Segmented interlocking type combined steel sheet pile cofferdam construction method

Abstract

The invention relates to the technical field of cofferdam construction, in particular to a sectional interlocking type combined steel sheet pile cofferdam construction method which comprises the steps of obstacle clearing, surveying and lofting, soil piling and filling of a conical operation platform, inserting and driving of steel sheet piles, soil filling and reinforcing, auxiliary engineering, building in a cofferdam and cofferdam dismantling. A river can be quickly separated, and the construction period is short.

Description

TECHNICAL FIELD

[0001] The present application relates to the cofferdam construction technology field, especially to a segmented interlocking combined steel sheet pile cofferdam construction method. BACKGROUND

[0002] Cofferdam is a temporary project for creating dry construction conditions for engineering construction in river regulation and pumping gate projects. The traditional earth cofferdam has a large cross section and occupies a large area. A large amount of soil is needed for preloading, and a large amount of residual soil is involved in disposal after removal. The load changes greatly before and after construction. Its application is limited in the case of surrounding important buildings and limited soil sources. Steel sheet pile cofferdam has the advantages of simple structure, small cross section and small land occupation, and is widely used in Shanghai area.

[0003] The pile body of the steel sheet pile cofferdam is generally selected from U-shaped Larsen steel sheet piles, including a main body with a U-shaped cross section and a lock opening integrally formed on both sides of the main body. Adjacent two Larsen steel sheet piles are positioned and connected through the lock opening, and the lock opening is used for water and mud sealing.

[0004] In order to ensure the construction quality of the steel sheet pile cofferdam, the skilled person in the art formulates a steel sheet pile cofferdam construction method, which mainly includes the following steps: step one, obstacle removal, removing stones and bricks in the steel sheet pile construction range and stacking them outside the construction range; step two, measurement and setting out, measuring and setting out the outer edge line of the steel sheet pile cofferdam with a total station instrument; step three, construction operation platform, constructing an operation platform according to the operation position, which can be a masonry platform or a mobile platform such as a car or a ship; step four, inserting and driving steel sheet piles, inserting and driving steel sheet piles along the measured and set edge line to obtain a cofferdam main body; step five, water pumping and reinforcement, pumping out the water in the cofferdam main body and installing corbels, surrounding purlins and steel rods for reinforcement; step six, cofferdam construction, cleaning the sludge at the bottom of the cofferdam and constructing buildings in the cofferdam main body; step seven, cofferdam removal, pouring water into the foundation pit and then removing the reinforcement structure and pulling out the steel sheet piles.

[0005] In step four, when the cofferdam is a single row of steel sheet piles, the steel sheet piles are continuously inserted and driven, the water is pumped out after closure, and then the buildings are constructed in the cofferdam main body. After the construction is completed, the cofferdam is removed, which is mainly used for the construction of independent buildings in the water body such as bridge piers; when the cofferdam is a double row of steel sheet piles, a segmented cofferdam is used. The first double row of steel sheet piles is constructed first, then a temporary working platform is made by filling soil, the second double row of steel sheet piles is constructed on the temporary working platform, and the cycle is repeated until the cofferdam main body is completed. Then the foundation pit is excavated in the cofferdam main body, and then the buildings are constructed, which is mainly used for the construction of buildings such as gates in water conservancy projects.

[0006] In the process of double-row steel sheet pile cofferdam construction, the steel sheet piles in the transverse direction of the two rows of longitudinal steel sheet piles are constructed to form multiple separated cofferdam cells, the cofferdam cells are filled with soil, and then the roads and operation platforms are constructed, which can ensure the cofferdam to gradually advance, and the disadvantage is that the construction speed is slow and the cofferdam cannot be quickly separated. SUMMARY

[0007] The present application aims to overcome the deficiencies in the prior art and provide a segmented interlocking combined steel sheet pile cofferdam construction method.

[0008] The present application is implemented by the following technical scheme: a segmented interlocking combined steel sheet pile cofferdam construction method, comprising the following steps, Step one: obstacle removal, remove the stones and bricks in the cofferdam construction range and stack them outside the construction range; Step two: measurement and setting out, set control measurement points on the land of the upstream and downstream riverbanks that are not affected by the construction, and measure and set out the outer lines of the two rows of steel sheet piles inside and outside the combined steel sheet pile with a total station; Step three: earth filling and conical operation platform construction, fill the earth to construct a conical operation platform at the connection part of the cofferdam and the riverbank, push the earth from the riverbank along the central axis of the combined steel sheet pile to the river center during the earth filling, and make the combined steel sheet pile smoothly connect with the riverbank during the filling; Step four: steel sheet pile insertion, the steel sheet pile is selected to be a Larsen steel sheet pile, the steel sheet pile has a lock on the side, the steel sheet pile forms outer steel sheet piles and inner steel sheet piles, the outer steel sheet piles and the inner steel sheet piles are alternately distributed, and the steel sheet pile is constructed from one side of the riverbank to the opposite side, after the construction of the starting section is completed, steel road plates are fully laid on the top of the steel sheet pile, the pile machine is driven to the top of the steel sheet pile, and the whole is advanced to the opposite side of the river for construction, at least two rows of steel sheet piles are constructed, and the steel road plates are laid between the upper ends of the steel sheet piles; Step five: soil filling and reinforcement, starting from the starting section, the steel road plates are removed section by section, and then the soil is filled, during the soil filling, the water in the combined steel sheet pile is drained from the inside to the outside of the combined steel sheet pile, until the water level in the combined steel sheet pile drops by 100 cm, to avoid the water level in the combined steel sheet pile rising during the soil filling, and to control the pressure of the combined steel sheet pile, after the soil of the section is higher than the water surface, the soil is continuously filled and compacted to obtain a first soil layer, the height of the first soil layer is the same as the water level outside the combined steel sheet pile, the soil is filled and compacted layer by layer at 30 cm per layer on the first soil layer, the pull rod perforation is pre-processed on the upper side of the steel sheet pile, when the soil is 5 cm away from the perforation, the surrounding rail and the pull rod are installed at 2 m per file, then the pull rod is inserted through the extension arm and the opening on the steel sheet pile, and after the position is adjusted, the nut is tightened to complete the installation of the pull rod, after the installation of the pull rod is completed, the soil is filled and compacted layer by layer at 30 cm per layer, until a predetermined height is reached, to obtain a second soil layer; Step six: auxiliary engineering, the steel road plates are removed as a whole, the hardened road surface is constructed on the surface of the second soil layer, the wave protection plate is constructed on the water surface of the hardened road surface, and the protective fence is constructed on both sides of the hardened road surface, to obtain the combined steel sheet pile. Step seven, cofferdam construction, combined steel sheet pile will cut off the river, when there is a lock upstream of the river, combined steel sheet pile only need to be constructed downstream of the cofferdam to prevent downstream river backflow, when there is no lock upstream of the river, combined steel sheet pile is constructed upstream and downstream of the cofferdam, after the construction of the combined steel sheet pile, the cofferdam is drained to expose the riverbed, the foundation pit is excavated at the preset position, and the retaining pile is constructed outside the foundation pit to prevent silt in the riverbed from entering the foundation pit, the foundation is constructed in the foundation pit, and the functional building is constructed on the foundation; Step eight, combined steel sheet pile removal, water is poured into the cofferdam to balance the pressure inside and outside the cofferdam, the hardened road surface, wave protection board, and guardrail are removed, then the steel road plate is laid, the second soil layer is excavated, the pull rod is removed, then the first soil layer is excavated, after the completion of the excavation, the extension arm and the bracket steel plate are removed in sections, and the steel sheet pile is pulled out, in the process of construction, the steel sheet pile head is first clamped by the pile driver and vibrated for 1-2 min to make the soil around the steel sheet pile loose and reduce the resistance of the soil to the steel sheet pile, then slowly vibrate and pull up.

[0009] Further, in step three, the elevation of the conical operation platform is within 10 cm of the elevation of the top of the cofferdam, and the piling machinery can drive from the riverbank to the conical operation platform for operation.

[0010] Further, in step four, butter mixture paste is applied in the lock before inserting and driving the steel sheet pile.

[0011] Further, the starting end construction includes the following steps, A. First, mark the pile position on the ground, and the pile driver is parked on the conical operation platform for piling; B. According to the position of the first edge pile, the pile driver is shifted, after positioning, the first steel sheet pile is inserted and driven into place, and the center line of the subsequent pile is controlled to coincide with the center of the first steel sheet pile; C. The mechanical hand clamps the steel sheet pile, the pile is aligned with the pile position by the pile supporting worker, and the pile is inserted in a vertical state, after the pile is inserted stably, the position and bidirectional perpendicularity of the steel sheet pile are re-measured, if it does not meet the requirements, the pile needs to be re-inserted until it is qualified; D. After the first pile is inserted and stabilized, the vibration function of the mechanical hand is intermittently started to implement small displacement setting of the first steel sheet pile, and the perpendicularity of the pile body is tracked and reviewed, until the pile body is sunk into the soil more than 3m, then continuously set to the designed pile top +3.0m elevation; E. The insertion and driving of the subsequent steel sheet pile is along the axis of the combined steel sheet pile along the lock of the previous steel sheet pile, after the pile is inserted into place, the vibration function is started to set to the design elevation in several times.

[0012] Furthermore, positioning piles are constructed before the first sheet pile is driven, and guide supports are installed. There are two positioning piles, and the line connecting the two positioning piles is on the straight line where the sheet piles are located. After the two positioning piles are driven, guide supports are installed between the upper ends of the two positioning piles. The guide supports include an outer guide arm and an inner guide arm, both of which are made of I-beams or channel steel. The outer guide arm and the inner guide arm are parallel. The bottom of the outer sheet pile mates with the outer guide arm, and the bottom of the inner sheet pile mates with the inner guide arm, thereby making the sheet piles in the same row straight. Adjusting pads are installed between the outer guide arm and the positioning pile. The outer guide arm, adjusting pads, inner guide arm and positioning pile are fixed with long bolts. During driving, the back of the sheet pile is close to the guide frame and gradually sinks.

[0013] Furthermore, the construction of the sheet piles in the advance section includes the following steps: a. After the pile driver completes the pile construction within the arm span of the conical working platform, a steel slab is fully laid on top of the two rows of steel sheet piles as a temporary working platform. The pile driver then moves to the temporary working platform to carry out pile driving construction. b. After the sheet piles within the arm span are completed, continue to lay steel slabs on top of the two rows of completed sheet piles, and construct the next section of sheet piles. Continue to advance towards the opposite bank for construction until all sheet piles are constructed.

[0014] Furthermore, the inner sheet piles are connected with reinforcing structures.

[0015] Furthermore, the reinforcing structure includes an H-beam welded to the inside of the inner sheet pile, and a slot that mates with the H-beam is installed on the inner sheet pile.

[0016] Furthermore, the reinforcing structure includes a curved steel plate with an S-shaped cross-section, one side of which is welded and fixed to the inner middle position of the inner steel sheet pile.

[0017] The beneficial effects of this invention are as follows: 1. Applicable to the flat southeastern region, Class II and Class III inland waterways, it can quickly create river barriers with a short construction period.

[0018] 2. The bottom of the outer sheet pile mates with the outer guide arm, and the bottom of the inner sheet pile mates with the inner guide arm, thus making the sheet piles in the same row straight. To control the distance between the outer guide arm and the inner guide arm, an adjustment pad is installed between the outer guide arm and the positioning pile. The adjustment pad is a steel plate, and the thickness value is selected as needed. The outer guide arm, adjustment pad, inner guide arm and positioning pile are fixed with long bolts. When driving, the back of the sheet pile is close to the guide frame and sinks gradually.

[0019] 3. The first soil layer has more contact with water and has poorer compaction. The second soil layer does not contact water and is easier to compact. Furthermore, the construction method of filling and compacting soil layer by layer results in higher resistance to settlement and deformation, thus avoiding cracking of the hardened pavement.

[0020] 4. The thickness of the H-beam is the same as the width of the inner sheet pile, thus forming a triangular pile body. This compensates for the insufficient stiffness of a single sheet pile cofferdam in soft soil, strengthens the supporting force of the sheet pile, ensures the stability and safety of the structure, and creates favorable conditions for the subsequent excavation of the foundation pit inside the cofferdam. 5. A positioning block is installed on the outer extension arm. The positioning block is a U-shaped block. The waist of the U-shaped block is fixed to the extension arm. When the inner steel sheet pile is driven, the bottom inner side of the inner steel sheet pile fits with the two wing ends of the U-shaped block, thus forming a guide and providing support for the inner steel sheet pile from the outside. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the distribution of composite steel sheet piles; Figure 2 A top view of the connection between the positioning pile structure and the guide arm; Figure 3 This is a schematic diagram showing the connection between the positioning pile structure and the guide arm; Figure 4 This is a schematic diagram of the initial stage of driving steel sheet piles. Figure 5 This is a schematic diagram of a steel slab structure. Figure 6 This is a schematic diagram of the connecting arm structure; Figure 7 This is a schematic diagram of the sheet pile structure after the sheet piles have been driven in. Figure 8 This is a top view diagram showing the completed installation of sheet piles. Figure 9 This is a schematic diagram of the sheet pile structure after backfilling. Figure 10 This is a schematic diagram of the tie rod distribution; Figure 11 This is a schematic diagram showing the connection between sheet piles and H-beams; Figure 12 This is a schematic diagram of the curved steel plate structure in Example 2.

[0022] The components include: 1. Riverbed; 2. Bank revetment; 3. Foundation pit; 4. Retaining piles. 5. Combined sheet piles; 501. Positioning piles; 502. Adjusting pads; 503. Outer guide arm; 504. Inner guide arm; 505. Sheet piles; 506. Fixing bolts; 507. Connecting plates; 508. Locking joints; 509. Extension arms; 510. Steel slabs; 511. Conical work platform; 512. Stop blocks; 513. Positioning blocks; 514. Hardened road surface; 515. First subsoil layer; 516. Second subsoil layer; 517. Tie rods; 518. Angle steel; 519. H-beams; 520. Curved steel plates. Detailed Implementation

[0023] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the following embodiments, The sheet pile 505 is a Larssen sheet pile. The sheet pile 505 has a locking lug 508 on its side. In the same row, two adjacent sheet piles 505 are connected by the locking lug 508 to form an interlock and strengthen the seal. The sheet piles 505 consist of two rows, spaced 400-500 cm apart, suitable for Class II and Class III inland waterways. When a steel slab 510 is laid between the upper ends of the two rows of sheet piles 505, the wheels of engineering vehicles can approach and be supported by the sheet piles 505, reducing deformation of the slab 510 and ensuring safety. Downward-facing stops 512 are fixed to both ends of the slab 510, engaging with the outer side of the sheet piles 505 to prevent slippage of the slab 510.

[0026] In the same row, sheet piles 505 form outer sheet piles and inner sheet piles, which are distributed alternately.

[0027] Example 1 like Figures 1-11 As shown, a construction method for a segmented interlocking composite steel sheet pile cofferdam includes the following steps: Step 1, Clearing Obstacles: Remove stones and bricks from the construction area of ​​sheet pile 505 and pile them outside the construction area to prevent the sheet pile 505 from encountering obstacles and being unable to sink when it is being lowered.

[0028] Step 2, Measurement and Layout: Select control measurement points on the riverbank land upstream and downstream of the cofferdam, unaffected by construction, and use a total station to measure and lay out the outer edges of the inner and outer rows of sheet piles 505 of the combined sheet pile 5. During the sinking of the sheet piles 505, two theodolites are used to control the verticality of the sheet piles 505 using the forward intersection method.

[0029] Step 3: Constructing the Conical Working Platform 511 by piling soil at the junction of the composite sheet pile 5 and the riverbank. During soil piling, advance from the riverbank along the central axis of the composite sheet pile 5 towards the center of the river. The elevation difference between the conical working platform 511 and the top elevation of the cofferdam should be within 10cm. The filling length should ensure a smooth connection between the composite sheet pile 5 and the existing riverbank, allowing the piling machinery to travel from the riverbank to the conical working platform 511. The conical working platform 511 should be compacted and stable to meet the bearing capacity requirements of the piling equipment.

[0030] Step 4, driving sheet piles 505: To reduce friction between the interlocks 508 during driving and to reduce leakage in the cofferdam, a mixture of grease and grease is applied to the inside of the interlocks 508 before driving the sheet piles 505. Construction proceeds from one side of the riverbank towards the opposite bank, dividing the combined sheet piles 5 into two sections according to the pile driver's operating position. The section closest to the riverbank (5-8m) is designated as the starting section. The pile driver is positioned on the filled conical operating platform 511, driving each sheet pile individually. After the starting section is completed, a steel slab 510 is fully laid on top of the sheet piles 505 in the starting section. The pile driver then moves to the top of the sheet piles 505 and continues construction towards the opposite bank.

[0031] In this step, the initial section construction includes the following steps: A. First, mark the pile positions on the ground, and then park the pile driver on the conical work platform 511 to drive the piles. B. Based on the position of the first side pile, direct the pile driver to move. After positioning, once the first pile is driven into place, ensure that the center line of subsequent piles coincides with the center of the first pile; C. The robotic arm picks up the steel sheet pile 505, and the pile-holding worker aligns the pile with the pile position, completing the pile insertion in a vertical state. After the pile is stable, the position and bidirectional verticality of the pile are re-measured. If it does not meet the requirements, the pile needs to be re-inserted until it is qualified. D. After the first pile is driven into the ground and stabilized, the vibration function of the manipulator is turned on intermittently to drive the first pile with a small displacement and to track and check the verticality of the pile until the pile sinks into the ground for more than 3m. Only then can it be continuously driven to the set elevation of the pile top + 3.0m. E. The subsequent sheet piles 505 are driven in sequence along the axis of the combined sheet pile 5 and the interlocking joint 508 of the previous sheet pile 505. After the piles are in place, the vibration function is activated and the piles are driven to the design elevation in stages.

[0032] To ensure the straightness of the sheet piles 505, positioning piles 501 are constructed before the first sheet pile 505 is installed, along with guide supports. Specifically, there are two positioning piles 501, and the line connecting the two positioning piles 501 lies on the straight line of the row of sheet piles 505. After the two positioning piles 501 are driven in, guide supports are installed between their upper ends. The guide supports include an outer guide arm 503 and an inner guide arm 504, both made of I-beams or channel steel, and are parallel to each other. The bottom of the outer sheet pile mates with the outer guide arm 503, and the bottom of the inner sheet pile mates with the inner guide arm 504, thus ensuring the straightness of the sheet piles 505 in the same row. To control the distance between the outer guide arm 503 and the inner guide arm 504, an adjusting shim 502 is installed between the outer guide arm 503 and the positioning pile 501. The adjusting shim 502 is made of steel plate, and the thickness is selected as needed. The outer guide arm 503, adjusting shim 502, inner guide arm 504, and positioning pile 501 are fixed with long bolts. During driving, the back of the sheet pile 505 is close to the guide frame and gradually sinks. At this time, theodolites are used to observe in two mutually perpendicular directions to ensure that the sheet pile 505 is inserted straight and upright.

[0033] The construction of the 505 sheet piles in the advance section includes the following steps: a. After the pile driver completes the pile construction within the arm extension range on the conical working platform 511, a steel slab 510 is fully laid on top of the two rows of steel sheet piles 505 as a temporary working platform. The pile driver then moves to the temporary working platform to carry out pile driving construction. b. After the sheet piles 505 within the arm's span are completed, continue laying steel slabs 510 on top of the two completed rows of sheet piles 505, and then construct the next section of sheet piles 505. This process is repeated until all sheet piles 505 are completed. During the driving of the sheet piles 505, a total station is used for tracking and measurement to check the deviation of the sheet piles 505 at any time. When a sheet pile 505 deviates, it is corrected promptly using a chain hoist. When a sheet pile 505 deviates, it is pulled upwards by 1.0-2.0m and then driven downwards, repeating this up-and-down motion several times to correct its position. If the deviation is too large to be corrected with a chain hoist, it is pulled out and re-inserted. During this process, the inner guide arm 504 and the outer guide arm 503 are connected to an extension arm 509 on the same straight line, which guides the sheet piles 505. After the sheet pile 505 is inserted, the extension arm 509 is fixed to the sheet pile 505 by fixing bolt 506, and then the next extension arm 509 is connected until the sheet pile 505 is driven in.

[0034] Step 5, Soil Filling and Reinforcement: Excavators are used to excavate and load soil, and 5-ton dump trucks transport the soil to the construction site. During underwater soil filling, construction proceeds from the initial section towards the opposite bank. After each layer of soil is laid on the composite sheet piles 5, it is compacted to prevent leakage and enhance the overall integrity of the dam. Areas that cannot be compacted by rolling are tamped using electric rammers or manually. During the filling process, water is drained from inside the composite sheet piles 5 on the opposite bank until the water level inside the composite sheet piles 5 drops by 100cm. Starting from the initial section, the steel sheet piles 510 are removed section by section, and then soil is filled to prevent the water level inside the composite sheet piles 5 from rising during the filling process, while controlling the pressure of the composite sheet piles 5. When the fill in this section is above the water surface, filling and compaction continue to obtain the first plain soil layer 515. The height of the first plain soil layer 515 is the same as the water level outside the composite sheet piles 5. On the first plain soil layer 515, soil is filled and compacted in 30cm layers. Pre-drill holes for tie rods 517 on the upper side of the sheet piles 505. When the backfill is 5cm from the hole, install the walers and tie rods 517 in 2m increments. In this embodiment, the extension arm 509 forms the walers, connecting the two rows of sheet piles 505 to form a whole. The tie rods 517 are made of Φ42mm round steel, and each end of each tie rod 517 is anchored with two high-strength nuts. A 20mm thick Q235 trapezoidal bracket steel plate (not shown in the figure) is installed on the lower edge of the extension arm 509. The bracket steel plate is welded to the sheet piles 505, and the weld thickness is not less than 8mm. Mark the installation position of the trapezoidal bracket steel plate vertically downwards 110mm from the center of the hole. Then, check whether the positions of each hole and the installation position of the trapezoidal bracket steel plate are on the same baseline by pulling a line. Adjust any that do not meet the requirements to ensure that the axial deviation is controlled within 10mm. Weld the cut trapezoidal bracket steel plates to the marked installation positions. Before welding, thoroughly clean the welding area of ​​rust, oil, and other debris. The welded trapezoidal bracket steel plates must be inspected on-site by the quality inspector according to the "Code for Acceptance of Construction Quality of Steel Structures" GB50205-2020, and there should be no twisting, incomplete welding, or other defects. Use a crane to lift the extension arm 509 onto the installed trapezoidal bracket steel plate. Then, pass the tie rod 517 through the openings on the extension arm 509 and the sheet pile 505, adjust the position, and tighten the nut to complete the installation of the tie rod 517.

[0035] After installing tie rod 517, continue filling soil in 30cm layers, compacting it until the predetermined height is reached, resulting in the second subgrade layer 516. The first subgrade layer 515 has more contact with water and thus lower density; the second subgrade layer 516 does not contact water and is easier to compact. This layer-by-layer filling and compaction method results in higher resistance to settlement and deformation, thereby preventing cracking of the hardened pavement 514.

[0036] For the conical slopes at both ends of the composite sheet pile 5, an excavator is used to spread the soil and shape it, followed by manual cleaning and leveling of the dam slope to ensure that the straightness, slope, and flatness of the slope meet the requirements. When the compaction of a local slope does not meet the design requirements, manual tamping should be used. After tamping, a geomembrane is laid on top, ensuring it is laid tightly against the dam slope, maintaining a natural flatness and moderate tightness. The geomembrane joints are overlapped, with an overlap width of at least 30 cm. The overlap joints should be longitudinal joints along the slope direction; horizontal joints are prohibited. The geomembrane should extend at least 1 m into the dam body. Laying personnel should wear soft-soled shoes to avoid damaging the geomembrane. After laying, a layer of concrete is poured to prevent water erosion of the dam foundation soil, thereby avoiding affecting the stability of the composite sheet pile 5. Backfilling is carried out section by section. After the previous section is backfilled, steel slabs 510 are laid before proceeding to the next section of backfilling.

[0037] Step Six, Ancillary Works: The steel slab 510 is completely dismantled, and a hardened road surface 514 is constructed on the upper surface of the second subgrade soil layer 516 to allow engineering vehicles to pass through during construction within the cofferdam. Wave-breaking slabs are constructed on the water-facing side of the hardened road surface 514, and guardrails are constructed on both sides of the hardened road surface 514 to obtain the composite steel sheet piles 5.

[0038] Step 7, Construction within the Cofferdam: Combined sheet piles 5 will cut off the river channel. When there is a sluice gate upstream, the combined sheet piles 5 only need to be constructed downstream of the cofferdam to prevent backflow of downstream river water. When there is no sluice gate upstream, combined sheet piles 5 will be constructed both upstream and downstream of the cofferdam. After the combined sheet piles 5 are completed, the cofferdam will be drained, exposing the riverbed 1. A foundation pit 3 will be excavated at the predetermined location, and a retaining cofferdam will be constructed outside the foundation pit 3. Retaining piles 4 will prevent silt from the riverbed 1 from entering the foundation pit 3. The foundation will be constructed within the foundation pit 3, and functional structures such as pump gates will be built on the foundation.

[0039] Step 8, Cofferdam Removal: Water is pumped into the cofferdam to balance the pressure inside and outside. The hardened road surface 514, wave barriers, guardrails, and other ancillary structures are removed, and then steel slabs 510 are laid. The second subgrade layer 516 is excavated, tie rods 517 are removed, and then the first subgrade layer 515 is excavated. After all excavation is completed, the extension arm 509 and bracket steel plates are removed section by section, and the sheet piles 505 are pulled out. During construction, the sheet pile head is first clamped with a pile driver and vibrated for 1-2 minutes to loosen the soil around the sheet pile 505, causing "liquefaction" and reducing the soil resistance to the sheet pile 505. Then, it is slowly pulled upwards. When pulling the pile, attention is paid to the load on the pile driver. If it is difficult to pull upwards or cannot be pulled out, the pulling should be stopped, paused for 1-2 minutes, then the pile is driven down 10-20cm, and then pulled upwards again to extract the pile.

[0040] The construction method of the segmented interlocking combined steel sheet pile cofferdam provided in this embodiment is especially applicable to the river channels in the southeastern region with gentle terrain. Since the elevation difference between the upstream and downstream of the cofferdam is small, when the upstream sluice is closed, the water level drop at the cofferdam is also small. Constructing the combined steel sheet pile 5 downstream of the cofferdam can prevent the backflow of the downstream river water. Due to the gentle terrain of the riverbed 1 and the deep silt layer of the riverbed 1, the steel sheet pile 505 is prone to tilt. In this embodiment, the inner steel sheet pile is connected with a strengthening structure, and the strengthening structure includes the H-shaped steel 519 welded on the inner side of the inner steel sheet pile. A card slot matching with the H-shaped steel 519 is installed on the inner steel sheet pile. Two angle steels 518 are welded on the inner side of the inner steel sheet pile. The angle steels 518 are distributed close to the edge of the inner steel sheet pile, and a card slot is formed between the two angle steels 518. After the card slot is installed, the weld is polished and then an anti-rust layer is coated. An H-shaped steel 519 with a length of about 2m is used as a standard block. The standard block is inserted into the card slot, and then a winch is used to pull the H-shaped steel 519 to translate in the card slot, moving from the end of the card slot to the tail of the card slot. If it passes smoothly without jamming, the card slot is qualified. The card slot extends upward to the upper end of the inner steel sheet pile, and the ratio of the length value of the card slot to the length value of the steel sheet pile 505 is 1:1-3, so as to guide the H-shaped steel 519 in the initial stage. During the pile insertion process, part of the card slot is inserted into the soil layer.

[0041] During the test, an attempt was made to directly weld and fix the strengthening structure to the inner steel sheet pile to shorten the pile insertion period. It was found during the test that when the strengthening structure was pre-fixed to the inner steel sheet pile, the pile insertion resistance increased, and the inner steel sheet pile was no longer flat. The vibration also weakened the effect of pile insertion, resulting in the inner steel sheet pile being unable to sink stably to the predetermined elevation. Later, the card slot form was adopted. During the pile insertion process, the inner steel sheet pile was first sunk to the predetermined elevation, and then the H-shaped steel 519 was inserted. Since the nearby soil layer was loosened by vibration during the sinking process of the inner steel sheet pile, the resistance of the H-shaped steel 519 during the sinking process was reduced. In this embodiment, the thickness value of the H-shaped steel 519 is the same as the width value of the inner steel sheet pile, thus forming a triangular pile body, compensating for the problem of insufficient stiffness of a single steel sheet pile cofferdam in soft soil layers, strengthening the supporting force of the steel sheet pile 505, ensuring the stability and safety of the structure, and creating favorable conditions for the subsequent excavation of the foundation pit 3 inside the cofferdam.

[0042] The angle steels 518 are located on both sides of the inner steel sheet pile, which can avoid interference when the manipulator grabs the steel sheet pile 505.

[0043] Due to the introduction of the strengthening structure, the inner steel sheet pile cannot fit with the extension arm 509 during the pile driving process. To ensure the guiding effect on the inner steel sheet pile, a positioning block 513 is installed on the outer extension arm 509. In this embodiment, the positioning block 513 is a U-shaped block, and the waist of the U-shaped block is fixed to the extension arm 509. When driving the inner steel sheet pile, the inner side of the bottom of the inner steel sheet pile fits with the two wing ends of the U-shaped block, thus forming a guide and being able to provide support for the inner steel sheet pile from the outside.

[0044] The segmented interlocking combined steel sheet pile cofferdam construction method provided in this embodiment is applicable to the flat terrain of the southeast region and Class II and Class III inland waterways. It can quickly form a river barrier with a short construction period.

[0045] Example 2 like Figure 12 As shown, a segmented interlocking composite sheet pile cofferdam construction method differs from Example 1 in that, during testing, a curved steel plate 520 with an S-shaped cross-section was also attempted as a reinforcing structure. One side of the curved steel plate 520 was welded and fixed to the inner middle of the inner sheet pile. Due to the elastic deformation of the curved steel plate 520 itself, during pile insertion and extraction, the curved steel plate 520 transmitted vibrations to the soil layer, thus preventing a significant increase in resistance during pile insertion and extraction. During use, the curved steel plate 520 extends into the backfill layer, reinforcing the support force of the inner sheet pile and buffering shear forces from the side. The disadvantage is that the connection between the curved steel plate 520 and the inner sheet pile is relatively weak.

[0046] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method of a segmented interlocked combined steel sheet pile cofferdam, characterized by, The method comprises the following steps: Step 1, removing obstacles, removing stones and bricks within the cofferdam construction range and stacking them outside the construction range; Step 2, measuring and setting out, setting control measurement points on the land of the upstream and downstream river banks not affected by the construction, and measuring and setting out the outer edge lines of the inner and outer rows of the combined steel sheet piles by using a total station instrument; Step 3, filling the conical operation platform with earth, filling the conical operation platform with earth at the joint between the combined steel sheet pile and the river bank, pushing forward along the central axis of the combined steel sheet pile from the river bank to the river center during the earth filling, and making the combined steel sheet pile and the river bank smoothly connect during the filling; Step 4, inserting and driving the steel sheet pile, the steel sheet pile is selected to be a Larsen steel sheet pile, the steel sheet pile has a lock on the side, the steel sheet pile forms outer steel sheet piles and inner steel sheet piles, the outer steel sheet piles and the inner steel sheet piles are alternately distributed, and the construction is started from one side of the river bank to the other side of the river, after the construction of the starting section is completed, the steel way board is fully laid on the top of the steel sheet pile, the pile machine is driven to the top of the steel sheet pile, the whole occupies the other side of the river to construct, at least two rows of steel sheet piles are constructed, and the steel way board is laid between the upper ends of the rows of steel sheet piles; Step 5, soil filling and reinforcement, starting from the starting section, the steel way board is removed section by section, then the soil is filled, during the soil filling, water is drained from the inside to the outside of the combined steel sheet pile at the other side, until the water level in the combined steel sheet pile drops by 100 cm, to avoid the water level in the combined steel sheet pile rising during the soil filling, and to control the pressure of the combined steel sheet pile, after the soil of the section is higher than the water surface, the soil is continuously filled and compacted to obtain a first soil layer, the height of the first soil layer is the same as the water level outside the combined steel sheet pile, the soil is filled and compacted layer by layer at 30 cm per layer on the first soil layer, the hole for the pull rod is pre-processed on the upper side of the steel sheet pile, when the soil is filled to 5 cm from the hole, the surrounding purlin and the pull rod are installed at 2 m per file, then the pull rod is inserted through the extension arm and the hole on the steel sheet pile, the position is adjusted, the nut is tightened to complete the installation of the pull rod, after the installation of the pull rod is completed, the soil is filled and compacted layer by layer at 30 cm per layer, until a predetermined height is reached, to obtain a second soil layer; Step 6, auxiliary engineering, the steel way board is removed as a whole, a hardened road surface is constructed on the upper surface of the second soil layer, a wave protection board is constructed on the water surface of the hardened road surface, and a protective fence is constructed on both sides of the hardened road surface, to obtain the combined steel sheet pile; Step 7, building in the cofferdam, the combined steel sheet pile cuts off the river channel, when there is a lock on the upstream of the river channel, the combined steel sheet pile only needs to be constructed downstream of the cofferdam to prevent the backflow of the downstream river water, when there is no lock on the upstream of the river channel, the combined steel sheet pile is constructed on the upstream and downstream of the cofferdam, after the construction of the combined steel sheet pile is completed, the cofferdam is drained to expose the riverbed, a foundation pit is excavated at a predetermined position, earth retaining piles are constructed outside the foundation pit to prevent silt in the riverbed from entering the foundation pit, a foundation is constructed in the foundation pit, and a functional building is constructed on the foundation; Step eight, combined steel sheet pile removal, to the cofferdam water, and further balance the pressure inside and outside the cofferdam, remove the hardening pavement, wave board, guardrails, and then lay steel plate, excavation of the second layer of soil, remove the pull rod, and then excavate the first layer of soil, all excavation is completed, section by section to remove the extension arm and bracket steel sheet, and pull out the steel sheet pile, in the process of construction, first with the pull pile machine clamped steel sheet pile head vibration 1-2 min, so that the soil around the steel sheet pile loose, reduce the resistance of the soil to the steel sheet pile, and then slowly up to the vibration.

2. The construction method of segmental interlocked combined steel sheet pile cofferdam according to claim 1, characterized in that, In step three, the elevation of the conical operation platform and the elevation of the cofferdam top differ within 10 cm, and the piling machine can drive from the river bank to the conical operation platform for operation.

3. The construction method of segmental interlocked combined steel sheet pile cofferdam according to claim 1, characterized in that, In step four, before inserting and driving the steel sheet pile, butter the lock port with a mixture of butter and oil.

4. The construction method of segmental interlocked combined steel sheet pile cofferdam according to claim 1, characterized in that, The starting end construction includes the following steps, A, first mark the pile position on the ground, and the pile machine is parked on the conical operation platform for piling; B, according to the position of the first edge pile, command the pile driver to move, after positioning, the first steel sheet pile is inserted and driven into place, and the center line of the subsequent piles is controlled to coincide with the center of the first steel sheet pile; C, the mechanical hand clamps the steel sheet pile, the pile is aligned with the pile position by the pile supporting worker, and the insertion is completed in the vertical state, after the insertion is stable, the position and bidirectional perpendicularity of the steel sheet pile are re-measured, if it does not meet the requirements, the pile needs to be re-inserted until it is qualified; D, after the first pile is inserted and stable, the vibration function of the mechanical hand is intermittently started, the first steel sheet pile is implemented with small displacement amount sinking, and the perpendicularity of the pile body is tracked and rechecked, until the pile body is sunk into the soil more than 3m, then continuously sinking to the set pile top +3.0m elevation; E, the insertion and driving of the subsequent steel sheet pile, along the axis of the combined steel sheet pile, insert into the lock port of the previous steel sheet pile, after the insertion is in place, start the vibration function to sink to the design elevation in stages.

5. The construction method of segmental interlocked combined steel sheet pile cofferdam according to claim 4, characterized in that, Before the construction of the first steel sheet pile, a positioning pile is constructed and a guide support is installed, the positioning pile has two, the connecting line of the two positioning piles is on the straight line where the steel sheet pile is located, after the two positioning piles are inserted and driven, a guide support is installed between the upper ends of the two positioning piles, the guide support includes an outer guide arm and an inner guide arm, the outer guide arm and the inner guide arm are both made of I-beam or channel steel, the outer guide arm and the inner guide arm are parallel, the bottom of the outer steel sheet pile cooperates with the outer guide arm, and the bottom of the inner steel sheet pile cooperates with the inner guide arm, so that the steel sheet piles in the same row are straight, an adjusting pad is installed between the outer guide arm and the positioning pile, the outer guide arm, the adjusting pad, the inner guide arm and the positioning pile are fixed by long bolts, and the steel sheet pile back is close to the guide support during insertion, and gradually sinks.

6. The construction method of segmental interlocked combined steel sheet pile cofferdam wall in accordance with claim 1, characterized by, The construction of the steel sheet pile in the occupation section includes the following steps, a, after the pile driver completes the pile construction within the arm spread range on the conical operation platform, steel plates are fully laid on the top of the two rows of steel sheet piles as a temporary operation platform, the pile driver is driven to the temporary operation platform for sinking pile construction; b, after the construction of the steel sheet piles within the arm spread range is completed, continue to fully lay steel plates on the top of the two rows of steel sheet piles constructed, construct the next section of steel sheet pile, and reciprocally occupy the construction to the opposite shore until the construction of all steel sheet piles is completed.

7. The construction method of segmental interlocked combined steel sheet pile cofferdam wall in accordance with claim 1, characterized by, The inner steel sheet pile is connected with a reinforcing structure.

8. The construction method of segmental interlocked combined steel sheet pile cofferdam according to claim 7, characterized in that, The reinforcing structure includes an H-shaped steel welded in the inner side of the inner steel sheet pile, and a clamping groove installed on the inner steel sheet pile and matched with the H-shaped steel.

9. The construction method of segmental interlocked combined steel sheet pile cofferdam according to claim 7, characterized in that, The reinforcing structure comprises a curved steel plate with an S-shaped cross section, and one side of the curved steel plate is welded and fixed with the middle position of the inner side of the inner steel sheet pile.

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