge-shaped slots on both sides, and wedge-shaped strips on both the inner and outer flanges. The inner and outer flanges are engaged with the wedge-shaped slots on the corresponding sides of the water-facing steel plate by their respective wedge-shaped strips.

3. The transition retaining wall of the cofferdam-type underwater foundation pit support system for underwater construction tunnels according to claim 1, characterized in that: A row of hanging rings is pre-embedded in the top plate of the left half of the underwater channel. Anchor holes are provided on the left flange plate of the steel waler. Hooks that hook the hanging rings are provided at the lower end of the diagonal tie rod. The upper end of the diagonal tie rod is a screw section with an adjusting nut. The upper end of the diagonal tie rod passes through the corresponding anchor hole of the steel waler and is tensioned by the adjusting nut.

4. The transition retaining wall of the cofferdam-type underwater foundation pit support system for constructing underwater passages according to claim 1, characterized in that: The two concrete protrusions are cast integrally with the top slab of the left half of the underwater channel; the cross-section of the left concrete protrusion is a wedge shape with the left side lower than the right side, and the cross-section of the right concrete protrusion is a wedge shape with the right side lower than the left side.

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