Construction method of bias tunnel half-and-half dark entrance hole

Abstract

The application belongs to the technical field of bias tunnel construction, and particularly relates to a bias tunnel semi-open and semi-hidden entrance construction method, which comprises seven steps of slope excavation protection, open part steel arch construction, semi-open and semi-hidden junction construction, open part initial support, pipe shed construction, hidden hole excavation support and vault backfilling in sequence. The method shortens the tunnel entrance construction time, saves the construction cost and improves the entrance safety.

Description

Technical Field

[0001] This invention belongs to the field of biased tunnel construction technology, and provides a method for constructing biased tunnels with semi-open and semi-closed entrances, which shortens tunnel entrance construction time, saves construction costs, and improves tunnel entry safety. Background Technology

[0002] During tunnel construction in mountainous areas, the terrain is often complex with significant undulations, and tunnel entrances are frequently located in areas with biased pressure. Traditional construction methods involve large-scale excavation with high slopes and strong supports, resulting in extensive earthwork excavation and transportation, high slope support, and severe damage to the original landform and natural landscape. Furthermore, the loss of support on the surrounding rock of the tunnel side can lead to instability of the upper surrounding rock, causing lining cracks and other quality and safety accidents, and even tunnel entrance collapse. Chinese Patent 2015103842326 discloses a method for constructing a bridge abutment entrances in tunnels with weak surrounding rock and partial exposure / biased pressure sections. This method overcomes to some extent the difficulties and significant safety hazards associated with construction in such areas, but its procedures are complex, and construction time and costs still need improvement. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a semi-open, semi-closed tunnel construction method for biased tunnels that shortens tunnel entrance construction time, saves construction costs, and improves tunnel entry safety.

[0004] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for constructing a partially open and partially closed tunnel under bias pressure, characterized by the following steps: ① Slope excavation and protection The slope was cleared and protected at the same time; based on the results of the survey and layout, the position of each steel arch frame in the exposed section and the position where the mountain slope and the tunnel intersect were accurately marked so that the steel arch frames could be stably fixed to the bedrock. ② Construction of the exposed steel arch frame. A C30 concrete enlarged foundation is constructed at the side wall of the exposed section, and a Q235 connecting steel plate is pre-embedded at a depth of 50cm. The steel arch frame and anti-collapse tie rod are connected and fixed to the Q235 connecting steel plate with bolts. The anti-collapse tie rod is set at intervals to take into account the load of the arch top concrete. The steel bars are welded into rings on the steel arch frame to facilitate the connection between the anti-collapse tie rod and the steel arch frame. Each steel frame is processed according to the standard arch frame. After the slope excavation and clearing, the support point positions are measured and laid out, and then cut and connected steel plates are installed to ensure coordinated connection of the arch frame in the concealed section after the openwork section is completed. Specifically, the positions of the upper node of B2 and the lower node of B1 are adjusted according to the actual support point positions. The arch frame is divided into three sections: A, B, and C. Each section is connected by bolts using connecting steel plates. Section C is embedded in the concrete foundation. Section B is divided into sections B1 and B2 according to the support point positions. When the support point is too far to the lower left corner, the left side of section A is divided into blocks. As construction progresses, the openwork structure becomes smaller, and the joints are gradually moved to the lower right side of section A, with the block positions being the same as section B. After on-site measurement and layout, the steel reinforcement is processed. The process involves first processing the complete A or B section structure, and then cutting it at the corresponding positions after on-site measurement and layout. Standard joint connecting steel plates are used to connect the cut parts. ③ Construction at the junction of light and shadow: At the junction of the steel arch frame and the mountain, U-shaped clips are used to fix the arch frame to the mountain. At the arch foot, Q235 steel plates and bolts need to be connected and welded to ensure a good connection with the initial support steel arch frame during the excavation of the tunnel. ④ Initial support for the exposed portion, After the steel arch frame is constructed, Φ8 steel mesh with a mesh spacing of 15×15cm is used to fill the gaps on both sides of the steel arch frame. From the upper edge to the lower edge of the steel arch frame, longitudinal connecting steel bars with a diameter of 22mm and HRB400 are arranged in a circumferential distribution to connect the steel arch frame longitudinally into a whole. Then, Φ127mm pipe roof guide pipes are welded and fixed on the outer ring of the steel arch frame at 50cm circumferential intervals. After that, the formwork is installed, and a 76cm thick initial support concrete is sprayed using a wet spraying machine. ⑤ Pipe Roof Construction: After the arch frame is constructed, the pipe roof is erected. Pipe roof holes are drilled along the pre-embedded pipe roof guide pipes in the arch frame. To ensure structural stability, the pipe roof steel pipes are installed immediately after each hole is drilled. The pipe roof steel pipes are made of Ф108mm hot-rolled seamless steel pipes. After the pipe roof steel pipes are installed, steel cages are inserted into the steel pipes, and grouting is carried out in the order from the arch foot to the arch top.

[0005] ⑥, Excavation and support of the tunnel: After the pipe roof is constructed, temporary soil is backfilled on the outside of the exposed part of the tunnel to counteract the initial support of the exposed part and temporarily resist the eccentric pressure before the tunnel is excavated. ⑦ Backfilling of the arch: After the secondary lining construction of the semi-open and semi-closed section is completed, a high counterweight retaining wall is constructed on the side away from the mountain. The height of the high counterweight retaining wall is equal to the backfill height of the tunnel top, i.e. the top of the tunnel portal wall drainage ditch. Because the eccentric pressure is large, the foundation is constructed in sections to prevent lateral displacement.

[0006] To further improve construction accuracy, in the above scheme: in the construction steps of the exposed steel arch frame, the steel arch frame uses 20b I-beams with a longitudinal spacing of 60cm. To prevent the exposed part from settling and encroaching on the limit, and to ensure the thickness of the secondary lining of the tunnel, the steel arch frame is extended outward by 12cm as a settlement allowance for excavation, as required by the design. The length of the 20b I-beams is determined by calculating the arch arc length of each steel arch frame that abuts against the mountain. One side of the exposed steel arch frame is erected on a C30 concrete enlarged foundation, and the other side is supported on the unexcavated slope.

[0007] To facilitate subsequent construction, further in the above scheme: during the construction of the exposed steel arch frame, the first arch frame is temporarily fixed with a steel pipe support to prevent lateral overturning, and adjacent arch frames are fixed together with connecting steel bars.

[0008] To facilitate subsequent construction, further in the above scheme: during the construction of the arch frame, the second, third, fourth, and subsequent arch frames are gradually stabilized by horizontally arranged connecting steel bars, and the steel pipe support used for temporary support of the first arch frame can be removed.

[0009] To improve construction progress and ensure construction safety, further in the above scheme: in the tunnel excavation and support steps, the tunnel excavation adopts the upper and lower bench method, the upper bench annular groove is excavated manually, the slightly harder rock is excavated with a pneumatic pick, and where blasting is necessary, weak blasting and vibration cracking can be used. The lower step is excavated mechanically, with staggered excavation on both sides. Each cycle of excavation does not exceed the position of two arch frames. The I-beam arch frames are erected according to the design requirements, and they are kept in good connection with the exposed arch frames to ensure the integrity of the arch frames. Initial support should be provided and closed into a ring as soon as possible, and the invert arch and secondary lining should be constructed as quickly as possible.

[0010] To ensure construction progress, furthermore, in the above scheme: during the arch backfilling step, the high-weight retaining wall can be constructed in one go. After the retaining wall is completed, the top of the tunnel is filled and compacted in layers to balance the lateral pressure.

[0011] The beneficial effects of this invention are: When tunnel construction encounters uneven terrain and an "open-pit" tunnel section on the outer side of the mountain, the construction team employs a method of first constructing the initial support of the exposed section. The side closest to the slope serves as the tunnel's cut-and-cover section, while the other side is the exposed section. This approach ensures the safety of construction personnel and equipment, shortens tunnel entrance construction time, saves construction costs, and improves safety upon entering the tunnel.

[0012] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0013] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure during slope clearing according to the present invention; Figure 2 This is a schematic diagram of the steel arch frame during construction of the present invention; Figure 3 This is a schematic diagram of the steel arch frame during construction of the present invention; Figure 4 This is a schematic diagram of the structure at the arch frame of the present invention; Figure 5 This is a structural schematic diagram of the arch frame during construction of the present invention; Figure 6 This is a structural schematic diagram of the Φ127mm pipe roof guide pipe during construction of the present invention; Figure 7 This is a schematic diagram of the structure of the Φ127mm pipe roof guide pipe of the present invention; Figure 8 This is a schematic diagram of the structure during the excavation and support construction of the tunnel according to the present invention; Figure 9 This is a structural schematic diagram of the arch backfilling construction of the present invention; Attached reference numerals: 1. C30 concrete spread foundation; 2. Q235 connecting steel plate; 3. Steel arch frame; 4. Anti-collapse tie rod; 5. Arch frame; 6. Steel pipe support; 7. Connecting reinforcement; 8. High load-bearing retaining wall; 9. U-shaped buckle; 10. Φ8 steel mesh; 11. Φ127mm pipe roof guide pipe. Detailed Implementation

[0014] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0015] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual photographs, and should not be construed as limiting this patent. To better illustrate the embodiments of the invention, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0016] like Figure 1-9 As shown, the semi-open / semi-closed tunnel construction method of the present invention is characterized by the following steps: ① Slope excavation and protection The slope was cleared and protected at the same time; based on the results of the survey and layout, the position of each steel arch frame 3 in the exposed part and the position where the mountain slope and the tunnel intersect were accurately marked so that the steel arch frame could be stably fixed to the bedrock. ② Construction of the exposed steel arch frame. A C30 concrete enlarged foundation 1 is constructed at the side wall of the exposed section, and a Q235 connecting steel plate 2 is pre-embedded at a depth of 50cm. The steel arch frame 3 and the anti-collapse tie rod 4 are connected and fixed to the Q235 connecting steel plate 2 with bolts. The anti-collapse tie rod 4 is set at intervals to take into account the load of the arch top concrete. The steel bars are welded into a ring on the steel arch frame 3 to facilitate the connection between the anti-collapse tie rod 4 and the steel arch frame 3. Each steel frame is processed according to the standard arch frame 5. After the slope excavation and clearing, the support point positions are measured and laid out, and then cut and connected steel plates are installed to ensure the connection of the arch frame 5 in the concealed section is coordinated after the construction of the exposed section is completed. Specifically, the positions of the upper node of B2 and the lower node of B1 are adjusted according to the actual support point positions. The arch frame 5 is divided into three sections: A, B, and C. Each section is connected by bolts using connecting steel plates. Section C is embedded in the concrete foundation. Section B is divided into sections B1 and B2 according to the support point positions. When the support point is too far to the lower left corner, the left section A is divided into blocks. As construction progresses, the exposed tunnel structure becomes smaller, and the joints are gradually moved to the lower right section A, with the block positions being the same as section B. After on-site measurement and layout, the steel reinforcement is processed. The process involves first processing the complete A or B section structure, and then cutting it at the corresponding positions after on-site measurement and layout. Standard joint connecting steel plates are used to connect the cut parts. ③ Construction at the junction of light and shadow: For the construction of the steel arch frame 3 at the junction with the mountain, U-shaped clips 9 are used to fix the arch frame 5 in the mountain. At the arch foot, Q235 steel plates and bolts need to be connected and welded to ensure a good connection with the initial support steel arch frame 3 during the excavation of the tunnel. ④ Initial support for the exposed portion, After the steel arch frame 3 is constructed, Φ8 steel mesh 10 with a mesh spacing of 15×15cm is used to fill the two sides of the steel arch frame 3. From the upper edge to the lower edge of the steel arch frame 3, longitudinal connecting steel bars with a diameter of 22mm and HRB400 are arranged in a circumferential distribution to connect the steel arch frame 3 longitudinally into a whole. Then, Φ127mm pipe roof guide pipes 11 are welded and fixed on the outer ring of the steel arch frame 3 at circumferential intervals of 50cm. Then, the formwork is installed and 76cm thick initial support concrete is sprayed using a wet spraying machine. ⑤ Pipe Roof Construction: After the arch frame 5 is constructed, the pipe roof is erected. Pipe roof holes are drilled along the pre-embedded pipe roof guide pipes in the arch frame. To ensure structural stability, the pipe roof steel pipes are installed immediately after each hole is drilled. The pipe roof steel pipes are made of Ф108mm hot-rolled seamless steel pipes. After the pipe roof steel pipes are installed, steel cages are inserted into the steel pipes, and grouting is carried out in the order from the arch foot to the arch top.

[0017] ⑥, Excavation and support of the tunnel: After the pipe roof is constructed, temporary soil is backfilled on the outside of the exposed part of the tunnel to counteract the initial support of the exposed part and temporarily resist the eccentric pressure before the tunnel is excavated. ⑦ After the secondary lining construction of the semi-exposed and semi-concealed section is completed, a high counterweight retaining wall 8 is constructed on the side away from the mountain. The height of the high counterweight retaining wall 8 is equal to the backfill height of the tunnel top, i.e., the top of the drainage ditch at the tunnel entrance. Due to the large eccentric pressure, the foundation is constructed in sections to prevent lateral displacement. In this embodiment, when tunnel construction is carried out in the case of eccentric terrain and the tunnel on the outer side of the mountain is exposed, the construction personnel adopt the method of constructing the initial support of the exposed part first, with the side near the slope as the tunnel excavation part and the other side as the exposed part. This ensures the safety of construction personnel and equipment, shortens the tunnel entrance construction time, saves construction costs, and improves the safety of entering the tunnel.

[0018] To improve construction accuracy, in the above embodiments, preferably: in the construction step of the exposed steel arch frame, the steel arch frame 3 is made of 20b I-beams with a longitudinal spacing of 60cm. To prevent the exposed part from settling and encroaching on the limit, and to ensure the thickness of the secondary lining of the tunnel, the steel arch frame is extended outward by 12cm as a settlement allowance for excavation, according to the design requirements. The length of the 20b I-beams is determined by calculating the arch arc length of each steel arch frame that abuts against the mountain. One side of the exposed steel arch frame 3 is erected on the C30 concrete enlarged foundation 1, and the other side is supported on the unexcavated slope.

[0019] To facilitate subsequent construction, in the above embodiment, preferably: during the construction of the exposed steel arch frame, the first arch frame 5 is temporarily fixed with a steel pipe support 6 to prevent the arch frame 5 from tilting to the side, and adjacent arch frames 5 are fixed together with connecting steel bars 7.

[0020] To facilitate subsequent construction, in the above embodiments, preferably: during the construction of the arch frame 5, the second arch frame 5, the third arch frame 5, the fourth arch frame 5 and subsequent arch frames 5 are gradually stabilized by the horizontally arranged connecting steel bars 7, and the steel pipe support 6 used for temporary support of the first arch frame 5 can be removed.

[0021] To improve construction progress and ensure construction safety, in the above embodiments, preferably: in the tunnel excavation and support steps, the tunnel excavation adopts the upper and lower bench method. The upper bench annular groove is excavated manually, with pneumatic picks used for slightly harder rock in some areas, and weak blasting is used for areas where blasting is necessary; the lower bench is excavated mechanically, with staggered excavation on both sides of the lower bench, and each cycle of excavation does not exceed the position of two arch frames; the I-beam arch frames are erected according to design requirements, maintaining a good connection with the exposed arch frames to ensure the integrity of the arch frames; initial support is performed to close the loop in a timely manner, and the invert arch and secondary lining are constructed as soon as possible. In this embodiment, the safety of the tunnel entrance is ensured, and conditions are provided for the rapid construction of the counterweight portal wall.

[0022] To ensure construction progress, in the above embodiments, preferably, the high-weight retaining wall 8 can be constructed in one continuous operation during the arch backfilling step. After the retaining wall is completed, the tunnel roof is filled and compacted in layers to balance the lateral pressure. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for constructing a partially open and partially closed tunnel under bias pressure, characterized in that: Includes the following steps, ① Slope excavation and protection: Clear the slope surface and protect it at the same time; Based on the results of the survey and layout, accurately mark the position of each steel arch frame in the exposed part and the position where the mountain slope and the tunnel intersect, so that the steel arch frame can be stably fixed on the bedrock. ② Construction of the exposed steel arch frame: A C30 concrete enlarged foundation (1) is constructed at the side wall of the exposed part, and a Q235 connecting steel plate (2) is pre-embedded at a depth of 50cm. The steel arch frame and the anti-collapse tie rod (4) are connected and fixed to the Q235 connecting steel plate (2) with bolts. The anti-collapse tie rod (4) is set at intervals to consider the load of the arch top concrete. The steel bars are welded into a ring on the steel arch frame to facilitate the connection between the anti-collapse tie rod (4) and the steel arch frame. The arch frame is divided into three sections: A, B, and C. These sections are connected by bolts using connecting steel plates. Section C is embedded in the concrete foundation. Section B is further divided into sections B1 and B2 based on the support point locations. When the support point is too far to the lower left corner, section A on the left is divided into blocks. As construction progresses, the open-cut structure becomes smaller, and the joints are gradually moved to the lower right section A, with the block locations matching those of section B. After on-site measurement and layout, the steel reinforcement is processed in sections. The process involves first processing the complete section A or B structure, then cutting it at the corresponding location based on on-site measurements and layout. Standard joint connecting steel plates are used to connect the cut sections. Each steel frame is processed according to the standard arch frame. After slope excavation and cleaning, the support point locations are measured and laid out, and then cut and connected steel plates are installed to ensure coordinated connection of the arch frame in the concealed section after the openwork section is completed. Specifically, the positions of the upper node of B2 and the lower node of B1 are adjusted according to the actual support point locations. ③ Construction at the junction of semi-bright and semi-dark areas: Construction at the junction of steel arch frame and mountain body. Use U-shaped buckles (9) to fix the arch frame in the mountain body. At the arch foot, Q235 steel plates and bolts need to be connected for welding construction so that the steel arch frame of the initial support can be well connected during the excavation of the dark tunnel. ④ For the initial support of the exposed part, after the steel arch frame is constructed, Φ8 steel mesh (10) with a mesh spacing of 15×15cm is used to fill the two sides of the steel arch frame; at the upper edge to the lower edge of the steel arch frame, longitudinal connecting steel bars of HRB400 diameter 22 are arranged and distributed in a circumferential manner to connect the steel arch frame longitudinally into a whole; then Φ127mm pipe roof guide pipe (11) is welded and fixed on the outer ring of the steel arch frame at a circumferential spacing of 50cm, and then the template is installed and the initial support concrete is sprayed using a wet spraying machine; ⑤ Pipe Roof Construction: After the arch frame is constructed, the pipe roof is erected. Pipe roof holes are drilled by positioning the guide pipes embedded in the arch frame. To ensure structural stability, the pipe roof steel pipes are installed immediately after each hole is drilled. The pipe roof steel pipes are made of Ф108mm hot-rolled seamless steel pipes. After the pipe roof steel pipes are installed, steel cages are inserted into the steel pipes, and grouting is carried out in the order from the arch foot to the arch top. ⑥, Excavation and support of the tunnel: After the pipe roof is constructed, temporary soil is backfilled on the outside of the exposed part of the tunnel to counteract the initial support of the exposed part and temporarily resist the eccentric pressure before the tunnel is excavated. ⑦ Backfilling of the arch: After the secondary lining construction of the semi-open and semi-closed section is completed, a high-weight retaining wall (8) is constructed on the side away from the mountain. The height of the high-weight retaining wall (8) is the same as the backfill height of the tunnel top, i.e. the top of the tunnel entrance wall drainage ditch. Because the eccentric pressure is large, the foundation is constructed in sections to prevent lateral displacement.

2. The method for constructing a semi-open, semi-closed tunnel under bias pressure according to claim 1, characterized in that: In the construction steps of the exposed steel arch frame, the steel arch frame adopts 20b I-beams with a longitudinal spacing of 60cm. In order to prevent the exposed part from sinking and encroaching on the limit, and to ensure the thickness of the secondary lining of the tunnel, the steel arch frame is extended by 12cm as the settlement allowance for excavation according to the design requirements. The length of the 20b I-beams is determined by calculating the arch arc length of each steel arch frame that abuts against the mountain. One side of the exposed steel arch frame is erected on the C30 concrete enlarged foundation (1), and the other side is supported on the unexcavated slope.

3. The method for constructing a semi-open, semi-closed tunnel under bias pressure according to claim 1 or 2, characterized in that: In the construction steps of the steel arch frame of the Mingzuo section, the first arch frame is temporarily fixed with a steel pipe support (6) to prevent the arch frame from overturning laterally, and the two adjacent arch frames are fixed together with connecting steel bars (7).

4. The method for constructing a semi-open, semi-closed tunnel under bias pressure according to claim 3, characterized in that: During the construction of the steel arch frame, the second, third, fourth and subsequent arch frames are gradually stabilized by the horizontally set connecting steel bars (7), and the steel pipe support (6) set for temporary support of the first arch frame can be removed.

5. The method for constructing a semi-open, semi-closed tunnel under bias pressure according to claim 1, characterized in that: In the tunnel excavation and support steps, the tunnel excavation adopts the upper and lower bench method. The upper bench annular groove is excavated manually, and the slightly harder rock is excavated with a pneumatic pick. If blasting is necessary, weak blasting and vibration can be used to crack the rock. The lower step is excavated mechanically, with staggered excavation on both sides. Each cycle of excavation does not exceed the position of two arch frames. The I-beam arch frames are erected according to the design requirements, and they are kept in good connection with the exposed arch frames to ensure the integrity of the arch frames. The initial support was promptly closed into a ring, and the invert arch and secondary lining were constructed as soon as possible; this ensured the safety of the opening and provided conditions for the rapid construction of the counterweight portal wall.

6. The method for constructing a partially exposed tunnel under bias pressure according to claim 1, characterized in that: In the arch backfilling step, the high-weight retaining wall (8) is constructed in one go. After the retaining wall is completed, the top of the tunnel is filled and compacted in layers to balance the lateral pressure.

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