An integral positioning and installation structure and construction method for a double-wall steel cofferdam and a short casing group

Abstract

The present invention discloses an integral positioning and installation structure of a double-wall steel cofferdam and a short casing group and a construction method. The integral positioning and installation structure comprises an inverted corbel column and a stiffening plate respectively welded to the ends of a crossbeam and a diagonal brace during the assembly of the steel cofferdam. The crossbeam and at least two steel casings are connected by a hanger rod. Adjacent steel casings are welded by longitudinal parallel joints, transverse parallel joints and connecting plates to form a short casing group, and the short casing group and the steel cofferdam form a whole. The land-based installation structure can ensure the positioning accuracy and installation verticality of the steel casing. In addition, there is no need to raise the steel casing above the water surface, thereby saving a large amount of steel casing materials and reducing the material cost. The steel casing installation process is changed from a critical process to a non-critical process, thereby shortening the total length of the critical line, accelerating the process connection, and effectively ensuring the construction period.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater bridge foundation engineering construction, and relates to an integral positioning and installation structure of a double-wall steel cofferdam and a short casing group and a construction method. Background Art

[0002] Currently, as water depths increase, double-walled steel cofferdams, known for their high rigidity and safety, are increasingly used as containment and water retaining structures for underwater bridge foundations. During underwater bridge pile foundation construction, steel casings are sunk below the local scour line in the riverbed, with the top of the casing elevated above the highest construction water level to stabilize the water head within the borehole. During bored pile construction, steel casings stabilize the surrounding soil, locate the piles, and guide the drilling process.

[0003] In the existing technology, the steel casing of the underwater foundation of the bridge is generally installed on the water after the double-wall steel cofferdam is in place, using methods such as vibration sinking and ramming, or installing and fixing the bottom section and then raising it section by section as the steel cofferdam sinks to the surface. The steel casing has a long cantilever length and a large weight. The vibration sinking and ramming construction on the water has high requirements for the capacity of the lifting equipment and machinery, and the positioning accuracy and verticality of the steel casing are difficult to control. The section-by-section method requires multiple welding, which is time-consuming and labor-intensive, and the welding quality is difficult to control. The amount of steel casing required for deep-water pile group foundations is huge, the recycling rate is low, and the material and cost investment is high. The water positioning and installation of the steel casing is located on the key route of deep-water foundation construction. The key process restricts the total construction period, and the total construction period is relatively long.

[0004] In addition, in thin overburden rock or bare rock formations, the steel casing cannot maintain a stable state because the depth of the steel casing embedded in the overburden or rock formation is insufficient. It is often necessary to pour concrete through the bottom of the casing or grout the overburden to solidify it in order to achieve the purpose of anchoring the steel casing. Summary of the Invention

[0005] The present invention provides an integral positioning and installation structure of a double-wall steel cofferdam and a short casing group and a construction method, which is convenient for construction, has high steel casing positioning accuracy, low material and cost investment, high efficiency, short construction period, and is safe and reliable.

[0006] The double-walled steel cofferdam and the short casing group integral positioning and installation structure of the present invention include an inverted corbel column (9) and a stiffening plate (10) respectively welded to the ends of a crossbeam (5) and a diagonal bracing member (6) during the assembly process of the steel cofferdam (1), the crossbeam (5) and at least two steel casings (2) are connected by a suspension rod (7), and adjacent steel casings (2) are welded by longitudinal parallel joints (4), transverse parallel joints (3) and connecting plates (8) to form a short casing group, and the short casing group and the steel cofferdam (1) form an integral whole.

[0007] The double-walled steel cofferdam and short casing group integral positioning and installation structure of the present invention, by integrally positioning and installing the short casing group and the steel cofferdam and launching the entire structure into water, changes the conventional process of steel casing insertion, positioning and extension into a land-based positioning and installation, which is beneficial to the control of positioning accuracy and installation quality, and changes the steel casing installation process from a critical process to a non-critical process. It can be constructed in parallel with underwater foundation pit blasting / excavation, thereby shortening the construction period.

[0008] In the above solution, preferably, the stiffening plate (10) is connected to the bottom of the inverted corbel column (9), the suspension rod (7) is hung on the beam, and the ends of the suspension rod (7) are welded to both sides of the top of the steel casing (2).

[0009] It can also be preferred that the inverted corbel column (9) is two-layer, and the crossbeam (5) is hoisted and placed on the upper inverted corbel column (9); one end of the diagonal brace (6) is welded to the crossbeam (5), and the other end is directly placed on the lower inverted corbel column (9).

[0010] It is also preferred that the longitudinal parallel joint (4) and the transverse parallel joint (3) are at least two layers each, and are respectively welded to the steel casing (2) via channel steel.

[0011] It is also preferred that a reserved gap is provided between the end of the crossbeam (5) and the steel cofferdam (1), and the width of the crossbeam (5) is smaller than the width of the inverted corbel column (9).

[0012] It is also preferred that the bottom of the steel casing (2) is sealed and poured with bottom concrete (12), and at least three annular anchoring ring bars (11) are welded at equal intervals on the outer wall of the steel casing (2) at the bottom concrete (12); and at least one anchoring ring bar (11) is fully welded to the outer wall of the steel casing (2).

[0013] The construction method of the above-mentioned double-wall steel cofferdam and short casing group integral positioning and installation structure of the present invention comprises the following steps:

[0014] The first step is to assemble and weld the double-walled steel cofferdam (1) in sections on land;

[0015] The second step is to roll the steel casing (2) and transport it to the construction site;

[0016] The third step is to weld the anchor ring reinforcement (11) on the outer wall of the steel casing (2), and weld the inverted corbel column (9) and the stiffening plate (10) on the inner wall of the steel cofferdam (1);

[0017] The fourth step is to hoist the steel casings (2) into place one by one, and hoist the crossbeam (5) onto the inverted corbel column (9);

[0018] The fifth step is to hang the steel casing (2) on the crossbeam (5), and weld the longitudinal parallel joints (4) and the transverse parallel joints (3) between the steel casings (2) to form a short casing group;

[0019] Step 6: Launch the steel cofferdam (1) and the short casing group into the water as a whole and float them to the pier position;

[0020] Step 7: The steel cofferdam (1) is connected to the high water injection and sunk, positioned, planted, anchored, and the foundation inside the steel cofferdam (1) is cleared;

[0021] In the eighth step, the bottom of the steel casing (2) is sealed, and bottom sealing concrete (12) is poured. After the bottom sealing concrete (12) reaches a preset strength, the suspension rod (7) is cut off and the crossbeam (5) is lifted out.

[0022] In the above scheme, it is preferred that, in the first step, when assembling the steel cofferdam (1), an unsealed closing opening is reserved on one side, and the closing opening is closed after the steel casing (2) is installed.

[0023] It is also preferred that, in the second step, the steel casing (2) is rolled into a cylindrical shape using a medium-thick steel plate, so that the diameter of the steel casing (2) is larger than the diameter of the pile foundation, the processing length of the steel casing (2) is larger than the preset thickness of the bottom sealing concrete (12), and at least two internal supports are arranged at equal intervals inside the steel casing (2).

[0024] It is also preferred that, in the fifth step, the bottom height of the steel casing (2) is made higher than the bottom height of the steel cofferdam (1).

[0025] It is also preferred that, in the eighth step, when the bottom of the steel casing (2) is sealed, the gap between the steel casing (2) and the riverbed is sealed using bagged sand bags or backfilled clay.

[0026] It is also preferred that in the eighth step, the suspension rod (7) suspended between the steel casing (2) and the cross beam (5) is cut underwater, and then the cross beam (5) and the diagonal bracing member (6) are lifted out from underwater by a lifting device.

[0027] The present invention can achieve the following beneficial effects:

[0028] The overall positioning and installation structure and construction method of the double-walled steel cofferdam and the short casing group of the present invention have the following specific advantages: (1) A construction method for the overall installation, positioning and launching of the short casing group and the double-walled steel cofferdam on land is proposed. Compared with the method of hoisting, inserting and fixing the steel casing on water, the process of steel casing installation is changed from a key process to a non-key process, shortening the total length of the key line, accelerating the process connection, and effectively guaranteeing the construction period; (2) With the short casing structure, the steel casing does not need to be raised above the water surface, saving a large amount of steel casing material and reducing the material cost investment; (3) The installation and positioning of the steel casing on water is changed to installation and positioning on land, providing a safe and reliable working environment for construction machinery, improving working efficiency, reducing safety risks, and reducing the performance of construction machinery. The requirements of the model are met, which reduces the investment in machinery costs; it overcomes the disadvantages of the existing technology in the construction of steel casings in water vibration sinking and ramming, such as the difficulty in controlling the positioning accuracy and verticality of the steel casing, the time-consuming and labor-intensive welding of each section, the poor welding quality, and the need to pour concrete or grouting reinforcement for the anchoring of the steel casing, and the convenient control of the positioning and verticality of the steel casing with high control accuracy; (4) The anchor ring reinforcement is welded on the outer wall of the steel casing to improve the bonding force between the steel casing and the bottom concrete, and improve the anti-floating and anti-sinking bearing capacity of the bottom concrete; and at least one anchor ring reinforcement is fully welded to effectively prevent water seepage at the joint between the steel casing and the bottom concrete in the later stage; (5) The flat joints fixed between the steel casings form a steel skeleton inside the bottom concrete, which improves the tensile strength and overall performance of the bottom concrete and reduces the safety risk during the foundation construction period of pumping construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0030] Figure 1 This is a plan view of the overall structure of the double-wall steel cofferdam and short casing group integral positioning and installation structure of the present invention.

[0031] Figure 2 It is a schematic diagram of the overall cross-sectional structure of the double-wall steel cofferdam and the short casing group integral positioning and installation structure of the present invention.

[0032] Figure 3 It is a schematic diagram of the longitudinal section structure of the overall positioning and installation structure of the double-wall steel cofferdam and the short casing group of the present invention.

[0033] Figure 4 It is an enlarged front view of the inverted corbel columns and stiffening plates of the integral positioning and installation structure of the double-wall steel cofferdam and the short casing group of the present invention.

[0034] Figure 5It is an enlarged side view of the inverted corbel columns and stiffening plates of the integral positioning and installation structure of the double-wall steel cofferdam and the short casing group of the present invention.

[0035] Figure 6 This is a schematic diagram of the first step of the construction method of the double-wall steel cofferdam and short casing group integral positioning and installation structure of the present invention.

[0036] Figure 7 This is a schematic diagram of the third step of the construction method of the double-wall steel cofferdam and short casing group integral positioning and installation structure of the present invention.

[0037] Figure 8 This is a schematic diagram of the fourth step of the construction method of the overall positioning and installation structure of the double-wall steel cofferdam and short casing group of the present invention.

[0038] Figure 9 This is a schematic diagram of the fifth step of the construction method of the double-wall steel cofferdam and short casing group integral positioning and installation structure of the present invention.

[0039] Figure 10 This is the first schematic diagram of the overall launching construction in the sixth step of the construction method of the overall positioning and installation structure of the double-wall steel cofferdam and the short casing group of the present invention.

[0040] Figure 11 This is a second schematic diagram of the overall launching construction in the sixth step of the construction method of the overall positioning and installation structure of the double-wall steel cofferdam and the short casing group of the present invention.

[0041] Figure 12 This is a schematic diagram of floating to the pier position in the sixth step of the construction method of the double-wall steel cofferdam and short casing group integral positioning installation structure of the present invention.

[0042] Figure 13 This is a schematic diagram of the seventh step of the construction method of the double-wall steel cofferdam and short casing group integral positioning installation structure of the present invention.

[0043] Figure 14 This is a schematic diagram of the eighth step of the construction method of the overall positioning and installation structure of the double-wall steel cofferdam and short casing group of the present invention.

[0044] In the figure, 1 is a steel cofferdam, 2 is a steel casing, 3 is a transverse parallel joint, 4 is a longitudinal parallel joint, 5 is a crossbeam, 6 is a diagonal brace, 7 is a hanger, 8 is a connecting plate, 9 is an inverted corbel column, 10 is a stiffening plate, 11 is an anchor ring reinforcement, 12 is a bottom seal concrete, 13 is a ground anchor, 14 is a winch, 15 is a pulley block, 16 is a cable breaker, 17 is an air bag, and 18 is a water level. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all 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.

[0046] The technical solutions provided by various embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0047] Example 1

[0048] A double-wall steel cofferdam and short casing group integral positioning installation structure, please see Figures 1 to 3 , including inverted corbel columns 9 and stiffening plates 10 welded to the ends of the crossbeam 5 and the diagonal bracing members 6 respectively during the assembly process of the steel cofferdam 1, the crossbeam 5 and at least two steel casings 2 are connected by a hanger 7, and adjacent steel casings 2 are welded by longitudinal parallel joints 4, transverse parallel joints 3 and connecting plates 8 to form a short casing group, which forms a whole with the steel cofferdam 1.

[0049] In this embodiment, the double-walled steel cofferdam and short casing group are integrally positioned and installed. Inverted corbels 9 are welded to the steel cofferdam 1, and crossbeams 5 are placed on the upper inverted corbels 9. One end of a diagonal brace 6 is supported at the bottom of the crossbeam 5, while the other end rests directly on the lower inverted corbel 9. The steel casings 2 are suspended from the crossbeams 5 via hangers 7. Longitudinal and transverse parallel connectors 4 and 3 connect the steel casings 2 and the steel cofferdam 1.

[0050] Example 2

[0051] The overall positioning and installation structure of the double-wall steel cofferdam and the short casing group of Example 1 is shown in FIG. Figure 4 and Figure 5 , the stiffening plate 10 is connected to the bottom of the inverted corbel column 9.

[0052] It can also be further that the inverted corbel column 9 is two layers, and the beam 5 is hoisted and placed on the upper inverted corbel column 9. Specifically, the end of the beam 5 is separated from the steel cofferdam 1 panel with a 5cm-10cm gap reserved, and the width of the beam 5 is 3-5cm smaller than the width of the inverted corbel column 9.

[0053] Furthermore, one end of the diagonal bracing member 6 is welded to the crossbeam 5 , and the other end is directly placed on the lower inverted corbel column 9 .

[0054] Furthermore, the suspension rod 7 is hung on the beam, and the ends of the suspension rod 7 are welded to both sides of the top of the steel casing 2.

[0055] Furthermore, the longitudinal parallel joint 4 and the transverse parallel joint 3 are respectively connected to the steel casing 2 by welding through channel steel.

[0056] Furthermore, the bottom of the steel casing 2 is sealed and poured with bottom concrete 12. At least three annular anchoring ring bars 11 are welded at equal intervals on the outer wall of the steel casing 2 at the bottom concrete 12. The anchoring ring bars 11 are threaded steel bars with high bonding strength. At least one anchoring ring bar (11) is fully welded to the outer wall of the steel casing (2).

[0057] Specifically, the inverted corbel column 9 is welded to the steel cofferdam 1 at a preset position according to the actual length of the steel casing 2, and the inverted corbel column 9 is reinforced with a stiffening plate 10 directly below the inverted corbel column 9. The crossbeam 5 is hoisted and placed on the inverted corbel column 9, and the crossbeam 5, the diagonal brace 6 and the inverted corbel column 9 are not welded or consolidated. This allows the crossbeam 5 and the diagonal brace 6 to be directly hoisted and removed by a crane before the pile foundation drilling construction after the steel cofferdam 1 is in place, thereby facilitating the pile foundation drilling.

[0058] After the crossbeam 5 is in place, one end of a diagonal brace 6 is welded directly below it. The other end of the diagonal brace 6 is placed directly on the lower inverted corbel column 9, facilitating the direct lifting of the crossbeam 5 later. The diagonal brace 6 reduces the span, stress, and deflection of the crossbeam 5. Furthermore, if the stress and deformation of the crossbeam 5 meet the design and specification requirements, the diagonal brace 6 and the lower inverted corbel column 9 can be eliminated.

[0059] Furthermore, the hanger 7 can be made of round steel material with good tensile strength, and can temporarily fix the height and plane position of the steel casing 2.

[0060] The longitudinal and transverse paralleling members 4 and 3 are each at least two layers, improving overall strength, rigidity, and stability. Furthermore, the number of layers of longitudinal and transverse paralleling members 4 and 3 can be determined based on the height of the steel casing 2, allowing individual steel casings 2 to be connected into a short, integrated cluster to enhance overall stability.

[0061] The above-described embodiment of the double-walled steel cofferdam and short casing group integrally positioned and installed structure specifically comprises a longitudinal cylindrical steel casing 2, at least two of which are arranged in a one-to-one correspondence with the pile foundation plan layout. The transverse paralleling member 3 comprises a longitudinal paralleling plate and two transverse paralleling plates, the two transverse paralleling plates evenly distributed above and below one side of the longitudinal paralleling plates. The longitudinal paralleling members 4 comprise horizontal and inclined connecting rods. Each longitudinal paralleling member 4 may comprise two horizontal connecting rods and two connecting rods cross-connected at the center, with the two horizontal connecting rods located above and below the two cross-connecting rods, respectively. The crossbeams 5 may be I-beams or H-beams, each of which may be formed by welding two parallel I-beams or H-beams. The diagonal braces 6 may be inclined rods. The hangers 7 may be longitudinal rods. The connecting plates 8 may be rectangular plates connected to the outer wall of the steel casing 2, connected to the ends of the longitudinal paralleling members 4, such as the ends of the horizontal and inclined connecting rods. The structure of the inverted corbel column 9 and the stiffening plate 10 is specifically that the inverted corbel column 9 is a transverse open hollow cylinder. The surface of the inverted corbel column 9 connecting to the steel cofferdam 1 is flat, and the surface overlapping the crossbeam 5 is an inclined surface. That is, the longitudinal cross-section of the inverted corbel column 9 is a right-angled trapezoid. To match this, the two end surfaces of the crossbeam 5 are inclined surfaces, and the longitudinal cross-section of the crossbeam 5 is an inverted trapezoid, preferably an inverted isosceles trapezoid. The stiffening plate 10 is a right-angled triangular plate, and its sides welded to the steel cofferdam 1 and the inverted corbel column 9 are right-angled sides.

[0062] Example 3

[0063] The construction method of the double-wall steel cofferdam and short casing group integral positioning and installation structure of the above embodiment includes the following steps:

[0064] See also Figure 6 ,The first step is to assemble and weld the double-walled steel cofferdam 1 in blocks on land;

[0065] The second step is to roll the steel casing 2 and transport it to the construction site;

[0066] See also Figure 7 The third step is to weld the anchor ring reinforcement 11 on the outer wall of the steel casing 2 and weld the inverted corbel column 9 and the stiffening plate 10 on the inner wall of the steel cofferdam 1;

[0067] See also Figure 8 , the fourth step is to hoist the steel casing 2 into place one by one, and hoist the beam 5 onto the inverted corbel column 9;

[0068] See also Figure 9 The fifth step is to hang the steel casing 2 on the beam 5, and weld the longitudinal parallel joints 4 and the transverse parallel joints 3 between the steel casings 2 to form a short casing group;

[0069] See also Figure 10 、 Figure 11 and Figure 12 In the sixth step, the steel cofferdam 1 and the short casing group are put into the water as a whole by using the cable-breaking airbag method on the ramp, and floated to the pier position;

[0070] See also Figure 13 , Step 7, connect the steel cofferdam 1 to the height and inject water to sink, position, plant and anchor it, and clean the foundation inside the steel cofferdam 1;

[0071] See also Figure 14 In the eighth step, the bottom of the steel casing 2 is sealed and the bottom concrete 12 is poured. After the bottom concrete 12 reaches the preset strength, the hanger 7 is cut off and the beam 5 is lifted out.

[0072] Example 4

[0073] In the construction method of the overall positioning and installation structure of the double-walled steel cofferdam and the short casing group of Example 3, in the first step, when assembling the steel cofferdam 1, an unclosed closing opening is reserved on one side, and the closing opening is closed after the steel casing 2 is installed.

[0074] Furthermore, in the second step, the steel casing 2 is rolled into a cylindrical shape using medium-thick steel plates, so that the diameter of the steel casing 2 is larger than the diameter of the pile foundation and the processed length of the steel casing 2 is larger than the preset thickness of the bottom sealing concrete 12.

[0075] Furthermore, in the second step, at least two inner supports are arranged at equal intervals inside the steel casing 2. Furthermore, the inner supports are cross-shaped steel sections.

[0076] Furthermore, in the third step, at least three anchoring ring bars 11 are welded at equal intervals on the outer wall of the steel casing 2 within the bottom concrete 12 ; and at least one anchoring ring bar 11 is fully welded to the outer wall of the steel casing 2 .

[0077] Furthermore, in the fifth step, the bottom height of the steel casing 2 is made higher than the bottom height of the steel cofferdam 1 .

[0078] Furthermore, in the eighth step, when the bottom of the steel casing 2 is blocked, the gap between the steel casing 2 and the riverbed is blocked by using bagged sand bags or backfilling clay.

[0079] Furthermore, in the eighth step, the suspension rod 7 suspended between the steel casing 2 and the cross beam 5 is cut underwater, and then the cross beam 5 and the diagonal bracing member 6 are lifted out from underwater by a lifting device.

[0080] During the specific construction, the construction method of the overall positioning and installation structure of the double-wall steel cofferdam and the short casing group can be summarized as follows: in the process of assembling the steel cofferdam 1, the steel casing 2 is first roughly positioned according to the designed position, and then the welding height of the inverted corbel column 9 is determined according to the actual height of the steel casing 2. The inverted corbel column 9 is welded to the inner wall of the steel cofferdam 1, and the stiffening plate 10 is located directly below the inverted corbel column 9; after the welding of the inverted corbel column 9 is completed and passed the inspection, the crossbeam 5 is hoisted and placed on the inverted corbel column 9, and then the diagonal bracing pieces 6 on both sides of the crossbeam 5 are connected to the crossbeam 5. The bottom of the beam 5 is welded; the steel casing 2 is connected to the crossbeam 5 by a hanger 7, which is in an inverted "U" shape. The hanger 7 is hooked on the crossbeam 5, and the position of the hanger 7 is adjusted according to the design position of the steel casing 2. The other end of the hanger 7 is fully welded to the steel casing 2 to locate and fix the elevation position of the steel casing 2; the longitudinal flat joints 4, transverse flat joints 3 and connecting plates 8 are used to weld between each steel casing 2 to connect and fix the steel casing 2 into a stable whole, and the short casing group and the steel cofferdam 1 are also fixed as a whole. Finally, after checking that the plane position and elevation of the steel casing 2 meet the requirements, the installation of the short casing group and the overall structure of the steel cofferdam is completed. Specifically, in the first step, when the steel cofferdam 1 is assembled, a closing opening is reserved on one side and is not closed, and it is used as an inlet and outlet for machinery, equipment and personnel. It is closed after the steel casing 2 is installed. In the second step, the steel casing 2 is rolled into a cylindrical shape using medium-thick steel plates. Furthermore, the diameter of the steel casing 2 is 30-40 cm larger than the diameter of the pile foundation, and the processing length of the steel casing 2 is 1.5-2.0 m larger than the designed thickness of the bottom concrete 12. In the second step, "cross" internal supports are set at equal intervals inside the steel casing 2 to prevent the steel casing 2 from deforming during stacking and transportation. In the third step, full welding is adopted between at least one anchor ring reinforcement 11 and the outer wall of the steel casing 2 to prevent water seepage at the joint between the steel casing 2 and the bottom concrete 12 in the later stage. In the fourth step, the role of the diagonal bracing member 6 is to reduce the deflection value of the beam 5 after bending, and the deflection deformation can also be controlled within the allowable range of the specification by increasing the bending stiffness of the beam 5. In this case, the diagonal bracing member 6 may not be set. In the fifth step, the bottom height of the steel casing 2 is 20-40cm higher than the bottom height of the steel cofferdam 1, and the height difference between the two is at least 20cm or 30cm, so as to avoid the impact of the local unevenness of the riverbed or the presence of raised parts on the sinking elevation and the landing effect of the short casing group and the steel cofferdam 1 when sinking and landing as a whole. At the same time, it can also avoid the bottom of the steel casing 2 cutting the airbag 17 when launching. In the sixth step, according to the actual situation of the construction site, mechanical equipment configuration, etc., the steel cofferdam 1 and the short casing group can be launched into the water by using large-scale lifting equipment as a whole, the airbag method of breaking the cable on the ramp, the slideway on the ramp, etc., which can ensure that after the steel cofferdam 1 is launched, the short casing group structure will not have open welding, weld falling off, obvious deformation of components, or tilting or falling off of the steel casing 2. In this embodiment, the airbag method of breaking the cable on the ramp is used for launching. Specifically, see Figure 10 and Figure 11After the steel cofferdam 1 and steel casing 2 are positioned and installed on the land-based working platform, a number of air bags 17 are evenly spaced at the bottom to support the overall weight of the cofferdam 1 and steel casing 2. The front winch 14 is first used to slowly pull the cofferdam 1 and steel casing 2 onto a slope with a certain downward slope. At the same time, to resist the horizontal component of the steel cofferdam 1's own weight on the slope, a ground anchor 13, a rear winch 14, and a pulley block 15 are installed at the rear end of the steel cofferdam 1 to secure it. The rear winch 14 is activated to slowly slide the steel cofferdam 1 to the water inlet. The cable cutter 17 is then activated, and the steel cofferdam 1 freely accelerates downward into the water under its own weight. It enters the water using inertia and gradually decelerates under the influence of water resistance until it stabilizes and floats. In the eighth step, the bottom of the steel casing 2 is sealed using bagged sandbags or backfilled with clay to tightly seal the gap between the steel casing 2 and the riverbed. This prevents concrete from flowing into the steel casing 2 during the bottom sealing process, thereby avoiding any impact on the subsequent pile foundation drilling construction. In the eighth step, underwater cutting is used to cut off all the suspension rods 7 hanging between the steel casing 2 and the beam 5, and then the beam 5 and the diagonal bracing member 6 are lifted out from underwater using lifting equipment, providing convenience for the pile foundation drilling construction.

[0081] The construction method of the double-walled steel cofferdam and short casing group integral positioning and installation structure of the above embodiment changes the installation process of the steel casing 2 from a critical process to a non-critical process, shortening the total length of the critical line and effectively ensuring the construction period; the short casing structure is adopted, and the steel casing 2 does not need to be raised above the water surface, saving a large amount of steel casing material and reducing material cost investment; the steel casing installation and positioning is changed from being installed on land to being installed on water, providing a safe and reliable working environment for construction machinery, improving work efficiency and reducing safety risks; the performance model requirements for construction machinery are reduced, and the machinery cost investment is reduced; and the positioning and verticality of the steel casing 2 are easy to control and have high control accuracy. The outer wall of the steel casing 2 is welded with anchor ring reinforcement 11, and the steel casing 2 has a high bonding strength with the bottom concrete 12, and the bottom concrete 12 has a high anti-floating and anti-sinking bearing capacity, and can effectively prevent water seepage at the joint between the steel casing 2 and the bottom concrete 12 in the later stage. The flat joints fixed between the steel casings 2 form a steel skeleton inside the bottom seal concrete 12, which improves the tensile strength and overall performance of the bottom seal concrete 12 and reduces the safety risk during the foundation foundation construction period of pumping construction.

[0082] The foregoing is merely an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A construction method for an integral positioning and installation structure of a double-walled steel cofferdam and a short casing group, characterized in that: The following steps are included: The first step is to assemble and weld the double-walled steel cofferdam (1) in blocks on land; The second step is to roll the steel casing (2) and transport it to the construction site; The third step is to weld the anchor ring reinforcement (11) to the outer wall of the steel casing (2), and to weld the inverted corbel column (9) and the stiffening plate (10) to the inner wall of the steel cofferdam (1); The fourth step is to hoist the steel casings (2) into place one by one, and to hoist the crossbeam (5) onto the inverted corbel column (9); The fifth step is to hang the steel casing (2) on the crossbeam (5), and weld the longitudinal parallel joints (4) and the transverse parallel joints (3) between the steel casings (2) to form a short casing group; Step 6: launching the steel cofferdam (1) and the short casing group as a whole into the water and floating them to the pier position; Step 7: The steel cofferdam (1) is raised and water is injected to sink, position, plant and anchor the cofferdam, and the foundation inside the steel cofferdam (1) is cleaned; Step 8: seal the bottom of the steel casing (2), pour the bottom sealing concrete (12), cut the suspension rod (7) after the bottom sealing concrete (12) reaches a preset strength, and lift out the crossbeam (5); In the first step, when assembling the steel cofferdam (1), an unsealed closing opening is reserved on one side, and the closing opening is closed after the steel casing (2) is installed; In the second step, the steel casing (2) is rolled into a cylindrical shape using a medium-thick steel plate, so that the diameter of the steel casing (2) is larger than the diameter of the pile foundation, the processed length of the steel casing (2) is larger than the preset thickness of the bottom sealing concrete (12), and at least two inner support members are evenly spaced inside the steel casing (2); In the fifth step, the bottom height of the steel casing (2) is made higher than the bottom height of the steel cofferdam (1); The steel cofferdam (1) is characterized in that the crossbeam (5) and at least two steel casings (2) are connected by a suspension rod (7), and adjacent steel casings (2) are welded by longitudinal parallel joints (4), transverse parallel joints (3) and connecting plates (8) to form a short casing group, and the short casing group and the steel cofferdam (1) form a whole; The stiffening plate (10) is connected to the bottom of the inverted corbel column (9), the suspension rod (7) is hung on the crossbeam, and the ends of the suspension rod (7) are welded to both sides of the top of the steel casing (2); The inverted corbel column (9) is two-layered, and the crossbeam (5) is hoisted and placed on the upper inverted corbel column (9); one end of the diagonal brace (6) is welded to the crossbeam (5), and the other end is directly placed on the lower inverted corbel column (9); The steel casings (2) are welded together by longitudinal flat joints (4), transverse flat joints (3) and connecting plates (8) to connect and fix the steel casings (2) into a stable whole, and the short casing group and the steel cofferdam (1) are also fixed into a whole; In the second step, the processed length of the steel casing (2) is 1.5 to 2.0 m greater than the designed thickness of the bottom seal concrete (12); In the fifth step, the bottom height of the steel casing (2) is 20 to 40 cm higher than the bottom height of the steel cofferdam (1), and the height difference between the two is at least 20 cm or 30 cm; By adopting a short casing structure, the steel casing (2) does not need to be raised above the water surface.

2. The construction method of the overall positioning and installation structure of the double-walled steel cofferdam and the short casing group as claimed in claim 1 is characterized in that: The longitudinal parallel connecting piece (4) and the transverse parallel connecting piece (3) are respectively at least two layers, and are respectively welded to the steel casing (2) via channel steel.

3. The construction method of the overall positioning and installation structure of the double-walled steel cofferdam and the short casing group as claimed in claim 1 is characterized in that: A reserved gap is provided between the end of the cross beam (5) and the steel cofferdam (1), and the width of the cross beam (5) is smaller than the width of the inverted corbel column (9).

4. The construction method of the overall positioning and installation structure of the double-walled steel cofferdam and the short casing group as claimed in claim 1 is characterized in that: The bottom of the steel casing (2) is sealed and poured with bottom sealing concrete (12); at least three annular anchor ring bars (11) are welded at equal intervals on the outer wall of the steel casing (2) at the bottom sealing concrete (12); and at least one anchor ring bar (11) is fully welded to the outer wall of the steel casing (2).

5. The construction method of the overall positioning and installation structure of the double-walled steel cofferdam and the short casing group as claimed in claim 1 is characterized in that: In the eighth step, the bottom of the steel casing (2) is sealed by using sand bags or backfilling clay to seal the gap between the steel casing (2) and the riverbed.

6. The construction method of the overall positioning and installation structure of the double-walled steel cofferdam and the short casing group as claimed in claim 1 is characterized in that: In the eighth step, the suspension rod (7) suspended between the steel casing (2) and the cross beam (5) is cut off underwater, and then the cross beam (5) and the diagonal bracing member (6) are lifted out from underwater by a lifting device.

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