Support structure for entering and exiting a shallow-buried large-section tunnel in soft strata and construction method thereof

Abstract

The present invention relates to a support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata and a construction method thereof. The support structure includes an upper bench socket arch, with embedded sleeves in the socket arch, and a circular-arc pipe shed combination of the tunnel crown is driven into the mountain body from the socket arch through the sleeves. Between the lower ends of the arc-shaped pipe shed in the mountain body at the tunnel entrance and exit, a horizontal pipe shed driven between the upper bench and the lower bench is also fixed. An intermediate upper pipe shed vertically arranged and in an arc shape is also driven between the upper part of the middle of the horizontal pipe shed and the circular-arc pipe shed of the tunnel crown. An intermediate lower pipe shed connected to the intermediate upper pipe shed is also driven between the lower part of the middle of the horizontal pipe shed and the bottom of the invert arch of the lower bench. The steps of the present invention are simple, with strong operability, land saving, and remarkable economic and social benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and particularly relates to a support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata and a construction method thereof. Background Art

[0002] With the development of cities, ground roads can no longer meet the growing vehicle traffic, and only the construction of underground roads can relieve the situation. Considering the limited urban ground space, the overburden depth of the entrance and exit sections of underground roads is generally shallow. Moreover, the geological conditions are poor, the construction excavation section is large, and if the area has a shallow groundwater level, the construction of the entrance and exit sections is very difficult.

[0003] How to safely complete the construction of the entrance and exit of underground roads is the key to restricting the penetration of underground roads. The following problems need to be solved:

[0004] 1. The buried depth of the tunnel entrance and exit is relatively shallow, and the overburden is generally urban backfill or garbage soil, which is non-native soil, and the self-stability of the soil mass is poor. It is very difficult to carry out excavation without pre-support.

[0005] 2. At present, in order to adapt to the rapid development of cities, the aperture of the reserved chamber of the underground road is large, resulting in a large excavation section. Given the poor stability of the surrounding rock, it is impossible to use multi-pilot tunnels for sectional excavation simultaneously.

[0006] 3. According to the tunnel excavation principle: "enter the tunnel early and exit the tunnel late", completing the excavation and support process of the portal section as soon as possible is the key to the smooth progress of the project. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the present invention provides a support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata and a construction method thereof, which saves the excavation and support time, greatly improves the construction efficiency, and achieves good social and economic benefits during the construction process of the heading face.

[0008] The present invention is realized through the following technical solutions:

[0009] A support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata is provided, including an upper bench casing arch. Sleeve pipes are pre-embedded in the casing arch, and a tunnel crown arc-shaped pipe shed is driven from the casing arch into the mountain body through the sleeve pipes. A horizontal pipe shed driven between the upper bench and the lower bench is also fixed between the lower ends of the two sides of the tunnel crown arc-shaped pipe shed in the mountain body. An intermediate upper pipe shed vertically arranged and in an arc shape is also driven between the top of the horizontal pipe shed and the crown of the tunnel crown arc-shaped pipe shed. An intermediate lower pipe shed fixed to the intermediate upper pipe shed is also driven between the bottom of the horizontal pipe shed and the bottom of the invert of the lower bench.

[0010] Furthermore, the intermediate upper pipe shed and the intermediate lower pipe shed are symmetrically arranged with respect to the horizontal pipe shed.

[0011] Furthermore, steel arch frames are also provided on the inner arc surfaces on the same side of the middle upper pipe shed and the middle lower pipe shed.

[0012] A construction method for a support structure for the entrance and exit of a shallow-buried large-section tunnel in a soft stratum includes constructing an upper bench ring arch along the excavation contour line of the heading face and pre-embedding sleeves, and also includes the following steps:

[0013] a. Driving pipe sheds: Simultaneously driving the arch crown arc-shaped pipe shed, horizontal pipe shed, and middle upper pipe shed of the tunnel, and constructing grouting;

[0014] b. Upper bench construction: The upper bench uses two pilot tunnels on the left and right sides to excavate the soil mass step by step and enter the tunnel for 10 - 15 m;

[0015] c. Lower bench pipe shed construction: Drive a middle lower pipe shed fixed to the middle upper pipe shed between the lower part of the middle of the horizontal pipe shed and the bottom of the invert arch of the lower bench, and construct grouting;

[0016] d. Lower bench construction: Excavate the soil mass to complete the initial support, and the excavation of the entrance and exit sections of the tunnel is closed to form a ring.

[0017] Furthermore, in step a, the arch crown arc-shaped pipe shed of the tunnel is driven into the mountain body from the ring arch through the sleeve, the horizontal pipe shed is driven between the upper bench and the lower bench and connects the lower ends of both sides of the arc-shaped pipe shed, and the middle upper pipe shed is arc-shaped and is driven between the upper part of the middle of the horizontal pipe shed and the arch crown of the arc-shaped pipe shed.

[0018] Furthermore, the pipe shed is driven in segments using a self-advancing pipe shed drilling rig, with each segment having a length of 3 m. According to the designed length of the entrance and exit sections, the one-time driving distance is not less than 30 m.

[0019] Furthermore, after step b and before step c, first construct a portal ring beam on the heading face of the portal, pre-embed the guiding pipes for driving the large pipe shed, and then carry out the pipe shed construction.

[0020] Advantages of the present invention:

[0021] During the construction process, a method of using pipe shed segmented support for the entrance and exit of a shallow-buried large-section tunnel in a soft stratum is proposed, changing the original traditional method of constructing a ring arch first and then driving a large pipe shed at the arch crown to advance into the tunnel. The full-section entry is adopted, and the pipe shed segmented support is used. The pipe shed is driven in one go along the cross-shaped excavation contour line of the heading face. With the support of the pipe shed, it is no longer necessary to drive the advanced small conduits separately for each cycle during excavation. The excavation and support time is saved, and the construction efficiency is greatly improved, achieving good social and economic benefits during the construction of the heading face.

[0022] The steps of the present invention are simple, highly operable, land-saving, and have remarkable economic and social benefits. Description of the Drawings

[0023] Figure 1 It is the overall structural schematic diagram of the support structure in the present invention;

[0024] Figure 2 is Figure 1 side view of.

[0025] As shown in the figure:

[0026] 1. Tunnel vault arch-shaped pipe shed, 2. Middle upper pipe shed, 3. Horizontal pipe shed, 4. Middle lower pipe shed, 5. Steel arch frame, 6. Upper bench, 7. Lower bench, 8. Inlet and outlet arch, 9. Inverted arch, 10. Pilot tunnel. Specific implementation mode

[0027] To clearly illustrate the technical features of this solution, the following will elaborate on this solution through specific implementation modes.

[0028] A support structure for the inlet and outlet of a shallow-buried large-section tunnel in soft strata, which relates to the field of underground engineering such as the construction of underground roads, utility tunnels, cable tunnels, etc. in the built-up core area of the city, and particularly relates to a method of using pipe shed segmented support for the inlet and outlet of a shallow-buried large-section tunnel in soft strata to construct related underground space structures such as underground expressways and rail transit.

[0029] It includes an upper bench inlet and outlet arch 8, with sleeves pre-embedded in the inlet and outlet arch 8, and a tunnel vault arch-shaped pipe shed 1 is drilled from the inlet and outlet arch 8 into the mountain body through the sleeves. Between the lower ends of the two sides of the tunnel vault arch-shaped pipe shed 1 in the mountain body at the tunnel inlet and outlet, a horizontal pipe shed 3 is also fixed between the upper bench 6 and the lower bench 7. Between the upper part of the middle of the horizontal pipe shed 3 and the vault of the tunnel vault arch-shaped pipe shed 1, a vertically arranged and tunnel-vault-arch-shaped middle upper pipe shed 2 is also drilled. Between the lower part of the middle of the horizontal pipe shed 3 and the bottom of the inverted arch of the lower bench 7, a middle lower pipe shed 4 fixed to the middle upper pipe shed 2 is also drilled. Among them: The middle upper pipe shed 2 and the middle lower pipe shed 4 are symmetrically arranged with respect to the horizontal pipe shed 3. On the inner arc surface on the same side of the middle upper pipe shed 2 and the middle lower pipe shed 4, a steel arch frame 5 is also provided.

[0030] A construction method for using the support structure for the inlet and outlet of a shallow-buried large-section tunnel in soft strata includes constructing an upper bench inlet and outlet arch 8 along the excavation contour line of the heading face and pre-embedding sleeves, and also includes the following steps:

[0031] First, clean the heading face at the inlet and outlet, along the cross-shaped excavation contour line of the heading face, construct the upper bench inlet and outlet arch 8, and leave pre-embedded sleeves.

[0032] a. Installation of pipe roofs: Simultaneously install the arch-shaped pipe roof 1 at the tunnel crown, the horizontal pipe roof 3, and the middle upper pipe roof 2, and carry out grouting construction. Among them: The arch-shaped pipe roof 1 at the tunnel crown is installed into the mountain body from the sleeve arch 8 through a casing. The horizontal pipe roof 3 is installed between the upper bench 6 and the lower bench 7 and connects the two lower ends of the arch-shaped pipe roof 1 at the tunnel crown. The middle upper pipe roof 2 is arc-shaped and is installed between the middle of the horizontal pipe roof 3 and the crown of the arch-shaped pipe roof 1 at the tunnel crown;

[0033] b. Construction of the upper bench: For the upper bench 6, two pilot tunnels 10 on the left and right sides are used to excavate the soil mass at a step distance of 10 m and enter the tunnel for 10 - 15 m;

[0034] At the portal face, construct the portal ring beam and embed the guiding pipes for the installation of large pipe roofs, and then carry out the pipe roof construction. When excavating the pilot tunnel, the advanced support at the arch and side wall positions of the tunnel can be omitted. In addition, steel arch frames 5 are provided on the inner arc surfaces of the middle upper pipe roof 2 and the middle lower pipe roof 4 on the same side, which can reduce the material model. Generally, I16 steel beams are used, saving material weight, reducing construction difficulty, and increasing construction efficiency. The number of excavation bays per cycle for the upper bench 6 can be 2 to 3 bays at a time, and the excavation footage per cycle is not more than 2 m.

[0035] c. Construction of the lower bench pipe roof: Install the middle lower pipe roof 4, which is fixed to the middle upper pipe roof 2, between the lower part of the middle of the horizontal pipe roof 3 and the bottom of the invert 9 of the lower bench 7, and carry out grouting construction;

[0036] d. Construction of the lower bench: After excavating the soil mass, carry out the initial support. The excavation of the tunnel entrance and exit sections is closed in a loop. When excavating the lower bench, the number of excavation bays per cycle can be appropriately increased. It can be 3 to 5 bays at a time, and the excavation footage per cycle is not more than 3 m, accelerating the construction progress and improving work efficiency.

[0037] The above installation of pipe roofs is carried out in sections using a self-advancing pipe roof drilling rig, with each section being 3 m long. According to the designed length of the entrance and exit sections of the tunnel, the one-time installation distance is not less than 30 m.

[0038] Of course, the above description is not limited to the above examples. The technical features not described in the present invention can be achieved by or adopted from existing technologies, and will not be elaborated here. The above embodiments and drawings are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. The present invention has been described in detail with reference to the preferred embodiments. Those of ordinary skill in the art should understand that any changes, modifications, additions, or substitutions made by those of ordinary skill in the technical field within the scope of the essence of the present invention do not depart from the purpose of the present invention and should also fall within the scope of the claims of the present invention.

Claims

1. A construction method for the support structure of the entrance and exit of a shallow-buried large-section tunnel in soft strata, including constructing an upper bench arch along the excavation contour line of the heading face and pre-embedding sleeves, characterized in that: The support structure for the tunnel entrance and exit includes an upper bench arch ring. Casing pipes are embedded in the arch ring, and an arc-shaped pipe shed for the tunnel crown is drilled from the arch ring into the mountain body through the casing pipes. Between the lower ends of the tunnel entrance and exit in the mountain body, a horizontal pipe shed drilled between the upper bench and the lower bench is fixed. An intermediate upper pipe shed vertically arranged and in an arc shape is drilled between the upper part of the middle of the horizontal pipe shed and the crown of the tunnel crown arc-shaped pipe shed. An intermediate lower pipe shed connected to the intermediate upper pipe shed is drilled between the lower part of the middle of the horizontal pipe shed and the invert bottom of the lower bench. It also includes the following steps: a. Drilling the pipe shed: Drill the tunnel crown arc-shaped pipe shed, the horizontal pipe shed, and the intermediate upper pipe shed simultaneously, and construct grouting. b. Construction of the upper bench: The upper bench uses two side drifts on the left and right to excavate the soil mass step by step and enter the tunnel for 10 - 15 m. c. Construction of the lower bench pipe shed: Drill an intermediate lower pipe shed fixed to the intermediate upper pipe shed between the lower part of the middle of the horizontal pipe shed and the invert bottom of the lower bench, and construct grouting. d. Construction of the lower bench: Excavate the soil mass to complete the initial support, and the excavation of the tunnel entrance and exit section is closed to form a ring.

2. The construction method of the support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata according to claim 1, characterized in that: The pipe shed is drilled in segments using a self-advancing pipe shed drilling rig, with each segment having a length of 3 m. According to the designed length of the tunnel entrance and exit section, the one-time drilling distance is not less than 30 m.

3. The construction method of the support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata according to claim 1, characterized in that: After step b and before step c, first construct the portal ring beam on the portal face, embed the guiding pipe for drilling the large pipe shed, and then carry out the pipe shed construction.

4. The construction method of the support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata according to claim 1, characterized in that: The intermediate upper pipe shed and the intermediate lower pipe shed are symmetrically arranged with respect to the horizontal pipe shed.

5. The construction method of the support structure for the entrance and exit of a shallow-buried large-section tunnel in soft strata according to claim 1, characterized in that: Steel arch frames are also provided on the inner arc surfaces on the same side of the intermediate upper pipe shed and the intermediate lower pipe shed.

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