JP5131524B2 - Open tunnel excavator and tunnel excavation method - Google Patents

Description

  The present invention relates to an open-type tunnel excavator and a tunnel excavation method for excavating a tunnel having mainly a rectangular cross section such as a road tunnel, an underpass, and a common groove.

  Conventionally, in a tunnel such as a road and a common groove provided in an urban area, it is considered rational and economical to make a necessary cross-sectional shape into a rectangular cross-section for its use. Therefore, in recent years, shield excavators that can excavate tunnels having a rectangular section have been used. With such a rectangular cross-section shield excavator, it is possible to excavate at a shallower depth than when using a circular shield excavator, without excavating more than necessary cross-sections as with a circular cross-section shield excavator. Therefore, it is suitable as an application when constructing an urban tunnel as described above (see, for example, Patent Documents 1 and 2).

In Patent Document 1, a plurality of excavators are connected and arranged over the entire circumference of the outer periphery of a rectangular section to be excavated, and these excavators are simultaneously propelled and a box is installed at the back of each excavator. A tunnel excavator is described in which a shell is formed and then the inside of the outer shell is excavated to construct a tunnel of rectangular cross section. One excavator has a substantially square shape when viewed from the front, and is provided with a cutter that is driven to rotate at the tip.
Further, in Patent Document 2, a plurality of shield machines that are substantially square in front view over the entire surface of a rectangular section to be excavated are arranged in the vertical direction and the horizontal direction, and the plurality of shield machines are dug simultaneously to form a rectangular shape. A closed shield excavator capable of excavating a cross section at a time is disclosed.
JP 2005-248546 A JP 2001-193386 A

  However, in the rectangular cross-section excavator provided with a plurality of shield machines disclosed in Patent Documents 1 and 2, a sealed shield machine capable of preventing subsidence of the ground surface for excavating shallow depths. Is used. As is well known, this sealed shield machine requires excavation while controlling the earth and water pressure of the ground in the face with the propulsive force and the amount of discharged soil, and the structure of the shield machine is complicated and more than one However, there is a problem that the cost increases.

  In addition, since a plurality of shield machines for excavating a rectangular cross section each excavate a substantially square cross section, a portion outside the circular cross sectional shape that can be excavated by the rotation of the cutter (that is, the cutter) It was necessary to excavate the four corners of a rectangular section that cannot be excavated only by rotation. For this reason, for example, a special mechanism such as a cutter pork or a copy cutter that expands and contracts at the four corner positions is used, and the structure of the cutter and its control method become complicated, resulting in an increase in cost. It was.

  The present invention has been made in view of the above-described problems, and the excavator has a simple structure that can eliminate the occurrence of ground subsidence in an open type and shallow tunnel, thereby reducing the cost of the excavator. It is an object of the present invention to provide an open type tunnel excavator and a tunnel excavation method capable of reducing the above.

In order to achieve the above object, the open tunnel excavator according to the present invention is an open tunnel excavator for excavating with an opening provided on the face side, wherein the tunnel cross section is divided into a plurality of small cross section excavation sections. And an opening / closing lid that opens and closes the opening on the face side of the small section excavation section, and the front face of the opening / closing lid is provided so that the outer shell body can be propelled while keeping the face pressed. Each of the expansion bag bodies is provided with an opening / closing lid provided in each of the small-section excavation sections, and is inflatable by allowing a fluid to flow inside. There alone is expandable, during advancement of the outer shell, while reducing by far the fluid inside the inflatable bag, is characterized that you hold the inflatable bag body in a state of constant pressure.

Further, in the tunnel excavation method according to the present invention, an outer shell body obtained by dividing the tunnel cross section into a plurality of small cross section excavation sections, an open / close lid that opens and closes a face side opening of the small cross section excavation section, and a front surface of the open / close lid A pressing means that can propel the outer shell while maintaining the state where the face is pressed, and the pressing means is provided on an opening / closing lid provided in each of the small section excavation sections, A tunnel excavation method using an open-type tunnel excavator that is inflatable by allowing fluid to flow inside, and each of the inflatable bags can be inflated independently. Open a part of the open / close lid in the excavation section, excavate the natural ground of the face through the opening, and then close the open / close lid and press the face with a predetermined pressure by the expansion bag provided on the front of the open / close lid Pressing with other small section digging Open the lid of the compartment, the step of pressing excavated natural ground cutting face from the opening, after which the working face by inflation bag which is provided on the front surface of the cover while closing the lid with a predetermined pressing force the provided, drilled all the small cross-section excavation section, after the pressed state by the expansion bag all front there is a risk of Face collapse of the small cross-section excavation section, at the time of forward movement of the outer shell, expanded bag It is characterized in that the open tunnel excavator is driven while the inside of the expansion bag is held at a constant pressure while the inside of the bag is drawn out and reduced .

In the present invention, in the small section excavation section obtained by dividing the tunnel section into a plurality of sections, a part of the opening and closing lid is opened to open the face face, and the face of the face face is reduced in a state where the area of the face face to be opened is reduced. Can be excavated. Then, the face after digging, which may cause the face to collapse, is pressed with a pressure that can withstand the earth and water pressure by the pressing means, and after the excavation of all the small section excavation sections, the face is kept pressed by the pressing means. However, by moving the outer shell forward, it is possible to suppress loosening of the face during excavation work. Therefore, even if the tunnel is shallow, the influence on the ground surface can be reduced, and the tunnel can be constructed by excavating so as not to cause ground surface settlement.
The tunnel excavator has a simple structure in which an open / close lid is provided in each of the small section excavation sections and an expansion bag body is provided in front of the open / close lid. The cost of the tunnel excavator can be reduced as compared with a sealed shield excavator having a complicated mechanism such as a cutter mechanism having a rectangular cross section.
In addition, after excavating the face in each small section excavation section, close the open / close lid and apply a pressure corresponding to the soil water pressure on the face of the face after excavation that may cause the face to collapse, so that the fluid flows into the expansion bag. The face can be pressed by inflating.

Moreover, in the open type tunnel excavator according to the present invention, it is preferable that a slide hood capable of projecting toward the face side is provided on the upper part of the outer shell body.
In the present invention, when the excavation is carried out, the slide hood protrudes toward the face and is inserted into the natural ground, so that the natural ground at the top of the slide hood can be pressed from below. It can be made smaller and can be safely excavated in a stable ground.

In the open tunnel excavator according to the present invention, it is preferable that the expansion bag body is provided with a relief valve that draws out the internal fluid and depressurizes when the expansion bag body reaches a predetermined pressure or higher. .
In the present invention, when the pressure in the inflatable bag becomes equal to or higher than the predetermined pressure, the internal air is released by the relief valve and the pressure is reduced, so that the pressure is maintained at a constant pressure. Therefore, even when the tunnel excavator moves forward after excavating all the small section excavation sections, even if the expansion bag interposed between the opening and closing lid and the face is pressurized and the internal pressure increases Since the pressure in the expansion bag body is maintained at a constant pressure by the relief valve, it is possible to suppress loosening of the face during excavation.

According to the open-type tunnel excavator and the tunnel excavation method of the present invention, an open-type tunnel excavator having a simple structure in which an open / close lid is provided in each of the small-section excavation sections and an expansion bag body is provided in front of the open / close lid. Can be excavated with a smaller opening area, and can stabilize the face during excavation and suppress ground subsidence even in shallow tunnels. The cost of the tunnel excavator can be reduced as compared with the type of shield excavator.

Hereinafter, an open type tunnel excavator and a tunnel excavation method according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.
1 is a side view showing an overall outline of a tunnel excavator according to an embodiment of the present invention, FIG. 2 is a front view of the tunnel excavator shown in FIG. 1, and FIG. 3 is a side view of an airbag provided in front of an opening / closing lid. FIG. 4A is a diagram showing a contracted state, FIG. 4B is a diagram showing an expanded state, FIG. 4A and FIG. 4B are diagrams showing an excavation process by a tunnel excavator, and FIG. FIGS. 6A and 6B are diagrams illustrating a digging process subsequent to FIG. 4B, and FIGS. 6A and 6B are diagrams illustrating a state in which the outer shell is advanced after digging.

As shown in FIG. 1, the open tunnel excavator according to the present embodiment (hereinafter simply referred to as “tunnel excavator 1”) has a rectangular cross section constructed for use in road tunnels, underpasses, joint grooves, and the like. It is for excavating tunnels, and is used for tunnels with relatively little water in the ground and shallow depth.
Basically, like a well-known shield excavator, the excavated earth and sand are carried out by an appropriate conveying means while excavating ground for one cycle, and concrete, steel, etc. are taken behind the tunnel excavator. The segment S (lining body) is assembled, and the reaction force is taken from the segment S for propulsion. Here, the one-cycle excavation distance is a distance at which one ring segment S can be installed.
In the present embodiment, the tunnel excavation direction is “front” and “front end”, and the opposite directions are “rear” and “rear end”.

  As shown in FIGS. 1 and 2, the tunnel excavator 1 includes an outer shell body 2 in which a tunnel section having a rectangular cross section is divided into a plurality of small section excavation sections 1A, 1B, 1C, and 1D, and each small section excavation. An opening / closing lid 3 that opens and closes the opening on the face side of each of the sections 1A to 1D, and an air bag 4 that is provided on the front surface 3b of the opening / closing lid 3 and that can propel the outer shell 2 while keeping the face pressed. A pressing means and an inflatable bag body). That is, the tunnel excavator 1 has two sections in the vertical direction and small section excavation sections 1A, 1B, 1C, and 1D that are divided into four rows in two rows in the left-right direction in the front view (toward the paper surface of FIG. 2). It has an arranged structure.

The outer shell body 2 is arranged in the vertical direction and the left-right direction in front view in order to partition the small-section excavation sections 1A to 1D at the front position in the skin plate 21 and the skin plate 21 having a rectangular shape located on the outer periphery. The partition wall 22 and the support frame portion 23 that is framed in a rectangular shape along the circumferential direction of the rear side inner surface in the skin plate 21. On the upper inner surface side of the skin plate 21, a slide hood 5 that can protrude toward the face is provided.
The front end 2a of the skin plate 21 has a shape inclined at a predetermined inclination angle with respect to a vertical plane orthogonal to the traveling direction of the tunnel excavator 1 so that the upper part protrudes from the lower part to the face side. In other words, the positions of the excavation surfaces (faces) in the upper small section excavation sections 1A and 1C are located on the front side in the forward direction of the tunnel excavator 1 from the lower small section excavation sections 1B and 1D.

  And the some outer periphery rear end part 23a of the support frame part 23 is provided with several propulsion jacks 6, 6, ... along the circumferential direction. These propulsion jacks 6, 6,... Are configured to advance the tunnel excavator 1 by pressing the tip of the jack against the segment S.

The slide hood 5 is positioned above the upper small section excavation sections 1A and 1C inside the skin plate 21, and the rear end side of the tunnel hood 1 is supported by the hood jack 51 supported by the front surface 23b of the support frame portion 23. It is provided so as to be able to advance and retreat in the propulsion direction, and protrudes into the ground of the face to prevent collapse of the upper ground during excavation. The front end of the slide hood 5 has a blade edge 5a formed with an inclined surface that inclines toward the face from the inside to the outside of the tunnel cross section.
And the slide hood 5 has the length dimension of the left-right direction (width direction) which covers the upper direction of small-section excavation division 1A-1D. The length of the slide hood 5 protruding forward is equal to or larger than the excavation distance for at least one cycle.

As shown in FIGS. 1 and 2, the open / close lid 3 has a flat plate shape with a size that closes the openings of the small cross section excavation sections 1 </ b> A to 1 </ b> D, and is surrounded by a partition wall 22 and a skin plate 21. An opening serving as an excavation section is arranged at a position to close the opening. In the small section excavation sections 1A and 1C located in the upper stage, the face plate of the opening / closing lid 3 is arranged in a state orthogonal to the tunnel axis direction (axis in the length direction of the tunnel excavator 1), and the small section excavation located in the lower stage In the sections 1 </ b> B and 1 </ b> D, the face plate of the opening / closing lid 3 is arranged along the inclined surface of the front end 2 a of the skin plate 21.
The open / close lid 3 has one side of a rectangle (in the upper section of the small section excavation section 1A, 1C, either side in the left-right direction in the front view shown in FIG. 2, or in the lower section of the section 1B, 1D. In the section, the upper side part) forms a rotation shaft 3a, and is supported rotatably about the rotation shaft 3a. That is, when the open / close lid 3 is open, the small section excavation section is opened with respect to the face, so that excavation is possible. When the open / close cover 3 is closed, the small section excavation section is closed with respect to the face. It becomes a state.

As shown in FIG. 2, the airbag 4 includes four rows in two rows in the vertical direction in each of the small-section excavation sections 1 </ b> A to 1 </ b> D and two rows in the left-right direction in a front view. An inflatable bag body that can be inflated over substantially the entire surface of ˜1D.
As shown in FIGS. 3A and 3B, specifically, the airbag 4 is fixed to the front surface 3 b of the opening / closing lid 3, and piping disposed in the opening / closing lid 3 inside the airbag 4. The structure expands at a predetermined pressure by flowing air (fluid) through 41. The air bag 4 is provided with a relief valve 42 in the pipe 41 for keeping the inside at a predetermined pressure and extracting the air to reduce the pressure when the inside becomes a predetermined pressure or higher.

The predetermined pressure of the airbag 4 is a pressure having a withstand pressure equal to or higher than the earth pressure on the front surface 3 b of the opening / closing lid 3. The size of the airbag 4 when inflated is close to the face of the face when excavated at a predetermined excavation distance (excavation distance corresponding to one ring of the segment S) in each of the small-section excavation sections 1A to 1D. The size is possible and can be pressed. And it is supposed that it is preferable that the four airbags 4, 4,... Provided in each of the small-section excavation sections 1A to 1D are in close contact with each other at the time of expansion.
In other words, in the present tunnel excavator 1, the opening / closing lid 3 is closed after excavating the face in each of the small-section excavation sections 1A to 1D, and the airbag 4 is inflated so as to apply pressure corresponding to the soil water pressure of the excavation part. It is configured to extend in the tunnel axis direction and press the face.

Next, the operation of the tunnel excavator 1 and the tunnel excavation method will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the tunnel excavation method using the present tunnel excavator 1 opens a part of the open / close lid 3 among the four small-section excavation sections 1 </ b> A to 1 </ b> D, and opens the face of the face from the opening. Excavating a mountain, then closing the open / close lid 3 and inflating the airbag 4 provided on the front surface of the open / close lid 3 to press the face with a predetermined pressing force; Open the open / close lid 3 in any of the excavation sections 1A to 1D, excavate the ground of the face from the opening, close the open / close lid 3, and inflate the airbag 4 provided in front of the open / close lid 3 And a step of pressing the face with a predetermined pressing force.
Then, all of the small-section excavation sections 1A to 1D are excavated, and the small-section excavation sections 1A to 1D of the small-section excavation sections 1A to 1D are pressed by inflating the airbag 4 with respect to the small-section excavation sections that are likely to collapse in the face. Put it in a state. And while maintaining the pressing state, the airbag 4 is reduced and the tunnel excavator 1 is propelled, and a tunnel is constructed by assembling the segment S in the rear.

  Further, the excavation procedure will be specifically described. In the present embodiment, the excavation order of the small section excavation sections is performed in the order of reference numerals 1A, 1B, 1C, and 1D. In the following description, the opening / closing lid and the airbag corresponding to each of the small-section excavation sections 1A to 1D will be described with reference numerals A to D as necessary.

  First, as shown in FIG. 4A, the slide hood 5 is protruded toward the face by inserting a reaction hood into the support frame 23 of the outer shell 2 and extending the hood jack 51, and inserted into the ground. The ground hood above the small section excavation sections 1A to 1D is pressed by the slide hood 5 from below. Thereby, in the excavation process mentioned later, the slack of the face in small section excavation section 1A, 1D can be made still smaller, and it can excavate safely with the stable ground.

  Next, one of the plurality of small-section excavation sections 1A to 1D (here, the small-section excavation section 1A) is opened and the cover 3A is opened, and the face side is opened. The excavation machine (not shown) or the like is used to excavate the face ground for an excavation distance of one cycle. The excavated earth and sand taken into the outer shell body 2 is carried out to the rear of the tunnel (outside the tunnel) by appropriate conveying means such as a transfer conveyor, a dump truck, and a conveying cart.

  As shown in FIG. 4 (b), after excavating one cycle, the open / close lid 3 is closed, air is introduced into the airbag 4A to be expanded, and the face face excavated with a predetermined pressure (reference numeral Ga) Press. The pressure in the airbag 4A at this time is maintained at a pressure that can withstand the earth pressure of the excavated face as described above, and the ground of the face is in a stable state.

Next, as shown in FIG. 5 (a), the opening / closing lid 3B of the lower section excavation section 1B in the lower stage of the small section excavation section 1A that has completed the excavation process described above is opened to open the face side, and the opening is opened from the opening. The face ground is excavated in the same manner as the small section excavation section 1A. Thereafter, as shown in FIG. 5B, the open / close lid 3B is closed, air is introduced into the airbag 4B to be expanded, and the face face Ga excavated with a predetermined pressure is pressed.
The open / close lid 3B of the small cross section excavation section 1B (similar to the small cross section excavation section 1C) located in the lower stage of the outer shell 2 is provided with an open / close rotary shaft 3a on the upper portion thereof. It can be opened and closed using a driving means (symbol M) such as an electric motor with a wire hung on the bottom.

  Thereafter, the entire cross section of the tunnel excavator 1 is excavated by sequentially repeating the same procedure as that of the small cross section excavation sections 1A and 1B described above in the order of the small cross section excavation section 1C on the left side of the upper stage and the small cross section excavation section 1D of the lower stage.

Then, as shown in FIG. 6 (a), the slide hood 5 is drawn into the outer shell body 2, and the propulsion jack 6 is pulled out while reducing the air in the airbag 4 in each of the small section excavation sections 1A to 1D. Is extended to advance (promote) the outer shell 2.
In this case, as described above, the pressure inside the airbag 4 is reduced by the relief valve 42 (see FIGS. 3A and 3B) when the pressure in the airbag 4 exceeds a predetermined pressure. It is held at a constant pressure. Therefore, when the outer shell body 2 moves forward, even if the airbag 4 interposed between the opening / closing lid 3 and the face is pressurized and the internal pressure increases, the relief valve 42 causes the interior of the airbag 4 to be increased. Since the pressure is maintained at a constant pressure, loosening of the face during excavation can be suppressed.

Then, the segment S assembled at the rear of the tunnel excavator 1 is used as a reaction force to extend the jacks 6, 6,... Provided at the rear of the skin plate 21, and the distance corresponding to the jack stroke (for one cycle) The outer shell 2 can be moved forward by a distance of excavation).
Subsequently, as shown in FIG. 6 (b), after the outer shell body 2 is moved forward, the extended propulsion jacks 6, 6,... Are contracted, and the contracted propulsion jacks 6, 6,. A new segment S for one ring is installed in a space formed between the existing segments S using an unillustrated erector or the like.
Up to here is the excavation process for one cycle in the tunnel excavator 1, and a tunnel having a rectangular cross section is constructed by sequentially repeating this process.

  As described above, in the open-type tunnel excavator and the tunnel excavation method according to the present embodiment, the open / close lid 3 is provided in each of the small-section excavation sections 1A to 1D, and the air pressure 4 is pressed on the front surface 3b of the open / close lid 3 The open-type tunnel excavator 1 having a simple structure can be used for excavation by reducing the area where the face is opened, and the face during excavation can be stabilized even in shallow tunnels. Since the settlement can be suppressed, the cost of the tunnel excavator can be reduced as compared with a sealed shield machine having a complicated structure.

The embodiments of the open tunnel excavator and the tunnel excavation method according to the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. is there.
For example, in the present embodiment, the airbag 4 that allows air to flow in is used. However, the present invention is not limited to the pressing means having such a structure, and other fluid such as water is put inside. It may be a water bag that can be pressurized. For example, the bellows-shaped pressing means that expands and contracts in the excavation direction of the tunnel excavator 1 is fixed to the front surface 3b of the opening / closing lid 3, and an expansion / contraction bag having a structure in which a fluid such as air flows in and out of the pressing means. It does not matter even if it is a body.
Then, in the present embodiment, an inflatable / reducible bag is used as the pressing means. However, the present invention is not limited to this, and for example, a pressing plate having an area capable of pressing the face surface, and a pressing plate The pressing means may be constituted by a hydraulic jack with a relief valve that can be extended and reduced in the tunnel axis direction provided on the back surface, and the pressing means may be attached to the front surface of the opening / closing lid.

In the present embodiment, the airbag 4 is fixed to the front surface 3b of the opening / closing lid 3, and the airbag 4 is present on the front surface 3b even when the airbag 4 is contracted. There is no particular limitation on the structure for attaching the airbag 4 to the air bag. For example, a configuration may be adopted in which a recess is provided in the front surface 3b of the open / close lid 3, and the airbag in a reduced state is accommodated in the recess.
Note that the number of airbags 4 provided in each of the small-section excavation sections 1A to 1D is not limited to four as in the present embodiment, and is one or more. It doesn't matter.

  Further, in this embodiment, the segment S is used as the lining body, and the outer shell body 2 is advanced by the propulsion jack 6 provided in the tunnel excavator 1. It is also possible to adopt a digging method in which a pipe is used and a tunnel excavator and a propulsion pipe following the tunnel digging machine are advanced by one ring (one cycle) at the same time by an extrusion jack provided in the starting part by a so-called propulsion method. . In this case, the tunnel excavator 1 may not be provided with the propulsion jack 6.

  And in this Embodiment, it is set as the structure which made the small cross-section excavation division 1A-1D into the rectangular cross section of the tunnel excavator 1 by dividing into 4 parts of 2 steps | paragraphs in the up-down direction, and 2 rows in the left-right direction. The number of divisions and the division form are not limited. For example, the small-section excavation section may be divided into six sections of two rows in the vertical direction and three rows in the horizontal direction. In short, the size of the small section excavation section, the number of divisions, and the like may be set in correspondence with the rectangular section shape of the outer shell body 2.

In this embodiment, the tunnel excavator 1 has a rectangular cross section. However, the tunnel excavator 1 is not limited to a rectangular cross section. For example, the outer shell has a circular shape, and the opening shape of the internal small cross section excavation section (opening / closing) The shape of the lid 3 is also the same, and an open type tunnel excavator having a quadrangular shape in front view may be used.
Further, in the present embodiment, the small-section excavation sections are excavated in the order of reference numerals 1A, 1B, 1C, and 1D, but the order is not limited to such a construction order, for example, two rows of small-section excavation sections 1A, After excavating 1C first, the lower two rows of small section excavation sections 1B and 1D may be excavated. Moreover, what is necessary is just to determine suitably according to the natural ground state about the excavation order of a small section excavation section.

  Further, in the present embodiment, one of the plurality (four) of small cross-section excavation sections 1A to 1D is constructed in order to excavate by opening the open / close lid 3 in order, that is, with a minimum open area to the face. For example, when the natural ground of the face is self-supporting and is a good natural ground with almost no looseness, for example, open and close the lids of the two small section excavation sections at the same time. May be.

  Furthermore, in this embodiment, the airbag 4 is inflated in all the small cross-section excavation sections 1A to 1D to press the face, but for example, there is a risk of collapse in the divided small cross-section excavation sections. In the case where it is confirmed that there is no natural ground, it is not necessary to perform an operation step of inflating the airbag 4 after excavation and pressing the face with a predetermined pressure. Moreover, in the section excavated last among the small section excavation sections, the outer shell body 2 can be moved forward and the opening / closing lid 3 can be moved to a position in contact with the face within an early time after the excavation. In some cases, the face may not be collapsed. In such a case, the face pressing process by the airbag 4 may be omitted.

1 is a side view showing an overall outline of a tunnel excavator according to an embodiment of the present invention. It is a front view of the tunnel excavator shown in FIG. It is a side view of the airbag provided in the front surface of an opening-and-closing lid, Comprising: (a) is a figure which shows the state which shrunk | reduced, (b) is a figure which shows the expanded state. (A), (b) is a figure which shows the excavation process by a tunnel excavator. (A), (b) is a figure which shows the excavation process following FIG.4 (b). (A), (b) is a figure which shows the state which advances an outer shell after excavation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tunnel excavator 1A-1D Small-section excavation section 2 Outer shell body 3 Opening-closing lid 4 Air bag (pressing means, expansion bag body)
5 Slide hood 42 Relief valve S segment (lining body)
Ga facet

Claims (4)

An open tunnel excavator for excavating with an opening on the face side,
An outer shell formed by dividing the tunnel cross section into a plurality of small cross section excavation sections;
An opening and closing lid for opening and closing the opening on the face side of the small section excavation section;
A pressing means that is provided on the front surface of the opening / closing lid, and that can propel the outer shell while maintaining a state in which the face is pressed;
Equipped with a,
The pressing means is an inflatable bag body that is provided on the opening / closing lid provided in each of the small-section excavation sections and is inflatable by allowing a fluid to flow inside.
Each of the inflatable bag bodies can be inflated independently,
Said outer During advancement of the shell, while reducing by far the fluid inside the said expansion bag, open tunnel boring machine characterized that you hold the inflation bag body in a state of constant pressure. The open-type tunnel excavator according to claim 1, wherein a slide hood capable of projecting toward the face side is provided on an upper portion of the outer shell body. The open type according to claim 1 or 2, wherein the expansion bag body is provided with a relief valve that draws out an internal fluid and depressurizes when the expansion bag body reaches a predetermined pressure or more. Tunnel excavator. An outer shell body obtained by dividing a tunnel cross section into a plurality of small cross section excavation sections, an open / close lid that opens and closes the opening on the face side of the small cross section excavation section, and a front face of the open / close lid that presses the face Pressing means that can propel the outer shell body while maintaining the state, and the pressing means is provided in the opening / closing lid provided in each of the small-section excavation sections, and allows fluid to flow into the inside. A tunnel excavation method using an open-type tunnel excavator in which each of the inflatable bag bodies can be inflated independently,
The expansion bag provided on the front surface of the open / close lid while opening a part of the open / close lid of the plurality of small section excavation sections, excavating the ground of the face from the opening, and then closing the open / close lid Pressing the face with a predetermined pressing force by the body;
Opening the opening / closing lid of another small section excavation section, excavating the ground of the cutting face from the opening, and then closing the opening / closing lid, the face is predetermined by the expansion bag body provided in front of the opening / closing lid Pressing with a pressing force of
With
After excavating all of the small-section excavation section and pressing all of the front surface of the small-section excavation section where there is a risk of collapsing the face with the expansion bag body, when the outer shell body moves forward, the expansion bag A tunnel excavation method characterized in that the fluid inside the body is drawn and reduced to propel the open-type tunnel excavator while holding the inside of the inflated bag at a constant pressure.

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