An offshore cap-type assembled steel hanging box cofferdam and its design and construction method

Abstract

The present invention is an offshore pedestal assembled steel box cofferdam and its design and construction method. The assembled steel box cofferdam includes a cofferdam bottom plate, a cofferdam side wall and an inner support. The cofferdam bottom plate is assembled from a number of bottom plate modules, and the cofferdam side wall is assembled from four basic arc-shaped side wall units, a number of basic side wall units and a number of supplementary side wall units; the inner support is installed between the inner wall of the cofferdam side wall. The design method includes: the design of the cofferdam outer structure, the design of the cofferdam side wall, the design of the cofferdam bottom plate, the design of the cofferdam connection, and the design of other components of the pedestal cofferdam. The present invention innovatively solves the difficult problems of low turnover rate and high construction cost of cofferdams caused by the large number of pedestals and their different shapes and sizes in offshore bridges. The design process is scientific and efficient. The steel box cofferdam adopts assembly design and construction thinking to achieve high-quality construction of offshore pedestals.

Description

Technical Field

[0001] The invention relates to the technical field of foundation cofferdam construction, and in particular to an offshore foundation assembled steel hanging box cofferdam and a design and construction method thereof. Background Art

[0002] Most sea-crossing bridges are high-pile caps, and most caps are designed in a standardized manner, that is, the shape, elevation, and size of the caps should be as similar as possible. However, due to factors such as span adjustment and different geology, there are still many caps of the same shape and different sizes in the same section. For such a large number of caps of the same shape and different sizes, the design and construction of the cofferdam is difficult, and the traditional approach has the following disadvantages:

[0003] 1. The cofferdam is manufactured as a whole on the shore and transported to the site and installed by floating crane overall lifting method. It not only uses large-scale lifting equipment, but also the cofferdam is difficult to circulate and use, and the construction cost is high.

[0004] 2. The "pier platform method" for offshore bridges turns offshore construction into land construction. The cofferdams of the piers lack the idea of ​​overall design and construction in the entire section. They are manufactured in blocks on the shore and assembled on site, but the cofferdams between piers of different sizes cannot be used flexibly. Summary of the invention

[0005] The present invention aims to solve the deficiencies of the prior art and provides an offshore cap assembly type steel hanging box cofferdam and a design and construction method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An offshore cap-type assembled steel hanging box cofferdam comprises a cofferdam bottom plate, a cofferdam side wall and an inner support;

[0008] The cofferdam bottom plate is assembled from a number of bottom plate modules, and the adjacent bottom plate modules are connected by wet joints. A pile foundation reserved hole is opened on the bottom plate module at the position corresponding to the pile foundation casing. A number of embedded connectors are symmetrically arranged on both sides of the wet joint on the bottom plate module. A shear connection key is arranged between the bottom plate module and the pile foundation casing. A number of peripheral connectors are arranged on the periphery of the cofferdam bottom plate. An inner end tooth key is installed on the inner side of the upper surface of the peripheral connector, and an outer end tooth key is installed on the outer side.

[0009] The cofferdam side wall is installed between the inner end tooth key and the outer end tooth key on the upper surface of the cofferdam bottom plate. The cofferdam side wall is composed of four basic arc-shaped side wall units, a number of basic side wall units and a number of supplementary side wall units.

[0010] Internal support supports are installed between the inner walls of the cofferdam side walls.

[0011] The basic arc-shaped side wall unit, the basic side wall unit and the supplementary side wall unit all include an annular main beam, a number of vertical secondary beams are equidistantly arranged on the inner side of the annular main beam, a number of annular secondary beams are arranged from top to bottom on the inner side of the vertical secondary beam, a steel formwork is arranged on the inner side of the annular secondary beam, and spliced ​​channel steels are arranged at both ends of the annular main beam. The basic arc-shaped side wall unit, the basic side wall unit and the supplementary side wall unit are connected by bolts to connect the corresponding spliced ​​channel steels.

[0012] The peripheral connectors on the cofferdam bottom plate correspond one to one with the positions of the vertical secondary beams on the cofferdam side walls.

[0013] The above-mentioned design method of an offshore cap assembled steel hanging box cofferdam has the following specific steps:

[0014] S1. Collect the information of all caps in the bid section, including the size, top and bottom elevations of the caps, and classify the caps;

[0015] S2. Design of cofferdam shape and structure:

[0016] The inner wall plane size of each cofferdam side wall is 3-5mm larger than the contour line of each side of the cap. The height of the cofferdam side walls in the bidding section is the same, and can meet the water blocking and wave protection requirements during the construction of the cap with the highest top elevation in the bidding section;

[0017] S3. Design of cofferdam side wall:

[0018] The side walls of the cofferdam in the bidding section adopt standard modular design. Each side of the cap in the bidding section can be spliced ​​by basic arc side wall units, basic side wall units and supplementary side wall units.

[0019] The required size of the basic arc-shaped side wall unit is determined according to the form of the abutment, and the corresponding length is A0;

[0020] The number of types of supplementary side wall units required and the lengths of the basic side wall units and supplementary side wall units need to be calculated and determined. The determination steps are as follows:

[0021] ① List all the side lengths of the cap within the bid section. The same side length is listed only once, generating a column {l0};

[0022] ② Subtract the length A0 corresponding to the two basic arc-shaped side wall units from the side length of the abutment to generate a new column of length {l1};

[0023] ③ Set the length of the basic side wall unit to A1, where A1 ranges from 2m to 3m and A1 is the common divisor of the numbers in {l1};

[0024] ④ Divide each number in {l1} by A1 to get the number of divisible numbers, the number of non-divisible numbers, and the remainder value;

[0025] ⑤ When the number of divisible elements and the minimum value of the remainder both meet the target value, the number of divisible elements is not less than 25% of the total number, and the minimum value of the remainder is not less than 300, the division of the basic side wall unit is completed, otherwise repeat steps ②~⑤ until the requirements are met;

[0026] When a remainder a1 is the same as other remainders or can be obtained by adding or subtracting multiples of other remainders, remainder a1 is a resolvable remainder, and the remaining remainders are non-resolvable remainders;

[0027] ⑥ The number of types of supplementary side wall units is the total number of non-solution remainders; the length of the basic arc-shaped side wall unit is A0, the length of the basic side wall unit is A1, and the length of the supplementary side wall unit is the value of the remaining non-solution remainders;

[0028] S4. Design of cofferdam bottom plate:

[0029] The shape of the cofferdam bottom plate is consistent with the overall contour of the cap. The cofferdam bottom plate is assembled from several bottom plate modules, which are modular reinforced concrete plates. The size of a single bottom plate module is determined based on the comprehensive transportation and hoisting conditions. The thickness of a single bottom plate module is determined based on the buoyancy of the highest water level cofferdam and the lifting capacity of the lifting machinery. The reinforcement of a single bottom plate module meets the deformation and cracking requirements under high water level conditions, and a single bottom plate module contains at least half or one pile foundation reserved hole to ensure that the bottom plate module can achieve a self-stabilizing state on the embedded parts of the pile foundation casing. The bottom plate module is designed with embedded connectors, shear connectors, peripheral connectors, inner end tooth keys, and outer end tooth keys.

[0030] S5. Design of cofferdam connection:

[0031] Including the connection between the units of the cofferdam side wall, the connection between the cofferdam side wall and the cofferdam bottom plate, the connection between the bottom plate modules, and the connection between the bottom plate modules and the pile foundation casing;

[0032] S6. Design of other components of the cap cofferdam:

[0033] Including the design of internal supports and side panel connectors to meet the needs of support and connection.

[0034] In step S4, the outer contour line of the cofferdam bottom plate is translated outward by 500 mm compared to the total contour line of the cap; the diameter of the reserved hole for the pile foundation is 20 cm larger than the outer diameter of the pile foundation casing.

[0035] In step S5, the basic arc-shaped side wall unit, the basic side wall unit, and the supplementary side wall unit are connected back to back by bolts through splicing channel steels, two rows of bolt holes are reserved in the web of the splicing channel steels, and a layer of 2-3 mm vulcanized rubber is provided on the free surface of the splicing channel steels;

[0036] The cofferdam side wall and the cofferdam bottom plate are connected by bolts. The inner end tooth key on the peripheral connecting piece of the cofferdam bottom plate is installed first, and the outer end tooth key is installed after the cofferdam side wall is placed on the cofferdam bottom plate stably. Bolt holes are reserved at the corresponding positions of the inner end tooth key and the vertical secondary beam of the cofferdam side wall, and double-row bolts are used for connection. A layer of 2-3mm vulcanized rubber is set on the contact surface of the peripheral connecting piece of the cofferdam side wall and the cofferdam bottom plate;

[0037] Multiple sets of embedded connectors are set along the wet joints of adjacent floor modules. The spacing between embedded connectors shall not exceed 1.2m. Horizontal connectors are used to connect the embedded connectors and temporarily lock the adjacent floor modules to facilitate the pouring of wet joints.

[0038] A plurality of embedded parts are evenly arranged in the reserved holes for pile foundation of the base plate module, and the embedded parts and the pile foundation casing are connected by shear connection key welds.

[0039] The above-mentioned construction method of an offshore cap assembled steel hanging box cofferdam comprises the following specific steps:

[0040] P1. While the pile foundation casing is being constructed, the cofferdam parts are processed and manufactured;

[0041] P2. After the construction of pile foundation casing is completed, the construction platform is removed and the bracket is installed at a certain height of the pile foundation casing;

[0042] P3. Lift the base plate modules piece by piece; pour the wet joints between the base plate modules;

[0043] Adjacent bottom plate modules are fixedly connected by horizontal connectors, the bottom formwork of the wet joints is installed, the overlapping steel bars of the wet joints are welded, and the concrete of the wet joints is poured to connect the entire cofferdam bottom plate into a whole;

[0044] P4. Place a distribution beam on the top of the pile foundation casing and use a hanging structure to connect the distribution beam and the cofferdam bottom plate;

[0045] P5. Install the cofferdam side walls and internal supports;

[0046] The specific steps of installing the cofferdam side wall are as follows: the crane is located on the supporting trestle and lifts a group of basic side wall units to the air above the designed position; the manual auxiliary crane moves the lifted basic side wall units, aligns the vertical secondary beams of the basic side wall units with the peripheral connectors on the cofferdam bottom plate, and slowly lowers them; when the basic side wall units are about to touch the cofferdam bottom plate, the basic side wall units are pressed against the inner end tooth keys; after the basic side wall units are in place, the outer end tooth keys are installed, and the bolts of the outer end tooth keys and the vertical secondary beams are connected to complete the installation of a group of basic side wall units; the basic side wall units of adjacent groups are completed in the same way; the basic arc side wall units and supplementary side wall units are installed in the same way;

[0047] P6. Lift the steel box cofferdam; cut off the corbels; lower the steel box cofferdam to the designed bottom elevation;

[0048] When the steel box cofferdam is lowered into place, padding should be done between the cofferdam bottom plate and the pile foundation casing in time to ensure that the cofferdam does not swing;

[0049] P7. Weld shear connection keys at low tide to connect pile foundation casing and cofferdam bottom plate to complete system transformation; dismantle the hanging system and cut off the redundant pile foundation casing;

[0050] P8, pouring bottom concrete;

[0051] At low tide, the bottom plate of the cofferdam is sealed; after the sealing is completed, the connecting holes on the side wall of the cofferdam are opened, and the bottom concrete is poured at low tide;

[0052] P9. After the bottom concrete reaches the designed strength, close the connecting holes on the cofferdam side wall, drain the water in the cofferdam, and carry out the construction of the foundation in a water-free environment;

[0053] P10. The construction of the foundation is completed and the piers are constructed to a certain height. At low tide, the side walls of the cofferdam are removed and the shore site is cleaned up. After the side walls of the cofferdam are reassembled, steps P1-P9 are repeated to move on to the construction of the next foundation.

[0054] In step P1, the processing quantity of each part of the cofferdam is determined according to the number of times each component is assembled and used in rotation. The processing quantity of each component of the cofferdam can ensure the requirements of on-site construction organization and schedule arrangement.

[0055] In step P2, a number of corbels are evenly arranged around each pile foundation casing, and all the corbels arranged on each pile foundation casing can stably support all the cofferdam bottom plates; the bottom surface of the corbels is higher than the high tide water level during the construction period.

[0056] In step P8, if the cofferdam deadweight + tensile strength of the shear connection key weld + the bond strength after pouring concrete between the cofferdam bottom plate and the pile foundation casing is ≥ the maximum water level buoyancy and there is a certain safety factor, the stage of pouring the bottom sealing concrete can be omitted, and only the concrete pouring operation between the cofferdam bottom plate and the pile foundation casing needs to be completed.

[0057] The beneficial effects of the present invention are as follows: the present invention innovatively solves the difficult problems of low turnover rate and high construction cost of cofferdams caused by a large number of piers and their different shapes and sizes in offshore bridges. The design process is scientific and efficient, and the steel hanging box cofferdam adopts assembly design and construction thinking to achieve high-quality construction of offshore piers. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a structural elevation view of the assembled steel hanging box cofferdam of the present invention;

[0059] Figure 2 It is a top view of the structure of the assembled steel hanging box cofferdam of the present invention;

[0060] Figure 3 It is a plan view of the cofferdam bottom plate of the assembled steel hanging box cofferdam of the present invention;

[0061] Figure 4 It is a structural schematic diagram of a basic side wall unit of the assembled steel hanging box cofferdam of the present invention;

[0062] Figure 5 It is a structural schematic diagram of a basic arc-shaped side wall unit of an assembled steel hanging box cofferdam of the present invention;

[0063] Figure 6 A reinforcement diagram of a bottom plate module of one form of the assembled steel hanging box cofferdam of the present invention;

[0064] Figure 7 A reinforcement diagram of another form of bottom plate module of the assembled steel hanging box cofferdam of the present invention;

[0065] Figure 8 It is a schematic diagram of step P5 of the offshore cap assembly steel hanging box cofferdam construction method of the present invention;

[0066] Fig. 9 It is a schematic diagram of step P8 of the offshore cap assembly steel hanging box cofferdam construction method of the present invention;

[0067] In the figure: 1-cofferdam bottom plate; 2-cofferdam side wall; 3-inner support; 4-pile foundation casing; 5-cap; 6-bottom sealing concrete; 7-pile foundation; 8-corbel; 9-distribution beam; 10-hanging structure;

[0068] 101-base module; 102-wet joint; 103-pre-pile foundation hole; 104-embedded connector; 105-shear connector key; 106-peripheral connector; 107-inner end tooth key; 108-outer end tooth key;

[0069] 201-basic arc side wall unit; 202-basic side wall unit; 203-supplementary side wall unit; 204-circumferential main beam; 205-vertical secondary beam; 206-circumferential secondary beam; 207-steel formwork; 208-jointed channel steel;

[0070] The following is a detailed description of the embodiments of the present invention with reference to the accompanying drawings. DETAILED DESCRIPTION

[0071] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The embodiments are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the accompanying drawings in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0072] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0074] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0075] An offshore cap-type assembled steel box cofferdam comprises a cofferdam bottom plate 1, a cofferdam side wall 2 and an inner support 3.

[0076] The cofferdam bottom plate 1 is assembled from a plurality of bottom plate modules 101, and adjacent bottom plate modules 101 are connected by wet joints 102. A pile foundation reserved hole 103 is provided on the bottom plate module 101 at a position corresponding to the pile foundation casing 4. A plurality of embedded connectors 104 are symmetrically provided on both sides of the wet joint 102 on the bottom plate module 101. A shear connection key 105 is provided between the bottom plate module 101 and the pile foundation casing 4. A plurality of peripheral connectors 106 are provided on the periphery of the cofferdam bottom plate 1, and an inner end tooth key 107 is installed on the inner side of the upper surface of the peripheral connector 106, and an outer end tooth key 108 is installed on the outer side.

[0077] The cofferdam side wall 2 is installed between the inner end tooth key 107 and the outer end tooth key 108 on the upper surface of the cofferdam bottom plate 1. The cofferdam side wall 2 is composed of four basic arc-shaped side wall units 201, a plurality of basic side wall units 202 and a plurality of supplementary side wall units 203.

[0078] The basic arc-shaped side wall unit 201, the basic side wall unit 202, and the supplementary side wall unit 203 all include an annular main beam 204, a plurality of vertical secondary beams 205 are equidistantly arranged on the inner side of the annular main beam 204, a plurality of annular secondary beams 206 are arranged on the inner side of the vertical secondary beams 205 from top to bottom, a steel formwork 207 is arranged on the inner side of the annular secondary beam 206 (the inner side is toward the side of the pedestal 5, and the outer side is away from the side of the pedestal 5), and splicing channel steels 208 are arranged at both ends of the annular main beam 204, and the corresponding splicing channel steels 208 are connected by bolts between the basic arc-shaped side wall unit 201, the basic side wall unit 202, and the supplementary side wall unit 203.

[0079] The positions of the peripheral connecting pieces 106 on the cofferdam bottom plate 1 and the vertical secondary beams 205 of the cofferdam side walls 2 correspond one to one.

[0080] The inner support 3 is supported and installed between the inner walls of the cofferdam side wall 2.

[0081] The above-mentioned design method of an offshore cap assembled steel hanging box cofferdam has the following specific steps:

[0082] S1. Collect the information of all capping platforms 5 in the bid section, including the size, top and bottom elevations of the capping platforms 5, and classify the capping platforms 5.

[0083] For example, there are five types of pedestals 5 within the section, with dimensions of 20.1×13.2m, 14.6×14.6m, 16×12.8m, 14.6×10.1m, and 14.6m×9.6m, and the chamfer radius is 1.8m.

[0084] S2. Design of cofferdam shape and structure:

[0085] The inner wall plane size of each cofferdam side wall 2 is 3-5mm larger than the contour line of each side of the pedestal 5. The height of the cofferdam side walls 2 in the section is the same and can meet the water-blocking and wave-proof requirements during the construction of the pedestal 5 with the highest top elevation in the section.

[0086] The bottom elevation of the cofferdam side wall 2 = the bottom elevation of the designed pedestal 5 - the thickness of the bottom concrete 6 - the thickness of the cofferdam bottom plate 1; the top elevation of the cofferdam side wall 2 = the high tide level once in 10 years (+4.54m) + the wave height H1% once in 10 years (3.9m) / 2 + the safety distance (0.5m-1m); according to the designed top and bottom elevations of the pedestal 5 in the section, calculate the top and bottom height difference of the cofferdam side wall 2 of each pedestal 5, and take the larger value as the unified height of the prefabricated steel box cofferdam. The height of the steel box cofferdam in this case is calculated to be 7.7m.

[0087] S3. Design of cofferdam side wall 2:

[0088] The cofferdam side wall 2 in the bid section adopts a standard modular design, and each side of the inner cap 5 of the bid section can be spliced ​​by the basic arc-shaped side wall unit 201, the basic side wall unit 202, and the supplementary side wall unit 203;

[0089] The required size of the basic arc-shaped side wall unit 201 is determined according to the form of the platform 5, and the corresponding length A0;

[0090] The number of types of the required supplementary side wall units 203 and the lengths of the basic side wall units 202 and the supplementary side wall units 203 need to be calculated and determined. The determination steps are as follows:

[0091] ① List all the side lengths of the cap 5 in the bid section. The same side length is listed only once, generating a column {l0};

[0092] In this embodiment, {l0}={20100, 14600, 16000, 13200, 12800, 10100, 9600}, and the length units are all in mm;

[0093] ② Subtract the length A0 corresponding to the two basic arc-shaped side wall units 201 from the side length of the platform 5. In this embodiment, A0 is 2300, 2A0=4600, and a new column length {l1} is generated;

[0094] In this embodiment, {l1}={15500, 10000, 11400, 8600, 8200, 5500, 5000};

[0095] ③ Set the length of the basic side wall unit 202 to A1, wherein the range of A1 is 2m-3m, and A1 is the common divisor of the numbers in {l1};

[0096] In this embodiment, A1 is set to 2500;

[0097] ④ Divide each number in {l1} by A1 to get the number of divisible numbers, the number of non-divisible numbers, and the remainder value;

[0098] In this embodiment, the numbers in {l1} are divided by A1, and the results are {6.2, 4, 4.56, 3.44, 3.28, 2.2, 2}, where the number that is divisible is 2, the number that is not divisible is 5, and the remainder values ​​are 500, 1400, 1100, 700, 500 respectively;

[0099] ⑤ When the number of divisible elements and the minimum value of the remainder both meet the target value, the number of divisible elements is not less than 25% of the total number, and the minimum value of the remainder is not less than 300, the division of the basic side wall unit 202 is completed, otherwise, steps ② to ⑤ are repeated until the requirements are met;

[0100] In this embodiment, the number of divisible units / the total number=2 / 7=0.28, which is greater than 25% and meets the requirement; the minimum value of the remainder is 500, which is not less than 300 and also meets the requirement, and the division of the basic side wall unit 202 is completed, that is, the length A1 of the basic side wall unit 202 is determined to be 2500;

[0101] When a remainder a1 is the same as other remainders or can be obtained by adding or subtracting multiples of other remainders, remainder a1 is a resolvable remainder, and the remaining remainders are non-resolvable remainders;

[0102] In this embodiment, since the remainder 1400 can be obtained by multiplying another remainder 700 by 2, 1400 is considered to be a solvable remainder. Since there are two remainders 500, only one can be taken. Therefore, 500, 1100, and 700 are non-solvable remainders.

[0103] ⑥ The number of types of supplementary side wall units 203 is the total number of non-solution remainders; the length of the basic arc-shaped side wall unit 201 is A0, the length of the basic side wall unit 202 is A1, and the lengths of the supplementary side wall units 203 are the values ​​of the remaining non-solution remainders.

[0104] In this embodiment, there are three types of supplementary side wall units 203, and the lengths thereof are 500, 1100, and 700 respectively.

[0105] The calculation process is detailed in Table 1.

[0106] Table 1

[0107]

[0108] S4. Design of cofferdam bottom plate 1:

[0109] The shape of the cofferdam bottom plate 1 is consistent with the overall contour shape of the pedestal 5, and the outer contour line of the cofferdam bottom plate 1 is translated 500 mm outwards than the overall contour line of the pedestal 5.

[0110] The cofferdam bottom plate 1 is assembled by a number of bottom plate modules 101, and the bottom plate module 101 is a modular reinforced concrete slab; the size of a single bottom plate module 101 is determined by comprehensive transportation and hoisting conditions, and the thickness of a single bottom plate module 101 is determined by comprehensive consideration of the buoyancy of the highest water level cofferdam and the lifting capacity of the lifting machinery. The reinforcement of a single bottom plate module 101 meets the deformation and cracking requirements under high water level conditions, and a single bottom plate module 101 contains at least half or one pile foundation reserved hole 103 to ensure that the bottom plate module 101 can achieve a self-stabilizing state on the embedded parts of the pile foundation casing 4; the bottom plate module 101 is designed with embedded connectors 104, shear connector keys 105, peripheral connectors 106, inner end tooth keys 107, and outer end tooth keys 108.

[0111] When the pile foundation 7 is arranged in a plum blossom shape, the single base plate module 101 should include at least half of the pile foundation reserved hole 103; when the pile foundation 7 is arranged in a rectangular shape, the single base plate module 101 should include at least one pile foundation reserved hole 103; the diameter of the pile foundation reserved hole 103 is 20 cm larger than the outer diameter of the pile foundation casing 4.

[0112] The base plate module 101 is pre-buried with peripheral connectors 106 spliced ​​with the cofferdam side wall 2, and the positions of the peripheral connectors 106 and the vertical secondary beams 205 of the cofferdam side wall 2 correspond one to one; the base plate module 101 is pre-set with a number of embedded parts along the pile foundation reserved holes 103, and the cofferdam base plate 1 is connected to the pile foundation casing 4 through the shear connection key 105; a number of pre-embedded connectors 104 are pre-set along the corresponding wet joints 102 between the base plate modules 101, and the base plate modules 101 are later connected by horizontal connectors to achieve relative fixation between the base plate modules 101.

[0113] The thickness of the bottom plate module 101 is determined comprehensively depending on the buoyancy of the cofferdam at the highest water level and the lifting capacity of the lifting machinery; in this embodiment, the thickness of the bottom plate module 101 is 20 cm. After the bottom plate module 101 is connected as a whole, it should be able to resist the negative bending moment caused by the maximum buoyancy; and when the self-weight of the cofferdam (the sum of the steel structures such as the cofferdam bottom plate 1 and the cofferdam side wall 2) + the tensile strength of the shear connection key 105 weld + the bond strength of the poured concrete between the cofferdam bottom plate 1 and the pile foundation casing 4 ≥ the maximum water level buoyancy and there is a certain safety factor, the bottom sealing concrete 6 can be omitted.

[0114] S5. Design of cofferdam connection:

[0115] It includes the connection between the units of the cofferdam side wall 2 , the connection between the cofferdam side wall 2 and the cofferdam bottom plate 1 , the connection between the bottom plate modules 101 , and the connection between the bottom plate modules 101 and the pile foundation casing 4 .

[0116] The basic arc-shaped side wall unit 201, the basic side wall unit 202 and the supplementary side wall unit 203 are connected back to back with bolts through the splicing channel steel 208, and the bolt holes are completely corresponding, so they are effectively connected by bolts; two rows of bolt holes are reserved in the upper and lower webs of the splicing channel steel 208, and a layer of 2-3mm vulcanized rubber is provided on the free surface of the splicing channel steel 208 to increase the water tightness of the steel formwork 207.

[0117] The cofferdam side wall 2 and the cofferdam bottom plate 1 are connected by bolts. The inner end tooth key 107 on the peripheral connecting piece 106 of the cofferdam bottom plate 1 is installed first, and the outer end tooth key 108 is installed after the cofferdam side wall 2 is placed on the cofferdam bottom plate 1 stably; bolt holes are reserved at the corresponding positions of the inner end tooth key 107 and the vertical secondary beam 205 of the cofferdam side wall 2, and double-row bolts are used for connection. A layer of 2-3mm vulcanized rubber is provided on the contact surface of the peripheral connecting piece 106 between the cofferdam side wall 2 and the cofferdam bottom plate 1 to increase the water tightness of the bottom and side joints.

[0118] Multiple groups of embedded connectors 104 are correspondingly arranged along the wet joints 102 of adjacent floor modules 101 . The spacing between the embedded connectors 104 does not exceed 1.2 m. Horizontal connectors are used to connect the embedded connectors 104 to temporarily lock the adjacent floor modules 101 for pouring the wet joints 102 .

[0119] A plurality of embedded parts are evenly arranged in the pile foundation reserved holes 103 of the base plate module 101 , and the embedded parts are connected to the pile foundation casing 4 by welding with a shear connection key 105 .

[0120] S6. Design of other components of the cap cofferdam:

[0121] Including the design of components such as internal support 3 and side panel connectors to meet the needs of support and connection.

[0122] The above-mentioned construction method of an offshore cap assembled steel hanging box cofferdam comprises the following specific steps:

[0123] While P1 and pile foundation casing 4 are being constructed, various parts of the cofferdam are being processed and manufactured;

[0124] The processing quantity of each part of the cofferdam is determined according to the number of times each component is assembled and used. The processing quantity of each component of the cofferdam can ensure the requirements of on-site construction organization and schedule arrangement.

[0125] After the construction of P2 and pile foundation casing 4 is completed, the construction platform is removed and the bracket 8 is installed at a certain height of the pile foundation casing 4;

[0126] A number of corbels 8 are evenly arranged around each pile foundation casing 4, and all the corbels 8 arranged on each pile foundation casing 4 can stably support all the cofferdam bottom plates 1; the bottom surface of the corbels 8 is higher than the high tide water level during the construction period.

[0127] P3, hoisting the bottom plate modules 101 piece by piece; pouring the wet joints 102 between the bottom plate modules 101;

[0128] Adjacent bottom plate modules 101 are fixedly connected by horizontal connectors, the bottom formwork of the wet joint 102 is installed, the overlapping steel bars of the wet joint 102 are welded and connected, and concrete of the wet joint 102 is poured to connect the entire cofferdam bottom plate 1 into a whole.

[0129] P4. Place a distribution beam 9 on the top of the pile foundation casing 4, and use a hanging structure 10 to connect the distribution beam 9 and the cofferdam bottom plate 1.

[0130] P5. Install the cofferdam side wall 2 and the inner support 3;

[0131] The specific steps of installing the cofferdam side wall 2 are as follows: the crane is located on the supporting trestle and lifts a group of basic side wall units 202 to the air above the designed position; the manual auxiliary crane moves the lifted basic side wall units 202, aligns the vertical secondary beams 205 of the basic side wall units 202 with the peripheral connectors 106 on the cofferdam bottom plate 1, and slowly lowers them; when the basic side wall units 202 are about to touch the cofferdam bottom plate 1, the basic side wall units 202 are pressed against the inner end tooth keys 107; after the basic side wall units 202 are in place, the outer end tooth keys 108 are installed, and the bolts of the outer end tooth keys 108 and the vertical secondary beams 205 are connected to complete the installation of a group of basic side wall units 202; in the same way, the basic side wall units 202 of the adjacent groups are completed; in the same way, the installation of the basic arc-shaped side wall units 201 and the supplementary side wall units 203 is completed;

[0132] One or more basic side wall units 202, basic arc-shaped side wall units 201, and supplementary side wall units 203 can be hoisted at the same time, and their weight should be less than the hoisting capacity of the hoisting equipment.

[0133] P6, lift the steel box cofferdam; cut off the corbel 8; lower the steel box cofferdam to the designed bottom elevation;

[0134] When the steel hanging box cofferdam is lowered into place, padding is performed between the cofferdam bottom plate 1 and the pile foundation casing 4 in time to ensure that the cofferdam does not swing.

[0135] P7. At low tide, weld the shear connection key 105 to connect the pile foundation casing 4 and the cofferdam bottom plate 1 to complete the system transformation; dismantle the hanging system and cut off the excess pile foundation casing 4.

[0136] P8, pouring bottom concrete 6;

[0137] At low tide, the bottom plate 1 of the cofferdam is plugged; after the plugging is completed, the connecting hole of the cofferdam side wall 2 is opened, and the bottom sealing concrete 6 is poured at low tide;

[0138] For example, when the deadweight of the cofferdam + the tensile strength of the weld of the shear connection key 105 + the bond strength after pouring concrete between the cofferdam bottom plate 1 and the pile foundation casing 4 is ≥ the maximum water level buoyancy and there is a certain safety factor, the stage of pouring the bottom sealing concrete 6 can be omitted, and only the concrete pouring operation between the cofferdam bottom plate 1 and the pile foundation casing 4 needs to be completed.

[0139] P9. After the bottom seal concrete 6 reaches the designed strength, the connecting holes of the cofferdam side wall 2 are closed, the water in the cofferdam is drained, and the construction of the foundation 5 is carried out in a waterless environment.

[0140] P10, the construction of the cap 5 is completed and the pier is constructed to a certain height; at low tide, the cofferdam side wall 2 is removed and the shore site is cleaned; after the cofferdam side wall 2 is reassembled, steps P1-P9 are repeated to turn to the construction of the next cap 5.

[0141] The present invention innovatively solves the problem of low turnover rate of cofferdams and high construction costs caused by a large number of caps 5 with different shapes and sizes in offshore bridges.

[0142] In the present invention, the cofferdam bottom plate 1 is designed as a reinforced concrete bottom plate, and the cofferdam bottom plate 1 is modularly designed and constructed, which reduces the lifting weight. By selecting a suitable thickness, the bottom concrete 6 can be free of sealing, which reflects obvious economic advantages in terms of materials, construction equipment, structure, etc.

[0143] In the present invention, the cofferdam bottom plate 1 adopts a reinforced concrete structure, which is beneficial to the long-term corrosion protection of the offshore cap 5 and improves the durability of the structure.

[0144] The length design process of the cofferdam side wall 2 in the present invention is scientific and efficient, and only 2-3 simple trial calculations are required to obtain the optimal solution suitable for the size of the pedestal 5 in the entire section.

[0145] The steel hanging box cofferdam in the present invention adopts assembly design and construction thinking, and makes full use of the existing piers and platforms to achieve high-quality construction of the offshore pier 5, which meets the core requirements of the national dual carbon strategy.

[0146] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made using the method concept and technical solution of the present invention, or are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A design method for an offshore cap assembly steel box cofferdam, characterized in that: The offshore capping platform assembled steel hanging box cofferdam comprises a cofferdam bottom plate (1), a cofferdam side wall (2) and an inner support (3); the cofferdam bottom plate (1) is assembled from a plurality of bottom plate modules (101), adjacent bottom plate modules (101) are connected via wet joints (102), pile foundation reserved holes (103) are provided on the bottom plate modules (101) at positions corresponding to pile foundation casings (4), and a plurality of embedded connecting pieces (103) are symmetrically provided on the bottom plate modules (101) on both sides of the wet joints (102). 4), a shear connection key (105) is provided between the bottom plate module (101) and the pile foundation casing (4), a plurality of peripheral connection members (106) are provided on the periphery of the cofferdam bottom plate (1), an inner end tooth key (107) is installed on the inner side of the upper surface of the peripheral connection member (106), and an outer end tooth key (108) is installed on the outer side; the cofferdam side wall (2) is installed between the inner end tooth key (107) and the outer end tooth key (108) on the upper surface of the cofferdam bottom plate (1), and the cofferdam side wall (2) is composed of four base The arc-shaped side wall unit (201), a plurality of basic side wall units (202) and a plurality of supplementary side wall units (203) are spliced ​​together; the basic arc-shaped side wall unit (201), the basic side wall unit (202) and the supplementary side wall unit (203) all comprise an annular main beam (204), a plurality of vertical secondary beams (205) are equidistantly arranged inside the annular main beam (204), a plurality of annular secondary beams (206) are arranged from top to bottom inside the vertical secondary beams (205), and the annular secondary beams (206) are provided inside the annular secondary beams (206). A steel formwork (207) is provided on the side, and spliced ​​channel steels (208) are provided at both ends of the annular main beam (204); the corresponding spliced ​​channel steels (208) are connected between the basic arc-shaped side wall unit (201), the basic side wall unit (202), and the supplementary side wall unit (203) by bolts; the inner support (3) is supported and installed between the inner walls of the cofferdam side wall (2); the peripheral connecting pieces (106) on the cofferdam bottom plate (1) correspond to the positions of the vertical secondary beams (205) of the cofferdam side wall (2); The specific steps of the design are: S1. Collecting information on all caps (5) within the bid section, including the size, top and bottom elevations of the caps (5), and classifying the caps (5); S2. Design of cofferdam shape and structure: The inner wall plane size of each cofferdam side wall (2) is 3-5 mm larger than the contour line of each side of the cap (5); the height of the cofferdam side walls (2) in the bid section is the same, and can meet the water blocking and wave protection requirements during the construction of the cap (5) with the highest top elevation in the bid section; S3. Design of cofferdam sidewall (2): The side wall (2) of the cofferdam in the bid section adopts a standard modular design, and each side of the inner cap (5) of the bid section can be spliced ​​by a basic arc-shaped side wall unit (201), a basic side wall unit (202), and a supplementary side wall unit (203); The required size of the basic arc-shaped side wall unit (201) is determined according to the form of the support platform (5), and the corresponding length A0; The number of types of the required supplementary side wall units (203) and the lengths of the basic side wall units (202) and the supplementary side wall units (203) all need to be calculated and determined. The determination steps are as follows: ① List all the side lengths of the cap (5) in the section, with the same side length listed only once, to generate a column {l0}; ② Subtract the length A0 corresponding to the two basic arc-shaped side wall units (201) from the side length of the abutment (5) to generate a new column length {l1}; ③ Setting the length of the basic side wall unit (202) to A1, wherein the range of A1 is 2m-3m, and A1 is the common divisor of the numbers in {l1}; ④ Divide each number in {l1} by A1 to get the number of divisible numbers, the number of non-divisible numbers, and the remainder value; ⑤ When the number of divisible elements and the minimum value of the remainder both meet the target values, the number of divisible elements is not less than 25% of the total number, and the minimum value of the remainder is not less than 300, the division of the basic side wall unit (202) is completed, otherwise, steps ② to ⑤ are repeated until the requirements are met; When a remainder a1 is the same as other remainders or can be obtained by adding or subtracting multiples of other remainders, remainder a1 is a resolvable remainder, and the remaining remainders are non-resolvable remainders; ⑥ The number of types of the supplementary side wall units (203) is the total number of non-solution remainders; the length of the basic arc-shaped side wall unit (201) is A0, the length of the basic side wall unit (202) is A1, and the lengths of the supplementary side wall units (203) are the values ​​of the remaining non-solution remainders; S4. Design of cofferdam bottom plate (1): The shape of the cofferdam bottom plate (1) is consistent with the overall contour shape of the cap (5). The cofferdam bottom plate (1) is assembled by a plurality of bottom plate modules (101), and the bottom plate module (101) is a modular reinforced concrete plate. The size of a single bottom plate module (101) is determined based on comprehensive transportation and hoisting conditions. The thickness of a single bottom plate module (101) is determined based on the buoyancy of the cofferdam at the highest water level and the lifting capacity of the lifting machinery. The reinforcement of a single bottom plate module (101) meets the deformation and cracking requirements under high water level conditions, and a single bottom plate module (101) includes at least half or one pile foundation reserved hole (103) to ensure that the bottom plate module (101) can achieve a self-stabilizing state on the embedded parts of the pile foundation casing (4). The bottom plate module (101) is designed with embedded connectors (104), shear connectors (105), peripheral connectors (106), inner end tooth keys (107), and outer end tooth keys (108). S5. Design of cofferdam connection: It includes connections between units of the cofferdam side wall (2), connections between the cofferdam side wall (2) and the cofferdam bottom plate (1), connections between the bottom plate modules (101), and connections between the bottom plate modules (101) and the pile foundation casing (4); S6. Design of other components of the cap cofferdam: The design of the inner support (3) and the side panel connector meets the requirements of support and connection.

2. The design method of an offshore cap assembly steel box cofferdam according to claim 1 is characterized in that: In step S4, the outer contour line of the cofferdam bottom plate (1) is translated outward by 500 mm relative to the overall contour line of the cap (5); and the diameter of the pile foundation reserved hole (103) is 20 cm larger than the outer diameter of the pile foundation casing (4).

3. The design method of an offshore cap assembly steel box cofferdam according to claim 2 is characterized in that: In step S5, the basic arc-shaped side wall unit (201), the basic side wall unit (202), and the supplementary side wall unit (203) are connected back to back by bolts through the splicing channel steel (208), two rows of bolt holes are reserved in the web of the splicing channel steel (208), and a layer of vulcanized rubber with a thickness of 2-3 mm is provided on the free surface of the splicing channel steel (208); The cofferdam side wall (2) and the cofferdam bottom plate (1) are connected by bolts. The inner end tooth key (107) on the peripheral connecting piece (106) of the cofferdam bottom plate (1) is installed first, and the outer end tooth key (108) is installed after the cofferdam side wall (2) is placed on the cofferdam bottom plate (1) stably. Bolt holes are reserved at the corresponding positions of the inner end tooth key (107) and the vertical secondary beam (205) of the cofferdam side wall (2). Double-row bolts are used for connection. A layer of vulcanized rubber with a thickness of 2-3 mm is provided on the contact surface of the peripheral connecting piece (106) of the cofferdam side wall (2) and the cofferdam bottom plate (1). A plurality of sets of embedded connectors (104) are correspondingly arranged along the wet joints (102) of adjacent floor modules (101), the spacing between the embedded connectors (104) does not exceed 1.2 m, and the embedded connectors (104) are fixedly connected by horizontal connectors to temporarily lock the adjacent floor modules (101) so as to facilitate the pouring of the wet joints (102); A plurality of embedded parts are evenly arranged in the pile foundation reserved holes (103) of the bottom plate module (101), and the embedded parts and the pile foundation casing (4) are connected by welding using shear connection keys (105).

4. A construction method for an offshore cap assembly steel hanging box cofferdam, characterized in that: The offshore cap assembled steel box cofferdam is designed by using the design method of the offshore cap assembled steel box cofferdam as claimed in claim 1; The specific steps are: P1. While the pile foundation casing (4) is being constructed, the various parts of the cofferdam are processed and manufactured; After the construction of P2 and the pile foundation casing (4) is completed, the construction platform is removed and a bracket (8) is installed at a certain height of the pile foundation casing (4); P3, hoisting the bottom plate modules (101) piece by piece; pouring the wet joints (102) between the bottom plate modules (101); Adjacent bottom plate modules (101) are fixedly connected using horizontal connectors, the bottom formwork of the wet joint (102) is installed, the overlapping steel bars of the wet joint (102) are welded and connected, and concrete of the wet joint (102) is poured to connect the entire cofferdam bottom plate (1) into a whole; P4. placing a distribution beam (9) on the top of the pile foundation casing (4), and connecting the distribution beam (9) and the cofferdam bottom plate (1) using a hanging structure (10); P5. Install the cofferdam side walls (2) and inner supports (3); The specific steps of installing the cofferdam side wall (2) are as follows: a crane is located on a supporting trestle bridge and lifts a group of basic side wall units (202) to the air above the designed position; a manual auxiliary crane moves the lifted basic side wall units (202), aligns the vertical secondary beams (205) of the basic side wall units (202) with the peripheral connecting pieces (106) on the cofferdam bottom plate (1), and slowly lowers them; when the basic side wall units (202) are about to touch the cofferdam bottom plate (1), the basic side wall units (202) are pressed against the inner end tooth keys (107); after the basic side wall units (202) are in place, the outer end tooth keys (108) are installed, and the bolts of the outer end tooth keys (108) and the vertical secondary beams (205) are connected to complete the installation of a group of basic side wall units (202); in the same way, the basic side wall units (202) of the adjacent groups are completed; in the same way, the basic arc-shaped side wall units (201) and the supplementary side wall units (203) are installed; P6. Lift the steel box cofferdam; cut off the corbels (8); lower the steel box cofferdam to the designed bottom elevation; When the steel box cofferdam is lowered into place, padding is promptly performed between the cofferdam bottom plate (1) and the pile foundation casing (4) to ensure that the cofferdam does not swing; P7. At low tide, the shear connection key (105) is welded to connect the pile foundation casing (4) and the cofferdam bottom plate (1) to complete the system transformation; the hanging system is dismantled and the redundant pile foundation casing (4) is cut off; P8, pouring bottom concrete (6); At low tide, the bottom plate (1) of the cofferdam is sealed; after the sealing is completed, the connecting hole of the side wall (2) of the cofferdam is opened, and the bottom sealing concrete (6) is poured at low tide; P9. After the bottom seal concrete (6) reaches the designed strength, the connecting holes of the cofferdam side wall (2) are closed, the water in the cofferdam is drained, and the construction of the foundation (5) is carried out in a water-free environment; P10, the construction of the cap (5) is completed and the pier is constructed to a certain height; at low tide, the cofferdam side wall (2) is removed and the shore site is cleaned; after the cofferdam side wall (2) is reassembled, steps P1-P9 are repeated to turn around to the construction of the next cap (5).

5. The construction method of an offshore cap assembly steel hanging box cofferdam according to claim 4 is characterized in that: In step P1, the processing quantity of each part of the cofferdam is determined according to the number of times each component is assembled and used in rotation. The processing quantity of each component of the cofferdam can ensure the requirements of on-site construction organization and schedule arrangement.

6. The construction method of an offshore cap assembly steel hanging box cofferdam according to claim 5 is characterized in that: In step P2, a plurality of brackets (8) are evenly arranged around each pile foundation casing (4), and all the brackets (8) arranged on each pile foundation casing (4) are capable of stably supporting all the cofferdam bottom plates (1); and the bottom surface of the brackets (8) is higher than the high tide water level during the construction period.

7. The construction method of an offshore cap assembly steel box cofferdam according to claim 6 is characterized in that: In step P8, if the cofferdam deadweight + the tensile strength of the weld of the shear connection key (105) + the bond strength after pouring concrete between the cofferdam bottom plate (1) and the pile foundation casing (4) is greater than or equal to the maximum water level buoyancy and there is a certain safety factor, the stage of pouring the bottom sealing concrete (6) can be omitted, and only the concrete pouring operation between the cofferdam bottom plate (1) and the pile foundation casing (4) needs to be completed.

Images