A method for constructing an auxiliary tunnel to a main tunnel and the tunnel structure

Abstract

This invention relates to the field of tunnel construction technology, and particularly to a method for constructing an auxiliary tunnel leading to a main tunnel and the tunnel structure. The construction method includes the following steps: excavating an auxiliary tunnel to a first position; installing a first locking arch frame at the first position; excavating a first cantilevered chamber along a first direction from the first locking arch frame to a second position, and installing at least two first cantilevered arch frames spaced apart along the first direction during the excavation process; installing a second locking arch frame at the second position, opposite to the first locking arch frame; installing a first cantilevered main tunnel arch frame below the first cantilevered arch frame, with one end of the first cantilevered main tunnel arch frame supported by the first locking arch frame and the other end supported by the second locking arch frame, with at least two first cantilevered main tunnel arch frames spaced apart along a second direction; cutting off the lower part of the first cantilevered arch frame and excavating the first main tunnel from the first cantilevered chamber along the second direction. This invention can significantly improve construction efficiency and safety.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a method for constructing an auxiliary tunnel into a main tunnel and a tunnel structure. Background Technology

[0002] In tunnel construction, the transition from auxiliary tunnel to main tunnel is a crucial step, and the quality of its construction directly impacts the progress, safety, and quality of tunnel construction. Current technology typically employs the cantilever method, with the general process as follows: A portal frame is erected at the cantilever, with pre-installed anchor and sprayed support. After this is completed, the main tunnel frame is installed. Once the main tunnel frame is erected within the intersection area of ​​the main tunnel and auxiliary tunnel, one leg of the portal frame is cut towards the greater (or less) mileage direction, and normal excavation and frame erection begin. After approximately 10 meters of tunnel length has been constructed, the tunnel face is sealed, and the temporary support on the other side of the cantilever is removed, allowing for the excavation and support of the other end of the main tunnel. After a certain length of the main tunnel has been constructed at both the greater and lesser mileage directions, a cross passage is excavated, and the above steps are repeated for the cantilever construction of the other side of the main tunnel.

[0003] Traditional tunnel-style cantilever construction has many problems. Due to the limited space in the working area, manual drilling and blasting are used during construction, which can easily lead to accidents such as collapse and explosion, resulting in high safety risks. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of high safety risks caused by the narrow working space in the shed-tunnel method of cantilever construction in the prior art, and to provide an auxiliary tunnel-to-main-tunnel construction method and tunnel structure.

[0005] In a first aspect, the present invention provides a method for assisting in the construction of a tunnel to a main tunnel, comprising the following steps:

[0006] Excavate the auxiliary tunnel to the first position, and install the first locking arch frame at the first position;

[0007] Excavate the first cantilevered chamber along the first direction from the first lock arch frame to the second position, and install the first cantilevered arch frame during the excavation process, with at least two first cantilevered arch frames spaced apart along the first direction;

[0008] A second lock arch is installed at the second position, the second lock arch being opposite to the first lock arch.

[0009] A first cantilever arch frame is installed below the first cantilever arch frame. One end of the first cantilever arch frame is supported by the first locking arch frame, and the other end is supported by the second locking arch frame. At least two first cantilever arch frames are arranged at intervals along the second direction.

[0010] The lower part of the first cantilever arch frame is cut off, and the first main tunnel is excavated from the first cantilever chamber along the second direction.

[0011] The auxiliary tunnel to main tunnel construction method of the present invention directly adopts the full-section excavation method of the auxiliary tunnel to enter the first main tunnel during the auxiliary tunnel to main tunnel construction process. Compared with the existing shed tunnel method of cantilever construction, the working surface is larger, and large-scale machinery can be directly used for construction, which greatly improves construction efficiency and safety. By arranging the first locking arch frame and the second locking arch frame on both sides of the first main tunnel, the support strength of the first cantilever tunnel can be enhanced and the construction safety risk can be reduced. The first cantilever tunnel arch frame can be used as the support structure of the first main tunnel. Installing the first cantilever tunnel arch frame below the first cantilever arch frame is a reinforcement support measure with little disturbance to the surrounding rock and no stress transfer, resulting in high safety.

[0012] Preferably, when excavating the first cantilevered tunnel, construction equipment is used for full-section excavation, and the width and height of the first cantilevered tunnel section in the first direction are both greater than the width and height of the auxiliary tunnel section.

[0013] Preferably, when excavating the first cantilevered chamber, an arched roof with low ends and high middle is formed by constructing obliquely upwards along the first direction; at least two of the first cantilevered arch frames are raised one after another along the first direction and then lowered one after another.

[0014] Preferably, before installing the first cantilevered tunnel arch frame: cover the arch portion of the first and second lock arch frames with geotextile, and then spray concrete onto the sidewall of the first cantilevered tunnel to form a first concrete layer.

[0015] Preferably, the auxiliary tunnel has a reinforced support section, which is close to the first position. The reinforced support section is provided with an inner arch frame and an outer arch frame. The outer arch frame is located outside the inner arch frame. The inner arch frame is arranged in a full ring, and the inner arch frame and the outer arch frame are arranged alternately.

[0016] Preferably, both the first and second locking arch frames are double arch frames; the first and second locking arch frames are arranged in a full circumference; and the first direction and the second direction are perpendicular to each other.

[0017] Preferably, after the second lock arch frame is completed: excavate from the second lock arch frame along the first direction to the third position, install the third lock arch frame at the third position, excavate the second cantilevered chamber along the first direction from the third lock arch frame to the fourth position, and install the second cantilevered arch frame during the excavation process, with at least two second cantilevered arch frames spaced apart along the first direction;

[0018] A second cantilever arch frame is installed below the second cantilever arch frame, and one end of the second cantilever arch frame is supported by the third locking arch frame;

[0019] The lower part of the second cantilever arch frame is cut off, and a second main tunnel is excavated from the second cantilever chamber along the second direction.

[0020] Preferably, before installing the second cantilevered tunnel arch frame: cover the arch of the third lock arch frame with geotextile, and then spray concrete onto the side wall of the second cantilevered tunnel to form a second concrete layer.

[0021] In a second aspect, the present invention provides a tunnel structure constructed using the auxiliary tunnel-to-main tunnel construction method described above, comprising an auxiliary tunnel and a first main tunnel. The auxiliary tunnel is connected to a first side of the first main tunnel, and a first locking arch is provided at the connection point. A second locking arch is provided on the side wall of the first main tunnel, and the second locking arch is opposite to the first locking arch. A first cantilevered main tunnel arch is provided inside the first main tunnel, with one end of the first cantilevered main tunnel arch supported by the first locking arch and the other end supported by the second locking arch.

[0022] In a third aspect, the present invention provides a tunnel structure constructed using the auxiliary tunnel-to-main tunnel construction method described above, comprising an auxiliary tunnel, a cross passage, a first main tunnel, and a second main tunnel. The auxiliary tunnel is connected to a first side of the first main tunnel, and a first locking arch is provided at the connection point. One end of the cross passage is connected to a second side of the first main tunnel, and a second locking arch is provided at the connection point. The other end of the cross passage is connected to a side of the second main tunnel, and a third locking arch is provided at the connection point. A first cantilevered main tunnel arch is provided inside the first main tunnel, with one end of the first cantilevered main tunnel arch supported by the first locking arch and the other end supported by the second locking arch. A second cantilevered main tunnel arch is provided inside the second main tunnel, with one end of the second cantilevered main tunnel arch supported by the ground and the other end supported by the third locking arch.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The auxiliary tunnel to main tunnel construction method of the present invention directly adopts the full-section excavation method of the auxiliary tunnel to enter the first main tunnel during the auxiliary tunnel to main tunnel construction process. Compared with the existing shed tunnel method of cantilever construction, the working surface is larger, and large-scale machinery can be directly used for construction, which greatly improves construction efficiency and safety. By arranging the first locking arch frame and the second locking arch frame on both sides of the first main tunnel, the support strength of the first cantilever tunnel can be enhanced and the construction safety risk can be reduced. The first cantilever tunnel arch frame can be used as the support structure of the first main tunnel. Installing the first cantilever tunnel arch frame below the first cantilever arch frame is a reinforcement support measure with little disturbance to the surrounding rock and no stress transfer, resulting in high safety. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the tunnel structure described in the embodiments of this application;

[0026] Figure 2 This is a side view of the tunnel structure described in the embodiments of this application [omitted: the cantilevered main tunnel arch frame].

[0027] Figure 3 This is a side view of the tunnel structure described in the embodiments of this application [the lower part of the cantilever arch has been removed];

[0028] Figure 4 This is a schematic diagram of the structure of the first cantilevered cavity in an embodiment of this application;

[0029] Figure 5 This is a cross-sectional schematic diagram of the first cantilevered cavity in an embodiment of this application;

[0030] Figure 6 This is a schematic diagram of the double-layer arch frame described in the embodiments of this application;

[0031] Figure 7 This is a side view of the first cantilevered cavity in an embodiment of this application;

[0032] Figure 8 This is a schematic diagram of the structure of the second cantilevered cavity in an embodiment of this application;

[0033] Figure 9 This is a cross-sectional schematic diagram of the second cantilevered cavity in an embodiment of this application;

[0034] Figure 10 This is a side view of the second cantilevered cavity in an embodiment of this application;

[0035] Figure 11 This is a schematic diagram of the construction process of the double-track main tunnel described in the embodiments of this application.

[0036] Marked in the image:

[0037] 1-Auxiliary tunnel;

[0038] 11-First position; 12-First locking arch frame; 13-Inner arch frame; 14-Outer arch frame; 15-Auxiliary tunnel arch frame;

[0039] 2-First cantilevered chamber;

[0040] 21-Second position; 22-Second locking arch frame; 23-First cantilever arch frame; 24-First cantilever main opening arch frame; 25-First concrete layer;

[0041] 3-First main tunnel;

[0042] 31-First main tunnel arch;

[0043] 4-Horizontal channel;

[0044] 41 - Third position; 42 - Third locking arch frame; 43 - Horizontal passage arch frame;

[0045] 5-Second cantilevered chamber;

[0046] 51 - Fourth position; 52 - Second cantilever arch frame; 53 - Second cantilever main tunnel arch frame; 54 - Second concrete layer;

[0047] 6-Second main tunnel;

[0048] 61-Second main tunnel arch;

[0049] 7-Secondary lining. Detailed Implementation

[0050] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0051] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.

[0052] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.

[0053] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0054] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.

[0055] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0056] Example

[0057] like Figures 1 to 10 As shown, in a first aspect, embodiments of this application provide a method for constructing an auxiliary tunnel to a main tunnel, comprising the following steps:

[0058] S1. Excavate the auxiliary tunnel 1 to the first position 11, and install the first locking arch frame 12 at the first position 11;

[0059] S2. Excavate the first cantilevered chamber 2 along the first direction from the first lock arch frame 12 to the second position 21, and install the first cantilevered arch frame 23 during the excavation process, with at least two first cantilevered arch frames 23 spaced apart along the first direction;

[0060] S3. Install the second locking arch 22 at the second position 21, with the second locking arch 22 facing the first locking arch 12;

[0061] S4. Install a first cantilever main tunnel arch 24 below the first cantilever arch 23. One end of the first cantilever main tunnel arch 24 is supported by the first lock arch 12, and the other end is supported by the second lock arch 22. At least two first cantilever main tunnel arch 24 are arranged at intervals along the second direction.

[0062] S5. Cut off the lower part of the first cantilever arch 23 and excavate the first main tunnel 3 from the first cantilever chamber 2 along the second direction.

[0063] The auxiliary tunnel to main tunnel construction method described in this embodiment directly adopts the full-section excavation method of the auxiliary tunnel 1 to enter the first main tunnel 3 during the construction of the auxiliary tunnel 1 to main tunnel. Compared with the existing shed tunnel method of cantilever construction, the working surface is larger, and large-scale machinery can be directly used for construction, which greatly improves construction efficiency and safety. By arranging the first locking arch frame 12 and the second locking arch frame 22 on both sides of the first main tunnel 3, the support strength of the first cantilever tunnel 2 can be enhanced, and the construction safety risk can be reduced. The first cantilever tunnel arch frame 24 can be used as the support structure of the first main tunnel 3. Installing the first cantilever tunnel arch frame 24 below the first cantilever tunnel arch frame 23 is a reinforcement support measure with little disturbance to the surrounding rock and no stress transfer, resulting in high safety.

[0064] In a second aspect, embodiments of this application provide a method for constructing an auxiliary tunnel to a main tunnel, comprising the following steps:

[0065] Step 1: Excavate the auxiliary tunnel 1 along the preset direction until the first position 11. The auxiliary tunnel 1 can be an inclined shaft, a cross passage, etc. As the auxiliary tunnel 1 is excavated, the initial support is gradually constructed in the auxiliary tunnel 1. The initial support preferably includes an initial support arch and a concrete layer. In this embodiment, the initial support arch in the auxiliary tunnel 1 is defined as the auxiliary tunnel arch 15. The first position 11 is the junction between the edge of the first main tunnel 3 and the auxiliary tunnel 1. After excavating to the first position 11, the first locking arch 12 is installed at the first position 11.

[0066] Furthermore, after the initial support is completed, a secondary lining can be constructed, such as... Figure 6 As shown.

[0067] In some embodiments, an advanced geological forecast is conducted when the excavation reaches approximately 1115 to 25 meters from the first location to determine the geological conditions ahead. A site survey is then organized, and the support parameters of the cantilever section and the advanced reinforcement measures are confirmed based on the forecast results. Dynamic adjustments and optimizations can be made if necessary.

[0068] In some embodiments, to improve construction safety, a reinforced support structure is provided within a certain length range of the auxiliary tunnel 1 near the first position 11 to form a reinforced support section. Compared with the support structure of the conventional section, the reinforced support structure has greater load-bearing capacity and better stability, thereby effectively resisting the deformation and pressure of the surrounding rock, preventing tunnel collapse, and ensuring construction safety. Preferably, the length of the reinforced support section is 8 to 12 meters.

[0069] Preferably, the reinforced support structure includes a double-layer arch frame structure, which serves as the initial support arch frame within the reinforced support section. The double-layer arch frame structure includes an inner arch frame 13 and an outer arch frame 14, with the outer arch frame 14 being larger than the inner arch frame 13. Figure 6As shown, the outer arch frame 14 is located outside the inner arch frame 13. The inner arch frame 13 is arranged in a full ring, and the two ends of the outer arch frame 14 are supported on the ground. The full ring arrangement refers to the installation of a closed arch frame along the tunnel excavation outline to form a ring support structure to enhance the stability of the surrounding rock. More preferably, the inner arch frame 13 and the outer arch frame 14 are arranged alternately. When installing the inner arch frame 13, a groove with an opening facing the longitudinal direction of the auxiliary tunnel 1 can be excavated at the edge of the working face of the auxiliary tunnel 1. The inner arch frame 13 is installed in the groove, and the surrounding rock is excavated forward after the support is stable. When installing the outer arch frame 14, a groove with an opening facing the radial direction of the auxiliary tunnel 1 can be excavated on the side wall of the auxiliary tunnel 1. The outer arch frame 14 is installed in the groove.

[0070] In some embodiments, after the support arch is installed, concrete is sprayed onto the tunnel wall to quickly fill the cracks on the surrounding rock surface, isolate air and water, and prevent weathering and spalling.

[0071] Step 2: After the first locking arch frame 12 is constructed and the inner arch frame 13 is completed and the inverted arch is closed into a ring, the first cantilevered chamber 2 is excavated from the first locking arch frame 12 along the first direction until the second position 21.

[0072] Preferably, the first direction is parallel to the longitudinal direction of the auxiliary tunnel 1 at the first position 11, that is, the first direction is parallel to the opening direction of the first locking arch 12.

[0073] In some embodiments, when constructing the first cantilevered tunnel 2, the reinforced support at the lock position is crucial. Therefore, preferably, the first lock arch frame 12 adopts a double arch frame. Specifically, the double arch frame can adopt a double I20b type steel frame with a spacing of 0.4m. The two steel frames are set vertically and a connector can be set between them. In addition to having greater support strength and stability, the double arch frame also has a larger width, which facilitates the subsequent placement of the first cantilevered tunnel arch frame 24. Specifically, the first cantilevered tunnel arch frame 24 can be placed on the steel frame of the double arch frame that is closer to the first cantilevered tunnel arch frame 24.

[0074] Preferably, in order to prevent the landing point of the first cantilever arch 24 on the first locking arch 12 from being covered by shotcrete, which would make subsequent removal difficult, the landing point can be marked on the top of the first locking arch 12 according to the spacing of the first cantilever arch 24, and geotextile can be covered before spraying circulating concrete. When installing the first cantilever arch 24, the geotextile can be removed, thus reducing the time for cleaning the shotcrete.

[0075] It should be noted that the first locking arch frame 12 must be accurately positioned and must not encroach on the clearance of the first cantilevered chamber 2. Because the excavation volume of the first cantilevered chamber 2 is large, attention should be paid to ensuring that the shotcrete is full and dense to prevent voids and to ensure the strength and stability of the locking.

[0076] In some embodiments, after excavation to the second position 21, a second locking arch 22 is installed at the second position 21. The second locking arch 22 is spaced apart from the first locking arch 12. The second locking arch 22 may adopt the same or similar structural form and construction method as the first locking arch 12. For details, please refer to the above description, which will not be repeated here.

[0077] In some embodiments, when excavating the first cantilevered chamber 2, large-scale mechanical equipment is used to excavate the first cantilevered chamber 2 from the full cross-section of the auxiliary tunnel 1, that is, to carry out full-section excavation. Full-section excavation refers to excavating and shaping the entire cross-section of the tunnel or underground project in one go, which can make full use of the cross-sectional advantages of the auxiliary tunnel 1, and large-scale mechanical equipment can be directly used for construction, greatly improving construction efficiency. Compared with the cantilevered construction of the existing tunnel, full-section excavation avoids the disadvantage of the narrow working space during cantilevered construction, which can only use manual drilling and blasting, and can greatly reduce construction risks.

[0078] In some embodiments, during the excavation of the first cantilevered chamber 2, a first cantilevered arch 23 is installed to support the first cantilevered chamber 2, and at least two first cantilevered arches 23 are spaced apart along a first direction; such as Figures 2 to 5 As shown, the first cantilever arch 23 can be parallel to the inner arch 13 and outer arch 14 of the auxiliary tunnel 1. The first cantilever arch 23 is a temporary support structure, which can be cut off or removed as needed later.

[0079] In some embodiments, in order to leave room for the installation of other support structures and not to encroach on the cavern space, when excavating the first cantilevered cavern 2, the width and height of the cross section of the first cantilevered cavern 2 in the first direction are both greater than the width and height of the cross section of the auxiliary tunnel 1. The first cantilevered arch 23 can be set against the wall, and the two ends of the first cantilevered arch 23 can be supported on the ground.

[0080] In some embodiments, further, in order to adapt to the shape of the arch of the first cantilevered main tunnel arch 24, when excavating the top of the first cantilevered tunnel 2, an arc-shaped arch with low ends and high middle is formed along the first direction by constructing obliquely upwards, and several first cantilevered arches 23 are raised one by one along the first direction and then lowered one by one. This construction method enables the arch of the first cantilevered main tunnel arch 24 to gradually take shape and meet the design requirements.

[0081] In some embodiments, after the first cantilever arch 23 is installed, concrete is sprayed onto the side wall of the first cantilever chamber 2 to form a first concrete layer 25.

[0082] Step 3: Install the first cantilever main tunnel arch frame 24 below the first cantilever arch frame 23, as follows: Figure 5As shown, the first cantilever arch frame 24 is arc-shaped and one end is supported by the first lock arch frame 12, and the other end is supported by the second lock arch frame 22. At least two first cantilever arch frames 24 are arranged at intervals along the second direction.

[0083] Preferably, all the first cantilever arch frames 23 can be located outside the first cantilever main tunnel arch frame 24, thereby reducing the excessive consumption and safety hazards caused by the outward expansion of the excavation outline; at the first cantilever tunnel 2, as the arch gradually rises and the width on the left and right sides gradually increases, the dimensions of each first cantilever arch frame 23 are different. Therefore, the first cantilever arch frames 23 need to be processed and numbered in advance to ensure that the widening of each steel frame is gradual and straight, and the tunnel is formed smoothly and beautifully; the first cantilever arch frames 23 are supported within the excavation range of the upper step of the main tunnel. The excavation section is constructed normally with anchor bolts. The footing position can be supported by φ42 locking anchor pipes, each 4m long. These anchor bolts and locking anchor pipes can enhance the connection between the steel frame and the surrounding rock and improve the stability of the support structure.

[0084] Preferably, the first cantilever arch frame 24 is a symmetrical structure, and the heights of the arches of the first locking arch frame 12 and the second locking arch frame 22 correspond to each other, so that the heights of the two ends of the first cantilever arch frame 24 are equal.

[0085] Preferably, before installing the first cantilevered main tunnel arch frame 24: cover the arch of the first locking arch frame 12 and the second locking arch frame 22 with geotextile, and then spray concrete onto the side wall of the first cantilevered tunnel 2.

[0086] Step 4: After the construction of the first cantilevered chamber 2 is completed, the excavation of the first main tunnel 3 can be carried out. During the excavation process, the first main tunnel arch frame 31 is installed for support. At this time, the tunnel construction enters the normal process. The subsequent excavation, support, lining and other work can be carried out in accordance with normal construction technology and standards. Specifically, the lower part of the first cantilevered arch frame 23 can be cut off, and then the first main tunnel 3 can be excavated from the first cantilevered chamber 2 along the second direction.

[0087] In this embodiment, the first direction is the orientation of the auxiliary tunnel 1 near the first main tunnel 3, and the second direction is the orientation of the first main tunnel 3 where it connects with the auxiliary tunnel 1; preferably, the second direction is perpendicular to the first direction.

[0088] Preferably, this application embodiment provides a specific construction step:

[0089] 1. Before entering the main tunnel 1, 15-20m before the roof is lifted, a set of advanced geological forecasts are carried out to determine the geological environment ahead; 20m before entering the main tunnel, the main responsible parties are organized to conduct on-site inspections, analyze the advanced geological forecast data, and dynamically confirm the support parameters and advanced reinforcement measures for the main tunnel roof lifting.

[0090] 3. Reinforcement support begins 10m from the top section of auxiliary tunnel 1;

[0091] 4. Construction of double arch frames at the cantilever lock joint location;

[0092] 5. Construct the cantilever arch frame along the outline of the main tunnel;

[0093] 6. Construction of the arch frame for the main opening;

[0094] 7. Normal construction of the main tunnel.

[0095] In a third aspect, embodiments of this application provide a method for constructing an auxiliary tunnel to a main tunnel, which, in addition to the steps described above, also includes the following steps: after installing the second locking arch frame 22, excavating a transverse passage 4 from the second locking arch frame 22 to a third position 41, installing a third locking arch frame 42 at the third position 41, excavating a second cantilevered chamber 5 along the first direction from the third locking arch frame 42 to a fourth position 51, and installing a second cantilevered arch frame 52 during the excavation process, with at least two second cantilevered arch frames 52 spaced apart along the first direction; installing a second cantilevered main tunnel arch frame 53 below the second cantilevered arch frame 52, with one end of the second cantilevered main tunnel arch frame 53 supported by the third locking arch frame 42; cutting off the lower part of the second cantilevered arch frame 52, and excavating a second main tunnel 6 from the second cantilevered chamber 5 along the second direction.

[0096] The transverse passage is a tunnel structure that connects the first main tunnel 3 and the second main tunnel 6. Preferably, the transverse passage 4 is parallel to the first direction and is excavated from the position of the second locking arch 22 along the first direction. This not only forms the transverse passage 4, but also allows the second main tunnel 6 to be formed by excavating through the transverse passage 4 to the main tunnel. During the excavation of the transverse passage 4, the transverse passage arch 43 is installed in a timely manner. The construction steps for the transverse passage 4 to the second main tunnel 6 can refer to the construction steps for the auxiliary tunnel 1 to the first main tunnel 3 as described above. That is, first, the second cantilever arch 52 is constructed, and the arch of the third locking arch 42 is covered with geotextile. Then, concrete is sprayed into the second cantilever chamber 5 to form the second concrete layer 54, and then the second cantilever main tunnel arch 53 is installed. After the second cantilever chamber 5 is completed, the lower part of the second cantilever main tunnel arch 53 can be cut off, and the second main tunnel 6 is excavated from the second cantilever chamber 5 along the second direction. During the excavation process, the second main tunnel arch 61 is constructed for support.

[0097] In this embodiment, the first position 11 is the junction of the auxiliary tunnel 1 and the first main tunnel 3, the second position 21 is the junction of the transverse passage 4 and the first main tunnel 3, the third position 41 is the junction of the transverse passage 4 and the second main tunnel 6, and the fourth position 51 is the side wall opposite to the second main tunnel 6 and the transverse passage 4.

[0098] Preferably, a fourth locking arch frame can also be set at the fourth position 51. The fourth locking arch frame is spaced apart from and opposite to the third locking arch frame 42. One end of the second cantilever tunnel arch frame 53 is supported by the third locking arch frame 42, and the other end is supported by the fourth locking arch frame. Of course, when excavating the second cantilever tunnel 5, if it is not necessary to continue excavating the passage on the other side of the second cantilever tunnel 5, the locking arch frame can be omitted at the fourth position 51, and one end of the second cantilever tunnel arch frame 53 can be supported on the ground.

[0099] Reinforced support sections can be installed at the locations of the transverse passage 4 near the first main tunnel 3 and the second main tunnel 6. That is, a reinforced support structure consisting of an inner arch frame 13 and an outer arch frame 14 can be installed, as described above.

[0100] like Figure 11 As shown, Figure 11 This is a schematic diagram of the construction process for a double-track main tunnel.

[0101] The auxiliary tunnel to main tunnel construction method described in this embodiment involves directly excavating the cross section of the auxiliary tunnel 1 into the first main tunnel 3 using the full-section excavation method. Then, through the cross passage 4 between the main tunnels, the second main tunnel 6 on the right line is entered from the first main tunnel 3 on the left line in one go. Within the range of the main tunnels on the left and right lines, construction is carried out by gradually raising the tunnel to the arch and then gradually lowering it, based on the precisely measured excavation outline of the main tunnel. This ensures the accurate reservation of the installation position of the main tunnel arch frame. Double arch frames are used for support at the lock position, the intersection of the cross passage 4, and the end position of the right line cantilever, which facilitates the landing of the cantilever main tunnel arch frame.

[0102] In a fourth aspect, this application provides a tunnel structure constructed using the auxiliary tunnel to main tunnel construction method described above. The structure includes an auxiliary tunnel 1 and a first main tunnel 3. The auxiliary tunnel 1 is connected to the first side of the first main tunnel 3, and a first locking arch 12 is provided at the connection point. A first cantilever arch 23 is provided in the first main tunnel 3 at the position corresponding to the auxiliary tunnel 1. A first cantilever main tunnel arch 24 is installed below the first cantilever arch 23, and one end of the first cantilever main tunnel arch 24 is supported on the first locking arch 12.

[0103] Preferably, a second locking arch frame 22 is provided inside the first main opening 3. The second locking arch frame 22 is opposite to the first locking arch frame 12, and the other end of the first cantilever main opening arch frame 24 is supported on the second locking arch frame 22.

[0104] In a fifth aspect, this application provides a tunnel structure constructed using the auxiliary tunnel-to-main tunnel construction method described above. The structure includes an auxiliary tunnel 1, a transverse passage 4, a first main tunnel 3, and a second main tunnel 6. The auxiliary tunnel 1 is connected to the first side of the first main tunnel 3, and a first locking arch 12 is provided at the connection point. One end of the transverse passage 4 is connected to the second side of the first main tunnel 3, and a second locking arch 22 is provided at the connection point. The other end of the transverse passage 4 is connected to the side of the second main tunnel 6, and a third locking arch 42 is provided at the connection point. A first cantilevered main tunnel arch 24 is provided inside the first main tunnel 3, with one end supported by the first locking arch 12 and the other end supported by the second locking arch 22. A second cantilevered main tunnel arch 53 is provided inside the second main tunnel 6, with one end supported on the ground and the other end supported by the third locking arch 42.

[0105] Compared with the prior art, the technical solution described in this embodiment has at least the following beneficial effects:

[0106] 1. Novel Construction Method: Compared with the traditional cantilever tunnel construction method, the construction method described in this embodiment transforms the cantilever tunnel construction process into normal auxiliary tunnel 1 construction and normal main tunnel frame support construction. During construction, the arch frames are raised one by one along the outer edge of the main tunnel excavation outline to ensure the main tunnel construction cross-section. Once the cantilever tunnel is completed, the cantilever tunnel arch frame can be constructed. This method has the following advantages: a. Mechanized construction, low risk, and high efficiency; b. Fast construction speed, rapid process conversion, and short construction period; c. No stress transfer in the cantilever tunnel support structure, with the main tunnel arch frame directly below the already constructed cantilever tunnel arch frame, constituting a reinforced support measure with high safety; d. Good overall alignment control of the cantilever tunnel, with the cantilever working surface formed in one step; e. No need for additional cantilever tunnel arch frame measures, resulting in low construction costs.

[0107] 2. Guaranteed construction quality: The construction of the cantilevered cavern is divided into two stages of shotcrete support, which minimizes the disturbance to the surrounding rock within the excavation outline and reduces the difficulty of controlling the excavation outline. This greatly ensures the construction quality of the cantilevered cavern and reduces the risk of voids in the initial support.

[0108] 3. Saves construction time: Using the construction method described in this embodiment, it only takes 28 days from the start of the reinforced support section of the auxiliary tunnel 1 to the completion of the 3 cantilevered tunnels to form 6 main tunnel working faces [including the construction of the approximately 43m cross passage 4 between the two main tunnels]. This saves one month compared to the original cantilevered tunnel scheme with a 61-day construction period, providing a better guarantee for the subsequent assembly of main tunnel equipment to form a normal construction state.

[0109] 4. Improved safety: ① The construction of the cantilevered tunnel is divided into two-stage support construction, and the main tunnel arch frame is constructed below the cantilevered support of auxiliary tunnel 1. The disturbance to the surrounding rock is small during the entire construction period and there is no change in the stress structure, so the safety is high; ② The cantilevered tunnel adopts the full-section advancement of auxiliary tunnel 1, which has a larger working surface than the tunnel construction method. Large machinery can be used directly for construction, which greatly improves construction efficiency and safety.

[0110] 5. Economic Benefits: When constructing within the main tunnel area, this construction method allows for the direct use of large machinery in the auxiliary tunnel section 1. These large machines possess high operational efficiency, enabling rapid completion of excavation and transportation. Compared to traditional tunnel roof construction, which relies solely on manual drilling and blasting, this significantly shortens the time required for each construction cycle. The rapid construction progress allows the tunnel to enter the normal construction phase more quickly, which is crucial for shortening the overall tunnel project duration, enabling earlier completion, reducing the construction cycle, and lowering project management costs.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing an auxiliary tunnel to a main tunnel, characterized in that, Includes the following steps: Excavate the auxiliary tunnel (1) until the first position (11), and install the first locking arch frame (12) at the first position (11). Excavate the first cantilevered chamber (2) along the first direction from the first lock arch frame (12) to the second position (21), and install the first cantilevered arch frame (23) during the excavation process, with at least two first cantilevered arch frames (23) spaced apart along the first direction; A second locking arch (22) is installed at the second position (21), the second locking arch (22) being opposite to the first locking arch (12); A first cantilever arch frame (24) is installed below the first cantilever arch frame (23). One end of the first cantilever arch frame (24) is supported by the first lock arch frame (12), and the other end is supported by the second lock arch frame (22). At least two first cantilever arch frames (24) are arranged at intervals along the second direction. Cut off the lower part of the first cantilever arch frame (23) and excavate the first main tunnel (3) from the first cantilever cave (2) along the second direction. When excavating the first cantilevered tunnel (2), construction equipment is used to carry out full-section excavation, and the width and height of the first cantilevered tunnel (2) in the first direction are both greater than the width and height of the auxiliary tunnel (1). When excavating the first cantilevered chamber (2), an arc-shaped arch with low ends and high middle is formed by constructing obliquely upwards along the first direction; at least two of the first cantilevered arch frames (23) are raised one by one along the first direction and then lowered one by one. The auxiliary tunnel (1) has a reinforced support section, which is close to the first position (11). The reinforced support section is provided with an inner arch frame (13) and an outer arch frame (14). The outer arch frame (14) is located outside the inner arch frame (13). The inner arch frame (13) is arranged in a full ring, and the inner arch frame (13) and the outer arch frame (14) are arranged alternately. The first locking arch frame (12) and the second locking arch frame (22) are both double arch frames; the first locking arch frame (12) and the second locking arch frame (22) are arranged in a full ring; the first direction and the second direction are perpendicular to each other; After the second lock arch frame (22) is completed: excavate from the second lock arch frame (22) along the first direction to the third position (41), install the third lock arch frame (42) at the third position (41), excavate the second cantilevered chamber (5) along the first direction from the third lock arch frame (42) to the fourth position (51), and install the second cantilevered arch frame (52) during the excavation process, with at least two second cantilevered arch frames (52) spaced apart along the first direction; A second cantilever arch (53) is installed below the second cantilever arch (52), and one end of the second cantilever arch (53) is supported by the third lock arch (42). Cut off the lower part of the second cantilever arch (52) and excavate the second main tunnel (6) from the second cantilever chamber (5) along the second direction.

2. The auxiliary tunnel to main tunnel construction method according to claim 1, characterized in that, Before installing the first cantilevered tunnel arch frame (24): cover the arch of the first lock arch frame (12) and the second lock arch frame (22) with geotextile, and then spray concrete onto the side wall of the first cantilevered tunnel (2) to form the first concrete layer (25).

3. The auxiliary tunnel to main tunnel construction method according to claim 1, characterized in that, Before installing the second cantilevered tunnel arch frame (53): cover the arch of the third lock arch frame (42) with geotextile, and then spray concrete onto the side wall of the second cantilevered tunnel (5) to form a second concrete layer (54).

4. A tunnel structure, characterized in that, The auxiliary tunnel to main tunnel construction method as described in any one of claims 1-3 is adopted, including an auxiliary tunnel (1) and a first main tunnel (3). The auxiliary tunnel (1) is connected to the first side of the first main tunnel (3) and a first locking arch frame (12) is provided at the connection. The side wall of the first main tunnel (3) is provided with a second locking arch frame (22), and the second locking arch frame (22) is opposite to the first locking arch frame (12). A first cantilevered main tunnel arch frame (24) is provided in the first main tunnel (3). One end of the first cantilevered main tunnel arch frame (24) is supported on the first locking arch frame (12), and the other end is supported on the second locking arch frame (22).

5. A tunnel structure, characterized in that, The auxiliary tunnel to main tunnel construction method as described in claim 1 or 3 is adopted, including an auxiliary tunnel (1), a cross passage (4), a first main tunnel (3) and a second main tunnel (6). The auxiliary tunnel (1) is connected to the first side of the first main tunnel (3) and a first locking arch frame (12) is provided at the connection. One end of the cross passage (4) is connected to the second side of the first main tunnel (3) and a second locking arch frame (22) is provided at the connection. The other end of the cross passage (4) is connected to the side of the second main tunnel (6) and a third locking arch frame (42) is provided at the connection. A first cantilevered main tunnel arch frame (24) is provided in the first main tunnel (3). One end of the first cantilevered main tunnel arch frame (24) is supported on the first locking arch frame (12) and the other end is supported on the second locking arch frame (22). A second cantilevered main tunnel arch frame (53) is provided in the second main tunnel (6). One end of the second cantilevered main tunnel arch frame (53) is supported on the ground and the other end is supported on the third locking arch frame (42).

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