JP2020079491A - Double circle circumferential shield excavator, shield starting base, and outer shell shielding method using a circumferential tunnel - Google Patents

Abstract

To provide a double circle circumferential shield excavator capable of efficiently constructing a circumferential tunnel with a horizontally long cross-section, a shield starting base, and an outer shell shielding method using a circumferential tunnel.SOLUTION: The double circle circumferential shield excavator excavates in the circumferential direction so that the tunnel alignment draws a constant circumferential curve. The double circle circumferential shield excavator includes: a shield machine body 2 that has a skin plate 20 that is formed in a double circle shape by partially overlapping a pair of circles in a sectional view as seen from the tunnel axis direction, and which includes a front torso plate 20A and a rear torso plate 20B are divided and joined in the front-rear direction; and a cutter head 3 whose center of rotation is the center of each of a pair of circles. The shield machine body 2 is provided with a partition wall 21 that is provided on the front body plate 20A and separates the chamber 3A on the working face side from the shield machine body. The front torso plate 20A and the rear torso plate 20B has a configuration that the inner circumference side in the circumferential direction is curved and joined at a predetermined angle according to the linear curvature due to the double-circular circumference shield excavator 1.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an outer shell shield construction method using a double circular circumference shield excavator, a shield starting base, and a circumferential tunnel.

In large-scale road tunnels, it was required to provide a large-section underground cavity at the junction of the main tunnel and ramp tunnel, which are constructed by the shield method. As a method of constructing such an underground cavity having a large cross section, for example, as shown in Patent Document 1, the outer shell portion of the branch confluence portion to be constructed is first constructed with a lining structure, and then the lining is performed. It is proposed to construct by excavating the inside of the frame structure.
For such a lining frame structure, a plurality of outer shell tunnels are constructed in the outer shell part of the branch confluence part by a shield method at intervals in the circumferential direction of the branch confluence part, and further ground protection work is applied by the freezing method. It is known that the structure is constructed by cutting open the outer shell tunnels next to each other, assembling the reinforcing bars and the formwork, and then placing concrete.

  In addition, when constructing the branch confluence part, a rectangle extending along the circumferential direction with the direction parallel to the tunnel axis direction as the central axis is surrounded so as to surround the main tunnel and the ramp tunnel excavated in advance. A construction method is known in which a circumferential tunnel having a cross section is constructed by a shield construction method, and the outer shell shield excavator is started by using this circumferential tunnel as a starting base to excavate the outer shell tunnel (see, for example, Patent Document 2). ).

Japanese Patent No. 4958035 JP, 2014-43738, A

However, the conventionally proposed method for constructing a circumferential tunnel that serves as a starting base for an outer shell shield excavator for excavating an outer shell tunnel has the following problems.
That is, the starting base formed by the circumferential tunnel requires a certain amount of space in the depth direction for starting the outer shell shield excavator. In other words, the cross-sectional shape of the circumferential tunnel is a horizontally long rectangular cross section that is long in the depth direction, which is effective and desirable for use as a starting base. However, excavation and lining with a circular shield machine having a rectangular cross section is structurally unstable with respect to an external force due to earth water pressure received from the surroundings, and there is a problem that construction is difficult.

  On the other hand, a shield having a circular cross section is relatively stable in construction management and is structurally stable even when excavating in the circumferential direction. However, as mentioned above, when constructing with a circular shield machine with an outer diameter that can secure space in the depth direction for starting the outer shell shield excavator, when using it as a starting base of the outer shell shield excavator, There was room for improvement in that respect, because large unnecessary spaces were created above and below the tunnel, resulting in inefficient construction.

  The present invention has been made in view of the above-mentioned problems, and a double circular circumferential shield excavator capable of efficiently constructing a circumferential tunnel having a laterally elongated cross-section, a shield starting base, and an outside using a circumferential tunnel. The purpose is to provide a shell shield method.

  In order to achieve the above object, the double circular circumferential shield excavator according to the present invention is a double circular circumferential shield excavator that is dug in the circumferential direction so that the tunnel line shape draws a constant circumferential curve. A shield machine main body having a skin plate formed in a compound circular shape by overlapping a part of a pair of circles in a cross-sectional view viewed from the tunnel axis direction, and having a skin plate that is split and joined to the front body plate and the rear body plate in the front-rear direction, A cutter head having the center of each of the pair of circles as the center of rotation of the cutter, and the shield machine main body is provided with a partition wall that divides the chamber on the face face and the inside of the shield machine from the front body plate. The front body plate and the rear body plate are refraction-bonded to each other on an inner peripheral side in the circumferential direction at a predetermined angle according to a linear curvature by the double circular circumferential shield excavator. I am trying.

  Further, the shield starting base according to the present invention is a shield starting base composed of a double circular circumferential tunnel constructed using the above-mentioned double circular circumferential shield excavator, wherein the double circular circumferential shield excavation is performed. With the excavation in the circumferential direction of the machine, a double-circular circumferential segment is constructed so as to extend in the circumferential direction, and on the inner side of the circumferential segment, there is a space for starting another shield excavator. It is characterized by being formed.

  Further, the outer shell shield construction method using the circumferential tunnel according to the present invention uses a double circular circumferential tunnel constructed using the double circular circumferential shield excavator described above, and An outer shell shield construction method using a circumferential tunnel for constructing an outer shell tunnel that is dug along a shell part, wherein a part of the compound circular circumference shield excavator is provided on a part of the construction base end side of the underground cavity. A step of constructing a first shield starting base forming a starting portion, and a step of starting the compound circular circumferential shield excavator from the first shield starting base and digging in the circumferential direction to construct the circumferential tunnel. And the circumferential tunnel is used as a second shield starting base, an outer shell shield excavator is started from the second shield starting base, and the outer shell tunnel is constructed by excavating along the longitudinal direction of the underground cavity. And a process.

In the present invention, the front body plate and the rear body plate of the skin plate of the double circular circumferential shield excavator are refracted and joined at a predetermined angle to the inner peripheral side in the circumferential direction, and with a constant curvature while maintaining a constant posture. It is possible to dig in the circumferential direction. Therefore, it is possible to efficiently construct a circumferential tunnel of a compound circular shape having an oblong cross section, which is dug in a tunnel shape that draws a circumferential curve that is a predetermined circumferential direction. Since the cross-sectional shape of the circumferential tunnel excavated by the double-circle circumferential shield excavator is a laterally long double-circular shape when viewed from the circumferential direction, the longitudinal direction of the cross section is the tunnel axial direction of the shield tunnel. It is possible to secure a starting space in the depth direction necessary for starting another shield excavator, and use it as a starting base.
In other words, as a method of constructing a circumferential tunnel having a horizontally long cross section, by using a double circular circumference circular shield excavator as in the present invention, a shield excavator having a rectangular cross section with a complicated structure like the conventional one can be obtained. Compared with the case where it is used or the method of excavating and connecting two shield excavators having a circular cross section in parallel, the construction is simpler and the cost can be reduced. Further, in the case of the double circular circumference shield excavator, there is an advantage that complicated attitude control is unnecessary as compared with a seal excavator having a rectangular cross section whose body is easily affected by rolling and which is generally difficult to control.

Further, in the present invention, the circumferential tunnel has a double circular shape formed by a curved line, so that a tunnel having a rectangular cross section and a plurality of circular tunnels are structurally connected to the soil pressure received from the ground as compared with a plurality of connected tunnels. This is advantageous and can be structurally stable, for example the thickness of the segments can be kept small.
In the present invention, for example, as another shield excavator, an outer shell shield excavator that constitutes an outer shell of an underground cavity having a large cross section is started at a plurality of intervals in the circumferential direction of the circumferential tunnel to form an outer shell. A plurality of outer shell tunnels are formed in the outer shell tunnel, and the plurality of outer shell tunnels are excavated and connected to each other to construct a frame structure in the outer shell portion.

  Further, in the double circular circumferential shield excavator according to the present invention, the shield machine main body has attitude control means, which is capable of protruding toward the natural rock side in a direction orthogonal to the tunnel axis direction and an overburdening device. Of these, at least one of them may be provided.

  In this case, the ground machine gripper is projected toward the outside in the radial direction of the tunnel, the reaction force is applied to the ground of the excavation wall surface, and the compound circular circumference shield excavator is excavated. It is possible to suppress deviation from the linear shape of the curvature. In particular, when excavating in the circumferential direction, the ground gripper on the outer peripheral side is overhanged to take a reaction force to the natural ground, and the ground on the side that is bent by the overdrilling device (the inner peripheral side in the circumferential direction) is left over. By digging, the shield machine main body can press the force toward the outer peripheral side to stabilize the posture during the excavation, which facilitates the posture control.

  Further, in the shield starting base according to the present invention, a plurality of middle pillars are provided along the circumferential direction at a center of a cross section of the circumferential tunnel having a double circle shape, and at least the middle pillars are provided. The center pillar located in the starting area of the another shield excavator in the circumferential tunnel may be removable so as to be removable before the another shield excavator is installed.

  Further, an outer shell shield construction method using a circumferential tunnel according to the present invention comprises a step of providing a plurality of middle pillars along the circumferential direction at a center of a cross section of the circumferential tunnel having a double circular shape, and the outer shell. Before installing the shield excavator, a step of removing at least the middle pillar located in the starting region of the outer shell shield excavator in at least the circumferential tunnel among the plurality of middle pillars may be included. ..

In this case, the starting region of another shield excavator (outer shell shield excavator) in the circumferential tunnel can be reinforced by the center pillar. In other words, in the present invention, by forming the compound circular circumferential tunnel having the central pillar, it is possible to structurally stabilize the soil tunnel against the soil water pressure received from the ground.
Then, at the stage after completing the excavation by the double circular circumferential shield excavator and before installing another shield excavator, by removing at least the middle pillar located in the starting area among the plurality of middle pillars, , It is possible to secure a space in the depth direction for arranging construction equipment necessary for excavating another shield excavator.

  Further, in the shield starting base according to the present invention, a cutting wall made of a material that can be excavated by the another shield excavator is provided in a portion of the circumferential segment located at a face where the other shield excavator starts. It may be characterized in that it is provided.

  In this case, by forming the wall surface of the face to be started by another shield excavator in the circumferential segment with a machinable material, it is possible to efficiently start while cutting with the cutting cutter.

  Further, in the outer shell shield construction method using the circumferential tunnel according to the present invention, the outer shell shield excavator at the time of starting is arranged in the first circular portion of one of the circumferential tunnels having a double circular shape, and the other The starting equipment having a reaction force wall at the time of starting the outer shell shield excavator may be arranged in the second circular portion.

  In this case, when starting the outer shell shield excavator from the circumferential tunnel, the outer shell shield excavator is installed in one of the first circular portions of the cross section of the compound circular shape, and the outer shell shield excavator at that time is installed. The reaction wall and the starting equipment for loading and unloading equipment can be arranged in the other second circular portion. That is, since it can be secured in the space where a reaction force wall is installed behind the outer shell shield excavator or in the second circular portion used for transporting materials or excavating excavated soil, the work of changeover is not necessary, and it is efficient. You can start.

  According to the outer shell shield construction method using the double circular circumferential shield excavator, the shield starting base, and the circumferential tunnel of the present invention, a circumferential tunnel having a laterally long sectional shape can be efficiently constructed.

It is a perspective view showing a schematic construction state of a branching and joining part by an embodiment of the present invention. It is a figure which shows the tunnel line shape of the branch merge part shown in FIG. It is the sectional view on the AA line shown in FIG. FIG. 3A is a cross-sectional view taken along the line BB shown in FIG. 2, and FIG. 3B is a cross-sectional view of a branching and joining portion constructed by excavating the inside of the outer shell structure of FIG. It is CC sectional view taken on the line in FIG. 3, Comprising: It is a figure which shows the circumferential shield starting base after starting a compound circular circumferential shield excavator. It is sectional drawing which looked at the circumferential tunnel from the tunnel axial direction. It is the side view seen from the tunnel inner side which shows the structure of the starting part reinforcement area which reinforces the starting opening of the outer shell shield excavator in the circumferential tunnel. It is a figure which shows the construction state of a circumferential tunnel, Comprising: It is a figure which showed each attitude|position of the compound circular circumference shield excavator during excavation. It is a side view which shows the structure of a compound circular circumference shield excavator. It is the front view which looked at the compound circular circumference shield excavator from the front. It is a figure which shows the state before the start of a compound circular circumference shield excavator in a circumference shield starting base.

  Hereinafter, an outer shell shield construction method using a compound circular circumference shield excavator, a shield starting base and a circumference tunnel according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the compound circular circumference shield excavator 1 according to the present embodiment is used for a large-scale road tunnel, for example, as a ramp for a main line tunnel 11 that has been previously constructed by a shield construction method in the ground. It is applied to the construction for constructing the large-section branching and joining part 10 at the location where the tunnel 12 joins and branches.

The branching and merging portion 10 surrounds the outer sides of the main tunnel 11 and the ramp tunnel 12, and includes a plurality of outer shell tunnels 13, 13,... Constructed so as to extend parallel to the branching and merging portion 10. It is a part. The branching/merging portion 10 forms an outer shell body structure 10A that is continuous in the circumferential direction by excavating and connecting the outer shell tunnels 13 that are adjacent to each other in the circumferential direction, and further, the outer shell body structure 10A. It is constructed by excavating the inside of. When constructing the branching and merging portion 10, as shown in FIG. 3 and FIGS. 4A and 4B, firstly, the main line tunnel 11 and the ramp tunnel 12 are preliminarily constructed, and the inside of the outer shell structure 10A is installed. When excavating, the segments 11A and 12A of the main tunnel 11 and the ramp tunnel 12 constructed inside the outer shell structure 10A are dismantled.
The plurality of outer shell tunnels 13 are the outer shell shield excavator 14 (another shield excavator) with the circumferential tunnel 15 pre-installed in a part of the branching and joining section 10 as a starting base (outer shell shield starting base 150). It is constructed by excavating.

  The outer shell shield excavator 14 is excavated outside the main tunnel 11 and the ramp tunnel 12 along the extending direction of the branching and joining section 10 from the outer shell shield starting base 150.

  As shown in FIGS. 2 and 5, the outer shell shield starting base 150 (circumferential tunnel 15) is constructed by the double circular circumferential shield excavator 1 having a glasses shape (double circular shape) in cross section, and It is composed of a circular tunnel 15 having a cross-sectional spectacle shape in which circular tunnels 15A and 15B are overlapped at the central portion, and is constructed in a ring shape along a circumferential direction E centered on an axis parallel to the central axis of the main line tunnel 11. There is.

  As shown in FIG. 6, the outer shell shield starting base 150 is a spectacle-shaped circumferential segment 151 constructed at the time of construction of the double circular circumferential shield excavator 1, and a center of the circumferential segment 151 in the left-right direction in a sectional view. The upper and lower constricted portions 15a, 15a are connected to each other, and the central pillar 157 extends in the vertical direction.

  Here, as shown in FIG. 5, in the circumferential tunnel 15 forming the outer shell starting point 150, the extension direction of a straight line passing through the respective tunnel centers O1 and O2 of the pair of circular tunnels 15A and 15B is defined as the lateral direction X. That is, the direction orthogonal to the left-right direction X in cross section is called the up-down direction.

  As shown in FIG. 6, one starting side circular tunnel 15A (first circular portion) of the circumferential tunnel 15 (outer shell shield starting base 150) is used as a starting space of the outer shield excavator 14, and after starting, Is used as a material carry-in space for sending materials into the shield machine and a carry-out space for excavated soil.

Here, in the area (starting area M) in the tunnel where the starting opening 152 of the outer shell shield excavator 14 is formed in the starting side circular tunnel 15A of the circumferential tunnel 15 (starting area M), as shown in FIGS. 6 and 7. For example, a plurality of middle pillars 157 made of a steel material such as H-section steel are arranged in the circumferential direction E at predetermined intervals (intervals for each ring of the circumferential segment).
A column reinforcing beam 155 is provided on each of the constricted portions 15a on the inner and outer peripheral sides of the starting region M so as to project inward in the vertical direction. The column reinforcing beam 155 extends in the circumferential direction E along the inner surface of the outer circumference side and the inner circumference side of the circumferential segment 151. A plurality of first middle pillars 157A and a plurality of second middle pillars 157B are provided so as to connect the pillar reinforcing beams 155 and 155 provided on the inner and outer circumference sides, respectively.

  The first middle pillar 157A is shown by a chain double-dashed line in FIG. 7, and is arranged between the pillar reinforcing beams 155 and 155 at a central portion in the circumferential direction Z and at a position overlapping the central portion of the starting opening 152. A plurality (two in FIG. 7) of the second middle pillars 157B are arranged on both sides of the plurality (five in FIG. 7) of the first middle pillars 157A in the circumferential direction Z.

The first middle pillar 157A is provided so as to be removable before the outer shell shield excavator 14 is installed. Since the first center pillar 157A is removed when the outer shell shield excavator 14 is installed as described later, the circumferential tunnel 15 of the starting area M during the period until the outer shell shield excavator 14 (see FIG. 6) is started. It is to reinforce to maintain the shape. That is, after the construction of the circumferential tunnel 15 is completed and before the outer shell shield excavator 14 is installed, by removing the first middle pillar 157A located in the starting area M, the outer shell shield excavator 14 is removed. It is possible to secure space for construction equipment in the depth direction. The second middle pillar 157B supports the circumferential segment through the pillar reinforcing beams 155 on the inner and outer circumference sides even after the first middle pillar 157A is removed.
In the present embodiment, a larger load acts on the side closer to the first middle pillar 157A among the two second middle pillars 157B, so that one having a larger load bearing capacity than the middle pillar 157 other than the starting area is used. Has been.
In addition, the arrangement interval of the first middle pillar 157A and the second middle pillar 157B, the load bearing capacity per one, and the material can be appropriately changed according to the design strength to be reinforced.

  Further, the other proximal end side circular tunnel 15B (second circular portion) is used as an arrangement space for reaction force receiving equipment at the time of starting the outer shell shield excavator 14, and is used for sending materials into the shield machine after starting. It is used as a material carry-in space and a carry-out space for excavated soil. Note that reference numerals 14A, 14B, and 14C in FIG. 6 indicate examples of the material carrying-in space and the excavating soil carrying-out space after the outer shell shield excavator 14 has started.

  The inner diameters of the pair of circular tunnels 15A and 15B are set to such dimensions that the outer shell shield excavator 14 can start. Further, in the starting side circular tunnel 15A, the wall surface 15b on the face face of the starting opening 152 of the outer shell shield excavator 14 has an outer wall formed by the circumferential segment 151 when the compound circular circumferential shield excavator 1 is being advanced. The material is, for example, concrete that can be cut with the cutting cutter of the outer shell shield excavator 14 at a suitable timing, as in a general shield construction method. It is also possible to use a segment in which the wall surface 15b made of a material that can be cut by a cutter is incorporated.

  As shown in FIG. 8, the compound circular circumferential shield excavator 1 is one of the circumferential direction E from the circumferential shield starting base 17 constructed by widening and excavating the ramp tunnel 12 (shown by reference numeral E1 in FIG. 8). The vehicle starts in the counterclockwise direction and makes one round in the circumferential direction E1 in the order of reference numerals 1A, 1B,... 1F in FIG. 8 and arrives at the circumferential shield starting base 17 as a reaching base. In this way, the double circular circumference shield excavator 1 can be advanced so that the tunnel alignment draws a constant curve, and the circumferential segment 151 assembled in the shape of glasses at the rear of the double circular circumference shield excavator 1 is Assembled one after another as the tunnel was dug.

As shown in FIGS. 9 and 10, the compound circular circumference shield excavator 1 includes a shield machine main body 2 having an eyeglass-shaped skin plate 20 forming an outer shell, and a plurality of shield machine main bodies 2 provided on the front side of the shield machine main body 2. It is provided with a cutter head 3 having a cutter bit, a sending and discharging device 4 for sending muddy water to the cutter head 3 and discharging excavated soil, and an erector device 5 for assembling the circumferential segment 151.
Here, in the double circular circumferential shield excavator 1, the direction along the excavator center line C0 is referred to as the front-rear direction Z, the face of the face along the front-rear direction Z is referred to as the front side, the front side, and the opposite side (start side). The rear side and the rear side.

  As shown in FIG. 9, the shield machine main body 2 is provided in the front body plate 20A and the skin plate 20 that is in the shape of glasses in a sectional view and is divided and joined to the front body plate 20A and the rear body plate 20B in the front-rear direction Z. The partition wall 21 for partitioning the chamber 3A on the cutting face side and the inside of the shield machine, the main body ring 22 protruding rearward from the outer peripheral portion of the partition wall 21, and the rear portion of the main body ring 22 arranged at intervals along the outer periphery. In addition, a plurality of propulsion jacks 23 and a natural ground gripper 24 that can project from the main body ring 22 toward the natural ground side are provided.

  The skin plate 20 is a spectacle-shaped tubular body having an outer cross-sectional shape and a constricted portion 20a (see FIG. 10) formed in the left and right central portions, and the front torso plate 20A is circular with respect to the back torso plate 20B. The inner circumferential side in the circumferential direction E is refracted and joined at a predetermined angle according to the linear curvature of the double circular circumferential shield excavator 1, and the portion located on the inner circumferential side in the circumferential direction E is located on the outer circumferential side. It is integrally formed with a shape whose length in the front-back direction Z is smaller than that of the portion.

The partition wall 21, the main body ring 22, and the natural ground gripper 24 are arranged inside the front body plate 20A. The front trunk plate 20A is formed with an opening through which the natural ground gripper 24 can project outward, and by allowing the natural ground gripper 24 to project from this opening with an appropriate amount of projection, the excavated natural ground By applying a reaction force to G, it is possible to control the direction of the double circular circumference shield excavator 1 during excavation and prevent the shield machine main body 2 from deviating from the track in the circumferential direction E.
In front of the partition wall 21 and inside the front body plate 20A, a space (chamber 3A) in which the mud water sent by the mud sending and discharging device 4 and the excavated earth and sand are stirred is formed.

  Inside the rear body plate 20B, the circumferential segment 151 is assembled by the erector device 5 along with the excavation. A tail seal 201 that seals a gap with the outer circumferential surface of the assembled circumferential segment 151 is attached to the rear portion of the rear body plate 20B over the entire circumference of the rear body plate 20B. Here, the tail seals 201 are wire brushes, and are arranged in three rows in the length direction of the skin plate 20 (the front-back direction Z).

  The skin plate 20 may be equipped with a backfilling simultaneous injection device (not shown) for injecting the backfilling material at the same time as the excavation is performed between the skin plate 20 and the ground surface. When excavating in the circumferential direction E using the double circular circumferential shield excavator 1 as in the present embodiment, the change in the posture of the excavator is larger than when excavating in the substantially horizontal direction, and the cutter is used. The wall surface of the excavated ground immediately after excavation easily collapses.Therefore, by providing a backfill simultaneous injection device, the backfill material is filled in the gap between the excavated ground and the ground immediately after excavation. Can be stabilized. Therefore, the attitude control of the shield excavator due to the collapse of the excavated ground becomes easy, and the direction control of the excavation in the circumferential direction E, which is difficult to control the direction, can be accurately performed.

The partition wall 21 is a partition wall that separates the face of the face from the inside of the shield machine so that water and earth and sand from the face do not flow into the inside of the shield machine body 2 (inside the shield machine). As shown in FIG. 10, the partition wall 21 has a shape in which two circular portions 21A and 21B are partially overlapped with each other, and the cutter rotating shaft 31 is rotatably supported at the centers C1 and C2 of the circular portions 21A and 21B. ing. A cutter ring 32 for rotating a cutter, which will be described later, is supported on each of the circular portions 21A and 21B so as to be rotatable around the centers C1 and C2 of the circular portions 21A and 21B.
Further, as shown in FIG. 9, the partition wall 21 is provided with a muddy water injection port 211 for sending mud and a sediment intake port 212 that communicate with the inside of the chamber 3A from the inside of the shield machine. The muddy water inlet 211 and the earth and sand inlet 212 are connected to respective pipes of the mud sending and discharging device 4 (mud sending pipe 41 and mud discharging pipe 42 described later).

  The body ring 22 includes an outer peripheral ring 22A to which the propulsion jack 23 is fixed, and an inner peripheral ring 22B that is provided inside the outer peripheral ring 22A and to which the cutter driving motor 25 is fixed. The length of the outer peripheral ring 22A in the front-rear direction Z is formed such that the outer peripheral side in the circumferential direction E is longer than the inner peripheral side.

  The outer peripheral ring 22A is formed in a spectacle shape along the outer peripheral portion of the partition wall 21, and the rear end surface 22a has a rear end portion of the front body plate 20A of the skin plate 20 (a boundary between the front body plate 20A and the rear body plate 20B is bent. Part). A plurality of propulsion jacks 23, 23,... Are fixed along the outer periphery to the rear end surface 22a of the outer peripheral ring 22A with the jack pressing surface 23a facing rearward. The outer peripheral ring 22A is provided with a natural ground gripper 24 capable of protruding toward the natural ground side in a direction orthogonal to the tunnel axis direction of the double circular circumferential shield excavator 1.

  The propulsion jack 23 is fixed to the main body ring 22 so that the telescopic rod can project rearward from the rear end surface 22 a of the main body ring 22. By extending the telescopic rod of the propulsion jack 23, the propulsion force of the shield body 2 is obtained by pressing against the front surface of the segment 151 that is sequentially assembled inside the rear body plate 20B of the skin plate 20 to take a reaction force. There is. The propulsion jack 23 may be equipped with a rolling prevention control device.

  The ground gripper 24 is a posture control means of the shield machine main body 2, and the reaction force surface 24a protruding outward is inclined so that the protruding length gradually increases from the front to the rear. The natural ground gripper 24 advances the double-circular circumferential shield excavator 1 while pressing the reaction surface 24a against the natural excavation ground G, so that the double-circular circumferential shield excavator 1 deviates from the circumferential direction E. The reaction force against the force toward the outer peripheral side or the inner peripheral side can be applied to the ground.

  The inner peripheral ring 22B is formed in a circular ring shape provided coaxially with the centers C1 and C2 of the circular portions 21A and 21B of the partition wall 21. The inner ring 22B is provided with a plurality of electric cutter drive motors 25 at intervals in the circumferential direction. A cutter ring 32 is supported inside the inner peripheral ring 22B so as to be rotatable around the centers C1 and C2.

  As shown in FIGS. 9 and 10, the cutter head 3 includes a cutter rotation shaft 31 provided at the centers C1 and C2 of the circular portions 21A and 21B of the partition wall 21, and a pair of cutter rotation shafts supported by the partition wall 21. A cutter ring 32 rotatably provided around each of the shafts 31, a center cutter 33 provided at the tip of the cutter rotating shaft 31, and a cutter ring 32 are supported, and the center portion is fixed to the center cutter 33. The spoke type cutaway pork 34A, 34B and the copy cutter 35 (excavator) provided on the outer peripheral ends of the cuttus pork 34A, 34B are provided.

The cutter rotating shaft 31 including the center cutter 33 is rotatably supported by a rotary joint (not shown) provided on the partition wall 21.
As shown in FIG. 9, the cutter ring 32 is supported by the inner peripheral ring 22B of the partition wall 21 and the front end thereof is integrally supported by the cutas pork 34A, 34B via a connecting member 36. A ring gear 32a is formed on the outer peripheral portion of the cutter ring 32, the motor rotation shafts 25a of a plurality of cutter drive motors 25 are meshed with each other, and are provided so as to be rotatable together with the cutter rotation shaft 31 by the drive of the cutter drive motor 25.

  As shown in FIG. 10, the pair of cutass pork 34A and 34B are arranged in a state of intersecting with the cutter rotating shaft 31 so as to have an X shape when viewed from the face of the face. A large number of cutter bits are attached to the front surfaces of the cutter spokes 34A and 34B along the length direction of the spokes. Rotation is controlled so that the cut-and-spokes 34, 34 provided on each of the circular portions 21A, 21B rotate about the cutter rotation shaft 31 so as not to interfere with each other, so that a cross section having a spectacle shape can be excavated.

  The copy cutter 35 is provided so as to be capable of projecting and retracting from a part of the spoke tip end portion 34a of the cutas pork 34A, 34B toward the outside of the spoke shaft. The copy cutter 35 is to excavate the outer side of the outer peripheral surface of the skin plate 20 by projecting toward the natural ground side with a predetermined amount of protrusion at a predetermined cutter rotation position. That is, the copy cutter 35 functions as the attitude control means of the shield machine body 2 like the natural ground gripper 24.

The mud sending and discharging device 4 includes a mud sending pipe 41 for sending mud into the face chamber 3A, a pair of mud sending pipes 42 (42A, 42B) for discharging the excavated sediment mixed with the mud, and a drain And a screw conveyor 43 provided at the intake in the mud pipe 42.
The mud feed pipe 41 is connected to a muddy water inlet 211 provided at the center of each circular portion 21A, 21B of the partition wall 21. During the excavation, mud water is injected into the chamber 3A from the mud feed pipe 41 to keep the cutting face at a constant pressure, and the mud can be mixed with the excavated earth and sand to be in an appropriately viscous mud discharge state.

  The sludge discharge pipes 42A and 42B are connected to the earth and sand intake ports 212 provided on the outer peripheral side and the inner peripheral side of the circular portions 21A and 21B of the partition wall 21, respectively. The pair of mud discharge pipes 42A and 42B are provided in the shield machine so as to be inclined so as to be in the center of the cross section toward the rear from the earth and sand intake port 212, and to the sediment discharge pipe 44 arranged in the center of the cross section. Connected to meet. A screw conveyor 43 is provided at the tip of each of the sludge discharge pipes 42A and 42B. The screw conveyer 43 is arranged such that the screw tip 43a projects from the sediment intake port 212 and is located inside the chamber, and the screw is rotated during excavation to take in the excavated sediment into the sludge discharge pipe 42 and the sediment discharge pipe 44. Exhaust through.

The pair of mud discharge pipes 42A and 42B are provided so as to be alternately switchable with respect to the sediment discharge pipe 44. Alternatively, both of the pair of mud discharge pipes 42A and 42B can be simultaneously in communication with the earth and sand discharge pipe 44.
That is, when the shield machine main body 2 is in a posture in which the inner peripheral side in the circumferential direction E1 is located lower than the outer peripheral side (postures 1D, 1E, and 1F shown in FIG. 8), the outer peripheral side sand intake port. By closing the outer peripheral side sludge discharge pipe 42A connected to 212A and communicating the inner peripheral side sludge discharge pipe 42B connected to the inner peripheral side sediment intake port 212B with the chamber 3A, the inner peripheral side sludge discharge pipe Since 42B is located in the lower part of the chamber 3A, excavated soil can be efficiently discharged through the inner peripheral side mud discharge pipe 42B.
Further, in the case where the shield machine body 2 is in a posture in which the outer peripheral side in the circumferential direction E1 is located lower than the inner peripheral side (postures 1A, 1B, 1C shown in FIG. 8), the inner peripheral side sludge discharge pipe 42B. And the outer peripheral side mud pipe 42A is communicated with the chamber 3A, the outer peripheral side mud pipe 42A is located in the lower part of the chamber 3A, so that the excavated soil is efficiently discharged through the outer peripheral side mud pipe 42A. be able to.

  The erector device 5 is provided inside the shield of the partition wall 21 for each of the circular portions 21A and 21B. Each of the erector devices 5 has a ring-shaped revolving frame 51 centered on the circular portions 21A and 21B, and a gripping device 52 supported by the revolving frame 51. The gripping device 52 includes a gripping portion to which the segment piece of the circumferential segment 151 can be attached and detached, and is provided so as to be slidable in the front-rear direction Z with respect to the revolving frame 51. Further, the gripping device 52 is provided so that the posture of the gripped segment piece of the circumferential segment 151 can be slid, for example, in the circumferential direction, the front-rear direction, the radial direction, etc., and the segment piece can be assembled at a predetermined position.

Next, a method of constructing the circumferential tunnel 15 using the above-mentioned double circular circumferential shield excavator 1, and a method of excavating the outer shell tunnel 13 by further using the circumferential tunnel 15 to construct the branch confluence portion 10. The method will be described with reference to the drawings.
First, as shown in FIG. 1, a starting base (circumferential shield starting base 17) of the double circular circumferential shield excavator 1 for excavating the circumferential tunnel 15 is constructed on a part of the side wall of the ramp tunnel 12.

  Specifically, the propulsion unit 16 is set at a predetermined position of the ramp tunnel 12 with the cutter head facing outward in the radial direction of the ramp tunnel 12, and propelled by the propulsion method. At the time of propulsion by the propulsion device 16, the frozen soil improving portion 100 is formed by performing ground improvement by freezing the ground at the installation position of the circumferential shield starting base 17 and the surrounding construction area by a freezing method. At this time, a plurality of freezing tubes 104 are radially arranged from the propulsion unit 16 to provide the frozen soil improving unit 100. After that, the ground shield starting base 17 having a substantially rectangular box-shaped region is provided by excavating the ground inside the frozen soil improving portion 100 by a conventional method. Then, the propulsion unit 16 for which the propulsion is completed is disassembled and removed. As shown in FIGS. 1 and 3, the circumferential shield starting base 17 to be constructed is constructed in a box shape by reinforced concrete construction, and is set to a size capable of starting the compound circular circumferential shield excavator 1.

  The ground improvement carried out here is not limited to forming the frozen soil improving portion 100 by the freezing method, and another ground improving method may be adopted. For example, it is also possible to adopt another ground improvement such as a chemical solution injecting process by driving an injection pipe from the rear of the propulsion unit 16 toward a target improvement area and injecting a chemical solution. Alternatively, if the ground is a hard ground that can stand on its own, ground improvement can be omitted.

  Next, as shown in FIG. 11, in the circumferential shield starting base 17, the double circular circumferential shield excavator 1 is assembled, and reaction force reception and subsequent equipment necessary for excavation are also installed to prepare for the start. To do. Since the double circular circumferential shield excavator 1 excavates along the circumferential direction E, it is set at the circumferential shield starting base 17 with the cutter head 3 facing downward. Here, the starting hole portion 17a of the circumferential shield starting base 17 is constructed with a material that can be cut by the compound circular circumferential shield excavator 1.

  Next, as shown in FIG. 8, the compound circular circumference shield excavator 1 is started, and the spectacle-shaped circumferential segment 151 is assembled in the rear trunk plate 20B of the shield machine main body 2 along with the excavation as in the conventional shield construction method. . Then, the work of injecting the backfill material between the segment 151 and the excavated ground is sequentially repeated, and as shown in FIGS. 3 and 4A and 4B, outside the main tunnel 11 and the ramp tunnel 12. By digging in the circumferential direction E to reach the circumferential shield starting base 17 again, the spectacle-shaped circumferential tunnel 15 in cross section is constructed.

  As shown in FIG. 9, in the double circular circumferential shield excavator 1, the skin plate 20 is aligned with the tunnel line shape, and the front body plate 20A is bent inward in the radial direction of the rear body plate 20B in the circumferential direction E. Since they are joined, the stroke of the propulsion jack 23 is also extended so that the outer peripheral side is longer than the inner peripheral side so that the circumferential tunnel 15 is constructed by excavating in a tunnel alignment in the circumferential direction E. Specifically, the items are dug counterclockwise (in the direction of arrow E1) in the order of reference numerals 1A to 1E shown in FIG. That is, the double circular circumferential shield excavator 1 first starts excavation from the circumferential shield starting base 17 in a downward attitude (postures of reference numerals 1A and 1B) and, after passing through the lowermost portion, gradually rises in the upward posture (reference numeral 1C). 1D, 1E posture) while heading to the uppermost part, passing through the uppermost part, and then excavating again while changing to the downward facing posture (reference symbols 1F, 1A) to reach the circular shield starting base 17 again. The circumferential tunnel 15 having a spectacle-shaped cross section is constructed by excavating once in the circumferential direction E.

  Further, in the double circular circumference shield excavator 1, as shown in FIG. 9, the ground gripper 24 provided on the outer peripheral portion of the partition wall 21 is excavated in a state in which the ground gripper 24 is projected toward the ground side of the excavated ground, thereby shielding the shield. The force that the machine body 2 tends to move toward the outer peripheral side can be suppressed, and the excavation direction can be easily controlled. The amount of protrusion of the natural ground gripper 24 at this time is preferably changed in real time according to the hardness of the natural ground during excavation, the condition of geology, the position and orientation of the shield machine body 2, and the like.

  When constructing the circumferential tunnel 15, as shown in FIG. 7, a plurality of middle pillars 157 are provided along the circumferential direction E at the center of the cross section of the circumferential tunnel 15 having a double circular shape. At this time, in the starting region M where the starting port 152 of the outer shell shield excavator 14 is formed, a plurality of first middle pillars 157A and second middle pillars 157B are provided via the pillar reinforcing beams 155, respectively. Then, before installing the outer shell shield excavator 14, all the first middle pillars 157A are removed to secure a space in the depth direction of the outer shell shield excavator 14.

  Next, as shown in FIGS. 1 and 2, the constructed circumferential tunnel 15 is used as an outer shell shield starting base 150, and a circle is formed at a predetermined position in the circumferential direction E in the starting side circular tunnel 15A of the outer shell shield starting base 150. An outer shell shield excavator 14 having a cross section is arranged to proceed with excavation. In the base-side circular tunnel 15B of the outer shell shield starting base 150, a reaction force wall for starting the outer shell shield excavator 14 and subsequent equipment are arranged. Note that the outer shell shield excavator 14 may use the outer shell shield starting base 150 to excavate a plurality of pieces simultaneously. The earth and sand excavated during the excavation by the outer shell shield excavator 14 is conveyed to the starting side in the excavated outer shell tunnel 13 and discharged from the outer shell shield starting base 150 to the outside through the circumferential shield starting base 17 and the ramp tunnel 12. To do. Further, materials such as segments necessary for excavation are carried from the inside of the ramp tunnel 12 into the outer shell tunnel 13 under excavation via the circumferential shield starting base 17 and the outer shell starting base 150.

  The outer shell tunnels 13 thus excavated by the outer shield excavator 14 are constructed at predetermined intervals in the circumferential direction E, and the main tunnel 11 and the ramp tunnel 12 are constructed by these outer shell tunnels 13. A part of the outer shell structure 10A is constructed around the. In addition, the outer shell shield excavator 14 excavates the outer shell tunnel 13 to reach the intended wall of the branching and merging portion 10, dismantles and collects it, assembles it again at the outer shell shield starting base 150, and starts it. The outer shell tunnel 13 may be repeatedly used so as to be constructed.

Subsequently, as shown in FIGS. 4A and 4B, ground improvement is performed between the outer shell tunnels 13 adjacent to each other in the circumferential direction E by a freezing method, a chemical injection method, or the like. After that, the outer shell tunnels 13, 13 are cut open, and the outer shell tunnels 13, 13 are connected to each other by the steel panels 18 arranged on the inner and outer circumferences. By filling the above with concrete, the outer shell skeleton structure 10A is integrated to form an outer shell skeleton structure 10A having a supporting function and a water blocking function.
After that, the inside of the outer shell structure 10A is excavated, and the segments of the main tunnel 11 and the ramp tunnel 12 at the locations covered by the outer shell structure 10A are disassembled and removed to construct a branching and merging portion 10 forming a large space. be able to.

Next, the operation of the outer shell shield method using the double circular circumferential shield excavator, the shield starting base and the circumferential tunnel will be described in detail with reference to the drawings.
In the present embodiment, as shown in FIG. 1, the front body plate 20A and the rear body plate 20B of the skin plate 20 of the double circular circumferential shield excavator 1 are bent at a predetermined angle toward the inner peripheral side in the circumferential direction E. By being joined, it becomes possible to excavate in the circumferential direction E with a constant curvature while maintaining a constant posture. Therefore, it is possible to efficiently construct the spectacle-shaped circumferential tunnel 15 having a horizontally long cross section that is dug in a tunnel shape that draws a circumferential curve that becomes the predetermined circumferential direction E.
Since the cross-sectional shape of the circumferential tunnel 15 excavated by the double circular circumferential shield excavator 1 is a laterally long double circular shape when viewed from the circumferential direction E, the longitudinal direction of the cross section is the tunnel axis of the shield tunnel. It is possible to secure a starting space in the depth direction necessary for starting the outer shell shield excavator 14 in the direction, and it can be used as a starting base.

That is, by using the compound circular circumferential shield excavator 1 having a compound circular shape as in the present embodiment as a method of constructing the circumferential tunnel 15 having a horizontally long section, a shield having a rectangular cross section having a complicated structure as in the past is used. Compared with the case of using an excavator or a method of excavating and connecting two shield excavators having a circular cross section in parallel, the construction is simpler and the cost can be reduced.
Further, in the case of the double circular circumference shield excavator 1, there is an advantage that complicated attitude control is unnecessary, as compared with a shield excavator having a rectangular cross section whose body is easily affected by rolling and which is generally difficult to control. .

In addition, in the present embodiment, the circumferential tunnel 15 is formed into a double circle shape formed by a curved line, so that the tunnel structure having a rectangular cross section or a plurality of circular tunnels can be structured against the soil water pressure received from the ground as compared with a plurality of connected tunnels. It is advantageous in terms of structure and can be structurally stable, and for example, the thickness of the segment can be kept small.
As described above, in the present embodiment, the outer shell shield excavator 14 that constitutes the outer shell of the branching and joining section 10 having a large cross section is provided as another shield excavator at intervals in the circumferential direction E of the circumferential tunnel 15. To form a plurality of outer shell tunnels 13 in the outer shell portion, and further excavate and connect between the plurality of outer shell tunnels 13 to construct the outer shell structure structure 10A in the outer shell portion. be able to.

  In addition, in the present embodiment, the ground gripper 24 is projected outward in the radial direction of the tunnel, and a reaction force is applied to the ground of the excavation wall surface to cause the compound circular circumferential shield excavator 1 to dig into the shield machine. It is possible to prevent the main body 2 from deviating from the linear shape having a predetermined curvature. In particular, when excavating in the circumferential direction E, the ground gripper 24 on the outer peripheral side is overhanged to exert a reaction force on the natural ground, or the ground on the side bent by the copy cutter 35 (the inner peripheral side in the circumferential direction E). By excavating a mountain, the shield machine main body 2 can suppress the force toward the outer peripheral side to stabilize the posture during excavation, and the posture control becomes easy.

Further, in the present embodiment, as shown in FIG. 7, the starting region M where the starting port 152 of the outer shell shield excavator 14 in the circumferential tunnel 15 is formed is reinforced by the first middle pillar 157A and the second middle pillar 157B. can do. That is, in this case, by using the compound circular circumferential tunnel 15 having the central pillars 157A and 157B, it is possible to structurally stabilize the soil pressure against the soil water pressure received from the ground.
Then, after the excavation by the double circular circumferential shield excavator is completed and before the outer shell shield excavator 14 is installed, the outer shell shield excavator is removed by removing the plurality of first middle pillars 157A. It is possible to secure a space in the depth direction for arranging the construction equipment necessary for excavating 14.

  Further, in the present embodiment, by forming the wall surface of the face, which is started by the outer shell shield excavator 14 (another shield excavator), of the circumferential segment 151 of the circumferential tunnel 15 by using a material capable of cutting, The outer shell shield excavator 14 can efficiently start while cutting with a cutting cutter.

  Furthermore, in the present embodiment, when the outer shell shield excavator 14 is started from the circumferential tunnel 15, the outer shell shield excavator 14 is installed in one of the start side circular tunnels 15A of the cross section of the compound circular shape. At this time, the reaction wall of the outer shell shield excavator 14 and the starting equipment for carrying in/out the equipment can be arranged in the other proximal circular tunnel 15B. That is, it is possible to secure the space in the rear side of the outer shell shield excavator 14 in the space where a reaction force wall is installed, or in the base end side circular tunnel 15B used for transporting materials and carrying out excavated soil, so that work for changing setup is unnecessary. Therefore, it is possible to start efficiently.

  As described above, in the outer shell shield method using the double circular circumferential shield excavator, the shield starting base, and the circumferential tunnel according to the present embodiment, the circumferential tunnel 15 having a laterally long sectional shape can be efficiently constructed.

  The embodiment of the outer shell shield construction method using the double circular circumferential shield excavator, the shield starting base and the circumferential tunnel according to the present invention has been described above, but the present invention is not limited to the above embodiment, Modifications can be made as appropriate without departing from the spirit of the invention.

  For example, the cross-sectional shape and size of the double circular circumferential shield excavator 1, the refraction angle of the skin plate 20, and the like are the tunnel alignment of the circumferential tunnel 15 and the outer shield excavator 14 for excavating the outer shell tunnel 13. It can be appropriately set according to conditions such as the outer diameter. For example, the length dimension in the front-rear direction Z of the front body plate 20A and the rear body plate 20B of the skin plate 20 can be changed.

  Further, in the present embodiment, the front body plate 20A of the skin plate 20 is provided with the natural ground gripper 24 that can project toward the natural ground, but such a natural ground gripper 24 can be omitted. However, a ground gripper having another shape may be applied. Further, the copy cutter 35 may be omitted if the attitude control can be performed only by the propulsion jack 23 depending on the natural condition.

In addition, the position, size, construction method, etc. of the circumferential shield starting base 17 for launching the double circular circumferential shield excavator 1 depend on the outer diameter, the arrangement, the ground conditions, etc. of the main line tunnel 11 and the ramp tunnel 12. It is possible to set appropriately.
Further, the size of the outer shell portion (outer shell structure 10A) forming the branching/merging portion 10, the structure of the outer shell, and the construction method are not limited to those in the above-described embodiment, and the road tunnel and ground conditions to be set are set. It is appropriately set according to specifications such as.

  Further, although the present embodiment is an application example in the case of constructing a large-section road tunnel, it is widely used in constructing tunnels of various scales, uses, and forms having a large-section underground cavity as described above. It is applicable, and various design changes can be made depending on the size and form of the underground cavity in the tunnel to be constructed and considering various conditions such as the surrounding environment.

  In addition, it is possible to appropriately replace the components in the above-described embodiments with known components without departing from the spirit of the present invention.

1 Double Circular Circumferential Shield Excavator 2 Shield Machine Main Body 3 Cutter Head 3A Chamber 4 Sewage Sludge Device 5 Electa Device 10 Branch Confluence Section 10A Outer Shell Body Structure 11 Main Tunnel 12 Lamp Tunnel 13 Outer Shell Tunnel 14 Outer Shell Shield Excavator (Another shield excavator)
15 Circumferential tunnel 15A Start side circular tunnel (first circular section)
15B Base end circular tunnel (second circular part)
17 Circumferential Shield Starting Base 20 Skin Plate 20A Front Body Plate 20B Rear Body Plate 21 Bulkhead 24 Ground Gripper 35 Copy Cutter (Excavator)
150 Outer Shell Shield Starting Base 151 Circumferential Segment 152 Starting Gate 155 Column Reinforcement Beam 157 Middle Pillar 157A First Middle Pillar 157B Second Middle Pillar E, E1 Circumferential Direction M Starting Area Reinforcing Area Z Front and Back Direction O1, O2 Circular Tunnel center

Claims (8)

A double circular circumferential shield excavator that is dug in the circumferential direction so that the tunnel alignment draws a constant circumferential curve,
A shield machine main body having a skin plate formed in a compound circular shape by overlapping a part of a pair of circles in a cross-sectional view viewed from the tunnel axis direction, and having a skin plate that is split and joined to the front body plate and the rear body plate in the front-rear direction,
A cutter having the center of each of the pair of circles as the center of rotation of the cutter,
The shield machine main body is provided with a partition wall that is provided on the front body plate and separates the chamber on the face side from the shield machine,
The front body plate and the rear body plate are refraction-bonded to each other on an inner peripheral side in the circumferential direction at a predetermined angle according to a linear curvature by the double circular circumferential shield excavator. Double circular circumference shield excavator.   The shield machine main body is provided with at least one of a natural ground gripper and an overdrilling device that can project toward the natural ground side in a direction orthogonal to the tunnel axis direction as attitude control means. The double circular circumferential shield excavator according to claim 1. A shield starting base comprising a double circular circumferential tunnel constructed using the double circular circumferential shield excavator according to claim 1 or 2.
The circumferential segment of the compound circular shape is constructed so as to extend in the circumferential direction together with the circumferential excavation of the compound circular circumferential shield excavator,
A shield starting base, wherein a space for starting another shield excavator is formed on the inner side of the circumferential segment. At the center of the cross section of the circumferential tunnel forming a double circle shape, a plurality of middle columns are provided along the circumferential direction,
Among the plurality of middle pillars, at least the middle pillar located in the starting area of the other shield excavator in the circumferential tunnel is provided so that it can be removed before the another shield excavator is installed. The shield starting base according to claim 3.   A cutting wall made of a material that can be excavated by the other shield excavator is provided in a portion of the circumferential segment located at a face where the another shield excavator starts. The shield starting base according to any one of 3 to 4. An outer shell tunnel excavated along the outer shell portion of an underground cavity is used by using a double circular circumference tunnel constructed by using the double circular circumference shield excavator according to claim 1 or 2. An outer shell shield construction method using a circumferential tunnel to be constructed,
A step of constructing a first shield starting base forming a starting portion of the double circular circumferential shield excavator on a part of a construction base end side of the underground cavity;
Starting the compound circular circumferential shield excavator from the first shield starting base and driving the compound in the circumferential direction to construct the circumferential tunnel;
A step of constructing the outer shell tunnel by setting the circumferential tunnel as a second shield starting base, starting an outer shell shield excavator from the second shield starting base, and digging along the longitudinal direction of the underground cavity; ,
An outer shell shield construction method using a circumferential tunnel characterized by having A step of providing a plurality of middle pillars along the circumferential direction at the center of the cross section of the circumferential tunnel forming a double circle shape;
Before installing the outer shell shield excavator, removing the middle pillar located in the starting region of the outer shell shield excavator in at least the circumferential tunnel of the plurality of middle pillars,
The outer shell shield construction method using the circumferential tunnel according to claim 6, wherein:   The outer shell shield excavator at the time of starting is arranged in one first circular portion of the circumferential tunnel having a double circle shape, and the reaction wall at the time of starting of the outer shell shield excavator in the other second circular portion. An outer shell shield construction method using a circumferential tunnel according to claim 6 or 7, characterized in that a starting facility having the above is arranged.

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