A method for full-section excavation of a pilot tunnel with micro-core soil left

Abstract

The present invention provides a method for excavating a pilot tunnel with a micro-core soil, and relates to the technical field of underground construction engineering. The method for excavating a pilot tunnel with a micro-core soil comprises the following steps: S1. A small guide tube is set along the top of the pilot tunnel excavation surface, and then grouting is performed in the small guide tube; S2. The pilot tunnel is excavated with a full section, and the micro-core soil is retained in the pilot tunnel at the same time; S3. Initial concrete is sprayed on the pilot tunnel excavation surface, and then a steel frame N2 with a large arch side wall grid is installed in the pilot tunnel; S4. Next, a side wall grid steel frame N3 is installed in the pilot tunnel, and a connecting plate is used to connect the side wall grid steel frame N2 with a large arch and the side wall grid steel frame N3; S5. Concrete is sprayed on the surface of the initial concrete spraying for a second time to a designed thickness. The present invention provides a method for excavating a pilot tunnel with a micro-core soil, which is convenient and quick to install, improves the excavation efficiency, and solves the problem of arch top sinking and low efficiency in step method excavation.

Description

Technical Field

[0001] The invention relates to the technical field of underground construction engineering, in particular to a full-section excavation method for a pilot tunnel with micro core soil left. Background Art

[0002] The pilot tunnel, also called the pilot pit, is a small-section tunnel that is first excavated when the mining method is used to build tunnels and underground projects. According to the layout position, it can be divided into upper pilot tunnel, lower pilot tunnel, upper and lower pilot tunnel, sidewall pilot tunnel and central pilot tunnel. When the tunnel is excavated by the mining method, the pilot tunnel is a small-section tunnel that is excavated before other parts. It is used for expansion, determination of tunnel excavation direction, verification of geological data, laying of transportation tracks, material transportation, mucking and ventilation and drainage equipment, etc. It is divided into advanced pilot tunnels, parallel pilot tunnels, etc. Its shape is usually trapezoidal or rectangular, sometimes arc-shaped. Its size depends on geological conditions, transportation requirements, support type, equipment conditions and ensuring the safety of construction personnel, and should not be too large.

[0003] At present, the pilot tunnel is usually excavated by the step method, which has cumbersome procedures, complex structural stress, and problems such as over-excavation and difficulty in controlling the sinking of the arch. When the excavation section of the pilot tunnel is small, the step method is still used for construction, which is time-consuming and laborious. Therefore, it is necessary to invent a pilot tunnel excavation method suitable for smaller sections to improve safety and construction efficiency. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the shortcomings of the prior art, the present invention provides a full-section excavation method for a pilot tunnel with micro-core soil retained, which solves the problems of the prior excavation method, such as complicated procedures, complex structural stress, over-excavation, and difficulty in controlling the sinking of the arch.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for full-section excavation of a pilot tunnel with micro-core soil, comprising the following steps:

[0008] S1. A small conduit is set along the top of the pilot tunnel excavation surface, and then grouting is performed into the small conduit;

[0009] S2. Excavate the pilot tunnel in full section and retain micro core soil in the pilot tunnel;

[0010] S3. Initially spray concrete on the excavation surface of the pilot tunnel, and then install the grid steel frame N2 with large arch side wall in the pilot tunnel;

[0011] S4. Next, the side wall grid steel frame N3 is installed in the pilot tunnel, and the large arch side wall grid steel frame N2 and the side wall grid steel frame N3 are connected by a connecting plate;

[0012] S5. Spray concrete twice on the surface of the primary sprayed concrete to the designed thickness, and seal the side wall grid steel frame N2 with large arch and the side wall grid steel frame N3;

[0013] S6. Excavate the micro core soil reserved in the pilot tunnel;

[0014] S7. Initially spray concrete on the bottom plate in the pilot tunnel, and then install the bottom grid steel frame N1. After the bottom grid steel frame N1 is installed, use a connecting plate to fix N1 with N2 and N3, and then spray concrete on the bottom plate for the second time to the designed thickness, and close the bottom grid steel frame N1;

[0015] S8. Re-spray the concrete to the designed thickness after the second spraying to completely seal the initial support structure;

[0016] S9. When making the initial support of the next adjacent section of the pilot tunnel, the steps remain the same as above, but the positions of the side wall grid steel frame N3 and the side wall grid steel frame with large arch N2 need to be swapped left and right.

[0017] Preferably, the curvature of the arch of the large-arch side wall grid steel frame N2 is 78°.

[0018] Preferably, the arch curvature of the side wall grid steel frame N3 is 38°.

[0019] Preferably, the small conduit presents a certain horizontal inclination when driven into the top of the guide hole, and the angle between the small conduit and the plane perpendicular to the horizontal plane is 10-15°.

[0020] (III) Beneficial effects

[0021] The present invention provides a method for full-section excavation of a pilot tunnel with micro-core soil. It has the following beneficial effects:

[0022] 1. The present invention adopts a full-section excavation method with reserved micro-core soil, eliminates the locking anchor holes on both sides of the tunnel construction by the upper and lower step method, improves the installation efficiency, and further improves the pilot tunnel excavation efficiency, solving the problem of over-excavation during the traditional pilot tunnel step method construction.

[0023] 2. The traditional up-and-down step method is prone to the problem of arch sinking. The grid steel frame structure of the present invention effectively solves the problem of difficult control of arch settlement. The grid arch connecting plates of adjacent advances of the support structure are staggered, which improves the longitudinal stiffness of the tunnel. At the same time, the connecting plates between the arch grids are arranged at the positive and negative bending moment conversion position of the support structure, which is beneficial to the structural stress and reasonable structural stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic diagram of the grouting process for installing small and medium-sized conduits according to the present invention;

[0025] FIG2 is a schematic diagram of the full-section excavation process in the present invention;

[0026] FIG3 is a schematic diagram of the process of installing a grid steel frame with a large arch side wall in the present invention;

[0027] FIG4 is a schematic diagram of the process of installing a grid steel frame with a small arch side wall in the present invention;

[0028] FIG5 is a schematic diagram of the process of excavating reserved core soil in the present invention;

[0029] FIG6 is a schematic diagram of the initial support structure in the present invention;

[0030] FIG7 is a schematic longitudinal section diagram of the initial support system of the pilot tunnel in the present invention;

[0031] FIG8 is a schematic diagram of the initial support body of adjacent sections of the pilot tunnel in the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example:

[0034] As shown in FIGS. 1-8 , an embodiment of the present invention provides a method for full-section excavation of a pilot tunnel with micro-core soil, comprising the following steps:

[0035] S1. A small pipe is set along the top of the pilot tunnel excavation surface, and then grouting is performed into the small pipe to reinforce the soil at the top of the pilot tunnel. The width of the pilot tunnel is set to 2700 mm, and the total height of the pilot tunnel is 2900 mm, of which the height of the arch is 857 mm and the curvature of the arch is 116°, as shown in Figure 1;

[0036] S2. Excavate the pilot tunnel in full section, and retain the micro core soil in the pilot tunnel. The cross section of the micro core soil is set to be a trapezoidal shape, with an upper width of 700 mm, a lower width of 1100 mm, and a height of 1000 mm, as shown in Figure 2;

[0037] S3. Initially spray concrete on the excavation surface of the pilot tunnel, and then install a large arch side wall grid steel frame N2 in the pilot tunnel. The arch top curvature of the large arch side wall grid steel frame N2 is 78o, as shown in Figure 3;

[0038] S4. Next, install the side wall grid steel frame N3 in the pilot tunnel. The arch curvature of the side wall grid steel frame N3 is 38 degrees, and use a connecting plate to connect the large arch side wall grid steel frame N2 and the side wall grid steel frame N3. Figure 4 As shown;

[0039] S5. Spray concrete on the surface of the primary sprayed concrete for the second time to the designed thickness, and seal the side wall grid steel frame N2 with large arch and the side wall grid steel frame N3, as shown in FIG5 ;

[0040] S6. Excavate the reserved micro core soil in the pilot tunnel, as shown in Figure 5;

[0041] S7. Initially spray concrete on the bottom plate in the pilot tunnel, and then install the bottom grid steel frame N1. The width of the bottom grid steel frame N1 is 1600mm. After the installation of the bottom grid steel frame N1, use the connecting plate to fix N1 with N2 and N3. Then spray concrete on the bottom plate for the second time to the designed thickness, and close the bottom grid steel frame N1, as shown in Figure 6;

[0042] S8. Re-spray the secondary sprayed concrete to the designed thickness, with a total concrete thickness of 250 mm, and completely seal the initial support structure, as shown in Figure 2;

[0043] S9. When making the initial support of the next adjacent section of the pilot tunnel, the steps remain the same as above, but the positions of the side wall grid steel frame N3 and the side wall grid steel frame with large arch N2 need to be swapped left and right to ensure that the connecting plates between the arch grids of the two adjacent sections are staggered, thereby improving the longitudinal stiffness of the tunnel, as shown in Figure 8.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for full-section excavation of a pilot tunnel with micro-core soil, characterized in that: The following steps are involved: S1. A small conduit is set along the top of the pilot tunnel excavation surface, and then grouting is performed into the small conduit; S2. Excavate the pilot tunnel in full section and retain micro core soil in the pilot tunnel; S3. Initially spray concrete on the excavation surface of the pilot tunnel, and then install the grid steel frame N2 with large arch side wall in the pilot tunnel; S4. Next, the side wall grid steel frame N3 is installed in the pilot tunnel, and the large arch side wall grid steel frame N2 and the side wall grid steel frame N3 are connected by a connecting plate; S5. Spray concrete twice on the surface of the primary sprayed concrete to the designed thickness, and seal the side wall grid steel frame N2 with large arch and the side wall grid steel frame N3; S6. Excavate the micro core soil reserved in the pilot tunnel; S7. Initially spray concrete on the bottom plate in the pilot tunnel, and then install the bottom grid steel frame N1. After the bottom grid steel frame N1 is installed, use a connecting plate to fix N1 with N2 and N3, and then spray concrete on the bottom plate for the second time to the designed thickness, and close the bottom grid steel frame N1; S8. Re-spray the concrete to the designed thickness after the second spraying, and completely seal the initial support structure. The initial support of the section is completely completed; S9. When making the initial support of the next adjacent section of the pilot tunnel, the steps remain the same as above, but the positions of the side wall grid steel frame N3 and the side wall grid steel frame with large arch N2 need to be swapped left and right.

2. A method for full-section excavation of a pilot tunnel with micro-core soil as claimed in claim 1, characterized in that: The curvature of the arch of the large arch side wall grid steel frame N2 is 78°.

3. The method for full-section excavation of a pilot tunnel with micro-core soil as claimed in claim 1, characterized in that: The arch curvature of the side wall grid steel frame N3 is 38°.

4. The method for full-section excavation of a pilot tunnel with micro-core soil as claimed in claim 1, characterized in that: When the small conduit is driven into the top of the guide hole, it presents a certain horizontal inclination, and the angle between the small conduit and the plane perpendicular to the horizontal plane is 10-15°.

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