Construction method for converting and expanding quadruple-arch tunnel into double-layer tunnel

Abstract

The present application relates to the technical field of tunnel engineering, and particularly relates to a construction method for reconstructing and expanding a four-arch tunnel into a double-deck tunnel, comprising the following steps: carrying out traffic closure construction on the third tunnel and the fourth tunnel, and using the first tunnel and the second tunnel as traffic passage during construction; constructing temporary reinforcement measures in the first tunnel and the second tunnel; excavating the third tunnel to form an upper tunnel; constructing a reinforced concrete plate and a second support pile for a right lower step of the upper tunnel; constructing a low parapet wall and a secondary lining of the upper tunnel, so that the upper tunnel is completely connected; excavating a lower tunnel and constructing a lining structure of the lower tunnel; and pouring a tunnel mid-plate to complete the construction of the double-deck tunnel. The present application solves the technical problem that the prior art does not have a process method capable of meeting the requirements of construction from the aspects of surrounding site limitation, construction deformation control, construction organization arrangement and reinforcement measures of old tunnels.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel engineering, in particular to a construction method for converting a four-arch tunnel into a double-deck tunnel. BACKGROUND

[0002] The reconstruction and expansion project of a tunnel refers to the reconstruction of an existing tunnel that has been in operation for many years, widening the cross section of the original tunnel and increasing its span to adapt to the increasing traffic demand in the city.

[0003] The reconstruction and expansion of urban tunnels presents the following technical problems: (1) There are existing buildings on both sides of the urban tunnel, and the site is limited, making it difficult to increase traffic capacity by widening or building tunnels. (2) There are many buildings and dense underground pipelines around the urban tunnel, so construction disturbance should be strictly controlled to reduce the impact of tunnel construction on the surrounding environment. (3) The traffic function of the urban tunnel is important, and interrupting traffic for construction will affect the city's economy, so a road needs to be left for traffic operation during construction. (4) The existing tunnel has serious diseases and is prone to further development under the influence of construction disturbance, so the existing tunnel needs to be reinforced during construction. However, the existing technology can only be used as a reference for traditional tunnel construction methods, and does not have a process method that can meet the requirements of site limitations, construction deformation control, construction organization arrangement, and reinforcement measures for old tunnels, which can easily lead to non-compliant construction or safety problems. SUMMARY

[0004] The present application aims to provide a construction method for converting a four-arch tunnel into a double-deck tunnel to solve the technical problem that the existing technology does not have a process method that can meet the requirements of site limitations, construction deformation control, construction organization arrangement, and reinforcement measures for old tunnels. The specific technical solution is as follows:

[0005] The present application provides a construction method for converting a four-arch tunnel into a double-deck tunnel. The existing four-arch tunnel is arranged from left to right as the first tunnel, the second tunnel, the third tunnel, and the fourth tunnel. The construction of a single-side expanded double-deck tunnel includes the following steps:

[0006] S1: Perform traffic closure construction on the third tunnel and the fourth tunnel, and use the first tunnel and the second tunnel as traffic passage during construction;

[0007] S2: Construct temporary reinforcement measures in the first tunnel and the second tunnel, and install anchor rods on the top of the third tunnel, first support piles on the bottom of the third tunnel, and a mid-partition wall on the left side of the third tunnel;

[0008] S3: Excavate the third tunnel and the fourth tunnel to form an upper tunnel, and install initial support and temporary support for the upper tunnel;

[0009] S4: Reinforced concrete plate and second support pile for tunnel right side lower step are made to upper layer tunnel;

[0010] S5: Temporary support of upper layer tunnel is removed, low side wall and secondary lining of upper layer tunnel are made, and upper layer tunnel is completely penetrated;

[0011] S6: Lower layer tunnel is excavated, and lining structure of lower layer tunnel is made;

[0012] S7: Tunnel middle partition plate is poured, and construction of double layer tunnel is completed.

[0013] Further improvement of the construction method for expanding four-arch tunnel into double layer tunnel is that when temporary reinforcement measures are constructed in the first tunnel and the second tunnel, steel support and carbon fiber cloth protection measures are constructed on the inner wall of the second tunnel; carbon fiber cloth is constructed on the inner wall of the first tunnel.

[0014] Further improvement of the construction method for expanding four-arch tunnel into double layer tunnel is that when the first support pile is made to the bottom of the third tunnel, one reinforced concrete cast-in-place pile is poured every meter at the bottom of the third tunnel, and anchor steel bars are reserved at the pile head of the concrete cast-in-place pile and a supporting beam is poured.

[0015] Further improvement of the construction method for expanding four-arch tunnel into double layer tunnel is that when S3 is performed, before the third tunnel and the fourth tunnel are excavated to form the upper layer tunnel, step S301 is performed, a plurality of support pipes are inserted into the upper layer tunnel to be constructed along the axial direction of the tunnel to form a pipe shed, a steel reinforcement cage is inserted into the support pipe, and cement slurry is injected into the support pipe.

[0016] Further improvement of the construction method for expanding four-arch tunnel into double layer tunnel is that when the initial support and the temporary support of the upper layer tunnel are made, step S302 is performed, a right pilot tunnel of the upper layer tunnel is excavated, when the right pilot tunnel is 15-20m long, the lining structure of the fourth tunnel in the range of the right pilot tunnel is removed, a second initial support is made, and a temporary support is made in the upper layer tunnel.

[0017] Further improvement of the construction method for expanding four-arch tunnel into double layer tunnel is that when the initial support is made, step S303 is performed, a left pilot tunnel of the upper layer tunnel is excavated, when the right pilot tunnel is 15-20m long, the lining structure of the third tunnel in the range of the left pilot tunnel is removed, a third initial support is made, step S304 is performed, a lower step of the right pilot tunnel is excavated, and a fourth initial support of the surrounding area of the lower step is made.

[0018] The further improvement of the four-arch tunnel reconstruction and expansion into a double-deck tunnel construction method lies in that, when the low side wall and the secondary lining of the upper tunnel are constructed, the distance between the low side wall and the tunnel face is less than 35m, and the secondary lining of the upper tunnel adopts 70cm-150cm thick steel water-proof concrete.

[0019] The further improvement of the four-arch tunnel reconstruction and expansion into a double-deck tunnel construction method lies in that, when the lower tunnel is excavated, the step S601 is adopted to excavate the lower tunnel in the order of upper, middle and lower layers, and the initial support of the lower tunnel and the temporary support of the lower tunnel are constructed.

[0020] The further improvement of the four-arch tunnel reconstruction and expansion into a double-deck tunnel construction method lies in that, when the lining structure of the lower tunnel is constructed, the step S602 is adopted to remove the temporary support of the lower tunnel in sections, and the step S603 is adopted to pour the inverted arch and the secondary lining of the lower tunnel.

[0021] The further improvement of the four-arch tunnel reconstruction and expansion into a double-deck tunnel construction method lies in that, the step S6 further comprises S604, pouring the inverted arch filling of the lower tunnel, and S605, pouring the side wall of the lower tunnel.

[0022] The technical scheme of the present application has the following beneficial effects:

[0023] The four-arch tunnel reconstruction and expansion into a double-deck tunnel construction method of the present application reconstructs and expands the existing city four-arch tunnel into a double-deck tunnel, fully utilizes the three-dimensional space, solves the site limitation problem in the city tunnel reconstruction and expansion, prevents the further development of the disease of the existing tunnel through the temporary reinforcement of the existing tunnel, well controls the disturbance of the construction and the influence on the surrounding environment through the use of the advanced support and the parallel tunnel excavation in the reconstruction and expansion construction, the use of the support pile as the support, etc., solves the influence of the tunnel closure on the city traffic in the city tunnel reconstruction and expansion construction through the form of the closed construction on one side and the traffic passing on the other side, improves the operation space of the lower tunnel excavation through the method of excavating the upper tunnel first, excavating the lower tunnel second, and then constructing the middle partition plate, and improves the construction efficiency of the lower tunnel.

[0024] In addition to the purposes, features and advantages described above, the present application has other purposes, features and advantages. The present application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings constituting a part of the present application are used to provide further understanding of the present application, the schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application. In the drawings:

[0026] Figure 1is a flow chart of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0027] Figure 2 is a schematic diagram of the temporary reinforcement measures and the anchor rod construction after the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0028] Figure 3 is a schematic diagram of the partition wall of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0029] Figure 4 is a schematic diagram of the pipe shed of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0030] Figure 5 is a schematic diagram of the excavation of the right guide pit of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0031] Figure 6 is a schematic diagram of the excavation of the left guide pit of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0032] Figure 7 is a schematic diagram of the construction of the fourth initial support of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0033] Figure 8 is a schematic diagram of the construction of the reinforced concrete slab of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0034] Figure 9 is a schematic diagram of the construction of the second support pile of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0035] Figure 10 is a schematic diagram of the removal of the temporary support of the upper tunnel of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0036] Figure 11 is a schematic diagram of the construction of the low parapet wall of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0037] Figure 12 is a schematic diagram of the construction of the secondary lining of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0038] Figure 13 is a schematic diagram of the excavation of the lower tunnel of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0039] Figure 14 is a schematic diagram of the construction of the inverted arch of the construction method of the four-arch tunnel of the present application being reconstructed and expanded into a double-deck tunnel;

[0040] Figure 15 is a schematic diagram of construction of the filling of the inverted arch of the four-arch tunnel reconstruction and expansion into a double-deck tunnel of the present application;

[0041] Figure 16 is a schematic diagram of construction of the side wall of the four-arch tunnel reconstruction and expansion into a double-deck tunnel of the present application;

[0042] Figure 17 is a schematic diagram of construction of the mid-plate of the four-arch tunnel reconstruction and expansion into a double-deck tunnel of the present application;

[0043] Figure 18 is a schematic diagram of construction after completion of the four-arch tunnel reconstruction and expansion into a double-deck tunnel of the present application.

[0044] 1.1, steel support and carbon fiber cloth protection measures; 1.2, carbon fiber cloth; 2, anchor rod; 3.1, first support pile; 3.2, second support pile; 4, joist; 5, partition wall; 6, upper tunnel initial support; 6.1, first initial support; 6.2, second initial support; 6.3, third initial support; 6.4, fourth initial support; 7, pipe shed; 8, upper tunnel temporary support; 9, reinforced concrete slab; 10, low side wall; 11, secondary lining; 12, lower tunnel initial support; 13, inverted arch; 14, inverted arch filling; 15, side wall; 16, mid-plate; 17, right guide pit; 18, left guide pit; 19, upper tunnel; 20, lower tunnel; 21, soil body. DETAILED DESCRIPTION

[0045] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0046] Referring to Figures 1-18 , a four-arch tunnel reconstruction and expansion into a double-deck tunnel construction method has a four-arch tunnel from left to right in order of a first tunnel, a second tunnel, a third tunnel and a fourth tunnel, and a single-side expansion double-deck tunnel construction includes the following steps:

[0047] S1: traffic closure construction is performed on the third tunnel and the fourth tunnel, and the first tunnel and the second tunnel are used as traffic passing during construction;

[0048] S2: as shown in Figure 1 and Figure 2 , temporary reinforcement measures are constructed in the first tunnel and the second tunnel, and an anchor rod 2 is applied to the top of the third tunnel, a first support pile 3.1 is applied to the bottom of the third tunnel, and a partition wall 5 is applied to the left side of the third tunnel;

[0049] S3: as shown in Figure 5As shown, the third tunnel and the fourth tunnel are excavated to form the upper tunnel 19, and the primary support and the temporary support 8 of the upper tunnel are constructed;

[0050] S4: as shown in Figure 8 and Figure 9 The reinforced concrete plate 9 of the lower step on the right side of the tunnel and the second support pile 3.2 of the upper tunnel are constructed;

[0051] S5: as shown in Figures 10-12 The temporary support 8 of the upper tunnel is removed, the dwarf wall 10 and the secondary lining 11 of the upper tunnel are constructed, and the upper tunnel 19 is completely penetrated;

[0052] S6: as shown in Figure 13 The lower tunnel 20 is excavated, and the lining structure of the lower tunnel is constructed;

[0053] S7: as shown in Figure 17 The tunnel partition 16 is poured, and the construction of the double-layer tunnel is completed.

[0054] Specifically, step S1 further comprises: separating the construction area from the passing area by the construction fence, establishing a traffic diversion channel, and guiding the traffic flow into the first tunnel and the second tunnel for temporary passing. The anchor rod 2 is a hollow grouting anchor rod with a diameter of 25mm and a length of 350mm. After the anchor rod is installed, grouting is performed. The number of anchor rods 2 is multiple, and the spacing of the multiple anchor rods 2 along the ring direction and the longitudinal direction is 100mm, and the anchor rods 2 are arranged in a divergent manner along the ring direction. Through the setting of the anchor rod 2, the temporary support and the first support pile 3.1, the third tunnel can remain stable during construction, and problems such as tunnel deformation or collapse can be avoided.

[0055] In this embodiment, as shown in Figure 2 The second tunnel and the third tunnel are the main holes of the existing tunnel, and the first tunnel and the fourth tunnel are auxiliary holes of the existing tunnel, as shown in Figure 2 and Figure 5As shown in the first tunnel, the second tunnel, the third tunnel and the fourth tunnel are surrounded by the soil 21, since the diameter of the double-layer tunnel after expansion will increase, so a part of the surrounding soil 21 needs to be excavated during the expansion process. In the construction of the partition wall 5, first build the partition wall 5 on the left side of the main hole of the third tunnel, and then apply the first primary support 6.1 outside the partition wall 5, and fill the C25 plain concrete inside the partition wall 5. The first primary support 6.1 adopts the form of shotcrete + steel mesh + steel support + anchor rod 2, first wet spray 4cm thick shotcrete, hang steel mesh, then erect steel support, construct anchor rod 2, and finally spray concrete layer by layer to the designed thickness, and the primary support of each stage is closed in a ring in time after construction. The shotcrete adopts early strength wet spray C25 shotcrete with a thickness of 31cm; the steel support adopts I-beam with a longitudinal spacing of 0.5m; and the anchor rod 2 adopts hollow grouting anchor rod 22 with a diameter of 25mm and a length of 350cm, with a ring spacing of 100cm and a longitudinal spacing of 50cm, arranged in a divergent manner.

[0056] Preferably, as shown in Figure 2 and Figure 3 When the temporary reinforcement measures are constructed in the first tunnel and the second tunnel, the steel support and the carbon fiber cloth protection measure 1.1 are constructed on the inner wall of the second tunnel, and the carbon fiber cloth 1.2 is constructed on the inner wall of the first tunnel. The carbon fiber cloth 1.2 can fix the structure of the tunnel as a whole, so that the first tunnel and the second tunnel can bear stress respectively as a whole, and the steel support can further enhance the strength of the main hole of the first tunnel and the second tunnel, avoiding deformation of the tunnel during construction of the double-layer tunnel and safety hazards.

[0057] Preferably, when the first support pile 3.1 is constructed on the bottom of the third tunnel, a reinforced concrete cast-in-place pile is poured every meter at the bottom of the third tunnel, and an anchor steel bar is reserved at the pile head of the concrete cast-in-place pile and a joist 4 is poured, which fixes all the reinforced concrete cast-in-place piles as a force whole, so as to have certain strength support to the tunnel. In this embodiment, the diameter of the reinforced concrete cast-in-place pile is 800mm. When the joist 4 is constructed, it should be constructed section by section and formed as soon as possible to ensure the safety and stability of the primary support of the tunnel. Meter is an engineering measurement for irregular strip or linear engineering.

[0058] Preferably, as shown in Figure 5 and Figure 6 The step S3 comprises:

[0059] S301, a plurality of support pipes are inserted into the tunnel axis direction at intervals above the top surface of the upper tunnel 19 to be constructed to form a pipe shed 7, a steel reinforcement cage is inserted into the support pipe, and cement slurry is injected into the support pipe. Specifically, the pipe shed 7 is in the form of a hot-rolled seamless steel pipe with a diameter of 159 mm at the portal, and a hot-rolled seamless steel pipe with a diameter of 89 mm is used after entering the hole. After the steel pipe is in place, the steel reinforcement cage is placed and the cement slurry is injected.

[0060] S302, excavate the right guide pit 17 of the upper tunnel 19, when the right guide pit 17 is 15-20m in length, remove the lining structure of the fourth tunnel in the range of the right guide pit 17, and construct the second primary support 6.2. The temporary support in the upper tunnel 19 is constructed. The temporary support is in the form of I-shaped steel + sprayed concrete. The sprayed concrete is early strength wet sprayed C25 sprayed concrete, 22cm thick, and the steel support is I-shaped steel with a longitudinal spacing of 0.5m.

[0061] S303, excavate the left guide pit 18 of the upper tunnel 19, when the right guide pit 17 is 15-20m in length, remove the lining structure of the third tunnel in the range of the left guide pit 18, and construct the third primary support 6.3;

[0062] S304, excavate the lower step of the right guide pit 17 and construct the fourth primary support 6.4 around the lower step. The tunnel can be excavated by non-explosive excavation method, strictly control the underbreak, and try to reduce the overbreak. The excavation, support and sprayed concrete during construction are closely followed, and the primary support is constructed in time to form a closed loop as soon as possible. The method of removing the lining structure of the existing tunnel can be mechanical crushing or mechanical cutting. When removing, it is possible to be flat as far as possible to provide a tunnel trolley running surface for subsequent upper tunnel lining construction. The primary support 6 of the upper tunnel includes the first primary support 6.1, the second primary support 6.2, the third primary support 6.3 and the fourth primary support 6.4.

[0063] Preferably, as shown in Figure 11 When constructing the dwarf wall 10 and the secondary lining 11 of the upper tunnel, the distance between the dwarf wall 10 and the working face during construction is not more than 35m, and the secondary lining 11 of the upper tunnel is made of 70-150cm thick reinforced waterproof concrete. When constructing the dwarf wall 10, the lining dwarf wall 10 should be constructed in time according to the surrounding rock monitoring situation after the primary support deformation is stable. And according to the surrounding rock monitoring situation, the secondary lining 11 of the upper tunnel should be constructed in time after the deformation of the tunnel primary support is basically stable.

[0064] Step S6 includes:

[0065] S601, excavate the lower tunnel 20 in the order of upper, middle and lower layers, that is, Figure 13 middle excavate in the order of I, II and III, as shown in Figure 14 andFigure 15 As shown in the figure, the lower tunnel initial support 12 and the lower tunnel temporary support are constructed.

[0066] S602, segmentally demolish the lower tunnel temporary support;

[0067] S603, as shown in the figure, the lower tunnel inverted arch 13 and the secondary lining 11 are poured. Figure 13 and Figure 14 As shown in the figure, the lower tunnel inverted arch filling 14 is poured.

[0068] S604, as shown in the figure, the lower tunnel side wall 15 is poured. Figure 15

[0069] S605, as shown in the figure, the lower tunnel side wall 15 is poured. Figure 16

[0070] The lower tunnel lining structure includes the lower tunnel inverted arch 13, the secondary lining 11, the lower tunnel inverted arch filling 14 and the lower tunnel side wall 15. The lower tunnel inverted arch 13 is in the form of 100cm thickness and C35 reinforced waterproof concrete. The lower tunnel side wall 15 is in the form of 80cm thickness and C35 reinforced waterproof concrete. The bulkhead 16 is in the form of 100cm thickness and C35 reinforced waterproof concrete. After the construction of the bulkhead 16, the right side tunnel is divided into upper and lower two layers, the construction of the upper tunnel 19 and the lower tunnel 20 is completed, and the same steps are used for the construction of the left side double-layer tunnel, and finally the bulkhead 5 of both sides is connected to form a complete bulkhead 5.

[0071] The four-arch tunnel reconstruction and expansion into a double-layer tunnel construction method of the application reconstructs and expands the existing city four-arch tunnel into a double-layer tunnel, fully utilizes the three-dimensional space, solves the site restriction problem in the reconstruction and expansion of the city tunnel, prevents the further development of the disease of the existing tunnel through the temporary reinforcement of the existing tunnel, and uses the advanced support and tunnel excavation in parallel, uses the support pile as the support and other ways in the reconstruction and expansion construction, well controls the disturbance of the construction and the influence on the surrounding environment, solves the influence of the tunnel closure on the city traffic in the reconstruction and expansion construction of the city tunnel through the form of closing the construction on one side and passing the traffic on the other side, improves the operation space of the lower tunnel excavation through the method of excavating the upper tunnel first, excavating the lower tunnel 20, and then constructing the bulkhead 16, and improves the construction efficiency of the lower tunnel.

[0072] The above only describes the preferred embodiments of the application and is not used to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application shall be included in the protection scope of the application.​​

Claims

1. A construction method for expanding a quadruple-arch tunnel into a double-deck tunnel, wherein the quadruple-arch tunnel has a first tunnel, a second tunnel, a third tunnel, and a fourth tunnel from left to right in order, characterized in that, The construction of the single-side expanded double-layer tunnel comprises the following steps: S1: performing traffic closure construction on the third tunnel and the fourth tunnel, and using the first tunnel and the second tunnel as traffic passing during construction; S2: constructing temporary reinforcement measures in the first tunnel and the second tunnel, and performing anchoring on the top of the third tunnel, performing first support pile (3.1) on the bottom of the third tunnel, and performing middle partition wall (5) on the left side of the third tunnel; S3: excavating the third tunnel and the fourth tunnel to form the upper-layer tunnel (19), and performing initial support and upper-layer tunnel temporary support (8); S4: performing steel reinforced concrete plate (9) and second support pile (3.2) on the right side of the upper-layer tunnel; S5: removing the upper-layer tunnel temporary support (8), performing low side wall (10) and upper-layer tunnel secondary lining (11), and making the upper-layer tunnel (19) completely through; S6: excavating the lower-layer tunnel (20), and performing lower-layer tunnel lining structure; S7: pouring the tunnel middle partition plate (16), and completing the construction of the double-layer tunnel; When performing the first support pile (3.1) on the bottom of the third tunnel, one steel reinforced concrete pile is poured every meter on the bottom of the third tunnel, and anchoring steel bars are reserved on the pile head of the concrete pile and a supporting beam (4) is poured; When performing S3, before excavating the third tunnel and the fourth tunnel to form the upper-layer tunnel, step S301 is performed, i.e., a plurality of support pipes are inserted into the upper-layer tunnel (19) to form a pipe shed (7) along the axial direction of the tunnel, a steel cage is inserted into the support pipe, and cement slurry is injected into the support pipe; When performing the initial support and the upper-layer tunnel temporary support (8), step S302 is performed, i.e., a right pilot tunnel (17) of the upper-layer tunnel (19) is excavated, when the right pilot tunnel (17) is 15-20 m long, the lining structure of the fourth tunnel in the range of the right pilot tunnel (17) is removed, the second initial support (6.2) is performed, and the temporary support in the upper-layer tunnel (19) is performed; When performing the initial support, step S303 is performed, i.e., a left pilot tunnel (18) of the upper-layer tunnel (19) is excavated, when the right pilot tunnel (17) is 15-20 m long, the lining structure of the third tunnel in the range of the left pilot tunnel (18) is removed, the third initial support (6.3) is performed, step S304 is performed, i.e., a lower step of the right pilot tunnel is excavated, and the fourth initial support (6.4) of the surrounding area of the lower step is performed; When excavating the lower-layer tunnel (20), step S601 is performed, i.e., the lower-layer tunnel (20) is excavated in the order of upper, middle and lower layers, and the lower-layer tunnel initial support (12) and the lower-layer tunnel temporary support are performed.

2. The method according to claim 1, wherein When constructing the temporary reinforcement measures in the first tunnel and the second tunnel, steel support and carbon fiber cloth protection measures (1.1) are constructed on the inner wall of the second tunnel; carbon fiber cloth (1.2) is constructed on the inner wall of the first tunnel.

3. The method according to claim 1, wherein When performing the low side wall (10) and the upper-layer tunnel secondary lining (11), the distance between the low side wall (10) and the working face is not more than 35 m, and the secondary lining (11) of the upper-layer tunnel adopts 70-150 cm thick steel reinforced waterproof concrete.

4. The method according to claim 1, wherein When the lower tunnel lining structure is constructed, the step S602 is performed to segmentally demolish the temporary support of the lower tunnel; and then the step S603 is performed to cast the inverted arch (13) and the secondary lining (11) of the lower tunnel.

5. The method according to claim 4, wherein The step S6 further includes S604, casting the inverted arch filling (14) of the lower tunnel; and S605, casting the side wall (15) of the lower tunnel.

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