Construction method of overwater viaduct special-shaped pile foundation bearing platform and asymmetric suspended splicing section box girder in limited space

Abstract

The invention discloses a construction method for an overwater viaduct special-shaped pile foundation bearing platform and an asymmetric suspended splicing section box girder in a limited space, and relates to the technical field of bridge construction. The invention provides a construction method of an overwater viaduct special-shaped pile foundation bearing platform and an asymmetric suspended splicing section box girder in a limited space. The construction method comprises the steps of construction platform building, bearing platform construction, pier column construction and box girder construction. The construction platform building comprises the steps of welding a six-pile floating type guide frame, building a six-pile working platform, driving other pile foundations, drilling holes and pouring; the construction of the bearing platform comprises the steps of high-water-level assembly of the combined pouring jacket, lowering of the combined pouring jacket in place, drainage and sealing of the pouring jacket and pouring of the bearing platform. The pier column construction comprises the steps of surveying and lofting, construction joint treatment, steel bar binding, formwork hoisting, concrete pouring and curing. The box girder construction comprises the steps of pier top box girder cast-in-place and box girder asymmetric suspension splicing. The construction method provided by the invention is small in occupied space for construction, simple in process and high in economical efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge construction, and more specifically to a construction method for a special-shaped pile foundation pedestal and an asymmetric cantilever segment box girder of a water viaduct in a confined space. Background Art

[0002] When constructing a water viaduct, open waters are generally chosen, which have better conditions for construction. However, there are strict construction area restrictions in the demarcation line area. For example, refer to Figure 1 As shown, the dotted line in the figure is the limit line. When constructing pile foundation caps and box beams in Singapore, according to relevant regulations, construction equipment, personnel, and structures cannot cross the limit line during construction. Therefore, the construction of pile foundation caps and box beams needs to be carried out under limited idleness. The process flow in the prior art cannot adapt to this construction condition. Summary of the invention

[0003] In view of this, the present invention provides a construction method for a special-shaped pile foundation pedestal and an asymmetric cantilever segment box girder of a water viaduct in a confined space, which occupies a small space for construction, has a streamlined process and is highly economical.

[0004] The present invention provides a method for constructing a special-shaped pile foundation cap and an asymmetric cantilever segment box girder of a water viaduct in a confined space, comprising: building a construction platform, cap construction, pier column construction and box girder construction; The construction platform construction includes: welding six-pile floating guide frame, building six-pile working platform, driving other pile foundations, drilling and pouring; The construction of the foundation includes: assembling the combined casing at high water level, lowering the combined casing into place, draining and sealing the casing, and pouring the foundation; The pier construction includes: measurement and setting out, construction joint treatment, steel bar binding, formwork hoisting, concrete pouring and maintenance; The box girder construction includes: cast-in-place box girder on pier top and asymmetric cantilever assembly of box girder.

[0005] In a possible implementation, the construction platform building includes: The welded six-pile floating guide frame: 6 steel casings are arranged in an array and connected to each other horizontally and vertically to form a six-pile floating guide frame; the six-pile floating guide frame is fixed on a pole-inserting crane ship; The six-pile working platform is constructed by using a vibrating hammer or an impact hammer to hit the steel casing, and installing a steel plate on the top of the steel casing to form a six-pile working platform; The said driving of other pile foundations: surrounding the said six-pile working platform, driving outwards a single said steel casing in sequence, and connecting with the adjacent said steel casing; The drilling and pouring: the drilling machine is installed on the steel casing to carry out the drilling construction; the bored pile construction is carried out on the steel casing after the drilling.

[0006] In a possible implementation, the high water level assembly of the combined casing includes: Install the steel support system: open a hole in the steel casing and place the steel in the hole to form the first force-bearing system; Installing the base plate: installing the divided base plate on the first force-bearing system; Wet joint construction: pouring concrete between the bottom plates of several blocks so that the bottom plates of several blocks form a complete bottom plate; Install the side steel formwork and steel inner supports to form a casing.

[0007] In a possible implementation, lowering the combined casing into place includes: Installation of hydraulic system: a shoulder pole beam is arranged on the top of the steel casing, and hydraulic jacks and steel strands are installed on both sides of the shoulder pole beam; the lower end of the steel strand is anchored on the bottom plate to form a second force bearing system; Lift the casing and convert the force: lift the casing by 20 cm using the hydraulic jack and keep it for at least 2 hours; if the hydraulic jack and the casing are stable, remove the first force system; Lowering the casing into place: lowering the casing into the water.

[0008] In a possible implementation, the casing drainage seal includes: Installation of tension and compression rod system: the bottom of the tension and compression rod is connected to the bottom plate, and the top of the tension and compression rod is connected to the steel casing; Casting underwater plugging to seal the casing and form dry working conditions; Shear members are arranged along the periphery of the steel casing; Remove the hydraulic jack and the tension and compression rods.

[0009] In a possible implementation, the foundation casting includes: Pouring concrete into the casing at a height of 800 mm to form an integral bottom plate; Pouring concrete into the casing at a height of 700 mm to form a consolidated whole with the pile foundation; dismantling the second force bearing system; Concrete is poured into the casing in layers for multiple times until the designed elevation is reached.

[0010] In a possible implementation, the pier top box girder is cast in situ, including: A bracket is provided on the top of the pier; Lift and install the first box beam block; Cast the pier top box girder between the first box girder blocks.

[0011] In a possible implementation, the asymmetrical cantilever assembly of the box beam includes: When the box girder on one side stops being cantilevered and the box girder on the other side continues to be cantilevered, a counterweight is set on the top of the box girder on the side where the cantilevering stops.

[0012] Compared with the prior art, the construction method of the special-shaped pile foundation cap and asymmetric cantilever segment box girder of a water viaduct in a confined space provided by the present invention achieves at least the following beneficial effects: In the embodiments provided by the present invention, first, by installing the drilling rig on the steel casing for construction, the speed is fast, the vibration is small, the area of ​​the water construction platform required is small, there is no mud pool, the environmental protection effect is good, and the drilling efficiency is high; second, the pedestal and the anti-collision pier adopt the bottom-free casing construction method, the casing does not need to sit on the bottom, the bottom of the casing is a prefabricated structure, which can be used as a bottom mold, and finally forms a permanent structure, with high construction efficiency and material saving; the casing wall is directly used as the side mold of the pedestal, reducing the construction space occupied and simplifying the construction process. Third, the pier top box girder adopts the bracket cast-in-place method, which omits the wet joint process, and uses block No. 1 as the end mold, making the bridge line smoother and saving templates; fourth, the box girder is installed by the asymmetric cantilever method, and the counterweight block is set at the short arm end according to the construction rhythm to offset the unbalanced bending moment. Compared with the traditional bracket method, this method occupies less space under the bridge and the construction measures are more economical.

[0013] Of course, any product implementing the present invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0014] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0016] Figure 1 This is an application scenario diagram of the construction method provided by the present invention; Figure 2 A flow chart of the construction method provided by the present invention; Figure 3 A top view of the construction platform provided by the present invention; Figure 4 This is one of the schematic diagrams of the process of constructing the construction platform provided by the present invention; Figure 5 The second schematic diagram of the process of constructing the construction platform provided by the present invention; Figure 6 The third schematic diagram of the process of constructing the construction platform provided by the present invention; Figure 7 The fourth schematic diagram of the process of constructing the construction platform provided by the present invention; Figure 8 This is one of the schematic diagrams of the high water level assembly process of the combined casing provided by the present invention; Fig. 9 The block bottom plate structure provided by the present invention; Fig.10 The second schematic diagram of the high water level assembly process of the combined casing provided by the present invention; Fig.11 The third schematic diagram of the high water level assembly process of the combined casing provided by the present invention; Fig.12 The fourth schematic diagram of the high water level assembly process of the combined casing provided by the present invention; Fig.13 This is a schematic diagram of the process of lowering the combined casing provided by the present invention into place; Fig.14 The present invention provides Fig.13 A partial enlarged view of Fig.15 The second schematic diagram of the process of lowering the combined casing provided by the present invention into place; Fig.16 One of the schematic diagrams of the process of drainage sealing of the casing provided by the present invention; Fig.17 The second schematic diagram of the process of drainage sealing of the casing provided by the present invention; Fig.18 The third schematic diagram of the process of drainage sealing of the casing provided by the present invention; Fig.19 The fourth schematic diagram of the process of drainage sealing of the casing provided by the present invention; Fig. 20 The fifth schematic diagram of the process of drainage sealing of the casing provided by the present invention; Fig.21 A schematic diagram of the structure of the bracket provided by the present invention; Fig. 22 A schematic diagram of the process of casting the pier top box girder provided by the present invention; Fig.23 A schematic diagram of the structure of the beam support provided by the present invention; Fig.24 One of the schematic diagrams of the process of asymmetric cantilever assembly of box beams provided by the present invention; Fig.25 The second schematic diagram of the process of asymmetric cantilever assembly of a box girder provided by the present invention; Fig.26The third schematic diagram of the process of asymmetric cantilever assembly of box girders provided by the present invention. DETAILED DESCRIPTION

[0017] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0018] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0019] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0020] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0021] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0022] The embodiment of the present invention provides a construction method for a special-shaped pile foundation cap and an asymmetric cantilever segment box girder of a water viaduct in a confined space, referring to Figure 2 As shown, the embodiment of the present invention provides a method for constructing a special-shaped pile foundation cap and an asymmetric cantilever segment box girder of a water viaduct in a confined space, including: building a construction platform, cap construction, pier column construction and box girder construction; Specifically, the construction platform includes: welding of six-pile floating guide frames, construction of six-pile working platforms, placement of other pile foundations, drilling and pouring; It is understandable that, referring to Figure 3 As shown, the pile foundation includes a cap pile foundation and a crash pier pile foundation arranged in an array; The pile foundation in the center of the square box in the figure is the cap pile foundation, and the other pile foundations in the polygon in the figure are the crash pier pile foundations. The cap pile foundation is located in the center, and the crash pier pile foundations are arranged around the cap pile foundation. Several pile foundations form an axisymmetric polygon.

[0023] In an optional embodiment, referring to Figures 4 to 7 As shown in the figure, the construction platform construction includes: Welded six-pile floating guide frame: Figure 4 As shown, 6 steel casings are arranged in an array and connected to each other horizontally and vertically to form a six-pile floating guide frame; the six-pile floating guide frame is fixed on a pole-inserting crane ship; Build a six-pile working platform: Use a vibrating hammer or impact hammer to hit the steel casing, and install a steel plate on the top of the steel casing to form a six-pile working platform; Driving other pile foundations: Driving single steel casings outwards in sequence around the six-pile working platform and connecting them with adjacent steel casings; It should be noted that in the case of thin pile foundation covering layer, no transition section, and direct access to the rock layer, in order to avoid possible perforation during concrete pouring, the standard for stopping hammering during steel casing construction is formulated: ① When the covering layer is less than 5m, SPT ≥ 100 hits, and the rock penetration depth is required to be ≥ 1.5m; ② When the covering layer is ≥ 5m, the hammering can be stopped after SPT ≥ 100 hits.

[0024] Drilling and pouring: Install the drilling rig on the steel casing, and perform drilling construction in sequence according to the order of steel casing injection; perform cast-in-place pile construction on the drilled steel casing in sequence. For example, the drilling rig can be an RCD reverse circulation drilling rig. When pouring concrete, the pump truck and mixer truck are transported by barge.

[0025] Furthermore, the foundation construction includes: high-water level assembly of the combined casing, lowering of the combined casing into place, drainage and sealing of the casing, and casting of the foundation; In one embodiment, the viaduct cap is rectangular in plane, and a polygonal anti-collision cap is provided on the outside of the slab. The cap (anti-collision cap + outer lining plate) has a plane size of 58.8m×23.0m (transverse bridge direction×longitudinal bridge direction) and a thickness of 5.0m.

[0026] It can be understood that in one embodiment, the base elevation is +98.8m, the top elevation is +103.8m, and the base height is 5.0m. The base is designed with a layer of concrete skirt slab, which is 0.275m thick, 7.0m high, with a base elevation of +96.8m, and the average water level of the construction area is +100.07m.

[0027] The box is mainly composed of the following three major component systems and four major force systems. Each part is processed separately, assembled at a high position on site, and lowered as a whole.

[0028] Three major component systems: 1. Floor system: The floor is composed of annular prefabricated blocks. After a single prefabricated block is installed on the steel casing support, the wet joint steel bars between the prefabricated blocks are welded and concrete is poured to form the entire floor system. 2. Side formwork system: The side formwork is assembled with prefabricated skirt panels; the skirt panels are configured to be inserted into the base plate in a snap-on manner, and the reserved steel bars are welded and concrete is poured to form a whole.

[0029] 3. Support system: Two layers of purlins and steel pipe internal supports are set inside the casing, with the upper and lower layers being 3m and 6m high respectively, to enhance the overall stability of the casing; Four major force systems: 1. Steel support system: After the cast-in-place piles are poured with concrete, holes are opened on the steel casing above the concrete surface, through which two steel sections are passed to support the annular prefabricated blocks of the bottom plate, thus forming a force support during the installation stage of the casing; 2. Hydraulic lowering system: a shoulder beam is set on the top of the steel casing, and hydraulic jacks and steel strands are installed on both sides of the shoulder beam. The lower end of the steel strand is anchored on the prefabricated bottom plate to form a force support during the lowering process of the casing; 3. Tie and compression rod fixing system: Before lowering, fix the lower end of the tie and compression rod on the prefabricated bottom plate. After the casing is lowered to the designed elevation, fix the upper part of the tie and compression rod on the steel casing (above the water surface) and remove the hydraulic lowering system. The tie and compression rod is pulled down and pressed up to form a force support after the casing enters the water; 4. Shear plate fixing system: welded and fixed on the prefabricated base plate and steel casing to form a shear plate and support for the construction of the foundation.

[0030] Specifically, in an optional embodiment, referring to Figures 8 to 12 As shown, the high water level assembly of the combined box includes: Installation of steel support system: Figure 8 As shown, a hole 01 is opened on the steel casing. Specifically, a hole is opened at the elevation of +102.0m of the steel casing, and a steel section is placed in the hole 01 to form a first force bearing system, i.e., a steel section bottom supporting system; Install the base plate: refer to Figures 9 to 11 As shown, the divided bottom plate is installed on the first force bearing system; Specifically, the reinforced concrete bottom plate is 25cm thick; the stiffening beam and stiffening ring are 25cm wide, with a total thickness of 50cm, and the top is 25cm higher than the top surface of the bottom plate. The bottom plate is divided into blocks. The spacing between the plate joints is 20cm, and the steel bars are reserved for post-casting. The lower edge of the skirt plate is prefabricated together with the bottom plate edge block.

[0031] Wet joint construction: pour concrete between several sub-slabs to form a complete sub-slab; Reference Fig.12 As shown, the side steel formwork and steel inner supports are installed to form a casing. Among them, two steel inner supports are installed, one at 3m and 6m of the side steel formwork.

[0032] At this point, the high water level installation of the casing is completed.

[0033] In an optional embodiment, referring to Figures 13 to 15 As shown, the combined box is lowered into place, including: Hydraulic system installation: refer to Fig.13 and Fig.14As shown in the figure, a shoulder beam is set at the top of the steel casing (+104m), and hydraulic jacks and steel strands are installed on both sides of the shoulder beam; the lower end of the steel strand is anchored on the bottom plate to form the second force system, namely the hydraulic lowering system; Lift the casing and convert the force: lift the casing by 20cm using the hydraulic jack, and convert the casing support from the first force-bearing system to the second force-bearing system. Keep the casing lifted for at least 2 hours; if the hydraulic jack and casing are stable, remove the first force-bearing system; Lower the box into place: refer to Fig.15 As shown, the casing is lowered into the water through the hydraulic linkage system, to the top elevation of the bottom plate +98.8m (the elevation of the bottom of the pedestal).

[0034] In an optional embodiment, referring to Fig.16 As shown, the casing drain seal includes: Installation of tension and compression rod system: connect the bottom of the tension and compression rod to the base plate, and connect the top of the tension and compression rod to the steel casing; It is understandable that before the casing is lowered, the bottom plate of the tension and compression rods is welded and fixed on the prefabricated ring beam of the bottom plate. After the casing is lowered into the water, the upper part of the tension and compression rods is welded and fixed on the steel casing. The combined casing force system is converted from the hydraulic jack to the tension and compression rod system.

[0035] Cast underwater plugging to seal the casing and create dry working conditions; It is understandable that when the water level is low, annular sealing concrete is poured to seal the combined casing and form dry working conditions.

[0036] Set shear members around the steel casing and remove the hydraulic jacks and tension and compression rods to complete the force conversion.

[0037] In an optional embodiment, referring to Figures 17 to 20 As shown, the foundation pouring is carried out under dry construction conditions, including: Pour concrete into the casing with a pouring height of 800mm to form an integral bottom plate; Pour concrete into the casing with a pouring height of 700mm to form a consolidated whole with the pile foundation; Dismantle the second force bearing system; Pour concrete into the casing in multiple layers until the designed elevation is reached.

[0038] In an optional embodiment, the lower part of the pier is a rectangular square pier with a cross-sectional size of 6.1m×6.1m and a height of 13.543m; the upper part of the pier is a regular tetrahedral pyramid with a top surface size of 9.1×9.1m and a height of 6.596m. The length of the molding strip is 81.2m, and the total concrete volume is 1122.31m³.

[0039] Furthermore, pier construction includes: measurement and layout, construction joint treatment, steel bar binding, formwork hoisting, concrete pouring and maintenance.

[0040] Specifically, after the construction of the foundation at the pier is completed, a surveying team is promptly organized to carry out construction layout to determine the center point and edge line of the pier column and the edge line of the pier body, and extend them 10 to 25 cm outside the diameter of the pier column along the axial direction to facilitate inspection after erecting the formwork.

[0041] Use a carpenter's line to draw a black line on the cap surface as the control line for the axis and edge of the pier column and the edge of the pier body, and then paint a striking red triangle on the black line to prevent it from being covered by cement slurry after concrete pouring. The elevation of the top of the pier column is re-measured using the total station trigonometric height, and the height from the cap surface to the top of the pier column is measured with a steel ruler for verification.

[0042] There is a horizontal construction joint between the top surface of the pedestal and the pier column. After the initial setting of the concrete, the surface slurry and weak layer should be immediately treated and washed with a high-pressure water gun. Before continuing to pour the upper layer of concrete, the garbage, cement film, loose sand and gravel on the surface and the weak concrete layer should be removed from the construction joint. At the same time, it should be roughened, rinsed with water and fully moistened. The accumulated water remaining on the concrete surface should be removed.

[0043] After the materials are delivered to the site, they must not be piled directly on the ground, but must be padded with square timber or other methods. When temporarily storing steel bars on site, a place with high terrain and dry ground should be selected. Depending on the weather conditions, a shed cloth should be added if necessary on rainy days. Before cutting the steel bars, first check the length and quantity of various specifications of steel bars in the construction drawings. Only after they are correct can they be cut. Based on the length of the original steel bar and the design length of the drawings and combined with the specifications, while meeting the design and specification requirements, minimize the loss of steel bars and reasonably match the steel bars.

[0044] The pier body steel bars are processed in the steel bar processing workshop, and the processed semi-finished products are transported to the corresponding pier body positions by flat barges. Four elevators were purchased on site. When the pier body steel bars are tied, the elevators are arranged on the cap, and the operators tie the steel bars in the elevators. During the tying process, the ground or steel bars are marked according to the spacing designed in the drawings, so as to strictly control the spacing between steel bars and the thickness of the protective layer.

[0045] The pier construction adopts the formwork technology of conventional combined formwork plus working platform, with each 4-6m section. The combined formwork mainly refers to the formwork system of Germany's peri company, and mainly adopts a formwork system composed of I-beams, steel back ribs, telescopic rods, connecting ties, linings and panels. It can adapt to the structural changes of the piers in this embodiment, and has the advantages of convenient disassembly and reuse. The modeling grooves on each side of the pier can be solved by installing modeling strips on the formwork. The working platform is arranged about 1 meter below the top of the pier formwork, connected to the vertical back ribs through steel trusses, and supported on the vertical back ribs by telescopic rods. The number of telescopic rods on each side is reasonably adjusted according to the width of the pier.

[0046] The piers and columns are all made of C40 concrete. The pier body and pier columns are poured at the same time and the pouring is completed in four times. The concrete is discharged at a height of more than 2 meters using a string tube to prevent the concrete from segregating during the discharge process.

[0047] In an optional embodiment, there are six single-chamber box girders with uniform cross-section from the national boundary line to the bridge pier; the other side of the bridge pier is a continuous steel structure with variable cross-section, with a beam width of 10.14m and a gradual beam height.

[0048] Furthermore, the box girder construction includes: cast-in-place box girder on pier top and asymmetric cantilever assembly of box girder.

[0049] Specifically, the cast-in-place box girder on the pier top includes: A bracket is provided on the top of the pier; Lift and install the first box beam block; Cast the pier top box girder between the first box girder blocks.

[0050] It is understandable that the box girders are prefabricated in the prefabrication yard according to the short-line matching method. After the finished products are transported to the dock by a flatbed trolley, they are transferred to a barge by a crane ship, and then transported to the site for installation by the barge.

[0051] The pier top box girder, i.e. the No. 0 box girder block, is cast in situ using the pier top bracket. Considering the need for bridge deck crane assembly and the construction needs of combining the pier top cast-in-situ box girder with the prefabricated box girder, a bracket is set up on the pier top to place some prefabricated beam sections before casting the No. 0 box girder block in situ. The bracket structure design is as follows: Fig.21 As shown, a 500t crane ship is used for lifting.

[0052] Further, refer to Fig. 22 As shown, after the bracket is installed, the first box beam block is hoisted and installed. Then the pier top box beam is cast between the first box beam blocks. After the pier top box beam block is cast, the bracket is removed.

[0053] In an optional implementation, since the bridge crane can only feed beams from the bottom, without exceeding the national boundary limit, a beam support on the top of the pedestal is set to temporarily place the segmental box beam to facilitate the bridge crane to feed beams. Fig.23 shown.

[0054] Reference Fig.24 As shown in the figure, the prefabricated box girder is gradually pushed forward from both ends to the middle of the span by a bridge crane for cantilever assembly construction, using two bridge cranes. The bridge crane uses a crane ship for assembly and dismantling.

[0055] Furthermore, the asymmetrical cantilevering of the box beam includes: when the cantilevering of the box beam on one side stops and the cantilevering of the box beam on the other side continues, a counterweight block is arranged on the top of the box beam on the side where the cantilevering stops.

[0056] Specifically, refer to Fig.25 As shown, the cantilever construction continues on the non-border side, and the cantilever end on the border side is loaded with counterweight blocks according to the number of cantilever blocks on the opposite side; the top beam support of the pedestal is removed. Fig.26 As shown, the adjacent piers are suspended, butt-jointed in the middle of the span, and prestressed tendons are installed.

[0057] In summary, the construction method of the special-shaped pile foundation cap and asymmetric cantilever segment box girder of a water viaduct in a confined space provided by the present invention achieves at least the following beneficial effects: In the embodiments provided by the present invention, first, by installing the drilling rig on the steel casing for construction, the speed is fast, the vibration is small, the area of ​​the water construction platform required is small, there is no mud pool, the environmental protection effect is good, and the drilling efficiency is high; second, the pedestal and the anti-collision pier adopt the bottom-free casing construction method, the casing does not need to sit on the bottom, the bottom of the casing is a prefabricated structure, which can be used as a bottom mold, and finally forms a permanent structure, with high construction efficiency and material saving; the casing wall is directly used as the side mold of the pedestal, reducing the construction space occupied and simplifying the construction process. Third, the pier top box girder adopts the bracket cast-in-place method, which omits the wet joint process, and uses block No. 1 as the end mold, making the bridge line smoother and saving templates; fourth, the box girder is installed by the asymmetric cantilever method, and the counterweight block is set at the short arm end according to the construction rhythm to offset the unbalanced bending moment. Compared with the traditional bracket method, this method occupies less space under the bridge and the construction measures are more economical.

[0058] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for constructing a special-shaped pile foundation cap and an asymmetric cantilever segmental box girder of a water viaduct in a confined space, characterized in that: include: Construction platform construction, foundation construction, pier construction and box beam construction; The construction platform construction includes: welding six-pile floating guide frame, building six-pile working platform, driving other pile foundations, drilling and pouring; The construction of the foundation includes: assembling the combined casing at high water level, lowering the combined casing into place, draining and sealing the casing, and pouring the foundation; The pier construction includes: measurement and setting out, construction joint treatment, steel bar binding, formwork hoisting, concrete pouring and maintenance; The box girder construction includes: cast-in-place box girder on pier top and asymmetric cantilever assembly of box girder.

2. The construction method according to claim 1, characterized in that: The construction platform construction includes: The welded six-pile floating guide frame: 6 steel casings are arranged in an array and connected to each other horizontally and vertically to form a six-pile floating guide frame; the six-pile floating guide frame is fixed on a pole-inserting crane ship; The six-pile working platform is constructed by using a vibrating hammer or an impact hammer to hit the steel casing, and installing a steel plate on the top of the steel casing to form a six-pile working platform; The said driving of other pile foundations: surrounding the said six-pile working platform, driving outwards a single said steel casing in sequence, and connecting with the adjacent said steel casing; The drilling and pouring: the drilling machine is installed on the steel casing to carry out the drilling construction; the bored pile construction is carried out on the steel casing after the drilling.

3. The construction method according to claim 2, characterized in that: The high water level assembly of the combined box comprises: Install the steel support system: open a hole in the steel casing and place the steel in the hole to form the first force-bearing system; Installing the base plate: installing the divided base plate on the first force-bearing system; Wet joint construction: pouring concrete between the bottom plates of several blocks so that the bottom plates of several blocks form a complete bottom plate; Install the side steel formwork and steel inner supports to form a casing.

4. The construction method according to claim 3, characterized in that: The combined casing is lowered into place, comprising: Installation of hydraulic system: a shoulder pole beam is arranged on the top of the steel casing, and hydraulic jacks and steel strands are installed on both sides of the shoulder pole beam; the lower end of the steel strand is anchored on the bottom plate to form a second force bearing system; Lift the casing and convert the force: lift the casing by 20 cm using the hydraulic jack and keep it for at least 2 hours; if the hydraulic jack and the casing are stable, remove the first force system; Lowering the casing into place: lowering the casing into the water.

5. The construction method according to claim 4, characterized in that: The casing drainage seal comprises: Installation of tension and compression rod system: the bottom of the tension and compression rod is connected to the bottom plate, and the top of the tension and compression rod is connected to the steel casing; Casting underwater plugging to seal the casing and form dry working conditions; Shear members are arranged around the steel casing; Remove the hydraulic jack and the tension and compression rods.

6. The construction method according to claim 5, characterized in that: The foundation casting comprises: Pouring concrete into the casing at a height of 800 mm to form an integral bottom plate; Pouring concrete into the casing at a height of 700 mm to form a consolidated whole with the pile foundation; dismantling the second force bearing system; Concrete is poured into the casing in layers for multiple times until the designed elevation is reached.

7. The construction method according to claim 1, characterized in that: The cast-in-place box girder on the pier top comprises: A bracket is provided on the top of the pier; Lift and install the first box beam block; Cast the pier top box girder between the first box girder blocks.

8. The construction method according to claim 1, characterized in that: The asymmetric cantilever assembly of the box beam comprises: When the box girder on one side stops being suspended and the box girder on the other side continues to be suspended, a counterweight is set on the top of the box girder on the side where the suspension is stopped.

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