Construction method of main and auxiliary tunnel connecting pre-support structure and main and auxiliary tunnel support structure

Abstract

The application belongs to the technical field of tunnel construction, and particularly discloses a main-attached tunnel connecting pre-supporting structure and a construction method of the main-attached tunnel supporting structure, which further comprises a vertically arranged expansion section ring beam, and an expansion section primary support is located between the expansion section ring beam and the inner wall of the expansion section; the main tunnel and the attached tunnel are connected and communicated through the middle passage of the expansion section ring beam; the corresponding section of the main tunnel and the expansion section serves as a connecting section, the connecting section is provided with a connecting section inverted arch concave downward, the bottom of the expansion section ring beam is connected with the connecting section inverted arch and forms an integral structure; and the structural steel bars of the expansion section ring beam are connected with the expansion section primary support steel frame through first steel bars. The connecting part of the main-attached tunnel can be stably supported under the condition of poor geology or extremely poor stress condition, the stability of stress transformation when the expansion section primary support steel frame located in the expansion section opening range is broken is realized, and the safety is ensured.

Description

Technical Field

[0001] This invention belongs to the technical field of tunnel construction, specifically relating to a construction method for a pre-support structure connecting the main and auxiliary tunnels and a support structure for the main and auxiliary tunnels. Background Technology

[0002] Mining methods, as one of the important construction methods for underground engineering, are widely used in tunnel construction in many industries in my country, including railways, highways, rail transit, and water conservancy. Tunnel construction often involves various ancillary chambers connected to the main tunnel, such as cross passages, connecting passages, passing bays, and branch passages. The construction of these ancillary chambers also typically employs mining methods. Currently, the common practice in the field of mining method tunnels is to excavate from the relatively large main tunnel to access the relatively smaller ancillary works for construction. Since the excavation location is generally at the sidewall of the main tunnel, the excavation process requires stress transfer, resulting in a complex stress system and significant safety risks. Therefore, the excavation of the main tunnel sidewall is a crucial step in ensuring the safety of the main tunnel and the smooth implementation of the ancillary chambers.

[0003] Currently, the industry's conventional approach to the construction method of opening the sidewall of the main tunnel to enter the auxiliary tunnel is "dismantle first, then support." This means taking advantage of the fact that good rock mass can remain relatively stable for a certain period of time, after breaking the initial support structure of the planned opening area of ​​the main tunnel, steel frames are promptly used as support at the junction of the main tunnel and the auxiliary tunnel to complete the stress transfer.

[0004] For example, Chinese patent document CN110905524A discloses a method for excavation and support of subway station tunnels using a cut-and-cover construction channel, employing a portal steel arch frame to support the junction of the main construction channel and the station tunnel. Another example is Chinese patent document CN107975383A, which discloses a construction method for excavation and support of a T-shaped intersection of underground caverns, using a steel portal frame to support the entrance of the auxiliary tunnel. Finally, Chinese patent document CN110486036A discloses a construction method using an enlarged arch foot initial support arch cover, employing a steel support structure to support the intersection of the main tunnel and the auxiliary tunnel.

[0005] While the aforementioned "dismantle first, then support" approach has been validated in existing engineering cases, it still relies on relatively favorable geological conditions, the availability of resources to address weak and unfavorable geological formations at the construction site, and relatively simple spatial relationships within the project. When encountering situations where unfavorable geological conditions cannot be addressed, or where the project itself has complex spatial relationships and extremely poor stress conditions, excavation work will face significant safety risks. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a construction method for a pre-support structure for the connection between the main and auxiliary tunnels and a support structure for the main and auxiliary tunnels. This method can stably support the connection between the main and auxiliary tunnels under poor geological conditions or extremely poor stress conditions, and achieve stability in the stress transformation when breaking the initial support steel frame of the excavation section located within the planned excavation area of ​​the widening section, thus ensuring safety.

[0007] The technical solution adopted by the present invention to solve its technical problem is as follows: a pre-support structure for connecting main and auxiliary tunnels, including a main tunnel and an auxiliary tunnel located outside the main tunnel; an enlarged section located on the side of the main tunnel is excavated at the connection between the main tunnel and the auxiliary tunnel, the enlarged section protrudes from the auxiliary tunnel radially and in a direction away from the auxiliary tunnel, and forms a stepped structure; an initial support for the enlarged section is provided in the enlarged section, the initial support for the enlarged section including an initial support steel frame for supporting the enlarged section, and an initial support concrete layer for the enlarged section provided on the inner wall of the enlarged section;

[0008] It also includes a vertically arranged widening section ring beam, the initial support of which is located between the widening section ring beam and the inner wall of the widening section; the main tunnel and the auxiliary tunnel are connected through the central passage of the widening section ring beam;

[0009] The corresponding sections of the main tunnel and the widened section serve as connecting sections. The connecting section is provided with a downwardly recessed connecting section invert. The bottom of the widened section ring beam is connected to the connecting section invert and forms an integral structure.

[0010] The structural steel reinforcement of the ring beam of the excavation section is connected to the initial support steel frame of the excavation section through the first steel reinforcement.

[0011] Furthermore, the first reinforcing bar is arranged radially along the widened section.

[0012] Furthermore, one end of the first reinforcing bar is welded to the structural reinforcing bar of the expanded section ring beam, and the other end is welded to the initial support steel frame of the expanded section.

[0013] Furthermore, the structural steel bars of the expanded section ring beam and the structural steel bars of the connecting section invert arch are connected by a second steel bar.

[0014] Furthermore, the two ends of the excavation section along its own radial direction are located between the two ends of the connecting section along its own axial direction.

[0015] The construction method for the main and auxiliary tunnel support structure, which adopts a pre-support structure connecting the main and auxiliary tunnels, includes the following steps:

[0016] S1, excavate the main tunnel and construct the initial support of the main tunnel. At the proposed opening location on the side of the main tunnel, excavate the widening section in a direction away from the main tunnel. Construct the initial support of the widening section in the widening section. The initial support of the widening section includes a steel frame for supporting the widening section and a concrete layer for the initial support of the widening section set on the inner wall of the widening section.

[0017] S2, erect the ring beam formwork in the excavation section and form the ring beam pouring space in the excavation section. In the ring beam pouring space, erect the structural steel bars of the ring beam in the excavation section. Connect the structural steel bars of the ring beam in the excavation section to the initial support steel frame of the excavation section through the first steel bar.

[0018] The main tunnel includes a connecting section and a regular section arranged along its own axis. The connecting section is arranged in a corresponding manner to the excavation section and is located between the two regular sections. The formwork for the invert arch of the connecting section is erected in the main tunnel to form the pouring space for the invert arch of the connecting section. The pouring space for the invert arch of the connecting section is connected to the pouring space for the ring beam of the excavation section. The structural steel reinforcement of the invert arch of the connecting section is erected in the pouring space for the invert arch of the connecting section.

[0019] Concrete is poured in the excavation section ring beam casting space to form the excavation section ring beam, and concrete is poured in the connecting section invert arch casting space to form the connecting section invert arch, so that the bottom of the excavation section ring beam is connected to the connecting section invert arch and forms an integral structure.

[0020] Once the strength requirements are met, the initial support steel frame of the excavation section located within the proposed opening area of ​​the excavation section will be dismantled.

[0021] S3, excavate the auxiliary tunnel and construct the initial support for the auxiliary tunnel; connect the auxiliary tunnel to the main tunnel through the central passage of the enlarged section ring beam;

[0022] S4, construct the secondary lining of the auxiliary tunnel, extending the secondary lining of the auxiliary tunnel to the widened section. The ring beam of the widened section is located between the secondary lining of the auxiliary tunnel and the initial support of the widened section. The secondary lining of the auxiliary tunnel includes the auxiliary tunnel invert, the auxiliary tunnel sidewall and the auxiliary tunnel arch, arranged sequentially from bottom to top.

[0023] The secondary lining of the ordinary section and the remaining secondary lining of the connecting section are constructed. The secondary lining of the ordinary section includes the ordinary section invert, the ordinary section sidewall, and the ordinary section arch, arranged sequentially from bottom to top. The remaining secondary lining of the connecting section includes the connecting section sidewall and the connecting section arch, arranged sequentially from bottom to top. The side connecting the main tunnel and the auxiliary tunnel is designated as the connecting side. The ordinary section sidewall located on the connecting side is connected to the adjacent auxiliary tunnel sidewall through the connecting section sidewall located on the connecting side, forming an integral structure. The auxiliary tunnel arch and the ordinary section arch are connected through the connecting section arch, forming an integral structure. The ring beam of the widened section is located between the secondary lining of the connecting section and the initial support of the widened section.

[0024] Furthermore, the expanded section ring beam in steps S2, S3 and S4 is constructed using an integral casting method.

[0025] Furthermore, in step S2, the initial support steel frame of the excavation section located within the proposed opening area of ​​the excavation section is broken up by a cutting machine.

[0026] Compared with the prior art, the beneficial effects of the present invention are: the present invention provides a construction method for a pre-support structure for the connection between the main and auxiliary tunnels and a support structure for the main and auxiliary tunnels, which can stably support the connection between the main and auxiliary tunnels under poor geological conditions or extremely poor stress conditions, and achieve stability in the stress transformation when breaking the initial support steel frame of the excavation section located within the planned opening range of the excavation section, thus ensuring safety. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the positional relationship between the connecting section invert arch and the widened section ring beam;

[0028] Figure 2 This is a schematic diagram of the initial support steel frame of the excavation section located within the proposed opening area of ​​the excavation section;

[0029] Figure 3 This is a planar schematic diagram of the present invention;

[0030] Figure 4 yes Figure 3 A schematic diagram of the cross-section along the line of sight AA;

[0031] Figure 5 yes Figure 4 A schematic diagram of the cross-section along the line of sight BB;

[0032] Figure 6 yes Figure 4 A schematic diagram of the cross-section along the line of sight CC;

[0033] Attached reference numerals: 1-Main tunnel; 101-Initial support of main tunnel; 102-Connecting section invert; 103-Connecting section sidewall; 104-Connecting section arch; 105-Ordinary section invert; 106-Ordinary section sidewall; 107-Ordinary section arch; 108-Connecting side; 2-Expanded section; 201-Expanded section initial support steel frame; 202-Expanded section initial support concrete layer; 203-Expanded section ring beam; 3-Auxiliary tunnel; 301-Auxiliary tunnel initial support; 302-Auxiliary tunnel invert; 303-Auxiliary tunnel sidewall; 304-Auxiliary tunnel arch; 4-First reinforcement. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] The pre-support structure connecting the main tunnel and the auxiliary tunnel includes a main tunnel 1 and an auxiliary tunnel 3 located outside the main tunnel 1. At the connection between the main tunnel 1 and the auxiliary tunnel 3, an enlarged section 2 is excavated on the side of the main tunnel 1. The enlarged section 2 protrudes from the auxiliary tunnel 3 radially and in a direction away from the auxiliary tunnel 3, forming a stepped structure. An initial support for the enlarged section 2 is provided, including an initial support steel frame 201 for supporting the enlarged section 2 and an initial support concrete layer 202 disposed on the inner wall of the enlarged section 2. It also includes a vertically arranged enlarged section ring beam. 203, the initial support of the excavation section is located between the ring beam 203 of the excavation section and the inner wall of the excavation section 2; the main tunnel 1 and the auxiliary tunnel 3 are connected through the central passage of the ring beam 203 of the excavation section; the corresponding sections of the main tunnel 1 and the excavation section 2 serve as connecting sections, and the connecting section is provided with a downwardly recessed connecting section invert 102; the bottom of the ring beam 203 of the excavation section is connected to the connecting section invert 102 and forms an integral structure; both the ring beam 203 of the excavation section and the connecting section invert 102 are reinforced concrete structures; the structural steel bars of the ring beam 203 of the excavation section are connected to the initial support steel frame 201 of the excavation section through the first steel bar 4.

[0036] The widened section 2 protrudes outwards towards the auxiliary tunnel 3, providing space for the construction of the widened section ring beam 203. Since the upper part of the widened section ring beam 203 contacts the initial support of the widened section at an arc surface, the stability of the widened section ring beam 203 is improved by installing the first reinforcing bar 4. When construction of the auxiliary tunnel is required under poor geological conditions or extremely poor stress conditions, breaking the initial support steel frame 201 of the widened section within the planned opening area of ​​the widened section 2 could easily prevent the main tunnel's initial support 101 from forming a ring to transmit force. By constructing the widened section ring beam 203 and the connecting section invert arch 102 as an integral structure, they jointly bear the load transmitted from the main tunnel's initial support 101, preventing the widened section ring beam 203 from overturning or overturning due to large horizontal forces, thus ensuring the integrity of the entire stress system.

[0037] Preferably, the first reinforcing bar 4 is arranged radially along the widened section 2.

[0038] One end of the first reinforcing bar 4 can be tied to the structural reinforcing bars of the ring beam 203 of the excavated section, and the other end can also be tied to the initial support steel frame 201 of the excavated section. Preferably, one end of the first reinforcing bar 4 is welded to the structural reinforcing bars of the ring beam 203 of the excavated section, and the other end is welded to the initial support steel frame 201 of the excavated section.

[0039] To further improve connection stability, preferably, the structural steel bars of the excavated section ring beam 203 and the structural steel bars of the connecting section invert arch 102 are connected by a second steel bar.

[0040] To further provide structural stability, preferably, the two ends of the excavated section 2 along its own radial direction are located between the two ends of the connecting section along its own axial direction.

[0041] The construction method for the main and auxiliary tunnel support structure, which adopts a pre-support structure connecting the main and auxiliary tunnels, includes the following steps:

[0042] S1. Excavate the main tunnel 1 and construct the initial support 101 of the main tunnel. At the proposed opening location on the side of the main tunnel 1, excavate the widening section 2 in a direction away from the main tunnel 1. Construct the initial support of the widening section 2 in the widening section 2. The initial support of the widening section includes a steel frame 201 for supporting the widening section 2, and a concrete layer 202 for the initial support of the widening section 2 set on the inner wall of the widening section 2.

[0043] S2, erect the excavation section ring beam formwork in the excavation section 2 and form the excavation section ring beam pouring space, erect the structural steel bars of the excavation section ring beam 203 in the excavation section ring beam pouring space, and connect the structural steel bars of the excavation section ring beam 203 to the excavation section initial support steel frame 201 through the first steel bar 4.

[0044] The main tunnel 1 includes a connecting section and a regular section arranged along its own axis. The connecting section is arranged correspondingly to the widened section 2 and is located between the two regular sections. The formwork for the connecting section invert arch is erected in the main tunnel 1 to form the casting space for the connecting section invert arch. The casting space for the connecting section invert arch is connected to the casting space for the ring beam of the widened section. The structural steel reinforcement of the connecting section invert arch 102 is erected in the casting space for the connecting section invert arch.

[0045] Concrete is poured in the excavation section ring beam casting space to form the excavation section ring beam 203, and concrete is poured in the connecting section invert arch casting space to form the connecting section invert arch 102, so that the bottom of the excavation section ring beam 203 is connected to the connecting section invert arch 102 and forms an integral structure.

[0046] Once the strength requirements are met, the initial support steel frame 201 of the excavation section located within the proposed opening area of ​​the excavation section 2 will be dismantled.

[0047] S3, excavate auxiliary tunnel 3, construct the initial support 301 of auxiliary tunnel; connect auxiliary tunnel 3 with main tunnel 1 through the central passage of the enlarged section ring beam 203.

[0048] S4, construct the secondary lining of the auxiliary tunnel, extending the secondary lining of the auxiliary tunnel to the widened section 2. The ring beam 203 of the widened section is located between the secondary lining of the auxiliary tunnel and the initial support of the widened section. The secondary lining of the auxiliary tunnel includes the auxiliary tunnel invert arch 302, the auxiliary tunnel sidewall 303 and the auxiliary tunnel arch cover 304 arranged sequentially from bottom to top.

[0049] The secondary lining of the ordinary section and the remaining secondary lining of the connecting section are constructed. The secondary lining of the ordinary section includes the ordinary section invert 105, the ordinary section sidewall 106 and the ordinary section arch 107 arranged from bottom to top. The remaining secondary lining of the connecting section includes the connecting section sidewall 103 and the connecting section arch 104. The connecting section invert 102, the connecting section sidewall 103 and the connecting section arch 104 are arranged from bottom to top. The side connecting the main tunnel 1 and the auxiliary tunnel 3 is designated as the connecting side 108. The ordinary section sidewall 106 located on the connecting side 108 is connected to the adjacent auxiliary tunnel sidewall 303 through the connecting section sidewall 103 located on the connecting side 108, forming an integral structure. The auxiliary tunnel arch 304 is connected to the ordinary section arch 107 through the connecting section arch 104, forming an integral structure. The widened section ring beam 203 is located between the secondary lining of the connecting section and the initial support of the widened section.

[0050] Preferably, the expanded section ring beam 203 in steps S2, S3 and S4 is constructed by integral casting.

[0051] Preferably, in step S2, the initial support steel frame 201 of the excavation section located within the proposed opening area of ​​the excavation section 2 is broken up by a cutting machine.

[0052] It ensures the structural strength of the entire main tunnel, achieves stable stress transfer, and improves construction safety. This is particularly effective in sections with weak or unfavorable geological formations, and in situations where complex spatial relationships and extremely poor stress conditions exist at the connection points between the main tunnel and auxiliary tunnels, leading to such conditions. It also has the advantages of not affecting the continuous construction of the main tunnel and facilitating construction efficiency.

[0053] The above are specific embodiments of the present invention. As can be seen from the implementation process, the present invention provides a construction method for a pre-support structure for the connection between the main and auxiliary tunnels and a support structure for the main and auxiliary tunnels. This method can stably support the connection between the main and auxiliary tunnels under poor geological conditions or extremely poor stress conditions, and achieve stability in the stress transformation when breaking the initial support steel frame of the excavation section located within the planned excavation area of ​​the widening section, thus ensuring safety.

Claims

1. A construction method for the main and auxiliary tunnel support structure, characterized in that, A pre-support structure connecting the main tunnel and the auxiliary tunnel is adopted, including a main tunnel (1) and an auxiliary tunnel (3) located outside the main tunnel (1); at the connection between the main tunnel (1) and the auxiliary tunnel (3), an enlarged section (2) located on the side of the main tunnel (1) is excavated. The enlarged section (2) protrudes from the auxiliary tunnel (3) radially and in a direction away from the auxiliary tunnel (3) and forms a stepped structure; an initial support for the enlarged section (2) is provided in the enlarged section (2). The initial support for the enlarged section includes an initial support steel frame (201) for supporting the enlarged section (2) and an initial support concrete layer (202) for the enlarged section (2) on the inner wall of the enlarged section (2). It also includes a vertically arranged widening section ring beam (203), the initial support of the widening section is located between the widening section ring beam (203) and the inner wall of the widening section (2); the main tunnel (1) and the auxiliary tunnel (3) are connected through the middle passage of the widening section ring beam (203); The corresponding sections of the main tunnel (1) and the widened section (2) are used as connecting sections. The connecting section is provided with a downwardly recessed connecting section invert (102). The bottom of the widened section ring beam (203) is connected to the connecting section invert (102) and forms an integral structure. The structural steel bars of the ring beam (203) of the excavation section are connected to the initial support steel frame (201) of the excavation section through the first steel bar (4); The first reinforcing bar (4) is arranged radially along the widened section (2); Including the following steps: S1, excavate the main tunnel (1) and construct the initial support (101) of the main tunnel. At the proposed opening location on the side of the main tunnel (1), excavate the enlarged section (2) in a direction away from the main tunnel (1). Construct the initial support of the enlarged section (2) in the enlarged section (2). The initial support of the enlarged section includes an initial support steel frame (201) for supporting the enlarged section (2) and an initial support concrete layer (202) for the enlarged section (2) set on the inner wall of the enlarged section (2). S2, in the excavation section (2), the formwork of the excavation section ring beam is erected and the excavation section ring beam pouring space is formed. In the excavation section ring beam pouring space, the structural steel bars of the excavation section ring beam (203) are erected. The structural steel bars of the excavation section ring beam (203) are connected to the initial support steel frame (201) of the excavation section through the first steel bar (4). The main tunnel (1) includes a connecting section and a regular section arranged along its own axis. The connecting section is arranged in correspondence with the excavation section (2) and is located between the two regular sections. The connecting section invert arch formwork is erected in the main tunnel (1) to form the connecting section invert arch pouring space. The connecting section invert arch pouring space is connected to the excavation section ring beam pouring space. The structural steel reinforcement of the connecting section invert arch (102) is erected in the connecting section invert arch pouring space. Concrete is poured in the excavation section ring beam pouring space to form the excavation section ring beam (203), and concrete is poured in the connecting section invert arch pouring space to form the connecting section invert arch (102), so that the bottom of the excavation section ring beam (203) is connected to the connecting section invert arch (102) and forms an integral structure. After the strength requirements are met, the initial support steel frame (201) of the excavation section located within the planned opening area of ​​the excavation section (2) is removed. S3, excavate the auxiliary tunnel (3), construct the initial support (301) of the auxiliary tunnel; connect the auxiliary tunnel (3) with the main tunnel (1) through the central passage of the enlarged section ring beam (203); S4, construct the secondary lining of the auxiliary tunnel, extending the secondary lining of the auxiliary tunnel to the widened section (2), and the ring beam (203) of the widened section is located between the secondary lining of the auxiliary tunnel and the initial support of the widened section; the secondary lining of the auxiliary tunnel includes the auxiliary tunnel invert arch (302), the auxiliary tunnel sidewall (303) and the auxiliary tunnel arch cover (304) arranged from bottom to top. The secondary lining of the ordinary section and the remaining secondary lining of the connecting section are constructed. The secondary lining of the ordinary section includes the ordinary section invert (105), the ordinary section sidewall (106), and the ordinary section arch (107) arranged from bottom to top. The remaining secondary lining of the connecting section includes the connecting section sidewall (103) and the connecting section arch (104). The connecting section invert (102), the connecting section sidewall (103), and the connecting section arch (104) are arranged from bottom to top. The main tunnel (1) is connected to the auxiliary tunnel (3). One side serves as the connecting side (108). The ordinary section sidewall (106) located on the connecting side (108) is connected to the adjacent auxiliary tunnel sidewall (303) through the connecting section sidewall (103) located on the connecting side (108), forming an integral structure. The auxiliary tunnel arch cover (304) is connected to the ordinary section arch cover (107) through the connecting section arch cover (104), forming an integral structure. The widened section ring beam (203) is located between the secondary lining of the connecting section and the primary support of the widened section.

2. The construction method of the main and auxiliary tunnel support structure as described in claim 1, characterized in that, The expanded section ring beam (203) in steps S2, S3 and S4 is constructed by integral casting.

3. The construction method of the main and auxiliary tunnel support structure as described in claim 1, characterized in that, In step S2, the initial support steel frame (201) of the excavation section located within the planned opening area of ​​the excavation section (2) is broken by a cutting machine.

4. The construction method of the main and auxiliary tunnel support structure as described in claim 1, characterized in that, One end of the first reinforcing bar (4) is welded to the structural reinforcing bar of the excavation section ring beam (203), and the other end is welded to the initial support steel frame (201) of the excavation section.

5. The construction method of the main and auxiliary tunnel support structure as described in claim 1, characterized in that, The structural steel bars of the excavated section ring beam (203) and the structural steel bars of the connecting section invert arch (102) are connected by a second steel bar.

6. The construction method of the main and auxiliary tunnel support structure as described in claim 1, characterized in that, The two ends of the excavation section (2) along its own radial direction are located between the two ends of the connecting section along its own axial direction.

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