JP5271212B2 - Construction method of large section tunnel and large section tunnel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a construction method a large cross section tunnel, and the large cross section tunnel allowing prestress to be effectively introduced to a top slab and a bottom slab of the tunnel in the ground to reduce the use of members and to rationalize tension members. <P>SOLUTION: The large cross section tunnel 1 with the tension members 30 disposed only in the top slab 2 and the bottom slab 3 out of the top slab 2, the bottom slab 3 and right and left sidewalls 4, formed by connecting a plurality of small cross section tunnels 10 to one another, is constructed by steps of disposing the tension members 30 across the plurality of small cross section tunnels 10, corresponding to the top slab 2 or the bottom slab 3, filling concrete 20 in the plurality of small cross section tunnels 10, with the tension members 30 disposed, introducing tensile force to the tension members 30, and connecting the top slab 2 and bottom slab 3 with the tensile force introduced therein, to the sidewalls 4. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for constructing a large section tunnel and a large section tunnel.

When constructing a large cross-section tunnel, the cross-sectional shape of the tunnel may be rectangular for the purpose of reducing the amount of excavated soil (see, for example, Patent Document 1).
However, rectangular tunnels are generally uneconomical because they generally have large-scale member specifications.

  Therefore, for the purpose of reducing the material specifications of the lining of the rectangular tunnel, there are cases where a plurality of tension members are disposed on each of the top plate portion, the bottom plate portion, and the left and right side wall portions to introduce prestress (for example, , See Patent Document 2).

JP 2000-073686 A JP 2001-003691 A

  However, the conventional tunnel introduces prestress because tension material is arranged throughout the tunnel lining and prestress is introduced integrally, or because the side walls are constrained by natural ground. In some cases, prestress cannot be effectively introduced due to the resistance of the side wall.

  Therefore, the present invention can effectively introduce prestress into the top and bottom plates of the tunnel in the ground, thereby reducing the use of members and rationalizing the tension members. It is an object to propose a construction method and a large section tunnel.

  In order to solve the above-mentioned problems, the present invention forms a top plate, a bottom plate, and left and right side walls by connecting a plurality of small-section tunnels, and a tension material is disposed only on the top plate and the bottom plate. A method for constructing a large cross-section tunnel, the step of constructing the small cross-section tunnel by connecting steel shells along the tunnel axis direction by a propulsion method, and the other of the steel shells of each adjacent small cross-section tunnel, Removing the outer shell of the portion facing the small cross-section tunnel, arranging the tension material across the plurality of small cross-section tunnels corresponding to the top plate or the bottom plate, and arranging the tension material A step of filling concrete in the plurality of small-section tunnels provided; a step of introducing a tension force into the tension material; and a step of connecting the top plate and the bottom plate into which the tension force is introduced to the side wall. And the top plate And at least part of the small cross-sectional tunnel disposed at one end of the bottom plate is disposed so as to project outward from the one side wall, and using the projecting portion of the small cross-sectional tunnel, It is characterized in that a tension force is introduced into the tension material in the internal space.

According to such a large-section tunnel construction method, it is possible to effectively introduce prestress into the top plate and the bottom plate because the restraint force from the side wall is not received when the prestress is introduced. As a result, it is possible to reduce the thickness of the outer shell member, thereby reducing the construction cost.
Moreover, since the tension | tensile_strength is introduce | transduced into a tension material using the overhang | projection part of a small cross-section tunnel, it is excellent in workability.

  The steel shell may have a rectangular cross section, the small cross section tunnel corresponding to the top plate or the bottom plate may be formed in a horizontally long cross section, and the small cross section tunnel corresponding to the left and right side walls may be formed in a vertically long cross section.

  The large cross section tunnel of the present invention is a large cross section tunnel having a top plate, a bottom plate, and left and right side walls, and the top plate and the bottom plate are configured by arranging a plurality of small cross section tunnels in parallel. In addition, a tension force is introduced into only the top plate and the bottom plate via a tension material disposed across the plurality of small cross-section tunnels.

  In such a large-section tunnel, prestress is effectively introduced into the top plate and the bottom plate, so that the thickness of the member can be reduced.

  Further, in the large-section tunnel, if a part of the small-section tunnel constituting the top plate or the bottom plate protrudes outside the one side wall, an apparatus for introducing prestress into the overhanging portion Etc. can be arranged, so that it is excellent in workability even though it is work in the ground.

  In addition, if the tension material is disposed on the natural mountain side at the end of the top plate or the bottom plate, and is disposed on the inner side in the central portion of the top plate or the bottom plate, it acts on a large-section tunnel. Prestress can be effectively introduced with respect to the stress to be applied.

  The small cross-sectional tunnel is formed by a plurality of steel shells connected along the tunnel axial direction, and the steel shell is disposed in a portion where stress acting on the top plate, the bottom plate, or the side wall becomes tensile. And the general part disposed in the portion to be compressed, and the amount of steel of the reinforcing part is such that the cross-sectional area of the general part is larger than the cross-sectional area of the general part. If it is distributed more than the amount of steel in the general part, the amount of steel can be reduced, which is economical.

  If a water-stopping member is arranged on the natural ground side of the joint between adjacent small-section tunnels, it is possible to omit water-stopping work such as chemical injection into the natural ground corresponding to the joint. Excellent in both cost and economy.

  The water stop member includes a V-shaped water stop plate fixed to one of the small cross section tunnels, and a water stop block fixed to a position corresponding to the water stop plate of the other small cross section tunnel, The water stop plate and the water stop block may be in contact with each other.

  In addition, a joining member that joins the small cross-sections is arranged in the joint portion on the ground mountain side of the side wall, and the joining member is disposed over the boundary between the small cross-sectional tunnels, and You may provide the end plate fixed to each small cross-section tunnel so that it may mutually oppose at the both ends of the said connection reinforcing bar.

  According to the method for constructing a large section tunnel and the large section tunnel of the present invention, prestress can be effectively introduced into the top and bottom plates of the tunnel in the ground, thereby reducing the use of members and rationalizing the tension members. Can be achieved.

It is sectional drawing which shows the large cross-section tunnel which concerns on suitable embodiment of this invention. It is a figure which shows the steel shell which comprises a small cross section tunnel, Comprising: (a) is a front view, (b) is AA sectional drawing of (a). (A) is BB sectional drawing of Fig.2 (a), (b) is CC sectional drawing. It is an expanded sectional view which shows the junction part of steel shells. (A) And (b) is sectional drawing which shows each construction step of the construction method of a large section tunnel. (A) And (b) is sectional drawing which shows each construction step of the construction method of the large section tunnel following FIG. It is sectional drawing which shows the modification of a large section tunnel.

Hereinafter, preferred embodiments of the present invention will be described.
In the present embodiment, as shown in FIG. 1, a large-section tunnel 1 having a rectangular cross section including a top plate 2, a bottom plate 3, and left and right side walls 4, 4 will be described.

  The top plate 2 is configured by connecting five small-section tunnels 10, 10,... Arranged side by side in the horizontal direction (left-right direction) and filling concrete 20 into the inside. The number of small cross-sectional tunnels 10 constituting the top plate 2 is not limited, and can be set as appropriate according to the planned size of the large cross-sectional tunnel 1.

  A tension force is introduced into the top plate 2 via tension members 30, 30,... Disposed across the small cross-sectional tunnels 10, 10,. In the present embodiment, a PC steel wire is used as the tendon 30, but the material constituting the tendon 30 is not limited.

  The tendon material 30 is disposed on the natural ground G side (upper side) at the end of the top plate 2, and is disposed on the inner side (lower side) of the large cross-section tunnel 1 in the center portion of the top plate 2. These are arranged in an arc shape so as to protrude downward.

  Among the small cross-section tunnels 10 constituting the top plate 2, a small cross-section tunnel 10 ′ disposed at one end portion (the right end in FIG. 1) partially protrudes from the side wall 4 to the natural mountain side (right side). It is formed in the state. That is, the total width of the plurality of small cross-sectional tunnels 10, 10,... Constituting the top plate 2 is larger than the width of the top plate 2 when completed (the width from the outer surface of one side wall 4 to the outer surface of the other side wall 4). A part of the large, small-section tunnel 10 ′ protrudes from the top plate 2.

  The overhanging portion of the small-section tunnel 10 ′ is used as a work space when a tension force is introduced into the tension member 30 by securing the space 5 without filling the concrete 20.

  The small cross section tunnel 10 is constructed by connecting steel shells 11 having a rectangular cross section along the tunnel axis direction.

  The steel shell 11 is a member formed in a rectangular tube shape by combining steel members. As shown in FIGS. 2 and 3, the steel shell 11 of the present embodiment includes a plurality of main girders 12, 12, 12 arranged in parallel with a predetermined interval in the tunnel axis direction and adjacent main girders 12, A plurality of vertical ribs 13 arranged between the two along the tunnel axis direction, an outer shell 14 covering the outer periphery of the main girders 12, 12, 12 and the vertical ribs 13, 13,. 15.

  The main girder 12 is formed in a frame shape by combining steel materials into a rectangular shape, and is sufficient for external forces (earth pressure, groundwater pressure, etc.) acting on the small section tunnel 10 in a state where it is placed in the ground. Has a high yield strength. In the present embodiment, three main girders 12, 12, and 12 are arranged for one steel shell 11, but the number of main girders 12 is not limited. Moreover, the steel material which forms the main girder 12 is not limited, H-shaped steel, L-shaped steel, groove-shaped steel, a steel pipe, etc. can be used, but in this embodiment, a steel plate is used. Shall. Moreover, in this embodiment, although the rectangular main girder 12 was formed by combining steel materials, the formation method is not limited.

The vertical ribs 13 are arranged between the adjacent main girders 12 and 12 so as to maintain the interval between the main girders 12 and to exhibit sufficient proof strength against the axial force acting during propulsion. ing.
In the present embodiment, a steel plate of the same type as the main girder 12 is used as the vertical rib 13, but the material constituting the vertical rib 13 is not limited, and H-shaped steel, L-shaped steel, and channel steel It is possible to use other steel materials as appropriate, such as steel pipes. Moreover, the quantity of the vertical rib 13 is not limited.

  The outer shell 14 is formed in a cylindrical shape so as to cover the plurality of main girders 12, 12, and 12, and is formed by joining a plurality of skin plates by welding.

  The main girder reinforcing member 15 is a grooved steel fixed to the main girders 12 and 12 disposed in front of and behind the steel shell 11, and against the external force acting on the small-section tunnel 10 having a rectangular cross section. It arrange | positions so that 12 can be reinforced.

  The main girder reinforcing member 15 is disposed across the upper and lower long sides 12 a and 12 a of the main girder 12. In the present embodiment, two main girder reinforcing members 15 are arranged for each main girder 12, but the number of main girder reinforcing members 15 is not limited. Moreover, the material which comprises the main girder reinforcement member 15 is not limited, It can select and use from well-known steel materials suitably. Further, the main girder reinforcing member 15 may be disposed as necessary, and may be omitted.

  The bottom slab 3 is configured by connecting five small-section tunnels 10, 10,... Arranged side by side in the horizontal direction (left-right direction) and filling the inside with concrete 20. The number of small cross-sectional tunnels 10 constituting the bottom plate 3 is not limited, and can be set as appropriate according to the planned size of the large cross-sectional tunnel 1.

  Tension force is introduced into the bottom plate 3 via tension members 30, 30,... Disposed across the small cross-sectional tunnels 10, 10,.

  The tendon material 30 is disposed on the natural ground G side (lower side) at the end of the bottom slab 3, and is disposed on the inner space side (upper side) of the large section tunnel 1 in the center of the bottom slab 3, so It is arranged in an arc shape so as to be convex.

  Among the small cross-section tunnels 10 constituting the bottom plate 3, a small cross-section tunnel 10 ′ disposed at one end (the right end in FIG. 1) partially protrudes from the side wall 4 to the natural mountain side (right side). It is formed in a state. That is, the entire width of the plurality of small cross-sectional tunnels 10, 10,... Constituting the bottom plate 3 is larger than the width of the bottom plate 3 at the time of completion (the width from the outer surface of one side wall 4 to the outer surface of the other side wall 4), A part of the small section tunnel 10 ′ protrudes from the bottom plate 3.

  The overhanging portion of the small-section tunnel 10 ′ is used as a work space when a tension force is introduced into the tension member 30 by securing the space 5 without filling the concrete 20.

  The side wall 4 is configured by filling concrete 20 into the inside of a small-section tunnel 10 disposed between the top plate 2 and the bottom plate 3. Note that the side wall 4 may be configured by connecting a plurality of small-section tunnels 10 arranged in parallel in the vertical direction (vertical direction).

  As shown in FIG. 1, the joint between the top plate 2 or the bottom plate 3 and the side wall 4 is integrally joined via a joining member 40 and an additional reinforcing bar 45. In addition, you may join via the joining member 40 also about the junction part of the small cross-sectional tunnels 10 which comprise the top plate 2 and the bottom plate 3. FIG.

  In the present embodiment, a bearing-type joining member 40 is disposed on the pulling side of the side wall 4 (the ground side of the side wall 4), and an additional reinforcing bar 45 is disposed on the compression side (the inner space side of the side wall 4).

As shown in FIG. 4, the joining member 40 is wound around the connecting reinforcing bars 41, 41,... And both ends of the connecting reinforcing bars 41, 41,. .., The end plates 43 and 43 fixed to the main beam 13, and the support that is fixed to the main beam 13 and reinforces the fixing degree of the end plate 43. Plates 44, 44, ... are provided.
In addition, the structure of the joining member 40 is not limited and can be set suitably.

  The additional reinforcing bar 45 is a reinforcing bar arranged between the side wall 4 and the top plate 2 or the bottom plate 3, and the top end of the side wall 4 and the top plate 2 and the bottom plate 3 can secure a sufficient fixing length. The bar is arranged in a state protruding from the lower end.

  Moreover, the water stop member 50 is arrange | positioned along the tunnel axial direction at the junction part of each small cross-section tunnel 10, and groundwater and earth and sand may flow in from the clearance gap between the adjacent steel shells 11 and 11. FIG. It is prevented.

In the present embodiment, as the water stop member 50, a water stop plate 51 having a V-shaped cross section is arranged at a corner of the steel shell 11 on the natural mountain side, and a position corresponding to the water stop plate 51 of the other steel shell 11. The water stop block 52 is disposed in the front. The water stop plate 51 is fixed to the steel shell 11 in a state where a part of the water stop plate protrudes from the side surface of the steel shell 11, and the water stop block 52 embedded in the steel shell 11 of the adjacent small cross-section tunnel 10 is water-stopped. Since the protruding portion of the plate 51 is in close contact, the water stoppage at the joint is maintained.
In addition, the structure of the water stop member 50 is not limited and can be set suitably. In this embodiment, a chlorobrene-based water-stopping rubber is employed as the water-stopping plate 51 and the water-stopping block 52. However, if the water-stopping capability that can withstand high water pressure can be expressed, The material constituting the block 52 is not limited.

In this embodiment, the steel material which comprises the steel shell 11 is used as a steel material of a large section tunnel structure. Then, with respect to the stress acting on the large-section tunnel structure, the tension-side section is made thicker (that is, the amount of steel material is larger) than the compression side, and the tension is arranged in the main body of the large-section tunnel 1 (in the steel shell 11) The number of reinforcing bars on the side (the amount of reinforcing bars) is reduced. By reducing the amount of reinforcing bars, it is possible to secure a larger internal working space during construction, improving workability and improving safety.
That is, for the steel shell 11 constituting the small-section tunnel 10, the portion where the stress is compressed with respect to the reinforcing portion disposed in the portion where the stress acting on the top plate 2, the bottom plate 3 or the side walls 4, 4 is pulled. The amount of steel material is distributed more than the general part arranged in the.
Note that the method of increasing the amount of steel material in the reinforcing portion is, for example, increasing the number of the longitudinal ribs 13, increasing the member thickness of the outer shell 14, increasing the cross-sectional area of the main girder 12 or the longitudinal ribs 13, It is not limited, such as increasing the amount.

Next, the construction method of the large section tunnel 1 according to the present embodiment will be described.
Such a large-section tunnel construction method includes a small-section tunnel construction process, a small-section tunnel connection process, a tension material placement process, a concrete placing process, a tension force introduction process, a side wall connection process, and an internal excavation process. And.

As shown in FIG. 5 (a), the small section tunnel construction process is a process of forming a plurality of small section tunnels 10, 10,. In the present embodiment, each small-section tunnel 10 is formed by connecting steel shells 11 having a rectangular cross section along the tunnel axis direction by a propulsion method.
The small cross-sectional tunnels 10, 10,... Are arranged so as to surround a region (natural ground G ′) that becomes the inner space of the large cross-sectional tunnel 1.

In the present embodiment, first, the first small cross-sectional tunnel 10 a disposed in the central portion of the bottom plate 3 is formed. When the construction of the first small cross-section tunnel 10a is completed or proceeds with a predetermined extension, the second small cross-section tunnel 10b and the third small cross-section tunnel 10c adjacent to the first small cross-section tunnel 10a are formed. Next, the fourth small cross section tunnel 10d and the fifth small cross section tunnel 10e are formed. Here, the construction of the second small cross-section tunnel 10b and the third small cross-section tunnel 10c and the construction of the fourth small cross-section tunnel 10d and the fifth small cross-section tunnel 10e may be performed simultaneously, or one of them may be preceded. You may go.
In addition, the small cross-sectional tunnels 10a to 10e corresponding to the bottom plate 3 are formed in a horizontally long cross section by a steel shell 11 having a rectangular cross section.

Next, among the small cross-section tunnels 10 and 10 corresponding to the side walls 4 and 4, the sixth small cross-section tunnel 10f and the seventh small cross-section tunnel 10g are constructed. The construction of the small-section tunnel 10 corresponding to the side wall 4 portion may precede the right-side small-section tunnel 10f or the left-side small-section tunnel 10g. At this time, the seventh small cross-section tunnel 10g is formed along the center of the upper surface of the fifth small cross-section tunnel 10e, and the ground-side end of the fifth small cross-section tunnel 10e (the side opposite to the third small cross-section tunnel 10c). The end part is constructed so that it protrudes.
In addition, the small cross-sectional tunnels 10f and 10g corresponding to the side wall 4 are formed in a vertically long cross section by the steel shell 11 having a rectangular cross section.

When the construction of the small cross-section tunnels 10f and 10g corresponding to the side wall 4 is completed (or when the construction of the small cross-section tunnels 10f and 10g proceeds by a predetermined extension), the construction of the small cross-section tunnel 10 corresponding to the top plate 2 is started. In the present embodiment, the small-section tunnels 10i to 10l are constructed sequentially from the eighth small-section tunnel 10h at the other end of the top plate 2. At this time, the 12th small cross section tunnel 10l is constructed such that the natural mountain side end (the end opposite to the 11th small cross section tunnel 10k) protrudes from the outer surface of the seventh small cross section tunnel 10g. Small cross-section tunnels 10h to 10l corresponding to the top plate 2 are formed in a horizontally long cross section by a steel shell 11 having a rectangular cross section.
Note that the small-section tunnel 10 corresponding to the side wall 4 and the small-section tunnel 10 corresponding to the top plate 2 or the bottom plate 3 are not connected at this stage.

The small cross-sectional tunnels 10 that are constructed in a subsequent manner are arranged side by side in a state where they are in contact with adjacent tunnels 10 that are constructed in advance or have a slight gap. At this time, the small-section tunnel 10 constituting the top plate 2 and the bottom plate 3 is temporarily fixed as necessary, but is disposed without being fixed to other adjacent small-section tunnels 10 (FIG. 5B). )reference).
Along with the construction of the small-section tunnel 10, a material having a lower adhesive strength than that of the surrounding ground G is used as the backfilling material to be filled around the steel shell 11. When introduced, it should function as a lubricant.

The small cross-section tunnel connection step is a step of connecting the small cross-section tunnels 10 disposed at positions corresponding to the top plate 2 and the bottom plate 3.
The small-section tunnels 10 are connected to each other by removing the outer shell 14 of the portion of the steel shell 11 of each small-section tunnel 10 facing the other small-section tunnel 10.
As a result, a continuous space is formed by the plurality of small cross-sectional tunnels 10, 10,... Corresponding to the top plate 2 and the bottom plate 3.

  As shown in FIG. 5 (b), the tension material disposing step is performed after the construction of the small-section tunnels 10a to 10e corresponding to the bottom plate and the construction of the small-section tunnels 10h to 10l corresponding to the top plate. This is a step of disposing tension members 30, 30,... Across the tunnels 10a to 10e and the small cross-sectional tunnels 10h to 10l.

  The tendon members 30, 30,... Are arranged so as to cross the space formed by the plurality of small cross-sectional tunnels 10, 10,... Are arranged in an arc. In addition, it is good also as what arrange | positions the tension material 30 more easily by providing the hole for the sheath of the tension material 30 in the longitudinal rib 13 of the steel shell 11 previously. Moreover, you may arrange | position the steel material for reinforcement as needed.

In this embodiment, one end of the tendon 30 is fixed in the fourth small section tunnel 10d or the eighth small section tunnel 10h, and the other end is disposed in the fifth small section tunnel 10e or the twelfth small section tunnel 10l. Has been.
In the present embodiment, the tension member 30 is disposed in a state of being accommodated in a sheath tube (not shown). However, the sheath tube may be disposed as necessary and may be omitted.

As shown in FIG. 6 (a), the concrete placing step is a step of filling concrete 20 into a plurality of small cross-sectional tunnels 10, 10,.
At this time, the space 5 is ensured without filling concrete in the protruding portions of the end portions of the fifth small cross-section tunnel 10e and the twelfth small cross-section tunnel 10l.

  In this embodiment, high strength concrete is filled. Moreover, in this embodiment, the main girder 12, the longitudinal rib 13, etc. which comprise the steel shell 11 are utilized for the main body, and the reduction of a compression reinforcing bar and a tension reinforcing bar shall be aimed at.

  In the tension introducing step, after the strength is developed in the concrete 20 filled in the top slab 2 and the bottom slab 3, the tension is introduced into the tension members 30, 30,. (See FIG. 6A).

  The tension force is introduced into the tension member 30 by using a jig, a jack or the like disposed in the space 5. After the introduction of the tension force, the rust prevention work of the fixing portion of the tension material 30 facing the space 5 is performed.

  In the side wall connecting step, as shown in FIG. 6 (a), the top plate 2 and the bottom plate 3 into which tension is introduced are connected to the side walls 4 and 4, and the outer shell of the large section tunnel 1 connected integrally is formed. It is a process to build.

  In the present embodiment, the joining of the top plate 2 and the side wall 4 and the joining of the bottom plate 3 and the side wall 4 are performed via the joining member 40 and the additional reinforcing bar 45. The disposing work of the joining member 40 and the additional reinforcing bar 45 is performed from the small-section tunnel 10 on the side wall 4 side.

  When the top plate 2 and bottom plate 3 are connected to the side walls 4 and 4, the side walls 4 and 4 are filled with concrete. In addition, you may perform the filling of the concrete to the side wall 4 when performing the concrete filling to the top plate 2 and the bottom plate 3 in a concrete placement process.

  The internal excavation step is a step of excavating a natural ground G ′ in the internal space of the large-section tunnel 1 surrounded by the top plate 2, the bottom plate 3, and the side walls 4, 4 as shown in FIG.

  As described above, according to the large-section tunnel 1 and the construction method thereof according to this embodiment, the top plate 2 and the bottom plate 3 and the side wall 4 are joined after the prestress (tensile force) is introduced. The resistance of internal earth and sand does not act. Therefore, prestress can be effectively introduced with little loss of prestress.

In addition, by introducing prestress to the top plate 2 and the top plate 3, even when a large-section tunnel is constructed at a high depth and under a high water pressure, sufficient proof stress can be expressed against the applied stress. it can.
Moreover, since the proof stress of the top plate 2 and the bottom plate 3 can be increased by introducing prestress, the use of the top plate 2 and the bottom plate 3 can be reduced.

  In addition, since the steel shell 11 constituting each small section tunnel 10 can be expected as a main body structure, the amount of reinforcing bars can be greatly reduced, the cost can be reduced, and the labor required for the bar arrangement work can be reduced. It becomes possible to reduce.

  Since the spaces 5 and 5 are formed along the ends of the top plate 2 and the bottom plate 3, it is possible to introduce prestress to the top plate 2 and the bottom plate 3 in the ground. In addition, it can be used as an inspection passage after construction of a large section tunnel.

  In addition, since a material having a lower adhesive strength than that of the surrounding ground is used as the backfill material, it is possible to reduce the loss of prestress caused by frictional resistance when prestress is introduced.

  Moreover, since the water stop member 50 is used in combination with the water stop plate 51 having a V-shaped cross section and the water stop block 52, the water stop at the joint portion between the small cross section tunnels 10 is excellent. Therefore, it is possible to omit auxiliary water stop work such as chemical injection to surrounding ground. Moreover, even if the space | interval of the small cross-section tunnels 10 opens or narrows by construction error, the cross-section V-shaped water stop plate 51 can follow.

  Moreover, since the connecting reinforcing bars 41 are intermittently arranged, the amount of reinforcing bars used can be greatly reduced. The combination of the connecting reinforcing bar 41 and the end plate 43 is excellent in stress transmission, so that the small-section tunnels 10 are fixed together.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and it goes without saying that the above-described constituent elements can be appropriately changed without departing from the spirit of the present invention.
For example, in the above-described embodiment, the case where the small-section tunnel is constructed by a steel shell having a rectangular cross section has been described. However, the cross-sectional shape of the steel shell is not limited and may be, for example, a square.

Moreover, in the said embodiment, although the case where the space 5 was formed by constructing | assembling so that a part of small-section tunnel 10 arrange | positioned at the edge part might protrude from the side wall 4 was demonstrated, the space 5 is required. It may be formed in accordance with this, and it is not always necessary to form it.
Moreover, it is good also as a structure which introduces tension | tensile_strength from both sides by forming the space 5 in the both ends of the top plate 2 and the bottom plate 3, respectively.

The number and arrangement of the small section tunnels 10 are not limited, and may be set as appropriate according to the planned shape of the large section tunnel.
Moreover, the construction order of the small cross-section tunnel 10 is not limited to the above order.

  In addition, the construction of the plurality of small cross-sectional tunnels 10, 10,... May be performed simultaneously using a plurality of excavating machines, or may be performed in order using one excavating machine.

  Moreover, although the said embodiment demonstrated the case where prestress was introduce | transduced after concrete placement, you may perform prestress introduction before concrete placement.

  Moreover, in the said embodiment, the connection member 40 is arrange | positioned at the tension | pulling side of the side wall 4, and the additional reinforcing bar 45 is arranged on the compression side, thereby connecting the top plate 2 and the bottom plate 3 to the side walls 4, 4. However, as shown in FIG. 7, the connection member 40 may be disposed on the compression side, and the connection method is not limited.

DESCRIPTION OF SYMBOLS 1 Large section tunnel 2 Top plate 3 Bottom plate 4 Side wall 5 Space 10 Small section tunnel 11 Steel shell 20 Concrete 30 Tensile material 40 Joint member 41 Connection reinforcement 43 End plate 50 Water stop member 51 Water stop plate 52 Water stop block G Ground mountain

Claims (9)

A method for constructing a large-section tunnel in which a plurality of small-section tunnels are connected to each other to form a top plate, a bottom plate, and left and right side walls, and a tension member is disposed only on the top plate and the bottom plate,
A step of constructing the small cross-section tunnel by connecting steel shells along the tunnel axis direction by a propulsion method; and
Removing the outer shell of the portion facing the other small-section tunnel among the steel shells of the adjacent small-section tunnels;
Disposing a tension material across a plurality of the small-section tunnels corresponding to the top plate or the bottom plate;
Filling the concrete into the plurality of small-section tunnels provided with tendons;
Introducing tension to the tendon;
Connecting the top plate and the bottom plate to which tension is introduced, to the side wall, and
At least part of the small cross-sectional tunnel disposed at one end of the top plate and the bottom plate is disposed so as to project outward from the one side wall, and the projecting portion of the small cross-sectional tunnel is used. And the construction method of the large section tunnel characterized by introduce | transducing tension | tensile_strength to the said tension | tensile_strength in the interior space. The steel shell is rectangular in cross section, and the small cross section tunnel corresponding to the top plate or the bottom plate is formed in a horizontally long cross section,
The method for constructing a large-section tunnel according to claim 1, wherein the small-section tunnel corresponding to the left and right side walls is formed in a vertically long section. A large-section tunnel comprising a top plate, a bottom plate, and left and right side walls,
The top plate and the bottom plate are configured by arranging a plurality of small-section tunnels in parallel,
A large cross-section tunnel, wherein a tension force is introduced to only the top plate and the bottom plate via a tension material disposed across the plurality of small cross-section tunnels.   The large cross-section tunnel according to claim 3, wherein a part of the small cross-section tunnel constituting the top plate or the bottom plate projects outward from one of the side walls.   The tension material is disposed on a natural ground side at an end portion of the top plate or the bottom plate, and is disposed on an inner side in a central portion of the top plate or the bottom plate. The large-section tunnel according to claim 4. The small-section tunnel is formed by a plurality of steel shells connected along the tunnel axis direction;
The steel shell includes a reinforcing portion disposed in a portion where a stress acting on the top plate, the bottom plate, or the side wall becomes tensile, and a general portion disposed in a portion serving as compression, and the strengthening The amount of the steel material of the strengthening part is distributed more than the amount of steel material of the general part so that the cross-sectional area of the part is larger than the cross-sectional area of the general part. The large-section tunnel according to any one of 5.   The large cross-section tunnel according to any one of claims 3 to 6, wherein a water stop member is disposed on a natural ground side of a joint portion between the adjacent small cross-section tunnels. The water stop member has a V-shaped water stop plate fixed to one of the small cross-section tunnels,
A water stop block fixed at a position corresponding to the water stop plate of the other small cross-section tunnel, and
The large cross-section tunnel according to claim 7, wherein the water stop plate and the water stop block are in contact with each other. A joining member that joins the small cross-sections to each other on the ground-side joining portion of the side wall is disposed,
The joining member includes a connection reinforcing bar disposed across a boundary between the small cross-section tunnels, and an end plate fixed to each small cross-section tunnel so as to face each other at both ends of the connection reinforcing bar. The large-section tunnel according to any one of claims 3 to 8, characterized by:

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