JPH0790875B2 - Body structure of PC egg digester - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a structure of a PC egg-type digester tank used for an anaerobic digestion method which is one of sludge treatment facilities.

"Prior art" Conventionally, the structure of the body of this type of PC egg digester is
As shown in the figure, it is known that the entire skeleton uses a prestressed concrete structure.

FIG. 5 shows a conventional prestressed concrete (hereinafter,
FIG. 6 is a side sectional view of a PC egg-type digestion tank using a structure of a skeleton (hereinafter simply referred to as “PC”), FIG. 6 is a VI-VI sectional view of the pile foundation, and FIG. , FIG. 8 to FIG. 10 are explanatory views during construction near the foundation part. In these figures, reference numeral T is a PC egg-type digestion tank, and the digestion tank main body 3 is supported above the group pile foundation 1 built in the ground G via the ring foundation 2. There is.

The group pile foundation part 1 is constructed by driving foundation piles 1a, 1a, ... In the ground G in a ring shape at predetermined intervals in the circumferential direction and the radial direction. A ring base 2 having a predetermined thickness is built to maintain a predetermined strength, and a digestion tank body 3 having an egg-shaped wall 4 is supported on the ring base 2, and The ring foundation 2 is integrated in the ground G so as to project from the wall 4 in the horizontal direction, and a bottom plate portion 5 of the digestion tank body 3 having an inverted conical shape is formed below the ring foundation 2. ing.

Further, as shown in FIG. 7, the body structure of the digester tank body 3 has a PC structure as a whole, and the wall portion 4 is made of PC steel material arranged in the latitudinal direction (circumferential direction) and the meridian direction. Pre-stressed in advance, the tensile stress caused by hydraulic pressure can be canceled out, the digestion tank body can be enlarged without thickening the wall part 4, and it has excellent crack prevention, watertightness, airtightness and corrosion resistance. It has become a thing. In addition, the bottom slab 5 has a special inverted cone shape,
The PC steel material is helically arranged, and the PC steel material is circumferentially arranged on the outer peripheral portion of the ring base portion 2.

Then, in order to build the slab 5, the foundation pile 1 in the ground G
As shown in FIG. 6, multiple rows of a, 1a, ... Are driven annularly to form the group pile foundation 1, and then, as shown in FIG. 8, on the outer periphery of the group pile foundation 1. After the steel sheet pile 6 is installed for soil retention and water stoppage, the ground Gi on the inside of the piled pile foundation part 1 that has been placed is improved by using a deep mixing agitation method or the like, and then the inside 7 of the steel sheet pile 6 is used. Is subjected to primary excavation to a predetermined depth, and the ground improvement portion Gi is subjected to secondary excavation with a 1: 1 gradient so as to form the bottom plate 5 of the digestion tank body 3 (portion 8). When the secondary excavation is completed, concrete is sprayed on the surface to form a concrete slope 5a which will be the formwork of the bottom slab 5, and then the PC steel material 9a is formed on the concrete slope 5a as shown in FIG. , 9, ... Are arranged in a helical shape. Next, as shown in FIG. 10, a form 10 using a ring beam type steel garter is installed at a predetermined interval above the concrete slope 5a, and concrete is placed between them to form the bottom slab 5 To build. Next, after the ring foundation 2 integrated with the upper portion of the bottom slab 5 is built on the upper portion of the group pile foundation portion 1 to complete the foundation portion, a PC structure is formed on the upper end portion from the bottom portion by a predetermined method. The wall 4 of the body is built.

"Problems to be solved by the invention" However, in the structure of the conventional PC egg-type digester tank structure, the entire structure has a PC structure, and in particular, the structure of the bottom plate part in which the PC steel material is helically arranged. Requires the ground improvement of the part that will be the formwork when building the bottom slab, and this ground improvement part will be subjected to secondary excavation with a 1: 1 normal gradient in an inverted conical shape to match the shape of the bottom slab. Necessary, it is necessary to construct highly accurate shotcrete on the excavated surface for protection of slope and outer form, PC of bottom slab
There is a problem that a lot of complicated work that requires high accuracy, such as a helical arrangement of steel materials, causes an increase in construction cost and a delay in construction period.

The present invention has been made in view of the above-mentioned problems, and excavation of the ground with a 1: 1 normal gradient of an inverted cone conforming to the shape of the bottom slab, and highly accurate shotcrete construction on the slope. In addition, it is possible to reduce the construction cost and shorten the construction period by eliminating the need for complicated work requiring high precision, such as the helical installation work of PC steel, and to smoothly transmit the stress generated in the skeleton. The object is to provide a structure of a PC egg-type digester that can be formed.

"Means for Solving Problems" The present invention, in order to solve the above problems, the wall portion is formed in an egg shape, and the bottom portion of the wall portion is integrally formed with a foundation portion embedded in the ground. The structure of the PC egg-type digester tank is formed, the wall of the egg-shaped and prestressed concrete structure, the base part is a reinforced concrete structure,
The skeleton in the middle part has a prestressed reinforced concrete structure, and the entire bottom surface of the foundation part is horizontally formed, and the wall part is provided above the bottom surface.

[Operation] In the core structure of the present invention, the egg-shaped wall part using the PC structure and the core structure of the middle part of the foundation part using the reinforced concrete structure are prestressed reinforced concrete structures, so the wall of the PC structure The stress is smoothly transmitted between the base and the foundation of the reinforced concrete structure. Further, as described above, in the conventional case, the bottommost portion of the wall portion is projected downward from the bottom surface of the foundation portion.However, in the present invention, the bottommost portion of the wall portion is prevented from projecting from the bottom surface of the foundation portion to form a foundation. Since the entire bottom surface of the part is formed horizontally, the structure of the bottommost part of the wall part and the foundation part is simplified and the workability is improved as compared with the conventional case.

[Examples] FIGS. 1 to 4 show an example of the present invention. FIG. 1 is a side sectional view of a PC egg-type digester tank using the structure of the present invention, and FIG. II-II sectional view of the pile foundation portion, FIG. 3 is a layout view of the PC steel material of the structure of the present invention, and FIG. 4 is a bar arrangement diagram showing a partial sectional view of the wall part of the structure of the PC structure. In these figures, the same elements as those shown in FIGS. 5 to 10 are designated by the same reference numerals and the description thereof will be omitted.

In these drawings, reference numeral T is a PC egg-type digestion tank, a pile foundation 11 is laid in a cylindrical shape in the ground G (see FIG. 2), and a bottom surface 12a is horizontally formed on the upper portion thereof. Foundation part 1
A digestion tank main body 3 is built in which 2 and an egg-shaped wall portion 4 are integrated. In the digester tank body 3, the foundation 12 is a reinforced concrete (hereinafter simply referred to as "RC") structure, the wall 4 is a PC structure, and the skeleton 4a in the middle between the foundation 12 and the wall 4 is a prestressed reinforced concrete (hereinafter , Abbreviated as “PRC”).

And, the PC structure of the wall portion 4 is as shown in FIG.
Reinforcing bars 13, 13, ... are arranged near the surface inside the concrete, between which PC steel materials 14, 14, ... in the parallel direction and PC steel materials 15, 15, ... in the longitudinal direction are respectively sheathed. 16,16, ...
・ The PC steel material 14 in the latitudinal direction is responsible for the circumferential axial tensile force generated in the circumferential direction of the digestion tank body 3 due to the hydrostatic pressure of sludge when the water is full, and the PC steel material 14 in the longitude direction. The PC steel material 15 has a prestressing force so as to take charge of the constant axial force and bending moment. Further, the skeleton 4a in the middle portion has a PRC structure which is almost the same as the PC structure of the wall portion 4, and the P 4
Along with C steel materials 14 and 15, PC reinforcing steel bar 13 is made to have strength.
It is configured to reinforce 14,15.

Further, in the pile foundation portion 11, steel pipe sheet piles 11a, 11a, ... Having various joints in the ground G are continuously provided in a circular closed shape having an outer diameter substantially the same as the outer diameter of the foundation portion 12. It is built by being done. The digester tank body 3 having the egg-shaped wall 4 has a circular cross-section that extends vertically while the outer peripheral surface 4o forms a curved surface that changes while gently expanding in the ground G. The outer peripheral surface 12o of the portion 12 is formed, and the inner peripheral surface 4i is formed so as to be smoothly continuous with the wall surface of the bottom plate portion 12i formed inside the base portion 12 in an inverted conical shape. Is provided in a range above the bottom surface 12a of the base portion 12. That is, unlike the prior art, the bottommost portion of the wall portion 4 does not project downward from the foundation portion 4, and therefore the bottom surface 12a of the foundation portion 12 is entirely horizontal. The foundation 12 has a reinforced concrete structure (not shown), and the steel pipe sheet piles 11a, 11a, ...
It has a fixed structure.

Next, a method for constructing the PC egg-type digestion tank T will be briefly described.

First, steel pipe sheet piles 11a, 11a, which have various joints in the ground G,
... is driven into a circular closed shape having an outer diameter substantially the same as the outer diameter of the foundation portion 12 to build the pile foundation portion 11. Next, after excavating the inside of the pile foundation 11, the excavated surface is subjected to abandoned concrete, and then reinforcing bars are arranged in a predetermined shape on the excavated concrete. A form frame using a garter made of gas is placed, and then concrete is placed inside the form frame to complete the foundation part 12 of the digestion tank body 3. When the foundation 12 is completed, the egg-shaped wall 4 is formed by a predetermined method while forming a curved surface which is smoothly continuous with the wall surfaces 12i and 12o from the upper end thereof, and the PC steel material is arranged as shown in FIG. And build while introducing prestress.

Therefore, in the skeleton structure of the PC egg-type digester tank T of the present invention, when excavating the foundation part 12, it is possible to give the soil retaining and water-stopping functions by the pile foundation part 11 constructed in advance. Since it is not necessary to install another steel sheet pile only for the purpose, since the entire bottom surface 12a of the foundation portion 12 is horizontal and the bottom plate portion 12i is formed on the upper portion (that is, inside the foundation portion 12), It is not necessary to improve the ground in the part that will be the formwork when building it, and the ground G is excavated with a 1: 1 gradient to match the shape of the bottom slab 12i, and concrete is sprayed onto the slope. There is no need to do it, and no need for a helical installation work of PC steel material on the bottom slab 12i, and many work types are unnecessary, and complicated work that requires precision is reduced, reducing the construction cost, It is possible to shorten the construction period.

Further, since the pile foundation 11 is formed by integrally connecting the steel pipe sheet piles 11a, 11a, ... In a cylindrical shape, the pile foundation 11 has a large horizontal resistance force as a whole, and is often used like a group pile foundation. Is not necessary, and further, the wall portion 4 of the digestive tank main body 3 having an egg-shaped curved surface is gradually thickened to be connected to the thick-walled foundation portion 12, and the outer peripheral surface 4o and the inner peripheral surface 4i are the foundations. The outer peripheral surface 12o having a circular cross section of the portion 12 and the inner peripheral surface of the conical bottom plate portion 12i are continuously formed by forming a curved surface that changes smoothly, and the shape is such that stress concentration is unlikely to occur near the connection portion. At the same time, the foundation 12 has a large mass, and the digestion tank body 3
The center of gravity of the can be lowered and the stability can be improved.

Further, since the structure of the egg-shaped wall part 4 using the PC structure and the skeleton 4a in the middle part of the foundation part 12 using the RC structure is the PRC structure, the number of PC steel materials of the skeleton 4a in the middle part In addition, the stress can be smoothly transmitted between the wall 4 of the PC structure and the base 12 of the RC structure.

The range of the PRC structure body 4a in the intermediate portion between the wall portion 4 and the base portion 12 can be arbitrarily changed.

"Effects of the Invention" As described above, the present invention uses the PC structure for the egg-shaped wall, the RC structure for the foundation, and the PRC for the body in the middle.
With the structure, the entire bottom surface of the foundation is formed horizontally and an egg-shaped wall is provided above it, in other words, the bottom of the wall is prevented from protruding below the bottom of the foundation. Conventionally, when constructing this type of PC egg-type digestion tank, there was no choice but to carry out excavation of the ground with an inverted conical 1: 1 slope that matches the shape of the bottom plate, and to the slope It is possible to reduce the construction cost and shorten the construction period by eliminating the complicated work that requires high precision such as highly accurate shotcrete construction and PC steel material helical arrangement work. Communication can be done smoothly.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a side sectional view of a PC egg-type digestion tank using the structure of the present invention, and FIG. 2 is a pile foundation. II-II cross-sectional view, FIG. 3 is a layout view of PC steel material of the digester tank body of the present invention, FIG. 4 is a bar arrangement view with a partial cross-section of the wall of the PC structure, and FIGS.
Fig. 10 is for explaining the conventional technology, Fig. 5 is a side sectional view of a conventional PC egg-type digester tank using a conventional PC structure, and Fig. 6 is a VI of the group pile foundation. -VI cross-sectional view, FIG. 7 is a layout drawing of PC steel material of the digester tank body shown in FIG. 5, and FIGS. 8 to 10 are explanatory views during construction near the foundation part, and FIG.
Figure is a cross-sectional side view of the ground near the bottom slab under construction. Figure 9 is a plan view of PC steel material helically arranged in the bottom slab. Figure 10 is the bottom slab under construction in the excavated ground. FIG. G: ground, T: PC egg digester, 3 ... digester body,
4 ... wall, 4a ... intermediate body, 12 ... base, 12a
…… Bottom, 13 …… Reinforcing bar, 14,15 …… PC steel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-57-133884 (JP, A) JP-A-60-219370 (JP, A) JP-A-62-260692 (JP, A) Actual development Sho-60- 113903 (JP, U)

Claims (1)

[Claims] 1. A skeleton structure of a PC egg-type digestive tank, wherein the wall portion is formed in an egg shape and the bottom portion of the wall portion is integrally formed with a foundation portion embedded in the ground, wherein the egg The mold wall portion is a prestressed concrete structure, the foundation portion is a reinforced concrete structure, the intermediate body is a prestressed reinforced concrete structure, and the entire bottom surface of the foundation portion is formed horizontally to form the wall above the bottom surface. The structure of the PC egg-type digester tank is characterized by the provision of a section.