Comprehensive construction method for Larsen steel sheet pile cofferdam of anti-typhoon cross-sea bridge

Abstract

The invention relates to a comprehensive construction method for a Larsen steel sheet pile cofferdam of an anti-typhoon cross-sea bridge. The comprehensive construction method comprises the steps that firstly, BIM and VR application is conducted; 2, construction preparation is conducted; thirdly, a first enclosing purlin is installed, and steel sheet piles are driven in an inserted mode; fourthly, steel enclosing purlins and water stops are installed; 5, bottom sealing concrete is constructed; sixthly, the elevator cage is installed; seventhly, a bearing platform is constructed; eighthly, dismantling construction is conducted; ninthly, the steel sheet piles are recycled; and step 10, intelligent monitoring application. The construction challenges caused by complex landforms at the bottom of the foundation are effectively overcome by adopting targeted construction measures, the resistance to typhoon and storm impact is enhanced, corresponding improvement measures are integrated in all construction processes, and positive effects are achieved.

Description

Technical Field

[0001] The present invention relates to the field of offshore construction, in particular to a comprehensive construction method for a Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge. Background Art

[0002] This construction method aims to address a series of complex issues encountered during the construction of cross-sea bridge cofferdams, particularly focusing on the diversity and complexity of the foundation's underlying topography. Effective cofferdam construction becomes a major challenge when encountering situations where there is no cover, a thin cover, or a cover thickness that fails to meet construction requirements. Furthermore, given the significant impact of strong winds and waves brought by typhoons on cofferdam structures, this method will focus on how to ensure the stability and safety of the cofferdam under these extreme natural conditions, thereby ensuring the smooth progress of the entire cross-sea bridge construction project.

[0003] Cross-sea bridges often span vast sea areas, where the geological conditions vary significantly. There may be no cover (such as exposed bedrock), thin cover (such as soft soil, silt layer), or uneven cover thickness. These complex geological conditions pose great challenges to cofferdam construction. The marine environment is complex and changeable, including currents, tides, waves, seabed topography, etc. These factors will affect the bottom topography of the foundation, making the construction environment more difficult to predict and control. The geological conditions of no cover or thin cover result in poor stability of the cofferdam foundation, which is easily affected by external factors. Interference and damage from environmental factors; for example, when constructing cofferdams on soft soil or silt layers, settlement and slippage are prone to occur; cross-sea bridge construction areas are often affected by extreme weather such as typhoons, and the strong winds and waves brought by these weather conditions can cause serious impact and damage to the cofferdam structure; especially when the cofferdam structure itself is less stable, it is more susceptible to the impact of typhoon winds and waves; the impact of typhoon winds and waves on the cofferdam will not only cause damage to the cofferdam structure, but may also cause safety accidents such as cofferdam collapse and damage to construction equipment, posing a threat to construction workers and the surrounding environment;

[0004] To address these issues, traditional construction methods include using materials such as clay, silty clay, or sandy clay to form a cofferdam. This method is suitable for shallow water areas with good foundation soil quality. Steel sheet piles are driven into the foundation to form the cofferdam. Steel sheet pile cofferdams have high strength and rigidity and are suitable for deep water areas and complex terrain. They consist of two layers of steel shell, with sand or concrete filling in between. Double-walled steel cofferdams offer extremely high strength and stability and are suitable for projects in deep water, complex terrain, and requiring high construction precision.

[0005] However, the traditional construction method has the following defects and shortcomings:

[0006] Stability issues: Traditional cofferdam construction technology is difficult to ensure the stability and safety of the cofferdam when facing complex terrain and deep water areas. Especially in strong winds and waves, the cofferdam is easily damaged;

[0007] Insufficient sealing: Some cofferdam construction methods have relatively poor sealing, which may cause water leakage and affect the construction progress and quality;

[0008] Environmental impact: Certain construction methods (such as the driving and pulling out of steel sheet pile cofferdams) may have certain impacts on the surrounding environment, including water pollution and soil damage;

[0009] High cost: For deepwater areas and complex terrain, the use of high-strength, high-stability cofferdam construction methods (such as double-walled steel cofferdams) is expensive, increasing construction difficulty and costs. Summary of the Invention

[0010] The present invention aims to overcome the defects of the existing technology and provide a comprehensive construction method for Larsen steel sheet pile cofferdams of typhoon-resistant cross-sea bridges, so as to solve the problems of difficulty in cofferdam construction of cross-sea bridges in areas with complex topography, the large impact of typhoon winds and waves on the cofferdams during the construction process, and the difficulty of construction due to different geological conditions under the sea.

[0011] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0012] A comprehensive construction method for Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that it comprises the following steps:

[0013] Step 1: BIM and VR application;

[0014] Step 2: Construction preparation;

[0015] Step 3: Installation of the first perimeter purlin and driving of steel sheet piles;

[0016] Step 4: Install steel purlins and waterstops;

[0017] Step 5: bottom concrete construction;

[0018] Step 6: Ladder cage installation;

[0019] Step 7: Capping construction;

[0020] Step 8: Demolition construction;

[0021] Step 9: Steel sheet pile recovery;

[0022] Step 10: Intelligent monitoring application.

[0023] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step one specifically comprises:

[0024] BIM model construction: Using BIM software, we constructed a three-dimensional model of the Larsen steel sheet pile cofferdam based on geological survey data and design requirements. The model included all key components, including steel sheet piles, purlins, and support systems, ensuring accurate dimensions and a reasonable structure.

[0025] Construction plan optimization: Using the BIM model, we compared multiple plans to optimize the steel sheet pile driving sequence, support system layout, and removal strategy. We also considered the impact of typhoon winds and waves on the cofferdam, simulated the cofferdam's stability under different working conditions, and adjusted the design to improve its wind and wave resistance.

[0026] VR simulation training: Using VR technology to transform BIM models into a virtual construction environment, construction personnel can undergo simulated operation training. This includes simulating the entire process of driving, connecting, installing, and removing the support system for steel sheet pile cofferdams, improving construction personnel's proficiency and their ability to respond to emergencies.

[0027] On-site construction preparation: Guide on-site construction preparation based on the BIM model, including the procurement and deployment of materials such as steel sheet piles, perimeter purlins, and support systems; set measurement control points on-site to ensure construction accuracy;

[0028] Steel sheet pile cofferdam construction: On-site construction was carried out according to the construction plan guided by the BIM model, including the driving and connection of steel sheet piles, and the installation of the support system. BIM models and VR technology were used for on-site guidance and monitoring to ensure construction quality.

[0029] Cofferdam dismantling: After construction is completed, the steel sheet pile cofferdam is dismantled according to the demolition plan developed by the BIM model. The demolition process is simulated and monitored using the BIM model and VR technology to ensure a safe and orderly demolition process.

[0030] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step 2 specifically comprises:

[0031] After the steel sheet piles are transported to the construction site, they are carefully inspected, measured, classified, and numbered, with special attention paid to their corrosion resistance and resistance to wind and wave impact. At the same time, a short pile of the same model with a length of 2 to 3 meters is used to conduct a pass test on both sides of the lock.

[0032] If the lock mouth cannot pass or the pile body has defects such as bending, twisting, and dead bend, it can be repaired by cold bending, hot knocking (temperature not exceeding 800~1000℃), welding, riveting, cutting, lengthening, etc.

[0033] The locking mouth of the steel sheet pile is coated with a high-performance lubricating grease mixture (graphite-based material mixed with kerosene, gasoline or light mineral oil) to reduce friction during insertion and enhance anti-seepage performance;

[0034] (1) Evenly apply: Use a brush or spray equipment to evenly apply the graphite-based lubricating grease mixture to the lock of the steel sheet pile; when applying, ensure that the grease mixture covers the lock surface without omission; pay attention to controlling the application thickness, which should not be too thick or too thin; too thick may cause waste, and too thin may affect the lubrication and anti-seepage effect;

[0035] (2) Multiple applications: Depending on the project requirements, multiple applications may be required to ensure that the lubricating grease mixture fully covers the lock mouth; after each application, wait for a certain amount of time for the grease mixture to fully penetrate and dry before applying the next application;

[0036] (3) Inspection and correction: After the application is completed, the steel sheet pile lock should be fully inspected to ensure that the lubricating grease mixture is evenly applied without omission; if uneven application or omissions are found, corrections and re-application should be made in a timely manner.

[0037] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step three specifically includes:

[0038] To install the first purlin, first measure and mark the precise position of the guide frame. Use the casing as support to install the purlin. Horizontally weld 14-inch channel steel and vertical 14-inch channel steel braces at an elevation of 3.8m on both sides of the casing to support the purlin and enhance its resistance to typhoons and seawater impact. Install the first purlin on the channel steel. Add rubber gaskets or sealing strips at the connection between the purlin and the casing to improve sealing.

[0039] Steel sheet pile driving:

[0040] (1) Equipment development and introduction:

[0041] To meet specific project requirements, we collaborate with automation equipment manufacturers to design and manufacture an automated steel sheet pile driving robot (intelligent steel sheet pile driving all-in-one machine). This robot must integrate high-precision sensors, control systems, and a powerful power system.

[0042] (2) Precision control system:

[0043] The Global Positioning System (GPS) is used to accurately locate the equipment on the construction site, ensuring the correct starting point for sheet pile driving. A laser plummet is installed to monitor and adjust the verticality of the sheet piles in real time, ensuring the piles remain vertical during driving and improving the stability of the overall structure.

[0044] (3) Adaptive adjustment function:

[0045] The robot is equipped with geological detection sensors that can analyze soil layer distribution, soil or rock hardness, density and other information in real time; based on geological data, the equipment automatically adjusts the driving force and frequency and starts driving steel sheet piles; during the process, a laser plumb line monitors the verticality of the pile body in real time to ensure driving accuracy; at corners, the steel sheet pile curtain is closed by adjusting the equipment axis or using special-shaped steel sheet piles.

[0046] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step four specifically includes:

[0047] 1. After the steel sheet piles are driven, the second steel purlin support needs to be installed at an elevation of 0.5m. The steel purlin is made of I45 double-jointed I-beams, and a support plate is welded under the I-beams. Five A610 steel pipe piles are used as inner cross braces at each steel purlin.

[0048] 2. Use drones to conduct on-site surveys before high-altitude work to determine the optimal location for purlin installation. A remote-controlled robot is used to perform the actual installation of the purlin. The equipment must have high-precision positioning, automatic gripping, and automatic calibration capabilities. The robot uses its mechanical arm to grab the purlin, precisely place it in the designed position, and secure it with bolts and other fasteners. The operator controls the work remotely from the ground via a console, reducing the risk of personnel working directly at height.

[0049] 3. The installation system starts the automatic calibration function and adjusts the position of the robotic arm or purlin through the hydraulic device to ensure that it is tightly connected and sealed with the steel sheet piles to prevent soil erosion.

[0050] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step five specifically includes:

[0051] 1. Excavate soil or backfill with sand and gravel within the cofferdam. Based on the actual seabed elevation, if the seabed surface is higher than -3.5, use a long-arm excavator to remove the silt and silt that is above the surface. If the seabed is lower than -3.5, use sand to backfill to the -3.5 elevation and remove the silt on the steel sheet pile wall. Set up a bottom sealing platform and lay out the conduit for underwater concrete pouring. Based on the actual bottom elevation, pour the concrete in stages and batches from low to high and from the periphery to the center. The technical surveyor will measure the bottom concrete elevation of each conduit to ensure that the bottom sealing concrete elevation meets the design requirements.

[0052] 2. Use environmentally friendly high-performance concrete; select low-carbon, low-energy cement substitutes such as fly ash and slag powder as the main raw materials for concrete to reduce cement usage; optimize mix design, adjust the mix ratio, and add special additives such as high-efficiency water reducers and air-entraining agents to improve the fluidity, impermeability, and durability of concrete;

[0053] 3. When sealing the cofferdam bottom, the above-mentioned environmentally friendly high-performance concrete was used to reduce carbon emissions while improving the cofferdam's waterproof performance and long-term stability. During the construction process, the concrete mixing, transportation, pouring and curing processes were strictly monitored to ensure that the concrete performance met the expected standards.

[0054] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step six specifically includes:

[0055] 1. After the Larsen steel sheet pile construction is completed, a ladder cage is installed inside the cofferdam to ensure safe and convenient access for workers. The installation position and height of the ladder cage are adjusted and optimized according to the actual water depth inside the cofferdam and the needs of the workers.

[0056] 2. The reflective stickers and anti-slip mats of the ladder cage should be firmly affixed to ensure the walking safety of the staff; when lifting the ladder cage, the lifting point should be fixed at the center of the ladder cage, and it should be ensured that there is no collision between the lifting rope and the ladder cage;

[0057] 3. During the installation of the ladder cage, the structure of the equipment should be stable and reliable, and the connection should be firm. After the installation of the ladder cage is completed, necessary quality acceptance work should be carried out to ensure that the equipment can meet the use requirements and avoid engineering accidents caused by equipment quality problems.

[0058] The comprehensive construction method for Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step seven specifically includes:

[0059] After the bottom seal concrete pouring is completed, the foundation construction process is as follows: ① Cut the casing above -2.5m → ② Pour the concrete cushion → ③ Break the pile head → ④ Tie the foundation reinforcement and pour the concrete → ⑤ Add 5 A610 steel pipe cross supports at the foundation position → ⑥ Remove the 3 cross supports at the 0.5m elevation pier → ⑦ Tie the reinforcement and pour the concrete at the 4m pier → ⑧ Add 3 A610 steel pipe supports at the 3.5m elevation → ⑨ Remove the 3 cross supports at the 4.0m elevation pier, and pour the pier body and cap beam upwards in turn to increase the monitoring and inspection of the stability and safety of the cofferdam.

[0060] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step eight specifically includes:

[0061] 1. After the pier construction is completed, the steel sheet piles will be removed. Before removing the steel sheet piles, the supports inside the cofferdam will be removed from bottom to top. Water will be gradually poured in until the water level is 1.0 to 1.5 meters above the cofferdam water level. This will balance the internal and external water pressures, eliminate the squeezing force of the sheet piles, and separate the sheet piles from the concrete (the part with underwater concrete bottom seal).

[0062] 2. Before dismantling, mark the Larsen steel sheet piles and record their location and usage status. When dismantling, first use hydraulic pliers to loosen the connection points, then use a vibratory hammer to gently vibrate the pile to loosen it. At the same time, wrap the pile with protective materials such as rubber pads to prevent scratches. During the dismantling process, pay attention to keeping the pile intact and avoid excessive bending or impact.

[0063] Step nine specifically includes:

[0064] 1. Select appropriate demolition methods, such as mechanical demolition, based on the recycling plan. Factors such as the construction environment, engineering requirements, and safety should be considered when selecting a demolition method. During the demolition process, the displacement and deformation of the Larsen steel sheet piles should be monitored to ensure that the demolition operation does not affect the surrounding environment and structure. The demolition speed should be controlled to avoid structural damage or project delays caused by excessively fast or slow demolition.

[0065] 2. Environmentally friendly lubricating grease mixture

[0066] (1) Material selection: Select recyclable and environmentally friendly lubricant grease mixtures that meet environmental standards: graphite-based lubricant grease mixtures to ensure that they do not cause pollution to soil and water during use;

[0067] (2) Recycling and treatment: After the construction is completed, a professional team will be organized to collect the used lubricants and send them to designated recycling points for treatment to avoid random discharge and environmental pollution. At the same time, the recycling volume will be recorded as part of the project's environmental management.

[0068] 3. After dismantling, the Larsen steel sheet piles are classified and stacked according to specifications and models for easy subsequent management; high-pressure water guns and cleaning agents are used to thoroughly clean the piles to remove dirt, rust and other pollutants; for slightly rusted piles, rust removers are used to treat them to restore their surface gloss; the cleaned and repaired piles are air-dried or baked to ensure that no moisture remains, so as to improve reuse rate and environmental performance.

[0069] The comprehensive construction method for the Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge is characterized in that step ten specifically includes:

[0070] 1. Accurate construction control: Utilizing a laser positioning system and intelligent control equipment, the steel sheet pile driving process is precisely controlled to ensure the verticality and interlocking quality of the steel sheet piles. By real-time monitoring of parameters such as the driving depth and inclination of the steel sheet piles, the construction plan can be adjusted promptly to ensure the overall stability of the cofferdam.

[0071] 2. Intelligent monitoring and early warning: Sensors are installed at key locations on the steel sheet pile cofferdam to monitor the cofferdam's deformation, stress, and displacement in real time. Combined with intelligent analysis algorithms, the monitoring data is analyzed in real time. Once an anomaly is detected, an alarm is immediately issued, triggering the corresponding emergency plan.

[0072] 3. Enhance environmental adaptability: Utilize intelligent monitoring technology to monitor typhoon winds and waves and other environmental parameters in real time, automatically adjust the cofferdam's support system or reinforcement measures according to environmental changes, and improve the cofferdam's ability to resist wind and waves; combine with a remote video monitoring system to conduct all-weather monitoring of the cofferdam construction site to ensure construction safety.

[0073] The beneficial effects of the present invention are as follows: As can be seen from the above technical solution, this application provides a comprehensive construction method for Larsen steel sheet pile cofferdams for typhoon-resistant cross-sea bridges. Compared with traditional technologies, this invention adopts targeted construction measures to effectively overcome the construction challenges posed by the complex topography of the foundation bottom. In addition, to enhance the ability to resist typhoons and wind and wave impacts, corresponding improvement measures have been incorporated into various construction processes, and positive results have been achieved:

[0074] 1. BIM technology, through the construction of 3D models, enables precise simulation and optimized design of the construction process, improving construction efficiency and quality. VR technology provides an immersive construction experience, helping construction workers familiarize themselves with complex working conditions in advance and enhancing their ability to respond. The combination of these two technologies not only enhances the innovation of construction technology but also significantly improves the safety and controllability of cofferdam construction, demonstrating the powerful support role of modern technology in complex engineering environments.

[0075] 2. By applying a high-performance lubricant mixture to the locking ends of the steel sheet piles, friction during insertion is effectively reduced, enhancing the stability of the cofferdam. This is particularly suitable for complex terrain and deep water areas, while also improving its ability to withstand wind and waves. Furthermore, this high-performance lubricant mixture enhances anti-seepage properties, resolves the issue of insufficient sealing, prevents water leakage, and ensures construction progress and quality.

[0076] Applying a graphite-based lubricant mixture not only significantly reduces friction during insertion and impact, enhancing the stability and impermeability of the cofferdam, but also achieves energy savings, efficiency gains, and carbon emission reductions. The superior properties of graphite-based materials facilitate smoother construction, reducing energy consumption and emissions. Its environmentally friendly properties mitigate pollution to the surrounding environment, such as water and soil, embodying the principles of sustainable development. Compared to traditional methods, this approach offers lower costs and greater ease of construction, making it a preferred solution that combines advanced technology, economic efficiency, and environmental performance.

[0077] 3. The use of automated sheet pile driving robots effectively addresses the stability and sealing issues encountered in traditional cofferdam construction. The robots, integrated with high-precision sensors and control systems, ensure precise placement and verticality of the sheet piles, significantly improving the stability of the cofferdam structure, making it particularly suitable for complex terrain and deepwater areas. Furthermore, an adaptive adjustment function adjusts driving parameters in real time based on geological data, ensuring construction efficiency and safety while reducing the risk of water leakage. Automated construction reduces manpower requirements, mitigates environmental impact, and ultimately helps lower construction costs. This method, combining high-precision, automated, and intelligent technologies, demonstrates significant advancements and advantages.

[0078] 4. The use of drone surveys and remote-controlled robots to install steel purlins significantly improved the safety and accuracy of cofferdam construction. Drone surveys from high altitude accurately determine the optimal purlin position, while remote-controlled robots enable highly precise, automated installation, reducing the risk of personnel working at height. This method uses automatic calibration to ensure a tight connection and seal between the purlin and steel sheet piles, effectively addressing the stability and sealing issues inherent in traditional construction. Furthermore, automated construction reduces environmental impact, minimizing risks such as water pollution and soil damage. This method also improves construction efficiency, contributing to lower long-term construction costs. It demonstrates significant advancements and advantages, particularly in deepwater areas and complex terrain.

[0079] 5. The use of this bottom seal concrete construction technology effectively solves the stability, sealing and environmental protection cost issues in cofferdam construction. By precisely controlling the seabed elevation and pouring in stages and batches, it is ensured that the bottom seal concrete elevation meets the design requirements, thereby improving the stability and waterproof performance of the cofferdam. The use of environmentally friendly high-performance concrete reduces cement consumption and carbon emissions, while improving the fluidity, impermeability and durability of the concrete, further enhancing the long-term stability of the cofferdam. This method also strictly monitors the construction process to ensure that the concrete performance meets the expected standards and reduces environmental impact. In summary, this construction method has significant advantages and advancements in improving the stability, sealing and environmental protection of the cofferdam, while reducing construction costs and difficulty.

[0080] 6. During the construction of the cross-sea bridge cofferdam, facing the challenges of complex terrain and typhoon-induced waves, the Larsen steel sheet pile cofferdam demonstrated significant advantages through the use of intelligent monitoring technology. This technology, through real-time high-definition monitoring, intelligent analysis, and early warning, accurately captured construction dynamics and environmental changes, ensuring the stability and safety of the cofferdam. The real-time and accurate nature of intelligent monitoring effectively reduced human error, improved emergency response, and provided a solid foundation for cofferdam construction in complex environments, demonstrating the core value of modern technology in large-scale engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0082] Figure 1 This is the construction process flow chart.

[0083] Figure 2 This is the plan view of steel sheet piles.

[0084] Figure 3 Steel sheet pile elevation.

[0085] Figure 4 Schematic diagram of steel sheet pile deformation Figure 1 .

[0086] Figure 5 Schematic diagram of steel sheet pile deformation Figure 2 .

[0087] Figure 6 Schematic diagram of steel sheet pile stress Figure 1 .

[0088] Figure 7 Schematic diagram of the deformation of the first layer of support Figure 1 .

[0089] Figure 8 Schematic diagram of the first layer support stress Figure 1 .

[0090] Figure 9 Schematic diagram of steel sheet pile deformation Figure 3 .

[0091] Figure 10 Schematic diagram of steel sheet pile stress Figure 2 .

[0092] Figure 11 Indicates support deformation Figure 2 .

[0093] Figure 12 Support stress diagram Figure 2 .

[0094] Figure 13 This is a schematic diagram of the cofferdam as a whole.

[0095] Figure 14 Schematic diagram for calculating the depth of multi-layer support embedded in the soil. DETAILED DESCRIPTION

[0096] The technical solutions of the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments; based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection requested by this application.

[0097] like Figure 1-3Shown: A comprehensive construction method for Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge, specifically including:

[0098] 1. Application of BIM and VR Technology

[0099] BIM Model Construction: Using BIM software, we constructed a 3D model of the Larsen steel sheet pile cofferdam based on geological survey data and design requirements. The model included all key components, including the sheet piles, purlins, and support systems, ensuring accurate dimensions and a sound structure.

[0100] Construction plan optimization: Using the BIM model, we compared multiple options to optimize the steel sheet pile driving sequence, support system layout, and removal strategy. We also considered the impact of typhoon winds and waves on the cofferdam, simulated the cofferdam's stability under different working conditions, and adjusted the design to improve its wind and wave resistance.

[0101] VR simulation training: Using VR technology to transform BIM models into a virtual construction environment, construction personnel can undergo simulated operation training. The entire process of driving and connecting steel sheet pile cofferdams, installing and removing support systems, and other tasks is simulated, improving construction personnel's proficiency and ability to respond to emergencies.

[0102] On-site construction preparation: Guide on-site construction preparation based on the BIM model, including the procurement and deployment of materials such as steel sheet piles, purlins, and support systems. Set measurement control points on-site to ensure construction accuracy.

[0103] Steel sheet pile cofferdam construction: On-site construction was carried out according to the construction plan guided by the BIM model, including the driving and connection of steel sheet piles, and the installation of the support system. BIM models and VR technology were used for on-site guidance and monitoring to ensure construction quality.

[0104] Cofferdam Dismantling: After construction is complete, the steel sheet pile cofferdam is dismantled according to the demolition plan developed using the BIM model. The demolition process is simulated and monitored using the BIM model and VR technology to ensure a safe and orderly demolition process.

[0105] 2. Construction Preparation

[0106] After the steel sheet piles are delivered to the construction site, they are carefully inspected, measured, classified, and numbered, with particular attention paid to their corrosion resistance and resistance to wind and wave impact. At the same time, a short pile of the same type, 2 to 3 meters long, is used to conduct a pass test on both sides of the lock.

[0107] If the lock mouth cannot pass or the pile body has defects such as bending, twisting, and dead bends, it can be repaired by cold bending, hot knocking (temperature not exceeding 800~1000℃), welding, riveting, cutting, and lengthening.

[0108] The locking mouth of the steel sheet pile is coated with a high-performance lubricating grease mixture (graphite-based material mixed with kerosene, gasoline or light mineral oil) to reduce friction during insertion and enhance anti-seepage performance.

[0109] (1) Evenly apply: Use a brush or spray equipment to evenly apply the graphite-based lubricating grease mixture to the inside of the steel sheet pile lock. When applying, ensure that the grease mixture covers the lock surface without omission. Pay attention to controlling the application thickness, which should not be too thick or too thin. Too thick may result in waste, while too thin may affect the lubrication and anti-seepage effect.

[0110] (2) Multiple applications: Depending on the project requirements, multiple applications may be required to ensure that the lubricating grease mixture fully covers the lock mouth. After each application, wait for a certain amount of time for the grease mixture to fully penetrate and dry before applying the next application.

[0111] (3) Inspection and correction: After the application is completed, the steel sheet pile lock should be fully inspected to ensure that the lubricating grease mixture is evenly applied without omission. If uneven application or omissions are found, corrections and re-application should be made in a timely manner.

[0112] 3. Installation of the first purlin and driving of steel sheet piles

[0113] To install the first purlin (using the purlin as a guide frame), first measure and mark the precise position of the guide frame. Using the casing as support, install the purlin. Horizontally weld 14-inch channel steel at an elevation of 3.8m on both sides of the casing, along with vertical 14-inch channel steel braces, to support the purlin and enhance its resistance to typhoons and seawater impact. Install the first purlin on the channel steel. Add rubber gaskets or sealing strips at the connection between the purlin and the casing to improve sealing.

[0114] Steel sheet pile driving:

[0115] (1) Equipment development and introduction:

[0116] To meet specific project requirements, we collaborate with automation equipment manufacturers to design and manufacture an automated sheet pile driving robot (intelligent sheet pile driving machine). This robot must integrate high-precision sensors, control systems, and a powerful power system.

[0117] (2) Precision control system:

[0118] The Global Positioning System (GPS) allows for precise positioning of the equipment on site, ensuring the correct starting point for sheet pile driving. A laser plummet is installed to monitor and adjust the verticality of the sheet piles in real time, ensuring the piles remain vertical during driving and improving overall structural stability.

[0119] (3) Adaptive adjustment function:

[0120] The robot is equipped with geological detection sensors that analyze soil layer distribution, soil or rock hardness, density, and other information in real time. Based on this geological data, the machine automatically adjusts the driving force and frequency to begin driving the steel sheet piles. During the process, a laser plummet monitors the verticality of the piles in real time to ensure accurate driving. At corners, the curtain of steel sheet piles can be closed by adjusting the machine axis or using special-shaped steel sheet piles.

[0121] 4. Install steel purlins and waterstops

[0122] 1. After the steel sheet piles are driven, a second set of steel purlin supports is installed at an elevation of 0.5m. The steel purlins are constructed of I45 double-jointed I-beams, with support plates welded underneath. Five A610 steel pipe piles are used as internal cross braces for each steel purlin.

[0123] 2. Use drones to conduct pre-height site surveys to determine the optimal location for purlin installation. Actual purlin installation is performed using a remote-controlled robot equipped with high-precision positioning, automatic gripping, and automatic calibration capabilities. The robot uses its mechanical arms to grasp the purlin, precisely placing it in the designed location and securing it with bolts and other fasteners. Operators operate remotely from a console on the ground, minimizing the risk of personnel working directly at height.

[0124] 3. The installation system starts the automatic calibration function and adjusts the position of the robotic arm or purlin through the hydraulic device to ensure that it is tightly connected and sealed with the steel sheet piles to prevent soil erosion.

[0125] 5. Bottom concrete construction

[0126] 1. Excavate soil or backfill with sand and gravel within the cofferdam. Based on the actual seabed elevation, if the seabed is higher than -3.5, use a long-arm excavator to remove the silt and silt that protrudes above. If the seabed is lower than -3.5, backfill with sand to -3.5 and remove the silt from the steel sheet pile walls. Set up a bottom sealing platform and lay out conduits for underwater concrete pouring. Based on the actual bottom elevation, pour concrete in phases and batches, from low to high and from the periphery toward the center. Technical surveyors measure the bottom concrete elevation of each conduit to ensure that the bottom sealing concrete elevation meets the design requirements.

[0127] 2. Use environmentally friendly, high-performance concrete. Select low-carbon, low-energy cement substitutes, such as fly ash and slag powder, as the primary raw materials for concrete, reducing cement usage. By optimizing mix design and adjusting the mix ratio, and adding special additives such as high-efficiency water reducers and air-entraining agents, the concrete's fluidity, impermeability, and durability can be improved.

[0128] 3. The aforementioned environmentally friendly, high-performance concrete was used to seal the cofferdam bottom, reducing carbon emissions while improving the cofferdam's waterproofing and long-term stability. During construction, the concrete mixing, transportation, pouring, and curing processes were strictly monitored to ensure that the concrete performance met the expected standards.

[0129] 6. Ladder cage installation

[0130] 1. After the Larsen steel sheet pile construction is completed, a ladder cage is installed inside the cofferdam to ensure safe and convenient access for workers. The installation position and height of the ladder cage are adjusted and optimized according to the actual water depth inside the cofferdam and the needs of the workers.

[0131] 2. The reflective stickers and anti-slip mats of the ladder cage should be firmly affixed to ensure the safety of the staff. When hoisting the ladder cage, the lifting point should be fixed in the center of the ladder cage, and it should be ensured that there is no collision between the lifting rope and the ladder cage.

[0132] 3. During the installation of the ladder cage, the structure of the equipment should be stable and reliable, and the connection should be firm. After the installation of the ladder cage is completed, necessary quality inspection work should be carried out to ensure that the equipment can meet the use requirements and avoid engineering accidents caused by equipment quality problems.

[0133] 7. Capping construction

[0134] After the bottom seal concrete pouring is completed, the foundation construction process is as follows: ① Cut the casing above -2.5m → ② Pour the concrete cushion → ③ Break the pile head → ④ Tie the foundation reinforcement and pour the concrete → ⑤ Add 5 A610 steel pipe cross supports at the foundation position → ⑥ Remove the 3 cross supports at the 0.5m elevation pier → ⑦ Tie the reinforcement and pour the concrete at the 4m pier → ⑧ Add 3 A610 steel pipe supports at the 3.5m elevation → ⑨ Remove the 3 cross supports at the 4.0m elevation pier, and pour the pier body and cap beam upwards in turn to increase the monitoring and inspection of the stability and safety of the cofferdam.

[0135] 8. Demolition Construction

[0136] 1. After the pier construction is completed, the steel sheet piles will be removed. Before removing the steel sheet piles, the supports inside the cofferdam will be removed from bottom to top. Water will be gradually poured in until it is 1.0 to 1.5 meters above the water level outside the cofferdam. This will balance the internal and external water pressures, eliminate the squeezing force of the sheet piles, and separate them from the concrete (referring to the underwater concrete bottom seal).

[0137] 2. Before dismantling, mark the Larsen steel sheet piles, recording their location and usage status. During dismantling, first use hydraulic pliers to loosen the connection points, then gently vibrate the pile with a vibratory hammer to loosen it. Wrap the pile with protective materials such as rubber pads to prevent scratching. During dismantling, take care to keep the pile intact and avoid excessive bending or impact.

[0138] 9. Steel Sheet Pile Recycling

[0139] 1. Based on the recycling plan, select an appropriate demolition method, such as mechanical dismantling. Factors such as the construction environment, project requirements, and safety should be considered when selecting a demolition method. During the demolition process, monitor the displacement and deformation of the Larsen steel sheet piles to ensure that the demolition operation does not impact the surrounding environment or the structure. Control the demolition speed to avoid structural damage or project delays caused by excessively fast or slow demolition.

[0140] 2. Environmentally friendly lubricating grease mixture

[0141] (1) Material selection: Select a recyclable and environmentally friendly lubricant grease mixture that meets environmental protection standards: a graphite-based lubricant grease mixture to ensure that it does not cause pollution to the soil and water during use.

[0142] (2) Recycling: After construction is completed, a professional team will be organized to collect the used lubricants and send them to designated recycling points for processing to avoid random discharge and environmental pollution. At the same time, the recycling volume will be recorded as part of the project's environmental management.

[0143] 3. After dismantling, Larsen steel sheet piles should be sorted and stacked by specification and model for easy management. Use a high-pressure water gun and detergent to thoroughly clean the piles to remove contaminants such as dirt and rust. For slightly rusted piles, use a rust remover to restore their surface gloss. After cleaning and repair, air-dry or bake the piles to ensure no residual moisture, thereby increasing their reusability and environmental performance.

[0144] 10. Application of Intelligent Monitoring

[0145] 1. Accurate construction control: Utilizing a laser positioning system and intelligent control equipment, the steel sheet pile driving process is precisely controlled to ensure verticality and joint quality. Real-time monitoring of sheet pile driving depth, inclination, and other parameters allows for timely adjustments to the construction plan to ensure the overall stability of the cofferdam.

[0146] 2. Intelligent Monitoring and Early Warning: Sensors are installed at key locations on the steel sheet pile cofferdam to monitor its deformation, stress, and displacement in real time. Combined with intelligent analysis algorithms, these data are analyzed in real time. Any anomalies detected are immediately reported, triggering appropriate emergency plans.

[0147] 3. Enhanced environmental adaptability: Utilizing intelligent monitoring technology, we monitor environmental parameters such as typhoon winds and waves in real time, automatically adjusting the cofferdam's support system and reinforcement measures based on environmental changes to improve its ability to withstand wind and wave surges. Combined with a remote video surveillance system, we provide 24 / 7 monitoring of the cofferdam construction site to ensure construction safety.

[0148] 11. Related Calculations

[0149] 1. Parameter values

[0150] (1) Basic parameters

[0151] The seawater velocity is 4m / s and the seawater density is 10.25KN / m³

[0152] Soil layer parameter values

[0153]

[0154] (2) Soil spring stiffness parameters

[0155] The horizontal reaction coefficient of the soil on the inner anchoring section of the cofferdam is calculated as follows:

[0156]

[0157] m- proportional coefficient of soil horizontal reaction coefficient

[0158] Z - the depth of the calculation point from the ground

[0159] h- excavation depth of foundation pit under calculation conditions

[0160] According to the Technical Specifications for Foundation Pit Engineering - Zhejiang Provincial Engineering Construction Standard DB33 / T 1096-2014, the silt soil is taken as 2000KN / m 4

[0161] (3) Material parameters

[0162] The purlin and support are made of Q235 steel, with an allowable stress of [б]=215MPa and [τ]=125MPa.

[0163] Steel sheet piles made of Q345 steel have an allowable stress of: [б]=345MPa [τ]=175Mpa

[0164]

[0165] (4) Load value

[0166] Then, water pressure Pw=10.25×5.24=53.7kPa

[0167] Water force

[0168]

[0169] Where:

[0170] Cw Water flow resistance, according to the port engineering load code continued table 13.0.3-1, take 1.1

[0171] ρ: water density (t / m³), 1.025 for seawater

[0172] V: Water flow velocity, calculated as 4.0m / s.

[0173] A: Projected area, water depth is 5.24m

[0174] To simplify the calculation, the water pressure load distribution takes an inverted triangle shape.

[0175] Pw=9.0kPa

[0176] The point of action is 1 / 3 below the water surface, with an elevation of 1.86m, which is consistent with the direction of water flow.

[0177] Active earth pressure coefficient Ka = tan2 (452-φ / 2) = 0.53

[0178] Passive earth pressure coefficient Ka = tan2 (452 ​​+ φ / 2) = 1.89

[0179] Soil pressure is calculated by water and soil separation.

[0180] The top of the silt layer

[0181] =5.24×10.25×0.53-0=28.5kPa

[0182] silt sand bottom

[0183] Vertical soil stress = 0.88 × 17 = 92.5 kPa

[0184] but =0.88×17+6.12×10.25=77.7kPa

[0185] Structural safety factor

[0186] According to the relevant provisions of the Zhejiang Province Construction Foundation Pit Engineering Technical Code, when the foundation pit excavation depth is greater than 5m and there are no special requirements for the surrounding environment, it is a secondary foundation pit, and the structural deformation is 0.9%h=6.12×0.09=55mm.

[0187] The safety factor of internal force of the supporting structure is 1.25.

[0188] Working Condition Classification: The cofferdam construction steps are as follows: First, steel sheet piles are driven, water is pumped to 0.5m below the first support layer, and the first support layer is installed. Then, water is pumped to 0.5m below the second support layer, and the second support layer is installed. The water in the foundation pit is then completely pumped out, and excavation begins. After excavation is completed, a 1m thick cushion layer is poured, followed by the foundation pile cap, and finally, the cofferdam is dismantled.

[0189] The working conditions are summarized as follows

[0190]

[0191] 2. Working condition calculation

[0192] (1) Calculation of working condition 1:

[0193] Water level at 1.9m high

[0194] After the steel sheet piles are installed, before starting the first layer of support installation, Figure 4 As shown: the deformation of 34.89mm is less than 55mm, which meets the requirements.

[0195] (2) Calculation of working condition 2

[0196] When water is pumped to the appropriate water level under the second support, after the first support is installed and before the second support is installed, Figure 5 As shown: the deformation of 13.83mm is less than 55mm, which meets the requirements.

[0197] like Figure 6 As shown: Steel sheet pile stress б=101.93MPa<=215 / 1.25=172MPa, which meets the requirements.

[0198] like Figure 7 As shown: The deformation of the first layer of support is as follows:

[0199] The support deformation of 8.37mm is less than 3800 / 400=9.5mm, which meets the requirements.

[0200] like Figure 8 As shown: The support stress is as follows:

[0201] Support stress б=85.1MPa<=215 / 1.25=172MPa, which meets the requirements.

[0202] (3) Calculation of working condition 3

[0203] like Figure 9 As shown: The deformation of the steel sheet pile is as follows:

[0204] The deformation of 10.96mm is less than 55mm, which meets the requirements.

[0205] like Figure 10 As shown: The stress of steel sheet pile is as follows:

[0206] The stress of steel sheet pile б=149.05MPa<=345 / 1.25=276MPa, which meets the requirements.

[0207] like Figure 11 Shown: The support deformation is as follows:

[0208] The support deformation of 8.19mm is less than 3800 / 400=9.5mm, which meets the requirements.

[0209] like Figure 12As shown: The support stress is as follows:

[0210] The stress of steel sheet pile б=90.63MPa<=345 / 1.25=276MPa, which meets the requirements.

[0211] 3. Calculation of the overall stability of the cofferdam, such as Figure 13 As shown:

[0212] The buckling characteristic value 22.1 is greater than 4, which meets the requirements.

[0213] 4. Calculation of minimum depth of cofferdam into the earth, such as Figure 14 As shown:

[0214] As can be seen from the figure,

[0215]

[0216] Where: L5=3.43m

[0217] H=3.69m

[0218] Calculation shows that X=3.05m, that is, the minimum depth of the steel sheet pile into the ground is 3.05×1.2=3.7m, which meets the requirements.

[0219] The current depth of steel sheet piles into the ground = 12-(3.61+3.51) = 4.88m, which is greater than 3.7m and meets the requirements.

[0220] Minimum thickness of bottom concrete

[0221] Upward water pressure line load on concrete after water is pumped out

[0222]

[0223] B: Take 1m wide concrete

[0224] but:

[0225] Concrete deadweight

[0226]

[0227] h1: thickness of bottom concrete, h1=1.0m

[0228] but: KN / m

[0229] Calculate loads

[0230]

[0231] but:

[0232] Without considering Poisson's ratio, the maximum bending moment is:

[0233]

[0234] L: The calculated span between adjacent steel casings, take the smaller value of the calculated spans lx and ly in two directions, L=2.99m

[0235] a1—bending moment coefficient, the value is determined according to the bending moment coefficient table (Table 4-45) of the Concise Construction Calculation Manual, China Architecture & Building Press, 4th edition;

[0236] but:

[0237] The bottom concrete is cast with C30 concrete.

[0238] According to Table 4.1.4 of the "Code for Design of Concrete Structures", the allowable tensile stress of the design strength when the bottom concrete strength reaches 80% is ft=1.43×0.8=1.14MPa.

[0239] The safety factor K is 2.65, then

[0240] m

[0241] The bottom concrete is 1m thick, with concrete as the load-bearing section, and the maximum tensile stress in the span

[0242] , meeting the requirements.

[0243] The above are only embodiments provided for this application and are not intended to limit this application. Although this application has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A comprehensive construction method for Larsen steel sheet pile cofferdam of a typhoon-resistant sea-crossing bridge, characterized in that It includes the following steps: Step 1: BIM and VR application; Step 2: Construction preparation; Step 3: Installation of the first perimeter purlin and driving of steel sheet piles; Step 4: Install steel purlins and waterstops; Step 5: bottom concrete construction; Step 6: Ladder cage installation; Step 7: Capping construction; Step 8: Demolition construction; Step 9: Steel sheet pile recovery; Step 10: Intelligent monitoring application.

2. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step 1 specifically includes: BIM model construction: Using BIM software, we constructed a three-dimensional model of the Larsen steel sheet pile cofferdam based on geological survey data and design requirements. The model included all key components, including steel sheet piles, purlins, and support systems, ensuring accurate dimensions and a reasonable structure. Construction plan optimization: Using the BIM model, we compared multiple plans to optimize the steel sheet pile driving sequence, support system layout, and removal strategy. We also considered the impact of typhoon winds and waves on the cofferdam, simulated the cofferdam's stability under different working conditions, and adjusted the design to improve its wind and wave resistance. VR simulation training: Using VR technology to transform BIM models into a virtual construction environment, construction personnel can undergo simulated operation training. This includes simulating the entire process of driving, connecting, installing, and removing the support system for steel sheet pile cofferdams, improving construction personnel's proficiency and their ability to respond to emergencies. On-site construction preparation: Guide on-site construction preparation based on the BIM model, including the procurement and deployment of materials such as steel sheet piles, perimeter purlins, and support systems; set measurement control points on-site to ensure construction accuracy; Steel sheet pile cofferdam construction: On-site construction was carried out according to the construction plan guided by the BIM model, including the driving and connection of steel sheet piles, and the installation of the support system. BIM models and VR technology were used for on-site guidance and monitoring to ensure construction quality. Cofferdam dismantling: After construction is completed, the steel sheet pile cofferdam is dismantled according to the demolition plan developed by the BIM model. The demolition process is simulated and monitored using the BIM model and VR technology to ensure a safe and orderly demolition process.

3. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step 2 specifically includes: After the steel sheet piles are transported to the construction site, they are carefully inspected, measured, classified, and numbered, with special attention paid to their corrosion resistance and resistance to wind and wave impact. At the same time, a short pile of the same model with a length of 2 to 3 meters is used to conduct a pass test on both sides of the lock. If the lock mouth cannot pass or the pile body has defects such as bending, twisting, and dead bend, it can be repaired by cold bending, hot knocking (temperature not exceeding 800~1000℃), welding, riveting, cutting, lengthening, etc. The locking mouth of the steel sheet pile is coated with a high-performance lubricating grease mixture (graphite-based material mixed with kerosene, gasoline or light mineral oil) to reduce friction during insertion and enhance anti-seepage performance; (1) Evenly apply: Use a brush or spray equipment to evenly apply the graphite-based lubricating grease mixture to the lock of the steel sheet pile; when applying, ensure that the grease mixture covers the lock surface without omission; pay attention to controlling the application thickness, which should not be too thick or too thin; too thick may cause waste, and too thin may affect the lubrication and anti-seepage effect; (2) Multiple applications: Depending on the project requirements, multiple applications may be required to ensure that the lubricating grease mixture fully covers the lock mouth; after each application, wait for a certain amount of time for the grease mixture to fully penetrate and dry before applying the next application; (3) Inspection and correction: After the application is completed, the steel sheet pile lock should be fully inspected to ensure that the lubricating grease mixture is evenly applied without omission; if uneven application or omissions are found, corrections and re-application should be made in a timely manner.

4. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step three specifically includes: To install the first purlin, first perform positioning measurements and mark the precise position of the guide frame. The purlin is then installed using the casing as support. Channel steel is welded horizontally at an elevation of 3.8m on both sides of the casing, along with 14 vertical channel steel braces, to support the purlin and enhance its resistance to typhoons and seawater impact. The first purlin is then installed on the channel steel. Rubber gaskets or sealing strips are added to the connection between the purlin and the casing to improve sealing. Steel sheet pile driving: (1) Equipment development and introduction: To meet specific project requirements, we collaborate with automation equipment manufacturers to design and manufacture an automated steel sheet pile driving robot (intelligent steel sheet pile driving all-in-one machine). This robot must integrate high-precision sensors, control systems, and a powerful power system. (2) Precision control system: The Global Positioning System (GPS) is used to accurately locate the equipment on the construction site, ensuring the correct starting point for sheet pile driving. A laser plummet is installed to monitor and adjust the verticality of the sheet piles in real time, ensuring the piles remain vertical during driving and improving the stability of the overall structure. (3) Adaptive adjustment function: The robot is equipped with geological detection sensors that can analyze soil layer distribution, soil or rock hardness, density and other information in real time; based on geological data, the equipment automatically adjusts the driving force and frequency and starts driving steel sheet piles; during the process, a laser plumb line monitors the verticality of the pile body in real time to ensure driving accuracy; at corners, the steel sheet pile curtain is closed by adjusting the equipment axis or using special-shaped steel sheet piles.

5. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step 4 specifically includes:

1. After the steel sheet piles are driven, the second steel purlin support needs to be installed at an elevation of 0.5m. The steel purlin is made of I45 double-jointed I-beams, and a support plate is welded under the I-beams. Five A610 steel pipe piles are used as inner cross braces at each steel purlin.

2. Use drones to conduct on-site surveys before high-altitude work to determine the optimal location for purlin installation. A remote-controlled robot is used to perform the actual installation of the purlin. The equipment must have high-precision positioning, automatic gripping, and automatic calibration capabilities. The robot uses its mechanical arm to grab the purlin, precisely place it in the designed position, and secure it with bolts and other fasteners. The operator controls the work remotely from the ground via a console, reducing the risk of personnel working directly at height.

3. The installation system starts the automatic calibration function and adjusts the position of the robotic arm or purlin through the hydraulic device to ensure that it is tightly connected and sealed with the steel sheet piles to prevent soil erosion.

6. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step 5 specifically includes:

1. Excavate soil or backfill with sand and gravel within the cofferdam. Based on the actual seabed elevation, if the seabed surface is higher than -3.5, use a long-arm excavator to remove the silt and silt that is above the surface. If the seabed is lower than -3.5, use sand to backfill to the -3.5 elevation and remove the silt on the steel sheet pile wall. Set up a bottom sealing platform and lay out the conduit for underwater concrete pouring. Based on the actual bottom elevation, pour the concrete in stages and batches from low to high and from the periphery to the center. The technical surveyor will measure the bottom concrete elevation of each conduit to ensure that the bottom sealing concrete elevation meets the design requirements.

2. Use environmentally friendly high-performance concrete; select low-carbon, low-energy cement substitutes such as fly ash and slag powder as the main raw materials for concrete to reduce cement usage; optimize mix design, adjust the mix ratio, and add special additives such as high-efficiency water reducers and air-entraining agents to improve the fluidity, impermeability, and durability of concrete; 3. When sealing the cofferdam bottom, the above-mentioned environmentally friendly high-performance concrete was used to reduce carbon emissions while improving the cofferdam's waterproof performance and long-term stability. During the construction process, the concrete mixing, transportation, pouring and curing processes were strictly monitored to ensure that the concrete performance met the expected standards.

7. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step six specifically includes:

1. After the Larsen steel sheet pile construction is completed, a ladder cage is installed inside the cofferdam to ensure safe and convenient access for workers. The installation position and height of the ladder cage are adjusted and optimized according to the actual water depth inside the cofferdam and the needs of the workers.

2. The reflective stickers and anti-slip mats of the ladder cage should be firmly affixed to ensure the walking safety of the staff; when lifting the ladder cage, the lifting point should be fixed at the center of the ladder cage, and it should be ensured that there is no collision between the lifting rope and the ladder cage; 3. During the installation of the ladder cage, the structure of the equipment should be stable and reliable, and the connection should be firm. After the installation of the ladder cage is completed, necessary quality acceptance work should be carried out to ensure that the equipment can meet the use requirements and avoid engineering accidents caused by equipment quality problems.

8. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step seven specifically includes: After the bottom seal concrete pouring is completed, the foundation construction process is as follows: ① Cut the casing above -2.5m → ② Pour the concrete cushion → ③ Break the pile head → ④ Tie the foundation reinforcement and pour the concrete → ⑤ Add 5 A610 steel pipe cross supports at the foundation position → ⑥ Remove the 3 cross supports at the 0.5m elevation pier → ⑦ Tie the reinforcement and pour the concrete at the 4m pier → ⑧ Add 3 A610 steel pipe supports at the 3.5m elevation → ⑨ Remove the 3 cross supports at the 4.0m elevation pier, and pour the pier body and cap beam upwards in turn to increase the monitoring and inspection of the stability and safety of the cofferdam.

9. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step 8 specifically includes:

1. After the pier construction is completed, the steel sheet piles will be removed. Before removing the steel sheet piles, the supports inside the cofferdam will be removed from bottom to top. Water will be gradually poured in until the water level is 1.0 to 1.5 meters above the cofferdam water level. This will balance the internal and external water pressures, eliminate the squeezing force of the sheet piles, and separate the sheet piles from the concrete (the part with underwater concrete bottom seal).

2. Before dismantling, mark the Larsen steel sheet piles and record their location and usage status. When dismantling, first use hydraulic pliers to loosen the connection points, then use a vibratory hammer to gently vibrate the pile to loosen it. At the same time, wrap the pile with protective materials such as rubber pads to prevent scratches. During the dismantling process, pay attention to keeping the pile intact and avoid excessive bending or impact. Step nine specifically includes:

1. Select appropriate demolition methods, such as mechanical demolition, based on the recycling plan. Factors such as the construction environment, engineering requirements, and safety should be considered when selecting a demolition method. During the demolition process, the displacement and deformation of the Larsen steel sheet piles should be monitored to ensure that the demolition operation does not affect the surrounding environment and structure. The demolition speed should be controlled to avoid structural damage or project delays caused by excessively fast or slow demolition.

2. Environmentally friendly lubricating grease mixture (1) Material selection: Select recyclable and environmentally friendly lubricant grease mixtures that meet environmental standards: graphite-based lubricant grease mixtures to ensure that they do not cause pollution to soil and water during use; (2) Recycling and treatment: After the construction is completed, a professional team will be organized to collect the used lubricants and send them to designated recycling points for treatment to avoid random discharge and environmental pollution. At the same time, the recycling volume will be recorded as part of the project's environmental management.

3. After dismantling, the Larsen steel sheet piles are classified and stacked according to specifications and models for easy subsequent management; high-pressure water guns and cleaning agents are used to thoroughly clean the piles to remove dirt, rust and other pollutants; for slightly rusted piles, rust removers are used to treat them to restore their surface gloss; the cleaned and repaired piles are air-dried or baked to ensure that no moisture remains, so as to improve reuse rate and environmental performance.

10. The comprehensive construction method of Larsen steel sheet pile cofferdam for typhoon-resistant sea-crossing bridge according to claim 1 is characterized in that Step 10: Specific include:

1. Accurate construction control: Utilizing a laser positioning system and intelligent control equipment, the steel sheet pile driving process is precisely controlled to ensure the verticality and interlocking quality of the steel sheet piles. By real-time monitoring of parameters such as the driving depth and inclination of the steel sheet piles, the construction plan can be adjusted promptly to ensure the overall stability of the cofferdam.

2. Intelligent monitoring and early warning: Sensors are installed at key locations on the steel sheet pile cofferdam to monitor the cofferdam's deformation, stress, and displacement in real time. Combined with intelligent analysis algorithms, the monitoring data is analyzed in real time. Once an anomaly is detected, an alarm is immediately issued, triggering the corresponding emergency plan.

3. Enhance environmental adaptability: Utilize intelligent monitoring technology to monitor typhoon winds and waves and other environmental parameters in real time, automatically adjust the cofferdam's support system or reinforcement measures according to environmental changes, and improve the cofferdam's ability to resist wind and waves; combine with a remote video monitoring system to conduct all-weather monitoring of the cofferdam construction site to ensure construction safety.

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