The present disclosure relates to a construction method for a double-shell tank.
For example, as shown in Patent Document 1, in order to store liquefied natural gas (LNG), a double-shell tank including an outer tank mainly made of concrete and a metallic inner tank disposed inside the outer tank is mainly used. Such a technique is disclosed in Patent Documents 2 to 4 as well.
Japanese Unexamined Patent Application, First Publication No. 2005-247324
Japanese Unexamined Patent Application, First Publication No. 2003-292091
Japanese Unexamined Utility Model Application, First Publication No. S55-041653
Japanese Unexamined Utility Model Application, First Publication No. H03-084557
In the case of constructing the above-described double-shell tank, a bottom cold insulating layer or the like which supports the inner tank is formed inside the outer tank. In order to maintain a cold insulation function, the bottom cold insulating layer needs to be prevented from becoming wet due to rainwater. For this reason, when the double-shell tank is constructed, a part of an outer tank ceiling is formed in advance to prevent entering of rainwater into the outer tank and then the bottom cold insulating layer is formed. More specifically, an outer tank side wall having a support metallic member embedded in its top is formed and then a part of the outer tank ceiling is formed in advance by lifting up a metal roof serving as a skeleton portion of the outer tank ceiling by air raising or the like and fixing the metal roof to the support metallic member.
However, the top of the outer tank side wall is exposed for several months until concrete is installed above the metal roof serving as the skeleton portion of the outer tank ceiling. For this reason, rainwater enters at a boundary between a concrete portion of the outer tank side wall and the embedded support metallic member and intrudes to an inner surface of the outer tank side wall in some cases. In this case, it is necessary to separately perform countermeasures or the like to prevent the bottom cold insulating layer or the like from getting wet, which causes prolonging or the like of construction or the like.
The present disclosure was made in view of the above-described problems, and an object thereof is to provide a construction method for a double-shell tank that includes an outer tank made of concrete for the purpose of preventing rainwater from intruding to an inner surface of an outer tank side wall before concrete is installed above a metal roof serving as a skeleton portion of an outer tank.
The present disclosure employs the following constitution as a means for solving the above-described problems.
The present disclosure is a construction method for a double-shell tank that includes a support metallic member embedded in an inner surface of an outer tank side wall made of concrete in a state where a part of the support metallic member is exposed and a metal roof supported by the support metallic member and forming a lower layer of an outer tank ceiling, the construction method for a double-shell tank including: an outer tank side wall formation step for forming the outer tank side wall by installing concrete so that an upper surface of the outer tank side wall is a water guide surface that descends toward an outside of an outer tank in a state where the outer tank side wall takes the support metallic member therein; and a metal roof formation step for forming the metal roof connected to the support metallic member.
According to the present disclosure, an upper surface of an outer tank side wall is a water guide surface which descends toward an outside of an outer tank. For this reason, rainwater pouring down on an upper surface of the outer tank side wall is drained from the outer tank side wall toward the outside of the outer tank side wall along a water guide surface. For this reason, a large amount of rainwater does not accumulate on the upper surface of the outer tank side wall and rainwater can be prevented from entering at a boundary between a support metallic member embedded in the outer tank side wall and a concrete portion near the support metallic member. Therefore, according to the present disclosure, rainwater can be prevented from intruding to an inner surface of an outer tank side wall before concrete is installed above a metal roof serving as a skeleton portion of an outer tank through a construction method for a double-shell tank including an outer tank made of concrete.
An embodiment of a construction method for a double-shell tank according to the present disclosure will be described below with reference to the drawings. It should be noted that the scale of members may have been appropriately changed to make the members have recognizable sizes in the following drawings.
The basement floor slab 2 is a member serving as a foundation which supports the outer tank 3, the inner tank 5, or the like from below and is formed in a substantially disk shape with a larger diameter than the outer tank 3 when viewed from above. The basement floor slab 2 has a heater (not shown) installed therein and prevents cold heat of stored liquefied natural gas (LNG) from being transferred to the ground. The outer tank 3 is a container made of pre-stressed concrete and is erected on the basement floor slab 2 to cover the inner tank 5. The outer tank 3 is mainly made of concrete and includes a cylindrical outer tank side wall 3a and an outer tank ceiling 3b connected to an upper edge of the outer tank side wall 3a.
A plurality of reinforcing bars 3a2 are erected from the basement floor slab 2 and are disposed over the entire region in a height direction of the outer tank side wall 3a. The plurality of reinforcing bars 3a2 are strength members which support the concrete layer 3a1 and are skeleton portions of the outer tank side wall 3a. The support metallic member 3a3 is a substantially annular member which is embedded in a top of the outer tank side wall 3a so that an inner surface thereof is flush with an inner surface of the concrete layer 3a1 (that is, an inner surface of the outer tank side wall 3a). The support metallic member 3a3 is partially connected to the reinforcing bars 3a2. The support metallic member 3a3 is a portion to which a metal roof 3b1 (which will be described later) of the outer tank ceiling 3b is connected. The water cut-off member 3a4 is a member which prevents rainwater from entering at the boundary between the concrete layer 3a1 and the support metallic member 3a3 during construction of the double-shell tank 1. Examples of the water cut-off member 3a4 can include a water-swelling water cut-off member which swells when it absorbs water.
The outer tank ceiling 3b includes the metal roof 3b1 and a concrete layer 3b2. The metal roof 3b1 is a steel framework member which forms a lower layer of the outer tank ceiling 3b, and includes a shoulder 3b3 and a central portion 3b4 as shown in
Referring to
The side cold insulating layer 6 is disposed between the outer tank side wall 3a and the inner tank side wall 5b and is formed from granular perlite filled therebetween. Furthermore, as shown in
The suspended deck 7 is a disk-shaped metallic member which is suspended and supported by the hangers 8 to block an upper end of the inner tank 5 which is an opening end from above. Each of the hangers 8 has an upper end fixed to the outer tank ceiling 3b and a lower end fixed to the suspended deck 7. As shown in
The retaining wall 9 is disposed in a substantially cylindrical shape along an outer edge of the suspended deck 7 and is formed from the outer tank ceiling 3b to the suspended deck 7. The retaining wall 9 prevents the side cold insulating layer 6 made of granular perlite from entering above the suspended deck 7 (inside the tank). The upper cold insulating layer 10 is placed on an upper surface of the suspended deck 7 and is disposed inside the retaining wall 9. The upper cold insulating layer 10 is formed of a polyurethane foam or the like.
Subsequently, the construction method for the double-shell tank 1 according to the embodiment will be described with reference to
First, as shown in
Subsequently, as shown in
Through the steps shown in
Subsequently, as shown in
As shown in
Here, according to the construction method for the double-shell tank 1 in the embodiment, an upper surface of the outer tank side wall 3a is the water guide surface 3a5 which descends toward the outside in the radial direction of the outer tank 3 until the concrete layer 3b2 is formed above the metal roof 3b1. Rainwater pouring down on the upper surface of the outer tank side wall 3a drains from the outer tank side wall 3a toward the outside of the outer tank side wall 3a along the water guide surface 3a5. For this reason, a large amount of rainwater does not accumulate on the upper surface of the outer tank side wall 3a and rainwater can be prevented from entering at a boundary between the support metallic member 3a3 embedded in the outer tank side wall 3a and the concrete layer 3a1 near the support metallic member 3a3. Therefore, according to the double-shell tank 1 in the embodiment, rainwater can be prevented from intruding to an inner surface of the outer tank side wall 3a before concrete is installed above the metal roof 3b1 serving as a skeleton portion of the outer tank 3.
Also, in the construction method for the double-shell tank 1 according to the embodiment, the water guide surface 3a5 is formed as an inclined surface which descends toward the outside of the outer tank 3. For this reason, rainwater can be reliably guided toward the outside of the outer tank side wall 3a in the entire region of the upper surface of the outer tank side wall 3a. Therefore, according to the construction method for the double-shell tank 1 in the embodiment, rainwater can be more reliably prevented from entering at the boundary between the support metallic member 3a3 and the concrete layer 3a1 near the support metallic member 3a3.
In the construction method for the double-shell tank 1 according to the embodiment, in the outer tank side wall formation step, the inner frame K2 which is brought into contact with the support metallic member 3a3 from an inside of an outer tank side wall formation region and the outer frame K1 which is disposed on an outside of the outer tank side wall formation region and has an upper end lower than an upper end of the support metallic member 3a3 are positioned and concrete is installed between the outer frame K1 and the inner frame K2. For this reason, since the upper end of the support metallic member 3a3 and the upper end of the outer frame K1 are used as references and an inclined surface connecting these upper ends is formed, the water guide surface 3a5 can be easily formed. Therefore, the water guide surface 3a5 with a uniform inclination can be formed over the entire circumference of the outer tank side wall 3a.
In the construction method for the double-shell tank 1 according to the embodiment, in the outer tank side wall formation step, concrete is installed after the water cut-off member 3a4 is adhered to the support metallic member 3a3. For this reason, the water cut-off member 3a4 can be easily disposed in the boundary between the support metallic member 3a3 and the concrete layer 3a1. Since the water cut-off member 3a4 is provided, rainwater can be prevented from intruding to the inner surface of the outer tank side wall 3a even when rainwater enters at the boundary between the support metallic member 3a3 and the concrete layer 3a1 near the support metallic member 3a3.
Also, in the construction method for the double-shell tank 1 according to the embodiment, the upper portion 3b6 of the shoulder 3b3 in the metal roof 3b1 protrudes outward from the lower portion 3b5. For this reason, rainwater falling on the metal roof 3b1 can be prevented from falling to the vicinity of the support metallic member 3a3 along the lower portion 3b5. Therefore, rainwater can be more reliably prevented from entering at the boundary between the support metallic member 3a3 and the concrete layer 3a1 near the support metallic member 3a3.
While the preferred embodiments of the present disclosure have been described above with reference to the drawings, the present disclosure is not limited to the above-described embodiments. The shapes, combinations, or the like of the constituent elements shown in the above-described embodiments are merely examples and various modifications are possible on the basis of design requirements or the like without departing from the gist of the present disclosure.
For example, a constitution in which the water guide surface 3a5 is an inclined surface has been described in the above-described embodiments. However, the present disclosure is not limited thereto and a constitution in which the water guide surface 3a5 is a stepped surface which gradually descends toward the outside of the outer tank side wall 3a can also be adopted. It is possible to prevent rainwater falling on a region of the upper surface in the outer tank side wall 3a close to the outer side from flowing in a direction toward the support metallic member 3a3 disposed close to the inner side, and It is possible to prevent rainwater from entering at the boundary between the support metallic member 3a3 and the concrete layer 3a1 near the support metallic member 3a3 even when such a constitution is adopted. Furthermore, a constitution in which the water guide surface 3a5 is configured to have a shape obtained by combining an inclined surface, a stepped surface, and the like can also be adopted.
A constitution in which a guide groove is formed in the water guide surface 3a5 can also be adopted in the above-described embodiment. When this constitution is adopted, a flow of rainwater can be more reliably guided due to the guide groove, and for example, rainwater can be intensively drained from a desired portion.
A constitution in which the water guide surface 3a5 is formed by disposing the outer frame K1 having the upper end lower than the upper end of the support metallic member 3a3 and using the upper end of the support metallic member 3a3 and the upper end of the outer frame K1 so as to form the inclined surface connecting these upper ends has been described in the embodiment. However, the present disclosure is not limited thereto and a constitution in which heights of the outer frame K1 and the inner frame K2 are the same and the inclined surface is formed by another method may be adopted.
Also, a constitution in which the water cut-off member 3a4 is adhered to the support metallic member 3a3 in advance before concrete is installed has been described in the embodiment. However, the present disclosure is not limited thereto and a constitution in which the water cut-off member 3a4 is not provided, a constitution in which the water cut-off member 3a4 is provided at another location after concrete is installed, and the like can also be adopted.
According to the present disclosure, rainwater can be prevented from intruding to an inner surface of an outer tank side wall before concrete is installed above a metal roof serving as a skeleton portion of an outer tank.
Number | Date | Country | Kind |
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2016-007722 | Jan 2016 | JP | national |
The present application is a continuation application of International Application No. PCT/JP2017/000592, filed Jan. 11, 2017, which claims priority to Japanese Patent Application No. 2016-007722, filed Jan. 19, 2016. The contents of these applications are incorporated herein by reference in their entirety.
Number | Date | Country | |
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Parent | PCT/JP2017/000592 | Jan 2017 | US |
Child | 16031149 | US |