JP5207086B2 - Construction method of underground tank - Google Patents

Description

  The present invention relates to a method for constructing an underground tank used for storing a low-temperature liquid such as liquefied natural gas.

Conventionally, as a storage tank for low-temperature liquid such as liquefied natural gas (LNG), a bottom slab, a side wall constructed along the periphery of the bottom slab, and a roof covering the top of the side slab are provided. A buried underground tank is used.
The construction procedure for such underground tanks is to construct a cylindrical underground wall in the ground, excavate the interior of the underground continuous wall, and then build a frame such as a bottom plate or side wall. The roof is built after the building is completed. For this reason, the excavation work inside the underground continuous wall and the construction work of the bottom slab and the side wall are performed without a roof and are light work, so the process depends on the weather.
This is one factor that makes it difficult to shorten the construction period in the construction of underground tanks.

  In recent years, an underground tank construction method for constructing a roof has been performed prior to excavation work inside an underground tank and construction work for a bottom slab and side walls (see, for example, Patent Documents 1 to 11). In these underground tank construction methods, excavation work inside the tank and bottom plate construction work can be performed with a roof, so that the process is less affected by the weather.

JP-A-7-279475 Japanese Patent No. 3501283 JP 2000-73385 A JP 2000-96588 A Japanese Patent Laid-Open No. 61-21277 JP-A 63-67380 JP-A-4-333784 JP-A-7-11807 Japanese Unexamined Patent Publication No. 7-91103 JP 2000-73384 A JP 2000-87371 A

  By the way, in the underground tank, all or most of the side wall is located above the ground surface before the underground tank is constructed, in addition to the underground tank buried in the ground. There is an underground tank that is buried in the ground by embankment on the outer periphery of the upper part of the basin.

Such an underground tank is constructed such that the upper end portion of the side wall is located, for example, about 10 m above the ground surface before construction.
Such underground tanks can reduce the amount of ground excavation during construction and counteract the lifting pressure caused by groundwater compared to underground tanks where all or most of the side walls are buried underground. Therefore, since it is not necessary to reinforce the casing or increase the volume of the casing, the construction period can be shortened and the cost can be reduced.

Therefore, in the construction of such an underground tank, as in the conventional underground tank construction method disclosed in Patent Documents 1 to 11, excavation work inside the underground tank with the roof erected, the bottom plate and the side wall When construction work is performed, it is possible to further shorten the construction period and reduce costs.
However, the conventional underground tank construction methods disclosed in Patent Documents 1 to 11 are intended for underground tanks in which all or most of the side walls are buried in the ground.
For example, in the construction method of the underground tank described in Patent Document 1, the roof is divided into a fan shape or a semicircle and can be slid in the horizontal direction. However, when the roof is positioned above the original ground surface, the horizontal direction It is difficult to move.
Further, for example, in the conventional underground tank construction methods described in Patent Documents 2 to 10, an opening for construction is formed in the roof during construction, and materials and earth and sand are carried in and out from this opening. However, if the roof is located above the ground surface, it is necessary to lift the equipment and earth and sand, etc., which increases the work period and cost.

  The present invention has been made in view of the circumstances described above, and in the construction of an underground tank in which the upper side of the side wall is located above the ground surface before the underground tank is constructed, It aims at providing the construction method of an underground tank which can perform the excavation process inside a tank, and the process of constructing a bottom slab and a side wall.

In order to achieve the above object, an underground tank construction method according to the present invention includes a bottom plate, a side wall constructed along the periphery of the bottom plate, and a main body roof covering an upper portion of the side wall, and the bottom plate, A method of constructing an underground tank in which the side wall is buried in the ground, a continuous underground wall construction step for constructing a cylindrical underground continuous wall in the ground, a roof portion serving as the main body roof, and the roof A roof assembling step for installing on the ground a roof provided with a separation part separable from the roof part on the outer periphery of the part, and an interior for excavating the inside of the underground continuous wall after installing the roof Excavating step, bottom plate building step for building the bottom plate, side wall building step for building the side wall to a height above the ground surface, separating the roof portion and the separating portion, and and a body roof installation step of fixing the upper end of the side wall, Serial body roof installation process, after the side wall is constructed in the side wall construction process, characterized in that fixed to the upper end of the side wall is raised to the roof.

Also, construction how underground tank according to the present invention includes a bottom plate, a side wall constructed along the periphery of the bottom plate, comprising a body roof covering an upper portion of said side wall, a, is said and said bottom plate side wall A method for constructing an underground tank buried in the ground, comprising a continuous underground wall construction step for constructing a cylindrical underground continuous wall in the ground, and a roof part to be the main body roof and an outer periphery of the roof part. A roof assembling step of installing on the ground a roof comprising the roof portion and a separation portion provided in a separable manner, and an internal excavation step of excavating the inside of the underground continuous wall after the roof is installed; A bottom plate construction step for constructing the bottom plate, a side wall construction step for constructing the side wall up to a height above the ground surface, the roof portion and the separation portion are separated, and the roof portion is an upper end portion of the side wall. and a body roof installation step of fixing the said side wall construction process A first side wall construction step of constructing a lower side than the ground surface of the side wall, and a second side wall construction step of constructing an upper side from the ground surface of the side wall after the first side wall construction step, In the main body roof installation step, between the first side wall construction step and the second side wall construction step, the roof is raised and temporarily installed above the upper end portion of the side wall, and after the second side wall construction step, While separating the said roof part and the said separation part, the said roof part is fixed to the upper end part of the said side wall, It is characterized by the above-mentioned .

Also, construction how underground tank according to the present invention includes a bottom plate, a side wall constructed along the periphery of the bottom plate, comprising a body roof covering an upper portion of said side wall, a, is said and said bottom plate side wall A method for constructing an underground tank buried in the ground, comprising a continuous underground wall construction step for constructing a cylindrical underground continuous wall in the ground, and a roof part to be the main body roof and an outer periphery of the roof part. A roof assembling step of installing on the ground a roof comprising the roof portion and a separation portion provided in a separable manner, and an internal excavation step of excavating the inside of the underground continuous wall after the roof is installed; A bottom plate construction step for constructing the bottom plate, a side wall construction step for constructing the side wall up to a height above the ground surface, the roof portion and the separation portion are separated, and the roof portion is an upper end portion of the side wall. and a body roof installation step of fixing the said side wall construction process A first side wall construction step of constructing a lower side than the ground surface of the side wall, and a second side wall construction step of constructing an upper side from the ground surface of the side wall after the first side wall construction step, In the second side wall construction process, the side walls are constructed in stages from the bottom to the top, and in the main body roof installation process, the roof is raised for each stage of the second side wall construction process, and is constructed at a stage immediately after. And temporarily separating the roof portion and the separation portion after the second sidewall construction step, and fixing the roof portion to the upper end portion of the sidewall. And

  According to the present invention, even if the upper side of the side wall is an underground tank located above the ground surface before the underground tank is constructed, the internal excavation process, the bottom slab construction process, and the side wall construction process are performed with the roof. By being able to carry out the work, the construction is not affected by the weather, so the construction period can be shortened and the cost can be reduced.

It is a figure which shows an example of the underground tank by embodiment of this invention. It is a figure explaining a ground improvement process and a ground surface layer part excavation process. It is a figure explaining a guide wall construction process and an underground continuous wall construction process. (A) is a figure explaining a temporary roof installation process, (b) is a top view of (a). (A) is a figure explaining the construction opening part of a temporary roof, (b) is a figure which shows the scaffold provided in the temporary roof, (c) is a figure explaining the behavior of the scaffold shown in (b). It is a figure explaining an internal excavation process. It is a figure explaining a bottom plate construction process. It is a figure explaining a side wall construction process. It is a figure explaining a roof installation process.

(First embodiment)
Hereinafter, an underground tank construction method according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 9.
(Underground tank)
As shown in FIG. 1, the underground tank 1 according to the present embodiment is used as, for example, an LNG storage tank, and has a bottom plate 2 having a substantially circular shape in plan view disposed below the ground G surface, and a substantially cylindrical shape. And a dome-shaped main roof 4 supported by an upper end 3 a of the side wall 3.

Further, the ground G on the outer periphery of the side wall 3 on the lower end 3b side is provided with an underground continuous wall 5 having a shape along the outer peripheral surface of the side wall 3 and having an annular shape in plan view. The ground improvement body 6 is constructed on the ground G. Moreover, between the underground continuous wall 5 and the ground improvement body 6, the guide wall 7 which supported the roof 21 (refer FIG. 4) mentioned later at the time of underground tank 1 construction, and the side heater 8 are provided. Yes.
The guide wall 7 serves as a ruler when the underground continuous wall 5 is constructed.

The bottom slab 2 is made of reinforced concrete, and is constructed on the crushed stone layer 11 provided on the ground G excavated. A bottom heater 12 that adjusts the temperature in the underground tank 1 is installed inside the bottom plate 2.
The side wall 3 is made of reinforced concrete, the lower end 3b is rigidly joined to the outer edge 2a of the bottom plate 2, and the bottom plate 2 and the side wall 3 are formed in a bottomed cylindrical shape.
If the ground surface before this underground tank 1 is constructed is the pre-construction ground surface Ga, the side wall 3 is located below the pre-construction ground surface Ga and the upper side is located above the pre-construction ground surface Ga. ing.
And since the embankment is carried out in the outer periphery of the upper side of the side wall 3 during construction of the underground tank 1, the underground tank 1 has the structure distribute | arranged underground.

The underground continuous wall 5 has a function of preventing the ground G from collapsing and a water stop function as a soil retaining. The underground continuous wall 5 is constructed deeper than the bottom slab 2 of the underground tank 1, and the lower end portion 5 b reaches the hardly permeable layer (cold clay layer) 13.
The underground continuous wall 5 is constructed of, for example, concrete.
The ground improvement body 6 is formed by, for example, a sand compaction pile method or the like, and is provided as a countermeasure against liquefaction of the ground G around the underground tank 1.

The main body roof 4 is formed in a circular shape in plan view, and includes a plurality of frame members 15 installed on the upper end portion 3 a of the side wall 3, a cold insulation material 16 disposed below the frame members 15, and the frame members 15. And a roofing material 17 disposed on the upper side.
On the inner surfaces of the bottom plate 2 and the side wall 3, a cold insulation layer (inner tub) 18 including a cold insulation material (not shown) and a membrane material made of, for example, a stainless steel sheet attached inside the cold insulation material is formed. .

(Underground tank construction method)
Next, the construction method of the underground tank 1 mentioned above is demonstrated using drawing.
The underground tank construction method according to the present embodiment precedes excavation of the ground G inside the underground continuous wall 5 where the underground tank 1 shown in FIG. As shown in FIG. 4, the roof 21 is disposed on the ground G.
(Ground improvement process)
First, as shown in FIG. 2, the ground of the ground G on the outer periphery side of the underground tank 1 is improved.
This ground improvement is performed by, for example, a sand compaction pile method. The shape and size of the ground improvement body 6 are determined in consideration of the shape of the underground tank 1 and the strength of the ground G.

(Surface surface layer excavation process)
Subsequently, the region where the underground tank 1 is disposed and the surface layer portion Gb of the ground G in the vicinity of the outer periphery thereof are excavated down so as to be lower than the surrounding ground G.
In the construction method of the underground tank 1 according to the present embodiment, the roof 21 (see FIG. 4A) is installed in the lowering region where the surface layer Gb of the ground G is excavated. As a result, the wind hitting the roof 21 during construction can be reduced, and materials and equipment can be easily carried in. As a result, the safety of work can be improved.
The depth of the ground excavation of the surface layer portion Gb of the ground G is determined in consideration of the shape of the temporary roof 21 and the topography.

(Guide wall installation process)
Subsequently, as shown in FIG. 3, a guide wall 7 which is a ruler for constructing the underground continuous wall 5 and is also a foundation for supporting the outer peripheral portion of the roof 21 (see FIG. 4A) is installed. .
The guide wall 7 includes an outer guide wall 7 a positioned outside the underground continuous wall 5 and an inner guide wall 7 b positioned inside the underground continuous wall 5. The outer guide wall 7a and the inner guide wall 7b are installed so as to sandwich the underground continuous wall 5, and are formed in an annular shape in plan view with concrete or the like.
The inner guide wall 7b is removed together with the ground G inside the underground continuous wall 5 in a later internal excavation step, and only the outer guide wall 7a remains in the ground G even after the underground tank 1 is completed.
In the guide wall installation step, the outer guide wall 7a and the inner guide wall 7a and the inner guide wall 7a are spaced so that there is an interval corresponding to the thickness of the underground continuous wall 5 between the inner peripheral surface of the outer guide wall 7a and the outer peripheral surface of the inner guide wall 7b. A guide wall 7b is installed.

(Underground continuous wall installation process)
Subsequently, the underground continuous wall 5 is constructed between the outer guide wall 7a and the inner guide wall 7b installed at intervals.
The underground continuous wall 5 is constructed by a well-known technique in which excavation grooves are provided along the periphery of the planned installation location of the underground tank 1 and concrete is placed by placing reinforcing bars in the grooves. At this time, the underground continuous wall 5 is constructed so that the lower end 5b reaches the hardly water-permeable layer 13.

(Roof assembly process)
Subsequently, as shown in FIGS. 4A and 4B, a roof 21 is installed. The roof 21 includes a roof portion 22 in which the main body roof 4 (see FIG. 1) is partially constructed, and a separation portion 23 provided on the outer peripheral portion of the roof portion 22 and separable from the roof portion 22. .

  The roof portion 22 is a plane among the frame material 15 and the cold insulation material 16 (see FIG. 1), the cold insulation material 16a disposed near the radial center in plan view, and the roof material 17 (see FIG. 1). And a roof material 17a partially disposed on the outer peripheral side as viewed from the radial center. The position of the outer peripheral side end portion of the roof material 17 a is arranged so as to be a position in the vicinity of the inner peripheral side of the side wall 3.

A construction opening 24 is formed in a portion of the roof portion 22 where the roof material 17a is not disposed. The construction opening 24 is used as an opening for carrying in / out materials and equipment during construction and for carrying out earth and sand. And as shown to Fig.5 (a), this construction opening part 24 is covered with the detachable covering material 25, and is opened and closed as needed.
The covering material 25 is, for example, a sheet-like member. When working (use), the covering material 25 is wound up in a roll shape to open the construction opening 24, and when the work is suspended (unused) The construction opening 24 may be covered with the construction opening 24.
Further, the covering material 25 is, for example, a member including a frame assembled slightly larger than the construction opening 24 and a sheet attached to the frame, and the entire covering material 25 is moved to construct the frame. The opening 24 for use may be opened or closed.
Further, a separate sheet-like covering material is also provided on the separation portion 23 of the roof 21 so that the entire roof 21 is protected against rain.

As shown in FIG. 4, the separation part 23 is made of a frame material connected to the frame material 15 of the roof part 22, and the opposite side (outer peripheral part) of the connection side of the roof part 22 to the frame material 15 is the outer side. It is supported by the guide wall 7a. The connection position between the roof portion 22 and the separation portion 23 is a position in the vicinity of the inner peripheral surface of the side wall 3.
The connection between the roof portion 22 and the separation portion 23 may be integrally connected or may be connected with a connecting tool such as a bolt. In any case, the roof portion 22 and the separation portion 23 are configured to be separable. For example, when the roof portion 22 and the separation portion 23 are integrally connected, they are separated by cutting, and when they are connected by a connector such as a bolt, they are separated by removing the connector. .

  And in a roof assembly process, while installing so that the outer peripheral part of the isolation | separation part 23 may be supported by the outer side guide wall 7a, the frame material 15 of the roof part 22 is arrange | positioned. At this time, the frame material 15 and the separation part 23 are connected.

Subsequently, the cold insulating material 16a and the roof material 17a are installed.
When installing the cold insulation material 16a, a scaffold 31 is used which is substantially the same length as the radius of the roof portion 22 as shown in FIGS. 5B and 5C and is formed in accordance with the curvature of the roof portion 22. To do. The scaffold 31 is supported by the frame member 15 and is slidably supported by a plurality of guide rails 32 extending concentrically in the circumferential direction of the roof portion 22, and is rotatable along the circumferential direction of the roof portion 22. It is configured.
The cold insulator 16a is installed while the scaffold 31 is rotated.
The roof material 17a is installed by lifting the roof material 17a with a crane or the like and installing it on the upper part of the frame material 15.

(Internal drilling process)
Subsequently, as shown in FIG. 6, the ground G inside the underground tank 1 is excavated.
In this step, the inside of the underground continuous wall 5 is excavated to a predetermined depth. At this time, the inner guide wall 7b arranged inside the underground continuous wall 5 is removed together with the excavation.
At this time, the excavation equipment and excavated earth and sand are carried in and out through a construction opening 24 formed in the roof 21.

(Bottom plate construction process)
Subsequently, as shown in FIG. 7, the bottom slab 2 is constructed on the ground G excavated in the internal excavation process.
The bottom plate 2 is constructed by placing the crushed stone layer 11 on the ground G, placing a reinforcing bar on the top thereof, and placing concrete into the bottom plate 2. At this time, the bottom heater 12 is installed on the bottom plate 2.
In the bottom plate construction process, materials and equipment are carried in and out through the construction opening 24 of the roof 21.

(Sidewall construction process)
Then, as shown in FIG. 8, the side wall 3 is constructed.
The side wall 3 is constructed by integrating with the bottom plate 2 and placing the reinforcing bars at predetermined heights from the lower end portion 3b side to the upper end portion 3a side, and successively casting concrete. At this time, since the upper end portion 3a side of the side wall 3 is higher than the ground G surface, the side wall 3 is constructed so as to involve the separation portion 23 of the roof 21. At this time, the side wall 3 is constructed with the covering material 25 (see FIG. 5A) removed.

(Main body roof installation process)
Subsequently, as shown in FIG. 9, the roof portion 22 is installed on the upper end portion 3 a of the side wall 3.
First, the roof fixing device 26 is attached to the upper end 3 a of the side wall 3. And the raising device 27, such as a jack, for raising the roof part 22 to the upper end part 3a of the side wall 3 is installed in a predetermined position.
And after setting the raising device 27 and the roof part 22 so that the roof part 22 can be raised, the roof 21 is separated into the roof part 22 and the separation part 23. At this time, the cold insulation material 16 and the roof material 17 may be applied to a part of the portion of the roof portion 22 where the cold insulation material 16 and the roof material 17 are not applied.

Next, by driving the lifting device 27, the roof portion 22 is raised to the height of the upper end portion 3 a of the side wall 3 and fixed to the roof fixing device 26. Thereby, the roof part 22 becomes the main body roof 4.
Further, the separation part 23 is removed except for the part of the side wall 3 that is caught in the concrete.
The outer guide wall 7a is left on the ground G as it is.
And simultaneously with this main body roof installation process, the inner tank construction which installs a cold insulating material and a membrane in the inner peripheral side of the side wall 3 is performed. Finally, the roof 24 is closed by applying the cold insulation material 16 and the roof material 17 to the opening 24 for construction, and the main body roof 4 is completed.

(Filling process)
Subsequently, returning to FIG. 1, embankment of the outer periphery on the upper side of the side wall 3 is performed.
Moreover, the side heater 8 is installed in the embankment process.
At this time, embankment is performed to the height near the upper end 3a of the side wall 3 so that the outer peripheral surface of the side wall 3 is buried in the ground. In FIG. 1, the ground G that has been embanked is denoted as Gc. The earth and sand used for this embankment is preferably the earth and sand excavated in the internal excavation process. In this way, by using the earth and sand excavated in the internal excavation process as the embankment, it is possible to reduce the amount of sediment generated in the internal excavation process.
At this time, if the outer guide wall 7a, the underground continuous wall 5 and the side wall 3 are integrated, the embankment above the outer guide wall 7a and the weight of the outer guide wall 7a and the underground continuous wall 5 are It can be estimated as the weight of the tank 1.
In addition, you may perform this embankment process in parallel with a main body roof installation process.

According to the construction method of the underground tank 1 according to the first embodiment, the internal excavation process, the bottom slab construction process, and the side wall construction process can be performed in a state where the roof 21 is present, so that the construction period is shortened regardless of the weather. And cost can be reduced.
Moreover, since there is no influence of rainfall on the concrete placement of the bottom plate 2 and the side wall 3, the quality of the underground tank 1 can be improved.
In addition, since the roof 21 to be the main body roof 4 is assembled on the ground G, workability and safety can be improved.
Moreover, the efficiency of the raising operation | work of the roof part 22 can be raised by raising the roof part 22 after constructing | assembling the side wall 3. FIG.

As mentioned above, although embodiment of the construction method of the underground tank by this invention was described, this invention is not limited to said embodiment, In the range which does not deviate from the meaning, it can change suitably.
For example, in the embodiment described above, the surface layer Gb of the ground G is excavated and the roof 21 is installed on the ground G from which the surface layer Gb is excavated, but the surface layer Gb of the ground G is not excavated. A temporary roof 21 may be installed on the roof.
In the above-described embodiment, the ground G around the ground G where the underground tank 1 is built is improved, but the ground may not be improved.
Moreover, in embodiment mentioned above, although the jack is used when raising the roof part 22, instead of a jack, a several crane is installed in the periphery of the roof part 22, and the roof 4 is covered with a some crane. It may be hung and raised.

  In the above-described embodiment, after the side wall is constructed in the side wall construction process, the roof portion is raised and fixed to the upper end of the side wall, but the side wall construction process is performed below the ground G surface of the side wall 3. The first side wall construction step is divided into a first side wall construction step of constructing the lower side of the first side wall construction step and a second side wall construction step of constructing the upper side above the ground G surface of the side wall 3 after the first side wall construction step After the step is almost completed, a step of temporarily raising the roof 21 in the main body roof installation step may be performed.

The step of raising the roof 21 in the main body roof installation step to temporarily install the roof 21 may be sequentially raised along with the rise of the side wall in the second side wall construction step, and may be temporarily installed at each height. After the construction process, it may be temporarily set up to the height above the upper end of the side wall 3.
By doing in this way, since the separation part 23 is not caught in the concrete of the side wall 3, it is not necessary to work on the formwork or the reinforcing bar of the side wall 3, and the side wall can be constructed efficiently.
In the second side wall construction process, the construction can always be performed with a roof, so that the entire process can be performed regardless of the weather.

An example of the process of sequentially raising the roof 21 in this case will be described.
After the first side wall construction process is completed, first, the separation part 23 of the roof 21 and the outer guide wall 7a are disconnected. At this time, the roof portion 22 and the separation portion 23 are connected.
Then, the roof 21 is raised to a predetermined height by a jack, a crane, or the like, and held at this height by a support member such as a spacer. Subsequently, the side wall 3 is constructed to a height below the roof 21, and the roof 21 is raised to a higher position and held at that height. Then, the rising of the roof 21 and the construction of the side wall 3 are alternately performed. When the side wall 3 is completed, the separation part 23 is separated from the roof 21 and the roof part 22 is installed on the roof fixing device 26 installed at the upper end of the side wall 3. Fix it.

  As another method of sequentially raising the roof 21, a plurality of temporary columnar structures higher than the height of the side wall 3 are erected on the ground at predetermined intervals in the circumferential direction of the outer periphery of the circular roof 21 in plan view. The top of the temporary columnar structure and the separation part 23 or the roof part 22 may be connected by a pulling material such as a wire, and the tensile material may be pulled up sequentially to raise the roof.

  In addition, in the other method using the above-mentioned temporary rising temporary columnar structure, it does not need to be sequentially increased. That is, it is possible to raise the roof 21 at a stretch to a position slightly higher than the upper end of the side wall 3. In this way, it is possible to avoid a plurality of adjustments between different types of work, that is, the step of raising the roof and the second side wall construction step.

  Moreover, in said embodiment, the construction of the inner tank which consists of a cold insulating material and a membrane on the inner peripheral side of the side wall 3 is started after the construction of the side wall 3 is completed. However, in order to further shorten the process, when the concrete on the side wall 3 is launched to a certain extent, the construction of the inner tub on the bottom plate 2 is started, and further, as the concrete on the side wall 3 is driven, It is also conceivable to construct an inner tank for the three side walls. In this case, in order to prevent the side wall work and the inner tank work from being up and down work, the construction site in the plan view is different, or in the case of vertical work, a protective material is provided between the side wall work and the inner tank work. It is considered necessary to consider safety such as

DESCRIPTION OF SYMBOLS 1 Basement tank 2 Bottom plate 3 Side wall 3a Upper end part 3b Lower end part 4 Main body roof 5 Underground continuous wall 6 Ground improvement body 21 Roof 22 Roof part 23 Separation part 24 Construction opening part 27 Lifting device G Ground

Claims (3)

The bottom plate,
Side walls built around the perimeter of the bottom plate,
A main body roof covering the upper part of the side wall,
It is a construction method of an underground tank in which the bottom plate and the side wall are buried in the ground,
Underground continuous wall construction process of constructing a cylindrical underground continuous wall in the ground,
A roof assembling step of installing on the ground a roof provided with a roof part to be the main body roof and a separation part provided on the outer periphery of the roof part so as to be separable from the roof part;
After installing the roof, an internal excavation process for excavating the interior of the underground continuous wall;
A bottom plate construction step of constructing the bottom plate;
A side wall construction step of constructing the side wall to a height above the ground surface;
A main body roof installation step for separating the roof portion and the separation portion and fixing the roof portion to an upper end portion of the side wall , and
In the main body roof installation process, after the side wall is constructed in the side wall construction process, the roof part is raised and fixed to the upper end part of the side wall . The bottom plate,
Side walls built around the perimeter of the bottom plate,
A main body roof covering the upper part of the side wall,
It is a construction method of an underground tank in which the bottom plate and the side wall are buried in the ground,
Underground continuous wall construction process of constructing a cylindrical underground continuous wall in the ground,
A roof assembling step of installing on the ground a roof provided with a roof part to be the main body roof and a separation part provided on the outer periphery of the roof part so as to be separable from the roof part;
After installing the roof, an internal excavation process for excavating the interior of the underground continuous wall;
A bottom plate construction step of constructing the bottom plate;
A side wall construction step of constructing the side wall to a height above the ground surface;
A main body roof installation step for separating the roof portion and the separation portion and fixing the roof portion to an upper end portion of the side wall, and
The side wall construction step includes a first side wall construction step of constructing a lower side than the ground surface of the side wall, and a second side wall construction of constructing an upper side from the ground surface of the side wall after the first side wall construction step. A process,
In the main body roof installation step, between the first side wall construction step and the second side wall construction step, the roof is raised and temporarily installed above the upper end portion of the side wall, and after the second side wall construction step, while separating the separation unit and the roof unit, the construction method of the underground tank you characterized by securing the roof portion to an upper end of the side wall. The bottom plate,
Side walls built around the perimeter of the bottom plate,
A main body roof covering the upper part of the side wall,
It is a construction method of an underground tank in which the bottom plate and the side wall are buried in the ground,
Underground continuous wall construction process of constructing a cylindrical underground continuous wall in the ground,
A roof assembling step of installing on the ground a roof provided with a roof part to be the main body roof and a separation part provided on the outer periphery of the roof part so as to be separable from the roof part;
After installing the roof, an internal excavation process for excavating the interior of the underground continuous wall;
A bottom plate construction step of constructing the bottom plate;
A side wall construction step of constructing the side wall to a height above the ground surface;
A main body roof installation step for separating the roof portion and the separation portion and fixing the roof portion to an upper end portion of the side wall, and
The side wall construction step includes a first side wall construction step of constructing a lower side than the ground surface of the side wall, and a second side wall construction of constructing an upper side from the ground surface of the side wall after the first side wall construction step. A process,
In the second side wall construction step, the side wall is constructed stepwise from below to above,
In the main body roof installation process, the roof is raised for each stage of the second side wall construction process, temporarily installed above the upper end of the side wall constructed in the stage immediately after, and after the second side wall construction process , together with separating the said roof portion the separation unit, the construction method of the underground tank you characterized by securing the roof portion to an upper end of the side wall.

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