Tunnel dividing structure suitable for small-clear-distance four-lane tunnel and construction method

Abstract

The invention provides a tunnel dividing structure suitable for a small-clear-distance four-lane tunnel and a construction method.The tunnel dividing structure comprises two tunnels with a certain distance, and each tunnel comprises a tunnel body and a plurality of concrete middle columns which are located in the middle of the tunnel body and are sequentially arranged at intervals in the advancing direction of the tunnel; the concrete middle column extends from the bottom of the tunnel body to the top of the tunnel body. The construction cost of the tunnel can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and particularly relates to a segmented tunnel structure and a construction method suitable for a four-lane tunnel with a small clear distance. Background Art

[0002] China is a mountainous country. In the construction of urban tunnels, with the rapid development of urbanization, the resources at urban road nodes are becoming increasingly scarce. Especially under the restriction of the tunnel construction red line, the traditional separated tunnel design is difficult to meet the connection requirements of urban infrastructure. It is often necessary to construct a four-lane tunnel structure (two-way eight lanes). The span of a conventional four-lane tunnel often exceeds 20m. In previous projects, the construction method of left and right double temporary double-layer pilot tunnels was generally adopted, and a large number of temporary supports needed to be demolished, resulting in a large amount of engineering waste. In addition, since urban tunnels need to have the function of pedestrian passage, the existence of the pedestrian passage further widens the span of the tunnel, leading to a further increase in the tunnel cost. Therefore, there is an urgent need for a new segmented tunnel structure suitable for a four-lane tunnel with a small clear distance to effectively reduce the tunnel cost. Summary of the Invention

[0003] The purpose of the present invention is to provide a segmented tunnel structure and a construction method suitable for a four-lane tunnel with a small clear distance to solve the problem of high construction cost of existing tunnels.

[0004] To solve the above technical problems, the present invention provides a segmented tunnel structure suitable for a four-lane tunnel with a small clear distance, including two tunnels with a small clear distance. The tunnel includes a tunnel body and a plurality of concrete middle columns arranged at intervals in the tunnel body along the tunnel traveling direction. The concrete middle columns extend from the bottom of the tunnel body to the top of the tunnel body.

[0005] Optionally, the tunnel further includes a connecting beam arranged on adjacent two concrete middle columns.

[0006] Optionally, the tunnel further includes a middle partition board arranged along the tunnel traveling direction and located on the concrete middle columns and the connecting beam.

[0007] Optionally, the middle partition board divides the tunnel body into upper and lower layers.

[0008] Optionally, the tunnel body includes a geotechnical matrix with a traveling passage, a primary lining arranged on the inner wall of the geotechnical matrix, and a secondary lining arranged on the inner wall of the primary lining. The concrete middle columns extend from the bottom of the primary lining through the secondary lining to the top of the primary lining, and the middle partition board extends laterally to the primary lining on both sides.

[0009] Optionally, the distance between the middle partition board and the top of the tunnel body is ≥ 3m.

[0010] Optionally, the concrete middle column is one of a reinforced concrete middle column or a concrete-filled steel tube middle column.

[0011] Optionally, adjacent concrete middle columns are arranged at intervals of 4-6 m.

[0012] Optionally, the tunnel body is symmetrically arranged with respect to the concrete middle column.

[0013] The present invention also provides a construction method for the segmented tunnel structure of the above-mentioned small clear distance four-lane tunnel, including: excavating the first of the two tunnels, including: excavating the soil layer on the first side of the upper bench to form a first semi-arch-shaped passage on the first side of the upper bench, constructing a first primary lining on the top of the first semi-arch-shaped passage and constructing a first locking foot small duct, constructing a concrete middle column on the side of the first semi-arch-shaped passage close to the second side, and connecting the concrete middle column to the first primary lining at the top of the semi-arch-shaped passage and extending downward to the bottom of the tunnel body, constructing a first middle partition board at the bottom of the first semi-arch-shaped passage, so that the first primary lining, the concrete middle column and the first middle partition board enclose a ring, excavating the soil layer on the first side of the middle bench to form a first middle bench passage on the first side of the middle bench, and retaining the first core soil at the bottom of the first middle bench passage, the side of the first middle bench passage close to the second side is the concrete middle column, constructing a second primary lining and a second locking foot small duct on the side of the first middle bench passage far from the second side, the top of the first middle bench passage is the first middle partition board, then, excavating the first core soil, constructing a temporary invert at the bottom of the first middle bench passage, so that the second primary lining, the first middle partition board, the concrete middle column and the temporary invert enclose a ring, constructing a connecting beam of the concrete middle column, excavating the soil layer on the first side of the lower bench to form a first lower bench passage on the first side of the lower bench, the side of the first lower bench passage close to the second side is the concrete middle column, constructing a third primary lining and a third locking foot small duct on the side of the first lower bench passage far from the second side, the top of the first lower bench passage is the temporary invert, constructing a fourth primary lining at the bottom of the first lower bench passage, the third primary lining, the fourth primary lining, the concrete middle column and the temporary invert enclose a ring, excavating the soil layer on the second side of the upper bench to form a second semi-arch-shaped passage on the second side of the upper bench, constructing a fifth primary lining on the top of the second semi-arch-shaped passage and constructing a fifth locking foot small duct, the side of the second semi-arch-shaped passage close to the first side is the concrete middle column, constructing a second middle partition board at the bottom of the second semi-arch-shaped passage, so that the fifth primary lining, the concrete middle column and the second middle partition board enclose a ring, excavating the soil layer on the second side of the middle bench to form a second middle bench passage on the second side of the middle bench, and retaining the second core soil at the bottom of the second middle bench passage, the side of the second middle bench passage close to the first side is the concrete middle column, constructing a sixth primary lining and a sixth locking foot small duct on the side of the second middle bench passage far from the first side, the top of the second middle bench passage is the second middle partition board, then, excavating the second core soil, excavating the soil layer on the second side of the lower bench to form a second lower bench passage on the second side of the lower bench, the side of the second lower bench passage close to the first side is the concrete middle column, constructing a seventh primary lining and a seventh locking foot small duct on the side of the second lower bench passage far from the second side, constructing an eighth primary lining at the bottom of the second lower bench passage, the sixth primary lining, the seventh primary lining and the eighth primary lining, the second middle partition board, the concrete middle column enclose a ring, constructing a secondary lining invert on the fourth primary lining and the eighth primary lining, and backfilling invert filling on the invert, constructing a first sidewall secondary lining on the second primary lining and the third primary lining, constructing a second sidewall secondary lining on the sixth primary lining and the seventh primary lining, and finally constructing an arch secondary lining on the first primary lining and the fifth primary lining, removing the temporary invert, wherein, the first side is one of the left side and the right side,The second side is the other one of the left side and the right side; the second of the two tunnels is excavated; wherein, the structure after the construction of the first tunnel is symmetrical to the structure after the construction of the second tunnel.

[0014] The segmented tunnel structure and construction method applicable to a small clear distance four-lane tunnel provided by the present invention have the following beneficial effects: Since the segmented tunnel structure applicable to a small clear distance four-lane tunnel includes two tunnels, concrete middle columns are arranged in both tunnels, and the concrete middle columns extend from the bottom of the tunnel body to the top of the tunnel body. In this way, the tunnel body can be supported by the middle columns, and the main span width can be reduced by dividing the spans by the middle columns. For example, for a conventional four-lane tunnel with a main span of 20 m, the main span of the tunnel can be reduced to 12 m. In this way, the tunnel cost can be reduced, and the reduction of the main span width can reduce the excavation area of the tunnel section, which is more environmentally friendly. Description of the Drawings

[0015] Figure 1 It is a schematic structural diagram of the segmented tunnel structure applicable to a small clear distance four-lane tunnel in an embodiment of the present invention; Figure 2 It is a schematic structural diagram of a single tunnel of the segmented tunnel structure applicable to a small clear distance four-lane tunnel in an embodiment of the present invention; Figure 3 It is a schematic structural diagram during the construction process of the segmented tunnel structure applicable to a small clear distance four-lane tunnel in an embodiment of the present invention; Figure 4 It is a schematic structural diagram of a single tunnel during the construction process of the segmented tunnel structure applicable to a small clear distance four-lane tunnel in an embodiment of the present invention.

[0016] Description of the Reference Numerals: 100 - Tunnel; 112 - Primary Lining; 113 - Secondary Lining; 120 - Concrete Middle Column; 130 - Connecting Beam; 140 - Middle Partition Board; 201 - First Semi-Arch Channel; 202 - First Primary Lining; 203 - First Locking Foot Small Duct; 204 - First Middle Partition Board; 205 - First Middle Step Channel; 206 - First Core Soil; 207 - Second Primary Lining; 208 - Second Locking Foot Small Duct; 209 - Temporary Inverted Arch; 210 - First Lower Step Channel; 211 - Third Primary Lining; 212 - Third Locking Foot Small Duct; 213 - Fourth Primary Lining; 214 - Second Semi-Arch Channel; 215 - Fifth Primary Lining; 216 - Fifth Locking Foot Small Duct; 217 - Second Middle Partition Board; 218 - Second Middle Step Channel; 219 - Second Core Soil; 220 - Sixth Primary Lining; 221 - Sixth Locking Foot Small Duct; 222 - Second lower - stage channel; 223 - Seventh primary lining; 224 - Seventh small pipe for locking feet; 225 - Eighth primary lining; 226 - Invert lining of the secondary lining; 227 - Invert filling; 228 - First side - wall secondary lining; 229 - Second side - wall secondary lining; 230 - Arch - part secondary lining. Specific implementation manners

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0019] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0020] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive distinction and cannot be understood as indicating or implying relative importance.

[0021] In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging vertically, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0022] In the description of the present invention, it should also be noted that, unless otherwise clearly specified and defined, the terms "set", "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] Reference Figure 1 and Figure 2 , Figure 1 is a schematic structural view of a segmented tunnel structure applicable to a small clear distance four-lane tunnel in an embodiment of the present invention. Figure 2 is a schematic structural view of a single tunnel of a segmented tunnel structure applicable to a small clear distance four-lane tunnel in an embodiment of the present invention. The present embodiment provides a segmented tunnel structure applicable to a small clear distance four-lane tunnel, including two tunnels 100 with a small clear distance. The tunnel 100 includes a tunnel body and a plurality of concrete middle columns 120 arranged at intervals in the traveling direction of the tunnel 100 in the middle of the tunnel body. The concrete middle columns 120 extend from the bottom of the tunnel body to the top of the tunnel body.

[0024] Since the segmented tunnel structure applicable to a small clear distance four-lane tunnel includes two tunnels 100, concrete middle columns 120 are arranged in both tunnels 100, and the concrete middle columns 120 extend from the bottom of the tunnel body to the top of the tunnel body. In this way, the tunnel body can be supported by the middle columns, and the main span width can be reduced by dividing the span by the middle columns. For example, for a conventional four-lane tunnel 100 with a main span of 20 m, the main span of the tunnel 100 can be reduced to 12 m. In this way, the cost of the tunnel 100 can be reduced, and the reduction of the main span width can reduce the excavation area of the tunnel section, which is more environmentally friendly.

[0025] Preferably, the tunnel 100 further includes a connection beam 130 arranged on two adjacent concrete middle columns 120. The middle columns plus the connection beam 130 form a space grid framework, and the overall stiffness of the tunnel 100 is improved. At the same time, compared with a conventional two-lane tunnel 100, since the middle columns of the tunnel 100 are arranged at intervals of 4-6 m and have good permeability, the depression of the driver during driving is relatively better than that of a conventional two-lane tunnel.

[0026] Preferably, the tunnel 100 further includes a middle partition 140 disposed along the traveling direction of the tunnel 100 and located on the concrete middle column 120 and the connecting beam 130. In this way, the space of the tunnel body above the middle partition 140 and the middle partition 140 can be used as an escape passage. Compared with the tunnel 100 with the escape passage arranged at the bottom of the tunnel body, the width of the main span of the tunnel 100 can be effectively reduced, thereby reducing the cost of the tunnel 100 and being more environmentally friendly. For example, for a conventional four-lane tunnel 100, the building clearance can be reduced by 2 m.

[0027] Furthermore, the middle partition 140 divides the tunnel body into upper and lower layers.

[0028] The middle partition 140 is ≥ 3 m away from the top of the tunnel body to meet the pedestrian needs and ensure mechanical operations.

[0029] Specifically, the tunnel body includes a geotechnical matrix having a traveling passage, a primary lining 112 provided on the inner wall of the geotechnical matrix, and a secondary lining 113 provided on the inner wall of the primary lining 112. The concrete middle column 120 extends from the bottom of the primary lining 112 through the secondary lining 113 to the top of the primary lining 112. The middle partition 140 extends laterally on both sides to the primary lining 112. By arranging the middle column, the thickness of the secondary lining 113 can be effectively reduced. For example, for a conventional four-lane tunnel 100, the thickness of the secondary lining 113 can be reduced from 70 cm to 45 cm.

[0030] Specifically, the concrete middle column 120 can be one of a reinforced concrete middle column or a concrete-filled steel tube middle column, or other concrete middle columns, and this embodiment does not limit this.

[0031] Specifically, adjacent concrete middle columns 120 are arranged at intervals of 4 - 6 m.

[0032] In this embodiment, the concrete middle column 120 is constructed by cast-in-place piles.

[0033] The tunnel body is symmetrically arranged with respect to the concrete middle column 120.

[0034] Reference Figure 3 and Figure 4 , Figure 3 are schematic structural diagrams during the construction process of the segmented tunnel structure applicable to the small clear distance four-lane tunnel in the embodiment of the present invention, Figure 4 is a schematic structural diagram of a single hole during the construction process of the segmented tunnel structure applicable to the small clear distance four-lane tunnel in the embodiment of the present invention. This embodiment also provides a construction method for the segmented tunnel structure applicable to the small clear distance four-lane tunnel, including: Excavating the first of the two tunnels 100, including: Excavate the soil layer on the first side of the upper bench to form a first semi-arch-shaped passage 201 on the first side of the upper bench. Apply a first primary lining 202 on the top of the first semi-arch-shaped passage 201 and install a first foot-locking small duct 203. Construct a concrete middle column 120 on the side of the first semi-arch-shaped passage 201, and connect the concrete middle column 120 to the first primary lining 202 at the top of the semi-arch-shaped passage and extend it downward to the bottom of the tunnel body. Construct a first middle partition 204 at the bottom of the first semi-arch-shaped passage 201 to form a ring with the first primary lining 202, the concrete middle column 120, and the first middle partition 204. Excavate the soil layer on the first side of the middle bench to form a first middle bench passage 205 on the first side of the middle bench, and retain the first core soil 206 at the bottom of the first middle bench passage 205. The side of the first middle bench passage 205 close to the second side is the concrete middle column 120. Apply a second primary lining 207 and a second foot-locking small duct 208 on the side of the first middle bench passage 205 far from the second side. The top of the first middle bench passage 205 is the first middle partition 204. After that, excavate the first core soil 206 and construct a temporary invert 209 at the bottom of the first middle bench passage 205 to form a ring with the second primary lining 207, the first middle partition 204, the concrete middle column 120, and the temporary invert 209. Construct a connecting beam 130 for the concrete middle column 120. Excavate the soil layer on the first side of the lower bench to form a first lower bench passage 210 on the first side of the lower bench. The side of the first lower bench passage 210 close to the second side is the concrete middle column 120. Apply a third primary lining 211 and a third foot-locking small duct 212 on the side of the first lower bench passage 210 far from the second side. The top of the first lower bench passage 210 is the temporary invert 209. Construct a fourth primary lining 213 at the bottom of the first lower bench passage 210. The third primary lining 211, the fourth primary lining 213, the concrete middle column 120, and the temporary invert 209 form a ring. Excavate the soil layer on the second side of the upper bench to form a second semi-arch-shaped passage 214 on the second side of the upper bench. Apply a fifth primary lining 215 on the top of the second semi-arch-shaped passage 214 and install a fifth foot-locking small duct 216. The side of the second semi-arch-shaped passage 214 close to the first side is the concrete middle column 120. Construct a second middle partition 217 at the bottom of the second semi-arch-shaped passage 214 to form a ring with the fifth primary lining 215, the concrete middle column 120, and the second middle partition 217. Excavate the soil layer on the second side of the middle bench to form a second middle bench passage 218 on the second side of the middle bench, and retain the second core soil 219 at the bottom of the second middle bench passage 218. The side of the second middle bench passage 218 close to the first side is the concrete middle column 120. Apply a sixth primary lining 220 and a sixth foot-locking small duct 221 on the side of the second middle bench passage 218 far from the first side. The top of the second middle bench passage 218 is the second middle partition 217. After that, excavate the second core soil 219. The soil layer on the second side of the lower step is excavated to form a second lower step channel 222 on the second side of the lower step. The side of the second lower step channel 222 close to the first side is a concrete center column 120. The side of the second lower step channel 222 away from the second side is constructed with a seventh primary lining 223 and a seventh locking foot small guide tube 224. The bottom of the second lower step channel 222 is constructed with an eighth primary lining 225. The sixth primary lining 220, the seventh primary lining 223, the eighth primary lining 225, the second middle partition plate 217, and the concrete center column 120 form a ring. A secondary lining invert 226 is constructed on the fourth primary lining 213 and the eighth primary lining 225, and the invert filler 227 is backfilled on the invert. A first side wall secondary lining 228 is constructed on the second primary lining 207 and the third primary lining 211. A second side wall secondary lining 229 is constructed on the sixth primary lining 220 and the seventh primary lining 223. Finally, an arch secondary lining 230 is constructed on the first primary lining 202 and the fifth primary lining 215, and the temporary invert 209 is removed. The first side is one of the left side and the right side, and the second side is the other of the left side and the right side; excavation of the second of the two tunnels 100; The structure of the first tunnel 100 after construction is symmetrical to the structure of the second tunnel 100 after construction.

[0035] In this embodiment, dual core soil retention reduces the exposed excavation surface and the amount of temporary support by 75%, thus reducing tunnel construction workload and being more environmentally friendly. A central column system replaces the traditional double-layered pilot tunnel, avoiding wasteful support removal and effectively lowering the cost of Tunnel 100. The timely installation of the first and second diaphragms, concrete central columns, and connecting beams, along with the core soil retention, significantly reduces the risk of landslides during construction. Furthermore, this embodiment utilizes a multi-part construction method that effectively minimizes the adverse disturbances caused by small clearances.

[0036] In this embodiment, the clearance of the upper step is no less than 3m at the highest point, ensuring that pedestrian functions are met. It can also effectively divide the tunnel 100 to reduce the peak bending moment of the tunnel 100, and facilitate the subsequent application of the second lining 113 with steel formwork.

[0037] The concrete center columns 120 are arranged at intervals of 4-6 meters.

[0038] The concrete center column 120 is constructed by cast-in-place piles.

[0039] The spacing of the temporary inverts 209 along the tunnel traveling direction is consistent with the spacing of the first primary lining 202 .

[0040] Among them, the clearance of the middle step is ≥4.5m to ensure mechanical construction.

[0041] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A segmented tunnel structure applicable to a four-lane tunnel with small clear distance, characterized in that, It includes two tunnels with a small clear distance. The tunnel includes a tunnel body and a plurality of concrete intermediate columns arranged at intervals along the tunnel traveling direction in the middle of the tunnel body. The concrete intermediate columns extend from the bottom of the tunnel body to the top of the tunnel body.

2. The segmented tunnel structure applicable to a four-lane tunnel with small clear distance as claimed in claim 1, wherein The tunnel further includes a connecting beam arranged on two adjacent concrete intermediate columns.

3. The split tunnel structure suitable for a small clearance four-lane tunnel according to claim 2, characterized in that: The tunnel further includes a middle partition arranged along the tunnel traveling direction and located on the concrete intermediate columns and the connecting beam.

4. The segmented tunnel structure applicable to a four-lane tunnel with small clear distance as claimed in claim 3, wherein The middle partition divides the tunnel body into upper and lower layers.

5. The segmented tunnel structure applicable to the small clear distance four-lane tunnel according to claim 4, characterized in that, The tunnel body includes a geotechnical matrix with a traveling passage, a primary lining arranged on the inner wall of the geotechnical matrix, and a secondary lining arranged on the inner wall of the primary lining. The concrete intermediate columns extend from the bottom of the primary lining through the secondary lining to the top of the primary lining. The middle partition extends laterally to both sides of the primary lining.

6. The segmented tunnel structure applicable to a closely spaced four-lane tunnel as claimed in claim 4, wherein The distance between the middle partition and the top of the tunnel body is ≥3m.

7. The segmented tunnel structure applicable to a small clear distance four-lane tunnel as described in claim 1, wherein The concrete intermediate column is one of a reinforced concrete intermediate column or a concrete-filled steel tube intermediate column.

8. The segmented tunnel structure applicable to a four-lane tunnel with small clear distance as claimed in claim 1, characterized in that, Adjacent concrete intermediate columns are arranged at intervals of 4 - 6m.

9. The segmented tunnel structure applicable to a closely spaced four-lane tunnel according to claim 1, wherein The tunnel body is symmetrically arranged with respect to the concrete intermediate columns.

10. A construction method for a segmented tunnel structure applicable to a four-lane tunnel with small clear distance as described in claim 5, characterized in that, It includes: Excavating the first of the two tunnels, including: Excavating the soil layer on the first side of the upper bench to form a first semi-arch-shaped passage on the first side of the upper bench. Constructing a first primary lining on the top of the first semi-arch-shaped passage and constructing a first locking foot small duct. Constructing a concrete intermediate column on the side of the first semi-arch-shaped passage close to the second side, and connecting the concrete intermediate column to the first primary lining at the top of the semi-arch-shaped passage, and extending downward to the bottom of the tunnel body. Constructing a first middle partition at the bottom of the first semi-arch-shaped passage to form a ring by the first primary lining, the concrete intermediate column and the first middle partition. Excavating the soil layer on the first side of the middle bench to form a first middle bench passage on the first side of the middle bench, and retaining the first core soil at the bottom of the first middle bench passage. The side of the first middle bench passage close to the second side is the concrete intermediate column. Constructing a second primary lining and a second locking foot small duct on the side of the first middle bench passage far from the second side. The top of the first middle bench passage is the first middle partition. Then, excavating the first core soil, constructing a temporary invert at the bottom of the first middle bench passage to form a ring by the second primary lining, the first middle partition, the concrete intermediate column and the temporary invert, and constructing a connecting beam for the concrete intermediate column. Excavating the soil layer on the first side of the lower bench to form a first lower bench passage on the first side of the lower bench. The side of the first lower bench passage close to the second side is the concrete intermediate column. Constructing a third primary lining and a third locking foot small duct on the side of the first lower bench passage far from the second side. The top of the first lower bench passage is the temporary invert. Constructing a fourth primary lining at the bottom of the first lower bench passage. The third primary lining, the fourth primary lining, the concrete intermediate column and the temporary invert form a ring. Excavating the soil layer on the second side of the upper bench to form a second semi-arch-shaped passage on the second side of the upper bench. Constructing a fifth primary lining on the top of the second semi-arch-shaped passage and constructing a fifth locking foot small duct. The side of the second semi-arch-shaped passage close to the first side is the concrete intermediate column. Constructing a second middle partition at the bottom of the second semi-arch-shaped passage to form a ring by the fifth primary lining, the concrete intermediate column and the second middle partition. The soil layer on the second side of the middle step is excavated to form a second middle step channel on the second side of the middle step, and the second core soil at the bottom of the second middle step channel is retained. The side of the second middle step channel close to the first side is a concrete middle column, and the side of the second middle step channel away from the first side is constructed with the sixth primary lining and the sixth locking foot small guide tube. The top of the second middle step channel is the second middle partition. After that, the second core soil is excavated. Excavate the soil layer on the second side of the lower step to form a second lower step channel on the second side of the lower step. The side of the second lower step channel close to the first side is a concrete center column. The side of the second lower step channel away from the second side is constructed with a seventh primary lining and a seventh locking foot small guide tube. The bottom of the second lower step channel is constructed with an eighth primary lining. The sixth, seventh and eighth primary linings, the second middle partition and the concrete center column form a ring. Construct the secondary lining of the inverted arch on the fourth and eighth primary linings, and backfill the inverted arch with the inverted arch filling material. Construct the secondary lining of the first side wall on the second and third primary linings, construct the secondary lining of the second side wall on the sixth and seventh primary linings, and finally construct the secondary lining of the arch on the first and fifth primary linings. Remove the temporary inverted arch. The first side is one of the left side and the right side, and the second side is the other of the left side and the right side; excavation of the second of two tunnels; Among them, the structure after the construction of the first tunnel is symmetrical with the structure after the construction of the second tunnel.

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