(1, foundation trench excavation

1, measure and release the foundation pit and groove edge, control the excavation elevation, carry out mechanical excavation and manual groove cleaning, and trim the slope according to 1: 0.50.

2. This project adopts the backhoe excavator pool excavation method. There are 6 drainage wells in the teaching building, administrative building, experimental building and library, and drainage ditches are set around the base tank, with a width of 50cm and a depth of 50cm.

3. Backhoe excavators are used for large-area excavation of the foundation trench in this project, and manual excavation is used for local and designed trench bottom elevation above 300 mm.. Due to the shallow excavation depth, the construction process should be strictly controlled and checked at any time to prevent over-excavation. Earthwork that can't be dug by mechanical construction should be dug by manpower at any time, and the earthwork should be transported to the place dug by mechanical energy by handcart so as to be dug in time. Before excavation, a trench should be manually excavated along the periphery of the trench to understand the direction of the underground pipeline. Be careful when digging near the pipeline, and cooperate with manpower to protect it in time.

4. At the place 500mm away from the design elevation of the tank bottom, professional survey technicians will copy the horizontal line to make horizontal piles. Then manually dig away the temporary 300mm soil layer. At the same time, both ends of the pile are driven to pull through the line, and the size is checked from the slot edge to determine the slot width standard. Trim the groove edge in this way, and finally remove the earthwork at the bottom of the groove. Quality inspection and acceptance shall be carried out after the tank bottom is repaired and leveled.

5. In foundation construction, if the actual geological conditions are found to be inconsistent with the design requirements, the design and investigation department must be notified to study and deal with them.

6. Immediately after foundation excavation, a closed steel pipe guardrail with a height of 1.2m shall be set at 600cm outside the trough, with a dense mesh safety net and warning lights around it. Generally, the bottom of the trough should be drilled, and the construction can only continue after the relevant departments have passed the inspection.

(2) pouring cushion concrete

1, pouring must be continuous, in one go, leaving no construction joints. When vibrating, the included angle between the vibrating rod and the horizontal plane is about 60 degrees, the head of the vibrating rod faces forward, and the moving distance should be about 400 mm In order to prevent vibration leakage, the vibrating time should be that bubbles emerge after the concrete surface boils.

2. The concrete surface should be leveled with a vibrator according to the elevation line. The concrete surface of the cushion should be as flat as possible to ensure the correct size and elevation of the structure and the smooth progress of the next process.

(3) Foundation reinforcement

Be familiar with the drawings before foundation construction and do a good job of sample inspection. Review the specification and quantity of steel bar application, prepare materials, and do a good job in material test, and mix the materials after the test is qualified.

The lap length of reinforcement meets the design requirements. The mid-span reinforcement (upper reinforcement) at the bearing is overlapped, and the mid-span reinforcement (lower reinforcement) is overlapped. The overlap length is 35d, and the overlap length between DL and DL is 42d. The straight length of stirrup hook is not less than 10 times d, and the hook is 135 degrees.

The position of reinforced lap joints shall be correct and staggered. The overlapping area shall not exceed 1/4 of the total cross-sectional area of steel bars, and all stressed steel bars and stirrups shall be uniformly bound without tripping.

Structural reinforcement shall be accurately bound according to structural requirements.

Steel bar connection adopts lap welding and binding. The welded joint shall be free of cracks, with a curvature of 4 degrees, and the deviation of steel bar axis shall not be greater than 0. 1d and < 2mm. When welding, the longitudinal bars of two steel bars should be aligned with each other.

Steel binding construction must be carried out in accordance with the design requirements and construction acceptance standards.

Reinforced by lap welding, single lap welding welding length should meet10d; ; The welding length of double-sided lap welding shall meet 5d, E42 series covered electrode shall be adopted for 1 grade reinforcement, and E50 series covered electrode shall be adopted for grade 2 reinforcement.

(4) Basic template

1. Steel formwork is used as the foundation formwork.

2, pay attention to when shuttering founder, vertical, smooth, tight and firm.

3, template surface requirements clean, smooth, brush isolation agent.

4, inspection qualified rear can install somehow stare blankly and steel pipe, all scaffolding to support, it is forbidden to use a sledgehammer when cleaning the template, this will cause uneven or damaged board face.

5, template assembly height according to the design elevation assembly height, not lower than the elevation or higher than the elevation, in order to avoid surface height error on the basis.

6, steel mold should install enough clips to ensure the connection stiffness of the template.

7. The fixed formwork is made of 48 steel pipes with enough transverse ribs and vertical ribs, which are fixed with fasteners and the beams are overlapped with each other.

8. Sufficient support shall be provided outside the foundation to ensure that the formwork has sufficient rigidity. Avoid deformation and mold explosion.

9. In case of deformation, immediately stop casting the formwork, dismantle the deformed formwork, chisel the concrete flat, and re-erect the formwork. After the formwork is established, re-chisel the concrete to ensure that the concrete is full and dense.

10, serious concrete quality problems found in the process of form removal will be handled in conjunction with the technical department.

(5) Foundation concrete construction

1, before concrete is cast, the formwork and flat plate should be wetted first. Cut the material in strict proportion.

2, due to the use of commercial concrete, to strictly control the slump of concrete 14- 18.

3, concrete vibrating should be moderate, not too vibration, so as to avoid the loss of cement slurry, stones, avoid concrete pits and too many water holes. Concrete pouring can't avoid vibration leakage and less vibration, so as to prevent possible porosity and reinforcement exposure on the concrete surface.

4. When the concrete surface is defective, the honeycomb pits with small area and not deep shall be cleaned, and the loose part shall be repaired with 1:2 cement mortar. If there is a small hole with a depth of less than 50mm, the loose concrete and pumice around the hole can be chiseled with high-pressure water, and the plain cement slurry is brushed, filled with dry fine stone concrete with a higher grade than the original concrete, filled with 0 dense, and watered for maintenance. If there are any quality problems that affect the structure and function, they should consult with the relevant technical departments such as design and put forward treatment opinions before rectification.

5. After concrete pouring is completed, cover it after 12h, and maintain it with heat preservation.

6, foundation concrete block production not less than 3 groups, each affecting not less than 1 group. After curing for 28 days, carry out pressure test.

(6) Backfill soil engineering

Backfill engineering should be carried out after the inspection and acceptance of concealed works. Backfill soil should be screened, the maximum particle size should not be greater than 5cm, the soil moisture content must meet the requirements of construction specifications, and compacted step by step. The virtual thickness of each layer of backfill soil should not be greater than 30cm, and it should cooperate with the construction of drainage works.

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