JP2000038894A - Underground excavator and constructing method of branch type shield tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an underground excavator and a constructing method of a branch type shield tunnel which enable excavation of tunnels with varied sections, including a large-section tunnel and a plurality of small-section tunnels, and which agitate no excessive earth at the time of excavation of the small-section tunnels and have few components becoming unnecessary at the time when the excavation changes from that for the large-section tunnel to that for the small-section ones. SOLUTION: An underground excavator 20 having a constitution wherein a plurality of separate shield machines are connected separably, with a connecting shield machine held between, so that they enable excavation of a tunnel 23 of a section of an underground railway double track station part, in the connected state and wherein the separate shield machines are separated by removing the connecting shield machine so that a plurality of small-section tunnels can be so excavated by each separate shield machine as to branch off from the tunnel 23 of the section of the underground railway double track station part. Each shield machine is provided with excavating parts which excavate a face by conducting parallel link movement respectively, and at the time of excavation of the tunnel 23 of the section of the underground railway double track station part, setting is made so that the excavating parts may excavate the face by conducting the parallel link movement integrally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground excavator suitable for excavating subways, road tunnels, water and sewage systems, etc. The present invention relates to an underground excavator capable of constructing a fork by separating in the ground and excavating as a separate shield machine, and a method of constructing a branch type shield tunnel.

[0002]

2. Description of the Related Art Conventionally, as this kind, there is one described in Japanese Patent No. 2604217 (see FIGS. 17 to 20).

[0003] This is because two shield machines 1, 1 are shown in FIG.
As shown in the figure, the excavating cutters 2 and 2 are rotatably arranged at the front of the shield machines 1 and 1. By rotating the excavating cutters 2 and 2,
The ground has been excavated.

First, in a state where the two shield machines 1 and 1 are connected, as shown in FIG. 18, a subway double-track cross section tunnel 3, which is one tunnel, is excavated. Then, as shown in FIG. The shield machines 1 and 1 are separated from each other, and as shown in FIG. 20, a tunnel 4 having a single-line cross section is excavated.

FIGS. 21 to 24 show another conventional example. This is a triple circular shield machine 6 consisting of a central circular shield machine 7 and a partially circular shield machine 8 arranged on both sides thereof.
Is configured. Excavation cutters 7a and 8a are provided in the circular shield machine 7 and the partially circular shield machine 8, respectively.

[0006] In the triple circular shield machine 6 shown in FIG.
After the subway double track station section tunnel 9 shown in FIG. 22 is constructed, the two broken circular shield machines 8 are separated, and the subway double track cross section tunnel 1 is cut by the circular shield machine 7 shown in FIG.
0 is constructed. In the figure, reference numeral 11 denotes a segment, 12 denotes a railway construction limit, 13 denotes on-site concrete, and 14 denotes a platform.

[0007]

However, FIG.
In FIG. 20 to FIG. 20, since only two shield machines 1 are separated from each other, it corresponds to a change in separation of a single line, but corresponds to a change in cross section from a single line to a station. Can not. Further, in order to excavate the subway double-track cross section tunnel 3 before separation, the excavating cutters 2
Since the excavation areas 2 are set so as to partially overlap with each other, as shown in FIG. 19, when the two shield machines 1 and 1 are separated from each other, the excavation section by the excavation cutter 2 It will be agitated, and in some cases, it is necessary to inject cement milk or the like to reinforce. Therefore, there arises a problem that the construction period and construction cost increase.

In addition, the one shown in FIGS. 21 to 24 can cope with a large cross-section tunnel such as a subway double-track station cross-section tunnel 9, but after separation, the central circular shield machine 7 is used. Therefore, it cannot be used for constructing a plurality of single-line tunnels 4 as shown in FIG. Further, since the two missing circular shield machines 8 are required only for excavation of a large-section tunnel such as a subway double-track station section tunnel 9, it is useless after the triple circular shield machine 6 is separated. Furthermore, since each of the excavating cutters 7a and 8a independently rotates, and since the excavating cutters 7a and 8a are face plates, the excavating cutter 7a of the circular shield machine 7 of the triple circular shield machine 6 is used.
And the excavating cutters 8a of the two cut-out circular shield machines 8 cannot be arranged on the same plane, and there is a step on the face, and the excavation stability is poor.

Therefore, the present invention can excavate a tunnel whose cross section has been changed between a large-section tunnel and a plurality of small-section tunnels. An object of the present invention is to provide an underground excavator and a method of constructing a branch type shield tunnel, which have a small number of unnecessary components when changing the excavation to the cross-section tunnel.

Another object is to improve excavation stability without generating a step on the face.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of separation shield machines are connected so as to be separable with a connection shield machine interposed therebetween. , Enabling the excavation of one large section tunnel,
By removing the connecting shield machine and separating the separation shield machines, underground tunnels that enable excavation of a plurality of small-section tunnels so as to branch off from the one large-section tunnel with each of the separation shield machines An excavator, wherein each of the shield machines is provided with an excavating portion for excavating a face by performing a parallel link motion, and when excavating the large-section tunnel, the excavating portions are integrated into a parallel link motion. , An underground excavator set to excavate a face face on the same plane.

[0012] According to a second aspect of the present invention, in addition to the configuration of the first aspect, when excavating the large-section tunnel,
It is characterized in that the excavating portions of the respective shield machines are integrally formed to perform a parallel link motion to excavate a face in the same plane.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, a separating shield hood portion is provided on a side of the excavating portion of the separating shield machine, and an annular one of the separating shield hood portion is provided. A notch portion is formed on the connection side of the connection shield machine at the connection portion, and a connection shield hood portion is provided on the excavation portion side of the connection shield machine, and when the large-section tunnel is excavated, the separation shield hood portion and the connection shield hood are provided. Are connected to each other to form a shape adapted to the large-section tunnel, and when the small-section tunnel is excavated, the notch is closed by a closing hood to form a shape adapted to the small-section tunnel. It is characterized by being comprised so that.

According to a fourth aspect of the present invention, in addition to the configuration of any one of the first to third aspects, a separation shield tube portion forming an outer shape of the separation shield machine is provided. On the rear side of the part, a separation shield tail part having a tail seal is provided, and a cutout part is formed on the connection shield machine connection side with an annular part of the separation shield tail part, while the outer shape of the connection shield machine is A connecting shield tubular portion to be formed is provided, a connecting shield tail portion having a tail seal is provided on the rear side of the connecting shield tubular portion, and at the time of excavating the large-section tunnel, the separating shield tail portion and the connecting shield tail portion are connected to each other. It is connected and formed in a shape adapted to the large-section tunnel, and when excavating the small-section tunnel, the notch is closed with a closed tail having a tail seal. To characterized in that said configured to be formed in a shape that is adapted to the small section tunnel.

According to a fifth aspect of the present invention, there is provided a branch shield for constructing the large-section tunnel and the small-section tunnel using the underground excavator according to any one of the first to fourth aspects. In the method of building a tunnel, the excavation of the large-section tunnel, excavation is performed in a state where the plurality of separation shield machines are connected with the connection shield machine interposed therebetween,
The excavation of the small-section tunnel is performed by removing the connection shield machine and separating the separation shield machine, excavating with each separation shield machine, and removing or attaching the connection shield machine in a shaft. The method is characterized in that a branch type shield tunnel is constructed.

[0016]

Embodiments of the present invention will be described below.

1 to 16 show an embodiment of the present invention.

First, the configuration will be described. The underground excavator 20 of this embodiment has a plurality (two in this embodiment).
Separation shield machines 21 and 21 are connected between the shield machines 22
Are connected so that they can be separated from each other. In this connection state, as shown in FIGS. 1, 2 and 3, it is possible to excavate a three-circle subway double track station section tunnel 23 which is a "one large section tunnel".
, And the separation shield machines 21 and 21 are separated from each other. As shown in FIGS. 1, 4 and 5, the separation shield machines 21 and 21 branch off from the subway double track station section section tunnel 23. As described above, it is possible to excavate a circular subway single-line cross-section tunnel 24 which is a “plurality of small-section tunnels”.

As shown in FIG. 1, a shaft 25 is constructed between the subway double-track station section tunnel 23 and the subway single-track section tunnel 24. As shown in FIG. 2, in the subway double track station section tunnel 23, a double track station section tunnel segment 26 is continuously arranged in a three-circle ring shape and a panel segment 27 is provided inside. I have. In addition, as shown in FIG. 4, a single-line section tunnel segment 28 is arranged in the subway single-line section tunnel 24 in a circular shape. In FIGS. 3 and 5, reference numeral 29 denotes a railway construction limit, reference numeral 30 denotes yard concrete, and reference numeral 31 denotes a platform.

Further, as shown in FIG. 1, the vertical shaft 25 is provided with an earth retaining wall 34, a wellhead concrete 35, and a wellhead seal 36.

Specifically, the separation shield machine 21
Has a separation shield cylinder 38 having a cylindrical shape, a separation shield partition 39 is provided on the front surface of the separation shield cylinder 38, and the connection shield machine 22 includes a connection shield cylinder 41 having a substantially drum-shaped cross section. A connection shield partition 42 is provided on the front surface of the connection shield cylinder 41.

The separation shield tube 38 and the connection shield tube 41 are fixedly connected by a connection bolt 43 or the like. Welding is also acceptable.

In the separation shield machine 21, a circular separation shield cut-spoke 45 as a “digging portion” supported by a crank 44 is provided in front of the separation shield partition wall 39. In the crank 44, a rotary drive shaft 44a is rotated by a cutter drive unit 46 provided on the separation shield partition 39, and a crank bearing 47 is mounted on a crank shaft 44b eccentric to the rotary drive shaft 44a. Shield Katas Spoke 4 separated via
5 are supported. A bit (not shown) for cutting the ground G is provided in the separation shield Katas pork 45.
Are configured to perform a parallel link motion via the crank 44. Although not shown, the cutter driving unit 46 is provided with a drive motor, a reduction gear, a pinion gear, a bearing, a shaft, and the like.

The connecting shield machine 22 is provided with a substantially drum-shaped connecting shield cut-spoke 50 supported by a crank 49 in front of the connecting shield partition wall 42. The crank 49 is connected to the connecting shield cutter support shaft 4.
9a is supported by a connecting shield cutter support portion 51 provided on the connecting shield partition wall 42, and is connected to the connecting shield cutter supporting shaft 49a via a crank bearing 52 on a crankshaft 49b which is eccentric to the connecting shield cutter support shaft 49a.
0 is supported. Although not shown, a bit for cutting the ground G is provided on the connecting shield cut-spoke 50.

The connecting shield cut spokes 50 and the separated shield cut spokes 45 on both sides are connected.
As shown in FIG. 6, they are fixed by bolts 55 via a cut-spoke connecting portion 54 and are integrated. The upper face is excavated. Each cutter driving unit 46 is configured to drive in synchronization. In addition, here, the separation shield Katas pork 45
A drive source is provided on the side, and a drive source is not provided in the connection shield cut spokes 50. However, a drive source may be provided, of course. Depending on the conditions, the connection shield cutter spoke 50 may not be provided with the connection shield cutter support shaft 49a, the crank shaft 49b, the crank bearing 52, the driving source, and the like.

The separation shield hood portion 57 of the separation shield tube portion 38 projecting forward from the separation shield partition wall 39 has a cutout shape in which a cutout portion 57a corresponding to a connection portion of the connection shield machine 22 is formed. The connecting shield hood portion 58 of the connecting shield tubular portion 41 protruding forward from the connecting shield partition wall 42 has an arc shape, and ends 57b, 58b of the hood portions 57, 58 are connected to each other by welding or the like. ing. As a result, an outer periphery of a triple circle is formed.

Further, an annular separation shield girder portion 61 having a mounting hole 61a into which the shield jack 60 is inserted is mounted in the separation shield tube portion 38, and a connection shield tube portion 41 is provided in the connection shield tube portion 41. A drum-shaped connecting shield girder portion 62 having a mounting hole 62a through which the shield jack 60 is inserted is mounted. Attachment holes 61a, 62 of these girder portions 61, 62
a shield jack 60 is disposed on
Is in contact with

At the time of excavation of the tunnel 23 at the cross section of the subway double track station, as shown in FIG.
It is not necessary to provide the shield jack 60 in the mounting hole 61a corresponding to the connection shield machine 22 side.

Further, the separation shield tail portion 65 behind the separation shield girder portion 61 of the separation shield tube portion 38 has an annular shape, and a cutout portion 65c is formed in a part of the connection shield machine 22 side so as to be omitted. While the connection shield girder portion 6 of the connection shield tube portion 41 is formed.
The connection shield tail portion 66 behind the second portion 2 has an arc shape, and ends 65a, 66a of the tail portions 65, 66 are connected to each other by welding or the like to form a triple circular outer periphery. In these tail portions 65 and 66, a double-track station section tunnel segment 26 is assembled in a triple circle by erectors (not shown) provided in each of the separation shield machine 21 and the connection shield machine 22.

Tail seals 65b and 66b are provided inside the rear ends of the tail portions 65 and 66, respectively, and are continuous in a triple circle shape.
The underground excavator 20 is insulated from the ground G side by contacting the outside of the double-track station section tunnel segment 26 in which the assembly 66b is assembled.

In the two separating shield machines 21, an earth discharging device 68 (screw conveyor) for discharging the excavated earth and sand is arranged, and a backfill 69 is injected as shown in FIG. A backfill injection device 70 is provided.

Next, the case where the underground double track station section tunnel 23 is excavated using the underground excavator 20 to which the shield machines 21 and 22 are connected will be described.

The underground excavator 20 is advanced by the reaction force by pushing the double track station section tunnel segment 26 with the spreaders 60a of the plurality of shield jacks 60.
Press the cutter bit against the face of the ground G. At the same time, the cutter driving sections 46 are driven synchronously to rotate the crank 4.
Each of the cut spokes 45 and 50 is caused to perform a parallel link motion via the link 4 and 49. As a result, a large number of cutter bits rotate with a predetermined radius, and the subway double track station section tunnel 23 is excavated. In this case, since the face face is excavated on the same plane, the stability of excavation can be improved without generating a step on the face face.

After digging to the predetermined position, the spreader 60a of the shield jack 60 is advanced to the predetermined position. Next, a large number of double-track station section tunnel segments 26 are combined with the panel segments 27 inside the shield tube sections 38 and 41 at positions forward of the tail seals 65b and 66b.
The station section tunnel section 26 combined in this way is pushed by the spreader 60a and excavated and advanced in the same manner as described above. By repeating this, the subway station section section is excavated at each segment 26 and 27 at the same time. Build the tunnel 23.

In this case, the tail seals 65b, 66
By being sealed by b and the double-track station section tunnel segment 26 assembled as described above, soil, water and the like do not collapse into the underground excavator 20.

Then, a case where the underground excavator 20 is separated to construct a tunnel with a cross section changed from the subway double-track station cross-section tunnel 23 to two subway single-track cross-section tunnels 24 will be described.

That is, after the underground excavator 20 reaches the shaft 25 shown in FIG.
The separation shield machine 21 is separated from zero and the remodeling work is performed.

This is a separation shield cut-spoke 45.
The bolts 55 are removed to separate the connection shield cut-spoke 50 from the connection shield cut-spoke 50, and the connection shield cut-spoke 50 is removed as shown in FIGS.

As shown in FIGS. 12 and 13, a cut is made at the connection between the end 57 b of the separation shield hood 57 and the end 58 b of the connection shield hood 58, and the notch of the separation shield hood 57 is cut out. As shown in FIG. 11, an arc-shaped closing hood portion 72 is newly attached to the portion 57a by welding or the like to form a circular continuous outer periphery.

Further, the circular separation shield tube 38 and the drum-shaped connection shield tube 41 are connected to connection bolts 43 shown in FIG.
And detach it.

Further, the connection shield partition 42 is cut off at a connection portion with the separation shield cylinder 38 by cutting or the like.

Further, the end 6 of the separation shield tail 65
The connecting portion between 5a and the end 66a of the connecting shield tail portion 66 is cut off by cutting or the like.

At this time, since the separation shield tail portion 65 is in the shape of a broken circle, an arc-shaped closing tail portion 76 is newly attached to the cutout portion 65c by welding or the like to form a circular outer periphery. Of course, a tail seal 76a is also attached to the closed tail portion 76.

Further, a shield jack 60 is installed in a portion of the mounting hole 61a of the separation shield girder portion 61 where the seal jack 60 has not been installed so far, and the shield jack 60 is arranged over the entire circumference of the circle. I do. At this time, the shield jack 60 to be attached is attached.
Is used as much as possible in the connection shield machine 22, but if it is not enough, a new one is installed.

In this manner, the two separation shield machines 2
After separation and remodeling into 1, 21, the separation shield machine 21 shown in FIG. 11 was restarted from the shaft 25, and as shown in FIG.
Two subway single-line cross-section tunnels 24 are constructed with two separation shield machines 21 and 21. In addition, the code | symbol 78 in FIG. 11 is a reaction force receiving support, and the code | symbol 79 is a temporary segment.

The construction is similar to the case of the subway double track station section section tunnel 23, in which the separation shield Kataspoke 45 is used.
Are parallel-linked to excavate the face, and move forward while assembling the single-line section tunnel segment 28.

As described above, since the connecting shield machine 22 is detached and separated into a plurality of separation shield machines 21, the tunnels in which the cross section of the subway double-track station section section 23 and the plurality of subway single-track section tunnels 24 are changed can be used. While excavating, when excavating the subway single-track cross section tunnel 24,
There is no need to stir the excess ground. In addition, there are few unnecessary configurations when the excavation changes from the subway double-track station section tunnel 23 to the plurality of subway single-track section tunnels 24. That is, in the conventional example, the two cut-out circular shield machines 8 on both sides are unnecessary, but in the present invention, the central connection shield machine 22 is unnecessary, so that there are few unnecessary configurations.

In the above-described embodiment, a description has been given of the construction of a three-section circular tunnel. However, the present invention is not limited to this. It can also be applied to the construction of a cross section tunnel. Also, even if it is not a triple, 4
A series, a series of five, etc. are also possible. Further, in the above-described embodiment, the tunnel construction in the case where the cross section changes from the large-section tunnel to the small-section tunnel has been described.

[0049]

As described above, according to the invention described in each claim, since the connecting shield machine is detached and separated into a plurality of separation shield machines, a large-section tunnel and a plurality of small shield machines are separated. It is possible to excavate a tunnel whose cross section has changed from that of a cross section tunnel, and there is no unnecessary configuration when excavating from a large cross section tunnel to a small cross section tunnel without excavating excess ground when excavating a small cross section tunnel. .

According to the second aspect of the present invention, in addition to the above effects, when excavating a tunnel having a large cross section, the excavated portions of a plurality of shield machines integrally perform a parallel link motion so that the face face on the same plane is formed. Drilling,
Excavation stability can be improved without generating a step on the face.

According to the third or fourth aspect of the present invention, in addition to the above-described effects, a cutout portion is provided in the separation shield hood portion and the separation shield tail portion, and the closing hood portion and the closing tail portion are attached and detached therefrom. With a small modification, large section tunnels and multiple small section tunnels can be constructed. Then, since there are few remodeling parts, the time required for remodeling can be shortened and it is economical.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a tunnel excavated by an underground excavator according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1 according to the embodiment;

FIG. 3 is a sectional view showing a case where the large section tunnel shown in FIG. 2 according to the embodiment is used for a subway station.

FIG. 4 is a sectional view taken along the line BB of FIG. 1 according to the embodiment;

FIG. 5 is a sectional view showing a case where the small-section tunnel shown in FIG. 4 according to the embodiment is used for a single subway line.

FIG. 6 is a sectional view showing the underground excavator according to the embodiment.

FIG. 7 is a sectional view taken along line CC of FIG. 6 according to the embodiment;

FIG. 8 is a sectional view taken along line DD of FIG. 6 according to the same embodiment.

FIG. 9 is a sectional view taken along the line EE in FIG. 6 according to the embodiment.

FIG. 10 is a sectional view taken along the line FF of FIG. 6 according to the embodiment;

FIG. 11 is a cross-sectional view of the case where the underground excavator according to the embodiment is separated.

FIG. 12 is a sectional view taken along line GG of FIG. 11 according to the same embodiment.

FIG. 13 is a sectional view taken along the line HH in FIG. 11 according to the same embodiment.

FIG. 14 is a sectional view showing a state where the underground excavator according to the embodiment is separated.

FIG. 15 is a sectional view taken along the line II of FIG. 14 according to the embodiment.

FIG. 16 is a sectional view taken along the line JJ of FIG. 14 according to the embodiment;

FIG. 17 is a front view showing a conventional example in a state where a pair of shield propulsion units are connected.

FIG. 18 is a sectional view showing a subway double-track station section sectional tunnel constructed by the shield propulsion device of FIG. 17 showing the same conventional example.

FIG. 19 is a front view showing a state in which a pair of shield propulsion devices showing the conventional example are separated.

FIG. 20 is a cross-sectional view showing a single-line cross-section tunnel constructed by the shield propulsion device of FIG. 19 showing the same conventional example.

FIG. 21 is a front view of a triple circular shield machine showing another conventional example.

FIG. 22 is a sectional view of a subway double-track station section tunnel constructed with a triple circular shield machine showing another conventional example.

FIG. 23 is a front view of a circular shield machine showing another conventional example.

FIG. 24 is a sectional view of a subway double-track cross-section tunnel constructed with a circular shield machine showing another conventional example.

[Explanation of symbols]

 20 Underground excavator 21 Separation shield machine 22 Connection shield machine 23 Subway double track station section tunnel (Large section tunnel) 24 Subway single line section tunnel (Small section tunnel) 25 Vertical shaft 38 Separation shield tube section 39 Separation shield wall section 41 Connection shield Cylinder part 42 Connecting shield wall part 45 Separating shield cut-spoke (digging part) 50 Connecting shield cut-spoke (digging part) 57 Separating shield hood part 57a Notch part 58 Connecting shield hood part 65 Separating shield tail part 65c Notch part 66 Connecting Shield tail 65b, 66b, 76a Tail seal 72 Closed hood 76 Closed tail

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takayoshi Hamada 1-24-4 Shinkawa, Chuo-ku, Tokyo Taitoyo Construction F-term (reference) 2D054 AA03 BA03 BA10 BB09 EA09

Claims (5)

[Claims] 1. A plurality of separation shield machines are separably connected to each other with a connection shield machine interposed therebetween, and in this connection state, a single large-section tunnel can be excavated. An underground excavator capable of excavating a plurality of small-section tunnels so as to branch from the one large-section tunnel in each of the separation shield machines by separating the separation shield machines, Each of the shield machines is provided with a digging portion for digging a face by performing a parallel link motion, and when digging the large-section tunnel, the digging portions integrally perform a parallel link motion to dig a face. An underground excavator characterized by being set to perform. 2. When excavating the large section tunnel, the excavating sections of the shield machines integrally perform a parallel link motion to excavate a face on the same plane. The underground excavator according to claim 1, wherein 3. A separating shield hood portion is provided on a side of a digging portion of the separating shield machine, and a cutout portion is formed on a connecting side of the connecting shield machine at an annular part of the separating shield hood portion, and the connecting shield is formed. A connection shield hood portion is provided on an excavation portion side of the machine, and when the large-section tunnel is excavated, the separation shield hood portion and the connection shield hood portion are connected to each other and formed in a shape adapted to the large-section tunnel, The underground according to claim 1, wherein, when excavating the small-section tunnel, the notch is closed by a closing hood to form a shape adapted to the small-section tunnel. Excavator. 4. A separation shield cylinder which forms an outer shape of the separation shield machine, a separation shield tail having a tail seal is provided on a rear side of the separation shield cylinder, and an annular shape of the separation shield tail is provided. A connection shield having a cutout portion on the connection side of the connection shield machine, a connection shield tube portion forming an outer shape of the connection shield machine, and a tail seal on a rear side of the connection shield tube portion. A tail section is provided, and when the large section tunnel is excavated, the separated shield tail section and the connection shield tail section are connected to each other to form a shape adapted to the large section tunnel. The notch portion is configured to be closed by a closing tail portion having a tail seal so as to be formed in a shape adapted to the small-section tunnel. Underground excavator according to any one of claims 1 to 3, characterized. 5. A method of constructing a branch-type shield tunnel for constructing the large-section tunnel and the small-section tunnel using the underground excavator according to any one of claims 1 to 4, The cross section tunnel is excavated in a state where the plurality of separation shield machines are connected with the connection shield machine interposed therebetween. The small section tunnel excavation is performed by removing the connection shield machine and removing the separation shield machine. And a method of constructing a branch type shield tunnel, wherein excavation is performed by each of the separation shield machines, and removal or attachment of the connection shield machine is performed in a shaft.