Environmentally friendly multi-arch dark-cut tunnel structure and construction method suitable for steep cliffs near rivers

Abstract

The present invention discloses an environmentally friendly continuous arch dark-cut tunnel structure suitable for steep cliffs near rivers, and relates to the technical field of tunnel engineering. It includes a left hole composite lining, a middle semi-integral middle wall and a right hole transparent dark-cut composite lining; the left hole composite lining includes a left hole secondary lining and a left hole initial support from the inside to the outside; the right hole transparent dark-cut composite lining includes a right hole secondary lining, a right hole initial support, a bottom plate, a top supporting beam, a bottom longitudinal beam and an inclined column. Aiming at the vertical terrain near the river, the present invention proposes for the first time a fully dark-cut transparent continuous arch tunnel scheme, which uses the self-stability of the surrounding rock to resist bias pressure, has a small excavation area, is environmentally friendly, and conforms to the concept of green highway construction. The present invention also relates to a construction method for this environmentally friendly continuous arch dark-cut tunnel structure suitable for steep cliffs near rivers.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and more specifically to an environmentally friendly multi-arch dark-drilled tunnel structure suitable for steep cliffs near rivers. The present invention also relates to a construction method of the environmentally friendly multi-arch dark-drilled tunnel structure suitable for steep cliffs near rivers. Background Art

[0002] When building tunnels in mountainous areas, it is inevitable to encounter vertical cliffs near rivers. When building tunnels in such areas, problems such as tunnel bias and slope treatment are often encountered. For the construction of riverside tunnels, rich theoretical and practical experience has been accumulated in the design and construction. With the development of tourist highway construction, especially the construction of mountain tunnels in recent years, riverside tunnels have been widely used.

[0003] In order to obtain better riverside scenery, existing riverside tunnels often adopt the open-cut method to build tunnels. This method involves large earth excavation and is not environmentally friendly. Especially for riverside steep cliff tunnel projects, if open-cut tunnels are used, it will inevitably cause great damage to the existing mountain.

[0004] For the steep cliff tunnel project near the river, the dark excavation method can indeed be implemented by shifting the line to the inner side of the mountain, but the natural landscape near the river will be lost.

[0005] In summary, the current construction of vertical steep cliff tunnels along rivers still has the following limitations: 1) The large excavation plan is not environmentally friendly, has a single construction method, and has complicated construction procedures, which seriously affects the construction period and cost.

[0006] 2) In the design of conventional dark excavation schemes, only the horizontal and vertical line parameters can be sacrificed to ensure the minimum cover thickness of the dark excavation tunnel to avoid the emergence of steep cliff tunnels near rivers.

[0007] 3) Tunnels along steep cliffs near rivers need to form a new type of tunnel structure to adapt to the terrain, which can not only avoid large-scale excavation, but also form a system with the surrounding rock to achieve overall stress on the tunnel structure and surrounding rock. However, research in this aspect is relatively lagging behind at home and abroad.

[0008] Therefore, it is necessary to develop an environmentally friendly multi-arch dark-cut tunnel structure and its construction method suitable for steep cliffs near rivers. Summary of the invention

[0009] The first purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide an environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers.

[0010] The second purpose of the present invention is to provide a construction method for the environmentally friendly multi-arch dark-cut tunnel structure suitable for steep cliffs near rivers.

[0011] In order to achieve the above first purpose, the technical solution of the present invention is: an environmentally friendly multi-arch dark excavation tunnel structure suitable for steep cliffs near rivers, characterized by: comprising a left hole composite lining located in the mountain from left to right, a semi-integral middle wall in the middle and a right hole transparent dark excavation composite lining, the right hole transparent dark excavation composite lining is on the river side;

[0012] The composite lining of the left tunnel includes the secondary lining of the left tunnel and the primary support of the left tunnel from the inside to the outside; the right side of the secondary lining of the left tunnel is connected to the left side of the middle semi-integral middle wall; the primary support of the left tunnel is not closed into a ring, one end of the primary support of the left tunnel is supported on the top of the middle semi-integral middle wall, and the other end is connected to the bottom of the left side of the middle semi-integral middle wall;

[0013] The right-hole transparent dark-excavation composite lining includes the right-hole secondary lining, the right-hole initial support, the bottom plate, the top supporting beam, the bottom longitudinal beam and the inclined column; the left end of the right-hole secondary lining is connected to the top of the middle semi-integral middle wall, and the right end is connected to the top supporting beam; the right-hole initial support is located at the top of the right-hole secondary lining, and the left end of the right-hole initial support is supported on the top of the middle semi-integral middle wall; the left end of the bottom plate is connected to the right bottom of the middle semi-integral middle wall, and the right end is connected to the bottom longitudinal beam; a plurality of the inclined columns are spaced between the top supporting beam and the bottom longitudinal beam.

[0014] In the above technical solution, a rockfall prevention beam is provided at the right end of the top supporting beam.

[0015] In the above technical solution, the left end of the secondary lining of the right hole is connected to the top of the intermediate semi-integral wall through embedded steel bars to form an integral structure.

[0016] In the above technical solution, the initial support of the left tunnel is connected to the top of the intermediate semi-integral middle wall through embedded parts to form an integral structure.

[0017] In the above technical solution, the bottom of the intermediate semi-integral middle wall, the bottom of the bottom longitudinal beam and the riverside slope of the mountain are reinforced with the mountain through small grouting pipes.

[0018] In the above technical solution, the center line of the guide tunnel of the intermediate semi-integral middle wall is offset by 30-50 cm toward the river side compared with the center line of the route.

[0019] In the above technical solution, a pre-buried welded steel plate is arranged in the top supporting beam; the initial support of the right hole is connected to the mountain through a prestressed anchor cable, and the pre-buried welded steel plate is connected to the mountain through a locking anchor rod.

[0020] In order to achieve the above second purpose, the technical solution of the present invention is: a construction method of an environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers, characterized in that it includes the following steps:

[0021] Step 1, middle guide hole construction:

[0022] The middle guide tunnel is constructed by the step method. After the upper half of the middle guide tunnel is excavated, the primary support of the arch of the middle semi-integral middle wall is constructed. Then, after the lower half of the middle guide tunnel is excavated, the primary support of the side wall of the middle semi-integral middle wall is constructed.

[0023] After the middle guide tunnel is penetrated, the middle semi-integral middle wall is constructed, and the bottom of the middle semi-integral middle wall is ensured to be reliably anchored to the mountain through the grouting small conduit;

[0024] Step 2, right hole construction:

[0025] Excavate the earthwork of the inclined column part, reinforce the bottom longitudinal beam and the riverside slope of the mountain through the grouting small pipe, then construct the bottom longitudinal beam, inclined column, lock anchor rod and pre-buried welding steel plate, and finally construct the top supporting beam;

[0026] Excavate the upper step of the pilot hole of the right tunnel and construct the upper support of the right tunnel with sprayed anchors, then excavate the lower step of the pilot hole of the right tunnel and construct the lower support of the right tunnel with sprayed anchors;

[0027] Excavate the earthwork above the core soil of the right tunnel; spray concrete and pre-embed the initial support steel of the right tunnel, and simultaneously install prestressed anchor cables to form the initial support of the right tunnel;

[0028] The secondary lining of the left tunnel is constructed in time. The secondary lining of the left tunnel is directly supported on the middle semi-integral wall and is reliably connected through embedded steel bars.

[0029] The core soil of the right main tunnel and the lower step of the right tunnel were excavated in sequence, and then the bottom plate was constructed. Finally, the upper support of the right tunnel and the lower support of the right tunnel were removed. The primary support of the side wall of the semi-integral middle wall was removed in the place where the three-dimensional space conflicted.

[0030] Step 3, left hole construction:

[0031] Excavate the upper step of the pilot hole of the left tunnel and apply sprayed anchor support to the upper part of the left tunnel, then excavate the lower step of the pilot hole of the left tunnel and apply sprayed anchor support to the lower part of the left tunnel;

[0032] Excavate the earthwork above the core soil of the left tunnel main tunnel; spray concrete and embed the upper steel of the left tunnel initial support. The upper steel of the left tunnel initial support is directly supported on the top of the middle semi-integral middle wall and reliably connected through embedded parts;

[0033] The core soil of the left tunnel main tunnel and the lower step of the left tunnel are excavated in sequence, and then the left tunnel inverted arch primary support is constructed and the lower steel of the left tunnel initial support is pre-buried; the upper steel of the left tunnel initial support and the lower steel of the left tunnel initial support are connected to form the left tunnel initial support;

[0034] The secondary lining of the inverted arch and the secondary lining of the arch waist and arch crown are constructed in sequence and closed into a ring to form the secondary lining of the left tunnel. The upper sprayed anchor support of the left tunnel and the lower sprayed anchor support of the left tunnel are removed.

[0035] Where the three-dimensional space conflicts, the initial support of the side walls of the middle semi-integral wall is removed.

[0036] In the above technical solution, in step 1, while constructing the middle semi-integral middle wall, a steel support is constructed simultaneously, and the steel support connects the middle semi-integral middle wall and the primary support of the side wall on the left side of the middle semi-integral middle wall.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1) In the design of conventional dark excavation schemes, only the horizontal and vertical line shape parameters can be sacrificed to ensure the minimum cover thickness of the dark excavation tunnel to avoid the emergence of steep cliff tunnels near rivers; however, the present invention proposes a new tunnel structure to adapt to the steep cliff terrain near rivers, and there is no need to sacrifice the horizontal and vertical line shape parameters to avoid the emergence of steep cliff tunnels near rivers. Not only does it achieve the overall force of the tunnel structure and the surrounding rock, it also complies with the construction concept of green highways and protects the environment.

[0039] 2) The present invention is the first to propose a fully concealed, transparent, multi-arch tunnel solution for vertical river terrain. It uses the self-stability of the surrounding rock to resist bias pressure, requires little excavation, is environmentally friendly, and complies with the concept of green highway construction.

[0040] 3) The transparent dark-excavated composite lining of the right tunnel of the present invention adopts the column-hole method for dark-excavation construction, and the left tunnel and the middle guide tunnel are both constructed by dark-excavation. It is the first dark-excavated multi-arch tunnel construction method in vertical terrain, which is suitable for vertical steep cliff terrain near the river. It can not only avoid large excavation, but also make the tunnel structure and surrounding rock form a system, so as to realize the overall stress of the tunnel structure and surrounding rock.

[0041] 4) The transparent dark excavation composite lining of the right hole on the river side of the present invention is supported by inclined columns, which provides a clear view and a good landscape effect.

[0042] 5) Since the present invention is a dark excavation support structure, it can adapt to the vertical river terrain, not only can it resist bias pressure, but also can form a system with the surrounding rock to achieve the overall force of the tunnel structure and the surrounding rock.

[0043] 6) The construction method of the present invention is more environmentally friendly while ensuring safety and stability, and has simple construction procedures, short construction period and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a structural schematic diagram of the present invention.

[0045] Figure 2 It is the construction drawing of the present invention.

[0046] Among them, 100-left tunnel composite lining, 110-left tunnel secondary lining, 120-left tunnel initial support, 200-middle semi-integral middle wall, 300-right tunnel transparent dark excavation composite lining, 310-right tunnel secondary lining, 320-right tunnel initial support, 330-bottom plate, 340-top supporting beam, 341-embedded welded steel plate, 350-bottom longitudinal beam, 360-inclined column, 370-rockfall prevention beam, 400-mountain, 410-steel mesh, 510-grouting small duct, 520-prestressed anchor cable, 530-locking foot anchor rod, Ⅰ1-upper half of the middle guide tunnel, Ⅰ2-arch initial support, Ⅰ3-lower half of the middle guide tunnel, Ⅰ4-side wall initial support, Ⅰ5-steel support, Ⅱ1-inclined column earthwork, Ⅲ1-right Upper step of the pilot tunnel of the right tunnel, Ⅲ2-upper support of shotcrete, Ⅲ3-lower step of the pilot tunnel of the right tunnel, Ⅲ4-lower support of shotcrete, Ⅳ1-earth above the core soil of the right tunnel main tunnel, Ⅳ2-initial support steel of the right tunnel, Ⅳ3-core soil of the right tunnel main tunnel, Ⅳ4-lower step of the right tunnel, Ⅴ1-upper step of the pilot tunnel of the left tunnel, Ⅴ2-upper shotcrete support of the left tunnel, Ⅴ3-lower step of the pilot tunnel of the left tunnel, Ⅴ4-lower shotcrete support of the left tunnel, Ⅵ1-earth above the core soil of the left tunnel main tunnel, Ⅵ2-upper steel of the initial support of the left tunnel, Ⅵ3-core soil of the left tunnel main tunnel, Ⅵ4-lower step of the left tunnel, Ⅵ5-lower steel of the initial support of the left tunnel, Ⅶ-secondary lining of the inverted arch, Ⅷ-secondary lining of the arch waist and arch crown, A-centerline of the pilot tunnel, B-centerline of the route, C-centerline of the left tunnel tunnel, D-centerline of the right tunnel tunnel. DETAILED DESCRIPTION

[0047] The following detailed description of the implementation of the present invention is made in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention will become clearer and easier to understand through the description.

[0048] Refer to the attached figure: Figure 1 As shown, the environmentally friendly multi-arch dark excavation tunnel structure suitable for steep cliffs near rivers is characterized by: comprising a left hole composite lining 100, a middle semi-integral middle wall 200 and a right hole transparent dark excavation composite lining 300 located in the mountain 400 from left to right, and the right hole transparent dark excavation composite lining 300 is on the river side;

[0049] The left tunnel composite lining 100 includes a left tunnel secondary lining 110 and a left tunnel primary support 120 from the inside to the outside; the right side of the left tunnel secondary lining 110 is connected to the left side of the middle semi-integral middle wall 200; the left tunnel primary support 120 is not closed into a ring, one end of the left tunnel primary support 120 is supported on the top of the middle semi-integral middle wall 200, and the other end is connected to the left bottom of the middle semi-integral middle wall 200; the right side profile of the left tunnel secondary lining 110 fits the left side profile of the middle semi-integral middle wall 200;

[0050] The right-hole transparent dark-excavation composite lining 300 includes a right-hole secondary lining 310, a right-hole initial support 320, a bottom plate 330, a top supporting beam 340, a bottom longitudinal beam 350 and an inclined column 360; the left end of the right-hole secondary lining 310 is connected to the top of the middle semi-integral middle wall 200, and the right end is connected to the top supporting beam 340; the right-hole initial support 320 is located at the top of the right-hole secondary lining 310, and the left end of the right-hole initial support 320 is supported on the top of the middle semi-integral middle wall 200; the left end of the bottom plate 330 is connected to the right bottom of the middle semi-integral middle wall 200, and the right end is connected to the bottom longitudinal beam 320; a plurality of the inclined columns 360 are arranged at intervals between the top supporting beam 340 and the bottom longitudinal beam 350; the right side of the middle semi-integral middle wall 200 directly forms the inner contour of the right-hole transparent dark-excavation composite lining 300.

[0051] The right end of the top supporting beam 340 is provided with a rockfall prevention beam 370 .

[0052] The left end of the right tunnel secondary lining 310 is connected to the top of the intermediate semi-integral middle wall 200 through embedded steel bars to form an integral structure; the inclined column 360 is supported on the bottom longitudinal beam 350 to ensure the overall safety of the tunnel.

[0053] The left tunnel initial support 120 is connected to the top of the intermediate semi-integral middle wall 200 through embedded parts to form an integral structure.

[0054] The bottom of the intermediate semi-integral middle wall 200, the bottom of the bottom longitudinal beam 350 and the riverside slope of the mountain 400 are reinforced with the mountain 400 through a small grouting pipe 510; the riverside slope of the mountain 400 is provided with a steel mesh 410 for slope protection.

[0055] The center line of the intermediate semi-integral middle wall 200 is offset by 30-50 cm toward the river side compared with the center line of the route, so as to ensure the compactness of the construction work on the top of the intermediate semi-integral middle wall 200.

[0056] The embedded welded steel plate 341 is arranged inside the top supporting beam 340 ; the right hole initial support 320 is connected to the mountain 400 via a prestressed anchor cable 520 , and the embedded welded steel plate 341 is connected to the mountain 400 via a locking anchor rod 530 .

[0057] like Figure 2 As shown, the construction method of the environmentally friendly multi-arch dark-cut tunnel structure suitable for steep cliffs near rivers is characterized by comprising the following steps:

[0058] Step 1, middle guide hole construction:

[0059] The middle guide tunnel is constructed by the step method. After excavating the upper half area Ⅰ1 of the middle guide tunnel, the arch initial support Ⅰ2 of the middle semi-integral middle wall 200 is constructed. Then, after excavating the lower half area Ⅰ3 of the middle guide tunnel, the side wall initial support Ⅰ4 of the middle semi-integral middle wall 200 is constructed.

[0060] After the middle guide tunnel is penetrated, the middle semi-integral middle wall 200 is constructed, and it is ensured that the bottom of the middle semi-integral middle wall 200 is reliably anchored to the mountain 400 through the grouting small conduit 510;

[0061] Step 2, right hole construction:

[0062] According to the calculated spacing, diagonal column earthwork II1 of the diagonal column 360 is excavated, and the bottom longitudinal beam 350 and the riverside slope of the mountain 400 are reinforced by grouting through a small grouting pipe 510, and then the bottom longitudinal beam 350 and the diagonal column 360 are successively constructed, the locking foot anchor rod 530 is constructed, and the pre-buried welding steel plate 341 is prepared, and finally the top supporting beam 340 is constructed;

[0063] Excavate the upper step Ⅲ1 of the pilot hole of the right tunnel and construct the upper support Ⅲ2 of the right tunnel sprayed anchor, then excavate the lower step Ⅲ3 of the pilot hole of the right tunnel and construct the lower support Ⅲ4 of the right tunnel sprayed anchor;

[0064] Excavate the earthwork Ⅳ1 above the core soil of the main tunnel of the right tunnel; spray concrete and pre-embed the initial support steel Ⅳ2 of the right tunnel, and simultaneously install prestressed anchor cables 520 to form the initial support 320 of the right tunnel;

[0065] The secondary lining 110 of the left tunnel is constructed in a timely manner. The secondary lining 110 of the left tunnel is directly supported on the intermediate semi-integral middle wall 200 and is reliably connected by embedded steel bars;

[0066] The right tunnel adopts the construction technology of dark excavation. The concrete of the initial support 320 of the right tunnel is sprayed directly on the rock wall. The initial support 320 of the right tunnel plus the prestressed anchor cable 520 can more effectively mobilize the self-stability of the surrounding rock itself, which is more in line with the construction concept of the New Austrian Tunneling Method and has a safer structure.

[0067] The core soil IV3 of the right main tunnel and the lower step IV4 of the right tunnel were excavated in sequence, and then the bottom plate 330 was constructed. Finally, the upper support Ⅲ2 of the right tunnel sprayed anchor and the lower support Ⅲ4 of the right tunnel sprayed anchor were removed; the primary support Ⅰ4 of the side wall of the middle semi-integral middle wall 200 was removed in the place where the three-dimensional space conflicted;

[0068] Step 3, left hole construction:

[0069] Excavate the upper step V1 of the pilot hole of the left tunnel and construct the upper sprayed anchor support V2 of the left tunnel, then excavate the lower step V3 of the pilot hole of the left tunnel and construct the lower sprayed anchor support V4 of the left tunnel;

[0070] Excavate the earthwork VI1 above the core soil of the main tunnel of the left tunnel; spray concrete and embed the upper steel VI2 of the initial support of the left tunnel. The upper steel VI2 of the initial support of the left tunnel is directly supported on the top of the middle semi-integral middle wall 200 and is reliably connected through embedded parts; the left tunnel adopts the construction technology of dark excavation, and the concrete of the initial support 120 of the left tunnel can be directly sprayed on the rock wall without the need for arch protection;

[0071] The core soil VI3 of the left tunnel main tunnel and the lower step VI4 of the left tunnel are excavated in sequence, and then the left tunnel inverted arch primary support is constructed and the lower steel VI5 of the left tunnel primary support is pre-buried; the upper steel VI2 of the left tunnel primary support and the lower steel VI5 of the left tunnel primary support are connected to form the left tunnel primary support 120;

[0072] The secondary lining VII of the inverted arch and the secondary lining VIII of the arch waist and arch crown are constructed in sequence and closed into a ring to form the secondary lining 110 of the left tunnel, and the upper sprayed anchor support V2 of the left tunnel and the lower sprayed anchor support V4 of the left tunnel are removed; the left tunnel adopts the dark excavation construction technology, and the secondary lining 110 of the left tunnel can be closed into a ring independently without the help of the intermediate semi-integral middle wall 200, which is equivalent to an independent closed structure, which is not interrupted and has a more favorable force resistance.

[0073] Where the three-dimensional space conflicts, the primary support Ⅰ4 of the side wall of the middle semi-integral middle wall 200 is removed.

[0074] In step 1, while constructing the middle semi-integral middle wall 200, a steel support Ⅰ5 is constructed simultaneously, and the steel support Ⅰ5 connects the middle semi-integral middle wall 200 and the side wall primary support Ⅰ4 on the left side of the middle semi-integral middle wall 200; the steel support Ⅰ5 improves the anti-disturbance capability of the middle guide tunnel.

[0075] Other parts not described belong to the prior art.

Claims

1. An environmentally friendly multi-arch tunnel structure suitable for steep cliffs near rivers, characterized by: The invention comprises a left hole composite lining (100), a middle semi-integral middle wall (200) and a right hole transparent dark excavation composite lining (300) located in the mountain (400) from left to right, wherein the right hole transparent dark excavation composite lining (300) is located on the river side; The left hole composite lining (100) comprises, from the inside to the outside, a left hole secondary lining (110) and a left hole primary support (120); the right side of the left hole secondary lining (110) is connected to the left side of the middle semi-integral middle wall (200); the left hole primary support (120) is not closed into a ring, one end of the left hole primary support (120) is supported on the top of the middle semi-integral middle wall (200), and the other end is connected to the left bottom of the middle semi-integral middle wall (200); The right hole transparent dark excavation composite lining (300) comprises a right hole secondary lining (310), a right hole initial support (320), a bottom plate (330), a top supporting beam (340), a bottom longitudinal beam (350) and an inclined column (360); the left end of the right hole secondary lining (310) is connected to the top of the middle semi-integral middle wall (200), and the right end is connected to the top supporting beam (340); the right hole initial support (320) is located at the top of the right hole secondary lining (310), and the left end of the right hole initial support (320) is supported on the top of the middle semi-integral middle wall (200); the left end of the bottom plate (330) is connected to the right bottom of the middle semi-integral middle wall (200), and the right end is connected to the bottom longitudinal beam (320); a plurality of the inclined columns (360) are arranged between the top supporting beam (340) and the bottom longitudinal beam (350) at intervals.

2. The environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers according to claim 1 is characterized by: The right end of the top supporting beam (340) is provided with a rockfall prevention beam (370).

3. The environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers according to claim 1 is characterized by: The left end of the right hole secondary lining (310) is connected to the top of the intermediate semi-integral middle wall (200) through embedded steel bars to form an integral structure.

4. The environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers according to claim 3 is characterized by: The left tunnel initial support (120) is connected to the top of the intermediate semi-integral middle wall (200) through embedded parts to form an integral structure.

5. The environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers according to claim 1 is characterized by: The bottom of the intermediate semi-integral middle wall (200), the bottom of the bottom longitudinal beam (350) and the riverside slope of the mountain (400) are all reinforced with the mountain (400) through a grouting small conduit (510).

6. The environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers according to claim 1 is characterized by: The center line (A) of the guide tunnel of the intermediate semi-integral middle wall (200) is offset by 30-50 cm toward the river side compared with the center line (B) of the route.

7. The environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers according to claim 3 is characterized by: A pre-buried welded steel plate (341) is arranged inside the top supporting beam (340); the right hole initial support (320) is connected to the mountain (400) via a prestressed anchor cable (520), and the pre-buried welded steel plate (341) is connected to the mountain (400) via a locking anchor rod (530).

8. A construction method for an environmentally friendly double-arch dark-cut tunnel structure suitable for steep cliffs near rivers, characterized in that: The following steps are involved: Step 1, middle guide hole construction: The middle guide tunnel is constructed by using a step method. After excavating the upper half area (Ⅰ1) of the middle guide tunnel, the initial arch support (Ⅰ2) of the middle semi-integral middle wall (200) is constructed. Then, after excavating the lower half area (Ⅰ3) of the middle guide tunnel, the initial side wall support (Ⅰ4) of the middle semi-integral middle wall (200) is constructed. After the middle guide tunnel is penetrated, the middle semi-integral middle wall (200) is constructed, and it is ensured that the bottom of the middle semi-integral middle wall (200) is reliably anchored to the mountain (400) through a grouting small conduit (510); Step 2, right hole construction: Excavate the inclined column earthwork (II1) of the inclined column (360), perform grouting reinforcement on the bottom longitudinal beam (350) and the riverside slope of the mountain (400) through a grouting small pipe (510), then sequentially construct the bottom longitudinal beam (350), the inclined column (360), construct the locking foot anchor rod (530) and prepare the pre-buried welding steel plate (341), and finally construct the top supporting beam (340); Excavate the upper step of the pilot hole of the right tunnel (Ⅲ1) and construct the upper support of the right tunnel with sprayed anchors (Ⅲ2), then excavate the lower step of the pilot hole of the right tunnel (Ⅲ3) and construct the lower support of the right tunnel with sprayed anchors (Ⅲ4); Excavate the earthwork above the core soil of the right tunnel main tunnel (Ⅳ1); spray concrete and pre-embed the right tunnel initial support steel (Ⅳ2), and simultaneously install prestressed anchor cables (520) to form the right tunnel initial support (320); The secondary lining (110) of the left tunnel is constructed in a timely manner. The secondary lining (110) of the left tunnel is directly supported on the intermediate semi-integral middle wall (200) and is reliably connected by embedded steel bars; The core soil of the right tunnel main tunnel (Ⅳ3) and the right tunnel lower step (Ⅳ4) are excavated in sequence, and then the bottom plate (330) is constructed. Finally, the upper support (Ⅲ2) and the lower support (Ⅲ4) of the right tunnel sprayed anchor are removed. The primary support (Ⅰ4) of the side wall of the middle semi-integral middle wall (200) is removed in the place where the three-dimensional space conflicts. Step 3, left hole construction: Excavate the upper step of the pilot hole of the left tunnel (V1) and apply sprayed anchor support on the upper part of the left tunnel (V2), then excavate the lower step of the pilot hole of the left tunnel (V3) and apply sprayed anchor support on the lower part of the left tunnel (V4); Excavating the earthwork above the core soil of the left tunnel main tunnel (VI1); spraying concrete and pre-embedding the left tunnel initial support upper steel (VI2), the left tunnel initial support upper steel (VI2) is directly supported on the top of the middle semi-integral middle wall (200) and is reliably connected through pre-embedded parts; The core soil of the left tunnel main tunnel (VI3) and the lower step of the left tunnel (VI4) are excavated in sequence, and then the left tunnel inverted arch primary support is constructed and the lower steel of the left tunnel initial support is pre-buried (VI5); the upper steel of the left tunnel initial support (VI2) and the lower steel of the left tunnel initial support (VI5) are connected to form the left tunnel initial support (120); The secondary lining of the inverted arch (VII) and the secondary lining of the arch waist and arch crown (VIII) are sequentially constructed and closed into a ring to form the secondary lining of the left tunnel (110), and the upper sprayed anchor support (V2) and the lower sprayed anchor support (V4) of the left tunnel are removed; Where the three-dimensional space conflicts, the primary support (Ⅰ4) of the side wall of the middle semi-integral middle wall (200) is removed.

9. The construction method of the environmentally friendly multi-arch dark-excavated tunnel structure suitable for steep cliffs near rivers according to claim 8, characterized in that: In step 1, while constructing the middle semi-integral middle wall (200), a steel support (Ⅰ5) is constructed simultaneously, and the steel support (Ⅰ5) connects the middle semi-integral middle wall (200) and the primary support (Ⅰ4) of the side wall on the left side of the middle semi-integral middle wall (200).

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