Semi-prefabricated construction method for large deep-water caissons in shallow dock

Abstract

The present application relates to a semi-prefabricated construction method for large deep-water caissons in a shallow dock. Concrete for a caisson base slab is poured in a dry dock, prefabricated slabs and steel trusses are mounted around the base slab to form an open box structure, then a box is towed to a bridge site, the construction of the caissons is completed by means of cast-in-place concrete pouring on the water, and finally the caisson is filled with water and sinks into place. The present application can greatly reduce the requirements for the excavation depth of the dry dock, and decrease the dredging workload of an undocking and floating channel, thereby reducing construction costs, and also facilitating shortening the construction period of the caissons.

Description

A semi-prefabrication construction method for large deep-water caissons in shallow docks

[0001] Cross-references

[0002] This application claims priority and benefit to patent application 202410902401.X, filed with the China National Intellectual Property Administration on July 6, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of deep-water bridge construction technology, specifically relating to a shallow-dock semi-prefabrication construction method for large deep-water caissons used as pier or tower foundations. Background Technology

[0004] When constructing bridges across the sea or river, in deep water, it is difficult to use conventional cofferdam or steel caisson methods for the construction of piers or tower foundations. Using large caisson foundations is a better option. A caisson is a concrete box structure, usually prefabricated in a temporary dry dock, transported to the pier location by water transport, and then sunk to serve as the pier foundation. After sinking, the top of the caisson rises above the water surface, facilitating the construction of the superstructure of the pier.

[0005] When constructing caissons in a dry dock, the depth of the temporary dry dock must be compatible with the height of the caisson. Therefore, for large deep-water caissons, they need to be prefabricated in an ultra-large and ultra-deep dry dock, which presents problems such as deep dock excavation depth, long construction period, and high investment cost. Moreover, large caissons have a large draft, and a lot of dredging work is often required when the caissons are moved from the dock to the waterway, which further increases the construction cost.

[0006] To address the aforementioned issues, patent CN112878357A proposes a caisson foundation structure and construction method for a deep-water cross-sea bridge exceeding 100 meters in depth. The caisson employs a stepped structure with a cross-sectional area gradually decreasing from bottom to top. It is prefabricated and towed in a horizontal position, and after floating to its designated location, the caisson is adjusted to a vertical position and lowered. While this solution reduces the excavation depth of the dry dock and the draft during caisson floating, the increased floor space required for horizontal prefabrication due to the caisson's height means that the construction workload, construction period, and cost of the dry dock are not significantly reduced. Furthermore, during floating, the large length of the caisson and the significant difference in volume and weight between its front and rear ends make it difficult to control its balance, resulting in low safety. Summary of the Invention

[0007] One of the purposes of this application is to provide a semi-prefabricated construction method for large deep-water caissons in shallow docks, thereby reducing the excavation depth of dry docks and the amount of dredging required for the floating transport channel of the caissons, and lowering construction costs.

[0008] The technical solution of one embodiment of this application is as follows:

[0009] A semi-prefabricated construction method for a large deep-water caisson in a shallow dock, wherein the lower half of the caisson is a large-diameter reinforced concrete cylindrical foundation and the upper half is a conical reinforced concrete pier, characterized by the following steps:

[0010] Step 1: Construct a shallow dry dock and supporting facilities for caisson construction;

[0011] Step 2: Pour the caisson bottom slab in the dry dock, and simultaneously construct the precast concrete slab and steel truss; install precast slabs around the top of the caisson bottom slab, and install and fix the steel truss on the inner wall of the precast slab to form an open steel-concrete composite box structure; the height of the precast slab and steel truss shall not be less than the height of the cylindrical foundation of the caisson.

[0012] Step 3: The container is undocking and towed to the pier.

[0013] Step 4: Concrete the caisson in place on the water; precisely adjust the position of the caisson, fill it with water and sink it into place.

[0014] In step 1 of the above-mentioned semi-prefabricated construction method for large deep-water caissons in shallow docks, the specific construction process for the shallow dry dock and supporting facilities is as follows:

[0015] Construction of dock cofferdam → Construction of dock perimeter walls within the dock cofferdam → Dewatering of the dock area → Excavation of dock foundation pit → Pouring of dock chamber floor slab → Construction of ancillary facilities → Demolition of dock cofferdam.

[0016] Depending on the topography, geomorphology, and hydrogeological conditions of the dock site, the cofferdam may be an earth dam, a double-row steel sheet pile cofferdam, or a steel sheet pile foundation pit cofferdam.

[0017] Ancillary facilities include a concrete mixing plant, a precast slab / steel structure processing area, and office and living areas.

[0018] In step 2 of the above-mentioned semi-prefabricated construction method for large deep-water caissons in shallow docks, the prefabricated slabs and steel trusses are prefabricated in sections, and the height of each prefabricated slab and steel truss is not less than the height of the caisson cylindrical foundation. Embedded steel plates connected to the steel trusses are set on the inner wall of each prefabricated slab.

[0019] Each precast slab is connected to the bottom of the caisson base plate and adjacent precast slabs using wet joint concrete. The steel truss is welded to the embedded steel plate on the inner wall of the precast slab, and the bottom of the steel truss is supported on the caisson base plate.

[0020] The specific construction method for step 3 of the above-mentioned semi-prefabrication construction method for large deep-water caissons in shallow docks is as follows:

[0021] (31) Conduct a tightness test on the steel-concrete composite box to ensure that it is waterproof;

[0022] (32) Four winches are symmetrically arranged on the top of the dock walls on both sides of the dock. The winches are connected to the steel-concrete composite box through cables to limit the cable position of the box.

[0023] (33) Remove the dock gate and fill the dock with water to make the container float;

[0024] (34) Use two tugboats to tow the container, and at the same time control the position of the container by four winches set on the dock wall to prevent the container from colliding with the dock wall. Slowly drag the container out of the dock and then transport it to the pier.

[0025] The specific construction method for step 4 of the above-mentioned semi-prefabrication construction method for large deep-water caissons in shallow docks is as follows:

[0026] (41) After the container is floated to the predetermined position, it is anchored and positioned;

[0027] (42) The precast slabs are used directly as the outer side wall panels of the side panels, and the steel truss is used as the steel frame of the side panels of the caisson column foundation. The inner partition steel bars of the caisson are installed in the caisson, and then the side panels and inner partitions of the caisson column foundation are cast in the caisson. The caisson steel bars are modularly tied in the field and transported to the site by barge for installation. The concrete is supplied by the mixing ship and directly pumped into the formwork for casting.

[0028] (43) After the cylindrical foundation of the caisson is poured, continue to pour the upper part of the caisson to the design height;

[0029] (44) After the caisson is poured, the caisson is precisely positioned by tugboats, anchoring systems and positioning piles, and then water is injected to sink it into place.

[0030] The embodiments described above in this application prefabricate only the lower half of the caisson's outer shell structure in a dry dock, pour only the concrete for the caisson's bottom slab, install prefabricated slabs and steel trusses around the bottom slab to form an open caisson structure, and then tow the caisson to the vicinity of the bridge site and use in-situ concrete pouring to elevate the caisson. Compared with the prior art, this has the following advantages:

[0031] 1. The height of the prefabricated box in the dry dock is much smaller than the overall height of the caisson, which can significantly reduce the excavation depth requirement of the dry dock, thereby reducing the amount of construction work and construction costs of the dry dock.

[0032] 2. The prefabricated box inside the caisson has a smaller draft, which can reduce the amount of dredging work in the floating transport channel after leaving the dock, and further reduce construction costs.

[0033] 3. The reduction in the amount of dock construction and dredging work will help shorten the construction period of the caissons;

[0034] 4. The precast slabs and steel trusses installed on the bottom plate of the caisson serve as part of the side plates of the caisson foundation and can be constructed simultaneously with the bottom plate of the caisson, further shortening the construction period of the caisson. Attached Figure Description

[0035] Figure 1 is a construction flowchart of an embodiment of this application;

[0036] Figure 2 is a schematic diagram of the elevation structure after the precast slabs and steel trusses on the bottom plate of the caisson are installed;

[0037] Figure 3 is a schematic diagram of the plan structure after the prefabricated slabs and steel trusses on the bottom plate of the caisson are installed;

[0038] Figure 4 is a schematic diagram of the state when the bottom plate of the caisson is being towed out of the dock.

[0039] Figure 5. Schematic diagram of the caisson bottom plate during floating;

[0040] Figure 6 is a schematic diagram of the construction status of the cast-in-place caisson on the water.

[0041] Figure 7 is a schematic diagram of the caisson after it has been poured. Detailed Implementation

[0042] The construction method of this application is described below through a specific embodiment. In this embodiment, the lower half of the caisson structure to be constructed is a large-diameter reinforced concrete cylindrical foundation, and the upper half is a conical reinforced concrete pier; wherein the lower cylindrical part includes a bottom plate, side plates, and inner partitions.

[0043] Figure 1 is a construction flowchart of one embodiment of this application, which is divided into 4 stages. The specific construction process is as follows:

[0044] Step 1: Construct a shallow dry dock and supporting facilities for caisson construction; the specific construction process is as follows:

[0045] Construction of dock cofferdam → Construction of dock perimeter walls within the dock cofferdam → Dewatering of the dock area → Excavation of dock foundation pit → Pouring of dock chamber floor slab → Construction of ancillary facilities → Demolition of dock cofferdam.

[0046] Depending on the topography, geomorphology, and hydrogeological conditions of the dock site, the cofferdam may be an earth dam, a double-row steel sheet pile cofferdam, or a steel sheet pile foundation pit cofferdam.

[0047] Ancillary facilities include a concrete mixing plant, a precast slab / steel structure processing area, and office and living areas.

[0048] Step 2, as shown in Figures 2 and 3, involves pouring the caisson bottom slab 1 in the dry dock, simultaneously constructing the precast concrete slab and steel truss; after the caisson bottom slab 1 is poured, precast slabs 2 are installed around the top of the bottom slab, and steel trusses 3 are installed and fixed on the inner wall of the precast slabs to form an open steel-concrete composite box structure; the height of the precast slabs and steel trusses is not less than the height of the cylindrical foundation of the caisson.

[0049] In the above structure, the precast slabs and steel trusses on the bottom slab are equivalent to forming a steel-concrete composite water-retaining cofferdam, and also serve as part of the caisson side slabs.

[0050] The precast slabs and steel trusses can be precast in sections. The height of each precast slab and steel truss is not less than the height of the caisson cylindrical foundation. Embedded steel plates connected to the steel trusses are provided on the inner wall of each precast slab.

[0051] When installing precast slabs and steel trusses on the base plate, the bottom of each precast slab is connected to the caisson base plate and adjacent precast slabs using wet joint concrete. The steel trusses are welded to the embedded steel plates on the inner wall of the precast slabs, and the bottom of the steel trusses is supported on the caisson base plate.

[0052] Step 3: The container is undocking and transported to the pier location; the specific construction method is as follows:

[0053] (31) Conduct a tightness test on the steel-concrete composite box to ensure that it is waterproof;

[0054] (32) As shown in Figures 4 and 5, four winches 5 are symmetrically arranged on the top of the dock walls 4 on both sides of the dock. The winches 4 are connected to the steel-concrete composite box through cables 6 to limit the cable position of the box.

[0055] (33) Remove the dock gate and fill the dock with water to make the hull float. In the actual construction, the difference in water head between the inside and outside of the dock should be measured before removing the dock gate. First, remove part of the dock gate in the center. After the difference in water head between the inside and outside is consistent, remove it from the middle to both sides.

[0056] (34) Use two tugboats to tow the container, and at the same time control the position of the container by four winches set on the dock wall to prevent the container from colliding with the dock wall. Slowly drag the container out of the dock and then transport it to the pier.

[0057] During the transport of the container, two tugboats can be used behind the container to provide a certain amount of counter-pull force to prevent the container from veering off course due to the impact of water flow and waves.

[0058] Furthermore, a tugboat 7 can be installed on each side of the container close to the container to prevent the container from shaking significantly due to the impact of wind and waves.

[0059] Step 4, as shown in Figures 6 and 7, involves constructing the caisson using cast-in-place concrete on the water. The caisson's position is then precisely adjusted, and it is lowered into place by filling with water. The specific construction method is as follows:

[0060] (41) After the container is floated to the predetermined position, it is anchored and positioned using the anchoring system 8;

[0061] (42) The precast slabs around the bottom plate of the caisson are used directly as the outer wall panels of the caisson side plates. The steel truss is used as the steel frame of the side plates of the caisson cylindrical foundation. The inner partition steel bars of the caisson are installed in the caisson. Then, the side plates 9 and inner partition plates 10 of the caisson cylindrical foundation are cast in the caisson. The caisson steel bars are modularly tied in the back field and transported to the site by barge for installation. The concrete is supplied by the mixing ship and directly pumped into the formwork for casting.

[0062] (43) After the caisson cylindrical foundation is poured, continue to pour the caisson pier body 11 to the design height;

[0063] (44) After the caisson is poured, the caisson is precisely positioned by tugboat, anchoring system 8 and positioning pile 12, and then water is injected into the caisson to make it sink and settle into place.

[0064] The embodiments described above in this application prefabricate only the lower half of the caisson's outer shell structure in a dry dock, pour only the concrete for the caisson's bottom slab, install prefabricated slabs and steel trusses around the bottom slab to form an open caisson structure, and then tow the caisson to the vicinity of the bridge site and use in-situ concrete pouring to elevate the caisson. Compared with the prior art, this has the following advantages:

[0065] 1. The height of the prefabricated box in the dry dock is much smaller than the overall height of the caisson, which can significantly reduce the excavation depth requirement of the dry dock, thereby reducing the amount of construction work and construction costs of the dry dock.

[0066] 2. The prefabricated box inside the caisson has a smaller draft, which can reduce the amount of dredging work in the floating transport channel after leaving the dock, and further reduce construction costs.

[0067] 3. The reduction in the amount of dock construction and dredging work will help shorten the construction period of the caissons;

[0068] 4. The precast slabs and steel trusses installed on the bottom plate of the caisson serve as part of the side plates of the caisson foundation and can be constructed simultaneously with the bottom plate of the caisson, further shortening the construction period of the caisson.

Claims

1. A semi-prefabrication construction method for a large deep-water caisson in a shallow dock, wherein the lower half of the caisson is a large-diameter reinforced concrete cylindrical foundation, and the upper half is a conical reinforced concrete pier, characterized in that... Includes the following steps: Step 1: Construct a shallow dry dock and supporting facilities for caisson construction; Step 2: Pour the caisson bottom slab in the dry dock, and simultaneously construct the precast concrete slab and steel truss; install precast slabs around the top of the caisson bottom slab, and install and fix the steel truss on the inner wall of the precast slab to form an open steel-concrete composite box structure; the height of the precast slab and steel truss shall not be less than the height of the cylindrical foundation of the caisson. Step 3: The container is undocking and towed to the pier. Step 4: Concrete the caisson in place on the water; precisely adjust the position of the caisson, fill it with water and sink it into place.

2. The semi-prefabrication construction method for large deep-water caissons in shallow docks according to claim 1, characterized in that, In step 1, the construction of the shallow dry dock and supporting facilities follows a specific construction process: Construction of dock cofferdam → Construction of dock perimeter walls within the dock cofferdam → Dewatering of the dock area → Excavation of dock foundation pit → Pouring of dock chamber floor slab → Construction of ancillary facilities → Demolition of dock cofferdam. Depending on the topography, geomorphology, and hydrogeological conditions of the dock site, the cofferdam may be an earth dam, a double-row steel sheet pile cofferdam, or a steel sheet pile foundation pit cofferdam. Ancillary facilities include a concrete mixing plant, a precast slab / steel structure processing area, and office and living areas.

3. The semi-prefabrication construction method for large deep-water caissons in shallow docks according to claim 1, characterized in that: In step 2, the precast slabs and steel trusses are precast in sections, and the height of each precast slab and steel truss is not less than the height of the caisson cylindrical foundation. Embedded steel plates connected to the steel trusses are provided on the inner wall of each precast slab. Each precast slab is connected to the bottom of the caisson base plate and adjacent precast slabs using wet joint concrete. The steel truss is welded to the embedded steel plate on the inner wall of the precast slab, and the bottom of the steel truss is supported on the caisson base plate.

4. The semi-prefabrication construction method for large deep-water caissons in shallow docks according to claim 1, characterized in that, The specific construction method for step 3 is as follows: (31) Conduct a tightness test on the steel-concrete composite box to ensure that it is waterproof; (32) Four winches are symmetrically arranged on the top of the dock walls on both sides of the dock. The winches are connected to the steel-concrete composite box through cables to limit the cable position of the box. (33) Remove the dock gate and fill the dock with water to make the container float; (34) Use two tugboats to tow the container, and at the same time control the position of the container by four winches set on the dock wall to prevent the container from colliding with the dock wall. Slowly drag the container out of the dock and then transport it to the pier.

5. The semi-prefabrication construction method for large deep-water caissons in shallow docks according to claim 4, characterized in that: Before dismantling the dock gate, the difference in water head between the inside and outside of the dock should be measured. First, dismantle the part in the center of the dock gate. After the difference in water head between the inside and outside is consistent, dismantle from the center outwards to both sides.

6. The semi-prefabrication construction method for large deep-water caissons in shallow docks according to claim 4, characterized in that: During the container transport, two tugboats are used behind the container to provide a certain amount of counter-pull force to prevent the container from deviating due to the impact of water flow and waves.

7. The semi-prefabrication construction method for large deep-water caissons in shallow docks according to claim 6, characterized in that: A tugboat is installed on each side of the container, close to it, to prevent the container from shaking significantly due to wind and waves.

8. The semi-prefabrication construction method for large deep-water caissons in shallow docks according to claim 1, characterized in that, The specific construction method for step 4 is as follows: (41) After the container is floated to the predetermined position, it is anchored and positioned; (42) The precast slabs are used directly as the outer side wall panels of the side panels, and the steel truss is used as the steel frame of the side panels of the caisson column foundation. The inner partition steel bars of the caisson are installed in the caisson, and then the side panels and inner partitions of the caisson column foundation are cast in the caisson. The caisson steel bars are modularly tied in the field and transported to the site by barge for installation. The concrete is supplied by the mixing ship and directly pumped into the formwork for casting. (43) After the cylindrical foundation of the caisson is poured, continue to pour the upper part of the caisson to the design height; (44) After the caisson is poured, the caisson is precisely positioned by tugboats, anchoring systems and positioning piles, and then water is injected to sink it into place.

Images