JP3103285B2 - Tunnel excavation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tunnel excavation method in which a tunnel face is divided into an upper bench and a lower bench, and the ground of each bench is excavated. It is.

[0002]

2. Description of the Related Art Conventionally, when a tunnel is excavated by a two-stage bench-cutting method, first, a cutting ground of an upper bench is excavated, and excavated earth and sand are carried out. Construction work, concrete spraying work is sequentially performed to perform temporary lining, and then excavation work is performed on the face ground of the lower bench. Temporary lining is being carried out by sequentially spraying concrete. Further, an invert is excavated on the bottom of the tunnel behind the lower bench, concrete is poured into the invert, and concrete for secondary lining is cast behind the invert to construct a tunnel.

[0003]

However, according to the tunnel excavation by the two-stage bench cut method as described above, a series of operations from the excavation of the face to the spraying of concrete on the excavated ground are performed on the upper bench. After performing the operation, the operation shifts from excavation work on the lower bench to spraying concrete on the excavation ground. Therefore, there is a problem that the workability of tunnel excavation is poor and a long construction period is required.

[0004] Such a problem can be solved by excavating the face ground of the upper bench and the lower bench at the same time and carrying out the excavated soil by a soil transport vehicle such as a dump truck. If the soil carrier is driven near the excavation site in a tunnel with a narrow space, the soil carrier will be mixed and dangerous, and in addition, the invert excavation work and concrete placement work on the rear side will be hindered. As a result, simultaneous drilling is difficult in practice.

[0005] The present invention has been made in view of the above-mentioned problems, and an object thereof is from excavation of earth and sand to the face ground of an upper bench and a lower bench to spraying of primary lining concrete on an excavated wall surface. It is an object of the present invention to provide a method of excavating a tunnel in which a series of steps and a concrete placing operation for an invert can be performed in parallel, and a tunnel excavating operation can be performed efficiently.

[0006]

In order to achieve the above object, a method for excavating a tunnel according to the present invention comprises dividing a tunnel face into an upper bench and a lower bench and excavating the face ground of both benches. A method of excavating a tunnel, wherein a front end pillar is movably supported on the upper bench, and a rear pillar is movably supported on inverted concrete behind a cutting face. The excavated sediment transporting device is suspended, and the excavated soil of the upper and lower benches is conveyed to the rear of the tunnel by the transporting device, and is carried out to the sediment transporting vehicle waiting at the rear end of the gantry. After carrying out the earth and sand, the primary lining from the installation of the support to the excavation wall of the upper and lower benches to the spraying of the concrete was carried out in parallel. Below the over is characterized in carrying out the pouring drilling and invert concrete new inverted in contact with the existing invert concrete.

In the above method, the excavation process of the face ground of the upper bench and the excavation process of the face ground of the lower bench are simultaneously performed, and the excavated earth and sand of the upper bench is carried out to the lower bench. The excavated soil of the face ground of the upper bench may be transported to the rear of the tunnel by a transport device suspended from the gantry together with the excavated ground of the lower bench. , The excavated earth and sand on the face ground of the lower bench may be carried out to the rear of the tunnel by the above-mentioned transport device. The invention described in claim 4 has a structure in which a trolley for transporting a support material or the like is movably disposed on the gantry.

[0008]

[Function] A gantry equipped with an excavated earth and sand transport device is movably installed in a state of being erected between the upper bench and the invert concrete, and the earth and sand excavated by an excavator on both benches is installed in the gantry. It is carried out to the rear end of the gantry by the device. At that time, the excavation work of the face of both benches is performed at the same time, and each excavated earth and sand is carried out by the transport device arranged in the gantry. Also, the excavated earth and sand on the upper bench side can be dropped onto the lower bench, and can be carried out from the lower bench side by a transport device. The excavated earth and sand on the lower bench side may be carried out after the excavated earth and sand on the upper bench side are carried out by the transport device.

Since the excavated earth and sand is carried out along the gantry which is installed so as to be able to travel from the upper bench to the invert concrete, the space below the gantry is not hindered by the earth and sand unloading operation. The assembly of the formwork for the invert and the concrete placement work can be performed in parallel at the section. Also, after discharging the excavated earth and sand on the upper bench side, while performing the primary lining from the construction of the support to the spraying of concrete on the excavation wall of the upper bench,
After the excavated earth and sand is discharged on the lower bench side, primary lining is performed in parallel with the upper bench side from the installation of the support to the spraying of concrete on the excavated wall.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
As shown in FIG. 1, the upper half of the face portion of the tunnel T is divided into an upper bench 1 and the lower half is divided into a lower bench 2, and the cutting ground of the upper and lower benches 1 and 2 is moved in the tunnel T excavation direction. After excavating for a certain length, the excavated earth and sand is removed, and after excluding the earth and sand, the primary lining 3 from the installation of the support to the spraying of the concrete on the excavated wall of the upper and lower benches 1 and 2 is performed in parallel. On the other hand, on the tunnel bottom surface behind the lower bench 2, the work of digging the invert 4 and placing the concrete 5 is performed in parallel with the work of the primary lining 3 from removing the excavated earth and sand.

A fixed length of the cutting ground relative to the upper and lower benches 1 and 2 (a distance of the support work is about 1 m).
The work process from excavation to the primary lining 3 as one cycle is 5 to 10 cycles, and the work process from excavation of the invert 4 to casting of concrete, which is performed during this cycle, is sequentially set as a construction length of one span. The tunnel is excavated by repeatedly performing the above-described operation steps during the span.

The excavation of the face ground of the upper bench 1 is performed by a cutter loader 6 having an arm 6b having a cutter 6a at the tip thereof, which is rotatable up and down, and a belt conveyor 6c provided at the rear end of the arm 6b. The arm 6b is provided with a chain conveyor (not shown) for scraping earth and sand excavated by the cutter 6a and transporting it to a belt conveyor 6c. On the other hand, excavation of the face ground of the lower bench 2 is performed by an excavator / loader 7 composed of a backhoe (shovel machine).

The excavated earth and sand is conveyed from the face of the tunnel T to the rear of the tunnel by a conveying device 9 provided on the gantry 8. The gantry 8 is provided with a pillar 82 at the front end of a horizontal long frame 81 which is erected in the length direction of the tunnel from above the upper bench 1 to above the inverted concrete 5 which has already been cast. The footnote 82 at the end
A longer pillar 83 is provided integrally. The long frame 81 is, as shown in FIGS.
A pair of upper and lower horizontal beams 8 horizontally arranged on both upper sides of
The structure has a structure in which the space between 4 and 85 is integrally connected by a vertical beam 86 at appropriate intervals in the length direction, and the upper beam members 84 and 84 are integrally connected by a horizontal beam 87.

As shown in FIG. 2, the short pillar 82 at the front end supporting the long frame 81 of the gantry 8 is provided at the foremost horizontal girder.
A running body 88 composed of an infinite crawler shoe that runs on the horizontal bottom surface of the upper bench 1 is attached to the lower ends of both side pillars 82, 82. The running body 88 is driven by a motor 88a. The gate-shaped space formed by the both-side pillars 82, 82 and the cross beam 87 is formed in such a size that the cutter loader 5 can freely enter and exit.

On the other hand, as shown in FIG. 1 and FIG. 3, the long pillar 83 on the rear side supporting the long frame 81 of the gantry 8 is located at a position slightly behind the center of the long frame 81. With front legs 83, 83 having upper ends fixed to both ends of the cross beam 87,
Rear pillars 83, 83 having upper ends fixed to both ends of the cross beam 87 near the rear end thereof, and at the lower ends of these rear front and rear pillars 83, the already-inverted concrete 5 Wheels 89 running on rails 10 laid thereon are rotatably supported. The wheels 89 are configured to be positively driven to rotate by a drive motor (not shown) provided at an appropriate position on the long frame 81.

The transporting device 9 disposed on the gantry 8 has a structure in which, for example, a belt conveyor 91 is movably supported by a long frame 81. Specifically, as shown in FIGS. 1 and 3, suspension support rails 92, 92 are provided on the lower surfaces on both sides of the center of the cross beam 87 of the long frame 81 over substantially the entire length of the long frame 81. Sticks,
A plurality of gate-shaped support frames 93 are supported on these suspension-support rails 92, 92 so as to be able to travel via wheels 94, and are juxtaposed at appropriate intervals.
The lower end of 93 is integrally fixed to both side surfaces of a rear horizontal conveyor frame 95 that houses the rear half of the belt conveyor 91. Further, at the front end of the rear horizontal conveyor frame 95, the rear end of a front tilting conveyor frame 96 which houses the front half of the belt conveyor 91 is pivotally mounted 97 so as to be vertically rotatable. The lower end of the chain block 99 is fixed to a frame 98 fixed to the frame 98, and the upper end of the chain block 99 is connected to the wheels 94 running along the suspension rails 92. Reference numeral 18 denotes a hopper attached to the front end of the tilting conveyor frame 96.

Therefore, by rotating the wheels 94 via an appropriate drive mechanism (not shown), the gate-shaped support frame 93 is rotated.
And the front and rear conveyor frames 95, 96 which integrally incorporate the belt conveyor 91 with the chain block 99, the suspension support rail 92,
The tiltable conveyor frame 96 is configured to be movable in the length direction of the gantry 8 along 92 and by operating the chain block 99 from the downward inclined state to the horizontal state with respect to the rear horizontal conveyor frame 95. It is configured to undulate. In addition, the gate type support frame 93 and the chain block
Naturally, the upper end of 99 is not directly hung from the wheel 94, but is integrally connected to the bearing member 11 which rotatably supports the wheel 94. The belt conveyor 91 is also driven to run endlessly by driving means (not shown) such as a motor disposed at the rear end of the rear horizontal conveyor frame 95. The length of the belt conveyor 91 is formed to extend from the lower bench 2 to the rear end of the gantry 8.

The gantry 8 has trolleys 12 running on both sides of the transport device 9 in the longitudinal direction of the gantry 8,
12 are arranged. In this trolley 12, a trolley suspension support rail 13 is fixed to the lower surface on both sides of the central portion of the cross beam 87 of the long frame 81 over substantially the entire length of the long frame 81, and an appropriate drive mechanism (not shown) ) Travels along the rail 13 in the front-rear direction, and carries and supports a shoring, a wire mesh, a formwork, or the like. Further, an upper rail 14 is laid on the long frame 81 of the gantry 8 over its entire length.
A concrete spraying machine 15 is provided on the upper front side and a ventilation axial fan 16 is provided on the rear side so as to be freely movable. Also, as shown in FIG. 2, a work cage 17 is provided on both upper sides of the front end of the long frame body 81 of the gantry 8.

The gantry 8 constructed as described above is horizontally installed from the upper bench 1 to the existing invert concrete 5 and its front and rear pillars 82 and 83 are respectively connected to the horizontal bottom surface of the upper bench 1 and the existing bottom. In this state, the excavated earth and sand are carried out during the excavation of the tunnel in this state. Next, the work order of the excavation of the tunnel is determined by the gantry 8 and the upper bench. 1, the lower bench 2, and the invert 4 will be described with reference to FIG.

First, when hardening of the invert concrete 5 for one span is completed, the invert concrete 5
The gantry 8 is advanced upward by the support interval (about 1 m). Hereinafter, this forward movement is defined as one cycle, and by repeating 5 to 10 cycles, the wheels 89 of the rear leg 83 of the gantry 8 run on the existing inverted concrete 5. On the other hand, the traveling body 88 of the front pillar 82 of the gantry 8
Is advanced by the drive motor 88a on the horizontal bottom surface of the upper bench 1 for the next cycle.

On the other hand, the transporting device 9 waiting on the rear side of the gantry 8 is advanced along the rail 92, and when the front tilting conveyor frame 96 reaches above the rear end of the lower bench 2, the tilting conveyor frame 96 is moved. 96 is rotated downward so that its front end is set on the rear end of the lower bench 2. Then, in the upper and lower benches 1 and 2, the cutting ground is simultaneously excavated by the cutter loader 6 and the excavator / loader 7, respectively, and the excavated earth and sand of the upper bench 1 is removed from the lower bench 2 by the belt conveyor 6c of the cutter loader 6 from behind. Falling on,
Deposit.

The excavated ground on the upper bench 1 side together with the excavated earth and sand on the lower bench 2 side is mounted on the front end of the tilting conveyor frame 96 of the conveyor 9 by the excavator / loader 7.
18 and is loaded on the transfer start end of the belt conveyor 91 of the transfer device 9 facing the lower end of the opening of the hopper 18 and transferred from the tilting conveyor frame 96 to the rear end side of the gantry 8 through the horizontal conveyor frame 95. Then, it is transferred to a transport vehicle 19 such as a dump truck waiting at the rear end of the gantry 8, and is carried out behind the tunnel.

In this way, when the face ground of the upper and lower benches 1 and 2 is excavated and removed by the tunnel length corresponding to the support interval, the primary lining 3 is formed on the excavation wall surface of the upper and lower benches 1 and 2. I do. The divided shoring and wire mesh for the primary lining are transported from the rear of the gantry 8 to the upper and lower benches 1 and 2 by the trolleys 12 and 12 arranged on the gantry 8, and are placed on the work cage 17. After the worker performs wire mesh work between the erection work on the excavation wall and the existing shoring work on the top face of the shoring work, the shoring work is carried out by the spraying machine 15 arranged on the upper surface of the front end of the gantry 8. The primary lining work is completed by spraying concrete up to the thickness.

On the lower bench 2 side, before the primary lining 3 is performed, the tilting conveyor frame 96 of the transporting device 9 is lifted by the chain block 99 to be in a horizontal state like the horizontal conveyor frame 95 on the rear side. Then, the entire transport device 9 is moved to the rear side of the gantry 8 and kept in standby so as not to hinder the primary lining work. Further, dust is generated when the concrete is sprayed by the spraying machine 15, and therefore, it is desirable to continuously perform the spraying operation on the lower bench 2 after the spraying operation on the upper bench 1 side.

When the work process of one cycle from excavation of the face ground to the upper and lower benches 1 and 2 to the primary lining is completed in this way, the excavation of the face ground for the support interval together with the advance of the gantry 8 in the same manner as described above. From 1 to the primary lining, and this process is repeated for 5 to 10 cycles.

On the other hand, in the inverting section,
In parallel with the ten-cycle work process, a concrete placing operation is performed on the invert 4 that has been continuously excavated for one span on the front end side of the existing invert concrete 5 before the first cycle. In this work, the formwork 20 removed from the invert concrete 5 after the previously cast invert concrete 5 has hardened is suspended by the trolley 12 arranged on the gantry 8 and transported to above the invert concrete 4. Set it down.

As shown in FIGS. 1, 4 and 5, this formwork 20 has a plurality of horizontal girders 21, 21 which are long in the length direction of the tunnel and are juxtaposed at appropriate intervals in the length direction. At the same time, they are integrally connected by beams 22, and a wand form 23 is suspended from the underside of the front ends of the girders 21 and 21, and the front end of the girder 21 projecting forward from this wive form 23 is expanded and contracted by jacks. Free leg
At the same time, a leg 26 with a roller 25 is attached to the rear end of the spar 21 by a jack. Further, side wall forms 27, 27 are mounted on both side ends of the juxtaposed beams 22, and a groove-shaped passage forming form 28 is provided at an appropriate position between the girders 21, 21 from the end form 23 to the back. It is arranged toward.

[0028] The mold 20 constructed as described above is mounted on an invert 4
Position the front leg 24 in the lower bench 2
The rear leg 26 is set on the front end of the existing invert concrete 5 while being installed on the bottom surface of the front end of the invert 4 in the vicinity and the height is adjusted by the two legs 24 and 26 to excavate the wife form 23 and the like. Close to a predetermined part of the surface. Thereafter, concrete 5a is poured into the invert 4 from behind the gantry 8 by a concrete mixer truck or the like.

During the curing of the poured concrete 5a, until the concrete is hardened, and after forming the primary lining 3 for one span with respect to the upper and lower benches 1, 2, the bottom of the lower bench 2 is excavated and piled. The excavator 7 is excavated in a curved shape in a tunnel shape by the insertion machine 7 to excavate an invert for the next one span. This excavated earth and sand may be carried backward by the above-mentioned transport device 5 while excavating, but since the excavation amount is relatively small, the excavated earth and sand is temporarily deposited on the lower bench 2, and excavation of the face ground of the lower bench 2 is performed. It can be carried out by the transport device 5 together with the earth and sand. As shown in FIG. 5, a secondary lining is applied to the thickness portion 30 between the primary lining 3 and the side wall forms 27, 27 at the rear of the tunnel.

As described above, the work process of the primary lining 3 from the excavation of the face ground to the upper and lower benches 1 and 2 is sequentially performed for several cycles to excavate the tunnel for one span, and at the same time, From the excavation of the invert to the concrete placement on the lower bench 2 side, the work is continued from the existing invert concrete 5 to the length of the span, and the tunnel formation of this unit span and the invert concrete 5
The construction of the tunnel is carried out by repeating the construction in sequence. After the concrete is hardened, the running rail 10 of the gantry 8 is laid on the invert into which the concrete is cast.

In the above embodiment, the gantry 8
, And a front end of a tilting conveyor frame 96 of the conveyance device 9 is arranged on a rear end of the lower bench 2, and excavation of the upper bench 1 dropped on the lower bench 2 is performed. The excavated earth and sand on the lower bench 2 side together with the earth and sand is carried out rearward by the transporting device 9, but as shown in FIG. 6, two transporting devices 9a and 9b are provided in the gantry 8 and one of the transporting devices 9a and 9b is provided. The excavated earth and sand on the upper bench 1 side and the excavated earth and sand on the lower bench 2 side may be simultaneously conveyed to the other conveying device 9b by the transport device 9a.

FIG. 10 shows a working process diagram of another excavation method for the upper and lower benches 1 and 2. In the above embodiment, the excavation of the face ground of the upper and lower benches 1 and 2 was performed simultaneously. In, after excavating the face ground of the upper bench 1 for the support interval and transporting it rearward by the transport device 9, excavating the face ground of the lower bench 2 for the support interval and transporting it rearward by the transport device 9. It is characterized by points.

That is, the tilting conveyor frame 96 of the conveying device 9 is lifted up to a horizontal state by the chain block 99, and in this state, the conveying device 9 is advanced along the rail 92, and the front end of the conveyor frame 96 is moved to the upper bench 1 The earth and sand excavated by the cutter loader 6 are put into the hopper 18 and conveyed backward by the belt conveyor 91 while facing the rear end. Next, the transporting device 9 is retracted, the tilting conveyor frame 96 is tilted downward by the chain block 99, and the excavating / loading machine 7 is set in a state where the lower tilting end is positioned on the rear end of the lower bench 2.
The earth and sand on the face ground of the lower bench 2 excavated by the above is carried out rearward by the belt conveyor 91 of the conveying device 9.

When the removal of the earth and sand from the upper and lower benches 1 and 2 is completed, the respective excavated walls are subjected to the transport of the support, the building, the wire mesh installation, and the primary lining by spraying the concrete in the same manner as in the above embodiment. This process is defined as one cycle, and as described in the above embodiment, the primary lining work for one span and the casting of the inverted concrete 5 are performed. Other working steps and the like are the same as the working steps in FIG. According to this method, it is suitable when the amount of excavation of the face ground of the lower bench 2 is large, and if the excavated soil is removed together with the excavated earth and sand on the side of the upper bench 1, it is possible to avoid the problem that the working time is long. In addition, when the upper bench 1 is excavated, the tilting conveyor frame 96 is lifted in a horizontal state, so that the work space on the lower bench 2 is widened, and the movement, assembly, and concrete casting work of the invert form 20 are performed in the upper stage. When the bench 1 is excavated, it can be easily and safely performed.

FIGS. 7 and 8 show another example of the transport device 9. In the above-mentioned embodiment, the transport device 9 is constituted by a belt conveyor 91, and the conveyor frames 95 and 96 are elongated frames of the gantry 8.
In this example, the electric chain block is attached to suspension rails 31, 31 fixed on both sides of the upper end lower surface of the long frame 81 over the entire length of the frame 81. A trolley 33 provided with 32 is supported so as to be able to travel freely, and a transporting device 9 ′ composed of a bucket whose bottom can be freely opened and closed is hung on these trolleys 33. Thus, the belt conveyor
If a transporting device 9 ′ composed of buckets is used instead of the transporting device 9 consisting of 91, it is possible to transport excavated earth and sand containing water, which is difficult to carry out with a belt conveyor. Other structures and operations are the same as those of the gantry shown in FIG.

[0036]

As described above, according to the tunnel excavation method of the present invention, the tunnel face is divided into an upper bench and a lower bench, and the tunnel is excavated by excavating the face of both benches. A gantry having a front-end-side pedestal movably supported on the upper bench and a rear-side pedestal supported on invert concrete behind the face section is provided with an excavated sediment transport device such as a belt conveyor. Suspension, transport the sediment excavated the face ground of the upper bench and the lower bench to the rear of the tunnel by the transport device and carry it out to the sediment transport vehicle waiting on the rear end side of the gantry, and after carrying out the sediment, The primary concrete lining was carried out in parallel with the erection of the excavation walls of the upper and lower benches, and the existing invert was installed below the gantry. Since it is characterized by excavating new inverts and placing invert concrete in contact with concrete, it is installed in a gantry that is erected from the upper bench to the existing invert concrete. The excavated soil on the face ground of the upper and lower benches can be continuously and smoothly carried out to the rear side of the tunnel by the transport equipment installed, and the kuncrete spraying from the erection work on the excavation wall of the upper and lower benches Since the primary lining is performed in parallel, the excavation work of the tunnel can be performed efficiently, and the construction period can be significantly reduced.

Further, the gantry has its front end pedestal movably supported on the upper bench and its rear pedestal movably supported on the invert concrete behind the cutting face. Efficient removal of excavated earth and sand can be carried out efficiently while advancing according to the length of the primary lining process for a fixed length on the excavated wall, and excavation work of the invert and assembly of a formwork for the invert in the space below the gantry Because it is the work of placing concrete, it is possible to create inverted concrete in parallel with the primary lining work on the upper and lower benches, without hindering the work of carrying out excavated earth and sand,
The operation efficiency of tunnel excavation can be further improved.

Further, by disposing a transport trolley such as a supporter on the gantry so as to be freely movable, members necessary for the primary lining can be easily and easily provided on the upper and lower benches from the rear side of the tunnel through the gantry. It can be transported efficiently, and can also be used for suspending and assembling a concrete casting formwork with respect to the invert, thereby improving workability.

[Brief description of the drawings]

FIG. 1 is a simplified longitudinal side view showing a tunnel excavation state;

FIG. 2 is an enlarged vertical sectional front view of the front end side;

FIG. 3 is an enlarged vertical sectional front view of an intermediate portion thereof;

FIG. 4 is a longitudinal sectional side view showing a form setting state with respect to an invert;

FIG. 5 is a partially cut-out longitudinal front view,

FIG. 6 is a simplified side view of a gantry equipped with two transport devices,

FIG. 7 is a simplified longitudinal side view showing a tunnel excavation state using a bucket as a transport device,

FIG. 8 is an enlarged vertical sectional front view thereof,

FIG. 9 is a block diagram showing a work process of tunnel excavation;

FIG. 10 is a block diagram showing another operation process of tunnel excavation.

[Explanation of symbols]

 T Tunnel 1 Upper Bench 2 Lower Bench 3 Primary Lining 4 Invert 5 Invert Concrete 6 Cutter Loader 7 Excavator / Loader 8 Gantry 9 Transporter 82 Front Leg 83 Rear Leg

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eikichi Kikyo 2-2-2 Matsuzakicho, Abeno-ku, Osaka-shi Okumura Gumi Co., Ltd. (56) References JP-A-56-73795 (JP, A) JP-A-49 -15225 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E21D 9/12 E21D 9/10 E21D 9/00

Claims (4)

(57) [Claims] 1. A method for digging a tunnel by dividing a tunnel face portion into an upper bench and a lower bench, and excavating the face ground of both benches, wherein a front pillar on a front end side can run on the upper bench. The excavated earth and sand transporting device such as a belt conveyor is hung on a gantry that supports the rear leg on the invert concrete behind the face part so that it can run freely, and excavates the face ground of the upper bench and the lower bench. The conveyed sediment is transported to the rear of the tunnel by the above-mentioned transport device and is carried out to the sediment transport vehicle waiting at the rear end of the gantry. The lining was performed in parallel, and a new invert was excavated and inverted in contact with the existing invert concrete below the gantry. A method for excavating a tunnel, comprising casting concrete. 2. The excavation of the face ground of the upper bench and the excavation of the face ground of the lower bench are carried out at the same time, and the excavated earth and sand of the upper bench is carried out to the lower bench, deposited and suspended on the gantry together with the excavated ground of the lower bench. 2. The tunnel excavation method according to claim 1, wherein the tunnel is transported to the rear of the tunnel by a supported transport device. 3. The excavated soil of the face ground of the upper bench is transported to the rear of the tunnel by the transport device, and the excavated soil of the face ground of the lower bench is transported to the rear of the tunnel by the transport device. The tunnel excavation method according to claim 1. 4. The tunnel excavation method according to claim 1, wherein a transport trolley such as a shoring is movably disposed on the gantry.