WO2021093751A1

WO2021093751A1 - Construction method for tunnel in transverse semi-soft and semi-hard section stratum

Info

Publication number: WO2021093751A1
Application number: PCT/CN2020/127977
Authority: WO
Inventors: 寇海军; 宋新海; 于建; 阎明东
Original assignee: 中铁十九局集团第五工程有限公司
Priority date: 2019-11-11
Filing date: 2020-11-11
Publication date: 2021-05-20
Also published as: CN110985002A; CN110985002B

Abstract

A construction method for a tunnel in a transverse semi-soft and semi-hard section stratum, comprising: S1, constructing a pre-buried advanced pipe shed (13) in the area on a tunnel face corresponding to a tunnel arch portion; S2, constructing a soft-rock-distribution left half section (1) and a hard-rock-distribution right half section (2) in sequence by using a center diaphragm method, after excavation is completed, dismantling temporary center diaphragm supports (5, 8), and ensuring that permanent support arch frames (3, 6, 9) respectively constructed on the upper portions of the left half section (1) and the right half section (2) along an arc roof and temporary inverts (7) on the lower portions form a closed support structure; and S3, performing invert excavation, constructing permanent support arch frames (10, 11, 12) at the bottom of the tunnel, dismantling the temporary inverts (7), and constructing a composite lining. The construction method is simple, effectively solves the problem of proneness to collapse during semi-soft and semi-hard section stratum construction, and ensures the normal progress of construction operations and the safety of the construction site.

Description

Tunnel construction method used in transverse semi-soft and semi-hard section stratum

Cross-references to related applications

This application claims the priority of the Chinese patent application filed on November 11, 2019 with the application number 201911097059.6 and the title of the invention "A tunnel construction method for transverse semi-soft and semi-hard section stratum", which is by reference All are incorporated into this article.

Technical field

This application relates to the technical field of tunnel construction, and in particular to a tunnel construction method used in transverse semi-soft and semi-hard section stratum.

Background technique

During the tunnel construction, due to the constraints of construction conditions and construction costs, the design must traverse the stratum with large differences in weathering of surrounding rock, especially along the longitudinal direction of the pre-construction tunnel, the surrounding rock on the left and right half of the tunnel face They are Devonian extremely soft carbonaceous slate and weakly weathered dolomitic limestone. Referring to Figure 1, the rock formation in the construction area indicated by the left half section 1 is Devonian extremely soft carbonaceous slate, and the rock formation in the construction area indicated by the right half section 2 is weakly weathered dolomitic limestone. The Devonian ultra-soft carbonaceous slate is a thin-layered and medium-thick layered structure, and its interlayer bonding is poor. The surrounding rock corresponding to the left half of section 1 of the construction site is extremely water-rich and presents a strand-like burst. The strand-shaped water outlet points are shown as A, B, C, and D in the figure.

At present, when tunnel construction is carried out in the above-mentioned strata, the upper and lower pilot pits are used to excavate the core soil method, but this construction method causes the upper step volley surface to be too large, and the Devonian carbonaceous slate on the left is softened by water. It is stable, and the phenomenon of block-dropping and slumping of the tunnel face is very serious. Among them, the position of the slippage of the smear is shown at P in Figure 1. This is not only difficult to ensure normal construction operations, but also seriously threatens the safety of the construction site.

Summary of the invention

(1) Technical problems to be solved

The purpose of this application is to provide a tunnel construction method used in transverse semi-soft and semi-hard section stratum, to solve the current problem of using upper and lower heading pits to reserve core soil method for tunnel construction in transverse semi-soft and semi-hard section stratum. During construction, serious landslides occurred, which not only affected the construction work, but also seriously threatened the safety of the construction site.

(2) Technical solution

In order to solve the above technical problems, the present application provides a tunnel construction method used in transverse semi-soft and semi-hard section stratum, including:

S1, pre-embedded and advanced pipe sheds are applied to the tunnel arch area corresponding to the tunnel face;

S2. Use the middle partition method to construct the soft rock distribution on the left half of the section and the hard rock distribution on the right half of the section in turn. After the excavation is completed, remove the temporary middle partition support, and ensure that the upper part of the left half section and the right half section The permanent supporting arch frame constructed along the vault and the temporary invert at the lower part form a closed supporting structure;

S3. Carry out invert excavation, construct permanent arch support at the bottom of the tunnel, remove temporary invert, and construct composite lining.

In one embodiment, the application further includes: before step S1, performing drainage treatment on the area where water gushing occurs on the palm face, and temporarily supporting the construction area on the back side of the palm face.

In an embodiment, step S1 in this application further includes:

S11, the steel pipe in the pre-embedded advanced pipe shed is used as a drill pipe for drilling. The head end of the steel pipe is connected to the guide plate drill bit, and the tail end of the steel pipe is connected to the drilling rig. The two sections of steel pipes are alternately connected, and the second section of steel pipes are provided with overflow holes;

S12. Remove the drilling rig and connect the grouting pump to the end of the steel pipe. The initial pressure of the grouting pump is controlled to be 0.5～1.0MPa and the final pressure is 2.0～3.0MPa during grouting, so that the spreading radius of the slurry is greater than 45cm .

In one embodiment, the size of the central angle of the pre-embedded advanced tube roof in this application is 90°～120°, and the symmetrical center line of the embedded advanced tube roof deviates from the tunnel toward the left half of the tunnel. The angle of the vertical centerline is 10°-20°; the extrapolation angle of the steel pipe is 10°-30°, and the slurry injected into the steel pipe is a glass double slurry.

In an embodiment, step S2 in this application further includes:

S21: Divide the left half-section from top to bottom into multi-layer construction areas, and excavate pilot tunnels layer by layer according to the divided construction areas. After the slag is discharged from the pilot tunnels on each layer, a corresponding closed supporting structure is installed. Permanent support arch, temporary invert and temporary intermediate wall support;

S22, using the step construction method to excavate a pilot tunnel in the area corresponding to the right half of the section.

In one embodiment, step S21 in this application includes: dividing the left half-section into a first construction area and a second construction area from top to bottom; step S22 includes: adopting the third construction area corresponding to the right half-section The two-step bench construction method excavates the pilot tunnel.

In one embodiment, step S3 in the present application further includes: the fourth construction area and the fifth construction area between the temporary invert at the lower part of step S2 and the pre-constructed invert. Excavate the pilot tunnel in a way, and install the corresponding permanent support arch after the slag is discharged;

The fourth construction area and the fifth construction area are correspondingly distributed on the left half-section and the right half-section respectively, and the lower side of the fourth construction area and the fifth construction area is the sixth construction of pre-inverted arch area.

In one embodiment, the pilot tunnel excavated in the second construction area described in this application lags behind the pilot tunnel excavated in the first construction area by a first preset distance; the pilot tunnel excavated in the third construction area A second preset distance behind the pilot tunnel excavated in the second construction area; the pilot tunnel excavated in the fourth construction area lags behind the pilot tunnel excavated in the third construction area by a third preset distance; The pilot tunnel excavated in the fifth construction area lags behind the pilot tunnel excavated in the fourth construction area by a fourth preset distance.

In one embodiment, in the present application, both the temporary intermediate wall support and the permanent support arch are inserted with retraction anchor pipes.

In one embodiment, in step S2 of the present application, the horizontal distance between the tunnel face and the closed section of the inverted arch along the longitudinal direction of the tunnel is less than 35 meters; in step S3, when the inverted arch is excavated once, the horizontal distance along the longitudinal direction of the tunnel is Less than 3m.

(3) Technical effects

The tunnel construction method provided by this application, when constructing the stratum with the Devonian extremely soft carbonaceous slate and weakly weathered dolomitic limestone on the left and right half of the cross-section respectively, the pre-embedded pipe shed is used in advance. Reinforce the water bulging, soft rock, and mud outburst on the left side of the tunnel face to ensure the stability of the stratum in front of the tunnel face. During the construction, the left half section and the right half section were carried out in turn by the middle partition method. Construction and establishment of a temporary closed support structure, and finally an inverted arch, which effectively avoids the collapse of the surrounding rock caused by the concentration of bias stress or the water softening of the surrounding rock, and can effectively resist the settlement and convergent deformation of the weak surrounding rock, thereby ensuring The normal progress of the construction work and the safety of the construction site.

Description of the drawings

In order to more clearly describe the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

Figure 1 is a schematic diagram of the surrounding rock distribution on the face of the tunnel currently facing during tunnel construction;

2 is a schematic diagram of a cross-sectional structure of a tunnel excavated according to an embodiment of the application;

FIG. 3 is a schematic diagram of a top view structure of a tunnel excavation shown in an embodiment of the application;

FIG. 4 is a flowchart of a tunnel construction method shown in an embodiment of the application;

Fig. 5 is a flowchart of further construction of step S1 shown in an embodiment of the application;

Fig. 6 is a flowchart of further construction of step S2 shown in an embodiment of the application.

In the figure: 1. Left half section; 2. Right half section; 3. First permanent support arch; 4. First temporary inverted arch; 5. First temporary intermediate wall support; 6. Second permanent support Arch; 7. The second temporary invert; 8. The second temporary intermediate wall support; 9. The third permanent support arch; 10. The fourth permanent support arch; 11. The fifth permanent support arch ; 12. The sixth permanent support arch; 13. The pre-embedded advanced pipe shed; 14. The anchor pipe with reduced foot.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by a person of ordinary skill in the art without creative work shall fall within the protection scope of this application.

In the description of this application, it should be noted that the terms "installation", "connection", and "connection" should be understood in a broad sense, unless otherwise clearly specified and limited. For example, it can be a fixed connection or a detachable connection. Connected or integrally connected; 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 internal communication between two components. For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in this application can be understood under specific circumstances.

Referring to Fig. 4, an embodiment of the present application provides a tunnel construction method used in transverse semi-soft and semi-hard section stratum, including:

Specifically, referring to Figures 1 to 2, the tunnel construction method shown in this embodiment is composed of Devonian extremely soft carbonaceous slate and weakly weathered dolomitic limestone in the left half and right half of the cross-section 1, respectively. When the stratum is being constructed, the pre-embedded advanced pipe shed 13 is used to reinforce the water, soft rock, and mud bursting parts on the left side of the tunnel face in advance to ensure the stability of the stratum in front of the tunnel face, and the construction is in progress. When using the middle partition method to construct the left half-section 1 and the right half-section 2 respectively, and establish a temporary closed support structure, which can ensure the stability of the initial support structure, and can be further used for permanent construction at the bottom of the tunnel. Supporting arch frame and composite lining, which effectively avoids the problem of collapse caused by the concentration of bias stress or the softening of the surrounding rock in contact with water, and can effectively resist the settlement and convergence deformation of the weak surrounding rock, thereby ensuring the normal progress of construction operations And the safety of the construction site.

Further, this embodiment further includes: before step S1, performing drainage treatment on the area where water gushing occurs on the palm face, and temporarily supporting the construction area on the back side of the palm face.

Specifically, the drainage treatment on the area where water gushing occurs on the tunnel face is mainly aimed at the water gushing on the left half section 1. Due to the serious collapse and water gushing in the left half of the section 1, firstly, the face of the face was closed with plain sprayed C25 concrete, and the muck was back-pressured to backfill the arch toe of the excavation and support section behind the face, and only the arch foot was reserved. The space for excavation and construction, the purpose of this move is to prevent the collapse from continuing to expand.

In addition, the construction method of the temporary support is as follows: the temporary invert and the hoop arch are aligned and arranged so that they can be closed into a ring and jointly bear the stress of the surrounding rock of the vault. Among them, the temporary invert is made of I20a steel. , Arranged in sequence along the longitudinal direction of the tunnel, with an interval of 1.2m.

Further, referring to FIG. 5, step S1 in this embodiment further includes:

S11, the steel pipe embedded in the advanced pipe shed is used as a drill pipe for drilling. The head end of the steel pipe is connected to the guide plate drill bit, and the tail end of the steel pipe is connected to the drilling rig. The steel pipe is drilled from the first section of the steel pipe to the second section. The steel pipes are alternately connected, and there is an overflow hole on the second section of the steel pipe;

Specifically, in this embodiment, when the pre-embedded advanced pipe shed 13 is constructed, the diameter of the steel pipe is 108mm, the wall thickness is 6mm, and the 4m long first section of steel pipe is alternately connected with the 6m long second section of steel pipe. In addition, the first section of steel pipe and the second section of steel pipe are connected by a thread.

Since there is an overflow hole on the second section of the steel pipe, grouting is injected into the alternately connected steel pipes, which can form an advanced supporting rigid body in the corresponding stratum. By controlling the grouting pressure of the grouting pump, the When the diffusion radius is greater than 45cm, it can ensure that the fullness of the embedded advanced pipe shed 13 for staggered grouting meets the standard, and it can also be used for secondary grouting through the overflow hole on the second section of the steel pipe. The injected grout is a grout that is easy to set and harden.

Further, referring to FIG. 2, in this embodiment, the vertical centerline of the tunnel is set to K1, and the symmetrical centerline of the embedded advanced tube shed 13 is K2, then the size of the central angle α of the embedded advanced tube shed 13 is It is 90°～120°, the angle β of the symmetrical center line K2 of the pre-embedded leading pipe shed 13 from the vertical center line K1 of the tunnel towards the left half section 1 is 10°～20°; the extrapolation angle of the steel pipe is 10°～ At 30°, the slurry injected into the steel pipe is preferably a glass double slurry.

Specifically, in this embodiment, it is preferable that the pre-embedded advanced pipe shed 13 is formed by arranging 45 steel pipes along the vault (circumferential direction) of the tunnel. The length of the steel pipes is 30m, and the circumferential spacing of the steel pipes is 30cm; in actual drilling When using a guide instrument to control the accuracy of the extrapolation angle of the steel pipe, so that the extrapolation angle of the steel pipe is 10°～30°, and the YZB-5 type double-slurry grouting pump is used to fill the steel pipe with double-glass grout. When grouting steel pipes, follow the principle of down first and then up, first thinning and then thickening, and grouting with separate holes. If necessary, intermittent grouting can be used for construction.

Further, referring to FIG. 6, step S2 in this embodiment further includes:

S21: Divide the left half of the cross-section into multi-layer construction areas from top to bottom, and excavate pilot tunnels layer by layer according to the divided construction areas. After the slag is discharged from the pilot tunnels on each layer, a permanent support corresponding to the closed supporting structure is installed. Arch retaining frame, temporary invert and temporary intermediate wall support;

S22, using the step construction method to excavate a pilot tunnel in the area corresponding to the right half of the cross-section.

Specifically, referring to Figures 2 and 3, the full-section tunnel face is divided into the first construction area, the second construction area, the third construction area, the fourth construction area, the fifth construction area, and the sixth construction area. The corresponding numbers of the six construction areas are ①, ②, ③, ④, ⑤ and ⑥.

In the actual construction, first, select the first construction area (upper left) for mechanical excavation and construction of the pilot tunnel, spray 8cm thick concrete to close the corresponding tunnel face in this area, and after the slag is discharged, the corresponding hole in the upper left Install the steel mesh and the first permanent support arch 3 on the arch, lay the mesh on the vertical wall corresponding to the right half of the section 2, and seal it with initial spraying. Then, install the first temporary intermediate wall support 5, and then The first temporary invert 4 is installed in a horizontal position, and the first permanent support arch 3, the first temporary invert 4 and the first temporary intermediate wall support 5 form a closed support structure.

Secondly, select the second construction area (middle left) for mechanical excavation and construction of the pilot tunnel, spray 8cm thick concrete to close the corresponding tunnel face in this area, and install steel mesh on the corresponding arch in the middle left after the slag is discharged According to the above operation, install the second temporary invert 7 in the horizontal position and install the second temporary intermediate wall support 8 on the vertical wall according to the above operation. Among them, the first permanent support arch 3 is butted along the axial direction with the second permanent support arch 6, the second temporary intermediate wall support 8 and the first temporary intermediate wall support 5 are butted in the vertical direction, and then the first temporary invert 4 is removed. At this time, The first permanent support arch 3, the second permanent support arch 6, the second temporary invert 7, the second temporary intermediate wall support 8 and the first temporary intermediate wall support 5 constitute a closed support structure.

It can be seen that for the construction of the left half section 1, the pilot tunnel is excavated in layers by dividing multiple construction areas, and immediately after excavation, a closed ring supporting structure is constructed, which further effectively avoids the stress due to bias. The collapse of concentrated or surrounding rock caused by water softening, and can effectively resist the settlement and convergence deformation of weak surrounding rock.

In addition, this embodiment uses a two-step step construction method to excavate the pilot tunnel for the third construction area (upper right).

Specifically, since the surrounding rock of the right half section 2 is mixed with dolomitic limestone, the block structure, and the stability of the surrounding rock is acceptable, the weak blasting method can be used to excavate the pilot tunnel when the two-step construction is carried out. After the slag is discharged , Install the third permanent support arch 9 on the corresponding arch on the upper right, the first spray is closed, and the first temporary intermediate wall support 5 and the second temporary intermediate wall support 8 are removed, facing the second temporary invert 7 The right half section 2 is extended so that the first permanent supporting arch 3, the second permanent supporting arch 6, the second temporary invert 7 and the third permanent supporting arch 9 form a closed supporting structure, Even if the supporting arch frame of the upper half of the entire tunnel is closed into a ring with the second temporary invert 7, the stability of the initial support is ensured.

Further, in the concrete construction of this embodiment, when the permanent supporting arch frame and the temporary invert at the lower part of the left half section and the right half section are respectively constructed along the vault to initially establish an integrated closed support structure, the selection is also selected The fourth construction area (lower left) is micro-blasted, the pilot tunnel is excavated, and after the slag is discharged, the fourth permanent support arch 10 is installed, and the first spray is closed; then, the fifth construction area (lower right) is selected for micro-blasting. After blasting, excavating the pilot tunnel, and after the slag is discharged, the fifth permanent support arch 11 is installed, and the first spray is closed. Among them, the fourth construction area and the fifth construction area are located at the temporary elevation when the overall closed support structure is initially established. The underside of the arch.

In addition, the sixth construction area (lower bottom) is selected for micro-blasting and excavation. After the slag is discharged, the sixth permanent supporting arch 12 is installed, so as to complete the full-section arch closed into a ring, and first spray closed.

It should be pointed out here that in order to ensure that the permanent supporting arches on the left and right sides of the upper section are not suspended at the same time, when the fourth and fifth construction areas are constructed, the excavation guide shall be carried out in a staggered manner. After excavation, spray 8cm thick concrete to seal the face of the corresponding area.

Further, referring to FIG. 3, the pilot tunnel excavated in the second construction area in this embodiment lags behind the pilot tunnel excavated in the first construction area by the first preset distance, and the first preset distance can be set to 3m; third The pilot tunnel excavated in the construction area lags behind the second preset distance of the pilot tunnel excavated in the second construction area, and the second preset distance can be set to 5m; the pilot tunnel excavated in the fourth construction area lags behind the third construction area The third preset distance of the excavated pilot tunnel, the third preset distance can be set to 20m; the pilot tunnel excavated in the fifth construction area lags behind the fourth preset distance of the pilot tunnel excavated in the fourth construction area, and the fourth preset distance The preset distance can be set to 3m, the pilot tunnel excavated in the sixth construction area lags the fifth preset distance of the pilot tunnel excavated in the fifth construction area, and the fifth preset distance can be set to 4m.

Further, in order to ensure the stability of the supporting structure and resist the influence of the deformation of the surrounding rock on the supporting structure, in this embodiment, the anchor pipes with reduced feet are inserted at the temporary intermediate wall supporting and each permanent supporting arch.

It should be pointed out here that this embodiment takes into account that the tunnel design adopts an elliptical force-bearing section, and the part above the center of the tunnel is in the best force. Therefore, the bottom surface of the middle step obtained from the construction of the left middle part is set on the horizontal axis of the center of the circle. Maximize the stability of the primary support structure. In order to meet the requirements of mechanized construction, it is determined that the height of the upper step obtained by the construction of the upper left part of the left half section 1 is set to 3.8m, the height of the middle step is set to 2.6m, and the right half section 2 is set to the height of the upper step during the two-step construction. It is set at 6.4m, the height of the steps under the entire section is set at 1.9m, and the invert excavation depth is set at 1.8m. In addition, because the surrounding rock of the formation is extremely unstable, in order to ensure absolute safety during construction, the horizontal distance between the tunnel face and the closed section of the inverted arch along the longitudinal direction of the tunnel is set to be less than 35 meters, and the excavation distance of the inverted arch shall not be greater than 3m. The closed invert section refers to the section where the full-section arch frame is initially closed into a ring.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the application, not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: The technical solutions recorded in the foregoing embodiments are modified, or some of the technical features are equivalently replaced; these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

A tunnel construction method used in transverse semi-soft and semi-hard section stratum, which is characterized in that it comprises:

S1, pre-embedded and advanced pipe sheds are applied to the tunnel arch area corresponding to the tunnel face;

S2. Use the middle partition method to construct the soft rock distribution on the left half of the section and the hard rock distribution on the right half of the section in turn. After the excavation is completed, remove the temporary middle partition support, and ensure that the upper part of the left half section and the right half section The permanent supporting arch frame constructed along the vault and the temporary invert at the lower part form a closed supporting structure;

S3. Carry out invert excavation, construct permanent arch support at the bottom of the tunnel, remove temporary invert, and construct composite lining.
The tunnel construction method according to claim 1, wherein:

It also includes: prior to step S1, performing drainage treatment on the area where water gushing occurs on the tunnel face, and temporarily supporting the construction area on the back side of the tunnel face.
The tunnel construction method according to claim 1, wherein:

Step S1 further includes:

S11, the steel pipe in the pre-embedded advanced pipe shed is used as a drill pipe for drilling. The head end of the steel pipe is connected to the guide plate drill bit, and the tail end of the steel pipe is connected to the drilling rig. The two sections of steel pipes are alternately connected, and the second section of steel pipes are provided with overflow holes;

S12. Remove the drilling rig and connect the grouting pump to the end of the steel pipe. The initial pressure of the grouting pump is controlled to be 0.5～1.0MPa and the final pressure is 2.0～3.0MPa during grouting, so that the spreading radius of the slurry is greater than 45cm .
The tunnel construction method according to claim 3, wherein:

The central angle of the pre-embedded advanced tube roof is 90°～120°, and the symmetrical center line of the embedded advanced tube roof deviates from the vertical center line of the tunnel by 10° toward the left half section. ~20°; the extrapolation angle of the steel pipe is 10°-30°, and the slurry injected into the steel pipe is a glass double slurry.
The tunnel construction method according to claim 1, wherein:

Step S2 further includes:

S21: Divide the left half-section from top to bottom into multi-layer construction areas, and excavate pilot tunnels layer by layer according to the divided construction areas. After the slag is discharged from the pilot tunnels on each layer, a corresponding closed supporting structure is installed. Permanent support arch, temporary invert and temporary intermediate wall support;

S22, using the step construction method to excavate a pilot tunnel in the area corresponding to the right half of the section.
The tunnel construction method according to claim 5, wherein:

Step S21 includes: dividing the left half section into a first construction area and a second construction area from top to bottom;

Step S22 includes: excavating a pilot tunnel with a two-step step construction method in the third construction area corresponding to the right half of the cross-section.
The tunnel construction method according to claim 6, wherein:

Step S3 also includes: for the fourth construction area and the fifth construction area between the temporary invert at the lower part of step S2 and the pre-constructed invert, the pilot tunnel is excavated in a staggered construction method, and the exit After the slag, set the corresponding permanent support arch;

The fourth construction area and the fifth construction area are correspondingly distributed on the left half-section and the right half-section respectively, and the lower side of the fourth construction area and the fifth construction area is the sixth construction of pre-inverted arch area.
The tunnel construction method according to claim 7, wherein:

The pilot tunnel excavated in the second construction area lags behind the pilot tunnel excavated in the first construction area by a first preset distance;

The pilot tunnel excavated in the third construction area lags behind the pilot tunnel excavated in the second construction area by a second preset distance;

The pilot tunnel excavated in the fourth construction area lags behind the pilot tunnel excavated in the third construction area by a third preset distance;

The pilot tunnel excavated in the fifth construction area lags behind the pilot tunnel excavated in the fourth construction area by a fourth preset distance.
The tunnel construction method according to claim 1, wherein:

Retractable anchor pipes are inserted at the temporary intermediate wall support and the permanent support arch.
The tunnel construction method according to any one of claims 1-9, characterized in that:

In step S2, the horizontal distance between the tunnel face and the closed section of the inverted arch along the longitudinal direction of the tunnel is less than 35 meters;

In step S3, when the invert is excavated once, the horizontal distance along the longitudinal direction of the tunnel is less than 3m.