JPH09302688A - Construction method for bottom plate of underground tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct an underground tank of economical and favorable quality. SOLUTION: A side wall 1 is sunk to the inside of the ground 5 in an open caisson construction method, and an inner part of the side wall 1 is dug in water. A float 17 is provided to float on a water surface 13. A bottom plate casing body 23 having a cavity 25 is provided on an upper surface of the float 17, a cement paste or the like is injected into the float 17, and it is sunk. After cut-off construction 27 is applied to a boundary part between the side wall and the bottom plate casing body 23, water 11 inside the side wall 1 is drained, and hardening material is injected into the cavity 25 to be filled. Connection concrete 29 to connect the side wall 1 to the bottom plate casing body 23 is then constructed, and a roof 31 is placed on the side wall 1 to complete an underground tank 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a bottom slab for an underground tank that stores low-temperature liquefied gas and the like.

[0002]

2. Description of the Related Art Generally, in the construction work of an underground tank for storing low-temperature liquefied gas, etc., a continuous underground wall is first provided for mountain retention and water stoppage, and then the inside of the continuous underground wall is excavated. Was building an underground tank.

Further, the weight of the skeleton concrete composed of the side wall and the bottom slab has resisted the lifting pressure exerted on the underground tank by the ground water.

[0004]

However, the construction of the underground wall is usually 30 to 4 of the total construction cost of the underground tank.
It occupies 0%, and as a result, the entire construction cost of the underground tank has become expensive. When the underground continuous wall reaches the impermeable layer, which differs depending on the location of the underground tank, the construction cost increases as the depth of the impermeable layer increases.

Further, although there is a tendency for the underground tank to have a large capacity, it is not easy to secure a site for construction, so that the capacity is often increased by using an underground tank having a large depth. A large uplift pressure works on a deep and large-capacity underground tank. In order to resist the lifting pressure, the underground concrete in the underground tank must be made very thick. Therefore, it has been a cause of increasing the construction amount and construction cost required to construct the underground tank.

[0006] In addition, the groundwater level lowering method and the method of providing the water blocking wall separately from the side wall increase special construction work for that purpose, and the construction cost becomes large.

The present invention has been made in view of the above problems, and an object thereof is to provide a method of constructing an underground tank of low construction cost and good quality.

[0008]

In order to achieve the above-mentioned object, the present invention provides a step of excavating the inside of a caisson which is a side wall of an underground tank and submerging the caisson into the ground, and a step of adding groundwater in the caisson. In a method for constructing a bottom slab of an underground tank, which comprises a step of floating a float and constructing a bottom slab on the float, a step of bottoming the bottom slab, and a step of draining groundwater in the caisson. is there.

In the present invention, after the side wall of the underground tank is pre-constructed in the natural water level state by the open caisson method,
Build the bottom plate on the float and allow the bottom plate to sink.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a flow chart showing the construction method of the present embodiment, and FIGS.
3 is an explanatory view showing a procedure of constructing an underground tank.

As shown in FIG. 2, first, a cylindrical open caisson made of reinforced concrete which becomes the side wall 1 of the underground tank is sunk downward from the ground surface 3 into the ground 5 (step 101). That is, the open caisson is submerged while adding lots on the ground.

Next, as shown in FIG. 3, the inside of the side wall 1 is underwater excavated in a natural water level state (step 102). Reference numeral 7 represents a groundwater level surface, and 9 represents an excavation surface. When the excavation surface 9 is deeper than the groundwater level surface 7 and the lower end portion of the side wall 1 does not reach the impermeable layer, the water 11 surrounded by the excavation surface 9 and the side wall 1 is surrounded by water at the bottom portion of the side wall 1. It communicates with groundwater. Therefore, even if the water is discharged together with the excavated soil, the water 11 spouts from the bottom one after another.

When the side wall 1 is added and sunk in this manner, the lower end portion of the side wall 1 bottoms on a predetermined excavation bottom surface 15 as shown in FIG. 4 (step 103). The excavation bottom surface 15 is deeper than the groundwater level surface 7, and the excavation bottom surface 15
If the water does not reach the impermeable layer, the water surface 13 inside the side wall 1
The position of is about the same as the groundwater level 7.

Next, the float 1 is placed on the water surface 13 inside the side wall 1.
7 is floated (step 104). 5 is float 17
It is explanatory drawing at the time of floating. The float 17 is made of steel having a thickness of 500 mm, for example, and has a cavity inside so as to have a large buoyancy. The cavity and the outside air in the upper part communicate with each other via a pipe 19.

The valve 2 is provided near the upper portion of the pipe 19.
1 is provided. Note that the valve 21 is closed and the cavity is filled with air from step 104 to step 106 described later.

Next, as shown in FIG. 6, the bottom plate box 23 is provided in close contact with the upper surface of the float 17 (step 1).
05).

Next, as shown in FIG. 7, the bottom plate box 23 is provided with a cavity 25 made of a closed can such as steel.
Reinforcing bars are installed around the cavity 25, and concrete is placed in the parts where the reinforcing bars are assembled (step 106).

After the bottom plate box 23 having the cavity 25 is completed, the structure in which the float 17 and the bottom plate box 23 are integrated is supported near the water surface 13 by a support member (not shown).
The valve 21 is opened, and the cement paste or water is injected into the cavity inside the float 17 through the pipe 19.

After the injection of the cement paste or water is completed, the valve 21 is closed, the float 17 and the bottom plate box 23 are separated from the support material, submerged in the water 11 and set to the excavation bottom surface 15 (step). 107). FIG. 8 is an explanatory view when the sinking of the float 17 and the bottom slab 23 is completed, and the entire upper surface of the excavation bottom surface 15 and the entire lower surface of the float 17 are brought into close contact with each other.

The cavity in the float 17 and the size of the cavity 25 in the bottom slab 23 are calculated and determined in consideration of the following points. That is, up to step 106, in a state where air is contained in the cavity in the float 17, the bottom plate box 23 made of reinforced concrete, the steel float 17, the work machine and the worker mounted on the bottom plate box 23 are exposed to the water surface. It has enough buoyancy to float on 13.

In the state where the cavity in the float 17 is filled with water or cement paste in step 107,
The specific gravity of the float 17 and the bottom plate box 23 as a whole must be slightly heavier than the specific gravity of the water 11 in which mud or the like is mixed.

Next, as shown in FIG. 9, a waterproofing work 27 is applied to the boundary portion between the side wall 1 and the bottom plate box 23 (step 10).
8). In addition, an auxiliary construction method such as injecting underwater non-separable concrete is added to the boundary surface between the bottom of the float 17 and the excavation bottom surface 15 if necessary.

Next, as shown in FIG. 10, the water 11 inside the side wall 1 is drained by a pump (not shown) or the like (step 109).

Next, as shown in FIG. 11, the bottom plate box 23
A drilling work is performed from the upper part of the to the upper surface of the cavity 25, and a solidifying material such as concrete or mortar is poured into the cavity 25 and filled (step 110). Step 11
After 0, it will be a dry construction.

When water is injected into the cavity inside the float 17 in step 107, the valve 21
Open and replace the water inside with a solidifying material such as concret.

Next, the upper surface of the bottom plate box 23 is finished by removing the upper portion of the pipe 19 and the valve 21 protruding from the upper surface of the bottom plate box 23.

Next, as shown in FIG. 12, a connecting concrete 29 for connecting the side wall 1 and the bottom slab 23 is applied (step 111).

Finally, as shown in FIG. 13, a heat insulating material and a membrane are installed on the side wall 1 in the underground tank 33 and the inner surface of the bottom slab 23, and the roof 31 is placed on the upper end portion of the side wall 1 to form the underground tank. 33 is completed (step 112).

As described above in detail, according to the present embodiment, after the side wall 1 is constructed by the open caisson method, the float 17 and the bottom plate box 2 floated on the water surface 13.
Since 3 is sunk to the excavation bottom surface 15, an underground tank can be constructed economically.

Further, since the bottom slab finishing work in and after step 110 is a dry construction, the quality of the bottom slab can be secured at a high level.

In this embodiment, the can 25 has the cavity 25 closed in step 106 of FIG. 1, but the cavity 25 has an inlet or a valve with a lid excellent in waterproofness. May be provided so that the inlet portion is not covered with concrete. In this case, step 110
Then, the solidifying material can be injected by loosening the lid or the valve without performing the drilling work.

[0032]

As described above in detail, according to the present invention, it is possible to construct an economical underground tank of good quality.

[Brief description of drawings]

FIG. 1 is a flowchart showing a construction method according to the present embodiment.

FIG. 2 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 3 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 4 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 5 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 6 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 7 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 8 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 9 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 10 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 11 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 12 is an explanatory diagram showing the procedure for constructing an underground tank.

FIG. 13 is an explanatory diagram showing the procedure for constructing an underground tank.

[Explanation of symbols]

 1 ... Sidewall 3 ... Ground surface 5 ... Ground 7 ... Groundwater level surface 9 ... Excavation surface 11 ... Water 13 ... Water surface 15 ... Excavation bottom surface 17 ... Float 19 ………… Pipe 21 ………… Valve 23 ………… Bottom plate box 25 ………… Cavity 27 ………… Water stoppage 29 ………… Connected concrete 31 ………… Roof 33 ……… Underground tank

Claims (2)

[Claims] 1. A step of excavating the inside of a caisson serving as a side wall of an underground tank and submerging the caisson in the ground, a step of floating a float in groundwater in the caisson, and constructing a bottom plate on the float, the bottom plate And a step of draining the groundwater in the caisson, the method for constructing a bottom slab of an underground tank. 2. A cavity is provided inside the float,
The method for constructing a bottom slab for an underground tank according to claim 1, wherein a liquid or a solid is injected into the float when the bottom slab is set on the bottom.