JP2015151675A - Method of constructing large-cross-section tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of constructing a large-cross-section tunnel that can secure cut-off performance between roof shields by backfilling as much as possible when constructing a large-cross-section tunnel using a plurality of small-diameter shield tunnels.SOLUTION: At a cross-sectional position smaller in cross-sectional area than a reference cross-sectional position, a number of small-diameter shield tunnels needed to obtain substantially the same arrangement intervals with the reference cross-sectional position are arranged along a cross-sectional contour 11, and the remainders are arranged behind them so that the respective small-diameter shield tunnels are all arranged at the reference cross-sectional position where the cross-sectional area of the widening predetermined region 3 is maximum along the cross-sectional contour 11 of the widening predetermined region 3. Each small-diameter shield tunnel along the cross-sectional contour 11 has two ridges 72a, 72b, provided in a backfilling region 71 of the small-diameter shield tunnel, connected to two ridges 72a, 72b provided in a backfilling region 71 of an adjacent small-diameter shield tunnel nearby tips thereof.

Description

  The present invention relates to a large-section tunnel construction method applied when a large-section tunnel is constructed using a plurality of small-diameter shield tunnels.

  When tunnel excavation is performed by the shield method, it is necessary to widen the tunnel cross section at the junction of the tunnel, typically at the junction of the main tunnel and the ramp tunnel.

  If the junction of the tunnel is a road tunnel, it will often have a large cross section with a width exceeding 20m, and even though shield machines with a diameter exceeding 15m have been manufactured, the limitation of the branch junction It is not realistic to excavate the entire section with a shield machine.

  Under such circumstances, as a technology that can widen the cross section of the shield tunnel, a plurality of small-diameter shield tunnels called roof shields are arranged along the tunnel axis direction so as to surround the branching junction in the shield tunnel of the main body. A construction method has been developed in which the outer shell of the widened portion is constructed in such a manner that they are interconnected in the circumferential direction, and then the inner region of the outer shell is excavated.

  Here, the outer shells described above are continuously constructed so as to extend through the gaps between the roof shields so as to pass through them in each roof shield. When building, it is necessary to temporarily receive earth pressure and water pressure from the surrounding ground by freezing or improving the ground by injecting a chemical solution into the ground spreading in the gap.

JP 2007-217911 A

  However, since the construction method described in Patent Document 1 is configured to surround the same number of roof shields at any cross-sectional position, when the size of the cross-section changes, the spacing between the roof shields changes accordingly, and the cross-sectional area changes. When the cross section position is large, the arrangement interval of the roof shields becomes coarse, and a large gap is naturally generated between the roof shields.

  For this reason, in the cross-sectional position where the arrangement interval of the roof shield is rough, there has been a problem that ground improvement work for temporarily receiving earth pressure and water pressure becomes large.

  In addition, even in the cross-sectional position where the roof shield is densely arranged, it is difficult to ensure the water-stopping of the above-mentioned place only by backfilling generally performed in shield construction. There was also a problem that was necessary.

  By the way, the above-mentioned problem that it is difficult to ensure waterproofing between the roof shields only by general backfilling is not only when widening the shield tunnel, but also constructing a large-section tunnel using a plurality of small-diameter shield tunnels The same occurs in the general case.

  The present invention has been made in consideration of the above-mentioned circumstances, and when constructing a large-section tunnel using a plurality of small-diameter shield tunnels, it is possible to ensure water-stopping between the roof shields only by backfilling. An object of the present invention is to provide a method for constructing a large-sized tunnel.

In order to achieve the above object, a method for constructing a large-section tunnel according to the present invention includes a plurality of methods along the tunnel axis direction of the large-section tunnel so as to surround the construction area of the large-section tunnel as described in claim 1. In a method for constructing a large-section tunnel in which a small-diameter shield tunnel made of a book is extended, an outer shell is constructed using the plurality of small-diameter shield tunnels as a receiving structure, and then an inner region surrounded by the outer shell is excavated. ,
Among the small-diameter shield tunnels, two small-diameter shield tunnels arranged adjacent to each other along the curved portion of the cross-sectional outline that forms the outer edge of the planned construction area, and adjacent to the backfill area of the small-diameter shield Two ridges projecting radially from two angular positions sandwiching a reference angular position at which the distance from the tunnel is the shortest are provided along the tunnel axial direction, and the center of curvature of the two angular positions is provided. The angle θ ₁ formed by the angle position closer to the reference angle position and the reference angle position is larger than the angle θ ₂ formed by the angle position far from the center of curvature and the reference angle position. In the region, two ridges provided on one side are respectively connected to two ridges provided on the other side in the vicinity of their tips.

The method for constructing a large-section tunnel according to the present invention is as described in claim 2, wherein a plurality of small-diameter shields are formed along the tunnel axis direction of the large-section tunnel so as to surround the construction area of the large-section tunnel. In a construction method of a large-section tunnel that extends a tunnel, constructs an outer shell using the plurality of small-diameter shield tunnels as a receiving structure, and then excavates an inner region surrounded by the outer shell.
Among the small-diameter shield tunnels, two small-diameter shield tunnels arranged adjacent to each other along the curved portion of the cross-sectional outline that forms the outer edge of the planned construction area, and adjacent to the backfill area of the small-diameter shield Two protrusions projecting radially from two angular positions sandwiching a reference angular position where the separation distance from the tunnel is the shortest are provided along the tunnel axial direction, and provided in the two backfill regions. One of the two back-filling regions so that each of the ridges on the side far from the center of curvature is larger in size or projecting length than each of the ridges on the side near the center of curvature. The two ridges provided on the other are connected to the two ridges provided on the other in the vicinity of their tips.

  Further, the method for constructing a large-section tunnel according to the present invention includes the widened portion formed in the shield tunnel as the large-section tunnel, the planned widening area as the planned construction area, and a maximum cross-sectional area of the planned widening area. The reference cross-sectional position is defined as a reference cross-sectional position, and at the reference cross-sectional position, the plurality of small-diameter shield tunnels are all arranged along the cross-sectional contour line of the region to be widened, and the cross-sectional area is larger than the reference cross-sectional position. At a small cross-sectional position, among the plurality of small-diameter shield tunnels, only the necessary number is arranged along the cross-sectional contour line so as to be substantially equal to the arrangement interval at the reference cross-sectional position, and the rest are the same. The receiving structure is constructed by extending the plurality of small-diameter shield tunnels so as to be arranged behind, and the widened region is In a section where the cross-sectional area monotonously increases, a small-diameter shield tunnel that is separated from the cross-sectional contour line is entered into a space formed between the small-diameter shield tunnels arranged along the cross-sectional contour line. The arrangement is changed to a state along the cross-sectional outline.

  In the construction method of a large-section tunnel according to the present invention, two small-diameter shield tunnels arranged adjacent to each other along a curved portion of a cross-sectional contour line that forms an outer edge of a construction-scheduled region among the small-diameter shield tunnels. In the backfill region, two protrusions projecting radially from two angular positions sandwiching a reference angular position where the distance from the adjacent small-diameter shield tunnel is the shortest are provided along the tunnel axis direction, respectively. Of the two backfill regions, two ridges provided on one side are respectively connected to two ridges provided on the other side in the vicinity of their tips.

  In this way, the gap between the small-diameter shield tunnels is reliably closed by the two pairs of protrusions that connect the vicinity of the tip, thus making it easy to ensure water-stopping at the above-mentioned locations only by backfilling and improving the ground. Even if construction is required separately, it is possible to minimize the extent and extent of improvement.

  The large-section tunnel to which the present invention can be applied includes a case where the cross-sectional outline is a circle or an ellipse, and includes a curved portion in a part of the cross-sectional outline, for example, the bottom and the top are constituted by flat plates, It is also included when each side connecting them is semi-cylindrical.

  When connecting the two ridges provided in one backfill area to the two ridges provided in the other backfill area in the vicinity of their tips, the outer edge of the planned construction area is planar, in other words Then, if the cross-sectional outline that forms the outer edge of the planned construction region is a straight line, the two ridges in each backfill region are the reference angular positions at which the distance from the adjacent small-diameter shield tunnel is the shortest. A line along the axis of symmetry can be symmetrical on the side close to and far from the planned construction area, but the outer edge of the planned construction area has a curved surface as in the present invention, in other words, the outer edge of the planned construction area. If the cross-sectional contour line forming the curved line is curved, the distance between the two protruding ridges on the side close to the bending center is shortened, and conversely on the side far from the bending center, the two protruding ridges The separation distance becomes longer.

Therefore, in the present invention,
(a) Of the two angular positions, the angle θ ₁ formed by the angle position closer to the bending center and the reference angular position is greater than the angle θ ₂ formed by the angular position far from the bending center and the reference angular position. To be larger, or
(b) Of the ridges provided in the two backfill regions, the ridges on the side far from the curve center are larger in size or projection length than the ridges on the side near the curve center. In addition,
Of the two backfill regions, two ridges provided on one side are respectively connected to two ridges provided on the other side in the vicinity of their tips.

  Here, when the ridge is excavated in the front ground with a shield machine, it is possible to cut and form a groove-like recess in the side ground, and fill the groove-like recess with a backfill material. However, in the case of (a), for example, four side cutters capable of cutting a groove-like recess having a semicircular cross section are provided in the shield machine, and the four side cutters have the curvature of the cross sectional contour line. Since it is only necessary to adjust the angular position of each other in accordance with the size and to make the whole pivotable as appropriate around the axis, it is easier to handle on the shield machine side than in the case of (b).

  The present invention can be applied to all cases of constructing a large-section tunnel using a plurality of small-diameter shield tunnels, and of course, when the cross-sectional size is constant at any cross-section position, When the size of the cross section changes depending on the position of the cross section, for example, the present invention can be applied to the case where the widened portion is formed in the shield tunnel.

  In forming the widened portion in the shield tunnel, in a configuration in which the region to be widened is simply surrounded by a plurality of small-diameter shield tunnels, the gap at the portion where the small-diameter shield tunnel is roughly arranged becomes excessive, and the present invention is applied to the portion. Although it is difficult to apply, all of the small-diameter shield tunnels are arranged along the cross-sectional contour line at the reference cross-sectional area where the cross-sectional area of the planned widening area is maximum, and the cross-section is wider than the reference cross-sectional position. At the cross-sectional position where the area is small, only the necessary number is arranged along the cross-sectional contour line so that it is almost the same as the arrangement interval at the reference cross-sectional position, and they are extended so that the rest is arranged behind it. If applied, the small-diameter shield tunnels along the cross-sectional contour lines are arranged at equal pitches at all cross-sectional positions. By adding a structure that, is further reduced need for ground improvement work.

  That is, in the above-described configuration, except for the transition section that attempts to move from a state separated from the cross-sectional outline to a state along or vice versa, the small-diameter shield tunnels are close to each other with a slight gap, and these small diameters The shield tunnel can generally support earth pressure and water pressure, and the gap between the small-diameter shield tunnels is reliably closed by the two pairs of protrusions connected near the tip as described above. Water stoppage in can be realized only by backfilling, and thus it is possible to greatly reduce the ground improvement work when forming the widened portion of the shield tunnel.

  As described above, the construction method of the large-section tunnel according to the present invention is effective when applied to a configuration in which the small-diameter shield tunnel along the cross-sectional contour line can be arranged at an equal pitch at all cross-section positions. It is demonstrated without hesitation.

  The widening part is typically formed as a branching / merging part of the shield tunnel, especially as a branching / merging part at the junction between the main tunnel and the lamp tunnel, but it is constructed for an emergency evacuation zone, emergency parking zone, or any other purpose. The widened portion to be included is included.

  The widened section has a start area of the small-diameter shield machine positioned near the outside of the shield tunnel as the base end side, and the cross-sectional position where the cross-sectional area becomes the maximum while the cross-sectional area monotonously increases from the base end side (reference cross section) The conical widened portion extending along the tunnel axis direction of the shield tunnel is a typical example, and for example, it has a shape that monotonously decreases after the cross-sectional area increases monotonically, such as the base end side and the end The cross-sectional area may be reduced on the side, and a shape that becomes a reference cross-sectional position in the vicinity of the cross-section may be used.

  In this case, in the section where the cross-sectional area of the planned widening area monotonously decreases, any small-diameter shield tunnel out of the small-diameter shield tunnel in the state along the cross-sectional contour line is allowed to exit from the adjacent small-diameter shield tunnel. What is necessary is just to change arrangement | positioning to the state spaced apart from the cross-sectional outline.

  In forming the widened portion, a plurality of small-diameter shield tunnels can be used as long as the cross-sectional position of the small-diameter shield tunnel is as long as the arrangement relationship with the cross-sectional contour line of the widened area at each cross-sectional position is as described above. Change the arrangement from the state separated from the cross-sectional contour line to the state along the cross-sectional contour line of the planned widening area, and conversely at which cross-sectional position from the state along the cross-sectional contour line of the planned widening area to the cross-sectional contour line It is optional to change the arrangement of the small-diameter shield tunnel along the cross-sectional contour line of the planned widening region from beginning to end.

  It is arbitrary whether the receiving structure of the present invention is used as a temporary structure or a permanent structure, and a form in which a part is used as a temporary structure and the other is used as a permanent structure is also possible. For example, a small-diameter shield tunnel segment may be used as a part of the main structure.

In the construction method of a large-section tunnel according to the present embodiment, a perspective view of a receiving structure composed of a plurality of small-diameter shield tunnels, omitting the intermediate portion thereof, (a) is an overall perspective view, (b) is the fragmentary perspective view which showed only start area 6b among start areas 6a and 6b provided in the base end side. It is the figure which showed the arrangement | positioning condition of the small diameter shield tunnel 4-1 to 4-18 and the small diameter shield tunnel 5-1 to 5-18, (a) is a top view which showed the cross-sectional position, (b) is A1-A1. (C) is A2-A2, (d) is A3-A3, (e) is a cross-sectional view which follows each cross-sectional line of A4-A4. It is the figure which similarly showed the arrangement | positioning condition of the small diameter shield tunnel mentioned above, (a) is A5-A5, (b) is A6-A6, (c) is A7-A7, (d) is A8-A8, (e ) Is A9-A9, and (f) is a cross-sectional view taken along each cross-sectional line of A10-A10. The whole perspective view which showed the arrangement | positioning condition of the small diameter shield tunnels 4-1 to 4-18. The whole perspective view which showed a mode that the small diameter shield tunnel 5-1 to 5-18 approached into the space 31 where the small diameter shield tunnel 4-1 to 4-18 are not arrange | positioned. How the small diameter shield tunnels 5-1 to 5-18 as the second tunnel group enter the space 31 formed by the small diameter shield tunnels 4-1 to 4-18 as the first tunnel group The schematic diagram which showed. The two ridges 72a and 72b provided in the backfill region 71 of the small-diameter shield tunnel 4-1 are replaced with the two ridges 72a and 72b provided in the back-fill region 71 of the small-diameter shield tunnel 5-1. The perspective view which showed a mode that each connection was carried out in the tip vicinity. Explanatory drawing which showed the relationship between the connection structure of protrusion 72a, 72a and protrusion 72b, 72b, and the curvature of the cross-sectional outline 11. FIG. The cross-sectional view which showed the formation condition of the backfill area | region 71 in cross-sectional position A10. Sectional drawing which showed a mode that the outer shell 81 was constructed | assembled by making a small diameter shield tunnel into a receiving structure. The cross-sectional view which showed the example of application to a general large section tunnel.

  Embodiments of a method for constructing a large section tunnel according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an example in which the present invention is applied to a case where a widened portion as a large-section tunnel is formed in the main tunnel so as to provide a branching / merging portion for joining the main tunnel 1 as a shield tunnel to the lamp tunnel 2. FIG. 2 is an overall perspective view of a receiving structure composed of a plurality of small-diameter shield tunnels, omitting an intermediate portion thereof and showing only a base end side and a terminal end side.

  As shown in the figure, in the construction method of the large-section tunnel according to the present embodiment, first, along the tunnel axis direction of the main tunnel 1 so as to surround the widening planned area 3 as the planned construction area that becomes the widened portion after excavation. A total of 36 small-diameter shield tunnels 4-1 to 4-18 and small-diameter shield tunnels 5-1 to 5-18 are constructed in advance.

  These 36 small-diameter shield tunnels 4-1 to 4-18 and the small-diameter shield tunnels 5-1 to 5-18 are used for constructing an outer shell (described later) required before excavation of the widened area 3. It becomes a structure.

  Two start areas 6a and 6b are provided in the vicinity of the outside of the main tunnel 1 so as to be separated from each other along the tunnel axis direction, and the small-diameter shield tunnels 4-1 to 4-18 are provided from the start area 6a. The small-diameter shield tunnels 5-1 to 5-18 are constructed by small-diameter shield machines that start from the start area 6b.

  Each of the start areas 6a and 6b is formed by partially cutting a lining segment (not shown) of the main tunnel 1 from the inside and inserting and installing a circumferential tunnel excavator, and using the circumferential tunnel excavator on the outside of the main tunnel 1 After the excavation of the surrounding ground to form an annular space with a rectangular cross section, the remaining lining segments can be cut open and exposed as an annular trench, and a small diameter shield can be formed from the annular trench. The machine can be started.

  In this embodiment, the widened portion formed by excavating and removing the planned widening region 3 has a cross-sectional area from the base end side where the start areas 6a and 6b are provided toward the terminal side where the ramp tunnel 2 is joined. It is a conically widened portion that monotonously increases, and the cross-sectional area is maximized at the cross-sectional position at the end. Hereinafter, this cross-sectional position is referred to as a reference cross-sectional position.

  Here, in FIG. 1, for convenience of drawing, the intermediate portion is omitted as described above, but a total of 18 small-diameter shield tunnels 4-1 to 4-18 extending from the start area 6a are ramps at the end. A total of 18 small-diameter shield tunnels 5-1 to 5-18 extending from the start area 6b and reaching the left half in FIG. 1 reach the main tunnel 1 side, in FIG.

  The small-diameter shield tunnels 4-1 to 4-18 and the small-diameter shield tunnels 5-1 to 5-18 are, as shown in the cross-sectional views of FIGS. 3 at all cross-sectional contour lines 11 and having a cross-sectional area smaller than the reference cross-sectional position (FIGS. 2 (b) to 3 (e)), it is almost the same as the arrangement interval at the reference cross-sectional position. Are arranged along the cross-sectional outline 11 as many as necessary, and the rest are arranged behind them.

  More specifically, the small-diameter shield tunnels 4-1 to 4-18 are shown in FIG. 2 and FIG. 3 as hatched as the first tunnel group. While extending from the starting area 6a on the base end side toward the reference cross-sectional position while being adjacent to each other, the circumferential length of the cross-sectional outline 11 gradually increases as the reference cross-sectional position approaches. As shown in FIG. 4, a space 31 in which the small-diameter shield tunnels 4-1 to 4-18 are not arranged is formed on the main tunnel 1 side.

  On the other hand, the small-diameter shield tunnels 5-1 to 5-18 are shown in FIG. 2 and FIG. It extends toward the above-described space 31 in such a manner that the small-diameter shield tunnel along the cross-sectional outline 11 is successively entered so as to change the arrangement along the outline.

  FIG. 5A shows three small-diameter shield tunnels 5-1 to 5-3, FIG. 5B shows a small-diameter shield tunnel 5-4 to 5-5, and FIG. 5C shows a small-diameter shield tunnel. The tunnels 5-6 to 5-8 are respectively shown to extend from the start area 6b toward the space 31, and in FIG. 4 described above, 18 small-diameter shield tunnels 4-1 to 4- In addition to 18, a state in which the small-diameter shield tunnel 5-1 is extended toward the space 31 is also drawn.

  FIG. 6 shows how the small-diameter shield tunnels 5-1 to 5-18 as the second tunnel group are compared with the space 31 formed by the small-diameter shield tunnels 4-1 to 4-18 as the first tunnel group. FIG. 2 is a schematic diagram showing whether or not the space 31 is extended together with the position of entry into the space 31. In FIGS. 2 and 3, when the right direction thereof is 0 ° and the counterclockwise direction is positive, ± 180 °. It is drawn as a developed view of the outer periphery as seen from the 0 ° side.

  Here, FIG. 9A shows only the small-diameter shield tunnels 4-1 to 4-18, and FIG. 11B shows only the small-diameter shield tunnels 5-1 to 5-18. In FIG. The arrangement state separated from the cross-sectional outline 11 is indicated by a solid line, the arrangement state along the cross-sectional outline 11 is indicated by a broken line, and the approach position to the space 31 is indicated by a black circle.

  As can be seen in FIG. 5A, the small-diameter shield tunnels 4-1 to 4-9 are extended from the start area 6a in the range of 0 ° to 180 ° and are at the reference cross-sectional position in the range of 90 ° to 180 °. The small-diameter shield tunnels 4-18 to 4-10 are extended from the start area 6a in the range of 0 ° to −180 °, and reach the reference cross-sectional position in the range of −90 ° to −180 °.

  On the other hand, with respect to the space 31 formed by these, the small-diameter shield tunnel 5-1 enters the space 31 past the cross-sectional position A1, as shown in FIG. The arrangement is changed from the above state to the state along the cross-sectional outline 11 and then extended to the reference cross-sectional position so as to approach the small-diameter shield tunnel 4-1.

  The small-diameter shield tunnel 5-2 extends from the start area 6b so as to intersect with the small-diameter shield tunnel 5-1 above, enters the space 31 after the cross-sectional position A2, and then enters the small-diameter shield tunnel. The small-diameter shield tunnel 5-3 is extended so as to be close to 5-1 and the small-diameter shield tunnel 5-3 is extended so as to intersect with the small-diameter shield tunnels 5-1 and 5-2, and then the cross-sectional position A3. After entering the space 31, the space 31 is extended to the reference cross-sectional position so as to snuggle up to the small-diameter shield tunnel 5-2, and thereafter the same is extended to the small-diameter shield tunnel 5-9.

  The same applies to the small-diameter shield tunnels 5-18 to 5-10, except that the small-diameter shield tunnels are symmetric with respect to the small-diameter shield tunnels 5-1 to 5-9 when viewed from the 0 ° direction. Since the arrangement is generally the same, the description thereof is omitted here.

  As described above, the small-diameter shield tunnels 5-1 to 5-18 are sequentially shifted from the base end side to the terminal end side along the tunnel axis of the main tunnel 1 while the position change by the entry into the space 31 is performed. 5-1 and 5-18, 5-2 and 5-17, 5-3 and 5-16, and so on, enter the space 31 and extend to the reference cross-sectional position.

  The small-diameter shield tunnels 4-1 to 4-18 and the small-diameter shield tunnels 5-1 to 5-18 can be basically constructed in an arbitrary order. For example, the small-diameter shield tunnels 4-1 to 4-4 After extending -18 in advance, the small-diameter shield tunnels 5-1 to 5-18 are sequentially arranged in the order of their approach positions to the space 31 from the base end side in the above-described embodiment. It may be possible to start from -1,5-18 and extend to 5-9, 5-10 sequentially. Conversely, in the above embodiment, the approach position is closer to the end side. It may be possible to start from 5-9, 5-10 and extend sequentially to 5-1, 5-18.

  In the former case, the small-diameter shield tunnels 5-1 to 5-18 enter the space 31 in a form of interrupting them while getting over the portion previously arranged along the cross-sectional contour line 11, and in the latter case Enters the space 31 so as to pass through the portion arranged in advance along the cross-sectional contour line 11 and close to the portion arranged in advance.

  In extending the small-diameter shield tunnels 4-1 to 4-18 and the small-diameter shield tunnels 5-1 to 5-18, two small-diameter shield tunnels arranged adjacent to each other along the cross-sectional contour line 11, for example, a reference cross section In the small-diameter shield tunnels 4-2 and 4-1 at the positions, as shown in FIG. 7, an angular position where the separation distance from the small-diameter shield tunnel 4-1 is the shortest in the backfill region 71 of the small-diameter shield tunnel 4-2. Two projecting ridges 72a and 72b projecting in the radial direction from two angular positions sandwiching the outer diameter are provided along the tunnel axial direction, and the small-diameter shield tunnel 4-2 and the back-fill region 71 of the small-diameter shield tunnel 4-1 Two projecting ridges 72a and 72b projecting radially from two angular positions sandwiching the angular position where the distance between them is the shortest are provided along the tunnel axis direction. The two protrusions 72a and 72b provided in the backfill area 71 of the small diameter shield tunnel 4-2 are replaced with the two protrusions 72a and 72b provided in the backfill area 71 of the small diameter shield tunnel 4-1. Each is connected in the vicinity of their tips.

  On the opposite side of the small-diameter shield tunnel 4-1, as described above, the two protrusions 72a and 72b provided in the backfill area 71 are provided in the backfill area 71 of the small-diameter shield tunnel 5-1. Two small-diameter shield tunnels connected to the two ridges 72a and 72b in the vicinity of their tips respectively and arranged adjacent to each other along the cross-sectional outline 11 in the same manner are configured as described above.

As shown in FIG. 7, the protrusions 72a and 72b are provided in each small-diameter shield tunnel in total, two on the left and right sides so as to face the adjacent small-diameter shield tunnel. In this case, as shown in FIG. 8 (a), the protrusions 72a and 72b of the backfill region 71 are angle θ formed by the respective angular positions with respect to the angular position where the separation distance from the adjacent small-diameter shield tunnel is the shortest. ₁ , θ ₂ ,
θ ₁ = θ ₂
However, when the cross-sectional outline 11 is curved as in the present embodiment, the two protruding ridges 72b and 72b facing each other on the side close to the center of the curve, that is, on the side of the planned widening region 3 are used. On the other hand, on the side far from the center of curvature, the distance between the two protruding ridges 72a, 72a becomes longer, so that the two protruding ridges 72a, 72a are as shown in FIG. Are not connected to each other.

Therefore, in the present embodiment, as shown in FIG. 3C, the angle θ ₁ formed by the angle position closer to the curve center with respect to the reference angle position is also the angle formed by the angle position far from the curve center. larger than θ ₂ , that is,
θ ₁ > θ ₂
In the state, the two ridges 72a and 72b provided on one of the two backfill regions 71 and 71 are respectively replaced with the two ridges 72a and 72b provided on the other in the vicinity of their tips. Connecting.

Here, the above relationship between θ ₁ and θ ₂ is a definition focused on between two adjacent small-diameter shield tunnels. When this is seen for each small-diameter shield tunnel, as shown in FIG. In addition, the angle α formed by the angular position at which the protrusions 72a and 72a are protruded and the angle β formed by the angular position at which the protrusions 72b and 72b are protruded can be replaced.
α> β
It becomes.

  The backfill area 71 includes, for example, a cutter head arranged in front of the cylindrical body, four side cutters arranged so as to partially protrude from the peripheral surface of the cylindrical body, and configured to be rotatable around the machine axis. In this shield machine, the segment is assembled at the rear end while excavating the front ground with the cutter head arranged in front of the cylindrical body. While advancing with the reaction force from the segment, the side ground is cut by four side cutters to form four groove-shaped recesses along the tunnel axis in the side ground, while these excavations and cuttings are performed. Inject backfill material into the back of the segment.

  In this way, the injected backfill material is filled along the outer peripheral surface of the segment and also reaches the four groove-shaped recesses, and after solidification, is formed into a cylindrical shape along the outer peripheral surface of the segment. A backfill region 71 is formed which includes a cylindrical portion, outer ridges 72a and 72a protruding radially from the cylindrical portion, and inner ridges 72b and 72b.

  Further, when excavating a new small-diameter shield tunnel in the vicinity of the small-diameter shield tunnel constructed in this way, the tip of the ridges 72a and 72b on the preceding small-diameter shield tunnel side is partially cut, respectively. If a backfilling material is injected into a groove-shaped recess on the side of a new small-diameter shield tunnel formed at that time, the backfilling material is formed by the protrusion 72a on the side of the preceding small-diameter shield tunnel. Since it solidifies in the state integrated with 72b, the protrusion 72a, 72a which opposes outside, and the protrusion 72b, 72b which opposes inside can be mutually connected.

  For example, when the small-diameter shield tunnel 4-1 is taken as an example, the adjacent small-diameter shield tunnel is vertically positioned at the cross-sectional position A1 (FIG. 2 (b)), but it is adjacent as it extends in the terminal direction. The relative position of the small-diameter shield tunnel rotates, and the cross-sectional position A4 is substantially 45 ° (FIG. 2 (e)), and at the cross-sectional position A10, that is, at the end, the small-diameter shield tunnel is adjacent to the left and right (see FIG. f)).

  Further, the cross-sectional outline 11 has a large curvature at the cross-sectional position A1, but the curvature decreases toward the end side. Therefore, the size of (α−β) needs to be large on the base end side and small on the end side. There is.

  Therefore, in the case of the above-mentioned example, four groove shapes are formed by turning the entire angular position little by little around the axis while adjusting the angular position of the four side cutters according to the progress of the shield machine. The recess is formed to be twisted around the tunnel axis.

  In this way, after the backfill material is solidified, the four protrusions 72a, 72a, 72b, 72b are formed so as to be twisted around the tunnel axis, and the protrusions 72a, 72a described in FIG. The tip connection structure of the protrusions 72b and 72b is realized at each cross-sectional position.

  FIG. 9 shows the formation state of the backfill region 71 at the cross-sectional position A10. Each backfill formed around the small-diameter shield tunnels 4-1 to 4-18 and the small-diameter shields 5-1 to 5-18. It can be seen that the protrusions 72a, 72a, 72b, 72b in the region 71 are connected to each other at their tips in an integrated state.

  In this way, a total of 36 small-diameter shield tunnels 4-1 to 4-18 and small-diameter shield tunnels 5-1 to 5-18 were constructed along the tunnel axis direction of the main tunnel 1 so as to surround the widening planned area 3. Then, the outer shell 81 is constructed as shown in FIG.

  FIG. 10 (b) shows two small-diameter shield tunnels 5-9 and 5-10 in a state (cross-section position A9) spaced from the cross-sectional outline 11 as shown in FIG. 10 (a). After passing through the transition section, as shown in FIG. 5 (c), it enters between the small-diameter shield tunnels 5-8 and 5-11, and is rearranged to a state along the cross-sectional contour line 11. These show how the outer shell 81 is constructed at these points.

  The outer shell 81 can be appropriately constructed as a reinforced concrete frame while appropriately cutting the segments of the small-diameter shield tunnel and communicating the internal spaces of the small-diameter shield tunnel with each other. In particular, in the present embodiment, the same figure (b) Since the small-diameter shield tunnels are arranged close to each other except for the transition section shown in Fig. 5, the earth pressure and the water pressure can be generally supported by them, and the gap between the small-diameter shield tunnels is also provided in the backfill region 71. Since the protrusions 72a, 72a, 72b, 72b are almost completely closed by the tip connection structure, it is possible to ensure water-stopping without performing ground improvement.

  On the other hand, only in the transition section shown in FIG. 5B, a gap is generated between the small-diameter shield tunnels 5-9 and 5-10 and the small-diameter shield tunnels 5-8 and 5-11. The ground improvement work such as freezing and chemical injection may be performed as appropriate.

  If the outer shell 81 is constructed, a widened portion 3 is formed by excavating the widened region 3 which is an inner region surrounded by the outer shell, and then the main tunnel 1 and the ramp tunnel 2 are branched into the widened portion. Build a junction.

  As described above, according to the construction method of the large cross-section tunnel according to the present embodiment, the cross-sectional position where the cross-sectional area of the widened area 3 is maximum is set as the reference cross-sectional position, and the small-diameter shield tunnel 4 is provided at the reference cross-sectional position. −1 to 4-18 and the small-diameter shield tunnels 5-1 to 5-18 are all arranged along the cross-sectional contour line 11 of the planned widening region 3, the cross-sectional area is smaller than the reference cross-sectional position. The above-mentioned small diameter shield tunnels are arranged along the cross-sectional contour line 11 as many as necessary so as to be almost equal to the arrangement interval at the reference cross-sectional position, and the rest are arranged behind the above-mentioned The receiving structure is constructed by extending the small-diameter shield tunnel, and the small-diameter shield tunnels 5-1 to 5-18 in a state of being separated from the cross-sectional outline 11 are Since it is made to enter the space 31 formed between the small-diameter shield tunnels 4-1 to 4-18 arranged along and is changed to the state along the cross-sectional outline 11, the planned widening region 3 The number along the cross-sectional contour line 11 of the small-diameter shield tunnel along the cross-sectional contour line 11 of the region to be widened 3 is increased or decreased so that the arrangement interval is substantially equal at any cross-sectional position. The arrangement density is almost the same at any cross-sectional position.

  For this reason, except for the transition section that attempts to move from the state separated from the cross-sectional contour 11 to the state along that, the small-diameter shield tunnels are brought close to each other with a slight gap, and the function of supporting earth pressure and water pressure is sufficiently exerted. Thus, as in the conventional case, the arrangement density of the roof shield varies depending on the cross-sectional position, and the gap between the roof shields becomes large at the rough cross-sectional position to support earth pressure and water pressure. The situation where ground improvement work becomes a major issue and freezing and chemical injection are indispensable can be avoided.

  Moreover, according to the construction method of the large-section tunnel according to the present embodiment, the gap between the small-diameter shield tunnels along the cross-sectional outline 11 is two pairs of protrusions in which the vicinity of the ends are connected, that is, the protrusion 72a. 72a and ridges 72b and 72b are securely closed.

  Therefore, if the transition section is excluded, it is possible to secure water-stopping only by backfilling, and even if ground improvement work is unnecessary or separately required, the improvement range and degree of improvement should be minimized. Is possible.

  Although not specifically mentioned in the present embodiment, the progress status of the main tunnel 1 and the ramp tunnel 2 is the same except that the main tunnel 1 needs to be dug up to at least that point when constructing the start areas 6a and 6b. It is possible to proceed with the construction work of each small-diameter shield tunnel independently, and each small-diameter shield tunnel may be constructed so as to surround the main tunnel 1 constructed in advance, or after each small-diameter shield tunnel is constructed, The main line tunnel 1 may enter the planned widening area 3 surrounded by.

  Further, in the present embodiment, the present invention is applied to the case where a widened portion as a large-section tunnel is formed in the main tunnel so as to provide a branching junction for joining the main tunnel 1 as a shield tunnel to the lamp tunnel 2. However, the present invention can be applied to all cases where a large-section tunnel is constructed using a plurality of small-diameter shield tunnels, and the cross-sectional size is constant at the cross-sectional position. Of course, the present invention can also be applied.

  For example, as shown in FIG. 11, a small-diameter shield tunnel consisting of a total of 36 is extended so as to surround the planned excavation area 93 of the large cross-section tunnel, and these are used as a receiving structure to provide the same outer shell 81 as the outer shell 81. A large section tunnel can be constructed by constructing a shell and then excavating a planned excavation area 93 which is an inner area surrounded by the outer shell.

  In each backfill area formed around these small-diameter shield tunnels, ridges 92a, 92a, 92b, and 92b similar to the ridges 72a, 72a, 72b, and 72b are provided, and outside the planned excavation area 93 The projecting ridges 92a and 92a facing each other and the projecting ridges 92b and 92b facing each other are connected to each other at their tips, but the other configurations and operations are the same as those of the above-described embodiment. The description is omitted.

1 Main tunnel (shield tunnel)
2 Lamp tunnel 3 Widened area 4-1 to 4-18 Small-diameter shield tunnel 5-1 to 5-18 Small-diameter shield tunnel 6a, 6b Start area 11 Cross-sectional outline 71 Back-fill area 72a, 72a, 72b, 72b
Ridge 81 outer shell 92a, 92a, 92b, 92b
Projection area 93 of large section tunnel

Claims (3)

A plurality of small-diameter shield tunnels are extended along the tunnel axis direction of the large-section tunnel so as to surround the construction area of the large-section tunnel, and the outer shell is formed using the plurality of small-diameter shield tunnels as a receiving structure. After constructing, in the construction method of the large section tunnel excavating the inner region surrounded by the outer shell,
Among the small-diameter shield tunnels, two small-diameter shield tunnels arranged adjacent to each other along the curved portion of the cross-sectional outline that forms the outer edge of the planned construction area, and adjacent to the backfill area of the small-diameter shield Two ridges projecting radially from two angular positions sandwiching a reference angular position at which the distance from the tunnel is the shortest are provided along the tunnel axial direction, and the center of curvature of the two angular positions is provided. The angle θ ₁ formed by the angle position closer to the reference angle position and the reference angle position is larger than the angle θ ₂ formed by the angle position far from the center of curvature and the reference angle position. A method for constructing a large-section tunnel, characterized in that two ridges provided on one side of the region are respectively connected to two ridges provided on the other side in the vicinity of their tips. A plurality of small-diameter shield tunnels are extended along the tunnel axis direction of the large-section tunnel so as to surround the construction area of the large-section tunnel, and the outer shell is formed using the plurality of small-diameter shield tunnels as a receiving structure. After constructing, in the construction method of the large section tunnel excavating the inner region surrounded by the outer shell,
Among the small-diameter shield tunnels, two small-diameter shield tunnels arranged adjacent to each other along the curved portion of the cross-sectional outline that forms the outer edge of the planned construction area, and adjacent to the backfill area of the small-diameter shield Two protrusions projecting radially from two angular positions sandwiching a reference angular position where the separation distance from the tunnel is the shortest are provided along the tunnel axial direction, and provided in the two backfill regions. One of the two back-filling regions so that each of the ridges on the side far from the center of curvature is larger in size or projecting length than each of the ridges on the side near the center of curvature. A method for constructing a large-section tunnel, characterized in that two ridges provided on the other side are respectively connected to two ridges provided on the other side in the vicinity of their tips. The wide section formed in the shield tunnel with the large cross-sectional tunnel, the widened planned area as the planned planned area, and the cross-sectional position where the cross-sectional area of the widened planned area is the maximum is the reference cross-sectional position, the reference cross-sectional position Then, the plurality of small-diameter shield tunnels are all disposed along the cross-sectional contour line of the region to be widened, and the cross-sectional area having a cross-sectional area smaller than the reference cross-sectional position is Of these, a plurality of small-diameter shields are arranged so that only the number necessary to be substantially equal to the arrangement interval at the reference cross-sectional position is arranged along the cross-sectional contour line, and the rest is arranged behind it. While constructing the receiving structure by extending a tunnel, in the section where the cross-sectional area of the planned widening area monotonously increases, The small diameter shield tunnel in a state separated from the contour line is moved into the space formed between the small diameter shield tunnels arranged along the cross sectional contour line, and the arrangement is changed to the state along the cross sectional contour line. The construction method of the large-section tunnel according to claim 1 or claim 2.