The construction of anaerobic tank mainly includes earthwork excavation and filling, anaerobic tank, water inlet and outlet pipes, etc. According to the principle of underground first and then on the ground, the construction will be arranged step by step from bottom to top. During the construction, the foundation of anaerobic tank shall be started first, and then the construction of anaerobic tank structure and underground pipeline shall be started.

The anaerobic tank is an underground project; According to the design drawings, the reinforced concrete construction is divided into two stages (once for the bottom plate and part of the pool wall and once for the pool wall), and the cover plate is prefabricated.

2. Foundation excavation and support

(1) Foundation excavation

In the area of anaerobic pool, clear the cultivated soil layer on the surface, excavate with excavator, excavate with PC-200 excavator, transport the vehicle to the backfill section of the site, slope according to the specifications, leave a protective layer of 20cm on the basement, and manually excavate to the design elevation. The excavation shall avoid disturbing the excavation face. After digging to the design elevation. Backfill compacted gravel and build C 15 concrete cushion.

2) Supporting structure scheme

Because the resettlement house in Hongqianshe is a shallow independent foundation, the designed anaerobic pool foundation is 4.0 meters deeper than the building foundation, and the distance from the building foundation is only 1.8 meters, which is less than a safe distance. Therefore, support should be adopted in the foundation pit excavation of anaerobic tank.

The excavation depth of the foundation pit support project is about 5.6 meters, and Larsen steel sheet pile is used as the vertical retaining wall. The width of steel sheet pile is 200MM, the designed pile length is 5M, the buried part is 1.0M, the supporting system is * * * 1 floor, and the elevation is-1.50. (Relative elevation of 0.00 is equivalent to absolute elevation. The support is made of steel structure, using hot-rolled seamless steel pipe (d=299, t= 10), and the peripheral beam is made of H-beam HW300×300× 10×5. The bracket is connected by electric welding, and the joint is fully welded.

3. Reinforcement engineering

Reinforcement is the skeleton of building engineering, which has a decisive influence on the internal quality of building engineering. It is necessary to strictly implement the system of acceptance of steel bars entering the site, and conduct raw material tests and welding tests on steel bars entering the site according to regulations to ensure the engineering quality. The specific structure is as follows:

(1) steel bar

The reinforcement of steel bars shall be carried out according to the specifications and length of drawings and the requirements of relevant codes. In order to facilitate processing and flow construction, the following requirements shall be followed.

Prepare in sections according to the drawings, pile them in categories and indicate the model. Specific preparation work, the preparation sequence should be roughly the same as the construction sequence. At the same time, the position of the upper and lower steel bar joints of the beam at the construction joint should meet the specification requirements.

(2) steel processing

Steel processing adopts centralized method, all in the steel processing plant on the construction site, and according to the specifications and length of steel bars on the design drawings, it is processed in the processing plant. According to the needs of the construction process, it will be transported to the operation surface in sections for binding, and the matters needing attention are as follows:

A, raw materials must have the factory certificate and raw material quality guarantee when they enter the site, and they shall be sampled and inspected according to the specification requirements, and can be processed only after they meet the requirements.

B, steel cold drawing, using the method of controlling cold drawing extension (limited to grade I steel bar), but the value of cold drawing rate must be determined by the laboratory. After the flash butt welding of secondary steel is completed, the steel bar joint can also be straightened by cold drawing method, but the cold drawing rate must be controlled within 65438 0%.

C, steel welding, the scene adopts flash butt welding or arc welding, the scene adopts manual arc welding.

D. The allowable percentage of the joint area of tensile reinforcement in the joint section is 25% when binding and 50% for others.

E, the minimum anchorage length and lap length of longitudinal tensile reinforcement shall be constructed as specified in the drawings.

F, reinforced after molding, hook and bending deviation conform to the requirements of drawings and specifications.

(3) Binding of reinforcement

A, steel vertical connection adopts electric welding technology, attention should be paid to stagger the joint position according to the figure.

Steel joints can be lapped. Unless otherwise specified in the drawing, the tensile reinforcement of grade I steel is 30d, and that of grade II steel is 42 d. Lap joints of steel bars should be staggered, and the number of steel bar joints with the same section should not be greater than 25% of the total.

B, steel joint (hook lap) should be staggered on the surrounding vertical steel bar, stirrup corner and the intersection of vertical steel bar should be bound firmly, at an angle of 45 with the template, and the binding steel bars of binding steel bar should be zigzag with each other.

C, the reinforced concrete slab of anaerobic tank, when the wall of the tank has embedded pipe fittings, in addition to the reinforcement according to the design, the reinforcement should be bypassed as far as possible and lengthened accordingly, and the end of the truncated reinforcement should be left with overlapping length or welded on the additional annular reinforcement.

When the reinforcement meets the cavity, it should be bypassed as far as possible and should not be truncated. If it must be cut off, the reinforcing ring reinforcement should be set in the cavity and welded firmly. The reinforcement of the pool wall and bottom plate at the sump should go deep into the sump for 35d, and shall not be cut off.

D, before the column roof (above) pouring, a closed hoop shall be set, which shall be firmly bound with the main reinforcement of the column to prevent the main reinforcement from deviating.

E, plate steel binding, pay attention to the upper reinforcement position, take necessary protective measures, in case of concrete construction is crushed.

F, steel surface must be carefully derusted to prevent oil pollution, so as to ensure good bonding between concrete and steel.

G, technical review and hidden acceptance of the tied steel bars, and concrete can be poured only after it meets the requirements.

H. covered electrode: E43, used for welding grade I steel.

First, at the intersection of the secondary beam and the main beam, additional stirrups and additional hanging bars are set at the main beam. The additional stirrups are 6φ8 and the additional suspenders are 2 φ 16.

J. C30 fine stone concrete is used for the protective layer of reinforcement, and fine iron wire is embedded in the concrete block. When binding reinforcement, the cushion block is scattered between the reinforcement and the formwork, and is firmly bound with the reinforcement to ensure the accurate thickness of the protective layer of the reinforcement.

K. Main reinforced concrete protective layer: 35mm for column, 25mm for bottom plate, beam and pool wall, and 20mm for the rest.

4. Formwork project

The height direction of the anaerobic tank is divided into two stages: pouring and formwork erection (the first time the upper part of the inclined bracket connected with the tank wall is 550mm, and the second time it is poured from the construction joint to the top of the tank). The position of the construction joint of the pool wall is set at 550mm above the inclined bracket connected with the bottom plate and the pool wall, and the hair should be cut before pouring.

(1). Construction preparation

The anaerobic tank of this project is of reinforced concrete structure. On the premise of ensuring quality, according to the characteristics of this project and the turnover materials of the enterprise, the following template scheme is adopted.

Formwork: wall: 18mm thick wood plywood, 50× 100 square meters, reinforced with steel bars and φ 16 bolts.

Beam 18mm thick wood plywood 50× 100 square wood keel.

Support system: the support system is made of Chinese fir with a diameter of > > 10cm, and the horizontal tie rod of steel pipe is @ 1500mm. The beam bottom is provided with the horizontal tie rod and Chinese fir support system. Horizontal tie rod @1500mm.

(2). Template making

The template model is processed and made in the workshop according to the supporting drawings. After the template is made, the location, model, size and quantity of the template shall be indicated. After passing the inspection, brush the release agent and pile it up in the specified order.

① Material requirements

Materials such as formwork keel and formwork support shall meet relevant acceptance standards, and model materials with better materials shall be selected.

(2) Template production requirements:

A, the surface mold is smooth, flat-fell seam is tight, and the rigidity is good.

B, purlin and support have sufficient rigidity and strength.

C, special parts of the template and component shape size position accurately.

D, simple structure, convenient disassembly and assembly, and convenient steel binding and installation.

(3) corners, special parts with shapes, and beam and column templates are transported to the site for installation by the processing plant, and the parts with sporadic insufficient size are assembled with bulk wooden patterns.

(3) Template installation

(1) Installation of formwork and wall formwork.

Release the column and the wall → properly bind the column rebar and cushion block → pull and fix the side wall panel of the wall formwork with φ 10 bolts, weld the water stop ring in the middle of the bolts, set conical cups near the formwork on both sides, and leave a 2~3cm conical groove on the concrete wall after formwork removal to facilitate the handling of the bolt head.

(2) Installation and construction sequence of beam and formwork

Pay-off → erection of formwork support → installation of beam bottom formwork → installation of plate bottom formwork → binding of beam and pad → installation of beam-column joint formwork → correction of beam side formwork → correction of plate bottom formwork.

③ Pay-off

Before formwork installation, mark the elevation, centerline and formwork installation of the pop-up beam on the wall or column according to the measurement, and determine the position line of the formwork column according to the design requirements of the whole house.

(4) Erection of formwork support

The formwork support is supported by pine, and the connection surface between vertical supports is integrated with horizontal and diagonal supports to ensure the stability and reliability of the support system.

When the ground is erected and the formwork is supported on the ground, the foundation soil should be leveled and compacted first, and cushion blocks should be placed to prevent the formwork from sinking and displacement after pouring concrete.

⑤ Template removal

The structural specimens shall be cured under the same conditions, and the formwork can be removed only after reaching the formwork removal strength specified in the specification. Cantilever member supporting formwork can not be dismantled until it reaches the design strength 100%. The foreman shall master the time of formwork removal for beam and column side formwork, and the technical director shall notify the bottom formwork of digital slab according to the strength pressure test report.

6. The quality shall meet the national quality acceptance standards.