Construction method for controlling settlement of shallow buried and deep-dug large-section tunnels

Abstract

A construction structure and construction method for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel. The full-section method has a larger excavation surface and reduced surrounding rock stability. The double-side wall pilot tunnel method is safe, but slow and costly. The present invention comprises: an elliptical structure formed by four fan-shaped caverns and a ground steel beam (2) laid on the ground. Each of the fan-shaped caverns is surrounded by a supporting structure. The supporting structure is composed of two layers of steel mesh (4) arranged outside the fan-shaped cavern and a plurality of steel grids (3) laid between the two layers of the steel mesh. A plurality of locking anchor rods (1) are provided on the ground steel beam and are welded to the steel grid after passing through holes in the ground. The present invention is a construction structure and construction method for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel.

Description

Technical Field

[0001] The invention relates to a construction structure and a construction method for controlling the settlement of a shallow buried and dark-excavated large-section tunnel. Background Art

[0002] Existing construction experience and technical achievements at home and abroad have shown that, depending on the geological conditions and the size of the excavation face, the main construction methods for shallow buried tunnels include the full-section method, the upper and lower step method, the single-side wall pilot tunnel method, and the double-side wall pilot tunnel method.

[0003] The bench method involves excavating the upper tunnel section (the upper bench) first, then advancing the upper bench a certain distance before excavating the lower section (the lower bench), with both upper and lower sections excavated simultaneously. Depending on the length of the bench, it can be categorized as short bench, long bench, and ultra-short bench (micro-bench) methods.

[0004] The single-sidewall pilot method is suitable for tunnels with large spans, low flatness, poor surrounding rock, generally Class IV-V surrounding rock, and where ground subsidence needs to be controlled. Key construction points include: 1. Divide the cross-section into a sidewall pilot, upper bench, and lower bench; 2. The sidewall pilot width should not exceed 0.5 times the tunnel width, and its height should ideally reach the arching line; 3. The distance between the pilot and bench should be such that pilot and bench construction do not interfere with each other; 4. The distance between the upper and lower benches should be determined based on the surrounding rock conditions, referring to the short bench method or the ultra-short bench method.

[0005] The double-sidewall pilot method, also known as the double-sidewall pilot tunnel method or the glasses method, is a branch of the New Austrian Tunneling Method (NATM) and is based on its fundamental principles. The section is generally divided into four parts: left and right sidewall pilot pits, upper core soil, and lower bench. The sidewall pilot pit dimensions should be determined to fully utilize the support provided by the bench, taking into account mechanical equipment and construction conditions. The width should not exceed one-third of the maximum span of the section, and the height should ideally reach the arch line. This allows for secondary excavation and support of the pilot pit, eliminating the need for a working platform and facilitating manual steel support erection. While there are no rigid regulations for the distance between the pilot pit and the bench, the principle is generally to ensure that the pilot pit and bench construction do not interfere with each other. Therefore, in short tunnels, the pilot pit can be excavated first, followed by the bench excavation. The distance between the upper and lower benches is determined based on the surrounding rock mass, as described in the short bench method or ultra-short bench method. The offset distance between the left and right pilot tunnels should be determined based on the principle that the influence of the surrounding rock stress redistribution caused by excavating the pilot tunnel on one side will not affect the existing pilot tunnel on the other side.

[0006] The common practices for controlling the deformation of the ground at the top of the tunnel are mainly small pipe grouting of single-row tunnel vault, small pipe grouting of double-row tunnel vault or large pipe grouting.

[0007] The full-section method has a larger excavation surface, which reduces the stability of the surrounding rock and requires a larger workload for each cycle. This method divides the excavation section into many blocks. Each block is immediately connected to the upper rod system after excavation, and the initial support is immediately applied. Each block is closed separately, so deformation hardly develops during construction. The double-side wall pilot tunnel method is safe to construct, but it is slower and more expensive. Compared with the double-side wall pilot tunnel method, the large-section shallow buried tunnel suspension method can save about 30,000 yuan per linear meter, with obvious economic benefits. It is also conducive to the safe and smooth completion of the project and ensures the construction period.

[0008] Currently, the common methods for controlling deformation of the ground at the top of tunnels are small-pipe grouting in single-row or double-row tunnel vaults, or large pipe grouting. Regardless of the advanced support method used, the ground surface experiences varying degrees of settlement and deformation during shallow tunnel construction. Furthermore, due to lax tunnel construction management and non-standard process operations, actual surface settlement and deformation far exceed design control standards. This method is beneficial for addressing the technical challenges of controlling surface settlement and deformation caused by shallow, deep-cut, large-section tunnel construction. Summary of the Invention

[0009] The purpose of the present invention is to provide a construction method for controlling the settlement of a shallow buried and dark-excavated large-section tunnel.

[0010] The above purpose is achieved through the following technical solutions:

[0011] A construction method for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel, comprising the following steps:

[0012] (1) Construct surface concrete beams and steel longitudinal beams, and reserve tie rod holes on the tie beams;

[0013] (2) Construct ground beams, bury finely rolled threaded steel bars, and install small conduits for the tunnel vaults. Install one row of small conduits for every two grids. Drill holes in the conduit wall every 100-200 mm, with a hole diameter of 6-8 mm. Use cement slurry according to the stratum. The grouting pressure is controlled at 0.4-0.6 MPa. The diameter of the grouting body is not less than 0.5 m. To prevent the slurry from leaking, a stopper is installed at the hole mouth.

[0014] (3) Before the construction of the secondary lining structure, φ42 water-gas pipes are pre-buried in the arch and side walls during the initial support construction, with a circumferential spacing of 3m and a longitudinal spacing of 3m, arranged in a plum blossom shape. The grouting depth is 0.5m behind the initial support. After the initial support is closed to a certain length, cement slurry is injected behind the initial support with a grouting pressure of 0.4-0.6MPa.

[0015] (4) When the secondary lining is being constructed, φ42 water-gas pipes are pre-buried in the vault and side walls, with a circumferential spacing of 3m and a longitudinal spacing of 3m, arranged in a plum blossom shape. High-strength non-shrinkage grouting is injected behind the secondary lining at a grouting pressure of 0.1-0.3MPa.

[0016] (5) Excavate No. 1 cavern, carry out initial support, install anchor bolts, and connect the primary support structure and finished rolled threaded steel bars;

[0017] (6) Excavate Cavern No. 2 and Cavern No. 3, carry out initial support, install grouting anchor pipes, connect the primary support structure and finished rolled threaded steel bars, and the longitudinal step distance between Cavern No. 1 and Cavern No. 2, and between Cavern No. 2 and Cavern No. 3 shall not be less than 15m;

[0018] (7) Excavate No. 4 cavern and provide initial support. The longitudinal step distance between No. 3 cavern and No. 4 cavern shall not be less than 15m;

[0019] (8) Grouting from the grouting anchor pipe into the supporting structure;

[0020] (9) According to the demolition section division, prestress the finished rolled threaded steel bars in batches, then demolish the lower part of the temporary middle partition wall, with the length of demolition not exceeding 8m at a time, level it, lay the waterproof layer, and finally apply the A part bottom plate and part of the side wall secondary lining. After the arch bottom structure reaches the design strength, support the temporary middle partition wall back to the structural bottom plate;

[0021] (10) Remove the temporary arch and middle partition wall in sections, with the length of each removal not exceeding 8m, and apply secondary lining to the side wall of section B to close the ring;

[0022] (11) After the secondary lining reaches the design strength, all temporary support structures shall be removed.

[0023] A construction structure for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel comprises an elliptical structure enclosed by four fan-shaped chambers and ground steel beams laid on the ground. A supporting structure is arranged outside each fan-shaped chamber. The supporting structure is composed of two layers of steel mesh arranged outside the fan-shaped chamber and a plurality of steel grids laid between the two layers of steel mesh. A plurality of locking anchor rods are arranged on the ground steel beams, which pass through holes in the ground and are welded to the steel grids.

[0024] The construction structure for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel, wherein the ground steel beam is a structure formed by vertically cross-welding transverse steel beams and longitudinal steel beams.

[0025] The construction structure for controlling the settlement of a shallow buried, dark-excavated, large-section tunnel, the locking foot anchor rod includes two parallel steel plates and a rib welded between the two steel plates, one end of the fine-rolled threaded steel bar passes through the two layers of the steel plates and is screwed with a nut, and the other end of the fine-rolled threaded steel bar is covered with a corrugated tube.

[0026] The construction structure for controlling the settlement of a shallow buried, dark-excavated, large-section tunnel comprises a steel grid comprising a plurality of stirrups arranged in parallel, main bars being passed through and welded at the four inner corners of the stirrups, and connecting bars being welded between two adjacent main bars. Beneficial effects

[0027] 1. In order to reduce surface settlement and deformation, the present invention adopts a suspension method for shallow buried and dark excavated large-section tunnel construction. The suspension method is an improved method based on the double-side wall pilot pit method. Before tunnel excavation, tie beams are set on the surface and drill holes are reserved on the tie beams. Pre-drilling is done deep into the stratum using the tie beam drill holes as a guide. After tunnel excavation, a grid arch frame or a steel arch frame is erected in time, and the arch frame and the tie beam are connected by fine-rolled threaded steel or prestressed anchor cables through the reserved drill holes. Prestress is applied in time to overcome the surface settlement and deformation caused by large-section tunnel excavation.

[0028] The suspension method of the present invention is an improvement on the double-side wall pilot tunnel construction method. It can effectively control the surface settlement and deformation caused by large-section tunnel construction, ensuring that surrounding existing pipelines and buildings (structures) will not suffer safety accidents caused by large surface settlement and deformation.

[0029] The suspension method of the present invention has clear mechanical principles, simple construction technology and strong operability. The research on its application in settlement control of large-section shallow buried dark-excavated tunnel construction is feasible.

[0030] The present invention reduces construction risks, construction cost investment and economic losses, thereby achieving a win-win effect in terms of technical, economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Attachment Figure 1 It is a structural schematic diagram of the present invention;

[0032] Attachment Figure 2 It is a structural diagram of the ground steel beam;

[0033] Attachment Figure 3 It is a structural diagram of the steel bar grid;

[0034] Attachment Figure 4 This is the expanded view of the steel grille;

[0035] Attachment Figure 5 It is a structural diagram of the locking foot anchor rod;

[0036] Attachment Figure 6This is a structural diagram of the construction of ground steel beams and locking anchor rods;

[0037] Attachment Figure 7 This is a schematic diagram of the structure of the small conduit for the tunnel vault during construction;

[0038] Attachment Figure 8 This is a structural diagram of the excavation of No. 1 cavern;

[0039] Attachment Figure 9 This is a structural diagram of the excavation of No. 2 and No. 3 caverns;

[0040] Attachment Figure 10 This is a structural diagram of the excavation of No. 4 cavern;

[0041] Attachment Figure 11 This is a structural diagram of the secondary lining of Part A;

[0042] Attachment Figure 12 This is a structural diagram of the secondary lining of Part B;

[0043] Attachment Figure 13 It is a structural diagram for removing the supporting structure;

[0044] In the figure: 1. Locking anchor rod; 2. Ground steel beam; 3. Steel grille; 4. Steel mesh; 5. Cavern No. 1; 6. Cavern No. 2; 7. Cavern No. 4; 8. Cavern No. 3; 9. Longitudinal steel beam; 10. Transverse steel beam; 11. High-quality rolled threaded steel bar; 12. Corrugated pipe; 13. Steel plate; 14. Rib; 15. Pad; 16. Nut; 17. Connecting reinforcement; 18. Main reinforcement; 19. Stirrups; 20. Small duct of tunnel vault. DETAILED DESCRIPTION Example

[0045] A construction structure for controlling the settlement of a shallow, dark-excavated, large-section tunnel. The construction structure for controlling the settlement of a shallow, dark-excavated, large-section tunnel comprises an elliptical structure enclosed by four fan-shaped chambers and a ground steel beam 2 laid on the ground. A supporting structure is arranged outside each fan-shaped chamber. The supporting structure is composed of two layers of steel mesh 4 arranged outside the fan-shaped chamber and a plurality of steel grids 3 laid between the two layers of the steel mesh. A plurality of locking anchor rods 1 are arranged on the ground steel beam and pass through holes in the ground and are welded to the steel grid. Example

[0046] According to the construction structure for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel described in Example 1, the ground steel beam is a structure formed by vertically cross-welding the transverse steel beam 10 and the longitudinal steel beam 9 . Example

[0047] According to the construction structure for controlling the settlement of shallow buried and large-section tunnels described in Example 1 or 2, the locking foot anchor rod includes two parallel steel plates 13 and a rib 14 welded between the two steel plates. One end of the fine-rolled threaded steel bar 11 passes through the two layers of the steel plates and is screwed with a nut 16. The other end of the fine-rolled threaded steel bar is covered with a corrugated tube 12. Example

[0048] According to the construction structure for controlling the settlement of a shallow buried, dark-excavated, large-section tunnel as described in Example 1, 2, or 3, the steel grid includes a plurality of stirrups 19 arranged in parallel, main bars 18 are passed through the four corners of the stirrups and welded, and connecting bars 17 are welded between two adjacent main bars. Example

[0049] A construction method for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel, comprising the following steps:

[0050] (1) Construct surface concrete beams and steel longitudinal beams, and reserve tie rod holes on the tie beams;

[0051] (2) Construct ground beams, bury finely rolled threaded steel bars, and install 20 small conduits for the tunnel vault, with one row installed for every two grids. Drill holes in the pipe wall every 100-200 mm, with a hole diameter of 6-8 mm. Use cement slurry according to the stratum, control the grouting pressure at 0.4-0.6 MPa, and install a grouting plug at the hole mouth to prevent slurry leakage.

[0052] (3) Before the construction of the secondary lining structure, φ42 water-gas pipes are pre-buried in the arch and side walls during the initial support construction, with a circumferential spacing of 3m and a longitudinal spacing of 3m, arranged in a plum blossom shape. The grouting depth is 0.5m behind the initial support. After the initial support is closed to a certain length, cement slurry is injected behind the initial support with a grouting pressure of 0.4-0.6MPa.

[0053] (4) When the secondary lining is being constructed, φ42 water-gas pipes are pre-buried in the vault and side walls, with a circumferential spacing of 3m and a longitudinal spacing of 3m, arranged in a plum blossom shape. High-strength non-shrinkage grouting is injected behind the secondary lining at a grouting pressure of 0.1-0.3MPa.

[0054] (5) Excavate No. 1 cavern, carry out initial support, install anchor bolts, and connect the primary support structure and finished rolled threaded steel bars;

[0055] (6) Excavate Cavern No. 2 and Cavern No. 3, carry out initial support, install grouting anchor pipes, connect the primary support structure and finished rolled threaded steel bars, and the longitudinal step distance between Cavern No. 1 and Cavern No. 2, and between Cavern No. 2 and Cavern No. 3 shall not be less than 15m;

[0056] (7) Excavate No. 4 cavern and provide initial support. The longitudinal step distance between No. 3 cavern and No. 4 cavern shall not be less than 15m;

[0057] (8) Grouting from the grouting anchor pipe into the supporting structure;

[0058] (9) According to the demolition section division, prestress the finished rolled threaded steel bars in batches, then demolish the lower part of the temporary middle partition wall, with the length of demolition not exceeding 8m at a time, level it, lay the waterproof layer, and finally apply the A part bottom plate and part of the side wall secondary lining. After the arch bottom structure reaches the design strength, support the temporary middle partition wall back to the structural bottom plate;

[0059] (10) Remove the temporary arch and middle partition wall in sections, with the length of each removal not exceeding 8m, and apply secondary lining to the side wall of section B to close the ring;

[0060] (11) After the secondary lining reaches the design strength, all temporary support structures shall be removed.

Claims

1. A construction method for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel, characterized by: The method comprises the following steps: (1) Construct surface concrete beams and steel longitudinal beams, and reserve tie rod holes on the tie beams; (2) Construct ground beams, bury finely rolled threaded steel bars, and install small conduits for the tunnel vaults. Install one row of conduits for every two steel grids. Drill holes in the conduit wall every 100-200 mm, with a hole diameter of 6-8 mm. Use cement slurry according to the stratum. The grouting pressure is controlled at 0.4-0.6 MPa. The diameter of the grouting body is not less than 0.5 m. To prevent the slurry from leaking, a slurry stopper is installed at the hole mouth. (3) Before the construction of the secondary lining structure, φ42 water-gas pipes are pre-buried in the arch and side walls during the initial support construction, with a circumferential spacing of 3m and a longitudinal spacing of 3m, arranged in a plum blossom shape. The grouting depth is 0.5m behind the initial support. After the initial support is closed to a certain length, cement slurry is injected behind the initial support with a grouting pressure of 0.4-0.6MPa. (4) When the secondary lining is being constructed, φ42 water-gas pipes are pre-buried in the vault and side walls, with a circumferential spacing of 3m and a longitudinal spacing of 3m, arranged in a plum blossom shape. High-strength non-shrinkage grouting is injected behind the secondary lining at a grouting pressure of 0.1-0.3MPa. (5) Excavate No. 1 cavern, carry out initial support, install anchor bolts, and connect the primary support structure and finished rolled threaded steel bars; (6) Excavate Cavern No. 2 and Cavern No. 3, carry out initial support, install grouting anchor pipes, connect the primary support structure and finished rolled threaded steel bars, and the longitudinal step distance between Cavern No. 1 and Cavern No. 2, and between Cavern No. 2 and Cavern No. 3 shall not be less than 15m; (7) Excavate No. 4 cavern and provide initial support. The longitudinal step distance between No. 3 cavern and No. 4 cavern shall not be less than 15m; (8) Grouting from the grouting anchor pipe into the supporting structure; (9) According to the demolition section division, prestress the finished rolled threaded steel bars in batches, then demolish the lower part of the temporary middle partition wall, with the length of demolition not exceeding 8m at a time, level it, lay the waterproof layer, and finally apply the A part bottom plate and part of the side wall secondary lining. After the arch bottom structure reaches the design strength, support the temporary middle partition wall back to the structural bottom plate; (10) Remove the temporary arch and middle partition wall in sections, with the length of each removal not exceeding 8m, and apply secondary lining to the side wall of section B to close the ring; (11) After the secondary lining reaches the design strength, all temporary support structures shall be removed.

2. The construction method for controlling the settlement of a shallow-buried, dark-excavated, large-section tunnel according to claim 1, wherein: The construction structure for controlling the settlement of shallow buried and dark-excavated large-section tunnels includes an elliptical structure formed by four fan-shaped caverns and ground steel beams laid on the ground. A supporting structure is arranged outside each fan-shaped cavern, and the supporting structure is composed of two layers of steel mesh arranged outside the fan-shaped cavern and a plurality of steel grids laid between the two layers of the steel mesh. A plurality of locking anchor rods are arranged on the ground steel beams and then welded into the steel grid after passing through holes in the ground; the ground steel beams are a structure formed by vertically cross-welding a transverse steel beam and a longitudinal steel beam; the locking anchor rods include two parallel steel plates and a rib welded between the two steel plates, one end of the fine-rolled threaded steel bar passes through the two layers of the steel plates and is screwed with a nut, and the other end of the fine-rolled threaded steel bar is covered with a corrugated tube; the steel grid includes a plurality of stirrups arranged in parallel, and the four corners inside the plurality of stirrups are provided with main bars and welded, and connecting bars are welded between two adjacent main bars.

Images