JPH0481679B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an underground tank for storing liquefied gases such as LNG and LPG, and in particular, the present invention relates to an underground tank for storing liquefied gases such as LNG and LPG, and in particular, in a tank where most of the upward loads such as groundwater pressure and frost heaving pressure act on the lower surface of the tank bottom plate. Concerning underground tanks with non-constructive structures.

[Conventional technology]

This type of underground tank has a tank bottom plate that is above the groundwater level, or a heater is installed at the bottom of the tank to prevent the above-mentioned upward load from acting on the bottom surface of the bottom plate even if the tank bottom plate is below the groundwater level. There are some that are designed to pump water.

[Problem that the invention seeks to solve]

In these underground tanks, almost no upward load acts on the bottom plate, but the weight of the stored material,
It is impossible to avoid the bottom plate being subjected to downward loads due to gas pressure, earthquake effects, etc., and therefore,
When such a load acts on the bottom plate,
A bending moment will be generated at the joint between the tank circumferential side wall and the bottom plate.

The present invention provides an underground tank that can cope with the occurrence of such bending moments.

[Means for solving problems]

The underground tank for storing liquefied gas of the present invention is an underground tank in which a bottom plate is arranged above groundwater, and an inner jaw part that protrudes inward is formed at the lower end of the circumferential wall, and an inner jaw part is formed above the inner jaw part. In addition to arranging thin bottom plates with low rigidity at predetermined intervals,
A thick bottom plate with high rigidity is arranged on the lower surface of the thin bottom plate at a predetermined interval so as to be horizontally displaceable, and the peripheral edge of the thick bottom plate is placed on the top surface of the inner flange of the peripheral side wall,
It is placed through a pair of shoes placed above and below,
The pair of shoes are characterized in that the contact surfaces that come into contact with each other protrude in a curved shape, and the thick sole plate is supported using the contact points of the pair of shoes as a fulcrum. .

[Effect]

According to the underground tank for liquefied gas storage of the present invention, when a downward load is applied to the thin bottom plate, the thin bottom plate is supported by the thick bottom plate, reducing the bending moment at the joint between the thin bottom plate and the peripheral side wall. be done.

In addition, the thick sole plate generates a bending moment by supporting the thin sole plate under load, but the thick sole plate has its peripheral edge at the contact point of the curved contact surfaces of the pair of shoes as a fulcrum. Since the thick bottom plate is supported on the upper surface of the inner jaw, the bending moment of the thick bottom plate is not applied to the peripheral side wall. Furthermore, since the rigidity of the thin bottom plate that holds the inner tank is reduced, local relative displacement between the thin bottom plate and the circumferential side wall is less likely to occur.

〔Example〕

Hereinafter, this invention will be explained in detail based on the embodiments shown in FIGS. 1 to 8.

FIGS. 1 and 2 are overall configuration diagrams of an underground tank according to an embodiment, and FIG. 3 is a detailed diagram of its main parts. first,
The type of underground tank in this embodiment is a pump type, and although the bottom slab is located below the groundwater level H, the groundwater under the bottom slab is pumped up and the groundwater pressure is applied to the bottom surface of the bottom slab. It is designed so that almost no upward load acts on it.

As shown in FIG. 3, the tank circumferential side wall 1 has an inner flange 1a projecting inwardly formed at its lower end. A thin bottom plate 3 having a low rigidity enough to hold the bottom plate 2 is provided almost integrally with the peripheral side wall 1.

In the space between the thin bottom plate 3 and the inner flange 1a, a thick bottom plate 4 having a rigidity large enough to support loads such as the weight of stored items, gas pressure, and the effects of earthquakes is arranged. .

As shown in FIG. 4, this thick bottom plate 4 is placed below the thin bottom plate 3 above it at a predetermined interval, and the space between them is filled with edge cutting material 5. By interposing the edge cutting material 5, the thin bottom plate 3 and the thick bottom plate 4 are in a state where their edges are cut (not integrated). Thereby, the thick bottom plate 4 can be horizontally displaced, that is, can rotate around the center of the thin bottom plate 3 or move in the radial direction.

Further, as shown in FIG. 5, the thick sole plate 4 has its peripheral portion placed on the upper surface of the inner flange portion 1a via a pair of shoes 6, 6 disposed above and below. These pair of shoes 6, 6 have contact surfaces that contact each other projected in a curved shape, and the thick sole plate 4 is supported using the contact points of these pairs of shoes 6, 6 as a fulcrum. There is.

In addition, as shown in FIG. 3, this thick sole plate 4 has a notch of a predetermined size along the entire circumference of the upper surface periphery, and the notch 4a has elastic deformation that easily absorbs deformation of styrofoam, etc. A joint filler 7 made of a suitable material is filled. Furthermore, a gap is provided between the outer periphery of the thick sole plate 4 and the inner circumferential surface of the circumferential side wall 1, as shown in FIG. A cushion material 8 is interposed to perform the function.

In addition, bolts (not shown) for fixing the inner tank 2 are implanted in the thin bottom plate 3, but the bolts (not shown) are installed on the top surface of the thin bottom plate 3 to prevent cracks from occurring from the bolt-embedded portions, as shown in FIG. As shown in FIG. 8, an induced joint 9 is formed. The induction joints 9 consist of a plurality of groove-shaped joints that are formed in advance at a predetermined depth in the circumferential direction and radial direction on the upper surface of the thin-walled bottom plate 3, and when bolts are inserted into the thin-walled bottom plate 3, the By absorbing the stress acting in the outward direction of
This prevents cracks from forming at the bolt installation locations.

In addition, 10 in FIGS. 1-3 is a roof, and 11 is a crushed stone layer.

In the underground tank configured as described above, the thick bottom plate 4 supports the thin bottom plate 3, which is subject to downward loads such as stored materials and frost heaving pressure, so that the connection between the thin bottom plate 3 and the circumferential side wall 1 is The bending moment at the location can be significantly reduced. Therefore, there is no need to increase the wall thickness at the joint between the circumferential wall 1 and the thin bottom plate 3, and costs can be reduced.

Here, the thick sole plate 4 generates a bending moment by supporting the thin sole plate 3 on which a load is applied. Since it is supported on the upper surface of the inner flange portion 1a using the abutment point of the abutment surface as a fulcrum, the bending moment generated in the thick sole plate 4 does not act on the circumferential side wall 1. Furthermore, since the thin bottom plate 3 has low rigidity as a whole, it is difficult to cause local relative displacement between it and the circumferential wall 1 even when a load is applied. Therefore, there is no risk of harmful displacement of the inner tank 2 held by the thin bottom plate 3. Further, when a downward load is applied to the thick sole plate 4, the thick sole plate 4 bends in a downward convex manner using the contact points of the pair of shoes 6, 6 as fulcrums, and accordingly As a result, the peripheral edge of the upper surface of the thick bottom plate 4 rises upward, but in the underground tank with the above structure, the peripheral edge is cut out by a predetermined dimension, and the cutout 4a is filled with the joint material 7. This rising phenomenon has never caused the thin bottom plate 3 to be pushed up from below and have a harmful effect on the inner tank. In this case, the dimensions of the notch 4a are determined by the thin bottom plate 3 due to the rising phenomenon.
It goes without saying that the value should be set at the design implementation stage so that it will not be pushed up.

Although the above example shows the case of a pumped-type underground tank, the present invention can be applied to any type of tank as long as there is almost no upward load acting on the bottom plate. Of course, it may also be of a type in which

〔Effect of the invention〕

As explained above, according to the underground tank for liquid gas storage of the present invention, the thin bottom plate to which downward loads such as stored materials and frost heaving pressure are applied is supported by the thick bottom plate. It is possible to significantly reduce the bending moment at the joint with the Therefore, it is not necessary to increase the wall thickness at the joint portion between the peripheral side wall and the thin bottom plate, and it is possible to reduce costs.

In addition, the thick bottom plate generates a bending moment by supporting the thin bottom plate under load.
This thick sole plate is supported on the upper surface of the inner flange with its peripheral edge abutting the curved contact surfaces of the pair of shoes as fulcrums, so the bending moment generated on the thick sole plate is It does not affect the side walls. In addition, since the rigidity of the thin bottom plate that holds the inner tank is reduced, local relative displacement between the thin bottom plate and the circumferential side wall is less likely to occur, and there is no harmful effect on the inner tank. can be prevented from joining.

[Brief explanation of the drawing]

Figures 1 to 8 show an embodiment of the present invention. Figure 1 is a side sectional view of the whole, Figure 2 is a plan view of the same, and Figure 3 is a view of the joint between the bottom plate and the side wall. The last cross-sectional view, Figures 4, 5, and 6 are detailed views of the circular part, circular part, and circular part in Figure 3, and Figure 7 is a detailed diagram of the circular part in Figure 3, respectively.
The figure is a plan view taken in the direction of the arrows in FIG. 3, and FIG. 8 is a sectional view showing details of the induced joint 9 in FIG. 7. 1... Circumferential wall, 1a... Inner flange, 2... Inner tank,
3... Thin bottom plate, 4... Thick bottom plate, 4a... Notch, 5... Edge cutting material, 6... Shoe, 7... Joint material, 8
...Cushion material, 9...Induced joint.

Claims (1)

[Scope of Claims] 1. In an underground tank in which a bottom slab is placed above groundwater, an internal jaw part that protrudes inward is formed at the lower end of the peripheral wall, and a predetermined interval is provided above the internal jaw part. At the same time, a thin bottom plate with low rigidity is disposed on the lower surface of the thin bottom plate, and a thick bottom plate with high rigidity is placed on the lower surface of the thin bottom plate at a predetermined interval so as to be horizontally displaceable, and the peripheral edge of the thick bottom plate is attached to the circumferential side wall. It is placed on the upper surface of the inner jaw via a pair of shoes arranged above and below, and each of these pairs of shoes has abutting surfaces that come into contact with each other and project in a curved shape, and the thick sole plate An underground tank for storing liquefied gas, characterized in that it is supported using the abutment points of the pair of shoes as fulcrums.