JPH06158671A - Method for preventing floating of underground structure - Google Patents

Abstract

PURPOSE:To prevent floating of an underground structure and to reduce costs by placing upper soil on a widened bottom portion formed in the lower portion of the underground structure, the dead load of the upper soil being greater than the result of subtraction of the dead load of the underground structure from pumping pressure acting on the underground structure CONSTITUTION:An underground wall 2 integrated to a container 1 or the like has its lowermost portion formed into a widened bottom portion 22 thicker than other wall portions 21. Next, granular upper soil 3 of specific gravity greater than that of water, such as earth and gravel, is packed above the widened bottom portion 22 to increase the dead load of the wall 2. In that case, the dead load of the upper soil 3 is greater than that obtained when the dead load of the container 1 including the wall 2 is subtracted from pumping pressure acting on the container 1 including the wall 2, so that the dead loads of the container 1, the wall 2 and the upper soil 3 resist a pumping force F. Therefore, costs can be reduced and the reliability of floating preventive effects can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents floating underground structures or semi-underground storage tanks and underground structures such as continuous underground walls from floating under the lifting pressure of ground water. Regarding prevention technology.

[0002]

2. Description of the Related Art Since an underground structure of this type is subjected to a lifting pressure by groundwater, it is necessary to take measures to prevent the floating of the underground structure against the expected lifting pressure. FIG. 3 shows a floating prevention technique when the underground structure is the storage tank a.
Up to now, the main body of the storage tank a and the underground wall b integral with the storage tank a are formed thick, and the own weight of the storage tank a and the underground wall b is used for the floating resistance of the storage tank a.

[0003]

[Problems to be Solved by the Invention] The above-described floating prevention technique for underground structures has the following problems.

<B> As the body thickness increases, a large amount of material such as concrete is used, and thus the economical burden is large.

<B> As the body thickness increases, the lifting pressure acting on the underground structure increases in proportion to the increase in the surface area,
The floating prevention effect due to the increase of the own weight is easily reduced by half. Therefore, there remains concern about the reliability of the floating effect of the underground structure.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to reduce the economic burden and to improve the reliability of the floating prevention effect. It is to provide technology for preventing the floating of structures.

[0007]

According to the present invention, a bottom expansion part is formed in the lower part of an underground structure, and the weight of the underground structure is reduced from the pumping pressure acting on the underground structure at the bottom expansion part. It is a method to prevent the floating of underground structures by placing an overburden of more than a certain weight.

[0008]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings.

<B> Storage Tank FIG. 1 shows an underground storage tank 1 as an example of an underground structure.
The storage tank 1 is a storage tank having a sealed structure in which the bottom of a concrete side slab 11 having a tubular shape is integrally closed by a concrete bottom slab 12, and the upper opening of the side slab 11 is covered with a roof 13. The entire circumference is covered with a thin metal plate (such as a membrane). The structure of the storage tank 1 itself is not limited to that shown in the drawing, and includes known storage tanks such as a steel storage tank and a double shell storage tank.
Further, the storage tank 1 is provided with a concrete underground wall 2 which is longer than the side slab 11 and which is installed on the side slab 11.

<B> Structure of underground wall The underground wall 2 integrated with the side plate 11 is constructed by a known method. When constructing the underground wall 2, the bottommost portion of the underground wall 2 is made thicker than the other wall portion 21 to form the expanded bottom portion 22. The expanded bottom portion 22 is a portion for transmitting the weight of the upper soil 3 to be described later to the underground wall 2, and in addition to being formed on both sides of the wall portion 21 as shown in the figure, it is also formed on one side only. You may form. The opening width of the trench 23 when constructing the underground wall 2 is determined in consideration of the formation width of the expanded bottom portion 22. The point is that it is only necessary to form a space above the expanded bottom portion of the underground wall 2 in which the top soil 3 can be filled.

<C> Means for increasing the self-weight of the underground wall Conventionally, the self-weight of the deeply formed underground wall 2 opposes the lift of ground water acting on the underground wall 2. In the present invention, a method is adopted in which the upper mounting soil 3 is filled above the expanded bottom portion 22 of the underground wall 2 to increase the own weight of the underground wall 2. As the overlaid soil 3, for example, particles such as earth and sand or gravel having a larger specific gravity than water are used. Further, the weight of the overlaid soil 3 that can prevent the storage tank 1 from floating is required to be equal to or more than the weight obtained by subtracting the weight of the storage tank 1 including the concrete underground wall 2 from the pumping pressure acting on the storage tank 1 including the underground wall 2. is there.

[0012]

[Action]

<A> Prevention of uplift Next, the mechanism against the lift of groundwater will be described with reference to FIG. In FIG. 1, the weight of the top soil 3 is transmitted to the underground wall 2 via the bottom expanding portion 22. Therefore, the total weight of the storage tank 1 is the sum of the following three weights. Self-weight of the concrete storage tank 1 Self-weight of the concrete underground wall 2 Self-weight of the top soil 3 In the present invention, the lifting force F of the groundwater can be counteracted by the above three self-weights, so that the storage tank 1 can be reliably prevented from rising.

<B> Consideration of Lifting Pressure Acting on Underground Wall The lifting pressure of groundwater acting on the underground wall 2 will be examined. Assuming that the filling range of the subterranean wall 2 is also made of concrete, the lifting pressure acting on the subterranean wall 2 in this case is determined by the surface area of the subterranean wall 2. On the other hand, in the present invention, since the underground wall 2 is made thin and the weight of the underground wall 2 is reduced by the weight of the top soil 3, the substantial surface area of the underground wall 2 can be reduced. Therefore, in the present embodiment, the lifting pressure acting on the underground wall 2 can be reduced while securing the same own weight as compared with the underground wall formed entirely of concrete. This is the wall portion 21 of the underground wall 2.
This is due to the fact that the top soil 3 has water permeability in addition to the fact that it is formed thin to reduce the surface area.

[0014]

[Embodiment 2] FIG. 2 shows another means for counteracting the lifting pressure of groundwater.
Shown in. In this embodiment, the anchor 4 may be tensioned and fixed to the underground wall 2 to obtain a reaction force on the anchor 4. The anchor 4 and the top soil 3 of the above embodiment may be combined.

[0015]

Since the present invention is as described above, the following effects can be obtained.

<B> Since the skeleton of the underground structure can be designed to be thin, the floating of the underground structure can be economically prevented.

<B> When the top soil is placed above the bottom expanding portion formed in the lower part of the underground structure, the groundwater that acts on the underground structure is lifted while retaining the weight of the underground structure. The pressure can be reduced. Therefore, the reliability with respect to the floating prevention effect of the underground structure is improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment that uses the load of top soil.

FIG. 2 is an explanatory diagram of a second embodiment using an anchor.

FIG. 3 is an explanatory diagram of a base technology of the present invention.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masao Arai 1-25-1 Nishishinjuku, Shinjuku-ku, Tokyo Within Taisei Corporation (72) Inventor Motoshige Ariyama 1-25-25 Nishishinjuku, Shinjuku-ku, Tokyo No. 1 Taisei Construction Co., Ltd.

Claims (1)

[Claims] 1. A bottom expansion part is formed in the lower part of the underground structure, and the topsoil having a weight equal to or more than the weight obtained by subtracting the own weight of the underground structure from the pumping pressure acting on the underground structure is placed on the bottom expansion part. Yes, a method of preventing the floating of underground structures.