A construction method for a subway station to pass under an existing line

Abstract

The application discloses a construction method of a subway station underpassing an existing line, and belongs to the technical field of line construction. The specific construction steps are as follows: S1, two straight wall arch sections are arranged at any end part below the existing station hall, and the straight wall arch sections are arranged correspondingly to the tunnel of the existing station hall; S2, a C-shaped support wall section is arranged below the station hall, the C-shaped support wall section is arranged along the direction of the tunnel, and the C-shaped support wall section is located at the side of the station hall with fewer station hall reserved columns; S3, a benching section is constructed at the side of the station hall away from the C-shaped support wall section; and S4, a cover excavation section is constructed below the station hall, the cover excavation section is excavated from the end part of the station hall without the straight wall arch section to the other end part, and the cover excavation section comprises a first cover excavation part and a second cover excavation part, the first cover excavation part is located at the side of the station hall away from the C-shaped support wall section, the first cover excavation part is close to the benching section, and the second cover excavation part is located between the first cover excavation part and the C-shaped support wall section. The application can guarantee the safe construction of the newly-built structure and the safe operation of the existing line.

Description

Technical Field

[0001] This invention relates to the field of railway construction technology, specifically to a construction method for a subway station to pass under an existing railway line. Background Technology

[0002] Due to urban planning adjustments or construction concepts, most existing railway lines were not designed with provisions for crossing planned lines, inevitably requiring new lines to be constructed near the existing lines. Under these circumstances, ensuring the safe operation of existing lines and the safety of the new rail transit structure itself are two major challenges that must be addressed.

[0003] During actual construction, the reserved columns need to be set according to the structure of the station hall to be crossed. Currently, the distribution of reserved columns under some station halls is not even, with more reserved columns on one side and fewer on the other. When crossing under such station halls, it is easy to affect the safe operation of the existing line. Summary of the Invention

[0004] The technical problem to be solved by this invention is that when passing under an existing railway line, it is easy to affect the safe operation of the existing line in the case of an existing station hall with uneven distribution of reserved columns below. This invention provides a construction method for subway stations to pass under existing railway lines to solve the above problem.

[0005] This invention is achieved through the following technical solution:

[0006] A construction method for a subway station to pass under an existing railway line, with the following specific construction steps:

[0007] S1. Two straight-walled arched sections are set at either end below the existing station hall, with each straight-walled arched section corresponding to a tunnel in the existing station hall.

[0008] S2. Set up a C-shaped support wall section under the station hall. The C-shaped support wall section is set along the extension direction of the tunnel and is located on the side of the station hall with fewer reserved columns. The C-shaped support wall section is connected to the corresponding straight wall arch section.

[0009] S3. Construction of the slope section on the side of the station hall away from the C-shaped support wall section;

[0010] S4. Construction of the cut-and-cover section under the station hall is carried out, starting from the end of the station hall without the straight wall arch section and moving towards the other end. The cut-and-cover section includes a first cut-and-cover section and a second cut-and-cover section. The first cut-and-cover section is located on the side of the station hall away from the C-shaped support wall section and is adjacent to the slope section. The second cut-and-cover section is located between the first cut-and-cover section and the C-shaped support wall section.

[0011] In the above construction steps, a straight-wall arch section is first set up to reinforce the structure below the tunnel and ensure the stability of the tunnel structure. Then, a C-shaped support wall section is set up to replace the reserved columns in the station hall to support the existing station. The straight-wall arch sections at both ends and the C-shaped support wall sections provide support for the existing station structure, which facilitates the subsequent construction of the slope section and the cut-and-cover section. The cut-and-cover section construction is also divided into two parts. While stabilizing the existing station structure, the excavation construction is carried out without affecting the safe operation of the existing line, thus completing the construction of the tunnel under the existing line.

[0012] Furthermore, one of the two straight-wall arched sections is connected to the C-shaped support wall section, and the other section is located on the side with more reserved columns in the station hall. During construction, the straight-wall arched section on the side with more reserved columns in the station hall will be constructed first. The construction steps for the straight-wall arched section are as follows:

[0013] S11. Grouting reinforcement is carried out at the preset arch position of the straight wall arch section. The reinforced part has an arch structure and grouting reinforcement is carried out using advanced small guide pipes (steel flower pipes).

[0014] S12. Excavate a cavern under the arch structure. The excavation direction of the cavern is consistent with the tunnel extension direction, and reserve core soil.

[0015] S13. Install reinforcement structures on the top and side walls of one of the excavated tunnels;

[0016] S14. When the excavation length of one cavern reaches 4-5m, the excavation of the second cavern shall be carried out below the first cavern. The length difference between the first cavern and the second cavern shall always be 4-5m until both have been excavated to the preset length.

[0017] S15. Install reinforcement structures on the side walls of the two caverns;

[0018] S16. When the excavation length of the second cavern reaches 4 to 5 meters, or when both the first and second caverns have been excavated to the preset length, the excavation of the third cavern shall be carried out below the second cavern.

[0019] S17. Install reinforcement structures on the side walls and bottom walls of the three caverns;

[0020] S18. Secondary lining shall be constructed on the inner sidewalls of the caverns formed by the first, second, and third caverns.

[0021] The excavation of the tunnel and the installation of the reinforcement structure were carried out simultaneously to improve the overall stability of the structure.

[0022] Furthermore, the specific installation steps for the reinforcement structure are as follows:

[0023] S131. Install steel frames on the side walls of the tunnel and install anchor bolts to fix them to the surrounding soil.

[0024] S132. Install steel mesh on the steel frame;

[0025] S133. Shotcrete support is applied to the steel mesh;

[0026] The steel frame on one cavern, the steel frame on the second cavern, and the steel frame on the third cavern together form a closed loop structure.

[0027] Furthermore, the specific steps for secondary lining are as follows:

[0028] S181. Construct a waterproof layer for the bottom slab and a secondary lining at the bottom of the three-part tunnel, and reserve steel bars and waterproof joints;

[0029] S182. Set the templates sequentially from bottom to top, creating a closed loop;

[0030] S183, Grouting and pouring into the template.

[0031] Furthermore, the specific construction steps for the C-shaped support wall section are as follows:

[0032] S21. The bench method is used for excavation, and the upper pilot tunnel is excavated first.

[0033] S22. A support structure is installed on the side wall of the upper guide tunnel;

[0034] S23. After the excavation length of the upper pilot tunnel reaches 4 to 5 meters, the lower pilot tunnel shall be excavated below the upper pilot tunnel.

[0035] S24. A support structure is installed on the side wall of the lower guide tunnel;

[0036] S25. Construct the waterproof layer and secondary lining of the bottom slab of the lower guide tunnel. Pour the secondary lining of the side wall using the longitudinal construction method to 1.3m below the existing station hall floor slab. The secondary lining is located on the side of the guide tunnel away from the station hall. Erect temporary steel supports between the other side wall of the upper guide tunnel and the secondary lining.

[0037] S26. Remove the top support structure of the upper guide tunnel, with each removal not exceeding 1 / 3 of the length. Pour the composite top slab and complete the pouring of the C-shaped support wall structure in 3 pours.

[0038] S27. Remove the horizontal temporary steel support frame and the steel frame that is not in contact with the secondary lining. Install temporary vertical steel columns with both ends supported between the waterproof layers of the composite top slab and bottom slab; or retain the secondary lining support system and remove it together after the cut-and-cover section is completed.

[0039] Furthermore, the specific installation steps for the support structure are as follows:

[0040] S221. Install steel frame along the side wall of the upper guide tunnel, close the steel frame in reverse direction, and install anchor bolts to fix it to the surrounding soil.

[0041] S222. Install steel mesh on the steel frame;

[0042] S223. Shotcrete support is applied to the steel mesh.

[0043] Furthermore, the construction of the slope section is carried out simultaneously with the construction of the first cut-and-cover section. The specific steps for the construction of the slope section are as follows:

[0044] S31. The excavation boundary adopts a 1:0.2 slope, and the slope is supported by reinforced mesh spraying and soil nailing wall.

[0045] S32. Excavate from the end of the station hall without a straight wall arch section to the other end, excavating in layers and sections. Each section is excavated to the reserved construction joint position of the cut-and-cover section. Slope support is carried out in a timely manner after the excavation is completed.

[0046] S33, Pouring.

[0047] Furthermore, the first slope section is backfilled and poured in layers and segments, with each segment not exceeding 15m in length; the pouring height of each layer of the first slope section does not exceed 4m; the formwork support for the backfilling and pouring of the slope section adopts a socket-type disc buckle support, and the formwork is made of 15mm thick composite wood fiberboard.

[0048] Furthermore, the remaining part of the first slope section is poured in layers. After the backfilling is completed, a waterproof layer is laid on one side of the slope section relative to the cut-and-cover section. After the backfilling of the slope section is completed, the cut-and-cover section structure is constructed.

[0049] Furthermore, the specific construction steps for the cut-and-cover section are as follows:

[0050] S41. Before excavation, the existing retaining piles of the station hall must be removed.

[0051] S42. Slope excavation, with a slope ratio of 1:0.2, and the slope direction is towards the second cut-and-cover section, while the first cut-and-cover section is being excavated.

[0052] S43. Grouting reinforced soil nails are installed at the excavation face for support.

[0053] S44. Lay steel mesh on the excavation face and spray concrete support;

[0054] S35. Excavate in layers and sections, with each section excavated to the reserved construction joint position;

[0055] S46. The slope is reinforced with anchor bolts and shotcrete.

[0056] S47. Backfilling and formwork construction;

[0057] S48. The second cut-and-cover section is excavated, and the slope is reinforced with anchor bolts and shotcrete.

[0058] S49. The connection between the first and second cut-and-cover sections is constructed by layering and stacking slabs.

[0059] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0060] This invention reinforces the tunnel structure by installing two straight-walled arched sections to stabilize the existing tunnel structure. It also includes C-shaped support walls to support the side of the existing station hall where the reserved columns are insufficient. The straight-walled arched sections and C-shaped support walls at both ends support the existing station structure, maintaining the stability and safe operation of the existing station hall. This facilitates subsequent construction of the slope section and the cut-and-cover section. Both the slope section and the cut-and-cover section are constructed by excavating and pouring concrete simultaneously. The cut-and-cover section construction is also divided into two parts, stabilizing the existing station structure while carrying out excavation work, ensuring the safe construction of the new structure while simultaneously guaranteeing the safe operation of the existing line. Attached Figure Description

[0061] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0062] Figure 1 This is a construction plan view of an embodiment of the present invention;

[0063] Figure 2 This is a schematic diagram of the construction process of the straight-walled arched section according to an embodiment of the present invention;

[0064] Figure 3 This is a schematic diagram of the construction process of the C-type support wall segment according to an embodiment of the present invention;

[0065] Figure 4 This is a schematic diagram of the slope protection section construction process according to an embodiment of the present invention;

[0066] Figure 5 This is a schematic diagram of the construction process of the cut-and-cover section according to an embodiment of the present invention.

[0067] The attached diagram shows the markings and corresponding component names:

[0068] 1-Straight wall arch section, 2-C-type support wall section, 3-Slope section, 41-First cut-and-cover section, 42-Second cut-and-cover section, 51-Advanced small guide pipe, 52-Core soil, 53-Secondary lining, 54-Steel frame, 55-Anchor bolt, 61-First cavern, 62-Second cavern, 63-Third cavern, 71-Upper guide tunnel, 72-Lower guide tunnel, 73-Temporary steel support, 74-Temporary vertical steel column, 8-Station hall reserved column. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0070] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0071] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0072] In the description of this invention, the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention. Example

[0073] This embodiment provides a specific application case of this construction method, employing a combination of cut-and-cover and tunneling methods. The tunneling section has three spans, and the cross-sectional forms of the tunnel are mainly of three types. The construction plan is shown below.Figure 1 As shown:

[0074] The first type is a single-layer rectangular frame structure located under the existing station hall main body using the cut-and-cover method.

[0075] The second type is a straight-walled arch structure located below one end of the station hall (constructed using the step method), with two sections of the straight-walled arch structure.

[0076] The third method is to set up a C-shaped support wall section 2 below the side with fewer reserved columns 8 in the station hall (using the step method for construction);

[0077] The underground section under the station hall is a three-span tunnel. The straight-wall arch section 1 is constructed first, followed by the C-shaped support wall section 2 to form the support wall. The main body of the station is supported by bench piles on the other side of the station hall, allowing for direct large-area excavation and construction of the cut-and-cover section. Construction proceeds from the open-cut foundation pits on both sides of the existing station hall towards the underground section in the middle. The remaining main body is constructed using the cut-and-cover method. Finally, the composite roof slab is poured and connected to the existing station hall floor slab.

[0078] The specific construction steps are as follows:

[0079] S1. Two straight-walled arched sections 1 are set at either end below the existing station hall, and the straight-walled arched sections 1 are set one-to-one with the tunnel of the existing station hall;

[0080] S2. Set up a C-shaped support wall section 2 under the station hall. The C-shaped support wall section 2 is set along the extension direction of the tunnel and is located on the side with fewer reserved columns 8 in the station hall. The C-shaped support wall section 2 is connected to the corresponding straight wall arch section 1.

[0081] S3. Construction of slope section 3 shall be carried out on the side of the station hall away from the C-shaped support wall section 2;

[0082] S4. Construction of the cut-and-cover section is carried out below the station hall. Excavation is carried out from the end of the station hall without the straight wall arch section 1 to the other end. The cut-and-cover section includes a first cut-and-cover section 41 and a second cut-and-cover section 42. The first cut-and-cover section 41 is located on the side of the station hall away from the C-shaped support wall section 2. The first cut-and-cover section 41 is adjacent to the slope section 3. The second cut-and-cover section 42 is located between the first cut-and-cover section 41 and the C-shaped support wall section 2.

[0083] First, a straight-wall arch section 1 is set up to reinforce the structure below the tunnel and ensure the stability of the tunnel structure. Then, a C-shaped support wall section 2 is set up to replace the reserved column 8 in the station hall and support the existing station. The straight-wall arch section 1 and the C-shaped support wall section 2 at both ends support the existing station structure, which facilitates the subsequent construction of the slope section 3 and the cut-and-cover section. The cut-and-cover section construction is also divided into two parts. While stabilizing the existing station structure, the excavation construction is carried out without affecting the safe operation of the existing line, and the construction of the tunnel under the existing line is completed.

[0084] One of the two straight-wall arched sections 1 is connected to the C-shaped support wall section 2, and the other section is located on the side with more than 8 reserved columns in the station hall. During construction, the straight-wall arched section 1 located on the side with more than 8 reserved columns in the station hall is constructed first. The construction steps of the straight-wall arched section 1 are as follows:

[0085] S11. Grouting reinforcement is carried out at the preset arch position of the straight wall arch section 1, and the reinforced part is an arch structure.

[0086] S12. Excavate a cavern 61 under the arch structure. The excavation direction of the cavern 61 is consistent with the tunnel extension direction, and reserve core soil 52.

[0087] S13. Install reinforcement structures on the top and side walls of one of the excavated tunnels 61;

[0088] S131. Install steel frame 54 on the side wall of the cavern and install anchor bolts 55 to fix it to the surrounding soil.

[0089] S132. Install steel mesh on the steel frame 54;

[0090] S133. Shotcrete support is applied to the steel mesh;

[0091] S14. After the excavation length of the first cavern 61 reaches 4-5m, the second cavern 62 is excavated below the first cavern 61. The first cavern 61 and the second cavern 62 always maintain a length difference of 4-5m until both are excavated to the preset length.

[0092] S15. Install a reinforcement structure on the side wall of the second cavern 62. The installation steps for the reinforcement structure are the same as above.

[0093] S16. When the excavation length of the second cavern 62 reaches 4 to 5 m, or when both the first cavern 61 and the second cavern 62 have been excavated to the preset length, the third cavern 63 shall be excavated below the second cavern 62.

[0094] S17. Install reinforcement structures on the side walls and bottom walls of the three-part cavern 63;

[0095] S18. Secondary lining 53 is constructed on the inner sidewalls of the caverns formed by the first cavern 61, the second cavern 62, and the third cavern 63. The specific steps of secondary lining 53 are as follows: S181. A waterproof layer and secondary lining are constructed at the bottom of the third cavern 63, and steel bars and waterproof joints are reserved; S182. Templates are set up sequentially from bottom to top and closed in a closed loop; S183. Grout is poured into the template.

[0096] The excavation of the tunnels and the installation of reinforcement structures were carried out simultaneously to improve the overall stability of the structure. The steel frame 54 on the first tunnel 61, the second tunnel 62, and the third tunnel 63 together form a closed loop structure, which facilitates the subsequent pouring of the secondary lining 53. The construction process of the straight-walled arch section 1 is shown in the figure below. Figure 2 As shown.

[0097] The specific construction steps for C-type support wall section 2 are as follows:

[0098] S21. The bench method is used for excavation. First, the upper guide tunnel 71 is excavated.

[0099] S22. A support structure is installed on the side wall of the upper guide tunnel 71;

[0100] S221. Install a steel frame 54 along the side wall of the upper guide tunnel 71. The steel frame 54 is closed by reversing direction. Install anchor rods 55 to fix it to the surrounding soil.

[0101] S222. Install steel mesh on the steel frame 54;

[0102] S223. Shotcrete support is applied to the steel mesh;

[0103] S23. After the excavation length of the upper guide tunnel 71 reaches 4 to 5 meters, the lower guide tunnel 72 is excavated below the upper guide tunnel 71.

[0104] S24. A support structure is installed on the side wall of the lower guide tunnel 72. The installation steps of the support structure are the same as above.

[0105] S25. Construct the waterproof layer and secondary lining of the bottom slab of the lower guide tunnel 72. Pour the secondary lining of the side wall using the sequential construction method to 1.3m below the existing station hall floor slab. The secondary lining is located on the side of the guide tunnel away from the station hall. Erect temporary steel replacement support 73 between the other side wall of the upper guide tunnel 71 and the secondary lining.

[0106] S26. Remove the top support structure of the upper guide tunnel 71, with each removal not exceeding 1 / 3 of the length. Pour the composite top slab and complete the pouring of the C-shaped support wall structure in 3 pours.

[0107] S27. Dismantle the horizontal temporary steel support frame, remove the steel frame 54 that is not in contact with the secondary lining, and install temporary vertical steel columns 74, with both ends of the temporary vertical steel columns 74 supported between the waterproof layers of the composite top slab and bottom slab; or retain the secondary lining support system and dismantle it together after the cut-and-cover section is completed; the construction process diagram of the C-type support wall is shown below. Figure 3 As shown.

[0108] The construction of slope section 3 and the first cut-and-cover section 41 are carried out simultaneously. The specific steps of the construction of slope section 3 are as follows, and the construction diagram is shown in the figure. Figure 4 As shown:

[0109] S31. The excavation boundary adopts a 1:0.2 slope, and the slope is supported by reinforced mesh spraying and soil nailing wall.

[0110] S32. Excavate from the end of the station hall without the straight wall arch section 1 to the other end, excavate in layers and sections, and excavate each section to the reserved construction joint position of the cut-and-cover section. After the excavation is completed, the slope support should be carried out in time.

[0111] S33, Casting, the structure after casting is as follows Figure 4 As shown.

[0112] During slope construction, the first slope section is backfilled and poured in layers and segments, with each segment not exceeding 15m in length. The pouring height of each layer in the first slope section does not exceed 4m. The formwork support for the backfilling and pouring of the slope section adopts a socket-type disc-lock scaffold, and the formwork is made of 15mm thick composite wood fiberboard. The remaining part of the first slope section is poured in layers. After the backfilling and pouring are completed, a waterproof layer is laid on one side of the slope section relative to the cut-and-cover section. The cut-and-cover section structure construction is carried out after the backfilling of the slope section is completed.

[0113] A schematic diagram of the construction steps for the cut-and-cover section is shown below. Figure 5 As shown, the specific construction steps are as follows:

[0114] S41. Before excavation, the existing retaining piles of the station hall must be removed.

[0115] S42, slope, slope ratio 1:0.2, slope direction towards the second cut-and-cover section 42, and excavation of the first cut-and-cover section 41.

[0116] S43. Grouting reinforced soil nails are installed at the excavation face for support.

[0117] S44. Lay steel mesh on the excavation face and spray concrete support;

[0118] S35. Excavate in layers and sections, with each section excavated to the reserved construction joint position;

[0119] S46. The slope is reinforced with 55mm anchor bolts and shotcrete.

[0120] S47. Backfilling and formwork construction;

[0121] S48, the second cut-and-cover section 42 is excavated, the slope is anchored with locking bolts 55, and shotcrete is used for support;

[0122] S49, the connection position of the first cut-and-cover section 41 and the second cut-and-cover section 42 is constructed by layering and stacking slabs.

[0123] The final pouring of the composite roof slab connects it to the existing station hall floor slab.

[0124] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A construction method for a subway station passing under an existing railway line, characterized in that, The specific construction steps are as follows: S1. Two straight-walled arched sections are set at either end below the existing station hall, and the straight-walled arched sections are set one-to-one with the tunnel of the existing station hall; S2. A C-shaped support wall section is installed below the station hall. The C-shaped support wall section is installed along the extension direction of the tunnel and is located on the side of the station hall with fewer reserved columns. The C-shaped support wall section is connected to the corresponding straight wall arch section. S3. Construction of the slope section is carried out on the side of the station hall away from the C-shaped support wall section; S4. Construction of the cut-and-cover section is carried out below the station hall. The excavation starts from the end of the station hall without the straight wall arch section and moves towards the other end. The cut-and-cover section includes a first cut-and-cover section and a second cut-and-cover section. The first cut-and-cover section is located on the side of the station hall away from the C-shaped support wall section and is adjacent to the slope section. The second cut-and-cover section is located between the first cut-and-cover section and the C-shaped support wall section.

2. The construction method for a subway station passing under an existing railway line according to claim 1, characterized in that, One of the two straight-wall arched sections is connected to a C-shaped support wall section, and the other section is located on the side of the station hall with more reserved columns. During construction, the straight-wall arched section located on the side of the station hall with more reserved columns is constructed first. The construction steps for the straight-wall arched section are as follows: S11. Grouting reinforcement is carried out at the preset arch position of the straight wall arch section, and the reinforced part is an arch structure. S12. Excavate a cavern under the arch structure. The excavation direction of the cavern is consistent with the tunnel extension direction, and reserve core soil. S13. Install reinforcement structures on the top and side walls of one of the excavated tunnels; S14. When the excavation length of one cavern reaches 4-5m, the excavation of the second cavern shall be carried out below the first cavern. The length difference between the first cavern and the second cavern shall always be 4-5m until both have been excavated to the preset length. S15. Install reinforcement structures on the side walls of the two caverns; S16. When the excavation length of the second cavern reaches 4 to 5 meters, or when both the first and second caverns have been excavated to the preset length, the excavation of the third cavern shall be carried out below the second cavern. S17. Install reinforcement structures on the side walls and bottom walls of the three caverns; S18. Secondary lining shall be constructed on the inner sidewalls of the caverns formed by the first, second, and third caverns. The excavation of the tunnel and the installation of the reinforcement structure were carried out simultaneously.

3. The construction method for a subway station passing under an existing railway line according to claim 2, characterized in that, The specific installation steps for the reinforcement structure are as follows: S131. Install steel frames on the side walls of the tunnel and install anchor bolts to fix them to the surrounding soil. S132. Install steel mesh on the steel frame; S133. Shotcrete support is applied to the steel mesh; The steel frame on one cavern, the steel frame on the second cavern, and the steel frame on the third cavern together form a closed loop structure.

4. The construction method for a subway station passing under an existing railway line according to claim 3, characterized in that, The specific steps for the secondary lining are as follows: S181. Construct a waterproof layer for the bottom slab and a secondary lining at the bottom of the three-part tunnel, and reserve steel bars and waterproof joints; S182. Set the templates sequentially from bottom to top, creating a closed loop; S183, Grouting and pouring into the template.

5. A construction method for a subway station passing under an existing railway line according to claim 1, characterized in that, The specific construction steps for the C-shaped support wall section are as follows: S21. The bench method is used for excavation, and the upper pilot tunnel is excavated first. S22. A support structure is installed on the side wall of the upper guide tunnel; S23. After the excavation length of the upper pilot tunnel reaches 4 to 5 meters, the lower pilot tunnel shall be excavated below the upper pilot tunnel. S24. A support structure is installed on the side wall of the lower guide tunnel; S25. Construct the waterproof layer and secondary lining of the bottom slab of the lower guide tunnel. Pour the secondary lining of the side wall using the longitudinal construction method to 1.3m below the existing station hall floor slab. The secondary lining is located on the side of the guide tunnel away from the station hall. Erect temporary steel supports between the other side wall of the upper guide tunnel and the secondary lining. S26. Remove the top support structure of the upper guide tunnel, with each removal not exceeding 1 / 3 of the length. Pour the composite top slab and complete the pouring of the C-shaped support wall structure in 3 pours. S27. Remove the horizontal temporary steel support frame and the steel frame that is not in contact with the secondary lining. Install temporary vertical steel columns with both ends supported between the waterproof layers of the composite top slab and bottom slab; or retain the secondary lining support system and remove it together after the cut-and-cover section is completed.

6. A construction method for a subway station passing under an existing railway line according to claim 5, characterized in that, The specific installation steps for the support structure are as follows: S221. Install steel frame along the side wall of the upper guide tunnel, close the steel frame in reverse direction, and install anchor bolts to fix it to the surrounding soil. S222. Install steel mesh on the steel frame; S223. Shotcrete support is applied to the steel mesh.

7. A construction method for a subway station passing under an existing railway line according to claim 1, characterized in that, The construction of the slope section is carried out simultaneously with the construction of the first cut-and-cover section. The specific steps for the construction of the slope section are as follows: S31. The excavation boundary adopts a 1:0.2 slope, and the slope is supported by reinforced mesh spraying and soil nailing wall. S32. Excavate from the end of the station hall without a straight wall arch section to the other end, excavating in layers and sections, with each section excavated to the reserved construction joint position of the cut-and-cover section, and slope support carried out in a timely manner after excavation is completed. S33, Pouring.

8. A construction method for a subway station passing under an existing railway line according to claim 7, characterized in that, The backfilling and pouring of the first slope section will begin in layers and segments, with each segment not exceeding 15m in length; the pouring height of each layer of the first slope section shall not exceed 4m; the formwork support for the backfilling and pouring of the slope section shall be a socket-type disc buckle support, and the formwork shall be made of 15mm thick composite wood fiberboard.

9. A construction method for a subway station passing under an existing railway line according to claim 8, characterized in that, The remaining part of the first slope section is poured in layers. After the backfilling is completed, a waterproof layer is laid on one side of the cut-and-cover section of the slope section. After the backfilling of the slope section is completed, the cut-and-cover section structure is constructed.

10. A construction method for a subway station passing under an existing railway line according to claim 1, characterized in that, The specific construction steps for the cut-and-cover section are as follows: S41. Before excavation, the existing retaining piles of the station hall must be removed. S42. Slope excavation, with a slope ratio of 1:0.2, and the slope direction is towards the second cut-and-cover section, while the first cut-and-cover section is being excavated. S43. Grouting reinforced soil nails are installed at the excavation face for support. S44. Lay steel mesh on the excavation face and spray concrete support; S35. Excavate in layers and sections, with each section excavated to the reserved construction joint position; S46. The slope is reinforced with anchor bolts and shotcrete. S47. Backfilling and formwork construction; S48. The second cut-and-cover section is excavated, and the slope is reinforced with anchor bolts and shotcrete. S49. The connection between the first and second cut-and-cover sections is constructed by layering and stacking slabs.

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