Pipe jacking working well supporting structure for pipe jacking construction of airport comprehensive pipe gallery

Abstract

The invention relates to the field of pipe-jacking construction, and discloses a pipe-jacking working well supporting structure for pipe-jacking construction of an airport comprehensive pipe gallery, which comprises a plurality of cast-in-situ bored piles arranged around the periphery of a working well foundation pit by one circle; the profile steel enclosing purlins are fixedly connected to the cast-in-situ bored piles, and each profile steel enclosing purlin is composed of a plurality of profile steels which are connected end to end and fixedly connected to the corresponding foundation pit face; the section steel inclined supports are fixedly connected between the two adjacent section steel enclosing purlins; the gusset plate is in an isosceles right triangle shape, and the two right-angle sides of the gusset plate are fixedly connected between the two adjacent profile steel enclosing purlins respectively. The structural steel inclined supporting steel enclosing purlins are adopted, the triangular gusset plates are adopted at the corners for full penetration welding, rigid nodes are formed, a three-dimensional stress network is formed in combination with an external pulling anchor supporting device, a space truss supporting system is formed, and the dual mechanism of rigid constraint and prestress compensation of deep foundation pit supporting is achieved; the problems that a traditional supporting structure is insufficient in rigidity, poor in adaptability and complex in construction are solved.

Description

Technical Field

[0001] The present application relates to the field of pipe jacking construction, and in particular to a pipe jacking working shaft support structure for pipe jacking construction of an airport integrated pipeline corridor. Background Art

[0002] During pipe jacking construction of airport utility tunnels, the working pit, a crucial structure serving as the installation site for the jacking equipment and the initial section of the pipeline, directly impacts construction safety and project progress. Traditional support methods for the working pit typically employ steel sheet piles, bored cast-in-place piles, or underground diaphragm walls combined with internal supports. The purlin, a key force-transmitting component of the support system, is crucial for maintaining the overall rigidity of the working pit.

[0003] However, in the existing technology, the purlin support structure still has the following problems: traditional purlins mostly adopt steel sections or composite beam structures, which are prone to deformation in large-span deep foundation pits or complex geological conditions, resulting in uneven force on the support system and affecting the stability of the working shaft. There is an urgent need for a new type of jacking working shaft support structure. By optimizing the purlin design, the support stiffness and adaptability can be improved, and the construction process can be simplified to meet the high standards of the airport integrated pipeline corridor jacking project. Summary of the Invention

[0004] This application aims to solve the problems of insufficient rigidity, poor adaptability and complex construction of traditional support structures by providing a jacking work pit support structure for jacking construction of airport integrated pipeline corridors.

[0005] The present application provides a jacking work pit support structure for jacking construction of an airport integrated pipeline corridor, comprising: bored cast-in-place piles, a plurality of which are arranged around the periphery of the work pit foundation pit; steel purlins, fixedly connected to the bored cast-in-place piles, wherein the steel purlins are composed of a plurality of steel sections connected end to end and respectively fixedly connected to each foundation pit surface; steel oblique supports, fixedly connected between two adjacent steel purlins, and each group of two adjacent steel purlins is fixedly connected with the steel oblique supports; a gusset plate, in the shape of an isosceles right triangle, and the two right-angled sides are respectively fixedly connected between two adjacent steel purlins, and the gusset plate is fixedly connected between two adjacent steel purlins.

[0006] Furthermore, each of the gusset plates is provided with an external anchor support device, and the external anchor support device includes: an inclined pedestal, fixedly connected to the gusset plate; a pressure plate, fixedly connected to the inclined surface of the inclined pedestal; an anchor, fixedly connected to the pressure plate; a plurality of steel strands are provided and pass through the inclined pedestal, the anchor plate, the anchor, the steel purlin and the bored piles in sequence, and enter the holes in the soil layer.

[0007] Furthermore, a portion of the steel strands in each group of the external anchor support devices passes through one of the corresponding two adjacent steel sections, and another portion of the steel strands passes through the other of the two adjacent steel sections.

[0008] Furthermore, the external anchor support device also includes a grouting pipe, which is located in the middle of the multiple steel strands and is provided with plum blossom holes for spraying slurry.

[0009] Furthermore, the external anchor support device also includes a centering bracket, which includes an intermediate ring and spacers arranged at equal intervals around the intermediate ring. The grouting pipe passes through the intermediate ring, and each steel strand is located between two adjacent spacers.

[0010] Furthermore, a section of each of the steel strands located in the soil layer close to the inclined platform is sheathed with a plastic tube, and the plastic tube extends to the outside of the inclined platform.

[0011] Furthermore, the length of the embedded section of the bored pile is not less than 1.2 times the depth of the foundation pit, and the bite thickness of adjacent piles is 150-300 mm.

[0012] Furthermore, the steel sections of the steel purlins are H-shaped steels, adjacent steel sections are connected by high-strength bolts, and the flange plates between adjacent steel purlins are welded by groove welding.

[0013] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0014] 1: Due to the use of steel inclined supports arranged at a 45° angle, triangular gussets are fully welded at the corners to form rigid nodes. Combined with external anchor support devices, a three-dimensional force network is formed, forming a spatial truss support system, realizing the dual mechanism of rigid constraint + prestressed compensation for deep foundation pit support, which is particularly suitable for large-scale underground projects that are sensitive to deformation, such as airport pipeline corridors.

[0015] 2: Because the steel strands are grouped and passed through two adjacent steel sections instead of a single steel section, the tension is evenly transmitted to the entire purlin system. The anchoring force forms a cross-tension effect in the purlin plane, similar to the structure of a spatial cable-stayed bridge. Compared with single-point anchoring, it can reduce the bending moment burden of a single steel section, making the overall force of the purlin closer to the axial tension state. In addition, under soft soil or nearby construction disturbance conditions, the foundation pit may be subjected to asymmetric soil pressure. The steel strands that pass through the steel sections can be differentially tensioned, flexibly compensating for unbalanced loads and preventing purlin torsion.

[0016] 3: Since the steel strands are grouped and passed through two adjacent steel sections rather than a single steel section, if all the steel strands are concentrated on a single steel section, once the connection node of the steel section fails, it may cause the entire anchoring system to collapse. However, after passing through adjacent steel sections, even if a single steel section has problems, the remaining steel strands can still provide more than 50% of the residual anchoring force, greatly improving the redundancy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the overall structure of the pipe jacking work pit support structure for pipe jacking construction of an airport integrated pipe gallery in an embodiment of the present application;

[0018] Figure 2 for Figure 1 A top view of

[0019] Figure 3 for Figure 1 Schematic diagram of the middle part structure;

[0020] Figure 4 This is a schematic diagram of the overall structure of the external anchor support device in the embodiment of the present application;

[0021] Figure 5 for Figure 4 The enlarged schematic diagram of part A in the middle mainly illustrates the structure of the centering bracket;

[0022] In the figure: 1. bored cast-in-place piles; 2. steel purlin; 3. steel inclined support; 4. gusset plate; 5. external anchor support device; 51. inclined pedestal; 52. bearing plate; 53. anchor; 54. steel strand; 55. grouting pipe; 551. plum blossom hole; 56. plastic pipe; 57. centering bracket; 571. intermediate ring; 572. spacer. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present application, the technical solution of the present application will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0024] Reference Figure 1 and Figure 2 The supporting structure of the jacking working pit for the jacking construction of the airport integrated pipeline corridor includes bored cast-in-place piles, steel purlins, steel inclined supports, gusset plates, and external anchor support devices.

[0025] The SR280 rotary drilling rig was used to construct interlocking bored piles on the periphery of the jacking pit. The pile diameter was 1.2m and the pile spacing was 1.0m, forming an interlocking thickness of 200mm to ensure a continuous closed support effect. During the construction process, the "two drilling and one cleaning" process was strictly adopted. First, a cylindrical drill bit was used to pre-drill the hole to the design elevation. Then, the air lift reverse circulation method was used to thoroughly clean the hole and replace the mud. Finally, a steel cage equipped with 28 HRB400 grade Φ25 main bars and Φ16@2000 reinforcement bars was lowered and connected using the conduit method. Continue pouring C30 concrete to 1.5m above the design elevation. To ensure the stability of the support system, the embedded depth of the pile body shall be controlled to be no less than 1.2 times the depth of the foundation pit, for example, the embedded depth of a 15m deep foundation pit shall be ≥18m. During the construction process, focus on controlling the verticality deviation ≤1 / 200 and the pile position deviation ≤50mm, and ensure that the construction interval between adjacent piles is >24h. This interlocking continuous pile wall structure can effectively form a closed water-stopping curtain, significantly improving the anti-overturning stability and soil retaining and water-stopping effects in soft soil and high water level strata.

[0026] In the pipe jacking work pit support structure, the steel purlins are made of H-shaped steel with a specification of HW400×400×13×21. They are arranged horizontally along the inner side of the bored piles and are fixed with pre-embedded 20mm thick Q345B steel plates and M30 chemical anchor bolts. The anchoring depth is not less than 300mm to ensure connection reliability. The purlins are installed using a modular segmented lifting solution, with the standard segment length controlled within 6m. Factory-prefabricated L-shaped special-shaped components are used at the corners. The adjacent steel sections are connected using a dual connection method of M24 high-strength bolts combined with full groove welding. The initial tightening torque of the bolts reaches 500N. m, final tightening torque 800N·m, CO2 gas shielded welding process is used for welding, the weld leg size is not less than 12mm, and it has passed UT inspection; in particular, isosceles right-angled triangle gussets made of 20mm thick Q345B steel plates are added at the four corners of the foundation pit. The two right-angled sides are fully penetrated and welded to the adjacent steel purlin flange plates to form rigid nodes. This structure can significantly improve the local stiffness of the corners, reduce the stress concentration factor, and effectively avoid the risk of cracking of the enclosure structure. At the same time, the modular installation solution improves construction efficiency and ensures the force transmission efficiency and overall stability of the connection nodes.

[0027] In the support system, the steel diagonal supports are made of hot-rolled H-shaped steel with a specification of HW350×350×12×19, and their ends are reliably connected to the adjacent steel purlins by welding. First, a 20mm thick Q345B steel bracket is welded to the predetermined position of the purlin as a support base. The bracket and the purlin are welded using a full-penetration groove weld and passed the UT flaw detection test. During the installation of the diagonal supports, the design inclination angle of 45° is strictly controlled, with an allowable deviation of no more than ±1°. After positioning using a temporary fixed bracket, welding is carried out, and the weld height is not less than 12mm. The spacing between each diagonal support is controlled within 3m, forming a regular spatial truss system. A preload device is used to apply a preload of 60% of the design value, and a vibrating wire axial force meter is used for real-time monitoring. This diagonal support system can improve the overall stiffness of the support structure and effectively control foundation pit deformation. At the same time, its standardized installation process improves construction efficiency and ensures effective force transmission and structural stability.

[0028] Each gusset plate is equipped with an external anchor support device, refer to Figure 3-Figure 5 The external anchor support device includes an inclined pedestal, a pressure plate, an anchor, steel strands, a grouting pipe, a plastic pipe, and a centering bracket. The inclined pedestal is fixedly connected to the gusset plate; the pressure plate is fixedly connected to the inclined surface of the inclined pedestal; the anchor is fixedly connected to the pressure plate; multiple steel strands are provided and sequentially pass through the inclined pedestal, anchor plate, anchor, steel purlin, and bored piles, and enter the holes in the soil layer; each steel strand located in the soil layer is sheathed with a plastic pipe near the inclined pedestal, which extends to the outside of the inclined pedestal to protect the free section and extend the service life of the steel strand; the centering bracket is located in the hole in the soil foundation and is used to support each steel strand.

[0029] Reference Figure 5 The centering bracket consists of a center ring and spacers arranged at equal intervals around the ring. The grouting pipe passes through the center ring, and each steel strand is located between two adjacent spacers. The centering bracket prevents strand entanglement and ensures uniform prestressing.

[0030] The installation steps of the external anchor support device include:

[0031] 1. The free section of the steel strand is covered with a plastic pipe, and multiple centering brackets are used to support the steel strand and the grouting pipe.

[0032] 2. Pass the steel strands and grouting pipes through the steel purlins and place them into the holes in the soil. Part of the steel strands pass through one of the two adjacent steel sections, and the other part of the steel strands pass through the other of the two adjacent steel sections.

[0033] 3. Weld an inclined platform on the gusset plate, with the inclined platform surface forming an angle of 15° with the horizontal plane.

[0034] 4. Install the pressure plate and anchor, and pass the outer ends of several steel strands and a grouting pipe through the anchor.

[0035] During the construction process, the steel strands are tensioned to 150kN and then locked, and the soil layer is solidified by grouting in the anchoring section. The grouting adopts a secondary pressurization process. The first grouting into the hole can have an injection pressure of 0.5MPa. The secondary grouting is performed by high-pressure grouting through a grouting pipe. The slurry flows out from the plum blossom hole of the grouting pipe to ensure that the slurry is full. The high-pressure grouting fills the cracks in the soil to form an enlarged head anchor body, thereby improving the pull-out resistance.

[0036] The use of external anchor support devices, through the arrangement of gusset fixation and steel strands passing through adjacent steel sections, significantly improves the force balance, coordinated load-bearing capacity, and deformation control of the support system. The specific effects are as follows:

[0037] The rigid node function of the gusset plate: The gusset plate is welded at the corner of the purlin to form a triangular rigid node, which disperses the concentrated tension of the external anchor to the two adjacent steel purlins, avoiding local buckling of a single steel section due to excessive force.

[0038] Load-sharing effect of steel strands passing through adjacent steel sections: Since the steel strands are grouped and passed through two adjacent steel sections instead of a single steel section, the tension is evenly transmitted to the entire purlin system, forming a "multi-anchor shared load" load mode. After the steel strands are passed through different steel sections, the anchoring force forms a cross-tensioning effect within the purlin plane, similar to the structure of a spatial cable-stayed bridge. Compared with single-point anchoring, this design can reduce the bending moment burden of a single steel section, making the overall load of the purlin closer to the axial tension state, thereby improving material utilization.

[0039] Resisting Asymmetric Loads: In soft soils or with nearby construction disturbances, foundation pits may experience asymmetric earth pressures. The strands of the split-through steel sections can be tensioned differently, allowing for adjustments to the prestress value on one side to flexibly compensate for unbalanced loads and prevent purlin torsion.

[0040] Reduce the risk of single-point failure: If all steel strands are concentrated on a single steel section, once the connection node of the steel section fails, it may cause the entire anchoring system to collapse. However, after passing through adjacent steel sections, even if a single steel section has a problem, the remaining steel strands can still provide more than 50% of the residual anchoring force, greatly improving the redundancy of the system.

[0041] This application can illustrate its functional principles and beneficial effects through the following operation methods:

[0042] Implementation principle:

[0043] Interlocking pile continuous support system: A rotary drilling rig is used to construct interlocking bored piles. A continuous and closed water-stop curtain is formed through a two-drilling and one-clearing process. The pile body is embedded to a depth of 1.2 times the depth of the foundation pit, effectively resisting the lateral pressure of soft soil and high water level strata.

[0044] Modular steel purlin system: The steel purlin is hoisted in sections and fixed with M30 chemical anchors and embedded steel plates. The gussets are fully welded at the corners to form rigid nodes and reduce the stress concentration factor.

[0045] Spatial truss support system: The steel diagonal supports are arranged at a 45° inclination and connected to the perimeter purlins through welded steel corbels. The axial force is pre-applied and monitored in real time. Combined with the external tension anchor device, a three-dimensional force network is formed to coordinately control deformation.

[0046] External anchor reinforcement technology: The free section of the steel strand is covered with a plastic pipe for corrosion protection, and then anchored on a 15° inclined pedestal. A secondary grouting process is used, with the first low-pressure grouting and the second high-pressure grouting forming an enlarged head to enhance the pull-out resistance of the anchor body.

[0047] Beneficial effects:

[0048] Improved structural stability: The 200mm interlocking thickness of the interlocking pile reduces the deformation of the anti-seepage coefficient compared to traditional support, and the rigid node design of the inclined support and gusset plate reduces the stress concentration coefficient at the corner.

[0049] Optimized construction efficiency: Modular purlin installation shortens construction time, and the two-drill-one-clearing process improves pile-forming efficiency compared to traditional methods. Centering brackets prevent entanglement of steel strands, saving time in the tensioning process.

[0050] Enhanced geological adaptability: The pile body is embedded to a depth of 1.2 times the foundation pit depth and combined with high-pressure grouting anchor rods, which enables stable construction in soft soil or when the groundwater level is 3m higher than the bottom of the foundation pit.

[0051] This application realizes the dual mechanism of rigid constraint + prestressed compensation for deep foundation pit support through the four-fold synergistic effect of interlocking piles, surrounding purlins, inclined supports and external tension anchors. It is particularly suitable for large-scale underground projects that are sensitive to deformation, such as airport pipeline corridors.

[0052] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

[0053] The above is only a preferred specific implementation method of the embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and concept of the present application within the technical scope disclosed in the present application, and they should be covered by the scope of protection of the present application.

Claims

1. The jacking work pit support structure for the jacking construction of the airport integrated pipeline corridor is characterized by: include: Bored piles (1), several of which are arranged around the periphery of the working pit; A steel purlin (2) is fixedly connected to the bored pile (1), wherein the steel purlin (2) is composed of a plurality of steel sections connected end to end and respectively fixedly connected to each foundation pit surface; A steel inclined support (3) is fixedly connected between two adjacent steel purlins (2), and each group of two adjacent steel purlins (2) is fixedly connected with the steel inclined support (3); The gusset plate (4) is in the shape of an isosceles right triangle, and the two right-angled sides are respectively fixedly connected between two adjacent steel purlins (2), and the gusset plate (4) is fixedly connected between each group of two adjacent steel purlins (2).

2. The jacking work pit support structure for jacking construction of an airport integrated pipe gallery according to claim 1, characterized in that: Each gusset plate (4) is provided with an external anchor support device (5), and the external anchor support device (5) comprises: An inclined platform (51) fixedly connected to the gusset plate (4); A pressure plate (52) is fixedly connected to the inclined table surface (511) of the inclined table seat (51); An anchor (53) fixedly connected to the pressure plate (52); A plurality of steel strands (54) are provided and sequentially pass through the inclined platform (51), the anchor plate (52), the anchor (53), the section steel purlin (2) and the bored pile (1), and enter the holes in the soil layer.

3. The jacking work pit support structure for jacking construction of an airport integrated pipe gallery according to claim 2, characterized in that: A portion of the steel strands (54) in each group of the external anchor support devices (5) passes through one of the corresponding two adjacent steel sections, and another portion of the steel strands (54) passes through the other of the two adjacent steel sections.

4. The jacking work pit support structure for jacking construction of an airport integrated pipe gallery according to claim 2, characterized in that: The external anchor support device (5) further comprises a grouting pipe (55), wherein the grouting pipe (55) is located in the middle of the plurality of steel strands (54), and a plum blossom hole (551) for slurry spraying is provided on the grouting pipe (55).

5. The pipe jacking work pit support structure for pipe jacking construction of an airport integrated pipe gallery according to claim 4, characterized in that: The external anchor support device (5) further comprises a centering bracket (57), the centering bracket (57) comprising an intermediate ring (571) and spacers (572) arranged at equal intervals around the intermediate ring (571), the grouting pipe (55) passing through the intermediate ring (571), and each steel strand (54) being located between two adjacent spacers (572).

6. The pipe jacking work pit support structure for pipe jacking construction of an airport integrated pipe gallery according to claim 2, characterized in that: A section of each of the steel strands (54) located in the soil layer close to the inclined platform (51) is sheathed with a plastic tube (56), and the plastic tube (56) extends to the outside of the inclined platform (51).

7. The pipe jacking work pit support structure for pipe jacking construction of an airport integrated pipe gallery according to claim 1, characterized in that: The length of the embedded section of the bored pile (1) is not less than 1.2 times the depth of the foundation pit, and the interlocking thickness of adjacent piles is 150-300 mm.

8. The pipe jacking work pit support structure for pipe jacking construction of an airport integrated pipe gallery according to claim 1, characterized in that: The steel sections of the steel purlins (2) are H-shaped steel, adjacent steel sections are connected by high-strength bolts (22), and the flange plates between adjacent steel purlins (2) are welded by groove welding.

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