JP7498146B2 - Tunnel box group and tunnel construction method - Google Patents

Description

The present invention relates to a group of tunnel boxes and a tunnel construction method.

In the jacking method, a plurality of jacking boxes formed of steel shells or the like are connected together via ring joints (in the form of inserting the end of one jacking box into the end of the other jacking box, or in the form of bolted joints, etc.), or a plurality of segment boxes are connected together via ring joints (in the form of bolted joints, etc.), to construct a tunnel box group such as a jacking box group or a segment box group underground. Hereinafter, in this specification, the jacking box and the segment box groups are collectively referred to as a tunnel box, and the jacking box group and the segment box group are collectively referred to as a tunnel box group.
There are various types of longitudinal alignment for tunnel box groups, including straight lines, circles, curved lines with multiple curvatures, and a mixture of straight and curved lines. For example, when constructing a tunnel box group that has curved sections in the vertical plane, the ring joints between adjacent tunnel boxes need to be bolted together in order to maintain the posture of the tunnel box group.
Incidentally, when constructing a group of tunnel boxes having a curved section in the vertical plane by using the jacking method, in order to ensure smooth advancement of the tunnel excavator and the following group of tunnel boxes in the curved section, a common construction method is to extend a copy cutter from the side of the cutter head of the tunnel excavator into the ground to perform over-excavation, and to fill the over-excavation section with lubricant while the tunnel excavator excavates and advances the group of tunnel boxes. At this time, since the tunnel excavator is present in the lubricant filled in the over-excavation section, there is a risk that the tunnel excavator will meander during the excavation process. In order to eliminate this meandering and to ensure that the excavation direction does not deviate from the control value of the planned vertical section alignment, for example, a direction control jack equipped on the tunnel excavator is operated to keep the excavation direction within the control value and to make the tunnel excavator excavate.

However, the tunnel box group following the tunnel tunneling machine is made of steel shells and is bolted to each other at ring joints, so the rigidity of the ring joints is extremely high.Furthermore, in areas where the actual alignment deviates from the planned alignment, the tunnel box group is restrained from lateral displacement by the surrounding ground, so there is a risk that sufficient directional control will not be possible even if an attempt is made to change the direction of the tunnel tunneling machine and the tunnel box group behind it using only the tunnel tunneling machine's directional control jack.
In view of the above, what is desired is a tunnel box group in which the tunnel boxes are bolted together at ring joints, and a method for constructing a tunnel using this tunnel box group, in which the tunnel boxes are connected to each other via ring joints that have both rigidity and flexibility, and a construction method for a tunnel formed by this tunnel box group.

Here, Patent Document 1 proposes a propulsion box that can flexibly respond to linear changes and a method for constructing a tunnel using this propulsion box. Specifically, the propulsion box is arranged continuously underground to form a tunnel having a curved section and a straight section, and is arranged between the tunnel face and the tunnel mouth end of the curved section, and a recess is formed on the top and bottom or left and right of one of the end faces on the face side or the tunnel mouth side, and a protrusion is formed at a position corresponding to the recess on the other end face, and the protrusion can be inserted into a recess formed in another propulsion box arranged continuously on the face side or the tunnel mouth side, and the contact surface with the recess is arc-shaped.
In addition, the tunnel construction method is a method in which a tunnel having curved sections and straight sections is constructed by arranging these thrust boxes in succession using a thrusting method, and a pushing force is applied from the tunnel entrance side with the convex portion of one thrust box inserted into the concave portion of the other thrust box that are arranged in succession.
In the ring joints between these propulsion boxes, the propulsion boxes are connected to each other by bolting them together with bolts having elastic washers.

JP 2007-70938 A

The method for constructing a tunnel and a propulsion box described in Patent Document 1 allows a tunnel to be constructed while flexibly responding to linear changes. However, since all bolts in the ring joints are equipped with elastic washers, there are concerns about ensuring the rigidity of the ring joints that connect the propulsion boxes together.

The present invention aims to provide a tunnel box group in which the tunnel boxes are bolted together at ring joints, and a method for constructing a tunnel using this tunnel box group, in which the tunnel boxes are connected to each other via ring joints that have both rigidity and flexibility, and a method for constructing a tunnel formed by this tunnel box group.

In order to achieve the above object, one aspect of the tunnel box group according to the present invention comprises:
A group of tunnel boxes consisting of a plurality of tunnel boxes that are installed in the ground by a jacking method and require directional control when being jacked up,
The present invention is characterized in that both endless joint plates forming the ring joints of two adjacent tunnel boxes are connected by a first bolt nut equipped with an elastic washer and a second bolt nut not equipped with an elastic washer.

According to this aspect, the endless joint plates that form the ring joint of two adjacent tunnel boxes are connected by a first bolt nut with an elastic washer and a second bolt nut without an elastic washer. Therefore, by loosening the second bolt nut, the flexibility of the ring joint is ensured by the first bolt nut, and by tightening the second bolt nut, the rigidity of the ring joint is ensured. This makes it possible to form a group of tunnel boxes in which the tunnel boxes are connected to each other via a ring joint that has both rigidity and flexibility.

In addition, another aspect of the tunnel box group according to this aspect is as follows:
The second bolt nut is provided with a double nut, and by adjusting the double nut, the opening amount in the ring joint can be freely adjusted.

According to this aspect, the second bolt nut is equipped with a double nut, and the amount of mesh in the ring joint when flexible can be freely adjusted by adjusting the double nut. This allows the inner nut that constitutes the double nut to take the reaction force by using the outer nut as a stopper, and the amount of mesh in the second bolt nut that is set for each location on the joint plate (for each position in the endless axial direction when the propulsion box is viewed from the front of the ring joint, for each position in the endless axial direction, and for each position in the vertical or horizontal width direction of the joint plate) can be guaranteed with high precision.

Another aspect of the tunnel box group according to the present invention is
The present invention is characterized in that in both of the joint plates of two adjacent tunnel boxes, a plurality of the first bolt nuts and a plurality of the second bolt nuts are arranged at intervals in the endless circumferential direction, and one or a plurality of the second bolt nuts are arranged between two adjacent first bolt nuts.

According to this aspect, the first bolt nuts and the second bolt nuts are arranged alternately in the endless circumferential direction, or multiple second bolt nuts are positioned between the first bolt nuts, thereby forming a group of tunnel boxes with as uniform rigidity and flexibility as possible over the entire area of the joint plate.

Another aspect of the tunnel box group according to the present invention is
In the tunnel box,
A plurality of main girders extending endlessly in a transverse direction perpendicular to the longitudinal direction of the group of tunnel boxes are arranged at intervals in the longitudinal direction, and the joint plates forming the ring joints at both ends are formed by the main girders,
A flange is attached to the outer peripheral edge or the inner peripheral edge of the joint plate so as to extend endlessly and protrude toward the inside of the tunnel box in the longitudinal direction,
The two adjacent tunnel boxes are configured so that the joint plates of both are in surface contact with each other,
The present invention is characterized in that a female fitting portion is provided at an end of the flange of one of the tunnel boxes, and a male fitting portion that fits into the female fitting portion is provided at an end of the flange of the other tunnel box.

According to this embodiment, of the multiple main girders that make up the tunnel box made of steel shell, two main girders are joint plates of the ring joint at both ends of the tunnel box, so that a ring joint with high rigidity can be formed. In addition, a flange is attached to the outer or inner edge of the joint plate, which extends endlessly and protrudes inward in the longitudinal direction (propulsion direction) of the tunnel box, and a mating female part provided at the end of the flange of one tunnel box is fitted to a mating male part provided at the end of the flange of the other tunnel box. In both cases where the joint plates of both tunnel boxes are in complete surface contact with each other in a straight section, and where the radially inner ends of both tunnel boxes are in line contact with each other in a curved section, the mating female part and the mating male part can suppress the misalignment of adjacent tunnel boxes. In addition, the mating structure at the end of the ring joint also improves the watertightness of the ring joint.

Another aspect of the tunnel box group according to the present invention is
The present invention is characterized in that an endless half groove is provided at corresponding positions of the endless contact surfaces of the joint plates of two adjacent tunnel boxes, which are in surface contact with each other, and an endless seal groove is formed by both of the endless half grooves, and an endless gasket is accommodated in the seal groove in a pressed state.

According to this aspect, the endless gasket is housed in a pressure-welded state in the endless seal groove formed by both endless half-grooves provided in the joint plates of the adjacent tunnel box bodies, thereby ensuring high water-tightness in the ring joint. In addition, when the ring joint has a fitting structure of a female fitting part and a male fitting part in both joint plates (flanges provided therein) as described above, a ring joint with even higher water-tightness can be formed.

In addition, one aspect of the tunnel construction method according to the present invention is to
A tunnel construction method for constructing a tunnel by forming a group of tunnel boxes by installing a plurality of tunnel boxes in the ground while controlling the direction of the tunnel boxes using a jacking method,
The tunnel box group is formed by connecting the endless joint plates of the two adjacent tunnel box ring joints with a first bolt nut having an elastic washer and a second bolt nut not having an elastic washer,
In the curved section of the tunnel box group, the second bolts and nuts are loosened to open the holes, and the elastic washers provided on the first bolts and nuts are expanded and contracted to control the direction of the tunnel box group while it is advanced.

According to this aspect, a tunnel box group is formed by connecting both endless joint plates that form the ring joints of two adjacent tunnel boxes with a first bolt nut equipped with an elastic washer and a second bolt nut that does not have an elastic washer.By loosening the second bolt nut, the flexibility of the ring joint is ensured by the first bolt nut, and the tunnel box group can be advanced while controlling its direction in curved sections.
More specifically, in the straight section, the rigidity of the ring joint is ensured by tightening the second bolt nut. On the other hand, in the curved section, the second bolt nut is loosened and opened in a suitable manner (amount of loosening) at the position of each second bolt nut on the joint plate according to the curvature, and the elastic washer is expanded and contracted at the first bolt nut, so that the ring joint is given flexibility due to the elastic washer and rigidity due to its spring force, and a curved section having both rigidity and flexibility can be formed. Therefore, it is possible to construct a tunnel having a straight section with a high-rigidity ring joint, a curved section having both rigidity and flexibility, and in the case of a single-circular tunnel (a circumferential tunnel in which the entire section is a curved section), a tunnel having both rigidity and flexibility.

The tunnel box group and tunnel construction method of the present invention can provide a tunnel box group in which the tunnel boxes are connected to each other via ring joints that have both rigidity and flexibility, and a construction method for a tunnel formed by this tunnel box group.

FIG. 2 is a diagram showing an example of the overall configuration of a tunnel box group according to an embodiment. FIG. 1 is a schematic diagram showing the state in which a tunnel tunneling machine advances a group of tunnel boxes in a curved section while constructing an overexcavation area and filling the overexcavation area with lubricant. FIG. 2 is a front view of an example of a tunnel box that constitutes a tunnel box group according to an embodiment, showing a joint plate that constitutes a ring joint as viewed from the front. 4 is a view taken along the line IV-IV in FIG. 3, and also shows the amount of mesh opening in a ring joint. FIG. 4 is an enlarged view of a portion V in FIG. 3 . FIG. 5 is an enlarged view of a portion VI in FIG. 4 . FIG. 7 is an enlarged view of part VII in FIG. 4 . FIG. 7 is a diagram showing a state in which the ring joint shown in FIG. 6 is opened. FIG. 8 is a diagram showing a state in which the ring joint shown in FIG. 7 is opened.

Below, the tunnel box group and tunnel construction method according to the embodiment will be described with reference to the attached drawings. Note that in this specification and the drawings, substantially identical components may be designated by the same reference numerals to avoid redundant description.

[Tunnel box group and tunnel construction method according to the embodiment]
An example of a tunnel box group and a tunnel construction method according to the embodiment will be described with reference to Fig. 1 to Fig. 9. Here, Fig. 1 is a diagram showing an example of the overall configuration of a tunnel box group according to the embodiment, and Fig. 2 is a schematic diagram showing a state in which a tunnel excavator constructs an over-excavation section in a curved section and advances the tunnel box group while filling the over-excavation section with a lubricant. Fig. 3 is a front view of an example of a tunnel box constituting a tunnel box group according to the embodiment, showing a joint plate constituting a ring joint from the front, Fig. 4 is a view taken along the arrow IV-IV in Fig. 3, showing the amount of opening in the ring joint, and Figs. 5, 6, and 7 are enlarged views of part V in Fig. 3, part VI in Fig. 4, and part VII in Fig. 4, respectively.

As shown in FIG. 1, when connecting and widening the main line tunnel HT (e.g., main line shield tunnel) that has already been constructed underground G with the ramp tunnel RT (e.g., ramp shield tunnel) located to the side of it underground, a shaft T is constructed that extends vertically below the ramp tunnel RT. Note that this shaft may extend diagonally downward instead of vertically.

The shaft T is constructed to a specified depth while supporting earth pressure and soil-water pressure with braces K arranged at specified intervals in the vertical direction, a reaction stand S is installed below the shaft T, and a push device BD equipped with a push jack BJ is installed on the reaction stand S. Here, the thrust device in the illustrated example is only the push device BD, but if necessary, a push device equipped with a push jack interposed inside the tunnel box group may be included, and further, if the direction control jack of the tunneling machine functions as a thrust jack, the thrust jack of the tunneling machine may also be included in the thrust device.

Tunnel boxes 20 (pushing boxes) are successively lowered from the ramp tunnel RT through the vertical shaft T in front of the main pushing device BD, and multiple tunnel boxes 20 are connected behind the tunnel excavator 10 located forward in the pushing direction, and a tunnel box group 50 formed by multiple tunnel boxes 20 is pushed through the ground G in the X1 direction to construct a circumferential tunnel 60 in a vertical plane.

The circular tunnel 60 in the illustrated example is a simple circle that surrounds the main tunnel HT and the ramp tunnel RT, but it may be a tunnel with a variety of longitudinal linear shapes, such as an ellipse or a track shape.

As shown in FIG. 2, the tunneling machine 10 has a front body 11 and a rear body 12, and between them is a propulsion jack (not shown) (a jack that controls the direction of the tunneling machine in addition to propelling the tunneling machine itself). The shape of the tunneling machine 10 when viewed from the front is, for example, a horizontally long rectangle, and multiple cutter heads 13 are arranged on the front side. Each cutter head 13 has a copy cutter 14 built in so that it can move freely in and out from the side. When creating the overexcavation area E, the copy cutter 14 extends outward from each cutter head 13, and the copy cutter 14 rotates in accordance with the rotation of the cutter head 13 to create the overexcavation area E. At this time, the size of the overexcavation area E can be adjusted as desired by adjusting the extension length of the copy cutter 14.

As the cutter head 13 rotates and the tunnel tunneling machine 10 excavates in the excavation direction along the planned longitudinal line, a pre-excavated area E of a specified width is created on the sides of the tunnel tunneling machine 10 and the following group of tunnel boxes 50, and the tunnel tunneling machine 10 fills the pre-excavated area E with lubricant U. A pre-excavated area E in the shape of a rectangular frame of a specified width is created around the tunnel tunneling machine 10, which is rectangular when viewed from the front.

As shown in Figures 3 and 4, the tunnel box 20 has a generally rectangular shape in front view (a rectangle with curved corners), a generally rectangular, endless main girder 21 in the center in the driving direction, and endless joint plates 22 in the left and right that form ring joints 29, and the entire structure is made up of a steel shell in which the main girder 21 and joint plates 22 are welded to skin plates 23 arranged around them. Here, the joint plates 22 are also main girders, and therefore the tunnel box 20 in the illustrated example has three generally rectangular main girders 21, 22 arranged at intervals in the driving direction as its main structural members. In addition to the illustrated example, the tunnel box may have a form that does not have a main girder 21.

The main girders 21, 22 have multiple vertical ribs 25 in the longitudinal direction of their endless shape. As shown in FIG. 3, the horizontally long, roughly rectangular tunnel box 20 has multiple columns 26 (two in the illustrated example) inside, which provide rigidity.

As shown in FIG. 4, the endless joint plates 22 that form the ring joints 29 of two adjacent tunnel box bodies 20 are connected by a first bolt nut 30 (see FIG. 6) equipped with an elastic washer 34 and a second bolt nut 40 (see FIG. 7) that does not have an elastic washer.

More specifically, as shown in FIG. 3, a plurality of first bolt nuts 30 and a plurality of second bolt nuts 40 are arranged at intervals in the circumferential direction of the endless joint plate 22, and one or more (two in the illustrated example) second bolt nuts 40 are arranged between two adjacent first bolt nuts.

Now, with reference to Figures 6 and 7, the specific configuration of the first bolt nut 30 and the second bolt nut 40 will be described.

As shown in FIG. 6, the first bolt nut 30 has a headed bolt 31, a tightening nut 32, and two sets of protective caps 33 and elastic washers 34. Bolt holes 22a are provided at corresponding positions on the two joint plates 22 that make up the ring joint 29, and a headed bolt 31 is inserted into the communicating bolt holes 22a. Two sets of elastic washers 34 that hold the two joint plates 22 between the head of the headed bolt 31 and the tightening nut 32 are disposed, and the tightening nut 32 is tightened with a predetermined tightening force to form a flexible bolt joint structure.

By tightening the clamping nut 32, the elastic washer 34 is evenly pressed into the protective cap 33 over its entire area, resulting in a predetermined thickness s1.

On the other hand, as shown in FIG. 7, the second bolt nut 40 has a headed bolt 41 and a double nut 42. The headed bolt 41 is inserted into the bolt holes 22a that are opened at corresponding positions on the two joint plates 22 that make up the ring joint 29, and by tightening one of the tightening nuts 42a of the double nut 42, the two joint plates 22 are clamped between the head of the headed bolt 41 and the tightening nut 42a.

The other reaction force receiving nut 42b constituting the double nut 42 is installed at a position separated by a distance s2 from the tightening nut 42a. This distance s2 is set according to the position of the second bolt nut 40 on the joint plate 22. More specifically, as shown in FIG. 4, the ring joint 29 has a larger mesh size from its radially inner end to its radially outer end, and therefore the mesh size that the first bolt nut 30 and the second bolt nut 40 should correspond to differs depending on the position of the ring joint 29. In FIG. 4, the mesh size at the installation position of each bolt nut from the radially inner to the radially outer side is indicated by t1 to t5.

Returning to FIG. 7, the spacing s2 set in the double nut 42 is set to correspond to the above-mentioned mesh size at the installation position of the second bolt nut 40 in the joint plate 22. For example, when there is no need to correspond to the mesh size in the ring joint 29 and the joint plates 22 are fastened together with the second bolt nut 40 to ensure the rigidity of the ring joint 29 for thrust construction, the ring joint 29 is formed with the clamping nut 42a tightened as shown in FIG. 7.

On the other hand, when adjusting the mesh size of the ring joint 29, as shown in FIG. 9, the tightening nut 42a is shifted to a position where it abuts against the reaction force receiving nut 42b on the outside, and the second bolt nut 40 is loosened in advance.

During the construction process of the tunnel box group 50, when the tunnel box group 50 meanders due to the meandering of the tunnel excavator 10, gaps may occur in the ring joint 29. In the tunnel box group 50 that constitutes the circumferential tunnel 60 in the vertical plane of the illustrated example, the gaps in the ring joint 29 caused by the meandering are particularly noticeable.

In this way, when the gap occurs in the ring joint 29, the first bolt nut 30 equipped with the elastic washer 34 and the second bolt nut 40 in a loose state as shown in FIG. 9 are arranged alternately in the endless circumferential direction of the ring joint 29, so that both bolt nuts follow the gap due to their inherent action.

Specifically, as shown in FIG. 8, when an opening of width s3 occurs between the joint plates 22, the first bolt nut 30 follows the opening of the ring joint 29 by deforming the two elastic washers 34 from thickness s1 to thickness s4.

On the other hand, the second bolt nut 40 is already set in a loose state as shown in FIG. 9, but when an opening of width s3 occurs between the joint plates 22, a gap s5 still remains between the tightening nut 42a and the joint plate 22, and the loose state is maintained. If the opening amount is excessively large and the gap s5 disappears, the reaction force from the tightening nut 42a pressed in from the joint plate 22 is received by the reaction force receiving nut 42b, preventing the tightening nut 42a from coming off the headed bolt 41.

In this way, when gaps form in the ring joint 29, the second bolt nut 40 is completely loosened, but the compressed elastic washer 34 of the first bolt nut 30 provides the ring joint 29 with a certain degree of rigidity. In other words, the ring joint 29 has flexibility to follow the gaps and has a certain degree of rigidity in the gapped state, making it a ring joint 29 that has both flexibility and rigidity. Therefore, as in the illustrated example, this ring joint has an ideal structure for constructing a circumferential tunnel 60 in a vertical plane where the entire area is a curved section and gaps are always expected.

In addition, in cases where the mesh size does not need to be considered (for example, when driving through a straight section), the rigidity of the ring joints 29 connecting the tunnel boxes 20 together can be increased by tightening the second bolt nuts 40 as shown in Figure 7, thereby forming a group of tunnel boxes 50 with high rigidity in the longitudinal direction.

In this way, the ring joints 29 have first bolt nuts 30 and second bolt nuts 40 alternating in the endless circumferential direction, so that a tunnel box group 50 can be formed having multiple ring joints 29 that have flexibility to follow the mesh opening, rigidity when the mesh is opened, and rigidity during construction.

As shown in detail in Figures 3 and 4 and Figures 6 to 9, a flange 24 that extends endlessly and projects inward in the longitudinal direction of the tunnel box is welded to the outer edge of the joint plate 22, and a skin plate 23 is welded to the outer surface of the flange 24.

For example, as shown in Figures 6 and 7, of the flanges 24 provided on the two joint plates 22 that make up the ring joint 29, a mating female portion 24b is provided at the end of one flange 24, and a mating male portion 24a that fits into the mating female portion 24b is provided at the end of the other flange 24.

As shown in Figures 6 and 7, when the two joint plates 22 of the ring joint 29 are in surface contact, the mating female portion 24b and the mating male portion 24a are mated.

As shown in Figures 6 and 7, endless half grooves 22b are provided at corresponding positions on the endless contact surfaces of both joint plates 22 that come into surface contact with each other. An endless seal groove 27 is formed by both endless half grooves 22b, and an endless gasket 28 is housed in this seal groove 27 in a pressure-welded state.

The gasket 28 is not a water-swelling type, but has many voids inside. Because it is not a water-swelling type, it can quickly achieve water-stopping properties after the tunnel box 20 is installed. In addition, because it has many voids inside, it has excellent deformation performance, and when the ring joint 29 opens, the gasket 28 follows it as shown in Figures 8 and 9, making it possible to ensure water-stopping properties.

In this way, the endless mating male portion 24a and the mating female portion 24b are mated with each other on the outer periphery of the ring joint 29, so that it is possible to suppress misalignment between adjacent tunnel boxes 20 in both cases, when the joint plates 22 of both tunnel boxes 20 are in complete surface contact with each other in straight sections, and when the radially inner ends of both tunnel boxes 20 are in line contact with each other in curved sections.

Furthermore, the endless male mating part 24a and the endless female mating part 24b are fitted together on the outer periphery of the ring joint 29, and an endless gasket 28 is housed in a pressure-welded state in an endless seal groove 27 located inside the joint plate 22 from this fitting structure, thereby ensuring high sealing performance in the ring joint 29 and forming a ring joint 29 that can follow the mesh opening and has high water-stopping properties.

Note that the configurations described in the above embodiments may be combined with other components, and the present invention is not limited to the configurations shown here. In this regard, changes can be made without departing from the spirit of the present invention, and can be determined appropriately according to the application form.

10: tunneling machine 11: front body 12: rear body 13: cutter head 14: copy cutter 20: tunnel box 21: main girder 22: joint plate (main girder)
22a: Bolt hole 22b: Half-split groove 23: Skin plate 24: Flange 24a: Male mating part 24b: Female mating part 25: Vertical rib 26: Pillar 27: Seal groove 28: Gasket 29: Ring joint 30: First bolt nut 31: Headed bolt 32: Clamping nut 33: Protective cap 34: Elastic washer 40: Second bolt nut 41: Headed bolt 42: Double nut 42a: Clamping nut 42b: Reaction-receiving nut 50: Tunnel box group 60: Circumferential tunnel G: Ground (underground)
HT: Main tunnel RT: Ramp tunnel T: Shaft K: Beam S: Reaction stand BD: Push-button device BJ: Push-button jack E: Overexcavation U: Sliding material

Claims (5)

A group of tunnel boxes consisting of a plurality of tunnel boxes that are installed in the ground by a jacking method and require directional control when being jacked up,
A tunnel box group, characterized in that in both endless joint plates forming the ring joints of two adjacent tunnel boxes, a first bolt nut provided with a plurality of elastic washers and a second bolt nut not provided with a plurality of elastic washers are arranged at intervals in the endless circumferential direction, one or more second bolt nuts are arranged between two adjacent first bolt nuts, and both of the endless joint plates are connected by the first bolt nut and the second bolt nut. The tunnel box group according to claim 1, characterized in that the second bolt nut is equipped with a double nut, and the opening amount in the ring joint can be freely adjusted by adjusting the double nut. In the tunnel box,
A plurality of main girders extending endlessly in a transverse direction perpendicular to the longitudinal direction of the tunnel box group are arranged at intervals in the longitudinal direction, and the joint plates forming the ring joints at both ends are formed by the main girders,
A flange is attached to the outer peripheral edge or the inner peripheral edge of the joint plate so as to extend endlessly and protrude toward the inside of the tunnel box in the longitudinal direction,
The two adjacent tunnel boxes are configured so that the joint plates of both are in surface contact with each other,
3. A tunnel box group as described in claim 1 or 2, characterized in that a mating female portion is provided at an end of the flange of one of the tunnel boxes, and a mating male portion that fits into the mating female portion is provided at an end of the flange of the other tunnel box. 4. The tunnel box group according to claim 3, wherein an endless half groove is provided at corresponding positions of the endless contact surfaces of the joint plates of two adjacent tunnel boxes that are in surface contact with each other, an endless seal groove is formed by both of the endless half grooves, and an endless gasket is accommodated in the seal groove in a pressure- welded state. A tunnel construction method for constructing a tunnel by forming a group of tunnel boxes by installing a plurality of tunnel boxes in the ground while controlling the direction of the tunnel boxes using a jacking method,
a first bolt nut having a plurality of elastic washers and a second bolt nut not having a plurality of elastic washers are disposed at intervals in the circumferential direction of the endless joint plates forming the ring joints of the two adjacent tunnel boxes, and one or more second bolt nuts are disposed between the two adjacent first bolt nuts, and the tunnel box group is formed by connecting the first bolt nut and the second bolt nut,
A tunnel construction method, characterized in that, in a curved section of the tunnel box group, the second bolts and nuts are loosened to open the holes, and the elastic washers provided on the first bolts and nuts are expanded and contracted while controlling the direction of the tunnel box group and advancing it.

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