Lock catch steel pipe pile cofferdam and PLC cofferdam construction method

Abstract

The invention belongs to the technical field of bridge construction, and particularly relates to a lock catch steel pipe pile cofferdam and a PLC cofferdam construction method.The lock catch steel pipe pile cofferdam construction method comprises the steps that at least two layers of steel wire ropes are arranged on the outer ring of the lock catch steel pipe pile cofferdam and on the overwater part and the underwater part in a sleeving mode, the steel wire ropes of each layer are connected into a circle, each layer forms a circle independently, and locking devices are installed at the connecting positions of the steel wire ropes; installing a device for testing tension on the steel wire rope, and reading the steel wire rope in real time; a guide bracket is installed on the steel casing, and after the enclosing purlins and the inner supports are installed layer by layer through lifting of the two crawler cranes, the steel pipe (plate) piles are driven in an inserted mode through the crawler cranes and a vibratory hammer; the mud surface elevation is rechecked, and two long-arm excavator grab buckets and a dredge pump are adopted for excavation with water to the bottom sealing elevation; a bottom sealing platform is erected on the steel casing, underwater bottom sealing concrete is poured, water is pumped after the bottom sealing concrete is equal in strength, and the steel casing is cut off; the locking device is mounted on the outer ring of the lock catch steel pipe pile cofferdam, so that the steel pipe piles or the steel sheet piles can be prevented from directly falling and collapsing outwards.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, in particular to a locking steel pipe pile cofferdam and a PLC cofferdam construction method. Background Art

[0002] Existing cap cofferdams mostly use a PLC (Plastic Load Chain) (PLC) composite steel pipe (sheet) pile design. Since these steel pipe piles are connected by locking clips, if the locking clips become welded or become desoldered after long-term use, they can fail, causing the cofferdam to lose its integrity and directly impacting the load. This can ultimately cause the steel pipe piles or steel sheet piles to fall outward (radially outward), leading to the collapse of the cofferdam and accidents. Therefore, a construction method for locking steel pipe pile cofferdams, or PLC cofferdams, has been proposed to address these issues. Summary of the Invention

[0003] In order to make up for the shortcomings of the existing technology and solve the problem that the lock buckle is welded or desoldered after long-term use, which will lead to the failure of the lock buckle, the present invention proposes a lock buckle steel pipe pile cofferdam and a PLC cofferdam construction method.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a locking steel pipe pile cofferdam and a PLC cofferdam construction method described in the present invention include the following steps: S1: On the outer ring of the locking steel pipe pile cofferdam, at least two layers of steel wire rope are placed above and below the water. Each layer of steel wire rope is connected into a circle, and each layer is individually coiled. A locking device is installed at the connection of the steel wire rope. A tension test device is installed on the steel wire rope to read the wire rope reading in real time. S2: Guide brackets are installed on the steel casing. Two crawler cranes are used to install the purlins and inner supports layer by layer. The steel pipe (plate) piles are then driven in using crawler cranes and vibratory hammers. S3: Recheck the mud surface elevation and use two long-arm excavator grab buckets and mud suction pumps to excavate to the bottom elevation with water; S4: Build a bottom sealing platform on the steel casing, pour underwater bottom sealing concrete, pump out water after the bottom sealing concrete is strong, and cut off the steel casing; S5: Using the "circular cutting method," a jackhammer is used to break the pile head, and a crawler crane is used for lifting operations. A truck-mounted pump is used to pour the leveling layer concrete. Rebar and cooling water pipes are processed into semi-finished products at the processing plant and transported to the site for installation using a flatbed truck, with a truck-mounted crane for lifting operations. Composite steel formwork is used for the formwork, and a truck-mounted pump is used to pour the cap concrete. S6: When the concrete strength of the cap reaches the design requirements, backfill sand and cast a concrete ring beam between the cap and the cofferdam. After the concrete strength of the ring beam meets the requirements, remove the last purlin and internal support to allow the cap to bear the load. After the cap bears the load, continue to construct the pier until it is out of the water; S7: After the construction of the foundation, pier body, embedded parts, etc. is completed, the cofferdam is removed. Before the cofferdam is removed, water must be returned. While returning water, the internal supports and purlins are removed from bottom to top. Finally, the "crawler crane + vibratory hammer" is used to remove the steel pipe piles.

[0005] Preferably, the S2: welding the corbels on the steel casing, installing the first layer of purlins, using the first layer of purlins as a guide, and driving the steel pipe (plate) piles with a crawler crane + vibratory hammer; the S3: setting up a bottom sealing platform on the steel casing, and pouring underwater bottom sealing concrete; the S4: after the bottom sealing concrete is strong, gradually pumping out water to install the second and third layers of purlins and internal supports, and cutting off the steel casing.

[0006] Preferably, the S3: using a long-arm excavator to backfill sand and soil into the foundation pit to the bottom elevation and level it.

[0007] Preferably, the S3: setting up a bottom sealing platform on the steel casing and pouring underwater bottom sealing concrete; the S4: pumping out water after the bottom sealing concrete is strengthened, installing the bottom plate formwork, welding shear keys, reinforcing plates, tying steel bars, pouring bottom plate concrete, cooperating with crawler crane for lifting operations, and cutting off the steel casing.

[0008] Preferably, the S3: setting up a bottom sealing platform on the steel casing and pouring underwater bottom sealing concrete; the S4: pumping out water after the bottom sealing concrete is strengthened, installing the bottom plate formwork, welding shear keys, reinforcing plates, tying steel bars, pouring bottom plate concrete, cooperating with crawler crane for lifting operations, and cutting off the steel casing.

[0009] Preferably, the S3: pumping water from the cofferdam, installing the bottom plate formwork, welding shear keys, reinforcing plates, tying steel bars, and pouring bottom plate concrete.

[0010] Preferably, the S2: welding the corbels on the steel casing, installing the first layer of purlins, using the first layer of purlins as a guide, and driving the steel pipe piles with a crawler crane + vibratory hammer; the S3: pumping water from the cofferdam, installing the second layer of purlins and internal supports; continuing to pump water from the cofferdam, installing the bottom plate formwork, welding shear keys, reinforcement plates, tying steel bars, and pouring bottom plate concrete.

[0011] Preferably, in S3: the water level inside the cofferdam is not lower than the water level outside by 1.0m, and the cofferdam is excavated with water to the bottom of the bottom seal; in S4: a bottom seal platform is set up on the steel casing, and underwater bottom seal concrete is poured. After the bottom seal concrete is strong, water is pumped out to install the second layer of purlins and internal supports, water is pumped out of the cofferdam to the top of the bottom seal, and the steel casing is cut off.

[0012] Preferably, the S2: using crawler crane + vibratory hammer to insert steel sheet piles until the joint is closed; S3: pumping water in the cofferdam to 1.0m from the center line of the first cofferdam, installing the first layer of purlins and temporary bracing, and welding the steel sheet piles to the purlins; pumping water in the cofferdam to 1.0m from the center line of the second cofferdam, installing the first layer of diagonal bracing, removing the temporary bracing, installing the second layer of purlins and inner supports, and welding the steel sheet piles to the purlins; S4: pumping water and excavating the inside of the cofferdam to the bottom of the bottom seal, cleaning the base and pouring the bottom seal concrete, pumping water after the bottom seal concrete is strengthened, and cutting off the steel casing.

[0013] The present invention is beneficial in that: 1. The present invention can prevent the steel pipe piles or steel sheet piles from falling directly outward (radially outward) and causing the cofferdam to collapse by installing a locking device on the outer ring of the locking steel pipe pile cofferdam.

[0014] 2. The present invention can read the wire rope reading in real time and issue an early warning by installing a device for testing tension.

[0015] 3. The present invention provides a wire rope locking device. As the height of the foundation construction increases, the wire rope can be automatically lifted to the set elevation, that is, lifted to a height close to the outside of the cofferdam wall. After the construction inside the cofferdam is completed, the wire rope is first loosened and then the cofferdam is dismantled, thereby improving the overall safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a plan layout drawing of the cofferdam design for Example 1; Figure 2 This is a plan view of the lifting and lowering of the inner support of the purlin in Example 1; Figure 3 This is a schematic diagram of the steel pipe (sheet) pile driving sequence in Example 1; Figure 4 This is a plan view of the construction of mud suction excavation in Example 1; Figure 5 This is a flow chart of the bottom construction process of Example 1; Figure 6 This is a schematic diagram of the calculation of the first concrete seal in the embodiment; Figure 7 This is a steel bar elevation drawing of the offshore approach bridge cap in Example 1; Figure 8 This is a side view of the reinforcement of the offshore approach bridge cap in Example 1; Figure 9 This is a plan view of the reinforcement of the cap of the offshore approach bridge in Example 1; Figure 10 This is a plan view of the reinforcement of the offshore approach bridge pedestal in Example 1. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] Example 1 A method for constructing a locking steel pipe pile cofferdam and a PLC cofferdam. The pier cofferdam adopts the pre-support method to seal the bottom underwater for construction. The main steps of the cofferdam and pier cap construction are as follows: Step 1: Dismantle the drilling platform. After the pile foundation construction is completed, the drilling platform will be dismantled. According to the construction drawings and the actual situation on site, the area to be demolished on site is 21m*30m, and the demolition equipment is a 100t crawler crane. Figure 1 As shown, at least two layers of wire rope are wrapped around the outer ring of the locking steel pipe pile cofferdam. Each layer of wire rope is connected to form a coil, and each layer is individually coiled. Locking devices are installed at the wire rope connections. The construction method for each layer of wire rope is divided into above-water and underwater stages. For the above-water stage, a construction platform can be welded outside the cofferdam, and personnel can be deployed to install it. For the underwater stage, a submersible robot can be developed to loop, connect, and lock the coils. A tensile testing device is installed on the wire rope to read the wire rope reading in real time. If the reading suddenly increases or the data is abnormal, an alert is issued, and the cofferdam can be immediately inspected or maintained. Concrete is poured layer by layer inside the cofferdam to form the bottom concrete and the foundation pile. Once the bottom concrete has been poured and reaches the design strength, a robotic device is used to lift the underwater wire rope to the concrete soil layer that has reached the design strength, so that the restrained wire rope at the cofferdam cantilever end is wrapped around it. As the foundation pile construction height increases, the wire rope is automatically raised to the set elevation (a certain height above the outside of the cofferdam wall). After the construction inside the cofferdam is completed, loosen the wire rope first and then dismantle the cofferdam.

[0020] Step 2: Re-measure the mud surface elevation. Based on the actual severity of the scour, use a long-arm excavator to pre-excavate the riverbed within the cofferdam to the bottom elevation of the bottom concrete seal.

[0021] Step 3: Weld the purlin corbel system on the casing. The purlins, internal supports and other components are processed in the back field according to the design drawings. To facilitate lifting and lowering, the purlins are processed in sections. The length of the sections must ensure that they can smoothly pass through the gap between the first layer of steel purlins and internal supports when lowered. The arc section purlins are bent by a bending machine using a tire frame. The straight section is made by directly cutting and welding steel sections. Referring to the steel cofferdam design drawings, the cofferdam purlins are processed in sections and spliced ​​on site. When segmenting, it is strictly forbidden to place the joints in the middle of the support span or at the end of the support. Before processing, a special support tire frame is made, and the surveying personnel will mark its plane position and elevation. After each section is processed, it needs to be placed on the tire frame to match the previous section. After all processing is completed, a trial assembly is carried out on the tire frame, and each section is numbered. During the back-end processing, railings are welded to the top of the purlins in advance for construction protection. Double-sided railings are set on the first floor, and single-sided railings are set on the inner side of the foundation pit on the second and third floors. The railings are welded with ∅48 steel pipes and installed together with the purlins during installation. Corbels and a shelving system are welded to the steel casing to serve as the assembly platform for the purlins and internal supports. A total of 6 corbels are set up, using steel sections and casings for reliable welding. For specific layout, please refer to Figure 2 .

[0022] Step 4: Assemble the third layer of purlins and internal supports on the corbel system, install a temporary fixing frame, and after the corbel and shelving system are installed, use a crawler crane to lift the purlins section by section and place them on the corbels for assembly. Use wire ropes and shackles to lift them into place, and use hand hoists and small jacks to adjust the position of the purlins. After the position is adjusted into place, the joints are firmly connected with high-strength bolts.

[0023] Step 5: The crawler crane lifts and lowers the third layer of purlins and inner supports, and places them on the lower corbel. After the third layer of purlins and inner supports are assembled, the position of the purlins is measured and verified. After the two 150t crawler cranes are in place, the wire rope is hung, and the purlins are lifted to a height of 20cm. After the upper corbel bolts are released, the twin crawler cranes are slowly lowered to the lower corbel, and the second layer of purlins and inner supports are assembled on the corbel system. The crawler crane lifts and lowers the second layer of purlins and inner supports, and places them on the middle corbel. The first layer of purlins and inner supports are assembled on the corbel system, and then adjusted and fixed.

[0024] Step six: Use crawler crane + vibratory hammer to drive the steel pipe (plate) pile cofferdam, set up a guide frame, and use the already installed three-layer purlin as the driving guide beam to drive the steel pipe (plate) piles. Weld a φ48mm steel pipe on the purlin before driving, set a safety rope hole on it, and install the safety rope during construction. Driving order: Use 2 crawler cranes and 2 vibratory hammers to drive the steel pipe piles and steel sheet piles of the combined steel cofferdam alternately. Drive the piles piece by piece, gradually correct the deviation, and drive them in stages. The specific operation is as follows: One crawler crane is used to erect the steel pipe (plate) piles, and the other is used to drive the piles. Start with the steel pipe piles. Start driving the first steel pipe pile from the center of the straight line segment measured by Ningbo, and then drive the piles one by one counterclockwise. Set the joint mouth in the straight line segment for joint closure. Please refer to Figure 3 .

[0025] Step 7: Re-measure the mud surface elevation, use air suction equipment to level the base to the designed elevation, check the base siltation, and use a long-arm excavator to excavate the cofferdam to the base. During the underwater excavation, use a pump to replenish water in the cofferdam to keep the liquid level in the pit unchanged. Figure 4 Step 8: Set up the bottom sealing platform and pour the bottom sealing concrete. The bottom sealing concrete is C30 underwater concrete with a thickness of 3.0m and a base elevation of -13.087m. The total volume of the bottom sealing concrete is 704m3. The bottom sealing concrete construction adopts the mobile hopper positioning plugging method for the first sealing and the underwater concrete bottom sealing process with multiple pipes. Set up the bottom sealing platform at the top of the steel casing, use an 18m³ large hopper + a 5m³ medium hopper for the first sealing, and two 37m truck pumps for pouring. After the first pouring of concrete is completed, a 0.5m³ hopper is used to continuously add material. When the concrete elevation reaches the requirement, the next concrete pouring pipe is replaced for concrete pouring, and the process is carried out in a step-by-step manner until the bottom sealing is completed. Please refer to the bottom sealing construction process flow chart. Figure 5 .

[0026] The volume of the first batch of concrete is calculated according to the following formula: V=h1πd2 / 4+Hc•πR2 / 3 Where: R-the effective radius of the duct, which is 3.5m; d-catheter diameter, taken as 325mm; Hc - the height of the first batch of concrete pouring, which is considered to be 1.3m (1m buried depth of the conduit); h1-the height (m) at which the concrete column inside the conduit is in equilibrium with the water pressure outside the conduit when the concrete height inside the cofferdam reaches Hc; h1=Hw×γw / γc=Hw / 2.2 Where: γw-density of water in the cofferdam, 11kN / m³ γc-bulk density of concrete mixture, taken as 24kN / m³.

[0027] Hw: The height from the water surface inside the cofferdam to the bottom of the cofferdam Hw = 17.96m (the water level inside the cofferdam is calculated based on the construction high water level of 4.87m, and needs to be recalculated according to the actual situation on site during actual construction).

[0028] Calculation shows: V = h1πd2 / 4 + HcπR2 / 3 = π×0.3252×8.2 / 4+π×3.52×1.3 / 3 = 17.35m³, so a large hopper with a capacity of 18m³ is selected.

[0029] Calculation diagram Figure 6 Step 9: Close the connecting tube and gradually pump out the water. Weld the corbels to the steel cofferdam, transfer the purlins and internal supports to the corbels, and remove the temporary guide system. Pumping can only begin when the bottom seal concrete reaches 90% of the design strength. Once the bottom seal concrete reaches the required strength, pump out the water using the existing water pump. During the pumping process, observe the deformation of the steel pipe (sheet) piles. If deformation is excessive, sudden, or unusual, stop pumping, analyze the cause, and address the problem before resuming construction.

[0030] Step 10: Remove the steel casing, chisel out the pile head, pour the screed, and once the bottom concrete reaches the design strength, begin desilting the cofferdam and pumping out the water. Based on the measured foundation base elevation, remove the excess steel casing using a gas cutter. Then, use a crawler crane to remove the casing from the foundation pit and transport it to the material yard. After the steel casing is removed, the pile head is treated using the circumferential cutting method. The basic process for the circumferential cutting method is: leveling and marking the elevation → circumferential cutting → stripping the rebar → cutting the pile head → lifting the pile head → trimming the pile head → straightening the rebar.

[0031] Step 11: Tie up the first section of steel bars for the pier and foundation, install other embedded parts, install the formwork, and pour the first section of concrete for the pier and foundation using a truck pump. The pier reinforcement is HRB400 steel bars, the steel bar hooks are standard hooks, and the net protective layer thickness is 7cm. The main structure steel bars are divided into 6 types: Φ32 / 28mm, Φ20 / 16mm, and Φ16 / 12mm. Among them, Φ32 / 28mm steel bars are the skeleton steel bars for the pier, and the pier frame steel bars and lateral reinforcements are all Φ20 / 16mm. Figure 7-10 .

[0032] Step 12: Remove the foundation formwork, backfill with sand, pour the ring beam concrete, remove the third layer of purlins and internal supports, continue to construct the pier body until the water is out, open the connecting valve, return the water to the cofferdam, remove the second and first layer of purlins and internal supports in turn, and finally remove the steel pipe (plate) piles to complete the cofferdam dismantling. After the foundation and pier body are constructed until the water is out, remove the formwork and the cofferdam dismantling construction can be carried out. The specific dismantling steps are as follows.

[0033] (1) Removal of purlins and internal supports After the cofferdam's internal cap and corresponding pier sections are completed, the steel cofferdam dismantling begins. Before dismantling the steel cofferdam, water must be backfilled to the required design height. The steel purlins and internal supports are then removed layer by layer from bottom to top. The order for dismantling a single layer of internal supports is: diagonal bracing, then bracing, then purlins.

[0034] (2) Removal of steel pipe (sheet) piles Pile extraction also starts from the downstream side and gradually moves to the upstream side. A 150t crawler crane is used in conjunction with a YZ-230F vibratory hammer to extract steel pipe piles. The steel pipe pile extraction method is as follows: 1. First, use a vibratory hammer to clamp the head of the steel plate (tube) pile and vibrate it for 1 to 2 minutes to loosen the soil (fine stone concrete) around the steel plate (tube) pile and reduce the frictional resistance of the stratum to the pile. Then slowly vibrate and pull it upwards. Pay attention to the load of the pile driver when pulling out the pile.

[0035] 2. If you find it difficult to pull out or you cannot pull it out at all, stop pulling out the pile. You can first push it down a little, then push it up, and repeat this process until the pile is pulled out.

[0036] 3. For piles with curled pile tips and deformed lock ends, the pile pulling force can be increased to pull out the adjacent piles together.

[0037] 4. For steel pipe piles with large pulling resistance, divers need to be sent into the water to cut them. Before cutting, the upper end must be securely hung with a crane before underwater cutting operations can be carried out.

[0038] 5. When the steel pipe pile is about to be pulled out from the cofferdam, control the pile to be completely pulled out and not swing when it is lifted off to prevent it from hitting the finished abutment, pier body, construction personnel or other equipment.

[0039] 6. Remove the soil and sand from the steel pipe piles and apply grease for protection. Sheet piles with large deformation need to be straightened, and intact sheet piles should be transported out of the construction site in time and properly stored.

[0040] The cofferdam demolition should be carried out strictly in accordance with the designed demolition timing and demolition steps, and the deformation of the foundation pit should be strengthened during the demolition process (including cofferdam settlement, sheet pile displacement, purlin strain, etc.). The monitoring period is from the start of cofferdam demolition to the completion of steel pipe pile extraction to ensure structural safety during the demolition process.

[0041] Example 2 Comparative Example 1, another embodiment of the present invention, welded corbels to the steel casing, installed the first layer of perimeter purlins, and used the first layer of perimeter purlins as a guide. Steel pipe (sheet) piles were driven by a crawler crane and vibratory hammer. A bottom sealing platform was constructed on the steel casing, and underwater bottom sealing concrete was poured. After the bottom sealing concrete reached a certain strength, the water was gradually pumped out to install the second and third layers of perimeter purlins and internal supports, and the steel casing was removed.

[0042] Example 3 Comparative Example 1, as another implementation of the present invention, a long-arm excavator is used to backfill sand and soil into the foundation pit to the bottom elevation and level it.

[0043] Example 4 Comparative Example 1, as another implementation method of the present invention, a bottom sealing platform is set up on the steel casing and underwater bottom sealing concrete is poured; after the bottom sealing concrete is strengthened, water is pumped out, the bottom plate formwork is installed, shear keys and reinforcement plates are welded, and steel bars are tied, and the bottom plate concrete is poured. The crawler crane cooperates with the lifting operation to cut off the steel casing.

[0044] Example 5 Comparative Example 1, as another implementation method of the present invention, a bottom sealing platform is set up on the steel casing and underwater bottom sealing concrete is poured; after the bottom sealing concrete is strengthened, water is pumped out, the bottom plate formwork is installed, shear keys and reinforcement plates are welded, and steel bars are tied, and the bottom plate concrete is poured. The crawler crane cooperates with the lifting operation to cut off the steel casing.

[0045] Example 6 Comparative Example 1, as another implementation of the present invention, water is pumped out of the cofferdam, the bottom plate formwork is installed, shear keys and reinforcement plates are welded, steel bars are tied, and bottom plate concrete is poured.

[0046] Example 7 Comparative Example 1, as another implementation method of the present invention, corbels are welded on the steel casing, the first layer of purlins are installed, the first layer of purlins are used as a guide, and the steel pipe piles are driven by a crawler crane + vibratory hammer; the cofferdam is pumped out, and the second layer of purlins and internal supports are installed; the cofferdam continues to be pumped out, the bottom plate formwork is installed, shear keys, reinforcement plates, and steel bars are tied, and the bottom plate concrete is poured.

[0047] Example 8 Comparative Example 7, as another implementation method of the present invention, the water level inside the cofferdam is not lower than the water level outside by 1.0m, the cofferdam is excavated with water to the bottom of the bottom seal, a bottom seal platform is set up on the steel casing, and underwater bottom seal concrete is poured. After the bottom seal concrete is strong, water is pumped out to install the second layer of purlins and internal supports, water is pumped out of the cofferdam to the top of the bottom seal, and the steel casing is cut off.

[0048] Embodiment 9 Comparative Example 1, as another implementation method of the present invention, a crawler crane + vibratory hammer is used to insert steel sheet piles until the joint is closed; water is pumped from the cofferdam to 1.0m from the center line of the first cofferdam, the first layer of purlins and temporary bracing are installed, and the steel sheet piles and purlins are welded; water is pumped from the cofferdam to 1.0m from the center line of the second cofferdam, the first layer of diagonal bracing is installed, the temporary bracing is removed, the second layer of purlins and inner supports are installed, and the steel sheet piles and purlins are welded; water is pumped and excavated from the inside of the cofferdam to the bottom of the bottom seal, the bottom seal concrete is poured after the base is cleaned, the water is pumped out after the bottom seal concrete is strengthened, and the steel casing is cut off.

[0049] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0050] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for constructing a locking steel pipe pile cofferdam or a PLC cofferdam, characterized by: The following steps are involved: S1: On the outer ring of the locking steel pipe pile cofferdam, at least two layers of steel wire rope are placed above and below the water. Each layer of steel wire rope is connected to form a circle, and each layer is individually coiled. A locking device is installed at the connection of the steel wire rope. A tension test device is installed on the steel wire rope to read the wire rope reading in real time. S2: Guide brackets are installed on the steel casing. Two crawler cranes are used to install the purlins and inner supports layer by layer. The steel pipe (plate) piles are then driven in using crawler cranes and vibratory hammers. S3: Recheck the mud surface elevation and use two long-arm excavator grab buckets and mud suction pumps to excavate to the bottom elevation with water; S4: Build a bottom sealing platform on the steel casing, pour underwater bottom sealing concrete, pump out water after the bottom sealing concrete is strong, and cut off the steel casing; S5: Using the "circular cutting method," a jackhammer is used to break the pile head, and a crawler crane is used for lifting operations. A truck-mounted pump is used to pour the leveling layer concrete. Rebar and cooling water pipes are processed into semi-finished products at the processing plant and transported to the site for installation using a flatbed truck, with a truck-mounted crane for lifting operations. Composite steel formwork is used for the formwork, and a truck-mounted pump is used to pour the cap concrete. S6: When the concrete strength of the cap reaches the design requirements, backfill sand and cast a concrete ring beam between the cap and the cofferdam. After the concrete strength of the ring beam meets the requirements, remove the last purlin and internal support to allow the cap to bear the load. After the cap bears the load, continue to construct the pier until it is out of the water; S7: After the construction of the foundation, pier body, embedded parts, etc. is completed, the cofferdam is removed. Before the cofferdam is removed, water must be returned. While returning water, the internal supports and purlins are removed from bottom to top. Finally, the "crawler crane + vibratory hammer" is used to remove the steel pipe piles.

2. A locking steel pipe pile cofferdam and PLC cofferdam construction method as claimed in claim 1, characterized in that: S2: Weld the brackets on the steel casing, install the first layer of purlins, use the first layer of purlins as a guide, and use a crawler crane + vibratory hammer to drive the steel pipe (plate) piles; S3: Set up a bottom sealing platform on the steel casing and pour underwater bottom sealing concrete; S4: After the bottom concrete is strong, gradually pump out the water to install the second and third layer purlins and internal supports, and cut off the steel casing.

3. The method for constructing a locking steel pipe pile cofferdam or PLC cofferdam according to claim 1, characterized in that: S3: Use a long-arm excavator to backfill sand and soil into the foundation pit to the bottom elevation and level it.

4. A locking steel pipe pile cofferdam and PLC cofferdam construction method as claimed in claim 1, characterized in that: S3: Set up a bottom sealing platform on the steel casing and pour underwater bottom sealing concrete; S4: After the bottom concrete is sealed and strengthened, water is pumped out, the bottom plate formwork is installed, shear keys and reinforcement plates are welded, steel bars are tied, and the bottom plate concrete is poured. The crawler crane cooperates with the lifting operation and the steel casing is cut off.

5. The method for constructing a locking steel pipe pile cofferdam or PLC cofferdam according to claim 1, characterized in that: S3: Set up a bottom sealing platform on the steel casing and pour underwater bottom sealing concrete; S4: After the bottom concrete is strong, pump out the water, install the bottom plate formwork, weld the shear keys, reinforcement plates, tie the steel bars, pour the bottom plate concrete, cooperate with the crawler crane for lifting operations, and cut off the steel casing.

6. The method for constructing a locking steel pipe pile cofferdam or PLC cofferdam according to claim 1, characterized in that: S3: Pump out the cofferdam, install the bottom plate formwork, weld shear keys, reinforcement plates, tie steel bars, and pour the bottom plate concrete.

7. The method for constructing a locking steel pipe pile cofferdam or PLC cofferdam according to claim 1, characterized in that: S2: Weld the brackets on the steel casing, install the first layer of purlins, use the first layer of purlins as a guide, and drive the steel pipe piles with a crawler crane and a vibratory hammer; S3: Pump out the cofferdam and install the second layer of purlins and internal supports; continue pumping out the cofferdam, install the bottom plate formwork, weld shear keys, reinforcement plates, tie steel bars, and pour the bottom plate concrete.

8. The method for constructing a locking steel pipe pile cofferdam or PLC cofferdam according to claim 7, characterized in that: S3: The water level inside the cofferdam shall not be lower than the water level outside by 1.0m, and the cofferdam shall be excavated with water to the bottom of the bottom seal; S4: Build a bottom sealing platform on the steel casing and pour underwater bottom sealing concrete. After the bottom sealing concrete is strong, pump out water to install the second layer of purlins and internal supports. Pump water from the cofferdam to the top of the bottom sealing and cut off the steel casing.

9. The method for constructing a locking steel pipe pile cofferdam or PLC cofferdam according to claim 1, characterized in that: S2: Use crawler crane + vibratory hammer to drive steel sheet piles until the joint is closed; S3: Pump water from the cofferdam to 1.0m from the centerline of the first cofferdam layer, install the first layer of purlins and temporary bracing, and weld the steel sheet piles to the purlins; pump water from the cofferdam to 1.0m from the centerline of the second cofferdam layer, install the first layer of diagonal bracing, remove the temporary bracing, install the second layer of purlins and internal bracing, and weld the steel sheet piles to the purlins; S4: Pump water from the inner side of the cofferdam to the bottom of the bottom seal, clean the base and pour the bottom seal concrete. After the bottom seal concrete is strong, pump water out and cut off the steel casing.

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