JP7408465B2 - storage tank - Google Patents

Description

The present invention relates to a concrete storage tank.

As an anaerobic fermentation/digestion tank for sewage sludge, there is an egg-shaped storage tank made of prestressed concrete with an agitator installed inside it (hereinafter referred to as a PC egg-shaped digestion tank), which has the advantage of being less likely to create dead areas and has high agitation performance. Excellent.

Basic structures for PC egg-shaped digesters include direct foundations, pile foundations, and caisson foundations, but pile foundations are often used because they are mostly installed in locations with weak ground. In a PC egg-shaped digester that uses a pile foundation, a ring foundation is built on a group of piles, and the lower part of the digestion tank that narrows downward is pulled from the ring foundation. The prestressing steel members are placed in a complex manner to introduce appropriate prestress to the lower part of the ring and the ring foundation. As a result, the construction cost for the lower part of the digester is more expensive than for the side walls installed above the lower part.

On the other hand, Patent Document 1 describes an egg-shaped digestion tank in which the side wall part has a prestressed concrete structure, the lower part has a reinforced concrete structure, and the middle part has a prestressed reinforced concrete structure. Construction is simplified by making the lower part a reinforced concrete structure.

Special Publication No. 7-90875

However, in the example of Patent Document 1, not only the lower part of the egg-shaped digester but the entirety is constructed with cast-in-place concrete. Therefore, when constructing an egg-shaped digester, the cycle of assembling the formwork, arranging reinforcement, pouring concrete, and removing the mold must be divided into 10 or more blocks and carried out in order from the bottom, which increases the construction period. In addition, the curve radius of the side wall of the egg-shaped digester differs depending on the height, and the formwork cannot be used for other purposes, so a large number of formworks are required, increasing costs.

Furthermore, since the prestressed steel material in the meridian direction of the digester is placed in advance with a length of several blocks, the reinforcing work must be done at high places, and since the prestressed steel material remains upright for a long period of time, it is difficult to maintain quality. There are challenges.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a storage tank that can shorten construction time and reduce construction costs.

The present invention for solving the above-mentioned problems is a concrete storage tank having a shape that narrows toward the top and bottom, and includes a lower structure and a side wall installed on the lower structure. The side wall portion is a prestressed concrete structure constituted by a plurality of precast segments obtained by dividing the side wall portion in the circumferential direction of the storage tank, the lower structure is a reinforced concrete structure, and the storage tank is approximately an egg -shaped structure. The top end of the lower structure has a slope that becomes lower toward the outside, and the lower end of the meridian PC steel member of the side wall is fixed in the lower structure, The storage tank is characterized in that the lower end and the inner surface of the upper end of the lower structure are inclined so as to be orthogonal to the inclination of the top end .

In the present invention, by using precast segments to construct the side walls of the storage tank, it is possible to eliminate the repetition of various processes for concrete pouring, eliminate the need for formwork, and minimize the need for high-altitude work and scaffolding and shoring. can do. On the other hand, in the lower structure, by using a reinforced concrete structure and eliminating the complicated reinforcement arrangement of prestressed steel materials, construction of the storage tank becomes easier, shortening the construction period and reducing construction costs.

Preferably, the lower structure has a plurality of upper and lower steps on the outer surface of the underground portion, and a pile is provided on the lower surface of the step.
By burying the underlying substructure underground, the airtightness and watertightness of the substructure can be ensured. Furthermore, by providing multiple levels of upper and lower steps on the outer surface of the underground portion of the substructure and providing piles on these steps, the amount of concrete used in the substructure can be reduced and a rational shape can be achieved.

Since the storage tank has a substantially egg- shaped vertical cross section, an egg-shaped storage tank suitable for an anaerobic fermentation and digestion tank can be constructed at low cost and in a short construction period.

In the present invention, the top end of the lower structure has a slope that becomes lower toward the outside . It is also desirable that a protrusion be provided on the outer edge of the top end, and that the outer surface of the lower end of the side wall portion be arranged along the protrusion.
By providing the above-mentioned inclination to the top end of the lower structure, it is possible to suppress the precast segments of the side wall portion arranged at the top end from falling inward. Further, by providing the protrusion, the protrusion can be used as a ruler when installing the precast segment of the side wall portion.

Further, in the present invention, the lower end of the meridian direction PC steel material of the side wall is fixed in the lower structure, and the lower end of the side wall and the inner surface of the upper end of the lower structure are inclined so as to be perpendicular to the slope of the top. By doing so , the compressive force introduced by the meridian direction PC steel material can be effectively applied to the frame of the storage tank.

According to the present invention, it is possible to provide a storage tank that can shorten the construction period and reduce construction costs.

FIG. 1 is a diagram showing a digestion tank 1. FIG. FIG. 1 is a perspective view schematically showing the frame of the digestion tank 1. FIG. FIG. 3 is a diagram showing an elevation of the segment 31; FIG. 4 is a diagram showing a joint between a segment 31 and a lower structure 4; The figure which shows the digestion tank 1a. FIG. 2 is a perspective view schematically showing the frame of the digestion tank 1a.

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

[First embodiment]
(1. Digestion tank 1)
FIG. 1 is a diagram showing a digestion tank 1 according to a first embodiment of the present invention, and shows a vertical cross section of the digestion tank 1. Further, FIG. 2 is a perspective view schematically showing the frame of the digestion tank 1. As shown in FIG.

The digestion tank 1 is a concrete storage tank installed in a sewage treatment plant or the like, and stores sewage inside. In the digestion tank 1, sewage sludge is treated by anaerobic digestion. A stirrer (not shown) is provided inside the digestion tank 1 to efficiently process sludge.

As shown in FIG. 1, the digestion tank 1 has a top portion 2, a side wall portion 3, a lower structure 4, and the like.

The digestion tank 1 is an oval-shaped digestion tank that has an approximately oval vertical cross section as a whole. More specifically, the middle portion in the height direction bulges outward in a spherical shape, and narrows linearly toward the top and bottom ends.

The top portion 2 is a truncated cone-shaped member installed on the side wall portion 3, and narrows upward in a straight line. The top part 2 is constructed, for example, from a one-piece precast member. An opening 21 is provided at the upper end of the top portion 2, and this opening 21 is closed with a steel plate or the like (not shown). A stirrer is attached to the steel plate.

The side wall part 3 is installed on the lower structure 4. The side wall portion 3 has a prestressed concrete structure in which prestress in the meridian direction of the digestion tank 1 is introduced by the meridian direction PC steel material 6, and prestress in the circumferential direction of the digestion tank 1 is introduced by the circumferential direction PC steel material 7. A plurality of meridional direction PC steel materials 6 are arranged at intervals in the circumferential direction of the digestion tank 1, and circumferential direction PC steel materials 7 are arranged at intervals in the meridian direction of the digestion tank 1 in a plurality of upper and lower stages.

The lower part of the side wall part 3 bulges outward in a spherical shape, and narrows toward the upper part in a curved shape. The upper part of the side wall part 3 has a truncated conical shape that narrows upward in a straight line.

The inner surface of the upper end of the side wall portion 3 is inclined at the same angle as the inner surface of the lower end of the top portion 2, and the inner surface of the side wall portion 3 and the inner surface of the top portion 2 are smoothly continuous.

The side wall portion 3 is configured by arranging a plurality of precast segments 31 (hereinafter referred to as segments 31) in the circumferential direction of the digestion tank 1. The segments 31 are precast concrete members manufactured in advance, and have a shape in which the side wall portion 3 is equally divided in the circumferential direction of the digestion tank 1. The segment 31 has an elongated shape in which the vertical length is larger than the horizontal width (the length in the circumferential direction of the digestion tank 1), and the width becomes narrower toward the upper end.

The lower structure 4 has a reinforced concrete structure made of cast-in-place concrete, and reinforcing bars (not shown) are buried inside. The lower structure 4 has a truncated cone shape (mortar shape) that narrows linearly downward, and is substantially entirely buried underground except for the upper end.

A plurality of upper and lower steps 42 are formed on the outer surface of the underground portion of the lower structure 4, and a pile 5 for supporting the digestion tank 1 is provided on the lower surface of each step 42. These step portions 42 are provided so as to be continuous in the circumferential direction of the digestion tank 1, and in each step portion 42, a plurality of piles 5 are arranged at intervals in the circumferential direction of the digestion tank 1.

The inner surface of the lower structure 4 is inclined at three angles θ ₁ , θ ₂ , and θ ₃ (angles relative to the horizontal plane) in order from the top, and the angles become smaller as they go downward. The inner surface of the upper end of the lower structure 4 is inclined at the same angle θ ₁ as the inner surface of the lower end of the side wall portion 3, and the inner surface of the side wall portion 3 and the inner surface of the lower structure 4 are smoothly continuous.

FIG. 3 is an elevational view of the segment 31. A plurality of meridian direction PC steel members 6 are embedded in the segment 31 . These plural meridian direction PC steel materials 6 are arranged at intervals in the width direction of the segment 31. The meridional PC steel material 6 is, for example, an unbonded PC steel material, and its upper end is anchored within the segment 31 by a dead anchor 61.

As described above, the width of the segment 31 becomes narrower toward the upper end. Therefore, in order to prevent the meridional direction PC steel material 6 from becoming overcrowded in the upper part of the segment 31, the upper end of the meridional direction PC steel material 6 should be placed at the center of the segment 31 in the width direction. They are arranged in a dispersed manner so that they are higher in the middle and lower towards both sides in the width direction. The lower end portion of the meridional direction PC steel material 6 protrudes from the lower surface of the segment 31.

FIG. 4 is a diagram showing a joint location of the segment 31 to the lower structure 4. As shown in FIG. 4, the segment 31 is placed on the top end 43 of the substructure 4, and the top end 43 has a slope that becomes lower toward the outside. The slope of the top end 43 is set to be perpendicular to the slope of the inner surface of the lower end of the segment 31 of the side wall portion 3 and the upper end of the lower structure 4.

Further, a protrusion 431 that protrudes upward is provided on the outer edge of the top end 43, and the outer surface of the lower end of the segment 31 is arranged along this protrusion 431.

A recess 44 is formed on the outer surface of the above ground portion of the lower structure 4. Inside the lower structure 4, a sheath pipe 45 reaching from the recess 44 to the top end 43 is provided, and the lower end of the meridian direction PC steel member 6 protruding from the lower surface of the segment 31 is tensioned through the sheath pipe 45. , is fixed in the recess 44 by the fixing body 62.

Since the upper part of the segment 31 has an inwardly bent shape (see Fig. 1), a moment that tends to cause it to fall inward acts.However, as described above, the top end 43 is sloped and the segment 31 is placed on top of it. This makes it possible to suitably resist such moments. Moreover, the segment 31 can be positioned by the projection 431, and the segment 31 can be placed on the top end 43 with high precision.

In addition, since the inner surfaces of the lower end of the segment 31 of the side wall portion 3 and the upper end of the lower structure 4 are inclined perpendicularly to the inclination of the top end 43, the compressive force introduced by the meridian direction PC steel material 6 is transferred to the digester tank 1. It can work effectively on the body. The meridian direction PC steel material 6 is arranged at a joint location between the segment 31 of the side wall portion 3 and the lower structure 4 so as to be perpendicular to the slope of the top end 43.

When constructing the digestion tank 1, after constructing the substructure 4 and the piles 5, the segments 31 of the side wall part 3 are installed on the top end 43 of the substructure 4, and the lower end of the meridian direction PC steel material 6 is attached to the top end 43 of the substructure 4. It is loosely fixed in the recess 44.

When installing the segments 31, for example, one segment 31 is supported from the inside with one end of a shoring material (not shown) provided on a scaffold (not shown) installed on the lower structure 4 and placed on the top end 43. After that, a segment 31 at a position symmetrical to the segment 31 across the planar center of the digestion tank 1 is supported by the other end of a support member (not shown) and placed on the top end 43. By repeating this process and sequentially installing the segments 31 in the circumferential direction of the digestion tank 1, stability during construction can be improved.

After all the segments 31 are installed, circumferential PC steel members 7 are placed along the outer periphery of the side wall portion 3 and tensioned. In this embodiment, the circumferential PC steel material 7 is used as an outer cable, but it may be buried inside the segment 31 and used as an inner cable.

Next, the lower end portion of the meridional direction PC steel material 6 is tensioned and fixed in the recess 44, and the circumferential direction PC steel material 7 is tensioned as necessary. Thereby, prestress in the circumferential direction and the meridian direction is appropriately introduced into the side wall portion 3. Thereafter, necessary members such as the top portion 2 are installed to complete the digestion tank 1.

As explained above, in this embodiment, by using precast segments 31 for constructing the side wall portion 3 of the digestion tank 1, it is possible to eliminate the repetition of various processes for concrete pouring, eliminate the need for formwork, and increase the height of the structure. Site work, scaffolding and shoring can also be minimized. On the other hand, by making the lower structure 4 a reinforced concrete structure, it is possible to eliminate the complicated reinforcement arrangement of PC steel materials that is required when the lower structure 4 is a prestressed concrete structure.

In this way, in this embodiment, the segments 31 are used for the side wall portion 3, which requires time and effort to construct with the cast-in-place construction method, and the lower structure 4, which requires time and effort to construct with the prestressed concrete structure, is made of reinforced concrete. construction becomes easier, shortening the construction period and reducing construction costs.

Moreover, since the segments 31 are manufactured in a factory that can maintain a good working environment regardless of the weather, high-quality concrete members can be stably obtained. By loading the meridional direction PC steel material 6 into the segments 31 in advance, reinforcement work on site becomes unnecessary, and there is no concern that the quality of the meridional direction PC steel material 6 will deteriorate due to long-term exposure.

In the digestion tank 1, by introducing prestress in the circumferential direction and the meridian direction to the side wall part 3, the side wall part 3 is made thin and resists internal pressure such as liquid pressure of the digestion tank 1, and the pressure from the digestion tank 1 is reduced. Liquid leakage etc. can be suitably prevented. The underlying substructure 4 is a reinforced concrete structure, but the liquid pressure is not high, and by burying the substructure 4 underground, the airtightness and watertightness of the substructure 4 are made suitable for a liquid container structure. can be secured.

Furthermore, by providing multiple upper and lower steps 42 on the outer surface of the underground portion of the substructure 4 and providing the piles 5 on the steps 42, the amount of concrete used in the substructure 4 can be reduced and the shape can be rationalized. can.

Furthermore, by providing the above-mentioned inclination to the top end 43 of the lower structure 4, it is possible to suppress the segments 31 of the side wall portion 3 arranged at the top end 43 from falling inward, and the circumferential direction PC steel material 7 can be prevented from falling inward. Inward compression of the side wall portion 3 due to tension is not inhibited. Further, by providing the protrusion 431 on the outer edge of the top end 43, the segment 31 can be positioned using the protrusion 431 as a ruler, and the segment 31 can be placed on the top end 43 with high precision.

Furthermore, the inner surfaces of the lower end of the segment 31 of the side wall portion 3 and the upper end of the lower structure 4 are inclined perpendicularly to the inclination of the top end 43, so that the compressive force introduced by the meridian direction PC steel material 6 is transferred to the digester tank 1. It can work effectively on the body.

Furthermore, the digestion tank 1 of this embodiment has a substantially egg-shaped vertical cross section, and has advantages such as less formation of dead areas, high agitation performance, and easy removal of scum and the like.

However, the present invention is not limited to the above embodiments. For example, in this embodiment, prestress is not introduced into the top portion 2, but prestress may be introduced into the top portion 2 if necessary.

Further, in this embodiment, the lower end portion of the meridional direction PC steel material 6 is fixed in the lower structure 4, but prestress is introduced into the segment 31 in advance by the meridional direction PC steel material 6 whose both ends are fixed to the segment 31. may be joined to the top end 43 of the lower structure 4.

Further, in this embodiment, an example of a digestion tank is described as a storage tank, but this embodiment is applicable not only to a digestion tank but also to various types of storage tanks. Further, the storage tank may have a shape that narrows toward the top end and the bottom end, and is not limited to an oval shape, but may be, for example, spherical as a whole.

Another example of the present invention will be described below as a second embodiment. The second embodiment will be described with respect to differences from the first embodiment, and similar configurations will be denoted by the same reference numerals in the figures, etc., and a description thereof will be omitted.

[Second embodiment]
FIG. 5 is a diagram showing a digestion tank 1a according to a second embodiment of the present invention, as seen in a vertical cross section of the digestion tank 1a. Moreover, FIG. 6 is a perspective view showing the outline of the frame of the digestion tank 1a.

Like the first embodiment, this digestion tank 1a also has a shape that narrows toward the top and bottom ends, but it is different from the first embodiment in that it is a tortoiseshell-shaped digestion tank that has a tortoiseshell-shaped vertical cross section as a whole. Mainly different.

The digestion tank 1a has a top portion 2, a side wall portion 3a, a lower structure 4a, and the like.

As in the first embodiment, in the side wall portion 3a, prestress in the meridian direction of the digestion tank 1a is introduced by the meridian direction PC steel material 6, and prestress in the circumferential direction of the digestion tank 1a is introduced by the circumferential direction PC steel material 7. Although this embodiment has a prestressed concrete structure, it differs from the first embodiment in that a truncated conical portion 30b is provided on a cylindrical portion 30a.

The cylindrical portion 30a is a cylindrical member provided along the vertical direction, and the truncated conical portion 30b is a truncated conical member that narrows upward in a straight line.

The cylindrical portion 30a and the truncated conical portion 30b are each constructed by arranging a plurality of segments 31a and 31b in the circumferential direction of the digestion tank 1a. The segments 31a and 31b each have a shape in which a cylindrical portion 30a and a truncated conical portion 30b are equally divided in the circumferential direction of the digestion tank 1a.

In the side wall portion 3a, the upper part of the cylindrical part 30a and the lower part of the truncated cone part 30b are thickened toward the inside, and the inner surface of the thickened part 311 of the cylindrical part 30a and the inner surface of the thickened part 315 of the truncated conical part 30b are thickened toward the inside. continue smoothly with the same slope. Further, the inner surface of the upper end of the truncated conical portion 30b and the inner surface of the lower end of the top portion 2 are also smoothly continuous with the same slope.

Like the first embodiment, the lower structure 4a is a reinforced concrete structure made of cast-in-place concrete, and has a truncated cone shape (mortar shape) that narrows downward. However, the inner surface 41 near the top end 43a is along the vertical direction and smoothly continues with the inner surface of the lower end of the cylindrical portion 30a. Below the vicinity of the top end 43a, the inner surface of the lower structure 4 is inclined at two angles θ ₄ and θ ₅ (angles with respect to the horizontal plane) in order from the top, and the angles become smaller as they go downward.

Similar to the first embodiment, a plurality of meridian PC steel members 6 are embedded in the segments 31a, 31b at intervals in the width direction of the segments 31a, 31b.

As in the first embodiment, the lower end of the meridian direction PC steel material 6 of the segment 31a is tensioned through a sheath pipe (not shown) buried in the upper end of the lower structure 4a, and the outer surface of the above ground portion of the lower structure 4a is tensioned. The image is fixed by the fixing body 62 in the recess 44 provided in the area. On the other hand, the upper end of the meridian direction PC steel material 6 of the segment 31a is fixed by a fixing body 63 at the top end 312 of the segment 31a.

The lower end of the longitudinal direction PC steel material 6 of the segment 31b is tensioned through a sheath tube (not shown) buried in the upper end of the segment 31a, and is fixed by the fixing body 62 in the recess 313 provided on the outer surface of the upper end. Ru. On the other hand, the upper end of the meridian direction PC steel material 6 of the segment 31b is fixed inside the segment 31b by a dead anchor 61. Since the width of the upper part of the segment 31b is narrower than the width of the lower part, the upper ends of the meridian direction PC steel members 6 are arranged with their positions shifted in the height direction as in the example of FIG.

Note that the top end 43a of the lower structure 4a is approximately horizontal, and the segment 31a is installed on top of the top end 43a. The top end 312 of the segment 31a is also approximately horizontal, but a protrusion 3121 that protrudes upward is provided on its outer edge, so that when the segment 31b is placed on the top end 312, are arranged along the protrusion 3121. Note that the aforementioned fixing body 63 is provided at the position of this protrusion 3121.

In this second embodiment, as in the first embodiment, it is possible to shorten the construction period and reduce construction costs. In this embodiment, the upper end of the meridian direction PC steel material 6 of the segment 31a is fixed at the top end 312 by the fixing body 63, but as in the first embodiment, it is fixed inside the segment 31a by the dead anchor 61. Good too. Alternatively, the meridian direction PC steel material 6 may be arranged in a U-shape, the bent portion thereof being buried in the lower structure 4a, and both ends fixed at the top end 312 of the segment 31a.

Also in the second embodiment, the segments 31a and 31b may be pre-stressed by the longitudinal direction PC steel material 6 whose both ends are fixed to the segments 31a and 31b. Alternatively, the circumferential PC steel material 7 may be buried inside the segments 31a, 31b to form an inner cable.

Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that those skilled in the art can come up with various changes or modifications within the scope of the technical idea disclosed in this application, and these naturally fall within the technical scope of the present invention. Understood.

1, 1a: Digestion tank 2: Top part 3, 3a: Side wall part 4, 4a: Lower structure 5: Pile 6: Meridian direction PC steel material 7: Circumferential direction PC steel material 30a: Cylindrical part 30b: truncated conical part 31, 31a, 31b: Precast segment 42: Step portion 43, 43a, 312: Top end 44, 313: Recessed portion 45: Sheath tube 61: Dead anchor 62, 63: Fixing body 431, 3121: Protrusion

Claims (3)

A concrete storage tank having a shape that narrows toward the top and bottom,
It has a lower structure and a side wall installed on the lower structure,
The side wall portion is a prestressed concrete structure constituted by a plurality of precast segments obtained by dividing the side wall portion in the circumferential direction of the storage tank,
The lower structure is a reinforced concrete structure,
The storage tank has a substantially oval vertical cross section,
The top end of the lower structure has a slope that becomes lower toward the outside,
A lower end of the meridian PC steel of the side wall is anchored in the lower structure;
A storage tank , wherein an inner surface of a lower end of the side wall portion and an upper end of the lower structure are inclined so as to be orthogonal to the inclination of the top end . 2. The storage tank according to claim 1, wherein the lower structure has a plurality of upper and lower steps on the outer surface of the underground portion, and a pile is provided on the lower surface of the step. 3. The storage tank according to claim 1, wherein a projection is provided on an outer edge of the top end, and an outer surface of a lower end of the side wall portion is arranged along the projection.

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