JP7217586B2 - Steel segment and shield tunnel - Google Patents

Description

The present invention relates to a steel segment and a shield tunnel having at least a part of the steel segment.

For example, when constructing a road tunnel in an urban area where soft ground is distributed, the open-cut method is generally applied, but the open-cut method has inherent problems such as noise and vibration during construction and traffic regulation. . In addition, since the space under the road in urban areas is congested with buried objects such as multiple subways and utility tunnels, the installation depth of new tunnels to be constructed tends to be deep. The deepening of the soil will directly lead to an increase in construction costs. Under such circumstances, the number of cases where the shield construction method is applied to the construction of road tunnels is increasing. By the way, in construction of this road tunnel, in the construction of a general road tunnel, for example, it is sufficient to construct a main tunnel with a circular cross section by excavating with one shield machine. On the other hand, the construction of the junction and junction of a road tunnel requires an extremely large-scale underground widening that encompasses each cross-section of the main tunnel and ramp tunnel. Therefore, it is necessary to take various measures for its construction.

Various proposals have been made for the construction method and tunnel structure of this large-section tunnel. For example, the structure of a large-section tunnel connecting two shield tunnels parallel to each other with a frame made of reinforced concrete, and a segment ring applied to this large-section tunnel have been proposed (see, for example, Patent Document 1). In the shield tunnel described in Patent Document 1, two shield tunnels are formed of steel segments. The rigidity of the reinforced concrete frame that connects the two shield tunnels formed by these steel segments is made greater than the rigidity of the shield tunnel formed by the steel segments, and the deformation of the segment ring due to the applied load causes the deformation of the reinforced concrete structure. It is made to be dominated by the deformation of the frame. In a shield tunnel formed of steel segments, which constitutes a large-section tunnel with such a configuration, the girder height of the steel segment at a portion where the bending moment generated at the joint of the steel segment is large is set higher than other portions. making it smaller.

JP 2004-204545 A

The large-section tunnel described in Patent Document 1 has a structure in which a shield tunnel formed of two steel segments is connected at its central position with a frame made of reinforced concrete with relatively high rigidity. In other words, under the design concept of positively bearing the load on the frame made of reinforced concrete, in the left and right shield tunnels, it is possible to relatively reduce the girder height of the steel segments where the bending moment is large. be done.
However, for example, in a large-section tunnel constructed such that a shield tunnel formed of two steel segments is connected at its center by a cutout made of a steel segment, all structural members of the tunnel are made of steel segments. Therefore, if each steel segment does not bear its own load, it will affect other steel segments. In other words, even if there is a portion where the bending moment becomes excessive during the construction process or in the state of completion of construction, it is necessary to deal with the excessive bending moment at that portion.

Here, an example in which all of the large-section tunnel is formed of steel segments will be described with reference to FIGS. In Fig. 1, a main tunnel ST1 formed of steel segments and a ramp tunnel ST2 similarly formed of steel segments are connected by a cut-out tunnel CT similarly formed of steel segments to form a large-section tunnel. It is a figure explaining the construction method to form. In the figure, first, the main tunnel ST1 is constructed by the shield construction method, and the ramp tunnel ST2 is also constructed by the shield construction method at the same time as or before or after the main tunnel ST1. It should be noted that, prior to this construction, suitable ground improvement construction is generally carried out around the construction area. Adjacent steel segments S are connected to each other through joint portions J formed by joint plates and segment joint bolts to form segment rings, and a plurality of segment rings are arranged in the axial direction of the tunnel and connected by ring joint bolts. As a result, the main line tunnel ST1 and the ramp tunnel ST2 are shielded. After that, for example, a pipe roof (not shown) is constructed so as to extend over the main tunnel ST1 and the ramp tunnel ST2, and this pipe roof is used as a shoring, and the pipe roof is constructed by hollowing the bottom and top of the pipe roof. A space is formed, and the segments S for the cut-open tunnel CT are connected to each other via joints J to bridge the main tunnel ST1 and the ramp tunnel ST2.

Next, construction is carried out to connect the main tunnel ST1, the ramp tunnel ST2, and the open tunnel CT. Specifically, as shown in FIG. 2, the outer skin plates of both the main tunnel ST1 and the ramp tunnel ST2 are removed, leaving the girders extending in the circumferential direction of both. Next, in order to remove this girder and complete the connection work, as shown in FIG. Beams SP1 to SP4 are installed, and girders of both the remaining main tunnel ST1 and ramp tunnel ST2 are removed.

By removing the girders, the main tunnel ST1, the ramp tunnel ST2, and the cut-away tunnel CT are completely communicated, forming a large-section tunnel. By the way, the removal of these girders deforms the large-section tunnel in the direction of crushing it vertically, but the earth pressure acting on the cut-open tunnel CT is transmitted to the main tunnel ST1 and the ramp tunnel ST2 via the reinforcing beams SP1 to SP4. , the large-section tunnel as a whole can withstand the applied earth pressure.

However, the axial forces N1 to N4 transmitted from the reinforcing beams SP1 to SP4 to the main tunnel ST1 and the ramp tunnel ST2 inevitably increase, and the excessive axial forces N1 to N4 in the main tunnel ST1 and the ramp tunnel ST2 Excessive bending moment is generated at the location pushed up by N4 and its surrounding area due to the excessive axial forces N1 to N4. For example, FIG. 2 also shows a bending moment distribution diagram generated at the axial forces N1 to N4. As shown in FIG. 2, an excessive bending moment M1 is generated in the vicinity of the portion pushed up by the axial force N1, and an excessive bending moment M2 is generated in the vicinity of the portion pushed up by the axial force N3. Therefore, the steel segments S forming the main tunnel ST1 and the ramp tunnel ST2 and the joints J connecting the steel segments S at the relevant locations need to have the rigidity to withstand such an excessive bending moment.

Increasing the girder height is effective in increasing the rigidity of steel segments. However, if the girder height is increased on the inner side of the tunnel, it often interferes with the construction gauge inside the tunnel. On the other hand, if the girder height is increased outside the tunnel, the amount of excavation of the ground increases, and the amount of excavated soil increases, resulting in an increase in the disposal cost, resulting in an increase in the construction cost. Therefore, instead of increasing the girder height, it is desired to increase the rigidity of the steel segments and increase the rigidity of the joints at the ends of the steel segments that connect the steel segments.

The present invention has been made in view of the above problems. It is intended to provide a shield tunnel.

In order to achieve the above object, one aspect of the steel segment according to the present invention is a plurality of girders extending in the circumferential direction of the tunnel and arranged side by side at intervals in the axial direction of the tunnel,
a flange extending in the circumferential direction and attached to the inner peripheral side and/or the outer peripheral side of the girder;
a joint plate attached to both ends of the girder and the flange;
The flange has a rigidity equivalent to that of the girder,
The joint plate is
provided with a plurality of segment joint bolt holes in the vicinity of the girder in a direction along the girder;
A plurality of segment joint bolt holes are provided in the vicinity of the flange in a direction along the flange and within a predetermined range from the beam.

According to this aspect, the rigidity of the steel segment is increased without increasing the height of the girder by attaching the flanges having a rigidity equivalent to that of the girder to the inner peripheral side and/or the outer peripheral side of the girder. be able to. Here, "equivalent rigidity" includes the same rigidity as the girder, the same degree of rigidity as the girder, or greater rigidity than the girder. In addition, since the joint plates at the ends of the girders and flanges are provided with segment joint bolt holes in the vicinity of these girders and flanges, the segment joint bolts are inserted through the segment joint bolt holes to connect the steel segments. It is possible to effectively transmit the axial force transmitted through the girders and flanges. Furthermore, since the segment joint bolt holes are also formed in the vicinity of the flange in the joint plate, the number of segment joint bolts can be increased, and the strength of the segment joint portion can be increased.

Here, "attached to the inner peripheral side and/or the outer peripheral side of the girder" means that the flange is attached only to the inner peripheral side of the girder (inner hollow side of the tunnel), the outer peripheral side of the girder ( It is meant to include all forms that are attached only to the ground side of the tunnel, and forms that are attached to both sides. In a steel segment having a flange on the inner peripheral side of the girder, a so-called positive bending moment acts on the joint portion of the steel segment, and an external force acting as an inward tension acts. In addition, in the steel segment having the flange on the outer peripheral side of the girder, a so-called negative bending moment acts on the joint portion of the steel segment, and an external force acting as an outward tension acts. Furthermore, in steel segments with flanges on both the inner and outer circumference sides of the girder, positive and negative bending moments act on the joints of the steel segments so that the inner tension and It acts so that the external force of the external pull fluctuates. Such fluctuations in the external force include, for example, fluctuations in the acting soil water pressure due to vertical fluctuations in the groundwater level.

The flanges may be in the form of connecting a plurality of girders together, or may be in the form of being attached to the girders so as to protrude by a predetermined length to the side of the girders without connecting the girders together.
The joint plate bolt holes are formed in the vicinity of the girders in the direction along the girders, so that the axial force from the segment joint bolts inserted through the segment joint bolt holes is effectively transmitted to the girders. be able to. Furthermore, by having a plurality of segment joint bolt holes in the vicinity of the flange in the direction along the flange and within a predetermined range from the girder, the axial force from the segment joint bolts inserted through the segment joint bolt holes is provided. can be effectively transmitted to the flange. In addition, the steel segment of this aspect may have a two-girder type steel shell structure having two girders, or a three or more main girder type steel shell structure having three or more girders. You may have

Another aspect of the steel segment according to the present invention is characterized in that the flange connects the plurality of girders only on the outer peripheral side.
According to this aspect, a steel segment having high rigidity can be formed by connecting the girders together with flanges having a rigidity equal to or higher than that of the girders. And skin plates can be eliminated by connecting the girders with the flanges on the outer peripheral side of the girders.

Another aspect of the steel segment according to the present invention is that the flange connects the plurality of girders only on the inner peripheral side, and a skin plate is attached to the outer peripheral side of the plurality of girders. characterized by
According to this aspect, a steel segment having high rigidity can be formed by connecting the girders together with flanges having a rigidity equal to or higher than that of the girders.

Another aspect of the steel segment according to the present invention is characterized in that the flange connects the plurality of girders together on both the outer peripheral side and the inner peripheral side.
According to this aspect, the flanges on both the inner and outer peripheral sides of the girders connect the girders together, thereby making it possible to form steel segments with extremely high rigidity while eliminating the need for skin plates.

In another aspect of the steel segment according to the present invention, the flange does not connect the plurality of girders, and a skin plate is attached to the outer peripheral side of the plurality of girders.
According to this aspect, since the flange does not have a width that connects the girders, it is possible to form a steel segment with high rigidity while reducing the material cost of the flange.

In another aspect of the steel segment according to the present invention, the predetermined range is a range from the girder to 16 times or less the thickness of the flange.
According to this aspect, the segment joint bolt hole can be set within the effective width of the flange, that is, within a range in which the flange can be considered as the main cross section of the structural member together with the girder, and the segment joint bolt can be inserted. According to the Specifications for Highway Bridges and Commentaries for Steel Bridges (Japan Road Association), the plate thickness of the tension flange free protrusion must be 1/16 or more of the free protrusion width regardless of the steel grade. there is In other words, the effective width of the tension flange can be defined as 16 times or less of the plate thickness. If the flanges connect the girders together and the width of the flanges is too wide, the full width of the flanges cannot be an effective range for the main cross section of the structural member. According to the above road bridge specifications, the range from both girders to 16 times the thickness of the flange can be made the effective width. Open a bolt hole.

Moreover, the steel segment according to the present invention may have longitudinal ribs connecting said plurality of girders. Longitudinal ribs can increase the stiffness of the steel segments. It is preferable that a plurality of vertical ribs be arranged at predetermined intervals in the circumferential direction.

Also, the steel segment according to the present invention may have hardened concrete between said plurality of girders. A composite segment is formed by arranging a hardened concrete body in the steel shell of a box-shaped steel segment formed by steel girders and flanges and integrating the steel girders and flanges with the concrete. forming a stiffer steel segment.

Further, in one aspect of the shield tunnel according to the present invention, a plurality of the steel segments are arranged in at least the necessary regions in the circumferential direction, and are connected to the corresponding segment joint bolt holes of the two opposing joint plates. A segment ring is formed by attaching the segment joint bolt,
A plurality of the segment rings are arranged in at least a required area in the axial direction, and the ring joint bolts are attached to the corresponding ring joint bolt holes of the facing girders. and

According to this aspect, the segment ring at least partly provided with a steel segment with increased rigidity (the joint portion is also increased in rigidity) without increasing the height of the girder extends at least in the axial direction of the tunnel. By arranging them in the necessary areas, it is possible to provide a shield tunnel without increasing construction costs while effectively arranging high-rigidity steel segments, for example, in areas where the bending moment is prominent. Here, ``the plurality of steel segments are disposed in at least the necessary regions in the circumferential direction'' means, for example, in FIG. It means a segmented ring with embedded steel segments. A segment ring made of the steel segment of the present invention is arranged in a region where the bending moment is particularly prominent, and a normal steel segment (a box-shaped steel segment composed of a skin plate and a girder) is arranged in other regions. Arranging to form a segmented ring is reasonable and economical. In addition, "the plurality of segmented rings are arranged in at least the required region in the axial direction" means that the segmented ring incorporating the steel segment of the present invention is arranged in the region in which the bending moment is prominent in the axial direction. means to set Since the girder height of the steel segments does not increase even in areas where the bending moment is prominent, there is no problem of the steel segments interfering with the construction gauge. No increase problem.

ADVANTAGE OF THE INVENTION According to the steel segment of this invention, the steel segment with which the rigidity of the whole including a joint part was improved can be provided, without raising girder height. Further, according to the shield tunnel of the present invention, the segment ring having at least a part of the steel segment of the present invention is connected in the axial direction of the tunnel. An economical shield tunnel can be provided while resisting an outstanding external force.

FIG. 4 is a cross-sectional view illustrating a construction method for forming a large-section tunnel by connecting a main tunnel and a ramp tunnel formed of steel segments with a cut-out tunnel formed of steel segments. FIG. 1 is a cross-sectional view illustrating the method of constructing a large-section tunnel following FIG. 1, showing an example of the bending moment distribution generated in the main tunnel and the ramp tunnel due to the axial force acting from the installed reinforcing beams. 1 is a perspective view showing both an assembled state and a completed state of steel segments according to the first embodiment; FIG. It is a figure explaining the design method of the joint plate of the steel shell structure which has two girders. FIG. 4 is a perspective view of a steel segment according to a second embodiment; FIG. 11 is a perspective view of a steel segment according to a third embodiment; FIG. 11 is a perspective view of a steel segment according to a fourth embodiment; FIG. 11 is a perspective view of a steel segment according to a fifth embodiment; FIG. 11 is a perspective view of a steel segment according to a sixth embodiment; FIG. 11 is a perspective view of a steel segment according to a seventh embodiment; FIG. 10 is a diagram for explaining a design method of a steel-shell joint plate having three or more girders when it is difficult to apply the corbel theory. FIG. 4 is a cross-sectional view for explaining a large-section tunnel having a shield tunnel according to the embodiment;

Each embodiment will be described below with reference to the accompanying drawings. In addition, in this specification and the drawings, substantially the same components are denoted by the same reference numerals, thereby omitting redundant explanations.

[Steel segment according to the first embodiment]
First, the steel segment according to the first embodiment will be described. FIG. 3 is a perspective view showing both the assembled state and the completed state of the steel segment according to the first embodiment. As shown in the upper diagram of FIG. 3, the steel segment 10 consists of two girders 1 with a predetermined curvature extending in the circumferential direction, and the outer peripheral side of the two girders 1 (the outer side of the formed segment ring ( It has a flange 2A extending in the circumferential direction by connecting the girders 1 on the ground side), and joint plates 3 attached to both ends of the girder 1 and the flange 2A. The steel segment 10 in which the flange 2A is arranged on the outer peripheral side of the girder 1 is, for example, a steel segment arranged at a location where the negative bending moment M1 is dominant. In practice, the steel segment 10 is arranged at a location where the bending compression side becomes severe due to the axial force and bending moment.

The girder 1 has a plurality of ring joint bolt holes 1a on its side surface. A plurality of longitudinal ribs 4 are arranged between the two girders 1 , and the plurality of longitudinal ribs 4 further increase the rigidity of the box-shaped steel segment 10 . The girder 1 and the flange 2A, the girder 1, the flange 2A and the longitudinal rib 4 are all welded by fillet welding, and the girder 1, the flange 2A and the joint plate 3 are welded by partial penetration welding. A steel segment 10 indicated by is formed. As shown, the steel segment 10 has a flange 2A connecting the two girders 1 on the outer peripheral side, thus eliminating the need for the skin plate of a normal steel segment.

The thickness of the girder 1 is t1, and the thickness of the flange 2A is t2. For example, t1 and t2 have thicknesses in the range of 30 to 70 mm. is set to For example, there are a form in which the rigidity of the flange 2A is set to be the same as the rigidity of the girder 1, a form in which the rigidity is set to be approximately the same, and a form in which the rigidity is set to be greater than the rigidity of the girder 1. Incidentally, the thickness of a commonly used skin plate is about 3 to 6 mm, and the thickness of the flange 2A is about 10 times thicker than the skin plate. . However, the range in which the flange 2A and the girder 1 can be considered as the main cross section of the structural member is not limited to the full width range of the flange 2A. Therefore, first, of the width of the flange 2A, the width that can be expected as the main cross section of the structural member together with the girder 1 (this is defined as the effective width) is set.

According to the Specifications for Highway Bridges and Commentaries for Steel Bridges (Japan Road Association), the plate thickness of the tension flange free protrusion must be 1/16 or more of the free protrusion width regardless of the steel grade. there is In other words, the effective width of the tension flange can be defined as a range of 16 times the thickness t2 of the flange 2 (16t2) or less. For example, if the full width of the flange 2 is equal to or less than the effective width, the full width of the flange 2 can be regarded as the effective width. On the other hand, if the full width of the flange 2 is wider than the effective width, the range from the girder 1 to 16 times the thickness t2 of the flange 2 can be considered as the effective width, and the effective width range of the flange 2 can be used as the main cross section for structural calculation. can. In the steel segment 10 shown in FIG. 3, the full width S of the flange 2A is 16t2 or less, which is the effective width. Therefore, the full width S of the flange 2A can be the effective width. Further, the steel segment 10 shown in FIG. 3 has a rectangular cross-sectional shape that is nearly square in the circumferential direction. This is because the generated negative bending moment M1 is extremely large and corresponds to the field situation where the width of the flange 2A cannot be increased.

Next, the opening positions of the segment joint bolt holes 3a and 3b opened in the joint plate 3 will be described. A plurality of segment joint bolt holes 3 a are provided in the vicinity of the girder 1 in the direction along the girder 1 . In the illustrated example, in the vicinity of each girder 1, four segment joint bolt holes 3a are opened on one line along the girder 1. As shown in FIG. In addition to the configuration in which a plurality of joint segment bolt holes 3a are formed in one row as in the illustrated example, for example, a plurality of joint segment bolt holes 3a may be formed in two rows, and one line may be formed. A plurality of segment joint bolt holes 3a may be opened in a zigzag arrangement on the left and right sides of the center line.

On the other hand, a plurality of segment joint bolt holes 3b are provided in the vicinity of the flange 2A in the direction along the flange 2A and are opened within the effective width of the flange 2A. In the illustrated example, since the full width of the flange 2A is the effective width, a plurality of segment joint bolt holes 3b are opened in the full width of the flange 2A. Although the bolt holes at the intersection of each row of the segment joint bolt holes 3a and 3b are common, in this specification, the segment joint bolt holes located at the intersection are included in the segment joint bolt holes 3a along the girder 1. to decide.

In the joint plate 3, the segment joint bolt hole 3a is provided in the vicinity of the girder 1 (separation s1), and the segment joint bolt hole 3b is provided in the vicinity of the flange 2A (separation s2). There is First, if the segment joint bolt holes 3a and 3b are formed in the joint plate 3 at a position distant from the girder 1 and the flange 2A (for example, near the center of the joint plate 3), the segment joint bolt holes 3a, 3b The distance until the axial force from the segment joint bolt inserted through 3b is transmitted to the girder 1 and the flange 2A becomes longer. In such a case, the joint plates 3 of the two steel segments 10 connected to each other by the segment joint bolts are deformed so as to open on both sides centering on the segment joint bolts. , the axial force from the segment joint bolt cannot be sufficiently transmitted to the girder 1 and the flange 2A through the joint plate 3. Therefore, in the steel segments according to all the following embodiments, including the first embodiment, the position where the axial force is sufficiently transmitted from the segment joint bolt to the girder 1 and the flange 2 is set to the vicinity of the girder 1 and the flange 2. In the joint plate 3 , the segment joint bolt holes 3 b formed near the flange 2 are formed near the flange 2 within the effective width range of the flange 2 .

Next, a method for designing the plate thickness of the joint plate 3 will be described. FIG. 4 is a diagram for explaining a design method of a steel-shell joint plate having two girders. The method of designing a joint plate of a steel shell structure having two girders is based on corbel theory so as not to generate a bending moment in the joint plate. Therefore, at the welding points of the girder 1 and the joint plate 3 as well, the welding points are checked against the reaction force based on the corbel theory, and the welding points are designed.

As shown in FIG. 4, when the plate thickness (thickness) of the joint plate 3 is t3 and the distance from the girder 1 to the segment joint bolt hole 3a of the joint plate 3 is s1, t3/s1≧1 is satisfied. Moreover, a design based on the corbel theory that does not generate a bending moment in the joint plate 3 becomes possible. More specifically, since the reaction force distribution based on the axial force P from the segment joint bolt B is triangular, the position of the separation s1 is the position of the center of gravity of the triangle (in the illustrated example, the position of the girder 1 within the width of the triangle). The distance from the position of 1/3 from the side) to the girder 1 is s1. Thus, the thickness t3 of the joint plate 3 is set by the design method based on the corbel theory. In addition, since the distance s1 from the girder 1 to the joint segment bolt hole 3a is also a variable in the above calculation formula, the distance s1 from the girder 1 to the joint segment bolt hole 3a depends on the thickness t3 of the joint plate 3. The distance s1 (near position described above) can also be set in various ways. This also applies to the setting of the distance s2 from the flange 2 to the segment joint bolt hole 3b (near position described above). From this, it can be said that it is rational to set the distances s1 and s2 to the same value, for example, when the thickness t3 of the joint plate 3 is set by the above calculation formula.

Using a plurality of steel segments 10 shown in FIG. 3, segment joint bolts are inserted through the corresponding segment joint bolt holes 3a and 3b of the abutting joint plate 3 and tightened to form a segment ring. It is desirable that this segment ring be arranged in a region of the shield tunnel where the negative bending moment M1 is particularly prominent. The steel segment 3 shown in FIG. 3 is formed by connecting the girders 1 to each other with a flange 2A having a rigidity equal to or greater than that of the girders 1, thereby increasing the rigidity. The height of girder 1 is not adjusted higher. Therefore, in the segment ring forming the shield tunnel, by arranging the steel segments 10 at least in the region where the bending moment is dominant, the problem of the steel segments 10 interfering with the construction gauge in the shield tunnel cannot occur. Also, the problem of increasing construction costs due to an increase in the amount of excavated soil and the amount of discharged soil cannot occur. Furthermore, in the joint plate 3, since the segment joint bolt holes 3b are also opened in the vicinity of the flange 2, it is possible to increase the number of segment joint bolts that connect the steel segments 10 in the circumferential direction. Axial force from the segment joint bolt can be smoothly transmitted to both the girder 1 and the flange 2 from the segment joint bolt. Therefore, the strength of the joint portion of the steel segment 10 can be particularly increased, and a joint portion that can sufficiently resist the excessive bending moment M1 can be formed.

[Steel segment according to the second embodiment]
Next, a steel segment according to the second embodiment will be described. FIG. 5 is a perspective view of a steel segment according to a second embodiment; As shown in FIG. 5, the steel segment 20 includes two girders 1 extending in the circumferential direction and having a predetermined curvature, and the inner peripheral sides of the two girders 1 (inner hollow side of the formed segment ring). It has flanges 2B that connect the girders 1 together and extend in the circumferential direction, and joint plates 3 that are attached to both ends of the girders 1 and the flanges 2B. The steel segment 20 with the flange 2B arranged on the inner peripheral side of the girder 1 is a steel segment arranged at a location where the positive bending moment M2 is dominant. In this way, the steel segment 20 is changed to the inner peripheral side of the girder 1, so that the steel segment 20 is a segment joint bolt that is opened in the vicinity of the flange 2B in the joint plate 3. The opening position of the hole 3b is also set at a distance s2 from the inner segment 2B.

Since the steel segment 20 does not have a flange on the outer peripheral side of the segment ring on the ground side, a skin plate 5 connecting the two girders 1 is arranged on the outer peripheral side of the two girders 1, It is connected to the girder 1 by fillet welding or the like.

Using a plurality of steel segments 20 shown in FIG. 5, segment joint bolts are inserted through the corresponding segment joint bolt holes 3a and 3b of the abutting joint plate 3 and tightened to form a segment ring. A plurality of segment rings are connected in the axial direction of the tunnel via ring joint bolts to form a shield tunnel, but the regions in which a predominant positive bending moment is generated in each segment ring in the axial direction of the tunnel are different. Therefore, the steel segments 20 are preferably arranged in suitable regions for each segment ring.

[Steel segment according to the third embodiment]
Next, a steel segment according to the third embodiment will be described. FIG. 6 is a perspective view of a steel segment according to a third embodiment; As shown in FIG. 6, the steel segment 30 includes two girders 1 having a predetermined curvature extending in the circumferential direction, and connecting the girders 1 on the outer and inner peripheral sides of the two girders 1. It has flanges 2A and 2B extending in the circumferential direction and joint plates 3 attached to both ends of the girder 1 and the flanges 2A and 2B.

Two girders 1 are connected by a flange 2A on the outer peripheral side and a flange 2B on the inner peripheral side, and a joint plate 3 is arranged at both ends, so that a steel segment 30 of a completely closed hexahedral structure is formed. is formed, resulting in a much stiffer steel segment. In addition, since all the end surfaces of the joint plate 3 are connected to the girder 1 and the flanges 2A and 2B, a stronger joint can be formed.

In addition, since the flange 2A is arranged on the outer peripheral side of the girder 1 and the flange 2B is arranged on the inner peripheral side of the girder 1, the predominant bending moment is the positive bending moment M2 and the negative bending moment M1. , it is desirable to locate the steel segments 30 in those regions within the segment ring where such varying dominant bending moments occur.

[Steel segment according to the fourth embodiment]
Next, a steel segment according to the fourth embodiment will be described. FIG. 7 is a perspective view of a steel segment according to a fourth embodiment; As shown in FIG. 7, the steel segment 40 includes two girders 1 having a predetermined curvature extending in the circumferential direction, and connecting the girders 1 on the outer peripheral side of the two girders 1 and extending in the circumferential direction. and a joint plate 3 attached to both ends of the girder 1 and the flange 2C. As can be seen from a comparison with the steel segment 10 shown in FIG. 3, the flange 2C is wider than the flange 2A, and the overall width of the flange 2C is twice the effective width (16t2) from the left and right girders 1. wider than

Thus, when the flange 2C has a width wider than twice the effective width, the range of the flange 2C that can be expected in the main cross section as a structural member is within the range of the left and right effective widths 16t2. Become. Therefore, in the joint plate 3, a segment joint bolt hole 3b is opened in a region corresponding to the range of the left and right effective widths 16t2 and in the vicinity of the flange 2C. Although illustration is omitted, in the case of a steel segment arranged in a region where positive bending moment is dominant, a member corresponding to the flange 2C shown in the figure is arranged on the inner peripheral side of the girder 1, A skin plate connecting two girders 1 is arranged on the outer peripheral side of 1 .

[Steel segment according to the fifth embodiment]
Next, a steel segment according to the fifth embodiment will be described. FIG. 8 is a perspective view of a steel segment according to a fifth embodiment; As shown in FIG. 8, the steel segment 50 includes two girders 1 having a predetermined curvature extending in the circumferential direction, and the two girders 1 on the outer peripheral side and the inner peripheral side of the two girders 1 without connecting the girders 1 to each other. flanges 2D and 2E extending in the circumferential direction, skin plates 5 disposed on the outer peripheral side of the left and right flanges 2D on the outer peripheral side, joint plates attached to both ends of the girder 1 and the flanges 2D and 2E 3. The steel segment 50 differs from the other steel segments 10 to 40 described so far in that the flanges 2D, 2E do not connect the two girders 1 together.

The flanges 2D and 2E have an effective width of 16t2 at most, and even in the cross-shaped joint plate 3 in plan view, the segment joint bolt holes 3b are formed in the vicinity of the flanges 2D and 2E and within the effective width of 16t2. In the vicinity of the girder 1, there are segment joint bolt holes 3a. In addition, for example, each width of the flanges 2D and 2E can be set such that the double width of each of the flanges 2D and 2E is 50% or more of the width (separation) between the two girders 1.

For example, assuming a case where two steel segments 50 are connected to each other at the sides of the girder 1 (connected by ring joint bolts), at the joint of both steel segments 50, the two girder 1 are The flanges 2E and 2D are juxtaposed and form an H-shaped cross section in which the flanges 2E and 2D protrude to the left and right at the upper and lower positions. Both flanges 2E, 2D allow the steel segment 50 to accommodate the case where the dominant bending moment fluctuates between the positive bending moment M2 and the negative bending moment M1.

If the width of the steel segment is relatively wide, it is not necessary to connect the two girders 1 with flanges. By adopting a configuration that protrudes laterally, it is possible to form a highly rigid steel segment without increasing the height of the girder while reducing the material cost by making the flange with a large thickness compact. Although illustration is omitted, a configuration having only the flange 2D on the outer peripheral side or a configuration having only the flange 2E on the inner peripheral side may be used. In any of these configurations, a skin plate is installed on the outer peripheral side. requires.

[Steel segment according to the sixth embodiment]
Next, a steel segment according to the sixth embodiment will be described. FIG. 9 is a perspective view of a steel segment according to a sixth embodiment; As shown in FIG. 9, the steel segment 60 includes two girders 1 with a predetermined curvature extending in the circumferential direction and two girders 1 on the outer peripheral side of the two girders 1, similar to the steel segment 40 shown in FIG. It has flanges 2C that connect the girders 1 together and extend in the circumferential direction, and joint plates 3 that are attached to both ends of the girders 1 and the flanges 2C. Further, the steel segment 60 further includes a hardened concrete body 6 inside the box-shaped steel shell, and a composite structure in which the girder 1, the flange 2C, the joint plate 3, and the longitudinal rib 4 are integrated with the concrete. forming a segment.

In this manner, the hardened concrete body 6 is arranged in the box-shaped steel shell, and the steel shell and the concrete are integrated to form a steel segment 60 with even higher rigidity. Furthermore, since the joint plate 3 is integrated with the concrete in addition to the girder 1, a joint portion with even higher strength is formed. Although illustration is omitted, the other steel segments 10, 20, 30, 50 described so far may be steel segments in which a concrete hardened body is disposed in the steel shell. As with the steel segment 60, the steel segment also becomes a steel segment with higher rigidity, and the strength of the joint portion is further increased.

[Steel segment according to the seventh embodiment]
Next, a steel segment according to the seventh embodiment will be described. FIG. 10 is a perspective view of a steel segment according to a seventh embodiment; As shown in FIG. 10, the steel segment 70 includes three girders 1 on the left and right and in the center with a predetermined curvature extending in the circumferential direction, and a central girder on the outer peripheral side of the left and right girders 1. a circumferentially extending flange 2D having a width no greater than 1; a joint plate 3 attached to the girder 1 and to the ends of the flange 2D; plate 5; For example, a steel segment 70 that is wider than the steel segment 40 shown in FIG. 7 and therefore has three girders 1 to increase the stiffness of the steel segment 70 . Note that the number of digits 1 may be four or more.

In order to counteract the prevailing negative bending moment M1, the steel segments 70 of the illustrated example do not extend to the central girder 1 on the outer peripheral side of the left and right girder 1, and flanges 2D with an effective width of 16t2 are provided. have. Although not shown, steel segments may be formed by flanges connecting the left and right girders 1 and the central girders 1, respectively. It may be a segment, or a steel segment having flanges on the inner and outer peripheral sides of the left and right girders 1 . Alternatively, a box-shaped steel shell forming the steel segment 70 may have a concrete hardened body inside.

Next, a method for designing the plate thickness of the joint plate 3 will be described. Even in the design of a joint plate with a steel shell structure having three (or more) girders, if the design method applying the corbel theory shown in Fig. 4 can be applied, the design method applying the corbel theory can be used to design the joint plate. design. On the other hand, if it is difficult to apply the corbel theory, there is a design method that allows the occurrence of a bending moment in the joint plate and then designs the plate thickness based on that bending moment. Outline. FIG. 11 is a diagram for explaining a design method for a joint plate with a steel shell structure having three (or more) girders on the premise that it is difficult to apply the corbel theory. In the method of designing a joint plate of a steel shell structure having three girders, a bending moment is allowed to occur in the joint plate, and the plate thickness is set according to the bending moment. Therefore, the welding points of the girder 1 and the joint plate 3 are also checked against the bending moment to design the welding points.

As shown in Fig. 11, in a steel shell structure having three or more girders, the bending moment Mt at the ends of a beam with both ends fixed is calculated from the formula Mt = ΣP x S(LS)/L. , the calculated bending moment Mt is divided by the bending rigidity EI of the joint plate 3 (E is the modulus of elasticity, I is the geometrical moment of inertia, and I is proportional to the cube of the thickness) to calculate the bending stress. The thickness of the joint plate 3 is set so that the calculated bending stress is within a predetermined allowable stress value.

According to the illustrated steel segment 70, even if the width between the left and right girders 1 is widened, there is another girder 1 in the center, and the left and right girders 1 have flanges 2D with an effective width of 16t2. By having, it is possible to increase the rigidity without increasing the height of the girder.

[Shield tunnel according to the embodiment]
Next, a shield tunnel according to an embodiment will be described. FIG. 12 is a cross-sectional view illustrating a large-section tunnel having a shield tunnel according to the embodiment. The large cross-section tunnel 300 shown in FIG. 12 has a main tunnel 100 made of a shield tunnel, a ramp tunnel 200 made of a shield tunnel, and a cut tunnel CT connecting the main tunnel 100 and the ramp tunnel 200 .

As in FIG. 2, in the process of constructing the large-section tunnel 300, the skin plates and girders of the main tunnel 100 and the ramp tunnel 200 are removed from locations that obstruct communication with the cut-open tunnel CT. Therefore, similar to FIG. 2, the skin plates and girders are removed after installing the reinforcing beams SP1 to SP4 that relieve the load from the cut-out tunnel CT to the main tunnel 100 and the ramp tunnel 200. In particular, due to the removal of the girders, the load from the cut-open tunnel CT acts on the main tunnel 100 and the ramp tunnel 200 as an excessive axial force via the reinforcing beams SP1 to SP4. An excessive bending moment will be generated at

Therefore, in the illustrated large-section tunnel 300, the steel segments 10 according to the first embodiment, for example, are applied to portions where excessive bending moments are generated in the main tunnel 100 and the ramp tunnel 200. FIG. That is, in a shield machine, a segment ring is formed from a conventional general steel segment S (a steel segment having no flange) and a steel segment 10 according to the first embodiment in an erector. Installed. The main tunnel 100 and the ramp tunnel 200 are formed by connecting a large number of segment rings in the tunnel axial direction with inter-ring bolts. The bending moment distribution map changes depending on the position of the steel segment 10 is applied.

According to the illustrated large-section tunnel 300, the steel segment 10 is applied to the region corresponding to the excessive bending moment, so that the steel segment 10 is not a segment that increases the rigidity by increasing the girder height. , the problem of interfering with the construction gauge in the large-section tunnel 300 cannot occur. In addition, when the girder height is increased, problems such as an increase in the amount of excavated and discharged soil and an increase in construction costs due to this, which occur when the girder height is increased to the outside (ground side), cannot occur. . Furthermore, in the joint plates 3 forming the steel segments 10, the segment joint bolt holes 3b are also formed in the vicinity of the flanges 2, so that the number of segment joint bolts that connect the segments can be increased. It is possible to increase the strength of the part. Although illustration is omitted, the steel segments 20 to 70 according to other embodiments may be applied to suitable locations of the main tunnel 100 and the ramp tunnel 200 that form the large-section tunnel 300. Two or more of the steel segments 10-70 may be applied in combination.

In the steel segment according to the embodiment shown in FIG. 3, the steel segment (comparative example) without segment joint bolt holes near the flange, Both allowable bending moments of (Example) were determined and compared. The steel segment of the comparative example has cross-sectional dimensions of a girder height of 700 mm and a girder width of 800 mm. (total of 8 segment joint bolts). On the other hand, the steel segment of the example has cross-sectional dimensions of a girder height of 700 mm and a girder width of 800 mm. and two segment joint bolts are arranged at a pitch of 164 mm on a line along the flange 85 mm from the inner surface of the flange (10 segment joint bolts in total).

As a result of verification, the allowable bending moment of the comparative example was -1750 kNm (negative bending moment), and the allowable bending moment of the example was -2700 kNm. Assuming that the allowable bending moment of the comparative example is 100%, the allowable bending moment of the example is 154%, and it has been confirmed that the allowable bending moment is increased by 54% compared to the comparative example.

It should be noted that other embodiments may be possible in which other components are combined with the configurations described in the above embodiments, and the present invention is not limited to the configurations shown here. Regarding this point, it is possible to change without departing from the gist of the present invention, and it can be determined appropriately according to the application form.

10, 20, 30, 40: Steel segments 50, 60, 70: Steel segment 1: Girder 1a: Ring joint bolt holes 2, 2A, 2B, 2C: Flanges 2D, 2E: Flanges 3: Joint plates 3a, 3b : Segment joint bolt hole 4 : Vertical rib 5 : Skin plate 6 : Concrete hardened body 100 : Shield tunnel (main line tunnel)
200: Shield Tunnel (Ramp Tunnel)
300: Large section tunnel S: Steel segment J: Joint part ST1: Shield tunnel (main line tunnel)
ST2: Shield Tunnel (Ramp Tunnel)
CT: Cut tunnel SP1, SP2: Reinforcement beam SP3, SP4: Reinforcement beam

Claims (6)

a plurality of girders extending in the circumferential direction of the tunnel and arranged side by side at intervals in the axial direction of the tunnel;
a flange extending in the circumferential direction and attached to the inner peripheral side and/or the outer peripheral side of the girder;
a joint plate attached to both ends of the girder and the flange;
The flange has a rigidity equivalent to that of the girder,
The joint plate is
provided with a plurality of segment joint bolt holes in the vicinity of the girder in a direction along the girder;
A plurality of segment joint bolt holes are provided in the vicinity of the flange in a direction along the flange and within a predetermined range from the girder,
The predetermined range is a range of 16 times or less the thickness of the flange from the girder ,
The plate thickness of the joint plate is between the inner surface of the girder and the centroid of the reaction force distribution acting on the joint plate from the segment joint bolt inserted through the segment joint bolt hole closest to the girder. A steel segment characterized in that the positions of the segment connection bolt hole and the segment connection bolt are set so that the distance is greater than or equal to . 2. A steel segment according to claim 1, wherein said flange connects said plurality of girders only on said peripheral side. 2. The steel segment according to claim 1, characterized in that said flanges connect said plurality of girders only on said inner peripheral sides, and skin plates are attached to said plurality of girders on their outer peripheral sides. . 2. A steel segment according to claim 1, wherein said flange connects said plurality of girders on both said outer circumference and said inner circumference. 2. A steel segment according to claim 1, wherein said flanges do not connect said plurality of girders, and skin plates are attached to said outer peripheral sides of said plurality of girders. A plurality of steel segments according to any one of claims 1 to 5 are arranged in at least a required region in the circumferential direction, and are arranged in the corresponding segment joint bolt holes of the two opposing joint plates. A segment ring is formed by attaching the segment joint bolt,
A plurality of segment rings are arranged in at least a required region in the axial direction, and ring joint bolts are attached to corresponding ring joint bolt holes of the facing girders. , shield tunnel.

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