JPS6354861B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION There are various methods for constructing a cylindrical underground tank, but the method for constructing the shell portion is basically the same for each method.

In other words, an earth retaining wall that also serves as a water barrier is constructed on the ground around the tank using a continuous underground wall method, a caisson method, a row of steel pipe columns, etc., a shell concrete lining is constructed on the inside using a reverse casting method, etc. The shell part of the underground tank is constructed by installing a steel skin plate to prevent oil from seeping into the tank.

On the other hand, the method of constructing the bottom plate of a cylindrical underground tank is
Varies depending on tank size, purpose, geology, groundwater level, etc.

Typical conventional methods of constructing this kind of bottom plate include a method of constructing a very thick reinforced concrete slab that can withstand uplift pressure from below, and a method of constructing a reinforced concrete slab by constructing piles at the bottom of the slab. There are methods to reduce the thickness, but these methods have the disadvantage that either the slab concrete is thick and the cost is extremely high, or the number of piles is quite large and the cost is high.

In addition, a permeable foundation method was previously adopted in which the underground tank was connected to an adjacent water level adjustment tank or underwater, and oil was stored in the underground tank by utilizing the difference in specific gravity between oil and water, without placing concrete slabs. However, this requires constructing two tanks, connecting pipes to the sea, and installing an oil separator, which is not only very expensive, but also affects the quality of the oil in the underground tanks. We regret that this may have a negative impact on

Recently, a technology has been developed to construct a water-shielding and earth-retaining wall in the shell part very deeply by penetrating the impermeable ground, so there is a way to prevent the groundwater around the underground tank from penetrating into the bottom of the tank. Now I can remove it. For this reason, underground tanks have come to be constructed by layering an impermeable layer on a permeable gravel and sand layer at the bottom of the tank, and placing a tank bottom plate made of steel plate on top of the impermeable layer. .

However, when constructing such an underground tank, when excavating the inside of the earth retaining wall after constructing a water-shielding earth retaining wall, if the ground is sticky, the ground may become loose due to stress release. In some cases, it can swell to several tens of centimeters.

For this reason, once the underground tank is completed and filled with oil, the ground is expected to sink several tens of centimeters. As the ground sinks in this way, the tank bottom plate sinks, and there is a risk that tensile force will be generated in the skin plate of the shell part, causing it to break.

The present invention was proposed in order to eliminate such defects. Shell concrete is poured integrally with the inner circumference of a water-blocking and earth-retaining wall constructed by penetrating impermeable ground. In an underground tank in which a skin plate is arranged on the inner periphery of shell concrete and a bottom plate is laid on an impermeable layer layered on permeable gravel and sand layer ground, the lower end position of the skin plate is A ring-shaped shoe that supports the skin plate is provided protruding from the inner peripheral surface of the shell concrete, and the water-blocking layer is made of a plastic material, and the layer thickness of the area of the water-blocking layer that is in contact with the ring-shaped shoe This relates to an underground tank characterized in that the layer thickness is greater than the layer thickness in the central area of the bottom of the tank.

As described above, in the underground tank according to the present invention, a ring-shaped shoe is provided at the lower end of the skin plate to protrude from the inner peripheral surface of the shell concrete, and the skin plate is supported by the ring-shaped shoe. There is no risk of the skin plate sinking due to ground subsidence.

Further, the bottom plate is disposed on an impermeable layer made of a plastic material such as asphalt mortar laid on the sand layer ground, and the thickness of the area of the impermeable layer in contact with the ring-shaped shoe is Since the layer thickness is larger than the layer thickness in the center area of the bottom of the tank, as the ground subsides, the impermeable layer near the ring-shaped shoe undergoes creep deformation, causing the bottom in contact with the impermeable layer to The plate deforms slowly and smoothly in response to the deformation of the ground, and is always maintained in a stress-free state.Coupled with the fact that the skin plate is supported by the ring-shaped shoe, the skin plate deforms slowly and smoothly. There is no risk of breakage due to tensile force.

The present invention will be described below with reference to the illustrated embodiments.

A water shielding/earth retaining wall 1 is constructed by penetrating the impermeable ground, and a shell concrete 2 is integrally constructed while excavating the internal ground A.

After excavating the ground to the foundation surface, a permeable embankment foundation 3 is constructed with gravel or the like, and a sand foundation 4 is constructed on top of it. A water collection pit 5 is provided within the permeable embankment foundation 3, and the groundwater collected in the water collection pit 5 is discharged by a pump 6, so that the groundwater level is always maintained at the location of the water collection pit 5. has been done.

A ring-shaped shew 7 is provided on the peripheral edge of the permeable embankment foundation 3 made of gravel or the like, protruding from the inner peripheral surface of the shell concrete 2, and a skin plate 8 is lined with the shell concrete 2 by the shew 7.
The lower end of is supported.

The ring-shaped shoe 7 is formed into an inclined surface that slopes downward toward the center of the bottom surface of the tank.

Impermeable asphalt mortar 9 is placed on the sand foundation 4 except for the lower surface of the ring-shaped shoe 7. This asphalt mortar 9 is formed so that the area close to the ring-shaped shoe 7 has a thicker layer thickness than other parts, that is, the center side of the tank bottom so that creep deformation occurs as the ground A sinks. There is.

Asphalt mortar 9 uses straight asphalt penetration of 40/60 as asphalt, asphalt amount: 15 to 20%, filler amount: asphalt amount ×
(2 to 2.5)% composition is used.

Further, a bottom plate 10 made of a steel plate is laid on the asphalt mortar 9, and its peripheral edge is welded to the skin plate 8.

In the illustrated underground tank, the lower edge of the skin plate 8 is connected to the ring-shaped shoe 7 that projects from the inner periphery of the shell concrete 2 that is cast inside the water-blocking and earth-retaining wall 1 and integrally therewith. Since it is supported in this manner, there is no risk that the skin plate 8 will sink even if the ground A sinks.

Further, the bottom plate 10 is placed on the asphalt mortar 9 laid on the sand foundation 4, and the layer thickness of the part of the asphalt mortar 9 in contact with the ring-shaped shoe 7 is as described above on the center side of the bottom of the tank. Since the asphalt mortar 9 near the ring-shaped shoe undergoes creep deformation as the ground A sinks, the bottom plate 10 in contact with the asphalt mortar 9 becomes as shown in FIG. As shown in 10', it deforms slowly and smoothly in response to the deformation of the ground A, and is always maintained in a stress-free state, which is compatible with the fact that the skin plate 8 is supported by the ring-shaped shoe 7. There is no risk that tensile force will be applied to the skin plate 8 and it will break.

At this time, the upper surface of the ring-shaped shoe 7 is slanted downward toward the center of the bottom of the tank, and there is a sufficient distance between the upper surface and the peripheral edge of the bottom plate 10. The allowable displacement of the peripheral edge of the bottom plate 10 due to ground subsidence increases, and the bottom plate 10 can more easily deform as the ground subsides.

Although the present invention has been described above with reference to embodiments, the present invention is, of course, not limited to such embodiments, and can be modified in various ways without departing from the spirit of the present invention. .

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the essential parts of an embodiment of an underground tank according to the present invention, and FIG. 2 is a vertical cross-sectional view showing the state of deformation of the bottom plate due to ground subsidence. 1...Waterproof and earth retaining wall, 2...Shell concrete, 3...Permeable embankment foundation, 4...Sand foundation,
7...Ring-shaped shoe, 8...Skin plate,
9...Asphalt mortar, 10...Bottom board.

Claims (1)

[Claims] 1 Shell concrete is placed on the inner periphery of the impermeable earth retaining wall constructed by penetrating the impermeable ground, and a skin plate is placed on the inner periphery of the shell concrete. In an underground tank in which a bottom plate is laid on an impermeable layer layered on gravel and sand layered ground, a ring-shaped shoe supporting the skin plate is protruded from the inner peripheral surface of the shell concrete at the lower end position of the skin plate. The impermeable layer is made of a plastic material, and the impermeable layer is configured such that a region of the impermeable layer in contact with the ring-shaped shoe is thicker than a region in the center of the bottom of the tank. An underground tank characterized by: