Precast components, flood barriers, and methods for constructing flood barriers

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

[Technical field]

[0001] The present disclosure relates to precast members, flood barriers, and methods of constructing flood barriers. [Background technology]

[0002] Conventionally, prestressed concrete tanks (hereinafter referred to as PC tanks) have been used as tanks for storing liquefied gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

[0003] PC tanks have a tank body with a steel outer tank and inner tank, and are configured to prevent liquid from leaking outside in the event of damage to the inner tank or other parts by constructing a cylindrical liquid containment dike along the outer periphery of the tank body.

[0004] One method for constructing this type of flood barrier is to use a precast construction method, in which precast concrete components manufactured in advance at a factory or the like are transported to the site and connected together, thereby shortening construction time and reducing costs (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-078268 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the above precast construction method, multiple precast members are placed at intervals around the circumference of the dike, and weatherstripping concrete is poured between each precast member to form a circular wall in which the precast members are integrated all around the circumference. The circular wall is then counted as one lot, and successive lots are stacked on top of each other in the height direction to build a dike of a specified height.

[0007] In this type of precast construction method, adjacent precast members in the circumferential direction remain independent of each other until the interfacial concrete hardens, and until one lot is integrated all around, the next lot cannot be installed on top of it in multiple tiers as a measure against wind load. This means that interfacial concrete must be poured for each lot, which takes time and effort, lengthening the construction period.

[0008] In addition, prestress is introduced into the flood barrier using tension members, which are inserted into sheath pipes embedded in the precast members. If the precast members are spaced apart in the circumferential direction, as in the above-mentioned precast construction method, the ends of the circumferential sheath pipes between the precast members must be connected with connecting sheath pipes, and watertight connections, such as by heating heat shrink tubing to seal them tightly, must be made to prevent filling concrete from seeping in through these connections, which creates the problem of additional work taking time and effort.

[0009] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a technology for constructing flood control dikes that is easy to work with and can shorten construction time. [Means for solving the problem]

[0010] The precast member of the present disclosure is a precast member that constitutes a cylindrical liquid containment dike that surrounds the outer periphery of a liquid storage tank, and comprises a main body made of concrete that is rectangular when viewed from the front and curved like an arc when viewed from above, and an outer cut-out portion that cuts out the corner where the curved outer surface of the main body intersects with the circumferential end face, and is characterized in that the outer cut-out portion faces the outer cut-out portion of another precast member that is arranged adjacently and has its circumferential end faces in face-to-face contact with each other, thereby defining an outer recess on the outer periphery of the liquid containment dike into which filling concrete can be poured.

[0011] It is also preferable that the precast member further includes an outer circumferential reinforcing bar extending circumferentially within the main body portion and having an end exposed within the outer cutout portion, and the end of the outer circumferential reinforcing bar is joined to the end of the outer circumferential reinforcing bar of the other precast member.

[0012] Furthermore, it is preferable that the main body further has an inner cutout portion cut out at the corner where the curved inner surface and the circumferential end face intersect, and that the inner cutout portion faces the inner cutout portion of the other precast member, thereby defining an inner recess on the inner side of the liquid retaining dike into which filling concrete can be poured.

[0013] It is also preferable that the precast member further includes an inner circumferential reinforcing bar extending circumferentially within the main body portion and having an end exposed within the inner cutout portion, and the end of the inner circumferential reinforcing bar is joined to the end of the inner circumferential reinforcing bar of the other precast member.

[0014] It is also preferable that the structure further comprises a circumferential sheath tube extending circumferentially within the main body and into which a circumferential tension member capable of introducing circumferential prestress into the liquid barrier is inserted.

[0015] It is also preferable that the dike further comprises a vertical sheath tube extending vertically within the main body and into which a vertical tension member capable of introducing vertical prestress into the dike is inserted.

[0016] The liquid retaining wall of the present disclosure is characterized in that it is constructed by arranging the precast members in a circumferential direction and rigidly connecting them, and by stacking and rigidly connecting them vertically.

[0017] The method for constructing a liquid containment dike disclosed herein is a method for constructing a liquid containment dike using the precast members, which comprises arranging a plurality of the precast members in a circumferential direction so that their circumferential end faces are in face contact with each other and temporarily connecting adjacent precast members in the circumferential direction to form a single stage of annular wall that is integrated all around, and repeating a wall formation process in which the annular walls are stacked in multiple stages to form a cylindrical wall, and a pouring process in which the filler concrete is poured into the cylindrical wall all at once at least once, and introducing prestress by providing permanent circumferential tension members to the cylindrical wall formed to a predetermined height and tensioning it.

[0018] In addition, in the wall forming process, when temporarily connecting adjacent precast members in the circumferential direction, it is preferable to provide temporary circumferential tension members in the annular wall body and tension it, thereby integrating the annular wall body all around. Effect of the Invention

[0019] According to the technology disclosed herein, the construction of a flood barrier can be achieved with excellent workability and with a shorter construction period. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic vertical cross-sectional view showing a portion of the PC tank according to the present embodiment. [Diagram 2] FIG. 2 is a schematic perspective view showing a PC tank according to the present embodiment. [Diagram 3] FIG. 2 is a schematic perspective view showing a precast member according to the present embodiment. [Figure 4] A schematic cross-sectional view illustrating the procedure for vertically connecting precast members according to this embodiment. [Diagram 5]A schematic cross-sectional view illustrating the procedure for connecting precast members in the circumferential direction in this embodiment. [Figure 6] FIG. 1 is a schematic diagram illustrating a method for constructing a flood barrier using precast members according to this embodiment. [Figure 7] FIG. 1 is a schematic diagram illustrating a method for constructing a flood barrier using precast members according to this embodiment. [Figure 8] FIG. 1 is a schematic diagram illustrating a method for constructing a flood barrier using precast members according to this embodiment. [Figure 9] FIG. 1 is a schematic diagram illustrating a method for constructing a flood barrier using precast members according to this embodiment. [Figure 10] FIG. 1 is a schematic diagram illustrating a method for constructing a flood barrier using precast members according to this embodiment. [Figure 11] FIG. 11 is a schematic perspective view showing a precast member according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the precast member, the flood barrier, and the method for constructing the flood barrier according to the present embodiment will be described with reference to the accompanying drawings. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

[0022] [PC Tank] FIG. 1 is a schematic vertical cross-sectional view showing a 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.

[0023] 1 and 2 is an aboveground tank that stores liquefied gas such as LNG or LPG. Note that the material stored in the PC tank 1 may be liquid other than liquefied gas, such as liquefied hydrogen, but the following description will be given taking LNG as an example.

[0024] As shown in Fig. 1, the PC tank 1 comprises a tank body 2, a bottom slab 5, multiple piles 6, and a liquid retaining dike 10 surrounding the outer periphery of the tank body 2. Note that the multiple piles 6 are not essential, and the bottom slab 5 can be supported directly on the ground depending on the specific size of the PC tank 1, ground conditions, etc.

[0025] The tank body 2 has a generally hollow cylindrical shape with closed upper and lower portions, and includes 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 formed, for example, from a steel plate or the like. A heat insulating material or the like is interposed between the inner tank 3 and the outer tank 4, and the LNG is kept cold between the inner tank 3 and the outer tank 4.

[0026] The bottom slab 5 is, for example, a reinforced concrete structure, and is formed in a substantially disk shape. In the illustrated example, the bottom slab 5 is supported by a plurality of piles 6 buried in the ground, but the piles 6 may be omitted depending on the ground conditions, etc. The tank body 2 and the liquid retaining dike 10 are installed on the upper surface of the bottom slab 5.

[0027] The liquid retaining dike 10 is a cylindrical prestressed concrete wall rising from the bottom slab 5, and is constructed in a generally cylindrical shape with an open top so as to surround the outer periphery of the tank body 2. The liquid retaining dike 10 is provided with outer reinforcing bars 13A consisting of a plurality of outer circumferential reinforcing bars 11A and a plurality of outer vertical reinforcing bars 12A combined in a lattice pattern. The liquid retaining dike 10 is also provided with inner reinforcing bars 13B consisting of a plurality of inner circumferential reinforcing bars 11B and a plurality of inner vertical reinforcing bars 12B combined in a lattice pattern.

[0028] The dike 10 includes a plurality of circumferential tendons 14 and a plurality of vertical tendons 15. As these tendons 14, 15, for example, PC steel materials such as PC steel wires and PC steel bars can be used.

[0029] The circumferential tendons 14 extend around the entire circumference of the dike 10 in the circumferential direction, and a plurality of them are provided at predetermined intervals in the vertical direction. The circumferential tendons 14 are inserted into circumferential sheath tubes 17 extending circumferentially within the dike 10. When the circumferential tendons 14 are tensioned, circumferential prestress is introduced into the dike 10, and a predetermined compressive stress is applied to the concrete. This makes it possible to counter the circumferential tensile force acting on the dike 10 due to the liquid pressure when LNG leaks from the tank body 2, and ensures the liquid-tightness of the dike 10. After the circumferential tendons 14 are tensioned, a filler such as mortar is filled into the circumferential sheath tube 17.

[0030] The vertical tendons 15 are disposed vertically within the dike 10, and a plurality of them are provided at a predetermined interval in the circumferential direction. The vertical tendons 15 are inserted into vertical sheath tubes 18 extending vertically within the dike 10. When the vertical tendons 15 are tensioned, a vertical prestress is introduced into the dike 10, which makes it possible to counteract the liquid pressure in the event of an LNG leak. In addition, a vertical bending moment caused by the circumferential prestress acts on the dike 10 during normal times when there is no leakage, but by introducing the vertical prestress, it becomes possible to counteract this bending moment as well. After the vertical tendons 15 are tensioned, a filler such as mortar is filled into the vertical sheath tube 18.

[0031] In this embodiment, the flood barrier 10 is composed of precast members 20 made of concrete. Specifically, as shown in Fig. 2, the flood barrier 10 is constructed by arranging a plurality of precast members 20 side by side in the circumferential direction and stacking them up in the vertical direction. Vertical joints 19A made of filling concrete, which will be described in detail later, are formed between each of the precast members 20 adjacent in the circumferential direction, and horizontal joints 19B made of mortar or the like are formed between each of the precast members 20 adjacent in the vertical direction. Details of the precast members 20 according to this embodiment will be described below.

[0032] [Precast materials] Fig. 3 is a schematic perspective view showing the precast members 20 according to this embodiment. Fig. 4 is a schematic cross-sectional view explaining a procedure for connecting the precast members 20 according to this embodiment in the vertical direction. Fig. 5 is a schematic cross-sectional view explaining a procedure for connecting the precast members 20 according to this embodiment in the circumferential direction.

[0033] As shown in Figure 3, the precast member 20 has a plate-shaped main body 21 that is approximately rectangular when viewed from the front and curved like an arc when viewed from above, a plurality of circumferential sheath tubes 17, a plurality of vertical sheath tubes 18, outer reinforcing bars 13A, and inner reinforcing bars 13B.

[0034] The main body 21 is configured in advance in a factory or the like by pouring and filling concrete into a formwork so as to integrally include the sheath pipes 17, 18 and the reinforcing bars 13A, 13B. In the following description, the outer side of the curve of the main body 21 is simply referred to as the outer side, and the inner side of the curve is simply referred to as the inner side.

[0035] The multiple circumferential sheath tubes 17 are embedded at predetermined intervals in the up-down direction in the main body 21. One end in the tube axis direction of each of the circumferential sheath tubes 17 opens into one end face 22A of the main body 21, and the other end in the tube axis direction of each of the circumferential sheath tubes 17 opens into the other end face 22B of the main body 21. The number of circumferential sheath tubes 17 is not limited to the illustrated example, and may be an optimal number depending on the construction conditions, etc.

[0036] A plurality of vertical sheath tubes 18 are embedded in the main body 21 at a predetermined interval in the circumferential direction. The upper end openings of the vertical sheath tubes 18 are located on the upper surface 23A side of the main body 21, and the lower end openings of the vertical sheath tubes 18 are located on the lower surface 23B side of the main body 21. Here, the upper and lower ends of the vertical sheath tubes 18 may be provided with male and female couplers in the shape of sockets that can be fitted in order to easily connect the vertical sheath tubes 18 of other precast members 20 stacked on the upper tier side. The vertical sheath tubes 18 are preferably embedded inwardly of the circumferential sheath tubes 17 of the main body 21. The number of the vertical sheath tubes 18 is not limited to the illustrated example, and may be an optimal number according to the construction conditions, etc.

[0037] The outer reinforcing bars 13A are embedded outside the circumferential sheath tube 17 of the main body 21. Specifically, the outer reinforcing bars 13A are formed by combining a plurality of outer circumferential reinforcing bars 11A and a plurality of outer vertical reinforcing bars 12A in a lattice pattern. Both ends of the outer circumferential reinforcing bars 11A are provided so as to be exposed in the outer cutouts 24A, 24B described later. The lower ends of the outer vertical reinforcing bars 12A are provided so as to protrude downward by a predetermined amount from the lower surface 23B of the main body 21. The number of each reinforcing bar 11A, 12A is not limited to the illustrated example, and may be an optimal number according to the construction conditions, etc.

[0038] The inner reinforcing bar 13B is embedded inside the vertical sheath tube 18 of the main body 21. Specifically, the inner reinforcing bar 13B is formed by combining a plurality of inner circumferential reinforcing bars 11B and a plurality of inner vertical reinforcing bars 12B in a lattice pattern. Both ends of the inner circumferential reinforcing bars 11B are provided so as to be exposed in inner cutouts 26A, 26B described below. The lower end of the inner vertical reinforcing bar 12B is provided so as to protrude downward by a predetermined amount from the lower surface 23B of the main body 21. The number of each reinforcing bar 11B, 12B is not limited to the illustrated example, and may be an optimal number according to the construction conditions, etc.

[0039] The main body 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 holes 28A are formed coaxially with the outer vertical reinforcing bars 12A, and the inner cylindrical holes 28B are formed coaxially with the inner vertical reinforcing bars 12B. The hole diameters of the cylindrical holes 28A, 28B are formed to be larger than the reinforcing bar diameters of the vertical reinforcing bars 12A, 12B, and the vertical reinforcing bars 12A, 12B of the other precast members 20 stacked on the upper tier are inserted into the cylindrical holes 28A, 28B, respectively.

[0040] Specifically, as shown in FIG. 4, a cylindrical coupler C is provided at the upper end of the vertical reinforcing bars 12A, 12B located at the bottom side of the cylindrical holes 28A, 28B. When stacking the precast members 20', the lower end side of the vertical reinforcing bars 12A', 12B' of the precast member 20' is inserted into the cylindrical holes 28A, 28B of the precast member 20 on the lower stage side and fitted into the coupler C, so that the 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, 20' may be provided in advance on the upper surface 23A of the precast member 20 on the lower stage side, or may be poured and filled after the precast member 20' on the upper stage side is stacked. When the filler M solidifies, the upper and lower precast members 20, 20' are integrated (rigidly connected).

[0041] 3, a pair of outer cutouts 24A, 24B having a substantially L-shape in top view are provided at two corners where the outer side surface 22C of the main body 21 intersects with the end surfaces 22A, 22B. A pair of inner cutouts 26A, 26B having a substantially L-shape in top view are provided at two corners where the inner side surface 22D of the main body 21 intersects with the end surfaces 22A, 22B. These outer cutouts 24A, 24B and inner cutouts 26A, 26B are provided over the entire height of the main body 21.

[0042] The ends of the outer circumferential reinforcing bars 11A are exposed in the internal spaces of the outer cutouts 24A and 24B, respectively, and the ends of the inner circumferential reinforcing bars 11B are exposed in the internal spaces of the inner cutouts 26A and 26B, respectively. These circumferential reinforcing bars 11A and 11B are joined to the circumferential reinforcing bars 11A and 11B of other precast members 20 that are arranged adjacent to each other in the circumferential direction. The joining of the circumferential reinforcing bars 11A and 11B to each other may be any of a mechanical joint, a lap joint, and a gas pressure welding joint.

[0043] As shown in Fig. 5(A), when connecting precast members 20, 20' in the circumferential direction, end face 22A of main body 21 and end face 22B' of main body 21' are brought into surface contact with each other. When end faces 22A, 22B' are brought into surface contact, outer cutout portions 24A, 24B' and inner cutout portions 26A, 26B' ​​face each other, thereby defining outer recesses 25 and inner recesses 27 between each of precast members 20, 20'.

[0044] In constructing the flood barrier 10, a number of precast members 20, 20'... are sequentially arranged in a line in the circumferential direction and connected to form one lot of annular wall. Since the end faces 22A, 22B' of adjacent precast members 20, 20' are in surface contact with each other, the annular wall can be integrated all around by fastening the ends of the circumferential reinforcing bars 11A, 11A', 11B, 11B' exposed in the recesses 25, 27 together with temporary bolts such as mechanical joints, or by inserting temporary circumferential tendons 14' (e.g., tendons with fewer numbers than the permanent circumferential tendons 14) into the circumferential sheath tube 17 for temporary tensioning, or by fastening buried bolts previously provided in the precast members 20, 20' with nuts.

[0045] That is, the precast members 20, 20' for one lot can be easily integrated all around by temporary bolts or tension members 14' without pouring filler concrete between each precast member 20, 20'. This makes it possible to install the next lot of precast members 20 in multiple stages without pouring filler concrete between each precast member as in the conventional technology, and effectively improves workability. In addition, the end faces 22A, 22B' of each precast member 20, 20' are brought into surface contact with each other, and a seal ring or the like is sandwiched between the ends of the circumferential sheath tubes 17, 17' to perform a watertight connection, so that it is possible to reduce incidental work required in the conventional technology when connecting sheath tubes, such as the work of connecting the sheath tubes with a connecting sheath tube and tightly attaching the heat shrink tube.

[0046] Once multiple lots have been installed in multiple tiers, formwork (not shown) is placed on the outside and inside between each precast member 20, 20', as shown in Figure 5(B), and filler concrete 30, 31 is poured into the outside recess 25 and the inside recess 27, respectively. At this time, the outside filler concrete 30 and the inside filler concrete 31 can be applied collectively in the vertical direction for multiple lots. In other words, it is no longer necessary to pour filler concrete for each lot as in the conventional technology, and it is possible to significantly shorten the construction period of the flood control dike 10.

[0047] Furthermore, by pouring outer filler concrete 30 into the outer recess 25 to introduce circumferential prestress, a compression area capable of withstanding liquid pressure in the event of an LNG leak is secured in the outer peripheral portion between each of the precast members 20, 20'. This reliably improves the liquid-tightness of the liquid retaining dike 10. Here, the outer filler concrete 30 should be formed so that the recess amount from the outer surface 22C of the outer cutout portions 24A, 24B is 10 cm or more, and a compression area thickness of 10 cm or more as stipulated in the Guidelines for Aboveground LNG Storage Tanks can be secured.

[0048] Moreover, by pouring inner filling concrete 31 into the inner recess 27 and burying the circumferential reinforcing bars 11B, the strength of the entire floodgate 10 can be effectively improved. This makes it possible to resist circumferential tensile forces and bending moments without significantly increasing the number of tendons 14, 15, simplifying the structure and reducing costs.

[0049] [How to build a flood barrier] Next, a method for constructing a flood barrier 10 using the precast members 20 according to this embodiment will be described with reference to Figures 6 to 10. Note that, although the following description will be given starting from a state where construction of the base slab 5 has been completed, the construction method of the present disclosure may or may not include construction of the base slab 5.

[0050] In the first step shown in Fig. 6, a plurality of precast members 20 are arranged in the circumferential direction on the upper surface of the base slab 5. At this time, adjacent precast members 20 are arranged with their end faces 22A, 22B in surface contact with each other. Once the plurality of precast members 20 are arranged in an annular shape, the ends of the circumferential reinforcing bars 11A, 11B exposed in the recesses 25, 27 are fastened together with temporary bolts such as mechanical joints, or a temporary circumferential tension member 14' (see Fig. 5(A)) is inserted into the circumferential sheath tube 17 and temporarily tensioned to form an annular wall W1 integrated all around. The first step corresponds to a part of the wall formation step of the present disclosure.

[0051] In the second step shown in FIG. 7, a plurality of precast members 20 are stacked on top of the annular wall body W1 and arranged in parallel in the circumferential direction, and the same operation as in the first step is performed to form an annular wall body W2 in which the precast members 20 are integrated all around. At this time, the upper and lower precast members 20 adjacent in the vertical direction are integrated by the filler M poured between them. The second step may be performed only once, or may be performed multiple times to stack the annular walls W1, W2, etc. in three or more stages. The number of stages to stack the annular walls W1, W2, etc. may be appropriately determined depending on the construction conditions such as the height and outer diameter of the flood barrier 10 and the dimensions of the precast members 20. The second step corresponds to a part of the wall formation step of the present disclosure.

[0052] As shown in Fig. 8, if the annular walls W1, 2, 3, ... are stacked in multiple stages (three stages in the illustrated example) to construct a cylindrical wall body WC, in the third step, the filling concrete 30, 31 is poured vertically in multiple stages into the outer recess 25 and the inner recess 27 at once. When the filling concrete 30, 31 hardens, the precast members 20 adjacent in the circumferential direction are rigidly connected to each other. Here, the order in which the outer and inner filling concretes 30, 31 are poured is not particularly limited, and one may be poured first, or they may be poured simultaneously. The third step corresponds to the pouring step of the present disclosure.

[0053] From the fourth step shown in Fig. 9 onwards, the second and third steps described above are repeated an appropriate number of times to build up the annular walls W4,5..., thereby building up the cylindrical wall body WC in the vertical direction. The number of times the second and third steps are repeated may be determined appropriately depending on the height of the liquid barrier 10 to be constructed, etc. Once the cylindrical wall body WC has been built up to the desired height, the process moves to the final step. Note that if the cylindrical wall body WC is to be built up all at once to the height of the liquid barrier 10 in the second step described above, the fourth step may be omitted and the process may move directly to the final step after the third step is performed.

[0054] In the final step shown in Figure 10, the temporary circumferential tendon 14' in the circumferential sheath tube 17 (see Figure 3) is replaced with the permanent circumferential tendon 14, and the permanent vertical tendon 15 is inserted into the vertical sheath tube 18 (see Figure 3), and these tendons 14, 15 are tensioned to introduce circumferential and vertical prestress into the dike 10. Once prestress has been introduced, mortar or other filler is filled into each of the sheath tubes 17, 18, and construction of the dike 10 is completed.

[0055] The floodgate 10 completed in this way has a full cross-sectional compression area including the interfacial concrete 30, 31, which can reliably improve the liquid-tightness of the floodgate 10. In addition, since the interfacial concrete 30, 31 can be applied in a batch in multiple stages, it can reliably improve workability and shorten the construction period.

[0056] [others] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present disclosure.

[0057] 11, a convex portion 29A extending in the vertical direction may be provided on one end face 22A of the main body 21, and a concave groove 29B extending in the vertical direction may be provided on the other end face 22B of the main body 21, so that when the precast members 20 are arranged side by side in the circumferential direction, the convex portion 29A and the concave groove 29B may be configured to fit together. With this configuration, it is possible to stably connect the precast members 20 in the circumferential direction.

[0058] Furthermore, 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. In this case as well, by forming a compressed region on the outer periphery of the liquid retaining wall 10, the liquid-tightness of the liquid retaining wall 10 can be effectively ensured. Furthermore, it may be configured such that only filling concrete 30, 31 is poured in each recess 25, 27, without exposing the circumferential reinforcing bars 11A, 11B.

[0059] Furthermore, the application of the present disclosure is not limited to the liquid retaining dike 10 of the PC tank 1, but can also be widely applied to the construction of other concrete structures. [Explanation of symbols]

[0060] 1...PC tank, 2...tank body, 3...inner tank, 4...outer tank, 5...bottom slab, 6...pile, 10...levee, 11A, 11B...circumferential rebar, 12A, 12B...vertical rebar, 13A, 13B...reinforcing bar, 14...circumferential tension member, 15...vertical tension member, 17...circumferential sheath tube, 18...vertical sheath tube, 20...precast member, 21...main body, 22A, 22B...end face, 22C, 22D...side face, 24A, 24B...outer cutout, 25...outer recess, 26A, 26B...inner cutout, 27...inner recess, 28A, 28B...cylindrical hole

Claims

1. A precast member constituting a cylindrical liquid barrier surrounding the outer periphery of a liquid storage tank, A main body made of concrete that is rectangular in front view and curved in an arc in top view; an outer cutout portion formed by cutting out a corner portion where the curved outer surface of the main body portion and a circumferential end surface intersect; a circumferential sheath tube extending circumferentially within the main body and into which a circumferential tendon capable of introducing circumferential prestress into the dike is inserted, The outer cutout portion faces the outer cutout portion of another precast member that is disposed adjacent to the precast member with the circumferential end faces in surface contact with each other, thereby defining an outer recess on the outer periphery of the floodwall into which filling concrete can be poured. A precast member characterized by:

2. The steel structure further includes an outer circumferential reinforcing bar extending circumferentially within the body portion and having an end exposed within the outer cutout portion, The ends of the outer circumferential rebars are joined to the ends of the outer circumferential rebars of the other precast members. The precast component of claim 1 .

3. The curved inner surface of the main body and a circumferential end surface of the main body are intersected by a corner portion, and the curved inner surface and the circumferential end surface of the main body are cut out by the inner cutout portion. The inner cutout portion faces the inner cutout portion of the other precast member to define an inner recessed portion on the inner periphery side of the floodwall into which filling concrete can be poured. A precast member according to claim 1 or 2.

4. The steel structure further includes an inner circumferential reinforcing bar extending circumferentially within the main body portion and having an end exposed within the inner cutout portion, The ends of the inner circumferential rebars are joined to the ends of the inner circumferential rebars of the other precast members. The precast component of claim 3.

5. The dike further includes a vertical sheath tube extending vertically within the main body and into which a vertical tendon is inserted, the vertical tendon being capable of introducing vertical prestress into the dike. A precast component according to any one of claims 1 to 4.

6. A vertical reinforcing bar extending vertically within the main body portion and having a lower end protruding downward a predetermined amount from the bottom surface of the main body portion; A cylindrical hole recessed downward from the upper surface of the main body by a predetermined depth and formed coaxially with the vertical reinforcing bar, in which an upper end of the vertical reinforcing bar is disposed; a cylindrical coupler provided at an upper end of the vertical reinforcing bar located within the cylindrical hole, The coupler is fitted with a lower end side of another vertical reinforcing bar protruding downward from a second other precast member arranged on the upper surface of the main body, thereby connecting the vertical reinforcing bar and the other vertical reinforcing bar. A precast component according to any one of claims 1 to 5.

7. A flood barrier constructed by arranging precast members as claimed in any one of claims 1 to 6 in a circumferential direction, rigidly connecting them, and stacking and rigidly connecting them vertically.

8. A method for constructing a flood barrier using the precast members according to any one of claims 1 to 6, comprising the steps of: a wall forming process in which a plurality of the precast members are arranged in a circumferential direction, and their circumferential end faces are brought into surface contact with each other, and adjacent precast members are temporarily connected in the circumferential direction to form a single stage of annular wall body that is integrated all around, and the annular wall body is stacked up in a plurality of stages to form a cylindrical wall body; A pouring step of pouring the filling concrete into the cylindrical wall body at once. This step is repeated at least once. A prestress is introduced by providing a permanent circumferential tension member to the cylindrical wall formed to a predetermined height and tensioning it. A method for constructing a liquid retaining wall.

9. In the wall forming process, when the precast members adjacent in the circumferential direction are temporarily connected, the annular wall is tensioned by providing a temporary circumferential tension member to the annular wall, thereby integrating the annular wall all around. A method for constructing a flood barrier as claimed in claim 8.

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