An in-situ expansion method for existing large-section tunnels without inverted arches

Abstract

The present invention provides a method for in-situ expansion of a large-section tunnel without inverted arch, comprising the following steps: S1. Perform circumferential cutting on the surrounding rock of the original tunnel along the initial support of the original tunnel, perform longitudinal cutting at the crown arch of the original tunnel lining, and simultaneously construct temporary inclined struts at the first position and the second position at the arch shoulders of the original tunnel; S2. Demolish the original tunnel lining and the initial support of the original tunnel at the crown arch part; perform excavation according to the new tunnel contour, and construct the initial support of the new tunnel; S3. Demolish the temporary inclined struts, and demolish the original tunnel lining and the initial support of the original tunnel at the side wall part step by step in zones from top to bottom and from left to right, perform excavation according to the new tunnel contour, and construct the initial support of the new tunnel; S4. Lay the waterproof layer and pour the new tunnel lining in sections. The present invention can provide a reasonable construction method for the in-situ expansion project of a large-section tunnel without inverted arch.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel construction, and in particular relates to a method for in-situ expansion of an existing large-section tunnel without inverted arch. Background Art

[0002] With the development of the national economy, the traditional two-way four-lane and even two-way six-lane highways can no longer meet the growing traffic demand, and the reconstruction and expansion projects of existing highways are developing rapidly. Highway tunnels are the key nodes affecting highway traffic capacity. Limited by the existing road connection and topographic and geological conditions, the reconstruction of existing highway tunnels often adopts the form of in-situ reconstruction and expansion.

[0003] Most of the conventional highway tunnels are in Class II or Class III surrounding rocks with good integrity. Considering economy and safety comprehensively, under the above surrounding rock conditions, there is no need to set a costly inverted arch structure in tunnel design and construction. Therefore, for the in-situ expansion project of a large-section tunnel without inverted arch, if the in-situ expansion construction plan of a tunnel with inverted arch is still copied, there will inevitably be problems such as excessive redundancy of the engineering support structure, insufficient engineering economy, and too long construction period. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for in-situ expansion of an existing large-section tunnel without inverted arch in view of the deficiencies in the prior art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for in-situ expansion of an existing large-section tunnel without inverted arch includes the following steps:

[0007] S1. Circumferentially cut the surrounding rock of the original tunnel along the primary support of the original tunnel, longitudinally cut at the crown of the original tunnel lining, and simultaneously construct temporary inclined struts at the first position and the second position at the arch shoulders of the original tunnel;

[0008] S2. Demolish the original tunnel lining and the primary support of the original tunnel at the crown part; excavate and expand according to the new tunnel contour, and construct the primary support of the new tunnel;

[0009] S3. Demolish the temporary inclined struts, and demolish the original tunnel lining and the primary support of the original tunnel at the side wall part step by step in a partitioned manner from top to bottom and from left to right, excavate and expand according to the new tunnel contour, and construct the primary support of the new tunnel;

[0010] S4. Lay a waterproof layer and cast the new tunnel lining in sections.

[0011] While adopting the above technical solutions, the present invention can also adopt or combine the following technical solutions:

[0012] As a preferred technical solution of the present invention: in step S2, the original tunnel lining is demolished in the following manner: the concrete of the original tunnel lining in the partition area is mechanically chiseled from top to bottom. After chiseling, a trolley is used to cut and demolish materials such as waterproof pipes, geotextiles, and drain pipes in this area and transfer them to a designated area outside the tunnel.

[0013] As a preferred technical solution of the present invention: in step S2, the original initial support of the tunnel is demolished in the following manner: the shotcrete is chiseled in partitions to expose the longitudinal connecting steel bars between the steel arch frames, and the longitudinal connecting steel bars are cut to make the steel arch frames independent; continue to chisel the shotcrete between the steel arch frames to expose all the steel arch frames and the wire mesh. Cut the wire mesh, steel arch frames, and the locking foot bolts at the bottom of the steel arch frames, and demolish the steel arch frames in this area.

[0014] As a preferred technical solution of the present invention: in step S2, the new tunnel contour is excavated in the following manner: for the area with an excavation thickness less than 40 cm, mechanical excavation is used, and for the area with an excavation thickness greater than 40 cm, smooth blasting method is used for construction.

[0015] As a preferred technical solution of the present invention: in step S2, the initial support of the original tunnel and the new tunnel includes one or a combination of more of the following: steel arch frames, wire mesh, shotcrete, and cartridge bolts.

[0016] The present invention provides a method for in-situ expansion of an existing large-section tunnel without inverted arch, which can provide a reasonable construction method for the in-situ expansion project of a large-section tunnel without inverted arch, and has the following advantages or beneficial effects:

[0017] Through reasonable design of the cutting process of the original tunnel lining and the temporary support system for tunnel excavation, this construction method makes full use of the self-stability of the original tunnel support structure, reduces the subsequent excavation and backfilling workload by means of the excavation sequence of the top arch, can significantly reduce the project duration, and fully improves the safety and economy of the in-situ expansion project of a large-section tunnel without inverted arch. Description of the Drawings

[0018] Figure 1 Tunnel cross-section diagram for circumferential cutting, longitudinal cutting of the original tunnel, and setting of temporary inclined supports.

[0019] Figure 2 Tunnel cross-section diagram for the demolition of the original tunnel lining and the original initial support of the upper bench (zone I).

[0020] Figure 3 Tunnel cross-section diagram for the demolition of the original tunnel lining and the original initial support of the left side of the middle bench (zone II).

[0021] Figure 4 Tunnel cross-section diagram for the demolition of the original tunnel lining and the original initial support of the right side of the middle bench (zone III).

[0022] Figure 5 It is a sectional view of the tunnel showing the removal of the original tunnel lining and the original primary support on the left side of the lower bench (Zone Ⅳ).

[0023] Figure 6 It is a sectional view of the tunnel showing the removal of the original tunnel lining and the original primary support on the right side of the lower bench (Zone Ⅴ).

[0024] Figure 7 It is a sectional view of the tunnel showing the segmented casting of the new tunnel lining.

[0025] Figure 8 It is a sectional structure view of the primary support of the new tunnel. Detailed implementation manners

[0026] The present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

[0027] Taking the in-situ expansion of a single-hole three-lane highway tunnel into a single-hole four-lane highway tunnel project as an example, the tunnel body section is basically grade Ⅲ surrounding rock, so an inverted-arch-free design is adopted both before and after the excavation. The construction method for the in-situ expansion of a large-section inverted-arch-free tunnel described in the present invention is used, and it includes the following steps:

[0028] Refer to Figure 1 As shown, the original tunnel lining is cut circumferentially and longitudinally. The circumferential cutting spacing is 1 m, and after the circumferential cutting is completed, longitudinal cutting is carried out at the positions shown in Figure 1 As shown. N1 / N2 temporary inclined braces are constructed. Connecting steel plates are arranged at both ends of the N1 / N2 temporary inclined braces, which are closely attached to and reliably connected to the original tunnel floor and the secondary lining respectively. The longitudinal layout spacing of the N1 / N2 temporary inclined braces is 1 m. (The longitudinal direction is the extension direction of the original tunnel, and the circumferential direction is the direction perpendicular to the extension direction of the original tunnel).

[0029] Refer to Figure 2 As shown, the original tunnel lining and the original primary support of the upper bench (Zone Ⅰ) are removed; the upper bench is excavated according to the contour of the new tunnel; after the excavation is completed, the primary support of the new tunnel in this area is constructed, including installing steel arch frames, hanging steel mesh sheets, shotcreting, and installing cartridge bolts; and locking bolts are driven at the bottom of the steel arch frames to enhance the stability of the steel arch frames, as shown in Figure 8 As shown.

[0030] Refer to Figure 3 As shown, the N1 temporary inclined brace is removed, and the original tunnel lining and the original primary support of the left side of the middle bench (Zone Ⅱ) are removed; the area is excavated by mechanical chiseling according to the contour of the new tunnel; after the excavation is completed, the primary support of the new tunnel in this area is constructed;

[0031] Refer to Figure 4As shown in the figure, remove the N2 temporary inclined strut and the original tunnel lining and the original primary support on the right side of the middle bench (Area Ⅲ), and use smooth blasting to expand the excavation according to the new tunnel contour; after the expansion excavation is completed, construct the primary support of the new tunnel in this area;

[0032] Refer to Figure 5 As shown in the figure, remove the original tunnel lining and the original primary support on the left side of the lower bench (Area Ⅳ), and use mechanical chiseling to expand the excavation according to the new tunnel contour; after the expansion excavation is completed, construct the primary support of the new tunnel in this area;

[0033] Refer to Figure 6 As shown in the figure, remove the original tunnel lining and the original primary support on the right side of the lower bench (Area Ⅴ), and use smooth blasting to expand the excavation according to the new tunnel contour; after the expansion excavation is completed, construct the primary support of the new tunnel in this area;

[0034] Refer to Figure 7 As shown in the figure, lay the waterproof layer and use a formwork trolley to pour the new tunnel lining in sections.

[0035] The above specific implementation manners are used to explain and illustrate the present invention, which are only the preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and the protection scope of the claims of the present invention all fall within the protection scope of the present invention.

Claims

1. An in-situ expansion method for a large cross-section tunnel without inverted arch, characterized in that: The in-situ expansion method includes the following steps: S1. Cut the original tunnel lining both circumferentially and longitudinally. After the circumferential cutting is completed, conduct the longitudinal cutting. Install N1 temporary inclined struts and N2 temporary inclined struts. Connecting steel plates are provided at both ends of the N1 temporary inclined struts and N2 temporary inclined struts, which are closely attached to and reliably connected to the original tunnel floor and the secondary lining respectively; S2. Demolish the original tunnel lining and the original tunnel initial support of the upper bench; Excavate the upper bench according to the new tunnel profile; after the excavation is completed, construct the initial support of the new tunnel in this area, and drive locking bolts at the bottom of the steel arch to enhance the stability of the steel arch; S3. Demolish the N1 temporary inclined strut, and demolish the original tunnel lining and the original tunnel initial support on the left side of the middle bench; Excavate this area according to the new tunnel profile by mechanical chiseling; after the excavation is completed, construct the initial support of the new tunnel in this area; Demolish the N2 temporary inclined strut and the original tunnel lining and the original tunnel initial support on the right side of the middle bench, and excavate by smooth blasting according to the new tunnel profile; after the excavation is completed, construct the initial support of the new tunnel in this area; Demolish the original tunnel lining and the original tunnel initial support on the left side of the lower bench, and excavate by mechanical chiseling according to the new tunnel profile; after the excavation is completed, construct the initial support of the new tunnel in this area; Demolish the original tunnel lining and the original tunnel initial support on the right side of the lower bench, and excavate by smooth blasting according to the new tunnel profile; after the excavation is completed, construct the initial support of the new tunnel in this area; S4. Lay the waterproof layer and use a formwork trolley to pour the new tunnel lining in sections.

2. The in-situ expansion method for existing large-section tunnels without inverted arches according to claim 1, characterized in that: In step S2, the original tunnel initial support is demolished in the following way: sectionally chisel the shotcrete to expose the longitudinal connecting steel bars between the steel arches, cut the longitudinal connecting steel bars to make the steel arches independent; continue to chisel the shotcrete between the steel arches to expose all the steel arches and the wire mesh, cut the wire mesh, the steel arches and the locking bolts at the bottom of the steel arches, and demolish the steel arches in this area.

3. The in-situ expansion method for an existing large-section tunnel without inverted arch according to claim 1, characterized in that: In step S2, the new tunnel profile is excavated in the following way: for the area with an excavation thickness less than 40 cm, mechanical excavation is adopted, and for the area with an excavation thickness greater than 40 cm, smooth blasting method is used for construction.

4. The in-situ expansion method for an existing large-section tunnel without inverted arch according to claim 1, characterized in that: In step S2, the initial support of the original tunnel and the new tunnel includes one or a combination of steel arches, wire mesh, shotcrete, and cartridge bolts.

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