Excavation construction method of double-arch multi-section variable cross-section underground excavation tunnel structure

Abstract

The invention discloses an excavation construction method of a double-arch multi-section variable-section underground excavation tunnel structure, and relates to the technical field of tunnel construction, the double-arch multi-section variable-section underground excavation tunnel structure comprises a tunnel main body, and is characterized in that the tunnel main body adopts a horseshoe-shaped section form, comprises a left hole and a right hole, and is provided with a primary support and a forepoling; a double-arch partition wall is arranged between the left hole and the right hole; the left hole comprises a pilot tunnel I and a pilot tunnel II; a temporary support is arranged between the first pilot tunnel and the second pilot tunnel, and the first pilot tunnel comprises a first upper left pilot tunnel and a first lower left pilot tunnel; the pilot tunnel II comprises a left upper pilot tunnel II and a left lower pilot tunnel II; the right hole comprises a pilot tunnel III and a pilot tunnel IV; a horseshoe-shaped section is adopted to adapt to the compression characteristic of surrounding rock; a plurality of pilot tunnels are excavated at intervals, so that the excavation interval of the left pilot tunnel and the right pilot tunnel is adjusted, the stress concentration of middle rock pillars is reduced, the risks of surrounding rock collapse and excessive surface settlement are reduced, and the safety and the stability of small-clear-distance double-arch tunnel construction are improved.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel construction, and in particular to an excavation construction method for a double-arch multi-section variable-section dark-cut tunnel structure. Background Art

[0002] A twin-arch tunnel is a special underground tunnel structure consisting of two adjacent single-arch tunnels connected by a central partition wall. Characterized by a large span, shallow burial depth, and complex geological conditions, it is often used in urban rail transit, municipal road projects, and other complex environments such as densely populated buildings and underground pipelines. Its construction requires comprehensive consideration of multiple factors, including structural stress, ground deformation control, and construction safety. The core objective is to control surface subsidence and structural deformation while ensuring construction safety, thereby ensuring a safe surrounding environment.

[0003] In the prior art, double-arch tunnel construction usually adopts the CD method (cross-diaphragm method) or the CRD method (an improved version of the cross-diaphragm method) for partial excavation.

[0004] Regarding the above-mentioned related technologies, the inventors believe that when the traditional CD method or CRD method is used in the construction of a small-spacing double-arch tunnel, the excavation interval between the left and right pilot pits is relatively short, which can easily lead to stress concentration in the middle rock column, which may cause surrounding rock collapse or excessive surface settlement. Summary of the Invention

[0005] The purpose of this application is to provide an excavation construction method for a double-arch multi-section variable-section dark-bored tunnel structure, so as to improve the problem that when constructing a double-arch tunnel with a small clearance distance using the traditional CD method or CRD method, the excavation interval between the left and right pilot pits is short, which easily leads to stress concentration in the middle rock column and may cause surrounding rock collapse or excessive surface settlement.

[0006] This application provides an excavation construction method for a double-arch multi-section variable-section dark-cut tunnel structure, which adopts the following technical solution:

[0007] A double-arch multi-section variable-section dark-excavated tunnel structure includes a tunnel body, characterized in that: the tunnel body adopts a horseshoe-shaped cross-section, the tunnel body includes a left tunnel and a right tunnel, the tunnel body is provided with initial support and advance support, a double-arch partition wall is provided between the left tunnel and the right tunnel; the left tunnel includes guide tunnel 1 and guide tunnel 2; a temporary support is provided between guide tunnel 1 and guide tunnel 2, the guide tunnel 1 includes upper left guide tunnel 1 and lower left guide tunnel 1; the guide tunnel 2 includes upper left guide tunnel 2 and lower left guide tunnel 2; the right tunnel includes guide tunnel 3 and guide tunnel 4 located below guide tunnel 3.

[0008] By adopting the above technical solution, a horseshoe-shaped cross-section is adopted to adapt to the compressive characteristics of the surrounding rock. The arc-shaped top of the initial support helps to evenly transfer the load and resist lateral pressure. The closed arch forms an integral bearing ring, reducing bottom uplift. The left tunnel is divided into the upper left pilot tunnel 1, the lower left pilot tunnel 1, the upper left pilot tunnel 2 and the lower left pilot tunnel 2, and the right tunnel is divided into pilot tunnels 3 and 4. Temporary supports and double-arch partition walls are set up, which changes the excavation mode of the traditional CD method or CRD method, enables the excavation interval of the left and right pilot pits to be adjusted, reduces the stress concentration of the middle rock column, reduces the risk of surrounding rock collapse and excessive surface settlement, and improves the safety and stability of the small-clearance double-arch tunnel construction. At the same time, multiple pilot tunnels are excavated in steps, which reduces the cross-sectional area of ​​a single excavation, reduces the construction difficulty and the disturbance to the surrounding rock, effectively controls the deformation of the surrounding rock, and improves construction safety.

[0009] Optionally, the initial support includes a primary sprayed concrete layer and a number of hollow grouting anchor rods arranged on the inner wall of the tunnel body, and the number of the hollow grouting anchor rods are in a plum blossom shape and penetrate the primary sprayed concrete layer and are inserted into the inner wall of the tunnel body. A steel frame mesh is fixed to one end of the several hollow grouting anchor rods located in the tunnel body, and a steel arch frame is provided on the side of the steel frame mesh away from the inner wall of the tunnel. The primary sprayed concrete layer is provided with a re-sprayed concrete layer, and the re-sprayed concrete layer covers the hollow grouting anchor rods, the steel frame mesh and the steel arch frame.

[0010] By adopting this technical solution, the initial sprayed concrete layer of the primary support can promptly seal the rock surface, preventing weathering and block shedding of the surrounding rock. Hollow grouting anchors are inserted into the inner wall of the tunnel body in a plum blossom pattern. Grouting tightly bonds the anchors to the surrounding rock, transferring the surrounding rock load to the deeper, stable rock mass and enhancing the surrounding rock's self-bearing capacity. The steel mesh and steel arch together form the skeleton of the primary support, improving the overall stiffness and load-bearing capacity of the support structure. The secondary sprayed concrete layer encases the hollow grouting anchors, steel mesh, and steel arch, forming a unified primary support structure. This further improves the stability and durability of the support structure and effectively ensures safety during tunnel construction and operation.

[0011] Optionally, the inner side wall of the tunnel body is provided with a number of locking bars passing through the steel frame mesh on both sides of the steel arch frame, and the several locking bars are located around the intersection of the horizontal and vertical steel bars of the steel frame mesh. A locking block is provided at one end of the locking bar passing through the steel frame mesh, and the locking block is provided with a number of perforations corresponding to the locking bar, and the perforation bending setting makes the locking bar bend outward; the locking block is provided with a clamping cylinder, and the locking blocks located on both sides of the steel arch frame are connected to the horizontal bar against the inner side wall of the steel arch frame through the clamping cylinder.

[0012] By adopting the above technical solution, the locking bars pass through the steel frame mesh and are connected to the cross bars through the locking blocks, and the locking bars are bent and divergent outward, which helps to better transfer the load borne by the steel arch frame to the surrounding rock, strengthens the connection between the steel arch frame and the surrounding rock, and enables the support structure and the surrounding rock to work together; the locking blocks bend the locking bars to fix the steel frame mesh, thereby improving the stability of the steel frame mesh. At the same time, the locking blocks fix the cross bars through the clamping cylinders, and the cross bars are against the inner wall of the steel arch frame, further limiting the deformation of the steel arch frame, improving the overall stability of the support structure, and being able to better maintain the structure when the tunnel is subjected to complex surrounding rock pressure.

[0013] Optionally, a plurality of locking anchor rods are provided on the inner side wall of the tunnel body, and the locking anchor rods are bent at one end away from the inner side wall of the tunnel body and fixed to the steel arch frame; a stabilizing plate is provided on the bottom surface of the steel arch frame along the traveling direction of the tunnel body.

[0014] By adopting the above technical solution, the end of the locking anchor rod away from the inner wall of the tunnel body is bent and fixed to the steel arch frame, which can limit the sinking and horizontal displacement of the steel arch frame and enhance the bottom stability of the support structure; the stabilizing plate arranged on the bottom surface of the steel arch frame increases the contact area between the steel arch frame and the surrounding rock, disperses the pressure transmitted from the steel arch frame to the surrounding rock, reduces the possibility of surrounding rock damage due to excessive local stress, and improves the safety of tunnel construction and operation under adverse geological conditions such as weak surrounding rock.

[0015] Optionally, the advance support is provided with a number of additional advance small ducts on the basis of the initial support. The advance small ducts are located on one side of the steel arch and are distributed in a plum blossom shape. The advance small ducts are arranged at an angle of 10° to 15° to the horizontal line along the direction of travel of the tunnel main body.

[0016] By adopting the above technical solution, before tunnel excavation, grouting is performed into the surrounding rock through the advance small guide tube, which can reinforce the surrounding rock in front of the excavation face, form an advance reinforcement arch, enhance the stability of the surrounding rock, and reduce the collapse and deformation of the surrounding rock during excavation; at the same time, the advance small guide tube can also play a certain advance support role, share part of the surrounding rock load, reduce the stress of the initial support, and ensure construction safety.

[0017] Optionally, the advance small tube is hollow and has a pointed cone drill bit at the front end. The outer wall of the advance small tube is plum blossom-shaped and connected to the interior with a grouting hole, and the grouting hole is inclined outward along the axial direction; the pointed cone drill bit is connected to the interior of the advance small tube and has several separation grooves to enhance the grouting efficiency.

[0018] By adopting the above technical solution, the hollow setting of the advance small guide tube and the pointed cone drill bit at the front end facilitate the insertion of the small guide tube into the surrounding rock, and the grouting holes on the outer wall are inclined outward along the axial direction, which is conducive to the diffusion of slurry in the surrounding rock, enhances the grouting effect, and enables the slurry to better fill the cracks in the surrounding rock and reinforce the surrounding rock; the dividing groove in the pointed cone drill bit further enhances the grouting efficiency, enables the slurry to be injected into the surrounding rock more quickly and evenly, and improves the construction quality and efficiency of the advance support.

[0019] Optionally, the tunnel body is provided with a secondary lining structure, which includes a left-line secondary lining in the left tunnel and a right-line secondary lining in the right tunnel. The bottom surfaces of the left tunnel and the right tunnel are both provided with inverted arches. The left-line secondary lining connects the inverted arch and the left side of the double arch partition wall, and the right-line secondary lining connects the inverted arch and the right side of the double arch partition wall.

[0020] By adopting the above technical solution, the secondary lining structure set up in the tunnel body includes the left-line secondary lining and the right-line secondary lining, which are connected with the invert arch and double-arch partition wall to form a closed structural system, thereby improving the overall bearing capacity and waterproof performance of the tunnel. During the operation of the tunnel, the secondary lining structure can withstand the long-term pressure of the surrounding rock and other external loads, ensuring the structural safety and normal use of the tunnel. At the same time, the closed structural system is also conducive to preventing groundwater leakage and protecting the equipment and environment in the tunnel.

[0021] Another object of the present application is to provide a method for excavating a double-arch multi-section variable-section dark-cut tunnel structure, which adopts the following technical solution: the left tunnel adopts the step method to sequentially excavate the upper left pilot tunnel 1, the lower left pilot tunnel 1, the upper left pilot tunnel 2, and the lower left pilot tunnel 2; the right tunnel adopts the tunnel CD method to sequentially excavate the pilot tunnel 3 and the pilot tunnel 4.

[0022] By adopting the above technical solution, the left tunnel adopts the step method and the right tunnel adopts the tunnel CD method for excavation construction, combining the advantages of the two methods. The step method of the left tunnel is excavated in steps, which reduces the excavation section and reduces the disturbance to the surrounding rock. The CD method of the right tunnel has certain advantages in controlling the deformation of the surrounding rock during the excavation process. It can coordinate the excavation of the left and right tunnels with each other, further reduce the impact on the central rock column, reduce stress concentration, help ensure construction safety, and improve construction efficiency.

[0023] Optionally, when the left-hole step method is used for excavation, the cyclic advance of the upper step and the upper left pilot tunnel 1 and the upper left pilot tunnel 2 shall not exceed the spacing of 1 steel frame, and the lower step and the lower left pilot tunnel 1 and the lower left pilot tunnel 2 shall lag behind the upper step by 2-3 steel frame spacings. After excavation, initial support and advance support shall be applied in time, and the temporary support shall be removed after the initial support is closed into a ring.

[0024] By adopting the above technical solution, the control of the cycle advance and step lag distance during the left-hole step method excavation, as well as the timely implementation of initial support and advance support, and the removal of temporary support after closing the ring, ensure the stability of the surrounding rock during the excavation process; the smaller cycle advance and reasonable step lag distance reduce the exposure time and deformation of the surrounding rock, and timely support can quickly reinforce the surrounding rock. The removal of temporary support after closing the ring enables the support structure to better play its overall role, effectively ensuring the safety and quality of the tunnel construction process.

[0025] Optionally, when the right tunnel adopts the CD method to excavate the pilot tunnel three and the pilot tunnel four, the advance per cycle shall not be greater than the spacing between 1 steel frames. The heading face shall be closed immediately after excavation, and the initial support and advance support shall be installed in time. The construction of the double arch section shall follow the principle of "left line first and right line later".

[0026] By adopting the above technical solution, measures such as limiting the cyclic advance when the CD method is used for excavation of the right tunnel, timely closing the tunnel face, and timely installing support can effectively control the risk of surrounding rock deformation and collapse during the excavation of the right tunnel; the advance per cycle is no more than the spacing between one steel frame, which reduces the impact range of a single excavation, timely closing the tunnel face prevents tunnel face collapse, and timely installation of initial support and advance support enhances the stability of the surrounding rock; the construction principle of "left line first, then right line" enables the construction of the left and right tunnels to cooperate with each other, better protect the middle rock pillar, reduce the possibility of surrounding rock collapse and excessive surface settlement during construction, and ensure construction safety and project quality.

[0027] In summary, the present application includes at least one of the following beneficial technical effects of the excavation construction method of a double-arch multi-section variable-section dark-cut tunnel structure:

[0028] 1. The horseshoe-shaped cross-section is adapted to the compressive characteristics of the surrounding rock. The arc-shaped top of the initial support helps to evenly transfer the load and resist lateral pressure. The closed inverted arch forms an integral load-bearing ring, reducing bottom uplift. The left tunnel is divided into the upper left pilot tunnel 1, lower left pilot tunnel 1, upper left pilot tunnel 2, and lower left pilot tunnel 2, and the right tunnel is divided into pilot tunnels 3 and 4. Temporary supports and double-arch partition walls are installed. This changes the excavation mode of the traditional CD or CRD method, allowing the excavation interval of the left and right pilot pits to be adjusted, reducing stress concentration in the middle rock column, lowering the risk of surrounding rock collapse and excessive surface settlement, and improving the safety and stability of the close-spacing double-arch tunnel construction. At the same time, multiple pilot tunnels are excavated in stages, reducing the cross-sectional area of ​​a single excavation, reducing construction difficulty and disturbance to the surrounding rock, effectively controlling surrounding rock deformation, and improving construction safety.

[0029] 2. The locking bars pass through the steel mesh and are connected to the cross bars through locking blocks. The locking bars are bent and divergent outward, which helps to better transfer the load on the steel arch to the surrounding rock, strengthen the connection between the steel arch and the surrounding rock, and enable the support structure and the surrounding rock to work together. The locking blocks bend the locking bars to fix the steel mesh, improving the stability of the steel mesh. At the same time, the locking blocks fix the cross bars through the clamping tubes. The cross bars abut against the inner wall of the steel arch, further limiting the deformation of the steel arch and improving the overall stability of the support structure. When the tunnel is subjected to complex surrounding rock pressure, it can better maintain the integrity of the structure.

[0030] 3. The excavation construction method of using the step method for the left tunnel and the tunnel CD method for the right tunnel combines the advantages of both methods. The step method for the left tunnel is excavated in steps, which reduces the excavation cross-section and minimizes disturbance to the surrounding rock. The CD method for the right tunnel has certain advantages in controlling surrounding rock deformation during excavation. It can coordinate the excavation of the left and right tunnels, further reduce the impact on the central rock column, reduce stress concentration, help ensure construction safety, and improve construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram for illustrating the left hole structure in the embodiment;

[0032] Figure 2 is a schematic diagram for illustrating the right hole structure in the embodiment;

[0033] Figure 3 It is a schematic diagram of the overall structure of a double-arch multi-section variable-section underground tunnel;

[0034] Figure 4 is a schematic cross-sectional view of the initial support structure in the embodiment;

[0035] Figure 5 It is a schematic diagram of the overall structure of the initial support structure in the embodiment;

[0036] Figure 6 yes Figure 5 A magnified schematic diagram of the structure at A in the middle;

[0037] Figure 7 It is a schematic diagram of the structure of the advanced small catheter in the embodiment.

[0038] In the figure, 1. Tunnel main body; 11. Left tunnel; 111. Pilot tunnel 1; 1111. Upper left pilot tunnel 1; 1112. Lower left pilot tunnel 1; 112. Pilot tunnel 2; 1121. Upper left pilot tunnel 2; 1122. Lower left pilot tunnel 2; 113. Temporary support; 12. Right tunnel; 121. Pilot tunnel 3; 122. Pilot tunnel 4; 13. Soil layer; 2. Initial support; 21. Initial shotcrete layer; 22. Hollow grouting anchor rod; 23. , steel frame mesh; 24, steel arch frame; 25, sprayed concrete layer; 3, advanced support; 4, locking reinforcement; 41, locking block; 411, perforation; 42, cartridge; 43, cross bar; 5, locking anchor rod; 51, stabilizing plate; 6, advance small guide tube; 61, pointed cone drill bit; 611, separation groove; 62, grouting hole; 7, secondary lining structure; 71, left line secondary lining; 72, right line secondary lining; 8, inverted arch; 9, double arch partition wall. DETAILED DESCRIPTION

[0039] The following is combined with Figure 1 -Attached Figure 7 , further details of this application are given.

[0040] Example 1:

[0041] A double-arch multi-section variable cross-section underground tunnel structure, referring to Figure 1 、 Figure 2 、 Figure 3 , including a tunnel body 1, the tunnel body 1 adopts a horseshoe-shaped cross-section, the tunnel body 1 includes a left tunnel 11 and a right tunnel 12, the tunnel body 1 is provided with an initial support 2 and an advance support 3, a reinforced concrete double arch partition wall 9 is provided between the left tunnel 11 and the right tunnel 12, a Φ22 tension anchor is provided in the middle rock column, the thickness of the double arch partition wall 9 matches the tunnel initial support 2, and the double arch partition wall 9 is part of the secondary lining structure 7; the left tunnel 11 includes a pilot tunnel One 111 and two guide tunnels 112; an I16 steel temporary support 113 is set between the guide tunnels 1 111 and the two guide tunnels 112, which are connected to the initial support 2 by welding. The guide tunnel 1 111 includes the upper left guide tunnel 1 1111 and the lower left guide tunnel 1 1112; the guide tunnel 2 112 includes the upper left guide tunnel 2 1121 and the lower left guide tunnel 2 1122; the right tunnel 12 includes the guide tunnel 3 121 and the guide tunnel 4 122 located below the guide tunnel 3 121.

[0042] Reference Figure 4 、 Figure 5The initial support 2 includes a C25 primary sprayed concrete layer 21 with a thickness of 40 mm, which is arranged on the inner wall of the tunnel body 1, and a number of Φ22 hollow grouting anchor rods 22 with a length of about 3 m and a spacing of 1.2 m × 1.0 m. The plurality of hollow grouting anchor rods 22 are inserted into the inner wall of the tunnel body 1 in a plum blossom shape through the primary sprayed concrete layer 21. A Φ8, 200 × 200 steel frame mesh 23 is fixed to one end of the plurality of hollow grouting anchor rods 22 located in the tunnel body 1, and is fixed to the steel frame mesh 23 by welding the tail hook of the hollow grouting anchor rod 22. An I16 / I18 steel arch frame 24 is set on the side of the steel frame mesh 23 away from the inner wall of the tunnel, with a spacing of 0.75-1.0m. The primary sprayed concrete layer 21 is provided with a re-sprayed concrete layer 25, which adopts C25 and has a total thickness of 240-260mm. The re-sprayed concrete layer 25 covers the hollow grouting anchor rods 22, the steel frame mesh 23 and the steel arch frame 24.

[0043] Reference Figure 5 The inner wall of the tunnel body 1 is located on both sides of the steel arch frame 24 and is provided with a plurality of Φ16 locking bars 4 passing through the steel frame mesh 23. In this embodiment, four locking bars 4 are preferably grouped together, and the spacing matches the nodes of the steel frame mesh 23. Several locking bars 4 are located around the intersection of the horizontal and vertical reinforcements of the steel frame mesh 23. A steel plate locking block 41 is provided at one end of the locking bar 4 passing through the steel frame mesh 23; the locking block 41 is provided with a plurality of perforations 411 corresponding to a group of locking bars 4. The diameter of the perforation 411 is 2-4 mm larger than the diameter of the locking bar 4. The perforation 411 is curved in an arc shape so that the end of the locking bar 4 diverges outward to enhance The concrete holding force is similar to the "barb" anchoring effect; the locking block 41 is provided with a circular clamping cylinder 42, and the locking blocks 41 located on both sides of the steel arch frame 24 are connected through the clamping cylinder 42 and are provided with a Φ20 cross bar 43 that is against the inner wall of the steel arch frame 24. The inner diameter of the clamping cylinder 42 matches the cross bar 43. After the two ends of the cross bar 43 are inserted into the clamping cylinder 42, the clamping cylinder 42 is knocked to deform and strengthen the locking cross bar 43, and at the same time, the locking block 41 is moved to further bend and lock the locking bar 4, and finally the cross bar 43 is welded to the locking block 41 to form a lateral constraint on the steel arch frame 24.

[0044] Reference Figure 5 A number of Φ25 locking anchor rods 5, about 4m long, are provided on the inner wall of the tunnel body 1. The end of the locking anchor rod 5 away from the inner wall of the tunnel body 1 is bent 90° and welded to the steel arch frame 24; a 14mm thick stable steel plate is provided on the bottom surface of the steel arch frame 24 along the direction of travel of the tunnel body 1, which is fixed to the bottom of the steel arch frame 24 by welding, thereby expanding the force-bearing area and helping to prevent the steel arch frame 24 from sinking.

[0045] Reference Figure 3 、 Figure 7On the basis of the initial support 2, the advance support 3 is additionally provided with several Φ42×4mm advance small pipes 6 with a length of about 3.5m. The advance small pipes 6 are located on one side of the steel arch 24 and are distributed in a plum blossom shape, with a circumferential spacing of 400mm and a longitudinal spacing of 1.5-2m. The advance small pipes 6 are arranged at an angle of 10° to 15° to the horizontal line along the direction of travel of the tunnel main body 1. The advance small pipes 6 are hollow and an alloy pointed cone drill bit 61 is arranged at the front end with a cone angle of 30°. The outer wall of the advance small pipe 6 is plum blossom-shaped and connected to the inside with Φ6-8 grouting holes 62 with a hole spacing of 20cm. The grouting holes 62 are arranged at an outward angle of 10° to 15° along the axial direction, which is adapted to the direction of the surrounding rock cracks to improve the grouting diffusion effect; the pointed cone drill bit 61 is connected to the advance small pipe 6. A plurality of separation grooves 611 are arranged inside, which are preferably four in this embodiment. The separation grooves 611 increase the slurry outflow path to enhance the grouting efficiency. The separation grooves 611 are 2mm wide.

[0046] Reference Figure 2 、 Figure 3 The tunnel body 1 is provided with a secondary lining structure 7, which includes a C40P8 reinforced concrete left-line secondary lining 71 in the left tunnel 11 with a thickness of 400-450mm, and a C40P8 reinforced concrete right-line secondary lining 72 in the right tunnel 12. The bottom surfaces of the left tunnel 11 and the right tunnel 12 are both provided with C40P8 reinforced concrete inverted arches 8 with the same thickness as the secondary linings. The left-line secondary lining 71 connects the inverted arch 8 and the left side of the double arch partition wall 9, and the right-line secondary lining 72 connects the inverted arch 8 and the right side of the double arch partition wall 9. The secondary lining is connected to the inverted arch 8 and the partition wall through steel bar connectors or embedded steel bars by welding to form an integral structure.

[0047] Example 2:

[0048] A double-arch multi-section variable cross-section dark excavation tunnel construction method, referring to Figure 1 、 Figure 2 、 Figure 3, the left tunnel 11 adopts the step method to excavate the upper left pilot tunnel 1111, the lower left pilot tunnel 1112, the upper left pilot tunnel 2 1121, and the lower left pilot tunnel 2 1122 in sequence; the right tunnel 12 adopts the tunnel CD method to excavate the pilot tunnel 3 121 and the pilot tunnel 4 122 in sequence; when the left tunnel 11 is excavated by the step method, the cycle advance of the upper step and the upper left pilot tunnel 1 1111 and the upper left pilot tunnel 2 1121 is not greater than the spacing of 1 steel frame, that is, 0.75-1.0m, and the lower step and the lower left pilot tunnel 1 1112 and the lower left pilot tunnel 2 1122 lag behind the upper step by 2-3 steel frames, about 2-3m. After excavation, the initial support 2 and the initial spraying of concrete, the installation of steel frame mesh 23 and steel arch Frame 24, locking bar 4, locking block 41 and cross bar 43 are sprayed with concrete again, and then advance support 3 is applied and advance small guide tube 6 is installed and grouting is carried out on the basis of initial support 2; after the initial support 2 is closed into a ring and the invert arch 8 is completed, the temporary support 113 is removed and removed in sections in the order of "top first and then side wall", and the stress of the temporary support 113 needs to be monitored when it is removed; when the CD method is used to excavate pilot tunnel three 121 and pilot tunnel four 122 for the right tunnel 12, the advance per cycle shall not exceed the spacing of one steel frame, and 5 cm thick C25 concrete shall be sprayed immediately after excavation to seal the heading face, and initial support 2 and advance support 3 shall be installed in time; the construction of the double arch section shall follow the principle of "left line first and then right line".

[0049] The implementation principle of the embodiment of this application is:

[0050] For the construction of double-arch tunnels, horseshoe-shaped cross-section excavation is adopted, with the 11-step method for the left tunnel and the 12CD method for the right tunnel. The initial support 2 adopts the "hollow grouting anchor rod 22 + steel arch frame 24 + steel mesh + shotcrete" system. In addition, locking bars 4, locking blocks 41 and cross bars 43 are added to strengthen the stability of the steel arch frame 24; advanced support 3 adopts advanced small guide tube 6 grouting reinforcement, and the arch frame stability is enhanced by locking foot anchor rods 5 and stabilizing steel plates. The construction adheres to the principle of "pipe ahead, short excavation, strong support, fast closure, and frequent measurement". The cycle advance of the upper step 11 in the left tunnel is ≤1 steel frame spacing, and the lower step lags behind 2-3 frames. The CD method of the right tunnel 12 is ≤0.75m per cycle. The double-arch section "first left line and then right line" is used. After the initial support 2 is closed into a ring, the temporary support 113 is removed. The secondary lining is constructed after the deformation is stable. At the same time, the construction parameters are dynamically adjusted through monitoring of surface settlement and arch crown sinking to ensure the safety of tunnel construction and the stability of the surrounding environment.

[0051] The examples of this specific embodiment are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, any equivalent changes made based on the structure, shape, and principle of this application should be included in the scope of protection of this application.

Claims

1. A double-arch multi-section variable-section underground tunnel structure, comprising a tunnel body (1), characterized in that: The tunnel body (1) adopts a horseshoe-shaped cross-section. The tunnel body (1) includes a left tunnel (11) and a right tunnel (12). The tunnel body (1) is provided with an initial support (2) and an advance support (3). A double-arch partition wall (9) is provided between the left tunnel (11) and the right tunnel (12); the left tunnel (11) includes a first pilot tunnel (111) and a second pilot tunnel (112); a temporary support (113) is provided between the first pilot tunnel (111) and the second pilot tunnel (112); the first pilot tunnel (111) includes a left upper pilot tunnel (1111) and a left lower pilot tunnel (1112); the second pilot tunnel (112) includes a left upper pilot tunnel (1121) and a left lower pilot tunnel (1122); and the right tunnel (12) includes a third pilot tunnel (121) and a fourth pilot tunnel (122) located below the third pilot tunnel (121).

2. The double-arch multi-section variable cross-section underground tunnel structure according to claim 1, characterized in that: The initial support (2) comprises a primary sprayed concrete layer (21) and a plurality of hollow grouting anchor rods (22) arranged on the inner side wall of the tunnel body (1); the plurality of hollow grouting anchor rods (22) are arranged in a plum blossom shape through the primary sprayed concrete layer (21) and inserted into the inner side wall of the tunnel body (1); a steel frame mesh (23) is fixedly provided at one end of the plurality of hollow grouting anchor rods (22) located in the tunnel body (1); a steel arch frame (24) is provided on the side of the steel frame mesh (23) away from the inner side wall of the tunnel; the primary sprayed concrete layer (21) is provided with a secondary sprayed concrete layer (25); and the secondary sprayed concrete layer (25) covers the hollow grouting anchor rods (22), the steel frame mesh (23) and the steel arch frame (24).

3. The double-arch multi-section variable cross-section underground tunnel structure according to claim 2, characterized in that: The inner side wall of the tunnel body (1) is provided with a plurality of locking bars (4) passing through the steel frame mesh (23) on both sides of the steel arch frame (24), and the plurality of locking bars (4) are located around the intersection of the horizontal and vertical steel bars of the steel frame mesh (23). One end of the locking bar (4) passing through the steel frame mesh (23) is provided with a locking block (41), and the locking block (41) is provided with a plurality of through holes (411) corresponding to the locking bar (4), and the through holes (411) are bent so that the locking bar (4) is bent and diverges outward; the locking block (41) is provided with a clamping cylinder (42), and the locking blocks (41) located on both sides of the steel arch frame (24) are connected to the horizontal bar (43) abutting against the inner side wall of the steel arch frame (24) through the clamping cylinder (42).

4. The double-arch multi-section variable cross-section underground tunnel structure according to claim 3, characterized in that: The inner wall of the tunnel body (1) is provided with a plurality of locking anchor rods (5), one end of the locking anchor rods (5) away from the inner wall of the tunnel body (1) is bent and fixed to the steel arch frame (24); the bottom surface of the steel arch frame (24) is provided with a stabilizing plate (51) along the traveling direction of the tunnel body (1).

5. The double-arch multi-section variable cross-section underground tunnel structure according to claim 2, characterized in that: The advanced support (3) is additionally provided with a plurality of advanced small conduits (6) on the basis of the initial support (2); the advanced small conduits (6) are located on one side of the steel arch frame (24) and are distributed in a plum blossom shape; the advanced small conduits (6) are arranged along the traveling direction of the tunnel main body (1) at an angle of 10° to 15° to the horizontal line.

6. The double-arch multi-section variable cross-section underground tunnel structure according to claim 5, characterized in that: The leading small conduit (6) is hollow and has a pointed cone drill bit (61) at its front end. The outer wall of the leading small conduit (6) is in a plum blossom shape and is connected to a grouting hole (62) provided inside. The grouting hole (62) is tilted outward in the axial direction. The pointed cone drill bit (61) is connected to the leading small conduit (6) and is provided with a plurality of separation grooves (611) inside to enhance grouting efficiency.

7. The double-arch multi-section variable cross-section underground tunnel structure according to claim 1, characterized in that: The tunnel body (1) is provided with a secondary lining structure (7), and the secondary lining structure (7) includes a left-line secondary lining (71) in the left tunnel (11) and a right-line secondary lining (72) in the right tunnel (12). The bottom surfaces of the left tunnel (11) and the right tunnel (12) are both provided with inverted arches (8). The left-line secondary lining (71) connects the inverted arch (8) and the left side of the double-arch partition wall (9), and the right-line secondary lining (72) connects the inverted arch (8) and the right side of the double-arch partition wall (9).

8. The excavation construction method of a double-arch multi-section variable-section dark-excavated tunnel structure according to any one of claims 1 to 7, characterized in that: The left tunnel (11) is excavated in sequence by using a step method to excavate a left upper pilot tunnel 1 (1111), a left lower pilot tunnel 1 (1112), a left upper pilot tunnel 2 (1121), and a left lower pilot tunnel 2 (1122); the right tunnel (12) is excavated in sequence by using a tunnel CD method to excavate a pilot tunnel 3 (121) and a pilot tunnel 4 (122).

9. The excavation construction method of a double-arch multi-section variable-section dark-excavated tunnel structure according to claims 1-8, characterized in that: When the left tunnel (11) is excavated using the step method, the cyclic advance of the upper step and the upper left guide tunnel 1 (1111) and the upper left guide tunnel 2 (1121) is no more than the spacing of one steel frame, and the lower step and the lower left guide tunnel 1 (1112) and the lower left guide tunnel 2 (1122) lag behind the upper step by 2-3 steel frame spacings. After excavation, the initial support (2) and the advance support (3) are promptly applied, and the temporary support (113) is removed after the initial support is closed into a ring.

10. The excavation construction method of a double-arch multi-section variable-section dark-excavated tunnel structure according to claims 1-8, characterized in that: When the right tunnel (12) is excavated using the CD method to excavate the pilot tunnel three (121) and the pilot tunnel four (122), the advance per cycle is no more than one steel frame spacing. After excavation, the tunnel face is immediately closed, and the initial support (2) and the advance support (3) are installed in time. The construction of the double arch section follows the principle of "left line first, then right line".

Images