Construction method for converting triple-arch tunnel into single-hole double-line tunnel

Abstract

This invention discloses a construction method for converting a three-arch tunnel to a single-bore double-track tunnel. The method includes the following steps: S1, constructing the three-arch tunnel; S2, constructing a transition section for the conversion from the three-arch tunnel to the single-bore double-track tunnel, the top of which extends obliquely upward from the cross-section of the three-arch tunnel and the single-bore double-track tunnel to the highest arch of the single-bore double-track tunnel; S3, constructing the transition section in the reverse direction from the transition section towards the three-arch tunnel. The upward-sloping top of the transition section ensures a smooth transition between the two different tunnel cross-sections during construction, avoiding uneven local stress and reducing construction risks. Furthermore, through the reasonable design of the transition section, only the initial support of the upper pilot tunnel needs to be changed along the top of the transition section, making construction easy to operate. Finally, during the reverse construction process, only the initial support of the upper pilot tunnel needs to be replaced, making the construction simple, economical, and safe.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to a construction method for converting a three-arch tunnel into a single-bore double-track tunnel. Background Technology

[0002] In urban rail transit tunnel engineering, the mining method is widely used. Due to the influence of professional requirements such as track setting, clearance, and ventilation, tunnel cross-section transformation is inevitable. If the tunnel cross-section transformation position is not handled properly, it will lead to uneven structural stress, high construction risk, and in severe cases, collapse. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of high construction risks caused by tunnel cross-section conversion in the prior art, and to provide a construction method for converting a three-arch tunnel into a single-bore double-track tunnel.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] This invention provides a construction method for converting a three-arch tunnel into a single-bore double-track tunnel, characterized in that the construction method includes the following steps:

[0006] S1. Construct the aforementioned three-arch tunnel;

[0007] S2. Construct a transition section for the conversion of the three-arch tunnel to the single-bore double-track tunnel. The top of the transition section extends obliquely upward from the cross-section of the three-arch tunnel and the single-bore double-track tunnel to the highest arch position of the single-bore double-track tunnel.

[0008] S3. Construct the transition section in the opposite direction from the transition section to the three-arch tunnel.

[0009] In this scheme, the top of the transition section from the three-arch tunnel to the single-tube double-track tunnel slopes upward, allowing for a smooth transition between the two different tunnel sections during construction. This avoids uneven local stress on the structure and reduces construction risks. Furthermore, through the reasonable design of the transition section, only the initial support of the upper pilot tunnel needs to be changed along the top of the transition section, making construction easy to operate. Finally, during the reverse construction process, only the initial support of the upper pilot tunnel needs to be replaced, making construction simple, economical, and safe.

[0010] Preferably, the transition section in step S2 is constructed using the CRD method with separate pilot tunnels, and step S2 specifically includes the following steps:

[0011] S21. Circular advance through the upper guide hole in the transition section;

[0012] S22. The upper guide tunnel of the transition section shall be provided with the first initial support. The first initial support shall extend obliquely upward from the cross section on one side of the top of the three-arch tunnel to the highest arch position of the first upper guide tunnel of the single-tunnel double-track tunnel.

[0013] In this scheme, the transition section is excavated using the CRD method. Because the initial support structures for each pilot tunnel are fabricated separately, the stability is very high. When the pilot tunnels are connected, the initial support structures can be disassembled and connected, facilitating subsequent reverse construction of the transition section, reducing the amount of replacement work for the first initial support, lowering construction costs, and ensuring safety. The shape of the first initial support changes with the top shape of the transition section, making the support more stable and ensuring a smooth and safe transition from the three-arch tunnel to a single-tunnel double-track tunnel.

[0014] Preferably, the construction in step S3 includes the following steps:

[0015] S31. Remove the first initial support of the upper guide tunnel of the transition section;

[0016] S32. Construction proceeds in the opposite direction from the transition section to the three-arch tunnel, with the upper guide tunnel of the transition section constructed to the highest arch position.

[0017] S33, The first initial support is replaced with the second initial support;

[0018] S34. Repeat S31 to S33 as described above until construction reaches the section where the single-bore double-track tunnel and the triple-arch tunnel transition.

[0019] In this scheme, construction is carried out segment by segment, which allows for better construction based on monitoring data. After removing the first initial support of one segment on the transition section, the next transition section is constructed in reverse to the highest arch position, and the first initial support of that segment is replaced with the second initial support, making the construction safer.

[0020] Preferably, the following steps are further included after S2 and before S3:

[0021] S200, construct the single-bore double-track tunnel.

[0022] In this plan, a single-tube double-track tunnel will be opened before the reverse construction transition section, so that the first initial support of the transition section can continue to support the transition section more stably for a longer period of time, further ensuring construction safety.

[0023] Preferably, the single-tunnel double-track tunnel in S200 is constructed using the CRD method with separate pilot tunnels, specifically including the following steps:

[0024] S2001, the first upper pilot tunnel of the single-bore double-track tunnel is constructed by cyclic advance;

[0025] S2002, Closed working face;

[0026] S2003. Perform the third initial support for the single-bore double-track tunnel.

[0027] In this scheme, the use of the CRD method for pilot tunnel construction of a single-bore double-track tunnel further ensures the safety of tunnel transition construction. Before constructing the transition section in the reverse direction, ensuring proper third initial support for the single-bore double-track tunnel allows the third initial support structure to be horizontally extended into the transition section to form a second initial support when constructing the transition section in the reverse direction from one end closer to the single-bore double-track tunnel, thus ensuring safety.

[0028] Preferably, the step S34 further includes the following steps:

[0029] S35. Construct the secondary lining structure of the single-bore double-track tunnel and the secondary lining structure of the transition section.

[0030] In this scheme, the secondary lining structure is constructed together after the second initial support is completed in both the single-tube double-track tunnel and the transition section. This ensures the overall integrity of the single-tube double-track tunnel and the transition section, resulting in high engineering quality and saving manpower.

[0031] Preferably, the step S21 further includes the following steps:

[0032] S221. A temporary end wall is made at the working face of the lower guide tunnel of the transition section;

[0033] S222, The lower guide tunnel of the transition section is constructed as a construction ramp, which extends from the bottom surface to the bottom of the upper guide tunnel of the transition section.

[0034] In this plan, a temporary end wall is constructed at the working face of the lower pilot tunnel before the upper pilot tunnel of the construction transition section to prevent dangerous situations such as collapse during the construction of the upper pilot tunnel, thus ensuring construction safety. The construction ramp facilitates workers and construction equipment to enter the upper pilot tunnel of the transition section for construction; at the same time, the construction ramp also provides support for the temporary end wall, better ensuring safety and allowing for a better transition between the cross-section of the single-tunnel double-track tunnel and the transition section.

[0035] Preferably, after step S22, the construction of the lower pilot tunnel for the transition section is included, specifically comprising the following steps:

[0036] S23. Circular advance of the lower guide tunnel in the transition section;

[0037] S24. Initial support shall be provided for the lower guide tunnel of the transition section;

[0038] S25. The initial support extends from the transition section into the single-bore double-track tunnel.

[0039] In this scheme, the initial support of the lower pilot tunnel in the transition section is consistent with the initial support of the lower pilot tunnel in the single-tunnel double-track tunnel, forming a whole. When the first initial support is replaced by the second initial support, it maintains good stability and support, ensuring construction safety, facilitating installation, and saving costs.

[0040] Preferably, step S3 includes the following steps:

[0041] S4. Construct the single-bore double-track tunnel.

[0042] In this plan, a single-bore double-track tunnel can also be constructed after the construction transition section. This construction method ensures that the single-bore double-track tunnel is constructed only after the transition section is completed and the area is stable, thus ensuring the smooth construction of the single-bore double-track tunnel.

[0043] Preferably, step S1 specifically includes the following steps:

[0044] S11, Closed working face;

[0045] S12. Construction of the initial support structure of the three-arch tunnel;

[0046] S13. Construct the secondary lining structure of the three-arch tunnel.

[0047] In this plan, the construction of the single-bore double-track tunnel and the transition section is carried out after the secondary lining structure of the three-arch tunnel is completed, which can ensure the stability and safety of the three-arch tunnel during the construction process.

[0048] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0049] The positive and progressive effects of this invention are as follows: In this invention, the top of the transition section from a three-arch tunnel to a single-tunnel double-track tunnel slopes upward, allowing for a smooth transition between the two different tunnel sections during construction, avoiding uneven local stress on the structure and reducing construction risks; furthermore, through the reasonable design of the transition section, only the first initial support of the upper pilot tunnel needs to be changed along the top of the transition section, making construction easy to operate; finally, during reverse construction, only the first initial support of the upper pilot tunnel needs to be replaced, making construction simple, economical, and safe. Attached Figure Description

[0050] Figure 1 This is a flowchart of the construction method for converting a three-arch tunnel into a single-tunnel double-track tunnel according to the present invention.

[0051] Figure 2 This is a schematic diagram of the structure of the triple-arch tunnel and the single-bore double-track tunnel of the present invention.

[0052] Figure 3This is a structural schematic diagram of the triple-arch tunnel and single-tunnel double-track tunnel of the present invention from another perspective.

[0053] Figure 4 This is a schematic diagram of the longitudinal section of the guide tunnel in the construction transition section of the present invention.

[0054] Figure 5 This is a schematic diagram of the longitudinal section of the lower guide tunnel in the construction transition section of this invention.

[0055] Figure 6 This is a schematic diagram of the longitudinal section of the reverse construction transition section of the present invention.

[0056] Figure 7 This is a schematic diagram of the longitudinal section of a single-bore double-track tunnel completed according to the present invention.

[0057] Figure 8 This is a schematic diagram of the cross-sectional structure of the first initial support of the present invention.

[0058] Figure 9 This is a schematic diagram of the longitudinal section of the first initial support of the present invention.

[0059] Explanation of reference numerals in the attached figures:

[0060] Three-arch tunnel 1

[0061] Section 11

[0062] Transition Section 2

[0063] Single-bore double-track tunnel 3

[0064] First upper guide tunnel 31

[0065] First lower pilot tunnel 32

[0066] First initial support 4

[0067] Initial support structure of the upper pilot tunnel 41

[0068] Initial support structure of the lower pilot tunnel 42

[0069] Upper Guide Tunnel 43

[0070] Lower pilot tunnel 44

[0071] Vertical middle partition wall of the upper guide tunnel 45

[0072] Horizontal septum 46

[0073] Vertical partition wall of the lower guide tunnel 47 Detailed Implementation

[0074] The present invention will be described more clearly and completely below by way of embodiments and in conjunction with the accompanying drawings, but the present invention is not limited to the scope of the embodiments described herein.

[0075] This invention discloses a construction method for converting a three-arch tunnel into a single-bore double-track tunnel, such as... Figure 1-9 As shown, the construction method includes the following steps:

[0076] S1, Construction of the three-arch tunnel 1;

[0077] S2, the transition section 2 where the construction of the three-arch tunnel 1 is transformed into the single-bore double-track tunnel 3. The top of the transition section 2 extends obliquely upward from the cross section 11 of the three-arch tunnel 1 and the single-bore double-track tunnel 3 to the highest arch position of the single-bore double-track tunnel 3.

[0078] S3. Construction of transition section 2 proceeds in the opposite direction from transition section 2 to the three-arch tunnel 1.

[0079] Specifically, the top of the transition section 2, where the three-arch tunnel 1 transitions to the single-bore double-track tunnel 3, slopes upwards, ensuring a smooth transition of the two tunnel sections 11 during construction. This avoids uneven local stress on the structure and reduces construction risks. Furthermore, the well-designed transition section 2 only requires the first initial support 4 of the upper pilot tunnel 43 to change along the top of the transition section 2, making construction easier. Finally, during reverse construction, only the first initial support 4 of the upper pilot tunnel 43 needs to be replaced, simplifying construction, making it economical and reasonable, and improving safety.

[0080] In this embodiment, the CRD method is used to construct the transition section 2 of the pilot tunnel in S2. S2 specifically includes the following steps:

[0081] S21. Circular advance in the upper guide tunnel 43 of transition section 2;

[0082] The upper guide tunnel 43 of S22 and transition section 2 is supported by the first initial support 4. The first initial support 4 extends obliquely upward from the top side section 11 of the triple arch tunnel 1 to the highest arch position of the first upper guide tunnel 31 of the single-tunnel double-track tunnel 3.

[0083] Specifically, the CRD method is existing technology and will not be elaborated here. The CRD method of this invention is constructed by dividing the tunnel into four pilot tunnels. The transition section 2 is excavated using the CRD method, with the cyclic advance determined based on the surrounding rock grade and grid spacing, improving safety. Because the initial support structures of each pilot tunnel are fabricated separately, the stability of the transition section 2 is very high. When the pilot tunnels are connected, the initial support structures can be disassembled and connected, facilitating the later reverse construction of the transition section 2, reducing the amount of replacement work for the first initial support 4, lowering construction costs, and ensuring safety. The first initial support 4 extends obliquely upwards from the top side section 11 of the three-arch tunnel 1 to the highest arch position of the first upper pilot tunnel 31 of the single-tunnel double-track tunnel 3. The shape of the first initial support 4 changes with the top shape of the transition section 2, making the support more stable and ensuring a smooth transition of the section 11 from the three-arch tunnel 1 to the single-tunnel double-track tunnel 3, thus ensuring safety.

[0084] The first initial support 4 includes an upper pilot tunnel initial support structure 41, a lower pilot tunnel initial support structure 42, an upper pilot tunnel vertical central partition wall 45, a horizontal central partition wall 46, and a lower pilot tunnel vertical central partition wall 47. The left and right sides of the upper pilot tunnel initial support structure 41 and the lower pilot tunnel initial support structure 42 are detachably connected, forming a ring. The left and right ends of the horizontal central partition wall 46 are connected to the connection points of the upper pilot tunnel initial support structure 41 and the lower pilot tunnel initial support structure 42, respectively. The upper and lower ends of the upper pilot tunnel vertical central partition wall 45 are connected to the upper pilot tunnel initial support structure 41 and the horizontal central partition wall 46, respectively. The upper and lower ends of the lower pilot tunnel vertical central partition wall 47 are connected to the horizontal central partition wall 46 and the lower pilot tunnel initial support structure 42, respectively. The upper pilot tunnel vertical central partition wall 45 and the lower pilot tunnel vertical central partition wall 47 are arranged vertically opposite each other, so that the cross-section of the first initial support 4 is divided into four regions, forming two upper pilot tunnels 43 and two lower pilot tunnels 44. Furthermore, the initial support structure 41 of the upper guide tunnel is a conical shell to adapt to the shape of the transition section 2.

[0085] During the construction of transition section 2, two upper guide tunnels 43 are constructed first, with one tunnel per section, and an initial support structure for that tunnel is built. The initial support structures of the two upper guide tunnels 43 form the upper part of the first initial support 4, which includes the upper guide tunnel initial support structure 41, the upper guide tunnel vertical central diaphragm wall 45, and the horizontal central diaphragm wall 46. This construction method can significantly improve safety.

[0086] In this embodiment, construction is carried out frame by frame in S3, specifically including the following steps:

[0087] S31, the first initial support 4 of the upper guide tunnel 43 of the transition section 2 is removed;

[0088] S32. Construction proceeds in the opposite direction from transition section 2 to the three-arch tunnel 1. The upper guide tunnel 43 of transition section 2 is constructed to the highest arch position.

[0089] S33, the first initial support 4 is replaced with the second initial support;

[0090] S34. Repeat S31 to S33 above until construction reaches the section 11 where the single-bore double-track tunnel 3 and the triple-arch tunnel 1 transition.

[0091] Specifically, dismantling and constructing one section at a time allows for better construction based on monitoring data, improving safety. Dismantling begins at the end of the first initial support 4 on the side furthest from the three-arch tunnel 1. After dismantling one section of the first initial support 4 on the transition section 2, the position of that section is constructed up to the highest arch crown, and then replaced with that section of the first initial support 4 as the second initial support, making construction safer.

[0092] When replacing the first initial support 4, only the initial support structure 41 of the upper guide tunnel and the vertical central partition wall 45 of the upper guide tunnel need to be replaced, which is convenient for replacement, saves time, and makes the entire initial support structure stable, thus ensuring safety.

[0093] In this embodiment, the following steps are included after S2 and before S3:

[0094] S200, construction of a single-bore double-track tunnel 3.

[0095] Specifically, before constructing the transition section 2 in the reverse direction, the single-bore double-track tunnel 3 can be opened first, so that the first initial support 4 of the transition section 2 can continue to support the transition section 2 more time and more stably, further ensuring construction safety, and the construction equipment can continue to work in the same direction, improving work efficiency.

[0096] In this embodiment, the CRD method is used in S200 to construct a single-tunnel double-track tunnel 3, which specifically includes the following steps:

[0097] S2001, the first upper pilot tunnel 31 of the single-bore double-track tunnel 3 constructed by cyclic advance;

[0098] S2002, Closed working face;

[0099] S2003, perform the third initial support for the single-bore double-track tunnel 3.

[0100] Specifically, the CRD method is used to construct the single-bore double-track tunnel 3 using pilot tunnels. At the transition point between the transition section 2 and the single-bore double-track tunnel 3, the top of the first initial support 4 has reached the required highest arch position. Therefore, the end of the first initial support 4 continues to extend horizontally, forming the third initial support of the single-bore double-track tunnel 3. After the single-bore double-track tunnel 3 is completed, the first initial support 4 and the third initial support of the single-bore double-track tunnel 3 form an integrated initial support structure, which has higher stability and better ensures the construction safety of the tunnel transition. Before constructing the transition section 2 in the reverse direction, completing the third initial support of the single-bore double-track tunnel 3 is beneficial for constructing the transition section 2 in the reverse direction from the end of the transition section 2 closest to the single-bore double-track tunnel 3. This allows the third initial support structure to be extended horizontally into the transition section 2 to form the second initial support of the transition section 2, ensuring safety and facilitating construction.

[0101] In this configuration, the construction space is larger and easier to construct when working in reverse from the single-tube double-track tunnel 3 to the transition section 2. Furthermore, the initial support structures of the single-tube double-track tunnel 3 and the transition section 2 form a unified whole, resulting in high stability. During reverse construction, only the initial support structure 41 of the upper pilot tunnel and the vertical central diaphragm 45 of the upper pilot tunnel need to be replaced, minimizing the overall impact and thus making the tunnel transition safer and ensuring high-quality engineering.

[0102] Specifically, after completing the construction of the upper guide tunnel 43 of the transition section 2, including the upper guide tunnel initial support structure 41, the upper guide tunnel vertical central partition wall 45, and the horizontal central partition wall 46 in the first initial support 4, the first upper guide tunnel 31 of the single-tunnel double-track tunnel 3 can be constructed until the single-tunnel double-track tunnel 3 is opened and the third initial support of the single-tunnel double-track tunnel 3 is completed.

[0103] In this embodiment, the following steps are included after S34:

[0104] S35, the secondary lining structure of the single-bore double-track tunnel 3 and the secondary lining structure of the transition section 2.

[0105] Specifically, after the third initial support of the single-bore double-track tunnel 3 and the second initial support of the transition section 2 are completed, the secondary lining structure is constructed together. This ensures the strong integrity of the tunnel between the single-bore double-track tunnel 3 and the transition section 2, enabling the secondary lining structure to be constructed as a whole, resulting in high project quality and saving manpower.

[0106] like Figure 6 , Figure 7 As shown, after the second initial support of transition section 2 is replaced, transition section 2 becomes an integral part of single-bore double-track tunnel 3.

[0107] In this embodiment, the following steps are included before S21:

[0108] S221, Temporary end wall to be constructed at the working face of the lower guide tunnel 44 of transition section 2;

[0109] S222, the lower guide tunnel 44 of transition section 2 is constructed as a construction ramp, which extends from the bottom surface to the bottom of the upper guide tunnel 43 of transition section 2.

[0110] Specifically, before the upper pilot tunnel 43 of the construction transition section 2, a temporary end wall is constructed at the working face of the lower pilot tunnel 44 of the transition section 2 to prevent dangerous situations such as collapse at the working face of the lower pilot tunnel 44 during the construction of the upper pilot tunnel 43, thus ensuring construction safety. The construction ramp facilitates workers and construction equipment access to the upper pilot tunnel 43 of the transition section 2 for construction; simultaneously, the construction ramp provides support for the temporary end wall, further ensuring safety and allowing for a smoother transition between the single-tube double-track tunnel 3 and the cross-section 11 of the transition section 2.

[0111] In this embodiment, the lower pilot tunnel 44, which includes the construction transition section 2, is located after S22, and specifically includes the following steps:

[0112] S23. Circular advance in the lower guide tunnel 44 of transition section 2;

[0113] S24, the lower guide tunnel 44 of transition section 2 is to be initially supported;

[0114] S25. The initial support extends from transition section 2 into the single-bore double-track tunnel 3.

[0115] Specifically, after the upper pilot tunnel 43 is constructed, the lower pilot tunnel 44 is constructed. The lower pilot tunnel 44 is advanced cyclically in the transition section 2, with the cyclic advancement determined based on the surrounding rock grade and grid spacing to improve safety. The lower pilot tunnel 44 is constructed segment by segment, consistent with each segment of the upper pilot tunnel 43. Initial support is then provided for each segment and detachably connected to the first initial support 4 of the upper pilot tunnel 43. The initial support of the lower pilot tunnel 44 refers to the initial support structure 42 and the vertical central diaphragm 47 of the lower pilot tunnel. The initial support of the lower pilot tunnel 44 extends horizontally from the transition section 2 to the single-tunnel double-track tunnel 3, forming a unified whole. It does not require replacement during reverse construction, ensuring the stability of the entire initial support structure. During the replacement of the first initial support 4 of the upper pilot tunnel 43, the stability of the entire initial support structure is also well maintained, improving safety. The initial support structure 42 of the lower pilot tunnel of transition section 2 is consistent with the initial support of the first lower pilot tunnel 32 of single-tunnel double-track tunnel 3, which is convenient for installation, saves costs, and has high safety.

[0116] In an alternative implementation, after the first initial support 4 of the upper guide tunnel 43 of the transition section 2 is completed, the construction of the lower guide tunnel 44 is temporarily suspended. Then, the first upper guide tunnel 31 of the single-line tunnel is constructed, and the transition section 2 is constructed in reverse.

[0117] In an alternative implementation, step S3 includes the following steps:

[0118] S4, Construction of a single-bore double-track tunnel 3.

[0119] Specifically, after completing the second initial support at transition section 2, construction of the single-bore double-track tunnel 3 will continue. Because transition section 2 is relatively short, its stability can be monitored more closely and precisely, and any problems that arise can be effectively addressed with minimal impact. This construction method ensures the stability of transition section 2 before proceeding with construction of the single-bore double-track tunnel 3, guaranteeing the stability of the transition section 11, ensuring the smooth construction of the single-bore double-track tunnel 3, and improving construction safety.

[0120] In this approach, the single-bore double-track tunnel 3 can be constructed after the secondary lining structure of transition section 2 is completed. In this way, the secondary lining structure of transition section 2 and the secondary lining structure of the three-arch tunnel 1 are sufficiently stable, and the position of section 11 is also stable. With the transition already stable, the construction of the single-bore double-track tunnel 3 can continue, which is safer.

[0121] In this embodiment, S1 specifically includes the following steps:

[0122] S11, Closed working face;

[0123] S12, the initial support structure of the construction of the three-arch tunnel 1;

[0124] S13, the secondary lining structure of the construction of the three-arch tunnel 1.

[0125] Specifically, the CRD method can be used to construct the three-arch tunnel 1 using pilot tunnels. The cyclic advance is determined based on the surrounding rock grade and grid spacing, improving safety. One tunnel face is constructed to close the construction direction, and the initial support structure is built for that face, until the transition section 11 between the three-arch tunnel 1 and the transition section 2 is reached. Afterwards, the secondary lining structure is constructed as a whole. Constructing the secondary lining structure of the three-arch tunnel 1 before proceeding with the construction of the single-bore double-track tunnel 3 and the transition section 2 ensures the stability and safety of the three-arch tunnel 1 during construction, better guarantees the construction of the transition section 2, ensures a safe transition between the three-arch tunnel 1 and the single-bore double-track tunnel 3, and improves the overall construction safety of the tunnel project.

[0126] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A construction method for converting a three-arch tunnel into a single-bore double-track tunnel, characterized in that: The construction method includes the following steps: S1. Construct the aforementioned three-arch tunnel; S2. Construct a transition section for the conversion of the three-arch tunnel to the single-bore double-track tunnel. The top of the transition section extends obliquely upward from the cross-section of the three-arch tunnel and the single-bore double-track tunnel to the highest arch position of the single-bore double-track tunnel. S3. Construct the transition section in the opposite direction from the transition section to the three-arch tunnel; The transition section in S2 is constructed using the CRD method with separate pilot tunnels. Specifically, S2 includes the following steps: S21. Circular advance through the upper guide hole in the transition section; S22. The upper guide tunnel of the transition section is provided with the first initial support. The first initial support extends obliquely upward from the cross section on one side of the top of the three-arch tunnel to the highest arch position of the first upper guide tunnel of the single-tunnel double-track tunnel. The construction of each section in S3 includes the following steps: S31. Remove the first initial support of the upper guide tunnel of the transition section; S32. Construction proceeds in the opposite direction from the transition section to the three-arch tunnel, with the upper guide tunnel of the transition section constructed to the highest arch position. S33, The first initial support is replaced with the second initial support; S34. Repeat S31 to S33 as described above until construction reaches the section where the single-bore double-track tunnel and the triple-arch tunnel transition.

2. The construction method for converting a three-arch tunnel to a single-bore double-track tunnel as described in claim 1, characterized in that: The following steps are included after S2 and before S3: S200, construct the single-bore double-track tunnel.

3. The construction method for converting a three-arch tunnel to a single-bore double-track tunnel as described in claim 2, characterized in that: The single-tunnel double-track tunnel in S200 is constructed using the CRD method with pilot tunnels, specifically including the following steps: S2001, the first upper pilot tunnel of the single-bore double-track tunnel is constructed by cyclic advance; S2002, Closed working face; S2003. Perform the third initial support for the single-bore double-track tunnel.

4. The construction method for converting a three-arch tunnel to a single-bore double-track tunnel as described in claim 3, characterized in that: The following steps are included after step S34: S35. Construct the secondary lining structure of the single-bore double-track tunnel and the secondary lining structure of the transition section.

5. The construction method for converting a three-arch tunnel to a single-bore double-track tunnel as described in claim 1, characterized in that: The following steps are included before step S21: S221. A temporary end wall is made at the working face of the lower guide tunnel of the transition section; S222, The lower guide tunnel of the transition section is constructed as a construction ramp, which extends from the bottom surface to the bottom of the upper guide tunnel of the transition section.

6. The construction method for converting a three-arch tunnel to a single-bore double-track tunnel as described in claim 1, characterized in that: Following S22, the construction of the lower pilot tunnel for the transition section includes the following steps: S23. Circular advance of the lower guide tunnel in the transition section; S24. Initial support shall be provided for the lower guide tunnel of the transition section; S25. The initial support extends from the transition section into the single-bore double-track tunnel.

7. The construction method for converting a three-arch tunnel to a single-bore double-track tunnel as described in claim 1, characterized in that: The step following S3 is as follows: S4. Construct the single-bore double-track tunnel.

8. The construction method for converting a three-arch tunnel to a single-bore double-track tunnel as described in claim 1, characterized in that: S1 specifically includes the following steps: S11, Closed working face; S12. Construction of the initial support structure of the three-arch tunnel; S13. Construct the secondary lining structure of the aforementioned three-arch tunnel.

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