JPH04272387A - Downward shield machine - Google Patents

Abstract

PURPOSE:To excavate a vertical shaft by a shield method and to collect an internal mechanism such as a cutter, etc., after the completion of excavation to reduce construction costs. CONSTITUTION:A main cutter 32 mounted to a spindle 31 and a peripheral cutter 34 mounted to an expansion arm 33 extended radially from the spindle 31 are provided to the lower end 22 of a shield machine body 21. A shield jack 24 capable of moving inward of a diametrical direction is provided upward thereof. In addition, a segment assembly device 27 having a segment holding arm 26 capable of expansion in a diametrical direction is provided to a position of the axial center 25. A cutter 23, the shield jack 24 and the segment assembly device 27 are borne on an internal frame 29. The internal frame 29 is mounted to an outside drum 28 so that it is capable of loading and unloading. Sludge is circulated through a sludge withdrawal pipe 64 having a sludge making material injection pipe 63 and a discharge pump 65 to stabilize the facing and, at the same time, excavated earth is removed to the ground.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new downward shield machine that excavates downward using a shield method.

0002

2. Description of the Related Art Generally, in order to excavate a relatively large diameter shaft such as a starting shaft in the shield construction method, it is necessary to excavate while preventing the collapse of surrounding earth and sand.

[0003] As shown in Fig. 8, conventionally, in this type of shaft excavation, in order to prevent the construction work from interfering with traffic, etc., the earth retaining pile method was first used to dig down about 5 m from the road surface to accommodate materials. After forming an under-road room 2, excavate vertically using a small shovel 4 or the like using a concrete wall 3, etc., and discharge the excavated earth and sand using a bucket 5 into a hopper 6 installed on the ground. This was to be transported by truck 7.

[0004]In recent years, tunnels such as deep tunnels have been excavated at deep locations, and the vertical shafts have also become long. For this reason, in the conventional construction method, it is difficult to retain the earth and discharge the excavated earth and sand, and there is a problem in that it is very dangerous for workers to enter the bottom of a deep hole and carry out excavation work. A safer caisson construction method is also in use, but it is difficult to manage high earth pressure and groundwater pressure.

[0005] In order to solve these problems, it is conceivable to excavate a shaft using, for example, a mud shield excavator.

As shown in FIG. 9, this muddy water type shield excavator has a cutter 13 provided at the front end 12 of a cylindrical outer shell 11, an erector (segment assembly device) 14 provided at the rear, It is mainly composed of a shield jack 16 that applies a propulsive reaction force to segments 15 assembled by an erector 14. Mud water is then sent to the front of the bulkhead 18 through the mud pipe 17, and the characteristics of the mud water and mud water pressure are used to counteract the earth pressure and water pressure acting on the face to stabilize the ground at the face, and the cutter 13 rotates to excavate. The excavation is carried out while discharging the soil through a mud removal pipe 19.

[0007] By arranging such a shield excavator vertically and applying it to vertical shaft excavation, problems in safety and measures against earth pressure and water pressure can be solved to a certain extent.

[0008]

However, conventional shield tunneling machines are left in the mine (face) after tunnel excavation is completed. That is, the excavating mechanism such as the cutter 13 was not recovered. This is not a problem in the case of main tunnel excavation where one step of excavation is several hundred meters to several kilometers, but in most cases the expensive cutter 13 is used to excavate a vertical shaft that is less than 50 meters in length. Leaving it behind will result in extremely high construction costs.

Furthermore, when excavating horizontally (in the lateral direction), muddy water (sludge) mixed with earth and sand gathers at the lower front of the bulkhead 18, so by transporting this to the rear, the discharge of excavated earth and sand is relatively reduced. Although this is easy to do, when excavating vertically, muddy water will accumulate on the face, so the conventional mechanism cannot be used as is.

Furthermore, in order to launch the shield machine in the vertical direction, it is necessary to set the shield machine body in the underground room 2 as shown in FIG. 8 and take a reaction force. The longer the road, the larger the under-street room 2 must be constructed.

In view of the above circumstances, the present invention provides a new backward shield machine that can easily collect cutters, etc., can reliably discharge excavated soil, and does not require a large-scale under-road room. It was created to realize vertical shaft excavation using the shield method.

0012

[Means for Solving the Problems] According to the present invention, a radially extensible cutter is provided at the lower end of a shield machine body that is propelled downward.

The present invention also includes a cutter that is provided at the lower end of the shield machine body and is extendable and retractable in the radial direction, and a shield jack that is provided above the cutter and is configured to be movable inward in the radial direction. It is something.

[0014] It is preferable that the shield machine main body is provided with a segment assembly device having a segment gripping arm that is erected at the axial center position and is extendable and retractable in the radial direction.

[0015] The present invention provides a cutter that is provided at the lower end of the shield machine main body and is extendable in the radial direction, a shield jack that is provided above the cutter and is formed so that it can be moved inward in the radial direction, and a shield machine main body. A segment assembly device has a segment gripping arm that is erected at the axial center position and is extendable in the radial direction, and a segment assembly device that supports the cutter, shield jack, and segment assembly device, and is detachably installed inside the outer shell of the shield machine body. It is equipped with an internal frame.

[0016] It is preferable that the shield machine main body is provided with a mud water circulation system for discharging excavated earth and sand to the ground.

[0017] It is preferable that the cutter is composed of a main cutter supported by a main shaft rotating at the axial center position of the shield machine body, and a peripheral cutter supported by telescopic arms extending radially from the axial center. .

Preferably, the peripheral cutter is supported by a sub-shaft that is provided at the tip of the telescoping arm and rotates in parallel with the main shaft.

Preferably, the subshaft is connected to and driven by a motor that rotates in forward and reverse directions.

Preferably, the telescoping arm is attached to the main shaft and rotated in synchronization with the main cutter.

[0021] It is preferable that the main cutter protrudes more downwardly than the peripheral cutters.

[0022] The shield jack may be installed on the internal frame via a jack support plate that swings about a swing axis located radially inward from the assembled segments.

[0023] The shield jack may be formed in multiple stages in the axial direction.

The mud water circulation system includes a mud material injection pipe for spraying mud material at a predetermined pressure onto the face side, a mud drainage pipe for discharging mud mixed with excavated soil to the ground, and a mud drainage pipe for discharging mud water mixed with excavated soil to the ground. It is preferable to include a delivery pump provided in the tube.

[0025] It is desirable that the main shaft has a mud water suction port which is the open end of the mud removal pipe.

[0026] It is desirable that the outer body is formed so that it can be divided in the vertical direction.

[0027] It is preferable that the shield machine main body includes a protective deck formed above the segment assembly device.

[0028]

[Operation] With the above structure, the cutter excavates the lower part of the shield machine body, and after excavation is completed, the cutter is reduced in diameter and pulled upward and recovered.

[0029] Also, with the structure including the cutter and the shield jack, the shield jack applies downward propulsive force to the shield machine body, and is pulled upward by being moved radially inward after excavation is completed. .

[0030] Due to the structure in which the shield machine main body is equipped with a segment assembly device, the segment gripping arm installs the segment on the wall of the hole excavated by the cutter, and after the excavation is completed, the segment gripping arm is contracted in the radial direction and pulled upward.

[0031]Furthermore, with the structure including the internal frame, the cutter, shield jack, and segment assembly device can be recovered as one unit by pulling up the internal frame after excavation is completed.

[0032] Since the shield machine main body is equipped with a muddy water circulation system, the face can be stabilized by the muddy water, and the earth and sand excavated by the cutter can be discharged to the ground.

[0033] Since the cutter is composed of a main cutter and a peripheral cutter, the telescopic arm is retracted and pulled upward after excavation is completed.

With the configuration in which the peripheral cutter is supported by the sub-shaft, the peripheral cutter excavates the peripheral portion of the face by rotating around the sub-shaft.

[0035] Due to the configuration in which the sub-shaft is connected to the motor, the peripheral cutter performs excavation by rotating in forward and reverse directions.

[0036] Due to the configuration in which the telescoping arm pivots in synchronization with the main cutter, the peripheral cutter excavates by pivoting about the axis and rotating about the sub-axis.

[0037] Due to the structure in which the main cutter protrudes lower than the peripheral cutters, the main cutter excavates the central part before the peripheral part.

[0038] Due to the configuration in which the shield jack is installed on the internal frame via the jack support plate, after the excavation is completed, the shield jack is positioned radially inward from the assembled segments due to the rocking of the jack support plate. Ru.

[0039] Due to the multi-stage structure of the shield jack, the overall height of the shield machine body can be reduced by reducing the size of the shield jack.

[0040] With the structure in which the mud water circulation system is composed of a mud making material injection pipe, a mud removal pipe, and a delivery pump, the mud making material injection pipe sprays the mud making material at a predetermined pressure to the face side and mixes it with the excavated soil. . The mud drain pipe discharges the muddy water to the ground by operating a delivery pump.

[0041] With the structure in which the main shaft has a muddy water suction port, the mud draining pipe sucks muddy water from the vicinity of the cutter.

[0042] Due to the structure in which the outer shell is formed so that it can be divided, the machine height is lowered by splitting the outer shell at the time of starting.

[0043] By virtue of the structure in which the shield machine main body is provided with a protective deck, the mechanism below the segment assembly device is protected from falling objects and the like.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 to 5 show an embodiment of a downward machine according to the present invention.

This downward shielding machine has a cutter 23 provided at the lower end 22 of the shielding machine main body 21 that is extendable in the radial direction, and a cutter 23 provided above the cutter 23 so as to be movable inward in the radial direction. shield jack 24
, a segment assembly device 27 having a segment gripping arm 26 that is erected at the axis 25 of the shield machine main body 21 and is extendable and retractable in the radial direction; It is mainly composed of an internal frame 29 that is removably installed inside the outer shell 28 of the machine body 21, and a muddy water circulation system 30 that discharges excavated earth and sand to the ground.

The cutter 23 is composed of a main cutter 32 supported by a main shaft 31 rotating at an axis 25, and a peripheral cutter 34 supported by a telescoping arm 33 extending radially from the main shaft 31. .

The main shaft 31 is rotatably supported by a partition plate 35, which is a part of the internal frame 29, via a bearing 36, and is connected to an output shaft 38 of a main cutter electric motor 37 via a pinion 39 and a cutter gear 40. has been done. Main cutter 3
2, three cutter frames 41 radially attached to the tip of the main shaft 31 protruding from the partition plate 35, and a bit 4 implanted on the lower surface and tip of the cutter frame 41.
2, and excavates the ground when a downward driving force and a rotational force around the axis 25 are transmitted.

The telescoping arm 33 has a base 44 and a base 44.
In this embodiment, three tip portions 45 are formed at equal intervals. The base 44 is attached to the main shaft 31 at a position above the main cutter 32, and when viewed from the front (see FIG. 2), the cutter frame 41
They are arranged so that they are staggered. The base portion 44 and the tip portion 45 are connected by a telescoping jack 46 installed inside the arm in the longitudinal direction, and the entire length of the arm can be extended or contracted by operating the telescoping jack 46.

[0050] At the tip of the tip portion 45, there is a
That is, a sub-shaft 47 parallel to the axis 25 of the shield machine body 21 is provided, and a peripheral cutter 34 formed substantially in the same manner as the main cutter 32 is attached. That is, the peripheral cutter 34 is
It is formed by three cutter frames 49 supported by a sub-shaft 47 and bits 50 appropriately implanted in the cutter frames 49. A hydraulic motor 51 is provided on the tip portion 45 to rotate the sub-shaft 47 in forward and reverse directions, and the peripheral cutter 3
4 to apply a predetermined rotational force.

Therefore, during excavation, the main cutter electric motor 37
By operating the hydraulic motor 51, the main cutter 32 rotates around the axis 25, the telescopic arm 33 rotates in synchronization with this, and at the end of the rotation, the peripheral cutter 34 rotates around the secondary shaft 47. I will do it. Note that the main cutter 32 and the peripheral cutter 34 have their tip rotation orbits 5 when viewed from the front.
2 and 53 are formed in such a size that they slightly overlap.

The internal frame 29 includes a partition plate 35 that defines a cutter chamber 54 between the inner frame 29 and the partition face.
It is composed of a partition plate 55 formed in parallel above, a column 57 erected appropriately on the peripheral portion 56 of the partition plate 55, and a segment assembly deck 58 provided on the column 57. The bulkhead plate 35 and the partition plate 55 are connected and formed as a unit, and are appropriately latched to a bracket portion 59 formed on the inner surface of the outer body 28, and are detachably bolted.

The shield jacks 24 are formed in multiple stages, and a plurality of shield jacks 24 are provided at predetermined intervals in the circumferential direction around the partition plate 56 via the jack support plate 60. The jack support plate 60 has a partition plate peripheral portion 56,
It is swingably attached to a swing shaft 62 formed at a position radially inward from the segment 61, and on its swing end side,
The base end portion of the shield jack 24 is placed thereon. This swing end moves between the top of the bracket part 59 near the inner wall of the outer shell 28 and the peripheral part 56 that is detached from the bracket part 59. Therefore, the shield jack 24 applies a propulsive force to the bracket part 59 and the internal frame 29 during digging, and is separated from the outer shell 28 after the digging is completed.

The mud water circulation system 30 includes a mud material injection pipe 63 for spraying mud material at a predetermined pressure onto the face side, and a mud drainage pipe 64 for discharging the mud mixed with excavated soil to the ground.
It is configured to include a delivery pump (mono pump) 65 provided in the middle of the mud removal pipe 64.

The mud-making material injection pipe 63 is extended from a mud-making material tank (not shown) installed on the ground, and its open end is connected to an injection hole 66 appropriately arranged in the partition plate 35. . The mud removal pipe 64 connects the outer shell 28 and the segment 61 from the ground.
It extends along the main shaft 31 and connects to a mud drainage path 67 formed inside the main shaft 31. That is, the mud removal pipe 6
4 is the bearing 68 on the partition plate 55 of the main shaft 31.
are connected to each other via a rotary joint 69 and a valve 70. The mud drainage path 67 extends along the axis 25 of the main shaft 31 beyond the partition wall plate 35 to below it, and radially outwards at a plurality of mud water suction ports 71 formed near the main cutter 32. It is opened. Also, the delivery pump 6
Reference numeral 5 is provided at a bent portion where a mud draining pipe 64 is bent toward the axis 25, and muddy water is sent out to the ground by rotation of a wing portion (not shown). Further, the input section 72 is connected to a pump motor 73 installed on the bulkhead plate 35 via a worm gear mechanism 74, and converts the drive rotation to a low speed to obtain a desired output power. . Note that the mud draining pipe 64 is formed so that it can be divided as appropriate by a plurality of flanges 75.

The segment assembly device 27 includes a cylindrical guide body 76 erected on the segment assembly deck 58 and a segment gripping arm 26 that pivots up and down along the guide body 76 and around the axis 25. It mainly consists of a chain 77 and a motor 78 for driving the segment gripping arm 26. The segment gripping arm 26 is formed in multiple stages so as to be able to expand and contract as appropriate in the radial direction, and is configured to grip the segments 61 at their tips and sequentially assemble them in the circumferential direction.

In addition, the outer shell 28 is divided into upper and lower halves at the position of the segment assembly deck 58, and by removing the bolts provided on the connecting flange 79,
An upper outer shell 81 provided with a known tail seal 80 can be separated from a lower outer shell (cutter side) 82.

Further, as shown in FIG. 5, a protection deck 83 is provided above the segment assembly device 27 to protect the internal mechanism and workers from falling objects. An arm member 84 extending outward in the radial direction is attached to this protective deck 83 so as to be latched to the segment 61, and is suspended from above by a chain 85 so as to follow the excavation. It is possible to go up and down. Further, the peripheral portion of the protective deck 83 is appropriately cut out to form a segment hanging space 86 and a piping wiring space 87.

[0059] The segment assembly deck 58 has
A transposition space 88 is appropriately cut out so that the shield jack 24 can be transposed inward. Further, manholes 8 are provided in the bulkhead plate 35 and the partition plate 55, respectively.
9 and 90 are formed, and the segment assembly deck and protective deck have opening/closing doors 91 to allow people to enter and exit.
, 92 are provided, respectively.

Next, the operation of the embodiment will be explained.

When excavating a shaft such as a starting shaft using the downward shield machine configured as described above, first, as shown in FIGS. 6 and 7, an underpass chamber 101 for starting downward excavation is constructed. That is, after retaining the surrounding earth and sand by placing earth retaining piles 102, it is dug into a rectangular parallelepiped shape, its side walls and top sides are reinforced with uprights 103 and support beams 104, and a lining board is placed on the top surface. 10
5 so that it can be placed. And the shield machine body 2
At the top of shaft position 106, which was excavated by the total height of 1,
Assemble H steel 107 into a crossbeam to obtain reaction force when starting. The height of the shield machine main body 21 at the time of starting is made low by separating the upper outer shell 81. Further, the shield jack 24 is installed so as to have the minimum overall length.

Then, the shield machine body 21 is set at the shaft position 106, and the main cutter electric motor 37 and hydraulic motor 51 shown in FIG. 1 are driven. Due to this drive, the main cutter 32 rotates around the axis 25 of the shield machine body 21 to excavate the center of the shaft position 106, and the telescopic arm 33 rotates in synchronization with this. At the end of the rotation, the peripheral cutter 34 rotates around the secondary shaft 47 to excavate the peripheral part of the shaft position 106. This peripheral cutter 3
Whether the cutter 4 rotates in the same direction as the main cutter 32 or in the opposite direction is selected depending on ground conditions such as soil quality and construction conditions such as hole diameter. On the other hand, the shield machine body 2
1, the shield jack 24 is extended and the H
The reaction force is taken by the steel 107 and the outer shell 28 and inner frame 2
Push 9 downward.

Further, before and after the rotation of the cutter 23 and the extension of the shield jack 24, the mud-making material is fed into the mud-making material injection pipe 63.
It is sprayed onto the face via the As this mud material, for example, an appropriate mixture of china clay (rock powder) and bentonite is used. Further, the concentration and injection pressure are appropriately selected depending on the soil quality, groundwater level (pressure), depth, etc. The mud material sprayed onto the face stabilizes the ground at the face of the cutter chamber 54 against earth pressure and water pressure, and mixes with earth and sand excavated by the cutter 23 to become muddy water (sludge). This muddy water is sucked out from a muddy water suction port 71 by a delivery pump 65, and is sent to a ground-based muddy water treatment plant (not shown) via a mud water channel 67 and a mud drainage pipe 64.
After the soil components are removed, the material is sent to the mud material injection pipe 63 again at a predetermined pressure.

When the shield machine main body 21 digs down by the width of the segment 61, the segment assembly device 27
At the same time, the chain 77 and motor 78 are actuated to move the segment gripping arm 26 vertically, radially, and around the axis to erect the segment into the wall of the hole in the excavated section. The shield jack 24 then applies a reaction force to the assembled segments 61.

After digging to a certain depth, add the upper outer shell 81 to the lower outer shell 82 and seal the tail seal 80.
A seal is formed between the outer shell 28 and the segment 61, and excavation and lining are repeated in the same manner to continue digging.

When the excavation has been completed to a predetermined depth, the mud drain pipe 64 and the like are dismantled, and after ensuring the stability of the bottom of the excavated hole by injecting chemicals or pouring concrete, the telescoping jack 46 of the telescoping arm 33 is retracted. By letting
As shown by the two-dot chain line in FIG. 2, the outer end of the peripheral cutter 34 is moved to be located inside the inner wall of the segment 61. In addition, as shown by the two-dot chain line in FIG. 3, the jack support plate 60 is rotated around the swing shaft 62,
Move the shield jack 24 inside the segment 61. Then, the segment assembly device 27 retracts the segment gripping arm 26 so that it does not interfere with the segment 61.

After separating the bulkhead plate 35 and the partition plate 55 from the outer shell 28, the entire inner frame 29 is lifted up to remove the cutter 23, shield jack 24, segment assembly device 27, and their peripheral equipment (main cutter electric motor). 37, etc.) are collected by pulling them up to the ground through the shaft.

In this way, the cutter 23 having the peripheral cutter 34 supported by the telescoping arm 33, the shield jack 24 provided on the internal frame 29 via the jack support plate 60, and the segment gripping arm formed in multiple stages. 26, a mud water circulation system 30 consisting of a mud making material injection pipe 63, and a mud drainage pipe 64 having a delivery pump 65, it is possible to excavate a vertical shaft using the shield method, which was not available in the past. At the same time, after the excavation is completed,
Main internal mechanisms such as the cutter 23, shield jack 24, and segment assembly device 27 can be recovered and reused. That is, even if the excavation length is short, the construction cost does not become excessive, and safe and reliable mud shield excavation can be achieved.

The ability to substantially reduce the diameter of the main internal mechanisms other than the outer shell 28 means that it can be applied to various excavation diameters simply by replacing the outer shell 28, making it possible to create an extremely versatile shield machine. .

Furthermore, a muddy water suction port 71 is provided on the main shaft 31,
Since the muddy water in the cutter chamber 54 is drained,
By actively sucking out the muddy water in the center where there is a high degree of mixing of soil and sand, the exchange (circulation) with newly supplied mud material is ensured, contributing to the stability of the face and smooth excavation.

[0071] Since the peripheral cutter 34 is configured to rotate around the rotating sub-shaft 47, the peripheral part of the shaft can be excavated efficiently. Since the subshaft 47 is designed to rotate in forward and reverse directions, excavation can be carried out according to the soil quality. In particular, when excavating vertically, the geological changes are more dramatic than when excavating horizontally, and the excavation conditions are also different. Therefore, it can be said that the cutter 23 of this embodiment is extremely useful for downward excavation.

Further, the cutter 23 of this embodiment has the main cutter 3
2 is made to protrude beyond the peripheral cutter 34, and the central part of the shaft is excavated in advance of the peripheral part, so that the free surface of the face increases and the peripheral cutter 34 can rotate around the secondary shaft 47. Combined with this, the efficiency of excavation can be improved and the speed of excavation can be increased.

Furthermore, since the outer fuselage 28 is divided into two parts and the shield jack 24 is formed in multiple stages, the height of the aircraft can be kept low during takeoff, and the roadside room 101 can be made small to the minimum necessary. It can contribute to reducing construction costs and shortening the construction period.

Furthermore, since the protective deck 83 is provided above the segment assembly device 27, it protects the workers and the main internal mechanisms inside the shield machine body 21 by catching falling objects from the roadside room 101 or the road. be able to.

In this embodiment, all of the main internal mechanisms other than the outer shell 28 are recovered, but in some cases only a part of them may be configured to be substantially reduced in diameter. It may also be possible to partially recover it.

[0076]

[Effects of the Invention] In summary, according to the present invention, the following excellent effects are achieved.

(1) According to the configuration described in claim 1, safe and reliable vertical shaft excavation is realized by the shield method, and the diameter of the cutter can be reduced to recover the excavation, and construction costs can be kept low. can.

(2) According to the configuration of claim 2, the shield jack can be recovered by further moving the shield jack radially inward.

(3) According to the configuration of claim 3, the segment assembly device can be recovered by further reducing the segment gripping arm.

(4) According to the configuration described in claim 4, the cutter, shield jack, and segment assembly device can be easily recovered by lifting the internal frame.

(5) According to the structure set forth in claim 5, the muddy water can stabilize the ground at the face and discharge the excavated earth and sand, and downward excavation can be performed reliably.

(6) According to the configuration described in claim 6, the circumferential cutter moves radially inward due to contraction of the telescoping arm, so that the cutter can be recovered and the diameter of the excavation hole can be adjusted.

(7) According to the configuration described in claim 7, the peripheral portion of the shaft can be efficiently excavated by rotating the peripheral cutter.

(8) According to the structure described in claim 8, by selecting the rotation direction of the peripheral cutter, excavation can be carried out according to the soil quality.

(9) According to the configuration described in claim 9, the main cutter and the peripheral cutters are linked to each other to efficiently perform excavation.

(10) According to the configuration described in claim 10,
The free surface of the face is increased and the excavation efficiency is improved.

(11) According to the configuration described in claim 11,
The shield jack can be easily moved radially inward.

(12) According to the configuration described in claim 12,
The height of the shield machine body can be lowered when starting, and there is no need for a large underground room.

(13) According to the structure recited in claim 13,
Mud water can be reliably circulated, the face ground can be stabilized, and excavated soil can be discharged.

(14) According to the configuration described in claim 14,
By sucking out muddy water that concentrates in the center of the face, excavated soil can be reliably discharged.

(15) According to the configuration described in claim 15,
The height of the shield machine body can be lowered when starting, and there is no need to enlarge the space below the road.

(16) According to the configuration described in claim 16,
Workers and internal mechanisms inside the shield machine can be protected from falling objects, improving safety.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of a downward shield machine according to the present invention.

FIG. 2 is a view taken along line AA in FIG. 1;

FIG. 3 is a sectional view taken along line BB in FIG. 1;

FIG. 4 is a sectional view taken along line CC in FIG. 1;

FIG. 5 is a sectional view taken along the line DD in FIG. 1;

FIG. 6 is a plan view showing the under-road room for explaining the operation of FIG. 1;

FIG. 7 is a side sectional view of FIG. 6;

FIG. 8 is a side sectional view showing a conventional shaft excavation method.

FIG. 9 is a side sectional view showing a conventional shield excavator, which is a technology to be compared with the present invention.

[Explanation of symbols]

21 Shield machine body 22 Lower end 23 Cutter 24 Shield jack 25 Axis center 26 Segment gripping arm 27 Segment assembly device 28 Outer body 29 Internal frame 30 Mud water circulation system 31 Main shaft 32 Main cutter 33 Telescopic arm 34 Peripheral cutter 47 Secondary axis 51 Motor (hydraulic motor) 60 Jack support plate 61 Segment 62 Swing axis 63　Sludge material injection pipe 64 Sludge drainage pipe 65 Delivery pump 71 Muddy water inlet 83 Protective deck

Claims (16)

[Claims] 1. A downward shield machine, characterized in that a cutter that can be freely expanded and contracted in a radial direction is provided at the lower end of a shield machine body that is propelled downward. 2. A shield machine comprising: a cutter that is provided at the lower end of the shield machine body and is expandable and retractable in the radial direction; and a shield jack that is provided above the cutter and is configured to be movable inward in the radial direction. A downward shield machine. 3. The shielding machine body according to claim 1, wherein the shielding machine body is provided with a segment assembly device having a segment gripping arm that is erected at an axial position of the shielding machine body and is extendable and retractable in the radial direction. Downward Shield Machine. 4. A cutter that is provided at the lower end of the shield machine main body and is expandable and retractable in the radial direction, a shield jack that is provided above the cutter and is formed so that it can be moved inward in the radial direction, and a cutter that is provided at the lower end of the shield machine main body. A segment assembly device having a segment gripping arm that is erected at an axial position and is extendable and retractable in the radial direction, and a segment assembly device that supports the cutter, shield jack, and segment assembly device, and is removably installed inside the outer body of the shield machine body. A downward shield machine characterized by an internal frame. 5. The downward shield machine according to claim 1, wherein the shield machine main body includes a mud water circulation system for discharging excavated soil to the ground. 6. The cutter comprises a main cutter supported by a main shaft rotating at an axial center position of the shield machine body, and a peripheral cutter supported by a telescoping arm extending radially from the shaft center. The downward shield machine according to any one of items 1 to 5. 7. The downward shield machine according to claim 6, wherein the peripheral cutter is supported by a subshaft provided at the tip of the telescoping arm and rotating in parallel with the main shaft. 8. The downward shield machine according to claim 7, wherein the subshaft is connected to and driven by a motor that rotates in forward and reverse directions. 9. The downward shield machine according to claim 8, wherein the telescoping arm is attached to the main shaft and rotates in synchronization with the main cutter. 10. The downward shield machine according to claim 6, wherein the main cutter projects further downward than the peripheral cutters. 11. Claims 2 to 10, wherein the shield jack is provided on the internal frame via a jack support plate that swings around a swing axis located radially inward from the assembled segments. The Downward Shield Machine described in any of the above. 12. The downward shield machine according to claim 2, wherein the shield jack is formed in multiple stages in the axial direction. 13. The mud water circulation system includes a mud material injection pipe for spraying mud material at a predetermined pressure onto the face side, and a mud drainage pipe for discharging mud water mixed with excavated soil to the ground; The downward shield machine according to any one of claims 5 to 12, further comprising a delivery pump provided in the sludge removal pipe. 14. The downward shield machine according to claim 13, wherein the main shaft has a mud water suction port which is an open end of the mud removal pipe. 15. The downward shield machine according to claim 4, wherein the outer shell is formed to be splittable in the vertical direction. 16. The downward shielding machine according to claim 3, wherein the shielding machine main body includes a protective deck formed above the segment assembly device.