A CONSTRUCTION METHOD FOR A HIGH-PILE STORAGE PLATFORM OF AN OFFSHORE BRIDGE

Abstract

The present invention discloses a construction method for a high-pile storage platform of an offshore bridge, which uses a reinforced concrete box construction, the box consisting of a box base plate and a steel side formwork. The manufacturing method comprises the following phases: a preparation phase, a box assembly phase, a box lowering phase, a box base plate closure and drainage phase, and a support beam concreting phase.The following steps are carried out in the preparatory phase: lowering the pile foundation protection sleeve, manufacturing the cast-in-place concrete piles, cutting the pile heads of the pile foundation protection sleeve, prefabrication of the box base plate and skirt plate, and manufacturing the steel side formwork. In the box assembly phase, the box base plate is assembled first, followed by the installation of the steel side formwork. The box base plate is installed using a suspension system comprising the pile head, counter-tension beams, and first cold-rolled threaded rods. In the box lowering phase, a hydraulic lowering system is installed on the box base plate. This system consists of an I-beam suspension, a yoke beam, a push-through hydraulic cylinder, and a prestressing steel cable. The method of the invention enables a significant reduction in the complexity of the construction while increasing the efficiency of the construction.

Description

A construction technology for high pile cap of offshore bridge Technical Field

[0001] The invention relates to a construction process for a high pile cap of an offshore bridge. Background Art

[0002] A cross-sea bridge consists of several offshore piers and several onshore piers. When constructing an offshore pier, the offshore pile foundation must first be sunk, followed by the construction of a cap on the pile foundation. Then, piers are built on the cap, and finally, the main beams are erected between the piers. The offshore pier located in the middle of the water area is located in deep water and a navigable area, so the cap has the largest planar dimensions and the piers are the tallest. To absorb the impact force of a ship collision, change the direction of the ship's travel, and protect the bridge structure from damage, the offshore pier in the middle of the water area must also have anti-collision measures, namely, a circle of anti-collision piers surrounding the outer side of the cap. Currently, the cap in the middle of the water area needs to be constructed underwater, which brings inconvenience to the construction operation. To this end, it is necessary to develop a construction process for offshore caps located in the middle of the water area.

[0003] Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a construction process for a high pile cap of an offshore bridge, which can greatly reduce the construction difficulty and improve the construction efficiency.

[0005] The object of the present invention is achieved as follows: a construction process for a high-pile cap of an offshore bridge, the cap comprising a main cap and a circle of anti-collision caps arranged on the outside of the main cap, the distance between the main cap and the anti-collision cap being A, and a circle of skirt panels extending into the bottom B of the anti-collision cap being provided on the outside of the anti-collision cap; the main cap having a rectangular plane and supported by twelve pile foundations arranged in three horizontal rows and four vertical columns; the circle of anti-collision caps having a plane that is a non-regular octagon that is narrow in the vertical direction and wide in the horizontal direction, the anti-collision cap being supported by thirty-six pile foundations, the pile foundations being cast-in-place piles; the construction process adopts a steel-concrete structure casing construction, the casing consisting of a prefabricated reinforced concrete casing bottom plate and steel side formwork;

[0006] The construction process of the high pile cap of the offshore bridge of the present invention comprises the following stages: a preparation stage, a casing installation stage, a casing lowering stage, a casing bottom plate sealing and pumping stage, and a cap concrete pouring stage;

[0007] The preparation stage includes the following steps: sinking pile casing, constructing cast-in-place piles, cutting pile casing pile heads, prefabricating casing bottom plates and skirt plates, and making steel side forms;

[0008] During the prefabrication steps of the casing bottom plate and skirt plate, the casing bottom plate is divided into multiple rectangular prefabricated panels, each of which covers 1 to 2 pile foundations; C-shaped wet joints are set between the prefabricated panels and overlapping steel bars are reserved; a stepped pile hole with a larger top and a smaller bottom is reserved on each prefabricated panel according to the position of the pile foundation; during prefabrication, a hanger rod is embedded in each of the four corners of each prefabricated panel; after the prefabrication of the prefabricated 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 casing bottom plate through embedded bolts;

[0009] The steel side formwork is made up of multiple side formworks; the bottom of each side formwork is supported on the bottom support angle steel, and each side formwork is supported in a vertical state by a diagonal brace fixed at the lower end to the bottom plate of the casing;

[0010] During the casing installation stage, the casing bottom plate is installed first, and then the steel side formwork is installed; the casing bottom plate is installed using a suspension frame, which includes a pile cap, an inverted hanging beam and two first fine-rolled threaded steel bars; the pile cap is installed on the top of the pile foundation casing; the inverted hanging beam is located directly above the pile hole of the prefabricated bottom plate; the lower ends of the two first fine-rolled threaded steel bars are pre-embedded in the prefabricated plate and are centrally symmetrically located outside each pile hole, and the upper parts of the two first fine-rolled threaded steel bars are anchored to the two ends of the inverted hanging beam in a one-to-one correspondence through gaskets and sleeves;

[0011] The following steps are included when installing the casing bottom plate:

[0012] Step 1: First, install a bottom formwork to seal the floating gap between the pile hole of the casing bottom plate and the pile casing on the pile casing, and then install a pile cap on the top of the pile casing;

[0013] Step 2: First, connect the crane of the crane ship to the rectangular frame hanger, then connect the hanger to the four hangers on the precast panel, and then use the crane of the crane ship to lift the precast panel to the top of the corresponding pile foundation casing and put the pile hole on the precast panel onto the corresponding pile foundation casing. Then, lower the precast panel until the anti-hanging beam on the precast panel falls on the corresponding pile cap, and then weld the anti-hanging beam to the pile cap. Finally, detach the hanger from the hanger, and support the precast panel with the suspension frame so that the precast panel is above the water surface.

[0014] Step 3: Install the remaining prefabricated panels piece by piece, referring to step 2, until the entire box bottom plate is installed;

[0015] Step 4: First weld the overlapping steel bars of the wet joints between the precast panels, and then pour the concrete of the wet joints to form a complete box bottom plate;

[0016] When installing the steel side formwork, first install two layers of water-stop expansion rubber sheets on the top surface of the bottom supporting angle steel on the outer side surface of the casing bottom plate, and then install the side formwork piece by piece on the top surface of the bottom supporting angle steel. Two rows of bolts are used to splice adjacent side formworks, and a water-stop rubber strip is provided in the middle and on both sides of the two rows of bolts on the splicing surface; the steel side formwork and the bottom supporting angle steel are connected by multiple vertical tie rods arranged at intervals, and a layer of water-stop expansion rubber sheet is provided between the lower inner side surface of the steel side formwork and the lower part of the overlapping surface of the casing bottom plate, and the gap between the lower inner side surface 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;

[0017] The casing lowering stage comprises the following steps:

[0018] Step 1: Install a jack lowering system on the casing bottom plate, which includes an I-shaped hanger, a shoulder pole beam, a through-hole jack, and a steel strand; the I-shaped hanger is fixed to the casing bottom plate by four second-grade fine-rolled threaded steel bars pre-buried in the casing bottom plate and is located between the two inverted hanging beams; the shoulder pole beam is erected between the middle parts of the top surfaces of the two inverted hanging beams; the through-hole jack is installed in the middle part of the top surface of the shoulder pole beam; the lower end of the steel strand is passed through the through-hole jack and the shoulder pole beam in sequence and then anchored in the middle part of the waist of the I-shaped hanger;

[0019] Step 2: First, install two anti-support rods on the outside of the pile casing. The bottom of the anti-support rod is fixed to the bottom plate of the casing by bolts, and the upper end of the anti-support rod is free.

[0020] Step 3: First, loosen the sleeves that anchor the first fine-rolled threaded steel bar and the inverted beam on each suspension frame, and then lower the entire casing into the water step by step using multiple through-hole jacks in the jack lowering system until the top elevation of the casing bottom plate reaches the designed bottom elevation of the pedestal;

[0021] The casing bottom plate sealing and pumping stage comprises the following steps:

[0022] Step 1: After the casing is lowered into place, the top elevation of the anti-support rod is also lower than the top elevation of the pile casing. First, weld the top of the anti-support rod to the outer surface of the pile casing, and then re-tighten the first precision-rolled threaded steel bar on each hanger and the sleeve anchored by the anti-hanging beam, so that the gravity of the casing is borne by the hanger again, and the buoyancy of the casing is resisted by the anti-support rod, and then remove the jack lowering system;

[0023] Step 2: At low tide, lift the gap-sealing bottom formwork pre-installed on the pile foundation casing until it fits tightly against the casing bottom plate, then pour a mixed mortar containing epoxy resin between the gap-sealing bottom formwork and the casing bottom plate, and let it solidify for 1 hour to complete the gap sealing between each pile foundation casing and the corresponding pile hole on the casing bottom plate;

[0024] Step 3: Drain the water in the casing to create dry working conditions;

[0025] The foundation concrete pouring phase includes the following steps:

[0026] Step 1: Welding a plurality of shear keys uniformly along the circumference of the outer circumference of each pile casing, wherein the inner ends of the plurality of shear keys are welded and fixed to the outer surface of the pile casing, and the lower ends of the plurality of shear keys are bolted and fixed to the stepped surface of the pile hole of the casing bottom plate;

[0027] Step 2: First, remove the counter-support rod and suspension frame so that the entire casing is supported by the shear key; then cut the pile foundation casing to the designed top elevation, and then use a rock splitting rod to drill 6 to 8 holes along the pile head radially 300 mm above the designed elevation of the pile top. The holes are 40 to 50 cm deep; 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. The remaining concrete at a height of 300 mm above the pile top is manually chiseled out with a jackhammer;

[0028] Step 3: First, set up a wooden inner formwork between the main bearing platform and the anti-collision bearing platform to separate the main bearing platform and the anti-collision bearing platform, then tie the steel bars in layers in the casing, and then pour concrete in three layers; when pouring the first and second layers of concrete, pour the diagonal braces of the side formwork into the concrete; after pouring the second layer of concrete, first install the tension screws on the side formwork above the second layer of concrete, then cut off the diagonal braces 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 tension screws control the verticality of the side formwork;

[0029] Step 4: First remove the steel side formwork, and then use the rope saw method to cut the casing bottom plate to ensure that the casing bottom plate is separated from the main pedestal and anti-collision pedestal.

[0030] The above-mentioned construction process of the high pile cap of the offshore bridge includes the following steps when prefabricating the casing bottom plate and skirt plate:

[0031] 1) Set up a steel platform as the prefabricated bottom formwork for the prefabricated panels;

[0032] 2) Locate the position of the pile hole on the prefabricated bottom formwork according to the center coordinates of the pile foundation and adjust the elevation;

[0033] 3) Tie the steel bars in the precast panel on the precast bottom formwork and install various embedded parts, including four hangers corresponding to each other at the four corners of the precast panel;

[0034] 4) When prefabricating the prefabricated panels at the edge of the casing bottom plate, the skirt side formwork should be installed on the prefabricated bottom formwork, and the tension bolts between the skirt side formwork and the prefabricated bottom formwork should be tightened;

[0035] 5) Pour concrete and remove the skirt side formwork and precast bottom formwork after 24 hours.

[0036] In the above-mentioned construction process of the high-pile cap of the offshore bridge, the gap-sealing bottom formwork is composed of an annular wooden formwork, an annular foam bottom plate and a rubber gasket stacked from bottom to top.

[0037] In the above-mentioned construction process of the high pile cap of the offshore bridge, during step two of the casing installation stage, the elevation and horizontal position of the prefabricated plate must be observed, and the positions of the gasket and sleeve on the first fine-rolled threaded steel bar are adjusted according to the observation results, and the elevation deviation of the prefabricated plate is adjusted to ≤5mm. Then, the plane position deviation of the prefabricated base plate is adjusted to ≤10mm using a jack radially arranged on the step surface of the pile hole.

[0038] The construction process of the high pile cap for offshore bridges of the present invention has the following characteristics:

[0039] 1. The box adopts a steel-concrete structure, that is, the box bottom plate is made of multiple prefabricated concrete panels, and the box side formwork adopts steel side formwork, which makes the transportation of the entire box more convenient, helps to save transportation space and save transportation costs;

[0040] 2. When installing the casing at sea, there is no need to set up a construction platform. Instead, the casing bottom plate is spliced ​​above the water surface using the suspension frame system with the support of the pile foundation casing. The spliced ​​casing bottom plate is then used as a construction platform to install the casing side formwork. The entire casing is then lowered into the water to the designed elevation using the jack lowering system. When the water level is low, the water in the casing is drained and the casing bottom plate and the pile foundation casing are sealed. Finally, the steel bars are tied and concrete is poured in the casing to complete 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.

[0041] 3. After the casing is lowered into place, shear keys are connected between the pile holes of the casing bottom plate and the pile foundation casing. This can not only prevent the horizontal movement of the casing, but also distribute the weight of the entire casing to the shear keys and transmit it to each pile foundation casing support, which is beneficial to improve the bearing capacity of the casing bottom plate and the pedestal, making it less likely for the casing bottom plate and the pedestal to crack when bearing the weight of the bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG1a is a plan view of a high pile cap involved in the construction process of the present invention;

[0043] FIG1b is a view in the direction A1-A1 in FIG1B ;

[0044] FIG1c is a view in the direction A2-A2 in FIG1B ;

[0045] FIG2a is a top view of a casing involved in the construction process of the present invention;

[0046] FIG2 b is a block diagram of the casing bottom plate involved in the construction process of the present invention;

[0047] FIG2c is an AA view of FIG2a.

[0048] Figure 2d is an enlarged view of the P portion in Figure 2c;

[0049] FIG3 is a top view of the suspension frame used in the casing installation stage of the construction process of the present invention;

[0050] FIG4 is an elevation view of the jack lowering system used in the casing lowering stage of the construction process of the present invention;

[0051] 5 is a plan view of the jack lowering system used in the casing lowering stage of the construction process of the present invention;

[0052] 6 is an elevation view of the pulling and supporting system used in the casing bottom plate sealing and pumping stage of the construction process of the present invention;

[0053] 7 is a schematic structural diagram of the shear key connected to the pile foundation casing used in the cap concrete pouring stage of the construction process of the present invention;

[0054] FIG8 is a schematic diagram of the construction process of the present invention during the cap concrete pouring stage. DETAILED DESCRIPTION

[0055] The present invention will be further described below with reference to the accompanying drawings.

[0056] Please refer to Figures 1 to 8. The construction process of the high-pile cap of the offshore bridge of the present invention involves a cap including a main cap 101 and a circle of anti-collision caps 102 arranged on the outside of the main cap 101. The distance A=0.8m between the main cap 101 and the anti-collision cap 102 is set. A circle of skirt plates 103 extending into the bottom of the anti-collision cap 102 by B=2m is set on the outside of the anti-collision cap 102; the plane of the main cap 101 is rectangular and supported by twelve pile foundations 4 arranged in three rows horizontally and four columns vertically; the plane of the circle of anti-collision caps 102 is a non-regular octagon that is narrow in the longitudinal direction and wide in the transverse direction. The anti-collision cap 102 is supported by thirty-six pile foundations 4, and the pile foundations 4 are cast-in-place piles (see Figures 1a, 1b and 1c).

[0057] The construction process of the present invention adopts a steel-concrete structure casing construction, and the casing consists of a casing bottom plate prefabricated with reinforced concrete and a steel side form.

[0058] The construction process of the present invention includes the following stages: preparation stage, casing installation stage, casing lowering stage, casing bottom plate sealing and pumping stage, and foundation concrete pouring stage;

[0059] The preparation stage includes the following steps: sinking of pile foundation casing, construction of cast-in-place piles, leveling of pile foundation casing pile heads, prefabrication of casing bottom plate 1 and skirt plate, and fabrication of steel side formwork 2;

[0060] The casing bottom plate 1 is divided into multiple rectangular prefabricated panels 10, each of which covers one or two pile foundations 4 (see Figures 2a and 2b). C-shaped wet joints 1A are set between the prefabricated panels 10, and overlapping steel bars are reserved. Each prefabricated panel 10 is reserved with a stepped pile hole 1B that is larger at the top and smaller at the bottom according to the position of the pile foundation 4. 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 rod is embedded in each of the four corners of each prefabricated panel 10.

[0061] The prefabrication steps of the box bottom plate and skirt plate include the following processes:

[0062] 1) Set up a steel platform as the prefabricated bottom formwork for the prefabricated panels;

[0063] 2) Locate the position of the pile hole on the prefabricated bottom formwork according to the center coordinates of the pile foundation and adjust the elevation;

[0064] 3) Tie the steel bars in the precast panel on the precast bottom formwork and install various embedded parts, including four hangers corresponding to each other at the four corners of the precast panel;

[0065] 4) When prefabricating the prefabricated panels at the edge of the casing bottom plate, the skirt side formwork should be installed on the prefabricated bottom formwork, and the tension bolts between the skirt side formwork and the prefabricated bottom formwork should be tightened;

[0066] 5) Pour concrete and remove the skirt board side formwork and precast bottom formwork after 24 hours;

[0067] After the prefabricated panels 10 are prefabricated, the bottom support angle steel 3 for supporting the steel side formwork is installed on the outer surface of each prefabricated panel 10 located at the edge of the casing bottom plate 1 through embedded bolts 30. The distance between the top surface of the bottom support angle steel 3 and the top surface of the prefabricated panel 10 is 20 cm.

[0068] The steel side formwork 2 is a wall-wrapped bottom structure, meaning the bottom of the steel side formwork 2 overlaps the outer surface of the casing bottom plate 1 by 20 cm. The steel side formwork 2 is composed of multiple side formwork pieces, each of which is 5.2 m high and 3 m long. The bottom of each side formwork piece is supported on the bottom support angle 3, and each side formwork piece is supported vertically by a diagonal brace 20 whose lower end is fixed to the casing bottom plate 1. The support height of the diagonal brace 20 is 4 m (see Figures 2c and 2d).

[0069] During the casing installation stage, the casing bottom plate 1 is installed first, and then the steel side formwork 2 is installed; the casing bottom plate 1 is installed using a suspension frame, which includes a pile cap 40, an anti-hanging beam 41 and two first fine-rolled threaded steel bars 42; the pile cap 40 is installed on the top of the pile foundation casing 4A; the anti-hanging beam 41 is located directly above each pile hole 1B of the prefabricated bottom plate 10; the lower ends of the two first fine-rolled threaded steel bars 42 are pre-buried in the prefabricated plate 10 and are located symmetrically on the outside of each pile hole 1B, and the upper parts of the two first fine-rolled threaded steel bars 42 are anchored to the two ends of the anti-hanging beam 41 through gaskets and sleeves (see Figure 3);

[0070] The following steps are included when installing the box bottom plate:

[0071] Step 1: First, install a floatable gap-sealing bottom formwork between the pile hole 1B of the casing bottom plate 1 and the pile casing 4A on the pile casing 4A. The gap-sealing bottom formwork consists of an annular wooden formwork 61, an annular foam bottom plate 62, and a rubber gasket 63 stacked from bottom to top. Then, install the pile cap 40 on the top of the pile casing 4A.

[0072] Step 2: First, connect the crane of the crane ship to the rectangular frame hanger, then connect the hanger to the four hangers on the precast panel 10, and then use the crane of the crane ship to lift the precast panel 10 above the corresponding pile foundation casing 4A and put the pile hole 1B on the precast panel 10 onto the corresponding pile foundation casing 4A, observe the elevation and horizontal position of the precast panel 10, adjust the position of the gasket and sleeve on the first fine-rolled threaded steel bar 42 according to the observation results, adjust the elevation deviation of the precast panel 10 to ≤5mm, and use the radial setting The jack on the stepped surface of the pile hole 1B adjusts the planar position deviation of the precast panel 10 to ≤10mm, then lowers the precast panel 10 until the counter-hanging beam 41 on the precast panel 10 falls on the corresponding pile cap 40. The counter-hanging beam 41 and the pile cap 40 are then welded and fixed. Finally, the hanger is separated from the hanger rod, and the precast panel 10 is supported by the hanger so that the precast panel 10 is above the water surface. At this time, the weight of the precast panel 10 is transmitted to the pile foundation casing 4A through the first fine-rolled threaded steel bar 42, the counter-hanging beam 41 and the pile cap 40.

[0073] Step 3: Install the remaining prefabricated panels piece by piece, referring to step 2, until the entire box bottom plate is installed. At this time, the suspension frames on each prefabricated bottom plate constitute a suspension frame system;

[0074] Step 4: First, weld the overlapping steel bars of the wet joints 1A between the prefabricated panels 10, and then pour concrete in the wet joints 1A to form a complete box bottom plate 1;

[0075] When installing the steel side formwork, first install two layers of water-stopping expansion rubber sheets 31 on the top surface of the bottom supporting angle steel 3 on the outer side surface of the casing bottom plate 1, and then install the side formwork piece by piece on the top surface of the bottom supporting angle steel 3. Two rows of bolts are used to splice the adjacent side formworks, and a water-stop rubber strip is provided in the middle and on both sides of the two rows of bolts on the splicing surface; the steel side formwork 2 and the bottom supporting angle steel 3 are connected by multiple vertical tie rods 2A arranged at intervals of 1.5m to restrict the horizontal movement of the casing bottom plate 1; a layer of water-stopping expansion rubber sheet 31 is provided between the lower inner side surface of the steel side formwork 2 and the lower part of the overlapping surface of the casing bottom plate 1, and the gap between the lower inner side surface of the steel side formwork 2 and the upper part of the overlapping surface of the casing bottom plate 1 is filled with structural adhesive 32, and then the lower end of the diagonal brace 20 of the side formwork is fastened to the casing bottom plate 1 (see Figures 2c and 2d);

[0076] The stage of lowering the box includes the following steps:

[0077] Step 1: Install a jack lowering system on the casing bottom plate 1, which includes an I-shaped hanger 50, a shoulder pole beam 52, a through-hole jack 53 and a steel strand 54; the I-shaped hanger 50 is fixed to the casing bottom plate 1 through four second fine-rolled threaded steel bars 51 pre-buried on the casing bottom plate 1 and is located between the two inverted hanging beams 41; the shoulder pole beam 52 is erected between the middle parts of the top surfaces of the two inverted hanging beams 41; the through-hole jack 53 is installed in the middle part of the top surface of the shoulder pole beam 52; the lower end of the steel strand 54 passes through the through-hole jack 53 and the through-hole of the shoulder pole beam 52 in sequence and is anchored in the middle part of the waist of the I-shaped hanger 50 (see Figures 4 and 5);

[0078] Step 2: First, symmetrically install two 4m long anti-support rods 6 on the outside of the pile casing 4A. The bottom of the anti-support rod 6 is fixed to the casing bottom plate 1 by bolts, and the upper end of the anti-support rod 6 is free;

[0079] Step 3: First, loosen the sleeve anchored by the first fine-rolled threaded steel bar 42 and the counter-hanging beam 41 on each hanger, then step by step lift the casing upward by 20 cm through the multiple through-hole jacks 53 in the jack lowering system, so that the casing is converted from being supported by the hanger system to being supported by the jack lowering system, and then lower the casing into the water, so that the gravity of the casing is transmitted to the pile foundation casing 4A through the casing bottom plate 1, the second fine-rolled threaded steel bar 51, the I-shaped hanger 50, the steel strand 54, the through-hole jack 53, the shoulder beam 52, the counter-hanging beam 41, and the pile cap 40, until the top elevation of the casing bottom plate 1 reaches the designed bottom elevation of the pedestal; the gap sealing bottom mold on each pile foundation casing 4A is pressed into the water as the casing is lowered;

[0080] The casing bottom plate sealing and pumping stage includes the following steps:

[0081] Step 1: After the casing is lowered into place, the top elevation of the anti-support rod 6 is also lower than the top elevation of the pile foundation casing 4A. First, the top of the anti-support rod 6 is welded and fixed to the outer surface of the pile foundation casing 4A, and then the first fine-rolled threaded steel bar 42 on each hanger is re-tightened to the sleeve anchored to the anti-hanging beam 41, so that the gravity of the casing is borne by the hanger again, and the buoyancy of the casing is resisted by the anti-support rod 6, forming a pulling and supporting system (see Figure 6), and then the jack lowering system is dismantled;

[0082] Step 2: At low tide, the gap-sealing bottom formwork pre-installed on each pile foundation casing 4A is lifted up until the top surface of the annular foam bottom plate is in close contact with the bottom surface of the casing bottom plate 1, and the rubber gasket 63 is inserted into the gap between the pile hole 1B and the pile foundation casing 4A. Then, a mixed mortar 60 containing epoxy resin is poured between the gap-sealing bottom formwork and the casing bottom plate 1 and solidified 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.

[0083] Step 3: Drain the water in the casing to create dry working conditions;

[0084] The foundation concrete pouring phase includes the following steps:

[0085] Step 1: Weld 7 to 8 shear keys 7 evenly distributed along the circumference of the outer surface 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);

[0086] Step 2: First remove the counter-support 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 foundation casing 4A to the designed top elevation. Then, 300 mm above the designed elevation of the pile top, use a rock splitting rod to drill 6 to 8 holes along the pile head radially, with a hole depth of 40 to 50 cm. Insert a hydraulic flange separator into the drilled holes to separate the concrete pile head. Then, lift the separated concrete pile head away as a whole. Use a jackhammer to manually remove the remaining 300 mm height of the concrete above the pile top.

[0087] Step 3: First, set up a wooden inner formwork between the main bearing platform and the anti-collision bearing platform, then use a rope saw method to cut the bottom plate of the casing to ensure that the main bearing platform and the anti-collision bearing platform are separated, then tie the steel 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 braces 20 of the side formwork 2 are poured in the concrete; after pouring the second layer of concrete, first install the tension screw 2B on the side formwork 2 above the second layer of concrete, that is, at a height of 4.7m, then cut off the diagonal braces 20 above the top surface of the second layer of concrete, and then pour the third layer of concrete (see Figure 8);

[0088] Step 4: Remove the steel side formwork.

[0089] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those skilled in the art may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the scope of the present invention and should be defined by the claims.

Claims

1. A construction process for a high-pile foundation of an offshore bridge, the foundation comprising a main foundation and a circle of anti-collision foundations arranged on the outside of the main foundation, the distance between the main foundation and the anti-collision foundation is A, and a circle of skirt plates extending into the bottom B of the anti-collision foundation is arranged on the outside of the anti-collision foundation; the plane of the main foundation is rectangular and supported by twelve pile foundations arranged in three rows horizontally and four columns vertically; the plane of a circle of anti-collision foundations is a non-regular octagon that is narrow in the vertical direction and wide in the horizontal direction, and the anti-collision foundation is supported by thirty-six pile foundations, and the pile foundations are cast-in-place piles; the construction process adopts a steel-concrete structure casing construction, and the casing is composed of a casing bottom plate and steel side molds prefabricated with reinforced concrete; the construction process includes the following stages: a preparation stage, a casing installation stage, a casing lowering stage, a casing bottom plate plugging and pumping stage, and a foundation concrete pouring stage; it is characterized in that, The preparation stage includes the following steps: sinking of pile foundation casing, construction of cast-in-place piles, cutting of pile foundation casing pile heads, prefabrication of casing bottom plates and skirt plates, and production of steel side forms; During the prefabrication steps of the casing bottom plate and the skirt plate, the casing bottom plate is divided into a plurality of rectangular prefabricated panels, each of which covers 1 to 2 pile foundations; C-shaped wet joints are arranged between the prefabricated panels and overlapping steel bars are reserved; a stepped pile hole with a larger top and a smaller bottom is reserved on each prefabricated panel according to the position of the pile foundation; during prefabrication, a suspension rod is embedded in each of the four corners of each prefabricated panel; after the prefabrication of the prefabricated panels is completed, the 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 casing bottom plate through embedded bolts; The steel side formwork is formed by splicing multiple side formworks; the bottom of each side formwork is supported on the bottom support angle steel, and each side formwork is supported in a vertical state by a diagonal brace fixed at the lower end to the bottom plate of the casing; During the installation stage of the casing, the casing bottom plate is installed first, and then the steel side formwork is installed; the casing bottom plate is installed by a suspension frame, and the suspension frame includes a pile cap, an anti-hanging beam and two first fine-rolled threaded steel bars; the pile cap is installed on the top of the pile foundation casing; the anti-hanging beam is arranged directly above the pile hole of the prefabricated bottom plate; the lower ends of the two first fine-rolled threaded steel bars are pre-buried in the prefabricated plate and are centrally symmetrically located outside each pile hole, and the upper parts of the two first fine-rolled threaded steel bars are anchored to the two ends of the anti-hanging beam one by one through gaskets and sleeves; The following steps are included when installing the casing bottom plate: Step 1: first install a bottom formwork for plugging the floating gap between the pile hole of the casing bottom plate and the pile casing on the pile casing, and then install a pile cap on the top of the pile casing; Step 2: first connect the crane of the crane ship to the rectangular frame hanger, then connect the hanger to the four hangers on the prefabricated plate, and then use the crane of the crane ship to lift the prefabricated plate to the top of the corresponding pile foundation casing and put the pile hole on the prefabricated plate on the corresponding pile foundation casing, and then lower the prefabricated plate until the anti-hanging beam on the prefabricated plate falls on the corresponding pile cap, and then weld the anti-hanging beam and the pile cap to fix, and finally separate the hanger from the hanger, and support the prefabricated plate by the suspension frame, so that the prefabricated plate is above the water surface; Step 3: Install the remaining prefabricated panels piece by piece according to step 2 until the entire casing bottom plate is installed; Step 4: First weld the overlapping steel bars of the wet joints between the prefabricated panels, and then pour the concrete of the wet joints to form a complete box bottom plate; When installing the steel side formwork, first install two layers of water-stop expansion rubber sheets on the top surface of the bottom support angle steel on the outer side surface of the casing bottom plate, and then install the side formwork piece by piece on the top surface of the bottom support angle steel. Two rows of bolts are used to splice the adjacent side formworks, and a water-stop rubber strip is respectively arranged in the middle and on both sides of the two rows of bolts on the splicing surface; the steel side formwork and the bottom support angle steel are connected by a plurality of vertical tie rods arranged at intervals, and a layer of water-stop expansion rubber sheet is arranged between the lower inner side surface of the steel side formwork and the lower part of the overlap surface of the casing bottom plate, and the gap between the lower inner side surface of the steel side formwork and the upper part of the overlap 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 casing lowering stage comprises the following steps: Step 1: Install a jack lowering system on the bottom plate of the casing, the jack lowering system includes an I-shaped hanger, a shoulder pole beam, a through-hole jack and a steel strand; the I-shaped hanger is fixed to the bottom plate of the casing through four second fine-rolled threaded steel bars pre-buried in the bottom plate of the casing and is located between the two inverted hanging beams; the shoulder pole beam is erected between the middle parts of the top surfaces of the two inverted hanging beams; the through-hole jack is installed in the middle part of the top surface of the shoulder pole beam; the lower end of the steel strand is successively passed through the through-hole jack and the shoulder pole beam and then anchored in the middle part of the waist of the I-shaped hanger; Step 2: First, install two anti-support rods on the outside of the pile foundation casing, the bottom of the anti-support rods is fixed to the bottom plate of the casing by bolts, and the upper end of the anti-support rods is free; Step 3: First, loosen the sleeves of the first finely rolled threaded steel bars and the anchoring sleeves of the anti-hanging beams on each suspension frame, and then step by step lower the entire casing into the water through multiple through-hole jacks in the jack lowering system until the top elevation of the casing bottom plate reaches the designed bottom elevation of the cap; The casing bottom plate plugging and pumping stage comprises the following steps: Step 1: After the casing is lowered into place, the top elevation of the anti-support rod is also lower than the top elevation of the pile foundation casing. First, the top of the anti-support rod is welded and fixed to the outer surface of the pile foundation casing, and then the first fine-rolled threaded steel on each suspension frame is re-tightened to the sleeve anchored by the anti-hanging beam, so that the gravity of the casing is borne by the suspension frame again, and the buoyancy of the casing is resisted by the anti-support rod, and then the jack lowering system is dismantled; Step 2: At low tide, the gap plugging bottom mold pre-set on the pile foundation casing is lifted up until it is tightly fitted with the casing bottom plate, and then a mixed mortar containing epoxy resin is poured between the gap plugging bottom mold and the casing bottom plate, and solidified for 1 hour to complete the gap plugging between each pile foundation casing and the corresponding pile hole on the casing bottom plate; Step 3: Drain the water in the casing to create dry working conditions; The cap concrete pouring stage includes the following steps: Step 1: Weld a plurality of shear keys evenly distributed along the circumference on the outer circumference of each pile foundation casing, the inner ends of the plurality of shear keys are welded and fixed on the outer surface of the pile foundation casing, and the lower ends of the plurality of shear keys are bolted and fixed on the step surface of the pile hole of the casing bottom plate; Step 2: first remove the anti-support rod and the suspension frame, so that the entire casing is supported by the shear key; then cut the pile foundation casing to the designed top elevation, and then use a rock splitting rod to drill 6 to 8 holes along the pile head radially 300mm above the designed elevation of the pile top, with a depth of 40 to 50cm; insert the hydraulic flange separator into the hole to separate the concrete pile head, and then lift the separated concrete pile head away as a whole, and manually chisel the remaining 300mm concrete on the top of the pile with a pneumatic pick; Step three, first set a wooden inner formwork between the main cap and the anti-collision cap to separate the main cap and the anti-collision cap, then tie the steel bars in layers in the casing, and then pour concrete in three layers; when pouring the first and second layers of concrete, the diagonal braces of the side formwork are poured in the concrete; after pouring the second layer of concrete, first install the tension screws on the side formwork above the second layer of concrete, then cut off the diagonal braces with a height 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 tension screws control the verticality of the side formwork; Step 4: first remove the steel side formwork, then use the rope saw method to cut the casing bottom plate to ensure that the casing bottom plate is separated from the main pedestal and the anti-collision pedestal.

2. The construction process of the high pile cap of the offshore bridge according to claim 1 is characterized in that: The prefabrication steps of the box bottom plate and skirt plate include the following processes: 1) Set up a steel platform as the prefabricated bottom formwork for the prefabricated panels; 2) Locate the position of the pile hole on the prefabricated bottom formwork according to the center coordinates of the pile foundation and adjust the elevation; 3) Tie the steel bars in the prefabricated plate on the prefabricated bottom formwork and install various embedded parts, including four hangers corresponding to each other at the four corners of the prefabricated plate; 4) When prefabricating the prefabricated plate located at the edge of the casing bottom plate, the skirt plate side mold should be installed on the prefabricated bottom mold, and the tension bolts between the skirt plate side mold and the prefabricated bottom mold should be tightened; 5) Pour concrete and remove the skirt side formwork and precast bottom formwork after 24 hours.

3. The construction process of the high pile cap of the offshore bridge according to claim 1 is characterized in that: The gap blocking bottom mold is composed of an annular wooden mold plate, an annular foam bottom plate and a rubber gasket stacked from bottom to top.

4. The construction process of the high pile cap of the offshore bridge according to claim 1 is characterized in that: During step 2 of the casing installation phase, the elevation and horizontal position of the precast panel must also be observed, and the position of the gasket and sleeve on the first fine-rolled rebar must be adjusted based on the observation results. The elevation deviation of the precast panel must be adjusted to ≤5mm, and then the plane position deviation of the precast base plate must be adjusted to ≤10mm using a jack radially arranged on the step surface of the pile hole.

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