JP7082888B2 - Construction method of tank bottom slab - Google Patents

Description

The present invention relates to a method of constructing a tank bottom slab.

In above-ground LNG tanks and underground LNG tanks, natural gas is cooled and stored in a liquefied state. A bottom heater is embedded in the bottom slab of the above-ground LNG tank and the underground LNG tank in order to prevent the foundation ground from freezing and expanding (see, for example, Patent Document 1). The bottom heater needs to be arranged so as not to come into contact with the reinforcing bars arranged in the bottom slab. The bottom heater is formed by disposing a heater member (for example, a heating wire or a heater tube) above the lower reinforcing bar arranged in the bottom slab of the tank.
The bottom slab is constructed by arranging the lower reinforcing bars, installing the pedestal for the bottom heater, installing the bottom heater using the pedestal for the bottom heater, installing the pedestal for reinforcing bars, and arranging the upper reinforcing bars using the pedestal for reinforcing bars. After performing in order, it is performed by placing concrete.

Japanese Unexamined Patent Publication No. 2009-299749

In the construction of the conventional tank bottom slab, it is necessary to carry out a large number of work steps in order from the arrangement of the lower reinforcing bars to the completion of the arrangement of the upper reinforcing bars, so that there is a limit to shortening the construction period. That is, the construction of the bottom heater could not be started until the installation of the bottom heater stand was completed. In addition, the work of arranging the upper reinforcing bars could not be started until the installation of the pedestal for arranging the reinforcing bars was completed after the bottom heater was installed. Further, although the bottom heater is formed by connecting a plurality of heater members, it takes time and effort to position the heater members. For example, when the bottom heater is composed of a heater tube piped in a spiral shape, it is difficult to position the pipe material in the intermediate portion. Therefore, it is necessary to connect the pipe materials by one-sided push construction, which is troublesome.
An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to propose a method for constructing a tank bottom slab that can shorten the construction period as compared with the conventional case.

In order to solve the above problems, the method of constructing the tank bottom slab of the present invention includes a lower reinforcing bar arranging step for arranging the lower reinforcing bar, a pedestal forming step for forming the bottom slab pedestal above the lower reinforcing bar, and the lower reinforcing bar. It is provided with a heater forming step of forming a bottom heater above the bottom plate, an upper reinforcing bar arranging step of arranging upper reinforcing bars on the bottom slab pedestal, and a placing step of placing concrete.
In the pedestal forming step, the bottom slab pedestal is formed by arranging a plurality of pedestal blocks including a scaffold and a heater member disposed below the scaffold. Further, in the heater forming step, the bottom heater is formed by connecting the heater members to each other.
According to the method of constructing the bottom slab, since the bottom slab has a scaffolding above the heater member, the upper reinforcing bars are arranged on the bottom slab in parallel with the construction of the bottom heater (heater forming process). Upper bar arrangement process) can be performed. Therefore, the construction period can be shortened. Further, since the bottom slab pedestal is formed by arranging a pedestal block provided with scaffolding and a heater member in advance, a conventional construction method in which a pedestal for a bottom heater and a pedestal for an upper reinforcing bar are individually formed. Compared to the above, the labor can be significantly reduced. Since the bottom heater may be installed by connecting the heater members arranged along with the installation of the gantry block, compared with the conventional construction method in which the heater members are positioned and connected after the heater members are carried in. And has excellent workability. The heater member includes, for example, a pipe material constituting the heater pipe, a heating wire, and the like.

It is desirable that the tank bottom slab construction method includes a temporary assembly step of forming the bottom slab pedestal at a temporary site provided at a position different from the tank construction site before the gantry forming step. In this case, in the gantry forming step, the bottom slab pedestal assembled in the temporary assembly step may be moved. Further, once the bottom pedestal is formed at the temporary site, the position of the heater member is determined, and at the time of the main installation, the bottom heater can be installed only by fine adjustment. Further, since the connecting portion of the heater member can be arranged at the joint portion between the gantry blocks, the workability is improved.
Further, in the gantry forming process, it is desirable to move the gantry block constituting the bottom slab pedestal from the temporary site to the tank construction site by using the lifting machine arranged between the tank construction site and the temporary site. By doing so, it is possible to reduce mistakes in the placement of the gantry block. Therefore, the positioning of the heater member is easy.
Further, in the gantry forming step, the heater member is temporarily fixed to the bottom slab pedestal in a state of being laterally displaced from a predetermined position, and in the heater forming process, the heater member is displaced to a predetermined position and then connected to another heater member. Is desirable. By doing so, it is possible to prevent the heater member from coming into contact with other members when installing the gantry block, and positioning is completed only by shifting the heater member, which is excellent in workability.

According to the construction method of the tank bottom slab of the present invention, it is possible to shorten the construction period as compared with the conventional construction method.

It is sectional drawing which shows the tank which concerns on embodiment of this invention. It is sectional drawing which shows a part of the tank bottom slab. It is a top view which shows the bottom slab stand. (A) is a perspective view showing the gantry block, and (b) is an enlarged side view showing the legs of the columns of the gantry block. (A) is a plan view showing the scaffolding of the gantry block, and (b) is a plan view showing the pipe support. It is a gantry block shown in FIG. 4, (a) is an arrow view of AA, and (b) is a view of arrow BB. It is a top view which shows a tank construction site and a temporary site. It is sectional drawing which shows the construction process of the construction method of the tank bottom slab, (a) is a lower bar arrangement process, (b) is a gantry forming process, (c) is a heater forming process.

In the present embodiment, a case where a tank bottom slab (hereinafter referred to as “bottom slab 10”) of an underground LNG tank (hereinafter referred to as “tank 1”) is constructed will be described. The tank 1 of the present embodiment is formed by a so-called membrane method, and as shown in FIG. 1, shields the bottom slab 10, the side wall 11 erected on the bottom slab 10, and the top of the space surrounded by the side wall 11. The roof 12 is provided with a continuous underground wall 13 formed around the side wall 11, and a membrane 14 attached to the inner surface of the bottom slab 10 and the side wall 11. The configuration of the tank 1 is not limited, and may be appropriately determined according to the tank method.

The side wall 11 is a concrete structure erected on the peripheral edge of the bottom slab 10. The side wall 11 of the present embodiment has a circular shape (cylindrical shape) in a plan view. The wall thickness, wall height, and planar shape of the side wall 11 may be appropriately determined.
The roof 12 is formed at the upper end of the side wall 11 and covers the upper surface of the membrane 14. The peripheral edge of the roof 12 is fixed to the upper end of the side wall 11. The roof 12 of this embodiment is formed of a steel member. The material constituting the roof 12 is not limited, and may be formed of, for example, a concrete member. Further, the cross-sectional dimensions of the roof 12 may be appropriately determined.
The continuous underground wall 13 is formed in a cylindrical shape so as to surround the outer circumference of the side wall 11. The continuous underground wall 13 is a retaining wall for forming the shaft 15, and a space for forming the tank 1 is formed inside the continuous underground wall 13. The depth, wall thickness, and the like of the continuous underground wall 13 are not limited and may be set as appropriate.

The bottom slab 10 is a concrete structure formed so as to cover the lower surface of the membrane 14. As shown in FIG. 2, the bottom slab 10 has two upper and lower reinforcing bars (lower reinforcing bar 21 and upper reinforcing bar 22) and a bottom heater 3 embedded therein. Further, in the bottom slab 10, a bottom slab pedestal 4 that supports the upper reinforcing bar 22 and the bottom heater 3 is embedded.
As shown in FIG. 3, the bottom slab pedestal 4 is formed by arranging a plurality of pedestal blocks 5, 5, ... In parallel. The bottom slab pedestal 4 of the present embodiment has a plan-viewing circular (polygonal) first pedestal block 51 arranged in the central portion and a plan-viewing arc shape arranged so as to surround the periphery of the first gantry block 51. The second gantry block 52 of the above is provided. A gap is secured between the gantry block 5 and another gantry block 5 adjacent to the gantry block 5. The shape, arrangement, quantity, etc. of the gantry block 5 may be appropriately determined according to the shape of the bottom slab 10.

As shown in FIG. 4A, the gantry block 5 includes two upper and lower scaffolds 6, 6 and a pipe material (heater member) 31 piped between the scaffolds 6 (below the upper scaffold 6a). It includes a pipe support 7 that supports the pipe material 31, and a plurality of columns 8 that support the scaffolding 6 and the pipe support 7.
As shown in FIG. 5A, the scaffold 6 includes a frame 61 formed by combining a plurality of channel steels and a mesh material (so-called mesh scaffold) 62 that covers the opening portion of the frame 61. There is. The structure of the scaffold 6 is not limited, and may be, for example, a steel plate or a mesh material 62 supported by a frame material. Further, the steel material forming the frame 61 is not limited to channel steel, and may be, for example, H-shaped steel or angle steel. Further, the gantry block 5 may be provided with at least an upper scaffolding 6a used for arranging the upper reinforcing bars 22, and the number of stages of the scaffolding 6 provided in the gantry block 5 is not limited. For example, when the thickness of the bottom slab 10 is large, scaffolding 6, 6, ... Of three or more steps may be provided on the gantry block 5.
As shown in FIG. 5B, the pipe support 7 is formed by combining angle steels. The material constituting the pipe support 7 is not limited. As shown in FIGS. 6A and 6B, the pipe support 7 is supported by the support column 8 at a distance from both scaffolds 6 between the upper and lower scaffolds 6. The pipe support 7 has a step depending on the arrangement of the bottom heater 3 (tube material 31). If necessary, diagonal lumber is installed between the upper and lower scaffolds 6 and between the scaffolds 6 and the pipe support 7.
The support column 8 is erected above the lower reinforcing bar 21. As shown in FIG. 4B, a steel plate is fixed to the lower end of the support column 8 as a support column base 81. The column base 81 is placed on four concrete blocks 82 erected on the bottom surface of the shaft 15. The concrete block 82 is arranged between the lower reinforcing bars 21 and projects above the lower reinforcing bars 21. A floor plate 83 is placed on the four concrete blocks 82, and the support column 81 is placed on the upper surface of the floor plate 83. If necessary, a mortar is provided between the support column base 81 and the floor plate 83 to adjust the height. The material used for height adjustment is not limited to mortar, and for example, a steel plate may be interposed between the support column base 81 and the floor plate 83. Further, the method of installing the support column 8 (mounting block 5) is not limited to the method using the concrete block 82. Further, the configuration of the base (concrete block 82 and floor plate 83) that supports the support column 8 is not limited. For example, the number of concrete blocks 82 does not necessarily have to be four.

The bottom heater 3 is a pipeline arranged in the bottom slab 10, and by circulating a heat medium (for example, antifreeze liquid or the like) inside, it is possible to prevent the foundation ground from freezing due to the temperature in the tank 1. .. The bottom heater 3 is formed by connecting a pipe material (heater member) 31. The bottom heater 3 of this embodiment is arranged in a coil shape. The configuration of the bottom heater 3 is not limited, and may be configured by, for example, a heating wire.

Next, the construction method of the tank bottom slab will be described. The method of constructing the tank bottom slab of the present embodiment includes a temporary assembly step, a lower bar arrangement step, a gantry forming step, a heater forming step, an upper bar arrangement step, and a placing step.
In the temporary assembly step, the bottom slab pedestal 4 is temporarily assembled at the temporary site S2 provided at a position different from the tank construction site S1 (the bottom of the shaft 15). As shown in FIG. 7, the temporary site S2 is provided in the vicinity of the tank construction site S1 and has an area equal to or larger than the tank construction site S1 (flat area of the shaft 15).
Temporary assembly of the bottom slab pedestal 4 is performed by arranging a plurality of pedestal blocks 5 constituting the bottom slab pedestal 4. The gantry block 5 may be assembled at the temporary site S2, or may be assembled at a site different from the temporary site S2, a factory, or the like.
In the temporary assembly step, the arrangement of each gantry block 5 is assembled so as to be the same arrangement as when assembling the bottom slab gantry 4 at the tank construction site S1.

In the lower reinforcing bar arrangement step, as shown in FIG. 8A, the lower reinforcing bar 21 is arranged at the tank construction site S1 (bottom of the shaft 15). The lower reinforcing bars 21 are assembled in a grid pattern at the bottom of the shaft 15. The lower reinforcing bar 21 is arranged with a spacer from the bottom surface of the shaft 15 with a gap. In the present embodiment, the lower bar arrangement step is performed in parallel with the temporary assembly step. The timing of carrying out the lower bar arrangement step is not limited as long as it is before the gantry forming step, and may be carried out before or after the temporary assembly step.
After arranging the lower reinforcing bars 21, the concrete block 82 is arranged at a predetermined position. The concrete block 82 is erected at the bottom of the shaft 15 by inserting a gap between the lower reinforcing bars 21 in a grid pattern. In the present embodiment, four concrete blocks 82 are arranged at positions corresponding to directly below the columns 8 of the gantry block 5. The concrete block 82 may be erected at a predetermined position when the gantry block 5 is arranged in the gantry forming step.

In the gantry forming step, as shown in FIG. 8B, the bottom slab pedestal 4 is formed above the lower reinforcing bar 21 by moving the bottom slab pedestal 4 assembled in the temporary assembly step. In the present embodiment, as shown in FIG. 7, the bottom slab mount 4 is moved from the temporary site S2 to the tank construction site S1 by using the lifting machine M arranged between the tank construction site S1 and the temporary site S2. do. The bottom slab pedestal 4 is moved by individually moving the gantry blocks 5 constituting the bottom slab pedestal 4. The gantry block 5 is moved to the tank construction site S1 so as to have the same arrangement as the temporary site S2. At this time, the gantry block 5 is arranged at a predetermined position while visually recognizing both the tank construction site S1 and the temporary site S2. The lifting machine M for suspending the gantry block 5 may be a crawler crane, a rough terrain crane, or the like, or a tower crane or the like. Further, a plurality of lifting machines M may be used. As shown in FIG. 8B, the gantry block 5 is arranged above the lower reinforcing bar 21 by placing the support column base 81 on the concrete block 82. At this time, the floor plate 83 is arranged on the upper surface of the concrete block 82. Further, in order to ensure the horizontality of the gantry block 5, when the height is adjusted, a height adjusting material such as mortar is interposed between the support column base 81 and the floor plate 83.
Further, the pipe material (heater member) 31 is temporarily fixed to the gantry block 5 in a state of being displaced laterally (direction away from the existing gantry block 5) from a predetermined position. By doing so, when the gantry block 5 is moved, the pipe material 31 is prevented from coming into contact with the existing gantry block 5.

In the heater forming step, the bottom heater 3 is formed above the lower reinforcing bar 21. The bottom heater 3 is formed by connecting the pipe members 31 temporarily fixed to the gantry block 5. The pipe materials 31 are connected to each other by welding with the end faces of the pipe materials 31 abutting each other. The pipe material 31 is displaced in the direction of the existing gantry block 5 (to the right in FIG. 8) so as to abut against the pipe material 31 attached to the existing gantry block 5. The pipe members 31 are connected to each other by a worker on the scaffolding 6b on the lower side of the bottom slab mount 4. The connection work of the pipe material 31 shall be performed sequentially after the gantry block 5 is arranged at the tank construction site S1. That is, the heater forming step shall be performed in parallel with the gantry forming step. The heater forming step may be performed after the bottom slab pedestal 4 is formed by the pedestal forming step.

In the upper reinforcing bar arrangement step, as shown in FIG. 8C, the upper reinforcing bar 22 is arranged on the bottom slab pedestal 4. The reinforcing bar arrangement work of the upper reinforcing bar 22 is performed on the scaffolding 6a on the upper side of the bottom slab pedestal 4 (frame pedestal block 5). Reinforcing the upper reinforcing bar 22 is sequentially performed from the place where the gantry block 5 is arranged. That is, the upper bar arrangement step may be performed in parallel with the gantry forming step and the heater forming step. The timing of carrying out the upper bar arrangement step is not limited as long as it is between the gantry forming step and the placing step, and may be carried out after the bottom slab pedestal 4 is formed by the gantry forming step. ..
In the placing step, concrete is placed at the bottom of the shaft 15 in which the lower reinforcing bar 21, the upper reinforcing bar 22, and the bottom heater 3 are arranged.

According to the method of constructing the tank bottom slab and the bottom slab pedestal 4 of the present embodiment, the construction of the bottom slab pedestal 4 is completed by moving the bottom slab pedestal 4 once formed at the temporary site S2 to the tank construction site S1. Is excellent. Since the position of the pipe material 31 is fixed at the temporary site S2, the bottom heater 3 can be installed only by fine adjustment at the time of main installation. That is, in order to adjust the length of the pipe material 31 carried in at a fixed length so that the welding points are between the gantry blocks 5 and to carry in the tank construction site S1 in a state where each gantry block 5 is numbered, the pipe material 31 is carried in. The labor of piping work can be significantly reduced. Further, since the connecting portion between the pipe members 31 is arranged at the joint portion (gap) between the gantry blocks 5, the workability is easy. That is, the construction period can be shortened by reducing the work at the tank construction site S1 as much as possible.
Since the gantry block 5 is moved by using the lifting machine M arranged between the tank construction site S1 and the temporary site S2, the time and effort required for the movement is small. Further, if the work is performed while visually recognizing both sites (tank construction site S1 and temporary site S2), it is possible to reduce mistakes in the arrangement of the gantry block 5.
Further, in parallel with the construction of the bottom heater 3 (heater forming step), the reinforcing bars 22 of the upper reinforcing bars 22 can be arranged on the bottom slab pedestal 4 (upper reinforcing bar arrangement process), so that the construction period can be shortened. Further, in the pedestal forming step, in order to form the bottom slab pedestal 4 by arranging the pedestal block 5 having the upper and lower two-stage scaffolds 6 and 6 and the pipe material 31 in advance, the pedestal for the bottom heater 3 and the upper reinforcing bar 22 are formed. Compared with the conventional construction method in which the frame for use is individually formed, the labor can be significantly reduced. Since the bottom heater 3 may be installed by connecting the pipe materials 31 arranged with the installation of the gantry block 5, the pipe material 31 is carried in separately from the pedestal, and the pipe material 31 is positioned and connected on the pedestal. It is superior in workability compared to the conventional construction method.

The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and each of the above-mentioned components can be appropriately modified without departing from the spirit of the present invention.
In the above embodiment, the bottom slab pedestal 4 is once formed at the temporary site S2 different from the tank construction site S1, but the bottom slab pedestal 4 does not necessarily have to be formed in advance.
Further, the temporary site S2 does not necessarily have to be adjacent to the tank construction site S1, and may be provided at a distant position. In this case, the gantry block 5 may be transported by using a transport vehicle such as a truck.

1 tank 10 bottom slab (tank bottom slab)
2 Reinforcing bar 21 Lower reinforcing bar 22 Upper reinforcing bar 3 Bottom heater 31 Pipe material (heater member)
4 Bottom slab pedestal 5 pedestal block 6 Scaffolding 6a Upper scaffolding 7 Pipe support 8 Strut M Lifter S1 Tank construction site S2 Temporary site

Claims (4)

The lower reinforcing bar arrangement process for arranging the lower reinforcing bars,
A pedestal forming step of forming a bottom slab pedestal above the lower reinforcing bar,
A heater forming step of forming a bottom heater above the lower reinforcing bar,
The upper reinforcing bar arrangement process for arranging the upper reinforcing bars on the bottom slab pedestal, and
It is a method of constructing a tank bottom slab that includes a casting process for placing concrete.
In the pedestal forming step, the bottom slab pedestal is formed by arranging a plurality of pedestal blocks including a scaffold and a heater member disposed below the scaffold.
The method for constructing a tank bottom slab, which comprises forming the bottom heater by connecting the heater members to each other in the heater forming step. Before the gantry forming process, a temporary assembly process for forming the bottom slab pedestal at a temporary site provided at a position different from the tank construction site is provided.
The method for constructing a tank bottom slab according to claim 1, wherein in the gantry forming step, the bottom slab pedestal assembled in the temporary assembly step is moved. The second aspect of claim 2, wherein a lifting machine arranged between the tank construction site and the temporary site is used to move the gantry block constituting the bottom slab pedestal from the temporary site to the tank construction site. Construction method of tank bottom slab. In the gantry forming process, the heater member is temporarily fixed to the gantry block in a state where it is laterally displaced from a predetermined position.
The method for constructing a tank bottom slab according to any one of claims 1 to 3, wherein in the heater forming step, the heater member is displaced to a predetermined position and then connected to another heater member.

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