JP2019019947A - Underground tank structure - Google Patents

Abstract

To provide an underground tank structure capable of reducing temperature load applied to a tank skeleton.SOLUTION: An underground tank structure 1 stores low-temperature liquefied gas such as LNG, and has a tank skeleton comprising a bottom slab 5 and a side wall 7, wherein the bottom slab 5 is divided into two layers of an upper layer bottom slab 5a and a lower layer bottom slab 5b. The upper layer bottom slab 5a is connected to the side wall 7, and the thickness of the upper layer bottom slab 5a is substantially identical to that of the side wall 7. The underground tank structure 1 is configured such that a frost line b indicating a position showing 0°C with utilization of a tank is managed at a position so as to become substantially the same separation distance from an inner surface of the tank skeleton at the side part and bottom part of the tank skeleton.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an underground tank structure.

  There is an underground tank as a facility for storing low-temperature liquefied gas such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas). In recent underground tanks, after excavating the inside of the underground continuous wall which is a mountain retaining, a tank frame comprising a bottom slab 5 made of reinforced concrete and a side wall 7 is constructed inside the underground continuous wall 9 as shown in FIG. In general, a steel roof 8 is provided thereon. Although illustration is omitted, a membrane is provided on the inner surface of the tank housing via a heat insulating material. A water collecting layer 4 made of crushed stone or the like is provided below the bottom plate 5.

  The bottom plate 5 and the side wall 7 may be pin-coupled or slidably coupled, but recently, the bottom plate 5 and the side wall 7 are often integrated to form a rigid connection. This is due to the advantage of the water stop surface and the need for a support structure between the bottom plate 5 and the side wall 7. In the case of such a structure type, it is common to provide a haunch 6 at the corners of the bottom plate 5 and the side wall 7 to smooth the flow of stress.

  The thickness of the bottom plate 5 is larger than that of the side wall 7 and is, for example, about 2.45 m on the side wall and 8.0 m on the bottom plate in an underground tank having a capacity of 200,000 KL. This member dimension is mainly determined so as to have a weight capable of preventing the floating due to the groundwater pressure at the time of air-liquid.

  Because underground tanks store liquefied gas such as LNG at low temperatures, heaters are installed on the side and bottom to prevent freezing of the surrounding ground when the tank is operating, and temperature stability is achieved. The position of the line indicating the position is maintained and managed (for example, Patent Documents 1-5). Some heater equipment uses a planar heating element, but many of them control the position of the freezing line by circulating a heat medium through the heater tube and exchanging the heat.

  In the example of FIG. 15, a heater tube 103 is embedded in the surrounding ground 3 as a side heater facility. The heater pipe 103 is, for example, a double pipe type in which an inner pipe is inserted into an outer pipe, and the upper end of the inner pipe and the outer pipe is connected to the header pipe 101 on the heat medium supply side via the branch pipe, and the header pipe on the recovery side. 105, respectively. In the side heater equipment, the freezing line is managed in the peripheral ground 3 outside the underground continuous wall 9 by exchanging heat between the heat medium in the heater tube 103 and the peripheral ground 3.

  On the other hand, as the bottom heater equipment, a brine heater for circulating a heat medium is installed in a heater tube 201 embedded in the vicinity of the lower surface of the bottom slab 5, and the freezing line is managed at the bottom of the bottom slab 5 so that the ground below the bottom slab 5 Prevents freezing.

Japanese Patent Laid-Open No. 11-182797 Japanese Patent Publication No.61-31360 Japanese Unexamined Patent Publication No. 8-145297 Patent No. 2789299 Japanese Patent Publication No.58-6118

  A load caused by a temperature drop of the tank housing and a load caused by a temperature difference between the tank housings are applied to the tank housing of the underground tank. The former is a load generated when the temperature of the tank housing constructed at normal temperature is lowered by the low-temperature liquefied gas when the tank is operating, and the latter is a load generated by a temperature difference between the inner and outer surfaces of the tank housing.

  In the former case, the contraction of the bottom slab and the side wall accompanying the temperature drop is constrained by the frictional force with the surrounding ground and the like, and an axial force (temperature load) is generated in the cross section of the bottom slab and the side wall. In addition, the difference in temperature drop between the bottom plate and the side wall can also cause a temperature load on the tank housing. For example, when the temperature of the side wall decreases while the temperature of the bottom plate does not decrease, the shrinkage of the side wall is constrained by the bottom plate, and a shearing force and a bending moment (temperature load) are generated at the lower end of the side wall.

  In the latter case, the temperature of the inner surface of the side wall of the tank housing is lowered by the low-temperature liquefied gas such as LNG when the tank is operating, whereas the temperature of the outer surface of the side wall is not lowered because it is heated by the side heater equipment. A temperature difference occurs between the outer surface and the inner surface of the side wall (the inner surface of the tank housing). Similarly, a temperature difference also occurs between the lower surface of the bottom plate in which the heater pipe is embedded and the upper surface of the bottom plate (the inner surface of the tank housing). In this case, the inner surface of the side wall and the upper surface of the bottom plate, where the temperature decreases, tend to shrink, but a bending moment (temperature load) is generated by restraining the shrinkage by the side wall and the bottom plate.

  As a result of such a temperature load, the underground tank needs to be reinforced by increasing the amount of reinforcing bars on the bottom plate and the side wall, which causes an increase in the cost of the underground tank.

  The cause of the large temperature load is also due to the structure of the tank housing. For example, as described above, since the bottom plate of the tank casing is formed thicker than the side wall, it is difficult to control the amount of temperature drop between the bottom plate and the side wall from the time of tank construction to be the same. It becomes easy to make a difference.

  In addition, the magnitude of the temperature load such as the axial force caused by the temperature drop and the bending moment caused by the temperature difference between the inner and outer surfaces of the tank housing is determined by the amount of temperature drop or the temperature difference and the member thickness as parameters. As the thickness of the member such as the bottom plate is large, the temperature load is also increased.

  This invention is made | formed in view of said problem, and it aims at providing the underground tank structure which can reduce the temperature load added to a tank housing.

  The present invention for solving the above-mentioned problems is an underground tank structure provided on the ground, and has a tank casing including a bottom plate and a side wall, and the bottom plate is provided in two layers of an upper layer bottom plate and a lower layer bottom plate. The upper layer bottom plate is connected to the side wall, and the thickness of the upper layer bottom plate and the side wall is substantially the same.

  In the present invention, the bottom plate is divided into two layers, the upper layer bottom plate and the lower layer bottom plate, and the thinned upper layer bottom plate and the side wall are connected with the same thickness, whereby the temperature load generated on the upper layer bottom plate and the side wall can be reduced. That is, it becomes possible to easily reduce the difference in temperature drop between the bottom plate and the side wall tank construction as occurs in the case of the conventional tank housing, and the temperature caused by the difference in temperature drop between the bottom plate and the side wall. The load can be reduced. Further, the fact that the upper layer bottom plate is thinner than the conventional bottom plate itself also brings about the effect of reducing the temperature load. As a result, the amount of reinforcing bars can be reduced by extremely reducing the temperature load applied to the upper bottom plate and the side wall. In addition, since the lower layer bottom plate constructed separately from the upper layer bottom plate is less constrained, almost no temperature load is generated. In addition, the double bottom slab of the lower bottom plate and the upper bottom plate can resist the lifting pressure (water pressure), and can also resist lifting due to groundwater pressure during air-liquid.

It is desirable that the freezing line indicating the position at which the temperature is 0 ° C. as the tank operates is at a position where the side and bottom of the tank housing are substantially the same distance from the inner surface of the tank housing.
In the present invention, the upper layer bottom plate and the side wall have the same thickness, and the distance from the inner surface of the tank housing to the freezing line of the side and bottom of the tank housing is substantially the same, so that The difference in temperature drop between the upper bottom plate and the side wall can be brought close to 0 by making the distributions substantially the same. In addition, since the frozen concrete having substantially the same thickness can be formed on the tank housing, a reliable and reliable water stop can be achieved.

It is desirable that a water stop portion is provided on the entire outer periphery of the boundary surface between the upper layer bottom plate and the lower layer bottom plate. It is also desirable that a connecting reinforcing bar is provided so as to straddle the boundary surface between the upper layer bottom plate and the lower layer bottom plate.
By providing a water stop portion at the outer peripheral portion of the boundary surface between the upper layer bottom plate and the lower layer bottom plate, water can be prevented from entering between the upper layer bottom plate and the lower layer bottom plate, and water pressure does not act on the upper layer bottom plate. Further, by providing the connecting reinforcing bars so as to straddle the boundary surface, it is possible to prevent water from entering between the upper layer bottom plate and the lower layer bottom plate by preventing the opening between the upper layer bottom plate and the lower layer bottom plate.

The upper layer bottom plate and the side wall are preferably rigidly connected.
Since the temperature load is often increased in the rigid tank tank, the present invention can be applied particularly favorably in such a case.

  The present invention can provide an underground tank structure capable of reducing the temperature load applied to the tank housing.

The figure which shows the underground tank structure 1. FIG. The figure which shows the upper layer bottom plate 5a and the lower layer bottom plate 5b. The figure which shows arrangement | positioning of the heater pipe | tube 13. FIG. The figure which looked at the plane of heater pipe 22. FIG. An example of temperature distribution of the side wall 7 and the bottom plate 5. The figure which shows heater pipe | tube 13 '. The figure which shows the underground tank structure 1a. The figure which shows the heater pipe | tube 13a. The figure which shows the example which makes the heater pipe | tube 13a and the heater pipe | tube 22 continue. The figure which shows heater pipe | tube 13a '. The figure which shows the underground tank structure 1b. The figure which shows the plane of the heater pipe | tube 32. FIG. The figure which shows the plane of the heater pipe | tube 32a. The figure which shows the plane of the heater pipe | tube 32b. An example of a conventional underground tank.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
(1. Underground tank structure 1)
FIG. 1 is a diagram showing an underground tank structure 1 according to a first embodiment of the present invention. The underground tank structure 1 is provided on the ground and stores (very) low-temperature liquefied gas (low-temperature liquid) such as LNG or LPG in the tank as a storage.

  In the underground tank structure 1, as in the example of FIG. 15, after excavating the inside of the underground continuous wall 9, which is a mountain retaining, a tank frame is constructed inside the underground continuous wall 9 by the bottom slab 5 and the side wall 7 made of reinforced concrete. The steel roof 8 is provided thereon. Although not particularly illustrated, a heat insulating material is provided on the inner surface of the tank housing, and a membrane and the like are further provided on the inner side. “Inside” means the one closer to the center of the tank housing, and “outside” means the opposite side.

  However, in this embodiment, unlike the example of FIG. 15, the bottom plate 5 is provided in two layers of an upper layer bottom plate 5a and a lower layer bottom plate 5b. When the bottom plate 5 is constructed, the upper bottom plate 5a and the lower bottom plate 5b are in contact with each other by placing the concrete of the lower layer plate 5b and setting the concrete after the concrete has hardened. It is assumed that the state has expired.

  The side wall 7 is formed in a cylindrical shape on the upper layer bottom plate 5 a, and the underground continuous wall 9 is provided in a cylindrical shape in the peripheral ground 3 outside the side wall 7. The thickness of the side wall 7 and the upper layer bottom plate 5a is substantially the same, for example, as thin as 1.75 m. The thickness of the underground continuous wall 9 is, for example, 1.2 m. The upper bottom plate 5a and the side wall 7 are connected and integrated (rigidly connected), and a haunch 6 is provided at the corner portion. The thickness of the lower bottom plate 5b is, for example, about 6.25m, and the thickness of the entire bottom plate 5 is secured to about 8.0m in order to prevent the bottom plate 5 from being lifted by the groundwater pressure during air-liquid. A water collection layer 4 made of crushed stone or the like is also provided below the lower layer bottom plate 5b.

  As shown in FIG. 2, the water stop part 51 is provided over the perimeter of the said outer peripheral part in the outer peripheral part of the boundary surface of the upper layer bottom plate 5a and the lower layer bottom plate 5b. The water stop part 51 is comprised from the water stop board etc. which straddle a boundary surface. Similarly, the connecting rebar 52 is also embedded so as to straddle the boundary surface between the upper layer bottom plate 5a and the lower layer bottom plate 5b.

  The boundary surface between the upper layer bottom plate 5a and the lower layer bottom plate 5b has no gap, and a water stop portion 51 is provided on the outer peripheral portion, and the opening of the upper layer bottom plate 5a and the lower layer bottom plate 5b is prevented by the connecting reinforcing bars 52. The groundwater does not enter and the water pressure does not act on the upper bottom plate 5a.

  In this embodiment, the outer peripheral surfaces of the bottom slab 5 (upper layer bottom slab 5a and lower layer bottom slab 5b) are in contact with the underground continuous wall 9, but the edges are cut off at the boundary surface, and reinforcing bars or the like are straddled across the boundary surface. By burying the shearing force transmission mechanism (not shown), the tank housing and the underground continuous wall 9 are connected, and the weight of the underground continuous wall 9 can be counted as a resistance force against lifting.

  Since underground tanks store low-temperature liquefied gases of less than 0 ° C, especially about -160 ° C, such as LNG, as in the example of Fig. 15, A partial heater facility and a bottom heater facility are provided.

  The side heater equipment is a circulation type heater equipment that circulates a heat medium, and includes a heating equipment, a circulation pump (not shown), header pipes 11 and 15, a heater pipe 13 and the like. The heater pipe 13 is a heater pipe on the side of the tank housing, and is provided in the vicinity of the outer boundary portion of the underground continuous wall 9 so that the inner surface of the side wall 7 (the inner surface of the tank housing) as compared with the case where it is provided in the peripheral ground 3. It is placed close to. The distance from the inner surface of the side wall 7 to the heater tube 13 is, for example, 2.95 m. The header pipes 11 and 15 are provided in an annular shape along the circumferential direction of the tank housing.

  In the side heater equipment, the heat medium is circulated in the order of the heating equipment and the circulation pump, the header pipe 11, the heater pipe 13, the header pipe 15, and the heating equipment, and the underground continuous wall 9 and the surrounding ground 3 and the heater pipe 13 are circulated. Heat exchange with the other heat medium.

  The bottom heater is also a circulating heater that circulates the heat medium. The heater pipe 22 (the heater pipe at the bottom of the tank housing) embedded in the lower layer bottom plate 5b is used with a heating equipment or a circulation pump (not shown). The heat medium is circulated to exchange heat between the concrete of the lower bottom slab 5b and the heat medium in the heater tube 22. The distance from the upper surface of the upper bottom plate 5a (the inner surface of the tank housing) to the heater tube 22 is, for example, 2.95 m, and is substantially the same as the distance from the inner surface of the side wall 7 (the inner surface of the tank housing) to the heater tube 13. .

  Each heater facility circulates a heat medium through the heater pipes 13 and 22, and performs heat exchange between the heat medium and the underground continuous wall 9, the surrounding ground 3, and the lower bottom slab 5b. Maintain.

  In the present embodiment, by adjusting the pipe diameters of the heater pipes 13 and 22, the pipe interval, the temperature of the heat medium, etc., the freezing line b as a whole becomes a line segment similar to the inner face shape of the tank housing, and the inner face of the side wall 7. The separation distance from the side of the tank housing to the freezing line b and the separation distance from the upper surface of the upper bottom plate 5a to the freezing line b of the bottom of the tank housing are made substantially the same. For example, as described above, the distance from the inner surface of the tank housing to the heater pipes 13 and 22 is made substantially the same, and the pipe diameters of the heater pipes 13 and 22, the pipe interval, and the temperature of the heat medium are made the same. The separation distance from the inner surface of the housing to the freezing line b on the side and bottom of the tank housing can be easily aligned.

  The position of the freezing line b approaches the inner surface of the tank housing as a whole, and the freezing line b on the side of the tank housing is managed in the underground continuous wall 9 and the freezing line b on the bottom is managed in the upper part in the lower layer bottom plate 5b. The separation distance of the freezing line b is, for example, about 2.0 m from the inner surface of the tank casing, and the frozen concrete having the same temperature is formed on the entire thickness of the side wall 7 of the tank casing and the upper bottom slab 5a (both thicknesses of 1.75 m). Realize reliable and reliable water stoppage. As the heat medium, an antifreeze such as Nybrine (registered trademark) is used to prevent the heat medium from freezing.

(2. Heater pipe 13 of side heater equipment)
FIG. 3 is a view showing the arrangement of the heater tubes 13 of the side heater equipment, and is a view showing a circumferential cross section of the underground continuous wall 9.

  The heater pipe 13 is a pipe in a substantially vertical direction, and as shown in FIG. 3, a plurality of heater pipes 13 are arranged at substantially equal intervals along the circumferential direction of the tank housing in the vicinity of the outer boundary portion of the underground continuous wall 9. The heater tube 13 is embedded and integrated near the outer boundary of the underground continuous wall 9.

  The heater tube 13 is of the double tube type as described above, and is configured by inserting the inner tube 131 into the outer tube 132. For the outer tube 132, for example, an STPG tube (carbon steel tube for pressure piping) can be used. Since the heater pipe 13 is embedded in the vicinity of the outer boundary portion of the underground continuous wall 9, it is necessary to use a PL pipe (polyethylene lining steel pipe) from the viewpoint of corrosion prevention as in the case where the heater pipe is embedded in the surrounding ground 3. In addition, the cost can be reduced by using an inexpensive STPG pipe.

  The upper end of the heater pipe 13 protrudes from the top of the underground continuous wall 9, and the upper end of the inner pipe 131 is connected to the header pipe 11 on the heat medium supply side via a branch pipe. The upper end of the outer pipe 132 is connected to the header pipe 15 on the heat medium recovery side via a branch pipe. In the heater pipe 13, the heat medium supplied from the header pipe 11 passes through the inner pipe 131, passes between the inner pipe 131 and the outer pipe 132, and is collected in the header pipe 15.

(3. Heater tube 22 of bottom heater equipment)
The heater tube 22 of the bottom heater facility is embedded in the concrete on the upper part of the lower bottom slab 5b. The heater tube 22 is disposed at a higher position as compared with the case where the heater tube 22 is embedded in the lower surface of the bottom plate 5 as in the prior art.

  FIG. 4 is a plan view of the heater tube 22. In FIG. 4, the positions of the bottom plate 5 (upper layer bottom plate 5a and lower layer bottom plate 5b), the side wall 7, the haunch 6, and the underground continuous wall 9 are indicated by broken lines.

  The heater tube 22 is arranged in a substantially spiral shape. More specifically, the heater pipe 22 has a plurality of circumferential pipes 222 arranged concentrically at substantially equal intervals. These circumferential pipes 222 are arranged along the circumferential direction of the tank housing, and the circumferential pipes 222 adjacent to each other inside and outside are connected by oblique pipes 223 inclined with respect to the circumferential pipe 222 in a plane, and are configured in a single stroke. Is done.

  The circumferential piping 222 is arranged at the same height above the lower layer bottom plate 5b. The lower end of the heater pipe 13 of the underground continuous wall 9 is located below the circumferential pipe 222 and prevents the freezing line b from coming out of the heater pipes 13 and 22 at the corner.

  However, the arrangement of the circumferential piping 222 is not limited to this. For example, as shown in the example of FIG. 7 to be described later, the circumferential pipe 222 at the outer peripheral portion may be arranged along the inclination of the haunch 6 so as to become higher as going outward. Thereby, also in the corner part of the upper-layer bottom plate 5a with the haunch 6 and the side wall 7, it becomes easy to align the separation distance from the inner surface of the tank housing to the freezing line b.

  The innermost circumferential pipe 222 and the outermost circumferential pipe 222 are respectively connected to substantially vertical vertical pipes 221 and 224 embedded in the side wall 7. These vertical pipes 221 and 224 protrude outward from the outer peripheral surface of the side wall 7 and form a closed flow path outside. Heating equipment and a circulation pump are arranged in this flow path.

(4. Temperature distribution in the side wall 7 and the bottom plate 5)
Lines A in FIGS. 5 (a) and 5 (b) show an underground tank storing LNG at −162 ° C., and the bottom slab 5 is composed of two layers as shown in FIG. Side wall 7 and bottom slab 5 in the steady state when the tank is operating when the bottom plate thickness is 1.75 m, the bottom bottom plate thickness is 6.25 m, the underground continuous wall thickness is 1.2 m, and the average temperature during construction of the tank housing is 16 ° C. It is an example of the temperature distribution of (upper layer bottom plate 5a and lower layer bottom plate 5b).

  The distance from the inner surface of the side wall 7 to the heater tube 13 is 2.95 m, the distance from the upper surface of the upper bottom plate 5 a to the heater tube 22 is 2.95 m, and the surface average temperature of the heater tubes 13 and 22 when the tank is operating ( The heater pipe line (average temperature of the heater pipes 13 and 22 on which the pipes are arranged) is 5.0 ° C. for both.

  In this case, the separation distance from the inner surface of the tank housing (the inner surface of the side wall 7 and the upper surface of the upper bottom plate 5a) of the freezing line b (position at 0 ° C.) of the side and bottom of the tank housing is substantially the same as about 2.5 m. It becomes. Moreover, since the thickness of the side wall 7 and the upper layer bottom plate 5a is the same, the temperature distribution along the thickness direction of the side wall 7 and the upper layer bottom plate 5a is substantially the same, and the side wall 7 and the upper layer bottom plate from the time of construction of the tank casing are formed. The temperature decrease amount (average value in the thickness direction) of 5a is approximately the same at about 27 ° C. The temperature difference between the inner and outer surfaces of the side wall 7 and the upper and lower surfaces of the upper layer bottom plate 5a is about 14 ° C.

  On the other hand, line B in FIGS. 5 (a) and 5 (b) shows a bottom tank 5 having a single layer as shown in the example of FIG. Temperature distribution of side wall 7 and bottom slab 5 in the steady state when the tank is in operation when the average temperature during construction of the tank is 16 ° C, with 2.45m, bottom plate thickness of 8.00m and underground continuous wall thickness of 1.2m. It is an example.

  Further, the heater tube 103 of the side heater equipment is embedded in the peripheral ground 3 so that the distance from the inner surface of the side wall 7 is 4.65 m, and the heater tube 201 of the bottom heater equipment is embedded in the vicinity of the lower surface of the bottom plate 5 and the bottom plate 5 The distance from the upper surface of the heater is 7.28 m, and the surface average temperatures of the heater tubes 103 and 201 when the tank is operating are 5.0 ° C. and 10.0 ° C., respectively.

  In this case, the freezing line b is formed at a position farther from the inner surface of the tank housing than the above-described example of the line A, and the distance from the inner surface of the tank housing to the freezing line b is different between the side portion and the bottom portion. For example, the freezing line b at the bottom of the tank casing is formed about 6 m below the upper surface of the bottom plate 5 and is lower than the example of the line A. Furthermore, the temperature drop (average value in the thickness direction) of the side wall 7 and the bottom slab 5 from the time of construction of the tank housing is also different from 35.2 ° C and 28.1 ° C. The temperature difference between the inner and outer surfaces of the side wall 7 and the upper and lower surfaces of the bottom plate 5 is 18.0 ° C. and 56.3 ° C., respectively.

  As can be seen from the example of line A, in this embodiment, the difference in the temperature drop between the upper bottom slab 5a and the side wall 7 from the time of construction of the tank housing can be reduced. In particular, since the member thicknesses of the upper layer bottom plate 5a and the side wall 7 are the same, and the distance between the freezing line b of the side portion and the bottom portion from the tank inner surface is the same, the temperature distribution of the upper layer bottom plate 5a and the side wall 7 in the steady state. Are almost the same, and the difference in temperature drop since the construction of the tank housing can be brought close to zero. Further, since the position of the freezing line b as a whole is close to the inner surface of the tank housing, the temperature drop amount itself from the construction of the tank housing of the upper bottom slab 5a and the side wall 7 can also be reduced.

  Furthermore, as described above, the temperature load increases due to the fact that the member thickness is large, but in this embodiment, the temperature load is reduced by making the upper layer bottom plate 5a thin. As a result, the amount of reinforcing bars required for the upper floor slab 5a and the side wall 7 can be greatly reduced, and the construction cost of the underground tank can be reduced.

  For example, in another example, the side wall thickness is 1.6 m, the bottom plate thickness is 1.6 m, the side wall inner surface and outer surface temperatures are -18.0 ° C and -3.0 ° C, respectively, and the bottom plate upper and lower surface temperatures are Underground tank temperature load of -6.0 ° C and 8.0 ° C, side wall thickness of 2.3m, bottom plate thickness of 8.0m, side wall inner surface and outer surface temperature of -32.0 ° C, -5.0 ° C, bottom plate upper and lower surface respectively When comparing the temperature load of the underground tank with the temperature of -60.0 ℃ and 16.0 ℃ respectively, the axial force and bending moment applied to the bottom plate and side wall in the former case are significantly reduced compared to the latter case, and the side wall There is also a trial calculation result that the shear force at the lower end is also reduced.

  As described above, in the present embodiment, the bottom plate 5 is divided into two layers of the upper layer bottom plate 5a and the lower layer bottom plate 5b, and the thinned upper layer plate 5a and the side wall 7 are connected to have the same thickness. 7 can be reduced.

  That is, when the bottom plate is formed thicker than the side wall as in the case of the conventional tank housing, it is difficult to control the bottom plate and the side wall at the same temperature drop from the tank construction, but in this embodiment, the upper layer bottom plate 5a and the side wall 7 are By using the same thickness, the difference in temperature drop between the upper layer bottom plate 5a and the side wall 7 can be easily reduced, and the temperature load caused by the difference in temperature drop between the upper layer bottom plate 5a and the side wall 7 is reduced. be able to.

  Further, the fact that the upper layer bottom plate 5a and the like are thinner than the conventional bottom plate itself also brings about the effect of reducing the temperature load. As a result, it is possible to extremely reduce the temperature load applied to the upper bottom slab 5a and the side wall 7 to reduce the amount of reinforcing bars.

  In addition, the bottom plate 5 is divided into two layers, an upper layer bottom plate 5a and a lower layer bottom plate 5b, so that each member is thinned due to the dimensional effect of the concrete member (its strength decreases as the member size increases). It is also effective in preventing a decrease in strength and maintaining a high shear strength.

  Further, the lower layer bottom plate 5b constructed separately from the upper layer bottom plate 5a is hardly restrained and hardly undergoes a temperature change, so that almost no temperature load is generated. Further, the double slab of the lower layer bottom plate 5b and the upper layer bottom plate 5a can resist lifting pressure (water pressure), and can also resist lifting due to groundwater pressure during air-liquid.

  In particular, in the present embodiment, the upper layer bottom plate 5a and the side wall 7 have the same thickness, and the separation distance from the inner surface of the tank housing to the side wall and bottom freezing line b of the tank housing is substantially the same, so By making the temperature distributions of the bottom plate 5a and the side wall 7 substantially the same, the difference in temperature drop from the construction of the tank housing of the upper layer bottom plate 5a and the side wall 7 can be brought close to zero. In addition, since the frozen concrete having substantially the same thickness can be formed on the tank housing, highly reliable and reliable water stopping is possible.

  Furthermore, in this embodiment, by providing the water stop part 51 in the outer peripheral part of the interface between the upper layer bottom plate 5a and the lower layer bottom plate 5b, water can be prevented from entering between the upper layer bottom plate 5a and the lower layer bottom plate 5b, and the upper layer bottom plate 5a. Water pressure does not act on the water. Further, by providing the connecting reinforcing bars 52 so as to straddle the boundary surface, it is possible to prevent the water from entering between the upper layer bottom plate 5a and the lower layer bottom plate 5b by preventing the opening between the upper layer bottom plate 5a and the lower layer bottom plate 5b. However, as a method for preventing water from entering, it is also effective to manage the freezing line b below the upper surface of the lower layer bottom plate 5b, for example, near 30 cm below the upper surface. As a result, the vicinity of the boundary surface between the upper layer bottom plate 5a and the lower layer bottom plate 5b is frozen, freeze-stopping is performed, and water does not enter the boundary surface. Therefore, the water stop part 51 and the connecting reinforcing bar 52 can be omitted.

  Further, the temperature load is often increased in the rigid type tank housing, but the configuration of the tank housing and the like of the present embodiment that reduces the temperature load can be applied particularly suitably in such a case. In addition, substantially the same frozen concrete thickness can be secured also in the upper bottom plate 5a with the haunch 6 and the corner portion (haunch 6) of the side wall 7.

  However, the present invention is not limited to this. For example, the specific positions of the heater tubes 13 and 22 and the temperature of the heat medium are determined according to the dimensions of each member of the underground tank structure 1, the thickness of the heat insulating material, the heat insulating performance, the depth of stored liquid, and the like, and are not particularly limited. Absent. For example, when the side wall 7 or the upper layer bottom plate 5a is thick, the heater tubes 13 and 22 can be embedded in the side wall 7 or the upper layer bottom plate 5a. Furthermore, it is also possible to manage the position of the freezing line b by using a planar heating element instead of the heater tubes 13 and 22.

  The position of the freezing line b is not limited to the above, and there may be a slight difference in the distance from the inner surface of the tank housing to the freezing line b on the side and bottom of the tank housing.

  It is also possible to further reduce the separation distance from the inner surface of the tank housing to the freezing line b and manage the freezing line b in the side wall 7 or the upper layer bottom plate 5a. In this case, the tank housing of the side wall 7 or the upper layer bottom plate 5a is also possible. The amount of temperature drop from the construction is reduced, the temperature load is further reduced, and the temperature load of the lower layer bottom plate 5b is further reduced by retaining the freezing line b in the upper layer bottom plate 5a. For example, the distance between the freezing line b and the inner surface of the tank housing can be reduced to about 1 m by reducing the piping interval between the heater tubes 13 and 22, and the heater tubes 13 and 22 are embedded in the side wall 7 and the upper bottom plate 5a. Thus, the freezing line b can be managed in the side wall 7 or the upper layer bottom plate 5a. In addition, it is desirable to secure the thickness of frozen concrete at least about 1 to 2 m from the viewpoint of securing watertightness and airtightness by performing freeze-stopping.

  The shape of the heater tubes 13 and 22 is not particularly limited. For example, in the present embodiment, a double tube type is used for the heater tube 13, but a U-shaped tube type shown in a heater tube 13 'in FIG. 6 may be used. In this case, both end portions of the heater tube 13 ′ are projected from the top of the underground continuous wall 9, and one end portion is connected to the supply side header tube 11 and the other end portion is connected to the recovery side header tube 15. A plurality of heater tubes 13 'are arranged along the circumferential direction of the underground continuous wall 9 (corresponding to the left-right direction in FIG. 6) so that the distances D1 between the vertical tubes are substantially equal.

  Hereinafter, another example of the present invention will be described as second and third embodiments. The second and third embodiments will be described with respect to differences from the embodiments described so far, and the same points will be denoted by the same reference numerals in the drawings and the like, and description thereof will be omitted.

[Second Embodiment]
FIG. 7 is a view showing an underground tank structure 1a according to the second embodiment, and FIG. 8 is a view showing a heater pipe 13a of a side heater facility. The second embodiment is different from the first embodiment in that the heater pipe 13a of the side heater facility is embedded in the side wall 7 and has a circumferential pipe 134 disposed in the circumferential direction of the tank housing.

  The heater tube 13a is a heater tube on the side of the tank housing, and is embedded in the vicinity of the outer boundary portion of the side wall 7 and arranged in a substantially spiral shape. More specifically, as shown in FIG. 8A, the heater pipe 13a has a plurality of upper and lower circumferential pipes 134, and the upper and lower circumferential pipes 134 are inclined with respect to the circumferential pipe 134 at an elevation. Connected in a single stroke by the inclined pipe 135.

  The lowermost and uppermost circumferential pipes 134 of the heater pipe 13a are connected to vertical pipes 133 and 136, respectively. These vertical pipes 133 and 136 protrude outward from the outer peripheral surface of the side wall 7 and form a closed flow path outside. A heating facility and a circulation pump (not shown) are provided in this flow path. In this embodiment, a heat medium is circulated through the heater pipe 13a in the side wall 7 using a heating facility or a circulation pump, and heat exchange is performed between the side wall 7 and the heat medium in the heater pipe 13a.

  The pipe diameter and length of the heater pipe 13a are determined by design according to the capacity and flow rate of the circulation pump. In the present embodiment, a JIS standard 2B pipe is used as the heater pipe 13a and the length thereof is about 1500 m at the maximum. As shown in FIG. 8B, the heater pipe 13a has a plurality of upper and lower stages corresponding to the height of the side wall 7. Buried in

  In the present embodiment, the heater tube 22 is embedded in the vicinity of the lower boundary portion of the upper layer bottom plate 5a. Further, as shown in FIG. 7, the circumferential pipe 222 in the outer peripheral portion is arranged along the inclination of the haunch 6 so that the outer one is positioned higher.

  Also in this embodiment, in each heater facility, the heat medium is circulated through the heater tubes 13a and 22 and heat exchange is performed between the heat medium and the side wall 7 and the upper layer bottom plate 5a. A line segment similar to the inner surface shape of the casing is formed, and the distance from the inner surface of the tank casing to the freezing line b on the side and bottom of the tank casing is made substantially the same. In the present embodiment, the separation distance is set to about 1.0 m, and the freezing line b is managed in the side wall 7 and the upper layer bottom plate 5a. The bottom plate 5 is composed of the upper layer bottom plate 5a and the lower layer bottom plate 5b, and the upper layer bottom plate 5a and the side wall 7 have the same thickness. Therefore, the same effects as in the first embodiment can be obtained in this embodiment.

  Further, in this embodiment, the heater tubes 13a and 22 of the side heater equipment and the bottom heater equipment have a similar annular structure, so that the freezing line b can be easily prevented from coming off at the corner portions of the upper bottom plate 5a and the side wall 7. can do. In the first embodiment, in order to prevent the freezing line b from coming out of the heater pipes 13 and 22 at the corner portion, the lower end of the heater pipe 13 of the side heater equipment is about 2.0 to 3.0 m, and the heater of the bottom heater equipment is used. Although it is necessary to bring the pipe 22 below the upper end, such waste is eliminated in this embodiment. Further, the header tubes 11 and 15 as in the first embodiment are not required.

  In the present embodiment, the workability is improved by connecting the pipes 134 in the horizontal direction along the horizontal plane, and the pipes are connected by the diagonal pipe 135. It is good also as a shape arrangement.

  In this embodiment, the heater pipe 13a of the side heater equipment is a 2B pipe and the maximum length is 1500 m. However, the present invention is not limited to this, and the capacity of the circulation pump and the heat medium between both ends of the heater pipe 13a. It is determined in consideration of the temperature drop. For example, the heater tube 13a can be made thicker (for example, as a 3B tube), and the maximum length can be increased to about 2000 m.

  In addition, in the present embodiment, the heater tube 13a may be continuous with the heater tube 22 at the bottom of the tank housing. That is, as shown in FIG. 9, the outermost circumferential pipe 222 of the heater pipe 22 is connected to the lowermost circumferential pipe 134 of the heater pipe 13a on the side of the tank housing by an oblique pipe 135 or the like.

  Conventionally, the side heater equipment and the bottom heater equipment are generally provided as separate heaters, but in the example of FIG. 9, the heater tubes 13a and 22 are continuous between the side wall 7 and the upper bottom plate 5a. It is easier to align the distance from the inner surface of the tank housing to the freezing line b on the side and bottom of the tank housing. Further, it is possible to more easily prevent the freezing line b from coming off at the corner portions of the upper layer bottom plate 5a and the side wall 7.

  In the examples of FIGS. 8B and 9, the heater tube 13a and the like are divided into a plurality of upper and lower stages due to the restriction of the flow path length. However, in the case of a small scale tank, FIG. 9) The heater tube 13a and the like in FIG. 9 can be realized as a single heater tube without dividing into blocks.

  Furthermore, as shown in FIG. 10, both ends of the circumferential pipes 138 in the upper and lower stages of the heater pipe 13a 'on the side of the tank housing can be connected to the vertical pipes 137 and 139, respectively. As described above, the vertical pipes 137 and 139 protrude outward from the outer peripheral surface of the side wall 7 and form a closed flow path outside. Heating equipment and a circulation pump are arranged in this flow path.

  Since the heater pipe 13a has a long flow path length, the heater pipes 13a are arranged in a plurality of stages in the side wall 7 due to the restriction of the flow path length. However, the heater pipe 13a ′ in FIG. Therefore, if the necessary circumferential pipes 138 are attached to the vertical pipes 137 and 139, there is no need to install the heater pipes 13a ′ in a plurality of stages. The vertical pipes 137 and 139 have the same function as the header pipes 11 and 15 of the first embodiment, but have a length longer than that of the header pipes 11 and 15 that need to be arranged over the entire circumference of the tank. It can be shortened and the cost is low. When the heater pipe at the bottom of the tank casing is connected to the heater pipe 13a 'as in the example of FIG. 9, the lower ends of the vertical pipes 137 and 139 are extended to the plane center of the upper-layer bottom slab 5a, and the tank casing is extended to the extended portion. What is necessary is just to connect the both ends of each circumferential piping of the heater pipe | tube of the bottom part.

[Third Embodiment]
FIG. 11 is a diagram showing an underground tank structure 1b according to the third embodiment. In the third embodiment, a heater pipe 32 continuous between the lower layer bottom plate 5b and the underground continuous wall 9 is provided, and the heater tube 32 is arranged in a substantially horizontal direction and a substantially vertical direction respectively in the lower layer bottom plate 5b and the underground continuous wall 9. This is different from the first and second embodiments in that piping is performed.

  The heater pipe 32 has a configuration in which a substantially vertical vertical pipe 321 and a substantially horizontal horizontal pipe 322 are connected, and for example, 2B pipes are used for these pipes. The vertical pipe 321 is a heater pipe on the side of the tank housing, and is buried near the outer boundary of the underground continuous wall 9. The horizontal pipe 322 is a heater pipe at the bottom of the tank housing, and is embedded in the upper part of the lower layer bottom plate 5b.

  FIG. 12 is a view showing the plane of the heater tube 32 as in FIG. FIG. 12 shows only a quarter range in the circumferential direction of the plane of the bottom plate 5 (upper layer bottom plate 5a and lower layer bottom plate 5b), but the other portions have the same shape.

  As shown in FIG. 12, the horizontal pipe 322 is substantially V-shaped or substantially U-shaped in plan view, and both ends thereof are connected to the vertical pipe 321 via connection pipes (90 ° elbows). The upper parts of both vertical pipes 321 exit from the top of the underground continuous wall 9 and are connected to header pipes 31 and 33 (see FIG. 11), respectively. The header pipes 31 and 33 are arranged in the circumferential direction of the tank housing at the top of the underground continuous wall 9.

  In the present embodiment, the plurality of heater pipes 32 are arranged along the circumferential direction of the tank housing, and the intervals D2 between the vertical pipes 321 are substantially equal. The horizontal pipe 322 extends toward the plane center of the lower bottom slab 5b, but in order to prevent the pipe from becoming too dense in the vicinity of the plane center of the lower layer slab 5b, the position of the tip of the horizontal pipe 322 is the plane center of the lower layer slab 5b. Are shifted so as to have different distances r1 to r4.

  In the present embodiment, the heating medium and the circulation pump (not shown), the header pipe 31, the heater pipe 32, the header pipe 33, and the heating equipment are circulated in the order, and the lower bottom plate 5b, the underground continuous wall 9 and the heater are circulated. By performing heat exchange with the heat medium in the pipe 32, the freezing line b as a whole becomes a line segment similar to the shape of the inner surface of the tank housing, and the freezing lines between the inner surface of the tank housing and the sides and bottom of the tank housing. The separation distance to b is made substantially the same. The bottom plate 5 is composed of the upper layer bottom plate 5a and the lower layer bottom plate 5b, and the upper layer bottom plate 5a and the side wall 7 have the same thickness. Therefore, the same effects as in the first embodiment can be obtained in this embodiment.

  Also in this embodiment, similarly to the example of FIG. 9, by using the heater tube 32 continuous between the lower bottom plate 5 b and the underground continuous wall 9, the freezing lines on the side and bottom of the tank housing from the inner surface of the tank housing. It becomes easier to align the separation distances up to b. In order to prevent the freezing line b from coming out of the heater pipe at the corner, hold the lower end of the heater pipe of the side heater equipment about 2.0 to 3.0 m below the upper end of the heater pipe of the bottom heater equipment. There is no waste.

  Furthermore, in this embodiment, since the flow path length per heater tube is short and a long pipe is not required, a heater pipe 32 of about 2B pipe can be adopted, resulting in low cost.

  In the present embodiment, the vertical pipe 321 of the heater pipe 32 is embedded in the underground continuous wall 9, but the vertical pipe 321 is embedded in the side wall 7 when the side wall 7 is thick, as in the first embodiment. It is also possible to do. The heater pipe 32 is, for example, an STPG pipe, but may be a SUS pipe (stainless steel pipe) or a PL pipe.

  Further, the shape of the heater tube is not limited to the above example. For example, in the example of FIG. 13, the horizontal pipes 322a of the heater pipes 32a are substantially L-shaped, and a plurality of these are arranged along a predetermined radial direction (upper right direction in the example in the figure) from the plane center of the lower layer bottom plate 5b. The intervals D3 between the sides of the horizontal pipes 322a that are arranged side by side are substantially equal. On the other hand, in the example of FIG. 14, the horizontal pipes 322b of the heater pipes 32b are substantially linear, and a plurality of them are arranged in parallel with the intervals D3 being substantially equal.

  In the examples of FIGS. 13 and 14, the temperature difference between the heater tubes 32a and 32b is reduced by making the flow of the heat medium of the adjacent heater tubes 32a and 32b face each other as indicated by arrows f1 and f2. be able to.

  13 and 14, the distance D3 is adjusted to an appropriate value (for example, the distance D3 is adjusted to the distance D2), and in order to prevent the pipe from becoming too dense, the horizontal pipe 322a, The position corresponding to the haunch 6 of 322b is bent with respect to the other portions, and some of the heater pipes 32a and 32b do not have horizontal pipes 322a and 322b that are substantially L-shaped or substantially straight. The lower ends of the vertical pipes 321 are formed in a substantially U shape (for example, the heater pipe 32a at the upper right in FIG. 13).

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1, 1a, 1b: Underground tank structure 3: Surrounding ground 4: Catchment layer 5: Bottom plate 5a: Upper layer bottom plate 5b: Lower layer bottom plate 6: Haunch 7: Side wall 8: Steel roof 9: Underground continuous walls 11, 15, 31, 33, 101, 105: Header pipes 13, 13 ′, 13a, 13a ′, 22, 32, 32a, 32b, 103, 201: Heater pipe 51: Water stop portion 52: Connection reinforcing bar 131: Inner pipe 132: Outside Pipes 133, 136, 137, 139, 221, 224, 321: vertical pipes 134, 138, 222: circumferential pipes 135, 223: diagonal pipes 322, 322a, 322b: horizontal pipes

The present invention for solving the above-mentioned problems is an underground tank structure provided on the ground, and has a tank casing including a bottom plate and a side wall, and the bottom plate is provided in two layers of an upper layer bottom plate and a lower layer bottom plate. is, the upper layer the bottom plate is connected with the side wall, the upper bottom plate and Ri substantially equal der thickness of the side wall, the upper bottom plate and the side wall is underground tank structure characterized that you have joined rigidly .

In the present invention, the bottom plate is divided into two layers, the upper layer bottom plate and the lower layer bottom plate, and the thinned upper layer bottom plate and the side wall are connected with the same thickness, whereby the temperature load generated on the upper layer bottom plate and the side wall can be reduced. That is, it becomes possible to easily reduce the difference in temperature drop between the bottom plate and the side wall tank construction as occurs in the case of the conventional tank housing, and the temperature caused by the difference in temperature drop between the bottom plate and the side wall. The load can be reduced. Further, the fact that the upper layer bottom plate is thinner than the conventional bottom plate itself also brings about the effect of reducing the temperature load. As a result, the amount of reinforcing bars can be reduced by extremely reducing the temperature load applied to the upper bottom plate and the side wall. In addition, since the lower layer bottom plate constructed separately from the upper layer bottom plate is less constrained, almost no temperature load is generated. In addition, the double bottom slab of the lower bottom plate and the upper bottom plate can resist the lifting pressure (water pressure), and can also resist lifting due to groundwater pressure during air-liquid. Since the temperature load is often increased in the rigid tank tank, the present invention can be applied particularly favorably in such a case.

It is desirable that the freezing line indicating the position at which the temperature is 0 ° C. as the tank operates is at a position where the side and bottom of the tank housing are substantially the same distance from the inner surface of the tank housing. Furthermore, it is desirable that the position of the freezing line is below the upper surface of the lower layer bottom plate at the bottom of the tank housing.
In the present invention, the upper layer bottom plate and the side wall have the same thickness, and the distance from the inner surface of the tank housing to the freezing line of the side and bottom of the tank housing is substantially the same, so that The difference in temperature drop between the upper bottom plate and the side wall can be brought close to 0 by making the distributions substantially the same. In addition, since the frozen concrete having substantially the same thickness can be formed on the tank housing, a reliable and reliable water stop can be achieved.

It is desirable that a water stop portion is provided on the entire outer periphery of the boundary surface between the upper layer bottom plate and the lower layer bottom plate. Moreover, it is also desirable that a connecting reinforcing bar is provided so as to straddle the boundary surface only at the outer peripheral portion of the boundary surface between the upper layer bottom plate and the lower layer bottom plate.
By providing a water stop portion at the outer peripheral portion of the boundary surface between the upper layer bottom plate and the lower layer bottom plate, water can be prevented from entering between the upper layer bottom plate and the lower layer bottom plate, and water pressure does not act on the upper layer bottom plate. Further, by providing the connecting reinforcing bars so as to straddle the boundary surface, it is possible to prevent water from entering between the upper layer bottom plate and the lower layer bottom plate by preventing the opening between the upper layer bottom plate and the lower layer bottom plate.

Claims (5)

An underground tank structure provided on the ground,
A tank housing including a bottom plate and side walls;
The bottom plate is provided in two layers, an upper layer bottom plate and a lower layer bottom plate,
The upper tank bottom plate is connected to the side wall, and the thickness of the upper layer bottom plate and the side wall is substantially the same.   The freezing line indicating a position that becomes 0 ° C. as the tank is operated is at a position that is at substantially the same distance from the inner surface of the tank housing at the side and bottom of the tank housing. Underground tank structure.   The underground tank structure according to claim 1 or 2, wherein a water stop portion is provided on an entire circumference of an outer peripheral portion of a boundary surface between the upper layer bottom plate and the lower layer bottom plate.   The underground tank structure according to any one of claims 1 to 3, wherein a connecting reinforcing bar is provided so as to straddle a boundary surface between the upper layer bottom plate and the lower layer bottom plate.   The underground tank structure according to any one of claims 1 to 4, wherein the upper layer bottom plate and the side wall are rigidly coupled.

Images