Small-clear-distance double-tunnel entrance and exit construction method for shallow-buried collapse slope accumulation body stratum

Abstract

The invention belongs to the technical field of tunnel entry construction under complex geological conditions, and particularly relates to a shallow-buried collapse slope accumulation body stratum small-clear-distance double-tunnel entry and exit construction method. The tunnel opening slope collapse accumulation body is disposed, and the tunnel opening reinforcing procedure and the tunnel excavation procedure are conducted in parallel; the tunnel excavation procedure comprises the steps that a main line left hole of the double-track tunnel is directly entered through a transverse through pilot tunnel, and a main line right hole is entered through a connecting channel during excavation of the main line left hole; the main line left hole and the main line right hole go out of the holes after the hole collapse slope accumulation body treatment and the hole reinforcing process are completed; according to the construction method, the transverse through pilot tunnel enters the main line left hole and then enters the main line right hole through the connection channel, simultaneous construction of the main line left hole and the main line right hole in large and small mileages can be achieved, construction of the main line left hole and the main line right hole, hole slope collapse accumulation disposal, hole reinforcement and the like is synchronously carried out, parallel operation of multiple procedures is achieved, and the construction period is effectively shortened.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tunnel construction under complex geological conditions, and particularly relates to a shallow-buried landslide deposit stratum small-spacing double-tunnel entry and exit construction method. BACKGROUND

[0002] With the vigorous development of China's highway industry, the construction scope is continuously extended to mountainous areas, and the southwest mountainous area has become an important region for highway tunnel construction. However, the special and complex geological structure of the southwest mountainous area has brought great challenges to highway tunnel construction. Different topography and geological conditions increase the construction difficulty during tunnel construction, especially the tunnel entry and exit construction under complex topography conditions, which is extremely technical. When the soil at the tunnel entrance is a landslide deposit, the problem is more prominent. The structure of the landslide deposit is loose and has poor stability, which greatly increases the difficulty of entry, and the reinforcement measures often require a long construction period, so the main tunnel construction cannot be quickly advanced. Therefore, exploring efficient and safe tunnel entry construction technology and exit protection scheme in adverse geological areas, breaking through the technical bottleneck of landslide deposit treatment, has become the key to ensuring the construction progress of mountainous highway and reducing engineering cost. SUMMARY

[0003] The present application is to solve the problem of long reinforcement period in landslide deposit geological area, which seriously interferes with the tunnel entry process.

[0004] The present application provides the following technical scheme: a shallow-buried landslide deposit stratum small-spacing double-tunnel entry and exit construction method, the tunnel entrance landslide deposit treatment, the tunnel entrance reinforcement process and the tunnel excavation process are parallel; the tunnel excavation process includes directly entering the left tunnel of the main line through the horizontal pilot tunnel, and entering the right tunnel of the main line through the connecting channel during the excavation of the left tunnel of the main line; after the tunnel entrance landslide deposit treatment and the tunnel entrance reinforcement process are completed, the left tunnel of the main line and the right tunnel of the main line are exited.

[0005] Further, the horizontal pilot tunnel and the left tunnel of the main line are perpendicular to each other, and a door-shaped steel frame is arranged outside the pilot tunnel arch frame at the intersection of the side wall of the horizontal pilot tunnel and the left tunnel of the main line; the door-shaped steel frame is welded with the pilot tunnel arch frame; the arch foot of the door-shaped steel frame is fixed by a lock foot anchor pipe, and the top of the door-shaped steel frame is supported by an advanced small guide pipe.

[0006] Further, the construction steps of the horizontal pilot tunnel entering the left tunnel of the main line are as follows: S1: the upper step of the horizontal pilot tunnel is constructed by upward toppling, and is excavated vertically to the main line left tunnel profile line, and a temporary portal and an advanced small guide pipe are arranged according to the excavation footage; the top of the left tunnel of the main line is supported by anchor rods and steel mesh sheets; finally, the concrete spraying operation is performed; S2: After the temporary portal is erected, the main tunnel arch is erected, the main tunnel arch is connected to the portal steel frame at the intersection of the main tunnel arch and the cross tunnel, and concrete spraying is performed; S3: The temporary portal is removed, and the remaining positions in the main left tunnel are excavated.

[0007] Further, in the intersection range of the main left tunnel and the cross tunnel, the secondary lining steel of the main left tunnel extends into the cross tunnel, and the secondary lining of the main left tunnel is poured together with the cross tunnel range to form an integral structure; the inverted arch steel of the main left tunnel extends into the cross tunnel, and the inverted arch of the main left tunnel is poured together with the floor in the cross tunnel.

[0008] Further, after the excavation space of the main left tunnel meets the construction conditions of the connecting passage, the connecting passage is constructed, and the connecting passage gradually expands from the main left tunnel to the main right tunnel.

[0009] Further, the reinforcement structure for the disposal of the slope collapse accumulation at the tunnel portal includes one or a combination of pile board wall, anti-slide pile, pile top lock mouth crown beam and grouting reinforcement.

[0010] Further, the portal reinforcement includes an advanced large pipe shed and an advanced small guide pipe. The drainage and water interception treatment of the side slope, the inverted slope outside the portal and the portal are performed before the portal reinforcement, and then the side slope and the inverted slope are excavated by the top-down method, the side slope is protected by the anchor rod frame beam, and the inverted slope is protected by the anchor rod frame beam and the anchor cable frame beam. The main left tunnel and the main right tunnel are excavated from inside to outside when they exit the tunnel, and the ground surface settlement is monitored in real time during the excavation process.

[0011] Further, the grouting reinforcement range includes the ground surface and the foundation at the tunnel top, the grouting range of the ground surface at the tunnel top is 16m on both sides of the axis of the main left tunnel and the main right tunnel, the grouting range of the ground surface at the tunnel top is located outside the tunnel contour line 0.5m, and the grouting holes are arranged in a plum blossom shape; the grouting range of the foundation is 6m on both sides of the axis of the main left tunnel and the main right tunnel, and the grouting holes are arranged in a plum blossom shape. The total grouting depth of the ground surface and the foundation at the tunnel top is 10m at positions where the thickness of the slope collapse accumulation is greater than 10m; the total grouting depth of the ground surface and the foundation at the tunnel top is 1m into the bedrock at positions where the thickness of the slope collapse accumulation is less than 10m.

[0012] Further, the entrance position of the cross tunnel is not more than 200m from the portal of the main tunnel.

[0013] Further, the upright column of the portal steel frame is attached to the upright rod segment of the guide tunnel arch, the cross beam of the portal steel frame is tangent to the circular segment of the guide tunnel arch; the cross beam and the upright column of the portal steel frame are connected by a diagonal brace, the diagonal brace is tangent to the circular segment of the guide tunnel arch, and the midpoint of the diagonal brace and the intersection of the upright column and the cross beam are connected by a top brace; the upright column and the cross beam of the portal steel frame are double-spliced I-beams.

[0014] Compared with the prior art, the present application has the advantages of: The present application adopts the horizontal through pilot tunnel to enter the left tunnel of the main line, and then enters the right tunnel of the main line through the connecting passage, so that the left tunnel and the right tunnel of the main line can be constructed at the same time, and the construction of the collapse accumulation body at the tunnel entrance and the reinforcement of the tunnel entrance can be carried out synchronously, so that multiple processes can be carried out in parallel, and the construction period can be effectively shortened.

[0015] The present application directly enters the left tunnel of the main line through the horizontal through pilot tunnel, skips the pre-processes of the collapse accumulation body at the tunnel entrance and the reinforcement of the tunnel entrance, greatly reduces the preparation time in the early stage, and speeds up the construction progress.

[0016] The present application innovatively changes the construction logic, changes the original design of “entering the tunnel from the tunnel entrance” to “leaving the tunnel from the tunnel”, and leaves the tunnel after the collapse accumulation body at the tunnel entrance is disposed and reinforced, so that the risk of slope instability and landslide is minimized.

[0017] The present application combines various technical measures to ensure safe and efficient construction, including the horizontal through pilot tunnel roof removal method, anti-slide pile + pile top lock mouth crown beam + ground surface grouting to dispose the collapse accumulation body, side and inclined slope protection + advanced large pipe shed to reinforce the tunnel entrance, to form a comprehensive technical system. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a general overhead view of the shallow-buried collapse accumulation body stratum small-distance double-tunnel entering and leaving the tunnel construction; Figure 2 It is an overhead view of the horizontal through pilot tunnel entering the left tunnel of the main line; Figure 3 It is Figure 2 A-A is a schematic view; Figure 4 It is Figure 2 B-B is a schematic view; Figure 5 It is a schematic view of the connection between the portal steel frame and the pilot tunnel arch frame; Figure 6 It is a schematic view of the lining structure in the left tunnel of the main line; Figure 7 It is an overhead view of the connecting passage; Figure 8 It is a sectional view of the connecting passage; Figure 9 It is a schematic view of the grouting reinforcement range.

[0019] In the diagram: 1-Transverse pilot tunnel; 1.1-Descending step; 2-Left main tunnel; 3-Right main tunnel; 4-Connecting passage; 5-Collection area; 6-Drainage ditch; 7-Anti-slide pile; 8-Slope protection at the tunnel entrance; 9-Pile top locking beam; 10-Portal steel frame; 10.1-Column; 10.2-Column; 10.3-Diagonal brace; 10.4-Top brace; 11-Temporary portal frame inside the left main tunnel; 12-Guide tunnel arch frame; 13-Main tunnel left tunnel main tunnel arch frame; 14-Secondary lining; 15-Invert arch; 16-Bottom slab inside the transverse guide tunnel; 17-Arch frame inside the connecting passage; 18-Gantry frame at the intersection of the connecting passage and the main tunnel left tunnel; 19-Gantry frame at the intersection of the connecting passage and the main tunnel right tunnel; 20-Temporary gantry frame inside the main tunnel right tunnel; 21-Main tunnel right tunnel main tunnel arch frame; 22-Grouting on the tunnel roof; 23-Grouting in the foundation. Detailed Implementation

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] like Figure 1 The diagram illustrates a construction method for a dual-tunnel entrance and exit system with a small clearance in shallow-buried colluvial strata. The colluvial treatment and reinforcement procedures at the tunnel entrance are carried out concurrently with the tunnel excavation. The tunnel excavation includes direct entry into the main left tunnel 2 of the dual-track tunnel via a transverse pilot tunnel 1. During the excavation of the main left tunnel 2, entry into the main right tunnel 3 is achieved via a connecting passage 4. After the colluvial treatment and reinforcement procedures at the tunnel entrance are completed, both the main left tunnel 2 and the main right tunnel 3 exit the tunnel. In this embodiment, the left and right tunnels are not absolute left and right; the tunnel intersecting with the transverse pilot tunnel 1 is the left tunnel, and the tunnel furthest from the transverse pilot tunnel 1 is the right tunnel.

[0022] The criteria for determining the entrance location of the transverse pilot tunnel 1 were that the geological conditions were better than those at the main tunnel entrance and the distance from the main tunnel entrance was no more than 200m. After protection measures were taken at the entrance of the transverse pilot tunnel 1, guide wall construction was carried out, followed by excavation of the transverse pilot tunnel 1. The transverse pilot tunnel 1 was excavated in two stages, and the guide tunnel arch frame 12 was installed as the excavation progressed.

[0023] like Figure 2 , Figure 3 As shown: the horizontal guide tunnel 1 intersects perpendicularly with the main left tunnel 2. A portal steel frame 10 is provided on the outside of the guide tunnel arch 12 at the junction of the side walls of the horizontal guide tunnel 1 and the main left tunnel 2. The portal steel frame 10 is welded to the guide tunnel arch 12. The arch foot of the portal steel frame 10 is fixed with a locking foot anchor pipe, and the top of the portal steel frame 10 is supported by an advanced small guide pipe.

[0024] likeFigure 5 As shown: the column 10.1 of the door-shaped steel frame 10 is in contact with the vertical rod section of the guide hole arch frame 12, the crossbeam 10.2 of the door-shaped steel frame 10 is tangent to the circular arc section of the guide hole arch frame 12; the crossbeam 10.2 and the column 10.1 of the door-shaped steel frame 10 are connected with the diagonal brace 10.3, the diagonal brace 10.3 is tangent to the circular arc section of the guide hole arch frame 12, the midpoint of the diagonal brace 10.3 and the intersection point between the column 10.1 and the crossbeam 10.2 are connected with the bracing rod 10.4; the column 10.1 and the crossbeam 10.2 of the door-shaped steel frame 10 are double-spliced I-beams.

[0025] The construction steps of the transverse guide hole 1 into the main line left hole 2 are as follows: S1: after the completion of the upper step support of the transverse guide hole 1, the upper step of the transverse guide hole 1 is constructed upward, the vertical main line left hole 2 line direction is excavated to the main line left hole 2 contour line, and the temporary portal (the main line left hole temporary portal 11) is set along with the excavation footage, the advanced small guide pipe is set; the top of the main line left hole 2 is supported by anchor rods and steel mesh sheets; two anchor rods are set at the arch foot of each main line left hole temporary portal 11 to reinforce; finally, the concrete spraying operation is performed; S2: after the completion of the erection of the main line left hole temporary portal 11, the main line left hole arch frame (the main line left hole arch frame 13) is erected, two locking foot anchor rods are set at the arch foot of the main line left hole arch frame 13, the main line left hole arch frame 13 is connected to the door-shaped steel frame 10 at the intersection of the main line left hole arch frame 13 and the transverse guide hole 1, and the concrete spraying operation is performed; S3: the main line left hole temporary portal 11 is removed, specifically, the crossbeam of the main line left hole temporary portal 11 is reserved, the supporting legs of the main line left hole temporary portal 11 are cut and removed, and the remaining positions in the main line left hole 2 are excavated, and the main line left hole arch frame 13 is connected during the excavation process.

[0026] As shown in the drawings: Figure 6 In the intersection range of the main line left hole 2 and the transverse guide hole 1, the secondary lining steel of the main line left hole 2 extends into the transverse guide hole 1 by 2 meters, and the secondary lining 14 of the main line left hole 2 is poured together with the 2-meter range in the transverse guide hole 1 to form an integral structure; the inverted arch steel of the main line left hole 2 extends into the transverse guide hole 1 by 2 meters, and the inverted arch 15 of the main line left hole 2 is poured together with the floor 16 in the transverse guide hole.

[0027] After the construction of the intersection range of the main line left hole 2 and the transverse guide hole 1 is completed, the main hole excavation construction is performed, first 10m towards the import end, then towards the export end, excavate 40m, provide a position for the inverted arch trestle and the secondary lining trolley assembly.

[0028] As shown in the drawings: Figure 7 , Figure 8As shown: after the excavation space of the main line left tunnel 2 meets the construction conditions of the connecting passage 4, the connecting passage 4 is constructed, and the connecting passage 4 gradually expands from the main line left tunnel 2 to the main line right tunnel 3, and the connecting passage 4 enters the main line right tunnel 3 again by roof picking.

[0029] The arch frame (the connecting passage inner arch frame 17) outside the intersection of the connecting passage 4 and the main line left tunnel 2 is provided with a door frame (the connecting passage and the main line left tunnel intersection door frame 18), and the arch frame (the connecting passage inner arch frame 17) outside the intersection of the connecting passage 4 and the main line right tunnel 3 is provided with a door frame (the connecting passage and the main line right tunnel intersection door frame 19). The connecting structure of the connecting passage inner arch frame 17 and the connecting passage and the main line left tunnel intersection door frame 18 is also the same Figure 5 The connecting structure of the connecting passage inner arch frame 17 and the connecting passage and the main line right tunnel intersection door frame 19 is also the same Figure 5 As shown.

[0030] As shown Figure 1 The reinforcement structure for the treatment of the hole opening collapse slope accumulation body includes one or more combinations of pile board wall, anti-slide pile 7, pile top lock crown beam 9 and grouting reinforcement.

[0031] In the embodiment, the diameters of the five anti-slide piles 7 on the right side of the main line right tunnel 3 are 2.5 m, the pile length is 30 m, the pile spacing (pile center) is 5 m, a 30 cm thick pile board wall is constructed to connect the five anti-slide piles 7, and the depth is embedded into the sliding surface by 0.5 m; the diameters of the anti-slide piles 7 near the main line left tunnel 2 are 3 m, the pile length is 30 m, the pile spacing (pile center) of the six anti-slide piles 7 on the left side of the main line left tunnel 2 is 6 m, and the pile spacing (pile center) of the remaining two anti-slide piles 7 on the right side of the main line left tunnel 2 is 6 m, and the pile spacing (pile center) of the two anti-slide piles 7 on the right side of the main line left tunnel 2 is 19 m, the pile top of the two anti-slide piles 7 is connected by a 2.6 m×1.5 m pile top lock crown beam 9, and the depth is embedded into the sliding surface by 0.5 m.

[0032] After the construction of the anti-slide pile 7, grouting reinforcement is performed; as shown Figure 9 The grouting reinforcement range includes the hole top ground surface and the foundation, the hole top ground surface grouting range is 16 m on both sides of the axis of the main line left tunnel 2 and the main line right tunnel 3, the hole top ground surface grouting range is located outside the tunnel contour line by 0.5 m, the grouting holes are arranged in the shape of a plum blossom, and the grouting hole spacing is 2 m×2 m; the foundation grouting range is 6 m on both sides of the axis of the main line left tunnel 2 and the main line right tunnel 3, the grouting holes are arranged in the shape of a plum blossom, and the grouting hole spacing is 2 m×2 m; The total grouting depth of the hole top ground surface and the foundation is 10 m at the position where the thickness of the collapse slope accumulation body is greater than 10 m; the total grouting depth of the hole top ground surface and the foundation is 1 m into the bedrock at the position where the thickness of the collapse slope accumulation body is less than 10 m.

[0033] The hole opening reinforcement includes an advanced large pipe shed and an advanced small guide pipe. Before the reinforcement of the hole opening, drainage and water interception treatment of the side slope, the outer side of the side slope and the hole opening are performed, C20 concrete hole top water interception ditch is arranged 5m outside the line of the side slope and the outer side of the side slope, then the side slope and the outer side of the side slope are excavated by the top-down method, the side slope is protected by the anchor rod frame beam; the outer side of the side slope is protected by the anchor rod frame beam and the anchor cable frame beam; The left hole of the main line and the right hole of the main line are excavated from inside to outside when exiting the hole, and the surface subsidence is monitored in real time during the excavation process.

[0034] Application examples The left line tunnel of Tiefengshan has an entrance mileage of K16+940 and an exit mileage of K25+575, and the right line tunnel has an entrance mileage of K16+965 and an exit mileage of K25+579, wherein the right hole K16+965-16+977 is a 12m bias pressure type open tunnel. The total length of the tunnel is 17249m, and the maximum buried depth of the tunnel is 923.2m.

[0035] The exit of the Tiefengshan tunnel is in the range of K25+575~K25+530 shallow buried collapse slope body stratum, which is designed to enter the hole at the hole opening, and after the hole is entered by the transverse through guide hole of the present application, the hole is exited. During the exit of the hole of the tunnel, the cumulative value of the surface subsidence of the left hole is-7.50mm, and the cumulative value of the surface subsidence of the right hole is-6.80mm, which effectively controls the exit construction safety of the collapse slope body stratum, and the monitoring items of the single day subsidence and the cumulative subsidence, the deformation rate and the cumulative value of the change meet the requirements of the highway tunnel specification.

[0036] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A construction method for dual tunnels with small clearance in shallow-buried colluvial strata, characterized in that: The treatment of landslide debris at the tunnel entrance and the reinforcement of the tunnel entrance are carried out in parallel with the tunnel excavation process. The tunnel excavation process includes directly entering the left tunnel of the main line of the double-track tunnel through the transverse pilot tunnel. During the excavation of the left tunnel, the right tunnel of the main line is entered through the connecting passage. After the treatment of landslide debris at the tunnel entrance and the reinforcement of the tunnel entrance are completed, the left tunnel and the right tunnel of the main line will exit the tunnel.

2. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 1, characterized in that: The horizontal guide tunnel intersects perpendicularly with the left tunnel of the main line. A portal steel frame is installed on the outside of the guide tunnel arch at the junction of the horizontal guide tunnel and the side wall of the left tunnel of the main line. The portal steel frame is welded to the guide tunnel arch. The arch foot of the portal steel frame is fixed with a locking foot anchor pipe, and the top of the portal steel frame is supported by an advanced small guide pipe.

3. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 2, characterized in that, The construction steps for the transverse pilot tunnel to enter the left tunnel of the main line are as follows: S1: The upper step of the transverse pilot tunnel is constructed upwards, and the tunnel is excavated perpendicular to the main line left tunnel line direction to the outline of the main line left tunnel. Temporary gantry frames are set up and advance small guide pipes are installed as the excavation progresses. The top of the main line left tunnel is supported by anchor bolts and steel mesh. Finally, shotcrete operation is carried out. S2: After all the temporary gantry frames are erected, the main tunnel arch frame is erected. At the intersection of the main tunnel arch frame and the transverse guide tunnel, the main tunnel arch frame is connected to the portal steel frame for shotcrete operation. S3: Remove the temporary gantry and excavate the remaining areas inside the left tunnel of the main line.

4. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 3, characterized in that: Within the area where the main left tunnel and the transverse guide tunnel intersect, the secondary lining reinforcement of the main left tunnel extends into the transverse guide tunnel. When the secondary lining of the main left tunnel is poured, it is poured together with the transverse guide tunnel area to form an integral structure. The invert reinforcement of the main left tunnel extends into the transverse guide tunnel. When the invert of the main left tunnel is poured, it is poured together with the bottom slab inside the transverse guide tunnel.

5. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 3, characterized in that: Once the excavation space of the left tunnel of the main line meets the construction conditions for the connecting passage, the construction of the connecting passage will proceed, and the connecting passage will gradually expand from the left tunnel of the main line to the right tunnel of the main line.

6. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 1, characterized in that: The reinforcement structure for the treatment of landslide debris at the tunnel entrance includes one or more combinations of pile-slab walls, anti-slide piles, pile top locking beams, and grouting reinforcement.

7. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 1, characterized in that: The aforementioned hole reinforcement includes advanced large pipe shed and advanced small pipe; Before reinforcing the tunnel entrance, drainage and water interception treatment were carried out on the outer side and back slope and the tunnel entrance. Then, the side and back slopes were excavated using the reverse construction method. The side slope was protected by anchor frame beams, and the back slope was protected by anchor frame beams and anchor cable frame beams. When the main line left tunnel and the main line right tunnel exit, the excavation work is carried out from inside the tunnel to outside, and the surface settlement is monitored in real time during the excavation process.

8. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 7, characterized in that: The grouting reinforcement scope includes the tunnel roof surface and foundation. The grouting scope of the tunnel roof surface is 16m on both sides of the axis of the main left tunnel and the main right tunnel. The grouting scope of the tunnel roof surface is located 0.5m away from the tunnel outline. The grouting holes are arranged in a quincunx pattern. The grouting scope of the foundation is 6m on both sides of the axis of the main left tunnel and the main right tunnel. The grouting holes are arranged in a quincunx pattern. Where the thickness of the colluvial deposit is greater than 10m, the total grouting depth of the tunnel roof surface and foundation is 10m; where the thickness of the colluvial deposit is less than 10m, the total grouting depth of the tunnel roof surface and foundation is 1m into the bedrock.

9. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 1, characterized in that: The entrance to the transverse guide tunnel is no more than 200m from the entrance to the main tunnel.

10. The construction method for dual tunnels with small clearance in shallow buried colluvial strata according to claim 2, characterized in that: The uprights of the portal steel frame are attached to the upright sections of the guide tunnel arch frame, and the crossbeams of the portal steel frame are tangent to the arc sections of the guide tunnel arch frame. Diagonal braces connect the crossbeams and the uprights of the portal steel frame, and the diagonal braces are tangent to the arc sections of the guide tunnel arch frame. A top brace connects the midpoint of the diagonal brace to the intersection of the upright and the crossbeam. The uprights and crossbeams of the portal steel frame are double-sectioned I-beams.

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