JP2022170978A - Precast member, dike and method for constructing dike - Google Patents

Abstract

To provide technology that is excellent in workability and can shorten the construction period for the construction of a dike.SOLUTION: A precast member 20 constituting a cylindrical dike 10 surrounding the outer periphery of a liquid storage tank 2, comprising: a body part 21 made of concrete and curved in a rectangular shape in a front view and an arc shape in a top view; and outer notches 24A, 24B notched at the corners where a curved outer side 22C of the body part 21 and circumferential end faces 22A, 22B intersect, the outer notches 24A, 24B are opposed to outside notch parts 24A', 24B' of another precast member 20' adjacently arranged by bringing the circumferential end faces 22A, 22B into surface contact with each other, thereby partitioning an outside recessed part 25 capable of placing gap filling concrete 30 on the outer peripheral side of the dike 10.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to precast members, dikes, and methods of constructing dikes.

Conventionally, prestressed concrete tanks (hereinafter referred to as PC tanks) are used as tanks for storing liquefied gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

A PC tank has a tank body with steel outer and inner tanks, and by constructing a cylindrical anti-liquid barrier along the outer circumference of the tank body, liquid leaks outside when the inner tank, etc., is damaged. It is configured to prevent

As a method of constructing this type of dike, precast construction is sometimes adopted, in which precast concrete members manufactured in a factory or the like are transported to the site and connected, thereby shortening the construction period and reducing construction costs. (See, for example, Patent Document 1).

JP 2017-078268 A

In the above precast construction method, a plurality of precast members are arranged at intervals in the circumferential direction of the dike, and filling concrete is placed between each precast member, so that each precast member extends along the entire circumference in the circumferential direction. Forms an integral toroidal wall. Then, the ring-shaped wall is taken as one lot, and the next lot is sequentially stacked in the height direction to construct a dike of a predetermined height.

In such a precast construction method, the precast members adjacent to each other in the circumferential direction are independent from each other until the interstitial concrete hardens. Multiple lots cannot be placed on the upper level. For this reason, it is necessary to place the interstitial concrete for each lot, and there is a problem that the construction period is prolonged because the placing work requires time and labor.

Also, a prestress is introduced into the dike by a tendon, and this tendon is inserted into a sheath pipe embedded in the precast member. When the precast members are spaced apart in the circumferential direction as in the above precast construction method, the ends of the circumferential sheath tubes are connected between the precast members by connecting sheath tubes, and the connecting portions are connected to each other. In order to prevent the infiltration of filling concrete, it is necessary to make a waterproof connection such as by heating the heat-shrinkable tube so that it adheres tightly.

The present disclosure has been made in view of the above circumstances, and aims to provide a technique that is excellent in workability and capable of shortening the construction period for constructing a dike.

The precast member of the present disclosure is a precast member that constitutes a cylindrical liquid barrier that surrounds the outer circumference of a liquid storage tank, and is a main body portion made of concrete that is rectangular in a front view and curved in an arc shape in a top view. and an outer notch formed by notching the corner where the curved outer surface of the main body and the circumferential end surface intersect, and the outer notch is provided so that the circumferential end surfaces are in surface contact with each other. It is characterized by defining an outer recessed portion in which interstitial concrete can be placed on the outer peripheral side of the dike by facing the outer cutout portion of another precast member arranged adjacently.

Further, an outer circumferential reinforcing bar extending in the main body portion in a circumferential direction and having an end portion exposed in the outer notch portion is further provided, and an end portion of the outer circumferential reinforcing bar is attached to the other precast member. It is preferably joined with the ends of the outer circumferential reinforcing bars.

In addition, an inner notch portion is provided by notching a corner portion where the curved inner surface and the circumferential end surface of the main body portion intersect, and the inner notch portion is the inner notch portion of the other precast member. It is preferable to define an inner recessed portion in which filling concrete can be placed on the inner peripheral side of the dike by facing the .

Further, an inner circumferential reinforcing bar extending circumferentially in the main body portion and having an end exposed in the inner notch portion is further provided, and an end portion of the inner circumferential reinforcing bar is attached to the other precast member. It is preferably joined with the ends of the inner circumferential reinforcing bars.

Moreover, it is preferable to further include a circumferential sheath tube extending in the circumferential direction inside the main body and into which a circumferential tendon capable of introducing a circumferential prestress to the liquid barrier is inserted.

Moreover, it is preferable to further include a vertical sheath pipe extending vertically in the main body and into which a vertical tendon capable of introducing a vertical prestress to the dike is inserted.

The dike of the present disclosure is characterized by being constructed by arranging the precast members side by side in the circumferential direction and rigidly connecting them, and stacking them in the vertical direction and rigidly connecting them.

A method for constructing a dike according to the present disclosure is a method for constructing a dike using the precast members, wherein a plurality of the precast members are arranged in parallel in the circumferential direction so that the circumferential end faces are in surface contact with each other, By temporarily connecting precast members adjacent to each other in the circumferential direction, a one-stage circular ring-shaped wall body integrated around the circumference is formed, and by stacking the circular ring-shaped wall bodies in multiple stages, a cylindrical wall body is formed. The step of forming the wall and the step of placing the interstitial concrete on the cylindrical wall are repeated at least once, and the cylindrical wall formed to a predetermined height is permanently installed. It is characterized by introducing a prestress by providing a circumferential tension member and tensioning it.

In the wall forming step, when precast members adjacent in the circumferential direction are temporarily connected, a temporary circumferential tension member is provided in the annular wall and tensioned, so that the annular wall is fully formed. It is preferable to integrate the periphery.

According to the technology of the present disclosure, it is possible to achieve excellent workability and shorten the construction period for constructing a dike.

FIG. 2 is a schematic longitudinal sectional view showing part of the PC tank according to the embodiment; 1 is a schematic perspective view showing a PC tank according to this embodiment; FIG. It is a typical perspective view showing a precast member concerning this embodiment. It is a typical sectional view explaining the procedure which connects the precast member concerning this embodiment in the perpendicular direction. It is a typical sectional view explaining the procedure which connects the precast member which concerns on this embodiment in the circumferential direction. It is a schematic diagram explaining the construction method of the dike using the precast member which concerns on this embodiment. It is a schematic diagram explaining the construction method of the dike using the precast member which concerns on this embodiment. It is a schematic diagram explaining the construction method of the dike using the precast member which concerns on this embodiment. It is a schematic diagram explaining the construction method of the dike using the precast member which concerns on this embodiment. It is a schematic diagram explaining the construction method of the dike using the precast member which concerns on this embodiment. FIG. 10 is a schematic perspective view showing a precast member according to another embodiment;

Hereinafter, a precast member, a dike, and a construction method of the dike according to the present embodiment will be described with reference to the accompanying drawings. The same parts are given the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[PC tank]
FIG. 1 is a schematic longitudinal sectional view showing part of a PC tank 1 according to this embodiment, and FIG. 2 is a schematic perspective view showing the PC tank 1 according to this embodiment.

The PC tank 1 shown in FIGS. 1 and 2 is an above-ground tank, and stores liquefied gas such as LNG and LPG. Note that the stored material in the PC tank 1 may be liquid other than liquefied gas, such as liquefied hydrogen, but LNG will be described below as an example.

As shown in FIG. 1 , the PC tank 1 includes a tank body 2 , a bottom slab 5 , a plurality of piles 6 , and a dike 10 surrounding the outer periphery of the tank body 2 . A plurality of piles 6 are not essential, and the bottom slab 5 can be directly supported on the ground according to the specific size of the PC tank 1, ground conditions, and the like.

The tank body 2 has a substantially hollow cylindrical shape with its upper and lower portions closed, and has an inner tank 3 for storing LNG and an outer tank 4 surrounding the inner tank 3 . The inner tank 3 and the outer tank 4 are made of, for example, steel plates. A heat insulating material or the like is interposed between the inner tank 3 and the outer tank 4 to keep the LNG cold between the inner tank 3 and the outer tank 4 .

The bottom plate 5 has, for example, a reinforced concrete structure and is formed in a substantially disc shape. In the illustrated example, the bottom slab 5 is supported by a plurality of piles 6 embedded in the ground, but the piles 6 may be omitted according to ground conditions and the like. A tank main body 2 and a dike 10 are installed on the upper surface of the bottom plate 5 .

The dike 10 is a cylindrical prestressed concrete wall that rises from the bottom slab 5 and is constructed in a substantially cylindrical shape with an open top so as to surround the outer periphery of the tank body 2 . The dike 10 is provided with an outer reinforcing reinforcing bar 13A in which a plurality of outer circumferential reinforcing bars 11A and a plurality of outer vertical reinforcing bars 12A are combined in a grid. In addition, the liquid barrier 10 is provided with an inner reinforcing reinforcing bar 13B in which a plurality of inner circumferential reinforcing bars 11B and a plurality of inner vertical reinforcing bars 12B are combined in a grid pattern.

The dike 10 includes a plurality of circumferential tendons 14 and a plurality of vertical tendons 15 . As these tendons 14 and 15, for example, PC steel materials such as PC steel wires and PC steel bars can be used.

The circumferential tendon 14 is a tendon extending along the entire circumference of the liquid barrier 10, and is provided with a plurality of tendons in the vertical direction at predetermined intervals. The circumferential tendon 14 is inserted into a circumferential sheath tube 17 extending circumferentially within the dike 10 . When the circumferential prestressing member 14 is tensioned, circumferential prestress is introduced into the dike 10, thereby applying a predetermined compressive stress to the concrete. As a result, the circumferential tensile force acting on the dike 10 due to the liquid pressure when LNG leaks from the tank body 2 can be resisted, and the liquid dike 10 is ensured to be liquid-tight. After tensioning the circumferential tendon 14, the circumferential sheath tube 17 is filled with a filling material such as mortar.

The vertical tendon 15 is a tendon arranged vertically in the liquid barrier 10, and a plurality of tendons are provided at predetermined intervals in the circumferential direction. The vertical tendon 15 is inserted into a vertical sheath tube 18 extending vertically through the dike 10 . When the vertical tendon 15 is tensioned, a vertical prestress is introduced into the dike 10 so that it can withstand the liquid pressure at the time of LNG leakage. In addition, when there is no leakage, a vertical bending moment caused by circumferential prestress acts on the dike 10, but by introducing a vertical prestress, it is possible to counteract this bending moment. Become. After the vertical tendon 15 is tensioned, the vertical sheath tube 18 is filled with a filler such as mortar.

In this embodiment, the dike 10 is constructed by a precast member 20 made of concrete. Specifically, as shown in FIG. 2, the dike 10 is constructed by arranging a plurality of precast members 20 side by side in the circumferential direction and piling them up in the vertical direction. Between the precast members 20 adjacent in the circumferential direction, vertical joints 19A are formed by filling concrete, the details of which will be described later, and horizontal joints 19B are formed by mortar or the like between the precast members 20 adjacent in the vertical direction. It is formed. Details of the precast member 20 according to the present embodiment will be described below.

[Precast parts]
FIG. 3 is a schematic perspective view showing the precast member 20 according to this embodiment. FIG. 4 is a schematic cross-sectional view illustrating a procedure for vertically connecting the precast members 20 according to this embodiment. FIG. 5 is a schematic cross-sectional view illustrating a procedure for circumferentially connecting the precast members 20 according to this embodiment.

As shown in FIG. 3, the precast member 20 includes a plate-shaped main body portion 21 that is substantially rectangular in front view and curved in an arc shape in top view, a plurality of circumferential sheath tubes 17, and a plurality of It has a vertical sheath tube 18, an outer reinforcing bar 13A, and an inner reinforcing bar 13B.

The body portion 21 is constructed so as to integrally include the sheath pipes 17 and 18 and the reinforcing reinforcing bars 13A and 13B by pouring and filling concrete in the formwork in a factory or the like in advance. In addition, below, the curved outer side of the main-body part 21 is only called an outer side, and the curved inner side is called an inner side.

The plurality of circumferential sheath tubes 17 are embedded in the main body 21 at predetermined intervals in the vertical direction. One end of the circumferential sheath tube 17 in the tube axis direction opens to the one end surface 22A of the body portion 21, and the other end of the circumferential sheath tube 17 in the tube axis direction opens to the other end surface 22B of the body portion 21. The number of circumferential sheath tubes 17 is not limited to the illustrated example, and may be an optimum number according to construction conditions and the like.

A plurality of vertical sheath tubes 18 are embedded in the main body 21 at predetermined intervals in the circumferential direction. The upper end opening of the vertical sheath tube 18 is located on the upper surface 23A side of the main body 21 , and the lower end opening of the vertical sheath tube 18 is located on the lower surface 23B side of the main body 21 . Here, the upper and lower ends of the vertical sheath tube 18 are provided with socket-shaped male and female couplers that can be fitted so that they can be easily connected to the vertical sheath tubes 18 of other precast members 20 stacked on the upper side. may be provided. The vertical sheath tube 18 is preferably embedded inside the body portion 21 relative to the circumferential sheath tube 17 . The number of vertical sheath pipes 18 is not limited to the illustrated example, and may be an optimum number according to construction conditions and the like.

The outer reinforcing bar 13A is embedded outside the circumferential sheath tube 17 of the main body 21 . Specifically, the outer reinforcing reinforcing bars 13A are configured by combining a plurality of outer circumferential reinforcing bars 11A and a plurality of outer vertical reinforcing bars 12A in a grid pattern. Both ends of the outer circumferential reinforcing bar 11A are provided so as to be exposed in outer notch portions 24A and 24B, which will be described later. A lower end portion of the outer vertical reinforcing bar 12A is provided so as to protrude downward from a lower surface 23B of the main body portion 21 by a predetermined amount. The number of reinforcing bars 11A and 12A is not limited to the illustrated example, and may be an optimum number according to construction conditions and the like.

The inner reinforcing bar 13B is embedded inside the vertical sheath pipe 18 of the main body 21 . Specifically, the inner reinforcing reinforcing bars 13B are configured by combining a plurality of inner circumferential reinforcing bars 11B and a plurality of inner vertical reinforcing bars 12B in a grid pattern. Both ends of the inner circumferential reinforcing bar 11B are provided so as to be exposed in inner notch portions 26A and 26B, which will be described later. A lower end portion of the inner vertical reinforcing bar 12B is provided so as to protrude downward from a lower surface 23B of the main body portion 21 by a predetermined amount. The number of reinforcing bars 11B and 12B is not limited to the illustrated example, and may be an optimum number according to construction conditions and the like.

The body portion 21 is provided with a plurality of outer cylindrical holes 28A and inner cylindrical holes 28B recessed downward from the upper surface 23A to a predetermined depth. The outer cylindrical hole 28A is formed coaxially with the outer vertical reinforcing bar 12A, and the inner cylindrical hole 28B is formed coaxially with the inner vertical reinforcing bar 12B. The hole diameter of each of the cylindrical holes 28A and 28B is formed to be larger than the diameter of each of the vertical reinforcing bars 12A and 12B. Vertical rebars 12A and 12B are inserted respectively.

Specifically, as shown in FIG. 4, cylindrical couplers C are provided at the upper ends of the vertical reinforcing bars 12A and 12B positioned on the bottom side of the cylindrical holes 28A and 28B. When stacking the precast members 20', the lower ends of the vertical reinforcing bars 12A' and 12B' of the precast members 20' are inserted into the cylindrical holes 28A and 28B of the precast members 20 on the lower side and fitted into the couplers C. , upper and lower vertical reinforcing bars 12A, 12A', 12B, 12B' are joined to each other. The filler M such as mortar to be filled between the upper and lower precast members 20 and 20' may be provided in advance on the upper surface 23A of the lower precast member 20, or may be stacked on the upper precast member 20'. It may be placed and filled later. When the filler material M is solidified, the upper and lower precast members 20, 20' are integrated (rigidly connected).

As shown in FIG. 3, at two corners where the outer surface 22C of the body 21 intersects with the end surfaces 22A and 22B, a pair of outer cutouts 24A and 24B which are approximately L-shaped when viewed from above are provided. is provided. A pair of inner cutouts 26A and 26B that are substantially L-shaped when viewed from above are provided at two corners where the inner surface 22D of the main body 21 intersects with the end surfaces 22A and 22B. . These outer notch portions 24A and 24B and inner notch portions 26A and 26B are provided over the entire height of the main body portion 21 .

The ends of the outer circumferential reinforcing bars 11A are exposed in the inner spaces of the outer cutouts 24A and 24B, and the ends of the inner circumferential reinforcing bars 11B are exposed in the inner spaces of the inner cutouts 26A and 26B. do. These circumferential reinforcing bars 11A, 11B are joined to each other with circumferential reinforcing bars 11A, 11B of other precast members 20 that are adjacently arranged in the circumferential direction. The circumferential reinforcing bars 11A and 11B may be joined together by any of a mechanical joint, a lap joint, and a gas pressure joint.

As shown in FIG. 5A, when connecting the precast members 20 and 20' in the circumferential direction, the end face 22A of the main body portion 21 and the end face 22B' of the main body portion 21' are brought into surface contact with each other. When the end faces 22A, 22B' are brought into surface contact, the outer notch portions 24A, 24B' and the inner notch portions 26A, 26B' face each other, thereby forming the outer concave portion 25 and the outer concave portion 25 between the precast members 20, 20'. , an inner recess 27 is defined.

In constructing the dike 10, a plurality of precast members 20, 20', . Since the end surfaces 22A, 22B' of the adjacent precast members 20, 20' are in surface contact with each other, the annular wall body has the circumferential reinforcing bars 11A, 11A', 11B, 11B exposed in the recesses 25, 27. ' ends are fastened with temporary bolts such as mechanical joints, or temporary circumferential tendons 14 ′ (for example, the number is smaller than the permanent circumferential tendons 14 in the circumferential sheath tube 17 Pre-tensioning is performed by inserting a tension material), or the precast members 20, 20' are fastened with embedded bolts provided in advance with nuts, so that the entire circumference can be integrated.

That is, one lot of precast members 20, 20', . configured to allow As a result, it is possible to install the precast members 20 of the next lot in multiple stages without placing interstitial concrete between each precast member as in the conventional technology, and it is possible to effectively improve the workability. Become. In addition, since the end faces 22A, 22B' of the precast members 20, 20' are brought into surface contact and a seal ring or the like is sandwiched between the ends of the circumferential sheath pipes 17, 17', a water-tight connection can be achieved. It is also possible to reduce the incidental work at the time of connection, such as the work of connecting the required sheath tubes with the connecting sheath tube and bringing the heat-shrinkable tubes into close contact with each other.

After installing a plurality of lots in multiple stages, as shown in FIG. Filling concrete 30, 31 is placed respectively. At this time, a plurality of lots of the outer filling concrete 30 and the inner filling concrete 31 can be collectively constructed in a vertical direction. That is, unlike the prior art, it is no longer necessary to place interstitial concrete for each lot, and the construction period for the dike 10 can be greatly shortened.

In addition, by placing the outer filling concrete 30 in the outer recess 25 and introducing prestress in the circumferential direction, the outer peripheral portion between the precast members 20 and 20' can withstand the liquid pressure at the time of LNG leakage. A compression area is secured. This makes it possible to reliably improve the liquid tightness of the dike 10 . Here, the outer filling concrete 30 is formed with a depression amount of 10 cm or more from the outer side surface 22C of the outer notch portions 24A and 24B, and can secure a thickness of 10 cm or more in the compression area specified by the LNG above-ground storage tank guidelines. You should do it like this.

In addition, by placing the inner filling concrete 31 in the inner recessed portion 27 and embedding the circumferential reinforcing bars 11B, the resistance of the entire liquid barrier 10 can be effectively improved. As a result, the tensile force in the circumferential direction and the bending moment can be resisted without significantly increasing the number of tendons 14 and 15, so that the structure can be simplified and the cost can be reduced.

[Method of constructing a dike]
Next, a method for constructing the dike 10 using the precast member 20 according to this embodiment will be described with reference to FIGS. In the following description, the construction of the bottom slab 5 is completed, but the construction method of the present disclosure may or may not include the construction of the bottom slab 5 .

In the first step shown in FIG. 6, a plurality of precast members 20 are arranged in parallel on the upper surface of the bottom plate 5 in the circumferential direction. At this time, the adjacent precast members 20 are arranged with their end surfaces 22A and 22B in surface contact with each other. After the plurality of precast members 20 are arranged in an annular shape, the ends of the circumferential reinforcing bars 11A and 11B exposed in the recesses 25 and 27 are fastened and fixed with temporary bolts such as mechanical joints, or A temporary circumferential tension member 14' (see FIG. 5(A)) is inserted into the sheath tube 17 and temporarily tensioned to form an annular wall body W1 integrated around the entire circumference. The first step corresponds to part of the wall forming step of the present disclosure.

In the second step shown in FIG. 7, a plurality of precast members 20 are stacked on the upper portion of the annular wall W1 and arranged side by side in the circumferential direction, and the same operation as in the first step is performed to obtain each precast member 20 form an annular wall body W2 integrally around the circumference. At this time, the upper and lower precast members 20 adjacent to each other in the vertical direction are integrated by the filler M placed between them. The second step may be performed only once, or may be performed multiple times so that the annular wall bodies W1, W2, . . . The number of steps to stack the annular walls W1, W2, . The second step corresponds to part of the wall forming step of the present disclosure.

As shown in FIG. 8, when a cylindrical wall body WC is constructed by stacking a plurality of stages (three stages in the illustrated example) of annular wall bodies W1, 2, 3, . . . A plurality of stages of filling concrete 30 and 31 are put together in the outer concave portion 25 and the inner concave portion 27 in a batch in the vertical direction. When the interfilling concrete 30, 31 hardens, the precast members 20 adjacent in the circumferential direction are rigidly connected to each other. Here, the order of placing the outer and inner filling concretes 30 and 31 is not particularly limited, and one of them may be placed first, or they may be placed at the same time. The third step corresponds to the placing step of the present disclosure.

After the fourth step shown in FIG. 9, the above-described second and third steps are repeated an appropriate number of times, and by stacking the annular wall bodies W4, 5, . . . start up. The number of times the second and third steps are repeated may be appropriately determined according to the height of the dike 10 to be constructed. When the cylindrical wall body WC is raised to the desired height, the final process is started. In the above-mentioned second step, when the cylindrical wall bodies WC are collectively piled up to the height of the dike 10, after the third step is performed, the fourth step is omitted and the final step is directly performed. should be transferred.

In the final step shown in FIG. 10, the temporary circumferential tendon 14' in the circumferential sheath pipe 17 (see FIG. 3) is replaced with the permanent circumferential tendon 14, and the vertical sheath pipe 18 (see FIG. 3) ), and by tensioning these tendons 14 and 15, circumferential and vertical prestresses are introduced into the dike 10. As shown in FIG. After the prestress is introduced, the sheath pipes 17 and 18 are filled with a filler such as mortar, and construction of the liquid barrier 10 is completed.

The dike 10 completed in this manner has a full cross-sectional compression area including the interfilling concretes 30 and 31, and the liquid-tightness of the dike 10 can be reliably improved. In addition, since the interstitial concrete 30 and 31 can be collectively constructed in a plurality of stages, the workability can be reliably improved, and the construction period can be shortened.

[others]
It should be noted that the present disclosure is not limited to the above-described embodiments, and can be appropriately modified and implemented without departing from the gist of the present disclosure.

For example, as shown in FIG. 11, one end face 22A of the body portion 21 is provided with a convex portion 29A extending in the vertical direction, and the other end face 22B of the body portion 21 is provided with a groove 29B extending in the vertical direction. When arranged side by side in the same direction, the projections 29A and the grooves 29B may be fitted to each other. With this configuration, it is possible to stably connect the precast members 20 in the circumferential direction.

Further, although the precast member 20 has been described as having both the outer recess 25 and the inner recess 27, it may be configured to have only the outer recess 25. FIG. In this case as well, by forming a compression region in the outer peripheral portion of the liquid barrier 10, the liquid tightness of the liquid barrier 10 can be effectively ensured. Alternatively, only the interstitial concrete 30, 31 may be placed in the recesses 25, 27 without exposing the circumferential reinforcing bars 11A, 11B.

Further, the application of the present disclosure is not limited to the liquid barrier 10 of the PC tank 1, and can be widely applied to the construction of other concrete structures.

DESCRIPTION OF SYMBOLS 1... PC tank, 2... Tank main body, 3... Inner tank, 4... Outer tank, 5... Bottom plate, 6... Pile, 10... Liquid barrier, 11A, 11B... Circumferential reinforcing bar, 12A, 12B... Vertical reinforcing bar, DESCRIPTION OF SYMBOLS 13A, 13B... Reinforcing bar, 14... Circumferential tendon, 15... Vertical tendon, 17... Circumferential sheath tube, 18... Vertical sheath tube, 20... Precast member, 21... Body part, 22A, 22B... End surface , 22C, 22D... Side surface, 24A, 24B... Outer notch, 25... Outer recess, 26A, 26B... Inner notch, 27... Inner recess, 28A, 28B... Cylindrical hole

Claims (9)

A precast member that constitutes a cylindrical liquid barrier that surrounds the outer periphery of the liquid storage tank,
a concrete main body having a rectangular shape when viewed from the front and curved in an arc shape when viewed from the top;
an outer notch portion obtained by notching a corner portion where the curved outer surface and the circumferential end surface of the body portion intersect,
The outer cut-out portion faces the outer cut-out portion of another precast member that is adjacently arranged with the circumferential end surfaces thereof in surface contact with each other, thereby enabling filling concrete to be placed on the outer peripheral side of the dike. A precast member defining a large outer recess. further comprising an outer circumferential reinforcing bar extending circumferentially within the main body and having an end exposed within the outer notch;
The precast member according to claim 1, wherein the ends of the outer circumferential reinforcing bars are joined to the ends of the outer circumferential reinforcing bars of the other precast member. further comprising an inner notch formed by notching a corner where the curved inner surface and the circumferential end surface of the main body intersect,
3. The inner notch faces the inner notch of the other precast member, thereby defining an inner recess in which filling concrete can be placed on the inner peripheral side of the dike. A precast member according to . further comprising an inner circumferential reinforcing bar extending circumferentially within the main body and having an end exposed within the inner notch;
4. The precast member according to claim 3, wherein the ends of the inner circumferential reinforcing bars are joined to the ends of the inner circumferential reinforcing bars of the other precast member. 5. A circumferential sheath tube extending circumferentially within the main body and into which a circumferential tendon capable of introducing a circumferential prestress to the dike is inserted, further comprising a circumferential sheath tube. A precast member according to . 6. A vertical sheath pipe extending vertically in the main body and into which a vertical tendon capable of introducing a vertical prestress to the dike is inserted, further comprising a vertical sheath pipe. A precast member according to . A liquid barrier constructed by arranging the precast members according to any one of claims 1 to 6 side by side in the circumferential direction and rigidly connecting them, and stacking them in the vertical direction and rigidly connecting them. A method for constructing a dike using the precast member according to any one of claims 1 to 6,
A plurality of the precast members are arranged in parallel in the circumferential direction so that the circumferential end faces are in surface contact with each other, and the precast members adjacent in the circumferential direction are temporarily connected to form a one-step annular wall that is integrated all around. a wall body forming step of forming a body and stacking the annular wall bodies in a plurality of stages to form a cylindrical wall body;
and a step of collectively placing the filling concrete against the cylindrical wall body at least once, and
A method of constructing a dike, characterized in that prestress is introduced by providing permanent tension members in the cylindrical wall formed to a predetermined height and tensioning them. In the wall forming step, when the precast members adjacent in the circumferential direction are temporarily connected, a temporary circumferential tension material is provided on the annular wall and tensioned, so that the annular wall is integrally formed around the entire circumference. The method for constructing a dike according to claim 8.

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