A method for in-situ expansion of an existing extra-large cross-section highway tunnel

Abstract

The invention provides an in-situ expansion method for an existing extra-large cross-section highway tunnel, comprising the following steps: S1, firstly cutting the existing tunnel lining, and applying advance support according to the new tunnel outline; S2, arranging a row of N1 temporary steel pipe supports at the top arch of the existing tunnel lining; arranging a row of N2 temporary vertical supports and a row of N3 temporary vertical supports for the lower half section of the tunnel; and backfilling the tunnel to the position of the tunnel waist with sandbags; S3, removing the existing tunnel lining of the upper half section of the tunnel; S4, removing the existing initial tunnel support of the left guide tunnel and the right guide tunnel of the upper step in sections and steps, and expanding the tunnel according to the new tunnel outline; S5, clearing the backfill material of the lower step, removing the existing initial tunnel support and tunnel lining of the left guide tunnel and the right guide tunnel of the lower step in sections and steps, and expanding the tunnel according to the new tunnel outline; S6, removing the invert and backfill structure of the existing tunnel, and expanding the arch bottom according to the new tunnel outline; and casting the new tunnel lining in sections.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and in particular relates to an in-situ expansion method for an existing extra-large cross-section highway tunnel. Background Art

[0002] In some developed regions and megacities, two-way four-lane or even two-way six-lane highway tunnels can no longer meet the growing demand for traffic volume, and there are more and more projects to convert existing highway tunnels into two-way eight-lane highway tunnels.

[0003] At present, the research on in-situ expansion of tunnels at home and abroad is basically limited to the in-situ expansion of existing small-section tunnels. Typical foreign projects include the Whitehaven Tunnel in the United States and the Daizo Tunnel in Japan, and typical domestic projects include the Damaoshan Tunnel, Yuzhou Tunnel, Mawei Tunnel, etc. At present, the construction method of in-situ expansion of small-section tunnels such as existing two-lane tunnels has been relatively mature, but for the challenging problem of in-situ expansion of extra-large-section highway tunnels such as existing three-lane highway tunnels, there are no similar successful cases at home and abroad, and there is very little experience for reference.

[0004] The surrounding rock load distribution and support mechanical characteristics of extra-large cross-section highway tunnels are complex, the structural stability is poor, and they are subjected to multiple disturbances during in-situ expansion construction. If the in-situ expansion construction plan for small-section tunnels with strong self-stabilization ability continues to be used, problems such as surrounding rock instability and cracking and damage of the tunnel lining structure are very likely to occur. Summary of the invention

[0005] The purpose of the present invention is to provide a method for in-situ expansion of an existing super-large cross-section highway tunnel in view of the construction difficulties of in-situ expansion of an existing super-large cross-section highway tunnel.

[0006] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] An in-situ expansion method for an existing extra-large cross-section highway tunnel, characterized in that the in-situ expansion method comprises the following steps:

[0008] S1. First, cut the existing tunnel lining and apply advance support according to the new tunnel contour;

[0009] S2. Set a row of N1 temporary steel pipe supports at the top arch of the existing tunnel lining, with the spacing between two adjacent N1 temporary steel pipe supports being 5 m. Install longitudinal double-jointed I-beams on the top of the N1 temporary steel pipe supports, which are arranged along the longitudinal direction of the tunnel and firmly support the existing tunnel lining; set a row of N2 temporary vertical supports and a row of N3 temporary vertical supports on the lower half of the tunnel, with the spacing between two adjacent N2 temporary vertical supports and N3 temporary vertical supports being 0.8 m; use sandbags to densely backfill to the tunnel arch waist position;

[0010] S3, remove the existing tunnel lining in the upper section of the tunnel, removing 0.8 m in each cycle; adjust the movable head on the upper part of the N1 temporary steel pipe support to make the longitudinal double-jointed I-beam top to the existing tunnel initial support concrete surface;

[0011] S4. Remove the existing initial tunnel support of the left and right guide tunnels of the upper step in stages, expand the tunnel according to the outline of the new tunnel, and construct the initial support and temporary support of the new tunnel;

[0012] S5. Remove the backfill material of the lower step, dismantle the existing initial tunnel support and tunnel lining of the left and right guide tunnels of the lower step in sections and steps, and expand the excavation according to the outline of the new tunnel, and construct the initial support of the new tunnel;

[0013] S6. Remove the existing tunnel invert and backfill structure, and expand the arch bottom according to the new tunnel contour; remove the N2 temporary vertical support and cast the new tunnel lining in sections.

[0014] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0015] As a preferred technical solution of the present invention: in step S1, the existing tunnel lining is cut in the following manner: first, the existing tunnel lining is cut circumferentially to divide the tunnel lining into blocks; then longitudinal cutting is performed along the tunnel vault to reduce the transmission of construction vibration when different guide tunnel linings are removed; at the same time, when cutting the existing tunnel lining, 5 cm should be reserved without cutting through to ensure the construction safety of the sections where the tunnel lining has not been removed.

[0016] As a preferred technical solution of the present invention: in step S1, the advance support includes one or more of the advance anchor support, the advance small pipe support or the advance pipe-roof support.

[0017] As a preferred technical solution of the present invention: in step S4, when excavating according to the new tunnel contour, when the excavated rock mass is less than 30 cm thick, mechanical excavation should be adopted.

[0018] As a preferred technical solution of the present invention: in step S4 and step S5: the existing initial tunnel support of the left pilot tunnel and the right pilot tunnel of the upper step is dismantled in sections and steps, and the existing initial tunnel support and tunnel lining of the left pilot tunnel and the right pilot tunnel of the lower step are dismantled in sections and steps in sections as follows: the advance of each cycle of the expansion of each pilot tunnel according to the new tunnel outline is 0.8 m;

[0019] The distance between the left and right guide tunnels of the upper step and the left and right guide tunnels of the lower step should be 3-5 m.

[0020] The distance between the right pilot tunnel of the upper step and the left pilot tunnel of the lower step should not be less than 10 m;

[0021] After each pilot tunnel has advanced 20 m in a cycle, the construction of the heading face should be stopped, and construction can only be continued after the invert construction reaches the same section.

[0022] As a preferred technical solution of the present invention: in step S4 and step S5, when initial support of the new tunnel is performed, longitudinal connecting bars and locking anchor rods are applied to the I-beams used for initial support of the new tunnel.

[0023] As a preferred technical solution of the present invention: in step S6, the existing tunnel invert and backfill structure are dismantled in the following manner: when dismantling the invert, channel steel and temporary staggered vertical bracing are used to ensure that the N2 temporary vertical bracing is not empty;

[0024] The temporary offset vertical brace is located below the N2 temporary vertical brace and the channel steel is used to connect the temporary offset vertical brace with the N2 temporary vertical brace.

[0025] The present invention provides an in-situ expansion method for an existing extra-large cross-section highway tunnel, aiming to reasonably solve the problem that the existing extra-large cross-section highway tunnel has poor structural stability and there is a great construction risk when using the traditional small-section tunnel expansion method, and has the following advantages or beneficial effects:

[0026] (1) Carry out circumferential and longitudinal cutting of the existing lining, and reasonably set up the existing lining cutting and segmentation method and temporary support system to prevent the existing lining from falling down due to its own weight during removal, and effectively eliminate the risk of instability during the removal of the existing lining with a large span;

[0027] (2) For the in-situ expansion of existing ultra-large-section highway tunnels under complex construction conditions, a reasonable demolition and excavation process is proposed in different areas and steps to effectively control the deformation of the surrounding rock and reduce the construction risk. This method has significant engineering significance and social and economic benefits, and has broad application prospects in the expansion construction of existing ultra-large-section tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of tunnel section for tunnel advance support construction for the new tunnel outline.

[0029] Figure 2 Schematic diagram of the tunnel section after the existing tunnel lining is removed for the upper step (Zone I and Zone II).

[0030] Figure 3 This is a schematic diagram of the tunnel section of the left pilot tunnel (Zone I) on the upper step after the initial support of the existing tunnel is removed and the surrounding rock is excavated.

[0031] Figure 4 This is a schematic diagram of the tunnel section of the upper step right pilot tunnel (Zone II), where the initial support of the existing tunnel is removed and the surrounding rock is expanded.

[0032] Figure 5 This is a schematic diagram of the tunnel section of the left pilot tunnel (Zone III) of the lower step, where the existing tunnel lining and initial support are removed and the surrounding rock is excavated.

[0033] Figure 6 This is a schematic diagram of the tunnel section of the right pilot tunnel (Zone IV) of the lower step, where the existing tunnel lining and initial support are removed and the surrounding rock is excavated.

[0034] Figure 7 Schematic diagram of the tunnel cross section after the demolition of the existing tunnel invert and backfill structure (V zone) and the excavation of the surrounding rock.

[0035] Figure 8 Schematic diagram of the tunnel section after the temporary vertical supports of N2 / N4 were removed.

[0036] Fig. 9 Schematic diagram of the setting of temporary staggered vertical supports.

[0037] Fig.10 This is the structural longitudinal section of the N1 temporary steel pipe support. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] Taking the expansion of a six-lane highway tunnel from a two-way highway to an eight-lane highway tunnel as an example, the cross section of the three-lane highway tunnel before expansion was 170 m. 3 , for a super-large cross-section tunnel, the in-situ expansion method of an existing super-large cross-section tunnel provided by the present invention comprises the following steps:

[0040] Reference Figure 1 As shown in the figure, advance support of the tunnel is constructed according to the outline of the new tunnel; the existing tunnel lining is cut circumferentially and longitudinally, and the circumferential cutting depth reserves 5 cm connection thickness without cutting through; N1 temporary steel pipe supports are constructed, and there is an independent structure between every two N1 temporary steel pipe supports, with a spacing of 5 m; double-jointed I-beams are constructed on the top of the N1 temporary steel pipe supports, and the double-jointed I-beams are arranged along the longitudinal direction of the tunnel and firmly support the existing tunnel lining; N2 / N3 temporary vertical supports are constructed in the lower half section, and the longitudinal spacing is the same as the spacing of the I-beams for the initial support of the new tunnel, with a spacing of 0.8 m; sandbags are used to backfill to the tunnel arch waist position, and the backfill is required to be dense.

[0041] Reference Figure 2As shown in the figure, the existing tunnel lining of the upper step (zone I and zone II) is removed, and 0.8 m is removed in each cycle; the longitudinal I-beam is pushed to the initial support concrete surface of the existing tunnel by adjusting the upper flexible head of the N1 temporary steel pipe support; the N5 temporary vertical support is constructed directly above the N3 temporary vertical support and pushed to the initial support concrete surface of the existing tunnel above; the N5 temporary vertical support is connected to the N3 temporary vertical support with connecting steel plates and bolts, and is welded into a whole through longitudinal connecting ribs.

[0042] Reference Figure 3 As shown in the figure, the initial support of the existing tunnel in the left pilot tunnel (zone I) of the upper step is removed, and the new tunnel contour is followed by excavation and removal; each cycle of excavation is 0.8 m; after the excavation is completed, the initial support of this zone is promptly implemented according to the new tunnel contour, and steel arch frames, steel meshes, anchor rods, and concrete are installed; temporary support is implemented in zone I, and the N4 temporary vertical support is installed above the N2 temporary vertical support. The two are connected by connecting steel plates and bolts, and are welded into a whole through longitudinal connecting bars.

[0043] Reference Figure 4 As shown, the N5 temporary vertical support is removed; when the construction reaches the next cycle N1 temporary steel pipe support section, the previous N1 temporary steel pipe support and the external double-jointed I-beam are removed; the existing tunnel initial support of the right guide tunnel (Zone II) on the upper step is removed, and the new tunnel contour is excavated and removed, with an excavation of 0.8 m per cycle; after the excavation is completed, the initial support of this area is promptly constructed according to the new tunnel contour and connected to the I-beam of the initial support of Zone I. The distance between the removal and excavation faces of Zones I and II is kept at 3~5 m.

[0044] Reference Figure 5 As shown, first remove the backfill material of the lower section and remove the temporary vertical support of N3 / N5; then remove the existing tunnel lining and initial support of the left pilot tunnel (Zone III) of the lower step, and excavate according to the outline of the new tunnel; each cycle of excavation is 0.8 m; after the excavation is completed, the initial support of this area is promptly applied, and the I-beam of the initial support is dropped to the bottom. The distance between the removal and excavation faces of Zone II and Zone III should not be less than 10 m.

[0045] Reference Figure 6 As shown, the existing tunnel lining and initial support of the right pilot tunnel (zone IV) of the lower step are removed, and the new tunnel contour is followed by chiseling and excavation; each cycle of excavation is 0.8 m; after the excavation is completed, the initial support of this area is promptly applied, and the I-beams of the initial support are brought to the bottom; the distance between the demolition and excavation faces of zones III and IV should not be less than 10 m.

[0046] Reference Figure 7 As shown in the figure, the existing tunnel invert and backfill structure (V zone) are demolished, and the new tunnel is excavated according to the new tunnel contour; each cycle of demolition and excavation is 1.5 m; refer to Fig. 9As shown in the figure, channel steel and N6 temporary staggered vertical bracing should be installed during the expansion to ensure that the N2 / N4 temporary vertical bracing is not empty; after the excavation of this part of the invert is completed, a plain concrete cushion layer is poured at the bottom of the arch for leveling.

[0047] Reference Figure 8 As shown, the temporary vertical supports of N2 / N4 are removed, the invert is cast in sections and the invert is backfilled; waterproof boards are laid, and the tunnel arch wall lining concrete is cast using a formwork trolley.

[0048] In order to improve the safety of the above-mentioned excavation method during implementation, in the above steps, it is required that the construction should be stopped after the excavation cycle advance of Area I, Area II, Area III and Area IV reaches 20 m, and the construction can be continued only after the invert construction reaches the same section.

[0049] Reference Fig.10 As shown, double I-beams are set on the top of the N1 temporary steel pipe support. The double I-beams are arranged along the longitudinal direction of the tunnel and firmly support the existing tunnel lining.

[0050] In order to further improve the safety of the above-mentioned excavation method, in the above-mentioned steps, longitudinal connecting bars and locking anchor rods should be applied to the initial supporting I-beams.

[0051] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for in-situ expansion of an existing extra-large cross-section highway tunnel. Features: The in-situ expansion method comprises the following steps: S1. First, cut the existing tunnel lining and apply advance support according to the new tunnel contour; S2. Set a row of N1 temporary steel pipe supports at the top arch of the existing tunnel lining, with the spacing between two adjacent N1 temporary steel pipe supports being 5 m. Install longitudinal double-jointed I-beams on the top of the N1 temporary steel pipe supports, which are arranged along the longitudinal direction of the tunnel and firmly support the existing tunnel lining; set a row of N2 temporary vertical supports and a row of N3 temporary vertical supports on the lower half of the tunnel, with the spacing between two adjacent N2 temporary vertical supports and N3 temporary vertical supports being 0.8 m; use sandbags to densely backfill to the tunnel arch waist position; S3, remove the existing tunnel lining in the upper section of the tunnel, removing 0.8 m in each cycle; adjust the movable head on the upper part of the N1 temporary steel pipe support to make the longitudinal double-jointed I-beam top to the existing tunnel initial support concrete surface; S4. Remove the existing initial tunnel support of the left and right guide tunnels of the upper step in stages, expand the tunnel according to the outline of the new tunnel, and construct the initial support and temporary support of the new tunnel; S5. Remove the backfill material of the lower step, dismantle the existing initial tunnel support and tunnel lining of the left and right guide tunnels of the lower step in sections and steps, and expand the excavation according to the outline of the new tunnel, and construct the initial support of the new tunnel; S6, dismantle the existing tunnel invert and backfill structure, and expand the arch bottom according to the new tunnel contour; dismantle the N2 temporary vertical support, and cast the new tunnel lining in sections; In step S1, the existing tunnel lining is cut in the following manner: first, the existing tunnel lining is cut circumferentially to divide the tunnel lining into blocks; then, longitudinal cutting is performed along the tunnel vault to reduce the transmission of construction vibration when the linings of different guide tunnels are removed; at the same time, when cutting the existing tunnel lining, a 5 cm gap is reserved to ensure the construction safety of the section where the tunnel lining has not been removed; In step S6, the existing tunnel invert and backfill structure are dismantled in the following manner: when dismantling the invert, channel steel and temporary staggered vertical bracing are used to ensure that the N2 temporary vertical bracing is not empty; The temporary offset vertical support is located below the N2 temporary vertical support and the channel steel is used to connect the temporary offset vertical support and the N2 temporary vertical support.

2. The in-situ expansion method of an existing extra-large cross-section highway tunnel according to claim 1, Features: In step S4, when the excavation is carried out according to the new tunnel contour, when the excavated rock mass is less than 30 cm thick, mechanical excavation is adopted.

3. The in-situ expansion method of an existing extra-large cross-section highway tunnel according to claim 1, Features: In step S4 and step S5: the existing initial tunnel support of the left pilot tunnel and the right pilot tunnel of the upper step is dismantled in sections and steps, and the existing initial tunnel support and tunnel lining of the left pilot tunnel and the right pilot tunnel of the lower step are dismantled in sections and steps as follows: the advance of each cycle of the expansion of each pilot tunnel according to the new tunnel outline is 0.8 m; The distance between the left and right guide tunnels of the upper step and the left and right guide tunnels of the lower step should be 3-5 m. The distance between the right pilot tunnel of the upper step and the left pilot tunnel of the lower step should not be less than 10 m; After each pilot tunnel has advanced 20 m in a cycle, the construction of the heading face should be stopped, and construction can only be continued after the invert construction reaches the same section.

4. The in-situ expansion method of an existing extra-large cross-section highway tunnel according to claim 1, Features: In step S4 and step S5, when the initial support of the new tunnel is performed, longitudinal connecting bars and locking anchor rods are applied to the I-beams of the initial support of the new tunnel.

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