A super deep buoyancy type large double-wall steel hanging box in severe sea conditions and a construction method thereof

Abstract

The application discloses a super-deep buoyancy type large double-wall steel hanging box in severe sea conditions, which comprises A section wall body, B section buoyancy cabin and C section wall body which are rigidly connected in sequence from bottom to top, and watertight sealing structures are arranged between the sections. A construction method of the super-deep buoyancy type large double-wall steel hanging box in severe sea conditions comprises the following steps: S1, prefabrication and processing; S2, section assembly; S3, floating and positioning; S4, bed fixation; S5, tide adaptation debugging; S6, bottom sealing concrete construction; S7, buoyancy conversion; S8, completion detection. The application effectively resists the erosion of high-speed water flow in super-deep water area to the base; four groups of pressure sensors arranged at the bottom can monitor the base contact stress in real time, ensure that the steel hanging box is uniformly stressed after bed fixation, and significantly improve the anti-sliding and anti-inclination stability of the structure in severe sea conditions, and reduce the safety hidden danger caused by the base erosion.

Description

A large double-walled steel caisson with ultra-deep buoyancy in harsh sea conditions and its construction method Technical Field

[0001] This invention relates to the field of deep-water foundation construction technology for cross-sea bridges, and in particular to a large double-walled steel caisson with ultra-deep buoyancy in harsh sea conditions and its construction method. Background Technology

[0002] As a key protective and operational platform in marine engineering foundation construction, the structural stability and resistance to harsh environments of steel caissons directly determine construction safety and project quality.

[0003] Existing steel caisson structures mostly employ a single-wall design or a simple buoyancy chamber structure, which have several drawbacks in ultra-deep waters and harsh sea conditions: First, traditional steel caissons lack sufficient scour resistance at the bottom. High-speed water currents in ultra-deep waters can easily cause severe scour and erosion of the base, leading to unstable placement of the steel caisson and even structural slippage, tilting, and other safety hazards. Second, the buoyancy control precision is low, making it difficult to dynamically adjust the buoyancy state according to the construction progress. During the bottom sealing concrete pouring process, the load on the steel caisson's legs is concentrated, which can easily lead to stress overload and structural deformation. Third, there is a lack of effective tidal adaptive capability. Water level fluctuations caused by tidal changes can expose or submerge the top of the steel caisson, affecting the continuity of construction and generating large dynamic loads due to water flow impacts, exacerbating structural fatigue damage. Fourth, the watertightness, structural strength, and corrosion resistance of existing steel caissons are insufficient to meet the long-term operation requirements of ultra-deep waters, making them prone to leakage, component corrosion, and other problems, reducing the reliability of the project.

[0004] Furthermore, in harsh sea conditions, the floating and positioning of traditional steel caissons is difficult, inefficient, and suffers from poor coordination among various construction stages, making precise control challenging. Therefore, developing an ultra-deep buoyancy-type large double-walled steel caisson with strong scour resistance, dynamic buoyancy control, tidal adaptability, and high structural stability has become an urgent need to solve the foundation construction challenges of deep-sea engineering, and is of great significance for promoting the development of marine engineering in deeper and more distant sea areas. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a large double-walled steel caisson with ultra-deep buoyancy in harsh sea conditions and its construction method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions includes a section A of the wall, a section B of the buoyancy chamber, and a section C of the wall, which are rigidly connected from bottom to top, and watertight sealing structures are provided between each section.

[0008] The A-section wall is a bottom reinforced section, which adopts a composite structure of a lower outer wall, internal longitudinal stiffening ribs, internal transverse stiffening ribs and a lower inner wall. The outer side of the A-section wall is sprayed with a wear-resistant alloy coating with a thickness greater than 15mm, and anti-erosion toothed ridges with a height greater than 300mm are set at intervals. Four sets of pressure sensors are evenly distributed at the bottom for real-time monitoring of the substrate contact stress.

[0009] The B-section buoyancy chamber is a closed chamber structure consisting of a middle outer wall and a middle inner wall. It is internally divided into multiple independent buoyancy control units. Each buoyancy control unit is equipped with a liquid level sensor, an automatic water pump with a flow rate greater than 50 m³ / h, and an emergency stop valve with a pressure rating greater than 1.2 MPa. Before the bottom sealing concrete is poured and reaches its design strength, all buoyancy control units maintain a waterless state, providing 1900t of buoyancy. After the bottom sealing concrete reaches more than 90% of its design strength, water inflow is controlled through the emergency stop valve, ensuring that the B-section buoyancy chamber functions uniformly with the other walls, sharing the structural load.

[0010] The C-section wall is a tidal adaptive section, employing a telescopic structure consisting of an upper outer wall, a telescopic box top, and an upper inner wall. The telescopic box top is slidably embedded between the upper outer and inner walls and has a built-in water level linkage adjustment device. This device includes a tidal water level sensor and a hydraulic push rod with a stroke of 1.5m. The top of the telescopic box top is equipped with a connector that is rigidly connected to the hydraulic push rod, which is fixedly installed on the inner wall of the steel caisson. Streamlined guide plates are spaced apart on the outer side of the upper outer wall, with the angle between the streamlined guide plates and the water flow direction being an acute angle.

[0011] Preferably, the top of each telescopic box is provided with a hanging leg for connecting the injection pipe, and a stress buffer damper is provided at the connection node between the hanging leg and the steel box wall to absorb the dynamic load generated by the water flow impact.

[0012] Preferably, the buoyancy control system of the B-section buoyancy chamber dynamically adjusts the liquid level of each buoyancy control unit through a PLC controller, so that the load-bearing capacity of a single leg is stably reduced from 550t under conventional construction conditions to less than 300t.

[0013] Preferably, the anti-erosion toothed sills of the A-section wall are spaced 0.8-1.2m apart and are fixed to the double-layer steel plate by welding, which is used to enhance the bottom's resistance to water flow erosion and reduce the erosion damage to the base caused by high-speed water flow in ultra-deep waters.

[0014] Preferably, the internal longitudinal stiffening ribs and internal transverse stiffening ribs of the A section wall are orthogonally distributed with a spacing of 800-1000mm. They are made of Q355B grade steel and have a cross-sectional size of 200mm×100mm×8mm. They are fixedly connected to the lower outer wall and the lower inner wall through double-sided fillet welds with a weld height greater than 8mm.

[0015] Preferably, the middle outer wall and middle inner wall of the B section buoyancy chamber are made of steel plates with a thickness of 16-20mm, and the inner wall of the chamber is coated with paint with a thickness of more than 200μm.

[0016] Preferably, the streamlined guide plate of the C-section wall is integrally formed, the plate thickness is 12-15mm, and the spacing between adjacent streamlined guide plates is 1-1.5m.

[0017] Preferably, the hanging leg is made of 45 seamless steel pipe with an outer diameter of 300mm and a wall thickness of 25mm. A flange connector is provided at the top, and bolt holes are evenly distributed along the circumference of the flange.

[0018] A construction method for a large, double-walled steel caisson designed for ultra-deep buoyancy in harsh sea conditions includes the following steps:

[0019] S1. Prefabrication: Process the components of section A wall, section B buoyancy chamber, and section C wall separately, strictly controlling the dimensional accuracy of each component. The blanking tolerance of the wall steel plate shall not exceed ±2mm, and the welding deformation shall be controlled within 3mm / m. Spray a wear-resistant alloy coating on the outside of section A wall and install anti-erosion toothed sills and pressure sensors. Install liquid level sensors, automatic water pumps, and emergency water stop valves in section B buoyancy chamber and complete the sealing test of each buoyancy control unit. Install streamlined guide plates, telescopic tank tops, and water level linkage adjustment devices on section C wall.

[0020] S2. Segment assembly: The prefabricated sections A, B, and C are rigidly connected at the prefabrication site. The connection is sealed with double welds, with the inner weld height greater than 12mm and the outer weld height greater than 10mm. After welding, a water tightness test is conducted with a test pressure greater than 0.3MPa and a pressure holding time greater than 30min. No leakage is considered acceptable.

[0021] S3. Floating and positioning: The assembled steel caisson is floated to the designated construction area by tugboat. The position of the steel caisson is adjusted using a GPS positioning system so that the deviation between the center of the steel caisson and the design center of the pile foundation does not exceed 50mm. The automatic water pump of the buoyancy chamber in section B is started to keep the buoyancy control unit dry and ensure the stable floating state of the steel caisson.

[0022] S4. Landing and Fixing: The liquid level of each buoyancy control unit is adjusted by the PLC controller to gradually lower the elevation of the steel caisson, so that the bottom of section A wall lands smoothly on the bed; the bottom pressure sensor is used to monitor the contact stress of the base to ensure that the contact stress is evenly distributed and the maximum stress does not exceed the design limit; the bottom of the steel caisson is fixed by backfilling with riprap to enhance anti-slip stability.

[0023] S5. Tidal adaptation debugging: Start the water level linkage adjustment device of the C section wall to carry out tidal response debugging, simulate the lifting and lowering action of the telescopic box top under different water level conditions, ensure that the hydraulic push rod runs smoothly, and control the lifting and lowering accuracy of the telescopic box top within ±5mm.

[0024] S6. Construction of bottom sealing concrete: The bottom sealing concrete is poured into the steel caisson by connecting the grouting pipe through the hanging leg. During the pouring process, the settlement and tilt data of the steel caisson are monitored in real time. The settlement is controlled within 10mm and the tilt does not exceed 1‰.

[0025] S7. Buoyancy conversion: After the bottom sealing concrete reaches more than 90% of the design value, the emergency water stop valve is opened by controlling the PLC controller to slowly introduce water into each buoyancy control unit. The water inlet rate is controlled within 20m³ / h until the buoyancy control unit is connected to the external water area, completing the conversion of the buoyancy chamber of section B from the buoyancy supply state to the load bearing state.

[0026] S8. Final inspection: Conduct a comprehensive inspection of the structural integrity, watertightness, and operational status of each functional device of the steel caisson to ensure that the design and usage requirements are met before completing the construction.

[0027] The present invention has the following beneficial effects:

[0028] 1. The wall of section A of this invention adopts a composite structure design of lower outer wall, double-layer stiffening ribs and lower inner wall. The outer side is sprayed with a wear-resistant alloy coating with a thickness of more than 15mm, and is equipped with anti-scouring toothed sills made of high manganese steel, which effectively resists the scouring and erosion of the base by the high-speed water flow in ultra-deep water. The four sets of pressure sensors installed at the bottom can monitor the base contact stress in real time, ensuring that the steel caisson is evenly stressed after landing, which significantly improves the anti-slip and anti-tilting stability of the structure under harsh sea conditions and reduces the safety hazards caused by base scouring.

[0029] 2. The buoyancy chamber of this invention is divided into 8 independent buoyancy control units, equipped with a high-flow automatic water pump, a high-pressure emergency water stop valve, and a liquid level sensor. The liquid level is dynamically adjusted through a PLC controller. During the bottom concrete pouring stage, it can stably provide 1900t of buoyancy, significantly reducing the load of a single hanging leg from 550t to less than 300t, thus avoiding structural deformation caused by stress concentration. After the concrete strength reaches the standard, the emergency water stop valve controls the water inflow to complete the buoyancy state transition, enabling the buoyancy chamber to cooperate with other walls to bear the load. This achieves functional adaptation at different construction stages and greatly improves construction safety and structural reliability.

[0030] 3. The C-section wall of this invention adopts a telescopic box top and water level linkage adjustment device. Through the cooperation of tidal water level sensor and hydraulic push rod, it can quickly respond to tidal changes and realize synchronous raising and lowering of the telescopic box top. The raising and lowering response time is less than 3 seconds, avoiding the problem of box top exposure or flooding caused by tidal fluctuations and ensuring construction continuity. The acute-angle streamlined guide plate set on the outer side of the upper outer wall can effectively divert high-speed water flow and reduce the impact pressure of water flow on the wall. In conjunction with the stress buffer damper at the hanging leg connection node, it can absorb the dynamic load generated by water flow impact, reduce structural fatigue damage, and extend service life.

[0031] 4. The steel caisson of this invention adopts a rigid connection and double-sealed weld design between each section. It has passed the water tightness test with a pressure of more than 0.3MPa without leakage, effectively preventing seawater from seeping into ultra-deep waters. The buoyancy chamber of section B is separated into independent units by weathering steel plates and full penetration welds. The inner wall is coated with a high-thickness anti-corrosion coating. The weld flaw detection pass rate is not less than 98%, which has both excellent structural strength and corrosion resistance. The orthogonal stiffening rib design of section A further enhances the overall rigidity, enabling the steel caisson to withstand complex loads under harsh sea conditions for a long time, which greatly improves the quality of engineering construction and long-term service stability.

[0032] 5. The steel caisson of this invention adopts a construction method that combines prefabrication and on-site assembly. The dimensional accuracy of each component is strictly controlled, which reduces the difficulty of offshore operations. During the floating and positioning process, the steel caisson can be accurately positioned with a center deviation of no more than 50mm with the help of GPS positioning and buoyancy control system. Precise control of tidal adaptation debugging, bottom sealing concrete pouring monitoring and other links ensures that the construction settlement is controlled within 10mm and the tilt is no more than 1‰, which significantly improves construction efficiency, shortens the offshore operation cycle and reduces the adverse effects of severe sea conditions on construction. Attached Figure Description

[0033] Figure 1 is a structural schematic diagram of a steel caisson with an ultra-large head for severe sea conditions proposed in this invention.

[0034] Figure 2 is a schematic diagram of the side structure of the A-section wall body proposed in this invention;

[0035] Figure 3 is a schematic diagram of the internal structure of the A-section wall body proposed in this invention;

[0036] Figure 4 is a side view of the buoyancy chamber B proposed in this invention;

[0037] Figure 5 is a top view of the buoyancy chamber in section B proposed in the invention;

[0038] Figure 6 is an enlarged schematic diagram of the structure at point A in Figure 5;

[0039] Figure 7 is a schematic diagram of the internal structure of the C-section wall proposed in this invention.

[0040] In the diagram: 1. Section A wall; 101. Lower outer wall; 102. Anti-erosion toothed sill; 103. Internal longitudinal stiffening rib; 104. Internal transverse stiffening rib; 105. Lower inner wall; 2. Section B buoyancy chamber; 201. Middle outer wall; 202. Automatic water pump; 203. Middle inner wall; 204. Liquid level sensor; 205. Emergency stop valve; 3. Section C wall; 301. Streamlined guide plate; 302. Telescopic box top; 303. Upper outer wall; 304. Upper inner wall; 4. Hanging leg; 5. Stress buffer damper; 6. Connecting component; 7. Hydraulic push rod. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0042] Referring to Figures 1-7, a large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions includes a section A wall 1, a section B buoyancy chamber 2, and a section C wall 3 rigidly connected from bottom to top, with watertight sealing structures provided between each section;

[0043] Section A wall 1 is the bottom reinforced section, which adopts a composite structure of a lower outer wall 101, internal longitudinal stiffening ribs 103, internal transverse stiffening ribs 104 and a lower inner wall 105. The outer side of Section A wall 1 is coated with a wear-resistant alloy coating with a thickness greater than 15mm, and anti-erosion toothed sills 102 with a height greater than 300mm are set at intervals. Four sets of pressure sensors are evenly distributed at the bottom for real-time monitoring of the substrate contact stress. The anti-erosion toothed sills 102 of Section A wall 1 are fixed to the double-layer steel plate by welding with a spacing of 0.8-1.2m to enhance the bottom's resistance to water flow erosion and reduce the erosion damage to the substrate caused by high-speed water flow in ultra-deep water.

[0044] The internal longitudinal stiffening ribs 103 and internal transverse stiffening ribs 104 of section A wall 1 are orthogonally distributed with a spacing of 800-1000mm. They are made of Q355B grade steel and have a cross-sectional size of 200mm×100mm×8mm. They are fixedly connected to the lower outer wall 101 and the lower inner wall 105 by double-sided fillet welds with a weld height greater than 8mm.

[0045] Section B, buoyancy chamber 2, is a closed chamber structure consisting of an outer middle wall 201 and an inner middle wall 203. Internally, it is divided into multiple independent buoyancy control units. Each buoyancy control unit is equipped with a liquid level sensor 204, an automatic water pump 202 with a flow rate greater than 50 m³ / h, and an emergency stop valve 205 with a pressure rating greater than 1.2 MPa. Before the bottom sealing concrete is poured and reaches its design strength, all buoyancy control units remain waterless, providing 1900t of buoyancy. After the bottom sealing concrete reaches more than 90% of its design strength, water intake is controlled through the emergency stop valve 205, unifying the function of section B, buoyancy chamber 2, with other walls to jointly bear the structural load. The buoyancy control system of section B, buoyancy chamber 2, can dynamically adjust the liquid level of each buoyancy control unit via a PLC controller, significantly reducing the load on a single hanging leg 4 from 550t under conventional construction conditions to below 300t.

[0046] The middle outer wall 201 and middle inner wall 203 of the buoyancy chamber 2 in section B are made of steel plates with a thickness of 16-20mm. The inner wall of the chamber is coated with epoxy zinc-rich primer and polyurethane topcoat with a thickness of more than 200μm.

[0047] Section C, wall 3, is a tidal adaptive section, employing a telescopic structure consisting of an upper outer wall 303, a telescopic box top 302, and an upper inner wall 304. The telescopic box top 302 is slidably embedded between the upper outer wall 303 and the upper inner wall 304, and has a built-in water level linkage adjustment device. The water level linkage adjustment device includes a tidal water level sensor and a hydraulic push rod 7 with a stroke of 1.5m. The top of the telescopic box top 302 is provided with a connector 6, which is rigidly connected to the hydraulic push rod 7. The hydraulic push rod 7 is fixedly installed on the inner wall of the steel caisson. Streamlined guide plates 301 are spaced apart on the outer side of the upper outer wall 303, and the angle between the streamlined guide plates 301 and the water flow direction is an acute angle.

[0048] The top of the telescopic box 302 is equipped with hanging legs 4 for connecting the injection pipe. Stress buffer dampers 5 are installed at the connection nodes between the hanging legs 4 and the steel box wall to absorb the dynamic load generated by the water flow impact. The streamlined guide plate 301 of the C section wall 3 is made of fiberglass and is integrally molded with a plate thickness of 12-15mm. The spacing between adjacent streamlined guide plates 301 is 1-1.5m.

[0049] The fourth hanging leg is made of 45 seamless steel pipe with an outer diameter of 300mm and a wall thickness of 25mm. It is equipped with a flange connector at the top. The flange has bolt holes evenly distributed around its circumference. The flange is 30mm thick and has 8 bolt holes evenly distributed around its circumference.

[0050] A construction method for a large, double-walled steel caisson designed for ultra-deep buoyancy in harsh sea conditions includes the following steps:

[0051] S1. Prefabrication: Process each component of section A (wall 1), section B (buoyancy chamber 2), and section C (wall 3) separately, strictly controlling the dimensional accuracy of each component. The tolerance for cutting the wall steel plate should not exceed ±2mm, and the welding deformation should be controlled within 3mm / m. Spray a wear-resistant alloy coating on the outside of section A (wall 1), and install anti-erosion toothed sills 102 and pressure sensors. Install a liquid level sensor 204, an automatic water pump 202, and an emergency water stop valve 205 in section B (buoyancy chamber 2), and complete the sealing test of each buoyancy control unit. Install a streamlined guide plate 301, a telescopic tank top 302, and a water level linkage adjustment device on section C (wall 3).

[0052] S2. Segment assembly: The prefabricated sections A (wall 1), B (buoyancy chamber 2), and C (wall 3) are rigidly connected at the prefabrication site. The connection is sealed with double welds, with the inner weld height greater than 12mm and the outer weld height greater than 10mm. After welding, a water tightness test is conducted with a test pressure greater than 0.3MPa and a pressure holding time greater than 30min. No leakage is considered acceptable.

[0053] S3. Floating and positioning: The assembled steel caisson is floated to the designated construction sea area by tugboat. The position of the steel caisson is adjusted using a GPS positioning system so that the deviation between the center of the steel caisson and the design center of the pile foundation does not exceed 50mm. The automatic water pump 202 of the buoyancy chamber 2 in section B is started to keep the buoyancy control unit dry and ensure the stable floating state of the steel caisson.

[0054] S4. Landing and Fixing: The liquid level of each buoyancy control unit is adjusted by the PLC controller to gradually lower the elevation of the steel caisson, so that the bottom of section A wall 1 lands stably. The bottom pressure sensor is used to monitor the contact stress of the base to ensure that the contact stress is evenly distributed and the maximum stress does not exceed the design limit. The bottom of the steel caisson is fixed by backfilling with riprap to enhance its anti-slip stability.

[0055] S5. Tidal adaptation debugging: Start the water level linkage adjustment device of section C wall 3 to carry out tidal response debugging, simulate the lifting and lowering action of the telescopic box top 302 under different water level conditions, ensure that the hydraulic push rod 7 runs smoothly, and control the lifting and lowering accuracy of the telescopic box top 302 within ±5mm.

[0056] S6. Construction of bottom sealing concrete: The bottom sealing concrete is poured into the steel caisson by connecting the grouting pipe through the hanging leg 4. During the pouring process, the settlement and tilt data of the steel caisson are monitored in real time. The settlement is controlled within 10mm and the tilt does not exceed 1‰.

[0057] S7. Buoyancy conversion: After the bottom sealing concrete reaches more than 90% of the design value, the emergency water stop valve 205 is opened by the PLC controller to slowly introduce water into each buoyancy control unit. The water inlet rate is controlled within 20m³ / h until the buoyancy control unit is connected to the external water area, completing the conversion of the buoyancy chamber 2 in section B from the buoyancy supply state to the load bearing state.

[0058] S8. Final inspection: Conduct a comprehensive inspection of the structural integrity, watertightness, and operational status of each functional device of the steel caisson to ensure that the design and usage requirements are met before completing the construction.

[0059] Example 1

[0060] Anti-erosion reinforced double-wall steel caisson structure

[0061] This embodiment focuses on optimizing the scour resistance and structural reinforcement design of section A wall for scenarios involving strong water flow in ultra-deep water.

[0062] Section A wall 1, serving as the bottom reinforcing section, employs a composite structure consisting of a lower outer wall 101, internal longitudinal stiffeners 103, internal transverse stiffeners 104, and a lower inner wall 105. Both the lower outer wall 101 and the lower inner wall 105 are constructed from 20mm thick Q355B grade weathering steel plates. The internal longitudinal stiffeners 103 and 104 are orthogonally distributed with a spacing of 900mm, and are rolled from the same type of steel, with a cross-sectional dimension of 200mm × 100mm × 8mm. They are fixedly connected to the two wall layers via double-sided fillet welds with a weld height of 8mm, significantly improving the overall rigidity and deformation resistance of Section A wall.

[0063] For erosion protection, the outer side of section A wall 1 is coated with a 16mm thick wear-resistant alloy coating. This coating is prepared using plasma spraying technology, achieving a hardness of HRC60 or higher, and possesses excellent wear and impact resistance. The spaced-apart erosion-resistant toothed supports 102 are made of ZGMn13 high-manganese steel, with a height of 300mm and a spacing of 1.2m. They are welded to the lower outer wall 101 via continuous fillet welds, with the weld length exceeding 95% of the toothed support circumference to ensure a strong and reliable connection. Four sets of high-precision pressure sensors are evenly distributed at the bottom of section A wall 1. The sensors have a range of 0-5MPa and a measurement accuracy of ±0.5%FS, collecting base contact stress data in real time and transmitting it to the control terminal. When local stress exceeds the design limit, stress optimization is performed by adjusting the riprap backfill position to ensure stable landing of the steel caisson.

[0064] Section B buoyancy chamber 2 and section C wall 3 adopt the basic design scheme. The interior of section B buoyancy chamber 2 is divided into 8 independent buoyancy control units. Each unit is equipped with an automatic water pump 202 with a flow rate of 50m³ / h, an emergency water stop valve 205 with a pressure rating of 1.2MPa, and a liquid level sensor 204. The outer side of section C wall 3 is equipped with a streamlined guide plate 301 with an angle of 15° with the water flow direction. The top of the telescopic box 302 is raised and lowered by a hydraulic push rod 7.

[0065] In this embodiment, the composite structure of section A wall works synergistically with the anti-scouring design to resist the scouring of high-speed water flow with a velocity greater than 3m / s, and improves the uniformity of base contact stress by more than 40%, making it suitable for foundation construction in ultra-deep water areas with strong scouring.

[0066] Example 2

[0067] Precision buoyancy control type double-wall steel caisson structure

[0068] This embodiment focuses on the dynamic buoyancy control requirements throughout the construction process, with a focus on optimizing the buoyancy control system of the buoyancy chamber in section B and the force design of the hanging legs.

[0069] Section B, buoyancy chamber 2, is a closed compartment consisting of an outer middle wall 201 and an inner middle wall 203. Both walls are made of 18mm thick weathering steel plates. The inner walls are coated with a 200μm thick epoxy zinc-rich primer and a 150μm thick polyurethane topcoat, forming double corrosion protection. Eight independent buoyancy control units are separated by 12mm thick steel plate bulkheads. The bulkheads are connected to the chamber walls by full penetration welds, which are ultrasonically tested with a 99% pass rate, ensuring independent and reliable watertightness of each unit.

[0070] Each buoyancy control unit is equipped with a liquid level sensor 204 with a measurement range of 0-5m and an accuracy of ±1mm, which monitors the liquid level changes within the unit in real time. The automatic water pump 202 is a submersible pump with a rated flow rate of 55m³ / h and a head of 30m, capable of quickly draining accumulated water from the unit and maintaining stable buoyancy. The emergency stop valve 205 uses a high-pressure ball valve structure with a nominal pressure of 1.6MPa, providing excellent sealing performance and ensuring no leakage even in ultra-deep water pressure environments. The buoyancy control system is equipped with a PLC controller and employs a PID adjustment algorithm to dynamically adjust the liquid level of each buoyancy control unit according to the construction progress. During the bottom sealing concrete pouring stage, by maintaining a waterless state in the buoyancy control units, a total buoyancy of 1900t is provided, reducing the load on a single hanging leg 4 from 550t in conventional construction to 280t, effectively preventing bending deformation of the hanging leg due to stress concentration.

[0071] The hanging leg 4 installed on the top of the telescopic box 302 is made of seamless steel pipe No. 45. The outer diameter of the steel pipe is 300mm and the wall thickness is 25mm. The top is welded with a flange with a thickness of 30mm. There are 8 bolt holes evenly distributed on the flange for connecting the injection pipe. At the connection node between the hanging leg 4 and the C section wall 3, a stress buffer damper 5 is installed. This damper adopts a rubber-metal composite structure, with a stroke of 50mm, a rated load capacity of 600t, and an operating temperature range of -20℃ to 60℃. It can absorb the dynamic load generated by the water flow impact, reduce the stress fluctuation at the hanging leg connection, and extend the service life of the structure.

[0072] Section A wall 1 has a 15mm thick wear-resistant alloy coating sprayed on its outer side, and the anti-erosion toothed sill 102 is made of high manganese steel; the water level linkage adjustment device of section C wall 3 is working normally, the hydraulic push rod 7 has a stroke of 1.5m, and the lifting response time does not exceed 3s.

[0073] In this embodiment, the buoyancy is precisely controlled by a PLC controller, the load fluctuation of the hanging leg is controlled within ±10t, the stress concentration phenomenon in the structure is significantly improved, and the settlement of the steel caisson is controlled within 8mm during the bottom sealing concrete pouring process. This method is suitable for foundation construction in ultra-deep waters where high buoyancy control precision is required.

[0074] Example 3

[0075] Tidal Adaptive Impact-Resistant Double-Wall Steel Suspended Casing Structure

[0076] This embodiment focuses on optimizing the tidal adaptability and water flow impact resistance design of the C-section wall to address severe sea conditions characterized by frequent tidal changes and strong water flow impact.

[0077] Section C, wall 3, serves as the tidal adaptive section. It employs a telescopic structure consisting of an upper outer wall 303, a telescopic box top 302, and an upper inner wall 304. Both the upper outer wall 303 and the upper inner wall 304 are constructed of 16mm thick weathering steel plates, with a 200mm gap between them, providing stable sliding guidance for the telescopic box top 302. The telescopic box top 302 utilizes a box-shaped steel structure with a 12mm thick panel and internal transverse stiffening ribs to ensure structural flatness and prevent deformation during lifting. It slides between the two wall layers with a clearance controlled within 5mm, ensuring smooth sliding and good watertightness.

[0078] The water level linkage adjustment device consists of a tidal level sensor, a data acquisition module, a logic control module, an execution drive module, and a hydraulic push rod 7. The tidal level sensor is installed on the outside of the C-section wall 3, with a measurement range of -2m to 8m and a sampling frequency of 10Hz, collecting tidal level data in real time. The logic control module presets a tidal response threshold. When a tidal level change exceeding 50mm is detected, it immediately sends a control signal to the execution drive module, driving the hydraulic push rod 7 with a stroke of 1.5m to move, causing the top of the telescopic tank 302 to rise and fall synchronously. The lifting and falling response time is 2.5s, and the lifting and falling accuracy is controlled within ±3mm, ensuring that the top of the telescopic tank always matches the water level and preventing the top of the tank from being exposed or submerged.

[0079] To reduce the impact of water flow, streamlined guide plates 301 are installed at intervals on the outer side of the upper outer wall 303. These guide plates are integrally molded from fiberglass, with a thickness of 14mm. The spacing between adjacent guide plates is 1.5m, and the flow-facing surface features a 100mm radius arc transition design, effectively reducing water flow resistance. The guide plates are detachably connected to the upper outer wall 303 using 8.8 grade high-strength bolts with a bolt spacing of 300mm and a bolt preload torque of 350N·m, facilitating installation, disassembly, and subsequent maintenance.

[0080] Section A wall 1 adopts a composite structure design with anti-erosion toothed sills 102 spaced 1.2m apart; the buoyancy control system of section B buoyancy chamber 2 is working normally to ensure buoyancy stability during construction.

[0081] In this embodiment, the tidal adaptive design of the C-section wall enables a rapid response to changes in tidal level. The streamlined guide plate reduces the water flow impact pressure by more than 35%, and the stress buffer damper absorbs dynamic loads, significantly improving the steel caisson's impact resistance and construction continuity under harsh sea conditions. It is suitable for offshore deep-water construction areas with large tidal ranges and rapid currents.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A large, double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions, characterized in that: The structure includes a rigidly connected section A (1), a section B (2), and a section C (3) from bottom to top, with watertight sealing structures between each section. Section A (1) is a bottom reinforced section, employing a composite structure of a lower outer wall (101), internal longitudinal stiffeners (103), internal transverse stiffeners (104), and a lower inner wall (105). The outer side of section A (1) is coated with a wear-resistant alloy coating with a thickness greater than 15 mm, and high-strength materials are spaced apart. The anti-erosion toothed sill (102) with a diameter greater than 300mm has four sets of pressure sensors evenly distributed at the bottom; the buoyancy chamber (2) of section B is a closed chamber structure with a middle outer wall (201) and a middle inner wall (203), and is divided into multiple independent buoyancy control units. Each buoyancy control unit is equipped with a liquid level sensor (204), an automatic water pump (202) with a flow rate greater than 50m³ / h, and an emergency stop valve (205) with a pressure rating greater than 1.2MPa. Before the bottom sealing concrete is poured and reaches the design strength, all buoyancy control units remain in a waterless state to provide buoyancy; after the bottom sealing concrete reaches more than 90% of the design value, water inflow is controlled by an emergency water stop valve (205); the C-section wall (3) is a tidal adaptive section, adopting a telescopic structure of an upper outer wall (303), a telescopic box top (302), and an upper inner wall (304), wherein the telescopic box top (302) is slidably embedded in the upper outer wall (303) and the upper inner wall (304). Between the inner wall bodies (304), a water level linkage adjustment device is built in. The water level linkage adjustment device includes a tidal water level sensor and a hydraulic push rod (7). The top of the telescopic box (302) is provided with a connector (6) which is rigidly connected to the hydraulic push rod (7). The hydraulic push rod (7) is fixedly installed on the inner wall of the steel box. Streamlined guide plates (301) are arranged at intervals on the outer side of the upper outer wall body (303). The angle between the streamlined guide plate (301) and the water flow direction is an acute angle.

2. The large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions according to claim 1, characterized in that, The top of each telescopic box (302) is provided with a hanging leg (4) for connecting the injection pipe, and a stress buffer damper (5) is provided at the connection node between the hanging leg (4) and the steel box wall.

3. The large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions according to claim 1, characterized in that, The buoyancy control system of the buoyancy chamber (2) in section B dynamically adjusts the liquid level of each buoyancy control unit through a PLC controller.

4. The large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions according to claim 1, characterized in that, The anti-erosion teeth (102) of the A section wall (1) are spaced 0.8-1.2m apart and are fixed to the double-layer steel plate by welding.

5. The large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions according to claim 1, characterized in that, The internal longitudinal stiffening ribs (103) and internal transverse stiffening ribs (104) of the A section wall (1) are orthogonally distributed and are fixedly connected to the lower outer wall (101) and the lower inner wall (105) by double-sided fillet welds, with a weld height greater than 8mm.

6. The large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions according to claim 1, characterized in that, The middle outer wall (201) and middle inner wall (203) of the buoyancy chamber (2) in section B are made of steel plates with a thickness of 16-20mm, and the inner wall of the chamber is coated with paint with a thickness of more than 200μm.

7. The large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions according to claim 1, characterized in that, The streamlined guide plate (301) of the C section wall (3) is integrally formed, with a plate thickness of 12-15mm and a spacing of 1-1.5m between adjacent streamlined guide plates (301).

8. A large double-walled steel caisson for ultra-deep buoyancy in harsh sea conditions according to claim 2, characterized in that, The top of the hanging leg (4) is provided with a flange connector, and bolt holes are evenly distributed along the circumference of the flange.

9. A construction method for a large, double-walled steel caisson with ultra-deep buoyancy in harsh sea conditions, as described in any one of claims 1-8, characterized in that... Includes the following steps: S1. Prefabrication: Process the components of section A (1), section B (2), and section C (3) of the wall respectively, strictly control the dimensional accuracy of each component, and ensure that the blanking tolerance of the wall steel plate does not exceed ±2mm and the welding deformation is controlled within 3mm / m; spray the wear-resistant alloy coating on the outside of section A (1), and install the anti-erosion toothed sill (102) and pressure sensor; install the liquid level sensor (204), automatic water pump (202), and emergency water stop valve (205) in section B (2), and complete the sealing test of each buoyancy control unit; install the streamlined guide plate (301), telescopic box top (302), and water level linkage adjustment device on section C (3); S2. Segment assembly: Assemble the prefabricated sections of the wall. The completed A section wall (1), B section buoyancy chamber (2) and C section wall (3) are rigidly connected at the prefabrication site. The connection is sealed with double welds. The height of the inner weld is greater than 12mm and the height of the outer weld is greater than 10mm. After welding, a water tightness test is carried out. The test pressure is greater than 0.3MPa and the pressure holding time is greater than 30min. No leakage is acceptable. S3. Floating and positioning: The assembled steel caisson is floated to the designated construction sea area by tugboat. The position of the steel caisson is adjusted using the GPS positioning system so that the deviation between the center of the steel caisson and the design center of the pile foundation does not exceed 50mm. The automatic water pump (202) of the B section buoyancy chamber (2) is started to keep the buoyancy control unit in a waterless state to ensure the stable floating state of the steel caisson. S4. Landing and Fixing: Adjust the liquid level of each buoyancy control unit through the PLC controller to gradually lower the elevation of the steel caisson, so that the bottom of section A wall (1) lands smoothly; use the bottom pressure sensor to monitor the base contact stress to ensure that the contact stress is evenly distributed and the maximum stress does not exceed the design limit; fix the bottom of the steel caisson by backfilling with riprap to enhance anti-slip stability; S5. Tidal Adaptation Debugging: Start the water level linkage adjustment device of section C wall (3) to perform tidal response debugging, simulate the lifting and lowering action of the telescopic box top (302) under different water level conditions, and ensure that the hydraulic push rod (7) runs smoothly and the lifting and lowering accuracy of the telescopic box top (302) is controlled within ±5mm; S6. Sealing Concrete Construction: Connect the grouting leg (4) to the bottom concrete construction. Injection pipe, pour bottom sealing concrete into the steel caisson, monitor the settlement and tilt data of the steel caisson in real time during the pouring process, control the settlement within 10mm and the tilt not more than 1‰; S7, buoyancy conversion, after the bottom sealing concrete reaches more than 90% of the design value, control the emergency water stop valve (205) to open through the PLC controller, slowly introduce water into each buoyancy control unit, control the water inlet rate within 20m³ / h, until the buoyancy control unit is connected to the external water area, and complete the conversion of the buoyancy chamber (2) of section B from the buoyancy supply state to the load bearing state; S8, completion inspection, conduct a comprehensive inspection of the structural integrity, water tightness and operation status of each functional device of the steel caisson, and ensure that the design and use requirements are met before completing the construction.

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