Integrated construction method of pile-column combined structure of subway station transfer node

Abstract

The present application relates to a kind of subway station transfer node pile-column combined structure integrated construction method, including steel pipe column and large-diameter bored pile, the steel pipe column is from bottom to top in turn by permanent column, tool column and replacement column is composed of, wherein: the permanent column bottom end is completely inserted into the inside of large-diameter bored pile, the steel pipe column needs early pile casing to be laid during lowering process.The method of the present application can ensure the stability of the underground two-story station foundation while being efficient and stable, facilitating later expansion.Overcomes the problem of difficult construction of traditional underground two-story station long-term reserved negative three-story transfer node, has the advantages of simple structure, easy operation, low labor cost, flexible use and other advantages.Through the proposed large-diameter bored pile-steel pipe column combination, an integrated construction method is summarized, providing an efficient solution for long-term reserved negative three-story transfer node of underground two-story station.

Description

Technical Field

[0001] The present invention relates to an integrated construction method for a subway station transfer node pile-column combination structure, and relates to the technical field of urban rail transit foundation construction. Background Art

[0002] With the accelerating pace of urbanization, urban rail transit networks are becoming increasingly sophisticated, with network density increasing year by year. The number and complexity of transfer stations has also significantly increased. Since rail transit networks are often constructed in phases and batches, many node transfer stations must meet the transfer needs of existing and future lines at different stages of construction. This phased construction approach presents challenges in the design of the reserved structures for node transfer stations, especially when the buried depth of lines in later construction is often greater than that of recent lines. This makes the relative instability of the route and station locations of later lines more demanding of the reserved design.

[0003] In the construction of node transfer stations, in order to ensure the smooth implementation of the subsequent negative three-story transfer node, it is necessary to reserve vertical structural space in advance during the recent station construction process. However, due to the need to simultaneously meet the construction and operation of the recent station and the long-term construction requirements of the negative three-story node, the vertical reservation design becomes complex and challenging. Existing pile foundation construction methods are mostly based on the stability requirements of single-stage construction. When faced with vertical reservation structures, they cannot effectively guarantee the structural stability and spatial rationality of the transfer node. At the same time, traditional construction methods make it difficult to take into account the foundation bearing capacity and settlement control during the multi-stage construction process. In particular, when the buried depth of the line at different depths changes and the structural constraints are high, it is easy to cause an imbalance between the reserved space and the bearing capacity of the pile foundation.

[0004] Therefore, it is crucial to develop a pile foundation construction method that is adaptable to multi-phase construction requirements and can ensure current operations while also reserving future nodes. This method must fully consider the varying depths and structural loads of phased construction during the pile foundation design and construction phases, providing a stable load-bearing foundation for future transfer nodes and meeting the long-term requirements of urban rail transit node locations. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide an integrated construction method for a subway station transfer node pile-column combination structure.

[0006] In order to solve the above technical problems, the technical solution of the present invention is: an integrated construction method for a subway station transfer node pile-column combination structure, the construction method comprising the following steps:

[0007] S1: Before construction, a positioning platform must be established to ensure the accuracy and stability of the pile foundation. The positioning platform must be strong enough to prevent settlement and provide an accurate positioning reference for subsequent construction.

[0008] S2: A drilling machine is used to dig a hole and lower a steel casing (6), which includes a guide casing (61) and an extra-long casing (62). A rotary drilling machine is used to start drilling, and the guide casing (61) is buried first. The extra-long casing (62) is inserted into the guide casing (61) to prevent the hole wall from collapsing. The extra-long casing (62) is used between the sand layer and the rock layer to ensure the stability of the hole wall and avoid disturbing the soil layer.

[0009] S3: Drill the hole to the designed depth and treat the bedrock to ensure the stability of the pile hole. When excavating the rock layer, use an impact drill to repair the hole to ensure the flatness of the hole bottom.

[0010] S4: Use a crawler crane to lift and lower the steel cage and pour concrete. After the steel cage is lifted and lowered into the hole, ensure its verticality and avoid deviation. Then pour concrete using the conduit method to ensure that the concrete fills the entire pile hole and meets the design requirements.

[0011] S5: In order to ensure the accurate installation of the steel pipe column (1), a full-rotation drilling platform (7) is set up; the full-rotation drilling platform (7) needs to be positioned using a total station before installation to ensure that it meets the design accuracy requirements during the construction process;

[0012] S6: Conduct on-site trial assembly of steel pipe columns (1);

[0013] S7: Hoist the permanent column (3) and the tool column (4) to the designated location using a crawler crane and a full-rotation drilling rig; ensure the verticality and position of the column are accurate, and perform necessary fixings;

[0014] S8: After the steel pipe column (1) is installed, it is pressed down with a full-rotation drilling rig platform (7). When the top flange of the tool column (4) reaches the designated position of the actual project, the flanges of the replacement column (5) and the tool column (4) are connected. The steel pipe column (1) is completely pressed in until the top flange of the tool column (4) is 0.5 m above the ground level.

[0015] S9: Remove the tool column (4), replacement column (5) and full-rotation drilling platform (7) above the ground and perform backfilling; fill the remaining space with concrete and gravel to ensure the stability of the construction area;

[0016] S10: Lower the structural reinforcement inside the permanent column (3), and then use 48-hour super slow-setting concrete to pour the concrete in the tube to ensure the integrity and durability of the concrete;

[0017] S11: After the concrete solidifies and reaches the designed strength, the casing (6) is removed to complete the entire pile foundation construction process.

[0018] Preferably, the pile-column combination structure includes a steel pipe column and a large-diameter bored pile. The steel pipe column is composed of a permanent column, a tool column and a replacement column from bottom to top. The bottom end of the permanent column is completely inserted into the large-diameter bored pile. The steel pipe column requires preliminary casing laying during the lowering process.

[0019] Preferably, welding allowances are reserved for the detailed processing of the permanent column, tool column and replacement column during the secondary head cutting. The steel specifications and quality need to be checked before cutting to ensure that the cutting line is accurate with an allowable deviation of ±1 mm. A multi-head cutting machine and a CNC cutting machine are used in the cutting process, and a planer or a semi-automatic gas cutting machine is used for welding. Automatic submerged arc welding is used for welding, and CO2 gas shielded welding is used for base laying, and 6 mm copper-plated welding wire is used for gas shielded welding base laying. Before assembly, surface oxides and rust should be thoroughly cleaned, and the carbon content of the welding wire should be controlled below 0.8%; a mixture of CO2 and Ar is used as welding gas, and the welding speed is controlled between 24-28 m per hour.

[0020] Preferably, the tool column is rolled from a steel plate. After the steel plate is inspected and qualified after being cut, the steel plate is rolled by a plate rolling machine. The maximum allowable diameter deviation of the steel plate after being rolled into a steel pipe is ±3 mm, and the roundness adjustment is completed by a roundness corrector. The steel pipe processing requirements include roundness and pipe end flatness: the roundness requirement is f / d = 3 / 1000, d is the outer diameter of the steel pipe, and f is the maximum deviation of the steel pipe. The inspection method is to use a tape measure with one end fixed, and the difference between the maximum size measured at the other end and the outer diameter of the circle shall not exceed 3d / 1000; the pipe end flatness requirement is f / d = 1 / 500, that is, the maximum unevenness f of the pipe end shall not exceed 1 / 500 of the outer diameter d of the round pipe.

[0021] Preferably, the permanent column, tool column and replacement column are assembled by segmented welding, and the vertical and horizontal welds are welded in a segmented reverse order. When the pipes are spliced ​​longitudinally, the vertical welds should be staggered.

[0022] Preferably, the large-diameter bored pile has a diameter of 2 m, adopts C45 underwater super slow-setting concrete, and has a pouring length of 6 m.

[0023] Preferably, the permanent column is made of Q355B steel, with a length greater than the excavation depth of the subway station foundation pit reserved for later use or greater than 7 m. A number of M19×80 studs are welded around the bottom within a height range of 6 m from bottom to top. The top is a 0.5 m high flange structure, the bottom column tip is a wedge-shaped structure, and the column body is a rounded rectangular structure.

[0024] Preferably, the tool column is made of Q355B steel, and is provided with a 0.5 m high flange structure at the top and bottom. The length of the column body corresponds to the excavation depth of the early subway station foundation pit.

[0025] Preferably, the replacement column is made of Q355B steel, and has an overall cylindrical structure with a diameter of 1.5 m. A 0.5 m high flange structure is provided at the bottom thereof, and the length is 6 m. A step ladder is provided inside the column.

[0026] Preferably, the casing includes a guide casing and an extra-long casing, the inner diameter of the guide casing is 2.3 m and the length is 5 m; the inner diameter of the extra-long casing is 2.1 m and the length is 14 m; the buried top of the casing should be 50-60 cm above the ground.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention overcomes the difficulty of constructing the future-stage transfer nodes at the lower third level, often found in conventional two-story underground stations, by combining large-diameter bored cast-in-place piles with steel pipe columns. This method uses tool columns to insert permanent columns into the foundation. Subsequently, during the excavation of the future lower third level nodes, the steel pipe columns and isolation piles at the nodes support the superstructure, creating a cover-and-excavate construction method.

[0029] This invention has the advantages of simple structure, easy operation, low labor costs, and flexible use. Through the proposed large-diameter bored pile-steel pipe column combination, an integrated construction method has been summarized, providing an efficient solution for reserving transfer nodes on the third underground level in the future for underground second-level stations.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the construction of an embodiment of the present invention.

[0032] Figure 2 Schematic diagram of an explosion of a steel pipe column according to an embodiment of the present invention.

[0033] Figure 3 2 is a cross-sectional view of a permanent column according to an embodiment of the present invention.

[0034] Figure 4 This is a pile position map for surface settlement monitoring according to an embodiment of the present invention.

[0035] In the figure: steel pipe column 1, large diameter bored pile 2, permanent column 3, longitudinal weld 31, inner lining plate 32, stud 33, tool column 4, replacement column 5, casing 6, guide casing 61, extra-long casing 62, full-rotation drilling rig platform 7, reinforced concrete platform plate 71. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] like Figures 1 to 4 As shown, this embodiment provides an integrated construction method for a pile-column combination structure of a subway station transfer node, including a steel pipe column 1 and a large-diameter bored pile 2. The steel pipe column 1 is composed of a permanent column 3, a tool column 4 and a replacement column 5 from bottom to top, wherein: the bottom end of the permanent column 3 is completely inserted into the large-diameter bored pile 2, and the steel pipe column 1 requires the laying of a casing 6 in advance during the lowering process.

[0040] During construction, a steel cage was lowered using ground drilling to construct the foundation for steel tubular column 1. Before the foundation concrete had fully set, permanent column 3 was inserted into the foundation using tool column 4 and replacement column 5. Within the height of the underground third floor, the voids outside the columns were backfilled with C30 self-compacting concrete to a depth of 500mm below the underground second floor base. After excavation reached the base of the immediate second-floor station, tool column 4 and replacement column 5 were removed, and the floor slab and bottom beams of the immediate second-floor station were subsequently constructed. After the pile-column foundation was completed, construction of the second-floor station continued using an open-cut and continuous construction process. For excavation of the future underground third-floor nodes, six steel tubular columns 1 and isolation piles at the nodes supported the superstructure, implementing a cover-cut and continuous construction method. Excavation was conducted using a sloping method. After excavation reached the base, the floor slab, node plates at the bottom slab steel tubular column nodes, and stiffeners were installed. Finally, construction of the underground third-floor side walls and transfer escalator openings was successfully completed.

[0041] In an embodiment of the present invention, the detailed processing of the permanent column 3, the tool column 4 and the replacement column 5 reserves a welding allowance during the secondary head cutting. The steel specifications and quality need to be checked before cutting to ensure the accuracy of the cutting line with an allowable deviation of ±1 mm. The cutting process uses a multi-head cutting machine and a CNC cutting machine, and a planer or a semi-automatic gas cutting machine for welding. The welding adopts an automatic submerged arc welding process, and CO2 gas shielded welding is used for base laying, and 6 mm copper-plated welding wire is selected for gas shielded welding base laying. Before assembly, the surface oxides and rust should be thoroughly cleaned, and the carbon content of the welding wire should be controlled below 0.8%; the welding gas is a mixture of CO2 and Ar, and the welding speed is controlled between 24-28 m per hour.

[0042] In an embodiment of the present invention, the tool column 4 is formed by rolling a steel plate. After the steel plate is inspected and qualified after being cut, the steel plate is rolled by a plate rolling machine. The maximum allowable diameter deviation of the steel plate after being rolled into a steel pipe is ±3 mm, and the roundness adjustment is completed by a roundness corrector. The steel pipe processing requirements include roundness and pipe end flatness: the roundness requirement is f / d = 3 / 1000, d is the outer diameter of the steel pipe, and f is the maximum deviation of the steel pipe, that is, the long side margin after deformation does not exceed 3 mm; the inspection method is to use a tape measure with one end fixed, and the difference between the maximum size measured at the other end and the outer diameter of the circle does not exceed 3d / 1000; the pipe end flatness requirement is f / d = 1 / 500, taking f = 3 mm, that is, the unevenness of the pipe end does not exceed 2 mm.

[0043] In an embodiment of the present invention, the permanent column 3, tool column 4 and replacement column 5 are assembled and processed by segmented welding. The vertical and horizontal welds are welded in a segmented reverse order. When the pipes are spliced ​​longitudinally, the vertical welds should be staggered. The welding wire can be H08MnA and the flux can be SJ101. They should comply with the requirements of GB50205-2020. Measures should be taken to reduce welding stress during welding. The manifestation of stress is deformation. The method of dealing with stress is to support the code plate for anti-deformation before welding and correction after welding, control the welding sequence, and try to weld the supports to prevent lateral deviation. The quality inspection level of steel pipe welds is the first-level standard. Each process should be inspected and recorded after completion. The steel pipe column should have a factory certificate of conformity and a test report when leaving the factory.

[0044] In the embodiment of the present invention, the sum of the lengths of the permanent column 3, tool column 4, and replacement column 5 meets actual engineering requirements. The tool column 4 and permanent column 3 are trial-assembled before installation. Firstly, this allows familiarity with the flange connection bolt positions of the tool column 4 and permanent column 3, facilitating successful docking during subsequent installation and shortening installation time. Secondly, after the trial assembly, a total station is used to scan the center point and center line of the steel pipe column. The scan results are then compared with the center line drawn in advance at the factory to ensure the accuracy of the column center line.

[0045] In the embodiment of the present invention, the diameter of the large-diameter bored pile 2 is 2 m, C45 underwater super slow-setting concrete is used, and the pouring length is 6 m.

[0046] In the embodiment of the present invention, the permanent column 3 is made of Q355B steel and has a length greater than the excavation depth of the subway station foundation pit reserved for later use or greater than 7 m. A plurality of M19×80 studs 33 are welded around the bottom of the column within a height range of 6 m from bottom to top. The top of the column is a 0.5 m high flange structure, the bottom column tip is a wedge-shaped structure, and the column body is a rounded rectangular structure with a longitudinal weld 31 provided thereon and an inner lining plate 32 provided therein.

[0047] In the embodiment of the present invention, the tool column 4 is made of Q355B steel, and has a 0.5 m high flange structure at the top and bottom. The length of the column body corresponds to the excavation depth of the foundation pit of the early subway station.

[0048] In the embodiment of the present invention, the replacement column 5 is made of Q355B steel and has a cylindrical structure as a whole with a diameter of 1.5 m. A flange structure with a height of 0.5 m is provided at the bottom thereof. The length is 6 m and a step ladder is provided inside thereof.

[0049] In an embodiment of the present invention, the casing 6 includes a guide casing 61 and an extra-long casing 62. The inner diameter of the guide casing 61 is 2.3 m and the length is 5 m; the inner diameter of the extra-long casing 62 is 2.1 m and the length is 14 m; the top of the casing 6 is buried 50-60 cm above the ground to facilitate the subsequent installation of the steel cage and the fixation of the permanent column 3.

[0050] In the embodiment of the present invention, the specific construction process of completely inserting the bottom end of the permanent column 3 into the large-diameter bored pile 2 is as follows:

[0051] S1: Before construction, a positioning platform must be established to ensure the accuracy and stability of the pile foundation. The positioning platform must be strong enough to prevent settlement and provide an accurate positioning reference for subsequent construction.

[0052] Specifically:

[0053] S1-1: Based on the location of the pile foundation to be constructed, pour a reinforced concrete platform slab 71 to provide a stable foundation;

[0054] S1-2: Review the positioning of the completed 6×5 m reinforced concrete platform slab to ensure it meets the design requirements and construction specifications;

[0055] S2: The drilling machine digs and drills a hole, and lowers a steel casing 6, which includes a guide casing 61 and an extra-long casing 62. A rotary drilling rig is used to start drilling. Due to the deep drilling depth and thick sand layer, the bedrock is processed slowly and the hole formation time is long. In addition, the rotary drilling rig and the impact drill generate huge vibrations in the process of processing the rock layer, which will disturb the original soil of the foundation pit and easily collapse the hole during the construction process. The traditional mud wall can no longer meet the construction needs, so the guide casing 61 needs to be buried first, and the extra-long casing 62 is inserted into the guide casing 61 to prevent the hole wall from collapsing. The extra-long casing 62 is used between the sand layer and the rock layer to ensure the stability of the hole wall and avoid disturbing the soil layer.

[0056] Specifically:

[0057] S2-1: Use a drilling machine to drill a hole at the designated location, creating a hole with a diameter of 2.4m and a depth of 4m. During the drilling process, the operator must ensure that the equipment is stable to meet the design specifications;

[0058] S2-2: After drilling is complete, a guide casing 61 with an inner diameter of 2.3 m and a length of 5 m is precisely placed within the drilled hole. The guide casing 61 provides a stable guide channel to ensure the accurate positioning of the subsequent extra-long casing 62 during the installation process, thereby reducing the risk of misalignment during construction.

[0059] S2-3: Press the extra-long casing 62 with an inner diameter of 2.1 m and a length of 14 m into the guide casing 61. During this process, the depth and verticality of the casing must be monitored in real time to ensure that it is inserted smoothly and firmly into the hole and reaches the predetermined burial depth requirement;

[0060] S3: Drill the hole to the designed depth and treat the bedrock to ensure the stability of the pile hole. When excavating the rock layer, use an impact drill to repair the hole to ensure the flatness of the hole bottom.

[0061] Specifically:

[0062] S3-1: After drilling into the medium- or slightly weathered granite strata, the large borehole diameter prevented the strata from being removed all at once. Therefore, a 1.5m diameter core hole was first drilled using a rotary drilling rig with a cone-type core drill bit. A 2m diameter drill bit was then used to enlarge the hole. Once the hole was deep enough to reach the designed depth, a percussion drill was used to repair the remaining fractured core at the bottom of the hole.

[0063] S3-2: After the rock wall excavation is completed, the excess debris at the bottom of the drill hole needs to be cleaned to ensure that the hole bottom is clean and tidy. To this end, an impact hammer is used to level the hole bottom to facilitate subsequent construction;

[0064] S4: Use a crawler crane to lift and lower the steel cage and pour concrete. After the steel cage is lifted and lowered into the hole, ensure its verticality and avoid deviation. Then pour concrete using the conduit method to ensure that the concrete fills the entire pile hole and meets the design requirements.

[0065] Specifically:

[0066] S4-1: After the clearance check is completed, the rebar cage is lowered and its positioning is monitored during the hoisting process. Due to the long empty pile of steel pipe column 1, the length of the rebar cage's hanging bars is approximately 29.1m. Relying on two hanging bars alone cannot meet the verticality requirements for the rebar cage installation, and it is easy for the rebar cage to fall to the bottom of the hole during the hoisting process.

[0067] To this end, four 16mm diameter steel bars are welded in sections for hoisting. By controlling the length of the four hanging bars, the verticality of the steel cage can be effectively adjusted to avoid collision with the steel cage due to excessive vertical deviation during installation, resulting in damage or deformation.

[0068] S4-2: For a 2m diameter pile foundation, four acoustic detection tubes with a diameter of 50mm and a wall thickness of 3mm must be pre-buried. To observe whether the steel cage floats during concrete pouring and installation of steel pipe column 1, the four acoustic detection tubes must be connected to the ground and fixed to the inner wall of the casing. During installation, the acoustic detection tubes must be securely tied to the steel cage and tightened with a pipe clamp to ensure that the acoustic detection tubes in the empty pile portion are strong and reliable.

[0069] S4-3: After the steel cage is lowered, a conduit needs to be placed for concrete pouring, with a pouring height of 6m. The steel pipe column pile foundation concrete is poured using the conduit method, and the air tightness of the conduit needs to be checked before pouring. Due to the large diameter of the pile foundation, in order to ensure that the concrete is sealed at one time without breaking, a 1.5m 3 Concrete is poured using a hopper and a 300mm diameter conduit. After the concrete is poured to the designed volume, the concrete elevation is re-measured using a measuring rope. To ensure sufficient installation time between the concrete pouring and initial setting of the steel pipe column, C45 slightly expansive concrete is used to ensure smooth construction.

[0070] S5: To ensure accurate installation of the steel pipe column 1, a full-rotation drilling platform 7 is set up. Before installation, the full-rotation drilling platform 7 needs to be positioned using a total station to ensure that it meets the design accuracy requirements during the construction process.

[0071] Specifically:

[0072] The full-rotation drilling rig platform 7 is set up according to the pile center setting position, and the working platform is aligned with the pile hole center. Then the full-rotation drilling rig is hoisted and the equipment legs are inserted into the working platform leg positioning rings to ensure that the equipment center is aligned with the drill hole center.

[0073] S6: Conduct on-site trial assembly of steel pipe column 1;

[0074] S7: Hoist the permanent column 3 and tool column 4 to the designated location using a 100t crawler crane and a full-rotation drilling rig; ensure the verticality and position of the columns, and perform necessary fixation.

[0075] Specifically:

[0076] S7-1: Use a crawler crane to hoist permanent column 3. First, move column 3 horizontally out of the assembly platform and then straighten it in mid-air to ensure it is vertically transported to the bottom of the target drill hole. Lower column 3 onto the fully rotary drilling rig platform 7 and perform alignment corrections.

[0077] S7-2: Tool column 4 is lowered and bolted to the upper and lower columns using the steel frame operating space at the bottom of the fully rotary drilling rig platform 7. After tool column 4 is connected to permanent column 3, the pile position is remeasured and adjusted using a total station. During the lowering process, the verticality of the steel column is measured using the total station, and a laser instrument is used to monitor the verticality of the steel column in real time.

[0078] S8: After the steel pipe column 1 is installed, it is pressed down into the pile foundation concrete using the full-rotation drilling rig platform 7. When the top flange of the tool column 4 reaches the specified position of the actual project, the flanges of the replacement column 5 and the tool column 4 are connected. The steel pipe column 1 is completely pressed in until the top flange of the tool column 4 is 0.5 m above the ground level.

[0079] Specifically, the replacement column 5 is lowered by bolting the upper and lower columns together using the steel frame operating space at the bottom of the fully rotary drilling rig platform 7. After the tool column 4 is connected to the replacement column 5, the pile position is remeasured and adjusted using a total station. During the lowering process, the verticality of the steel pipe column is measured using the total station, and a laser instrument monitors the verticality of the steel pipe column in real time. The fully rotary drilling rig is then used to fully drive the steel pipe column into the pile foundation concrete.

[0080] S9: After the steel pipe column 1 is fixed, the tool column 4, replacement column 5, and full-rotation drilling platform 7 above the ground are removed; then, the reserved area between the basement level 3 and the basement level 2 is backfilled with C30 self-compacting concrete, and the upper part is backfilled with crushed stone to ensure the stability of the structure;

[0081] S10: Lower structural reinforcement inside permanent column 3, and then use 48-hour super slow-setting concrete to pour concrete in the tube to ensure the integrity and durability of the concrete;

[0082] S11: After the concrete solidifies and reaches the designed strength, the casing 6 is removed to complete the entire pile foundation construction process. The casing 6 is pulled out by a crawler crane and a vibrating hammer. Before pulling out, sand and gravel must be backfilled to prevent collapse during the pulling process.

[0083] In the embodiment of the present invention, in order to prevent the steel pipe column 1 from being affected by the full-rotation drilling rig during installation and causing the ground to sink, resulting in changes in the level of the operating platform and thus affecting the verticality of the installation of the steel pipe column 1, surface settlement observation points are buried on the upper, lower, left and right sides of each pile of the positioning platform, such as Figure 4 According to the actual on-site measurement of the initial settlement value of the observation point and the final settlement value after the installation of the steel pipe column 1, the maximum settlement is 1.87mm and the minimum is 1.09mm. The settlement of the positioning platform hardening solution does not affect the verticality of the installation of the steel pipe column 1. See Table 1 below for details.

[0084] Table 1 Surface subsidence monitoring data

[0085]

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. An integrated construction method for a subway station transfer node pile-column combination structure, characterized by: The construction method comprises the following steps: S1: Before construction, a positioning platform must be established to ensure the accuracy and stability of the pile foundation. The positioning platform must be strong enough to prevent settlement and provide an accurate positioning reference for subsequent construction. S2: A drilling machine is used to dig a hole and lower a steel casing (6), which includes a guide casing (61) and an extra-long casing (62). A rotary drilling machine is used to start drilling, and the guide casing (61) is buried first. The extra-long casing (62) is inserted into the guide casing (61) to prevent the hole wall from collapsing. The extra-long casing (62) is used between the sand layer and the rock layer to ensure the stability of the hole wall and avoid disturbing the soil layer. S3: Drill the hole to the designed depth and treat the bedrock to ensure the stability of the pile hole. When excavating the rock layer, use an impact drill to repair the hole to ensure the flatness of the hole bottom. S4: Use a crawler crane to lift and lower the steel cage and pour concrete. After the steel cage is lifted and lowered into the hole, ensure its verticality and avoid deviation. Then pour concrete using the conduit method to ensure that the concrete fills the entire pile hole and meets the design requirements. S5: In order to ensure the accurate installation of the steel pipe column (1), a full-rotation drilling platform (7) is set up; the full-rotation drilling platform (7) needs to be positioned using a total station before installation to ensure that it meets the design accuracy requirements during the construction process; S6: Conduct on-site trial assembly of steel pipe columns (1); S7: Hoist the permanent column (3) and the tool column (4) to the designated location using a crawler crane and a full-rotation drilling rig; ensure the verticality and position of the column are accurate, and perform necessary fixings; S8: After the steel pipe column (1) is installed, it is pressed down with a full-rotation drilling rig platform (7). When the top flange of the tool column (4) reaches the designated position of the actual project, the flanges of the replacement column (5) and the tool column (4) are connected. The steel pipe column (1) is completely pressed in until the top flange of the tool column (4) is 0.5 m above the ground level. S9: Remove the tool column (4), replacement column (5) and full-rotation drilling platform (7) above the ground and perform backfilling; fill the remaining space with concrete and gravel to ensure the stability of the construction area; S10: Lower the structural reinforcement inside the permanent column (3), and then use 48-hour super slow-setting concrete to pour the concrete in the tube to ensure the integrity and durability of the concrete; S11: After the concrete solidifies and reaches the designed strength, the casing (6) is removed to complete the entire pile foundation construction process; The pile-column combination structure comprises a steel pipe column (1) and a large-diameter bored pile (2), wherein the steel pipe column (1) is composed of a permanent column (3), a tool column (4) and a replacement column (5) in order from bottom to top, and the bottom end of the permanent column (3) is completely inserted into the large-diameter bored pile (2). During the lowering process of the steel pipe column (1), a casing (6) needs to be laid in advance; Within the height range of the negative third floor, the voids outside the columns are backfilled with C30 self-compacting concrete to 500mm below the base of the negative second floor; after the foundation pit is excavated to the base of the near second floor station, the "tool column (4) and replacement column (5)" are cut off, and then the base plate and bottom beam of the near second floor station are constructed; after the pile-column foundation construction is completed, the second floor station is continued to be constructed using the open excavation process; for the excavation of the long-term negative third floor node, the six steel pipe columns (1) and isolation piles at the node are used to support the upper structure, forming a cover excavation construction method; the earthwork excavation adopts the slope method, and after excavation to the base, the base plate and the node plate and stiffening plate at the base plate steel pipe column node are constructed, and finally the construction of the negative third floor side wall and the transfer escalator hole is successfully completed.

2. The integrated construction method for the subway station transfer node pile-column combination structure according to claim 1, characterized in that: The detailed processing of the permanent column (3), tool column (4) and replacement column (5) reserves welding allowance during the secondary cutting. Before cutting, the steel specifications and quality must be checked to ensure the accuracy of the cutting line, with an allowable deviation of ±1 mm. The cutting process uses a multi-head cutting machine and a CNC cutting machine, and a planer or a semi-automatic gas cutting machine for welding. The welding adopts an automatic submerged arc welding process, CO2 gas shielded welding is used for base laying, and 6 mm copper-plated welding wire is used for gas shielded welding base laying. Before assembly, the surface oxides and rust should be thoroughly cleaned, and the carbon content of the welding wire should be controlled below 0.8%; the welding gas is a mixture of CO2 and Ar, and the welding speed is controlled between 24-28 m per hour.

3. The integrated construction method for the subway station transfer node pile-column combination structure according to claim 1 is characterized by: The tool column (4) is formed by rolling a steel plate. After the steel plate is inspected and qualified, the steel plate is rolled by a plate rolling machine. The maximum allowable diameter deviation of the steel plate after being rolled into a steel pipe is ±3 mm, and the roundness adjustment is completed by a roundness correction machine. The steel pipe processing requirements include roundness and pipe end flatness: the roundness requirement is f / d = 3 / 1000, d is the outer diameter of the steel pipe, and f is the maximum deviation of the steel pipe; the inspection method is to use a tape measure with one end fixed, and the difference between the maximum size measured at the other end and the outer diameter of the steel pipe does not exceed 3d / 1000; the pipe end flatness requirement is f / d = 1 / 500, that is, the maximum unevenness f of the pipe end shall not exceed 1 / 500 of the outer diameter d of the steel pipe.

4. The integrated construction method for the subway station transfer node pile-column combination structure according to claim 1 is characterized by: The permanent column (3), tool column (4) and replacement column (5) are assembled by segmented welding. The vertical and horizontal welds are welded in a segmented reverse order. When the pipes are longitudinally spliced, the vertical welds should be staggered.

5. The integrated construction method of the subway station transfer node pile-column combination structure according to claim 1 is characterized by: The large-diameter bored pile (2) has a diameter of 2 m, adopts C45 underwater super slow-setting concrete, and has a pouring length of 6 m.

6. The integrated construction method of the subway station transfer node pile-column combination structure according to claim 1 is characterized by: The permanent column (3) is made of Q355B steel, and its length is greater than the excavation depth of the subway station foundation pit reserved in the later stage or greater than 7 m. A number of M19×80 studs (33) are welded on the bottom side within a height range of 6 m from bottom to top. The top is a 0.5 m high flange structure, the bottom column tip is a wedge-shaped structure, and the column body is a rounded rectangular structure.

7. The integrated construction method for the subway station transfer node pile-column combination structure according to claim 1, characterized in that: The tool column (4) is made of Q355B steel, and has a 0.5 m high flange structure at its top and bottom. The length of the column body corresponds to the excavation depth of the foundation pit of the early subway station.

8. The integrated construction method for the subway station transfer node pile-column combination structure according to claim 1 is characterized by: The replacement column (5) is made of Q355B steel and is a cylindrical structure with a diameter of 1.5 m. A flange structure with a height of 0.5 m is provided at the bottom thereof. The length thereof is 6 m and a step ladder is provided inside thereof.

9. The integrated construction method for the subway station transfer node pile-column combination structure according to claim 1, characterized in that: The inner diameter of the guide casing (61) is 2.3 m and the length is 5 m; the inner diameter of the extra-long casing (62) is 2.1 m and the length is 14 m; the top of the casing (6) is buried 50-60 cm above the ground.

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