JP2000130698A - Structure of low temperature underground tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the development of a crack by connecting a lower end of a side wall with a base without providing a joint therebetween and providing a cutout part in a lower fringe part at the outer periphery of the base, in a low temperature underground tank constituted by the side wall, the base, and an underground continuous wall provided at the outer periphery of the side wall. SOLUTION: When a low temperature underground tank is constructed, a cylindrical underground continuous wall 1 is first constructed, its inside is digged down to a deepest part, and concrete is placed in a base 2. After that, concrete is placed in a side wall 3 to construct an uppermost part and a roof 4. At this time, when the base 2 and the side wall 3 are mutually connected, a rigid connection structure in which a joint is not provided between a lower end of the side wall 3 and the base 2 is employed. Moreover, the base 2 is like a thick disc, and a cutout part is provided in a lower fringe part at the outer periphery of the base 2. Consequently, a cutout oblique face 5 is formed in the lower fringe part at the outer periphery of the base 2, and a nonwoven fabric is attached to the cutout oblique face 5 to cut a fringe and make water pressure act in this part securely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a low-temperature underground tank.

[0002]

2. Description of the Related Art In a conventional low-temperature underground tank, a water-resistant strength plate type is designed so as to be able to withstand the groundwater pressure by the strength of a bottom plate. In this case, as shown in FIG. 3, a joint c between the side wall a of the tank and the bottom plate b is joined.
And a separate structure is adopted.

[0003]

When joints are provided, the number of steps and materials required for construction are required as compared with the case where a structure having no joints is constructed. For this purpose, a joint may be provided at the joint between the side wall and the bottom slab to provide a direct rigid connection without separating the joint, but there are the following problems. <B> A circumferential axial tensile force is generated at the lower end of the side wall of the tank due to a temperature stress due to the cold heat of the low-temperature content liquid, or an external force such as a liquid pressure or a gas pressure. In addition, temperature stress is also generated by heat of hydration due to the hydration reaction of cement. For this reason, in the rigidly coupled tank, there is a possibility that a through crack may occur at the lower end portion of the side wall or that watertightness may be impaired. <B> In order to ensure watertightness, it is conceivable to install an iron plate or the like on the outer periphery of the lower end of the side wall, but in this case, the cost is increased as compared with the conventional type, and no advantage is found. <C> In the case of the rigid connection type, stress concentrates on the lower end of the side wall due to external force such as earth pressure or water pressure. Therefore, it is necessary to arrange a large number of reinforcing bars, but it is difficult to arrange the reinforcing bars in a narrow space. For this reason, it is necessary to increase the thickness of the side wall, which increases the amount of excavation and the material, and increases the cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has a low-temperature underground tank structure capable of suppressing the occurrence of cracks without increasing material costs and construction costs. The purpose is to provide.

[0005]

In order to achieve the above object, a low-temperature underground tank according to the present invention has a low-temperature underground tank comprising a side wall, a bottom plate, and an underground continuous wall installed on the outer periphery of the side wall. , A low-temperature underground tank characterized by being joined without providing joints between a lower end of a side wall and a bottom plate and notching a lower edge portion of an outer periphery of the bottom plate.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the structure of a low-temperature underground tank according to the present invention will be described below with reference to the drawings.

<A> Construction of a tank. The low-temperature underground tank first constructs the underground connecting wall 1 in a cylindrical shape,
The inside is excavated to the deepest part, and concrete of the bottom slab 2 is poured. Thereafter, the construction up to the uppermost portion is performed while the concrete of the side wall 3 is poured, and the roof 4 is erected and completed.

<B> A joint portion between the bottom plate 2 and the side wall 3. In the underground tank of the present invention, as described above,
No rigid joint is provided between the lower end of the base plate and the bottom plate 2, and a rigid connection structure is adopted.

<C> Notch on the outer periphery of the bottom plate 2. Generally, the bottom plate 2 is in the form of a disk having a large thickness, but the bottom plate 2 of the present invention is formed by cutting off the lower edge of the outer periphery of the bottom plate 2 in particular. By notching the lower edge of the outer periphery, a notch slope 5 is formed at the lower edge of the outer periphery of the bottom plate 2. A non-woven fabric or the like is attached to the notched slope 5 to cut the edge, and water pressure is reliably applied to this portion.

<D> Setting of cutout range A notched slope 5 in which the lower edge of the outer periphery of the bottom plate 2 is cut out
Is set to a range in which the thermal stress affecting the bottom plate 2 can be relaxed. The range in which the thermal stress can be reduced is, for example, the side wall 3.
And the temperature distribution of the joint portion of the bottom plate 2. For example, figure including side wall 3, bottom slab 2, underground connecting wall 1, surrounding ground
In the case where the temperature distribution is as shown in FIG. 5, a portion that may generate a higher temperature than a predetermined temperature line is cut out from the bottom plate 2 and eliminated. As a result, a notched slope 5 is formed. By this notch, the difference in the average temperature between the outer peripheral portion of the bottom plate and the lower end portion of the side wall can be reduced, and the circumferential axial pulling force of the lower end portion of the side wall due to the difference in the amount of thermal contraction can be reduced.

<E> PC cable. At least a lower part of the side wall 3 is arranged in a circumferential direction, in a circumferential direction PC.
The cables 6 are arranged in a plurality of stages. This circumferential PC cable 6 is tensioned to introduce prestress. Further, in some cases, the vertical PC cable 7 is arranged in the vertical direction, and a prestress is introduced in the vertical direction.

[0012]

The structure of the low-temperature underground tank according to the present invention is as described above, and the following effects can be achieved. <B> In the low temperature tank, temperature stress is generated by the cold of the content liquid. However, in the low-temperature tank of the present invention, a range in which such thermal stress can be relaxed is set, and a range in which a higher temperature stress is generated is notched. Further, by applying water pressure to the notched slope, a radial axial compression force is generated at a lower end portion of the side wall due to a radial component thereof, and an external force such as a temperature stress due to the low-temperature content liquid, a liquid pressure, a gas pressure, etc. , And the circumferential axial tensile force generated by the thermal stress due to the heat of hydration due to the hydration reaction of the cement can be reduced. Therefore, there is a low possibility that a through crack is generated in the connection portion between the bottom plate 2 and the side wall 3, and the watertightness is not impaired. <B> Since the structure for suppressing the temperature stress is simple, there is no particular problem that the amount of the reinforcing bar does not increase and the bar arrangement operation is affected. <C> If the excavation is performed in a shape corresponding to the notch slope 5, the excavation amount may decrease, but the thickness of the floor slab and the side wall 3 increases and the excavation amount increases as in the related art. Such a problem does not occur. <D> A rigid connection structure in which no joint is interposed at the joint between the side wall 3 and the bottom plate 2. Therefore, economical construction can be performed without the need for materials and careful work for forming joints. <E> At least at the lower portion of the side wall 3, circumferential PC cables 6 are arranged in a plurality of stages in the circumferential direction and are strained. For this reason, it is possible to prevent the occurrence of through cracks due to the circumferential axial tensile force and the temperature stress due to the heat of hydration, and to secure watertightness. If necessary, a vertical PC is used at the lower end of the side wall.
By arranging the cables and introducing prestress, it is possible to avoid the dense arrangement of the reinforcing bars in the vertical direction.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment of the structure of a low-temperature underground tank according to the present invention.

FIG. 2 is an explanatory diagram of a temperature distribution.

FIG. 3 is an explanatory diagram of a state where a PC cable is arranged at a lower portion of a side wall.

FIG. 4 is an explanatory view of an embodiment of the structure of a conventional low-temperature underground tank.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuo Tsubone 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Inside Taisei Construction Co., Ltd. (72) Inventor Katsutoshi Tsuda 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Shoichi Watanabe 1-25-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term (reference) 2D047 AB02 AB08 3E073 AA01 AB03 BA02 BA11 BA21

Claims (3)

[Claims] 1. A low-temperature underground tank comprising a side wall, a bottom plate, and an underground continuous wall provided on the outer periphery of the side wall, wherein the lower plate and the bottom plate are connected to each other without providing a joint, and a lower edge of the outer periphery of the bottom plate is provided. The structure of a low-temperature underground tank with a cut-out part. 2. The structure of a low-temperature underground tank according to claim 1, wherein a cutout range of a lower edge portion of an outer periphery of the bottom plate is set to a range in which thermal stress affecting the bottom plate can be reduced. 3. The low-temperature underground tank according to claim 1, wherein a plurality of circumferential PC cables are arranged circumferentially at least at a lower portion of the side wall, and the circumferential PC cables are tensioned. Structure.