A method for rapid construction of bottom sealing concrete of a steel hanging box of a high-pile pile cap of a submarine approach bridge

Abstract

This application discloses a rapid construction method for the bottom sealing concrete of a steel caisson for a high-pile pier cap in the sea, comprising six major steps: construction preparation, concrete transportation and placement, rapid direct pouring, layered vibration, continuous operation, and curing monitoring. A double-cylinder multi-point placing pipe system is installed on the top of the steel caisson, combined with a concrete mixer truck with a volume ≥10m³ to achieve direct pouring of C30 bottom sealing concrete. Continuous pouring is performed when the tide level is below -1.00m. Layered vibration is achieved using a φ50 vibrator. After pouring, a film is used for curing while maintaining the communication device, and the limit switch and water level difference are monitored simultaneously. This invention eliminates the need for traditional truck-mounted pumps, achieving a maximum pouring time of ≤2 hours for a single pier cap with a volume of 105m³, significantly improving construction efficiency, reducing the space occupied by the trestle bridge, achieving a concrete density ≥98%, low leakage rate, adapting to the short-window construction requirements during low tide in the sea, ensuring project safety and quality, reducing construction costs, and demonstrating significant practicality and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of concrete construction technology, specifically to a rapid construction method for sealing the bottom of a steel caisson for a high-pile pier of a sea-crossing approach bridge with concrete. Background Technology

[0002] In large-scale infrastructure projects such as cross-sea bridges, the construction of high-pile foundations for approach bridges in the sea is a crucial step. High-pile foundations typically utilize steel caissons as cofferdam structures to achieve a dry construction environment. After the steel caisson is installed, the gap between its bottom and the steel pipe piles and the seabed must be sealed by pouring bottom-sealing concrete. This is a prerequisite for ensuring the safe conduct of subsequent main foundation construction under waterless and dry conditions. The quality of the bottom-sealing concrete construction directly affects the stability and durability of the entire foundation structure and is one of the core procedures in offshore bridge foundation construction.

[0003] The Hangzhou Bay area possesses unique and harsh natural conditions, such as strong currents, high current velocities, complex seabed geology, and frequent typhoon impacts, all of which pose significant challenges to offshore construction. Particularly during the concrete pouring for the steel caisson bottom sealing, work must be carried out during the brief window of low tide, which is extremely limited, typically only a few hours. Therefore, how to efficiently and effectively complete the bottom sealing concrete pouring within a very short timeframe is a pressing technical challenge that the engineering community urgently needs to solve.

[0004] The existing construction methods for sealing the bottom of the steel caisson of the high-pile pier of an approach bridge in the sea generally use a truck-mounted concrete pump for concrete pouring. This method mainly has the following technical problems: Slow pouring speed makes it difficult to meet the required pouring window: The concrete output efficiency of a truck-mounted concrete pump is limited by its own pumping capacity and the moving speed of the placing boom. For the sealing of large foundations, the volume of concrete to be poured is huge, and truck-mounted pumps often need to operate continuously for a long time to complete the work. This can easily cause the construction to exceed the low tide window. Once the tide rises, the uncured concrete will be washed away by seawater, resulting in construction failure and causing safety and quality accidents.

[0005] The large size of the equipment impacts traffic flow: Truck-mounted concrete pumps are bulky, requiring significant space on trestle bridges or construction platforms for operation. In offshore construction, trestle bridges are the only passage for material transport, personnel access, and equipment scheduling. The space occupied by truck-mounted pumps severely affects traffic flow and construction efficiency on the main trestle bridge, potentially causing delays in other processes and creating a construction bottleneck.

[0006] Insufficient placement flexibility can easily lead to construction defects: The placing boom of a truck-mounted concrete pump has a limited coverage area, and for complex-shaped or large-area sealing areas, there may be blind spots or hard-to-reach corners. This can result in uneven concrete pouring, inadequate compaction in localized areas, and quality defects such as honeycomb, pitted surfaces, or even cold joints, affecting the integrity and impermeability of the sealing concrete.

[0007] High equipment dependence and significant construction risks: The complex marine environment, with its winds and waves, threatens the stability of heavy machinery like truck-mounted concrete pumps. Any equipment malfunction could disrupt the entire pouring operation, making repairs difficult during the window of opportunity, resulting in substantial economic losses and project delays.

[0008] Currently, C30 concrete is commonly used for sealing the bottom of steel caissons for approach bridges in the sea. The designed thickness of the sealing concrete is mostly 0.7m, and the maximum volume of sealing a single pier can reach 105m³. Concrete must be supplied by a mixing plant and poured under dry conditions at low tide. The sealing construction must be carried out when the tide level is below -1.00m, and the construction time during each slack tide period is about 4 hours. Traditional truck-mounted pump pouring takes more than 3 hours, which is very easy to cause the risk of erosion by rising tide due to exceeding the time limit. In addition, a construction passage needs to be built before sealing, and curing and monitoring are required after pouring. Existing technology lacks an efficient adaptation solution for the entire process of 'preparation-pouring-curing' within the window period.

[0009] In conclusion, traditional truck-mounted concrete pump casting methods are no longer adequate for the stringent requirements of modern large-scale cross-sea engineering projects regarding construction efficiency and space utilization. Therefore, there is an urgent need to develop a new method for constructing the bottom concrete of high-pile piers for offshore approach bridges using steel caissons, which enables rapid casting and requires minimal space, to address the shortcomings of existing technologies and ensure the safe, efficient, and high-quality progress of the project. Summary of the Invention

[0010] This application proposes a rapid construction method for sealing the bottom concrete of a steel caisson for a high-pile pier cap of a sea-crossing approach bridge. This method overcomes the shortcomings of existing technologies and provides a rapid construction method for sealing the bottom concrete of a steel caisson for a high-pile pier cap of a sea-crossing approach bridge. It solves the technical problems of slow pouring speed, large space occupation, and impact on traffic organization caused by traditional truck-mounted concrete pump pouring methods, and achieves rapid and efficient construction of the bottom concrete sealing.

[0011] To achieve the above objectives, this application adopts the following technical solution: a rapid construction method for sealing the bottom of a steel caisson for a high-pile pier cap of a sea-crossing bridge with concrete, comprising: S1: Construction preparation: After the steel caisson is installed and the dredging and leak sealing pretreatment are completed, a double-cylinder multi-point material distribution pipe system is installed on the top of the steel caisson. At the same time, a horizontal passage is built on the top surface of the steel pipe pile, and the existing ladders are used as the working passage for construction personnel. S2: Concrete transportation and placement: C30 bottom sealing concrete is transported to the construction position using concrete mixer trucks, with the truck's discharge port aligned with the inlet of the double-drum multi-point distribution pipe system. The design thickness of the bottom sealing concrete is 0.7m. S3: Rapid direct pouring: When the tide level is below -1.00m, start the concrete mixer truck to unload and pour the concrete directly into the bottom sealing area of ​​the steel caisson through the double-tube multi-point material distribution pipe system. During pouring, the concrete is pushed from the upstream or downstream side to the other side to ensure that the concrete is poured continuously and uninterruptedly in one go. S4: Layered vibration: Use a φ50 vibrator to vibrate the poured concrete in layers. When vibrating the upper layer of concrete, the vibrator should be inserted 50-100mm into the lower layer of concrete. S5: Continuous operation until completion: Maintain the continuous supply of concrete from the concrete mixer trucks and the uninterrupted pouring of the double-tube multi-point concrete distribution pipe system until the bottom sealing concrete pouring of a maximum volume of 105m³ for a single foundation is completed. S6: Maintenance and monitoring: After the bottom sealing concrete is poured, cover the top surface with a thin plastic sheet. Keep the communicating vessel in a connected state until the bottom sealing concrete reaches 90% strength. Simultaneously monitor the limit status of the steel caisson and the water level difference between the inside and outside, and set up warning lights around the caisson.

[0012] Furthermore, in step S1, the dual-drum multi-point feeding pipe system includes at least two vertically arranged drums, each of which is connected to a horizontally rotatable feeding pipe at its lower end, and the feeding pipe is provided with a discharge port at its end.

[0013] Furthermore, the fabric tube is a retractable rigid tube or a flexible hose, which achieves full coverage of the bottom sealing area through rotation and extension.

[0014] Furthermore, in step S1, the double-tube multi-point material distribution pipe system is installed on the steel distribution beam at the top of the steel caisson by a fixed bracket, and the bracket is welded and fixed to the distribution beam.

[0015] Furthermore, in step S3, by simultaneously operating the rotation and extension of multiple material distribution pipes, the concrete is evenly distributed from multiple discharge ports, avoiding the occurrence of blind spots in the pouring process.

[0016] Furthermore, in step S4, the vibration points are arranged evenly in a quincunx pattern, with the spacing controlled within 50cm. The vibration time for each insertion point is 20-30s to ensure that the concrete density is ≥98%.

[0017] Furthermore, in step S2, concrete mixer trucks with a volume of ≥10m³ are used, and multiple trucks supply concrete continuously in a "delivery upon arrival and departure" mode to avoid interruption of pouring.

[0018] Furthermore, the diameter of the cistern is 250-350mm, and the inner wall is smooth and inclined to prevent concrete from sticking to the wall or segregating.

[0019] Furthermore, in step S6, the limit status of the steel caisson and the difference in water level inside and outside are monitored every 2 hours during the maintenance period. The warning lights are powered by solar energy and are continuously lit at night, with an effective warning range of ≥50m.

[0020] The present invention has the following beneficial effects: 1. This application provides a rapid construction method for sealing the bottom of a steel caisson for a high-pile pier of a marine approach bridge with concrete. This method utilizes direct pouring from a concrete mixer truck combined with multi-point placement using a double-drum system, directly eliminating the time wasted on truck-mounted pumps and significantly increasing the concrete pouring speed. Based on actual engineering application data, this construction method can reduce the original 3-hour bottom sealing concrete construction time to less than 1 hour, improving efficiency by over 200%. It easily addresses the low-tide window limitations of offshore construction, avoids construction risks caused by high tides, and significantly shortens the overall construction period.

[0021] 2. This application provides a rapid construction method for sealing the bottom of the steel caisson of a high-pile pier for a sea-crossing approach bridge with concrete. This method eliminates the need for large concrete pump trucks, allowing for quick removal of the concrete mixer trucks after unloading, and requiring only minimal space on the trestle bridge during the pouring process. This facilitates smoother traffic flow on the main trestle bridge, eliminating obstacles to material transport, equipment scheduling, and personnel access. It effectively alleviates the pressure caused by limited construction space, optimizes the overall construction process, and improves construction management efficiency.

[0022] 3. This application provides a rapid construction method for the bottom concrete sealing of a steel caisson for a high-pile pier cap of a sea-crossing approach bridge. Through a double-cylinder, multi-point concrete placement pipe system, uniform and synchronous concrete pouring can be achieved. Combined with layered vibration compaction, this effectively avoids problems such as concrete accumulation, segregation, and insufficient compaction, reducing quality defects such as honeycomb, pitting, and cold joints. This helps improve the integrity, density, and impermeability of the bottom concrete sealing, thereby enhancing the water-stopping effect of the steel caisson cofferdam, providing a reliable dry construction environment for subsequent pier cap construction, and ultimately improving the durability and safety of the entire bridge foundation structure. Attached Figure Description

[0023] The accompanying drawings, which form part of this specification, illustrate embodiments disclosed in this application and, together with the specification, serve to explain the principles disclosed in this application.

[0024] This disclosure will become clearer with reference to the accompanying drawings and the following detailed description, wherein: Figure 1 This is a flowchart of the present invention; Figure 2 This is a side view of the double-tube multi-point feeding pipe system used in this invention; Figure 3 This is a schematic diagram of the structure of the double-tube multi-point material distribution pipe system used in this invention; Figure 4 This is a plan view of the concrete sealing construction of the present invention; Figure 5 This is a schematic diagram of the elevation layout of the concrete sealing platform of the present invention; Figure 6 This is a schematic diagram of the plan layout of the concrete sealing platform of the present invention; Figure 7 This invention relates to a tide table for concrete construction. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] A rapid construction method for sealing the bottom of the steel caisson of a high-pile pier cap in a marine approach bridge using concrete includes the following steps: S1: Construction Preparation: After the steel caisson is installed and pre-treatment work such as dredging and leak sealing is completed, the transportation route and parking position of the concrete mixer truck are planned according to the design volume and pouring range of the bottom sealing concrete. A double-drum multi-point placing pipe system is installed at the designated position on the top of the steel caisson. The double-drum multi-point placing pipe system includes at least two vertically arranged drums. The lower end of each drum is connected to a horizontally rotatable and telescopic placing pipe. The end of the placing pipe is provided with a discharge port to guide the flow of concrete. Multiple discharge ports can cover the entire bottom sealing concrete pouring area. At the same time, a horizontal passage is built in advance on the top surface of the steel pipe pile, and the existing ladders are used as the working passage for construction personnel.

[0027] S2: Concrete Transportation and Placement: Use large-capacity concrete mixer trucks to transport ready-mixed concrete directly to the designated location on the construction trestle or platform, aligning the truck's discharge port with the inlet of the double-drum multi-point distribution pipe system.

[0028] S3: Rapid Direct Pouring: The concrete mixer truck's unloading system is activated, directly and rapidly pouring concrete through a double-drum multi-point placing pipe system into the sealed area at the bottom of the steel caisson. By operating the rotation and extension of the placing pipes, the concrete is evenly and synchronously spread and accumulated from multiple outlets, forming a continuous concrete flow. Pouring is carried out when the tide level is below -1.00m. Pouring begins after the ebb tide level recedes to -1.00m and is completed before the next high tide level rises to -1.00m. Pouring proceeds from upstream or downstream to the other side, ensuring continuous and uninterrupted pouring in one go.

[0029] S4: Layered Vibration: During concrete pouring, an immersion vibrator is used to vibrate the poured concrete in layers. During vibration, the vibrator should be inserted quickly and withdrawn slowly, with insertion points evenly spaced and moved point by point in sequence to ensure the concrete is compacted. When vibrating the upper layer of concrete, the vibrator should be inserted 50-100mm into the lower layer to eliminate the joint between the two layers.

[0030] S5: Continuous Operation to Completion: Maintain a continuous supply of concrete from the concrete mixer trucks and uninterrupted pouring using the dual-drum multi-point placing pipe system until the designed thickness and range of the bottom sealing concrete are completed. During the pouring process, assign dedicated personnel to direct traffic and coordinate the dispatch of concrete mixer trucks to ensure a smooth construction process.

[0031] In this system, the shunt tubes of the double-spool multi-point material distribution pipe system are mounted on the steel distribution beams at the top of the steel caisson via fixed supports. The material distribution pipes are rigid structures and can rotate at a limited angle on the horizontal plane. This design is simple in structure, has good stability, and is suitable for sealing areas with regular shapes and moderate areas.

[0032] S6: Curing and Monitoring: After the bottom sealing concrete is poured, cover the entire top surface with a thin plastic sheet for curing; before the steel caisson is lowered to the bottom sealing concrete strength reaches 90%, the communicating vessel should be kept in a connected state to ensure the water pressure balance inside and outside the steel caisson; during the curing period, strengthen the monitoring of the limit position of the steel caisson and the difference in water level inside and outside, and set up warning lights around the caisson to prevent passing ships from approaching and ensure the safety of the bottom sealing concrete forming.

[0033] In existing technologies, the delivery of concrete from the concrete mixer truck to the work site relies on a truck-mounted concrete pump, which is an inefficient and space-consuming process. This invention, by setting up a dual-drum multi-point distribution pipe system, directly connects the concrete mixer truck's discharge port to the work site, eliminating the intermediate truck-mounted pump and achieving "direct pouring" of concrete. The unloading speed of the concrete mixer truck is much higher than the pumping speed of the truck-mounted pump, and the dual-drum multi-point distribution system enables simultaneous pouring through multiple channels, greatly improving overall pouring efficiency and allowing the work to be completed within a very short low tide window. The concrete mixer truck can leave immediately after unloading, without occupying the trestle space for extended periods like a truck-mounted pump, significantly alleviating traffic pressure on the construction platform and ensuring the smooth progress of other processes. The multi-point distribution pipe system allows for simultaneous pouring of concrete from multiple points to different areas. Combined with the flexible adjustment of the distribution pipes, it can more effectively cover the entire sealing area, avoiding accumulation and blind spots that may occur with single-point pouring, and improving the overall density of the concrete. Application Example: Construction of the bottom sealing of a 16.6m × 9.6m circular end cap for a cross-sea bridge The sea-crossing approach bridge pier in this embodiment has a planar dimension of 16.6m × 9.6m and a rounded end. The designed thickness of the bottom sealing concrete is 0.7m, and the designed volume is approximately 110m³. The construction window is during low tide, lasting approximately 2 hours. The bottom sealing concrete used is C30 concrete, with a designed thickness of 0.7m and a volume of 110m³. Pouring will begin when the tide level is below -1.00m and will be completed before the next high tide rises to -1.00m.

[0034] The rapid construction method of this invention comprises the following specific steps: S1: Construction Preparation: After the steel caisson is installed and dredged, two sets of double-drum multi-point material distribution pipe systems are symmetrically arranged along the length of the top of the steel caisson according to the shape and size of the foundation. Each system consists of two drums with a diameter of 300mm. The bottom of the drums is connected to a material distribution pipe that can rotate horizontally by 180° and has an extendable length. The four discharge ports are evenly distributed in key positions in the sealing area.

[0035] S2: Concrete Transportation and Placement: Arrange 4 concrete mixer trucks with a capacity of 12m³ to transport C30 underwater sealing concrete to the designated location on the trestle in advance, and have them queue up in order to ensure a continuous supply of concrete.

[0036] S3: Rapid Direct Pouring: The first concrete mixer truck is positioned, its discharge chute is connected to the feed inlet of the tremie pipe, and unloading is initiated. Concrete is rapidly and evenly poured into the bottom of the steel caisson through the double-tremie pipe multi-point distribution system. Simultaneously, the second concrete mixer truck is immediately positioned and ready. Through manual operation of the distribution pipe, the concrete is simultaneously spread outwards from four points, forming a fan-shaped pouring surface.

[0037] S4: Layered Vibration: When the concrete is poured to a thickness of approximately 25cm, four workers will use handheld vibrators to compact the poured area. The spacing between vibration points should be controlled at approximately 50cm to ensure that the vibration covers all areas.

[0038] S5: Continuous Operation to Completion: The tanker trucks adopted a "delivery upon arrival and departure" method to maintain continuous unloading. Two concrete placement systems worked simultaneously, with pouring and vibration carried out concurrently. The entire pouring process lasted 1 hour and 50 minutes. Immediately after pouring, the concrete was covered with a thin plastic sheet. During the curing period, the communicating vessel was kept open, and the limit status of the steel caisson and the difference in water levels inside and outside were monitored simultaneously. No abnormalities occurred, and the pouring of 110m³ of concrete was successfully completed. The concrete surface elevation met the design requirements, and the surface was smooth.

[0039] S6: Curing and Monitoring: After the bottom sealing concrete is poured, immediately cover the entire top surface with a thin plastic sheet for moisture retention and curing; before the steel caisson is lowered to the bottom sealing concrete strength reaches 90%, keep the communicating vessel in a connected state to ensure water pressure balance inside and outside the steel caisson; during the curing period, arrange for a dedicated person to monitor the limit status of the steel caisson and the water level difference between the inside and outside every 2 hours, and no loosening of the limit or abnormal water level difference is found; at the same time, 4 sets of warning lights are evenly set around the caisson to prevent passing ships from approaching and ensure the safety of bottom sealing concrete forming.

[0040] In this embodiment, the bottom sealing construction was completed efficiently within the specified window period. After testing, the concrete density was good, and the strength reached 105% of the design value after 28 days. No leakage was found, and the construction quality was excellent.

Claims

1. A method for rapid construction of bottom sealing concrete of a steel hanging box of a high-pile pile cap of a sea approach bridge, characterized in that, include: S1: Construction preparation: After the steel caisson is installed and the dredging and leak sealing pretreatment are completed, a double-cylinder multi-point material distribution pipe system is installed on the top of the steel caisson. At the same time, a horizontal passage is built on the top surface of the steel pipe pile, and the existing ladders are used as the working passage for construction personnel. S2: Concrete transportation and placement: C30 bottom sealing concrete is transported to the construction position using concrete mixer trucks, with the truck's discharge port aligned with the inlet of the double-drum multi-point distribution pipe system. The design thickness of the bottom sealing concrete is 0.7m. S3: Rapid direct pouring: When the tide level is below -1.00m, start the concrete mixer truck to unload and pour the concrete directly into the bottom sealing area of ​​the steel caisson through the double-tube multi-point material distribution pipe system. During pouring, the concrete is pushed from the upstream or downstream side to the other side to ensure that the concrete is poured continuously and uninterruptedly in one go. S4: Layered vibration: Use a φ50 vibrator to vibrate the poured concrete in layers. When vibrating the upper layer of concrete, the vibrator should be inserted 50-100mm into the lower layer of concrete. S5: Continuous operation until completion: Maintain the continuous supply of concrete from the concrete mixer trucks and the uninterrupted pouring of the double-tube multi-point concrete distribution pipe system until the bottom sealing concrete pouring of a maximum volume of 105m³ for a single foundation is completed. S6: Maintenance and monitoring: After the bottom sealing concrete is poured, cover the top surface with a thin plastic sheet. Keep the communicating vessel in a connected state until the bottom sealing concrete reaches 90% strength. Simultaneously monitor the limit status of the steel caisson and the water level difference between the inside and outside, and set up warning lights around the caisson.

2. The method according to claim 1, wherein the method is characterized by, In step S1, the dual-drum multi-point feeding pipe system includes at least two vertically arranged drums, each drum having a horizontally rotatable feeding pipe connected to its lower end, and the feeding pipe having a discharge port at its end.

3. The method according to claim 2, wherein the method is characterized by, The fabric tube is a retractable rigid tube or a flexible hose, which achieves full coverage of the bottom sealing area through rotation and extension.

4. The method according to claim 1 or 2, characterized in that, In step S1, the double-tube multi-point material distribution pipe system is installed on the steel distribution beam at the top of the steel caisson by a fixed bracket, and the bracket is welded and fixed to the distribution beam.

5. The method according to claim 1, wherein the method is characterized by, In step S3, by simultaneously operating the rotation and extension of multiple material distribution pipes, the concrete is evenly distributed from multiple discharge ports, avoiding the occurrence of blind spots in the pouring process.

6. The method according to claim 1, wherein the method is characterized by, In step S4, the vibration points are arranged evenly in a quincunx pattern, with the spacing controlled within 50cm. The vibration time for each insertion point is 20-30s to ensure that the concrete density is ≥98%.

7. The method according to claim 1, wherein the method is characterized by, In step S2, concrete mixer trucks with a volume of ≥10m³ are used, and multiple trucks supply concrete continuously in a "delivery and departure" mode to avoid interruption of pouring.

8. The method according to claim 2, wherein the method is characterized by, The cistern has a diameter of 250-350mm, a smooth inner wall, and an inclined angle to prevent concrete from sticking to the wall or segregating.

9. The method according to claim 1, wherein the method is characterized by, In step S6, the limit status of the steel caisson and the difference between the internal and external water levels are monitored every 2 hours during the maintenance period. The warning lights are powered by solar energy and are continuously lit at night, with an effective warning range of ≥50m.

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