Large arch foot bench method based on rigid support system

Abstract

The invention provides a large arch foot bench method based on a rigid support system, and belongs to the technical field of tunnel engineering. The large arch foot bench method based on the rigid support system comprises the following steps that S1, an advance support is constructed on the outer side of a tunnel primary support; s2, an upper step is excavated; s3, constructing a tunnel primary support with a large arch springing in an upper step range; s4, lagging behind the upper step for a certain distance, and excavating a lower step; s5, a lower step primary support in the lower step range is constructed; and S6, follow-up procedures are conducted according to a normal step construction method. The method combines the advantages of a pipe-roofing underground excavation technology, a shallow-buried underground excavation method and a large-arch-foot bench method, construction can be organized according to the conventional bench method under a rigid support system, a large-arch-foot tunnel primary support is arranged on an upper step, the influence on the upper step during excavation of a lower step can be obviously reduced, the implementation difficulty of the construction method is greatly reduced, the operability is high, and the construction efficiency is high. And the construction safety and the construction efficiency are guaranteed, and remarkable economic and social benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and relates to a tunnel construction method, in particular to a large arch foot step method based on a rigid support system. Background Art

[0002] The East Ring Line of Chongqing Railway Hub is located in the vicinity of the city, with very complex environmental conditions and many important structures such as roads and tracks underpassed. In order to solve the problems of construction safety and settlement control, it adopts a shallow tunnel pipe curtain dark excavation full-section construction method under complex environmental conditions disclosed in a Chinese patent (patent number ZL201910647079.X). It combines the pipe curtain dark excavation technology with the shallow tunnel construction safety and settlement control technology, and takes the following measures: (1) Try to shorten the distance range of each invert bottoming, the spatial distance range between the bottoming process and the tunnel excavation face, and the spatial distance range between the secondary lining and the tunnel excavation face; (2) Simultaneously construct the secondary lining of the invert and the arch wall, and close the secondary lining into a ring in time; (3) When necessary, under the protection of the super-strong pipe curtain, the tunnel excavation face is reinforced to achieve the stability of the tunnel excavation face under full-section excavation.

[0003] Due to the full-section excavation and the shortening of the distance between each process, the distance between the second lining and the face is effectively shortened. The ring and longitudinal force system composed of the second lining, primary support, soil in front of the face and pipe curtain is better than the "shallow buried dark excavation method" in terms of safety guarantee and surface settlement control. However, it still has the following problems: 1. The operability is not strong. The construction method strictly controls the step distance of each process. The technical requirements for on-site implementation are high and the implementation is difficult; 2. The construction method requires the second lining to follow closely, the face is short from the second lining, and there are multiple operations in a small range between the face and the second lining. The support, waterproof board, second lining construction and other processes cannot be carried out in parallel, resulting in large construction interference and low construction efficiency; 3. The construction method requires the second lining to follow closely, and the second lining operation space is 3 to 10 meters away from the face. The face adopts full-section construction, and there is a risk of instability on the face, which has certain safety hazards. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned problems in the existing technology and to propose a large arch foot step method based on a rigid support system that can meet the requirements of safe and rapid tunnel construction under complex environmental conditions.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The large arch foot step method based on the rigid support system includes the following steps:

[0007] S1. Apply advanced support outside the initial support of the tunnel;

[0008] S2, excavation and stepping up;

[0009] S3. Initial support of the tunnel with large arch foot in the upper step range;

[0010] S4, lag behind the upper step for a certain distance and excavate the lower step;

[0011] S5. Carry out the initial support of the lower step within the range of the lower step;

[0012] S6. Carry out subsequent procedures according to normal step construction methods.

[0013] In the above-mentioned large arch foot step method based on the rigid support system, the large arch foot of the initial support of the tunnel should extend outward beyond the initial support of the lower step by at least 1m.

[0014] In the large arch foot step method based on the rigid support system, the large arch foot of the initial support of the tunnel is reinforced with a locking anchor pipe.

[0015] In the above-mentioned large arch foot step method based on the rigid support system, the tunnel initial support includes a first layer of rigid initial support located on the outer layer and a second layer of rigid initial support located on the inner layer. The first layer of rigid initial support is formed by a steel frame and early-strength shotcrete, and the second layer of rigid initial support is formed by a grid steel frame and C30 steel fiber shotcrete.

[0016] In the above-mentioned large arch foot step method based on the rigid support system, the advanced support is a pipe curtain.

[0017] In the large arch foot step method based on the rigid support system, a guide wall is constructed in the opening or the pipe curtain working room, and the pipe curtain is constructed through the guide wall.

[0018] Compared with the existing technology, the large arch foot step method based on the rigid support system has the following advantages: it provides practical safety guarantees through the ring longitudinal rigid support system and the large arch foot technology, has no special requirements for the tunnel construction step distance, and does not need to compress the spatial distance between each process, which greatly reduces the difficulty of implementing the method and has strong operability; the rigid support system can effectively ensure the safety of construction operations and has strong safety assurance capabilities; each process can be operated in a cyclic and parallel manner, which improves construction efficiency and has strong technical and economic advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a cross-sectional schematic diagram of the large arch foot step method.

[0020] Figure 2 It is a longitudinal section diagram of the large arch foot step method.

[0021] In the figure, 1. pipe curtain; 2. first layer of rigid initial support; 3. second layer of rigid initial support; 4. locking foot anchor pipe; 5. guide wall; 6. subsequent process; 7. pipe curtain studio; 8. upper step excavation face; 9. lower step excavation face. DETAILED DESCRIPTION

[0022] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0023] The large arch foot step method based on the rigid support system includes the following steps:

[0024] S1, from the tunnel entrance or the pipe curtain studio 7, the pipe curtain 1 is applied through the guide wall 5 on the outside of the initial support of the tunnel to form an advanced support;

[0025] S2, excavation and stepping up;

[0026] S3. Construct the outer steel frame and early-strength shotcrete in the upper step range to form the first layer of rigid initial support 2; construct the inner grid steel frame and C30 steel fiber shotcrete in the upper step range to form the second layer of rigid initial support 3;

[0027] S4. According to the requirements of the ordinary step method, such as Figure 2 As shown, the lower step is excavated after the upper step for a certain distance; that is, the excavation face 9 of the lower step lags behind the excavation face 8 of the upper step for a certain distance;

[0028] S5. Carry out the initial support of the lower step within the range of the lower step;

[0029] S6. Carry out subsequent step 6 according to the normal step method.

[0030] like Figure 1 As shown in the figure, a large arch foot is formed at the bottom of the initial support of the tunnel to ensure that the foot of the upper step wall is not exposed when the lower step is excavated. To ensure the stability of the upper step steel frame foundation, Figure 1 As shown, the large arch foot should extend at least 1m beyond the initial support of the lower step. At the same time, a small grouting tube is used at the large arch foot to strengthen the locking foot and grouting the foundation (i.e., the locking foot anchor pipe 4).

[0031] The first layer of rigid initial support 2 near the rock layer uses steel frame and early strength spraying concrete to quickly support the excavated rock mass and ensure construction safety. The second layer of rigid initial support 3 uses grid steel frame and C30 steel fiber spraying concrete to achieve the support effect of reinforced concrete structure.

[0032] like Figure 1 and Figure 2As shown in the figure, the advanced pipe-roof longitudinal support system is used to bear the surrounding rock pressure in advance, and the settlement of the arch and the ground surface caused by the excavation relaxation of the upper step excavation face 8 is minimized. The double-layer steel frame primary support and the longitudinal pipe-roof form a ring and longitudinal rigid support force system, which can effectively ensure the safety of tunnel construction and settlement control requirements under the complex environment conditions of shallow tunnel burial.

[0033] Due to the existence of rigid ring and longitudinal support system, the large arch foot step method is adopted, and construction safety can be effectively guaranteed. The method does not require special requirements for construction step distance.

[0034] For shallow tunnels under complex environmental conditions, due to higher requirements for construction safety and surface settlement control, this embodiment combines the advantages of pipe curtain dark excavation technology with the shallow dark excavation method and the large arch foot step method. Under the rigid support system, the construction can be organized according to the conventional step method. The large arch foot tunnel initial support is set on the upper step, which can also significantly reduce the impact of the lower step excavation on the upper step. This method greatly reduces the difficulty of implementation of the method, has strong operability, and ensures construction safety and efficiency. It greatly reduces the difficulty of coordination, engineering risks and investment. This method can be effectively applied to complex environmental conditions similar to the East Ring Line, and has significant economic and social benefits.

[0035] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A large arch foot step method based on a rigid support system, characterized in that: The following steps are involved: S1. Apply advanced support outside the initial support of the tunnel; S2, excavation and stepping up; S3. Initial support of the tunnel with large arch foot in the upper step range; S4, lag behind the upper step for a certain distance and excavate the lower step; S5. Carry out the initial support of the lower step within the range of the lower step; S6. Carry out the subsequent process (6) according to the normal step construction method.

2. The large arch foot step method based on the rigid support system according to claim 1 is characterized in that: The large arch foot of the initial support of the tunnel should extend outwards beyond the initial support of the lower step by at least 1m.

3. The large arch foot step method based on the rigid support system according to claim 1 or 2 is characterized in that: The large arch foot of the initial support of the tunnel is reinforced by a locking foot anchor pipe (4).

4. The large arch foot step method based on the rigid support system according to claim 1 is characterized in that: The tunnel initial support comprises a first layer of rigid initial support (2) located at the outer layer and a second layer of rigid initial support (3) located at the inner layer, wherein the first layer of rigid initial support (2) is formed by a steel frame and early-strength shotcrete, and the second layer of rigid initial support (3) is formed by a grid steel frame and C30 steel fiber shotcrete.

5. The large arch foot step method based on the rigid support system according to claim 1 is characterized in that: The advanced support is a pipe curtain (1).

6. The large arch foot step method based on the rigid support system according to claim 5 is characterized in that: A guide wall (5) is constructed in the opening or the tube curtain working room (7), and the tube curtain (1) is constructed through the guide wall (5).

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