Pile foundation underpinning construction method based on immersed tube connecting section

Abstract

The invention relates to the technical field of tunnel construction, in particular to a pile foundation underpinning construction method based on an immersed tube connecting section, and the construction method comprises the following steps: S1, underpinning piles are constructed on two opposite sides of an underpinned pier pile, and the underpinning pile on one side of the underpinned pier pile penetrates through a to-be-constructed area of a mid-partition wall; s2, an underpinning bearing platform is constructed on the top of the underpinning pile; s3, an underpinning beam is constructed based on the soil layer supporting formwork, and a vertical gap is formed between the underpinning beam and the underpinning bearing platform; s4, a jacking assembly is installed in a vertical gap between the underpinning bearing platform and the underpinning beam, the jacking assembly is used for jacking the underpinning beam, and the part, located below the underpinning beam and interfering with the immersed tube connecting section, of the underpinned pier pile is dismantled; and S5, an immersed tube connecting section is constructed below the underpinning beam. According to the pile foundation underpinning construction method based on the immersed tube connecting section, the distance between the adjacent underpinning supporting assemblies can be reduced under the condition that an internal channel of the immersed tube connecting section is not occupied, and therefore the maximum bending moment and deflection of the underpinning beam are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel construction, in particular to a pile foundation underpinning construction method based on a immersed tube connecting section. BACKGROUND

[0002] In underwater tunnel construction, the immersed tube method is often used. The general construction process is as follows: the tunnel pipe section is prefabricated at another place (such as a dry dock), then floated to the water site, and finally sunk to the predetermined position on the seabed and connected to form a complete underwater immersed tube tunnel; the underwater immersed tube tunnel needs to be connected with the overland highway to form a traffic network. The part connecting the underwater immersed tube tunnel with the overland highway can be referred to as the overland immersed tube connecting section. In order to adapt to the cross section of the immersed tube tunnel, the cross section width of the immersed tube connecting section is usually designed to be similar to the cross section width of the immersed tube tunnel, which is much larger than that of a conventional tunnel such as a subway tunnel. The cross section shape of the immersed tube connecting section is also usually designed to be similar to that of the immersed tube tunnel, that is, it usually includes a roof, a floor, side walls and a mid wall, which is located between the two side walls and connected with the roof and the floor.

[0003] The height of the immersed tube tunnel is lower than the height of the shore surface. The immersed tube connecting section for connecting the immersed tube tunnel and the overland highway is mostly lower than the shore surface, and is mostly buried underground. In road planning and design, it is sometimes unavoidable that the immersed tube connecting section needs to pass under an existing bridge. In this case, the immersed tube connecting section and the bridge pile of the existing bridge are likely to interfere with each other, that is, the bridge pile of the existing bridge occupies the construction space of the immersed tube connecting section. In order to free up the construction space of the immersed tube connecting section without removing the existing bridge, the pile underpinning technology is thought of, that is, the bridge pier (or the upper part of the bridge pile) is supported by underpinning beams and underpinning piles, and the bridge pile in the interference area with the immersed tube connecting section is removed after the stress system is converted. However, the width of the immersed tube connecting section is large. If the underpinning piles are arranged in the soil layer on both sides of the immersed tube connecting section according to the prior art, the spacing between the underpinning piles supporting the same underpinning beam will become very large, the spacing between adjacent support points on the underpinning beam will be too large, and the underpinning beam will have a large bending moment and deflection, which is not conducive to structural safety and cost control. SUMMARY

[0004] The present application provides a pile foundation underpinning construction method based on an immersed tube connecting section, which aims to at least partially solve the problem that in the pile foundation underpinning process of the immersed tube connecting section, if the underpinning piles are arranged according to the prior art, the spacing between adjacent support points on the underpinning beam will be too large, the underpinning beam will have a large bending moment and deflection, and it is not conducive to structural safety and cost control.

[0005] The application provides a pile foundation underpinning construction method based on a pipe jacking connecting section, which comprises the pipe jacking connecting section, the pipe jacking connecting section has a partition wall, and the pipe jacking connecting section has a to-be-constructed area with a to-be-underpinned pile;

[0006] The method comprises the following steps: S1. Constructing underpinning piles on both sides of the to-be-underpinned pile, embedding the underpinning piles into the soil layer, and penetrating the to-be-constructed area of the partition wall with the underpinning piles on one side of the to-be-underpinned pile; S2. Excavating a foundation pit at the underpinning pile construction position to expose the top of the underpinning pile, constructing an underpinning pile cap on the top of the underpinning pile, and consolidating the underpinning pile cap with the underpinning pile; S3. Supporting a formwork based on the soil layer to construct an underpinning beam, erecting the underpinning beam on at least two underpinning pile caps, having a vertical gap between the underpinning beam and the underpinning pile cap, and consolidating the underpinning beam with the to-be-underpinned pile; S4. Installing a jacking assembly in the vertical gap between the underpinning pile cap and the underpinning beam, jacking up the underpinning beam by using the jacking assembly, and removing the part of the to-be-underpinned pile that is below the underpinning beam and interferes with the pipe jacking connecting section; S5. Constructing the pipe jacking connecting section below the underpinning beam, and embedding the partition wall of the pipe jacking connecting section with at least part of the underpinning pile.

[0007] In some embodiments, in step S2, the soil layer of the to-be-constructed area of the underpinning beam is excavated to adapt to the bottom surface of the underpinning beam formwork; In step S3, when the underpinning beam is constructed, the following steps are included: S301. Providing a supporting cushion member on the underpinning pile cap, and the supporting cushion member is used to support the underpinning beam; S302. Installing a formwork on the soil layer of the to-be-constructed area of the underpinning beam, supporting the formwork on the soil layer, extending both ends of the formwork above the underpinning pile cap, and penetrating the to-be-underpinned pile through the pouring cavity enclosed by the formwork; S303. Pouring concrete into the pouring cavity enclosed by the formwork to form the underpinning beam.

[0008] In some embodiments, step S4 comprises the following steps: S401. Pre-jacking the underpinning beam by using the jacking assembly to make the vertical gap larger; S402. Unloading the jacking assembly, and then reloading the jacking assembly to 90% to 100% of the underpinning load; locking the stroke of the jacking assembly, and defining the height of the underpinning beam in this state as the control height; S403. Cutting the underpinning pile under the underpinning beam, monitoring the settlement of the underpinning beam during the cutting process, if the settlement reaches the preset value, stopping the cutting, unlocking the jacking assembly and driving the jacking assembly to jacking to make the underpinning beam return to the control height, locking the stroke of the jacking assembly and then continuing to cut; S404. After the cutting is completed, the jacking assembly is removed and the gap between the underpinning beam and the underpinning pile cap is poured.

[0009] In some embodiments, the space to be poured between the underpinning pile cap and the underpinning beam is divided into a first pouring area and a second pouring area, the first pouring area and the second pouring area are horizontally distributed, the jacking assembly is located in the second pouring area, and the second pouring area is in communication with the external space; Step S404 includes the following steps: S4041. Forming and pouring the first pouring area to form a first concrete structure, the first concrete structure supporting the underpinning beam; S4042. Removing and moving out the jacking assembly in the second pouring area; S4043. Forming and pouring the second pouring area to form a second concrete structure.

[0010] In some embodiments, before step S2, a surrounding structure is constructed in the range near the end of the immersed tube connecting section of the immersed tube tunnel; Two surrounding structures are located on the two sides of the immersed tube connecting section respectively, the surrounding structure includes a first surrounding structure and a second surrounding structure arranged in a spaced manner away from the side wall of the immersed tube connecting section, and a rotary jet isolation wall located between the first surrounding structure and the second surrounding structure; In step S1, the underpinning pile part on the other side of the underpinning pile passes through the rotary jet isolation wall.

[0011] In some embodiments, the first surrounding structure and the second surrounding structure each include a plurality of cast-in-place piles and first rotary jet piles alternately arranged and engaged.

[0012] In some embodiments, when the first surrounding structure is constructed, the bottom surface of the cast-in-place pile is arranged to be lower than the bottom surface of the first rotary jet pile, and the bottom surface of the first rotary jet pile is arranged to be lower than the bottom surface of the area to be constructed of the immersed tube connecting section.

[0013] In some embodiments, before cutting the underpinning pile under the underpinning beam, the part of the bridge pile outside the underpinning area is reinforced. including the following steps: A1. With the reinforced bridge pile as the center, at least three circles of second rotary jet piles are spirally applied from inside to outside, the second rotary jet piles applied later are engaged with at least one second rotary jet pile applied earlier, and the innermost second rotary jet pile is spaced from the reinforced bridge pile; A2. After all the second rotary jet piles are applied, three third rotary jet piles are applied in three directions of the reinforced bridge pile, the third rotary jet piles are engaged with the innermost second rotary jet piles, and the third rotary jet piles are closer to the reinforced bridge pile than the second rotary jet piles.

[0014] In some embodiments, step S5 comprises the following steps: S501. Excavate a foundation pit to the bottom surface height of the immersed tube connecting section to be applied, and construct a foundation pit support assembly during the excavation of the foundation pit, the foundation pit support assembly comprising vertical supports and horizontal supports, and the horizontal supports being located above the immersed tube connecting section to be applied; S502. Form and pour the immersed tube connecting section, part of the underpinning pile being embedded in the partition wall, and part of the vertical supports being embedded in the immersed tube connecting section; S503. Remove the vertical supports in the internal passage of the immersed tube connecting section; S504. Construct a ground structure above the immersed tube connecting section, and the ground structure being supported by the vertical supports; The space between the ground structure and the top surface of the immersed tube connecting section is left empty or filled with lightweight fillers with a unit weight less than that of backfill soil.

[0015] In some embodiments, the underpinning pile defined as a first underpinning pile throughout the partition wall comprises an outer sleeve steel pipe and a concrete pile body, the upper end of the outer sleeve steel pipe being higher than the top surface of the immersed tube connecting section, and the lower end of the outer sleeve steel pipe being lower than the bottom surface of the immersed tube connecting section.

[0016] Compared with the prior art, the present application has the following beneficial effects: The pile foundation underpinning construction method based on the immersed tube connecting section provided by the application can reduce the distance between the underpinning piles on the two sides of the underpinning pier pile without occupying the internal passage of the immersed tube connecting section, thereby reducing the distance between the support points on the underpinning beam, and compared with the case that two groups of underpinning piles are arranged on the two sides of the immersed tube connecting section, the present application can form more stable support for the underpinning beam, reduce the maximum bending moment and deflection of the underpinning beam, improve the structural safety, and reduce the construction cost. Meanwhile, the underpinning pile cap is constructed by embedding the underpinning pile into the soil layer first and then excavating the foundation pit to expose the top of the underpinning pile, so that the surrounding soil body can be used to support the formwork of the underpinning pile cap, thereby simplifying the construction steps and saving the construction cost. The formwork is supported based on the soil layer to construct the underpinning beam, and no additional structure is arranged to support the formwork of the underpinning beam, thereby simplifying the construction steps and saving the construction cost. Meanwhile, the vertical gap is formed between the underpinning beam and the underpinning pile cap in advance, the jacking assembly is installed, the load of the underpinning pier pile under the underpinning beam is unloaded by the jacking assembly, and the underpinning pier pile is cut more safely. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure is a schematic view of the position interference between the immersed tube connecting section and the underpinning pier pile. Figure 2 The figure is a structural schematic view of the pile foundation underpinning structure based on the immersed tube connecting section. Figure 3 The figure is a schematic view of the arrangement of the jacking assembly (side cross-section). Figure 4 The figure is a schematic view of the arrangement of the jacking assembly (top cross-section). Figure 5 The figure is a plan schematic view of the pile foundation underpinning construction method based on the immersed tube connecting section. Figure 6 The figure is a construction schematic view of the pile foundation underpinning construction method based on the immersed tube connecting section. Figure 1 Figure 7 The figure is a construction schematic view of the pile foundation underpinning construction method based on the immersed tube connecting section. Figure 2 Figure 8 The figure is a construction schematic view of the pile foundation underpinning construction method based on the immersed tube connecting section. Figure 3 Figure 9 The figure is a schematic view of the arrangement of the transverse support and vertical support. Figure 10 The figure is a schematic view of the arrangement of the immersed tube connecting section and the overhead support structure.​​​ Figure 11 The concrete pouring schematic diagram between the underpinning beam and the underpinning pile cap according to the embodiment of the present application; Figure 12 The reinforcement schematic diagram of the reinforced bridge pile according to the embodiment of the present application; Figure 13 The plane schematic diagram of the guide positioning frame according to the embodiment of the present application; Figure 14 The plane position schematic diagram of the bored pile and the first rotary jet pile in the enclosure structure according to the embodiment of the present application; Figure 15 The flow chart of the pile foundation underpinning construction method according to the embodiment of the present application; Figure 16 The construction process flow chart of the first underpinning pile according to the embodiment of the present application; Figure 17 The construction process flow chart of the second underpinning pile according to the embodiment of the present application.

[0018] Markings in the figure: 100 - immersed tube connecting section; 110 - mid-partition wall; 120 - side wall; 130 - top plate; 140 - bottom plate; 200 - underpinning beam; 210 - guide positioning frame; 300 - underpinned pier pile; 310 - underpinned bridge pile; 320 - underpinned bridge pier; 400 - underpinning pile; 410 - first underpinning pile; 420 - second underpinning pile; 500 - underpinning pile cap; 510 - vertical gap; 520 - jacking assembly; 521 - jack; 522 - cushion block; 550 - grouting channel; 560 - air outlet channel; 600 - enclosure structure; 610 - first enclosure structure; 620 - second enclosure structure; 630 - rotary jet isolation wall; 640 - bored pile; 650 - first rotary jet pile; 660 - crown beam; 670 - waist beam; 700 - vertical support; 800 - horizontal support; 900 - reinforced bridge pile. DETAILED DESCRIPTION

[0019] The present application will be further described below in conjunction with specific embodiments. However, it should not be understood that the above-mentioned subject matter of the present application is limited to the following embodiments only, and any technology realized based on the content of the present application falls within the scope of the present application.

[0020] In the description of specific embodiments of the present application, the terms of orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer" and the like are expressed based on the orientation or positional relationship shown in the drawings or the orientation or positional relationship in which the product / device / apparatus of the present application is usually used, unless otherwise specified. These terms of orientation or positional relationship are only for the convenience of describing the present application or simplifying the description in specific embodiments to facilitate the quick understanding of the scheme by the skilled person, and do not indicate or imply that a specific device / component / element must have a specific orientation or be constructed and operated in a specific positional relationship, and therefore cannot be understood as a limitation on the present application.

[0021] In addition, the terms "horizontal", "vertical", "parallel" and the like do not mean that the corresponding device / component / element must be absolutely horizontal or vertical or parallel, but can be slightly inclined or deviated, as long as it does not affect the normal function of the related component. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. Alternatively, it can be simplified to understand that the corresponding device / component / element is set in the direction of "horizontal", "vertical", "parallel" and the like, and can have an error / deviation of ±10% with respect to the corresponding direction, more preferably an error / deviation of ±8% or less, more preferably an error / deviation of ±6% or less, more preferably an error / deviation of ±5% or less, and more preferably an error / deviation of ±4% or less. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its role in the scheme of the present application.

[0022] In addition, the terms "first", "second", "third" and the like in the description of the present application are only used to distinguish the same or similar components for description, and should not be understood as emphasizing or implying the relative importance of the specific components.

[0023] In addition, in the description of the embodiments of the present application, "a plurality of" and "several" represent at least 2. It can be 2, 3, 4, 5, 6, 7, 8, 9, etc. in any case, or even more than 9.

[0024] In addition, in the description of the technical scheme of the present application, unless otherwise specified / limited / limited, the terms "set", "install", "connect", "connect", "set", "arrange" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected, such as welding, riveting, bolting, screwing and other commonly used connection means in the art. The connection can be mechanical connection, electrical connection or communication connection; it can be directly connected or indirectly connected through an intermediate medium; it can be the communication between two elements.

[0025] The land immersed tube connecting section (referred to as immersed tube connecting section 100) of the immersed tube tunnel is buried underground and one end is connected to the immersed tube tunnel and the other end is connected to the ground highway. In some construction scenarios, in combination with Figure 1 , the existing bridge piles of the immersed tube connecting section 100 to be constructed exist, resulting in the construction area of the immersed tube connecting section 100 being occupied and unable to be constructed. In order to enable the immersed tube connecting section 100 to be smoothly connected to the immersed tube tunnel and the number of lanes not to be significantly reduced at the junction, the width of the cross section of the immersed tube connecting section 100 is close to the width of the cross section of the immersed tube tunnel and is much larger than the width of the cross section of the existing ordinary underground tunnel, resulting in the problem of the length of the underpinned beam being too large, the bending moment and deflection of the middle part of the underpinned beam being too large if the conventional pile foundation underpinning process is used to underpin the bridge piles interfering with the construction of the immersed tube connecting section 100, there is a large structural safety hazard, and the construction cost is also significantly increased.

[0026] The area to be constructed of the immersed tube connecting section 100 refers to the area of the immersed tube connecting section 100 to be constructed according to the engineering plan, and the areas to be constructed of other structures described below are the same.

[0027] The application will be described below in conjunction with the drawings and with reference to specific embodiments.

[0028] In combination with Figures 2 to 8 In a first aspect, the embodiments of the present application provide a pile foundation underpinning construction method based on an immersed tube connecting section, which is used to solve the problem that the land immersed tube connecting section of the immersed tube tunnel is occupied by the existing bridge piles of the bridge, and the conventional pile foundation underpinning process is not suitable for the immersed tube connecting section 100, and can ensure the safe completion of the construction of the immersed tube connecting section 100 to a certain extent without affecting the use of the existing bridge.

[0029] Similar to the immersed tube tunnel, the immersed tube connecting section 100 is also provided with a partition wall 110; exemplarily, the immersed tube connecting section 100 includes a top plate 130, a bottom plate 140, a side wall 120 and a partition wall 110, the partition wall 110 is located between the two side walls 120, the top plate 130, the bottom plate 140, the side wall 120 and the partition wall 110 are enclosed to form two passages for passing through, the partition wall 110 is connected with the top plate 130 and the bottom plate 140, and can play a role in reinforcing and supporting the top plate 130 and the bottom plate 140. Unlike the immersed tube tunnel which is usually prefabricated, the immersed tube connecting section 100 is usually formed by site pouring.

[0030] The existing bridge piles or bridge piers that need to be underpinned can be collectively referred to as underpinned pier piles 300, that is, the underpinned pier piles 300 include underpinned bridge piles 310 and underpinned bridge piers 320, the underpinned bridge piers 320 are connected with the underpinned bridge piles 310, the underpinned bridge piles 310 are buried underground, and the underpinned bridge piers 320 are located above the underpinned bridge piles 310. Based on the structural characteristics of the immersed tube connecting section 100, the present embodiment provides a construction method as follows, which comprises the following steps: S1. Constructing the underpinning piles 400 on both sides of the underpinned pier pile 300, and embedding the underpinning piles 400 in the soil layer, and making the underpinning pile 400 on one side of the underpinned pier pile 300 penetrate the to-be-constructed area of the middle partition wall 110; S2. Excavating the foundation pit at the position where the underpinning pile 400 is constructed to expose the top of the underpinning pile 400, and constructing the underpinning pile cap 500 on the top of the underpinning pile 400, and consolidating the underpinning pile cap 500 with the underpinning pile 400; S3. Constructing the underpinning beam 200 based on the soil layer support formwork, and supporting the underpinning beam 200 on at least two underpinning pile caps 500, and having a vertical gap 510 between the underpinning beam 200 and the underpinning pile cap 500, and consolidating the underpinning beam 200 with the underpinned pier pile 300; S4. Installing the jacking assembly 520 in the vertical gap 510 between the underpinning pile cap 500 and the underpinning beam 200, jacking the underpinning beam 200 by using the jacking assembly 520, and removing the part of the underpinned pier pile 300 that is below the underpinning beam 200 and interferes with the immersed tube connecting section 100; S5. Constructing the immersed tube connecting section 100 below the underpinning beam 200, and embedding the middle partition wall 110 of the immersed tube connecting section 100 with at least part of the underpinning pile 400.

[0031] The pile foundation underpinning construction method based on the immersed tube connecting section, by setting the underpinning pile 400 on one side of the underpinned pier pile 300 to penetrate the to-be-constructed area of the middle partition wall 110, can reduce the distance between the underpinning piles 400 on both sides of the underpinned pier pile 300 without occupying the internal passage of the immersed tube connecting section 100, thereby reducing the distance between the support points on the underpinning beam 200, and compared with setting two groups of underpinning piles 400 on both sides of the to-be-constructed area of the immersed tube connecting section 100, the present scheme can form a more stable support for the underpinning beam 200, reduce the maximum bending moment and deflection of the underpinning beam 200, and be beneficial to improving the structural safety and reducing the construction cost. Meanwhile, the underpinning pile cap 500 is constructed by first embedding the underpinning pile 400 in the soil layer and then excavating the foundation pit to expose the top of the underpinning pile 400, which can use the surrounding soil to support the formwork of the underpinning pile cap 500, thereby simplifying the construction steps and saving the construction cost. The underpinning beam 200 is constructed based on the soil layer support formwork, without the need for additional structures for supporting the formwork of the underpinning beam 200, which is beneficial to simplifying the construction steps and saving the construction cost. Meanwhile, the vertical gap 510 is constructed in advance between the underpinning beam 200 and the underpinning pile cap 500, which facilitates the installation of the jacking assembly 520, and thereby the jacking assembly 520 can complete the load relief of the underpinned pier pile 300 below the underpinning beam 200, so that the underpinned pier pile 300 can be cut more safely.

[0032] In step S1, the underpinning piles 400 are constructed on both sides of the underpinned pier pile 300. The underpinning piles 400 can be end-bearing piles or friction piles, and the underpinning piles 400 are embedded in the soil layer. The underpinning pile 400 on one side of the underpinned pier pile 300 penetrates the to-be-constructed area of the partition wall 110.

[0033] In some embodiments, before the underpinning piles 400 are constructed, the concrete pavement or asphalt pavement on the ground surface can be broken to expose the underlying soil layer. Exemplarily, the floor and cushion within the underpinning range of the pile foundation are chiseled. A cannon machine can be used for mechanical chiseling. The chiseling can be stopped when the backfill soil layer is reached. For example, the chiseling depth can be 15 cm to 25 cm. During the chiseling process, attention should be paid to the control of construction dust. A fog cannon or a spraying system is used for dust prevention. The chiseled concrete debris should be concentrated and transported to the stacking point by a self-unloading truck.

[0034] In some embodiments, in step S1, the underpinning piles 400 are constructed on both sides of the underpinned pier pile 300. At least one underpinning pile 400 is arranged on each side of the underpinned pier pile 300, and the underpinning pile 400 on one side penetrates the to-be-constructed area of the partition wall 110. Alternatively, the underpinning pile 400 is a cast-in-situ pile. During construction, a vertical hole can be drilled by using a drilling device, a steel reinforcement cage is then placed in the vertical hole, and finally, concrete is poured into the vertical hole to form the underpinning pile 400. Alternatively, a steel casing is placed in the vertical hole to prevent the hole from collapsing, and the steel casing is located at the upper end of the cast-in-situ pile. During the construction of the underpinning pile 400 that penetrates the to-be-constructed area of the partition wall 110, an outer sleeve steel pipe and a steel reinforcement cage are placed in the vertical hole, and then concrete is poured to form a steel pipe concrete pile. Exemplarily, the hole is formed by using a sectional mud wall, the steel pipe is placed in the hole in sections, the hole is then cleaned, and finally, concrete is injected into the hole. The height of the underpinning pile 400 is controlled according to design requirements, or the underpinning pile 400 can be over-poured and cut before the underpinning pile cap 500 is constructed.

[0035] The underpinning pile 400 that penetrates the partition wall 110 is defined as a first underpinning pile 410, and the underpinning pile 400 that does not penetrate the partition wall 110 is defined as a second underpinning pile 420. The second underpinning pile 420 is located outside the to-be-constructed area of the immersed tube connecting section 100.

[0036] In an optional embodiment, the first underpinning pile 410 comprises a steel sleeve and a concrete pile body, the steel sleeve completely penetrates the area to be constructed of the partition wall 110, the upper end of the steel sleeve is higher than the top surface of the immersed tube connecting section 100, and the lower end of the steel sleeve is lower than the bottom surface of the immersed tube connecting section 100. In a first aspect, the steel sleeve can play a role in restraining the concrete, effectively avoiding the first underpinning pile 410 from being expanded when pouring the concrete, and avoiding the intrusion into the internal passage space of the immersed tube connecting section 100. In a second aspect, in the case that the size of the first underpinning pile 410 is limited by the thickness of the partition wall 110, the steel sleeve can increase the structural strength of the first underpinning pile 410, so that the first underpinning pile 410 can meet the support needs. In a third aspect, the steel sleeve has high hardness and good external wall integrity, and after the immersed tube connecting section 100 is poured and completed, a sealing member can be used to seal the joint between the steel sleeve and the immersed tube connecting section 100.

[0037] Further, the lower end of the concrete pile body protrudes from the lower end of the steel sleeve, so as to be connected with the surrounding soil layer and improve the bearing capacity of the first underpinning pile 410. In construction, a drill hole with a depth exceeding the bottom surface of the immersed tube connecting section 100 can be drilled, then the steel sleeve is placed in the drill hole and the bottom of the steel sleeve is at a certain distance from the bottom surface of the drill hole, then the concrete is poured and grouted to form the first underpinning pile 410. Further, the upper end of the steel sleeve can extend to the vicinity of the opening of the drill hole.

[0038] Illustratively, in the construction of the first underpinning pile 410, a vertical hole can be drilled by using a drilling device, then the steel sleeve and the steel reinforcement cage are placed in the vertical hole, the external wall of the steel sleeve is as close as possible to the hole wall of the vertical hole, the upper end of the steel sleeve is connected with the hole lock, the lower end of the steel sleeve is higher than the hole bottom of the vertical hole, the steel reinforcement cage is arranged in the steel sleeve, and finally the concrete is poured into the steel sleeve to form the first underpinning pile 410.

[0039] Illustratively, in the construction of the second underpinning pile 420, a vertical hole can be drilled by using a drilling device, then the steel reinforcement cage is placed in the vertical hole, and finally the concrete is poured into the vertical hole to form the second underpinning pile 420.

[0040] In combination Figure 16 and Figure 17 , Figure 16 a construction process of a first underpinning pile 410 is shown, Figure 17 a construction process of a second underpinning pile 420 is shown. As Figure 16As shown, when the first underpinning pile 410 is constructed, the following steps are included: first, measurement and positioning are performed, and then a casing is buried; after completion, the reverse circulation pile machine is positioned, and segmented hole forming is started, and the circulating slurry wall and slag removal are simultaneously performed during hole forming; after hole forming, segmented steel pipe installation is performed (the steel pipe needs to be segmented and made in advance), and then hole cleaning is performed, and waste slurry and slag are simultaneously discharged during hole cleaning; after hole cleaning, final hole acceptance is performed; after acceptance, the reinforcement cage is installed (the reinforcement cage needs to be segmented and made in advance), and then the guide pipe is installed; then, secondary hole cleaning is performed, and then final hole acceptance is performed again; after acceptance, underwater concrete is poured (the concrete needs to be prepared in advance), and waste slurry is simultaneously discharged during pouring, and a concrete test block is simultaneously made; after concrete pouring is completed, the guide pipe and the casing are pulled out, and then pile head concrete is removed, and the first underpinning pile 410 construction is completed; after the first underpinning pile 410 construction is completed, the underpinning pile cap 500 construction is performed. Figure 17 As shown, when the second underpinning pile 420 is constructed, the following steps are included: first, measurement and positioning are performed, and then a casing is buried; after completion, the reverse circulation pile machine is positioned, and hole forming is performed, and the circulating slurry wall and slag removal are simultaneously performed during hole forming; after hole forming, hole cleaning is performed, and waste slurry and slag are discharged during hole cleaning; after hole cleaning, final hole acceptance is performed; after acceptance, the reinforcement cage is installed (the reinforcement cage needs to be segmented and made in advance), and then the guide pipe is installed; then, secondary hole cleaning is performed; after hole cleaning is completed, underwater concrete is poured (the concrete needs to be prepared in advance), and waste slurry is discharged during pouring, and a concrete test block is simultaneously made; after concrete pouring is completed, the guide pipe and the casing are pulled out, and then pile head concrete is removed, and the second underpinning pile 420 construction is completed; after the second underpinning pile 420 construction is completed, the underpinning pile cap 500 construction is performed.

[0041] Optionally, the diameter of the first underpinning pile 410 is smaller than the diameter of the second underpinning pile 420, by reducing the diameter of the first underpinning pile 410, the part of the first underpinning pile 410 extending into the partition wall 110 can be completely embedded in the partition wall 110, avoiding occupying the internal passage space of the immersed tube connecting section 100; exemplarily, the diameter of the first underpinning pile 410 is 0.8 meters, the diameter of the second underpinning pile 420 is 1.0 meter, and the diameter of the underpinning pier pile 300 is 1.2 meters.

[0042] In an optional embodiment, in order to adapt to the bridge deck height limit, the drill holes of each underpinning pile 400 below the bridge deck are formed by reverse circulation pile machines, and the reinforcement cage and the steel pipe are segmented and hoisted and installed, and the connection mode preferentially adopts lap welding, and secondarily adopts mechanical sleeve connection. In order to reduce the construction disturbance time of the original bridge pile position, the underpinning pile 400 construction sequence is: from near to far, first, the pile close to the original bridge pile is constructed, and then the pile far from the original bridge pile is constructed.

[0043] In an optional embodiment, in order to improve the verticality of the pile foundation, the steel pipe is positioned by the guide positioning frame 210 during segmented welding, and the guide positioning frame 210 is combined with the guide positioning frame 210 of the underpinning pile cap 500 to form a guide positioning system. Figure 13The guiding positioning frame 210 can include two layers of positioning sub-frames arranged vertically and parallel to each other, each of which includes a rectangular frame and inclined rods arranged at four corners of the rectangular frame, the inclined rods being connected to two adjacent sides of the rectangular frame, and the rectangular frame and the inclined rods together defining an installation space matching the cross section of the steel pipe. For example, the rectangular frame is formed by welding angle steels with a size of 100 mm x 100 mm x 4 mm, and four lifting lugs are arranged at four corners of the frame body and welded by Φ12 round steel. During the lowering and welding of the steel pipe, the verticality of the steel pipe above the guiding frame is checked by using a total station instrument, and the steel pipe is slowly lowered and timely corrected.

[0044] In some embodiments, before the underpinning construction starts, the original bridge structure crossing the area of the immersed tube connecting section 100 is detected and its safety is evaluated; further, the bridge piles adjacent to the immersed tube connecting section 100 crossing area but not needing underpinning are reinforced to increase the safety of the bridge structure; according to the site conditions, the reinforcement of the bridge piles can also be delayed, as long as it is completed before the stress system is converted.

[0045] In an optional embodiment, the existing bridge piles within a range of 15 m around the immersed tube connecting section 100 (excluding the underpinned bridge pile 310) are reinforced, the soil layer within a range of 1.5 m around the bridge pile is reinforced by using rotary jet piles, and the rotary jet piles are reinforced to a depth of 12 m; combined with the underpinning of the immersed tube connecting section 100, the soil layer within a range of 15 m around the immersed tube connecting section 100 is reinforced by using rotary jet piles, and the rotary jet piles are reinforced to a depth of 12 m. Figure 12 When the bridge pile is reinforced, the following steps are included: A1. Taking the reinforced bridge pile 900 as the center, at least three circles of second rotary jet piles (Nos. 1-39) are spirally applied from inside to outside, the second rotary jet piles applied later are engaged with at least one second rotary jet pile applied earlier, and the innermost second rotary jet pile is spaced from the reinforced bridge pile 900; A2. After all the second rotary jet piles are applied, three third rotary jet piles (Nos. 40-42) are applied in three directions of the reinforced bridge pile 900, the third rotary jet piles are engaged with the innermost second rotary jet piles, and the third rotary jet piles are closer to the reinforced bridge pile 900 than the second rotary jet piles.

[0046] Figure 12 It is a horizontal sectional view, the middle circle represents the reinforced bridge pile 900, the surrounding circles represent the rotary jet piles, and the numbers in the circles are the application numbers, which are applied from No. 1 to No. 42 in sequence.

[0047] In the above scheme, the second rotary jet grouting pile and the reinforced bridge pile 900 are left with sufficient safety spacing, which can reduce the shaking of the reinforced bridge pile 900 caused by the disturbance of the soil during the construction of the second rotary jet grouting pile, thereby helping to maintain the safety of the bridge structure. The safety spacing can be selected according to the geological conditions; after the soil around the reinforced bridge pile 900 is reinforced and constrained by the previously constructed second rotary jet grouting piles, the third rotary jet grouting piles are constructed, which are closer to the reinforced bridge pile 900 and have better reinforcement effect. Moreover, since the soil around the reinforced bridge pile 900 has been reinforced, the disturbance to the soil during the construction of the third rotary jet grouting piles is small.

[0048] In some embodiments, before the underpinning construction starts, a local construction control network point in the area is established. The plane control network can use GPS static observation post-processing data, and the elevation control network uses an electronic level. The closed loop is measured by second-order leveling.

[0049] The number and arrangement of the underpinning piles 400 should be selected according to the relative position of the immersed tube connecting section 100 and the underpinned pier pile 300. For the first underpinning piles 410 that penetrate the partition wall 110 of the immersed tube connecting section 100, the first underpinning piles 410 can be arranged longitudinally along the partition wall 110. The size of each first underpinning pile 410 can be slightly smaller than the thickness of the partition wall 110, so that the part of the first underpinning pile 410 that penetrates the immersed tube connecting section 100 can be completely located within the partition wall 110. On the one hand, this can avoid the first underpinning pile 410 occupying the internal passage space of the immersed tube connecting section 100. On the other hand, this can simplify the construction and avoid the appearance of a joint between the first underpinning pile 410 and the concrete of the immersed tube connecting section 100 in the internal passage space of the immersed tube connecting section 100, thereby improving the water stopping effect.

[0050] In some embodiments, before the excavation of the foundation pit to expose the top of the underpinning pile 400 in step S2, the enclosure structure 600 is constructed in the range of the end of the immersed tube connecting section 100 close to the immersed tube tunnel. Two enclosure structures 600 are located on both sides of the immersed tube connecting section 100, which play the roles of water stopping and supporting the foundation pit. The construction of the enclosure structure 600 can be carried out before, during or after the construction of the underpinning pile 400.

[0051] The docking position of the immersed tube connecting section 100 and the immersed tube tunnel is the junction area of the water area and the land area, which is rich in water and has higher requirements for waterproofing. In addition, the area needs to be provided with underpinning piles 400, and a deep foundation pit needs to be constructed when the immersed tube connecting section 100 is constructed by the open excavation method, which has a large lateral soil pressure and higher requirements for the enclosure structure 600. In order to meet the requirements of waterproofing and resisting soil pressure, in an optional implementation manner, the enclosure structure 600 includes a first enclosure structure 610 and a second enclosure structure 620 arranged at intervals away from the side wall of the immersed tube connecting section 100, and a jet grouting isolation wall 630 located between the first enclosure structure 610 and the second enclosure structure 620. The first enclosure structure 610 and the second enclosure structure 620 can be a waterproof curtain, a diaphragm wall, etc. The first enclosure structure 610 and the second enclosure structure 620 both extend longitudinally along the immersed tube connecting section 100. The jet grouting isolation wall 630 can be formed by the jet grouting process, that is, the original stratum structure is cut and destroyed by high-pressure jet flow, and cement-based slurry is injected at the same time, so that the soil particles and the slurry are forcibly mixed, and a consolidated body with certain strength and extremely low permeability is formed after solidification.

[0052] By arranging multiple layers of enclosure structures, the waterproof effect can be further improved, and the underground water can be effectively cut off. The jet grouting isolation wall 630 is constructed between the two layers of enclosure structures. On the one hand, the jet grouting isolation wall 630 can further improve the blocking effect of the enclosure structure 600 on underground water. On the other hand, the jet grouting isolation wall 630 can improve the supporting effect of the enclosure structure 600 on the foundation pit, and can resist the soil pressure of the side wall of the foundation pit to a certain extent, so as to reduce the supporting pressure of the foundation pit supporting assembly when the deep foundation pit is excavated for the open excavation construction of the immersed tube connecting section 100, and make the foundation pit supporting assembly more easily meet the requirements and reduce the difficulty of later construction. On the third hand, the jet grouting isolation wall 630 can reinforce the soil outside the immersed tube connecting section 100. In step S1, the second underpinning pile 420 located outside the immersed tube connecting section 100 can be partially arranged in the jet grouting isolation wall 630, so as to improve the supporting strength of the foundation on the second underpinning pile 420 through the jet grouting isolation wall 630, and effectively ensure that the settlement amount of the second underpinning pile 420 meets the supporting requirements. At the same time, the second underpinning pile 420 is arranged between the first enclosure structure 610 and the second enclosure structure 620, so as to reduce the water content of the soil layer around the second underpinning pile 420 through the second enclosure structure 620, and reduce the erosion of the underground water to the second underpinning pile 420.

[0053] In an optional implementation manner, further Figure 14, the first retaining structure 610 and the second retaining structure 620 each include a plurality of cast-in-place piles 640 and first rotary jet piles 650 arranged alternately and engaged with each other; during construction, the cast-in-place piles 640 can be constructed first, and then the first rotary jet piles 650 are constructed between adjacent cast-in-place piles 640 by using a rotary jet process, so that the first rotary jet piles 650 engage with two adjacent cast-in-place piles 640 at the same time, and the cast-in-place piles 640 and the first rotary jet piles 650 cooperate with each other to form a retaining wall, thereby playing a role of blocking underground water and supporting a lateral soil layer.

[0054] In an optional embodiment, further, during construction of the first retaining structure 610, the bottom surface of the cast-in-place pile 640 is arranged to be lower than the bottom surface of the first rotary jet pile 650, and the bottom surface of the first rotary jet pile 640 is arranged to be lower than the bottom surface of the area to be constructed of the pipe jacking connection section 100; in combination with Figure 9 and Figure 10 The above scheme can make the cast-in-place pile 640 and the first rotary jet pile 650 of the first retaining structure 610 extend below the bottom of the deep foundation pit during excavation of the deep foundation pit for construction of the pipe jacking connection section 100, so that the first retaining structure 610 can better prevent underground water from seeping into the area to be constructed of the pipe jacking connection section 100, thereby facilitating construction safety and reducing water seepage in the passage of the pipe jacking connection section 100; at the same time, by further increasing the burial depth of the cast-in-place pile 640, the lateral resistance of the cast-in-place pile 640 can be increased, and the supporting force of the cast-in-place pile 640 on the lateral soil layer can be improved, thereby reducing the difficulty of deep foundation pit support in the later stage and reducing the lateral pressure on the pipe jacking connection section 100.

[0055] In an optional embodiment, further, the top surface of the second retaining structure 620 is higher than the top surface of the first retaining structure 610, and the top surface of the second retaining structure 620 can be close to or level with the ground surface; during excavation of the deep foundation pit in step S5, the slope can be formed from the top surface of the second retaining structure 620 to the top surface of the first retaining structure 610, and then the soil layer between the first retaining structures 610 on both sides can be excavated downward to form the deep foundation pit, and the deep foundation pit is excavated to the bottom surface height of the pipe jacking connection section 100 to be constructed, and a transverse support 800 can be arranged in the deep foundation pit to connect and support the first retaining structures 610 on both sides, and the transverse support 800 can be a transverse concrete support.

[0056] Optionally, the top surfaces of the cast-in-place pile 640 and the first rotary jet pile 650 in the first retaining structure 610 are at approximately the same height, and the top surfaces of the cast-in-place pile 640 and the first rotary jet pile 650 are provided with a crown beam; the cast-in-place pile 640 and the first rotary jet pile 650 in the first retaining structure 610 are provided with a waist beam toward the side wall of the foundation pit, and the crown beam and the waist beam can be connected by the transverse support 800.

[0057] Optionally, the bottom surface of the second enclosure 620 is higher than the bottom surface of the first enclosure 610, the bottom surface of the bored pile 640 and the first rotary jet pile 650 in the second enclosure 620 are at a similar height, and the top surface height is also similar, and a corbel can also be arranged on the top surface thereof.

[0058] Based on construction errors, a height difference of 10 cm can also be considered as being at the same height.

[0059] Optionally, the immersed tube connecting section 100 is attached to the side wall of the first enclosure 610.

[0060] In an optional embodiment, the top surface of the rotary jet isolation wall 630 is lower than the top surface of the first enclosure 610 and the second enclosure 620, and the bottom surface of the rotary jet isolation wall 630 is higher than the bottom surface of the first enclosure 610 and the second enclosure 620, the first enclosure 610 and the second enclosure 620 can be constructed first, and then the rotary jet isolation wall 630 is constructed.

[0061] Illustratively, when the first enclosure 610 / second enclosure 620 is constructed, the bored pile 640 is constructed first, and then the first rotary jet pile 650 is constructed, in order to reduce the disturbance of the original pile position, the pile closer to the original bridge pile is constructed first, and then the other areas are constructed. When the bored pile 640 is constructed, the following steps can be performed: ① Before formal construction, the thickest sand layer is selected to test the hole forming, so as to determine the reasonable construction parameters; ② When constructing, the jump hitting should be used, the safety distance between the pile just completed with concrete pouring and the adjacent pile should be not less than 4 times the pile diameter, and the interval time should be not less than 36 hours, so as to avoid the influence of adjacent pile hole forming on the quality of the constructed pile; ③ The pile hole diameter should be not less than the design pile diameter, the pile body verticality control is ≤1 / 200, the pile position deviation is ≤50 mm, and the pile bottom sediment thickness is <100 mm. Further, when the first enclosure 610 and the second enclosure 620 are constructed, after the bored pile 640 and the first rotary jet pile 650 are constructed, the corbel 660 can be constructed on the top surface thereof, before the corbel 660 is constructed, the pile top should be chiseled to the fresh concrete surface, the exposed reinforcement should be straight, and the exposed length required by the design should be ensured, before the pile top corbel 660 is poured, the residual slag, floating soil and water are cleaned, so that the pile row is firmly connected with the corbel 660, and the weak surface at the connection is avoided, and the construction mainly includes earthwork excavation, chiseling of the hole pile top floating slurry, reinforcement preparation, formwork installation, concrete pouring and other construction contents.

[0062] In step S2, after the underpinning piles 400 on both sides of the underpinned pier pile 300 are constructed, a foundation pit is excavated at the underpinning pile 400 construction position to expose the top of the underpinning pile 400, and the underpinning pile cap 500 is constructed on the top of the underpinning pile 400, and the underpinning pile cap 500 is consolidated with the underpinning pile 400. In combination with Figure 6The location of the replacement pile 400 refers to the position where the replacement pile 400 is driven into the ground. A shallow foundation pit is excavated at this location until the top of the replacement pile 400 is exposed. Then, a replacement pile cap 500 is constructed in the shallow foundation pit. The replacement pile cap 500 connects one or more adjacent replacement piles 400. The replacement beam 200 and the replacement piles 400 together form a replacement support assembly to support the replacement beam 200 constructed subsequently. In each replacement support assembly, the horizontal projected area of ​​the replacement pile cap 500 is greater than the sum of the horizontal projected areas of all the replacement piles 400 connected to it. On the one hand, the larger top surface area of ​​the replacement pile cap 500 can increase the support surface area and reduce the probability of the replacement beam 200 being damaged by the punching shear of the replacement piles 400. On the other hand, the replacement pile cap 500 can cause the multiple replacement piles 400 connected to it to settle synchronously.

[0063] In some embodiments, combined with Figure 6 To facilitate formwork support for the replacement beam 200, the shallow foundation pit in step S2 can be excavated as follows: Figure 6 The shape shown indicates that the soil layer at the corresponding position of the replacement pile 400 is excavated to the height for the installation of the bottom formwork of the replacement pile 500, and the soil layer between the two replacement support components is excavated to the height for the installation of the bottom formwork of the replacement beam 200. This allows the shallow foundation pit excavation to simultaneously meet the pouring needs of the replacement pile 500 and the replacement beam 200, and the soil layer can be used to directly support the formwork, reducing the use of scaffolding and simplifying the construction process. Optionally, the shallow foundation pit can be excavated in layers. The bottom layer is excavated manually, while the other layers are excavated mechanically. After the shallow foundation pit is excavated, a 500mm support platform is reserved. Then, the bottom surface of the shallow foundation pit is hardened to provide a good working surface for subsequent construction. After the shallow foundation pit is excavated, drainage ditches and sump pits should be set up in time to prevent water from accumulating at the bottom of the pit. The drainage ditches are set on both sides of the sloping earthwork, and sump pits are set up at the bottom platform. For example, a sump pit can be set up every 20-30 meters to allow seepage water and construction wastewater in the shallow foundation pit to flow into them. Then, the water is pumped into a surface sedimentation tank for sedimentation before being discharged into the municipal drainage system. The drainage ditches and sump pits are deepened as they are excavated, keeping the bottom of the ditches at least 0.5m lower than the bottom of the shallow foundation pit, and the sump pits at least 0.5m lower than the bottom of the ditches.

[0064] After exposing the top surface of the replacement pile 400, reinforcing bars are tied and the formwork for the replacement pile cap 500 is arranged using the soil layer. Then, concrete is poured to form the replacement pile cap 500, with the top of the replacement pile 400 embedded in the replacement pile cap 500 to ensure a bond between the two. Optionally, the process flow for the replacement pile cap 500 is as follows: excavation of the foundation pit → construction of the foundation layer → construction of the pile cap reinforcement and formwork → pouring of the pile cap concrete → demolding → curing. The foundation layer is located between the replacement pile 400 and the replacement pile cap 500.

[0065] In step S3, the template is supported by the soil layer to form the underpinning beam 200. The opposite sides of the underpinning pier 300 are provided with underpinning support assemblies. The underpinning beam 200 is supported on the underpinning pile cap 500 of at least two underpinning support assemblies. The underpinning beam 200 and the underpinning pile cap 500 have a vertical gap 510 therebetween. The underpinning beam 200 is fixed to the underpinning pier 300.

[0066] In an optional embodiment, when the underpinning beam 200 is formed, the following steps are included. S301. A supporting pad member is arranged on the underpinning pile cap 500. The supporting pad member is used to support the underpinning beam 200. S302. A template is arranged on the soil layer where the underpinning beam 200 is to be formed. The template is supported by the soil layer. The two ends of the template extend above the underpinning pile cap 500. The underpinning pier 300 penetrates the template to form a pouring cavity. The pouring cavity has underpinning beam reinforcement. S303. Concrete is poured into the pouring cavity formed by the template to form the underpinning beam 200. The underpinning beam 200 is fixed to the underpinning pier 300.

[0067] The supporting pad member can be an I-shaped steel, a steel wedge or the like. The horizontal projection area of the supporting pad member is smaller than the area of the horizontal projection overlap of the underpinning pile cap 500 and the underpinning beam 200. The supporting pad member is arranged on the underpinning pile cap 500. When the underpinning beam 200 is supported on the supporting pad member, a vertical gap 510 is left between the underpinning pile cap 500 and the underpinning beam 200 for installation of the jacking assembly 520. A hole is left in the bottom template of the underpinning beam 200 for the supporting pad member to extend into. The top surface of the supporting pad member can directly contact the cast-in-place concrete, which facilitates removal of the bottom template.

[0068] In an optional embodiment, to improve the fixing strength of the underpinning pier 300 and the underpinning beam 200, the underpinning pier 300 is chiseled and anchored before the concrete of the underpinning beam 200 is poured. For example, a pile diameter hole is reserved at the interference position of the underpinning beam 200 and the underpinning pier 300. The underpinning pier 300 and the underpinning beam 200 are connected through chiseling and anchoring. Twelve steel bars are arranged along the circumferential direction. The steel bars are implanted into the underpinning pier 300 by about 200 mm. The chiseling depth is 10 mm to 20 mm. The construction process of the anchoring is as follows: line positioning, drilling, hole cleaning, steel bar processing, glue injection, anchoring and curing. Before the underpinning beam 200 is poured, the combined part of the underpinning pier 300 needs to be watered to ensure the combination is compact. The concrete is poured in layers and cured in time. Since the anchoring positions are few, the main reinforcement structure of the underpinning pier 300 needs to be removed at each anchoring position, so as to avoid damage to the original structure when the anchoring hole is drilled. In addition, the number of single drilling holes should not be too many, otherwise the stress of the underpinning pier 300 will be affected. The optimal scheme for on-site construction is to drill one hole and anchor one steel bar to ensure the stress.

[0069] In step S4, the jacking assembly 520 is installed in the vertical gap 510 between the underpinning pile cap 500 and the underpinning beam 200, the underpinning beam 200 is jacked up by the jacking assembly 520, and the part of the underpinned pier pile 300 below the underpinning beam 200 and interfering with the immersed tube connecting section 100 is removed. This step performs the stress system conversion, which refers to transferring the dead weight and the upper load of the underpinned pier pile 300 above the consolidation position of the underpinning beam 200 and the underpinned pier pile 300 to the underpinning beam 200 and the underpinning support assembly, completing the unloading of the part of the underpinned pier pile 300 below the consolidation position, and then removing the underpinned pier pile 300 in the range interfering with the immersed tube connecting section 100.

[0070] Optionally, to avoid damaging the underpinning pile cap 500 or the underpinning beam 200 by the jacking assembly 520, a steel plate is arranged between the jacking assembly 520 and the underpinning beam 200 and between the jacking assembly 520 and the underpinning pile cap 500, so as to disperse the jacking force and avoid damaging the single region of the concrete.

[0071] In the pile foundation underpinning process, the settlement deformation of the old pile has generally tended to be stable without new influencing factors, the new underpinning pile bears the bridge deck load after the system conversion, and the settlement deformation cannot be avoided. How to effectively control the settlement deformation of the new underpinning pile is the key to the pile foundation underpinning construction. Therefore, the embodiment provides the following solution.

[0072] In one embodiment, the jacking assembly 520 is first used for jacking, then the underpinned pier pile 300 below the underpinning beam 200 is cut, the height of the underpinning beam 200 is controlled by the jacking assembly 520 during the cutting process, the jacking assembly 520 is removed after the cutting is completed, and the gap between the underpinning beam 200 and the underpinning pile cap 500 is filled by pouring.

[0073] In another embodiment, the jacking assembly 520 is first loaded to 90% to 100% of the underpinning load to expose the settlement of the underpinning pile 400 in advance, then the jacking assembly 520 is removed, the gap between the underpinning beam 200 and the underpinning pile cap 500 is filled by pouring, and the underpinned pier pile 300 below the underpinning beam 200 is cut.

[0074] That is, the jacking assembly 520 and the gap between the filled pile cap 500 and the pile cap 200 can be removed before or after cutting the pile 300. The advantage of removing the jacking assembly 520 before cutting the pile 300 is that the entire gap is filled with concrete, and the structure is rigid, which is safer for construction. The advantage of removing the jacking assembly 520 after cutting the pile 300 is that the jacking assembly 520 still exists after cutting the pile 300. If there is a large settlement, the original bridge can still be jacked up using the jacking assembly 520 to prevent large changes in settlement. In actual construction, the pre-jacking and formal jacking deformation can be considered comprehensively. If the pre-jacking and formal jacking deformation are small, the gap can be filled with concrete, which is safer for construction. If the pre-jacking and formal jacking deformation are large, some safety must be sacrificed to ensure that the settlement can still be jacked up.

[0075] For the first embodiment described above, in some embodiments, step S4 includes the following steps: S401. Pre-jack the pile cap 200 using the jacking assembly 520 to increase the vertical gap 510; S402. Unload the jacking assembly 520 and then reload it to 90% to 100% of the pile cap load. Lock the stroke of the jacking assembly 520 and define the height of the pile cap 200 in this state as the control height. S403. Cut the pile 300 under the pile cap 200. Monitor the settlement of the pile cap 200 during cutting. If the settlement reaches a preset value, stop cutting, unlock the jacking assembly 520, and drive the jacking assembly 520 to jack up the pile cap 200 to the control height. Lock the stroke of the jacking assembly 520 and then continue cutting. S404. After cutting is complete, remove the jacking assembly 520 and fill the gap between the pile cap 200 and the pile cap 500.

[0076] The pile cap load refers to the calculated load that the pile cap support assembly needs to bear. Locking the stroke of the jacking assembly 520 means keeping the length of the jacking assembly 520 constant. When cutting the pile 300, multiple cutting can be used to complete the cutting.

[0077] The pre-jacking operation can be performed after the concrete of the underpinning pile cap 500 reaches 90% of the strength, and the strength of the underpinning beam 200 reaches 85% of the design strength. The significance of pre-jacking is to expose the deformation of the bridge and the settlement of the underpinned pier pile 300 in advance, and to provide preliminary data support for the formal jacking. Alternatively, in order to test the fastening degree of the connection between the underpinning beam 200 and the underpinned pier pile 300, and to ensure that it has a certain safety factor, the maximum jacking force of the jacking assembly 520 during pre-jacking is greater than or equal to 105% of the underpinning load, and further greater than or equal to 110% of the underpinning load. If the connection part is damaged during the pre-jacking process, it is convenient to handle, and the whole risk is still controllable. If the node connection firmness is damaged at 101% of the underpinning load, a relatively large risk will be caused when the use of the original bridge changes or is damaged.

[0078] The process of the pre-jacking operation can be: selection and arrangement of the jack → determination of the target value of the pre-jacking amount → recording of the data monitored by the displacement sensor and the static level gauge → analysis of the group data → determination of whether to continue to pressurize according to the monitoring group data → cyclic operation according to the above → closing of the stop valve, installation of the jack sleeve to prevent the jack from falling back → keeping the state for a certain period of time until the underpinning pile 400 settlement monitoring tends to be stable, and ending the pre-jacking operation.

[0079] In an optional embodiment, during pre-jacking, the jacking is carried out in stages according to 60%→70%→80%→90%→100%→110% of the underpinning load, and after each stage of jacking, the jacking is observed for 30 minutes without any abnormality before the next stage of jacking is carried out; after the pre-jacking is completed, the unloading is carried out in stages, and finally the unloading is returned to 0% of the force. During the formal jacking, the jacking is carried out in stages according to 60%→70%→80%→90%→95% of the underpinning load, or according to 20%→40%→60%→80%→95% of the underpinning load, and the jacking is observed after each stage, and the jacking is completed after reaching the stress.

[0080] In an optional embodiment, in combination with Figure 4 The jacking assembly 520 includes a plurality of jacks 521, which can be double-acting hydraulic jacks. The jacks 521 are located between the underpinning pile cap 500 and the underpinning beam 200, and the jacks 521 can be upwardly jacked to lift the underpinning beam 200, so that the self-weight and part or all of the upper load of the underpinned pier pile 300 are transferred to the underpinning beam 200. Further, the jacking assembly 520 further includes a pad 522 arranged on the opposite sides of the jacks 521. The pad 522 can be a plurality of steel wedges, I-beams or other components that can be arranged in layers. When the jacks 521 jacks up the underpinning beam 200, the steel wedges, I-beams or other components can be timely supplemented and inserted between the underpinning pile cap 500 and the underpinning beam 200 to increase the height of the pad 522, so as to prevent the jacks 521 from suddenly failing and causing the underpinning beam 200 to drop. The newly inserted pad 522 can be located on the support pad member described above.

[0081] During the jacking process, the working pressure of the jack 521 is slowly increased or decreased to avoid adverse consequences caused by load mutation of the underpinning unit structure. After each jacking load and unloading is completed, the jack is immediately locked, the safety self-locking device is tightened, and the next step of construction is guided according to the feedback analysis of the monitoring information. During each jacking load process, if the stress and deformation of the underpinning system unit member are not coordinated or not clear through monitoring data analysis, the operation should be immediately stopped, the jack and safety self-locking device are locked, and the jacking system and underpinning system are inspected. If necessary, unload to the initial state, and then continue the work after the cause is found out and the countermeasures are researched. When the maximum design preloading value is reached and held for a certain period of time, the new pile settlement speed of each level of holding is ≤0.1 mm / hr, and other monitoring information reflects that the system deformation is basically stable, the pile foundation load transfer is completed, and the jack 521 and safety self-locking device are locked.

[0082] Exemplarily, the specific position of the cut pile is the underpinned bridge pile 310 at the bottom of the underpinning beam 200, which is cut by using a rope saw. The steel reinforcement of the underpinned bridge pile 310 is first cut in a ring direction, and then the core concrete is gradually cut. The process of cutting the pier column is divided into seven steps: the underpinned bridge pile 310 under the underpinning beam 200 is cut according to the steps of cutting in 25%-25%-10%-10%-10%-10%-10%, and multiple underpinned bridge piles 310 connected to the same underpinning beam 200 are cut at the same time; the cutting equipment can use a new type of non-vibration linear cutting equipment. When cutting, a layer-by-layer symmetrical cutting-in method along the pile periphery can be used. After cutting off 25% of the cross section for the first time, a steel plate is added at the cutting opening. The second process is the same as the first process; after cutting off 50% of the cross section, a steel plate is added and the pile cutting construction is temporarily stopped after cutting off 10% of the cross section each time. After the real-time monitoring system feedback information indicates that the underpinning system gradually realizes stable load transfer, the next step of cutting construction is performed until the underpinned bridge pile 310 is cut off and the load transfer is realized. If the settlement approaches the control value, the jacking assembly 520 is used to gradually pre-apply the jacking force in stages, the jack 521 and the safety self-locking device are locked, and the cutting is continued until the cutting is completed. Exemplarily, the monitoring instruments continuously monitor the settlement deformation during the cutting process until the pile cutting is completed. The maximum settlement of the underpinning beam 200 during this period should not be greater than the design settlement value, and the jacking adjustment settlement should not exceed 3 mm as a warning line. During the entire process of cutting the bridge pile, the vehicles on the bridge deck are prohibited from passing through, and it is best to carry out the construction at night to completely ensure the construction quality and safety.

[0083] After the pier pile 300 is cut off by the underpinning, most of the weight of the superstructure and the underpinning beam 200 is supported by the jacks, the pressure-keeping ring of the jacks is in a locked state, and the gap between the underpinning beam 200 and the underpinning pile cap 500 is filled and compacted twice by using self-compacting grouting material, vertical steel bars and steel pads are welded, and closed stirrups are arranged outside the vertical steel bars. Exemplarily, the process flow is as follows: fine adjustment of the self-locking device to be locked → first welding of the connecting steel bars and pre-reserving of the anchoring steel bars → installation of the formwork → first pouring of the self-compacting grouting material → reaching the strength → cutting of the jack bottom leveling layer by using a rope saw → taking out the jacks in sequence → second regional welding of the connecting steel bars → second installation of the formwork → second pouring of the self-compacting grouting material → maintenance. Steel bar holes for connection are reserved during the construction of the pile cap, grouting is performed in the reserved steel bar holes, and the connecting steel bars and the formwork are constructed. Meanwhile, grouting holes 550 and air outlet holes 560 are reserved on the underpinning beam 200 or the underpinning pile cap 500, one end of the grouting holes 550 and the air outlet holes 560 communicates with the gap between the underpinning beam 200 and the underpinning pile cap 500, and the other end of the grouting holes 550 and the air outlet holes 560 communicates with the outside, the grouting holes 550 and the air outlet holes 560 can be formed by arranging pipes before pouring the concrete on the underpinning beam 200 or the underpinning pile cap 500, and the self-compacting grouting material is poured into the gap along the grouting holes 550 when filling the gap between the underpinning beam 200 and the underpinning pile cap 500.

[0084] For the latter embodiment, in some embodiments, the method comprises the following steps: B401. Pre-jacking the underpinning beam 200 by using the jacking assembly 520 to make the vertical gap 510 larger; B402. Unloading the jacking assembly 520 and reloading to 90% to 100% of the underpinning load; B403. Taking out the jacking assembly 520 and pouring the gap between the underpinning beam 200 and the underpinning pile cap 500; B404. Cutting the underpinning pier pile 300 below the underpinning beam 200.

[0085] In some embodiments, the method is combined with Figure 11 dividing the space to be poured between the underpinning pile cap 500 and the underpinning beam 200 into a first pouring area and a second pouring area, the first pouring area and the second pouring area are horizontally distributed, the jacking assembly 520 is located in the second pouring area, and the second pouring area communicates with the outside space; when the jacking assembly 520 is taken out and the gap between the underpinning beam 200 and the underpinning pile cap 500 is poured, that is, the steps S404 and B403 are performed, the following steps are used: First step: supporting the formwork and pouring the first pouring area to form a first concrete structure, the first concrete structure supports the underpinning beam 200; Second step: disassembling and moving out the jacking assembly 520 in the second pouring area; Third step: form the second concrete structure by pouring the second pouring area.

[0086] The first and second concrete structures can be reinforced concrete structures, and the two can jointly form a filling layer between the underpinned pile cap 500 and the underpinned beam 200. The first and second concrete structures are poured in sections, the first concrete structure is used to support the underpinned beam 200, and the jacking assembly 520 can be easily removed from between the underpinned pile cap 500 and the underpinned beam 200.

[0087] Figure 11 The figure shows the concrete pouring between the underpinned beam and the underpinned pile cap 500 according to the embodiments of the present application. The first pouring area is poured first and forms the first concrete structure, and the second pouring area is poured later and forms the second concrete structure. The jacking assembly 520 is located in the second pouring area. When the first concrete structure reaches a certain strength, the jacking assembly 520 is removed, and the second pouring area is poured again.

[0088] In some embodiments, to reduce the additional torque during jacking and reduce the impact on the upper bridge, a PLC synchronous control jacking system is provided to control all jacking assemblies 520 in the underpinned area, so as to achieve synchronous jacking of all jacking assemblies 520.

[0089] The jacking assembly 520 includes several jacks 521, and the PLC synchronous control jacking system can include a hydraulic system, a computer control system, detection sensors, etc. The hydraulic system can include an oil pump, a balance protection valve, a proportional valve, an inlet and outlet oil pipe, etc. The oil pump is used to inject and discharge hydraulic oil to the jacks 521. The balance protection valve is used to prevent the load from accidentally falling during jacking and supporting, and allows the operator to safely and controllably lower the load. The proportional valve is used to achieve precise and proportional continuous control of the jacking force and the lowering speed. The inlet and outlet oil pipe is used to connect the oil pump and the jacks 521. The computer control system can include computer hardware, software, an operation table, an electric control box, etc. The computer control system is used to receive control signals and data measured by the detection sensors, and control the hydraulic system to work. The detection sensors can include displacement sensors and force sensors. The displacement sensors can be arranged between the underpinned beam 200 and the underpinned pile cap 500, and the force sensors can be arranged between the jacks 521 and the underpinned beam 200, or integrated jacks 521 with force sensors can be used.

[0090] Optionally, a plurality of jacks 521 can be arranged on each underpinned pile cap 500, all jacks 521 on each underpinned pile cap 500 can be set as a jacking control point, one or more PLC hydraulic pump stations can be configured to control the plurality of control points on the plurality of underpinned pile caps 500, further, a total control station of a multi-point synchronous control system can be used to control all PLC hydraulic pump stations. The hydraulic pump stations and the hydraulic components configured therewith are controlled by computer industrial control software, the jacks 521 are controlled by computer instructions, then the pressure changes and jacking distances of the jacks 521 are fed back to the computer screen through displacement and force sensors, so as to facilitate timely adjustment by the operator.

[0091] In an optional embodiment, the detection sensor further comprises the following components: an electronic displacement meter arranged on the underpinned pile 400 or the underpinned pile cap 500, used to measure the vertical displacement of the underpinned pile 400 or the underpinned pile cap 500, the electronic displacement meter can have the following parameters: accuracy 0.01 mm; an electronic displacement meter and a longitudinal and transverse inclinometer arranged on the underpinned pier 320, the electronic displacement meter can be arranged on the top surface of the underpinned pier 320, used to measure the vertical displacement of the underpinned pier 320, the longitudinal and transverse inclinometer can be arranged on the top surface of the underpinned pier 320, used to monitor the longitudinal and transverse inclination of the underpinned pier 320, the inclinometer can have the following parameters: accuracy 2 seconds; a strain gauge, an inclinometer and a displacement meter arranged on the underpinned beam 200, wherein the strain gauge can be attached to different cross sections of the underpinned beam 200, used to closely monitor the internal stress of the underpinned beam 200 during the underpinning process, for example, the strain gauge is attached to the L / 8, L / 4, L / 2, 5L / 8 and 3L / 4 cross sections in the horizontal direction of the underpinned beam 200, the inclinometer can be arranged at the four corners of the underpinned beam 200, used to monitor and control the bending and torsion of the underpinned beam 200 during the jacking process, to ensure that the underpinned beam 200 is not inclined and lifted horizontally during the jacking process, the displacement meter can be arranged at both ends and the middle position of the underpinned beam 200, used to monitor the deflection deformation of the underpinned beam 200, and can also be arranged at the engagement position of the underpinned beam 200 and the underpinned pier 300, used to monitor the gripping force of the underpinned beam 200 on the underpinned pier 300.

[0092] In an optional embodiment, a steel pipe is pre-buried in the underpinned beam 200, clean water is injected into the pipe, a thermometer is hung in the pipe, used to monitor the hydration heat of the underpinned beam 200 during the concrete curing period, to guide the concrete curing, a crack observation instrument can be used to measure the crack deformation of the underpinned beam 200 during the underpinning process and after the underpinning is completed.

[0093] Optionally, the displacement sensor is selected with the following parameters: stroke: (10m-12m) or (1m-2m); jacking control standard: position deviation control within ±1mm; measurement accuracy: <0.1mm. The jack 521 can be a double-acting hydraulic jack, and the selected parameters can be: rated load capacity 200 tons, maximum working pressure 60 MPa, installation height 370 mm, base diameter 320 mm, maximum stroke 140 mm, equipped with mechanical nut self-locking function (self-locking stroke 50 mm), safety factor designed according to CT6 level, greater than 1.5 times the rated load.

[0094] In step S5, the immersed tube connecting section 100 is constructed below the underpinning beam 200, and the bulkhead 110 of the immersed tube connecting section 100 is embedded with at least part of the underpinning pile 400.

[0095] In some embodiments, step S5 includes the following steps: S501. Excavate the foundation pit to the bottom surface height of the area where the immersed tube connecting section 100 is to be constructed, and construct the foundation pit support assembly during the excavation of the foundation pit, in combination with Figure 9 The foundation pit support assembly includes vertical supports 700 and horizontal supports 800, and the horizontal supports 800 are located above the area where the immersed tube connecting section 100 is to be constructed; S502. Form and pour the immersed tube connecting section 100, with part of the first underpinning pile 410 embedded in the bulkhead 110, and part of the vertical support 700 embedded in the immersed tube connecting section 100; S503. Remove the vertical supports 700 in the internal passage of the immersed tube connecting section 100.

[0096] After the pile foundation underpinning is completed, the immersed tube connecting section 100 can be constructed using the open excavation method, i.e., the foundation pit is excavated to the bottom surface height of the immersed tube connecting section 100, then the immersed tube connecting section 100 is constructed by cast-in-place in the foundation pit, and finally a new ground structure is constructed above the immersed tube connecting section 100; when the immersed tube connecting section 100 is constructed by cast-in-place, part of the first underpinning pile 410 is located within the formwork of the bulkhead 110, so that the first underpinning pile 410 is partially embedded in the bulkhead 110 formed by pouring.

[0097] In step S501, the deep foundation pit is excavated to the bottom surface height of the area where the immersed tube connecting section 100 is to be constructed. When the deep foundation pit is excavated, vertical supports 700 can be first driven into the area to be excavated, with the bottom surface of the vertical supports 700 being lower than the bottom surface of the area where the immersed tube connecting section 100 is to be constructed. Then, horizontal supports 800 are sequentially arranged from top to bottom as the excavation proceeds, with the middle part of the horizontal supports 800 being connected to the vertical supports 700 and the two ends of the horizontal supports 800 being connected to the first enclosing structure 610, so as to prevent the first enclosing structure 610 from being inwardly overturned. The horizontal supports 800 can all be located above the area where the immersed tube connecting section 100 is to be constructed, or the horizontal supports 800 can be first arranged in the area where the immersed tube connecting section 100 is to be constructed, and then removed to leave a construction space for the immersed tube connecting section 100 before the immersed tube connecting section 100 is poured. After the immersed tube connecting section 100 is poured and has a certain strength, a waterproof structure can be arranged at the junction between the top surface of the immersed tube connecting section 100 and the vertical supports 700, and the vertical supports 700 in the internal passage of the immersed tube connecting section 100 can be removed. At this time, the vertical supports 700 above the immersed tube connecting section 100 are supported on the immersed tube connecting section 100, and the vertical supports 700 below the immersed tube connecting section 100 can support the immersed tube connecting section 100 and reduce the settlement of the immersed tube connecting section 100.

[0098] In some embodiments, considering that the vertical height from the top surface of the immersed tube connecting section 100 to the ground surface is large, if the top surface of the immersed tube connecting section 100 is covered with soil to the ground surface, the immersed tube connecting section 100 will bear a very large vertical pressure, which can easily cause the immersed tube connecting section 100 to be crushed. In order to reduce the probability of crushing, an overhead support structure is arranged above the immersed tube connecting section 100, which supports the first enclosing structures 610 on both sides to bear the lateral and upper loads, thereby forming an overhead space above the immersed tube connecting section 100. The overhead space can be a cavity, or can be filled with lightweight fillers such as EPS (expanded polystyrene) blocks, bubble-mixed lightweight soil, volcanic pumice, ceramsite, slag, etc., which have a smaller unit weight than backfill soil, so as to reduce the vertical load applied to the top surface of the immersed tube connecting section 100.

[0099] The overhead support structure can be formed by a foundation pit support assembly constructed as the deep foundation pit is excavated, i.e., a plurality of vertical supports 700 and a plurality of horizontal supports 800 as described above, with the lower end of the vertical supports 700 being supported on the immersed tube connecting section 100. Specifically, step S5 further includes the following steps: S504. Constructing a ground structure on the upper part of the foundation pit, with the ground structure being supported on the vertical supports 700; Leaving the space between the ground structure and the top surface of the immersed tube connecting section 100 empty or filling it with lightweight fillers having a smaller unit weight than backfill soil.

[0100] In combination with Figure 10The vertical supports 700 and the horizontal supports 800 are cross-connected to form a frame structure, the horizontal supports 800 can be horizontal concrete supports, the vertical supports 700 can be lattice columns, the ends of the horizontal concrete supports can be connected to the first enclosure 610, the lattice columns are connected to the middle parts of the horizontal concrete supports to reduce the bending moment and deflection of the middle parts of the horizontal concrete supports, and the lower ends can be supported on the top surface of the immersed tube connecting section 100. Further, the top surface of the first enclosure 610 can be provided with a crown beam 660, the uppermost horizontal concrete support is connected with the crown beam 660, the top surface height of the uppermost horizontal concrete support can be close to or level with the top surface height of the first enclosure 610, and the side wall of the first enclosure 610 can be provided with a waist beam 670, and the other horizontal concrete supports can be connected with the concrete waist beam 670.

[0101] In combination Figure 15 With reference to the embodiments of the present application, a pile foundation underpinning construction method is exemplified, which comprises the following steps: Step one: construction area is enclosed for construction, and measurement and setting out are performed; step two: pipelines are relocated and in-situ protection is performed; step three: the original bridge is detected and safety is evaluated; step four: the pile 900 of the bridge to be reinforced is reinforced by high-pressure jet grouting; step five: the underpinning pile 400 is constructed; step six: enclosure structure and auxiliary facilities are constructed; step seven: the foundation pit is excavated, and well-point dewatering is performed; step eight: the underpinning pile cap 500 is constructed, including fabrication and installation of steel bars and formworks, and transportation and pouring of commercial concrete; step nine: the underpinning beam is constructed, including roughening and planting of steel bars in advance on the original bridge pile (the underpinned pier pile 300); step ten: the force system is converted, including installation of the jack 521 and the adjustable self-locking system (i.e., the safety self-locking device), and steel wedges are driven and welded in place during the formal jacking process; step eleven: the original bridge pile is truncated, and monitoring and measurement are maintained during the truncation process; step twelve: the jack is removed, and the gap between the underpinning pile cap 500 and the underpinning beam is treated; and step thirteen: the main structure of the immersed tube connecting section is constructed.

[0102] In a second aspect, an embodiment of the present application provides a pile foundation underpinning structure based on an immersed tube connecting section, which comprises the immersed tube connecting section 100, the underpinned pier pile 300, the underpinning beam 200 and at least two underpinning support assemblies, the immersed tube connecting section 100 has a partition wall 110, the underpinned pier pile 300 is provided with the underpinning support assembly on each of the opposite sides, the underpinning beam 200 is fixed to the underpinned pier pile 300 in the middle part, the underpinning beam 200 is supported on the underpinning support assemblies on the opposite sides of the underpinned pier pile 300, and the underpinning support assembly comprises the underpinning pile 400, and the underpinning pile 400 on one side of the underpinned pier pile 300 penetrates the partition wall 110.

[0103] The underpinning beam 200 is located above the immersed tube connecting section 100, and is used to connect and support the underpinned pier pile 300 of the bridge structure, so that the part of the underpinned pier pile 300 located below the underpinning beam 200 and interfering with the immersed tube connecting section 100 can be removed to leave space for the construction of the immersed tube connecting section 100, so as to meet the support needs of the bridge structure; in order to improve the vertical bearing capacity of the underpinning beam 200, at least two underpinning support assemblies are embedded in the stratum structure, and the underpinning beam 200 is supported on the at least two underpinning support assemblies, so that most of the self-weight and upper load of the underpinning beam 200 can be transmitted to the stratum structure through the underpinning support assemblies, and the settlement of the underpinned pier pile 300 is maintained within the permitted range, so as to avoid damage to the bridge structure; for example, the underpinning beam 200 can be supported on two underpinning support assemblies, or can be supported on three or more underpinning support assemblies.

[0104] For example, in combination with Figure 5 In the first arrangement, the same underpinning beam 200 is connected with one second underpinning support assembly and one first underpinning support assembly, the first underpinning pile 410 in the first underpinning support assembly penetrates the partition wall 110, and the second underpinning support assembly is located on one outer side of the immersed tube connecting section 100; in the second arrangement, the same underpinning beam 200 is connected with two second underpinning support assemblies and one first underpinning support assembly, the two second underpinning support assemblies are distributed on two outer sides of the immersed tube connecting section 100, and the first underpinning support assembly is located between the two second underpinning support assemblies; in the third arrangement, the same underpinning beam 200 is connected with two first underpinning support assemblies and one second underpinning support assembly, the two first underpinning support assemblies are arranged longitudinally along the partition wall 110, and the second underpinning support assembly is located on one outer side of the immersed tube connecting section 100.

[0105] Figure 5 The planar schematic diagram of the pile foundation underpinning construction method based on the immersed tube connecting section according to the embodiments of the present application is shown in the figure, and the black solid circles in the figure represent the underpinning piles 400, wherein the underpinning piles 400 located between the two first enclosure structures 610 are the first underpinning piles 410, and the underpinning piles 400 located in the area of the jet grouting isolation wall 630 are the second underpinning piles 420, and all the first underpinning piles 410 are arranged in a linear shape; Figure 5 The left area in the figure is an immersed tube tunnel, and the enclosure structure 600 is arranged at the end of the immersed tube connecting section 100 close to the immersed tube tunnel, and the specific range is determined according to the waterproof requirement.

[0106] Figure 5 The strip-shaped blocks supported on the first underpinning piles 410 and the second underpinning piles 420 are the underpinning beams 200, and the black hatched circles on the underpinning beams 200 represent the underpinned pier piles 300.

[0107] Optionally, the longitudinal mid-axis of the bent cap 200 can be perpendicular to the longitudinal direction of the immersed tube joint section 100, or can form an angle with the longitudinal direction of the immersed tube joint section 100.

[0108] In some embodiments, the underpinned pier 300 is located on the longitudinal mid-axis of the bent cap 200 to reduce the probability of lateral overturning of the bent cap 200; optionally, the underpinned pier 300 is located at the midpoint of the underpinning support assembly connecting line to make the axial pressure borne by the underpinning support assemblies supporting the same bent cap 200 approximately equal. Of course, considering the various distribution positions of the underpinned pier 300 relative to the immersed tube joint section 100, the distances of the underpinned pier 300 to different underpinning support assemblies can be different, at this time, the stress and settlement on the bent cap 200 can be balanced by increasing the size and material strength of the underpinning pile 400 in the underpinning support assembly closer to the underpinned pier 300 to reduce the eccentricity effect.

[0109] In some embodiments, in combination with Figure 1 The bulkhead 110 of the immersed tube joint section 100 connects the top surface and the bottom surface of the immersed tube joint section 100. Further, within the height range of the bulkhead 110, the first underpinning pile 410 is spaced apart from the side wall of the bulkhead 110, that is, the side wall of the first underpinning pile 410 is spaced apart from the side wall of the bulkhead 110 close to the passage, for isolating the first underpinning pile 410 from the internal passage of the immersed tube joint section 100 and preventing underground water from flowing directly into the internal passage along the first underpinning pile 410. Further, the axis of the first underpinning pile 410 intersects the mid-axis of the bulkhead 110, and the diameter of the first underpinning pile 410 is smaller than the width of the bulkhead 110, so that the width of the bulkhead 110 can remain consistent in the longitudinal direction of the immersed tube joint section 100, reducing the occupation of the passage space. Optionally, all the underpinning piles 400 are vertically arranged, and the horizontal projection of the first underpinning pile 410 is located within the horizontal projection of the bulkhead 110.

[0110] Optionally, the first underpinning pile 410 is a steel pipe concrete pile, and the second underpinning pile 420 is a cast-in-situ pile. Further, the bottom surface of the underpinning pile 400 of all the underpinning support assemblies is lower than the bottom surface of the immersed tube joint section 100.

[0111] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for pile foundation underpinning construction based on a pipe section connection, characterized in that, The immersed tube connecting section (100) has a partition wall (110), and the area to be constructed of the immersed tube connecting section (100) has a jacked pile (300); The method comprises the following steps: S1. Jacked piles (400) are constructed on both sides of the jacked pile (300), and the jacked piles (400) are embedded in the soil layer, and the jacked piles (400) on one side of the jacked pile (300) penetrate the area to be constructed of the partition wall (110); S2. A foundation pit is excavated at the construction position of the jacked piles (400) to expose the top of the jacked piles (400), and a jacked pile cap (500) is constructed on the top of the jacked piles (400), and the jacked pile cap (500) is consolidated with the jacked piles (400); S3. A jacked beam (200) is constructed based on a soil layer support formwork, the jacked beam (200) is supported on at least two jacked pile caps (500), and a vertical gap (510) is formed between the jacked beam (200) and the jacked pile caps (500), and the jacked beam (200) is consolidated with the jacked pile (300); S4. A jacking assembly (520) is installed in the vertical gap (510) between the jacked pile caps (500) and the jacked beam (200), the jacked beam (200) is jacked up by using the jacking assembly (520), and the part of the jacked pile (300) below the jacked beam (200) and interfering with the immersed tube connecting section (100) is removed; S5. The immersed tube connecting section (100) is constructed below the jacked beam (200), and the partition wall (110) of the immersed tube connecting section (100) is embedded in at least part of the jacked piles (400).

2. The construction method of pile foundation underpinning based on immersed tube connecting section according to claim 1, characterized in that: In step S2, the soil layer in the area to be constructed of the jacked beam (200) is excavated to adapt to the bottom surface of the bottom formwork of the jacked beam (200); In step S3, the following steps are included when the jacked beam (200) is constructed: S301. A support cushion member is arranged on the jacked pile cap (500), and the support cushion member is used to support the jacked beam (200); S302. A formwork is installed on the soil layer in the area to be constructed of the jacked beam (200), the formwork is supported on the soil layer, both ends of the formwork extend above the jacked pile caps (500), and the jacked pile (300) penetrates a pouring cavity formed by the formwork; S303. Concrete is poured into the pouring cavity formed by the formwork to form the jacked beam (200).

3. The construction method of pile foundation underpinning by using immersed tube connecting section according to claim 1, characterized in that, Step S4 comprises the following steps: S401. The jacked beam (200) is pre-jacked by using the jacking assembly (520) to increase the vertical gap (510); S402. The jacking assembly (520) is unloaded and then reloaded to 90% to 100% of the jacking load, the stroke of the jacking assembly (520) is locked, and the height of the jacked beam (200) in this state is defined as the control height. S403. Cutting the underpinning pier pile (300) under the underpinning beam (200), monitoring the settlement of the underpinning beam (200) during the cutting process, if the settlement reaches the preset value, stopping cutting, unlocking the jacking assembly (520) and driving the jacking assembly (520) to jacking to make the underpinning beam (200) return to the control height, locking the stroke of the jacking assembly (520) and then continuing to cut; S404. After cutting is completed, the jacking assembly (520) is removed and the gap between the underpinning beam (200) and the underpinning pile cap (500) is poured and filled.

4. The construction method of pile foundation underpinning by using immersed tube connecting section according to claim 3, characterized in that, The space to be poured between the underpinning pile cap (500) and the underpinning beam (200) is divided into a first pouring area and a second pouring area, the first pouring area and the second pouring area are horizontally distributed, the jacking assembly (520) is located in the second pouring area, and the second pouring area is in communication with the external space; Step S404 includes the following steps: S4041. Forming and pouring the first pouring area to form a first concrete structure, the first concrete structure supporting the underpinning beam (200); S4042. Removing and moving out the jacking assembly (520) in the second pouring area; S4043. Forming and pouring the second pouring area to form a second concrete structure.

5. The construction method of pile foundation underpinning by using immersed tube connecting section according to claim 1, characterized in that, Before step S2, a surrounding structure (600) is constructed in the range near the end of the immersed tube connecting section (100) of the immersed tube tunnel; Two surrounding structures (600) are respectively located on the two sides of the immersed tube connecting section (100), the surrounding structure (600) includes a first surrounding structure (610) and a second surrounding structure (620) arranged in a spaced manner away from the side wall of the immersed tube connecting section (100), and a rotary jet isolation wall (630) located between the first surrounding structure (610) and the second surrounding structure (620); In step S1, the underpinning pile (400) on the other side of the underpinning pier pile (300) partially penetrates the rotary jet isolation wall (630).

6. The construction method of a pile foundation underpinning by using a pipe-connection section according to claim 5, characterized in that, The first surrounding structure (610) and the second surrounding structure (620) each include a plurality of cast-in-place piles (640) and first rotary jet piles (650) arranged alternately and engaged.

7. The construction method of a pile foundation underpinning by using a immersed tube connecting section according to claim 6, characterized in that, When the first surrounding structure (610) is constructed, the bottom surface of the cast-in-place pile (640) is arranged to be lower than the bottom surface of the first rotary jet pile (650), and the bottom surface of the first rotary jet pile (650) is arranged to be lower than the bottom surface of the area to be constructed of the immersed tube connecting section (100).

8. A construction method of pile foundation underpinning based on immersed tube connecting section according to any one of claims 1-7, characterized in that, Before cutting the underpinning pier pile (300) under the underpinning beam (200), reinforcing the part of the bridge pile outside the underpinning area; Including the following steps: A1. Taking the reinforced bridge pile (900) as the center, at least three circles of second rotary jet piles are sequentially and spirally constructed from the inside to the outside, the second rotary jet pile constructed later is engaged with at least one second rotary jet pile constructed earlier, and the innermost second rotary jet pile is spaced from the reinforced bridge pile (900). A2. After all the second rotary jet grouting piles are completed, three third rotary jet grouting piles are constructed in three directions of the reinforced bridge pile (900), the third rotary jet grouting piles are engaged with the innermost second rotary jet grouting piles, and the third rotary jet grouting piles are closer to the reinforced bridge pile (900) than the second rotary jet grouting piles.

9. A construction method of pile foundation underpinning based on immersed tube connecting section according to any one of claims 1-7, characterized in that, Step S5 comprises the following steps: S501. Excavate the foundation pit to the bottom surface height of the area where the immersed tube connecting section (100) is to be constructed, and construct the foundation pit support assembly during the excavation of the foundation pit, the foundation pit support assembly comprises vertical supports (700) and horizontal supports (800), and the horizontal supports (800) are located above the area where the immersed tube connecting section (100) is to be constructed; S502. Form and pour the immersed tube connecting section (100), part of the underpinning pile (400) is embedded in the partition wall (110), and part of the vertical support (700) is embedded in the immersed tube connecting section (100); S503. Remove the vertical support (700) in the internal passage of the immersed tube connecting section (100); S504. Construct the ground structure above the immersed tube connecting section (100), and the ground structure is supported on the vertical support (700); The space between the ground structure and the top surface of the immersed tube connecting section (100) is left empty or filled with lightweight filler with a unit weight less than that of backfill soil.

10. A driven pile underpinning construction method based on a pipe section according to any one of claims 1 to 7, characterized in that, Define the underpinning pile (400) penetrating through the partition wall (110) as a first underpinning pile (410), the first underpinning pile (410) comprises an outer sleeve steel pipe and a concrete pile body, the upper end of the outer sleeve steel pipe is higher than the top surface of the immersed tube connecting section (100), and the lower end of the outer sleeve steel pipe is lower than the bottom surface of the immersed tube connecting section (100).

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