Deepwater foundation

Abstract

The deepwater foundation is designed into a rectangular buoyancy tank, and the section of the rectangular buoyancy tank is designed into a honeycomb shape so as to resist water pressure. Preformed holes are formed in a bottom plate of the honeycomb, so that the piles can smoothly penetrate through the holes, and the buoyancy tanks are fixed to the seabed through the piles. During construction, the foundation can be constructed on the water surface through buoyancy of water, and the influence of water pressure is avoided. When in use, the buoyancy of water to the buoyancy box is utilized to bear the weight of the whole bridge; the pile bears the weight of the running vehicle. By means of the method, the pier foundation can be built in the water area with the depth of more than 100 meters, and the problem of deep water foundation construction is solved.

Description

Technical Field

[0001] This invention relates to a bridge pier foundation for deep-sea applications, which utilizes the buoyancy of water to avoid the influence of water and allows for the construction of foundations in water depths exceeding 100 meters. Background Technology

[0002] The Hong Kong-Zhuhai-Macau Bridge is 55 kilometers long, with the main bridge spanning 29.6 kilometers and a maximum water depth of 44 meters. Due to the extreme difficulty of deep-water foundation construction, a bridge-tunnel approach had to be adopted to build the cross-sea bridge. This required the construction of two artificial islands in the sea, with a tunnel connecting the two islands. As a result, the construction period was long, lasting nearly 9 years, and the cost was particularly high, amounting to 126.9 billion RMB.

[0003] The Qiongzhou Strait is 19.4 kilometers at its narrowest point, with a maximum depth of 114 meters and an average depth of 44 meters. The design plan calls for a dual-purpose road-rail bridge. However, due to the maximum depth of 114 meters, significantly exceeding 44 meters, building a bridge across the Qiongzhou Strait using current construction technology would be far more difficult than building the Hong Kong-Zhuhai-Macau Bridge, and the estimated cost would exceed 140 billion RMB, possibly even more. Furthermore, there are unforeseen factors. Due to the high difficulty and cost of foundation construction, the Qiongzhou Strait Bridge project has not yet commenced. The key to building the bridge lies in constructing the foundation in deep water.

[0004] Deep-water foundation construction is a major challenge because water has pressure, and the pressure increases with depth, making foundation construction increasingly difficult, sometimes to the point of being impossible. The Hong Kong-Zhuhai-Macau Bridge had a maximum water depth of 44 meters, making pier foundation construction impossible. The Qiongzhou Strait, with a maximum water depth of 114 meters, makes pier foundation construction even more impossible. Traditional construction methods are simply not feasible for building a bridge across the Qiongzhou Strait.

[0005] Alternatively, water has another characteristic: buoyancy. If we can avoid the pressure of water and make full use of its buoyancy, we can avoid the difficult aspects and choose the easier ones, which can significantly reduce the difficulty and cost of deep-water foundation construction and solve the problems associated with it. Summary of the Invention

[0006] The foundation is designed as a floating box, which is then secured to the seabed by piles. The buoyancy of the floating box supports the weight of the bridge pier foundation and the entire superstructure—the total dead load. The piles support the weight of passing vehicles—the live load. The foundation can be constructed on the water surface, avoiding the influence of water, using conventional construction methods. With only piles, underwater construction is relatively simple and easy to implement.

[0007] The foundation is designed as a rectangular reinforced concrete box with a honeycomb-shaped cross-section. The honeycomb walls resist seawater pressure. The box consists of a base plate and honeycomb walls. Pre-drilled holes are provided in the base plate to allow piles to pass through smoothly; pre-embedded steel pipes are installed above these holes. Four hydraulic outriggers are installed at the four corners of the foundation's base, and the foundation is secured to the seabed by piles. The thickness and spacing of the honeycomb walls are determined based on the seawater depth. The number of honeycomb cells is determined based on the bridge's own weight to adjust the foundation's buoyancy in the water. The number of piles is determined based on the weight of passing vehicles.

[0008] The hydraulic outrigger consists of a bracket, hydraulic jack, support rod, pipe clamp, sealing device, and base. The hydraulic outrigger is designed to bear a load of over 1,000 tons.

[0009] The pile has a diameter of 3 meters and a design bearing capacity of over 1000 tons. The pile consists of a precast casing, a precast pile tip, and post-cast reinforced concrete. The casing is composed of precast reinforced concrete and a steel cylinder, with the steel cylinder inside and the precast reinforced concrete outside. The casing is 3 meters long and 150 mm thick. Inner flanges and reinforcing plates are installed at both ends of the steel cylinder, with bolt holes on the inner flanges. Casings are bolted together and connected to the pile tip. After the casing connections are completed, the reinforcing steel in the post-cast reinforced concrete is tied, and the concrete is poured to complete the pile construction.

[0010] Deep-water foundations resist seawater pressure through honeycomb walls. During foundation construction, buoyancy is utilized to avoid water pressure, allowing the foundation to be constructed on the water surface using conventional methods. The foundation is then installed using buoyancy. It serves as a support for piling machines, enabling pile construction. The piles then anchor the foundation to the seabed, allowing it to float in the seawater. During use, buoyancy bears the entire dead load of the bridge, while the piles support the live load of passing vehicles. Because most of the load is borne by buoyancy, the load is relatively small, which is beneficial for earthquake resistance. Utilizing the characteristic of seawater to absorb seismic energy, some of the seismic energy is offset, giving deep-water foundations earthquake resistance. This method of constructing deep-water foundations not only avoids the construction challenge of water pressure but also allows for foundation construction using conventional methods. Furthermore, it is simpler, safer, easier to control in terms of quality, faster in terms of construction speed, and lower in cost. Attached Figure Description

[0011] Figure 1 This is a lateral side view of the deep-water foundation of the present invention:

[0012] Figure 2 This is a longitudinal side view of the deep-water foundation of the present invention:

[0013] Figure 3 This is a top view of the deep-water foundation of the present invention:

[0014] Figure 4 This is a cross-sectional view (A-A) of the deep-water foundation of the present invention:

[0015] Figure 5 This is a B-B cross-sectional view of the deep-water foundation of the present invention.

[0016] Figure 6 This is a top view of the sleeve of the present invention:

[0017] Figure 7 This is a C-C cross-sectional view of the sleeve of the present invention.

[0018] Figure 8 This is a top view of the pile tip of the present invention:

[0019] Figure 9 This is a D-D cross-sectional view of the pile tip of the present invention:

[0020] Figure 10 Here is a schematic diagram of the hydraulic outrigger of this invention:

[0021] Figure 11 This is a schematic diagram of the construction of the pile of the present invention;

[0022] Figure 12 This is a schematic diagram of the connection between the base plate and the sleeve of the present invention:

[0023] Figure 13 This is a detailed drawing of the connection between the foundation slab and the piles of this invention:

[0024] Figure 14 This is a schematic diagram of the connection between the foundation slab and the piles of the present invention:

[0025] In the diagram: 1. Foundation, 2. Pier, 3. Hydraulic outrigger, 4. Pile, 5. Honeycomb outer wall, 6. Honeycomb inner wall, 7. Reserved hole, 8. Base plate, 9. Guide wheel, 10. Precast reinforced concrete, 11. Inner flange, 12. Screw hole, 13. Steel cylinder, 14. Reinforcing plate, 15. Bracket, 16. Hydraulic jack, 17. Support rod, 18. Pipe clamp, 19. Sealing device, 20. Base, 21. Cover plate, 22. Inlet valve, 23. Steel pipe, 24. Connecting plate, 25. Sleeve, 26. Weld, 27. Flange, 28. Flat iron, 29. Hemp fiber, 30. Sealing ring, 31. Post-cast reinforced concrete. Detailed Implementation

[0026] like Figures 1-13As shown, the foundation (1) is designed as a rectangular reinforced concrete box with a honeycomb-shaped cross-section. The honeycomb walls resist the pressure of seawater. The box consists of a base plate (8) and honeycomb walls. A pre-drilled hole (7) is provided on the base plate (8) so that the piles (4) can pass smoothly through it. A pre-embedded steel pipe (23) is installed above the hole (7). Four hydraulic outriggers (3) are installed at the four corners of the bottom of the foundation (1). The foundation (1) is fixed to the seabed by the piles (4). The thickness and spacing of the honeycomb walls are determined according to the depth of the seawater. The number of honeycombs is determined according to the weight of the bridge itself to adjust the buoyancy of the foundation in the water. The number of piles (4) is determined according to the weight of the vehicles traveling on it.

[0027] The hydraulic outrigger (3) consists of a bracket (15), a hydraulic jack (16), a support rod (17), a pipe clamp (18), a sealing device (19), and a base (20). The hydraulic outrigger (3) is designed to bear a load of more than 1,000 tons.

[0028] The diameter of the pile (4) is 3m, and the design bearing capacity is over 1000 tons. The pile (4) consists of a precast sleeve (25), a precast pile tip, and a post-cast reinforced concrete (31). The sleeve (25) consists of a precast reinforced concrete (10) and a steel cylinder (13), with the steel cylinder (13) inside and the precast reinforced concrete (10) outside. The sleeve (25) is 3m long and has a wall thickness of 150mm. The upper and lower ends of the steel cylinder (13) are equipped with inner flanges (11) and reinforcing plates (14), and bolt holes (12) are provided on the inner flanges (11). The sleeves (25) are connected to each other and to the pile tip by bolts. After the connection of the sleeves (25) is completed, the reinforcing bars in the post-cast reinforced concrete (31) are tied, and the concrete is poured to complete the construction of the pile (4).

[0029] Design of Foundation (1): Taking the maximum water depth of the Qiongzhou Strait (114m) as an example, the foundation (1) is designed as follows. The foundation (1) is designed as a rectangular reinforced concrete box, with length × width × height = 60.2m × 40.2m × 118m. The cross-section of the foundation (1) is designed as a honeycomb, with a honeycomb wall spacing of 5 meters, 12 honeycombs in the long direction, 8 honeycombs in the wide direction, and a honeycomb inner wall (6) thickness of 400mm. The honeycomb outer wall (5) adopts an arched structure to resist the strong seawater pressure. The foundation (1) consists of a base plate (8), honeycomb outer wall (5), and honeycomb inner wall (6) forming a multi-walled box. A reserved hole (7) is set on the base plate (8) to facilitate the passage of the pile (4). A section of steel pipe (23) is pre-embedded on the inner wall of the reserved hole (7) and connected to the pile (4) by this section of steel pipe (23). The foundation (1) is a reinforced concrete structure with a concrete grade of C40 and a design strength of 19.1 N / mm, which can withstand the pressure of water depth of 114 m.

[0030] The diameter of the hydraulic outrigger (3) base (20) is 6m and the height is 4m. The maximum height of the foundation (1) in the water is 114m-4m=110m. The foundation (1) should be 8m higher than the top. Therefore, the design height of the foundation (1) is 110m+8m=118m.

[0031] The area of ​​seawater displaced by the foundation (1) is 60.2m × 40.2m = 2420㎡, and the volume of seawater displaced by the foundation (1) at a height of 1m is 2420m³ / m. The density of seawater is greater than 1. For ease of description, we assume that the density of seawater is 1 ton / m³, and the buoyancy that the foundation (1) can obtain at a water depth of 1m is 2420 m³ / m × 1 ton / m³ = 2420 tons / m. The thickness of the floor (8) of the foundation (1) is 1m, the volume of concrete is about 1692m³, and the weight is 1692m³ × 2.5 tons / m³ (density of reinforced concrete) = 4230 tons. The volume of concrete in the honeycomb wall of the foundation (1) at a height of 1m is about 502m³ / m, and the weight is 502m³ / m × 2.5 tons / m³ = 1255 tons / m. The height of the honeycomb wall is 117m, and the weight of its concrete is 1255 tons / m × 117m = 146835 tons. The weight of the foundation (1) is 146835 tons + 4230 tons = 151065 tons. The height of the foundation (1) in the seawater is 110m, and the buoyancy it receives from the seawater is 2420 tons / m × 110m = 266200 tons. The net buoyancy is 266200 tons - 151065 tons = 115135 tons. When the weight of the piers, the bridge and all supporting facilities does not exceed 115135 tons, the pile (4) does not bear pressure.

[0032] Design of the hydraulic outrigger (3): The hydraulic outrigger (3) consists of a bracket (15), a hydraulic jack (16), a support rod (17), a pipe clamp (18), a sealing device (19), and a base (20). The working principle of the hydraulic outrigger (3) is similar to that of a static pressure pipe driving machine. The function of the pipe clamp (18) is to clamp the support rod (17) and control the support rod (17) to prevent it from moving forward, backward, left, or right. When the support rod (17) exits the base plate (8), the sealing device (19) prevents seawater from entering the honeycomb. The specific steps for adjusting the height of the hydraulic outrigger (3) are as follows: First, temporarily fix the bracket (15) to the honeycomb wall, loosen the pipe clamp (18), start the hydraulic jack (16), press out the support rod (17), then tighten the support rod (17) with the pipe clamp (18), release the temporary fixation between the bracket (15) and the honeycomb wall, retract the piston rod in the hydraulic jack (16), the bracket (15) and the hydraulic jack (16) will move downward, fix the bracket (15) to the honeycomb wall again, and perform the next round of operation until the base (20) reaches the predetermined position. No matter how long the support rod (17) is, it can be adjusted.

[0033] The Qiongzhou Strait is 19.5 km at its narrowest point and 114 m at its deepest point. The seabed conditions must be very complex. Before determining the location of the foundation (1), a geological survey and exploration should be conducted. Based on the geological survey, the location of the foundation (1) should avoid areas with large topographic elevation differences and select an area with a topographic elevation difference of no more than 6 m. Based on the results of the geological exploration, determine which soil layer the pile (4) sits on.

[0034] Design of pile (4): The diameter of pile (4) is 3m. Pile (4) consists of precast sleeve (25), precast pile tip, and post-cast reinforced concrete (31). Sleeve (25) consists of precast reinforced concrete (10) and steel cylinder (13), with precast reinforced concrete (10) on the outside and steel cylinder (13) on the inside. Inner flange (11) and stiffening plate (14) are provided at the upper and lower ends of steel cylinder (13). Screw holes (12) are provided on the inner flange (11). The length of sleeve (25) is 3m and the wall thickness is 150mm. Sleeve (25) is bolted to each other and to the pile tip. After the precast pile tip and sleeve (25) reach the predetermined position, post-cast reinforced concrete (31) is poured to form pile (4).

[0035] Construction of Foundation (1): First, a section of foundation (1) with a height of 15m is constructed on land. Then, this section of foundation (1) is moved to the sea, and the construction of the upper part of foundation (1) continues. The height of foundation (1) is 15m, and its weight is 14m×1255 tons / m+4230 tons=21800 tons. The height of foundation (1) in the seawater is 21800 tons÷2420 tons / m=9m. The height of the top surface (construction surface) of foundation (1) from the water surface is 15m-9m=6m. Foundation (1) can float on the water like a boat. The upper part of foundation (1) can be constructed without water using conventional construction methods. Its construction method is the same as that of chimneys, cooling towers, and bridge piers. Formwork is used for construction, and the height of each formwork is 2m to 3m. The construction method for the foundation (1) is the same whether it is on land or at sea: first, the reinforcing bars are tied, the formwork is sealed, and then the concrete is poured. After the concrete of the foundation (1) is poured to a height of 15m, the foundation (1) is transferred from land to sea, and then the reinforcing bars are tied, the formwork is sealed, and the concrete is poured. This process is repeated step by step until the foundation (1) reaches the designed height.

[0036] (1) The method of transferring from land to sea can refer to the method of launching ships, or adopt the method of launching the immersed tunnel of the Hong Kong-Zhuhai-Macau Bridge.

[0037] Before the foundation (1) is lowered into the water, the reserved hole (7) on the bottom plate is temporarily sealed with a cover plate (21) before the water is lowered. A water inlet valve (22) is installed on the cover plate (21). The cover plate (21) is fixed to the bottom plate (8) with bolts. The water inlet valve (22) is closed to prevent seawater from entering the honeycomb.

[0038] As the height of the foundation (1) increases, the height of the construction surface above the water surface also increases. For example, when the height of the foundation (1) reaches 51 meters, the weight of the foundation (1) is 50m × 1255 tons / m + 4230 tons = 66980 tons, the height of the foundation (1) in the water is 66980 tons ÷ 2420 tons / m = 27.7m, and the height of the construction surface above the water surface is 51m - 27.7m = 23.3m. If the construction surface is too much higher than the water surface, it will increase the vertical transportation distance of various materials and will also be detrimental to the movement of construction personnel. It is advisable to control the height of the construction surface above the water surface to be around 6 meters. In order to control the height of the construction surface, the cover plates (21) should be removed one by one in a timely manner. The internal space of a honeycomb is approximately 4.6m × 4.6m = 21.16㎡. Each time a cover plate (21) is removed, the area of ​​the foundation (1) that can drain water decreases by 21.16㎡, and the buoyancy of the seawater on the foundation (1) decreases by 21.16 tons. Using this method, the height of the construction surface above the water surface is always controlled at about 6 meters. As the height of the foundation (1) increases, the cover plates (21) are removed one by one in a timely manner until the construction of the foundation (1) is completed.

[0039] When removing the cover plate (21), first remove the bolts that fix the cover plate (21). Under the pressure of seawater, seawater cannot enter the honeycomb. It is necessary to open the water inlet valve (22) to allow seawater to enter the honeycomb through the valve (22). When the water level in the honeycomb is the same as the water level outside the foundation (1), without the pressure of seawater, the cover plate (21) will fall off by itself under the weight. The fallen cover plate (21) is collected in a unified manner, and the recovered cover plate (21) can be reused.

[0040] When the foundation (1) is being constructed in the sea, four steel cables are installed at its four corners to prevent it from moving freely with the wind and waves. After the foundation (1) is completed, it is towed to the designated position, and seawater is pumped into the foundation (1) to increase its weight, causing it to sink to the seabed. The flatness of the foundation (1) is controlled by hydraulic outriggers (3). At this point, the weight of the foundation (1) in the water plus the weight of the seawater pumped into it equals the buoyancy of the seawater on the foundation (1). The four steel cables are then tightened to prevent the foundation (1) from swaying due to the wind and waves.

[0041] Each hydraulic outrigger (3) has a bearing capacity of over 1000 tons. After the foundation (1) is in place and leveled, 4000 tons of seawater are injected into the foundation (1) again, so that the weight of the foundation (1) plus the weight of the seawater injected into it is greater than the buoyancy of the seawater on the foundation (1). This not only increases the stability of the foundation (1) but also creates conditions for the construction of the piles (4). The construction principle of the piles (4) is the same as that of the static pressure driven pipe piles. The hydraulic device for driving the piles (4) has a pressure of 2000 tons. When the piles (4) are driven down, a counterweight of over 2000 tons is required. If the foundation (1) does not have enough weight, the hydraulic device will lift the foundation (1) under the action of the reaction force when driving the piles (4), and the construction of the piles (4) cannot be completed.

[0042] Construction of pile (4): After the foundation (1) is in place (construction terminology), the construction of pile (4) can be carried out. Since the foundation (1) serves as a support, the construction of pile (4) is much simpler. The outer diameter of pile (4) is 3000mm, the inner diameter of the reserved hole (7) is 3030mm, and the gap between the two is 15mm. The gap between the two is small, and the pile (4) is not easy to pass through. In order to ensure that the sleeve (25) can accurately pass through the reserved hole (7), four guide wheels (9) are set on the base plate (8).

[0043] First, the pile tip and the casing (25) are connected together with bolts, and then they are pressed into the predetermined position using a hydraulic device. Under the action of the sealing ring (30), the seawater inside and outside the foundation (1) is isolated, and the seawater inside the honeycomb is pumped out. At the same time, the casing (25) above the bottom plate (8) is removed section by section. The sealing ring (30) is a temporary seal and also the first seal. The gap between the casing (25) and the reserved hole (7) is filled with hemp fiber (29) and waterproof paste to form a second seal, and then five 20mm×3mm flat irons (28) or 15mm diameter round steels are embedded. Finally, the pre-embedded steel pipe (13) above the reserved hole (7), the flat iron (28), and the flange (27) above the casing (25) are welded together, and the weld (26) is used as the third seal. Bridge design is a long-term project, and the sealing ring (30) will age and lose its sealing function over time. The hemp fiber (29) and waterproof paste filling and the weld (26) are The weld (26) is permanently sealed. Hemp fiber (29) is used for waterproofing below the weld (26), and reinforced concrete is used to cover the weld (26). The weld (26) does not come into contact with air or water, which ensures that the seal is effective for a long time. After the sealing work is completed, the pre-embedded steel pipe (13) and flange (27) are welded together by connecting plate (24) to form a rigid connection. After the sleeve (25) is connected to the foundation (1), starting from the pile tip, the steel bars in the post-cast reinforced concrete (31) are tied, and concrete is poured to complete the construction of the pile (4). The foundation (1) and the pile (4) are connected into a whole.

[0044] After the construction of pile (4) is completed, the top of the foundation is sealed to prevent rainwater from entering the foundation (1), and then the construction of the pier (2) is carried out. As the construction of the pier (2) progresses, the weight of the upper part of the foundation (1) becomes heavier and heavier. According to the increase in weight, the seawater in the foundation (1) should be pumped out in a timely manner to reduce the weight of the foundation (1) and minimize the stress on the pile (4) from beginning to end. After the bridge construction is completed, the seawater in the foundation (1) should also be pumped out so that the total weight of the foundation (1) above the water surface is equal to the buoyancy of the seawater on the foundation (1).

Claims

1. A deep-water foundation, characterized in that: The foundation (1) is designed as a rectangular reinforced concrete box with a honeycomb-shaped cross section. The box consists of a bottom plate (8) and honeycomb walls. Pre-drilled holes (7) are provided on the bottom plate (8). Four hydraulic outriggers (3) are provided at the four corners of the bottom of the foundation (1). The foundation (1) is fixed to the seabed by piles (4). The thickness and spacing of the honeycomb walls of the foundation (1) are determined according to the depth of the seawater, the number of honeycombs is determined according to the weight of the bridge itself, and the number of piles (4) is determined according to the weight of the vehicles.

2. The basis (1) according to claim 1, characterized in that: The hydraulic outrigger (3) consists of a bracket (15), a hydraulic jack (16), a support rod (17), a pipe clamp (18), and a base (20).

3. The basis (1) according to claim 1, characterized in that: The pile (4) consists of a precast sleeve (25), a precast pile tip, and a post-cast reinforced concrete (31); the sleeve (25) consists of precast reinforced concrete (10) and a steel cylinder (13), with the steel cylinder (13) inside and the precast reinforced concrete (10) outside; the upper and lower ends of the steel cylinder (13) are provided with inner flanges (11) and stiffening plates (14), and the inner flange (11) is provided with screw holes (12), and the sleeve (25) is connected to the sleeve (25) by bolts.

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