There are three kinds of independent foundations: step foundation, slope foundation and cup foundation.
All the connection points must be bound.
The independent foundation under the column is the same principle.
1、 What is the independent foundation under the column? When the superstructure of the building adopts frame structure or single-layer bent structure to bear the load, the foundation often adopts square, cylindrical and polygonal independent foundations.
The normal temperature curing shall not be less than 7d, and the special concrete curing shall not be less than 14d.
This is the basis of independence.
The upper vibrator shall be inserted into the lower layer for 3 ~ 5cm.
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Formwork removal: the side formwork can be removed only when the concrete strength can ensure that its edges and corners will not be damaged due to the removal of the formwork.
Leveling is to make the foundation bottom elevation meet the design requirements.
(2) pay attention to the elevation of cup bottom and the position of cup mouth formwork when pouring cup foundation, Prevent the cup die from floating and tilting.
The maintenance shall be checked and implemented by special personnel to prevent cracks on the concrete surface due to untimely maintenance.
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Pay attention to the finished product protection of reinforcement, and do not collide with reinforcement arbitrarily, resulting in reinforcement displacement.
Cushion construction: after the foundation trench inspection is completed, the cushion concrete construction shall be carried out immediately.
The material is cut in layers, and the thickness of each layer is the effective vibration length of the vibrating rod.
The two positioning bars must be replaced after the foundation concrete pouring.
The cushion concrete must be vibrated and compacted, and the surface must be flat.
Try to avoid collision with embedded parts and embedded bolts to prevent displacement of embedded parts.
Concrete leveling: after concrete pouring, the concrete with large surface shall be vibrated once with a flat vibrator, then scraped with a scraper rod, and then rubbed with a wooden trowel.
This kind of foundation is called independent foundation, also known as independent foundation.
Concrete vibration: the immersion vibrator shall be used, and the distance between the inserted persons shall not be greater than 1.25 times the length of the acting part of the vibrator.
Before foundation construction, the foundation bottom elevation shall be determined on the foundation surface.
Foundation pit cleaning and leveling: cleaning the foundation pit is to remove the surface floating soil and disturbing soil, No ponding.
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Formwork: the formwork shall be installed immediately after the reinforcement binding and construction of relevant disciplines.
Reinforcement binding: after the pouring of the cushion is completed and the concrete reaches 1.2MPa, snap lines on the surface for reinforcement binding.
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During pouring, the concrete at the bottom of the cup mouth shall be vibrated and stopped for a moment, and then the concrete around the cup mouth formwork shall be poured symmetrically and evenly.
Prevent honeycomb, pitted surface or holes caused by excessive blanking, improper vibration or missing vibration, and mortar gushing from the root of the lifting wall.
It is not allowed to impact the formwork with heavy objects, and it is not allowed to set up scaffolds on the formwork for lifting, so as to ensure the firmness and tightness of the formwork.
When the slope is ≤ 30 °, steel wire mesh (spacing 30cm) shall be used to prevent the concrete from falling.
After the binding of the upper and lower stirrups and positioning stirrups, the column joint bar shall be adjusted in place and temporarily fixed with a well shaped wooden frame, and then the remaining stirrups shall be bound to ensure that the column joint bar is not deformed and out of shape.
After the reinforcement is bound, plastic cushion blocks for the protective layer shall be placed on the bottom and side.
Make a larger concrete pier under the relatively thin column, arrange reinforcement inside, and make one under each column.
The preventive measures are: stop for 0.5 ~ 1H after the pouring of the first step, and pour the next step after the lower part is solid.
Concrete curing: the poured concrete shall be covered and watered within about 12h.
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In order to ensure the correct position of the reinforcement, a layer of 5 ~ 10cm thick concrete shall be poured first to fix the reinforcement.
After it sinks, another layer shall be poured.
When the gradient of conical foundation is less than 30 °, inclined formwork support shall be adopted, and bolts and bottom plate reinforcement shall be tightened to prevent floating Ventilation and vibration holes shall be set at the upper part of the formwork.
The thickness shall be the thickness of the design protective layer, and the spacing of cushion blocks shall not be greater than 100mm (determined according to the design reinforcement diameter) to prevent common quality problems of exposed reinforcement.
Before receiving, the concrete surface elevation must be checked, and those that do not meet the requirements shall be rectified immediately.
The height of each step of the stepped foundation shall be poured and vibrated as a whole.
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Cleaning: remove wood chips, soil and other sundries in the formwork, water and wet the wooden formwork, and block the slab joints and holes.
The independent foundation under the column is easy to imagine.
Missing buckle is not allowed in reinforcement binding.
The hook part of the column joint reinforcement must be bound at 45 ° with the bottom plate reinforcement.
4、 Precautions (1) when pouring stepped foundation, pay attention to prevent void and honeycomb (i.e.
(3) When pouring the conical foundation, if the slope is flat, the formwork may not be erected, but attention shall be paid to the tamping and compaction of the concrete at the slope and corners.
construction method 1.
The column is very thin and will be inserted into the soil; But if you make the bottom very large, it’s not easy to get into the soil, right.
After the vibration is completed, the slope surface shall be corrected, leveled and compacted manually..
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After each step is poured, it shall be stopped for 0.5h.
Cushion construction is to protect the reinforcement of the foundation.
2、 Construction sequence: Foundation Pit cleaning and leveling → concrete cushion → foundation setting out → reinforcement binding → relevant professional construction → cleaning → formwork erection → cleaning → concrete mixing → concrete pouring → concrete vibration → concrete leveling → concrete curing → formwork removal III.
Positioning and setting out: use the total station to set out the center lines and control lines of all independent foundations.
C10 fine aggregate concrete cushion shall be poured on the foundation surface.
hanging feet and rotten neck) in the concrete at the junction of upper and lower steps during construction.
Well shaped wood shall be set at the upper opening to control the position of reinforcement.
It is strictly prohibited to dry the foundation soil.
The formwork shall be small steel formwork or wood formwork, which shall be reinforced by shelf pipe or wood.
The first stirrup shall be bound 5cm away from the bottom plate and the last stirrup shall be bound 5cm away from the foundation top as elevation control reinforcement and positioning reinforcement, A positioning bar shall be bound at the top of the column joint bar.
During the removal, the crowbar shall be used to remove it from one side in sequence, and the sledgehammer or crowbar shall not be used to pry randomly, so as to avoid the damage of concrete edges and corners.
Concrete pouring: the concrete shall be poured continuously in layers, and the rest time shall not exceed the initial setting time of the concrete, generally not more than 2H.
Before the removal of the formwork, a special person shall be assigned to check the concrete strength.
