JP7117212B2 - Storage tank, construction method of storage tank - Google Patents

Description

The present invention relates to a storage tank and its construction method.

As an anaerobic fermentation digester for sewage sludge, there is an egg-shaped storage tank made of prestressed concrete with an agitator inside (hereinafter referred to as a PC egg-shaped digester), which has high agitation performance because it is difficult to create a dead water area. Excellent at

However, when constructing a PC egg-shaped digester using conventional cast-in-place concrete, it is necessary to pour concrete, attach heat insulating materials, and apply anti-corrosion coating. I needed scaffolding. In addition, the PC egg-shaped digester has a complicated shape and requires the introduction of prestress in the circumferential and longitudinal directions, making construction difficult.

On the other hand, Patent Document 1 describes a PC egg-shaped digester made of precast segments (hereinafter sometimes referred to as segments), and the use of such segments simplifies construction.

Patent No. 4309835

FIG. 14 is a schematic perspective view showing a side wall of a PC egg-shaped digester cut in half. In the example of Patent Literature 1, the side wall of the PC egg-shaped digester is divided into upper and lower parts, and the upper and lower parts of the side wall are divided in the circumferential direction of the PC egg-shaped digester to form a plurality of segments 200 .

The segment 200 is continuous from the height center of the side wall to the top or bottom end, and the segment 200 tapers to a fairly narrow width at the tip. Therefore, a problem arises in manufacturing the segment 200 and the like. For example, narrowing the width of the tip of the segment 200 makes it difficult to manufacture the segment 200 . In addition, the arrangement of the PC steel material in the meridional direction at the tip of the segment 200 becomes tight, and it is also difficult to provide a fixing portion for fixing the PC steel material at the tip.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a storage tank or the like using segments that can be easily manufactured.

A first invention for solving the above-described problems is a concrete storage tank having a shape that narrows toward the top end, and the side wall of the storage tank is divided into a middle portion and a top portion in the height direction. , the middle part of the side wall in the height direction is divided into the middle part of the side wall in the circumferential direction of the storage tank, and the lower part of the outer surface rises vertically and the lower surface is horizontal . At the boundary between the intermediate portion and the top portion of the side wall, the length of the member forming the top portion in the circumferential direction of the storage tank is greater than the length of the precast segment of the intermediate portion in the circumferential direction of the storage tank, In the middle part of the sidewall a longitudinal prestress is introduced, and at the upper end of the precast segment of the middle part a longitudinal PC steel member for introducing the longitudinal prestress is anchored , below the middle part. A side wall portion in contact with the tank is constructed so as to be exposed to the ground with cast-in-place concrete, the outer surface of the side wall portion rises in a vertical direction, and the upper surface is horizontal .

In the present invention, the use of precast segments for the construction of the storage tank facilitates the construction of the storage tank, making it possible to shorten the construction period. In addition, by dividing the side wall of the storage tank into an intermediate portion and a top portion in the height direction, the segment that constitutes the intermediate portion does not continue to the top end of the storage tank, and the width of the tip of the segment (the length of the circumferential direction of the storage tank) becomes wider. As a result, the segment can be easily manufactured, and there is room in the arrangement of the PC steel material in the longitudinal direction, making it easy to provide the fixing portion at the tip. Also, by constructing the top portion of the side wall with a wider member, the number of members can be reduced and the construction period can be shortened.

Preferably, a circumferential prestress is introduced in said intermediate portion of said sidewall.
This allows the sidewalls of the reservoir to resist the internal pressure of the reservoir.

An opening is provided at the top end of the storage tank, and the member constituting the top of the side wall is a plurality of precast segments obtained by dividing the top of the side wall in the circumferential direction of the storage tank, and the top of the side wall is a precast segment. The number of divisions into which the sidewall is divided into precast segments is less than the number of divisions into which the intermediate portion of the sidewall is divided into precast segments.
As described above, according to the present invention, the top portion of the side wall can also be composed of segments obtained by dividing the top portion in the circumferential direction of the reservoir. Since the number of divisions in the top portion of the side wall is smaller than that in the middle portion, the segments at the top portion are wider than the segments in the middle portion and are easy to manufacture.

Preferably, the storage tank is a sludge digestion tank, and the middle portion of the side wall narrows in a curve toward the top end.
As a result, it is possible to form a digestion tank having advantages such as a high agitation property and a low dead water area.

It is also desirable that the bottom end of said reservoir is constituted by horizontal slab concrete. Further, in the present invention, the side wall portion below the intermediate portion is made of cast-in-place concrete .
Construction of the storage tank is facilitated by forming the floor slab concrete for the bottom end of the storage tank and by constructing the lower side wall portion of the intermediate part by cast-in-place concrete.

A second aspect of the invention is a method for constructing a concrete storage tank having a shape that tapers toward the top, comprising: constructing an intermediate portion in the height direction of the side wall of the storage tank; and a middle portion of the side wall in the height direction is obtained by dividing the middle portion of the side wall in the circumferential direction of the storage tank , the lower portion of the outer surface rising vertically, and the lower surface being horizontal. It is composed of a plurality of precast segments, and at the boundary between the intermediate portion and the top portion of the side wall, the length of the member forming the top portion in the circumferential direction of the storage tank is equal to the circumference of the storage tank of the segment of the intermediate portion. A longitudinal prestress is induced in the intermediate portion of the sidewall, which is greater than the length of the direction, and at the upper end of the precast segment of the intermediate portion, a longitudinal PC steel member is anchored for introducing the longitudinal prestress. and a side wall portion in contact with the lower portion of the intermediate portion is configured to be exposed to the ground with cast-in-place concrete, the outer surface of the side wall portion rises in a vertical direction, and the upper surface is horizontal. The method.

According to the present invention, it is possible to provide a storage tank or the like using segments that can be easily manufactured.

The figure which shows the digestion tank 1. FIG. The figure which shows the digestion tank 1. FIG. The figure which shows the construction method of the digestion tank 1. FIG. The figure which shows the construction method of the digestion tank 1. FIG. The figure which shows the construction method of the digestion tank 1. FIG. The figure which shows the digestion tank 1a. The figure which shows the digestion tank 1a. The figure which shows the construction method of the digestion tank 1a. The figure which shows the construction method of the digestion tank 1a. The figure which shows the digestion tank 1b. The figure which shows the digestion tank 1b. The figure which shows the construction method of the digestion tank 1b. The figure which shows the construction method of the digestion tank 1b. A diagram showing the side walls of a PC egg-shaped digester.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

[First Embodiment]
(1. Digestion tank 1)
FIG. 1 shows a digestion tank 1 according to a first embodiment of the present invention. FIG. 1(a) is a vertical cross section of the digestion tank 1, and FIG. 1(b) is a schematic perspective view showing a side wall of the digestion tank 1 cut in half.

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

As shown in FIG. 1, the digester 1 has a steel shell piece 5, a bottom segment ring 7, a middle segment ring 9, a top segment ring 11 and so on.

Digester 1 is a PC oval digester with a generally oval vertical cross-section, narrowing towards the top and bottom ends. More specifically, the intermediate portion in the height direction of the digestion tank 1 swells outward in a spherical shape and narrows in a curve toward the top and bottom ends, and the top and bottom portions of the digestion tank 1 are truncated cones, each having a top end. and narrows linearly towards the bottom end.

The steel shell piece 5 is a mortar-shaped concrete placing frame forming the bottom end of the digestion tank 1 , and concrete is placed inside the steel shell piece 5 . The steel shell piece 5 has an inclined portion 53 around a bottom portion 51 . In this embodiment, it is assumed that the inclined portion 53 is inclined at an angle of 45° with respect to the horizontal direction.

A bottom segment ring 7, a middle segment ring 9 and a top segment ring 11 constitute the side walls of the digester 1 and are located at the bottom, middle and top of the side walls of the digester 1 respectively. Thus, in this embodiment, the side wall of the digestion tank 1 is divided into a middle portion, a top portion, and a bottom portion in the height direction. In this embodiment, precast segments are used as the members constituting these segment rings.

A bottom segment ring 7 is installed on the steel shell piece 5 . The bottom segment ring 7 is a truncated conical member that narrows downward. The bottom segment ring 7 is constructed by arranging a plurality of precast segments 71 in the circumferential direction of the digestion tank 1 .

A middle segment ring 9 is mounted on the bottom segment ring 7 . The intermediate segment ring 9 is a barrel-shaped cylindrical member that bulges outward in a spherical shape.

The intermediate segment ring 9 is divided at the center in the height direction into a lower intermediate segment ring 9-1 and an upper intermediate segment ring 9-2. The intermediate segment rings 9-1 and 9-2 are constructed by arranging a plurality of precast segments 91 in the circumferential direction of the digestion tank 1. As shown in FIG.

A top segment ring 11 is mounted on the middle segment ring 9 . The top segment ring 11 is a truncated conical member that narrows upward. The top segment ring 11 is configured by arranging a plurality of precast segments 111 in the circumferential direction of the digestion tank 1 .

An opening 18 is provided at the top end of the digestion tank 1, and this opening 18 is closed with a steel plate or the like (not shown). A stirrer is attached to the steel plate.

In this embodiment, the bottom segment ring 7 is inclined at the same angle (45°) as the inclined portion 53 of the steel shell piece 5 and is smoothly continuous with the steel shell piece 5 . The lower end of the middle segment ring 9 is inclined at the same angle (45°) as the bottom segment ring 7 and continues smoothly with the bottom segment ring 7 .

Also, the top segment ring 11 is inclined at an inclination angle of 45° with respect to the horizontal direction. The upper end of the intermediate segment ring 9 is inclined at the same angle (45°) as the top segment ring 11 and smoothly continues with the top segment ring 11 .

FIG. 2(a) is a top view of the digestion tank 1. FIG. FIG. 2(b) is an elevation view of the segment 91 forming the upper intermediate segment ring 9-2, and FIG. 2(c) is an elevation view of the segment 111 forming the top segment ring 11. FIG.

Segments 91 and 111 have shapes obtained by equally dividing the upper middle segment ring 9-2 and the top segment ring 11 in the circumferential direction of the digestion tank 1 along a radial vertical plane passing through the central axis of the digestion tank 1. FIG.

Here, the number of divisions of the top segment ring 11 is smaller than the number of divisions of the middle segment ring 9-2. In the example of FIG. 2( a ), the middle segment ring 9 - 2 is divided into 36 segments 91 while the top segment ring 11 is divided into 6 segments 111 .

Therefore, at the boundary 20 between the intermediate segment ring 9-2 and the top segment ring 11, the width W1 of the segment 91 (length in the circumferential direction of the digestion tank 1) is smaller than the width W2 of the segment 111. FIG.

As shown in FIG. 2(b), the segment 91 of the intermediate segment ring 9-2 in the lower stage has an elongated shape with a vertical length greater than the horizontal width, and a main body 92 whose width narrows toward the upper end. It has a bent portion 93 provided at the lower end of 92 and bent outward.

The segment 91 of the intermediate segment ring 9-1 in the lower stage has a shape obtained by vertically inverting the segment 91 shown in FIG. 2(b). Further, at the upper end of the segment 91 in FIG. 2(b), a fixing portion (not shown) is provided for fixing the strained longitudinal PC steel material 15 (see FIG. 1).

As shown in FIG. 2(c), the segment 111 of the top segment ring 11 has a main body 112 whose width narrows toward the upper end and a bent portion 113 provided at the upper end of the main body 112 and bent upward. Also, the vertical length is shorter than the segment 91 . The segment 71 of the bottom segment ring 7 has substantially the same shape as the body 112 of the segment 111 turned upside down.

These segments 71, 91, 111 are prefabricated precast concrete members. In the segments 71, 91, and 111, sheath pipes are embedded for passing the circumferential PC steel material 13 and the longitudinal PC steel material 15 (see FIG. 1). When constructing the digestion tank 1, the inner surfaces of the segments 71, 91 and 111 are coated with anti-corrosion coating in advance, and the outer surfaces of the segments 71, 91 and 111 are attached with heat insulating materials.

In this embodiment, as shown in FIG. 1(a), the lower part of the digester 1 is buried under the ground surface, and a ring foundation 19 is provided around the lower part. The ring foundation 19 is ring-shaped cast-in-place concrete and is supported by foundation piles 17 .

(2. Construction method of digestion tank 1)
Next, a construction method for the digestion tank 1 will be described with reference to FIGS. 3 to 5. FIG.

When constructing the digestion tank 1, first, as shown in FIG. The excavated portion 21 has a recessed portion 24 near the center of the bottom surface. The foundation pile 17 is provided around the recess 24 .

After that, as shown in FIG. 3(b), leveling concrete 23 is placed on the bottom surface of the excavated portion 21. Next, as shown in FIG. Then, the steel shell piece 5 is installed in the concave portion 24 and concrete is placed in the steel shell piece 5 .

Next, as shown in FIG. 3(c), the segment 71 is installed on the steel shell piece 5 to assemble the bottom segment ring 7. As shown in FIG. Then, the circumferential PC steel material 13 and the longitudinal PC steel material 15 are inserted into the sheath tube of the segment 71, and prestress is introduced to the bottom segment ring 7 in the circumferential direction and the longitudinal direction due to the tension thereof.

Also, the lower stage of the ring foundation 19 is constructed by placing concrete (cast-in-place concrete) on the leveling concrete 23 outside the bottom segment ring 7 . The lower stage and the bottom segment ring 7 are connected by a steel material such as a dowel attached to the segment 71 in advance.

Next, as shown in FIG. 4(a), the segment 91 is mounted on the bottom segment ring 7 to assemble the lower intermediate segment ring 9-1. The segments 91 are supported by supports (not shown) installed on the ring foundation 19 .

Then, the circumferential PC steel material 13 and the longitudinal PC steel material 15 are inserted into the sheath tube of the segment 91, and prestress in the circumferential direction and the longitudinal direction is introduced to the intermediate segment ring 9-1 by the tension thereof.

Next, as shown in FIG. 4(b), the support material (not shown) is removed, concrete (cast-in-place concrete) is placed on the lower ring foundation 19, and the upper ring foundation 19 is placed. To construct. The upper stage and the intermediate segment ring 9-1 are connected by a steel material such as a dowel attached to the segment 91 in advance.

In addition, the excavated portion 21 (see FIG. 3A) outside the ring foundation 19 is backfilled with backfill soil 27, and the center tower 25 is installed on the steel shell piece 5. As shown in FIG.

After that, as shown in FIG. 5(a), the intermediate segment ring 9-2 is assembled by installing the segment 91 on the intermediate segment ring 9-1. The segments 91 of the upper and lower intermediate segment rings 9-1 and 9-2 are connected to each other at the bent portion 93 by PC steel bars, bolts, or the like (not shown).

Then, the circumferential PC steel material 13 and the longitudinal PC steel material 15 are inserted into the sheath tube of the segment 91 of the intermediate segment ring 9-2, and the intermediate segment ring 9-2 is prestressed in the circumferential and longitudinal directions by the tension thereof. to introduce

Next, as shown in FIG. 5(b), the top segment ring 11 is assembled by installing the segment 111 on the intermediate segment ring 9-2. In addition, the circumferential PC steel material 13 and the longitudinal PC steel material 15 are inserted into the sheath tube of the segment 111, and prestress is introduced to the top segment ring 11 in the circumferential direction and the longitudinal direction due to the tension thereof.

When the segment 91 of the middle segment ring 9-2 and the segment 111 of the top segment ring 11 are installed, the segments 91 and 111 are supported using support members (not shown) extending from the center tower 25. FIG. For example, after a certain segment 91, 111 is supported and arranged from the center tower 25, the segment 91, 111 positioned diagonally across the center tower 25 from the segment 91, 111 is supported and arranged from the center tower 25. do. By repeating this process to install the segments 91 and 111, stability during construction can be ensured.

After the top segment ring 11 is completed, the center tower 25 is removed and the remaining necessary members are attached to complete the digestion tank 1 .

Thus, in the first embodiment, precast segments 71, 91, and 111 are used for construction of the digester 1, thereby minimizing the scaffolding required in conventional construction of a digester using cast-in-place concrete. It becomes possible to install the heat insulating material and apply anti-corrosion coating at the factory or on the ground before the segments 71, 91 and 111 are installed. Therefore, construction of the digestion tank 1 is facilitated, which contributes to shortening the construction period and reducing costs. In addition, even an inexperienced worker can easily perform construction, and it is easy to ensure quality.

Furthermore, by dividing the side wall of the digestion tank 1 into the middle segment ring 9, the bottom segment ring 7, and the top segment ring 11, the segment 91 of the middle segment ring 9 can be continuous to the top end and the bottom end of the digestion tank 1. Therefore, the width of the tip of the segment 91 can be widened. As a result, the segment 91 can be easily manufactured, and the longitudinal PC steel material 15 can be easily arranged, making it easy to provide a fixing portion for the longitudinal PC steel material 15 at the tip.

In this embodiment, the middle segment ring 9 , the top segment ring 11 and the bottom segment ring 7 are composed of segments 91 , 111 and 71 obtained by dividing these segment rings in the circumferential direction of the digestion tank 1 . Since the number of divisions of the top segment ring 11 and bottom segment ring 7 is made smaller than the number of divisions of the intermediate segment ring 9, the number of segments 111 and 71 can be reduced and the construction period can be shortened. Moreover, since the segments 111 and 71 are wider members than the segment 91, they are easy to manufacture.

In addition, by introducing prestress in the circumferential direction and longitudinal direction to the intermediate segment ring 9, the bottom segment ring 7, and the top segment ring 11, the side wall of the digestion tank 1 resists the internal pressure such as the hydraulic pressure of the digestion tank 1. It is possible to suitably prevent liquid leakage from the digestion tank 1.

Furthermore, in the present embodiment, since the segment 91 is vertically symmetrical between the lower middle segment ring 9-1 and the upper middle segment ring 9-2, the segment 91 can be manufactured using the same formwork. The mold cost required for manufacturing 91 can be reduced.

In addition, the digestion tank 1 of this embodiment has a substantially oval shape with an intermediate segment ring 9 that narrows in a curved shape toward the top and bottom ends. It has advantages such as being easy.

However, the present invention is not limited to this. For example, in the present embodiment, prestress is introduced after the segments 71, 91, 111 are installed, but prestress may be introduced to the segments 71, 91, 111 during the manufacturing stage before the segments 71, 91, 111 are installed. Moreover, since a large sectional force does not act on the segment 111, the segment 111 may be a member to which no prestress is introduced.

Furthermore, in this embodiment, the top segment ring 11 and the bottom segment ring 7 are divided into the segments 111 and 71, but it is also possible to construct them as an integral member without division, which is similar to cast-in-place concrete members. It is also possible to Even in these cases, it is possible to omit the introduction of prestress.

Moreover, although the example of the digestion tank 1 was described as a storage tank in this embodiment, this embodiment is applicable not only to the digestion tank 1 but to various storage tanks. Moreover, the reservoir may have a shape that narrows toward the top end, for example, it may be spherical as a whole.

Other examples of the present invention will be described below as second and third embodiments. In each embodiment, points different from the embodiments described so far will be described, and descriptions of similar configurations will be omitted by attaching the same reference numerals in the drawings and the like. In addition, the configurations described in each embodiment, including the first embodiment, can be combined as necessary.

[Second embodiment]
6 and 7 are diagrams showing a digestion tank 1a according to a second embodiment of the present invention. FIG. 6 shows a vertical section of the digestion tank 1a. FIG. 7(a) is a top view of the digestion tank 1a, and FIG. 7(b) is an elevational view of the segment 91a of the intermediate segment ring 9a.

This digestion tank 1a is mainly different from the first embodiment in that the intermediate segment ring 9a is not divided into upper and lower stages, but erected on a ring base 19a.

When constructing the digestion tank 1a, first, the steel shell piece 5 is installed in the same procedure as in the first embodiment (see FIGS. 3(a) and 3(b)), and then as shown in FIG. 8(a). Next, the segment 71a is installed on the steel shell piece 5 to assemble the bottom segment ring 7a. In addition, the circumferential PC steel material 13 is inserted through the sheath tube in the segment 71a, and the tension thereof introduces circumferential prestress to the bottom segment ring 7a. The segment 71a has a shorter vertical length than the segment 71 of the first embodiment.

In addition, the lower stage of the ring foundation 19a is constructed by placing concrete (cast-in-place concrete) on the leveled concrete 23 outside the bottom segment ring 7a. The lower stage and the bottom segment ring 7a are connected by a steel material such as a dowel attached in advance to the segment 71a.

Then, the longitudinal PC steel material 15 is inserted into the sheath tube previously embedded in the lower stage of the segment 71a and the ring foundation 19a, and the tension thereof introduces prestress in the longitudinal direction to the bottom segment ring 7a. The upper and lower ends of the longitudinal PC steel material 15 are respectively anchored to the upper surface of the lower stage of the ring foundation 19a and the lower end of the segment 71a.

Next, as shown in FIG. 8B, concrete (cast-in-place concrete) is placed on the lower stage of the ring foundation 19a to construct the middle stage of the ring foundation 19a. Then, the circumferential prestressing steel material 13 is inserted into the sheath pipe embedded in advance in the concrete of the middle stage, and the tension thereof introduces circumferential prestress to the middle stage of the ring foundation 19a.

Subsequently, as shown in FIG. 8(c), concrete (cast-in-place concrete) is placed on the middle stage of the ring foundation 19a to construct the upper stage of the ring foundation 19a. Then, the circumferential PC steel material 13 is inserted into the sheath pipe previously embedded in the concrete of the upper stage, and the tension thereof introduces circumferential prestress to the upper stage of the ring foundation 19a. In this embodiment, the upper surface of the ring foundation 19a is located below the center of the digestion tank 1a (see FIG. 6) in the height direction.

In addition, the excavated portion 21 (see FIG. 3(a)) outside the ring foundation 19a is backfilled with backfill soil 27, and the center tower 25 is installed on the steel shell piece 5. As shown in FIG.

Next, as shown in FIG. 9(a), the intermediate segment ring 9a is assembled by installing the segment 91a on the ring foundation 19a. Then, the circumferential PC steel material 13 is inserted into the sheath tube of the segment 91a, and the tension thereof introduces circumferential prestress to the intermediate segment ring 9a. Both ends of the circumferential PC steel material 13 are fixed by, for example, notches (not shown) provided on the inner surface of the segment 91a.

In addition, the longitudinal PC steel material 15 is inserted into the sheath pipe previously embedded in the segment 91a and the ring foundation 19a, and its tension introduces prestress in the longitudinal direction to the intermediate segment ring 9a. The upper and lower ends of the longitudinal PC steel material 15 are anchored within the upper end of the segment 91a and the ring foundation 19a, respectively.

After that, in the same procedure as in the first embodiment, the top segment ring 11 is assembled on the intermediate segment ring 9a as shown in FIG. Circumferential and longitudinal prestresses are introduced into the ring 11 .

As in the first embodiment, when the segments 91a and 111 are installed, support members (not shown) extended from the center tower 25 are used to support them. After the top segment ring 11 is completed, the center tower 25 is removed and the remaining necessary members are attached to construct the digestion tank 1a.

This second embodiment can also obtain the same effect as the first embodiment. Further, in the second embodiment, since the middle segment ring 9a is not divided into upper and lower stages, there is an advantage that there is no connection point between the upper and lower middle segment rings, which is a structurally weak part.

[Third Embodiment]
10 and 11 are diagrams showing a digestion tank 1b according to a third embodiment of the present invention. FIG. 10 shows a vertical section of the digestion tank 1b. 11(a) is a top view of the digestion tank 1b, and FIG. 11(b) is an elevational view of the segment 91b of the intermediate segment ring 9b.

In this digestion tank 1b, the intermediate segment ring 9b is not divided into upper and lower stages, and is erected on the concrete pedestal 33. The inner surface becomes the inner surface of the digestion tank 1b, and the bottom end of the digestion tank 1b is composed of a horizontal floor slab concrete 31, and a bottom surface 30 wider than the opening 18 is provided in the internal space of the digestion tank 1a. is the main difference from the first embodiment.

When constructing the digestion tank 1b, first, as shown in FIG. 12(a), the foundation piles 17 are placed and the excavation portion 21b is excavated. The bottom surface of the excavated portion 21b is flat. After that, leveling concrete 23b is placed on the bottom surface of the excavation portion 21b, and floor slab concrete 31 is constructed on the leveling concrete 23b. The floor slab concrete 31 is made of cast-in-place concrete and supported by foundation piles 17 .

Next, as shown in FIG. 12(b), a base concrete 33 is constructed on the outer peripheral portion of the floor slab concrete 31. Next, as shown in FIG. The pedestal concrete 33 is formed of cast-in-place concrete, and the concrete is cast in two steps, for example. In this embodiment, the upper surface of the concrete pedestal 33 is located below the center of the digestion tank 1b (see FIG. 10) in the height direction.

The excavated portion 21 b (see FIG. 12( a )) outside the base concrete 33 is backfilled with backfill soil 27 . Further, the upper surface of the floor slab concrete 31 and the inner surface of the pedestal concrete 33 are coated with anti-corrosion coating, and the center tower 25 is installed in the central portion of the floor slab concrete 31 .

Next, as shown in FIG. 13(a), the segment 91b is installed on the base concrete 33 to assemble the intermediate segment ring 9b. Then, the circumferential PC steel material 13 is inserted into the sheath tube of the segment 91b, and the tension thereof introduces circumferential prestress to the intermediate segment ring 9b. Similar to the above, both ends of the circumferential PC steel material 13 are fixed, for example, by notches (not shown) provided on the inner surface of the segment 91b. Note that the segment 91b is slightly shorter in vertical length than the segment 91a of the second embodiment.

In addition, the longitudinal prestressing steel material 15 is inserted into the sheath pipe previously embedded in the segment 91b and the concrete pedestal 33, and its tension introduces prestress in the longitudinal direction to the intermediate segment ring 9b. The upper end and the lower end of the longitudinal PC steel material 15 are fixed in the upper end of the segment 91b and the base concrete 33, respectively.

After that, the top segment ring 11 is assembled on the middle segment ring 9b as shown in FIG. 13(b) by the same procedure as in the first embodiment. It is also possible to connect the base concrete 33 and the segment 91b, and the segment 91b and the segment 111, using a mortar-filled mechanical joint, a PC steel bar, or the like (not shown).

Also in the third embodiment, when the segments 91b and 111 are installed, support members (not shown) extended from the center tower 25 are used to support them. After completion of the top segment ring 11, the digester 1b is constructed by removing the center tower 25 and attaching the remaining necessary members.

In this embodiment, no prestress in the circumferential and longitudinal directions is introduced into the top segment ring 11, but prestress in the circumferential and longitudinal directions can be introduced by the circumferential PC steel material 13 and the longitudinal PC steel material 15. is.

This third embodiment can also obtain the same effect as the first embodiment. Further, as in the second embodiment, there is an advantage that there is no connection point between the upper and lower intermediate segment rings, which is a structurally weak point.

Furthermore, in the third embodiment, by making the bottom end of the digestion tank 1b horizontal slab concrete, the truncated conical portion of the bottom like the digestion tanks 1 and 1a of the first and second embodiments can be omitted, and the construction period can be further shortened.

Furthermore, in this embodiment, the lower side wall portion of the intermediate segment ring 9b is made of cast-in-place concrete (pedestal concrete 33). This portion is a portion where a large cross-sectional force is generated due to hydraulic pressure, etc., and if it is composed of a plurality of segments, an increase in steel materials such as joints between segments and an increase in man-hours will occur. In some cases, it is advantageous in terms of construction period and cost. This also applies to the above-described second embodiment, in which the lower side wall portion of the intermediate segment ring 9a is made of cast-in-place concrete (ring foundation 19a).

Although the 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 obvious that a person skilled in the art can conceive of various modifications or modifications within the scope of the technical ideas disclosed in the present application, and these also belong to the technical scope of the present invention. Understood.

1, 1a, 1b: Digestion tank 5: Steel shell pieces 7, 7a: Bottom segment ring 9, 9-1, 9-2, 9a, 9b: Middle segment ring 11: Top segment ring 13: Circumferential PC steel material 15 : Longitudinal direction PC steel material 17: Foundation pile 18: Openings 19, 19a: Ring foundation 20: Boundary parts 21, 21b: Excavation parts 23, 23b: Leveled concrete 24: Depression 25: Center tower 27: Backfill soil 30: Bottom 31: Floor slab concrete 33: Base concrete 71, 71a, 91, 91a, 91b, 111, 200: Segment

Claims (6)

A concrete storage tank having a shape that narrows toward the top,
The side wall of the storage tank is divided into a middle portion and a top portion in the height direction,
The intermediate portion in the height direction of the side wall is divided into the intermediate portion of the side wall in the circumferential direction of the storage tank, and the lower portion of the outer surface rises vertically and the lower surface is horizontal .
At the boundary between the intermediate portion and the top portion of the side wall, the length of the member forming the top portion in the circumferential direction of the storage tank is greater than the length of the precast segment of the intermediate portion in the circumferential direction of the storage tank,
introducing a longitudinal prestress in the intermediate portion of the sidewall;
at the upper end of said intermediate precast segment a longitudinal PC steel is anchored for introducing a longitudinal prestress ;
A storage tank , wherein a side wall portion contacting the lower portion of the intermediate portion is exposed to the ground with cast-in-place concrete, the outer surface of the side wall portion rises vertically, and the upper surface is horizontal . 2. Reservoir according to claim 1, characterized in that a circumferential prestress is induced in the middle part of the side wall. an opening is provided at the top end of the reservoir;
The member forming the top of the side wall is a plurality of precast segments obtained by dividing the top of the side wall in the circumferential direction of the storage tank,
3. A reservoir according to claim 1 or 2, characterized in that the number of divisions into which the top portion of the side wall is divided into precast segments is smaller than the number of divisions into which the middle portion of the side wall is divided into precast segments. 4. The storage tank according to any one of claims 1 to 3, wherein the storage tank is a sludge digestion tank, and the middle portion of the side wall narrows in a curve toward the top end. 5. The storage tank according to any one of claims 1 to 4, characterized in that the bottom end of the storage tank is constructed of horizontal floor slab concrete. A method for constructing a concrete storage tank having a shape that narrows toward the top, comprising:
constructing an intermediate portion in the height direction of the sidewall of the reservoir;
building a top portion of a sidewall of the reservoir;
has
The intermediate portion in the height direction of the side wall is divided into the intermediate portion of the side wall in the circumferential direction of the storage tank, and the lower portion of the outer surface rises vertically and the lower surface is horizontal .
At the boundary between the intermediate portion and the top portion of the side wall, the length of the member forming the top portion in the circumferential direction of the storage tank is greater than the length of the segment of the intermediate portion in the circumferential direction of the storage tank,
introducing a longitudinal prestress in the intermediate portion of the sidewall;
at the upper end of said intermediate precast segment a longitudinal PC steel is anchored for introducing a longitudinal prestress ;
A method for constructing a storage tank , wherein a side wall portion in contact with the lower portion of the intermediate portion is configured to be exposed to the ground with cast-in-place concrete, the outer surface of the side wall portion rises vertically, and the upper surface is horizontal .

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