JP4637465B2 - Rectangular cross section shield tunnel - Google Patents

Description

  The present invention relates to a rectangular cross-section shield tunnel whose cross-sectional shape is substantially rectangular.

  Conventionally, shield tunnels have cross-sectional shapes such as circles, ellipses, horseshoe shapes, rectangles, etc., and the tunnel's purpose of use and various construction restrictions (technical restrictions, economic restrictions, construction space, The shape is determined according to legal restrictions.

  That is, these have advantages and disadvantages, and shapes that can be safely and inexpensively constructed are selected according to design conditions, ground conditions, and the like. Of these, the rectangular cross-section shield tunnel is often selected because of its merit that the occupied area, the occupied width, and the excavated cross-sectional area are smaller than the circular cross-section.

  For example, Patent Documents 1 and 2 show a typical form of a rectangular cross-section shield tunnel in which one ring is composed of a plurality of segments. For a cross section perpendicular to the tunnel axis direction, a top plate, a bottom plate, The left and right side walls are formed in a straight line having a constant thickness. Moreover, in such a rectangular cross-section shield tunnel, the corner portion is often formed in an arc shape in order to avoid stress concentration.

  Patent Documents 3 and 4 describe a rectangular cross-section shield tunnel in which a top plate, a bottom plate, and left and right side walls are formed in a bow shape with a constant thickness. While taking advantage of the rectangular cross-section such as width and excavation cross-sectional area, the mechanical properties of the arch structure are given to improve the strength and reduce the plate thickness.

In addition, as a special form, there is an invention described in Patent Document 5 by the applicant of the present application, a tension member is arranged on the inner peripheral surface side of a tunnel of a concrete segment having an inward rib, and prestress is introduced. Yes.
JP 05-248191 A Japanese Patent Laid-Open No. 06-146796 Japanese Patent Publication No. 08-0183030 No. 08-009276 JP 2001-003691 A

  In the case of the so-called box-shaped rectangular cross-section shield tunnel 21 having a right-angled corner as shown in FIG. 2, stress concentration occurs in the corner as described above. For example, as shown in FIG. As a rectangular cross-section shield tunnel 31 with a circular arc shape at the corner, stress concentration at the corner is reduced.

  In addition, in a rectangular cross-section shield tunnel, unless a highly rigid segment is used, it is common to provide a middle column or middle wall 25, 35 at the center of the cross section, and a mounting portion of the middle column or middle wall 25, 35 is provided. A large shearing force acts on the member. However, if the width is about the same or smaller than the height in the cross section, the middle pillar or the middle wall may not be provided.

  Furthermore, the segments constituting the segment ring in a normal tunnel have a constant thickness within the ring. However, in the case of a rectangular cross-section shield tunnel, regarding the top plate portion and the side wall portion, when a member having a constant thickness is formed on both the outer diameter side and the inner diameter side, the bending moment is excellent and the stress becomes severe.

  Therefore, in the conventional rectangular cross-section shield tunnel having a constant member thickness, when the member does not have a stress, it is necessary to increase the outer diameter to obtain a member thickness having a stress. This inevitably increases excavation cross-sectional area and leads to cost increase.

  Those described in Patent Documents 3 and 4 described above are substantially in the middle of a shield tunnel having a circular cross section and a shield tunnel having a rectangular cross section, and are thought to have the advantages of both. However, since it is an intermediate configuration, the occupied area, occupied width, and excavation cross-sectional area must be considerably larger than those of a normal rectangular cross-section shield tunnel, while it is inferior to a circular cross-section in terms of structural stability. This is just one of the variations in selecting the shape of the shield tunnel.

  The present invention is intended to solve the problems in the conventional rectangular cross-section shield tunnel as described above. By maintaining the basic shape of the rectangular cross-section shield tunnel on the outer peripheral surface, the occupied width and the excavation cross-sectional area are reduced. Taking advantage of the rectangular cross section such as the above, it is possible to use a machine for the shield of the rectangular cross section for the construction machine, while making the structure that the axial force in the circumferential direction works by reducing the bending of the cross section force. An object of the present invention is to provide a tunnel structure that reduces the average thickness of the entire cross section and is excellent in economy.

The invention according to a first aspect of the present invention, the top plate, bottom plate, and the left and right side walls possess, the tunnel circumferential direction, the rectangular cross-section shield tunnel segments made of a plurality of concrete formed by connecting the tunnel axis The outer peripheral surface side of the right-angled cross section is an arc-shaped rectangular cross section only at the corners, and the inner peripheral surface side is a cross-sectional shape composed of an arc-shaped curve without an inflection point, and the top plate, the bottom plate, and the left and right side walls The member thickness of the central part is made smaller than the member thickness of the corner part, and the member thickness of each segment is continuously changed in the tunnel circumferential direction .

  The shape on the outer peripheral surface side is the same as the conventional shape in which only the corner portion is arcuate (including an arc) in order to reduce stress concentration in the corner portion.

  Regarding the shape of the inner peripheral surface side, the member thickness of the tunnel is not made constant as in the prior art, but by giving a curvature to the inner cross section, priority is given to the transmission of the axial force in the circumferential direction within the cross section. Allow thickness change.

  Specifically, the inner peripheral surface side is a cross-sectional shape made of an arc-shaped curve without an inflection point, and an arc-shaped curve without an inflection point is a combination of a plurality of arcs with different curvatures Or a curve whose curvature changes continuously, or a combination thereof. Also, the absence of an inflection point inevitably means that there is no sudden change in curvature in such a curve and no large stress concentration occurs, but the curvature change is continuous or discontinuous. Even in this case, it is desirable that the curvature change is small.

  It should be noted that, in terms of production, it is easy to make a combination of a plurality of arcs having different curvatures from the production surface of segments or the like as members constituting the tunnel.

  The member thickness at the center of the top plate, bottom plate, and left and right side walls is smaller than the member thickness at the corner. The thickness of the top plate, the bottom plate, and the central portion of the left and right side walls is made small so that the thickness is increased.

  With such a configuration, the transmission of axial force in the circumferential direction of the tunnel reduces the burden of bending moments on the top plate, bottom plate, and left and right side walls, and the member thickness is determined by the magnitude of the bending moment acting so far. The top plate, the bottom plate, and the side wall portions that have been used become mechanically easy, and the required member thickness can be reduced.

  The present invention is particularly effective in a rectangular cross-section shield tunnel using a concrete segment that has a large compressive strength and is weak in tensile force or bending tensile force. The concrete segments include reinforced concrete segments, fiber reinforced concrete segments, prestressed concrete segments, and the like.

  The joints between the segments are not particularly limited, and various joints used in conventional concrete segments can be applied.

The invention according to claim 2, the top plate, bottom plate, have a left and right side walls, and the connecting top plate and a bottom plate center post or mid wall, the tunnel circumferential direction is segment made of a plurality of concrete are connected In the shield tunnel having a rectangular cross section, the outer peripheral surface side of the cross section perpendicular to the tunnel axis direction is a rectangular cross section with only the corners arced, and the inner peripheral surface side is changed at least except for the junction with the middle column or the inner wall. The cross-sectional shape is an arc-shaped curve having no inflection point, and the center thickness of the middle column or the middle wall of the top plate and the bottom plate and the left and right side walls, and the member thickness of the middle portion of the left and right side walls are the corner angles. The segment thickness is made smaller than the thickness of the member, and the thickness of each segment is continuously changed in the tunnel circumferential direction except for the junction with the middle pillar or the middle wall. .

As described above, a rectangular cross-section shield tunnel is generally provided with a middle pillar or a middle wall. Claim 2 defines the rectangular cross-section shield tunnel having such a middle pillar or middle wall.

  The basic idea of the invention is the same as that of the invention according to claim 1, but the arcuate curve with no inflection point is formed at the junction with the middle column or the middle wall position where the axial force in the vertical direction is generated. Since this cannot be continued, this part is an exception.

Further, with the exception of the junction with the middle column or the middle wall, the segment member thickness is continuously changed in the tunnel circumferential direction.

  In the present invention, by maintaining the same shape as the conventional rectangular cross-section shield tunnel on the outer peripheral face side, the inner peripheral face side should be a combination of arc-shaped curves without detracting from the advantages of the rectangular cross-section shield tunnel. Thus, the flow of the axial force also becomes smooth in the top plate part and the side wall part, and from the bending superiority to the axial force superiority in design, the member thickness can be suppressed as a whole tunnel.

  Therefore, more economical design is possible.

  Further, in terms of workability, the excavation cross-sectional shape is not particularly different from that of a conventional rectangular cross-section shield tunnel, so that conventional construction machines can be used almost as they are.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of a rectangular cross-section shield tunnel according to claim 2 of the present application. In this embodiment, the rectangular cross-section shield tunnel 1 includes a top plate 2, a bottom plate 3, left and right side walls 4, and a middle column or a middle wall 5 that connects the top plate 2 and the bottom plate 3.

In this example, the outer peripheral surface side of the rectangular cross-section shield tunnel 1, the radius of curvature for only corner 6 to alleviate the stress concentration is an arc of r _5, the other portions are the straight lines.

Further, the inner peripheral surface side of the rectangular cross-section shield tunnel 1 is configured by combining four types of arcs having curvature radii of r ₁ to r _{4 in} this example, except for the joint portion 7 with the middle column or the middle wall 5 portion. ing. In the case of the conventional rectangular section shield tunnel in which the member thickness is uniform, the corners 6 have the same center of curvature, but in this example, the center of curvature of the arc on the outer peripheral surface side and the arc on the inner peripheral surface side is the same. (The center for r ₃ is farther than the center for r ₅ ).

  Therefore, except for the joint portion 7 between the top plate 2 and the bottom plate 3 and the middle column or the middle wall 5, the member thickness of the corner portion 6 is the largest, and the center portion of the left and right side walls 4, the top plate 2, and the bottom plate 3 The member thickness of the intermediate portion (the central portion between the left and right side walls 4 and the middle column or the middle wall 5) is thin.

  This is because the influence of the bending moment acting on the components of the shield tunnel due to earth pressure or water pressure from the natural ground is large when the member thickness is constant as shown in FIG. The transmission of axial force in the circumferential direction of the tunnel is smoothed by the arcuate curved form continuous on the surface side, and the bending moment acting on the constituent members of the shield tunnel is reduced.

  Regarding the transmission of the axial force, the left and right portions sandwiching the middle column or the middle wall 5 form an axial force transmission path close to the circumference, respectively, and the middle column or the middle wall 5 usually has other portions. In this example, since the member having higher strength is used, the middle column or the inner wall 5 is a straight member, but it is also conceivable that these also have a shape including a curve.

  FIG. 4 and FIG. 5 compare the force and deformation generated in the rectangular cross-section shield tunnel 31 of FIG. 3 and the rectangular cross-section shield tunnel 1 of FIG.

  Regarding the axial force diagram, compared with FIG. 4 (a) (conventional example) where the member thickness is constant, in FIG. 5 (a) (the invention of the present application), the axial force is large at the portion where the member thickness is large and the portion where the member thickness is small. The axial force at is small.

  Regarding the bending moment diagram, in FIG. 4 (b) (conventional example), the value is large at the center between the left and right side walls and the middle column or middle wall of the top plate and bottom plate, whereas FIG. (In the present invention), the bending moment of the corresponding part is greatly reduced. This relationship is the same for the modified drawings (FIG. 4 (d), FIG. 5 (d)).

  Regarding the shear force diagrams, there was no significant difference between the two (FIGS. 4 (c) and 5 (c)).

  From these, it can be seen that the structure of FIG. 1 which is an embodiment of the present invention is structurally advantageous as compared to the rectangular cross-section shield tunnel of FIG. 3 having a constant member thickness. In particular, even if the member thickness is reduced for the central portion of the left and right side walls 4 and the middle pillar or the middle wall 5 and the central portion of the side wall 4 in the top plate 2 and the bottom plate 3, the bending moment and deformation of the portions are small. Therefore, by making the member thickness of these portions thinner than that of the corner portion 6, a more rational rectangular cross-section shield tunnel structure can be obtained.

  FIG. 6 shows an example of segment division in the case where there is a middle pillar or middle wall 5. In this example, two rings of five types 1a to 1e are combined to form one ring. However, various combinations are conceivable, for example, when the shapes of all the segments constituting the ring are different, or when a plurality of the same type is used for only some of the segments.

  To give specific numerical examples, for example, height H = 6865 mm and width B = 10538 mm on the outer peripheral surface side of the rectangular cross-section shield, a = 918 mm, b = 350 mm, c = 391 mm, d = 399.4 mm in FIG. E = 408.1 mm, f = 416.6 mm, g = 362.8 mm, h = 350 mm, i = 403.3 mm, j = 350 mm.

FIG. 7 shows an example of the arrangement of segments in an embodiment of the rectangular cross-section shield tunnel according to claim 1 of the present application. Since there are no center pillars or inner walls as compared with FIG. 13 and left and right side walls 14, and the outer peripheral surface side has a simple form in which only the corner portion 16 is an arc.

  In this example, a plurality of arcs with different curvatures are combined on the inner peripheral surface side of the rectangular cross-section shield tunnel 11, but instead of a complete arc, an arcuate curve whose curvature gradually changes may be continued.

  Also in this case, the member thickness is large at the corner portion 16, and the member thickness is small between them.

  Moreover, about the segment which comprises the rectangular cross-section shield tunnel 11, the four types of segments of 11a-11d are combined 2 pieces, and one ring is comprised, but when the shape of all the segments which comprise a ring differs Various combinations are conceivable, such as when a plurality of the same type is used for only some segments.

It is sectional drawing at right angles to the tunnel axial direction which shows one Embodiment of the rectangular cross-section shield tunnel concerning Claim 2 of this application. It is sectional drawing at right angles to the tunnel axial direction which shows an example of the conventional rectangular cross-section shield tunnel. It is sectional drawing at right angles to the tunnel axial direction which shows an example of the rectangular cross-section shield tunnel which used the conventional corner part as circular arc shape. 3A and 3B show the force and deformation generated in the conventional shield tunnel of FIG. 3, where FIG. 3A is an axial force diagram, FIG. 3B is a bending moment diagram, FIG. 3C is a shear force diagram, and FIG. FIG. FIG. 3 shows forces and deformations generated in the rectangular cross-section shield tunnel of FIG. 1 which is an embodiment of the invention according to claim 2 of the present application, in which (a) is an axial force diagram, (b) is a bending moment diagram, (c ) Is a shear force diagram, and (d) is a deformation diagram. It is sectional drawing at right angles to the tunnel axial direction which shows the member thickness of each part in other embodiment of the rectangular cross-section shield tunnel concerning Claim 2 of this application, and the example of arrangement | positioning of a segment. It is sectional drawing at right angles to the tunnel axial direction which shows the example of arrangement | positioning of the segment in one Embodiment of the rectangular cross-section shield tunnel concerning Claim 1 of this application.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rectangular cross-section shield tunnel (this invention), 1a-1e ... Segment, 2 ... Top plate, 3 ... Bottom plate, 4 ... Side wall, 5 ... Middle pillar or inner wall, 6 ... Corner, 7 ... Top plate or bottom plate And the junction between the inner pillar and the inner wall,
11 ... Rectangular cross-section shield tunnel (the present invention), 11a to 11d ... segment,
21, 31 ... Rectangular cross-section shield tunnel (conventional example)

Claims (2)

Top plate, bottom plate, and the left and right side walls possess, the tunnel circumferential direction, the rectangular cross-section shield tunnel made more concrete segment is coupled, corner the outer peripheral surface side of the tunnel axis perpendicular cross-section Only the portion has an arc-shaped rectangular cross section, and the inner peripheral surface side has a cross-sectional shape composed of an arc-shaped curve without an inflection point, and the thickness of the top plate, the bottom plate, and the central part of the left and right side walls is the corner portion. The rectangular cross section shield tunnel is characterized in that the thickness of each segment is continuously reduced in the circumferential direction of the tunnel. Top plate, bottom plate, have a left and right side walls, and the connecting top plate and a bottom plate center post or mid wall, the tunnel circumferential direction, the rectangular cross-section shield tunnel segments made of a plurality of concrete formed by connecting tunnel The outer peripheral surface side of the cross section perpendicular to the axial direction is a rectangular cross section with only the corners arcuate, and the inner peripheral surface side is at least from an arcuate curve having no inflection point other than the junction with the middle column or the inner wall. The cross-sectional shape is such that the center thickness of the middle column or the middle wall of the top and bottom plates and the left and right side walls, and the thickness of the left and right side walls are smaller than the thickness of the corners. The rectangular cross-section shield tunnel is characterized in that the thickness of each segment is continuously changed in the circumferential direction of the tunnel except for the junction with the middle pillar or the middle wall .

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