Construction method for slowly lifting and jacking auxiliary channel of highway tunnel

Abstract

The invention relates to a construction method of a highway tunnel, in particular to a construction method of a highway tunnel auxiliary channel slow lifting and jacking hole. The method specifically comprises the following steps: reinforcing an auxiliary channel support, mounting an arch frame at a junction part, constructing a supporting arch frame advance support, excavating an intersection main tunnel, determining and processing the length of a main tunnel arch frame, welding a supporting steel frame fixing steel plate, mounting a main tunnel intersection arch frame, dismounting a vertical portal stand column, and constructing a main tunnel section. The auxiliary channel is supported and reinforced at the position close to the intersection of the main tunnel, after the main tunnel arch frame of the intersection is installed, the stress capacity of the position can be improved, large-range damage caused by stress concentration at the position of the intersection is avoided, meanwhile, the continuous supporting arch frame is arranged at the junction of the auxiliary channel and the main tunnel, and the supporting effect is improved. Support is provided for connection of the main tunnel arch frame at the position, and continuity of a stress system is guaranteed; and the situation that the field welding quality cannot meet the requirement is effectively avoided through the arranged gradually-changed arch frame part, and the connecting quality is guaranteed.

Description

Technical Field

[0001] The invention relates to a construction method for a highway tunnel, in particular to a construction method for a highway tunnel auxiliary channel to slowly lift and top into the tunnel. Background Art

[0002] As is known, for extra-long tunnels or highway tunnels with complex engineering geological conditions and tight construction period requirements, auxiliary passages such as inclined shafts, cross tunnels, and parallel pilot pits are usually set up at appropriate locations near the middle of the tunnel to enter the main tunnel through the auxiliary passages, so as to achieve the purpose of breaking the whole into parts, opening more working faces, shortening the length of single-headed excavation construction, and reducing the risks of main tunnel construction. Auxiliary passages are divided into temporary and permanent ones, and the cross-sections vary according to different functions. Auxiliary passages with larger cross-sections and slow lifting and top-into-tunneling have the following disadvantages: (1) The width and height of the auxiliary channel section are both relatively large, almost the same as those of the main tunnel. The auxiliary channel is directly pushed into the tunnel with the same width, and the intersection area is almost T-shaped and intersecting at a flat angle, which is not conducive to structural safety during the excavation process; (2) When the same width of the top is inserted into the hole, during the process of force structure conversion, the initial force system is completely horizontal, and the support structure is arranged horizontally along the width direction. The length is too long, and after the joint is formed at the arch, the most unfavorable force state is formed, which easily leads to the risk of deformation and collapse; (3) The cross-section of the intersection process conversion is too large, the process operation time is long, it cannot be quickly closed into a ring after excavation, and the support system cannot play its due support role in time. Summary of the invention

[0003] In order to overcome the shortcomings of the background technology, the present invention discloses a construction method for slowly lifting and top-entering an auxiliary channel of a highway tunnel.

[0004] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme: A construction method for slowly lifting and top-entering an auxiliary channel of a highway tunnel specifically comprises the following steps: (1) Strengthening the support of auxiliary channels When the auxiliary channel is constructed to a position 15m to 10m away from the main tunnel excavation section, the initial support of the auxiliary channel from the subsequent auxiliary channel to the main tunnel excavation section contour line segment should be strengthened; (2) Install arch frame at the junction Continuously install 2 to 3 supporting arch frames of the auxiliary channel outside the excavation section of the main tunnel near the auxiliary channel, which are used as supporting arch frames of the main tunnel arch frame within the intersection range. The 2 to 3 supporting arch frames continuously installed in this part shall not invade the clearance in the initial support section of the main tunnel, and can be installed in the direction of the auxiliary channel; (3) Advance support of supporting arch After the support arch is installed, advance support is applied along the arch range of the support arch toward the excavation section of the main tunnel; (4) Excavation of intersection tunnel After the construction of supporting arch frame and advanced support is completed, the step method is used to construct the intersection main tunnel expansion section forward along the center line of the auxiliary channel perpendicular to the center line of the main tunnel. The advance per cycle is no more than 1 arch frame for Grade V surrounding rock, and no more than 2 arch frames for Grade IV surrounding rock. The supporting arch frames of the intersection main tunnel expansion section are all gate-type arch frames. The length of the gate frame column of the gate-type arch frame changes with the curvature of the intersection main tunnel expansion section, and the length of the gate frame crossbeam at the top of the gate-type arch frame remains unchanged; After each portal arch is installed, a locking top anchor rod is driven upward at an angle of 45° at the left and right arch interface. The length of the locking top anchor rod is not less than 3.5m. The locking foot anchor pipe is driven downward at an angle of 45° to firmly fix the portal arch. At the same time, a system anchor rod is set radially in the middle. After the construction is completed, spray concrete to complete the initial support. (5) Determination and processing of the main tunnel arch length The main tunnel arch frame within the intersection of the auxiliary channel and the main tunnel excavation section consists of two parts: a normal section arch frame and an intersection gradient section arch frame. The intersection gradient section arch frame needs to be processed gradually according to different lengths according to different positions. Starting from the center line of the auxiliary channel, the main tunnel arch frames within the intersection range are arranged symmetrically according to the designed spacing, and the distances from the center line of the auxiliary channel are L1, L2, L3..., respectively. The installation positions of the above multiple main tunnel arch frames are marked on the supporting arch frame, and the installation position of each main tunnel arch frame on the supporting arch frame is determined. Synchronously, according to one-to-one correspondence, the vertical lengths a, b, c... of the main tunnel arch frames in the main tunnel excavation section when distributed on the supporting arch frame are measured on the supporting arch frame along the direction of the auxiliary channel. After measuring the above lengths, the gradient arch frame section is designed; (6) Welding of supporting steel frame fixing steel plate After the vertical marks a, b, c, etc. of the supporting arch are completed, the corresponding fixing steel plate is processed according to the shape and size of the cut section of the gradient arch at that position. The thickness of the steel plate is not less than 12 mm. After the processing is completed, the fixing steel plate is evenly and firmly welded to the side of the supporting arch close to the main hole direction with the marking points a, b, c, etc. as the center; (7) Arch installation at the main tunnel intersection When the cross section of the main tunnel is expanded along the horizontal construction to the side wall of the main tunnel excavation section far away from the auxiliary channel, the expansion will not be continued. The excavation will continue forward according to the normal main tunnel excavation section until the entire upper step of the main tunnel is completely excavated. The main tunnel arch frame will be installed in the cross section of the main tunnel that has completed the initial support. When the gradual arch frame section in the main tunnel arch frame is close to the auxiliary channel, it will be firmly welded and fixed to the fixed steel plate on the supporting arch frame; (8) Removal of vertical portal columns After all the arch frames of the main tunnel within the intersection are installed, the initial support of the main tunnel within the intersection is completed by spraying concrete. Along the centerline of the main tunnel, the connecting steel plates between the portal crossbeam and the portal column in the expanded section of the main tunnel of the intersection are untied. The portal column of the expanded section of the main tunnel of one side of the intersection is removed manually with the help of machinery, and excavation is carried out forward along the centerline of the main tunnel according to the normal excavation section of the main tunnel; (9) Construction of the main tunnel section After the gantry columns on one side are removed, the construction is organized forward according to the normal main tunnel excavation section, and the main tunnel section of the intersection is no longer expanded until all the main tunnel arch frames within the intersection are installed and have exceeded the width of the auxiliary channel and can be installed normally. Two reinforced arch frames are installed continuously across the auxiliary channel interface in the main tunnel excavation section, and the other side is constructed in the same way as above.

[0005] In the construction method for slowly lifting and top-entering the auxiliary channel of a highway tunnel, the strengthening method in step (1) is: the model of the original auxiliary channel support arch frame is raised by one level, and the spacing between the arch frames is uniformly set to no more than 0.6m, until the construction reaches a position 0.5m away from the main tunnel excavation section in the auxiliary channel.

[0006] In the construction method for slowly lifting and top-entering the tunnel for the auxiliary channel of a highway tunnel, in step (3), the advance support selects an advance small guide tube or an advance middle pipe shed, the circumferential spacing of the advance small guide tube is not greater than 0.4m, the length is not less than 3.5m, the length of the advance middle pipe shed is not less than 9m, and the circumferential spacing is not greater than 0.4m; when the surrounding rock is relatively hard, has good integrity and has undeveloped joints, the advance small guide tube is reinforced; when the surrounding rock is low in strength, has poor integrity and has developed joints, the advance middle pipe shed is reinforced, and the small guide tube reinforcement is added in time according to the situation.

[0007] In the construction method of the auxiliary channel of the highway tunnel slowly lifting and jacking into the tunnel, the step height of the enlarged section 11 of the intersection main tunnel in step (4) is sufficient to meet the operation of mechanical equipment, and the net width of the section is controlled at 4-5m.

[0008] The construction method for the auxiliary channel of a highway tunnel with a slow lift and top entry, the step of designing the gradual intersection gradual section arch frame in step (5) is as follows: along the vertical direction of the supporting arch frame 3, starting from the clearance in the initial support section of the main tunnel, mark the lengths a, b, c and so on downward in sequence, set a connecting steel plate at an appropriate position deviating from the center line of the main tunnel, and use the connecting steel plate at this position as the boundary, process the main tunnel arch frame close to the auxiliary channel side into a gradual arch frame, and process the far side into a normal section arch frame; connect the center line of the connecting steel plate with the vertical markings a, b, c... of the fixed steel plate, adjust the connecting line into an arc shape, ensure that the gradual arch frame is smoothly connected with the normal section arch frame, and the adjusted connecting line is the processing length of the center line of the gradual arch. After determining the processing length, process the gradual arch frame according to the groove of the interface position.

[0009] The construction method of the auxiliary channel of the highway tunnel slowly lifting and top-entering the tunnel adopts the step method in the process of forward construction organization, controls the construction progress in each cycle, and organizes and implements it according to the procedures of advanced support, tunnel excavation, arch installation, system anchor rod application, and shotcrete spraying.

[0010] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: 1. The construction method of the highway tunnel auxiliary channel slowly lifting and cantilevering into the tunnel described in the present invention is that the auxiliary channel is supported and strengthened at the position close to the intersection with the main tunnel. After the main tunnel arch frame at the intersection is installed, it helps to improve the force-bearing capacity of this part, thereby avoiding large-scale damage at the intersection due to stress concentration. At the same time, a continuous supporting arch frame is set at the junction of the auxiliary channel and the main tunnel to provide support for the connection of the main tunnel arch frame at this position, thereby ensuring the continuity of the force system; the auxiliary channel adopts a small-section gate-type arch frame construction toward the main tunnel, cuts the large section into small sections, and completes the cantilevering conversion of the auxiliary channel toward the main tunnel in the small section, thereby reducing the risk of large-section, smooth cantilevering construction.

[0011] 2. The construction method of the highway tunnel auxiliary channel slowly lifting and top-entering tunnel described in the present invention processes the main tunnel arch frame within the intersection range into a fixed arch frame and a gradual arch frame, the size and shape of the fixed arch frame part remain unchanged, only the gradual arch frame part changes, and the fixed connecting steel plate is welded in advance on the supporting steel frame, and the gradual arch frame part is directly welded and fixed to the connecting steel plate, which effectively avoids the situation that the on-site welding quality cannot meet the requirements and ensures the connection quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the construction plan layout diagram of the intersection of the auxiliary channel and the main tunnel of the present invention.

[0013] Figure 2 It is a longitudinal section layout diagram of the cantilever construction at the intersection of the auxiliary passage and the main tunnel of the present invention.

[0014] Figure 3 It is a gradual installation diagram of the connection between the supporting arch frame and the main hole arch frame of the present invention.

[0015] Figure 4 This is a schematic diagram of the door-type arch installation.

[0016] Figure 5 This is the installation drawing of the main tunnel arch frame at the intersection along the auxiliary channel direction.

[0017] In the figure: 1. Auxiliary channel; 2. Initial support of auxiliary channel; 3. Support arch; 4. Main tunnel excavation section; 5. Strengthening arch; 6. Initial support of main tunnel; 7. Gradual arch section; 8. Gate arch; 9. Gradual arch section of intersection; 10. Advance support; 11. Enlarged section of intersection main tunnel; 12. Connecting steel plate; 13. Normal arch; 14. Locking top anchor; 15. Fixed steel plate; 16. Gate beam; 17. System anchor; 18. Gate column; 19. Locking foot anchor; 20. Auxiliary channel center line; 21. Main tunnel arch; 22. Main tunnel center line; 23. Gradual arch. DETAILED DESCRIPTION

[0018] The present invention can be explained in detail by the following examples, and the purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention.

[0019] Combined with Figure 1-5 The construction method of the highway tunnel auxiliary channel slowly lifting and top-entering the tunnel specifically includes the following steps: (1) Strengthening the support of auxiliary channels When the auxiliary channel 1 is constructed to a position of about 15m to 10m from the main tunnel excavation section 4, the auxiliary channel initial support 2 of the subsequent auxiliary channel 1 to the main tunnel excavation section 4 contour line segment is considered to be strengthened; the strengthening method is: the model of the original auxiliary channel support arch frame is increased by one level. For example, if the original design uses the Gong 16 arch frame, the Gong 18 arch frame is used within the section range, and the spacing between the arch frames is uniformly set to no more than 0.6m, until the construction reaches a position of 0.5m from the main tunnel excavation section 4 in the auxiliary channel 1; (2) Install arch frame at the junction Continuously install 2 to 3 supporting arch frames 3 of the auxiliary channel outside the main tunnel excavation section 4 near the auxiliary channel 1, which are used as supporting arch frames 3 of the main tunnel arch frame within the intersection range. The 2 to 3 supporting arch frames 3 continuously installed at this position shall not invade the clearance in the section 6 of the initial support of the main tunnel, and can be installed in the direction of the auxiliary channel 1; (3) Advance support of supporting arch After the support arch frame 3 is installed, the advance support 10 is applied along the arch range of the support arch frame 3 toward the direction of the main tunnel excavation section 4; the advance support 10 selects an advance small pipe or an advance middle pipe shed. When the advance small pipe is used, the circumferential spacing of the advance small pipe is not greater than 0.4m, and the length is not less than 3.5m; when the advance middle pipe shed is used, the length of the advanced middle pipe shed is not less than 9m, and the circumferential spacing is not greater than 0.4m; when the surrounding rock is relatively hard, the integrity is good, and the joints are not developed, the advance small pipe reinforcement is applied; when the surrounding rock strength is low, the integrity is poor, and the joints are developed, the advance middle pipe shed reinforcement is constructed, and the small pipe reinforcement is added in real time according to the situation; (4) Excavation of intersection tunnel After the construction of the supporting arch frame 3 and the advanced support 10 is completed, the step method is used to construct the intersection main tunnel expansion section 11 forward along the auxiliary channel center line 20 perpendicular to the center line of the main tunnel. The height of the intersection main tunnel expansion section 11 can meet the operation of mechanical equipment, and the net width of the section is controlled at 4-5m. The footage of each cycle is not more than 1 arch frame for Grade V surrounding rock, and not more than 2 arch frames for Grade IV surrounding rock. The supporting arch frames of the intersection main tunnel expansion section 11 all use portal arch frames 8. The length of the portal frame column 18 of the portal arch frame 8 changes with the curvature of the intersection main tunnel expansion section 11, and the length of the portal frame crossbeam 16 at the top of the portal arch frame 8 remains unchanged; After each door-shaped arch frame 8 is installed, a locking top anchor rod 14 is driven upward at an angle of 45° at the left and right arch frame interfaces. The length of the locking top anchor rod 14 is not less than 3.5m. The locking foot anchor pipe 19 is driven downward at an angle of 45° to tightly fix the door-shaped arch frame 8. At the same time, a system anchor rod 17 is radially set in the middle part. After the construction is completed, the initial support is completed by spraying concrete. (5) Determination and processing of the main tunnel arch length The main tunnel arch frame 21 within the intersection of the auxiliary channel 1 and the main tunnel excavation section 4 is composed of a normal section arch frame 13 and an intersection gradient section arch frame 9. The intersection gradient section arch frame 9 needs to be processed gradually according to different lengths according to different positions. Starting from the center line 20 of the auxiliary channel, the main tunnel arch frames 21 within the intersection are arranged symmetrically according to the designed spacing, and the distances from the center line of the auxiliary channel are L1, L2, L3..., respectively. The installation positions of the above multiple main tunnel arch frames 21 are marked on the supporting arch frame 3, and the installation position of each main tunnel arch frame 21 on the supporting arch frame 3 is determined. Synchronously, according to one-to-one correspondence, the vertical lengths a, b, c... of the main tunnel arch frames 21 in the main tunnel excavation section 4 when distributed on the supporting arch frame 3 are measured on the supporting arch frame 3 along the direction of the auxiliary channel 1. After measuring the above lengths, the gradient arch frame 23 is designed; The steps of designing the gradual arch frame section 7 are as follows: along the vertical direction of the supporting arch frame 3, starting from the clearance in the initial support section of the main tunnel, mark the lengths a, b, c and so on downward in sequence, set the connecting steel plate 12 at an appropriate position deviating from the center line 22 of the main tunnel, and use the connecting steel plate 12 at this position as the boundary, the main tunnel arch frame 21 close to the auxiliary channel 1 side is processed into a gradual arch frame 23, and the far side is processed into a normal section arch frame 13; connect the center line of the connecting steel plate 12 with the vertical markings a, b, c... of the fixed steel plate 15, adjust the connecting line to an arc, ensure that the gradual arch frame 23 is smoothly connected to the normal section arch frame 13, and the adjusted connecting line is the processing length of the center line of the gradual arch. After determining the processing length, the gradual arch frame 23 is processed according to the groove of the interface position; (6) Welding of supporting steel frame fixing steel plate After the vertical marks a, b, c, etc. of the supporting arch frame 3 are completed, the corresponding fixing steel plate 15 is processed according to the cross-sectional shape and size of the cutout of the gradual arch frame 23 at this position. The thickness of the steel plate is not less than 12 mm. After the processing is completed, the fixing steel plate 15 is uniformly and firmly welded to the side of the supporting arch frame 3 close to the positive hole direction with the marking points a, b, c, etc. as the center; (7) Arch installation at the main tunnel intersection When the intersection main tunnel enlarged section 11 is constructed horizontally to the side wall position of the main tunnel excavation section 4 far away from the auxiliary channel 1, the construction and expansion will no longer continue, and the excavation will continue forward according to the normal main tunnel excavation section until the entire upper step of the main tunnel is completely excavated, and the main tunnel arch frame 21 is installed in the intersection main tunnel enlarged section 11 where the initial support has been completed, and the intersection gradient section arch frame 9 in the main tunnel arch frame 21 is firmly welded and fixed to the fixed steel plate on the support arch frame 3 when it is close to the auxiliary channel 1. (8) Removal of vertical portal columns After all the main tunnel arches 21 within the intersection are installed, the initial support 6 of the main tunnel within the intersection is completed by spraying concrete, and the connecting steel plates 12 between the portal crossbeams 16 and the portal columns 18 in the expanded section 11 of the intersection main tunnel are untied along the centerline 22 of the main tunnel. The portal columns 18 of the expanded section 11 of the intersection main tunnel are removed manually and mechanically, and the excavation is carried out forward along the centerline 22 of the main tunnel according to the normal excavation section 4 of the main tunnel; (9) Construction of the main tunnel section After the gantry columns 18 on one side are removed, the construction is organized forward according to the normal main tunnel excavation section 4, and the intersection main tunnel expansion section 11 is no longer implemented. The step method is adopted in the forward construction process, and the construction progress is controlled in each cycle. The process is organized and implemented according to the steps of advance support, tunnel excavation, arch installation, system anchor application, and shotcrete spraying until all the main tunnel arches 21 within the intersection are installed and have exceeded the width of the auxiliary channel and can be installed normally. Two reinforced arches 5 are installed continuously at the main tunnel excavation section 4 across the interface of the auxiliary channel 1, and the other side is constructed in the same way as above.

[0020] The parts not described in detail in this invention are prior art.

[0021] The embodiments selected herein for the purpose of disclosing the invention are currently considered to be suitable, but it should be understood that the invention is intended to include all changes and modifications of the embodiments that fall within the scope of the concept and invention.

Claims

1. A construction method for slowly lifting and top-entering an auxiliary channel of a highway tunnel, characterized by: The specific steps include the following: (1) Strengthening of auxiliary channel support When the auxiliary channel is constructed to a position 15m to 10m away from the main tunnel excavation section, the initial support of the auxiliary channel from the subsequent auxiliary channel to the main tunnel excavation section contour line segment should be strengthened; (2) Install arch frame at the junction Continuously install 2 to 3 supporting arch frames of the auxiliary channel outside the excavation section of the main tunnel near the auxiliary channel, which are used as supporting arch frames of the main tunnel arch frame within the intersection range. The 2 to 3 supporting arch frames continuously installed in this part shall not invade the clearance in the initial support section of the main tunnel, and can be installed in the direction of the auxiliary channel; (3) Advance support of supporting arch After the support arch is installed, advance support is applied along the arch range of the support arch toward the excavation section of the main tunnel; (4) Excavation of intersection tunnel After the construction of the supporting arch frame and the advanced support is completed, the step method is used to construct the intersection main tunnel expansion section forward along the center line of the auxiliary channel perpendicular to the center line of the main tunnel. The advance of each cycle is no more than 1 arch frame for Grade V surrounding rock, and no more than 2 arch frames for Grade IV surrounding rock. The supporting arch frames of the intersection main tunnel expansion section are all portal arch frames. The length of the portal frame columns of the portal arch frame follows the curvature of the intersection main tunnel expansion section, and the length of the portal frame crossbeam at the top of the portal arch frame remains unchanged; after each portal arch frame is installed, a locking top anchor rod is driven at an angle of 45° upward at the arch frame interface on the left and right sides. The length of the locking top anchor rod is not less than 3.5m, and the locking foot anchor pipe is driven at an angle of 45° downward to fix the portal arch frame tightly. At the same time, a system anchor rod is set radially in the middle part. After the construction is completed, spray concrete to complete the initial support; (5) Determination and processing of the main tunnel arch length The main tunnel arch frame within the intersection of the auxiliary channel and the main tunnel excavation section consists of two parts: a normal section arch frame and an intersection gradient section arch frame. The intersection gradient section arch frame needs to be processed gradually according to different lengths according to different positions. Starting from the center line of the auxiliary channel, the main tunnel arch frames within the intersection range are arranged symmetrically according to the designed spacing, and the distances from the center line of the auxiliary channel are L1, L2, L3..., respectively. The installation positions of the above multiple main tunnel arch frames are marked on the supporting arch frame, and the installation position of each main tunnel arch frame on the supporting arch frame is determined. Synchronously, according to one-to-one correspondence, the vertical lengths a, b, c... of the main tunnel arch frames in the main tunnel excavation section when distributed on the supporting arch frame are measured on the supporting arch frame along the direction of the auxiliary channel. After measuring the above lengths, the gradient arch frame section is designed; (6) Welding of supporting steel frame fixing steel plate After the vertical marks a, b, c, etc. of the supporting arch are completed, the corresponding fixing steel plate is processed according to the shape and size of the cut section of the gradient arch at that position. The thickness of the steel plate is not less than 12 mm. After the processing is completed, the fixing steel plate is evenly and firmly welded to the side of the supporting arch close to the main hole direction with the marking points a, b, c, etc. as the center; (7) Arch installation at the main tunnel intersection When the cross section of the main tunnel is expanded along the horizontal construction to the side wall of the main tunnel excavation section far away from the auxiliary channel, the expansion will not be continued. The excavation will continue forward according to the normal main tunnel excavation section until the entire upper step of the main tunnel is completely excavated. The main tunnel arch frame will be installed in the cross section of the main tunnel that has completed the initial support. When the gradual arch frame section in the main tunnel arch frame is close to the auxiliary channel, it will be firmly welded and fixed to the fixed steel plate on the supporting arch frame; (8) Removal of vertical portal columns After all the arch frames of the main tunnel within the intersection are installed, the initial support of the main tunnel within the intersection is completed by spraying concrete. Along the centerline of the main tunnel, the connecting steel plates between the portal crossbeam and the portal column in the expanded section of the main tunnel of the intersection are untied. The portal column of the expanded section of the main tunnel of one side of the intersection is removed manually with the help of machinery, and excavation is carried out forward along the centerline of the main tunnel according to the normal excavation section of the main tunnel; (9) Construction of the main tunnel section After the gantry columns on one side are removed, the construction is organized forward according to the normal main tunnel excavation section, and the main tunnel section of the intersection is no longer expanded until all the main tunnel arch frames within the intersection are installed and have exceeded the width of the auxiliary channel and can be installed normally. Two reinforced arch frames are installed continuously across the auxiliary channel interface in the main tunnel excavation section, and the other side is constructed in the same way as above.

2. The construction method for slowly lifting and top-entering the auxiliary channel of a highway tunnel according to claim 1 is characterized by: The strengthening method in step (1) is: the model of the original auxiliary channel support arch frame is raised by one level, and the spacing between the arch frames is uniformly set to no more than 0.6m, until the construction reaches a position 0.5m away from the main tunnel excavation section in the auxiliary channel.

3. The construction method for slowly lifting and top-entering the auxiliary channel of a highway tunnel according to claim 1 is characterized by: In step (3), the advance support is selected as an advance small conduit or an advance medium pipe shed. The circumferential spacing of the advance small conduit is not more than 0.4m, and the length is not less than 3.5m. The length of the advance medium pipe shed is not less than 9m, and the circumferential spacing is not more than 0.4m. When the surrounding rock is relatively hard, has good integrity and undeveloped joints, the advance small conduit reinforcement is implemented. When the surrounding rock strength is low, has poor integrity and developed joints, the advance medium pipe shed reinforcement is constructed, and the small conduit reinforcement is added in time according to the situation.

4. The construction method for slowly lifting and top-entering the auxiliary channel of a highway tunnel according to claim 1 is characterized by: In step (4), the step height of the expanded section 11 of the intersection main tunnel is sufficient to meet the needs of mechanical equipment operation, and the net width of the section is controlled at 4-5m.

5. The construction method for slowly lifting and top-entering the auxiliary channel of a highway tunnel according to claim 1 is characterized by: The steps for designing the gradual intersection gradual section arch frame in step (5) are as follows: along the vertical direction of the supporting arch frame 3, starting from the clearance in the initial support section of the main tunnel, mark the lengths a, b, c and so on downward in sequence, set a connecting steel plate at an appropriate position deviating from the center line of the main tunnel, and use the connecting steel plate at this position as the boundary. The main tunnel arch frame close to the auxiliary channel side is processed into a gradual arch frame, and the side away from the auxiliary channel side is processed into a normal section arch frame; connect the center line of the connecting steel plate with the vertical markings a, b, c... of the fixed steel plate, adjust the connecting line to an arc shape, ensure that the gradual arch frame is smoothly connected to the normal section arch frame, and the adjusted connecting line is the processing length of the center line of the gradual arch. After determining the processing length, the gradual arch frame is processed according to the groove of the interface position.

6. The construction method for slowly lifting and top-entering the auxiliary channel of a highway tunnel according to claim 1 is characterized by: In the process of organizing construction forward, the step method is adopted to control the construction progress in each cycle, and the construction is organized and implemented according to the procedures of advance support, tunnel excavation, arch installation, system anchor application, and shotcrete spraying.

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