JP2012077448A - Tunnel connection structure and tunnel construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tunnel connection structure and a tunnel construction method, capable of sufficiently suppressing subsidence of upper ground and reducing a construction cost.SOLUTION: Since ground subsidence is greatly affected by a lining form constituting a upper half-side cross-section of a tunnel, a solid structure such as a reinforced concrete, steel or composite structure is employed as upper connection lining, so as to suppress the ground subsidence by suppressing displacement of tunnel lining. On a lower half side hardly affecting the upper ground subsidence, horseshoe-shaped lining having not a constant curvature but a rise different from that of an upper half side is constructed. Rational lining specifications based on acting earth pressure are applied to enable a drastic reduction in construction cost.

Description

  The present invention relates to a tunnel connection structure and a tunnel construction method in which a pair of tunnels adjacent in the horizontal direction are connected to form one tunnel cross section.

Conventionally, in a tunnel using shield tunnel lining such as a road tunnel, the main line tunnel and the branch line tunnel are connected to form a junction. A structure in which connection linings are installed vertically is proposed (see, for example, Patent Document 1).
In the connection structure described in Patent Document 1, the main line and branch line linings and the upper and lower connection linings are connected so that the cross section of the tunnel junction is an overall oval (oval or egg-shaped). These connecting portions are configured so that the linings are continuous and smoothly curved.

Moreover, as a construction method for constructing a tunnel junction, a method using a curved pipe roof that is a temporary material has also been proposed (for example, see Non-Patent Document 1).
The construction method of the tunnel merge part described in Non-Patent Document 1 is that, prior to tunnel excavation, a curved pipe roof is driven in the transverse direction from the guide tunnel shield, and a rigid receiving construction is constructed. A ground arch is formed by ground improvement (freezing) work, the ground is deformed (spray concrete), and the main body (lining concrete) is constructed after the deformation has converged.

JP 2005-248478 A

Deep Tunnel Technology Review Committee, “2nd Deep Tunnel Technology Review Committee, Material-1 Review of Construction Technology”, pages 5, 6 [online], December 5, 2005, Ministry of Land, Infrastructure, Transport and Tourism, Kanto Regional Development Bureau Road Department, [Search September 7, 2010], Internet <URL: http://www.ktr.mlit.go.jp/gaikan/pi_kouhou/dsi/02/index.html>

In the conventional connection structure described in Patent Document 1, since both the upper and lower tunnel connection lining structures are steel shells, it is considered to be light and have high bending strength and relatively less deformation of the lining. . However, in the lower half compared to the upper half, the effect of deformation of the lining on the upper part of the tunnel is small. That is, when both the upper and lower connection linings have a large rise, the excavation cross-sectional area of the ground increases. For example, in road tunnels and the like, road surfaces are installed in the lower half, so there is no need for a large rise in the lower half. Furthermore, in the conventional connection structure, the upper and lower connection linings are both steel shells, and the use of both upper and lower steel shells that require complicated machining processes in the manufacturing plant in advance leads to an increase in construction costs. It is considered easy.
Further, the conventional construction method described in Non-Patent Document 1 is a method for reducing the load acting on the lining by utilizing the self-supporting action of the ground due to the arch effect of the ground, that is, the ground subsidence in the upper part of the tunnel. Therefore, there is concern about the impact of land subsidence on the upper part of the tunnel or the surface structure. Furthermore, this construction method, when using a freezing method as a countermeasure for groundwater, will create a soil retaining wall for constructing a tunnel of arbitrary cross section by creating frozen soil, but it is necessary to make the frozen soil considerably thicker. There is a problem that the cost increases. In addition, it is necessary to construct a guide shaft prior to tunnel excavation, which leads to an increase in construction cost.

  The objective of this invention is providing the tunnel connection structure and tunnel construction method which can aim at reduction of construction cost while being able to fully suppress subsidence of an upper ground.

  The tunnel connection structure of the present invention is a tunnel connection structure in which a first tunnel and a second tunnel adjacent to each other in a substantially horizontal direction are connected to form one tunnel cross section, and the tunnel is a lining of the first tunnel. A first lining composed of the outer portion of the second tunnel, a second lining composed of the outer portion of the lining of the second tunnel, and an upper connection lining connecting the upper portions of the first and second linings; A lower connection lining connecting the lower portions of the first and second linings, wherein the upper connection lining includes a first connection portion connected to the first lining and the first connection lining. A second connecting portion connected to the two linings and formed in a circular arc shape having a constant curvature and projecting upward; the lower connecting lining includes a third connecting portion connected to the first lining; Convex downwards over the fourth connecting part connected to the second lining, and not a constant curvature but a cross-section horseshoe shape Is formed, characterized in that the upper connection lining and the lower connection lining are different construction types.

  According to the present invention described above, it is possible to expect a reduction in the generated sectional force due to the arch effect due to the rise of the upper half of the connection lining, in which the deformation of the tunnel lining easily affects the ground deformation at the upper part of the tunnel. In addition, the connection lining in the lower half where the vertical earth pressure does not act and the deformation of the tunnel lining is unlikely to affect the ground deformation at the top of the tunnel applies a horseshoe shape that can reduce the amount of excavated soil compared to the circular shape. Since an appropriate lining member according to the applied load can be applied, the construction cost can be reduced. For example, in the case of a road tunnel, since the road surface is installed on the lower half side, there is no particular problem even if the tunnel shape is a horseshoe shape.

  At this time, in the tunnel connection structure of the present invention, the tangent line along the upper connection lining, the first lining, and the second lining at the connection position between the upper connection lining and the first and second tunnels. It is preferred that the tangent lines along each of these do not match.

In the tunnel connection structure of the present invention, the upper connection lining protrudes upward over a first connection portion connected to the first tunnel and a second connection portion connected to the second tunnel. The apex height of the upper connection lining from a straight line that is formed in an arc shape and connects the first connection portion and the second connection portion is relative to the separation distance between the first connection portion and the second connection portion. The first connection portion is provided in a range from about 0 ° to about 45 ° toward the outside from a vertical line passing through the center of the first tunnel. The two connecting portions are preferably set to be about 0 ° or more and about 45 ° or less outward from a vertical line passing through the center of the second tunnel.
According to such a configuration, the deformation can be suppressed while reducing the bending stress acting on the upper connection lining against the earth pressure from the upper ground acting on the upper connection lining from above. It is possible to appropriately suppress the amount of subsidence of the upper ground.

Further, in the tunnel connection structure of the present invention, the lining constituting the first and second tunnels and the upper connection lining and the lower connection lining each have RC structures and steel shells formed from reinforced concrete, respectively. It is preferable to be composed of a plurality of segments made of a steel structure or a composite structure made of steel shell and concrete, or a combination thereof.
According to such a configuration, the structure of the segment can be properly used according to the performance required for the tunnel lining, and the upper and lower connection linings are connected via the connection portions corresponding to various segments. Only one tunnel can be constructed. Furthermore, in the case of a steel structure or a composite structure, the weight of the lining is lighter than that of the RC structure, so that deformation of the lining can be further suppressed.

In the tunnel connection structure of the present invention, the lower connection lining may be formed of cast-in concrete.
According to such a configuration, it is easy to construct a horseshoe-shaped tunnel lining that can reduce the excavation cross section, and the construction cost can be reduced because the lining can be constructed at a lower cost than when the lower connection lining is constructed with a steel shell. . Moreover, when producing a horseshoe-shaped RC segment, a plurality of molds having different shapes are required, so that cast-in-place concrete can reduce the construction cost.

Further, in the tunnel connection structure of the present invention, a curved pipe roof is provided in an upwardly convex shape on the outer peripheral side of the upper connection lining, and the connection position between the curved pipe roof and the first tunnel and the second tunnel is as follows. It is preferable that each of the first connection part and the second connection part is provided on the outer side.
According to such a configuration, since it is possible to support the ground by utilizing the rigidity of the pipe roof, the ground improvement range of the surrounding ground at the time of construction can be reduced, and the construction cost can be reduced. .

Furthermore, in the tunnel connection structure of the present invention, it is preferable that, in addition to the curved pipe roof, lock bolts are provided radially on the ground from the inner side of the curved pipe roof and connected to the curved pipe roof.
According to such a configuration, since the earth pressure acting on the pipe roof can be reduced by installing the lock bolt, the earth pressure acting on the pipe roof and the connection lining can be reduced, leading to a reduction in construction cost.

On the other hand, the tunnel construction method of the present invention is a tunnel construction method using any one of the above tunnel connection structures, and after the first and second tunnel constructions, depending on the case, from one of the tunnel inner sides to the other side The pipe roof is constructed up to the tunnel, and the surrounding ground where the upper connecting lining and the lower connecting lining are installed is improved from the inside of the tunnel to stabilize the surrounding ground. Supporting the lining and the second lining, partially excavating the ground in the tunnel, and if necessary, installing rock bolts radially on the ground from the inside of the tunnel of the pipe roof, It is characterized by constructing a work and a lower connection lining, and removing a removal part lining and a supporting work.
Here, the support work is preferably a type in which a steel member such as H steel is fixed with a member such as a bolt because the construction time can be shortened.
At this time, in order to reduce the ground improvement range around the installation position of the upper connection lining, after the construction of the first and second tunnels in advance, a curved pipe roof is constructed so as to connect the cross sections from both tunnels, The ground may be improved only around it, or a lock bolt may be installed in addition to the ground improvement in order to prevent the collapse of the ground around the installation position of the upper connection lining. Furthermore, when installing a curved pipe roof, it is preferable to backfill the space formed by the pipe roof and the upper connection lining after the upper connection lining is installed.
According to such a construction method, the rigidity of the pipe loop can be utilized to support the surrounding ground, so that the ground improvement range can be suppressed to a small size, leading to reduction of construction costs and safety against collapse of the ground during construction. Can increase the sex.

  According to the tunnel connection structure and the tunnel construction method of the present invention as described above, the deformation of the tunnel lining is likely to affect the subsidence of the upper part of the tunnel. However, in the lower half part, which has a small influence, by making the horseshoe shape convex downward, the amount of excavated soil can be reduced and the construction cost can be reduced. In addition, if the lower half side connection structure is a cast-in-place concrete structure, a horseshoe-shaped lining can be constructed relatively easily and the construction cost can be reduced.

It is sectional drawing which shows the tunnel connection part using the connection structure of this invention. It is a figure which shows the shape of the said tunnel connection part. It is a figure which shows the other shape of the said tunnel connection part. It is a figure which shows the further another shape of the said tunnel connection part. It is a figure which shows the further another shape of the said tunnel connection part. It is a figure which shows the further another shape of the said tunnel connection part. It is a figure which shows the analysis model which concerns on the Example of the said tunnel connection part. It is a graph which shows the relationship between the rise ratio and vertical displacement in the said Example. It is a graph which shows the relationship between the rise ratio and displacement rigidity in the said Example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the tunnel connection structure of the present invention constructs a tunnel junction 3 by connecting a main tunnel 1 as a first tunnel and a branch tunnel 2 as a second tunnel adjacent to each other on the left and right. is there. The main line tunnel 1 and the branch line tunnel 2 are shield tunnels that extend in the longitudinal direction of the tunnel, which is the depth direction of FIG. 1, respectively. In the present embodiment, each of the centers O1, O1 of the main line tunnel 1 and the branch line tunnel 2 is shown. A connection structure at a position where O2 is adjacent to each other by a distance (distance between centers) L will be described. Note that the center-to-center distance L may vary depending on the position in the longitudinal direction of the tunnel.

  The main tunnel 1 and the branch tunnel 2 are each configured by connecting a plurality of segments in the tunnel longitudinal direction and the tunnel circumferential direction. That is, the main line tunnel 1 and the branch line tunnel 2 assemble a segment in a space formed by excavating a natural ground with a shield machine (excavator), and take a reaction force on the assembled segment and advance the shield machine with a jack. In addition, the procedure of excavating the natural ground has been built repeatedly. Here, each segment may be an RC structure formed from reinforced concrete, a steel structure having a steel shell, or a composite structure in which concrete is packed inside the steel shell. There may be.

  The tunnel junction 3 is constructed between the main tunnel 1 and the branch tunnel 2 constructed in advance as described above, and is a first lining composed of the outer portion of the lining of the main tunnel 1. 11, a second lining 21 made of an outer portion of the lining of the branch tunnel 2, an upper connection lining 4 connecting the upper ends of the first lining 11 and the second lining 21, and a first lining 11 and the lower connection lining 5 of the horseshoe shape connecting the lower ends of the second lining 21 and the upper ends of the first lining 11 and the second lining 21 are connected above the upper connection lining 4. A curved pipe roof 6 is provided. In addition, in the surrounding ground of the curved pipe roof 6 and the upper half region of the first lining 11 and the second lining 21 are provided frozen soil 7 in which the ground is frozen as a countermeasure against ground peeling and groundwater during construction. A ground improvement body 8 in which the surrounding ground is improved is provided in the lower half area outside the first lining 11 and the second lining 21 and the lower side of the lower connection lining 5.

  As shown in FIG. 3, the upper connection lining 4 extends upward across the first connection portion 41 connected to the first lining 11 and the second connection portion 42 connected to the second lining 21. It is formed in a convex arc shape. As the structure of each of these connection portions 41, 42, an appropriate connection structure can be selected according to the material and structure of each segment. For example, each connection portion 41, 42 is configured by an appropriate segment piece. You may combine with 1 and the 2nd linings 11 and 21, and in that case, the connection structure using a suitable anchor material, a mechanical coupling, etc. is employable. Further, when the first and second linings 11 and 21 and the upper connection lining 4 are made of steel, connection portions 41 and 42 that are joined to these by welding joining may be used. When the two linings 11 and 21 and the upper connection lining 4 are made of RC, connection portions 41 and 42 of on-site RC construction or precast RC construction (PCa) may be used.

  The shape of such an upper connection lining 4 is set as follows. Here, the dimensions of each part are based on the cross sections of the center lines P1, P2, which are vertical lines passing through the centers O1, O2 of the main tunnel 1 and the branch tunnel 2, and the first and second linings 11, 21 ( (Thickness) center lines Q1 and Q2 and the center line R of the cross section (thickness) of the upper connecting lining 4 and the intersections of the center lines Q1 and Q2 and the center line R are the first intersection X1 and the second intersection, respectively. Let X2 be a straight line connecting these intersections X1 and X2 as a rise reference line Y.

The arc shape that is convex above the upper connection lining 4, that is, the rise shape, has a distance a between the first intersection point X 1 of the first connection portion 41 and the second intersection point X 2 of the second connection portion 42, and the intersection points X 1 and X 2. It is defined by the relationship with the height dimension b from the connecting rise reference line Y to the apex T of the upper connection lining 4, that is, the rise ratio (b / a). And in the tunnel junction part 3 of this embodiment, the rise ratio (b / a) of the upper connection lining 4 is set to 8% or more and 40% or less. That is, the rise ratio (b / a) is set so as to satisfy the following expression (1).
0.08 ≦ b / a ≦ 0.4 (1)
The curved pipe roof 6 has a larger curvature than the upper connection lining 4 and is formed in an upwardly convex arc shape. That is, the rise ratio of the curved pipe roof 6 is the rise ratio ( It is set larger than b / a).

In addition, the connection position between the upper connection lining 4 and the first lining 11 is defined by the position of the first intersection X1 of the first connection portion 41, specifically, the first intersection X1 and the center of the main tunnel 1 It is defined by the intersection angle θ1 between the straight line S1 passing through O1 and the center line P1 of the main tunnel 1. On the other hand, the connection position between the upper connection lining 4 and the second lining 21 is defined by the position of the second intersection X2 of the second connection portion 42. Specifically, the second intersection X2 and the center of the branch tunnel 2 are specified. It is defined by the intersection angle θ2 between the straight line S2 passing through O2 and the center line P2 of the branch line tunnel 2. Here, the intersection angles θ1 and θ2 are set so as to be positive from the centerlines P1 and P2 toward the outside. And in the tunnel junction part 3 of this embodiment, intersection angle (theta) 1 and (theta) 2 which are the connection positions of the upper connection lining 4 are set to the range of 0 degree or more and 45 degrees or less. That is, the intersection angle θ1 is set so as to satisfy the following expression (2), and the intersection angle θ2 is set so as to satisfy the following expression (3).
0 ° ≦ θ1 ≦ 45 ° (2)
0 ° ≦ θ2 ≦ 45 ° (3)
The curved pipe roof 6 is connected to the first lining 11 and the second lining 21 outside the connection position of the upper connection lining 4.

  As an example of the tunnel junction 3 that defines the shape and connection position as described above, the upper connection lining 4 shown in FIG. 3 has a rise ratio (b / a) set to 8% and an intersection angle θ1 of 0 °. And the intersection angle θ2 is set to about 5 °. In the example shown in FIG. 4, the rise ratio (b / a) is set to 25%, the crossing angle θ1 is set to 22.5 °, and the crossing angle θ2 is set to 22.5 °. Further, in the case shown in FIG. 5, the rise ratio (b / a) is set to 40%, the crossing angle θ1 is set to 45 °, and the crossing angle θ2 is set to 45 °.

In FIG. 2, after the construction of the main tunnel 1 and the branch tunnel 2, the tunnel construction procedure is to improve the ground from inside the tunnel to the outside of the lower half tunnel and the outside of the upper half and the lower half of the connection portion. The curved pipe roof 6 is constructed from the main line or branch line tunnel in the upper half. A frozen material 7 is formed by injecting frozen material into the ground from the curved pipe roof 6. The connecting portions 41 and 42 and the upper connection lining 4 are constructed between the first lining 11 and the second connection lining 21. Similarly, the connecting portions 51 and 52 and the lower connection lining 5 are constructed between the first lining 11 and the second connection lining 21. FIG. 6 shows the curved pipe roof 6 drilled from the curved pipe roof 6 after the curved pipe roof 6 shown in FIG. Alternatively, the rocks 13 may be formed by drilling a natural ground from the tunnel, and may be coupled to the curved pipe roof 6 via a connecting material (not shown).
After that, the support work 9 shown in FIG. 2 is installed, and the ground between the main tunnel 1 and the branch tunnel 2 is excavated. Next, the connection portions 41 and 42 and the upper connection lining 4 are constructed between the first lining 11 and the second lining 21. Similarly, the connecting portions 51 and 52 and the lower connection lining 5 are constructed between the first lining 11 and the second lining 21. Thereafter, the removal part linings 12 and 22 and the support work 9 are removed. FIG. 1 shows a tunnel cross section when completed, and FIG. 2 shows a tunnel cross section when constructed.

According to the above embodiment, the following effects can be obtained.
That is, since the upper part of the tunnel connection part 3 is constituted by the upper connection lining 4, the rigidity of the upper ground can be sufficiently suppressed by this rigidity, and the ground improvement range can be reduced as compared with the conventional construction method. Therefore, construction costs can be greatly reduced. And, for the lower connection lining 5 having a small impact on ground subsidence, it is only necessary to construct a horseshoe-shaped concrete structure after improving the ground with respect to the surrounding ground corresponding to the lower half of the tunnel connection part 3, so The construction cost can be greatly reduced. Moreover, as shown in FIG. 6, the safety | security to the collapse of a natural ground at the time of construction can be improved by constructing the lock bolt 13 from the curved pipe roof 6 to the outer peripheral ground after the construction of the curved pipe roof 6.

Hereinafter, with respect to the embodiments of the present invention, an FEM analysis model in which the main tunnel 1, the branch tunnel 2 and the tunnel junction 3 are modeled, the rise ratio (b / a) and the intersection angles θ1 and θ2 are used as parameters. The result of having examined the amount of subsidence (vertical displacement) of the vertex T of the upper connection lining 4 by applying a load from the ground will be described.
As parameters of intersection angles θ1 and θ2 that are connection positions of the upper connection lining 4 and the first and second linings 11 and 21, three types of 0 °, 22.5 °, and 45 °, respectively, and −22.5 A range of 0% to 40% was set as a parameter for the rise ratio (b / a).
An analysis model of this example is shown in FIG. The analysis model uses a uniform rigidity model of one ring, and the ground is evaluated with an appropriate spring (see FIG. 7B), and earth pressure and water pressure from the ground side are added as loads (FIG. 7A). )reference). The first lining 11, the second lining 21, the upper connection lining 4 and the lower connection lining 5 in the analysis model are composed of steel segments having steel shells, and the cross section is shown in FIG. As shown, it has a pair of main girders with a girder height of 1000 mm and a plate thickness of 90 mm, and a skin plate with a plate thickness of 6 mm that connects these main girders on the ground mountain side. Table 1 shows the specifications of the analysis model.

FIG. 8 and FIG. 9 are graphs showing the relationship between the rise ratio and the vertical displacement amount, and the rise ratio and displacement rigidity based on the analysis results. Here, in FIG. 9, the reciprocal of the ratio of the vertical displacement amount of the other model to the vertical displacement amount when the rise ratio (b / a) is 0% is expressed as displacement stiffness.
As shown in FIG. 8, the vertical displacement amount decreases as the rise ratio (b / a) increases from 0% when the crossing angles θ1, θ2 are 0 °, 22.5 °, and 45 °, When the rise ratio (b / a) is about 20%, the minimum value is reached, and the rise ratio (b / a) is maintained at the minimum value from 20% to 40% or slightly increased. As shown in FIG. 9, the displacement rigidity is such that the rise ratio (b / a) is about 8% to about 40% in each of the intersection angles θ1, θ2 of 0 °, 22.5 °, and 45 °. It can be seen that, in the range, a bending rigidity of 2 times or more of the rise ratio (b / a) of 0% is secured.

In the present invention, the horseshoe shape of the lower connection lining 5 is desirably a shape as close as possible to the lining curves of the main tunnel 1 and the branch tunnel 2.
According to such a configuration, the remaining main line tunnel 1 and branch line tunnel 2 can be utilized as much as possible, and the construction range of cast-in-place concrete as the lower connection lining 5 can be reduced, so that the construction cost can be reduced.
Further, the ground improvement range of the lower half is preferably longer than the length of the lower connection lining 5 by the ground improvement width, and the gap between the ground improvement body 8 and the main tunnel 1 and the branch tunnel 2 is in contact. The ground must be improved so that it does not occur. It is desirable that the material used for ground improvement has a high water-stopping property. Moreover, the strength of the ground improvement body 8 is required to be higher than the level that can prevent deformation of the natural ground when the lower half is constructed.

In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.
For example, in the above-described embodiment, the rise shape and connection position of the upper connection lining 4 are in the range of the formulas (1) to (3). And the connection position with the 2nd linings 11 and 21 can be set arbitrarily.
Further, in the above embodiment, the main tunnel (first tunnel) 1 and the branch tunnel (second tunnel) 2 are shield tunnels constructed by combining a plurality of segments. The tunnel structure and construction method can be arbitrarily selected as appropriate.

In addition, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, the invention has been illustrated and described with particular reference to certain specific embodiments, but without departing from the spirit and scope of the invention, Various modifications can be made by those skilled in the art in terms of material, quantity, and other detailed configurations.
Therefore, the description limiting the shape, material, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

  DESCRIPTION OF SYMBOLS 1 ... Main line tunnel (1st tunnel), 2 ... Branch line tunnel (2nd tunnel), 3 ... Tunnel junction, 4 ... Upper connection lining, 5 ... Lower connection lining, 6 ... Curve pipe roof, 8 ... Ground improvement Body, 9 ... Supporting work, 11 ... First lining, 12 ... Removal part lining, 13 ... Lock bolt, 21 ... Second lining, 22 ... Removal part lining, 41 ... First connection part, 42 ... First 2 connection parts, a: separation distance of connection parts of connection lining, b ... apex height dimension, L ... distance between tunnel centers, T ... apex.

Claims (8)

A tunnel connection structure in which a first and second tunnels adjacent in a substantially horizontal direction are connected to form one tunnel cross section,
The tunnel includes a first lining comprising an outer portion of the lining of the first tunnel, a second lining comprising an outer portion of the lining of the second tunnel, and the first and second linings. An upper connection lining connecting the upper portions, and a lower connection lining connecting the lower portions of the first and second linings,
The upper connection lining is formed in a cross-section arc shape having a constant curvature and projecting upward over a first connection portion connected to the first lining and a second connection portion connected to the second lining. And the lower connection lining is convex downward over the third connection portion connected to the first lining and the fourth connection portion connected to the second lining, and is not a constant curvature but a cross-section horseshoe shape A tunnel connection structure formed in a shape, wherein the upper connection lining and the lower connection lining have different structural types. The tunnel connection structure according to claim 1,
The tangent along the upper connection lining and the tangent along each of the first lining and the second lining do not coincide with each other at the connection portion position between the upper connection lining and the first and second tunnels. Tunnel connection structure characterized by In the tunnel connection structure according to claim 1 or 2,
The upper connection lining is formed in an upwardly protruding arc shape across a first connection portion connected to the first tunnel and a second connection portion connected to the second tunnel, and the first connection The apex height of the upper connection lining from the straight line connecting the part and the second connection part is set to about 8% or more and about 40% or less with respect to the separation distance between the first connection part and the second connection part. And
The first connection portion is provided in a range of about 0 ° or more and about 45 ° or less outward from a vertical line passing through the center of the first tunnel, and the second connection portion extends from the center of the second tunnel. A tunnel connection structure, wherein the tunnel connection structure is set to about 0 ° or more and about 45 ° or less outward from a vertical line passing through. In the tunnel connection structure according to any one of claims 1 to 3,
The lining constituting the first and second tunnels and the upper connection lining and the lower connection lining are each made of RC structure formed from reinforced concrete, steel structure with steel shell, or steel shell and concrete. A tunnel connection structure characterized in that the tunnel connection structure is composed of a plurality of segments composed of any one of the above structures or a combination thereof. In the tunnel connection structure according to any one of claims 1 to 4,
A tunnel connection structure, wherein the lower connection lining is made of cast-in concrete. In the tunnel connection structure according to any one of claims 1 to 5,
A curved pipe roof is provided in an upwardly convex shape on the outer peripheral side of the upper connection lining, and the connection position between the curved pipe roof and the first tunnel and the second tunnel is the first connection portion and the second connection portion. A tunnel connection structure characterized by being provided on the outer side of each. The tunnel connection structure according to claim 6, wherein, in addition to the curved pipe roof, lock bolts are provided radially on the ground from the inner side of the curved pipe roof, and are connected to the curved pipe roof. Tunnel connection structure. A tunnel construction method using the tunnel connection structure according to any one of claims 1 to 7,
After construction of the first and second tunnels, a pipe roof is constructed from one of the tunnels inside to the other side of the tunnel in some cases, and around the position where the upper connection lining and the lower connection lining are installed from inside the tunnel The ground is improved to stabilize the surrounding ground, and then a supporting work is installed to support the first lining and the second lining, and after partially excavating the ground in the tunnel, Tunnel construction characterized by constructing rock bolts radially on the ground from the inner side of the tunnel of the pipe roof, constructing the upper connection lining and the lower connection lining, and removing the removal portion lining and supporting work Method.

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