Cofferdam construction structure of conical prefabricated caisson foundation and construction method thereof

Abstract

The application provides a cofferdam type construction structure of a conical prefabricated caisson foundation and a construction method thereof. The conical prefabricated caisson foundation comprises a conical bottom caisson constructed in a dry dock, and a conical side wall coaxially arranged in a central region and constructed in a wet dock. A water stop connecting member is arranged on the top of the conical bottom caisson and surrounds the periphery of the conical side wall. A cofferdam main body is arranged on the top of the water stop connecting member, and the cofferdam main body comprises a bottom initial section which is installed in the dry dock. By using the construction scheme of sitting on the bottom and increasing the height in the wet dock, the safety risks of overturning, failure of mooring system and damage of facilities during the construction of the traditional floating pouring method in the typhoon period are fundamentally solved, and the stability and safety of the caisson height increasing process are significantly improved. By arranging the cofferdam main body which is installed in stages, the stability of the caisson during the two floating processes of floating to the wet dock and floating to the pier position is ensured, and a whole-process dry operation environment is provided for the caisson sitting on the bottom and increasing the height in the wet dock.

Description

Technical Field

[0001] This invention relates to the field of bridge construction, and in particular to a cofferdam-type construction structure and construction method for a conical precast caisson foundation. Background Technology

[0002] Conical caissons, with their variable cross-section structure that is smaller at the top and larger at the bottom, have demonstrated significant advantages in the construction of deep-water cross-sea bridge foundations. This structure not only saves on engineering materials by optimizing the cross-sectional distribution, but also possesses excellent mechanical properties and economy. Furthermore, it excels in adapting to complex sea conditions, geological conditions, and seismic resistance, making it an important selection option for deep-water bridge foundations.

[0003] The earliest engineering application of conical caissons was the Rion-Antirion Bridge in Greece, whose caisson had a bottom diameter of 90m and a top diameter of 27m, pioneering the application of this type of structure in deep-water bridge foundations. Subsequently, similar structures were successfully applied to major projects such as the Osman Gazi Bridge and the Çanakkale Bridge in Turkey, verifying their applicability in different marine environments.

[0004] However, deep-water bridge foundations must withstand enormous water flow forces and wave loads. Caisson foundations must rely on their own structural weight to resist overturning moments, resulting in extremely high self-weights. For example, the caissons of the Rion-Antirion Bridge weigh over 80,000 tons, making floating operations difficult solely based on their own buoyancy. Furthermore, the conical caisson's "smaller at the top, larger at the bottom" cross-sectional characteristic leads to a smaller waterline area, lower tilt height, and lower metacentric height, making it prone to tilting or even overturning under wind and wave loads. The structural stability in a floating state is insufficient to meet construction requirements.

[0005] In the past, similar caisson construction often employed the floating casting method. Taking the Rion-Antirion Bridge caisson construction as an example, the process was as follows: First, the caisson was cast to the designated elevation in a dry dock. Then, the dock gate was opened, water was injected into the dock, and the caisson was floated to a wet dock. After the caisson was secured with anchor cables in the wet dock, casting continued to the design elevation. Finally, the caisson was towed to the permanent pier, and water was injected into the compartments to allow it to sink and settle. While this method is suitable for sea areas with favorable wind and wave conditions, it has significant drawbacks in typhoon-prone areas: First, during the long-term casting of the caisson in the wet dock, the strong winds and waves caused by typhoons generate huge horizontal loads and overturning moments, significantly increasing the risk of caisson overturning. Second, extreme typhoon loads can easily cause anchor chains to break, leading to mooring system failure and causing the caisson to drift out of control. Third, the caisson's movement response is violent in the floating state, and the construction facilities such as tower cranes mounted on it are easily damaged by vibration and collision, seriously affecting construction safety and efficiency. Therefore, a cofferdam-type construction structure and construction method for a conical precast caisson foundation are proposed to solve the above problems. Summary of the Invention

[0006] The main objective of this invention is to provide a cofferdam-type construction structure and construction method for a conical precast caisson foundation, which solves the problems of overturning, anchor chain breakage, and damage to construction facilities caused by the traditional floating casting method in typhoon-prone sea areas due to the low center of gravity height and poor overturning resistance of the caisson.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a cofferdam construction structure for a conical precast caisson foundation. The conical precast caisson foundation includes a conical bottom box constructed in a dry dock and a conical sidewall coaxially arranged in its central area and constructed in a wet dock. The top of the conical bottom box is provided with a water-stop connecting component surrounding the conical sidewall. The top of the water-stop connecting component is provided with a cofferdam body. The cofferdam body includes an initial bottom section installed in the dry dock and a remaining cofferdam section installed in the wet dock. When the conical bottom box is seated in the wet dock, the top of the initial bottom section is higher than the horizontal plane. A cofferdam cavity for water injection is reserved between the cofferdam body and the conical sidewall, and an internal support is also provided between the two.

[0008] In the preferred embodiment, the water-stop connection component includes a ring array of pre-embedded reinforcing bars embedded in a conical bottom box with ends extending to the outside, and a cofferdam bottom section covering the pre-embedded reinforcing bars. The cofferdam bottom section has a water-stop cavity inside, with both the upper and lower ends of the water-stop cavity being open. Water-stop rubber is installed on both side walls of the water-stop cavity, and water-stop concrete is poured inside the cavity. A rear-clamping component is provided on both side walls of the cofferdam bottom section. This component penetrates the wall panel of the cofferdam bottom section and the water-stop rubber and extends into the water-stop concrete, and is used to press the wall panel of the cofferdam bottom section tightly against the water-stop rubber and the water-stop concrete.

[0009] In the preferred embodiment, the post-clamping assembly includes a ring array of reinforcing vertical beams on the outside of the cofferdam bottom section. One or more spliced ​​steel sections are connected between the reinforcing vertical beams and arranged along the height direction of the water-stop concrete. The inner wall of the spliced ​​steel section fits against the outer wall of the cofferdam bottom section. Perforations are provided on the spliced ​​steel section, the cofferdam bottom section, and the water-stop rubber. The spliced ​​steel section is provided with through perforations that extend into the water-stop concrete to form a post-clamping part for locking and clamping.

[0010] In the preferred embodiment, the rear clamping part specifically includes an internally threaded sleeve, which is located in the water-stop cavity and its end abuts against the perforation of the water-stop rubber. An anchor rod is threadedly installed at the end of the internally threaded sleeve away from the water-stop rubber, and an anchor plate is fixedly connected to the other end of the anchor rod. A locking screw protruding from the perforation is threadedly installed at the end of the internally threaded sleeve close to the water-stop rubber, and a washer and a nut are sequentially fitted on the outside of the locking screw.

[0011] In the preferred embodiment, the internal threaded sleeve is a tapered sleeve.

[0012] In the preferred embodiment, the reserved reinforcing bars are "L" shaped, with the horizontal section embedded in the conical bottom box and fixedly connected to the reinforcing bars in the conical bottom box, and the vertical section extending to the outside of the conical bottom box, with a hook structure at the end.

[0013] In the preferred embodiment, the reserved steel bars are specifically set up with two rings, inner and outer, and the reserved steel bars in the two rings are arranged symmetrically.

[0014] In the preferred design, the main body of the cofferdam is cylindrical.

[0015] In the preferred embodiment, the main body of the cofferdam is a double-wall structure composed of two cofferdam walls, one inner and one outer, with multiple annularly distributed vertical adjustment cavities formed between the two cofferdam walls.

[0016] In the preferred embodiment, the bottom of the vertical adjustment cavity and the cofferdam cavity are provided with drainage outlets equipped with valves.

[0017] In the preferred embodiment, both the conical sidewall and the main body of the cofferdam are multi-segment composite structures formed by sequentially raising them from bottom to top.

[0018] In the preferred embodiment, the internal support specifically includes multiple rings of horizontal bracing arranged vertically. The horizontal bracing of each ring is distributed equidistantly in a ring. One end of the horizontal bracing is welded and fixed to the inner wall of the main body of the cofferdam, and the other end is provided with a wedge-shaped seat. A wedge-shaped block is inserted between the wedge-shaped seat and the outer wall of the conical sidewall. Circular bracing is provided between the horizontal bracing of the same ring near the end of the conical sidewall. Vertical bracing and diagonal bracing are also provided between adjacent horizontal bracing.

[0019] The method includes: S1. Complete the prefabrication of the conical bottom box in the dry dock, and pre-embed the reserved steel bars at the top of the conical bottom box. Then install the water-stop connection structure at the reserved steel bars, and add the bottom initial section of the cofferdam body to the specified height on it. S2. After removing the dock gate and allowing seawater to enter the dry dock, float the conical bottom box and the initial bottom section formed in step S1 to the wet dock. S3. Water is injected into the conical bottom box to make it sit on the bottom. At this time, the top of the initial section of the bottom is higher than the horizontal plane. Conical sidewalls are constructed on the conical bottom box, and the remaining sections of the cofferdam are assembled at the same time. During this process, water in the conical bottom box is gradually pumped into the cofferdam cavity to keep the caisson sitting on the ground and to create a dry working environment inside the caisson. Then the internal structure of the caisson is constructed to form the caisson. S4. Discharge an appropriate amount of water from the cofferdam cavity to make the caisson float and tow it as a whole to the pier location. S5. After the caisson is towed to the pier, multiple gravity positioning systems are quickly connected and then precisely adjusted. Finally, water is injected into the cofferdam cavity to make it sink and settle quickly. During this process, the overall tilt of the caisson is precisely controlled by adjusting the water injection volume of different vertical adjustment cavities in the main body of the cofferdam. After the caisson is settled and fixed, the main body of the cofferdam can serve as a temporary construction platform for the main tower above it. S6. After the main tower construction is completed, the main body of the cofferdam will be dismantled in layers and sections.

[0020] In the preferred embodiment, the installation method of the water-stop connection component includes installing the bottom section of the cofferdam onto the conical bottom box and enclosing the reserved reinforcing steel bars within it. Then, water-stop rubber is installed on both inner walls of the water-stop cavity, and reinforcing vertical beams and splicing steel sections are fixedly installed on both outer walls of the bottom section of the cofferdam. Next, the internal threaded sleeve, anchor rod, anchor plate, and locking bolt are installed, with the end of the internal threaded sleeve abutting against the perforation of the water-stop rubber. The locking bolt extends through the perforation to the outside of the splicing steel section. A washer and nut are then fitted onto the locking bolt, and the nut is tightened appropriately to keep the anchor rod horizontal. Water-stop concrete is then poured into the water-stop cavity. After the water-stop concrete reaches its design strength, the portion of the rear clamping component located within it is anchored. Finally, the nut is tightened to ensure that the water-stop rubber on the inner side of the cofferdam bottom section is in close contact with the water-stop concrete.

[0021] In the preferred embodiment, the gravity positioning system specifically includes a gravity anchor anchored on the seabed, a connecting seat anchored on the gravity anchor, a guide wheel fixed to the outer wall of the cofferdam body, and a cable guide frame and a positioning jack fixed to the top. The cable guide frame, guide wheel, and connecting seat are distributed colinearly, and a positioning wire rope is connected to the connecting seat. The other end of the positioning wire rope is connected to the positioning jack via the guide wheel and the cable guide frame.

[0022] This invention provides a cofferdam-type construction structure and construction method for a conical precast caisson foundation. By adopting a bottom-mounted and height-adjusted construction scheme in a wet dock, it fundamentally solves the safety risks of overturning, mooring system failure, and facility damage during typhoon seasons associated with traditional floating casting methods, significantly improving the stability and safety of the caisson height-adjustment process. By setting up a cofferdam body installed in stages, it not only ensures the stability of the caisson during the two floating processes—to the wet dock and to the pier—but also provides a completely dry working environment for the caisson's bottom-mounted and height-adjusted construction in the wet dock, further enhancing the typhoon resistance safety factor during the height-adjustment stage. Simultaneously, the cofferdam body can also serve as a gravity positioning system and a temporary simple platform for the main tower construction, achieving integrated functionality. Furthermore, by setting up water-stop connection components, it effectively solves the technical problems of large differences in stiffness and strength, stress concentration, and difficulty in water-stopping when connecting steel structures and concrete. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a cross-sectional view of the overall structure of the present invention; Figure 2 This is the present invention. Figure 1 Enlarged view of the A-structure; Figure 3 This is a top view of the overall structure of the invention; Figure 4 This is the present invention. Figure 3 Enlarged view of the B-structure; Figure 5 This is a half-sectional view of the water-stop connecting component of the present invention; Figure 6 This is the present invention. Figure 5 Enlarged view of the C-structure; Figure 7 This is a structural diagram of the rear clamping assembly of the present invention; Figure 8 This is a structural diagram showing the connection between the conical bottom box and the reserved reinforcing steel bars of the present invention; Figure 9 This is a structural diagram showing the connection between the conical bottom box, the reserved reinforcing bars, the bottom section of the cofferdam, and the rear clamping assembly of the present invention. Figure 10 This is a schematic diagram of step S1 of the present invention; Figure 11 This is a schematic diagram of step S2 of the present invention; Figure 12 This is a schematic diagram of sitting on the bed in step S3 of the present invention; Figure 13 This is a schematic diagram of the connection in step S3 of the present invention; Figure 14 This is a schematic diagram of step S4 of the present invention; Figure 15 This is a schematic diagram of step S5 of the present invention; Figure 16 This is a structural diagram of the gravity positioning system of the present invention; Figure 17 This is a schematic diagram of step S6 of the present invention.

[0024] In the diagram: 1. Conical bottom box; 2. Water-stop connecting component; 21. Reserved steel bar; 22. Cofferdam bottom section; 23. Water-stop rubber; 24. Water-stop concrete; 25. Rear clamping assembly; 250. Reinforcing vertical beam; 251. Spliced ​​steel section; 252. Rear clamping part; 2520. Internal threaded sleeve; 2521. Anchor rod; 2522. Anchor plate; 2523. Locking screw; 2524. Washer; 2525. Nut; 26. Water-stop cavity; 3. Cofferdam body; 301. Cofferdam wall panel; 302. Vertical adjustment cavity; 31. Initial bottom section; 32. Remaining section of cofferdam; 4. Conical sidewall; 5. Internal support; 501. Horizontal brace; 502. Wedge seat; 503. Wedge block; 504. Vertical brace; 505. Diagonal brace; 6. Cofferdam cavity; 8. Gravity positioning system. Detailed Implementation

[0025] Example 1 like Figure 1-9 As shown, a cofferdam-type construction structure for a conical precast caisson foundation is described. The conical precast caisson foundation, hereinafter referred to as the caisson, includes a conical bottom box 1 constructed in a dry dock and a conical sidewall 4 coaxially arranged in its central area and constructed in a wet dock. This is prior art in the field and therefore will not be described in detail here.

[0026] The top of the conical bottom box 1 is provided with a water-stop connecting component 2 surrounding the conical side wall 4. The top of the water-stop connecting component 2 is provided with a cofferdam body 3, and a cofferdam cavity 6 for water injection is reserved between it and the conical side wall 4. At the same time, an internal support 5 is provided between the two to ensure the structural stability of the cofferdam body 3.

[0027] The main body of the cofferdam 3 includes the initial bottom section 31 installed in the dry dock and the remaining section 32 installed in the wet dock. The height of the initial bottom section 31 meets the requirement that the top of the conical bottom box 1 is higher than the horizontal plane after it is seated in the wet dock, so that the interior can be kept dry for construction.

[0028] In this embodiment, both the conical sidewall 4 and the main body of the cofferdam 3 are multi-segment composite structures formed by sequentially raising them from bottom to top.

[0029] In this embodiment, the main body 3 of the cofferdam is cylindrical, which can more effectively disperse the lateral pressure from the water flow and enhance the stability of the overall structure. Compared with square or other irregular structures, the cylindrical cofferdam main body 3 has a more uniform stress distribution when under force, which can reduce local stress concentration, reduce the risk of structural deformation or damage, and has better hydrodynamic performance during floating, which can reduce the swaying and displacement caused by the water flow, and further improve the stability of the caisson floating.

[0030] This design expands the overall drainage volume and waterline area of ​​the structure through the main body 3 of the cofferdam, thereby increasing the structural stability height and enhancing the stability of the caisson during floating operations. At the same time, water can be injected into the cofferdam cavity 6 to complete the caisson's bottoming process, ensuring a dry working environment throughout the entire process of bottoming and raising the caisson in the wet dock. Compared with floating casting, bottoming and raising increases the typhoon resistance safety factor when raising the caisson.

[0031] In the preferred embodiment, the bottom of the cofferdam cavity 6 is provided with a drain outlet with a valve to facilitate the discharge of internal ballast water.

[0032] The water-stop connection component 2 includes a ring array of reserved steel bars 21 embedded in the conical bottom box 1 and extending to the outside of it, and a cofferdam bottom section 22 covering the reserved steel bars 21. In this embodiment, the reserved steel bars 21 are specifically "L" shaped, with their horizontal sections embedded in the conical bottom box 1 and fixed to the steel bars in the conical bottom box 1, and their vertical sections extending to the outside of the conical bottom box 1, with hook structures formed at their ends. The reserved steel bars 21 are specifically provided with inner and outer rings, and the two rings of reserved steel bars 21 are symmetrically arranged.

[0033] The bottom section 22 of the cofferdam is equipped with a water-stopping cavity 26. Both the upper and lower ends of the water-stopping cavity 26 are open. The cavity encloses the reserved steel bars 21. Water-stopping rubber 23 is installed on both side walls of the water-stopping cavity 26, and water-stopping concrete 24 is poured inside the cavity.

[0034] In addition, a rear clamping assembly 25 is provided on both side walls of the bottom section 22 of the cofferdam. This assembly penetrates the wall panel and the water-stop rubber 23 of the bottom section 22 of the cofferdam and extends into the water-stop concrete 24. It is used to press the wall panel tightly against the water-stop rubber 23 and the water-stop concrete 24 to ensure that the two are in close contact, thereby ensuring the water-stopping effect. At the same time, the water-stop concrete 24 and the reserved steel bar 21 are connected by anchoring to form an integral load-bearing system, which effectively enhances the structural strength and deformation resistance of the connection.

[0035] The rear clamping assembly 25 includes a ring array of reinforcing vertical beams 250 on the outside of the cofferdam bottom section 22. One or more spliced ​​steel sections 251 are connected between the reinforcing vertical beams 250 and arranged along the height direction of the waterstop concrete 24. The inner wall of the spliced ​​steel section 251 is in contact with the outer wall of the cofferdam bottom section 22. In this embodiment, since the top of the conical bottom box 1 is a sloping surface and the top of the waterstop concrete 24 is horizontal after pouring, the side height near the center is smaller than the side height on the other side. Therefore, one spliced ​​steel section 251 is provided on the side with the smaller side height and two spliced ​​steel sections 251 are provided on the higher side. The spliced ​​steel section 251 is specifically an I-beam, and multiple reinforcing plates are spaced apart between its upper and lower flanges.

[0036] With this design, a hoop can be formed on the outside of the bottom section 22 of the cofferdam by splicing steel 251, which makes it easier to apply pressure to the whole structure.

[0037] The spliced ​​steel section 251 is provided with a rear clamping part 252 that penetrates the spliced ​​steel section 251, the bottom section of the cofferdam 22 and the water-stop rubber 23 and extends into the water-stop concrete 24. The rear clamping part 252 is specifically arranged in two rows and is symmetrically distributed with the web in the middle of the spliced ​​steel section 251 as the center. The specific number of rear clamping parts 252 in each row is determined according to the actual length of the spliced ​​steel section 251 and the clamping effect.

[0038] It should be noted that the spliced ​​steel section 251, the bottom section of the cofferdam 22, and the water-stop rubber 23 are provided with perforations for the rear clamping part 252 to pass through.

[0039] The rear clamping part 252 specifically includes an internal threaded sleeve 2520, which is located in the water-stopping cavity 26 and its end abuts against the perforation of the water-stopping rubber 23. Its outer diameter is larger than the diameter of the perforation. In this embodiment, the internal threaded sleeve 2520 is a tapered sleeve, with its larger outer diameter end abutting against the perforation, thereby ensuring the abutting effect.

[0040] An anchor rod 2521 is threadedly installed at one end of the internal threaded sleeve 2520 away from the water-stop rubber 23. An anchor plate 2522 is fixed to the other end of the anchor rod 2521. The anchor rod 2521 and the anchor plate 2522 can ensure the anchoring effect between the rear clamping part 252 and the water-stop concrete 24.

[0041] The end of the internal threaded sleeve 2520 near the water-stop rubber 23 is threaded with a locking screw 2523 that passes through the perforation. The locking screw 2523 is fitted with a washer 2524 and a nut 2525 in sequence.

[0042] During installation, first, the bottom section 22 of the cofferdam is installed onto the conical bottom box 1, and the reserved reinforcing steel 21 is encased within it. Then, water-stop rubber 23 is installed on both inner walls of its water-stop cavity 26. The water-stop rubber 23 can be fixed by adhesive. Next, reinforcing vertical beams 250 and spliced ​​steel sections 251 are installed sequentially on the outside of the bottom section 22 of the cofferdam. The installation method can be welding. Then, the internal threaded sleeve 2520, anchor bolt 2521, anchor plate 2522, and locking bolt 2523 are installed, and the end of the internal threaded sleeve 2520 is abutted against the perforation of the water-stop rubber 23. The locking bolt 2523 is extended through the hole to the outside of the splicing steel 251 wing plate. Then, a washer 2524 and a nut 2525 are installed on the locking bolt 2523. The nut 2525 is tightened appropriately to keep the anchor bolt 2521 horizontal. Then, water-stop concrete 24 is poured into the water-stop cavity 26. After the water-stop concrete 24 reaches the design strength, the part of the rear clamping component 25 located in it is anchored. Finally, the nut 2525 is tightened to ensure that the water-stop rubber 23 squeezed on the inside of the cofferdam bottom section 22 is in close contact with the water-stop concrete 24, thereby ensuring the sealing of the connection.

[0043] Meanwhile, after the caisson construction is completed, the locking bolt 2523 can be removed from the perforation by rotation, which facilitates the removal of the bottom section 22 of the cofferdam.

[0044] It should be noted that after the initial bottom section 31 of the cofferdam body 3 is completed, the water-stop connecting component 2 is spliced ​​onto it section by section, and the connection is fixed by welding to ensure the sealing of the connection.

[0045] In the preferred embodiment, the main body of the cofferdam 3 is a double-wall structure composed of two cofferdam wall panels 301, one inside and one outside. Multiple annularly distributed vertical adjustment cavities 302 are formed between the two cofferdam wall panels 301, so that the verticality of the entire caisson installation can be adjusted by adding different amounts of water to each vertical adjustment cavity 302.

[0046] It should be noted that the bottom end of the vertical adjustment cavity 302 is sealed by the water-stop connecting component 2, thereby ensuring the sealing of its bottom end. In this embodiment, each section of the cofferdam body 3 is welded together from six sections.

[0047] In the preferred embodiment, the bottom of the vertical adjustment cavity 302 is provided with a drain outlet with a valve to facilitate the discharge of water inside, thereby regulating the internal water volume.

[0048] In the preferred embodiment, the inner support 5 specifically includes multiple rings of horizontal braces 501 arranged vertically. The horizontal braces 501 of each ring are distributed equidistantly in a ring, and their length is determined according to the distance between the main body 3 of the cofferdam and the conical sidewall 4 at the same height. One end of the horizontal brace 501 is welded and fixed to the inner wall surface of the main body 3 of the cofferdam, and the other end is provided with a wedge seat 502. A wedge block 503 is inserted between the wedge seat 502 and the outer wall surface of the conical sidewall 4. Through the cooperation of the wedge seat 502 and the wedge block 503, the inner support 5 and the conical sidewall 4 are abutted. A circumferential brace 506 is provided between the horizontal braces 501 of the same ring near the end of the conical sidewall 4. Vertical braces 504 and diagonal braces 505 are also provided between adjacent horizontal braces 501, thereby effectively improving the support stability of the inner support 5.

[0049] Example 2 Further explanation in conjunction with Example 1, such as Figure 10-17 The structure shown illustrates a construction method for a cofferdam-type construction structure, the method comprising: S1. Complete the prefabrication of the conical bottom box 1 in the dry dock, and pre-embed the reserved steel bars 21 at the top of the conical bottom box 1. Then, install the water-stop connection component 2 at the reserved steel bars 21 according to the installation method of the water-stop connection component 2 described in Example 1, and add the bottom initial section 31 of the cofferdam body 3 to the specified height. The height of the bottom initial section 31 meets the requirement that the top of the conical bottom box 1 is higher than the horizontal plane after it is seated in the wet dock.

[0050] S2. After removing the dock gate and allowing seawater to enter the dry dock, the conical bottom box 1 and the initial bottom section 31 formed in step S1 are floated to the wet dock by tugboats. During the floating process, the added cofferdam body 3 increases the overall structure's drainage volume and waterline area, and increases the structure's center of gravity height, thereby increasing the stability of the caisson during the floating process.

[0051] S3. After the partial caisson structure formed in step S1 is floated to the wet dock, water is immediately injected into the conical bottom box 1 to make it sit on the bottom. At this time, the top of the initial section 31 at the bottom is higher than the horizontal plane, so its interior maintains a dry working environment, which facilitates the extension of the high conical sidewall 4. The conical sidewall 4 is constructed at 6m / section, and the remaining section 32 of the cofferdam is assembled simultaneously. During this process, the water in the conical bottom box 1 is gradually pumped into the cofferdam cavity 6 to keep the caisson sitting on the ground while making the interior of the caisson a dry working environment. Then the construction of the internal structure of the caisson is carried out. The main body of the cofferdam 3 ensures a dry working environment throughout the entire process of the caisson sitting on the bottom and being extended in the wet dock. Compared with floating pouring, sitting on the bottom and extending increases the typhoon resistance safety factor when the caisson is extended.

[0052] S4. Discharge an appropriate amount of water from the cofferdam cavity 6 to make the caisson float, and use a tugboat to tow it as a whole to the pier location.

[0053] S5. After the caisson is towed to the pier position, multiple gravity positioning systems 8 are quickly connected and then precisely adjusted. Finally, water is injected into the cofferdam cavity 6 to make it sink and be fixed quickly. During the caisson positioning stage, the cofferdam body 3 provides an installation platform for the gravity positioning system 8 when the caisson is positioned and placed. At the same time, by adjusting the water injection volume of different vertical adjustment cavities 302 in the cofferdam body 3, the overall tilt of the caisson can be precisely controlled to ensure that its installation verticality meets the design requirements. In addition, after the caisson is fixed, the cofferdam body 3 can serve as a temporary construction platform for the main tower above it.

[0054] The gravity positioning system 8 specifically includes a gravity anchor 801 anchored to the seabed, a connecting seat 804 anchored on the gravity anchor 801, a guide wheel 803 fixed on the outer wall of the cofferdam body 3, a cable guide frame 802 and a positioning jack 801 fixed on the top, wherein the cable guide frame 802, the guide wheel 803 and the connecting seat 804 are distributed colinearly, and a positioning steel wire rope 805 is connected to the connecting seat 804, the other end of the positioning steel wire rope 805 is connected to the positioning jack 801 via the guide wheel 803 and the cable guide frame 802, wherein the positioning jack 801 is specifically a through-hole jack.

[0055] With this design, the angle difference between the adjusting jack 801 and the wire guide frame 802 can be adjusted to adapt to the arc-shaped installation position at the top of the cofferdam body 3. Thus, by extending and retracting the adjusting jack 801 of the different gravity positioning systems 8, the adjusting wire rope 805 can be pulled, thereby adjusting the sinking position of the caisson.

[0056] S6. After the main tower construction is completed, the cofferdam body will be dismantled in three layers and sections. The horizontal section will be dismantled in two layers and the vertical section in six sections. Each section weighs about 225t and will be dismantled using a 600t floating crane. The dismantling process is convenient, does not affect the durability of the main structure, and does not occupy the critical path.

[0057] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be defined as the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A cofferdam-type construction structure for a conical precast caisson foundation, the conical precast caisson foundation comprising a conical bottom caisson (1) constructed in a dry dock, and a conical sidewall (4) coaxially disposed in its central region and constructed in a wet dock, characterized in that: The top of the conical bottom box (1) is provided with a water-stop connecting component (2) around the conical sidewall (4). The top of the water-stop connecting component (2) is provided with a cofferdam body (3). The cofferdam body (3) includes the bottom initial section (31) installed in the dry dock and the remaining cofferdam section (32) installed in the wet dock. When the conical bottom box (1) is seated in the wet dock, the top of the bottom initial section (31) is higher than the horizontal plane. A cofferdam cavity (6) for water injection is reserved between the cofferdam body (3) and the conical sidewall (4), and an internal support (5) is also provided between the two.

2. The cofferdam-type construction structure for a conical precast caisson foundation according to claim 1, characterized in that: The water-stop connection component (2) includes a ring array of pre-embedded steel bars (21) embedded in the conical bottom box (1) and extending to the outside of it, and a cofferdam bottom section (22) covering the pre-embedded steel bars (21). The cofferdam bottom section (22) is provided with a water-stop cavity (26) inside. The upper and lower ends of the water-stop cavity (26) are open. Water-stop rubber (23) is installed on both side walls of the water-stop cavity (26). Water-stop concrete (24) is poured into the cavity. A rear clamping component (25) is provided on both side walls of the cofferdam bottom section (22). The component penetrates the wall panel of the cofferdam bottom section (22) and the water-stop rubber (23) and extends into the water-stop concrete (24) to clamp the wall panel of the cofferdam bottom section (22) to the water-stop rubber (23) and the water-stop concrete (24).

3. The cofferdam construction structure for a conical precast caisson foundation according to claim 2, characterized in that: The rear clamping assembly (25) includes a ring array of reinforcing vertical beams (250) on the outside of the bottom section (22) of the cofferdam. One or more spliced ​​steel sections (251) are connected between the reinforcing vertical beams (250) along the height direction of the waterstop concrete (24). The inner wall of the spliced ​​steel section (251) is in contact with the outer wall of the bottom section (22) of the cofferdam. The spliced ​​steel section (251), the bottom section (22) of the cofferdam and the waterstop rubber (23) are all provided with perforations. The spliced ​​steel section (251) is provided with a through perforation that extends into the waterstop concrete (24) to form a rear clamping part (252) for locking and clamping.

4. The cofferdam construction structure for a conical precast caisson foundation according to claim 3, characterized in that: The rear clamping part (252) specifically includes an internal threaded sleeve (2520). The internal threaded sleeve (2520) is located in the water-stop cavity (26), and its end abuts against the perforation of the water-stop rubber (23). An anchor rod (2521) is threadedly installed at the end of the internal threaded sleeve (2520) away from the water-stop rubber (23). An anchor plate (2522) is fixedly connected at the other end of the anchor rod (2521). A locking screw (2523) that passes through the perforation is threadedly installed at the end of the internal threaded sleeve (2520) close to the water-stop rubber (23). A washer (2524) and a nut (2525) are sequentially fitted on the outside of the locking screw (2523).

5. The cofferdam construction structure for a conical precast caisson foundation according to claim 4, characterized in that: The internal threaded sleeve (2520) is a tapered sleeve.

6. A cofferdam-type construction structure for a conical precast caisson foundation according to any one of claims 2-5, characterized in that: The reserved steel bar (21) is "L" shaped. Its horizontal section is embedded in the conical bottom box (1) and fixed to the steel bar in the conical bottom box (1). The vertical section extends to the outside of the conical bottom box (1) and has a hook structure at the end.

7. The cofferdam-type construction structure for a conical precast caisson foundation according to claim 5, characterized in that: The reserved steel bars (21) are specifically set with two rings, inner and outer, and the two rings of reserved steel bars (21) are arranged symmetrically.

8. The cofferdam construction structure for a conical precast caisson foundation according to claim 1, characterized in that: The main body of the cofferdam (3) is cylindrical.

9. The cofferdam construction structure for a conical precast caisson foundation according to claim 1, characterized in that: The main body of the cofferdam (3) is a double-wall structure composed of two cofferdam wall panels (301) inside and outside, and multiple vertical adjustment cavities (302) are formed between the two cofferdam wall panels (301).

10. The cofferdam construction structure for a conical precast caisson foundation according to claim 9, characterized in that: The bottom of the vertical adjustment chamber (302) and the cofferdam chamber (6) is provided with a drain outlet with a valve.

11. The cofferdam construction structure for a conical precast caisson foundation according to claim 1, characterized in that: Both the conical sidewall (4) and the main body of the cofferdam (3) are multi-segment composite structures formed by sequentially raising them from bottom to top.

12. The cofferdam-type construction structure for a conical precast caisson foundation according to claim 1, characterized in that: The internal support (5) specifically includes a multi-ring horizontal brace (501) arranged vertically. The horizontal brace (501) of each ring is distributed equidistantly in a ring. One end of the horizontal brace (501) is welded and fixed to the inner wall of the cofferdam body (3), and the other end is provided with a wedge seat (502). A wedge block (503) is inserted between the wedge seat (502) and the outer wall of the conical sidewall (4). A circumferential brace (506) is provided between the horizontal braces (501) of the same ring and near the end of the conical sidewall (4). Vertical brace (504) and diagonal brace (505) are also provided between the horizontal braces (501) of the upper and lower adjacent horizontal braces (501).

13. The construction method of the cofferdam-type construction structure according to any one of claims 1-12, characterized in that: The method includes: S1. Complete the prefabrication of the conical bottom box (1) in the dry dock, and pre-embed the reserved steel bars (21) at the top of the conical bottom box (1). Then install the water-stop connection component (2) structure at the reserved steel bars (21), and add the bottom initial section (31) of the cofferdam body (3) to the specified height on it. S2. After removing the dock gate and allowing seawater to enter the dry dock, float the conical bottom box (1) and the initial bottom section (31) formed in step S1 to the wet dock. S3. Water is injected into the conical bottom box (1) to make it sit on the bottom. At this time, the top of the initial section (31) at the bottom is higher than the horizontal plane. Conical sidewalls (4) are constructed on the conical bottom box (1), and the remaining section (32) of the cofferdam is assembled at the same time. During this process, water in the conical bottom box (1) is gradually pumped into the cofferdam cavity (6) to keep the caisson sitting on the ground while making the inside of the caisson a dry working environment. Then the internal structure of the caisson is constructed to form the caisson. S4. Discharge an appropriate amount of water from the cofferdam cavity (6) to make the caisson float and tow it as a whole to the pier location; S5. After the caisson is towed to the pier, multiple gravity positioning systems (8) are quickly connected and then precisely adjusted. Finally, water is injected into the cofferdam cavity (6) to make it sink and settle quickly. During this process, the overall tilt of the caisson is precisely controlled by adjusting the water injection volume of different vertical adjustment cavities (302) in the main body of the cofferdam (3). After the caisson is settled, the main body of the cofferdam (3) can be used as a temporary construction platform for the main tower above it. S6. After the main tower construction is completed, the main body of the cofferdam (3) is dismantled in layers and blocks.

14. The construction method of the cofferdam-type construction structure according to claim 12, characterized in that: The installation method of the water-stop connecting component (2) includes installing the bottom section (22) of the cofferdam onto the conical bottom box (1) and enclosing the reserved steel bars (21) inside. Then, water-stop rubber (23) is installed on both inner walls of the water-stop cavity (26), and reinforcing vertical beams (250) and spliced ​​steel sections (251) are fixedly installed on both outer walls of the bottom section (22). Then, the internal threaded sleeve (2520), anchor rod (2521), anchor plate (2522) and locking screw (2523) are installed, and the end of the internal threaded sleeve (2520) is abutted against the perforation of the water-stop rubber (23). The locking screw (2523) extends through the hole to the outside of the splicing steel (251). Then, a washer (2524) and a nut (2525) are fitted on the locking screw (2523). The nut (2525) is tightened appropriately to keep the anchor rod (2521) horizontal. Then, water-stop concrete (24) is poured into the water-stop cavity (26). After the water-stop concrete (24) reaches the design strength, the part of the rear clamping component (25) located in it is anchored. Finally, the nut (2525) is tightened to ensure that the water-stop rubber (23) squeezed inside the bottom section (22) of the cofferdam is in close contact with the water-stop concrete (24).

15. The construction method of the cofferdam-type construction structure according to claim 12, characterized in that: The gravity positioning system (8) specifically includes a gravity anchor (801) anchored on the seabed, an anchor connection seat (804) on the gravity anchor (801), a guide wheel (803) fixed on the outer wall of the cofferdam body (3), a cable guide frame (802) and a positioning jack (801) fixed on the top, wherein the cable guide frame (802), the guide wheel (803) and the connection seat (804) are distributed along the same line, and a positioning steel wire rope (805) is connected to the connection seat (804), and the other end of the positioning steel wire rope (805) is connected to the positioning jack (801) through the guide wheel (803) and the cable guide frame (802).

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