Structure and construction method of bamboo-cutting arch tunnel entrance in the mountain pass terrain of the protected area

Abstract

A bamboo-cutting arch tunnel portal structure and construction method for a protected area mountain pass terrain is disclosed. The structure includes left / right tunnel composite lining and a central pilot tunnel. The central pilot tunnel is equipped with double rows of anti-slide piles perpendicular to the tunnel alignment and a reinforced concrete cover slab. The cover slab is fixed by pre-reserved reinforcing bars at the top of the anti-slide piles. Continuous steel plates on both sides of the central pilot tunnel connect the initial support steel sections of the left / right tunnels. The straight sidewalls of the left / right tunnels are connected to the anti-slide piles by reinforcing bars. A floor slab and temporary steel frame support are also provided inside the central pilot tunnel. The construction method includes: constructing double rows of anti-slide piles and excavating the tunnel portal side slope; pouring the cover slab and then excavating the central pilot tunnel and constructing the floor slab and temporary supports; excavating the main tunnel, left and right pilot tunnels, and the main tunnel in stages, connecting the initial support of the main tunnel to the cover slab via continuous steel plates, and connecting the secondary lining sidewalls to the anti-slide piles; finally, conventional excavation and backfilling of the bamboo-cutting open tunnel. This invention does not alter the original terrain of the protected area and can increase the number of anti-slide piles to ensure the safety of the tunnel portal side slope.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering, specifically to a bamboo-cutting arch tunnel entrance structure and construction method for protected mountain pass terrain. Background Technology

[0002] In highway tunnel construction, arch tunnels are often used when encountering mountain passes in environmentally protected areas. These passes typically have thick layers of gravelly soil and gravelly topsoil, and the excavation span of arch tunnels is large (for example, on the Shuangsi Expressway, the arch tunnel's span exceeds 30m; the presence of reinforced concrete partition walls prevents the installation of anti-slide piles between the left and right tunnel sections). Therefore, anti-slide pile treatment is necessary for the tunnel entrance slopes. However, because the excavation span of arch tunnels exceeds 30m, anti-slide pile solutions are often unfeasible due to the inability to install them on the tunnel body excavation cross-section, and surface grouting causes significant environmental damage to the protected area. Therefore, there is an urgent need for a tunnel entrance structure that not only adapts to environmentally friendly tunnel designs but also allows for the use of anti-slide piles for slope reinforcement. Summary of the Invention

[0003] This invention provides a bamboo-cutting arch tunnel entrance structure and construction method for protected area mountain pass terrain, to solve the problems of existing protected area mountain pass arch tunnels needing reinforcement but surface treatment is not environmentally friendly, and the central partition wall restricts the installation of anti-slide piles, thus limiting the reinforcement of the entrance. It can maintain the original terrain of the protected area and increase the number of anti-slide piles to ensure the safety of the slope at the entrance.

[0004] A bamboo-cutting arch tunnel entrance structure suitable for the mountain pass terrain of a protected area includes:

[0005] The left tunnel composite lining, the right tunnel composite lining, and the central guide tunnel located between the left tunnel composite lining and the right tunnel composite lining;

[0006] The central tunnel includes anti-slide piles and a cover plate. The anti-slide piles are arranged in two rows perpendicular to the tunnel alignment, and the cover plate is connected to the top of the anti-slide piles.

[0007] The two sides of the central tunnel are provided with continuous steel plates, which are used to connect the initial support steel of the left tunnel composite lining and the right tunnel composite lining.

[0008] The sidewalls of the left tunnel composite lining and the right tunnel composite lining are straight sidewalls, which are connected to the anti-slide piles by steel bars.

[0009] Furthermore, each row of the anti-slide piles consists of 4 piles, and the spacing between the rows of double-row anti-slide piles is 3-8 meters.

[0010] Furthermore, the cover plate is a reinforced concrete cover plate, and the top of the anti-slide pile has a reserved connecting steel bar, and the cover plate is fixedly connected to the anti-slide pile through the reserved connecting steel bar.

[0011] Furthermore, the continuous steel plate is arranged along the longitudinal direction of the central guide hole and is located on both sides of the cover plate. The continuous steel plate is welded and fixed to the initial support steel of the left hole composite lining and the right hole composite lining.

[0012] Furthermore, the straight side wall is connected to the anti-slide pile by means of rebar installation, and the rebar penetrates the lining structure of the straight side wall and is embedded in the anti-slide pile.

[0013] Furthermore, the central tunnel is provided with a bottom plate and temporary steel frame support. The bottom plate is located at the bottom of the central tunnel, and the temporary steel frame support is arranged at intervals along the longitudinal direction of the central tunnel.

[0014] A construction method for a bamboo-cutting arch tunnel entrance structure suitable for mountain pass terrain in a protected area, as described above, includes the following steps:

[0015] Step 1: Construction of anti-slide piles and excavation of the tunnel entrance:

[0016] Double rows of anti-slide piles are installed perpendicular to the tunnel alignment, with four piles in each row. Reinforcing bars are pre-installed at the top of the anti-slide piles. The slope at the tunnel entrance is excavated under the protection of the anti-slide piles to address the stability of the slope at the tunnel entrance.

[0017] Step 2, Construction of the pilot tunnel:

[0018] A reinforced concrete cover plate is poured through the reserved connecting steel bars at the top of the anti-slide pile to fix the cover plate to the anti-slide pile; under the protection of the anti-slide pile and the cover plate, a central guide tunnel is excavated, a bottom slab of the central guide tunnel is constructed, and a temporary steel frame is set up in the central guide tunnel to enhance the stability of the central guide tunnel;

[0019] Step 3: Construction of the left and right pilot tunnels of the main tunnel of the twin-arch tunnel:

[0020] Excavate the upper step of the left tunnel pilot tunnel and install shotcrete and anchor support; then excavate the lower step of the left tunnel pilot tunnel and install shotcrete and anchor support; excavate the upper right part of the right tunnel pilot tunnel step, spray concrete and pre-embed steel sections, and install locking foot grouting pipes to form the initial support closed structure of the upper right part of the right tunnel pilot tunnel.

[0021] Step 4: Construction of the left and right main tunnels of the twin-arch tunnel:

[0022] Excavate the soil above the core soil of the left main tunnel, spray concrete and pre-embed steel sections, so that the initial support of the left main tunnel is connected to the cover plate through the continuous steel plates on both sides of the central guide tunnel; excavate the core soil and lower step of the left main tunnel in sequence, and construct the initial support of the bottom invert arch; excavate the core soil and lower step of the right main tunnel in the same way, construct the initial support of the right main tunnel and connect it with the cover plate; construct the secondary lining of the left and right main tunnels, and connect the sidewalls of the secondary lining to the anti-slide piles through steel bars;

[0023] Step 5: Excavation and backfilling of conventional arch tunnels and bamboo-cut open-cut tunnels:

[0024] Continue excavating the conventional arch tunnel section, construct the bamboo-cut open-cut structure, and carry out greening and backfilling to restore the original surface topography.

[0025] Furthermore, in step 1, the row spacing of the double-row anti-slide piles is twice the pile diameter, and the pile spacing is 3-5 meters.

[0026] Furthermore, in step 2, after the cover plate is poured, the top of the anti-slide pile is backfilled with the original soil to maintain the original ground topography.

[0027] Furthermore, in step 4, if there is a three-dimensional spatial conflict between the initial support structure and the anti-slide piles during the secondary lining construction of the left and right main tunnels, the temporary support structure at the conflicting part shall be removed before the secondary lining is poured.

[0028] Furthermore, in step 4, if there is a three-dimensional spatial conflict between the initial support structure and the anti-slide piles during the secondary lining construction of the left and right main tunnels, the temporary support structure at the conflicting part shall be removed before the secondary lining is poured.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. Environmental friendliness: This invention achieves the purpose of reinforcing the slope at the entrance of the tunnel by setting up multiple rows and multiple anti-slide piles, without adopting surface reinforcement methods, thus meeting the requirements of environmental protection areas.

[0031] 2. Economic efficiency: Due to the isolation provided by multiple anti-slide piles in the left and right tunnels of the twin-arch tunnel, interference from the excavation of the left and right tunnels can be effectively reduced, thus reducing the amount of temporary support work for the left and right tunnels. In addition, the reinforced concrete partition wall of the central pilot tunnel can be eliminated.

[0032] 3. Construction safety: This invention first sets up double rows of anti-slide piles. Under the protection of the anti-slide piles, the safety of the slope at the opening can be effectively ensured. In addition, the isolation of the anti-slide piles reduces the mutual influence between the construction of the left and right openings, and the safety can also be effectively improved. Attached Figure Description

[0033] Figure 1 This is a schematic elevation view of the entrance structure of the bamboo-cutting arch tunnel in the protected mountain pass terrain of this invention.

[0034] Figure 2 yes Figure 1 Enlarged view of section A in the middle.

[0035] Figure 3 yes Figure 2 Enlarged view of section B.

[0036] Figure 4This is a schematic plan view of the entrance structure of the bamboo-cutting arch tunnel in the protected mountain pass terrain of this invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Please see Figure 1-4 This invention provides a bamboo-cutting arch tunnel entrance structure suitable for mountain pass terrain in a protected area, comprising: a left tunnel composite lining, a right tunnel composite lining, and a central guide tunnel located between the left tunnel composite lining and the right tunnel composite lining.

[0039] The central tunnel includes anti-slide piles and a cover plate. The anti-slide piles are arranged in two rows perpendicular to the tunnel alignment, and the cover plate is connected to the top of the anti-slide piles.

[0040] In one embodiment, four anti-slide piles are arranged in each row, and the spacing between the rows of double-row anti-slide piles is 3-8 meters. The cover plate is a reinforced concrete cover plate, and connecting steel bars are reserved at the top of the anti-slide piles. The cover plate is fixedly connected to the anti-slide piles through the reserved connecting steel bars.

[0041] In one embodiment, the central tunnel is provided with a bottom plate and temporary steel frame support, the bottom plate is located at the bottom of the central tunnel, and the temporary steel frame support is arranged at intervals along the longitudinal direction of the central tunnel.

[0042] The two sides of the central tunnel are provided with continuous steel plates, which are used to connect the initial support steel of the left tunnel composite lining and the right tunnel composite lining.

[0043] In one embodiment, the continuous steel plate is arranged along the longitudinal direction of the central guide hole and is located on both sides of the cover plate. The continuous steel plate is welded and fixed to the initial support steel of the left hole composite lining and the right hole composite lining.

[0044] The sidewalls of the left and right tunnel composite linings are straight sidewalls, which are connected to the anti-slide piles by reinforcing bars. The straight sidewalls are connected to the anti-slide piles by rebar installation, with the rebars penetrating the lining structure of the straight sidewalls and embedded within the anti-slide piles.

[0045] This invention also provides a construction method for the entrance of a bamboo-cutting arch tunnel suitable for mountain pass terrain in a protected area, comprising the following steps:

[0046] Taking the excavation of the left tunnel of the main tunnel first as an example:

[0047] Step 1: Construction of anti-slide piles and excavation of the tunnel entrance:

[0048] ① Two rows of anti-slide piles are installed perpendicular to the tunnel alignment, with four piles in each row. Anti-slide piles I1, I2, I3, and I4 are installed sequentially. Connecting steel bars are pre-installed at the top of anti-slide piles I1 and I2 to connect with the top reinforced concrete cover plate. ② The tunnel entrance slope is excavated under the protection of the anti-slide piles.

[0049] Step 2: Construction of the pilot tunnel:

[0050] ① The reinforced concrete cover plate Ⅱ1 on top of the anti-slide piles I1 and I2 is firmly connected by the pre-reserved connecting steel bars at the top of the anti-slide piles I1 and I2. Steel plates are reserved on both sides of the cover plate to facilitate connection with the initial support of the left and right main tunnels. The original soil is backfilled at the top of the anti-slide piles to ensure that the original ground topography is not changed.

[0051] ② Under the protection of anti-slide piles I1 and I2 and reinforced concrete cover plate II1, excavate the central guide tunnel II2 and construct the central guide tunnel bottom slab II3. Finally, construct temporary steel frame I20a to support the central guide tunnel bottom slab II3 to enhance the stability of the central guide tunnel.

[0052] Step 3: Construction of the left and right pilot tunnels of the main tunnel of the twin-arch tunnel:

[0053] ① Excavate the upper step Ⅲ1 of the left pilot tunnel and install shotcrete and anchor support Ⅲ2, then excavate the lower step Ⅲ3 of the left pilot tunnel and install shotcrete and anchor support Ⅲ4.

[0054] ② Excavate the upper right section of the pilot tunnel step IV1, spray concrete and pre-embed steel section IV2, and construct the locking foot grouting pipe. Then construct the bottom steel section IV3 of the upper right section, and the initial support of the upper right section of the pilot tunnel is formed and closed.

[0055] Step 4: Construction of the left and right main tunnels of the twin-arch tunnel:

[0056] ① Excavate the soil above the core soil of the left main tunnel (V1), spray concrete and pre-embed steel sections (V2), and the initial support is directly supported on the cover plate of the central guide tunnel and reliably connected through pre-embedded parts on both sides of the central guide tunnel. Then construct the longitudinal drainage pipe (V3).

[0057] The core soil V4 is excavated sequentially, and a temporary transverse connecting steel section V5 is installed at the bottom. Then, the lower step V6 is excavated, a continuous steel plate V7 is constructed, and then the initial support V8 for the bottom invert arch is constructed.

[0058] ② Excavate the soil above the core soil of the right main tunnel VI1, spray concrete and pre-embed steel VI2, the initial support is directly supported on the cover plate of the central guide tunnel and reliably connected through the pre-embedded parts on both sides of the central guide tunnel. Then construct the longitudinal drainage pipe VI3. Finally, excavate the core soil VI4.

[0059] ③ Excavate VII1, and construct the bottom of the right half-arch and the initial support VII2 of the sidewall, and construct the locking foot grouting pipe.

[0060] Excavate the lower left rock and soil mass VII3 of the right tunnel, construct the continuous steel plate VII4, and then construct the initial support VII5 for the bottom left half of the arch.

[0061] ④ Construction of the secondary lining of the left main tunnel: promptly construct the invert arch of the secondary lining of the left tunnel VIII, and then construct the arch and sidewalls of the secondary lining IX. The left and right sidewalls are firmly connected to the anti-slide piles by rebar installation (remove the initial support V5 where there is a conflict in three-dimensional space).

[0062] Construction of the secondary lining of the right main tunnel: promptly construct the invert arch of the X secondary lining of the right tunnel, and then construct the arch of the XI secondary lining and the side wall. The left and right side walls are firmly connected to the anti-slide piles by rebar installation (the initial support of the multi-compartment pipe gallery structure IV3 is removed where there is a conflict in three-dimensional space).

[0063] Step 5: Excavation and backfilling of conventional arch tunnels and open-cut tunnels:

[0064] ① For conventional arch tunnel sections, further excavation is carried out, starting with the construction of the central pilot tunnel, followed by the construction of the central partition wall of the central pilot tunnel, and then the construction of the left and right tunnels.

[0065] ② Finally, construct the bamboo-cut tunnel structure and backfill with greenery.

[0066] This invention addresses three major pain points in the construction of traditional arch tunnels in environmentally friendly areas through innovative design: First, by integrating concealed anti-slide piles with bamboo-cut tunnel portals, it solves the problem of surface reinforcement damaging the ecological environment; second, by adopting a pile-cover plate composite central tunnel structure, it overcomes the technical limitation that anti-slide piles cannot be installed in the central tunnel of tunnels with spans of more than 30 meters; finally, it establishes a double-row anti-slide pile spatial isolation system to achieve precise control over the mutual influence between the excavation of the left and right tunnels.

[0067] This invention is particularly applicable to tunnel projects with two or more lanes and arches, and has significant advantages, especially in mountain pass terrain where the surface gravel cover layer is more than 8 meters thick and environmental protection requirements are strict. Its core value lies in constructing a new paradigm for environmentally friendly tunnel construction.

[0068] This invention has the following characteristics:

[0069] First, an integrated design combining concealed anti-slide piles and a bamboo-cutting-style portal is adopted. The anti-slide piles are embedded inside the portal structure, preserving the original terrain while forming a rigid support system. This is particularly suitable for mountain pass terrain with a gravel cover layer thickness exceeding 8 meters.

[0070] Secondly, the unique double-row anti-slide pile + cover plate composite central guide tunnel structure, through the synergistic effect of the pile body and the precast cover plate, forms a continuous support barrier within a 30-meter span, with its bending stiffness reaching 1.5 times that of the traditional central partition wall, while eliminating the construction step of the central partition wall.

[0071] Finally, an optimization model for spatial isolation effect was constructed. By adjusting the pile spacing (3-8 meters), the attenuation rate of blasting vibration transmission in the left and right tunnels reached 60%, significantly reducing the amount of temporary support work.

[0072] In practice, a construction process of "piling first, tunnel later" is adopted: first, double rows of anti-slide piles are constructed and a cover slab is poured to form a rigid central guide tunnel; then, the left and right tunnels are excavated in stages, utilizing the isolation effect of the piles to achieve asymmetrical support—the temporary support strength of the later tunnel can be reduced by 30%. This scheme has been verified by finite element analysis, and in the Double 4 Expressway project, it can reduce the overall cost of the tunnel entrance section by 22% and shorten the construction period by 15%.

[0073] This invention demonstrates significant advantages in terms of environmental friendliness, economy, and construction safety.

[0074] First, the concealed anti-slide pile design completely avoids the ecological damage to the protected area caused by traditional surface grouting, achieving zero-pollution construction, which is particularly suitable for tunnel construction in ecologically sensitive areas.

[0075] Secondly, the isolation effect of the double-row anti-slide piles reduces the amount of temporary support work for the left and right tunnels by 30%, and the elimination of the central partition wall construction saves about 15% in material costs, resulting in a 22% reduction in overall cost compared to the traditional solution.

[0076] Finally, the innovative pile-and-cover plate support system reduces the construction risk of the tunnel portal section by 40%, and its spatial isolation characteristics effectively control the transmission of blasting vibrations, reducing mutual interference between the excavation of the left and right tunnels by 60%. Actual engineering data shows that this technology not only shortened the construction period by 15% in the Double 4 Expressway project, but also increased the structural safety factor of the tunnel portal section to 1.8 times, providing a solution for tunnel construction in environmentally friendly zones that combines ecological and economic benefits.

[0077] For continuous arch tunnels, this invention utilizes a central guide tunnel formed by anti-slide piles and cover plates. For the first time, it reduces the mutual impact of left and right tunnel excavation by using anti-slide piles for protection and isolation. Under the premise of ensuring the stability of the tunnel entrance reinforcement, it eliminates the need for reinforced concrete central partition walls, does not change the original terrain, and does not cause environmental pollution like surface grouting reinforcement. It conforms to the construction concept of new products among the five new technologies, is economical, and environmentally friendly.

[0078] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A construction method of a bamboo-cutting type multi-arch tunnel portal structure suitable for protecting a pass landform, characterized in that, The method comprises the following steps: Step 1, construction of anti-slide piles and excavation of a tunnel portal: Double rows of anti-slide piles are arranged perpendicularly to the tunnel line, each row of anti-slide piles is provided with four anti-slide piles, and the top of each anti-slide pile is provided with reserved connecting steel bars; the side slope of the tunnel portal is excavated under the protection of the anti-slide piles to process the stability of the side slope of the tunnel portal; Step 2, construction of a middle pilot tunnel: A reinforced concrete cover plate is cast through the reserved connecting steel bars at the top of the anti-slide piles, so that the cover plate is fixedly connected with the anti-slide piles; the middle pilot tunnel is excavated under the protection of the anti-slide piles and the cover plate, a bottom plate of the middle pilot tunnel is constructed, and a temporary steel frame support is arranged in the middle pilot tunnel to enhance the stability of the middle pilot tunnel; Step 3, construction of left and right pilot tunnels of a multi-arch tunnel main tunnel: An upper step of the left pilot tunnel is excavated, and a shotcrete and anchor support is constructed, then a lower step of the left pilot tunnel is excavated, and a shotcrete and anchor support is constructed; an upper step of the right pilot tunnel is excavated, a concrete is sprayed, a profile steel is pre-buried, a locking foot grouting pipe is constructed, and an initial support closed structure of the upper part of the right pilot tunnel is formed; Step 4, construction of left and right main tunnels of the multi-arch tunnel: The earthwork above the core soil of the left main tunnel is excavated, a concrete is sprayed, and a profile steel is pre-buried, so that the initial support of the left main tunnel is connected with the cover plate through the through steel plates on both sides of the middle pilot tunnel; the core soil and the lower step of the left main tunnel are excavated in sequence, and an initial support of a bottom inverted arch is constructed; the core soil and the lower step of the right main tunnel are excavated in the same manner, an initial support of the right main tunnel is constructed and connected with the cover plate; secondary lining of the left main tunnel and the right main tunnel is constructed, and the side walls of the secondary lining are connected with the anti-slide piles through steel bars; Step 5, excavation of a conventional multi-arch tunnel and construction of a backfill of a bamboo-cut type open tunnel: The conventional multi-arch tunnel is continuously excavated, a bamboo-cut type open tunnel structure is constructed, and a green backfill is performed to restore the original appearance of the ground surface.

2. The method according to claim 1, wherein In step 1, the row distance of the double rows of anti-slide piles is 3-8 meters.

3. The method of claim 1, wherein, In step 2, after the cover plate is cast, the top of the anti-slide piles is backfilled with original soil to maintain the original ground surface.

4. The method of claim 1, wherein, In step 4, when the initial support structure of the secondary lining of the left main tunnel and the right main tunnel conflicts with the anti-slide piles in three-dimensional space, the temporary support structure at the conflict position is removed before the secondary lining is cast.

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