JP6892955B1 - Easy-to-cut segment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy-to-cut segment having excellent machinability, load resistance and water-stopping property at a manufacturing cost as low as possible. SOLUTION: In an easy-to-cut segment 10, a barbed material formed of fiber reinforced plastic is embedded in concrete which is a base material, and steel fibers 30 are dispersed inside the base material. The concrete design standard strength is in the range of 42N / mm2 to 60N / mm2, the mixing ratio of steel fiber 30 is in the range of 0.3% by volume to 1.0% by volume, and the elastic modulus of fiber reinforced plastic is 30kN / mm2. It is in the range of 120 kN / mm2. [Selection diagram] Fig. 1

Description

The present invention relates to an easy-to-cut segment.

For example, after constructing the main tunnel and the ramp tunnel separately by the shield method, the underground widening part is constructed by cutting and expanding a part of the main tunnel and the ramp tunnel by non-cutting construction, and both tunnels are constructed in the area. Construction will be carried out to connect at the medium widening part. The main tunnel is, for example, a deep underground tunnel with a depth of 40 m or more underground, and a ramp tunnel accessed from an interchange junction on the ground extends to this underground tunnel, and both tunnels can be connected at an underground widening portion.
In the construction of this underground widening part, the main tunnel and the ramp tunnel, which are located next to each other at intervals, are surrounded by, for example, a cylindrical underground structure with a relatively large cross section, and then the inside of the underground structure is excavated. However, the underground widening part will be constructed by removing the communication part of both tunnels. When constructing the underground structure, water stop treatment is performed on the construction area of the underground structure as necessary.
As a method for constructing the above-mentioned large-section underground structure, there is a method in which a plurality of small-section tunnels are arranged side by side in a tubular shape to construct an outer shell (large-section lining body). More specifically, after constructing a plurality of leading small section tunnels in a ring shape at intervals, a plurality of trailing small section tunnels are constructed in a ring shape while cutting a part of the leading small section tunnels at the interval. A part of the trailing small section tunnel will be removed to communicate with the leading small section tunnel. That is, the leading small-section tunnel and the trailing small-section tunnel are alternately connected to form a large-section lining body, and the respective small-section tunnels are communicated with each other. Then, an underground structure, which is a large cross-section lining body, is constructed by arranging a main bar extending in the circumferential direction with respect to the annular communication portion having a large cross section and constructing the filled concrete.
By the way, both the leading small-section tunnel and the trailing small-section tunnel forming the above-mentioned large-section lining body are sequentially constructed by the shield method. The leading small section tunnel in which a part thereof is cut in the trailing small section tunnel may be constructed in, for example, an RC (Reinforced Concrete) segment, and the trailing small section tunnel may be constructed in, for example, a steel segment. Among them, it is desirable that an easy-to-cut segment that can be cut by a shield excavator for construction of a trailing small-section tunnel is applied to the segment that forms the leading small-section tunnel.

Here, in Patent Document 1, in a cutting segment using concrete as a base material and a resin reinforced material as a reinforced material, the concrete contains an aggregate, and the aggregate contains a coarse aggregate and a fine aggregate, and is coarse. A cutting segment has been proposed in which lightweight aggregate or blast furnace slag aggregate is used for the aggregate and the reinforced material consists of glass fiber rods with continuous threads. In this cutting segment, 0.25% by volume to 0.5% by volume of aramid fiber is mixed in concrete as an additive for preventing crack extension.

JP-A-2019-49191

According to the cutting segment described in Patent Document 1, crack extension can be prevented by mixing 0.25% by volume to 0.5% by volume of aramid fiber. However, it is uncertain whether or not the expansion of cracks can be effectively prevented by mixing at most 0.5% by volume of low-rigidity aramid fibers. Furthermore, there is no description here regarding the problem that the crack width becomes large due to the concentration of cracks in one place (or as few places as possible) and the water stopping property of the cutting segment becomes low. Of course, there is no description of the means. It should be noted that it is extremely difficult to disperse the cracks, reduce the crack width of each crack, and improve the water stopping property only by mixing 0.5% by volume of the low-rigidity aramid fiber. Therefore, it is described in Patent Document 1. It is hard to say that the characteristic configuration is effective in improving the crack dispersibility and water stopping property of the cutting segment.

An object of the present invention is to provide an easy-to-cut segment having excellent machinability, load resistance, and water-stopping property at a manufacturing cost as low as possible.

In order to achieve the above object, one aspect of the easy-to-cut segment according to the present invention is:
A barbed material formed of fiber reinforced plastic is embedded inside the concrete, which is the base material, and steel fibers are dispersed inside the base material.
Concrete design strength of the base material is in the range of 42N / mm ² to 60N / mm ^2,
The mixing ratio of the steel fibers is in the range of 0.3% by volume to 1.0% by volume.
The elastic modulus of the fiber-reinforced plastic is in the range of ^{30 kN / mm 2 to} 120 kN / mm ^2.

According to this aspect, since the reinforcing bar made of fiber reinforced plastic is embedded in the concrete of the base material, an easy-to-cut segment having excellent machinability is formed as compared with the RC segment in which the reinforcing bar is embedded, for example. Will be done. In particular, since the elastic modulus of the fiber reinforced plastic ^{is in the range of 30 kN / mm 2 to} 120 kN / mm ² , the elastic modulus is smaller (low rigidity) than that of a reinforcing bar having an elastic modulus of ^{about 200 kN / mm 2.} Of course, glass fiber reinforced plastics and the like are applied as fiber reinforced plastics having an elastic modulus in this numerical range, while highly elastic carbon fiber reinforced plastics (elastic modulus is equivalent to reinforcing bars) are excluded, so that they are expensive. It does not contain reinforced plastic made of highly elastic carbon fiber reinforced plastic, so the manufacturing cost is as low as possible, and it is an easy-to-cut segment with excellent machinability.

Further, since the steel fibers in the range of 0.3% by volume to 1.0% by volume are dispersed in the concrete, the crack dispersibility is improved due to the cross-linking effect of the steel fibers, and the cracks of each crack are cracked. The width is suppressed as much as possible and the water stopping property is improved.
For example, in the form in which only the reinforcing material made of rods such as glass fiber reinforced plastic is embedded in the base material, the rods of glass fiber reinforced plastic have low rigidity, so that cracks having a large crack width are likely to occur, and the water is stopped. However, such a problem is solved by the dispersion of steel fibers in the concrete. Here, the steel fiber is a reinforcing material for concrete that is made of a steel material and processed into a discontinuous fibrous form, and is a fiber material having a significantly higher rigidity than, for example, an aramid fiber.
Further, since the reinforcing bar and the steel fiber made of fiber reinforced plastic are embedded inside the base metal, the bending strength is enhanced and the load bearing capacity is improved as compared with the RC segment in which the reinforcing bar is embedded, for example. For example, in the form in which only the reinforcing material made of a rod such as glass fiber reinforced plastic is embedded in the base material, the bending strength and the plastic deformation performance may be lowered, but in addition to the rod made of glass fiber reinforced plastic or the like. By dispersing a predetermined amount of steel fibers, the load bearing capacity of the easy-to-cut segment is significantly improved.
Needless to say, it may be an easy-to-cut segment formed of a fiber-reinforced plastic rod and having all the main muscles, the force distribution muscles, the hoop muscles, and the like.

Another effect of mixing the steel fibers described above is that the easy-to-cut segment of this embodiment does not become a segment in which brittle bending compression fracture or shear fracture occurs in advance. For example, when a reinforcing material made of a low-rigidity glass fiber-reinforced plastic rod is applied as a reinforcing material made of fiber-reinforced plastic, a measure for increasing the amount of glass fiber-reinforced plastic can be considered in order to increase the rigidity of the segment. However, if the amount of the glass fiber reinforced plastic is excessively increased, this time, the segment in which the bending tensile fracture occurs in advance becomes the segment in which the brittle fracture occurs in advance, which is not preferable. On the other hand, in the easy-to-cut segment of this embodiment, a fiber-reinforced plastic (for example, low-rigidity glass fiber-reinforced plastic) that forms a reinforcing material by dispersing a predetermined amount of steel fibers in the base material. It is possible to increase the rigidity of the segment without increasing the amount of the fiber, and it is possible to form an easily machinable segment in which bending tensile fracture occurs in advance.
Here, concrete design strength of the base material by a range of 42N / mm ² to 60N / mm ^2, in the tunnel standard How to Display Manual [shield tunneling Functions, same description 2016, are applied to the segment Satisfy the design standard strength of concrete.

Further, since the mixing ratio of steel fibers (the volume percentage, which is the total volume of steel fibers with respect to the total volume of the segments) is in the range of 0.3% by volume to 1.0% by volume, the segments in the concrete plant. It is possible to ensure the manufacturability at the time of manufacturing and the effect of reinforcing the segment by the steel fiber.

Further, in another aspect of the easy-to-cut segment according to the present invention, the maximum tensile stress after cracking of the base material in which the steel fibers are dispersed is larger than the maximum tensile stress of plain concrete composed of the base material alone. It is characterized by that.
According to this aspect, since the steel fibers are dispersed in the base material made of concrete, the stress-strain characteristics of the base material in which the steel fibers are dispersed can be improved, and the maximum tensile stress after the occurrence of cracks can be obtained. , Can be greater than the maximum tensile stress of plain concrete.

Further, another aspect of the easy-to-cut segment according to the present invention is that the tensile stress of the base material in which the steel fibers are dispersed at the strain level at break of the fiber reinforced plastic is larger than 0 ^{N / mm 2.} It is a feature.
According to this aspect, since the steel fibers are dispersed in the base material made of concrete, the base material and the steel fibers cooperate with each other even at the strain level when the fiber reinforced plastic forming the streaks breaks. , The tensile stress of the base metal in which the steel fibers are dispersed can be made larger than zero, and the bending moment acting can be resisted.

In addition, another aspect of the easy-to-cut segment according to the present invention is
A barbed material formed of fiber reinforced plastic is embedded inside the concrete, which is the base material, and steel fibers are dispersed inside the base material.
The maximum tensile stress after cracking of the base material in which the steel fibers are dispersed is larger than the maximum tensile stress of plain concrete composed of the base material alone.
According to this aspect, since the steel fibers are dispersed in the base material made of concrete, the stress-strain characteristics of the base material in which the steel fibers are dispersed can be improved, and the maximum tensile stress after the occurrence of cracks can be obtained. , Can be greater than the maximum tensile stress of plain concrete.

In addition, another aspect of the easy-to-cut segment according to the present invention is
A barbed material formed of fiber reinforced plastic is embedded inside the concrete, which is the base material, and steel fibers are dispersed inside the base material.
The tensile stress of the base material in which the steel fibers are dispersed at the strain level at break of the fiber reinforced plastic is larger than 0 ^{N / mm 2.}
According to this aspect, since the steel fibers are dispersed in the base material made of concrete, the base material and the steel fibers cooperate with each other even at the strain level when the fiber reinforced plastic forming the streaks breaks. , The tensile stress of the base metal in which the steel fibers are dispersed can be made larger than zero, and the bending moment acting can be resisted.

Further, in another aspect of the easy-to-cut segment according to the present invention, the reinforcing material is formed of any one of a glass fiber reinforced plastic rod, an aramid fiber reinforced plastic rod, and a medium elastic carbon fiber reinforced plastic rod. It is characterized by being.

According to this aspect, the reinforcing material is expensive because it is formed of a rod made of glass fiber reinforced plastic or the like (elastic modulus is in ^{the range of 30 kN / mm 2 to} 120 kN / mm ^{2 and has low rigidity).} It does not contain reinforced plastic made of highly elastic carbon fiber reinforced plastic, so that the manufacturing cost is as low as possible, and it is possible to form an easy-to-cut segment having excellent machinability due to the low rigidity of the rod.

Another aspect of the easy-to-cut segment according to the present invention is that the steel fiber has a linear central bar and one or more stepped hooks at both ends of the central bar. And.
According to this aspect, since the steel fiber has one or more stepped hook members at both ends of the linear central bar, the adhesion of the steel fiber to the base material is enhanced, and as a result, the rigidity is low. The stress-strain characteristics of the easy-to-cut segment with the reinforcing material made of fiber reinforced plastic are improved, and the water stopping property is improved due to the improved crack dispersibility.

Further, in another aspect of the easy-to-cut segment according to the present invention, the easy-to-cut segment has two ring joint surfaces and two segment joint surfaces.
The ring joint surface is provided with either a tenon or a tenon groove into which the tenon fits.
It is characterized in that the tenon of the other easy-to-cut segment is fitted into the tenon of the easy-to-cut segment of one of the two easy-to-cut segments to be ring-joined. To do.
According to this aspect, the tenon of the other easy-to-cut segment is fitted into the tenon of one of the two easy-to-cut segments to be ring-joined. As a result, the bending moment on the segment joint surface can be effectively transmitted to the adjacent easy-to-cut segment via the tenon and tenon groove engagement structure of the ring joint surface.

Another aspect of the easy-to-cut segment according to the present invention is characterized in that a share strip is attached to the surface of the tenon.
According to this aspect, the shear strip is attached to the surface of the tenon, and thus the shear strip can be buffered and evenly transmitted by the interposition of the shear strip at the interface between the tenon and the tenon groove. It is possible to prevent the tenon from being locally hit and destroyed.

According to the easy-to-cut segment of the present invention, it is possible to provide an easy-to-cut segment having excellent machinability, load resistance, and water-stopping property while the manufacturing cost is as low as possible.

It is a perspective view which shows an example of the easy-to-cut segment which concerns on embodiment. It is a perspective view which shows the internal structure of an example of the easy-to-cut segment which concerns on embodiment. It is a figure which shows the tensile stress-strain relationship graph of various muscles. It is a perspective view of an example of a steel fiber. It is a figure which shows the bending moment-curvature relation graph of various segments. It is a schematic diagram which shows an example of the crack which occurs in the easy-to-cut segment of the comparative form (only the rod of the glass fiber reinforced plastic is embedded). It is a schematic diagram which shows an example of the crack which occurs in the easy-to-cut segment of embodiment. It is an enlarged view which shows the tenon groove provided on the ring joint surface of the easy-to-cut segment which concerns on embodiment. It is an enlarged view which shows the tenon provided on the ring joint surface of the easy-to-cut segment which concerns on embodiment. It is a vertical cross-sectional view which shows the engaging structure of a tenon and a tenon groove. It is a test outline figure of the destructive energy test. It is a figure which shows the load | crack opening displacement relation graph. It is a figure which shows the tensile stress-crack width relation graph. It is a figure which shows the tensile stress-strain relationship graph.

Hereinafter, the easy-to-cut segment according to the embodiment will be described with reference to the attached drawings. In the present specification and the drawings, substantially the same components may be designated by the same reference numerals to omit duplicate explanations.

[Easy-to-cut segment according to the embodiment]
First, an example of the easy-to-cut segment according to the embodiment will be described with reference to FIGS. 1 to 8. Here, FIG. 1 is a perspective view showing an example of an easy-to-cut segment according to an embodiment, and FIG. 2 is a perspective view showing an internal structure of an example of an easy-to-cut segment according to an embodiment. Further, FIG. 4 is a perspective view of an example of a steel fiber. Further, FIGS. 7A and 7B are enlarged views of a tenon and a tenon provided on the ring joint surface of the easy-to-cut segment according to the embodiment, and FIG. 8 shows the tenon and the tenon. It is a vertical sectional view which shows the engaging structure. In addition, in FIG. 2, the illustration of the steel fiber embedded in the base material is omitted. Further, in FIGS. 7 and 8, the illustration of the muscle material embedded in the base material is omitted.

The illustrated easy-to-cut segment 10 has reinforced materials 21 and 22, 23 formed of fiber reinforced plastic and a large number of dispersed steel fibers 30 inside concrete as a base material. The easy-to-cut segment 10 has a curved shape having the curvature of the segment tunnel to be constructed, and has a pair of ring joint surfaces 11 and a pair of segment joint surfaces 12.

Concrete design strength of the base material is in the range of 42N / mm ² to 60N / mm ^2, in the tunnel standard How to Display Manual [shield tunneling Functions, same explanation 2016, design strength of the concrete to be applied to the segment Is satisfied.

Further, as shown in FIG. 2, in the concrete of the base material, a main bar 21 (inner main bar and outer main bar) that tensilely resists the bending moment acting on the easy-to-cut segment 10 and a force distribution bar 22 are provided. The assembly bar 23 is arranged. Here, each of the reinforcing materials 21, 22, and 23 is formed of fiber reinforced plastic, and more specifically, a rod of glass fiber reinforced plastic (GFRP: Glass Fiber Reinforced Plastics) and an aramid fiber reinforced plastic (AFRP: Aramid). It is made of one of Fiber Reinforced Plastics) rods and medium elastic carbon fiber reinforced plastics (medium elastic CFRP: Carbon Fiber Reinforced Plastics) rods, and high elastic carbon fiber reinforced plastic rods are not applicable.

As shown in FIG. 3, the elastic modulus of these fiber reinforced plastics is in ^{the range of 30 kN / mm 2 to} 120 kN / mm ² , and the elastic modulus is ^{about 200 kN / mm 2} or the elastic modulus equivalent to that of the reinforcing bar. It is a rod with lower rigidity than the highly elastic carbon fiber reinforced plastic that it has. As described above, by having the muscle members 21, 22, and 23 made of low-rigidity rods, the machinability of the easy-to-cut segment 10 is improved. Further, by not applying the highly elastic carbon fiber reinforced plastic, which has a high material cost, the manufacturing cost of the easy-to-cut segment 10 can be reduced as much as possible.

By the way, in the form in which only the streaks 21, 22, 23 made of rods such as glass fiber reinforced plastic are embedded in the base material, the rods made of glass fiber reinforced plastic have low rigidity, so that cracks having a large crack width are generated. It tends to occur and the water stopping property may decrease. Therefore, in the easy-to-cut segment 10, a configuration in which a large number of steel fibers 30 are dispersed in the base material is applied. More specifically, the steel fibers 30 having a mixing ratio in the range of 0.3% by volume to 1.0% by volume are dispersed in the base metal.

As shown in FIG. 4, the steel fiber 30 has a linear central bar 31 and one or more stepped hooks 32 at both ends of the central bar 31. Since the steel fiber 30 has one or more stepped hook members 32 at both ends of the linear central bar member 31, the adhesiveness of the steel fiber to the base material is enhanced, and the steel fiber 30 is made of a low-rigidity fiber reinforced plastic. It is possible to improve the stress-strain characteristics of the easy-to-cut segment 10 including the reinforcing materials 21, 22, and 23. Further, the crack dispersibility is improved due to the cross-linking effect of the steel fiber 30, the crack width of the cracks that may occur can be suppressed as much as possible, and the water stopping property is improved.

Here, as the steel fiber 30, it is preferable to apply a high performance steel fiber (HPSF: High Performance steel Fiber) having a high tensile strength of about ^{1800 N / mm 2.} The stepped hook material 32 of the steel fiber 30 in the illustrated example has a substantially Z-shape, but in addition to the illustrated example, for example, two or more substantially Z-shaped multi-step hook materials and the like are various. A stepped hook material having various shapes and forms can be applied. Further, although the central bar 31 of the steel fiber 30 in the illustrated example has a linear shape, it may have a zigzag shape, a corrugated shape, a curved shape, or the like.

Since the mixing ratio of the steel fiber 30 is in the range of 0.3% by volume to 1.0% by volume, both the manufacturability when manufacturing the segment in the concrete plant and the segment reinforcing effect by the steel fiber are guaranteed. be able to. That is, when the mixing ratio of the steel fiber 30 is less than 0.3% by volume, it is not possible to disperse enough steel fiber to guarantee the load resistance and water stopping property over the entire area of the segment, so that the steel fiber 30 is mixed. The rate is specified as 0.3% by volume or more. On the other hand, if the mixing ratio of steel fibers exceeds 1.0% by volume, it is not possible to manufacture an easily machinable segment in which a predetermined slump (for example, 5 cm ± 1.5 cm) is secured due to slump loss. From the viewpoint of manufacturability, the mixing ratio of the steel fiber 30 is specified to be 1.0% by volume or less.

Further, when the steel fiber 30 is mixed in the base material, the effect that the easy-to-cut segment 10 does not become a segment in which brittle bending compression fracture or shear fracture occurs in advance is exhibited. The easy-to-cut segment 10 includes reinforced materials 21, 22, 23 made of rods such as low-rigidity glass fiber reinforced plastic. However, when the rigidity of the segment is increased to suppress the crack width, the glass fiber is used. Measures to increase the amount of reinforced plastic etc. can be considered. However, if the amount of the glass fiber reinforced plastic or the like is excessively increased, this time, the segment in which the bending tensile fracture occurs in advance becomes the segment in which the brittle fracture occurs in advance, which is not preferable. On the other hand, in the easy-to-cut segment 10, a predetermined amount of steel fibers are dispersed in the base material, so that the amount of low-rigidity glass fiber reinforced plastic or the like forming the streaks 21, 22, 23 is increased. It is possible to increase the rigidity of the easy-to-cut segment 10 without increasing it, and it is possible to form an easy-to-cut segment in which bending tensile fracture occurs in advance.

Further, as shown in FIG. 5, a general RC is formed by burying a reinforcing material 21 made of a rod such as glass fiber reinforced plastic in the concrete of the base material and further dispersing a predetermined amount of steel fibers 30. An easy-to-cut segment having M-φ characteristics (dotted line graph) superior to the M-φ characteristics (solid line graph) of the segment and having high load bearing capacity is formed.

Here, with reference to FIGS. 6A and 6B, improvement of crack dispersibility and water stopping property due to the cross-linking effect of the steel fiber 30 will be described. Here, FIGS. 6A and 6B are schematic views showing an example of cracks occurring in the easy-to-cut segment of the comparative form (only the rod of the glass fiber reinforced plastic is embedded) and the embodiment, respectively.

As shown in FIG. 6A, in the easy-to-cut segment in which only the reinforcing material 21 made of a glass fiber reinforced plastic rod is embedded, the crack width of the crack c1 generated due to the low rigidity of the reinforcing material 21. w1 is generally larger.

On the other hand, as shown in FIG. 6B, in the easy-to-cut segment 10, since a large number of steel fibers 30 are dispersed in the base metal, the crack dispersibility is improved by the cross-linking effect of the steel fibers 30. The crack width w2 of each crack c2 can be significantly suppressed as compared with the crack width w1 of the crack c1 shown in FIG. 6A.

Since the muscular material 21 made of fiber reinforced plastic and the steel fiber 30 are embedded inside the base material, only the muscular material 21 as the main reinforcement that resists the bending moment is arranged, and the force is distributed to the steel fiber 30. By exerting the function of the muscle 22 (or the hoop muscle or the like), it is possible to omit the force distribution muscle 22 and the assembly muscle 23.

Returning to FIG. 1, the easy-to-cut segment 10 is provided with a tenon 13 on one ring joint surface 11 and a tenon 14 on the other ring joint surface 11 (see FIG. 7B). In the illustrated example, one ring joint surface 11 is provided with three mortise grooves 13, and the other ring joint surface 11 is provided with three mortises 14 at positions corresponding to the three mortise grooves 13. .. Therefore, the three mortises 14 of the other easy-to-cut segment 10 are engaged with the three mortises 13 of one easy-to-cut segment 10 to be ring-joined. The number of the tenon 13 and the tenon 14 provided on the ring joint surface 11 is not limited to the illustrated example.

On the segment joint surface 12, for example, a butt joint is applied. As shown in FIG. 2, the resin assembly insert 26 embedded in one easy-to-cut segment 10 is similarly fitted with a resin diagonal assembly bolt 25 from the other easy-to-cut segment 10 side. A butt joint is formed by inserting and screwing. Further, on the ring joint surface 11, a plurality of (three in the illustrated example) partial tenon joints can be applied, and the bending moment on the segment joint surface 12 is applied to the engagement structure of the tenon 14 and the tenon groove 13 of the ring joint surface 11. It can be effectively transmitted to the adjacent easy-to-cut segment 10 via (see FIG. 8). Various types of joints other than butt joints can be applied to the segment joints.

Here, an example of the tenon groove and the shape of the tenon will be described with reference to FIGS. 7A and 7B. As shown in FIG. 7A, the mortise groove 13 has a tapered side surface 13b recessed from the ring joint surface 11 in a plan view track shape, and a plan view track-shaped bottom flat surface 13a at the bottom of the tapered side surface 13b. Further, for example, a water-expandable sealing material 16 made of chloroprene synthetic rubber is attached to the ring joint surface 11.

On the other hand, as shown in FIG. 7B, the tenon 14 projects from the ring joint surface 11 in a plan view track shape and has a taper side surface 14b complementary to the taper side surface 13b of the tenon groove 13 and a plan view track at the top of the taper side surface 14b. It has a top flat surface 14a that spreads out in a shape and fits into the bottom flat surface 13a. Further, a plurality of share strips 15 (two in the illustrated example) are attached to the surface of the tenon 14.

As shown in FIG. 8, the tenon 14 of the other easy-to-cut segment 10 is fitted into the tenon 13 of one of the two easy-to-cut segments 10 to be ring-joined. , An engaging structure of the tenon 13 and the tenon 14 is formed on both ring joint surfaces 11. The gap between the facing ring joint surfaces 11 and 11 is sealed with the water-expandable sealing material 16 to ensure water stoppage. Further, the share strip 15 is interposed in the gap in the engagement structure between the tenon groove 13 and the tenon 14 in a state of being pressure-welded.

When a shearing force S acts on the ring joint surface 11 in which the tenon 13 and the tenon 14 are engaged with each other, a punched shear surface L starting from the boundary between the tapered side surface 13b of the tenon 13 and the bottom flat surface 13a is formed. obtain. However, in the easy-to-cut segment 10, a large number of steel fibers 30 are dispersed so as to straddle the left and right regions via the punched shear surface L. As a result, a large number of steel fibers 30 resist the punching shear force S1 in the direction along the punching shearing surface L, and the shearing strength in the vicinity of the ring joint surface 11 of the easy-to-cut segment 10 is improved. , Punching shear failure can be suppressed.

Further, the shear strip 15 arranged in the gap in the engagement structure between the tenon groove 13 and the tenon 14 can buffer the shearing force and evenly transmit the shearing force, whereby the tenon 14 is locally hit and destroyed. Can be suppressed.

As the ring joint to be applied, various types of joints such as a one-touch type joint may be applied in addition to the tenon type joint shown in the illustrated example. For example, in a one-touch type joint, a ring joint is formed by, for example, pushing a male side joint provided on the ring joint surface of the other segment into a female side joint provided on the ring joint surface of one segment. Is formed. When this form of ring joint is applied to an easy-to-cut segment, it is preferable that both the female side joint and the male side joint are resin joints that are easy to cut.

As described above, according to the easy-to-cut segment 10, the barbed material 21 or the like formed by the rod or the like of low-rigidity glass fiber reinforced plastic is embedded in the concrete base material, so that the cost is as low as possible. Easy-to-cut segments with excellent machinability can be obtained at a low manufacturing cost.

Further, in addition to the low-rigidity barbed material 21 and the like, a predetermined amount of steel fibers 30 having high tensile strength and fixing performance are dispersed in the base metal, so that the base metal has high load resistance and brittle bending. Bending and tensile fractures occur in advance without compression fractures and shear fractures occurring in advance, and an easy-to-cut segment having excellent crack dispersibility and high water stopping property can be obtained.

[Fracture energy test and its results]
Next, the destructive energy test carried out by the present inventors and the results thereof will be described with reference to FIGS. 9 to 12.

<Examination outline>
Concrete design standard strength: f'ck = 60N / mm ² (actual concrete strength: f'c = 76.9N / mm ² ), high-performance steel fiber (Dramix (registered trademark) 4D 80 / 60BG, manufactured by BEKAERT) , The destructive energy test was carried out with 4 test pieces under the condition of fiber mixing ratio of 1.0 vol.%. A schematic diagram of the destructive energy test is shown in FIG. In this test device, the test piece is placed on two roller bearings to support it at two points, a notch is provided in advance in the center of the lower surface of the test piece, and the load is loaded on the center of the upper surface of the test piece by the tester head. P was allowed to act. A fracture energy test was performed on each test piece, and the relationship between load-bearing load and crack opening displacement (CMOD) was measured. The relationship graph of the four test specimens and the average value graph of the relationship graph are shown in FIG. In FIG. 10, the values on the vertical axis are normalized by dividing the loaded load by the design crack generation load. Here, the design crack generation load: P _d was calculated by the following method. _{That is, the design value of bending crack strength: f bcd} is calculated by dividing the characteristic value of bending crack strength: f _bck by the material coefficient of fiber reinforced concrete, and the design value of this bending crack strength: f _bcd and the test piece. _{The design crack generation bending moment: M d} was calculated by dividing the value obtained by multiplying the cross-sectional coefficient of: Z by the member coefficient. _{Then, the design crack generation load: P d} is calculated from the design crack generation bending moment: M _d and the distance between the bearing-load loading point in the test piece.

<Inverse analysis>
Inverse analysis was performed using the load-crack opening displacement (CMOD) relationship measured in the fracture energy test, and the tensile stress-crack width relationship (tensile softening curve) was estimated. Here, an inverse analysis was performed using the average value of four test specimens. Using the average value (P-CMOD) of four test specimens, the tensile softening curve estimated by inverse analysis is used as the modeled average curve, and by considering the reduction coefficient in the modeled average curve, the test results vary. Was corrected to a risk probability of 5%, and the tensile softening curve was used as the characterization curve.

_{The calculation method of the tensile strength of concrete is based on the characteristic value of compressive strength of general concrete: f'ck} (design standard strength) according to the concrete standard specification / design edition 2017 [main part] 5.3.1. it can be expressed by ^{_{f tk = 0.23f 'ck 2/3 N}} / mm 2. Incidentally, this formula, f _'ck not only ordinary concrete about 20~50N / mm ^2, f' _ck can be applied to the following concrete about 80 N / mm ^2.

<Reduction coefficient of concrete>
Next, a method of setting the reduction coefficient of concrete will be described. Since the test results vary depending on the dispersibility and orientation of the fibers, it is necessary to determine the reduction coefficient based on sufficient test results. However, the number of Dramix 4D 80 / 60BG 1.0 vol.% Specimens is 4, which is not a sufficient test result.

On the other hand, the previous experiments were conducted with 124 BUNDREX (registered trademark) 60/30 0.4vol.%: KOSTEEL test specimens, and the tensile softening curve obtained from the experiments showed that the fracture energy up to an opening width of 1 mm. The experimental data is assumed to be a normal distribution, and the characteristic value with a risk probability of 5% is set to 0.79 N / mm ² . From this, the tensile softening curve used in the design is determined by characterizing the average softening curve modeled using the reduction rate (β = 0.79 / 1.33 = 0.59) with respect to the average value of fracture energy. This reduction rate (β = 0.59) shall be used as the reduction coefficient.

<Tension softening curve>
The tensile softening curve was obtained by multiplying the modeled average curve by the above-mentioned reduction coefficient of concrete. FIG. 11 shows a modeled average curve and a obtained tensile softening curve.

In FIG. 11, the concrete tensile ^{_{strength: f t = 0.23f 'c 2/3}} , f' and _c = 76.9N / mm ^2, and the normalized value = 0.98 f _t.

<Tensile stress-strain curve>
Next, the tensile stress-strain curve was set using the tensile softening curve shown in FIG. Here, there is a relationship of strain ε = crack width w (mm) / crack interval L _cr (mm) between the strain ε and the crack width w (mm), and the crack interval is determined from the experimental bar arrangement specifications by L _cr. By setting = 247 mm, the tensile stress-strain curve shown in FIG. 12 can be obtained. The vertical axis in FIGS. 11 and 12 is a value obtained by normalizing a value in which the material coefficient of the fiber reinforced concrete is expected with respect to the tensile stress by the characteristic value of the tensile strength of the concrete: f _tk.

In FIG. 12, cracks occur with a strain of about 100 μm. The normalized value of the value obtained by multiplying the normalized value of the tensile strength of plain concrete by the reduction coefficient β is 0.58.

In the illustrated tensile stress-strain curve, the tensile stress linearly increases up to the strain level at the time of cracking, and then the tensile stress decreases slightly with the occurrence of cracks, and then the tensile force of the steel fiber acts. As a result, the tensile stress increases, and the tensile stress tends to be larger than the tensile stress of plain concrete. Then, for example, in a range of at least a strain of 5000 μ (crack width of about 1.5 mm), the maximum tensile stress after cracking of the base material in which steel fibers are dispersed is equal to or greater than the maximum tensile stress of plain concrete composed of only the base material. It has been specified that it can have tensile stress and can effectively suppress cracks.

The range of breaking strain (tensile strength / elastic modulus) of GFRP is 1205/70100 = 17200μ for the nominal diameter (φ8) and 1170/58500 = 20000μ for the nominal diameter (φ12). Become. It has also been specified that the tensile stress of the base metal in which the steel fibers are dispersed ^{is larger than 0 N / mm 2 even in the breaking strain range (bending strength improvement range) of this GFRP.}

It should be noted that the configuration or the like described in the above embodiment may be another embodiment in which other components are combined, and the present invention is not limited to the configuration shown here. This point can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form thereof.

10: Easy-to-cut segment 11: Ring joint surface 12: Segment joint surface 13: Groove 13a: Bottom flat surface 13b: Tapered side surface 14: Tenon 14a: Top flat surface 14b: Tapered side surface 15: Shear strip 16: Water expansion Sealing material 21: Muscle material (main reinforcement)
22: Muscle material (strength distribution muscle)
23: Muscle material (assembled muscle)
25: Diagonal bolt for assembly 26: Insert for assembly 30: Steel fiber 31: Central bar 32: Stepped hook material c1, c2: Crack w1, w2: Crack width

Claims (5)

A barbed material formed of fiber reinforced plastic is embedded inside the concrete, which is the base material, and steel fibers are dispersed inside the base material.
Concrete design strength of the base material is in the range of 42N / mm ² to 60N / mm ^2,
The mixing ratio of the steel fibers is in the range of 0.3% by volume to 1.0% by volume.
Elastic modulus of the fiber-reinforced plastic Ri range near the 30 kN / mm ² to 120 kN / mm ^2,
Maximum tensile stress after Cracking of the base material in which the steel fibers are dispersed has a size Kunar strain range than the maximum tensile stress of plain concrete comprising only the base material,
An easy-to-cut segment characterized in that the tensile stress of the base material in which the steel fibers are dispersed at the strain level at break of the fiber reinforced plastic ^{is larger than 0 N / mm 2.} The ease according to claim 1, wherein the reinforcing material is formed of any one of a glass fiber reinforced plastic rod, an aramid fiber reinforced plastic rod, and a medium elastic carbon fiber reinforced plastic rod. Machinability segment. The easy-to-cut segment according to claim 1 or 2 , wherein the steel fiber has a linear central bar and one or more stepped hooks at both ends of the central bar. .. The easy-to-cut segment has two ring joint surfaces and two segment joint surfaces.
In the ring joint surface comprises a plurality of tenon noncontiguous to one another, one of the plurality of mortise grooves said plurality of tenons are not continuous with each other to fit respectively,
The plurality of mortises of the other easy-to-cut segment are fitted into the plurality of mortises of the easy-to-cut segment of one of the two ring-joined easy-to-cut segments. The easy-to-cut segment according to any one of claims 1 to 3, wherein the segment is easy to cut. The easy-to-cut segment according to claim 4 , wherein a share strip is attached to the surface of the tenon.

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