A partition construction method for a large-section flat-top straight-wall tunnel passing through an underground station

Abstract

The present application relates to the technical fields of invention and underground tunnel construction, and particularly relates to a partition construction method for large-section flat-top straight-wall tunnel underpassing underground station, which divides the underground tunnel into several zones, and the zones are pilot holes, the pilot holes on both sides of the underground tunnel are side pilot holes, the pilot hole in the middle of the underground tunnel is a middle pilot hole, the space between the side pilot holes and the middle pilot hole is a remaining pilot hole, the side pilot holes include the first zone pilot hole and the second zone pilot hole which are divided into two layers, the middle pilot hole includes the third zone pilot hole and the fourth zone pilot hole which are divided into two layers, and the remaining pilot hole includes the fifth zone pilot hole and the sixth zone pilot hole which are divided into two layers; the side pilot holes on both sides are constructed first, then the middle pilot hole is constructed, and finally the remaining pilot hole is constructed, which can reduce the excavation span of the pilot hole, and each partition pilot hole can be constructed with a secondary lining structure to complete the stress conversion, protect the existing underground station, avoid settlement, and isolate the underground water of the subsequent pilot hole construction through the completed side pilot holes, so that the construction is safer.

Description

Technical Field

[0001] This invention relates to the field of underground tunnel construction technology, and in particular to a zoned construction method for a large-section flat-top straight-wall tunnel passing under an underground station. Background Technology

[0002] With the rapid development of urban underground transportation, the use of mining tunnels to pass under existing buildings and structures is becoming increasingly common. Examples include tunnels under multi-story or high-rise buildings, important pipelines or culverts, and existing highways, bridges, railways, or urban rail transit. When tunneling under such important structures, a crucial issue is minimizing the excavation cross-section, reducing soil disturbance, controlling building settlement, and ensuring the safety of the structures.

[0003] If a new subway station is to be built to connect with an existing underground station, the new subway station will generally adopt a combination of open and cut methods. The three underground levels of the new subway station will usually be constructed by cutting a large-section flat-top straight-wall tunnel through the main structure of the existing underground station, while the rest will be constructed by open cut. The cut tunnel of the new subway station will generally be constructed using the mining method.

[0004] However, when the geological conditions beneath existing underground stations are poor, such as being composed of completely weathered mixed granite or strongly weathered mixed granite, resulting in the construction of new subway station tunnels situated within such granite, the conventional large-section flat-top straight-wall mining method for tunnel excavation may lead to poor self-stability of the tunnel due to the poor geological conditions. This could easily impact the existing underground station, causing excessive settlement and creating construction risks. Summary of the Invention

[0005] The purpose of this invention is to address the problem in the background art where, when the geological conditions beneath an existing underground station are poor, conventional construction methods for constructing a new underground station through a tunnel can easily lead to poor self-stability of the tunnel, potentially impacting the existing underground station, causing excessive settlement, and creating construction risks. This invention provides a zonal construction method for a large-section, flat-top, straight-wall tunnel passing under an underground station.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for zoning construction of a large-section flat-top straight-wall tunnel passing under an underground station, which divides the mined tunnel into several pilot tunnels.

[0008] The side guide tunnels are located on both sides of the tunnel, the middle guide tunnel is located in the middle of the tunnel, and the remaining guide tunnel is located between the side guide tunnels and the middle guide tunnel. The side guide tunnels include Zone I and Zone II, which are divided into upper and lower layers. The middle guide tunnel includes Zone III and Zone IV, which are divided into upper and lower layers. The remaining guide tunnel includes Zone V and Zone VI, which are divided into upper and lower layers.

[0009] S1: The side guide tunnel is constructed using the step-up method. The construction is carried out by bidirectional excavation at both the large and small mileage ends. During construction, the guide tunnel in Zone I is first excavated to the design length and the first initial support is constructed. Then the guide tunnel in Zone II is excavated and the first initial support is constructed. Then the secondary lining sidewall of the side guide tunnel is constructed until the entire length of the side guide tunnel is connected.

[0010] S2: The intermediate guide tunnel is constructed using the step-up method. The construction is carried out by bidirectional excavation at both large and small mileage ends. During construction, the guide tunnel in Zone III is first excavated to the designed length, and the second initial support (22) is constructed. Then, Zone IV is excavated, and the second initial support is constructed. Then, the middle partition wall of the intermediate guide tunnel is constructed until the entire length of the intermediate guide tunnel is connected.

[0011] S3: The remaining pilot tunnel is constructed using the step-by-step method, employing bidirectional excavation at both the large and small mileage ends. During construction, the V-zone pilot tunnel is first excavated to the designed length, and the third initial support is constructed. Then, the VI-zone pilot tunnel is excavated, and the third initial support is constructed, so that the first, second, and third initial supports form the initial support. Then, the secondary lining slab and secondary lining top slab of the remaining pilot tunnel are constructed, so that the secondary lining sidewalls, the secondary lining slabs, the secondary lining top slab, and the central partition wall form the secondary lining structure, until the remaining pilot tunnel is fully connected.

[0012] This application describes a sectional construction method for a large-section, flat-top, straight-wall tunnel passing under an underground station. The tunnel is divided into side guide tunnels, a central guide tunnel, and a remaining guide tunnel. First, the side guide tunnels on both sides of the tunnel are constructed. After completion, the initial support and secondary lining walls at the side guide tunnels prevent groundwater from seeping into the soil of the subsequent guide tunnels, thus isolating groundwater for later construction. Simultaneously, the secondary lining walls of the side guide tunnels can transfer the load of the existing underground station, acting as a stress transfer mechanism and reducing settlement. After the central guide tunnel is constructed, the central partition wall acts as a span reduction and stress transfer mechanism, effectively supporting the existing underground station and further reducing settlement. After the remaining guide tunnel is constructed, the tunnel construction is complete. Furthermore, since the side guide tunnels, central guide tunnel, and remaining guide tunnel are all divided into upper and lower layers, construction is carried out using upper and lower... The bench method effectively controls the stability of the surrounding rock, reduces the risk of collapse and sliding caused by large-area excavation, and improves the safety of the construction process. Furthermore, the bench method allows for phased excavation, enabling parallel construction operations and effectively shortening the construction period. The zonal construction method for a large-section flat-top straight-wall tunnel passing under an underground station, as described in this application, reduces the span of the pilot tunnel excavation. The side and intermediate pilot tunnels can be constructed with secondary lining structures in advance to complete the stress transfer, thereby reducing the settlement of the existing underground station. Furthermore, the multi-pilot tunnel construction in stages—first constructing the side pilot tunnels on both sides to effectively block groundwater and reduce subsequent construction risks, then constructing the intermediate pilot tunnel to support the existing underground station structure, and finally constructing the remaining pilot tunnels—effectively prevents convergence deformation and settlement of the support structure and surrounding rock, reduces groundwater leakage during construction, and ensures the safety and stability of the tunnel roof structure.

[0013] Preferably, it also includes a temporary steel frame and inverted bracing, wherein the temporary steel frame includes temporary horizontal bracing and temporary vertical bracing;

[0014] In S1, during the construction of the first initial support of the side guide tunnel, the temporary steel frame is constructed inside the side guide tunnel to support the first initial support. After the construction of the second lining sidewall of the side guide tunnel, the inverted support is constructed inside the side guide tunnel to support the second lining sidewall.

[0015] In S2, during the construction of the second initial support of the intermediate guide tunnel, the temporary steel frame is constructed inside the intermediate guide tunnel to support the second initial support;

[0016] In S3, after the third initial support of the remaining guide tunnel is constructed, the temporary vertical supports in the side guide tunnel and the middle guide tunnel are removed. Then, the second lining plate and the second lining top plate of the remaining guide tunnel are constructed. After the second lining plate and the second lining top plate are completed, the temporary horizontal supports in the side guide tunnel and the middle guide tunnel, as well as the inverted supports in the side guide tunnel are removed.

[0017] Preferably, when excavating the cut-and-cover tunnel, a groove is first cut on the working face to form a clear cross-section. Then, splitting holes are drilled on the clear cross-section, splitting rods are inserted, and a hydraulic splitting machine is used to split the rock on the tunnel cross-section. The split rock is then cut and transported out.

[0018] Preferably, before step S1, a first WSS grouting hole is set in the area between the mined tunnel and the existing underground station, and WSS grouting is performed. By performing WSS grouting, without changing the stratum composition, the water existing between the soil particles in the area between the mined tunnel and the existing underground station is forced out, so that the voids between the particles are filled with grout and solidified, thereby achieving the purpose of improving the soil properties.

[0019] Before step S1, second WSS grouting holes are arranged on both sides of the arch crown and arch waist of the tunnel, and WSS grouting is carried out. By performing WSS grouting, without changing the geological composition, the water existing between soil particles in the arch crown and arch waist areas of the tunnel is forced out, so that the voids between the particles are filled with grout and solidified, thereby improving the soil properties.

[0020] Preferably, prior to step S1, advanced pipe roofs are arranged on both sides of the arch and waist of the mined tunnel. These advanced pipe roofs are located inside the second WSS grouting holes and are used to grout and reinforce the surrounding rock. Grouting the surrounding rock of the mined tunnel through these advanced pipe roofs reinforces the rock around them, making the advanced pipe roofs a protective structure for subsequent excavation of the mined tunnel, thus achieving the goal of safe construction.

[0021] Preferably, before each excavation of the tunnel, advance small guide pipes are arranged on both sides of the arch and waist of the tunnel to grout and stabilize the loose rock strata.

[0022] Preferably, after the initial support construction of each of the pilot tunnels, grouting holes are opened on the excavation outline of the initial support, and radial grouting is performed to stop the water seepage in the surrounding rock through the grouting holes.

[0023] Preferably, the cross-sectional width of each of the pilot tunnels is less than or equal to 5 meters to reduce the excavation span of the pilot tunnels. Each excavation span is controlled within 5 meters, resulting in a small construction span, rapid closure of the ring, and quick structural stability, effectively suppressing the deformation of the existing structure.

[0024] Preferably, during the initial support construction, an initial support grouting pipe is pre-embedded in the initial support. After the initial support is completed, grout is injected through the initial support grouting pipe to fill and reinforce the space between the initial support and the surrounding rock, so that the initial support and the surrounding rock are firmly and tightly bonded, and the waterproofing effect is achieved.

[0025] During the construction of the secondary lining structure, two grouting pipes are pre-embedded in the secondary lining structure. After the secondary lining structure is completed, grout is injected into the space between the initial support and the secondary lining structure through the two grouting pipes, so that the initial support and the secondary lining structure are firmly and tightly bonded, and the waterproofing effect is achieved.

[0026] Preferably, a waterproof layer is provided between the initial support and the secondary lining structure, and a first waterstop is provided at the longitudinal construction joint of the cut-and-cover tunnel.

[0027] A second waterstop is provided at the annular joint of the secondary lining structure, and a drainage ditch is provided inside the mined tunnel. A water collection trough is provided at the upper edge of the secondary lining structure.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] This application describes a sectional construction method for a large-section, flat-top, straight-wall tunnel passing under an underground station. The tunnel is divided into side guide tunnels, a central guide tunnel, and a remaining guide tunnel. First, the side guide tunnels on both sides of the tunnel are constructed. After completion, the initial support and secondary lining walls at the side guide tunnels prevent groundwater from seeping into the soil of the subsequent guide tunnels, thus isolating groundwater for later construction. Simultaneously, the secondary lining walls of the side guide tunnels can transfer the load of the existing underground station, acting as a stress transfer mechanism and reducing settlement. After the central guide tunnel is constructed, the central partition wall acts as a span reduction and stress transfer mechanism, effectively supporting the existing underground station and further reducing settlement. After the remaining guide tunnel is constructed, the tunnel construction is complete. Furthermore, since the side guide tunnels, central guide tunnel, and remaining guide tunnel are all divided into upper and lower layers, construction is carried out using upper and lower... The bench method effectively controls the stability of the surrounding rock, reduces the risk of collapse and sliding caused by large-area excavation, and improves the safety of the construction process. Furthermore, the bench method allows for phased excavation, enabling parallel construction operations and effectively shortening the construction period. The zonal construction method for a large-section flat-top straight-wall tunnel passing under an underground station, as described in this application, reduces the span of the pilot tunnel excavation. The side and intermediate pilot tunnels can be constructed with secondary lining structures in advance to complete the stress transfer, thereby reducing the settlement of the existing underground station. Furthermore, the multi-pilot tunnel construction in stages—first constructing the side pilot tunnels on both sides to effectively block groundwater and reduce subsequent construction risks, then constructing the intermediate pilot tunnel to support the existing underground station structure, and finally constructing the remaining pilot tunnels—effectively prevents convergence deformation and settlement of the support structure and surrounding rock, reduces groundwater leakage during construction, and ensures the safety and stability of the tunnel roof structure. Attached image description:

[0030] Figure 1 This is a schematic diagram of the tunnel excavated in this application and the existing subway station.

[0031] Figure 2 yes Figure 1 Side view.

[0032] Figure 3 This is a schematic diagram of the surrounding layout of the tunnel excavated in this application.

[0033] Figure 4 yes Figure 3 A magnified view of part A.

[0034] Figure 5 This is a schematic diagram of advanced pipe roof and advanced pipe duct.

[0035] Figure 6 This is a schematic diagram of the zoning of the cut-and-cover tunnel.

[0036] Figure 7 This is a diagram of cut-and-cover tunnel construction. Figure 1 (Cross-section view)

[0037] Figure 8 This is a diagram of cut-and-cover tunnel construction. Figure 2 (Cross-section view)

[0038] Figure 9 This is a diagram of cut-and-cover tunnel construction. Figure 2 (Floor plan)

[0039] Figure 10 This is a diagram of cut-and-cover tunnel construction. Figure 3 (Cross-section view)

[0040] Figure 11 This is a diagram of cut-and-cover tunnel construction. Figure 3 (Floor plan)

[0041] Figure 12 This is a diagram of cut-and-cover tunnel construction. Figure 4 (Cross-section view)

[0042] Figure 13 This is a diagram of cut-and-cover tunnel construction. Figure 5 (Cross-section view)

[0043] Figure 14 This is a diagram of cut-and-cover tunnel construction. Figure 5 (Floor plan)

[0044] Figure 15 This is a diagram of cut-and-cover tunnel construction. Figure 6 (Cross-section view)

[0045] Figure 16 This is a diagram of cut-and-cover tunnel construction. Figure 6 (Floor plan)

[0046] Figure 17 This is a diagram of cut-and-cover tunnel construction. Figure 7 (Cross-section view)

[0047] Figure 18 This is a diagram of cut-and-cover tunnel construction. Figure 8 (Cross-section view)

[0048] Figure 19 This is a diagram of cut-and-cover tunnel construction. Figure 8 (Floor plan)

[0049] Figure 20 This is a diagram of cut-and-cover tunnel construction. Figure 9 (Cross-section view)

[0050] Figure 21 This is a diagram of cut-and-cover tunnel construction. Figure 10 (Cross-section view)

[0051] Figure 22This is a diagram of cut-and-cover tunnel construction. Figure 10 (Floor plan)

[0052] Figure 23 This is a schematic diagram of the radial grouting and water-blocking cross-section of the surrounding rock around the tunnel.

[0053] Figure 24 yes Figure 23 Floor plan.

[0054] Figure 25 This is a schematic diagram of the grouting section of the initial support and secondary lining of a mined tunnel.

[0055] Figure 26 yes Figure 25 Floor plan.

[0056] Figure 27 This is a schematic diagram of waterproof grouting in the longitudinal section of a mined tunnel.

[0057] Figure 28 This is a schematic diagram of the waterproof layer and the first waterstop.

[0058] Figure 29 This is a schematic diagram of the waterproof cross-section of a cut-and-cover tunnel.

[0059] Markings in the diagram: 1-Cut tunnel, 2-Initial support, 21-First initial support, 22-Second initial support, 23-Third initial support, 201-Steel arch frame, 3-Second lining structure, 301-Second lining sidewall, 302-Second lining slab, 303-Second lining top slab, 304-Intermediate partition wall, 5-First WSS grouting hole, 6-Second WSS grouting hole, 7-Advanced pipe roof, 8-Advanced small guide pipe, 9-Surrounding rock grouting hole, 10-Second lining grouting pipe, 20-Locking foot grouting anchor pipe, 30-Temporary steel frame, 310-Temporary horizontal brace, 320-Temporary vertical brace, 40-Inverted brace, 50-Existing underground station, 60-Working face, 70-Initial support grouting pipe, 80-Waterproof layer, 90-First waterstop, 100-Geomembrane buffer layer, 200-Second waterstop, 300-Drainage ditch, 400-Water collection trough. Detailed Implementation

[0060] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0061] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0062] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0063] Furthermore, the use of terms such as "first," "second," "third," etc. in terminology is merely for distinguishing identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0064] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as two, three, four, five, six, seven, eight, or nine, and can even exceed nine.

[0065] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0066] Example 1

[0067] like Figures 1-22 The zoning construction method for a large-section flat-top straight-wall tunnel passing under an underground station, as described in this embodiment, divides the mined tunnel 1 into several pilot tunnels.

[0068] like Figure 6 As shown, the side guide tunnels are located on both sides of the tunnel 1, the middle guide tunnel is located in the middle of the tunnel 1, and the remaining guide tunnel is located between the side guide tunnels and the middle guide tunnel. The side guide tunnels include the I zone guide tunnel and the II zone guide tunnel, which are divided into upper and lower layers. The middle guide tunnel includes the III zone guide tunnel and the IV zone guide tunnel, which are divided into upper and lower layers. The remaining guide tunnel includes the V zone guide tunnel and the VI zone guide tunnel, which are divided into upper and lower layers.

[0069] S1: As Figures 7-9 As shown, the side pilot tunnel is constructed using the stepped excavation method, employing bidirectional excavation at both the large and small mileage ends. During construction, the pilot tunnel in Zone I is first excavated to the designed length, and the first initial support 21 is constructed. Then, the pilot tunnel in Zone II is excavated, and the first initial support 21 is constructed. Figures 10-11 As shown, then the secondary lining sidewall 301 of the side guide tunnel is constructed until the entire length of the side guide tunnel is completed.

[0070] Among them, after the designed length of the pilot tunnel in Zone I at the high mileage end is excavated, the excavation is stopped and the first initial support 21 of the pilot tunnel in Zone I is constructed. Then, the pilot tunnel in Zone II at the high mileage end is excavated. After the designed length of the pilot tunnel in Zone II is excavated, the excavation is stopped and the first initial support 21 of the pilot tunnel in Zone II is constructed.

[0071] After the designed length of the pilot tunnel in Zone I at the low mileage end is excavated, excavation is stopped and the first initial support 21 of the pilot tunnel in Zone I is constructed. Then, the pilot tunnel in Zone II at the low mileage end is excavated. After the designed length of the pilot tunnel in Zone II is excavated, excavation is stopped and the first initial support 21 of the pilot tunnel in Zone II is constructed. Then, the secondary lining sidewall 301 of the pilot tunnel on the side at the low mileage end is constructed. At the same time, the pilot tunnels in Zone I and Zone II are excavated from the high mileage end until they are connected. Then, the secondary lining sidewall 301 of the pilot tunnel on the side at the high mileage end is constructed.

[0072] The side guide tunnel was excavated from both the large and small mileage ends until the entire length of the side guide tunnel was completed.

[0073] S2: As Figures 12-14 As shown, the intermediate pilot tunnel was constructed using the stepped excavation method, employing bidirectional excavation at both the large and small mileage ends. During construction, the pilot tunnel in Zone III was first excavated to the designed length, and the second initial support 22 was constructed. Then, Zone IV was excavated, and the construction of the second initial support 22 continued. Figures 15-16 As shown, then the 304 construction of the central partition wall of the intermediate guide tunnel is carried out until the entire length of the intermediate guide tunnel is completed;

[0074] Among them, after the designed length of the pilot tunnel in Zone III at the high mileage end is excavated, the excavation is stopped and the second initial support 22 of the pilot tunnel in Zone III is constructed. Then, the pilot tunnel in Zone IV at the high mileage end is excavated. After the designed length of the pilot tunnel in Zone IV is excavated, the excavation is stopped and the second initial support 22 of the pilot tunnel in Zone IV is constructed.

[0075] After the designed length of the pilot tunnel in Zone III at the low mileage end is excavated, excavation is stopped and the second initial support 22 of the pilot tunnel in Zone III is constructed. Then, the pilot tunnel in Zone IV at the low mileage end is excavated. After the designed length of the pilot tunnel in Zone IV is excavated, excavation is stopped and the second initial support 22 of the pilot tunnel in Zone IV is constructed. Then, the central partition wall 304 of the intermediate pilot tunnel at the low mileage end is constructed. At the same time, the pilot tunnels in Zone III and Zone IV are excavated from the high mileage end until they are connected. Then, the central partition wall 304 of the intermediate pilot tunnel at the high mileage end is constructed.

[0076] The intermediate pilot tunnel was excavated from both the large and small mileage ends until its entire length was completed.

[0077] S3: As Figures 17-20 As shown, the remaining pilot tunnel is constructed using the step-up method, with bidirectional excavation at both the large and small mileage ends. During construction, the pilot tunnel in zone V is first excavated to the designed length, and the third initial support 23 is constructed. Then, the pilot tunnel in zone VI is excavated, and the third initial support 23 is constructed, so that the first initial support 21, the second initial support 22, and the third initial support 23 form the initial support 2. Then, the secondary lining slab 302 and the secondary lining top slab 303 of the remaining pilot tunnel are constructed, so that the secondary lining sidewall 301, the secondary lining slab 302, the secondary lining top slab 303, and the central partition wall 304 form the secondary lining structure 3, until the remaining pilot tunnel is fully connected.

[0078] Among them, after the designed length of the V zone pilot tunnel at the high mileage end is excavated, the excavation will stop and the third initial support 23 of the V zone pilot tunnel will be constructed. Then the VI zone pilot tunnel at the high mileage end will be excavated. After the designed length of the VI zone pilot tunnel is excavated, the excavation will stop and the third initial support 23 of the VI zone pilot tunnel will be constructed.

[0079] After the designed length of the V-zone pilot tunnel at the low mileage end is excavated, excavation is stopped and the third initial support 23 of the V-zone pilot tunnel is constructed. Then, the VI-zone pilot tunnel at the low mileage end is excavated. After the designed length of the VI-zone pilot tunnel is excavated, excavation is stopped and the third initial support 23 of the VI-zone pilot tunnel is constructed. Then, the secondary lining plate 302 and secondary lining top plate 303 of the remaining pilot tunnels at the low mileage end are constructed. At the same time, the V-zone pilot tunnel and the VI-zone pilot tunnel are excavated from the high mileage end until they are connected. Then, the secondary lining plate 302 and secondary lining top plate 303 of the remaining pilot tunnels at the high mileage end are constructed.

[0080] The remaining pilot tunnels were excavated from both the large and small mileage ends until the entire length of the remaining pilot tunnels was completed, thus completing the construction of the first underground tunnel.

[0081] In this embodiment, the mined tunnel 1 is first divided into side guide tunnels, intermediate guide tunnels, and remaining guide tunnels. Construction of the side guide tunnels on both sides of the mined tunnel 1 is carried out first. The first initial support 21 and the secondary lining sidewall 301 at the side guide tunnels prevent groundwater from seeping into the soil at the subsequent guide tunnel locations, thus isolating groundwater for the subsequent guide tunnel construction. Simultaneously, the secondary lining sidewall 301 of the side guide tunnels can also transfer the load of the existing underground station 50, playing a role in force transfer and reducing the settlement of the existing underground station 50. After the intermediate guide tunnel is constructed, the central partition wall 304 can reduce the span and transfer the load, effectively supporting the existing underground station 50 and further reducing its settlement. After the remaining guide tunnel is constructed, the mined tunnel 1 construction is completed. Furthermore, since the side guide tunnels, intermediate guide tunnels, and remaining guide tunnels are all divided into upper and lower layers, the upper and lower step method is used during construction, which can effectively control... This method improves the stability of the surrounding rock, reduces the risk of collapse and sliding caused by large-area excavation, and enhances the safety of the construction process. Furthermore, the use of the step-by-step method allows for phased excavation, enabling parallel construction operations and effectively shortening the construction period. The zonal construction method for a large-section flat-top straight-wall tunnel passing under an underground station, as described in this embodiment, reduces the span of the pilot tunnel excavation. The side and intermediate pilot tunnels can be constructed in advance with secondary lining structures 3 to complete the stress transfer, protecting the existing underground station 50 and preventing settlement. Moreover, the multi-pilot tunnel construction in stages—first constructing the side pilot tunnels on both sides to effectively block groundwater and reduce subsequent construction risks, then constructing the intermediate pilot tunnel to support the existing underground station 50 structure, and finally constructing the remaining pilot tunnels—effectively prevents convergence deformation and settlement of the support structure and surrounding rock, reduces groundwater leakage during construction, and ensures the safety and stability of the tunnel roof structure.

[0082] In this application, as Figure 6 As shown, the mined tunnel 1 is divided into side pilot tunnels, middle pilot tunnels and remaining tunnels. The side pilot tunnels include pilot tunnels in zone I and zone II, which are divided into upper and lower layers. The middle pilot tunnels include pilot tunnels in zone III and zone IV, which are divided into upper and lower layers. The remaining tunnels include pilot tunnels in zone V and zone VI, which are divided into upper and lower layers.

[0083] Meanwhile, the initial support 2 is also divided according to the pilot tunnel zones, such as Figure 18 It is divided into the first primary branch 21, the second primary branch 22 and the third primary branch 23. The first primary branch 21 is located in the side guide tunnel, the second primary branch 22 is located in the middle guide tunnel, and the third primary branch 23 is located in the remaining guide tunnel.

[0084] Meanwhile, the secondary lining structure 3 is also divided according to the pilot tunnel zones, such as... Figure 20It is divided into secondary lining sidewalls 301, secondary lining plates 302, secondary lining top plates 303 and central partition walls 304. The secondary lining sidewalls 301 are located in the side guide tunnels, the central partition walls 304 are located in the middle guide tunnels, and the secondary lining plates 302 and secondary lining top plates 303 are located in the remaining guide tunnels.

[0085] like Figure 7 , Figure 10 As shown, it also includes a temporary steel frame 30 and a reverse brace 40. The temporary steel frame 30 includes a temporary horizontal brace 310 and a temporary vertical brace 320.

[0086] like Figures 7-8 As shown, in the first initial support 21 of the side guide tunnel, a temporary steel frame 30 is constructed to support the first initial support 21. First, the pilot tunnel in zone I is excavated, then the first initial support 21 of the pilot tunnel in zone I is constructed, and the temporary steel frame 30 is constructed to support the first initial support 21 of the pilot tunnel in zone I. Then, the pilot tunnel in zone II is excavated, the first initial support 21 of the pilot tunnel in zone II is constructed, and the temporary steel frame 30 is constructed to support the first initial support 21 of the pilot tunnel in zone II. After the secondary lining sidewall 301 of the side guide tunnel is constructed, an inverted brace 40 is constructed to support the secondary lining sidewall 301. Figures 10-11 ;

[0087] like Figures 12-16 As shown, during the construction of the second initial support 22 of the intermediate guide tunnel, a temporary steel frame 30 is constructed to support the second initial support 22. Specifically, the guide tunnel in zone III is excavated first, then the second initial support 22 of the guide tunnel in zone III is constructed, and the temporary steel frame 30 is constructed to support the second initial support 22 of the guide tunnel in zone III. Then, the guide tunnel in zone IV is excavated, the second initial support 22 of the guide tunnel in zone IV is constructed, and then the temporary steel frame 30 is constructed to support the second initial support 22 of the guide tunnel in zone IV. Finally, the intermediate partition wall 304 inside the guide tunnels in zones III and IV is constructed.

[0088] like Figures 17-19 As shown, after the third initial support 23 of the remaining guide tunnel is completed, the temporary vertical supports 320 of the side guide tunnels and the middle guide tunnel are removed, and the secondary lining plate 302 and the secondary lining top plate 303 of the remaining guide tunnel are constructed, as follows. Figure 20 After the secondary lining structure 3 is completed, the temporary horizontal supports 310 in the side guide tunnels and the middle guide tunnel, as well as the inverted supports 40 in the side guide tunnels, are removed. Figure 21 ;

[0089] In actual construction, for example, during the construction of the first initial support 21 of the side guide tunnel, a temporary steel frame 30 is constructed to support the first initial support 21 of the side guide tunnel. After the construction of the secondary lining sidewall 301 of the side guide tunnel is completed, an inverted support 40 is constructed to support the secondary lining sidewall 301. By setting up the temporary steel frame 30 and the inverted support 40, the overall performance of the mined tunnel 1 is effectively improved, making the mined tunnel 1 more stable. After the secondary lining structure 3 is stabilized, the temporary steel frame 30 and the inverted support 40 are gradually removed during construction to avoid affecting the construction progress.

[0090] A preferred method, such as Figures 7-8 As shown, the temporary steel frame 30 includes temporary horizontal bracing 310 and temporary vertical bracing 320, and multiple temporary horizontal bracing 310 and temporary vertical bracing 320 are combined to form the temporary steel frame 30.

[0091] In a preferred manner, during the construction of the mined tunnel 1, after excavation, depending on the stability of the working face, shotcrete is used to seal the working face and the bottom of the steps, and anchor pipes 20 are installed at the arch foot to control settlement.

[0092] A preferred method, such as Figures 23-24 After the initial support 2 of each pilot tunnel is constructed, grouting holes 9 are opened on the excavation outline of the initial support 2. Radial grouting is then performed through the grouting holes 9 to stop the water seepage in the surrounding rock of the tunnel 1.

[0093] In areas where groundwater is exposed after the excavation of the cut-and-cover tunnel 1, areas where water leakage still occurs after initial support and backfill grouting, and areas with fractured surrounding rock, grouting holes 9 should be opened on the deep surrounding rock behind the lining, depending on the specific circumstances. The grouting holes 9 should be arranged in a quincunx pattern with a circumferential spacing of about 1800 mm at the hole openings, a circumferential spacing of about 2500 mm at the hole bottoms, and a longitudinal spacing of 2600 mm. The hole opening pipes should be 50 mm thick, 3.5 mm thick hot-rolled seamless steel pipes, 1 m long, and should be firmly embedded with good grout-stopping measures.

[0094] A preferred method, such as Figures 25-26 During the construction of the initial support 2, the initial support grouting pipe 70 is pre-embedded in the initial support 2;

[0095] During the construction of the secondary lining structure 3, the secondary grouting pipe 10 is pre-embedded in the secondary lining structure 3.

[0096] During the construction of the initial support 2, grout is injected into the space between the initial support 2 and the surrounding rock through the initial support grouting pipe 70 to fill and reinforce the space, so that the initial support 2 is firmly and tightly bonded to the surrounding rock and achieves a waterproof effect.

[0097] During the construction of the secondary lining structure 3, a secondary grouting pipe 10 is pre-embedded in the secondary lining structure 3. After the secondary lining structure 3 is completed, grout is injected into the space between the initial support 2 and the secondary lining structure 3 through the secondary grouting pipe 10, so that the initial support 2 and the secondary lining structure 3 are firmly and tightly bonded, and the waterproofing effect is achieved.

[0098] During actual construction, 0.8m long Φ32 welded grouting steel pipes are pre-embedded in the initial support structure 2, arranged in a staggered pattern along the tunnel arch and sidewalls. The circumferential spacing is 2.0m at the arch and 3.0m at the sidewalls, with a longitudinal spacing of 3.0m. The grout pressure is controlled between 0.3 and 0.5 MPa, with a final pressure of 0.5 MPa. The grout diffusion radius is 1.4 to 1.8m, and the grouting speed is no more than 50 L / min. The grouting depth is 0.5m behind the initial support 2, and the grout is cement grout. Grouting parameters can be adjusted on-site according to geological conditions.

[0099] 1.4m long Φ42 grouting steel pipes are pre-embedded in the secondary lining structure 3, and arranged in a quincunx pattern along the tunnel arch and sidewalls. The circumferential spacing is 3.0m, and the longitudinal spacing is 5.0m. The grouting pressure should not be too high; grouting can be stopped when it reaches 0.2MPa. The grout is a high-strength cement mortar with micro-expansion. The grouting parameters can be adjusted on-site according to the geological conditions.

[0100] A preferred method, such as Figures 27-29 As shown, a waterproof layer 80 is also provided between the initial support 2 and the secondary lining structure 3, and a first waterstop 90 is provided at the longitudinal construction joint of the cut-and-cover tunnel 1.

[0101] A waterproof layer 80 is installed between the initial support 2 and the secondary lining structure 3 to enhance the waterproof performance of the tunnel lining 1. Simultaneously, a first waterstop 90 is installed at the longitudinal construction joint of the tunnel 1 to prevent external water from seeping out. In actual construction, after the initial support 2 is constructed, the waterproof layer 80 and the first waterstop 90 are installed, followed by the construction of the secondary lining structure 3. Finally, grouting is performed in sections between the initial support 2 and the secondary lining structure 3 through the grouting pipe 10. The waterproof layer 80 solidifies with the cast-in-place concrete, ensuring a stable installation of the waterproof components between the initial support 2 and the secondary lining structure 3, achieving a seamless waterproof seal. The waterproof layer 80 is made of PVC board, and the first waterstop 90 is a PVC waterstop. Figure 28 As shown, the first waterstop 90 is fixed to the waterproof layer 80 by hot air welding.

[0102] A preferred method, such as Figures 27-29As shown, a geotextile buffer layer 100 is provided between the initial support 2 and the secondary lining structure 3. The geotextile buffer layer 100 is made of geotextile nonwoven fabric with a strength of not less than 400g / ㎡. The geotextile buffer layer 100 is tightly attached to the initial support 2. The geotextile buffer layer can also play a certain role in waterproofing and isolation, preventing groundwater from eroding the tunnel structure or reducing water infiltration, and ensuring the service life of the mined tunnel 1.

[0103] A preferred method, such as Figure 29 As shown, a second waterstop 200 is provided at the annular joint of the secondary lining structure 3, and a drainage ditch 300 is provided inside the mined tunnel 1. A water collection trough 400 is provided at the upper edge of the secondary lining structure 3.

[0104] In a preferred manner, the cross-sectional width of each pilot tunnel is less than or equal to 5 meters to reduce the excavation span of the pilot tunnel. Each excavation span is controlled within 5 meters, resulting in a small construction span, rapid closure of the ring, and quick structural stability, effectively suppressing the deformation of the existing structure.

[0105] A preferred method for hard rock excavation, considering the need to pass under an existing underground station 50, employs a low-vibration construction method to avoid vibration. First, a trench is cut at the tunnel face 60 to create a clear cross-section. Then, splitting holes are drilled in the clear cross-section, and splitting rods are inserted. A hydraulic rock splitter is used to split the rock in the tunnel cross-section, and the split rock is then cut and transported out. Specifically, the tunnel face 60 is first prepared to create the necessary clear cross-section (approximately 3.0m) for the equipment operating arm. After preparing the design clearance section, it is necessary to drill forward about 1m on the clearance section without splitting it, and then construct 1-2 initial support sections. The tunneling machine drills holes on the design section with a theoretical depth of 1.2m and close spacing between holes. Among them, 2-4 splitting holes are drilled on the section (the number of holes is set according to the actual site conditions) with a theoretical depth of 1.2m. Then, splitting rods are inserted, steel plate wedges are supported, and a hydraulic splitting machine is used to hydraulically split the rock on the section. The split rock is then cut and transported out.

[0106] In the application, the large-section flat-roofed straight-walled tunnel is described as follows:

[0107] Large cross-section refers to a tunnel with a larger cross-section (or tunnel section). It is usually used in situations where it is necessary to accommodate large vehicles or provide more spacious passage. Large cross-section tunnels are designed with the comfort and safety of vehicle passage in mind and can accommodate more traffic flow.

[0108] A flat top refers to a tunnel with a flat top, rather than an arch or other shape. A flat top design helps reduce construction difficulty and costs, while ensuring sufficient height for passage.

[0109] Straight walls: This refers to tunnels whose sidewalls are vertical or nearly vertical, rather than sloping or curved. Straight wall design simplifies construction procedures and provides a stable tunnel structure.

[0110] Example 2

[0111] Based on Example 1, such as Figures 1-4 As shown in this embodiment, a zonal construction method for a large-section flat-top straight-wall tunnel passing under an underground station is described. Before S1, a first WSS grouting hole 5 is set in the area between the mined tunnel 1 and the existing underground station 50, and WSS grouting is performed. By performing WSS grouting, without changing the stratum composition, the water existing between the soil particles in the area between the mined tunnel 1 and the existing underground station 50 is forcibly squeezed out, so that the voids between the particles are filled with grout and solidified, thereby achieving the purpose of improving the soil properties.

[0112] A preferred method, such as Figures 3-4 As shown, before S1, a second WSS grouting hole 6 is arranged on both sides of the arch crown and arch waist of the tunnel 1, and WSS grouting is carried out. By performing WSS grouting, without changing the stratum composition, the water existing between the soil particles in the arch crown and arch waist areas of the tunnel 1 is forced out, so that the voids between the particles are filled with grout and solidified, thereby achieving the purpose of improving the soil properties.

[0113] In a preferred manner, prior to S1, advance pipe roofs 7 are arranged on both sides of the arch and waist of the tunnel 1. The advance pipe roofs 7 are located inside the second WSS grouting hole 6 and are used to grout and reinforce the surrounding rock. By grouting the surrounding rock of the tunnel 1 through the advance pipe roofs 7, the surrounding rock is reinforced, making the advance pipe roofs 7 a protective canopy for subsequent excavation of the tunnel 1, thus achieving the purpose of safe construction.

[0114] like Figures 1-4 As shown, before the actual construction work, the pre-excavation pipe roof 7 and WSS grouting construction need to be carried out before the excavation of the tunnel 1. That is, the pre-excavation pipe roof 7 and WSS grouting holes are set on the working face 60. The pre-excavation pipe roof 7 is arranged in a single row on both sides of the arch crown and arch waist of the tunnel 1. The pre-excavation pipe roof 7 adopts a diameter of φ159mm and is arranged at a circumferential interval of 350mm. The length on one side of the arch crown is about 8.9m (including the retaining structure), and the length on both sides of the arch waist is about 15m to 35m (including the retaining structure). The WSS grouting is mainly located on both sides of the arch crown and arch waist of the tunnel 1. On one side of the arch waist, it is arranged at a circumferential interval of 750mm, with a length of about 6m to 35m (including the retaining structure). Between the tunnel 1 and the existing underground station 50, that is, at the pedestrian crossing of the existing underground station 50, it is arranged in a 1.5m*1.5m quincunx pattern, with a total of 6 rows, with a length of about 2m to 8.9m.

[0115] In a preferred manner, during WSS grouting construction, the arch waist section of the mined tunnel 1 is grouted from the lower mileage end to the higher mileage end, and the arch crown section of the mined tunnel 1 is grouted from the lower mileage end and the higher mileage section respectively.

[0116] In a preferred manner, when performing WSS grouting, the opening diameter of the WSS grouting hole should be at least 20mm larger than the diameter of the grouting pipe, and the grouting pressure should be strictly controlled. At the same time, the grouting volume should be closely monitored. If the pressure suddenly rises, grouting should be stopped immediately, and after identifying the cause, measures such as adjusting the grouting parameters or shifting the grouting ratio should be taken to re-grout. When soil, sand, schist, or water are present, which may easily cause the hole to collapse, forward grouting should be used; otherwise, backward grouting should be used.

[0117] The grouting materials are AB mixture (water glass: phosphoric acid = 50:1) and AC mixture (water glass: cement grout = 1:1). The water glass modulus is 2.6, the cement is P042.5 ordinary Portland cement, the cement grout water-cement ratio is 1:1, and the grouting is carried out using an integrated drilling and grouting machine.

[0118] Grouting sequence: First, inject AB mixture, with the final grouting pressure controlled between 0.3MPa and 0.5MPa, for a duration of 10 to 15 minutes. Then, inject AC mixture, with the final grouting pressure controlled between 0.3MPa and 0.5MPa (the grouting pressure within 50 meters of the tunnel top and the existing underground station should be gradually increased, and the final grouting pressure should not exceed 0.5MPa), for a duration of 10 to 15 minutes.

[0119] Grouting termination criteria: Grouting can be considered terminated when the grouting volume reaches 80% of the designed grouting volume or reaches the designed final pressure value and stabilizes within 10 to 15 minutes.

[0120] In a preferred manner, when constructing the advance pipe roof 7, the advance pipe roof 7 is drilled from the lower mileage end to the higher mileage end. The advance pipe roof 7 uses Φ159mm×8mm hot-rolled seamless steel pipes, each section is 4m to 6m long, and the circumferential spacing is 35cm. During construction, the steel pipes are driven into the surrounding rock along the tunnel perimeter at a 0° outward insertion angle. The construction error of the steel pipes is: radial not greater than 20cm, and circumferential not greater than 10cm between adjacent steel pipes.

[0121] The pre-installed pipe roof is divided into 7 sections, with the section length determined by site conditions. Adjacent sections are connected by pipe roof connecting sleeves, and the joints of adjacent pipe roofs are staggered. The number of joints in the same cross section along the longitudinal direction of the tunnel does not exceed 50%. The first pipe roof section with odd-numbered sections uses 4m steel pipe, the first pipe roof section with even-numbered sections uses 6m steel pipe, and all subsequent sections use 6m steel pipe.

[0122] A preferred method, such as Figure 5As shown, before each excavation of the tunnel 1, advance small guide pipes 8 are arranged on both sides of the arch and waist of the tunnel 1 to grout and stabilize the loose rock layer through the advance small guide pipes 8.

[0123] In actual construction, a row of φ42mm advanced small guide pipes 8 are installed on the arch top and side walls on both sides of the tunnel 1 before excavation, with a longitudinal spacing of 0.35m and a circumferential spacing of 0.25m. In addition, when the advanced pipe roof 7 cannot be constructed on both sides of the arch waist of the tunnel 1, two rows of advanced small guide pipes 8 with a vertical spacing of 175mm can be used as a substitute.

[0124] The advanced small guide pipe 8 is made of φ42mm seamless hot-rolled steel pipe. Grouting holes are drilled at the front with a diameter of 8mm and a spacing of 150mm, arranged in a quincunx pattern. The front end is processed into a cone shape, and the tail length is not less than 30cm, serving as a grout-stopping section. Furthermore, the advanced small guide pipe 8 is used in conjunction with the steel arch frame 201 of the initial support 2, and the horizontal overlap length of two adjacent rows of small guide pipes is not less than 1.0m.

[0125] The pre-installed small guide pipe 8 is installed by drilling. The pre-installed small guide pipe 8 is driven through the steel arch frame 201 of the initial support 2 and pushed in with a drilling rig. After the pre-installed small guide pipe 8 is installed, the hole and surrounding cracks are sealed with fireproof mortar. If necessary, concrete is sprayed near the installation of the pre-installed small guide pipe 8 and on the working face to prevent the working face from collapsing.

[0126] During the grouting process of the advanced small-diameter pipe No. 8, strengthen the automated monitoring of the existing Line 7, observe changes in grouting pressure and grout pump discharge at any time, analyze the grouting situation, and prevent pipe blockage, grout leakage, and grout runoff. Keep good grouting records for analysis of grouting effect.

[0127] In this application, as Figures 6-22 As shown, the force system transformation process is as follows:

[0128] Side pilot tunnel excavation stage: 7 advanced pipe roofs, 2 initial support, and soil for the six unexcavated intermediate pilot tunnels (soil for the unexcavated intermediate pilot tunnels and the remaining pilot tunnels);

[0129] →Intermediate pilot tunnel excavation stage: secondary lining sidewall 301, initial support 2, soil of the four unexcavated pilot tunnels (soil at the remaining unexcavated pilot tunnels);

[0130] → Remaining pilot tunnel excavation stage: secondary lining sidewall 301, initial support 2, intermediate partition wall 304;

[0131] →After all construction is completed, the initial support 2 and the secondary lining structure 3 will share the responsibility.

[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for zoned construction of a large-section, flat-roof, straight-wall tunnel passing under an underground station, characterized in that: Divide the mined tunnel (1) into several pilot tunnels; The side guide tunnels are located on both sides of the tunnel (1), the middle guide tunnel is located in the middle of the tunnel (1), and the remaining guide tunnel is located between the side guide tunnels and the middle guide tunnel. The side guide tunnels include the I zone guide tunnel and the II zone guide tunnel, which are divided into upper and lower layers. The middle guide tunnel includes the III zone guide tunnel and the IV zone guide tunnel, which are divided into upper and lower layers. The remaining guide tunnel includes the V zone guide tunnel and the VI zone guide tunnel, which are divided into upper and lower layers. S1: The side guide tunnel is constructed using the step-up method. The construction is carried out by bidirectional excavation at both large and small mileage ends. During construction, the guide tunnel in Zone I is first excavated to the design length, and the first initial support (21) is constructed. Then the guide tunnel in Zone II is excavated, and the first initial support (21) is constructed. Then the secondary lining wall (301) of the side guide tunnel is constructed until the entire length of the side guide tunnel is connected. S2: The intermediate guide tunnel is constructed using the step-up method. The construction is carried out by bidirectional excavation at both large and small mileage ends. During construction, the guide tunnel in Zone III is first excavated to the design length, and the second initial support (22) is constructed. Then, Zone IV is excavated, and the second initial support (22) is constructed. Then, the central partition wall (304) of the intermediate guide tunnel is constructed until the entire length of the intermediate guide tunnel is connected. S3: The remaining guide tunnel is constructed using the step-up method. The construction is carried out by bidirectional excavation at both large and small mileage ends. During construction, the V zone guide tunnel is first excavated to the design length, and the third initial support (23) is constructed. Then the VI zone guide tunnel is excavated, and the third initial support (23) is constructed. The first initial support (21), the second initial support (22), and the third initial support (23) form the initial support (2). Then the secondary lining plate (302) and the secondary lining top plate (303) of the remaining guide tunnel are constructed. The secondary lining sidewall (301), the secondary lining plate (302), the secondary lining top plate (303), and the middle partition wall (304) form the secondary lining structure (3) until the remaining guide tunnel is fully connected. It also includes a temporary steel frame (30) and a reverse brace (40), wherein the temporary steel frame (30) includes a temporary horizontal brace (310) and a temporary vertical brace (320); In S1, during the construction of the first initial support (21) of the side guide tunnel, the temporary steel frame (30) is constructed in the side guide tunnel to support the first initial support (21). After the construction of the second lining sidewall (301) of the side guide tunnel, the inverted support (40) is constructed in the side guide tunnel to support the second lining sidewall (301). In S2, during the construction of the second initial support (22) of the intermediate guide tunnel, the temporary steel frame (30) is constructed inside the intermediate guide tunnel to support the second initial support (22); In S3, after the construction of the third initial support (23) of the remaining guide tunnel is completed, the temporary vertical supports (320) in the side guide tunnel and the middle guide tunnel are removed, and then the second lining plate (302) and the second lining top plate (303) of the remaining guide tunnel are constructed. After the second lining plate (302) and the second lining top plate (303) are completed, the temporary horizontal supports (310) in the side guide tunnel and the middle guide tunnel and the inverted supports (40) in the side guide tunnel are removed. During the construction of the initial support (2), the initial support grouting pipe (70) is pre-embedded in the initial support (2); During the construction of the secondary lining structure (3), two grouting pipes (10) are pre-embedded in the secondary lining structure (3); A geotextile buffer layer (100) is provided between the initial support (2) and the secondary lining structure (3).

2. The method for zoned construction of a large-section flat-roof straight-wall tunnel passing under an underground station according to claim 1, characterized in that, When excavating the tunnel (1), a groove is first cut on the face (60) to form a clear cross section. Then, splitting holes are drilled on the clear cross section, and splitting rods are inserted. A hydraulic splitting machine is used to split the rock on the tunnel cross section, and then the split rock is cut and transported out.

3. The method for zoned construction of a large-section flat-roof straight-wall tunnel passing under an underground station according to claim 1, characterized in that, Before S1, a first WSS grouting hole (5) is set in the area between the mined tunnel (1) and the existing underground station (50), and WSS grouting is performed; Second WSS grouting holes (6) are arranged on both sides of the arch and waist of the tunnel (1) and WSS grouting is carried out.

4. The method for zoned construction of a large-section flat-roof straight-wall tunnel passing under an underground station according to claim 3, characterized in that, Before S1, advance pipe roofs (7) are arranged on both sides of the arch and waist of the tunnel (1). The advance pipe roofs (7) are located inside the second WSS grouting hole (6). The advance pipe roofs (7) are used to grout and reinforce the surrounding rock.

5. The method for zoned construction of a large-section flat-roof straight-wall tunnel passing under an underground station according to claim 4, characterized in that, Before each excavation of the tunnel (1), advance small guide pipes (8) are arranged on both sides of the arch and waist of the tunnel (1) to grout and stabilize the loose rock layer through the advance small guide pipes (8).

6. The method for zoned construction of a large-section flat-roof straight-wall tunnel passing under an underground station according to claim 1, characterized in that, After the initial support (2) of each of the pilot tunnels is constructed, grouting holes (9) are opened on the excavation outline of the initial support (2).

7. The method for zoned construction of a large-section flat-roof straight-wall tunnel passing under an underground station according to claim 1, characterized in that, The cross-sectional width of each of the aforementioned pilot tunnels is less than or equal to 5 meters.

8. The method for zoned construction of a large-section flat-roof straight-wall tunnel passing under an underground station according to claim 1, characterized in that, A waterproof layer (80) is also provided between the initial support (2) and the secondary lining structure (3), and a first waterstop (90) is provided at the longitudinal construction joint of the cut-and-cover tunnel (1). A second waterstop (200) is provided at the annular joint of the secondary lining structure (3), and a drainage ditch (300) is provided inside the mined tunnel (1). A water collection trough is provided at the upper edge of the secondary lining structure (3).

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