Single-arch column-free super-large cross-section metro station arch cover method of underground excavation construction method

Abstract

The application discloses a single-arch non-column super-large-section subway station arch cover method excavation construction method and belongs to the technical field of subway station construction, and specifically comprises the following steps: S1, performing advanced support on the side of the profile line of the to-be-excavated arch; S2, excavating side pilot holes on the left side and the right side of the arch and performing initial support, temporary support and arch foot longitudinal beams at corresponding positions; S3, excavating an upper pilot hole of the arch and also performing initial support and temporary support at corresponding positions; S4, performing reinforced initial support of the arch and removing the temporary support of the arch; S5, excavating core soil of the arch; S6, excavating middle soil in stages, and performing initial support of side walls; S7, excavating lower soil in stages, and performing initial support of side walls and inverted arches; and S8, laying a waterproof layer in the whole section and performing secondary lining. The reinforced initial support is used to form an arch support structure together with the initial support in advance, so that the working efficiency is improved, the construction period of the arch cover method is shortened, and the safety of the arch support structure is improved.

Description

Technical Field

[0001] This invention relates to the field of subway station construction technology, and in particular to a method for the underground excavation of a single-arch, column-free, ultra-large cross-section subway station using the arch cover method. Background Technology

[0002] Urban subway stations, often constructed using cut-and-cover methods, are frequently located in complex geological and mechanical environments. Their excavation inevitably disrupts the existing stress field, causing gravity redistribution and resulting in varying degrees of settlement on the surface and in important buildings. Therefore, employing appropriate excavation methods and sequences is crucial for ensuring construction quality and safety, shortening the construction period, and reducing project costs.

[0003] The double-layer composite initial support arch cap method is a common construction method for underground subway stations in urban areas. Its core principle is to utilize the high stability and bearing capacity of the underlying surrounding rock as the main load-bearing structure during construction. The key structures are the arch cap and large arch foot formed by the reinforced initial support. With the protection of the reinforced initial support, the lower half of the cross-section can be excavated with slope, ensuring construction safety and improving efficiency. (See attached image) Figure 1 As shown, in the traditional double-layer composite initial support arch cap method, when excavating the core soil of the arch, pilot tunnels are first excavated on both sides of the core soil, then temporary supports are constructed, and finally, reinforced initial supports are constructed. Figure 1 In the diagram, I-IX represent the sequence of soil excavation.

[0004] Because the cross-sectional span of a single-arch, column-free, ultra-large-section subway station is very large, it is crucial that the arch can be formed in a timely manner during construction, and that the arch has sufficient strength and stability to support the overburden. The traditional double-layer composite initial support arch method for the underground excavation of a single-arch, column-free, ultra-large-section subway station requires the excavation of multiple pilot tunnels, resulting in complex procedures, a long construction period, and delayed formation of the reinforced initial support. This makes it difficult to control the deformation of the surrounding rock in a timely manner, while also limiting the excavation of the core soil, leading to high construction costs.

[0005] Regardless of the construction method, pre-support is required before excavation to ensure the safety of the excavation profile. Pre-support often employs small pipes or large pipe roofs, supplemented by pre-grouting reinforcement. A utility model patent with authorization announcement number CN212202078 U discloses a tunnel pipe roof support structure. This structure features axial reinforcement within the pipe roof tubes to enhance their structural strength. Limiting elements are installed between adjacent pipe roof tubes on the arch frame, with at least two elements spaced apart. These limiting elements restrict the radial movement of the pipe roof tubes, ensuring stable position during pressurized grouting and thus increasing structural stability. However, this support structure cannot adjust the height of the arch frames, making it unsuitable for pipe roofs of varying heights. Furthermore, disassembly requires dismantling each pipe roof tube individually, and both arch frames must be dismantled separately, resulting in a large workload and cumbersome disassembly process. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to provide a single-arch, column-free, ultra-large cross-section subway station arch-cover method for underground excavation, which can replace the traditional double-layer composite initial support arch-cover method, improve the construction efficiency of single-arch, column-free, ultra-large cross-section subway stations, thereby shortening the construction period and saving project construction costs, while ensuring the safety and quality of the construction process; in addition, this invention also provides a large pipe roof support structure, which can be height adjusted, has better stability, and is easy to disassemble the pipe roof pipes.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation, characterized by the following steps:

[0009] S1: Apply advance support around the outline of the arch to be excavated;

[0010] S2: Excavate the side guide tunnels on the left and right sides of the arch, and construct the initial support, temporary support and arch foot longitudinal beams at the corresponding locations;

[0011] S3: Excavate the upper guide tunnel of the arch, and also construct initial support and temporary support at the corresponding locations;

[0012] S4: Construct the initial reinforcement support for the arch and remove the temporary supports for the arch;

[0013] S5: Excavate the core soil of the arch;

[0014] S6: Excavate the central soil in stages and construct the initial support for the side walls;

[0015] S7: Excavate the lower soil in stages, and construct the initial support for the side walls and the invert arch;

[0016] S8: Lay a waterproof layer across the entire cross section and perform secondary lining.

[0017] Furthermore, the advanced support described in step S1 uses small pipes or large pipe sheds and is reinforced by advanced grouting.

[0018] Furthermore, the specific structure of the large pipe shed support includes four height-adjustable legs. A mounting plate is fixed to the top of each of the four legs. An extension plate is movably connected to one end of the mounting plate near the excavation face. Two arch frames corresponding to the outline of the arch to be excavated are slidably connected to the mounting plate. The rear arch frame is also slidably connected to the extension plate. Each arch frame has multiple support holes for supporting the pipe shed pipes. Multiple arc-shaped plates, corresponding one-to-one with the support holes, are also fixed to the top of the mounting plate. These arc-shaped plates are located between two arch frames and staggered front to back.

[0019] Furthermore, the outrigger includes an outer sleeve and an inner rod. The inner rod is slidably sleeved inside the outer sleeve near the top. A fixed cone is slidably connected inside the outer sleeve near the bottom. A drive assembly for simultaneously driving the inner rod and the fixed cone to move in opposite directions is provided between them. Both ends of the drive assembly penetrate the outer sleeve. Both sides of the outer sleeve have axial clearance holes that communicate with the interior of the outer sleeve.

[0020] Furthermore, the drive assembly includes a bidirectional lead screw, with matching lead screw nuts on both helical directions. Each lead screw nut has a connecting rod movably connected to its top and bottom, and the end of the connecting rod away from the lead screw nut is movably connected to a corresponding inner rod or fixed cone.

[0021] A connecting plate is fixed between the four outer sleeves. A bidirectional drive motor is mounted on the connecting plate. The two output ends of the bidirectional drive motor are connected to the corresponding lead screw nuts on the two outer sleeves. A partition is also fixed on the connecting plate. A rotating shaft is fixed at the end of the corresponding lead screw nuts on the other two outer sleeves near the partition. The rotating shaft is rotatably connected to the partition, and the two rotating shafts are drively connected to the two output ends of the bidirectional drive motor.

[0022] Furthermore, the side tunnel in step S2 and the upper tunnel in step S3 are both excavated sequentially from top to bottom using the step method; and the initial support and temporary support mentioned in steps S2 and S3 are both formed by steel bars or steel frame plus shotcrete.

[0023] Furthermore, the cross-section of the arch foot longitudinal beam described in step S2 is stepped.

[0024] Furthermore, the reinforced initial support mentioned in step S4 adopts the form of "steel profile + shotcrete + anchor bolt", and its thickness is greater than that of the initial support.

[0025] Furthermore, the excavation progress of the side guide tunnel and the upper guide tunnel is staggered by at least 10m, and the excavation progress of the upper guide tunnel and the core soil is staggered by at least 10m.

[0026] Furthermore, the middle soil body mentioned in step S6 and the lower soil body mentioned in step S7 are excavated in stages from the middle to both sides using the trenching method.

[0027] The beneficial effects of this invention are:

[0028] 1. Compared with existing technologies, the single-arch, column-free, ultra-large cross-section subway station arch-cover method of the present invention provides a method for underground excavation. By readjusting the soil excavation sequence, the method first excavates the side guide tunnels on the left and right sides of the arch and constructs initial and temporary supports for the side guide tunnels. Then, it excavates the soil of the upper guide tunnel and constructs initial and temporary supports. Finally, it constructs reinforced initial supports before excavating the core soil, thus forming the arch cover in a timely manner. The timely formation of the arch cover support system ensures the stability of the single-arch, column-free, ultra-large cross-section subway station. Moreover, since it is formed before the core soil excavation, it avoids the need to excavate the small guide tunnels on the left and right sides before excavating the core soil, making the construction simpler, more convenient, and faster, with better economic benefits. Furthermore, the earlier formation of the reinforced initial supports and the removal of the temporary supports corresponding to the upper guide tunnels before the core soil excavation of the arch can increase the construction working area. At the same time, setting the longitudinal beams at the arch foot to a stepped shape can enhance their resistance to lateral displacement, thereby effectively limiting the displacement of the arch.

[0029] 2. The construction method of this invention is used for the tunnel excavation of a single-arch, column-free, ultra-large cross-section subway station using the arch cover method. Overall, the construction work area is wider, the construction efficiency is higher, which is conducive to shortening the construction period, saving engineering resources and reducing project costs; it is also conducive to improving the safety factor of the arch support structure and ensuring construction safety, as well as the safety of construction workers and project quality.

[0030] 3. This invention also provides a large pipe roof support structure. The height of the two arch frames can be adjusted synchronously by adjusting the height of the outriggers, making the support structure suitable for pipe roof support of different heights. Moreover, the two arch frames are slidably connected on the mounting plate, which can ensure the stability of the two arch frames along the extension direction of the pipe roof and prevent lateral misalignment, thereby avoiding the tilting of the pipe roof pipe. The corresponding support holes on the two arch frames play a supporting and limiting role for the pipe roof pipe. After the pre-support construction is completed, the exposed pipe roof pipe is cut off, and the cut pipe roof pipe is separated from the arch frame by moving the arch frame back and forth. The pipe roof pipe is supported by the arc plate, which facilitates the removal of the cut pipe roof pipe. Moreover, it is not necessary to disassemble each pipe roof pipe and arch frame separately, making the operation more convenient, time-saving and labor-saving.

[0031] 4. The large pipe shed support structure in this invention can not only adjust the height of the outriggers, but also fix the entire support structure by inserting a fixed cone into the ground, which improves stability. Through the cooperation of the two-way screw, the two-way drive motor and the connecting rod, the height of the four outriggers can be adjusted simultaneously, resulting in good stability. Attached Figure Description

[0032] Figure 1 This is a construction procedure diagram for the traditional double-layer composite initial support arch cover method in existing technology.

[0033] Figure 2 This is a schematic diagram of the transverse cross-section after the excavation of the side guide tunnel in step S2 of this invention.

[0034] Figure 3 This is a schematic diagram of the transverse section after the initial support, temporary support and arch foot longitudinal beam construction of the side guide tunnel in step S2 of this invention are completed.

[0035] Figure 4 This is a schematic diagram of the transverse cross-section after the excavation of the upper guide tunnel and the application of initial and temporary support in step S3 of the present invention.

[0036] Figure 5 This is a cross-sectional view of the temporary support after the completion of the initial support construction in step S4 of this invention and the removal of the temporary support.

[0037] Figure 6 This is a schematic diagram of the transverse cross-section after the core soil excavation in step S5 of this invention.

[0038] Figure 7 This is a schematic diagram of the transverse cross-section after the excavation of the middle and lower soil in steps S6 and S7 of this invention, the initial support of the sidewall, and the construction of the inverted arch.

[0039] Figure 8 This is a schematic diagram of the transverse section after the completion of the secondary lining in step S8 of this invention, where a waterproof layer is laid across the entire cross section.

[0040] Figure 9 This is a diagram illustrating the soil excavation process for the single-arch, column-free, ultra-large cross-section subway station arch cover method in this invention.

[0041] Figure 10 This is a front view of the large pipe shed support structure in Embodiment 2 of the present invention.

[0042] Figure 11 This is a side view of the top structure of the mounting plate in Embodiment 2 of the present invention.

[0043] Figure 12 This is a side view of the extended plate in its folded state in Embodiment 2 of the present invention.

[0044] Figure 13 This is a front view of the arc-shaped plate structure in Embodiment 2 of the present invention.

[0045] Figure 14 This is a top view of the connecting plate structure in Embodiment 2 of the present invention.

[0046] Figure 15 This is a top view of the mounting plate structure in Embodiment 2 of the present invention.

[0047] Among them: 1-Side pilot tunnel, 2-Upper pilot tunnel, 3-Core soil, 4-Advanced support, 5-Initial support, 6-Temporary support, 7-Reinforced initial support, 8-Anchor bolt, 9-Middle soil, 10-Lower soil, 11-Invert arch, 12-Waterproof layer, 13-Secondary lining, 14-Arch foot longitudinal beam, 15-Support leg, 1501-Outer sleeve, 1502-Inner rod, 1503-Fixing cone, 1504-Displacement hole, 16-Mounting plate, 1601-First 17-Sliding groove, 17-Extension plate, 1701-Second sliding groove, 18-Arch frame, 1801-First upright, 19-Pipe shed pipe, 20-Support hole, 21-Arc plate, 2101-Second upright, 22-Double-direction screw, 23-Screw nut, 24-Connecting rod, 25-Connecting plate, 26-Double-direction drive motor, 27-Partition plate, 28-Rotating shaft, 29-Fixing plate, 30-Fixing bolt, 31-Driven gear, 32-Drive gear, 33-Belt. Detailed Implementation

[0048] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0049] Example 1:

[0050] The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch-cover method with tunnel excavation includes the following steps.

[0051] S1: Apply advanced support 4 around the outline of the arch to be excavated;

[0052] Specifically, the aforementioned advanced support 4 adopts small pipes or large pipe sheds and is reinforced by advanced grouting.

[0053] S2: Excavate the pilot tunnels 1 on the left and right sides of the arch, and construct the initial support 5, temporary support 6, and arch foot longitudinal beam 14 at the corresponding locations; a schematic diagram of the transverse section after the excavation of the pilot tunnel 1 is attached. Figure 2 As shown, Figure 2 In the diagram, I and II indicate the excavation sequence; a schematic diagram of the transverse section after the completion of the initial support 5, temporary support 6, and arch foot longitudinal beam 14 of the pilot tunnel 1 is attached. Figure 3 As shown;

[0054] Specifically, the pilot tunnel 1 is excavated sequentially from top to bottom using the step method. The construction of the initial support 5 should strictly follow the principles of the New Austrian Tunneling Method (NATM), namely, "advanced pipe installation, strict grouting, short advance, strong support, tight sealing, and frequent measurement." Both the initial support 5 and the temporary support 6 are formed by reinforced steel or steel frame with shotcrete, effectively ensuring the quality and strength of the initial support 5 and improving the safety and quality of the project. The longitudinal beam 14 at the arch foot has a stepped cross-section. Where there are gaps between the pilot tunnel 1 and the initial support 5, micro-expansion concrete of the same joint as the main structure is used for backfilling and compaction, eliminating gaps between the initial support 5 and the tunnel sidewall, and ensuring the support strength of the arch.

[0055] Because the excavation is carried out in soil with relatively good conditions and the excavation area of ​​the pilot tunnel 1 is not large, the use of the bench excavation method makes construction more convenient, faster, and cheaper. The timely application of initial support 5 and temporary support 6 after the excavation of the pilot tunnel 1 helps ensure the stability of the surrounding rock.

[0056] S3: Excavate the upper guide tunnel 2 of the arch, and construct initial support 5 and temporary support 6 at the corresponding locations, as shown in the attached document. Figure 4 As shown;

[0057] Specifically, the upper guide tunnel 2 is also excavated from top to bottom using the step method, and the upper guide tunnel 2 is excavated from the middle to both sides. After all the soil is excavated, temporary support 6 is constructed. Both the initial support 5 and the temporary support 6 are formed by steel bars or steel frame plus shotcrete.

[0058] S4: Construct the initial reinforcement support 7 for the arch and remove the temporary support 6 for the arch, as shown in the attached document. Figure 5 As shown;

[0059] Specifically, the reinforced initial support 7 adopts a "steel section + shotcrete + anchor bolt" structure, with a thickness greater than that of the initial support 5. Simultaneously, anchor bolts 8 can be installed at the arch foot, with at least 0.5m of each anchor bolt embedded in the arch foot longitudinal beam 14 to ensure sufficient load-bearing capacity. The arch foot longitudinal beam 14 has a stepped cross-section, placing the reinforced initial support 7 atop it. According to the arch cap method of construction, pile foundations supporting the arch foot must be constructed within the side guide tunnel 1. The arch foot longitudinal beam 14 not only meets the load-bearing requirements and effectively supports the arch structure but also has low construction costs and simple procedures.

[0060] After the excavation of the upper pilot tunnel 2 is completed and the initial support 5 and temporary support 6 are installed, the reinforced initial support 7 is installed. This allows the reinforced initial support 7 and the initial support 5 to form an arch support system in a timely manner, ensuring the stability of the surrounding rock. At the same time, after the reinforced initial support 7 is installed, the temporary support 6 can be removed, which facilitates the excavation of the core soil 3 of the arch, improves work efficiency, and reduces the construction period.

[0061] S5: Excavation of the core soil of the arch, 3, as shown in the attached document. Figure 6 As shown.

[0062] During the excavation process, the excavation progress of the side guide tunnel 1 and the upper guide tunnel 2 is staggered by at least 10m, and the excavation progress of the upper guide tunnel 2 and the core soil 3 is staggered by at least 10m; the left and right side guide tunnels 1 are excavated simultaneously, which makes the construction progress faster and reduces the construction period. The 10m distance between adjacent excavation faces enhances the safety during the construction process.

[0063] S6: Excavate the central soil in stages 9, and construct the initial support for the side walls 5;

[0064] S7: Excavate the lower soil 10 in stages, and construct the initial support 5 for the sidewalls and the invert arch 11; excavate the middle soil 9 and the lower soil 10, and after the initial support 5 for the sidewalls and the invert arch 11 are completed, the transverse section diagram is attached. Figure 7 As shown;

[0065] Specifically, the middle section of soil 9 and the lower section of soil 10 are excavated in stages from the middle outwards using the trenching method. The excavation areas of the middle section of soil 9 and the lower section of soil 10 are relatively large, and using the trenching bench method for staged excavation helps improve the stability of the tunnel and ensures construction safety.

[0066] S8: Lay a waterproof layer across the entire cross-section 12, and construct secondary lining 13, as per attached. Figure 8 As shown.

[0067] Specifically, the waterproof layer 12 and the secondary lining 13 are constructed in one go across the entire cross section; the waterproof layer 12 is laid across the entire cross section to ensure the waterproofness of the tunnel structure, and the secondary lining 13 is constructed in one go across the entire cross section to ensure its overall integrity and provide support for the initial support 5.

[0068] In summary, the excavation process diagram for the single-arch, column-free, ultra-large cross-section subway station arch-cover method of the present invention is attached. Figure 9 As shown, firstly, the side guide tunnels 1 on the left and right sides of the arch are excavated, and the initial support 5 and temporary support 6 of the side guide tunnels are constructed. Then, the soil of the upper guide tunnel 2 is excavated, and the initial support 5 and temporary support 6 are constructed. Then, before the core soil 3 is excavated, the reinforced initial support 7 is constructed to form the arch cover in time. The timely formation of the arch cover support system ensures the stability of the single-arch column-free ultra-large cross-section subway station. Moreover, it is formed before the core soil 3 is excavated, avoiding the need to excavate the small guide tunnels on the left and right sides first when excavating the core soil, making the construction simpler and more convenient, the construction speed faster, and the economic benefits better. In addition, the reinforced initial support 7 is formed earlier, and the temporary support 6 corresponding to the upper guide tunnel 2 is removed before the core soil of the arch is excavated, which can increase the construction working surface. At the same time, the longitudinal beam 14 of the arch foot is set in a stepped shape, which can enhance its resistance to lateral displacement, thereby effectively limiting the displacement of the arch.

[0069] Example 2:

[0070] Example 2, based on Example 1, provides a specific structure for a large pipe shed support, as shown in the attached figure. Figure 10-15 As shown, the device includes four height-adjustable outriggers 15. A mounting plate 16 is fixed to the top of each outrigger 15. An extension plate 17 is movably connected to one end of the mounting plate 16 near the excavation face. The extension plate 17 is hinged to the mounting plate 16. Two arch frames 18, corresponding to the outline of the arch to be excavated, are slidably connected to the mounting plate 16. The rear arch frame 18 is also slidably connected to the extension plate 17. A first sliding groove 1601 is provided on the mounting plate 16, and a second sliding groove 1701 is provided on the extension plate 17. When the extension plate 17 is in the extended state, the mounting plate 16 and the extension plate 17... On the same plane, the first sliding groove 1601 and the second sliding groove 1701 are completely spliced ​​together. Guide rails are installed in both the first sliding groove 1601 and the second sliding groove 1701. When the extension plate 17 is in the unfolded state, the slide rail in the first sliding groove 1601 on the rear side of the mounting plate 16 is spliced ​​together with the slide rail in the second sliding groove 1701 on the extension plate 17. Two first uprights 1801 are fixed at the bottom of the arch frame 18. The first uprights 1801 are slidably connected to the first sliding groove 1601 and the second sliding groove 1701 through the slide rails to prevent the first uprights 1801 from detaching from the mounting plate 16 or the extension plate 17.

[0071] Each arch frame 18 has multiple support holes 20 for supporting the pipe roof pipes 19. The top of the mounting plate 16 is also fixed with multiple arc-shaped plates 21 that support the pipe roof pipes 19 and correspond one-to-one with the support holes 20. These arc-shaped plates 21 are located between two arch frames 17 and staggered to prevent interference between the pipe roof pipes 19. Each arch frame 18 has fixing plates 29 fixed on its bottom left and right sides. Fixing bolts 30 are threaded onto the fixing plates 29. The mounting plate 16 has threaded grooves (not shown in the figure) that match the fixing bolts 30. During advanced support construction, the support structure is moved to the face of the excavation site. The extension plate 17 is folded to the bottom of the mounting plate 16. The rear arch frame 18 is moved backward to near the face of the excavation site and fixed with fixing bolts 30. The front arch frame 18 is also moved to a suitable position and fixed with fixing bolts 30. Insert the pipe roof tube 19 into the support hole 20 and drive it into the soil to be excavated. The two support holes 20 can limit the driving direction of the pipe roof tube 19 and prevent the pipe roof tube 19 from tilting during the driving process. After the pipe roof tube 19 is driven in, cut off the exposed pipe roof tube 19. Then rotate the extension plate 17 to the unfolded state, move the rear arch frame 18 backward and the front arch frame 18 forward, so that the arch frame 18 and all the cut pipe roof tubes 19 are disengaged at the same time. At the same time, the cut pipe roof tubes 19 are only supported by the arc plate 21, so the cut pipe roof tubes 19 can be quickly and easily removed.

[0072] Specifically, the support leg 15 includes an outer sleeve 1501 and an inner rod 1502. The outer sleeve 1501 has a hollow interior. The inner rod 1502 is slidably sleeved inside the outer sleeve 1501 near the top. A fixed cone 1503 is slidably connected inside the outer sleeve 1501 near the bottom. A drive assembly for simultaneously driving the inner rod 1502 and the fixed cone 1503 to move in opposite directions is provided between them. The two ends of the drive assembly pass through the corresponding outer sleeve 1501 in the horizontal direction. Both sides of the outer sleeve 1501 have axially arranged clearance holes 1504 that communicate with the interior of the outer sleeve 1501.

[0073] More specifically, the drive assembly includes a bidirectional lead screw 22, which extends horizontally through the outer sleeve 1501, and the center of the bidirectional lead screw 22 corresponds to the center of the outer sleeve 1501. The two helical directions of the bidirectional lead screw 22 are provided with matching lead screw nuts 23. Each lead screw nut 23 is hinged to a connecting rod 24 at its top and bottom. The end of the connecting rod 24 away from the lead screw nut 23 is hinged to a corresponding inner rod 1502 or fixed cone 1503.

[0074] A connecting plate 25 is fixed between the four outer sleeves 1501. A bidirectional drive motor 26 is mounted on the connecting plate 25. The two output ends of the bidirectional drive motor 26 are connected horizontally to the lead screw nuts 23 on the two corresponding outer sleeves 1501. A partition plate 27 is also fixed on the connecting plate 25. A rotating shaft 28 is fixed at one end of the corresponding lead screw nuts 23 on the other two outer sleeves 1501 near the partition plate 27. The rotating shaft 28 is rotatably connected to the partition plate 27 through bearings. A driven gear 31 is fixedly sleeved on both rotating shafts 28. A driving gear 32 is fixedly sleeved on both output ends of the bidirectional drive motor 26. The driving gears 32 and driven gears 31 corresponding to each other are connected by belts to ensure that the two corresponding bidirectional lead screws 22 can rotate synchronously and in the same direction. When the bidirectional drive motor 26 is started, its two output ends rotate synchronously in the same direction, thereby driving the two bidirectional lead screws 22 connected to it to rotate. At the same time, under the action of the driving gear 32, the driven gear 31, and the belt 33, the two rotating shafts 28 can be driven to rotate synchronously. When the rotating shafts 28 rotate, they drive the other two bidirectional lead screws 22 to rotate. At this time, the four bidirectional lead screws 22 maintain synchronous rotation in the same direction. When each bidirectional lead screw 22 rotates, it will drive the two lead screw nuts 23 on it to move closer to each other or further away from each other. Under the action of the connecting rod 24, the inner rod 1502 and the fixed cone 1503 move in opposite directions. When the inner rod 1502 moves upward, the fixed cone 1503 moves downward and inserts into the ground, improving the stability of the entire support structure. When the inner rod 1502 moves downward, the fixed cone 1503 is pulled out of the ground, reducing the height of the entire support structure, thereby reducing its volume and facilitating relocation.

[0075] Application examples:

[0076] Taking a large-section subway station project in a certain region as the construction background, the station adopts a single-arch, column-free design, with a standard section width of approximately 19.9 m and a maximum excavation area of ​​334 m². 2 This is an ultra-large cross-section tunnel. The station is located in a layered dolomite interbedded with thin layers of mudstone and shale, with relatively good rock properties. The construction background of this application example is the construction of a single-arch, column-free ultra-large cross-section tunnel using the arch cap method, and the stability of the arch cap support system is an important aspect of the project consideration.

[0077] The construction method of this application example includes the excavation of two side pilot tunnels 1 and four parts of tunnel soil. The specific excavation steps are as follows: first excavate the side pilot tunnels 1, then excavate the upper pilot tunnel 2, then excavate the core soil 3, and then excavate the middle soil 9 and the lower soil 10.

[0078] Specifically, the single-arch, column-free, ultra-large cross-section subway station arch-cover method of tunnel excavation provided in this application includes the following steps:

[0079] S1: Advanced support 4 construction; before the excavation of the side tunnel 1, small pipes or pipe roofs are installed radially in front of the excavation face along the tunnel arch and the outline of the excavation of the side tunnel 1 with larger external inserts, and advanced grouting reinforcement is added to form pre-reinforcement of the excavated area to prevent the collapse due to the excessively large tunnel excavation cross section.

[0080] S2: Excavation of pilot tunnel 1: Refer to Appendix Figure 2 The left and right side guide tunnels 1 are excavated simultaneously. Since the excavation area of ​​the side guide tunnels is not large, the step method can be used to improve construction efficiency and speed up the construction progress.

[0081] Then, at the location corresponding to the pilot tunnel 1, construct the initial support 5, temporary support 6, and arch foot longitudinal beam 14, as shown in the attached diagram. Figure 3 After the excavation of the pilot tunnel 1, temporary supports 6 were promptly constructed along the excavation outline, and initial arch support 5 was applied. Due to the favorable properties of the surrounding rock strata, both the initial support 5 and the temporary supports 6 adopted a "steel mesh + shotcrete" support method. For the construction of the arch foot longitudinal beam 14, the stepped longitudinal beam was first poured. After reaching the required strength, anchor bolts 8 were installed at the arch foot, ensuring that 0.5 m of the bolts were anchored into the arch foot longitudinal beam 14 to provide sufficient load-bearing capacity.

[0082] S3: Excavation of the upper guide tunnel 2 of the arch and construction of initial support 5, temporary support 6: Refer to Appendix Figure 4 After the excavation of the side guide tunnel 1 is completed and the temporary supports 6 and initial support 5 reach their strength, the upper guide tunnel 2 of the arch is excavated. The excavation of the upper guide tunnel 2 adopts an excavation method similar to the double-side-wall guide tunnel method. First, the middle soil is excavated, the temporary supports 6 are installed, and then the soil on both sides is excavated. After the excavation of the upper guide tunnel 2 is completed, the initial support 5 is installed in a timely manner.

[0083] S4: Construction of the initial support for arch reinforcement (7), removal of temporary support (6): Refer to Appendix Figure 5 After the excavation of the upper guide tunnel 2 is completed, the construction of the reinforced initial support 7 will proceed. Due to the large span of the arch, the reinforced initial support 7 adopts a "steel + shotcrete" support method. The reinforced initial support 7 is placed at the arch foot longitudinal beam 14 of the side guide tunnel, which provides reliable load-bearing capacity. After the reinforced initial support 7 reaches sufficient strength, the temporary support 6 inside the arch will be removed to facilitate the next stage of construction. There is a gap between the side guide tunnel 1 and the initial support 5, which will be filled and sealed with micro-expansion concrete of the same strength as the initial support 5 to improve the load-bearing capacity of the arch support system. The reinforced initial support 7 should be constructed in the following sequence: "arch foot anchor installation, longitudinal beam pouring, left-side arch concrete pouring, right-side arch concrete pouring, and middle-side arch concrete pouring". To prevent formwork bursting, the left and right parts of the arch will be poured in two stages. The initial support 5 and the reinforced initial support 7 are connected with steel bars to ensure that they form the arch structure.

[0084] S5: Excavation of the core soil of the arch: Refer to the appendix Figure 6 After the temporary support 6 is removed, the arch cover forms a support system, and the excavation of the core soil 3 of the arch will then begin. Since the temporary support 6 has been removed, there is sufficient working face for the excavation of the core soil 3, making construction convenient. The step method of excavation can effectively improve construction efficiency.

[0085] S6: Excavation of Central Soil Section 9: Refer to Appendix Figure 7 After the core soil 3 was excavated, the soil in the middle of the tunnel was excavated. The excavation area of ​​the middle soil 9 was relatively large, and the trenching bench method was used for staged excavation. First, the middle soil was excavated, followed by the soil on both sides. After the excavation was completed, the initial support 5 of the sidewalls was promptly constructed to ensure the stability of the surrounding rock. During the construction of the sidewalls, the excavation and shaping of the soil played a crucial role in the overall stability of the arch. Therefore, over-excavation and damage to the surrounding rock at the arch foot should be reduced as much as possible by controlling the vibration during excavation.

[0086] S7: Excavation of the lower soil section 10: Refer to the appendix Figure 7 The excavation of the lower soil 10 of the tunnel is carried out in stages using the trenching bench method, similar to the excavation of the middle soil 9. This process proceeds from the middle outwards. After excavation, the initial support 5 for the sidewalls and the invert arch 11 are promptly constructed to ensure the stability of the surrounding rock.

[0087] S8: Construction of waterproof layer 12 and secondary lining 13: Refer to the appendix. Figure 8 A waterproof layer 12 is laid across the entire tunnel cross-section. This waterproof layer 12 can be made of waterproof membrane or other waterproof materials. The secondary lining 13 is constructed of reinforced concrete, with the entire cross-section constructed in one go to ensure good integrity and provide a certain load-bearing capacity for the initial support 5. The pouring sequence of each layer of concrete secondary lining begins from the end where the concrete has already been poured, to ensure the joint quality of the concrete construction joints and facilitate venting. The key to the construction of the secondary lining 13 is that, after the initial support of the invert arch 11 is completed, the invert arch reinforcement and concrete should be constructed as soon as possible. For the joint areas, the arch wall lining should be constructed quickly to ensure the overall stability of the arch cap.

[0088] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for underground excavation construction of a single-arch, column-free, ultra-large cross-section subway station using the arch cover method, characterized in that... Includes the following steps, S1: Apply advance support around the outline of the arch to be excavated (4). S2: Excavate the side guide tunnels (1) on the left and right sides of the arch, and construct the initial support (5), temporary support (6) and arch foot longitudinal beam (14) at the corresponding positions. S3: Excavate the upper guide tunnel of the arch (2), and also construct initial support (5) and temporary support (6) at the corresponding locations. S4: Construct the primary support for the arch (7) and remove the temporary support for the arch (6). S5: Excavate the core soil of the arch (3); S6: Excavate the central soil in stages (9) and construct the initial support for the side walls (5). S7: Excavate the lower soil in stages (10), and construct the initial support (5) for the side wall and the invert arch (11). S8: Lay a waterproof layer across the entire cross section (12) and construct a secondary lining (13). Among them, the advanced support (4) mentioned in step S1 adopts small pipe support or large pipe roof support and is reinforced by advanced grouting. The specific structure of the large pipe shed support includes four height-adjustable support legs (15). The top of the four support legs (15) is fixed with an installation plate (16). An extension plate (17) is movably connected to one end of the installation plate (16) near the excavation face. Two arch frames (18) corresponding to the outline of the arch to be excavated are slidably connected on the installation plate (16). The arch frame (18) located on the rear side is also slidably connected to the extension plate (17). Each arch frame (18) is provided with multiple support holes (20) for supporting the pipe shed pipe (19). The top of the installation plate (16) is also fixed with multiple arc plates (21) for supporting the pipe shed pipe (19) and corresponding one-to-one with the support holes (20). The multiple arc plates (21) are located between the two arch frames (18) and staggered front and back.

2. The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation as described in claim 1, characterized in that: The support leg (15) includes an outer sleeve (1501) and an inner rod (1502). The inner rod (1502) is slidably sleeved inside the outer sleeve (1501) near the top. A fixed cone (1503) is also slidably connected inside the outer sleeve (1501) near the bottom. A drive assembly for simultaneously driving the inner rod (1502) and the fixed cone (1503) is provided between them. Both ends of the drive assembly penetrate the outer sleeve (1501). Both sides of the outer sleeve (1501) are provided with clearance holes (1504) that communicate with the inside of the outer sleeve (1501) along the axial direction.

3. The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation as described in claim 2, is characterized in that: The drive assembly includes a bidirectional lead screw (22), and each of the two helical directions of the bidirectional lead screw (22) is provided with a matching lead screw nut (23). Each lead screw nut (23) is movably connected to a connecting rod (24) at its top and bottom. The end of the connecting rod (24) away from the lead screw nut (23) is movably connected to a corresponding inner rod (1502) or a fixed cone (1503). A connecting plate (25) is fixed between the four outer sleeves (1501). A bidirectional drive motor (26) is installed on the connecting plate (25). The two output ends of the bidirectional drive motor (26) are connected to the corresponding lead screw nuts (23) on the two outer sleeves (1501). A partition plate (27) is also fixed on the connecting plate (25). A rotating shaft (28) is fixed at one end of the corresponding lead screw nuts (23) on the other two outer sleeves (1501) near the partition plate (27). The rotating shaft (28) is rotatably connected to the partition plate (27), and the two rotating shafts (28) are drively connected to the two output ends of the bidirectional drive motor (26).

4. The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation as described in claim 1, characterized in that: The side guide tunnel (1) in step S2 and the upper guide tunnel (2) in step S3 are excavated sequentially from top to bottom using the step method; and the initial support (5) and temporary support (6) mentioned in steps S2 and S3 are formed by steel bars or steel frame plus shotcrete.

5. The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation as described in claim 1, characterized in that: The cross section of the arch foot longitudinal beam (14) mentioned in step S2 is stepped.

6. The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation as described in claim 1, characterized in that: The reinforced initial support (7) mentioned in step S4 adopts the form of "steel section + shotcrete + anchor rod", and its thickness is greater than that of the initial support (5).

7. The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation as described in claim 1, characterized in that: The excavation progress of the side tunnel (1) and the upper tunnel (2) is staggered by at least 10m, and the excavation progress of the upper tunnel (2) and the core soil (3) is staggered by at least 10m.

8. The method for constructing a single-arch, column-free, ultra-large cross-section subway station using the arch cover method with tunnel excavation as described in claim 1, characterized in that: The middle soil (9) mentioned in step S6 and the lower soil (10) mentioned in step S7 are excavated in stages from the middle to both sides using the trenching method.

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