Ultra-deep buoyancy type double-wall steel hanging box design and construction method based on sea-crossing bridge bearing platform with strong tide reciprocating flow

Abstract

The invention discloses a construction method of an ultra-deep buoyancy type double-wall steel hanging box based on a strong tide reciprocating flow sea-crossing bridge bearing platform. The construction method comprises the five process steps of preparation before construction of the steel hanging box, hoisting and lowering of the steel hanging box, preparation before pouring of bottom sealing concrete, pouring of the bottom sealing concrete and construction of the bearing platform. According to the design and construction method for the ultra-deep buoyancy type double-wall steel hanging box based on the strong tide reciprocating flow sea-crossing bridge bearing platform, the buoyancy cabin is arranged for the double-wall steel hanging box of the strong tide rapid flow ultra-large water head to ingeniously solve the problem that the self weight of the steel hanging box is large, four pile casing post-cast strips are reserved to serve as stabilizing measures for resisting reciprocating flow impact in the bearing platform construction period, and the construction efficiency is improved. The construction technology is ingenious, a foundation is laid for smoothly achieving the construction period target of the Hangzhou bay cross-sea railway bridge, and good economical efficiency, practicability and application and popularization value are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of steel hanging boxes, and in particular to a design and construction method of an ultra-deep buoyancy double-walled steel hanging box for a sea-crossing bridge foundation based on strong tidal reciprocating flow. Background Art

[0002] With the continuous development of my country's economic construction, more and more bridges are built across rivers. For most underwater bridge pile foundations, steel cofferdams are needed for construction. When the hydrological conditions in the construction area are poor, the tidal range is large, the scouring and silting are deep, the flow rate is rapid, and the construction conditions are poor, the construction safety risk of traditional steel hanging boxes is high. Due to the large changes in scouring and silting in the construction area, the risk of the steel hanging box being stranded is high. The overall installation weight of the steel hanging box is large and it needs to be quickly lowered into place and locked during low tide. The construction organization requirements are high, and the risks of marine transportation and hoisting are high. In addition, the head difference of the hanging box is large, the limit and bottom sealing construction requirements are high under high flow conditions, the single pouring volume of the foundation is large, and the control requirements for large-volume concrete construction at sea are high. Summary of the invention

[0003] The present application proposes a design and construction method for an ultra-deep buoyancy double-walled steel hanging box for a sea-crossing bridge pier based on strong tidal reciprocating flow. The application has the advantages of setting a buoyancy cabin in the B section of the double-walled wall body to reduce vertical gravity. Four steel casings are reserved during the pier construction to reduce the reciprocating horizontal force caused by the reciprocating flow, and to reduce the shaking of the double-walled steel hanging box caused by the reciprocating horizontal force, thereby reducing the seepage and separation between the wall body and the bottom concrete, and even the falling of the steel hanging box. The application has the advantages of stable measures to resist the impact of reciprocating flow during the pier construction and ingenious construction technology, which are used to solve the problem of the self-weight of the steel hanging box.

[0004] To achieve the above purpose, the present application adopts the following technical scheme: a construction method of an ultra-deep buoyancy double-walled steel hanging box for a bridge foundation under strong tidal reciprocating flow, including five process steps: preparation before construction of the steel hanging box, lifting and lowering of the steel hanging box, preparation before pouring of bottom concrete, pouring of bottom concrete and foundation construction, as follows: Step 1: Preparation before steel hanging box construction: Step 1.1: Use a telescopic arm excavator to pre-excavate the area within 2m of the steel hanging box area, and pre-excavate the riverbed to below the bottom elevation of the steel hanging box to ensure that the steel hanging box can be lowered into place smoothly; Step 1.2: Use crawler crane to hoist and clean the outer wall of each steel casing; Step 1.3: Use crawler crane to complete the installation of the hanging beam of the steel hanging box and the telescopic beam of the hanging system; drill holes in the steel casing, weld the inner bracket, and install the guide beam and cantilever beam; Step 2: Lifting and lowering the steel hanging box, including: Step 2.1, ship anchoring positioning: crane ship and steel box transport ship anchor downstream of the drilling area platform, in the order of transport ship first and crane ship later, the crane ship berthing position is not less than 300m away from the platform; Step 2.2, lifting and lowering of the steel hoisting box: the crane ship hoists the steel hoisting box forward to the main pier pedestal area, and the initial plane position of the steel hoisting box is achieved through the point alignment of the pedestal and the steel hoisting box axis; the steel hoisting box is lowered to 50cm from the top of the steel casing guide, and the bottom plate of the steel hoisting box is ensured to pass through the steel casing smoothly through the steel casing through the top guide device of the steel casing. When the steel hoisting box enters the water 6.3m, the bottom wall of the steel hoisting box begins to automatically fill with water and sink to the designed elevation; during the lifting process, the inner communicating vessel, the outer communicating vessel, and the vent valve are all in the open state, and the connecting valve is in the closed state; Step 2.3, positioning and locking the hanging box: the rough positioning of the steel hanging box is achieved through the casing bottom plate guide device between the side wall of the wall and the casing; the precise positioning of the steel hanging box is achieved through the wall body guide device for plane position and elevation control of the steel hanging box; the final positioning of the steel hanging box is achieved through the docking of the 8 hanging legs and hanging beams of the hanging leg limit guide device; Locking of the hoisting box: After the steel hoisting box hanging legs are welded to the hanging beam, monitor that the water depth in each buoyancy compartment does not exceed 0.5m, unload the hook by stages on the crane ship, and check the condition of the bracket every time the crane ship's lifting weight is reduced by 100t until the crane ship's lifting weight is reduced to 0; The crane ship loosens the hook and uses the low tide to immediately complete the three-layer limit locking and the installation of the pull rods of the 8 hanging legs. Then the crane ship wire rope connection can be released. During the construction process, the rope status monitoring after the hook is loosened during high and low tides is strengthened, and the crane ship must not carry any force; Step 3: Preparation before pouring the bottom concrete, including: Step 3.1, installation of tension and compression rods: The installation of tension rods is generally divided into two stages. The first stage is to complete the installation of 28 tension rods at 8 hanging legs after the steel hoisting box is lowered into place and before the crane ship unhooks; the second stage is to complete the installation of the remaining tension rods after the steel hoisting box is locked and before the first high tide arrives; Step 3.2, plugging plate installation: There are 42 holes in the bottom plate of the hanging box, all of which are plugged with plugging plate clamps. The plugging plate of a single casing is divided into 4 Haver plates. Before the steel hanging box leaves the factory, the clamp plate is temporarily fixed on the lower support of the pull rod and lowered to the surrounding of each casing together with the hanging box. Before sealing the bottom, the divers gather the clamps. The plugging plate needs to be fixed to the steel casing by underwater welding or bolting. After the clamps are installed, the divers use bagged cement stacking to underwater plug the local gaps; Step 3.3, cleaning the bottom plate and contact surface: After the plugging plate clamp is installed, the diver first checks the mud and sand on the bottom plate of the steel hanging box, and uses a dredging pump for local cleaning. The diver thoroughly investigates and cleans the mud, marine organisms and other debris on the casing and the hanging box wall within the bottom sealing range; Step 4: pouring the bottom concrete, including: Step 4.1, bottom cover platform erection: the bottom cover platform consists of Bailey beam, steel springboard, conductor frame, channel and guardrail; Step 4.2, Catheter and equipment layout: Lay bottom sealing concrete conduit and arrange concrete pouring points; Step 4.3, bottom seal concrete pouring: The concrete distribution points are distributed in sequence according to the distribution points in the underwater bottom seal pouring point arrangement number, and are promoted as a whole from the downstream to the upstream side. During the pouring process, the conduit that has been poured is supplemented with material every 30 minutes. The supplementing time is generally 5 minutes until the design elevation is reached; Step 5: Capping construction, including: Step 5.1, pumping and clearing the foundation and system conversion: After the strength of the bottom concrete reaches the design requirements, carry out pumping operations, arrange high-power submersible pumps to pump water to form dry construction conditions; open the buoyancy tank connector underwater, close the internal and external connectors and the air valve, control the water level of the sandwich wall to about -5.13m, and check the wall leakage at the same time; after the pumping and clearing of the foundation of the hanging box is completed, install structural diagonal braces between the casing and the steel hanging box wall along the periphery of the hanging box; after the steel hanging box system conversion construction is completed, clean the bottom concrete surface and complete the 20cm leveling layer construction; Step 5.2, cutting off the steel casing and breaking the pile head: The cutting of the steel casing is divided into two stages according to the position of the pile head. During construction, the part of the steel casing above the reinforcement cage at the top of the pile is cut first, and then the steel casing at the pile head is divided into two halves in the vertical direction and cut off. After cutting, it is lifted away by a crawler crane, the silt on the top is cleaned, and the pile head is cut and chiseled off by the ring cutting method.

[0005] Step 5.3, pedestal construction: During the construction of the first-floor pedestal, retain the four casing limits at the four corners of the hanging box as limiting measures for the first-floor pedestal construction stage. Set a post-casting section for the casing limit position. After the first-floor pedestal concrete reaches a certain strength, remove it for post-casting section construction. The overall construction sequence is: first construction of the first-floor pedestal → construction of the first-floor pedestal post-casting strip → construction of the second-floor pedestal. After the concrete is poured, follow the principle of "inside reduction and outside protection" and use cooling water pipes to pass water to reduce the temperature difference between the inside and outside of the pedestal. The curing period is not less than 14 days.

[0006] Furthermore, in step 2.2 of lifting and lowering the steel hoisting box, the distance between the bottom of the steel hoisting box and the platform is controlled to be more than 2m, and the lifting width is 60m.

[0007] Furthermore, in step 2.2, during the lifting and lowering of the steel box, the crane vessel should always remain under stress, and the lowering of the box should be controlled by the hook speed of the crane vessel. The speed should not exceed 1m / min. When the box is close to the elevation with 2m remaining, the lowering speed should be reduced so that the box can be gradually and slowly lowered to the designed elevation.

[0008] Further, step 2.3, the hanging box is in place and locked: the plane position error of the hanging box is controlled within 10cm, and the top elevation error is controlled within 2cm. In order to ensure that the force on each hanging leg is uniform, rubber bearings are installed on the hanging beam in advance. After the steel hanging box is adjusted, a 10mm steel plate is padded to make it dense according to the contact between the hanging beam and the hanging leg.

[0009] Further, step 3.1, installation of tension and compression rods: select the appropriate water level according to the guide beam elevation to install the tension and compression rods in batches, push the cantilever beam to the designed position, install the pad and apply 9kN pre-tension to the tension rods. When the cantilever length of the cantilever beam is less than 440mm, weld the limit block on site; when the cantilever length of the cantilever beam is greater than 440mm, weld the limit slot on site. After the tension rods are installed, select the low tide position to release the bottom plate hanger connection nut and convert the bottom plate force.

[0010] The ultra-deep buoyancy double-walled steel hanging box for the sea-crossing bridge cap based on strong tidal reciprocating flow includes the cap and the steel hanging box, and the steel hanging box serves as a water retaining and formwork structure during the construction of the cap; The steel hanging box includes a wall, a bottom plate, a bottom plate truss, an inner support, a hanging system, a hanging rod, a hanging leg, a hanging beam, a hanging lug, a guide device, a limit device, a connecting vessel, a vent valve, and a connecting valve; The inner contour of the steel hanging box wall is expanded by 100mm based on the outer contour of the pedestal. The wall body has sections A, B and C, and a buoyancy tank is arranged in section B of the double-wall body; The wall and bottom plate form a steel hanging box; The steel hanging box is equipped with three bottom plate trusses; The bottom plate of the steel hoisting box adopts a beam-slab structure. Holes are opened by drawing envelope lines based on the measured top and bottom plate position data of the steel casing after pile formation to ensure a net spacing of 12~20cm during the lowering process. The steel hanging box is equipped with 5 layers of internal supports; Hanging legs are set on the wall of the steel hanging box, and hanging beams are set on the steel casing to limit the vertical position of the steel hanging box; hanging legs are set at the corresponding positions of 8 steel casings selected around the wall of the steel hanging box, and hanging beams are set on the top surface of the steel casing; When the steel hanging box is lowered, a three-layer guide device is provided, including: casing bottom plate guide device; wall guide device; hanging leg limit guide device; The steel hanging box is equipped with three layers of limit devices, including: hanging leg and hanging beam limit devices, that is, the hanging legs and hanging beams are fixed by welding with stiffening plates; limit parallel joint limit devices, that is, the wall and casing steel pipe are fixed by parallel joint welding; steel wedge block limit devices, that is, the plug pad guide limit block limit; The hanging system consists of a telescopic beam, a suspender rod, and upper and lower supports. The suspender rod consists of upper and lower pull rods. The steel hanging box is symmetrically provided with 8 lifting lugs at the top; An inner connecting vessel, an outer connecting vessel, a vent valve and a connecting valve are arranged on the wall.

[0011] Furthermore, the bottom plate during the lowering period is connected to the inner support through 10 suspension rods, and the bottom plate during the bottom sealing period is connected to the steel casing through tie rods, and 3-4 tie rods are arranged on each steel casing; a hole is opened at the pile position in the bottom plate of the steel hanging box, and the hole size is φ3.24m.

[0012] Furthermore, the steel hanging box is manufactured as a whole in the processing plant. The internal support, lifting ears, hanging legs, bottom plate trusses, guide devices, and limit devices are processed together when the wall is processed. When the bottom plate is processed, the pull rod and the lower end support of the hanger are processed and manufactured together in combination with the pull rod and hanger structure diagram; the manufacturing unit divides the hanging box wall and the bottom plate into unit blocks according to the actual situation of the processing site and the lifting and installation capacity. Equal strength welding is used when assembling each unit block of the steel hanging box, and all splicing welds are continuous and full welds.

[0013] Furthermore, in order to enable the bottom plate of the steel hoisting box to be smoothly put on the steel casing, it is necessary to open holes at the corresponding positions of the bottom plate of the steel hoisting box according to the actual position of the steel casing, and to reduce the gap between the bottom plate and the steel casing as much as possible when opening the holes, so as to facilitate the sealing of the gap; There are 42 holes in the bottom plate of the hoisting box, all of which are blocked with sealing plates and clamps. The sealing plates of a single steel casing are divided into 4 Haver plates. Before the steel hoisting box leaves the factory, the clamp plates are temporarily fixed on the lower support of the pull rod and lowered along with the hoisting box to the four sides of each casing. The sealing plates are fixed to the steel casing by underwater welding or bolt connection.

[0014] Furthermore, the cap is round-ended, with a plane size of 51.9m×36.4m and a thickness of 7m. 42 φ2.5m piles are set under the cap, the steel casing has a diameter of 2.8m and a wall thickness of 20mm.

[0015] The present invention has the following beneficial effects: 1. The present application provides a design and construction method for an ultra-deep buoyant double-walled steel hanging box for a sea-crossing bridge pier based on strong tidal reciprocating flow. During the construction process, due to the heavy weight of the double-walled steel hanging box, the hanging legs are usually relied on to bear all the weight of the double-walled steel hanging box when it is lowered into place during construction. However, considering the harsh construction conditions such as strong tides, rapids and large tidal ranges in the water area, the present invention adopts a method in which water is not allowed to enter the B-section wall before the bottom concrete pouring reaches the strength during the construction process. This is an effective measure to increase buoyancy and reduce the weight of the double-walled steel hanging box, reduce the weight borne by the hanging legs, and actively control the overall vertical force. In addition, water is allowed to enter the buoyancy cabin after the bottom concrete reaches the strength. At this time, the buoyancy cabin has the same function as other double-walled steel hanging box walls.

[0016] 2. The present application provides a design and construction method for an ultra-deep buoyant double-walled steel hanging box for a sea-crossing bridge pier based on strong tidal reciprocating flow. Aiming at the double-walled steel hanging box with ultra-large water head in strong tidal rapids, a buoyancy cabin is provided to cleverly solve the problem of the self-weight of the steel hanging box. Four casing post-cast strips are reserved as a stabilizing measure to resist the impact of reciprocating flow during pier construction. The construction process is ingenious, laying the foundation for the smooth realization of the construction schedule target of the Hangzhou Bay Sea-Crossing Railway Bridge, and has good economy, practicality and promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute a part of the specification, illustrate embodiments disclosed in the present application and, together with the description, serve to explain the principles disclosed in the present application.

[0018] The present disclosure may be more clearly understood from the following detailed description with reference to the accompanying drawings, in which: Figure 1 This is the construction process flow chart for this application; Figure 2 For this application, the steel hanging box layout Figure 1 ; Figure 3 For this application, the steel hanging box layout Figure 2 ; Figure 4 For this application, the steel hanging box layout Figure 3 ; Figure 5 This is the layout drawing of the steel hanging box bottom plate for this application; Figure 6 for Figure 2 AA section view; Figure 7 for Figure 2 BB cross-sectional view; Figure 8 It is a schematic diagram of the limiting device and the guiding device.

[0019] In the figure: 1. wall; 2. bottom plate; 3. bottom plate truss; 4. internal support; 5. hanging system; 6. hanging rod; 10. guide device; 11. limit device; 12. connecting vessel; 13. air valve; 14. connecting valve; 15. steel casing. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] See attached Figure 1As shown in the figure, the construction method of the ultra-deep buoyancy double-walled steel hanging box for the cap of the cross-sea bridge based on the strong tidal reciprocating flow includes five process steps: preparation before the steel hanging box construction, lifting and lowering of the steel hanging box, preparation before the bottom concrete pouring, bottom concrete pouring and cap construction, which are as follows: Step 1: Construction preparation: Step 1.1: The bottom elevation of the steel hanging box is -19.458m. Use a telescopic arm excavator to pre-excavate within 2m of the hanging box area. The riverbed surface is pre-excavated to an elevation of -20.5m to ensure that the steel hanging box can be lowered into place smoothly.

[0022] Step 1.2: Before lowering the steel hoisting box, use a crawler crane to clean the outer wall of each casing. The cleaning tool includes high-pressure water and wire brushes, and divers are arranged to dive down to investigate and clean.

[0023] Step 1.3: Use crawler crane to complete the installation of hanging beam of hanging box and telescopic beam of hanging system, drill holes in steel casing, weld inner bracket, install guide beam and cantilever beam.

[0024] Step 2: Lift and lower the steel hanging box: Step 2.1, ship anchoring and positioning: the crane ship and the steel box transport ship anchor downstream on the platform, in the order of transport ship first and crane ship later. The crane ship's anchor cable length is not less than 500m, and the crane ship's berthing position is not less than 300m from the platform. A trial lift is carried out before lifting the box.

[0025] Step 2.2, lifting and lowering of the steel hoisting box: The crane ship lifts the steel hoisting box forward to the main pier pedestal area, and aligns the pedestal and steel hoisting box axis points to control the distance between the bottom of the steel hoisting box and the platform to more than 2m, with a lifting width of 60m, to achieve the initial positioning of the plane position of the steel hoisting box.

[0026] The steel box is lowered to 50cm from the top of the casing guide. The bottom plate of the steel box is fine-tuned by the crane ship to pass through the casing top guide device to ensure that the bottom plate of the steel box passes through the casing smoothly. When the box enters the water 6.3m, the bottom wall of the steel box begins to automatically fill with water and sink. During the lowering process, the crane ship should always maintain a stress state, and the lowering of the box is controlled by the speed of the crane ship's hook. The speed should not exceed 1m / min. When the box is close to the elevation and there is 2m left, the lowering speed is reduced to allow the box to gradually and slowly descend to the design elevation.

[0027] During the lifting process, the inner communicating vessel, outer communicating vessel and vent valve are all in the open state, and the connecting valve is in the closed state.

[0028] Step 2.3, positioning and locking the hanging box: The precise positioning of the steel hanging box before it is in place is mainly achieved by plane position and elevation control. The plane position error of the hanging box is controlled within 10cm, and the top elevation error is controlled within 2cm. Rough positioning is performed through the guide device between the side wall and the casing; when the hanging box is close to the final elevation, the crane ship is used to fine-tune the plane position of the hanging box so that the hanging legs enter the guide of the hanging beam, and the final positioning is achieved by connecting 8 hanging legs and hanging beams. In order to ensure that the force on each hanging leg is uniform, rubber bearings are installed on the hanging beam site in advance. After the steel hanging box is adjusted, a 10mm steel plate can be added to make it dense according to the contact between the hanging beam and the hanging leg.

[0029] Locking of the hoisting box: After the steel hoisting box hanging legs and hanging beams are welded, the water depth in each buoyancy compartment is monitored to be no more than 0.5m. The crane ship unloads the hook in stages, and the condition of the bull leg is checked every time the crane ship's lifting weight is reduced by 100t until the crane ship's lifting weight is reduced to 0. The crane ship uses the low tide to immediately complete the three-layer limit locking, i.e., the hanging legs and hanging beams, the limit flat joint, the locking of the steel wedge block, and the installation of the pull rods of the 8 hanging legs. The crane ship's wire rope connection can then be released. During the construction process, the monitoring of the rope status after the hook is loosened during the rising and falling tides should be strengthened, and the crane ship should not be loaded.

[0030] After the steel box is launched, the internal connecting vessel is submerged in the water when it is about 6.0m deep, and water is automatically injected into the sandwich wall to assist the steel box to sink. During the sinking process of the steel box, the floating belt load slowly falls. The steel box is lowered into place at low tide, and the hanging beam is stably placed on the steel casing.

[0031] After the steel hanging box sinks into place, the hanging legs are firmly connected to the steel casing with stiffening plates and pads; the water level in the buoyancy tank is monitored in real time. When the water level in the buoyancy tank exceeds 1m, a water pump is used to pump out the water in the buoyancy tank through the connecting pipe. After the water level in the buoyancy tank is controlled at 0.5m or below, the floating hook is loosened and the four diagonal braces at the arc section hanging point are cut off.

[0032] Use wedge blocks to temporarily fix the guide transfer and steel casing; use welding limit flat joints at low tide to connect the wall and steel casing; pour concrete between the hoop and the steel casing to firmly connect the bottom limit and steel casing.

[0033] Monitor the water level in the buoyancy tank in real time. The water level in the buoyancy tank shall not be greater than 1m. When it exceeds 0.5m, an alarm will be issued and excess water will be pumped out with a water pump.

[0034] Step 3: Preparation before pouring the bottom concrete, including: Step 3.1, installation of tension and compression rods: The installation of tension rods is generally divided into two stages: the first stage is to complete the installation of 28 tension rods on 8 hanging legs after the steel hoisting box is lowered into place and before the crane ship unhooks; the second stage is to complete the installation of the remaining tension rods after the steel hoisting box is locked and before the first high tide arrives. According to the elevation of the guide beam, select the appropriate water level to install the tension and compression rods in batches, push the cantilever beam to the designed position, install the pad and apply 9kN pre-tension to the tension rod. When the cantilever length of the cantilever beam is less than 440mm, the limit stopper is welded on site; when the cantilever length of the cantilever beam is greater than 440mm, the limit slot is welded on site. After the tension rod is installed, select the low tide level to release the bottom plate hanger connecting nut and convert the bottom plate force.

[0035] Step 3.2, plugging plate installation: There are 42 holes in the bottom plate of the hanging box, all of which are plugged with plugging plate clamps. The plugging plate of a single casing is divided into 4 Haver plates. Before the steel hanging box leaves the factory, the clamp plate is temporarily fixed on the lower support of the pull rod and lowered to the surrounding of each casing together with the hanging box. Before sealing the bottom, the diver gathers the clamp. The plugging plate needs to be fixed to the steel casing by underwater welding or bolting. After the clamp is installed, the diver uses bagged cement to pile up and plug the gaps underwater.

[0036] Step 3.3, cleaning the bottom plate and contact surface: After the plugging plate clamp is installed, the diver first checks the mud and sand on the bottom plate of the steel hanging box and uses a dredging pump for local cleaning. The diver thoroughly investigates and cleans the mud, marine organisms and other debris on the casing and the hanging box wall within the bottom sealing range.

[0037] Step 4: pouring the bottom concrete, including: Step 4.1, bottom platform erection: the bottom platform consists of Bailey beam, steel springboard, conductor frame, passage and guardrail.

[0038] Step 4.2, arrangement of conduits and equipment: The bottom concrete conduit is made of seamless steel pipe with an inner diameter of φ325mm and a wall thickness of δ=8mm. The bottom of the conduit is installed 20~30cm away from the bottom of the hoisting box. 30 sets of conduits are configured on site for turnover, and the length of each set of conduits is 27m. According to the situation of the hoisting box, a total of 49 casting points are arranged. Two 30m3 large hoppers are arranged at the 1# and 2# points for the first sealing, and 3m³ medium hoppers are used at the remaining points. Two 52m automobile pumps are arranged on the surrounding trestle platforms for pumping at the bottom of the hoisting box, and two self-unloading casting points are set up on the material platform side. A 150t crawler crane is arranged on the trestle on the ship side, and two 100t crawler cranes are arranged on the material platform side.

[0039] Step 4.3, pouring of bottom concrete: a 20cm thick leveling layer is reserved for the hanging box, the bottom concrete pouring volume is 5168m³, the planned pouring time is 45 hours, and the initial setting time of concrete is not less than 50h. The concrete distribution points are distributed in sequence according to the distribution points in the underwater bottom pouring point arrangement number, and the whole is promoted from the downstream to the upstream side. During the pouring process, the conduit that has been poured is supplemented every 30 minutes, and the supplementary time is generally 5 minutes until the design elevation is reached. The bottom top elevation of the first design of the bottom is -15.3m. During the construction process, the concrete elevation is measured according to the sequential measuring points, and detailed records are made.

[0040] Step 5: Capping construction, including: Step 5.1: Pumping and clearing the foundation and system conversion: After the strength of the bottom concrete reaches the design requirements, pumping operations are carried out. 8 high-power submersible pumps are arranged, and the pumping volume is about 15,000m 3 , forming dry construction working conditions. Open the buoyancy tank connector underwater, close the internal and external connectors and the air valve, control the wall water level to about -5.13m, and check the wall leakage at the same time.

[0041] After the water is pumped out and the foundation is cleared for the hanging box, structural diagonal braces are installed between the casing and the hanging box wall along the periphery of the hanging box.

[0042] After the steel hanging box system conversion construction is completed, clean the bottom concrete surface and complete the 20cm leveling layer construction.

[0043] Step 5.2: Cutting off the steel casing and breaking the pile head: The cutting of steel casing is divided into two stages according to the position of the pile head. During construction, the part of the steel casing above the reinforcement cage at the top of the pile is cut first, and then the steel casing at the pile head is cut into two halves in the vertical direction. After cutting, it is lifted away by a crawler crane and the silt on the top is cleaned. The pile head is cut and chiseled by the ring cutting method.

[0044] Step 5.3: Capping construction: During the construction of the first-floor pedestal, in order to ensure the stability of the hanging box under the impact of reciprocating flow, the four casing limits at the four corners of the hanging box are retained as limiting measures during the construction of the first-floor pedestal. A post-casting section is set for the casing limit position. After the first-floor pedestal concrete reaches a certain strength, it is removed for post-casting section construction. The overall construction sequence is: first construction of the first-floor pedestal → construction of the post-casting strip of the first-floor pedestal → construction of the second-floor pedestal. During the construction of the pedestal, four casings are reserved to reduce the reciprocating horizontal force caused by the reciprocating flow, reduce the shaking of the double-walled steel hanging box caused by the reciprocating horizontal force, and thus reduce the seepage, separation, and even falling of the steel hanging box between the wall and the bottom concrete caused by the shaking. During the construction of the foundation, the buoyancy of the steel box wall is affected by the tide, and the vertical force direction of the wall changes due to the tide. The vertical force direction of the steel box wall changes four times in one day, and the force is large, with the maximum force reaching 1207t; the reciprocating flow twice a day has a great influence on the swing and deformation of the steel box wall; under such a huge vertical and horizontal repeated force, it is very easy to cause the bottom seal concrete to separate from the steel box wall, the bond failure, the concrete cracking and leakage, and the steel box sinking, and the construction risk is extremely high. This kind of steel box sinking has occurred in the construction process of other cross-sea bridges, which is extremely dangerous and delays the construction period. In order to ensure safety during the construction of the first layer of the pier, reduce the wall swing amplitude of the reciprocating flow velocity, enhance the holding strength of the casing, and assist in the stress under large tidal conditions, and also as a safeguard measure after learning from the lessons of leakage and falling of steel hanging boxes in other similar cross-sea bridge projects, it is necessary to retain the 4 casings of the pier as a limiting measure for the hanging box during the construction phase of the first layer of the pier.

[0045] The maximum single pouring height of the cap concrete is 3.5m, and the maximum pouring volume is 5617m3. After the concrete is poured, according to the principle of "lowering the temperature inside and protecting the outside", cooling water pipes are used to reduce the temperature difference between the inside and outside of the cap, and the curing period is not less than 14 days.

[0046] During the low tide period, 4m thick bottom concrete is poured at one time. During the pouring of the bottom concrete, the connecting valve is always open. After the bottom concrete reaches the design strength, the connecting valve is opened at an appropriate water level, and the inner and outer connecting valves and the air valve are closed. Water is pumped out in stages in the hanging box and the sandwich wall until the water in the hanging box is drained and the sandwich wall water level is controlled at about -5.13m (it can float up and down by 0.5m).

[0047] Install a ladder on the inside of the steel hanging box, cut off the steel casing and tie rod structure, level the top surface of the bottom concrete, clean the pile head, tie the steel bars, and pour the first layer of 3.5m thick foundation.

[0048] After the first layer of the foundation reaches the designed strength, 1.38m of water is injected into the sandwich wall and the water level of the sandwich wall is controlled at -3.75m.

[0049] Remove the fifth-layer internal support and the connecting supports and diagonal supports between the fourth and fifth layers, clean the concrete surface, tie the steel bars, and pour the second-layer 3.5m thick foundation.

[0050] After the concrete of the foundation reaches the required strength, the fourth-layer internal support, the third-layer two-side straight supports, and the connecting supports and diagonal supports between the third and fourth-layer internal supports are removed, the tower base steel bars are tied, and the tower base concrete is poured. After the tower base concrete reaches the required strength, the tower body steel bars are tied, and the tower columns are constructed layer by layer.

[0051] After all the construction is completed, open the external communicating vessel to keep the water level inside and outside the wall consistent, remove the internal support layer by layer from bottom to top underwater, cut off the wall underwater, and recycle the steel.

[0052] The ultra-deep buoyancy double-walled steel hanging box for the sea-crossing bridge cap based on strong tidal reciprocating flow includes the cap and the steel hanging box, and the steel hanging box serves as a water retaining and formwork structure during the construction of the cap; The steel hanging box includes a wall 1, a bottom plate 2, a bottom plate truss 3, an inner support 4, a hanging system 5, a hanging rod 6, a hanging leg, a hanging beam, a hanging lug, a guide device 10, a limit device 11, a connecting vessel 12, a vent valve 13, and a connecting valve 14; The inner contour dimensions of the steel hanging box wall 1 are expanded by 100mm based on the outer contour dimensions of the pedestal. The thickness of the wall 1 is 1.8m, and the outer contour dimensions are 55.7m×40.2m. The top elevation of the hanging box is +6.0m, the top elevation of the double wall is +4.5m, the bottom elevation of the bottom cover is -19.10m, the bottom cover is 4m thick, and the total height of the wall 1 is 25.1m, of which the single wall is 1.5m high.

[0053] The wall body 1 comprises section A, section B and section C. In order to reduce the pressure on the hanging legs after the hanging box is in place, a buoyancy cabin is arranged in section B of the double-walled wall body. During the construction process, due to the heavy weight of the double-walled steel hanging box, the hanging legs are usually relied on to bear all the weight of the double-walled steel hanging box when it is lowered into place during construction. However, considering the adverse construction conditions such as strong tides, rapids and large tidal ranges in the water area, the method of not allowing water to enter the section B wall body before the bottom concrete pouring reaches the strength is adopted during the construction process of the present invention. This is an effective measure to increase buoyancy and reduce the weight of the double-walled steel hanging box, reduce the weight borne by the hanging legs, and actively control the overall vertical force. In addition, water is allowed to enter the buoyancy cabin after the bottom concrete reaches the strength. At this time, the buoyancy cabin has the same function as other double-walled steel hanging box walls.

[0054] The wall body 1 and the bottom plate 2 enclose the box body of the steel hanging box, and 5 internal supports 4 and 3 bottom plate trusses 3 are vertically arranged inside the box body, and the height of the bottom plate trusses 3 is 3.375m. During the lowering period, the bottom plate is connected to the internal supports 4 through 10 suspension rods 6; during the bottom sealing period, the bottom plate is connected to the steel casing 15 through tie rods, and 3-4 tie rods are arranged on each steel casing 15. A hole is opened at the pile position in the bottom plate 2 of the steel hanging box, and the hole size is φ3.24m; the bottom plate 2 of the steel hanging box adopts a beam-slab structure, and the size of the bottom plate is 55.8×40.3m. The bottom plate 2 of the steel hanging box is opened by drawing an envelope line based on the measured top mouth of the steel casing 15 after the pile is formed and the data at the position of the bottom plate 2 to ensure a net spacing of 12~20cm during the lowering process; The steel hanging box is set with 5 layers of internal supports and 4; The thickness of the bottom concrete is 4.0m. Hanging legs are set on the wall of the steel hanging box 1, and hanging beams are set on the steel casing 15 to limit the vertical position of the steel hanging box; to ensure that the hanging box is in a stable state when it sinks into place, 8 steel hanging legs are set at the corresponding positions of the steel casing 15 around the steel hanging box, and hanging beams are set on the top surface of the steel casing; During the lowering construction of the hanging box, a three-layer guide device 10 is provided, which specifically includes: ① casing bottom plate guide device; ② wall guide device; ③ hanging leg limit guide device.

[0055] The hanging box is provided with three layers of limiting devices 11, specifically including: ① a hanging leg and hanging beam limiting device, that is, the hanging leg and the hanging beam are fixed by welding with a stiffening plate; ② a limiting parallel joint limiting device, that is, the wall and the casing steel pipe are fixed by parallel joint welding; ③ a steel wedge limiting device, that is, a plug pad guide limiting block limiting device; The hanging system 5 is composed of a telescopic beam, a suspension rod 6, and upper and lower supports. The suspension rod 6 is composed of upper and lower tie rods. The lower tie rod is made of HN250×125 steel and welded to the bottom plate main beam, and the upper tie rod is made of φ50 finely rolled threaded steel. Considering the actual lifting conditions, 8 lifting lugs are symmetrically set at the top of the steel lifting box; In order to ensure the water head difference inside and outside the steel hanging box during the construction of the hanging box, external and internal connecting vessels, air valves and connecting valves are installed on the wall.

[0056] The steel hanging box is processed and assembled in the factory in blocks. During the production process, the sealed cabin is tested for water tightness. Before leaving the factory, the temporary fixing of the tie rod, the installation of the anti-sand surge rubber ring of the bottom plate, the pre-tightening of the hanging rod and the installation of auxiliary facilities are completed. After the steel hanging box is produced and inspected and qualified, it is rolled onto the ship and transported to the pier for installation by a self-propelled deck barge.

Claims

1. A construction method for an ultra-deep buoyancy double-walled steel hanging box for a bridge foundation under strong tidal reciprocating flow, characterized in that: It includes five process steps: preparation before steel hoisting box construction, lifting and lowering of steel hoisting box, preparation before pouring bottom concrete, pouring bottom concrete and foundation construction, as follows: Step 1: Preparation before steel hanging box construction: Step 1.1: Use a telescopic arm excavator to pre-excavate the area within 2m of the steel hanging box area, and pre-excavate the riverbed to below the bottom elevation of the steel hanging box to ensure that the steel hanging box can be lowered into place smoothly; Step 1.2: Use crawler crane to hoist and clean the outer wall of each steel casing; Step 1.3: Use crawler crane to complete the installation of the hanging beam of the steel hanging box and the telescopic beam of the hanging system; drill holes in the steel casing, weld the inner bracket, and install the guide beam and cantilever beam; Step 2: Lifting and lowering the steel hanging box, including: Step 2.1, ship anchoring positioning: crane ship and steel box transport ship anchor downstream of the drilling area platform, in the order of transport ship first and crane ship later, the crane ship berthing position is not less than 300m away from the platform; Step 2.2, lifting and lowering of the steel hoisting box: the crane ship hoists the steel hoisting box forward to the main pier pedestal area, and the initial plane position of the steel hoisting box is achieved through the point alignment of the pedestal and the steel hoisting box axis; the steel hoisting box is lowered to 50cm from the top of the steel casing guide, and the bottom plate of the steel hoisting box is ensured to pass through the steel casing smoothly through the steel casing through the top guide device of the steel casing. When the steel hoisting box enters the water 6.3m, the bottom wall of the steel hoisting box begins to automatically fill with water and sink to the designed elevation; during the lifting process, the inner communicating vessel, the outer communicating vessel, and the vent valve are all in the open state, and the connecting valve is in the closed state; Step 2.3, positioning and locking the hanging box: the rough positioning of the steel hanging box is achieved through the casing bottom plate guide device between the side wall of the wall and the casing; the precise positioning of the steel hanging box is achieved through the wall body guide device for plane position and elevation control of the steel hanging box; the final positioning of the steel hanging box is achieved through the docking of the 8 hanging legs and hanging beams of the hanging leg limit guide device; Locking of the hoisting box: After the steel hoisting box hanging legs are welded to the hanging beam, monitor that the water depth in each buoyancy compartment does not exceed 0.5m, unload the hook by stages on the crane ship, and check the condition of the bracket every time the crane ship's lifting weight is reduced by 100t until the crane ship's lifting weight is reduced to 0; The crane ship loosens the hook and uses the low tide to immediately complete the three-layer limit locking and the installation of the pull rods of the 8 hanging legs. Then the crane ship wire rope connection can be released. During the construction process, the rope status monitoring after the hook is loosened during high and low tides is strengthened, and the crane ship must not carry any force; Step 3: Preparation before pouring the bottom concrete, including: Step 3.1, installation of tension and compression rods: The installation of tension rods is generally divided into two stages. The first stage is to complete the installation of 28 tension rods at 8 hanging legs after the steel hoisting box is lowered into place and before the crane ship unhooks; the second stage is to complete the installation of the remaining tension rods after the steel hoisting box is locked and before the first high tide arrives; Step 3.2, plugging plate installation: There are 42 holes in the bottom plate of the hanging box, all of which are plugged with plugging plate clamps. The plugging plate of a single casing is divided into 4 Haver plates. Before the steel hanging box leaves the factory, the clamp plate is temporarily fixed on the lower support of the pull rod and lowered to the surrounding of each casing together with the hanging box. Before sealing the bottom, the divers gather the clamps. The plugging plate needs to be fixed to the steel casing by underwater welding or bolting. After the clamps are installed, the divers use bagged cement stacking to underwater plug the local gaps; Step 3.3, cleaning the bottom plate and contact surface: After the plugging plate clamp is installed, the diver first checks the mud and sand on the bottom plate of the steel hanging box, and uses a dredging pump for local cleaning. The diver thoroughly investigates and cleans the mud, marine organisms and other debris on the casing and the hanging box wall within the bottom sealing range; Step 4: pouring the bottom concrete, including: Step 4.1, bottom cover platform erection: the bottom cover platform consists of Bailey beam, steel springboard, conductor frame, channel and guardrail; Step 4.2, Catheter and equipment layout: Lay the bottom sealing concrete conduit and arrange the concrete pouring points; Step 4.3, bottom seal concrete pouring: The concrete distribution points are distributed in sequence according to the distribution points in the underwater bottom seal pouring point arrangement number, and are promoted as a whole from the downstream to the upstream side. During the pouring process, the conduit that has been poured is supplemented with material every 30 minutes. The supplementing time is generally 5 minutes until the design elevation is reached; Step 5: Capping construction, including: Step 5.1, pumping and clearing the foundation and system conversion: After the strength of the bottom concrete reaches the design requirements, carry out pumping operations, arrange high-power submersible pumps to pump water to form dry construction conditions; open the buoyancy tank connector underwater, close the internal and external connectors and the air valve, control the water level of the sandwich wall to about -5.13m, and check the wall leakage at the same time; after the pumping and clearing of the foundation of the hanging box is completed, install structural diagonal braces between the casing and the steel hanging box wall along the periphery of the hanging box; after the steel hanging box system conversion construction is completed, clean the bottom concrete surface and complete the 20cm leveling layer construction; Step 5.2, cutting off the steel casing and breaking the pile head: The cutting of the steel casing is divided into two stages according to the position of the pile head. During construction, the part of the steel casing above the reinforcement cage at the top of the pile is cut first, and then the steel casing at the pile head is divided into two halves in the vertical direction and cut off. After cutting, it is lifted away by a crawler crane, the silt on the top is cleaned, and the pile head is cut and chiseled off by the ring cutting method. Step 5.3, pedestal construction: During the construction of the first-floor pedestal, retain the four casing limits at the four corners of the hanging box as limiting measures for the first-floor pedestal construction stage. Set a post-casting section for the casing limit position. After the first-floor pedestal concrete reaches a certain strength, remove it for post-casting section construction. The overall construction sequence is: first construction of the first-floor pedestal → construction of the first-floor pedestal post-casting strip → construction of the second-floor pedestal. After the concrete is poured, follow the principle of "inner reduction and outer protection" and use cooling water pipes to pass water to reduce the temperature difference between the inside and outside of the pedestal. The curing period is not less than 14 days.

2. The method for constructing an ultra-deep buoyancy double-walled steel hanging box for a bridge foundation based on strong tidal reciprocating flow according to claim 1 is characterized in that: In step 2.2, when lifting and lowering the steel hoisting box, the distance between the bottom of the steel hoisting box and the platform is controlled to be more than 2m, and the lifting width is 60m.

3. The method for constructing an ultra-deep buoyancy double-walled steel hanging box for a bridge foundation based on strong tidal reciprocating flow according to claim 2 is characterized in that: Step 2.2, during the lifting and lowering of the steel box, the crane vessel should always be kept under stress, and the lowering of the box should be controlled by the hook speed of the crane vessel. The speed should not exceed 1m / min. When the box is close to the elevation with 2m remaining, the lowering speed should be reduced so that the box can be lowered gradually and slowly to the designed elevation.

4. The method for constructing an ultra-deep buoyancy double-walled steel hanging box for a bridge foundation based on strong tidal reciprocating flow according to claim 3 is characterized in that: Step 2.3, positioning and locking the hanging box: the plane position error of the hanging box is controlled within 10cm, and the top elevation error is controlled within 2cm. To ensure uniform force on each hanging leg, rubber bearings are installed on site in advance. After the steel hanging box is adjusted, 10mm steel plates are added to pad it densely according to the contact between the hanging beam and the hanging leg.

5. The design and construction method of the ultra-deep buoyancy double-walled steel hanging box for the sea-crossing bridge cap based on strong tidal reciprocating flow according to claim 4 is characterized in that: Step 3.1, installation of tension and compression rods: Select the appropriate water level according to the guide beam elevation to install the tension and compression rods in batches, push the cantilever beam to the designed position, install the pad and apply 9kN pre-tension to the tension rod. When the cantilever length of the cantilever beam is less than 440mm, weld the limit block on site; when the cantilever length of the cantilever beam is greater than 440mm, weld the limit slot on site. After the tension rod is installed, select the low tide position to release the bottom plate hanger connection nut and convert the bottom plate force.

6. Ultra-deep buoyancy double-walled steel hanging box for sea-crossing bridge foundation based on strong tidal reciprocating flow, characterized by: It includes a cap and a steel hanging box. The steel hanging box serves as a water retaining and formwork structure during the construction of the cap. The steel hanging box includes a wall, a bottom plate, a bottom plate truss, an inner support, a hanging system, a hanging rod, a hanging leg, a hanging beam, a hanging lug, a guide device, a limit device, a connecting vessel, a vent valve, and a connecting valve; The inner contour of the steel hanging box wall is expanded by 100mm based on the outer contour of the pedestal. The wall body has sections A, B and C, and a buoyancy tank is arranged in section B of the double-wall body; The steel hanging box is equipped with three bottom plate trusses; The bottom plate of the steel hoisting box adopts a beam-slab structure. Holes are opened by drawing envelope lines based on the measured top and bottom plate position data of the steel casing after pile formation to ensure a net spacing of 12~20cm during the lowering process. The steel hanging box is equipped with 5 layers of internal supports; Hanging legs are set on the wall of the steel hanging box, and hanging beams are set on the steel casing to limit the vertical position of the steel hanging box; hanging legs are set at the corresponding positions of 8 steel casings selected around the wall of the steel hanging box, and hanging beams are set on the top surface of the steel casing; When the steel hanging box is lowered, a three-layer guide device is provided, including: casing bottom plate guide device; wall guide device; hanging leg limit guide device; The steel hanging box is equipped with three layers of limit devices, including: hanging leg and hanging beam limit devices, that is, the hanging legs and hanging beams are fixed by welding with stiffening plates; limit parallel joint limit devices, that is, the wall and casing steel pipe are fixed by parallel joint welding; steel wedge block limit devices, that is, the plug pad guide limit block limit; The hanging system consists of a telescopic beam, a suspender rod, and upper and lower supports. The suspender rod consists of upper and lower pull rods. The steel hanging box is symmetrically provided with 8 lifting lugs at the top; An inner connecting vessel, an outer connecting vessel, a vent valve and a connecting valve are arranged on the wall.

7. The ultra-deep buoyancy double-walled steel hanging box for the sea-crossing bridge foundation based on strong tidal reciprocating flow according to claim 6 is characterized in that: The bottom plate during the lowering period is connected to the inner support through 10 suspension rods, and the bottom plate during the bottom sealing period is connected to the steel casing through tie rods. 3-4 tie rods are arranged on each steel casing; a hole is opened at the pile position in the bottom plate of the steel hanging box, and the hole size is φ3.24m.

8. The ultra-deep buoyancy double-walled steel hanging box for the sea-crossing bridge foundation based on strong tidal reciprocating flow according to claim 7 is characterized in that: The steel hanging box is manufactured as a whole in the processing plant. The internal support, lifting ears, hanging legs, bottom plate trusses, guide devices and limit devices are processed together when the wall is processed. When the bottom plate is processed, the tie rods and the lower end supports of the hanger are processed and manufactured together in combination with the tie rods and hanger structure drawings. The manufacturing unit divides the hanging box wall and the bottom plate into unit blocks according to the actual situation of the processing site and the lifting and installation capacity. Equal strength welding is used when assembling each unit block of the steel hanging box, and all splicing welds are continuous and full welds.

9. The ultra-deep buoyancy double-walled steel hanging box for the sea-crossing bridge foundation based on strong tidal reciprocating flow according to claim 8 is characterized in that: In order to make the bottom plate of the steel hoisting box fit smoothly onto the steel casing, it is necessary to make holes at the corresponding positions of the bottom plate of the steel hoisting box according to the actual positions of the steel casing. When making holes, the gap between the bottom plate and the steel casing should be reduced as much as possible to facilitate the sealing of the gap. There are 42 holes in the bottom plate of the hoisting box, all of which are blocked with sealing plates and clamps. The sealing plates of a single steel casing are divided into 4 Haver plates. Before the steel hoisting box leaves the factory, the clamp plates are temporarily fixed on the lower support of the pull rod and lowered along with the hoisting box to the four sides of each casing. The sealing plates are fixed to the steel casing by underwater welding or bolt connection.

10. The ultra-deep buoyancy double-walled steel hanging box for the sea-crossing bridge foundation based on strong tidal reciprocating flow according to claim 9 is characterized in that: The pedestal is round-ended, with a plane size of 51.9m×36.4m and a thickness of 7m. 42 φ2.5m piles are set under the pedestal. The steel casing has a diameter of 2.8m and a wall thickness of 20mm.

Images