Construction process of offshore bridge high-pile pile cap

Abstract

The application discloses a construction technology of offshore bridge high-pile pile cap, which adopts a steel-mix structure of a box, the box is composed of a reinforced concrete prefabricated box bottom plate and a steel side mold, and the construction technology comprises the following stages: a preparation stage, a box installation stage, a box lowering stage, a box bottom plate plugging and water pumping stage and a pile cap concrete pouring stage. The preparation stage comprises the following steps: pile foundation casing sinking, cast-in-place pile construction, pile foundation casing pile head cutting, box bottom plate and apron prefabrication and steel side mold manufacturing; in the box installation stage, the box bottom plate is installed first, and then the steel side mold is installed; the box bottom plate is installed by using a suspension frame, and the suspension frame comprises a pile cap, an inverted beam and two first finish rolling threaded steels; in the box lowering stage, a jack lowering system is installed on the box bottom plate, and the jack lowering system comprises a I-shaped hanger, a carrying pole beam, a through core jack and a steel wire. The construction technology can greatly reduce the construction difficulty and improve the construction efficiency.

Description

Technical Field

[0001] This invention relates to a construction process for high-pile foundations for offshore bridges. Background Technology

[0002] Cross-sea bridges consist of several offshore piers and several onshore piers. The construction of offshore piers involves first laying offshore pile foundations, then constructing pile caps on the pile foundations, followed by building piers on the pile caps, and finally erecting the main beams between the piers. Offshore piers located in the middle of the waterway, due to their location in deep water and navigable areas, have the largest pile cap dimensions and the tallest piers. To absorb the impact force of ship collisions, change the direction of ships, and protect the bridge structure from damage, offshore piers in the middle of the waterway must also have anti-collision measures, namely, surrounding the outside of the pile cap with anti-collision piers. Currently, construction of offshore piers in the middle of the waterway requires working underwater, which is inconvenient. Therefore, it is necessary to develop a construction technology for offshore piers located in the middle of the waterway. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a construction process for high-pile foundations of marine bridges, which can greatly reduce construction difficulty and improve construction efficiency.

[0004] The objective of this invention is achieved as follows: a construction process for a high-pile cap for a marine bridge, the cap comprising a main cap and a ring of anti-collision caps located outside the main cap, the distance between the main cap and the anti-collision caps being A, and a skirt plate extending into the bottom B of the anti-collision caps being provided on the outer side of the anti-collision caps; the main cap is rectangular in plan and supported by twelve piles arranged in three rows laterally and four columns longitudinally; the anti-collision caps are non-regular octagons in plan, narrow longitudinally and wide laterally, and are supported by thirty-six piles, the piles being cast-in-place piles; the construction process employs a steel-concrete cofferdam construction method, the cofferdam consisting of a precast reinforced concrete base plate and steel side formwork;

[0005] The construction process of the high-pile pier cap for marine bridges of the present invention includes the following stages: preparation stage, caisson installation stage, caisson lowering stage, caisson bottom plate sealing and dewatering stage, and pier cap concrete pouring stage.

[0006] The preparation stage includes the following steps: pile foundation casing installation, cast-in-place pile construction, pile foundation casing head cutting, prefabrication of the casing bottom plate and skirt plate, and steel side formwork fabrication.

[0007] During the prefabrication of the base plate and skirt plate of the caisson, the base plate is divided into multiple rectangular prefabricated panels, each covering 1 to 2 pile foundations; C-shaped wet joints are set between the prefabricated panels and lapped steel bars are reserved; a stepped pile hole with a larger top and smaller bottom is reserved on each prefabricated panel according to the location of the pile foundation; during prefabrication, a hanger rod is pre-embedded at each of the four corners of each prefabricated panel; after the prefabrication of the panels is completed, bottom support angle steel for supporting the steel side formwork is installed on the outer surface of each prefabricated panel located at the edge of the base plate of the caisson by pre-embedded bolts;

[0008] The steel side mold is composed of multiple side templates spliced ​​together; the bottom of each side template is supported on the bottom support angle steel, and each side template is supported vertically by diagonal braces fixed to the bottom plate of the casing at the lower end;

[0009] During the installation of the casing, the casing bottom plate is installed first, followed by the steel side formwork. The casing bottom plate is installed using a suspension frame, which includes a pile cap, an anti-hanging beam, and two first precision-rolled threaded steel bars. The pile cap is installed on top of the pile foundation casing. The anti-hanging beam is positioned directly above the pile holes in the precast bottom plate. The lower ends of the two first precision-rolled threaded steel bars are embedded in the precast slab and are symmetrically located on the outside of each pile hole. The upper parts of the two first precision-rolled threaded steel bars are anchored to the two ends of the anti-hanging beam one-to-one through gaskets and sleeves.

[0010] The installation of the base plate of the casing includes the following steps:

[0011] Step 1: First, install the bottom formwork on the pile casing to seal the floating gap between the pile hole and the pile casing. Then, install the pile cap on the top of the pile casing.

[0012] Step two: First, connect the crane of the crane vessel to the rectangular frame gantry. Then, connect the gantry to the four lifting rods on the precast slab. Next, use the crane of the crane vessel to lift the precast slab above the corresponding pile casing and fit the pile hole on the precast slab onto the corresponding pile casing. Then, lower the precast slab until the anti-lifting beam on the precast slab lands on the corresponding pile cap. Then, weld the anti-lifting beam to the pile cap and fix it. Finally, detach the gantry from the lifting rods and let the suspension frame support the precast slab so that the precast slab is above the water surface.

[0013] Step 3: Install the remaining prefabricated panels one by one, referring to Step 2, until the entire bottom plate of the housing is installed.

[0014] Step 4: First, weld the lapped reinforcing bars at the wet joints between the precast panels, then pour the concrete at the wet joints to form a complete casing bottom slab.

[0015] When installing the steel side formwork, first install two layers of water-stopping expansion rubber sheets on the top surface of the bottom support angle steel on the outer side of the casing bottom plate. Then, install the side formwork piece by piece on the top surface of the bottom support angle steel. Adjacent side formwork pieces are spliced ​​together with two rows of bolts. A water-stopping strip is set on the spliced ​​surface in the middle and on both sides of the two rows of bolts. The steel side formwork is connected to the bottom support angle steel by multiple spaced vertical tie rods. A layer of water-stopping expansion rubber sheet is set between the lower inner side of the steel side formwork and the lower part of the overlapping surface of the casing bottom plate. The gap between the lower inner side of the steel side formwork and the upper part of the overlapping surface of the casing bottom plate is filled with structural adhesive. Then, the lower end of the diagonal brace of the side formwork is fastened to the casing bottom plate.

[0016] The box lowering stage includes the following steps:

[0017] Step 1: Install the jack lowering system on the bottom plate of the casing. The jack lowering system includes an I-beam hanger, a spreader beam, a through-hole jack, and steel strands. The I-beam hanger is fixed to the bottom plate of the casing by four pre-embedded second precision-rolled threaded steel bars and is located between two inverted lifting beams. The spreader beam is erected between the middle of the top surfaces of the two inverted lifting beams. The through-hole jack is installed in the middle of the top surface of the spreader beam. The lower end of the steel strand passes through the through-hole jack and the spreader beam in sequence and is then anchored in the middle of the waist of the I-beam hanger.

[0018] Step 2: First, install two counter-bracing rods on the outside of the pile foundation casing. The bottom of the counter-bracing rods is fixed to the bottom plate of the casing with bolts, while the upper end of the counter-bracing rods is free.

[0019] Step 3: First, loosen the sleeves anchoring the first fine-rolled threaded steel bar on each suspension frame to the anti-hanging beam. Then, use multiple through-hole jacks in the jack lowering system to lower the entire casing into the water step by step until the top elevation of the casing bottom plate reaches the design bottom elevation of the foundation.

[0020] The sealing and pumping stage of the bottom plate of the casing includes the following steps:

[0021] Step 1: After the casing is lowered into place, the top elevation of the counter-bracing rod is also lower than the top elevation of the pile foundation casing. First, weld and fix the top of the counter-bracing rod to the outer surface of the pile foundation casing. Then, re-tighten the sleeve anchored to the first precision-rolled threaded steel bar on each suspension frame and the counter-bracing beam, so that the weight of the casing is borne by the suspension frame again and the buoyancy of the casing is resisted by the counter-bracing rod. Then, remove the jack lowering system.

[0022] Step 2: During low tide, lift the gap sealing bottom mold pre-fitted on the pile foundation casing upwards until it fits tightly against the bottom plate of the casing. Then, pour mixed mortar containing epoxy resin between the gap sealing bottom mold and the bottom plate of the casing. Let it solidify for 1 hour to complete the gap sealing between each pile foundation casing and the corresponding pile hole on the bottom plate of the casing.

[0023] Step 3: Drain the water from the casing to create dry working conditions;

[0024] The concrete pouring stage of the foundation cap includes the following steps:

[0025] Step 1: Weld several shear keys evenly around the circumference on the outer periphery of each pile casing. Weld the inner ends of the shear keys to the outer surface of the pile casing and bolt the lower ends of the shear keys to the stepped surface of the pile hole in the bottom plate of the casing.

[0026] Step two: First, remove the counter-bracing rod and suspension frame, so that the entire casing is supported by shear keys; then cut the pile casing to the design top elevation, and then, 300mm above the design elevation of the pile top, use a rock splitter to drill 6 to 8 holes radially along the pile head, with a hole depth of 40 to 50cm; insert the hydraulic flange separator into the holes to separate the concrete pile head, and then lift the separated concrete pile head away as a whole, leaving the remaining 300mm of concrete at the top of the pile to be manually chiseled away with a pneumatic pick.

[0027] Step 3: First, set up a wooden inner formwork between the main bearing platform and the anti-collision bearing platform to separate them. Then, tie the reinforcing bars in layers inside the casing, and then pour the concrete in three layers. When pouring the first and second layers of concrete, the diagonal bracing of the side formwork is poured into the concrete. After pouring the second layer of concrete, first install tie rods on the side formwork above the second layer of concrete, then cut off the diagonal bracing above the top surface of the second layer of concrete, and then pour the third layer of concrete. When pouring the third layer of concrete, the verticality of the side formwork is controlled by the tie rods.

[0028] Step four: First, remove the steel side formwork, then use a wire saw to cut the bottom plate of the casing, ensuring that the bottom plate of the casing is separated from the main bearing platform and the anti-collision bearing platform.

[0029] The construction process for the high-pile foundation of the aforementioned offshore bridge includes the following steps when prefabricating the caisson bottom plate and skirt plate:

[0030] 1) Erect a steel platform as the precast bottom formwork for the precast panels;

[0031] 2) Based on the center coordinates of the pile foundation, mark out the position of the pile hole on the precast bottom formwork and adjust the elevation accordingly;

[0032] 3) Tie the reinforcing bars inside the precast slabs on the precast bottom formwork and install various embedded parts, including four hanging rods that are set at the four corners of the precast slabs in a one-to-one correspondence.

[0033] 4) When prefabricating the precast slabs located at the edge of the bottom plate of the housing, the skirt side molds should be installed on the precast bottom mold and the tie bolts between the skirt side molds and the precast bottom molds should be tightened.

[0034] 5) Pour concrete, and remove the side formwork of the skirt panel and the precast bottom formwork 24 hours later.

[0035] The above-mentioned construction process for high-pile foundations of marine bridges includes a void sealing bottom mold consisting of annular wooden templates, annular foam base plates, and rubber gaskets stacked from bottom to top.

[0036] In the above-mentioned construction process of high pile caps for offshore bridges, during step two of the caisson installation stage, it is necessary to observe the elevation and horizontal position of the precast slabs. Based on the observation results, the position of the shims and sleeves on the first precision-rolled threaded steel is adjusted to adjust the elevation deviation of the precast slabs to ≤5mm. Then, the planar position deviation of the precast base plate is adjusted to ≤10mm using jacks radially set on the stepped surface of the pile hole.

[0037] The construction process of the high-pile cap for marine bridges of the present invention has the following characteristics:

[0038] 1. The container adopts a steel-concrete structure, that is, the bottom plate of the container is spliced ​​together from multiple precast concrete slabs, and the side formwork of the container is made of steel side formwork, which makes the transportation of the entire container more convenient, helps to save transportation space and reduce transportation costs;

[0039] 2. When installing the caisson at sea, there is no need to build a construction platform. Instead, the bottom plate of the caisson is first spliced ​​at a position above the water surface using a suspension frame system with the support of the pile foundation casing. Then, the spliced ​​bottom plate of the caisson is used as a construction platform to install the side formwork of the caisson. Next, the entire caisson is lowered to the design elevation in the water using a jack lowering system. Then, when the water level is low, the water in the caisson is pumped out and the bottom plate of the caisson is sealed to the pile foundation casing. Finally, the steel bars are tied and concrete is poured in sequence inside the caisson to complete the construction of the underwater foundation. The entire construction process is carried out in a waterless environment, which greatly reduces the construction difficulty and improves the construction efficiency.

[0040] 3. After the caisson is lowered into place, shear keys are connected between the pile holes of the caisson bottom plate and the pile foundation casing. This not only prevents the caisson from moving horizontally, but also distributes the weight of the entire caisson to the shear keys and transfers it to the supports of each pile foundation casing. This helps to improve the load-bearing capacity of the caisson bottom plate and the pile cap, making the caisson bottom plate and the pile cap less prone to cracking when bearing the weight of the bridge. Attached Figure Description

[0041] Figure 1a This is a plan view of the high pile cap involved in the construction process of this invention;

[0042] Figure 1b yes Figure 1a A1-A1 direction view;

[0043] Figure 1c yes Figure 1a A2-A2 view in the middle;

[0044] Figure 2a This is a top view of the casing involved in the construction process of this invention;

[0045] Figure 2b This is a block diagram of the bottom plate of the casing involved in the construction process of the present invention;

[0046] Figure 2c yes Figure 2a AA direction view in

[0047] Figure 2d yes Figure 2c Enlarged view of the P-region;

[0048] Figure 3 This is a top view of the suspension frame used in the casing installation stage of the construction process of this invention;

[0049] Figure 4 This is an elevation view of the jack lowering system used in the caisson lowering stage of the construction process of this invention;

[0050] Figure 5 This is a plan view of the jack lowering system used in the lowering stage of the caisson in the construction process of this invention;

[0051] Figure 6 This is an elevation view of the tension and bracing system used in the sealing and pumping stage of the bottom plate of the casing in the construction process of this invention;

[0052] Figure 7 This is a schematic diagram of the shear key and pile casing connection used in the construction process of the present invention during the concrete pouring stage of the foundation.

[0053] Figure 8 This is a schematic diagram of the construction process of the present invention during the concrete pouring stage of the foundation. Detailed Implementation

[0054] The invention will now be further described with reference to the accompanying drawings.

[0055] Please refer to Figure 1 to Figure 8 The construction process of the high-pile pier cap for marine bridges of the present invention involves a pier cap including a main pier cap 101 and a ring of anti-collision pier caps 102 arranged outside the main pier cap 101. The distance between the main pier cap 101 and the anti-collision pier cap 102 is A = 0.8m. A skirt plate 103 extending into the bottom of the anti-collision pier cap 102 is provided on the outside of the anti-collision pier cap 102. The main pier cap 101 is rectangular in plan and supported by twelve piles 4 arranged in three rows laterally and four columns longitudinally. The anti-collision pier cap 102 is a non-regular octagon with a narrow longitudinal direction and a wide transverse direction. The anti-collision pier cap 102 is supported by thirty-six piles 4, which are cast-in-place piles (see...). Figure 1a , Figure 1b and Figure 1c ).

[0056] The construction process of this invention adopts a steel-concrete structure caisson construction, which consists of a precast reinforced concrete caisson bottom plate and steel side formwork.

[0057] The construction process of this invention includes the following stages: preparation stage, caisson installation stage, caisson lowering stage, caisson bottom plate sealing and dewatering stage, and foundation concrete pouring stage.

[0058] The preparation stage includes the following steps: pile casing installation, cast-in-place pile construction, pile casing head cutting, prefabrication of the bottom plate 1 and skirt plate of the casing, and fabrication of the steel side formwork 2;

[0059] The base plate 1 of the casing is divided into multiple rectangular precast panels 10, each precast panel 10 covering 1 to 2 piles 4 (see...). Figure 2a and Figure 2b C-shaped wet joints 1A are set between precast slabs 10 and lapped steel bars are reserved; a stepped pile hole 1B with a larger upper part and a smaller lower part is reserved on each precast slab 10 according to the position of the pile foundation 4, and the radius of the lower part of the pile hole 1B is 75mm larger than the radius of the pile foundation casing 4A; a hanger is pre-embedded at each of the four corners of each precast slab 10.

[0060] The prefabrication process for the bottom plate and skirt plate of the casing includes the following steps:

[0061] 1) Erect a steel platform as the precast bottom formwork for the precast panels;

[0062] 2) Based on the center coordinates of the pile foundation, mark out the position of the pile hole on the precast bottom formwork and adjust the elevation accordingly;

[0063] 3) Tie the reinforcing bars inside the precast slabs on the precast bottom formwork and install various embedded parts, including four hanging rods that are set at the four corners of the precast slabs in a one-to-one correspondence.

[0064] 4) When prefabricating the precast slabs located at the edge of the bottom plate of the housing, the skirt side molds should be installed on the precast bottom mold and the tie bolts between the skirt side molds and the precast bottom molds should be tightened.

[0065] 5) Pour concrete, and remove the side formwork and precast bottom formwork of the skirt panel 24 hours later;

[0066] After the prefabricated slab 10 is prefabricated, a bottom support angle steel 3 for supporting the steel side mold is installed on the outer side of each prefabricated slab 10 located at the edge of the bottom plate 1 of the housing by pre-embedded bolts 30. The distance from the top surface of the bottom support angle steel 3 to the top surface of the prefabricated slab 10 is 20cm.

[0067] The steel side formwork 2 is a wall-embracing bottom structure, meaning the bottom of the steel side formwork 2 overlaps with the outer side of the casing bottom plate 1 by 20cm; the steel side formwork 2 is composed of multiple side formwork panels, each with a height of 5.2m and a length of 3m; the bottom of each side formwork panel is supported on the bottom support angle steel 3, and each side formwork panel is supported vertically by diagonal braces 20 fixed at the lower end to the casing bottom plate 1; the support height of the diagonal braces 20 is 4m (see...). Figure 2c and Figure 2d );

[0068] During the casing installation phase, the casing base plate 1 is installed first, followed by the steel side formwork 2. The casing base plate 1 is installed using a suspension frame, which includes a pile cap 40, a reverse lifting beam 41, and two first precision-rolled threaded steel bars 42. The pile cap 40 is installed on top of the pile foundation casing 4A. The reverse lifting beam 41 is positioned directly above each pile hole 1B of the precast base plate 10. The lower ends of the two first precision-rolled threaded steel bars 42 are pre-embedded in the precast plate 10 and are symmetrically located on the outside of each pile hole 1B. The upper parts of the two first precision-rolled threaded steel bars 42 are each anchored to the two ends of the reverse lifting beam 41 one-to-one by gaskets and sleeves (see...). Figure 3 );

[0069] The following steps are included when installing the bottom plate of the housing:

[0070] Step 1: First, install a floating gap sealing bottom mold between the pile hole 1B of the casing bottom plate 1 and the pile casing 4A on the pile foundation casing 4A. The gap sealing bottom mold consists of annular wooden template 61, annular foam bottom plate 62 and rubber gasket 63 stacked from bottom to top. Then, install a pile cap 40 at the top of the pile foundation casing 4A.

[0071] Step two: First, connect the crane of the crane vessel to the rectangular frame gantry. Then, connect the gantry to the four lifting rods on the precast slab 10. Next, use the crane of the crane vessel to lift the precast slab 10 above the corresponding pile foundation casing 4A and fit the pile hole 1B on the precast slab 10 onto the corresponding pile foundation casing 4A. Observe the elevation and horizontal position of the precast slab 10. Based on the observation results, adjust the position of the shim and sleeve on the first precision-rolled threaded steel bar 42 to adjust the elevation deviation of the precast slab 10 to ≤5mm. Then, use radial... The jacks on the stepped surface of pile hole 1B adjust the plane position deviation of the precast slab 10 to ≤10mm, and then lower the precast slab 10 until the anti-lifting beam 41 on the precast slab 10 falls on the corresponding pile cap 40. Then, the anti-lifting beam 41 and the pile cap 40 are welded and fixed. Finally, the hanger and the hanger rod are separated, and the precast slab 10 is supported by the suspension frame so that the precast slab 10 is above the water surface. At this time, the weight of the precast slab 10 is transferred to the pile foundation casing 4A through the first fine-rolled threaded steel bar 42, the anti-lifting beam 41 and the pile cap 40.

[0072] Step 3: Install the remaining prefabricated panels one by one, referring to Step 2, until the entire base plate of the housing is installed. At this point, the suspension structure on each prefabricated base plate forms a suspension system.

[0073] Step 4: First, weld the lapped steel bars of the wet joint 1A between each precast panel 10, and then pour the concrete of the wet joint 1A to form a complete casing bottom plate 1.

[0074] When installing the steel side formwork, first install two layers of water-stopping expansion rubber sheets 31 on the top surface of the bottom support angle steel 3 on the outer side of the bottom plate 1 of the housing. Then, install the side formwork piece by piece on the top surface of the bottom support angle steel 3. Adjacent side formwork pieces are spliced ​​together with two rows of bolts. A water-stopping rubber strip is set in the middle and on both sides of the splicing surface of the two rows of bolts. The steel side formwork 2 and the bottom support angle steel 3 are connected by multiple vertical tie rods 2A set at intervals of 1.5m to constrain the horizontal movement of the bottom plate 1 of the housing. A layer of water-stopping expansion rubber sheet 31 is set between the lower inner side of the steel side formwork 2 and the lower part of the overlapping surface of the bottom plate 1 of the housing. The gap between the lower inner side of the steel side formwork 2 and the upper part of the overlapping surface of the bottom plate 1 of the housing is filled with structural adhesive 32. Then, the lower end of the diagonal brace 20 of the side formwork is fastened to the bottom plate 1 of the housing (see Figure 2c and Figure 2d );

[0075] The container placement phase includes the following steps:

[0076] Step 1: Install the jack lowering system on the base plate 1 of the housing. This system includes an I-beam hanger 50, a spreader beam 52, a through-hole jack 53, and steel strands 54. The I-beam hanger 50 is fixed to the base plate 1 by four pre-embedded second precision-rolled threaded steel bars 51 and is located between two counter-lifting beams 41. The spreader beam 52 is positioned between the top midpoints of the two counter-lifting beams 41. The through-hole jack 53 is installed at the midpoint of the top surface of the spreader beam 52. The lower end of the steel strands 54 passes through the holes in the through-hole jack 53 and the spreader beam 52 and is then anchored to the midpoint of the waist of the I-beam hanger 50 (see...). Figure 4 and Figure 5 );

[0077] Step 2: First, install two 4m long counter-bracing rods 6 symmetrically on the outside of the pile foundation casing 4A. The bottom of the counter-bracing rods 6 is fixed to the bottom plate 1 of the casing with bolts, and the upper end of the counter-bracing rods 6 is free.

[0078] Step 3: First, loosen the sleeves anchoring the first fine-rolled threaded steel bar 42 and the anti-lifting beam 41 on each suspension frame. Then, using multiple through-hole jacks 53 in the jack lowering system, lift the casing upwards by 20cm in a step-by-step manner, so that the casing is switched from being supported by the suspension frame system to being supported by the jack lowering system. Then, lower the casing into the water, so that the weight of the casing is transferred to the pile foundation casing 4A through the casing bottom plate 1, the second fine-rolled threaded steel bar 51, the I-shaped suspension frame 50, the steel strand 54, the through-hole jacks 53, the spreader beam 52, the anti-lifting beam 41, and the pile cap 40, until the top elevation of the casing bottom plate 1 reaches the design bottom elevation of the pile cap. The bottom formwork sealing the gaps on each pile foundation casing 4A is pressed into the water as the casing is lowered.

[0079] The bottom plate sealing and pumping stage of the casing includes the following steps:

[0080] Step 1: After the casing is lowered into place, the top elevation of the counter-bracing rod 6 is also lower than the top elevation of the pile foundation casing 4A. First, weld and fix the top of the counter-bracing rod 6 to the outer surface of the pile foundation casing 4A. Then, retighten the sleeves anchored to the first precision-rolled threaded steel bar 42 and the counter-bracing beam 41 on each suspension frame, so that the weight of the casing is once again borne by the suspension frame, and the buoyancy of the casing is resisted by the counter-bracing rod 6, forming a system that both tensions and supports (see...). Figure 6 Then, the jack lowering system was dismantled;

[0081] Step 2: During low tide, lift the gap-sealing bottom mold that is pre-fitted on each pile foundation casing 4A until the top surface of the annular foam bottom plate is tightly attached to the bottom surface of the casing bottom plate 1, and let the rubber gasket 63 enter the gap between the pile hole 1B and the pile foundation casing 4A. Then, pour the mixed mortar 60 containing epoxy resin between the gap-sealing bottom mold and the casing bottom plate 1, and let it solidify for 1 hour to complete the gap sealing between each pile foundation casing 4A and the corresponding pile hole 1B on the casing bottom plate 1.

[0082] Step 3: Drain the water from the casing to create dry working conditions;

[0083] The concrete pouring stage of the foundation cap includes the following steps:

[0084] Step 1: Weld 7-8 shear keys 7 evenly distributed around the circumference of the outer periphery of each pile casing 4A. The inner end of each shear key 7 is welded and fixed to the outer surface of the pile casing 4A, and the lower end of each shear key 7 is bolted and fixed to the stepped surface of the pile hole 1B of the casing bottom plate 1 (see...). Figure 7 );

[0085] Step 2: First, remove the counter-bracing rod 6 and the suspension frame, so that the weight of the entire casing is supported by the shear key 7. Then, remove the pile cap 40 and cut the pile casing 4A to the design top elevation. Then, 300mm above the design elevation of the pile top, use a rock splitter to drill 6 to 8 holes radially along the pile head, with a hole depth of 40 to 50cm. Insert the hydraulic flange separator into the drilled holes to separate the concrete pile head. Then, lift the separated concrete pile head away as a whole. The remaining 300mm of concrete at the top of the pile is manually removed with a pneumatic pick.

[0086] Step 3: First, set up a wooden inner formwork between the main bearing platform and the anti-collision bearing platform. Then, use a wire saw to cut the bottom plate of the casing to ensure separation of the main bearing platform and the anti-collision bearing platform. Next, tie the reinforcing bars in layers inside the casing and pour concrete in three layers. The pouring height of the first layer of concrete is 1m; the pouring height of the second layer of concrete is 2m; and the pouring height of the third layer of concrete is 3m. When pouring the first and second layers of concrete, the diagonal bracing 20 of the side formwork 2 is poured into the concrete. After pouring the second layer of concrete, first install tie rods 2B on the side formwork 2 above the second layer of concrete, at a height of 4.7m. Then, cut off the diagonal bracing 20 above the top surface of the second layer of concrete, and then pour the third layer of concrete (see...). Figure 8 );

[0087] Step 4: Remove the steel side formwork.

[0088] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the scope of the invention and should be defined by the claims.

Claims

1. A construction process for a high-pile pier cap for a marine bridge, the pier cap comprising a main pier cap and a ring of anti-collision piers surrounding the main pier cap, the distance between the main pier cap and the anti-collision piers being A, and a skirt plate extending into the bottom B of the anti-collision piers being provided on the outer side of the anti-collision piers; the main pier cap is rectangular in plan and supported by twelve piles arranged in three rows laterally and four columns longitudinally; the anti-collision piers are non-regular octagons, narrow longitudinally and wide laterally, and supported by thirty-six piles, the piles being cast-in-place piles; the construction process employs a reinforced concrete caisson construction method, the caisson consisting of a precast reinforced concrete caisson bottom slab and steel side formwork; the construction process includes the following stages: preparation stage, caisson installation stage, caisson lowering stage, caisson bottom slab sealing and dewatering stage, and pier cap concrete pouring stage; characterized in that… The preparation stage includes the following steps: pile foundation casing installation, cast-in-place pile construction, pile foundation casing head cutting, prefabrication of the casing bottom plate and skirt plate, and steel side formwork fabrication. During the prefabrication of the base plate and skirt plate of the caisson, the base plate is divided into multiple rectangular prefabricated panels, each covering 1 to 2 pile foundations; C-shaped wet joints are set between the prefabricated panels and lapped steel bars are reserved; a stepped pile hole with a larger top and smaller bottom is reserved on each prefabricated panel according to the location of the pile foundation; during prefabrication, a hanger rod is pre-embedded at each of the four corners of each prefabricated panel; after the prefabrication of the panels is completed, bottom support angle steel for supporting the steel side formwork is installed on the outer surface of each prefabricated panel located at the edge of the base plate of the caisson by pre-embedded bolts; The steel side mold is composed of multiple side templates spliced ​​together; the bottom of each side template is supported on the bottom support angle steel, and each side template is supported vertically by diagonal braces fixed to the bottom plate of the casing at the lower end; During the installation of the casing, the casing bottom plate is installed first, followed by the steel side formwork. The casing bottom plate is installed using a suspension frame, which includes a pile cap, an anti-hanging beam, and two first precision-rolled threaded steel bars. The pile cap is installed on top of the pile foundation casing. The anti-hanging beam is positioned directly above the pile holes in the precast bottom plate. The lower ends of the two first precision-rolled threaded steel bars are embedded in the precast slab and are symmetrically located on the outside of each pile hole. The upper parts of the two first precision-rolled threaded steel bars are anchored to the two ends of the anti-hanging beam one-to-one through gaskets and sleeves. The installation of the base plate of the casing includes the following steps: Step 1: First, install the bottom formwork on the pile casing to seal the floating gap between the pile hole and the pile casing. Then, install the pile cap on the top of the pile casing. Step two: First, connect the crane of the crane vessel to the rectangular frame gantry. Then, connect the gantry to the four lifting rods on the precast slab. Next, use the crane of the crane vessel to lift the precast slab above the corresponding pile casing and fit the pile hole on the precast slab onto the corresponding pile casing. Then, lower the precast slab until the anti-lifting beam on the precast slab lands on the corresponding pile cap. Then, weld the anti-lifting beam to the pile cap and fix it. Finally, detach the gantry from the lifting rods and let the suspension frame support the precast slab so that the precast slab is above the water surface. Step 3: Install the remaining prefabricated panels one by one, referring to Step 2, until the entire bottom plate of the housing is installed. Step 4: First, weld the lapped reinforcing bars at the wet joints between the precast panels, then pour the concrete at the wet joints to form a complete casing bottom slab. When installing the steel side formwork, first install two layers of water-stopping expansion rubber sheets on the top surface of the bottom support angle steel on the outer side of the casing bottom plate. Then, install the side formwork piece by piece on the top surface of the bottom support angle steel. Adjacent side formwork pieces are spliced ​​together with two rows of bolts. A water-stopping strip is set on the spliced ​​surface in the middle and on both sides of the two rows of bolts. The steel side formwork is connected to the bottom support angle steel by multiple spaced vertical tie rods. A layer of water-stopping expansion rubber sheet is set between the lower inner side of the steel side formwork and the lower part of the overlapping surface of the casing bottom plate. The gap between the lower inner side of the steel side formwork and the upper part of the overlapping surface of the casing bottom plate is filled with structural adhesive. Then, the lower end of the diagonal brace of the side formwork is fastened to the casing bottom plate. The box lowering stage includes the following steps: Step 1: Install the jack lowering system on the bottom plate of the casing. The jack lowering system includes an I-beam hanger, a spreader beam, a through-hole jack, and steel strands. The I-beam hanger is fixed to the bottom plate of the casing by four pre-embedded second precision-rolled threaded steel bars and is located between two inverted lifting beams. The spreader beam is erected between the middle of the top surfaces of the two inverted lifting beams. The through-hole jack is installed in the middle of the top surface of the spreader beam. The lower end of the steel strand passes through the through-hole jack and the spreader beam in sequence and is then anchored in the middle of the waist of the I-beam hanger. Step 2: First, install two counter-bracing rods on the outside of the pile foundation casing. The bottom of the counter-bracing rods is fixed to the bottom plate of the casing with bolts, while the upper end of the counter-bracing rods is free. Step 3: First, loosen the sleeves anchoring the first fine-rolled threaded steel bar on each suspension frame to the anti-hanging beam. Then, use multiple through-hole jacks in the jack lowering system to lower the entire casing into the water step by step until the top elevation of the casing bottom plate reaches the design bottom elevation of the foundation. The sealing and pumping stage of the bottom plate of the casing includes the following steps: Step 1: After the casing is lowered into place, the top elevation of the counter-bracing rod is also lower than the top elevation of the pile foundation casing. First, weld and fix the top of the counter-bracing rod to the outer surface of the pile foundation casing. Then, re-tighten the sleeve anchored to the first precision-rolled threaded steel bar on each suspension frame and the counter-bracing beam, so that the weight of the casing is borne by the suspension frame again and the buoyancy of the casing is resisted by the counter-bracing rod. Then, remove the jack lowering system. Step 2: During low tide, lift the gap sealing bottom mold pre-fitted on the pile foundation casing upwards until it fits tightly against the bottom plate of the casing. Then, pour mixed mortar containing epoxy resin between the gap sealing bottom mold and the bottom plate of the casing. Let it solidify for 1 hour to complete the gap sealing between each pile foundation casing and the corresponding pile hole on the bottom plate of the casing. Step 3: Drain the water from the casing to create dry working conditions; The concrete pouring stage of the foundation includes the following steps: Step 1: Weld several shear keys evenly around the circumference on the outer periphery of each pile casing. Weld the inner ends of the shear keys to the outer surface of the pile casing and bolt the lower ends of the shear keys to the stepped surface of the pile hole in the bottom plate of the casing. Step two: First, remove the counter-bracing rod and suspension frame, so that the entire casing is supported by shear keys; then cut the pile casing to the design top elevation, and then, 300mm above the design elevation of the pile top, use a rock splitter to drill 6 to 8 holes radially along the pile head, with a hole depth of 40 to 50cm; insert the hydraulic flange separator into the holes to separate the concrete pile head, and then lift the separated concrete pile head away as a whole, leaving the remaining 300mm of concrete at the top of the pile to be manually chiseled away with a pneumatic pick. Step 3: First, set up a wooden inner formwork between the main bearing platform and the anti-collision bearing platform to separate them. Then, tie the reinforcing bars in layers inside the casing, and then pour the concrete in three layers. When pouring the first and second layers of concrete, the diagonal bracing of the side formwork is poured into the concrete. After pouring the second layer of concrete, first install tie rods on the side formwork above the second layer of concrete, then cut off the diagonal bracing above the top surface of the second layer of concrete, and then pour the third layer of concrete. When pouring the third layer of concrete, the verticality of the side formwork is controlled by the tie rods. Step four: First, remove the steel side formwork, then use a wire saw to cut the bottom plate of the casing, ensuring that the bottom plate of the casing is separated from the main bearing platform and the anti-collision bearing platform.

2. The construction technology for high-pile foundations of marine bridges according to claim 1, characterized in that, The prefabrication process for the bottom plate and skirt plate of the casing includes the following steps: 1) Erect a steel platform as the precast bottom formwork for the precast panels; 2) Based on the center coordinates of the pile foundation, mark out the position of the pile hole on the precast bottom formwork and adjust the elevation accordingly; 3) Tie the reinforcing bars inside the precast slabs on the precast bottom formwork and install various embedded parts, including four hanging rods that are set at the four corners of the precast slabs in a one-to-one correspondence. 4) When prefabricating the precast slabs located at the edge of the bottom plate of the housing, the skirt side molds should be installed on the precast bottom mold and the tie bolts between the skirt side molds and the precast bottom molds should be tightened. 5) Pour concrete, and remove the side formwork of the skirt panel and the precast bottom formwork 24 hours later.

3. The construction technology for high-pile foundations of marine bridges according to claim 1, characterized in that, The gap sealing bottom mold consists of annular wooden templates, annular foam base plates, and rubber gaskets stacked from bottom to top.

4. The construction technology for high-pile foundations of marine bridges according to claim 1, characterized in that, During step two of the casing installation stage, it is also necessary to observe the elevation and horizontal position of the precast slabs. Based on the observation results, adjust the position of the shims and sleeves on the first precision-rolled threaded steel bar to adjust the elevation deviation of the precast slabs to ≤5mm. Then, use the jacks radially set on the stepped surface of the pile hole to adjust the plane position deviation of the precast base plate to ≤10mm.

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