JP2020063093A - Storage tank and method of constructing storage tank - Google Patents

Abstract

To provide a storage tank etc., having a support mechanism capable of improving stability and cost performance.SOLUTION: A side wall 3 of a digestion tank 1 is in a substantially oval shape getting narrower toward the top end and bottom end. The side wall 3 of the digestion tank 1 is vertically separated, and an upper part 3b and a lower part 3c of the side wall 3 are composed of a plurality of segments 31 formed by dividing the upper part 3b and the lower part 3c of the side wall 3 equally in a circumferential direction of the digestion tank 1. The segments 31 in the same shape are used for the upper part 3b and the lower part 3c of the side wall 3, and the lower part 3c of the side wall 3 is accommodated in surface contact with pedestal concrete 5 and not rigidly connected to the pedestal concrete 5.SELECTED DRAWING: Figure 1

Description

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

  As an anaerobic fermentation digestion tank for sewage sludge, there is a stirrer inside an egg-shaped storage tank made of prestressed concrete (hereinafter referred to as a PC egg-shaped digestion tank), which is difficult to create dead water and has high agitation. Is excellent at.

  However, when constructing a PC egg-shaped digestion tank using conventional cast-in-place concrete, it is necessary to place concrete, attach heat insulating material, and perform anti-corrosion coating work, and each of these operations requires complicated work along the egg-shaped curved surface. I needed a scaffold. In addition, the PC egg-shaped digestion tank was difficult to construct because it was necessary to introduce prestress in the circumferential and meridian directions on a special shape.

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

Patent No. 4309835

  Since the PC egg digester has a special shape, it is necessary to devise its support structure. For example, in Patent Document 1, a columnar support member is attached to the tip of a lower beam segment that extends radially from the pile foundation, and the storage tank is supported by this support member, but there is room for improvement in terms of structural stability and construction cost. is there.

  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 or the like having a support mechanism capable of improving stability and cost.

  The present invention for solving the above-mentioned problems is a storage tank having a concrete side wall that narrows toward the top end and the bottom end, wherein the side wall is composed of a plurality of precast segments, and the lower part of the side wall is a pedestal concrete. A storage tank, which is housed in surface contact with a recess formed by the above, and is in a non-rigid state with the pedestal concrete.

  In the present invention, by constructing the side wall of the storage tank with the precast segment, the side wall can be easily constructed and the construction period can be shortened. In addition, as the storage tank support mechanism, the lower part of the side wall is accommodated in the pedestal concrete and is in surface contact, so the stability of the storage tank against sinking, sliding, and falling can be improved with a simple configuration. It is also possible to omit the rigid connection between the pedestal and the pedestal concrete. As described above, it is possible to provide a storage tank having a support mechanism capable of improving stability and cost.

The side wall is divided into upper and lower parts, and the precast segment is one in which the upper part and the lower part of the side wall are equally divided in the circumferential direction of the storage tank, and the same shaped precast segment is used for the upper part and the lower part of the side wall. Is desirable.
In this way, by using the same shaped segment on the upper part and the lower part of the side wall, the segment can be manufactured using one type of mold, and the mold cost required for manufacturing the segment can be reduced.

The lower portion of the side wall is preferably rigidly connected to the bottom concrete provided inside the side wall.
Thereby, the side wall of the storage tank is supported by the pin structure, and the stability is further enhanced.

Prestress is preferably introduced into the sidewall.
This allows the side wall of the storage tank to resist the internal pressure of the storage tank.

It is preferable that the storage tank is a sludge digestion tank, and that an intermediate portion in a height direction of the side wall is curvedly curved toward a top end and a bottom end.
This makes it possible to form a substantially oval-shaped digestion tank which has advantages such as a dead water area being difficult to form and high agitation.

A second invention is a method of constructing a storage tank having a concrete side wall that narrows toward the top end and the bottom end, and has a step of constructing the side wall and pedestal concrete, the side wall being formed by a plurality of precast segments. A construction method of a storage tank, characterized in that the lower part of the side wall is housed in surface contact with a recess formed by pedestal concrete and is in a non-rigid state with the pedestal concrete.
A second invention is a method for constructing a storage tank according to the first invention.

When constructing the side wall, while supporting the lower end of the precast segment with a support material capable of contracting in the radial direction of the storage tank, a plurality of the precast segments are arranged side by side in the circumferential direction of the storage tank with a water blocking material interposed therebetween. After that, it is desirable to temporarily tighten the tension material in the circumferential direction of the storage tank provided in the precast segment.
By temporarily tightening the tension material in the circumferential direction, it is possible to make multiple segments in the circumferential direction self-supporting during construction and facilitate the construction.In this case, the displacement of each segment is absorbed by the contraction of the support material It is possible to prevent cracking and chipping.

When constructing the side wall, a plurality of the precast segments arranged side by side in the circumferential direction of the storage tank are supported from below by a ring-shaped support wall, and when constructing the pedestal concrete, the support wall is used as an embedded formwork. It is desirable to place concrete inside.
By using a ring-shaped support wall to support the segments and constructing a pedestal concrete by placing concrete using the support wall as an embedded formwork, the pedestal concrete and the like can be easily constructed and the construction period can be shortened.

  According to the present invention, it is possible to provide a storage tank or the like having a support mechanism capable of improving stability and cost.

The figure which shows the digestion tank 1. The figure which shows the side wall 3. The figure shown about the segment 31. The figure which shows the construction method of the digestion tank 1. The figure which shows the construction method of the digestion tank 1. The figure which shows the construction method of the digestion tank 1. The figure which shows the construction method of the digestion tank 1. The figure which shows the digestion tank 1 '. 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 temporary tightening of the circumferential PC steel material 33, and main tension. 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. The figure which shows the digestion tank 1b '.

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

[First Embodiment]
(1. Digestion tank 1)
FIG. 1 is a view showing a digestion tank 1 according to the first embodiment of the present invention, and is a vertical cross section of the digestion tank 1. 2 is a perspective view showing the side wall 3 in half.

  The digestion tank 1 is a storage tank provided in a sewage treatment plant or the like, and stores sewage therein. In the digestion tank 1, sewage sludge is processed by anaerobic digestion. Inside the digestion tank 1, a stirrer (not shown) is provided in order to efficiently process sludge.

  As shown in FIG. 1, the digestion tank 1 is a PC egg-shaped digestion tank having a substantially oval shape as a whole, and includes a side wall 3, a pedestal concrete 5, a bottom concrete 6, a lid 7, and the like.

  The side wall 3 is a substantially oval member made of concrete that narrows toward the top end and the bottom end. More specifically, the intermediate portion 3a of the side wall 3 in the height direction bulges outward in a spherical shape, and the upper and lower portions of the intermediate portion 3a are truncated cone-shaped toward the top end and the bottom end. The horizontal cross section of the side wall 3 has a substantially circular shape.

  When the vertical cross-section of the side wall 3 is viewed, the intermediate portion 3a in the height direction of the side wall 3 bulges outward in an arc shape with a predetermined radius of curvature R and a central angle α, and narrows in a curved shape toward the top end and the bottom end. The upper part and the lower part of the intermediate portion 3a are narrowed toward the top end and the bottom end, respectively, in a straight line smoothly continuous with the above arc. In the present embodiment, the central angle α is 90 ° and the inclination angle β of the side wall 3 above and below the intermediate portion 3a is 45 ° with respect to the horizontal direction, but the present invention is not limited to this.

  The side wall 3 is vertically divided at a position where the distance from the central axis O of the digestion tank 1 is maximum, that is, at the center of the side wall 3 in the height direction. As shown in FIG. 2, the upper part 3 b and the lower part 3 c of the side wall 3 are formed by arranging a plurality of precast segments 31 in the circumferential direction of the digestion tank 1.

  The pedestal concrete 5 is provided around the lower portion 3c of the side wall 3 and is formed to have a mortar-shaped recess for accommodating the lower portion 3c of the side wall 3. The pedestal concrete 5 has a shape in which the inner peripheral surface of the concave portion is along the outer peripheral surface of the segment 31 of the lower portion 3 c of the side wall 3, and supports the side wall 3 by making surface contact with the outer peripheral surface.

  In the present embodiment, the segment 31 of the lower portion 3c of the side wall 3 is not rigidly connected (fixed) to the pedestal concrete 5 by a connecting material or the like, and the lower portion 3c of the side wall 3 only comes into surface contact with the pedestal concrete 5. It becomes a non-rigid state. That is, the shearing force and the moment are not substantially transmitted between the lower portion 3c of the side wall 3 and the pedestal concrete 5. Here, "substantially" means excluding the transmission of minute force through friction or adhesion of concrete. In the example of FIG. 1, the upper end of the pedestal concrete 5 is located above the lower end of the intermediate portion 3a of the side wall 3 (the position where the vertical cross section switches from a curved shape to a straight shape).

  The bottom concrete 6 constitutes the bottom surface of the internal space of the digestion tank 1. The bottom concrete 6 is arranged at the bottom end of the side wall 3 inside the segment 31 of the lower portion 3c of the side wall 3. The outer peripheral surface of the bottom concrete 6 is in contact with the inner peripheral surface of the segment 31 of the lower portion 3c of the side wall 3, and the bottom concrete 6 and the segment 31 are connected by the connecting member 15 and are rigidly connected. Thereby, the side wall 3 is supported by the pin structure.

  The lid 7 is provided at the top end of the side wall 3 and closes the opening at the top end. A stirrer (not shown) is attached to the lid 7.

  FIG. 3A is a view of the upper portion 3b of the side wall 3 as viewed from above. As shown in FIG. 3 (a), the segment 31 of the upper part 3 b of the side wall 3 divides the upper part 3 b of the side wall 3 into equal parts in the circumferential direction of the digestion tank 1 with a radial vertical plane passing through the central axis O of the digestion tank 1. It has a shape.

  3B is a view of the segment 31 of the upper portion 3b of the side wall 3 as viewed along the vertical plane, and FIG. 3C is an elevation view of the segment 31.

  As shown in FIG. 3B, the segment 31 of the upper portion 3b of the side wall 3 has a main body 311, a bent portion 312 provided at the lower end of the main body 311, and a bent portion 313 provided at the upper end of the main body 311. . The bent portion 312 is bent to the outside of the main body 311, and the bent portion 313 is bent to the upper side of the main body 311. As shown in FIG. 3 (c), the segment 31 has an elongated shape having a vertical length larger than the left and right width (length in the circumferential direction of the digestion tank 1), and the width of the main body 311 becomes narrower toward the upper end. .

  In addition, the segment 31 of the lower portion 3c of the side wall 3 has a shape obtained by equally dividing the lower portion 3c of the side wall 3 in the circumferential direction of the digestion tank 1 by a radial vertical plane passing through the central axis O of the digestion tank 1. The same shape as the segment 31 shown in FIGS. 3 (b) and 3 (c), which is turned upside down.

  A precast concrete member manufactured in advance is used for the segment 31. In addition, a sheath pipe (not shown) for passing a PC steel material in the circumferential direction of the side wall 3 (hereinafter referred to as a circumferential PC steel material) and a PC steel material in a meridional direction of the side wall 3 (hereinafter referred to as a meridional PC steel material) in the segment 31. ) Is buried. When constructing the digestion tank 1, the inner surface of the segment 31 is coated in advance with anticorrosion, and the heat insulating material is attached to the outer surface of the segment 31.

(2. Construction method of digestion tank 1)
Next, the construction method of the digestion tank 1 will be described with reference to FIGS. 4 to 7.

  When constructing the digestion tank 1, first, as shown in FIG. 4 (a), the foundation piles 9 and the excavation portion 11 of the ground are excavated. Then, as shown in FIG. 4B, the leveling concrete 13 is placed on the bottom surface of the excavation section 11, and the concrete is placed on the leveling concrete 13 to construct the bottom concrete 6.

  Thereafter, as shown in FIG. 4C, the segment 31 is installed around the bottom concrete 6 to assemble the lower portion 3c of the side wall 3. The segment 31 is supported by the support member 17 installed between the segment 31 and the wall surface of the excavation portion 11. In addition, the bent portion 313 of the segment 31 is rigidly connected to the side surface of the bottom concrete 6 by the connecting material 15 using a screw bar or the like.

  Then, a circumferential PC steel material and a meridional PC steel material (not shown) are inserted into the sheath tube of the segment 31, and the pre-stress in the circumferential and meridional directions is introduced into the lower portion 3c of the side wall 3 due to the tension.

  After that, as shown in FIG. 5A, concrete is poured on the leveled concrete 13 to construct the lower stage of the pedestal concrete 5. When the pedestal concrete 5 has hardened to a state where it can support the segment 31 of the lower portion 3c of the side wall 3, the support material 17 is removed.

  After removing the support material 17, concrete is poured as shown in FIG. 5B to construct the upper stage of the pedestal concrete 5. Then, the excavated portion 11 around the pedestal concrete 5 is backfilled with backfill soil 19 as shown in FIG. 6, and the center tower 21 is installed on the bottom concrete 6.

  Next, as shown in FIG. 7, the segment 31 of the upper portion 3b of the side wall 3 is installed on the segment 31 of the lower portion 3c of the side wall 3 to assemble the upper portion 3b of the side wall 3. The segment 31 of the upper portion 3b and the segment 31 of the lower portion 3c are connected at the bent portion 312 by a bolt, a PC steel rod or the like (not shown).

  Then, a circumferential PC steel material and a meridional PC steel material (not shown) are inserted into the sheath tube of the segment 31 of the upper portion 3b of the side wall 3, and the tension causes the pre-stress in the circumferential direction and the meridian direction to be introduced into the upper portion 3b of the side wall 3. To do.

  When the segment 31 of the upper portion 3b of the side wall 3 is installed, the support member (not shown) extending from the center tower 21 is used to support the segment 31. For example, after a certain segment 31 is supported and arranged from the center tower 21, the segment 31 located diagonally with respect to the segment 31 with the center tower 21 interposed therebetween is arranged and supported from the center tower 21. By repeating this process and installing the segment 31, stability during construction can be secured.

  After the assembly of the upper portion 3b of the side wall 3 is completed, the center tower 21 is removed, the lid 7 is attached to the top end of the side wall 3 as shown in FIG. 1, and the remaining necessary members are attached to complete the digestion tank 1. To do.

  As described above, in the present embodiment, by constructing the side wall 3 of the digestion tank 1 with the precast segment 31, the scaffolding required in the construction of the conventional digestion tank using cast-in-place concrete is minimized when the side wall 3 is constructed. Therefore, it becomes possible to install a heat insulating material or perform anticorrosion coating in a factory or on the ground before installing the segment 31. Therefore, the construction of the side wall 3 is facilitated, which contributes to shortening the construction period and cost. In addition, even an inexperienced worker can easily perform construction and ensure quality.

  Further, as a supporting mechanism of the digestion tank 1, the lower portion 3c of the side wall 3 is housed in the pedestal concrete 5 and is in surface contact with the pedestal concrete 5, so that the stability of the digestion tank 1 against sinking, sliding, and falling is simplified. It is possible to improve the structure, and it is not necessary to resist shear or moment between the segment 31 of the lower portion 3c of the side wall 3 and the pedestal concrete 5, and it becomes possible to omit these rigid connections by a connecting material or the like. . Therefore, it is possible to provide the digestion tank 1 having a support mechanism capable of improving stability and cost.

  Further, the lower portion 3c of the side wall 3 is rigidly connected to the bottom concrete 6 provided inside the side wall 3, and the side wall 3 is supported by the pin structure, so that the stability can be further enhanced.

  Further, since the segments 31 having the same shape can be used for the upper portion 3b and the lower portion 3c of the side wall 3, the segment 31 can be manufactured using one type of mold, and the mold cost required for manufacturing the segment 31 can be reduced.

  Further, in the present embodiment, the pre-stress in the circumferential direction and the meridian direction is introduced into the side wall 3 by the segment 31 to make the side wall 3 of the digestion tank 1 resist the internal pressure such as the liquid pressure of the digestion tank 1 and the digestion tank 1 It is possible to suitably prevent liquid leakage from the.

  In addition, the digestion tank 1 of the present embodiment has a substantially oval shape in which the intermediate portion 3a of the side wall 3 is curvilinearly narrowed toward the top end and the bottom end, which makes it difficult to form a dead water area and has high agitation property, and scum etc. can be removed. It has advantages such as being easy.

  However, the present invention is not limited to this. For example, in the present embodiment, the prestress is introduced after the installation of the segment 31, but the prestress may be introduced into the segment 31 at the manufacturing stage before the installation of the segment 31.

  Further, in the present embodiment, the segment 31 having the same shape is used for the upper portion 3b and the lower portion 3c of the side wall 3, but the shape may be slightly different, and the same type of mold is used for portions other than the different shape. Can be manufactured. For example, the segment 31 'of the lower portion 3c of the side wall 3'of the digestion tank 1'shown in FIG. 8 is different from the segment 31 of the upper portion 3b in that the bent portion 313 is omitted, and the lower end of the main body 311 of the segment 31'. Is connected to the bottom concrete 6 by the connecting member 15.

  Moreover, although the example of the digestion tank 1 is described as the storage tank in the present embodiment, the present embodiment is not limited to the digestion tank 1 and can be applied to various storage tanks. The side wall of the storage tank may have a shape that narrows toward the top end and the bottom end, and may have a spherical shape, for example.

  Hereinafter, another example of the present invention will be described as second and third embodiments. The second and third embodiments will mainly describe differences from the above-described embodiments, and description of the same points as the above-described embodiments will be omitted. Further, the configurations described in the respective embodiments, including the first embodiment, can be used in combination as necessary.

[Second Embodiment]
(1. Digestion tank 1a)
FIG. 9: is a figure which shows the digestion tank 1a which concerns on the 2nd Embodiment of this invention, and looked at the vertical cross section of the digestion tank 1a. The first embodiment of the digestion tank 1a is that the bottom concrete 6a has a floor slab 61 having a convex portion near the center of the plane and a padding portion 62 provided between the convex portion and the segment 31. Mainly different from the digestive tank 1 in the form.

(2. Construction method of digestion tank 1a)
The construction method of the digestion tank 1a will be described with reference to FIGS.

  When constructing the digestion tank 1a, first, similarly to the above, as shown in FIG. 10 (a), the foundation piles 9 are laid and the excavated portion 11 of the ground is excavated, and the bottom surface of the excavated portion 11 is leveled with concrete 13 To place. Then, by placing concrete on the leveling concrete 13, the floor slab 61 of the bottom concrete 6a is constructed.

  Thereafter, as shown in FIG. 10B, the jack 23 (support material) is arranged around the convex portion of the floor slab 61, and the support wall 24 of the segment 31 is erected on the outer peripheral portion of the floor slab 61. Then, the segment 31 is installed while being supported from below by the support wall 24, and the lower portion 3c of the side wall 3 is assembled. As shown in FIG. 12A, a water blocking material 32 is provided in the gap between the segments 31 adjacent to each other in the circumferential direction. As the water blocking material, for example, a water-expandable water blocking rubber is attached to the segment 31 in advance and used.

  The jack 23 is arranged in the radial direction of the digestion tank 1a, and can be expanded and contracted in the radial direction. One end of the jack 23 contacts the side surface of the convex portion of the floor slab 61, and the other end contacts the bent portion 313 at the lower end of the segment 31. By this jack 23, the lower end of the segment 31 is supported in the radial direction of the digestion tank 1a.

  The support wall 24 is formed by providing a support portion 242 made of steel or the like on the upper end of a main body 241 made of concrete, and is constructed in a ring shape along the circumferential direction of the digestion tank 1a.

  After the segment 31 of the lower portion 3c of the side wall 3 is installed in this way, the circumferential PC steel material (tensile material) is inserted into the sheath tube of the segment 31, and the temporary PC steel material 33 is temporarily attached as shown in FIG. 12 (b). The gap between the segments 31 adjacent to each other in the circumferential direction is closed by tightening (initial tension). As a result, the water blocking material 32 is crushed and comes into close contact with the segments 31, while the respective segments 31 of the lower portion 3c of the side wall 3 can be made to stand by themselves.

  When the circumferential PC steel material 33 is temporarily tightened, each segment 31 of the lower portion 3c of the side wall 3 is slightly displaced inward, but the jack 23 contracts according to the displacement without restraining the displacement, and the displacement of the segment 31 Since it is possible to absorb the cracks, the segment 31 can be prevented from cracking and chipping, and the initial tensioning work can be stably performed.

  When the gap between the segments 31 adjacent to each other in the circumferential direction becomes about 1 cm, grout 34 (curing material) is filled in the gap as shown in FIG. 12C, and after the grout 34 is cured, the jack 23 is removed. The main tension of the circumferential PC steel material 33 is performed, and circumferential prestress is introduced into the lower portion 3c of the side wall 3. After the introduction of the prestress, concrete is placed in the gap between the convex portion of the floor slab 61 and the segment 31 to form the padding portion 62 as shown in FIG. 10 (c).

  Further, by placing concrete on the inside of the support wall 24 as an embedded formwork, a pedestal concrete 5 composed of the concrete and the support wall 24 is constructed.

  Subsequently, the excavated portion 11 around the pedestal concrete 5 is backfilled with the backfill soil 19 as shown in FIG. 11, and the center tower 21 is installed on the convex portion of the floor slab 61 of the bottom concrete 6a.

  Thereafter, the segment 31 of the upper portion 3b of the side wall 3 is installed by the same procedure as in the first embodiment, and pre-stress in the circumferential direction and the meridian direction is introduced into the upper portion 3b of the side wall 3. Then, the center tower 21 is removed and the lid 7 and the like are attached as shown in FIG. 9 to complete the digestion tank 1a.

  Also in the present embodiment described above, the support mechanism of the digestion tank 1a is the pedestal concrete 5, and the lower portion 3c of the side wall 3 and the pedestal concrete 5 are made non-rigid, which is similar to the first embodiment. The effect is obtained. In addition, by temporarily tightening the circumferential PC steel material 33 provided on the segment 31 of the lower portion 3c of the side wall 3, it is possible to make the plural segments 31 in the circumferential direction self-supporting during the construction and facilitate the construction. By absorbing the displacement of the segment 31 by the contraction of the jack 23, it is possible to prevent the segment 31 from cracking and chipping.

  Further, in the present embodiment, a ring-shaped support wall 24 erected on the bottom concrete 6a is used to support the segment 31 of the lower portion 3c of the side wall 3, and concrete is cast by using the support wall 24 as an embedded formwork to mount the pedestal concrete 5 To build. This facilitates the construction of the pedestal concrete 5 and the like as compared with the case where the support member 17 is erected from the wall surface of the excavation portion 11 as in the first embodiment, and saves the labor such as the removal of the support wall 24 and the construction period. Can be shortened. However, it is possible to support the segment 31 using the support material 17 of the first embodiment.

  In this embodiment, unlike the first embodiment, the segment 31 of the lower portion 3c of the side wall 3 and the bottom concrete 6a are not rigidly connected by the connecting material 15 or the like, but can be rigidly connected by the connecting material 15. It is also possible to perform pin joining using a steel material such as a reinforcing bar. It is also possible to perform similar pin joining between the segment 31 of the lower portion 3c of the side wall 3 and the pedestal concrete 5. This is the same in the first embodiment, and the pin joint that does not transmit the bending moment is included in the range of the "non-rigid connection state".

  Further, as shown in FIG. 12 and the like, in the configuration in which the circumferential PC steel material 33 is temporarily tightened and then the main tension is performed, and the jack 23 is contracted during the temporary tightening, the side wall 3 is divided into an upper portion 3b and a lower portion 3c as in the present embodiment. The present invention is not limited to the case where the lower portion 3c of 3 and the pedestal concrete 5 are in surface contact and in a non-rigid state, and can be applied to all of the plurality of segments arranged in the circumferential direction to form the side wall.

[Third Embodiment]
(1. Digestion tank 1b)
FIG. 13: is a figure which shows the digestion tank 1b which concerns on the 3rd Embodiment of this invention, and looked at the vertical cross section of the digestion tank 1b. The digestion tank 1b is mainly different from the first and second embodiments in that the bottom concrete 6b is formed in a floor slab shape and has a mortar-shaped recess made of a bowl-shaped steel shell 63 near the center of the plane. The wall surface of the recess is formed so as to be continuous with the slope of the lower portion 3c of the side wall 3 ″.

  In addition, in the present embodiment, a step-like protrusion 314 is provided in the height direction between the segment 31a of the upper portion 3b and the segment 31b of the lower portion 3c of the side wall 3 ″, and the segment 31b of the lower portion 3c has the above-mentioned protrusion. The bent portion 313 is omitted and the lower end is formed thicker.

(2. Construction method of digestion tank 1b)
The construction method of the digestion tank 1b will be described with reference to FIGS.

  When constructing the digestion tank 1b, first, similarly to the above, as shown in FIG. 14 (a), the foundation pile 9 is placed and the excavation part 11 of the ground is excavated, and the bottom surface of the excavation part 11 is leveled with concrete 13 To place. Then, the bottom concrete 6b is constructed by placing concrete on the leveling concrete 13. At this time, by using the steel shell 63 as an embedded mold, a recess is formed near the center of the plane of the bottom concrete 6b.

  After that, as shown in FIG. 14B, the ring-shaped support wall 24a is constructed from concrete on the outer peripheral portion of the bottom concrete 6b. Further, the pedestal 25 is constructed in the steel shell 63, and the jack 23 is arranged on the pedestal 25 at the upper surface level of the bottom concrete 6b. Then, the segment 31b is installed while being supported by the support wall 24, and the lower portion 3c of the side wall 3 ″ is assembled. As in the second embodiment, a waterproof material is provided in the gap between the segments 31b adjacent in the circumferential direction. The segment 31b is supported by the support wall 24a on the horizontal surface of the protrusion 314.

  Similarly to the above, the jack 23 can extend and contract in the radial direction of the digestion tank 1b, and one end thereof abuts on the lower end of the segment 31b. The other end of the jack 23 comes into contact with the lower end of the segment 31b at a position facing the segment 31b with the jack 23 interposed therebetween.

  After the installation of the segment 31b of the lower portion 3c of the side wall 3 "in this way, the circumferential PC steel material is inserted into the sheath tube of the segment 31b, and similarly to the second embodiment, the temporary fastening is performed to adjoin in the circumferential direction. The gap between the segments 31b is narrowed in. Similar to the second embodiment, the jack 23 contracts in accordance with the displacement of each segment 31b during temporary fastening.

  Similarly to the second embodiment, when the gap between the circumferential segments 31b becomes about 1 cm, the gap is filled with grout, and after the grout is hardened, the jack 23 is removed to perform the main tension of the circumferential PC steel material. A circumferential prestress is introduced into the lower portion 3c of the side wall 3 ″. Further, a waterproofing treatment is performed by providing a waterproofing material at the boundary between the segment 31b and the steel shell 63.

  By removing the pedestal 25 and placing concrete on the inside of the support wall 24a using the support wall 24a as an embedded form, a pedestal concrete 5 composed of the concrete and the support wall 24a is formed, as shown in FIG. 14 (c). To be done.

  The excavated portion 11 around the pedestal concrete 5 is backfilled with backfill soil 19 as shown in FIG. 15, and the center tower 21 is installed on the bottom surface of the steel shell 63 of the bottom concrete 6b.

  Thereafter, the segment 31a of the upper portion 3b of the side wall 3 ″ is installed and the pre-stress in the circumferential direction and the meridian direction is introduced to the upper portion 3b of the side wall 3 ″ by the same procedure as in the first embodiment. After that, the center tower 21 is removed and the lid 7 and the like are attached as shown in FIG. 13 to complete the digestion tank 1b.

  Also in the present embodiment described above, the support mechanism of the digestion tank 1b is the pedestal concrete 5, and the lower portion 3c of the side wall 3 ″ and the pedestal concrete 5 are in a non-rigid state, and thus the first embodiment is different from the first embodiment. The same effect can be obtained. Further, by using the jack 23 and the support wall 24a for installing the segment 31b of the lower portion 3c of the side wall 3 ″, the same effect as that of the second embodiment is obtained.

  As for the upper part 3b and the lower part 3c of the side wall 3 ″, the segments 31a and 31b can be integrated into one on the site by further dividing these into upper and lower parts, and the segment will become large in a large-sized digestion tank and transported. This is effective when there are surface problems.

  For example, in the example of the digestion tank 1b ′ of FIG. 16, the upper portion 3b of the side wall 3 ″ is constructed by small segments 311a and 311b having a shape obtained by vertically dividing the segment 31a (see FIG. 13) into two parts. After the small segments 311a and 311b are integrated on site to form a segment 31a ', this segment 31a' is installed.

  Similarly, the lower portion 3c of the side wall 3 ″ is also constructed by small segments 311b and 311c having a shape obtained by vertically dividing the segment 31b (see FIG. 13) into two parts. At the time of construction, the upper and lower small segments 311b and 311c are integrated on site. After segmentation into segment 31b ', this segment 31b' is installed.

  The lower small segment 311b in the upper portion 3b of the side wall 3 "and the upper small segment 311b in the lower portion 3c of the side wall 3" are in the range corresponding to the intermediate portion 3a in the height direction of the side wall 3 "and have the same shape. It is upside down.

  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 is obvious 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 naturally, these also belong to the technical scope of the present invention. Understood.

1, 1 ', 1a, 1b, 1b': Digestion tank 3, 3 ', 3 ": Side wall 3a: Intermediate part 3b: Upper part 3c: Lower part 5: Pedestal concrete 6, 6a, 6b: Bottom concrete 7: Lid 31 , 31 ', 31a, 31b, 31a', 31b ': Precast segment 32: Water stop material 33: Circumferential PC steel material 34; Grout

Claims (8)

A storage tank having a concrete side wall that narrows toward the top end and the bottom end,
The sidewall is composed of a plurality of precast segments,
A storage tank, wherein a lower portion of the side wall is housed in surface contact with a recess formed by pedestal concrete and is in a non-rigid state with the pedestal concrete. The side wall is divided into upper and lower parts,
The precast segment is one in which the upper portion and the lower portion of the side wall are equally divided in the circumferential direction of the storage tank,
The storage tank according to claim 1, wherein precast segments having the same shape are used for the upper portion and the lower portion of the side wall.   The storage tank according to claim 1 or 2, wherein a lower portion of the side wall is rigidly connected to a bottom concrete provided inside the side wall.   Pre-stress is introduced into the said side wall, The storage tank in any one of Claim 1 to 3 characterized by the above-mentioned.   The said storage tank is a sludge digestion tank, and the intermediate part of the height direction of the said side wall is constricted in the shape of a curve toward the top end and the bottom end, It is characterized by the above-mentioned. Storage tank. A method of constructing a storage tank having a concrete side wall that narrows toward the top and bottom edges,
Having a step of building the side wall and pedestal concrete,
The sidewall is composed of a plurality of precast segments,
A method of constructing a storage tank, characterized in that the lower part of the side wall is housed in surface contact with a recess formed by pedestal concrete and is in a non-rigid state with the pedestal concrete.   When constructing the side wall, while supporting the lower end of the precast segment with a support material capable of contracting in the radial direction of the storage tank, a plurality of the precast segments are arranged side by side in the circumferential direction of the storage tank with a water blocking material interposed therebetween. The method for constructing a storage tank according to claim 6, further comprising temporarily tightening a tension material in a circumferential direction of the storage tank provided in the precast segment. When constructing the side wall, a plurality of the precast segments arranged side by side in the circumferential direction of the storage tank are supported from below by a ring-shaped support wall,
The method for constructing a storage tank according to claim 6 or 7, wherein when the pedestal concrete is constructed, the support wall is used as an embedded formwork and concrete is placed inside thereof.

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