A control method for dynamic regulation and quick closure of a lock catch steel pipe pile cofferdam

Abstract

This invention belongs to the field of cofferdam construction technology, specifically relating to a control method for the rapid closure of a cofferdam with interlocking steel pipe piles. It includes the following steps: S1: Construction preparation: Determine the location of the cofferdam site and pre-fabricate the interlocking steel pipe piles, walers, and internal supports; obtain foundation components; S2: Positioning guide frame construction: Based on the edge location of the cofferdam site; S3: Driving steel pipe piles: Using the guide frame, drive steel pipe piles from the upstream side, then drive steel pipe piles on both sides; S4: Cofferdam closure and water sealing at the interlocking point; S5: Dewatering and sand removal within the cofferdam: Dewatering sand using a negative pressure agitation system with an air compressor, symmetrically excavating to form a basin bottom and maintaining water pressure balance to ensure the bottom sealing thickness; S6: Installing internal supports; S7: Concrete sealing at the bottom; The bottom sealing concrete uses an underwater tremie pipe method, supplementing the lower parts to the design elevation, and lifting the tremie pipe before final pouring to ensure a smooth surface; S8: Construction of the pier cap and pier body; S9: Cofferdam demolition; The cofferdam can only be demolished after the pier body and continuous beam blocks are constructed.

Description

Technical Field

[0001] This invention belongs to the field of cofferdam construction technology, specifically relating to a control method for the dynamic regulation and rapid closure of a cofferdam using interlocking steel pipe piles. Background Technology

[0002] Interlocking steel pipe pile cofferdams, as an important type of underwater deep foundation pit retaining structure, are widely used in the construction of underwater piers and abutments for bridges and municipal engineering projects across rivers and lakes due to their advantages such as high strength, high rigidity, good waterproof performance, fast construction speed, and reusability. For deep-water foundation construction with large pier dimensions and complex geological conditions, interlocking steel pipe pile cofferdams offer better structural stress performance compared to sheet pile cofferdams, and are more economical and have a more convenient construction process compared to double-walled steel cofferdams.

[0003] In existing technologies, the construction of interlocking steel pipe pile cofferdams typically includes processes such as steel pipe pile prefabrication, guide frame installation, vibratory hammer pile driving, internal support installation, and underwater sealing. Regarding guidance and positioning, the conventional approach is to use guide frames to control pile positions. For example, in the construction of the cofferdam for the east anchorage of the Lingdingyang Bridge in the Shenzhen-Zhongshan Bridge, a specialized guide frame was used in conjunction with hydraulic clamps for precise positioning, controlling the planar error of each steel pipe pile within a reasonable range. In terms of pile driving technology, for riverbeds with thick overburden, direct pile driving with a vibratory hammer is generally used; for geological conditions involving rock strata or significant depths, a combined "pre-drilling + pile planting" process is often employed. For instance, in the construction of the cofferdam for the No. 15 main pier of the Langhe Grand Bridge, a rotary drilling rig was used for pre-drilling followed by the implantation of interlocking steel pipe piles, effectively solving the pile driving problem under rock strata conditions.

[0004] However, the existing construction methods for interlocking steel pipe pile cofferdams still have the following technical shortcomings: The precision control during the closure phase is challenging. Due to accumulated errors, the interlocks on both sides of the closure joint often fail to align parallelly, requiring the cutting or adjustment of steel pipe piles. This not only affects construction progress but may also lead to poor water-stopping effects. Although there are management principles of "strict pre-construction control, in-process monitoring, and post-construction re-inspection," a systematic control method for dynamic adjustments before closure is lacking. Secondly, the interlock area is a weak point in the cofferdam's waterproofing. Traditional water-stopping methods often use materials such as clay and sawdust for filling, but the material ratios and filling techniques lack standardized specifications, making the water-stopping effect highly susceptible to human factors. Localized leakage often occurs after pumping, requiring divers to perform underwater leak repairs, increasing construction risks and costs. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a control method for the dynamic regulation and rapid closure of a locking steel pipe pile cofferdam.

[0006] The objective of this invention can be achieved through the following technical solutions: A control method for rapid closure of a cofferdam with interlocking steel pipe piles includes the following steps: S1: Construction preparation: Determine the location of the cofferdam site and prepare the interlocking steel pipe piles, walers and internal supports in advance; obtain the foundation components; S2: Positioning guide frame construction: Based on the edge of the cofferdam site, a guide frame composed of double 45a I-beams with sufficient rigidity and a flat surface is pre-set; S3: Driving steel pipe piles: Using the guide frame, steel pipe piles are driven from the upstream side, then steel pipe piles on both sides are driven in sequence, and finally steel pipe piles on the downstream side are driven, so that the closure is formed at the downstream corner of the cofferdam. S4: Cofferdam closure and water-stopping at the lock: Before closure, the number of remaining piles is calculated. During the closure process, the verticality and deviation of each pile are measured and controlled, and the deviation is corrected in time to ensure that the lock is parallel. Water-stopping is done by manually filling and compacting clay and cotton wool. Leaks are repaired underwater by divers. S5: Water pumping and sand removal within the cofferdam: A long-arm excavator is used in conjunction with water pumping and sand removal for underwater foundation cleaning. The slurry is settled and transported off-site to prevent pollution. Sand is pumped out by negative pressure disturbance using an air compressor. Symmetrical excavation is carried out to form a pot bottom and maintain water pressure balance. The height difference of the base is strictly controlled within 30cm to ensure the thickness of the sealing bottom. S6: Install internal supports; first install the central main support, then install the diagonal braces and straight braces on both sides of the main support; a column is erected in the middle of the main support, and the column is connected to the main support by a bracket formed by welding channel steel; S7: Concrete bottom sealing; The bottom sealing concrete is poured using the underwater tremie method, advancing from the transverse bridge to one side and then to the other; The elevation of the measuring points is strictly monitored and recorded during the process; At the end, a comprehensive re-measurement is carried out, and any low-lying areas are poured to the design elevation. Before the final pour, the tremie pipe is lifted to ensure a smooth surface. S8: Construction of the pier cap and pier body; Bailey beams are used to form a support frame, with the span arranged on the top of the steel pipe piles, and I-beams are added in the middle of the span for reinforcement; the platform is set with pouring points and filling points, and the ducts are arranged at a certain interval with a diffusion radius of 4m, and are equipped with pouring ducts and filling ducts for grouting. S9: Cofferdam removal; the cofferdam can only be removed after the construction of the pier body and continuous beam blocks is completed.

[0007] As a further technical solution of the present invention, in step S1, the material of the interlocking steel pipe pile is Q345B, and the specifications are a spiral pipe with an outer diameter of 820mm, a wall thickness of 14mm, and a length of 26m; the interlocking structure is as follows: the female end adopts a seamless steel pipe with an outer diameter of 180mm and a wall thickness of 8mm with a 20mm wide and continuous straight gap, and the male end adopts I16 I-beams; the waler bracket is a triangular bracket made of 20mm thick steel plate, which is welded to the perimeter of the steel pipe pile, with a weld height of 6mm and a spacing of 2.4m / weld.

[0008] As a further technical solution of the present invention, in step S1, the walers are manufactured in sections. The first waler is made of 2I45C (Q235) steel, and the second to fourth walers are made of 2I56C (Q345) steel. The inner support is in the form of steel pipe. The first support is a steel pipe with an outer diameter of 609mm and a wall thickness of 16mm, and the second to fourth supports are steel pipes with an outer diameter of 800mm and a wall thickness of 20mm.

[0009] As a further technical solution of the present invention, in step S2, the guide frame is made of double 45a I-beams, its horizontal length is controlled at 10m, and the width of the guide frame is 2cm greater than the diameter of the steel pipe pile, that is, 1cm on each side, to ensure that the steel pipe pile is inserted smoothly.

[0010] As a further technical solution of the present invention, step S3, the driving of steel pipe piles specifically includes the following sequential steps: 1) Using a crawler crane in conjunction with a vibratory hammer, the steel pipe piles are hoisted into place through a guide frame and engaged with the interlocking joints of the already driven piles. The piles are then vibrated until they stop sinking. 2) Use an impact hammer to hammer the pile starting from the first pile until it stops sinking; 3) A rotary drilling rig is used to drill a pilot hole inside the interlocked steel pipe pile, with the pilot hole depth reaching at least 1m from the bottom of the steel pipe pile; 4) Use an impact hammer to hammer each of the steel pipe piles after the pilot hole is completed a second time until the design elevation is reached.

[0011] As a further technical solution of the present invention, the equipment used in step S3 is specifically: HGC100A crawler crane, EP200 vibratory hammer, YC-10 impact hammer and SR285R rotary drilling rig, wherein the drill bit diameter of the rotary drilling rig is 70cm.

[0012] As a further technical solution of the present invention, the measurement and control before closure in step S4 is as follows: when the distance between the two ends of the cofferdam is 8 piles, the remaining number of piles required for closure is calculated; after that, for each pile driven in, a total station is used to measure and control its verticality, net distance between pipe piles and plane deviation, so as to correct the deviation one by one and ensure that the locks on both sides of the closure joint are parallel to each other.

[0013] As a further technical solution of the present invention, in step S5, the pumping and sand removal are specifically carried out in the following manner: a mud tank is set up on the support bridge as a sedimentation tank; a screw air compressor is used to create negative pressure in the pressure storage tank, which is connected to the pumping and sand removal pipe through a pipeline to disturb the stratum and pump sand; the principle of symmetry and uniformity is followed during construction to form a pot bottom at the bottom of the cofferdam, and the elevation change of the sand removal surface is closely monitored by measuring rope to ensure the water pressure balance inside and outside the cofferdam.

[0014] As a further technical solution of the present invention, in step S7, the thickness of the bottom sealing concrete is 2m, the radius of action of the tremie pipe is 4m in the underwater tremie pipe construction, and the tremie pipe is lifted before the final pouring of the concrete so that the top elevation of the bottom sealing concrete is controlled at a position 20cm lower than the bottom elevation of the foundation.

[0015] As a further technical solution of the present invention, in step S8, the bottom sealing platform is assembled from Bailey beams, with each span arranged at 27m; a total of 18 pouring points and 20 filler grouting points are set on the platform, with the spacing of the guide pipes along the bridge direction being 5.8m and the spacing of the guide pipes across the bridge direction being 6.5m; a total of 2 sets of pouring guide pipes and 2 sets of filler guide pipes are provided on site for grouting construction.

[0016] The beneficial effects of this invention are as follows: 1. By employing construction techniques such as "a combination of vibratory hammer, impact hammer, and rotary drilling rig with internal boreholes for steel pipe pile driving" and "long-arm excavators combined with dewatering and sand removal for foundation pit excavation," the interlocking steel pipe pile cofferdam was successfully applied in the complex strata of the upper and middle reaches of the Yellow River. This effectively solved the technical challenges of driving interlocking steel pipe piles in complex strata and pile head deformation, saving costs and accelerating the construction progress. It also created conditions for the pier cap to emerge above the water surface.

[0017] 2. The steel pipe piles used are reusable, generating minimal waste during construction and causing no environmental pollution. The construction technique employing a "long-arm excavator combined with dewatering and sand removal method for foundation pit excavation" effectively solves the problem of preventing the discharge of mud, sand, and water into the Yellow River. The environmental benefits are significant. Attached Figure Description

[0018] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 This is a flowchart illustrating the construction process of the present invention. Figure 2 This is a structural layout diagram of the steel cofferdam with interlocking joints according to the present invention; Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided. Example

[0021] refer to Figures 1-2 This invention proposes a dynamic control method for rapid closure of interlocking steel pipe pile cofferdams, applicable to the protection construction of deep underwater foundation pits in railway, highway, and municipal engineering projects with large pier plane dimensions under various complex underwater geological conditions such as crossing rivers and lakes. The method specifically includes the following steps: S1: Construction preparation: Determine the location of the cofferdam site and prepare the interlocking steel pipe piles, walers and internal supports in advance; obtain the foundation components; Specifically, in S1, the steel pipe pile cofferdam with interlocking joints is determined to be of the "CⅠ type" structural form, using Q345B material with an outer diameter of 820mm, a wall thickness of 14mm, and a length of 26m spiral pipe. The interlocking joint uses a seamless steel pipe with an outer diameter of 180mm and a wall thickness of 8mm for the female joint and an I16 I-beam for the male joint. The female joint steel pipe is processed in the factory with a 20mm wide, straight gap to facilitate the smooth insertion of the male joint I-beam.

[0022] S1 also includes step S11, the fabrication of walers and internal supports; 20mm thick steel plates are cut to form triangular brackets, which are directly welded to the steel pipe piles to form waler brackets; waler brackets are welded inside the steel pipe pile cofferdam, with the welds being circumferential welds, continuous fillet welds with a weld height of 6mm, and a spacing of 2.4m / section. After the walers are segmented, they are processed in sections and then hoisted onto the waler brackets using crawler tracks. The first waler is made of 2I45C (Q235), and the second to fourth are made of 2I56C (Q345). The waler sections are spliced ​​together at the waler brackets to ensure a tight connection between the waler sections and the steel pipe piles; the internal supports of the cofferdam are made of steel pipes, with the first support being a 609mm outer diameter, 16mm wall thickness steel pipe, and the second to fourth being an 800mm outer diameter, 20mm wall thickness steel pipe.

[0023] S1 also includes step S12: fabrication of interlocked steel pipe piles; on-site, existing ordinary steel pipe piles are joined to the designed length and processed, then seamless steel pipes with an outer diameter of 180mm and a wall thickness of 8mm and I16 I-beams are positioned and welded to the spiral steel pipes, and finally stiffening ribs are welded; interlocked steel pipe piles are fabricated; it is required that the interlocks on each steel pipe pile be symmetrically located on the same diameter line of the steel pipe; before butt welding the interlocks, the ends of the interlocks should be ground flat and tightened, using semi-penetration welding, and ensuring no weld slag. The weld quality grade is Class III weld, requiring the weld to be full, without cracks, and leak-proof, so that the interlocked steel pipe piles are straight, without bending or folding.

[0024] S2: Positioning guide frame construction: Based on the edge of the cofferdam site, a guide frame composed of double 45a I-beams with sufficient rigidity and a flat surface is pre-set; Specifically, in order to accurately control the planar position of the interlocking steel pipe pile after it is driven in, a guide frame needs to be set up. The guide frame should be made of double 45a I-beams with sufficient rigidity and a flat surface. The horizontal length of the guide frame should not be too large, and should be controlled within 10m. In order to facilitate the smooth insertion of the steel pipe pile into the guide frame, the width of the guide frame should be 2cm greater than the diameter of the pipe pile, that is, 1cm larger on each side.

[0025] S3: Driving steel pipe piles: Using the guide frame, steel pipe piles are driven from the upstream side, then steel pipe piles on both sides are driven in sequence, and finally steel pipe piles on the downstream side are driven, so that the closure is formed at the downstream corner of the cofferdam. Specifically, the following sequential insertion method is adopted: 1) When driving steel pipe piles, use an HGC100A crawler crane with an EP200 vibratory hammer to lift the steel pipe piles and transfer them to the designed pile position. Place them in the guide frame and lower them slowly. During the lowering process, adjust the pile angle to ensure that the interlocking direction is parallel to the longitudinal direction of the cofferdam. During driving, strengthen the control of the position and verticality of the steel pipe piles. Stop after lowering a certain distance and check that the verticality meets the requirements. Use the vibratory hammer to drive until the steel pipe pile stops sinking. Install the next steel pipe pile, ensuring its interlocking is engaged with the interlocking of the already driven pile. Slowly lower it from the guide frame until it enters the sand layer and stabilizes. Then restart the vibratory hammer to drive the pile until it can no longer sink. Then, install the interlocking steel pipe piles one side at a time.

[0026] 2) Use a YC-10 impact hammer to hammer the first pile and continue to drive it down until it stops sinking.

[0027] 3) Use an SR285R rotary drilling rig to drill a pilot hole inside the interlocked steel pipe pile. The SR285R rotary drilling rig has a drill bit lifting height of 6m, a drill bit diameter of 70cm, and a pilot hole depth of more than 1m to the bottom of the steel pipe pile.

[0028] 4) Continue to use the YC-10 impact hammer to hammer each of the steel pipe piles after the pilot hole is completed until the design elevation is reached.

[0029] S4: Cofferdam closure and water-stopping at the lock: Before closure, the number of remaining piles is calculated. During the closure process, the verticality and deviation of each pile are measured and controlled, and the deviation is corrected in time to ensure that the lock is parallel. Water-stopping is done by manually filling and compacting clay and cotton wool. Leaks are repaired underwater by divers. The layout of the interlocking steel pipe pile cofferdam is as follows: the interlocking steel pipe piles are 26m long; the top elevation of the cofferdam is 1056m, 1.5m above the normal water level; the 100-year flood level is 1056.43m; the depth of the steel pipe piles embedded in the ground is 18-20m; the net distance between the inner wall of the steel pipe pile cofferdam and the pile cap is 1.5m. See the structural layout diagram of the interlocking steel cofferdam. Figure 2 .

[0030] As the closure nears completion, the straight-line distance between the bottom of the steel pipe piles is measured and calculated. Based on the width of the steel pipe piles, the remaining number of piles required for closure is calculated. After each pile is driven, its verticality, net distance between the piles, and planar deviation are controlled using a total station. Specifically, to ensure the interlocking joints on both sides are parallel during the closure of the steel pipe pile cofferdam, when the distance between the two ends of the steel pipe piles is 8 piles, the verticality of each subsequent pile is controlled using a total station. If any pile is skewed, it should be corrected one by one to disperse the deviation and adjust for closure. During the closure process, the net distance between the piles and the planar deviation at the top, riverbed, and other locations should be measured to prevent spatial misalignment.

[0031] When sealing the interlocks, a mixture of clay and cotton is manually stuffed into the interlocks, and then manually compacted with a simple rammer made of steel bars. More specifically, sealing the interlocks is a crucial step in the construction of steel cofferdams, and the selection of the sealing material is paramount. The material must not be washed away by water, and its strength cannot be too high, otherwise it will hinder the removal of the interlock steel pipe piles. Field tests determined that a mixture of clay and cotton is manually stuffed into the interlocks, and then manually compacted with a simple rammer made of steel bars, to achieve the sealing effect. If leakage is found in individual interlocks during or after pumping, divers can be sent underwater to check the specific location of the leak and patch it with waterproof cloth.

[0032] S5: Water pumping and sand removal within the cofferdam: Underwater foundation cleaning is carried out using a long-arm excavator in conjunction with water pumping and sand removal methods. The sedimented mud is transported off-site to prevent pollution. Sand is pumped out by negative pressure disturbance using an air compressor, and symmetrical excavation is carried out to form a pot bottom while maintaining water pressure balance. The height difference of the base is strictly controlled within 30cm to ensure the thickness of the sealing layer. Step S5 also includes step S51: underwater cleaning of the cofferdam wall and casing wall; the excavation of the foundation pit is carried out using a long-arm excavator in conjunction with the dewatering and sand removal method. Two mud tanks are set up side by side on the trestle bridge as sedimentation tanks for pumping out mud, sand and gravel, which are then transported to a designated location by excavators and dump trucks to ensure that the river is not polluted.

[0033] A 132SCF+-8B screw air compressor was used to create negative pressure in a pressure storage tank. This negative pressure was then piped to a dewatering and sand-draining pipe inside the cofferdam. Water pipes further assisted in disturbing the ground. Sand and gravel were gradually pumped out of the cofferdam from upstream to downstream and from the center outwards. During the dewatering process, the water head difference between the inside and outside of the cofferdam was constantly monitored to ensure pressure balance. The construction followed a symmetrical and uniform principle, creating a basin-like bottom for the cofferdam, allowing the sediment to settle smoothly. Surveyors closely monitored the elevation changes of the dewatering surface using measuring ropes. A long-arm excavator was used for bottom leveling, and multi-point measurement was employed to precisely control the bottom elevation, ensuring a maximum height difference of no more than 30cm, and that the highest point met the requirements for the thickness of the sealing concrete.

[0034] S6: Install internal supports; first install the central main support, then install the diagonal and vertical braces on both sides of the main support. A column is erected in the middle of the main support, and the column is connected to the main support using a bracket formed by welding channel steel.

[0035] S7: Concrete bottom sealing; The bottom sealing concrete is poured using the underwater tremie method, advancing from the transverse bridge to one side and then to the other; The elevation of the measuring points is strictly monitored and recorded during the process; At the end, a comprehensive re-measurement is carried out, and any low-lying areas are poured to the design elevation. Before the final pour, the tremie pipe is lifted to ensure a smooth surface.

[0036] In step S7, the bottom sealing concrete is poured. The bottom sealing concrete is 2m thick and is constructed using the underwater tremie method. The overall pouring sequence is from one side of the bridge to the other. During the pouring process, attention is paid to controlling the elevation of each pouring point and the elevation of the measuring points within a 4m radius around it, and the pouring and measurement times are recorded. Near the end of the concrete pouring, the elevation of the concrete surface is measured comprehensively, with a focus on the intersection of the tremie pipe's radius of action, the perimeter of the casing, and the inner perimeter of the cofferdam. Based on the results, the pouring volume is increased near measuring points with low elevations. The top elevation of the underwater bottom sealing concrete is 20cm lower than the bottom elevation of the pier cap. Based on the actual measured concrete surface elevation at the measuring points, it is determined whether the point should be poured to its final position. Before final pouring, the tremie pipe is raised to appropriately reduce the embedment depth and to empty as much concrete as possible from the tremie pipe to make its surface flat.

[0037] S8: Construction of the pier cap and pier body; Bailey beams are used to assemble a support frame, with the span arranged on top of the steel pipe piles, and I-beams are added in the middle of the span for reinforcement. The platform is equipped with pouring points and filling points, and the duct pipes are arranged at certain intervals with a diffusion radius of 4m, equipped with pouring duct pipes and filling duct pipes for grouting.

[0038] The bottom sealing platform was erected and the ductwork was laid out. The bottom sealing platform consisted of Bailey bridges, with each group of Bailey bridges consisting of two sections connected by a support frame. They were arranged at 27m intervals per span. The Bailey bridges were supported at both ends on the top surface of steel pipe piles, and upper and lower reinforcing chords were installed. Two I-beams were transversely connected at the mid-span of each Bailey bridge group, and the I-beams were fastened to the upper chord of the Bailey bridges with U-bolts. Three pouring points were arranged on each Bailey bridge group. The ductwork used φ300mm inner diameter steel pipes, with a concrete diffusion radius of 4m. The ductwork was spaced 5.8m longitudinally and 6.5m transversely, with 6 rows transversely and 3 rows longitudinally, totaling 18 pouring points and 20 filler grouting points. Two sets of pouring ductwork and two sets of filler ductwork were provided on site.

[0039] S9: Cofferdam removal; the cofferdam can only be removed after the construction of the pier body and continuous beam blocks is completed.

[0040] The interlocking steel pipe piles were dismantled in stages using an EP200 vibratory hammer. The dismantling of the cofferdam was carried out in the order of downstream to upstream, first supporting the structure, then removing the walers, and finally pulling out the interlocking steel pipe piles. The dismantled inner supports, walers, and steel pipe piles should be cleaned, repaired neatly, rust-free, and coated with anti-rust paint. They should be stored separately for use in the next project.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A control method for rapid closure of a cofferdam with interlocking steel pipe piles, comprising the following steps: S1: Construction preparation: Determine the location of the cofferdam site and prepare the interlocking steel pipe piles, walers and internal supports in advance; obtain the foundation components; S2: Positioning guide frame construction: Based on the edge of the cofferdam site, a guide frame composed of double 45a I-beams with sufficient rigidity and a flat surface is pre-set; S3: Driving steel pipe piles: Using the guide frame, steel pipe piles are driven from the upstream side, then steel pipe piles on both sides are driven in sequence, and finally steel pipe piles on the downstream side are driven, so that the closure is formed at the downstream corner of the cofferdam. S4: Cofferdam closure and water-stopping at the lock: Before closure, the number of remaining piles is calculated. During the closure process, the verticality and deviation of each pile are measured and controlled, and the deviation is corrected in time to ensure that the lock is parallel. Water-stopping is done by manually filling and compacting clay and cotton wool. Leaks are repaired underwater by divers. S5: Water pumping and sand removal within the cofferdam: A long-arm excavator is used in conjunction with water pumping and sand removal for underwater foundation cleaning. The slurry is settled and transported off-site to prevent pollution. Sand is pumped out by negative pressure disturbance using an air compressor. Symmetrical excavation is carried out to form a pot bottom and maintain water pressure balance. The height difference of the base is strictly controlled within 30cm to ensure the thickness of the sealing bottom. S6: Install internal supports; first install the central main support, then install the diagonal braces and straight braces on both sides of the main support; a column is erected in the middle of the main support, and the column is connected to the main support by a bracket formed by welding channel steel; S7: Concrete bottom sealing; The bottom sealing concrete is poured using the underwater tremie method, advancing from the transverse bridge to one side and then to the other; The elevation of the measuring points is strictly monitored and recorded during the process; At the end, a comprehensive re-measurement is carried out, and any low-lying areas are poured to the design elevation. Before the final pour, the tremie pipe is lifted to ensure a smooth surface. S8: Construction of the pier cap and pier body; Bailey beams are used to form a support frame, with the span arranged on the top of the steel pipe piles, and I-beams are added in the middle of the span for reinforcement; the platform is set with pouring points and filling points, and the ducts are arranged at a certain interval with a diffusion radius of 4m, and are equipped with pouring ducts and filling ducts for grouting. S9: Cofferdam removal; the cofferdam can only be removed after the construction of the pier body and continuous beam blocks is completed.

2. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 1, characterized in that, In step S1, the material of the interlocking steel pipe pile is Q345B, and the specifications are a spiral pipe with an outer diameter of 820mm, a wall thickness of 14mm, and a length of 26m. The interlocking structure is as follows: the female end uses a seamless steel pipe with an outer diameter of 180mm and a wall thickness of 8mm with a 20mm wide, continuous straight slit, and the male end uses I16 I-beams. The waler brackets are triangular brackets made of 20mm thick steel plates, which are welded to the perimeter of the steel pipe pile. The weld height is 6mm and the spacing is 2.4m / weld.

3. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 1, characterized in that, In step S1, the walers are manufactured in sections. The first waler is made of 2I45C (Q235) steel, and the second to fourth walers are made of 2I56C (Q345) steel. The inner supports are made of steel pipes. The first support is a steel pipe with an outer diameter of 609mm and a wall thickness of 16mm, and the second to fourth supports are steel pipes with an outer diameter of 800mm and a wall thickness of 20mm.

4. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 1, characterized in that, In step S2, the guide frame is made of double 45a I-beams, with its horizontal length controlled at 10m. The width of the guide frame is 2cm greater than the diameter of the steel pipe pile, that is, 1cm larger on each side, to ensure that the steel pipe pile is inserted smoothly.

5. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 1, characterized in that, Step S3 specifically includes the following sequential steps: 1) Using a crawler crane in conjunction with a vibratory hammer, the steel pipe piles are hoisted into place through a guide frame and engaged with the interlocking joints of the already driven piles. The piles are then vibrated until they stop sinking. 2) Use an impact hammer to hammer the pile starting from the first pile until it stops sinking; 3) A rotary drilling rig is used to drill a pilot hole inside the interlocked steel pipe pile, with the pilot hole depth reaching at least 1m from the bottom of the steel pipe pile; 4) Use an impact hammer to hammer each of the steel pipe piles after the pilot hole is completed a second time until the design elevation is reached.

6. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 5, characterized in that, In step S3, the specific equipment models used are: HGC100A crawler crane, EP200 vibratory hammer, YC-10 impact hammer, and SR285R rotary drilling rig, wherein the drill bit diameter of the rotary drilling rig is 70cm.

7. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 1, characterized in that, In step S4, the measurement and control before closure is as follows: when the distance between the two ends of the cofferdam is 8 piles, the remaining number of piles required for closure is calculated; after that, for each pile driven in, a total station is used to measure and control its verticality, net distance between pipe piles and plane deviation, so as to correct the deviation one by one and ensure that the locks on both sides of the closure joint are parallel to each other.

8. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 1, characterized in that, In step S5, the pumping and sand removal are carried out in the following ways: a mud tank is set up on the support bridge as a sedimentation tank; a screw air compressor is used to create negative pressure in the pressure storage tank, which is connected to the pumping and sand removal pipe through a pipeline to disturb the strata and pump sand; the construction follows the principle of symmetry and uniformity to make the bottom of the cofferdam form a pot bottom, and the elevation change of the sand pumping surface is closely monitored by measuring rope to ensure the water pressure balance inside and outside the cofferdam.

9. The control method for dynamic adjustment and rapid closure of a cofferdam with interlocking steel pipe piles according to claim 1, characterized in that, In step S7, the thickness of the bottom sealing concrete is 2m. In the underwater tremie pipe construction, the radius of action of the tremie pipe is 4m. Before the final pouring of the concrete, the tremie pipe is lifted up so that the top elevation of the bottom sealing concrete is controlled at a position 20cm lower than the bottom elevation of the foundation.

10. The control method for dynamic adjustment and rapid closure of the interlocking steel pipe pile cofferdam according to claim 1, characterized in that, In step S8, the bottom sealing platform is assembled from Bailey beams, with each span arranged at 27m. A total of 18 pouring points and 20 filler grouting points are set on the platform, with the guide pipes spaced 5.8m along the bridge direction and 6.5m across the bridge direction. A total of 2 sets of pouring guide pipes and 2 sets of filler guide pipes are provided on site for grouting construction.

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