Construction structure and construction method for large-section tunnel exit

Abstract

The invention discloses a construction structure and a construction method for large-section tunnel out-of-hole, and belongs to the technical field of large-section tunnel out-of-hole. The construction structure comprises a tunnel body and a temporary transverse support, the temporary transverse support is located in a large-section core soil layer in the tunnel body, the large-section core soil layer is divided into an upper step layer and a lower step layer by the temporary transverse support, a temporary support is arranged above the temporary transverse support, and the temporary support is arranged above the temporary transverse support. And a temporary longitudinal support is arranged at the upper end of the temporary support. In order to solve the problems that the collapse risk is extremely high and the tunnel out-of-hole operation is difficult to safely carry out when a large-section tunnel is out of hole, a large-section core soil layer to be excavated is divided into a plurality of small-section core soil layers through temporary transverse supports and temporary supports, and each small-section core soil layer is circularly constructed; and the excavated small-section area is subjected to primary support and then subsequent excavation operation, so that the possibility of tunnel collapse is reduced, and the life safety of personnel is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of large-section tunnel exits, and in particular to a construction structure and a construction method for large-section tunnel exits. Background Art

[0002] The structure of a tunnel consists of two parts: a main building and ancillary equipment. The main building consists of a tunnel body and a tunnel portal. The ancillary equipment includes a car shelter, fire-fighting facilities, emergency communications and drainage facilities. Long tunnels also have special ventilation and lighting equipment. At present, with the rapid development of transportation, the areas that tunnels pass through are becoming more and more complex. Tunnel construction often encounters situations where the tunnel entrance is located on a steep rock wall, the access road is inaccessible, and there is no operating platform. In this case, the general construction can choose to excavate in one direction from another entrance until the cliff entrance, and then exit the cave in the opposite direction from the cave; or add a horizontal tunnel or inclined shaft at a suitable position in the tunnel to enter the tunnel, and then excavate to both ends.

[0003] The cliff entrance generally adopts the reverse exit from the cave, but the surrounding rock at the entrance is generally weak and shallow, and the rock on the mountain surface is severely weathered, which brings huge challenges to tunnel construction, especially large-section highway tunnels. With the increase of traffic volume, the tunnel cross-section is as high as more than 200 square meters, which makes the large-section tunnel exit have a very high risk of collapse and it is difficult to safely carry out the tunnel exit operation; therefore, it does not meet the existing needs. In this regard, the present application proposes a construction structure and construction method for large-section tunnel exit. Summary of the invention

[0004] The purpose of the present invention is to provide a construction structure and a construction method for a large-section tunnel exit. The large-section core soil layer in the tunnel body is divided into an upper step layer and a lower step layer by a temporary transverse support. The temporary support further divides the upper step layer into a left guide tunnel and a right guide tunnel. After the personnel cyclically construct the left guide tunnel and the right guide tunnel to the tunnel entrance, the lower step layer invert arch construction is carried out, thereby reducing the risk of tunnel collapse, ensuring the life safety of personnel, and solving the problems in the prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a construction structure for a large-section tunnel exit, comprising a tunnel body and a temporary transverse support, wherein the temporary transverse support is located inside the large-section core soil layer in the tunnel body, and the temporary transverse support divides the large-section core soil layer into an upper step layer and a lower step layer. A temporary support is arranged above the temporary transverse support, and a temporary longitudinal support is arranged at the upper end of the temporary support. An initial support is arranged on the inner wall of the tunnel body, and the outside of the tunnel body is a surrounding rock layer. A pipe shed is arranged between the initial support and the surrounding rock layer, and an invert is arranged on the bottom surface of the tunnel body, and the initial support is fixed to the inner wall of the tunnel body by locking anchor rods.

[0006] Preferably, the temporary support is an arc-shaped structure, the temporary support is completely located on one side of the tunnel centerline, the temporary support divides the upper step layer into a left guide tunnel and a right guide tunnel, and the temporary longitudinal support is fixed inside the core soil layer of the large section.

[0007] Preferably, a slope is provided at one end of the lower step layer close to the inverted arch, and one end of the upper step layer and the lower step layer are connected by the slope.

[0008] Preferably, the invert arch comprises a primary invert arch support, a secondary invert arch lining and an invert arch filling, the secondary invert arch lining is located between the primary invert arch support and the invert arch filling, and the primary invert arch support is connected to the bottom surface inside the tunnel body.

[0009] Preferably, a guide pipe is provided at one end of the pipe rack, and a sleeve arch is provided at the other end of the pipe rack, which is located between the initial support and the surrounding rock layer. The sleeve arch is located at the exit end of the tunnel body, and the pipe rack extends through the guide pipe to the interior of the sleeve arch.

[0010] A construction method for a large-section tunnel exit is implemented based on a construction structure for a large-section tunnel exit, and includes the following steps:

[0011] Step 1: Expand the upper step layer at a distance of two arch frames from the designed position of the pipe shed to form an expanded excavation space with a length of 2m and a radius of 0.3m greater than the radius of the upper step layer;

[0012] Step 2: spray concrete on the inner wall of the expanded excavation space, then lay a steel mesh along the inner wall of the expanded excavation space, fix the steel mesh with locking anchor rods, and finally construct two arch frames, and set a guide pipe between the arch frame and the surrounding rock layer, so as to complete the initial support in the expanded excavation space;

[0013] Step 3: Drill a hole into the surrounding rock layer through the guide pipe, install the flower pipe, steel cage and grouting nozzle, and then inject grout into the long hole through the grouting nozzle. One end of the flower pipe should be at least 2m beyond the hole, thus completing the pipe shed construction;

[0014] Step 4: Carry out circular construction of left and right pilot tunnels along the pipe shed area to the tunnel opening. The left and right pilot tunnels are staggered by 15m. If the distance is less than 15m, the pilot tunnel is constructed to the tunnel opening first. Each construction includes initial support, temporary horizontal support, temporary longitudinal support and temporary support.

[0015] Step 5: After the left and right pilot tunnels are constructed to the openings, the opening protection and arch construction are carried out;

[0016] Step 6: Construct guide pits on both sides of the lower step layer along the tunnel body toward the entrance, and construct left and right guide grooves in a cycle. The maximum depth of each construction is 3m, and the construction includes initial support;

[0017] Step 7: Remove temporary transverse supports, temporary longitudinal supports and temporary supports, and carry out invert construction. The maximum depth of each construction is 3m, until it is connected with the initial invert inside the tunnel body, thus completing the tunnel exit operation.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention divides the core soil layer with a large section in the tunnel body into an upper step layer and a lower step layer by means of temporary transverse supports, and the temporary support further divides the upper step layer into a left guide tunnel and a right guide tunnel. After the personnel cyclically construct the left guide tunnel and the right guide tunnel to the tunnel entrance, they carry out tunnel entrance protection and sleeve arch construction, and finally carry out the invert construction of the lower step layer until the constructed invert is connected with the original invert inside the tunnel body, that is, the tunnel exit operation is completed, thereby improving the standardization of opening a large-section tunnel entrance on a steep rock wall, thereby reducing the risk of tunnel collapse and ensuring the life safety of personnel.

[0020] 2. The present invention first carries out pipe shed and initial support construction, and then carries out left and right guide tunnels in a cyclic construction along the pipe shed, wherein each guide tunnel construction includes initial support, temporary transverse support, temporary longitudinal support and temporary support construction, and then the guide pits on both sides of the lower step layer are constructed, and finally the lower step layer invert arch construction is carried out, wherein the guide pit construction includes initial support, so that the core soil layer of the large section is divided into a plurality of small sections for excavation, and at the same time, the excavated small section area is initially supported and then the subsequent excavation operation is carried out, thereby reducing the possibility of tunnel collapse and improving the operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a cross-sectional view of the tunnel body of the present invention;

[0022] Figure 2 It is a longitudinal section view of the tunnel body of the present invention.

[0023] In the figure: 1. temporary support; 2. temporary longitudinal support; 3. temporary transverse support; 4. locking anchor rod; 5. pipe shed; 501. sleeve arch; 6. tunnel body; 7. invert; 701. primary support of invert; 702. secondary lining of invert; 703. filling of invert; 8. initial support. DETAILED DESCRIPTION

[0024] 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.

[0025] In order to solve the problem that the exit of large-section tunnels has a high risk of collapse and is difficult to carry out tunnel exit operations safely, please refer to Figure 1-2 , this embodiment provides the following technical solutions:

[0026] A construction structure for a large-section tunnel exit comprises a tunnel body 6 and a temporary transverse support 3, wherein the temporary transverse support 3 is located inside a large-section core soil layer in the tunnel body 6, and the temporary transverse support 3 divides the large-section core soil layer into an upper step layer and a lower step layer, a temporary support 1 is arranged above the temporary transverse support 3, a temporary longitudinal support 2 is arranged at the upper end of the temporary support 1, an initial support 8 is arranged on the inner wall of the tunnel body 6, the outside of the tunnel body 6 is a surrounding rock layer, a pipe shed 5 is arranged between the initial support 8 and the surrounding rock layer, an invert 7 is arranged on the bottom surface inside the tunnel body 6, and the initial support 8 is fixed to the inner wall of the tunnel body 6 by a locking anchor rod 4.

[0027] The temporary support 1 is an arc-shaped structure. The temporary support 1 is completely located on one side of the center line of the tunnel. The temporary support 1 divides the upper step layer into a left guide tunnel and a right guide tunnel. The temporary longitudinal support 2 is fixed inside the core soil layer of the large section. A slope is arranged at one end of the lower step layer close to the inverted arch 7. One end of the upper step layer and the lower step layer are connected by the slope. The inverted arch 7 includes an initial inverted arch support 701, an inverted arch secondary lining 702 and an inverted arch filling 703. The inverted arch secondary lining 702 is located between the initial inverted arch support 701 and the inverted arch filling 703. The initial inverted arch support 701 is connected to the bottom surface inside the tunnel body 6. A guide pipe is arranged at one end of the pipe shed 5. A sleeve arch 501 is arranged at the other end of the pipe shed 5 and is located between the initial support 8 and the surrounding rock layer. The sleeve arch 501 is located at the exit end of the tunnel body 6. The pipe shed 5 extends to the inside of the sleeve arch 501 through the guide pipe.

[0028] Specifically, the large-section core soil layer to be excavated is divided into multiple small-section core soil layers such as the left pilot tunnel, the right pilot tunnel and the lower step layer through temporary transverse supports 3 and temporary supports 1. Each small-section core soil layer is constructed cyclically, and the excavated small-section area is initially supported 8 before subsequent excavation operations, thereby reducing the possibility of tunnel collapse. Compared with the method of building access roads and platforms to enter the tunnel forward, it not only ensures the quality of tunnel construction and the occupational health and safety of operators, but also improves the operating efficiency, improves the standardization of opening large-section tunnel entrances on steep rock walls, and further ensures the safety of personnel.

[0029] A construction method for a large-section tunnel exit is implemented based on a construction structure for a large-section tunnel exit, and is characterized by comprising the following steps:

[0030] Step 1: Expand the upper step layer at a distance of two arch frames from the design position of pipe shed 5 to form an expanded excavation space with a length of 2m and a radius of 0.3m greater than the radius of the upper step layer;

[0031] Step 2: spray concrete on the inner wall of the expanded excavation space, then lay a steel mesh along the inner wall of the expanded excavation space, fix the steel mesh with a locking anchor rod 4, and finally construct two arch frames. At the same time, set a guide pipe between the arch frame and the surrounding rock layer, and one end of the guide pipe is upward at an angle of 3°-5°, thereby completing the initial support 8 in the expanded excavation space;

[0032] Step 3: Drill a long hole into the surrounding rock layer through the guide pipe, install the flower pipe, steel cage and grouting nozzle, and then inject grout into the long hole through the grouting nozzle. No hole should be drilled within 2.5m of the end of the flower pipe. One end of the flower pipe should exceed the light and dark boundary of the hole by at least 2m, and the end of the pipe should be blocked, so as to complete the construction of pipe shed 5;

[0033] Step 4: Carry out circular construction of the left pilot tunnel and the right pilot tunnel along the pipe shed 5 area to the hole position. The left pilot tunnel and the right pilot tunnel are staggered by 15m. If it is less than 15m, the first pilot tunnel is constructed to the hole position first. Each construction includes excavation of the core soil layer of the left pilot tunnel or the right pilot tunnel, initial support 8, temporary horizontal support 3, temporary longitudinal support 2 and temporary support 1. When the left pilot tunnel or the right pilot tunnel is excavated for the last time, a small hole slow expansion method should be adopted;

[0034] Step 5: After the left and right pilot tunnels are constructed to the opening, the opening protection and the cover arch 501 are constructed. The cover arch 501 is combined with the portion of the flower pipe in step 3 that exceeds the light and dark boundary line of the opening by at least 2m;

[0035] Step 6: Construct a pilot pit on both sides of the lower step layer along the tunnel body 6 toward the tunnel entrance, and construct the left and right guide grooves in a cycle. The maximum depth of each construction is 3m. The construction includes core soil layer excavation and initial support 8 in sequence until the initial support footing construction is completed in the section adjacent to the tunnel entrance;

[0036] Step seven, dismantle the temporary transverse support 3, temporary longitudinal support 2 and temporary support 1, and construct the invert 7, with the maximum depth of each construction being 3m, until it is connected with the original invert 7 inside the tunnel body 6, thus completing the tunnel exit operation.

[0037] Working principle: The large-section core soil layer to be excavated is divided into multiple small-section core soil layers such as the left pilot tunnel, the right pilot tunnel and the lower step layer through temporary transverse supports 3 and temporary supports 1. Each small-section core soil layer is constructed cyclically, and the excavated small-section area is initially supported 8 before subsequent excavation operations, thereby reducing the possibility of tunnel collapse, while improving operating efficiency, improving the standardization of opening large-section tunnel entrances on steep rock walls, and ensuring the safety of personnel.

[0038] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0039] 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 construction structure for exiting a large-section tunnel, comprising a tunnel body (6), characterized in that: The invention also comprises a temporary transverse support (3), wherein the temporary transverse support (3) is located inside the core soil layer with a large cross section in the tunnel body (6), and the temporary transverse support (3) divides the core soil layer with a large cross section into an upper step layer and a lower step layer. A temporary support (1) is arranged above the temporary transverse support (3), and a temporary longitudinal support (2) is arranged at the upper end of the temporary support (1). An initial support (8) is arranged on the inner wall of the tunnel body (6), and the outside of the tunnel body (6) is a surrounding rock layer. A pipe shed (5) is arranged between the initial support (8) and the surrounding rock layer. An invert (7) is arranged on the bottom surface of the tunnel body (6), and the initial support (8) is fixed to the inner wall of the tunnel body (6) by means of a locking anchor rod (4).

2. A construction structure for a large-section tunnel exit according to claim 1, characterized in that: The temporary support (1) is an arc-shaped structure. The temporary support (1) is completely located on one side of the tunnel centerline. The temporary support (1) divides the upper step layer into a left guide tunnel and a right guide tunnel. The temporary longitudinal support (2) is fixed inside the core soil layer of the large cross-section.

3. A construction structure for exiting a large-section tunnel according to claim 1, characterized in that: One end of the lower step layer close to the inverted arch (7) is provided with a slope, and one end of the upper step layer and the lower step layer are connected via the slope.

4. A construction structure for exiting a large-section tunnel according to claim 1, characterized in that: The inverted arch (7) comprises an inverted arch primary support (701), an inverted arch secondary lining (702) and an inverted arch filling (703), wherein the inverted arch secondary lining (702) is located between the inverted arch primary support (701) and the inverted arch filling (703), and the inverted arch primary support (701) is connected to the bottom surface inside the tunnel body (6).

5. The construction structure for exiting a large-section tunnel according to claim 1, characterized in that: A guide pipe is provided at one end of the pipe shelf (5), and a sleeve arch (501) is provided at the other end of the pipe shelf (5), which is located between the initial support (8) and the surrounding rock layer. The sleeve arch (501) is located at the exit end of the tunnel body (6), and the pipe shelf (5) extends through the guide pipe to the interior of the sleeve arch (501).

6. A construction method for a large-section tunnel exit, implemented based on a construction structure for a large-section tunnel exit according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Excavate the upper step layer at a position two arch frame distances away from the designed position of the pipe shed (5) to form an excavated space with a length of 2 m and a radius of 0.3 m greater than the radius of the upper step layer; Step 2: spray concrete on the inner wall of the expanded excavation space, then lay a steel mesh along the inner wall of the expanded excavation space, fix the steel mesh with a locking anchor rod (4), and finally construct two arch frames, and at the same time set a guide pipe between the arch frames and the surrounding rock layer, thereby completing the initial support in the expanded excavation space (8); Step 3: Drill a hole into the surrounding rock layer through the guide pipe, install the flower pipe, steel cage and grouting nozzle, and then inject grout into the long hole through the grouting nozzle. One end of the flower pipe is at least 2m beyond the hole opening, thereby completing the construction of the pipe shed (5); Step 4: construct the left pilot tunnel and the right pilot tunnel in a cycle along the pipe shed (5) area toward the hole opening, with the left pilot tunnel and the right pilot tunnel staggered by 15 m. If the distance is less than 15 m, construct the pilot tunnel first to the hole opening. Each construction includes initial support (8), temporary transverse support (3), temporary longitudinal support (2) and temporary support (1); Step 5: After the left pilot tunnel and the right pilot tunnel are constructed to the opening, the opening protection and the arch (501) are constructed; Step 6: construct a guide pit on both sides of the lower step layer along the tunnel body (6) towards the tunnel entrance, and construct the left and right guide grooves in a cycle. The maximum depth of each construction is 3m. The construction includes initial support (8); Step 7: Remove the temporary transverse support (3), temporary longitudinal support (2) and temporary support (1), and carry out the construction of the invert (7), with the maximum depth of each construction being 3m, until it is connected with the initial invert (7) inside the tunnel body (6), thus completing the tunnel exit operation.

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