JP3022362B2 - Culvert fittings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
It relates to the joint of a culvert such as a cave.

[0002]

2. Description of the Related Art Conventional culvert joints are formed by adding a reinforcing material such as cloth or cord to an elastic material such as rubber or synthetic resin and forming both ends of a flexible water blocking member formed in a short cylindrical shape. The two culverts facing each other are attached to the inner peripheral surfaces of the ends in a watertight manner to absorb the relative displacement of the culvert due to uneven settlement of the ground and to stop water between these culverts. There are types.

[0003] An example of this type of conventionally used joint is shown in the sectional view of FIG. In FIG. 9, a joint b is provided on a pair of square tubular or cylindrical culverts a and a ′ facing each other at the inner peripheral surfaces of opposed ends thereof with a flexible member made of rubber, synthetic resin, or the like.
Both ends e and e 'of a flexible water-stopping member d which is formed into a short cylindrical shape as a whole and has an elongated portion c at the center by adding a reinforcing member such as a cord are provided in a watertight manner.

The joint b is provided with a margin in the width of the extension c in advance to absorb the relative displacement between the culverts. However, due to the external water pressure applied from the outside of the culvert, the extension c
However, as shown in FIG. For this reason, in a culvert such as a sewer, the downflow resistance becomes large, causing problems such as generation of accumulated water.

In this type of joint, as shown in FIG. 10, a bulging portion g bulging inwardly is provided at the extending portion c of the flexible water-stopping member d so that the extending portion c becomes bellows-like. Although this joint is formed, also in this joint, as in the joint of FIG. 9, the swelling portion of the extending portion c develops as a whole in an arc-shaped cross section due to the external water pressure and escapes from the disadvantage that the bulging portion largely swells inward. Absent.

In order to prevent this disadvantage, a joint as shown in FIG. 11 is also used. This configuration has culverts a, a '
Are provided on the inner peripheral surface of the stepped portion, and the stepped portions f, f 'are provided.
The joint b is attached to the peripheral surface of the culvert a, so that even if the extension c of the joint b bulges inward due to the external water pressure, it does not protrude inward from the inner peripheral surface of the culverts a and a '. .

However, in the configuration of FIG.
The provision of the steps f and f 'in the underdrain has a problem that the strength of the underdrain is weakened and the work of attaching the joint becomes difficult. In particular, in the case of a rectangular culvert such as a box culvert, it is impossible to fit a joint with an arch-shaped cross section into a short cylindrical shape at each corner, so bend in advance to the corner. I am doing the cumbersome task of attaching what I did.

Further, in a culvert such as a sewer, there is a problem that decay substances, earth and sand, etc. are accumulated in the steps f, f '.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the above-mentioned conventional underdrain, and the extension of the joint bulges toward the inner periphery of the underdrain due to external water pressure, thereby increasing the downflow resistance. It is an object of the present invention to provide a joint of a culvert capable of absorbing relative displacement between culverts without generating accumulated water or the like and without providing a deep step portion in the culvert.

[0010]

In order to achieve the above object of the present invention, a culvert joint according to the first aspect of the present invention comprises:
It is made of a flexible sheet made of a flexible material such as rubber or synthetic resin, and is formed in a short cylindrical shape as a whole, and is a flexible sheet disposed across a joint between a pair of opposed culvert ends. A joint having anchoring portions fixed to the ends of the culvert at both ends, and extending along the displacement when the culverts formed between the anchoring portions are displaced away from each other. In a joint of a culvert having an extended portion, the extended portion is provided so as to cover at least a part of the folded portion formed by folding a part of the flexible sheet, and a predetermined value or more. A folded maintenance sheet adhered to the flexible sheet in the vicinity of the folded portion so as to maintain the folded state of the flexible sheet with an adhesive force that peels off when receiving a force. I do.

According to a second aspect of the present invention, a joint of a culvert is formed of a flexible sheet made of rubber, synthetic resin, or the like, is formed in a short tubular shape as a whole, and has a pair of opposed ends of a culvert. A flexible joint that is disposed across joints between the sections, and has anchoring portions fixed to ends of the culvert at both ends, and the culverts formed between the anchoring portions are separated from each other. In a joint of a culvert having an extension that extends following the displacement when displaced in the direction, the extension has a folded portion formed by folding a part of the flexible sheet, and A part of the sheet is adhered to another part of the flexible sheet so as to maintain the folded state of the flexible sheet with an adhesive force that peels off when subjected to a force equal to or more than a predetermined value. Features.

The joint of a culvert according to the invention of claim 3 is made of a flexible sheet made of a flexible material such as rubber or synthetic resin, and is formed in a short cylindrical shape as a whole. A flexible joint arranged across a joint between opposite ends of a culvert, having anchoring portions fixed to the ends of the culvert at both ends and formed between the anchoring portions. When the culvert is displaced in a direction away from each other, in a joint of the culvert having an extension that extends following this displacement, the extension is:
A plurality of bulging portions formed by bulging a part of the flexible sheet to the inner peripheral side; and a plurality of bulging portions provided so as to cover the plurality of bulging portions, and peeled off when subjected to a force of a predetermined value or more. A swelling prevention sheet adhered to the flexible sheet with such an adhesive force.

[0013]

According to the first aspect of the present invention, the extending portion of the joint is provided so as to cover a part of the flexible sheet that is folded back, and the folded part is provided with a force equal to or greater than a predetermined value. The flexible sheet is provided with a folded maintenance sheet adhered to the flexible sheet in the vicinity of the folded portion so as to maintain the folded state of the flexible sheet with an adhesive force that peels off when received. By setting appropriate values that exceed the tension due to external water pressure and are equal to or less than the strength of the reinforcing material and are equal to or less than the force that causes relative displacement in the direction in which the opposed culverts are separated from each other, the folded sheet is returned from the flexible sheet by external water pressure. The folded state of the flexible sheet at the folded portion can be maintained without peeling, and therefore, it is possible to prevent the extending portion of the joint from bulging inward by the external water pressure. Also, when the opposing culverts are relatively displaced in a direction away from each other due to an earthquake or the like, the folded-back maintenance sheet is peeled off from the flexible sheet, and the folded-back flexible sheet in the folded portion is sometimes loosened, and the joint is extended. The portion can absorb this relative displacement by extending following the relative displacement between the culverts.

According to the second aspect of the present invention, the extending portion of the joint has a folded portion formed by folding a part of the flexible sheet, and a part of the flexible sheet of the folded portion has a predetermined value or more. Since the flexible sheet is adhered to the other portion of the flexible sheet so as to maintain the folded state with an adhesive force such that the flexible sheet is peeled off when subjected to a force, the predetermined value is adjusted by the external water pressure. The adhesive strength of the flexible sheet is removed by the external water pressure by setting an appropriate value that exceeds the strength of the reinforcing material and the force that causes relative displacement in the direction in which the opposed culverts separate from each other. Thus, the folded state of the flexible sheet at the folded portion can be maintained, and therefore, it is possible to prevent the extending portion of the joint from bulging inward due to external water pressure. Further, when the opposing culverts are relatively displaced in a direction away from each other due to an earthquake or the like, the adhesive of the flexible sheet of the folded portion is peeled off, the folded flexible sheet of the folded portion is sometimes loosened, and the joint of the joint is loosened. The extension portion can absorb the relative displacement by extending following the relative displacement between the culverts.

According to the third aspect of the present invention, the extending portion of the joint includes a plurality of bulging portions formed by bulging a part of the flexible sheet to the inner peripheral side, and the plurality of bulging portions. The bulging prevention sheet is provided so as to cover the protrusion and is adhered to the flexible sheet with an adhesive force such that the bulge is peeled off when subjected to a force greater than a predetermined value. The swelling prevention sheet is peeled off from the flexible sheet by external water pressure by setting the appropriate value exceeding the strength of the reinforcing material and the force causing relative displacement in the direction in which the opposing culverts are separated from each other. Therefore, it is possible to prevent the extending portion of the joint from bulging inward due to external water pressure. When the opposed culverts are relatively displaced in a direction away from each other due to an earthquake or the like, the bulging prevention sheet is peeled off from the flexible sheet, the bulging portion of the flexible sheet is deployed, and the extension of the joint is culverted. This relative displacement can be absorbed by extending following the relative displacement between them.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 show an embodiment in which the present invention is applied to a precast box culvert. FIG. 1 is a cross-sectional view taken along a line II of FIG. It is a perspective view.

In FIG. 2, reference numeral 1 denotes a culvert joint according to the present invention, and reference numerals 2 and 2 'denote culverts composed of precast box culverts. Opposite ends of the pair of culverts 2 and 2 'are connected by a joint 1 according to the present invention.

As shown in FIG. 1, the joint 1 is made of a flexible sheet 3 made of a flexible material such as rubber or synthetic resin and a reinforcing material such as cloth or cord added thereto. It is formed as a flexible joint which is disposed on the inner peripheral surface of the culvert 2, 2 'over the joint 5 between the ends of the culverts 2, 2' facing each other. Reference numeral 6 denotes a joint material made of sponge rubber, urethane rubber, or the like inserted into the joint 5.

The joint 1 has anchoring portions 7, 7 'fixed to the ends of the culverts 2, 2' at both ends, and is formed between the anchoring portions 7, 7 'to form the culverts 2, 2'. When the members are displaced in directions away from each other, the extension portions 4 extend following the displacement.
Having.

In this embodiment, the anchoring portions 7, 7 'are formed by folding both ends of the flexible sheet 3. The anchoring parts 7, 7 'are fixed to the ends of the culverts 2, 2' by a plurality of anchor bolts 9, 9 'arranged in the circumferential direction of the culverts 2, 2' via the holding plates 8, 8 '. ing.

The extending portion 4 has annular folded portions 10 and 10 'formed by folding a part of the flexible sheet 3 at two locations in the joint axial direction, and covers the folded portions 10 and 10'. Folded maintenance sheet adhered to the flexible sheet 3 on both sides 11a, 11b and 11a ', 11b' of the folded parts 10, 10 'with adhesive strength such that they are peeled off when subjected to a pressure equal to or greater than a predetermined value. 12,1
2 '. The mounting height h of the extension portion 4 is set so that the anchor bolts 9 and
It is preferable that the height of the hexagonal bolts 9a, 9a 'of the 9' is set to be equal to or slightly higher than the height of the bolts 9a, 9a 'as shown in FIG.

As the flexible sheet 3, for example, as shown in the sectional view of FIG. 4, a reinforcing sheet or cord 3b having sufficient strength such as nylon cloth or nylon cord is sandwiched between rubber sheets 3a. It is preferable to use a member that is interposed and integrally joined.

It is convenient to use a sheet made of the same material as the flexible sheet 3 if vulcanization bonding is possible, but other cloths, resin sheets, etc. are also required as the folded-back maintaining sheets 12, 12 '. Any material having a high strength can be used.

In order to bond the folded-back maintaining sheets 12, 12 'to the flexible sheet 3, both the folded-back maintaining sheets 12, 12' and the flexible sheet 3 are provided with a reinforcing material between rubber sheets as shown in FIG. In the case of an interposed sheet, the two are bonded by vulcanization bonding. When an adhesive is used, a rubber-based or resin-based adhesive or an instant adhesive can be used. Flexible sheet 3 of folded-back maintenance sheets 12, 12 '
Is set to an appropriate value less than the force that exceeds the tension applied to the flexible sheet 3 due to the external water pressure and causes relative displacement in the direction in which the opposing culverts 2, 2 'are separated from each other.

Next, the operation of the joint 1 will be described.
The joint 1 is in the state shown in FIG. 1 when the joint 1 is installed and in a normal state where displacement such as extension displacement does not occur between the culverts 2 and 2 ′.

In normal times, the culvert 2 passes through the joint 6.
The tension is applied to the flexible sheet 3 by the external water pressure caused by the intrusion of water from the outside of the sheet 2 '.
Since the adhesive force between the flexible sheets 2 and 12 'and the flexible sheet 3 is set to a value exceeding this tension, the folded maintenance sheets 12 and 12'
12 'is not peeled off from the flexible sheet 3, and the folded state of the flexible sheet 3 at the folded portions 10, 10' can be maintained. Swelling to the inner peripheral side can be prevented.

If the opposed culverts 2, 2 'are extended and displaced due to an earthquake or the like, that is, relatively displaced in a direction away from each other, the adhesion between the folded-back maintenance sheets 12, 12' and the flexible sheet 3 is broken, The folded maintenance sheets 12, 12 'are peeled off from the flexible sheet 3 simultaneously or one after another, the folded flexible sheet 3 of the folded parts 10, 10' is loosened, and the extended parts 10, 10 'of the joint 1 are removed. This relative displacement is absorbed by extending following the relative displacement between the culverts 2 and 2 '.

FIG. 3 is a sectional view similar to FIG. 1 showing another embodiment of the joint according to the present invention. In FIG. 3, FIG.
The same components as those described above are denoted by the same reference numerals, and description thereof is omitted.

The embodiment of FIG. 3 differs from the embodiment of FIG. 1 in that the joint 20 of FIG. 3 does not have the folded-back maintenance sheets 12, 12 'in the extension 4 as in the joint 1 of FIG. Instead, a part of the flexible sheet 3 at both ends of the folded parts 10 and 10 'is adhered to the other part with a predetermined adhesive force. That is, in the embodiment shown in FIG. 3, the portion 10a of the flexible sheet 3 is adhered to the opposing portion 10b at the portion 14 at the end of the folded portion 10, and the portion 15a at the other end of the folded portion 10 is flexible. The portion 10b of the sheet 3 is bonded to the opposing portion 10c. Similarly, at the portion 14 'at one end of the folded portion 10', the portion 10a 'of the flexible sheet 3 is bonded to the opposing portion 10b', and at the portion 15 'at the other end of the folded portion 10', The portion 10b 'of the sheet 3 is
c '.

In this joint 20, the folded portions 10, 1
The bonding of the flexible sheets 3 at 0 'is of a simple configuration, and the bonding strength is smaller than the bonding strength between the folded-back maintaining sheets 12, 12' and the flexible sheet 3 in the joint 1 of FIG. small. Therefore, the joint 20 of FIG. 3 is applicable when the external water pressure acting on the joint is relatively small.

The operation of the joint 20 is the same as that of the joint 1. That is, the adhesive strength of the flexible sheets 3 of the folded portions 10 and 10 'is set to an appropriate value which is less than the force that exceeds the tension caused by the external water pressure and causes relative displacement in the direction in which the opposed culverts are separated from each other. By doing so, it is possible to maintain the folded state of the flexible sheet 3 at the folded portions 10 and 10 'without peeling off the bonded portion of the flexible sheet 3 due to the external water pressure, and therefore, the extension portion 4 of the joint becomes outside. It is possible to prevent swelling inward due to water pressure. When the opposed culverts 2, 2 'are displaced relative to each other due to an earthquake or the like, the folded portions 10, 1 are displaced.
When the mutual adhesion of the flexible sheets 3 at the portions 14, 14 ', 15, 15' at 0 'is broken, the folded portion 1 is formed.
The 0,10 'folded back flexible sheet 3 is unraveled, and the joint extension 4 can absorb this relative displacement by extending following the relative displacement between the culverts.

In the above embodiments, the folded portions are provided at two places (10, 10 '), but may be provided at only one place or at three or more places. Further, although the flexible sheet is folded twice in each folded portion in each of the above embodiments, the present invention is not limited to this, and the flexible sheet may be folded three or more times.

In the embodiment shown in FIG. 1, the folded-back maintaining sheets 12, 12 'are provided so as to cover the entire folded portions 10, 10', and are bonded to the flexible sheet 3 on both sides of the folded portions 10, 10 '. However, the present invention is not limited to this. For example, as shown in FIG.
0 '), the folded back maintenance sheet 1
2 (12 '), and the folded-back maintenance sheet 12 (1'
2 ′) may be bonded to the flexible sheet 3 at both ends.

In the embodiment shown in FIG.
0 (10 ') at both ends 14, 15 of the flexible sheet 3
Is adhered to the other part, but is not limited to this. For example, as shown in FIG.
In the central portion 17 of 0 '), the portion 10a of the flexible sheet 3 is bonded to the opposing flexible sheet portion 10b, and the flexible sheet portion 10b is bonded to the flexible sheet portion 10c at the central portion 18. You may do so. Further, when the external water pressure is relatively small, in the embodiment of FIG.

In short, in each embodiment, there is no particular limitation on the bonding portion as long as it can maintain the folded state in the folded portion of the flexible sheet.

Further, the folding type bonding method of the embodiment shown in FIG. 5 and the embodiment shown in FIG. 3 as shown in FIG. 7 may be adopted. That is, 11a (11a ') of the folded portion 10 (10')
Side, the folded back sheet 12 (12 ') is adhered to the flexible sheet 3, while the side 10b of the flexible sheet 3 at the portion 15 (15') on the side 11b (11b ').
(10b ') and the part 10c (10c') are mutually bonded.

FIG. 8 is a sectional view similar to FIG. 1 showing another embodiment of the joint according to the present invention. In FIG. 8, FIG.
The same components as those described above are denoted by the same reference numerals, and description thereof is omitted.

In the embodiment shown in FIG. 8, the extending portion 4 has two bulging portions 22, 22 formed by bulging a part of the flexible sheet 3 inward, and these bulging portions 22, 2
And a swelling prevention sheet 23 adhered to the flexible sheet 3 at both ends 23a, 23a 'with an adhesive force that peels off when a force equal to or more than a predetermined value is applied.

In this embodiment, the predetermined value is set to an appropriate value that exceeds the tension caused by the external water pressure and is equal to or less than the strength of the reinforcing material and equal to or less than the force that causes relative displacement in the direction in which the opposed culverts 2 and 2 'are separated from each other. By stipulating, the swelling prevention sheet 23 does not peel off from the flexible sheet due to the external water pressure, and therefore, it is possible to prevent the extension portion 4 of the joint from bulging inward due to the external water pressure. Further, when the opposed culverts 2 and 2 'are relatively displaced in a direction away from each other due to an earthquake or the like, the bulging prevention sheet 23 is peeled off from the flexible sheet 3 at one end 23a or 23a', and bulges. The part 22 is unfolded, and the extension part 4 of the joint is the culvert 2,
This relative displacement can be absorbed by extending following the relative displacement between 2 '.

[0040]

As described above, according to the first aspect of the present invention, the extended portion of the joint covers the folded portion formed by folding a part of the flexible sheet and at least a part of the folded portion. The flexible sheet is adhered to the flexible sheet on both sides of the folded portion so as to maintain the folded state of the flexible sheet with an adhesive force that peels off when subjected to a force equal to or more than a predetermined value. Since the folded back maintenance sheet is provided, by setting this predetermined value to an appropriate value that exceeds the external water pressure and is equal to or less than the strength of the reinforcing material and is equal to or less than a force that causes relative displacement in a direction in which the opposed culverts are separated from each other. Therefore, the folded sheet can be maintained in the folded portion at the folded portion without being peeled off from the flexible sheet by the external water pressure, and therefore, the extended portion of the joint is swelled inward by the external water pressure. Prevent It is possible. Also, when the opposing culverts are relatively displaced in a direction away from each other due to an earthquake or the like, the folded-back maintenance sheet is peeled off from the flexible sheet, and the folded-back flexible sheet in the folded portion is sometimes loosened, and the joint is extended. The portion can absorb this relative displacement by extending following the relative displacement between the culverts.

According to the second aspect of the present invention, the extending portion of the joint has a folded portion formed by folding a part of the flexible sheet, and a part of the flexible sheet at the folded portion has a predetermined value or more. Since the flexible sheet is adhered to the other portion of the flexible sheet so as to maintain the folded state with an adhesive force such that the flexible sheet peels off when subjected to a force, the predetermined value exceeds the external water pressure. In addition, by setting an appropriate value equal to or less than a force that causes relative displacement in a direction in which opposed culverts are separated from each other, the bonded portion of the flexible sheet is not peeled off by the external water pressure, and the flexible sheet in the folded portion is not peeled off. Can be maintained, and therefore, it is possible to prevent the extended portion of the joint from bulging inward due to external water pressure. Further, when the opposing culverts are relatively displaced in a direction away from each other due to an earthquake or the like, the adhesive of the flexible sheet of the folded portion is peeled off, and the folded flexible sheet of the folded portion is sometimes loosened, and the joint of the joint is loosened. The extension portion can absorb the relative displacement by extending following the relative displacement between the culverts.

According to the third aspect of the present invention, the extending portion of the joint includes a plurality of bulging portions formed by bulging a part of the flexible sheet toward the inner periphery, and a plurality of bulging portions. The bulging prevention sheet is provided so as to cover the protrusion and is adhered to the flexible sheet with an adhesive force such that the bulge is peeled off when subjected to a force greater than a predetermined value. The swelling prevention sheet is peeled off from the flexible sheet by external water pressure by setting the appropriate value exceeding the strength of the reinforcing material and the force causing relative displacement in the direction in which the opposing culverts are separated from each other. Therefore, it is possible to prevent the extending portion of the joint from bulging inward due to external water pressure. When the opposed culverts are relatively displaced in a direction away from each other due to an earthquake or the like, the bulging prevention sheet is peeled off from the flexible sheet, the bulging portion of the flexible sheet is deployed, and the extension of the joint is culverted. This relative displacement can be absorbed by extending following the relative displacement between them.

Therefore, if the joint of the present invention is used in a culvert such as a sewer system, it is possible to prevent an increase in flow resistance and stagnant water due to bulging of the joint extension to the inner peripheral side without providing a step in the culvert. In addition, any relative displacement between the culverts that can be expected can be sufficiently dealt with by adjusting the amount of turn of the turn portion.

Further, since the joint of the present invention has a low extension portion and a substantially straight cross-sectional shape without exhibiting an arch-shaped cross-sectional shape unlike a conventional joint, it has a rectangular cylindrical shape such as a box culvert. Even in culverts, the joint can be easily fitted to the corner of the culvert simply by holding the joint with the presser plate and fitting it into the corner of the culvert. Since it is not necessary to join with other parts of the joint after attaching to, the construction is simple.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing one embodiment of a joint of a culvert according to the present invention.

FIG. 2 is a perspective view of a precast box culvert to which the joint of FIG. 1 is applied.

FIG. 3 is a partial sectional view showing another embodiment of the joint according to the present invention.

FIG. 4 is a sectional view showing an example of a flexible sheet.

FIG. 5 is a sectional view showing another example of the bonding method.

FIG. 6 is a sectional view showing another example of the bonding method.

FIG. 7 is a sectional view showing another example of the bonding method.

FIG. 8 is a partial sectional view showing another embodiment of the joint according to the present invention.

FIG. 9 is a partial sectional view showing an example of a conventional culvert joint.

FIG. 10 is a partial cross-sectional view showing another example of a conventional culvert joint.

FIG. 11 is a partial cross-sectional view showing another example of a conventional culvert joint.

[Explanation of symbols]

 1,20 joint 2,2 'culvert 3 flexible sheet 4 extension part 7,7' anchoring part 10,10 'folded part 12,12' folded maintenance sheet

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) E03F 3/04 E21D 11/04 F16L 27/10

Claims (3)

(57) [Claims] 1. A flexible sheet made of a flexible material such as rubber or synthetic resin, formed as a short tube as a whole, and straddling a joint between a pair of opposed culvert ends. A flexible joint to be disposed, having anchoring portions fixed to the ends of the culvert at both ends, and when the culvert formed between the anchoring portions is displaced in a direction away from each other, this displacement In a joint of a culvert having an extension portion extending following the extension portion, the extension portion is provided so as to cover a folded portion obtained by folding a part of the flexible sheet and at least a part of the folded portion. A folded maintenance sheet adhered to the flexible sheet in the vicinity of the folded portion so as to maintain the folded state of the flexible sheet with an adhesive force that peels off when receiving a force equal to or more than a predetermined value. A culvert joint comprising: 2. A flexible sheet made of a flexible material such as rubber or synthetic resin, formed as a short tube as a whole, and straddling a joint between ends of a pair of opposed culverts. A flexible joint to be disposed, having anchoring portions fixed to the ends of the culvert at both ends, and when the culvert formed between the anchoring portions is displaced in a direction away from each other, this displacement In a joint of a culvert having an extension portion that extends following the above, the extension portion has a folded portion formed by folding a part of the flexible sheet, and a part of the flexible sheet of the folded portion has a predetermined value or more. Characterized in that the flexible sheet is adhered to another portion of the flexible sheet so as to maintain the folded state of the flexible sheet with an adhesive force such that the flexible sheet peels off when subjected to the force of the above. 3. A flexible sheet made of a flexible material such as rubber or synthetic resin, formed as a short tube as a whole, and straddling a joint between a pair of opposed culvert ends. A flexible joint to be disposed, having anchoring portions fixed to the ends of the culvert at both ends, and when the culvert formed between the anchoring portions is displaced in a direction away from each other, this displacement In a joint of a culvert having an extension portion extending in conformity with the above, the extension portion includes a plurality of bulging portions formed by bulging a part of the flexible sheet to the inner peripheral side, and the plurality of bulging portions. A culvert joint comprising a bulge prevention sheet provided so as to cover the projecting portion and adhered to the flexible sheet with an adhesive force such that the bulge is peeled off when subjected to a force equal to or more than a predetermined value.