Technology to build basements from top to bottom

 
Technology to build basements from top to bottom
In civil construction, when it is necessary to "build" up to 3 basements, people do not only build from the 3rd basement up, but can build the 1st basement first, then continue construction from top to bottom. called top-down technology (from top to bottom).
 
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Excavators are excavating soil from the lower floor, rebar is waiting to complete the beams and columns
 
At that time, floating floors also allowed them to be built higher at the same time. Construction time will be faster. Of course, the load-bearing foundation piles must be drilled for both the basement and aboveground floors beforehand.
Construction method - Basement construction technology from top to bottom
In top-down technology, basements are constructed by: Diaphragm walls made of barrette piles driven deep around the house. At the beginning, people dug trenches on the ground, made a mold to cast beams for the first basement, then poured the "00 core" concrete floor, at this time they left a reasonable area, later the area could be used for other purposes. will be the area to build stairs and elevators. This area is enough to put excavators, excavators and soil trucks down. The excavators and excavators will gradually dig up the soil, avoiding touching the foundation drilling column.
Speaking of these bored columns with foundations, people have already calculated the height of the basement floors to pre-place waiting steel, or structure the "shoulders", which will later form the basement beams.
When the entire volume of soil is excavated, the space and all columns of basement floor 1 are exposed. At this time, it is necessary to complete the columns and walls according to load-bearing standards.
The next job is to cast "beams close to the ground", dig trenches on the ground, use the ground to make molds, and continue pouring tunnel floor 1... leaving a reasonable area to take the machine down to dig out the second floor. And so on. , each of the following "beams close to the ground" will be the load-bearing beams when the soil is removed. The tunnel floors are firmly connected to the waiting steel reinforcement columns (mentioned above), and firmly connected to the diaphragm wall system.
Completing the project – Technology for building basements from top to bottom
Finishing, decoration, as well as electricity and water installation in the basement are carried out like the above floors.
Due to the requirement of continuous construction, the formwork must be removed early in order to excavate the ground to continue construction on the lower part, so engineers use additives to help the concrete achieve strength in a short time, possibly reaching over 90%. Design strength within 7 days.
When constructing basements using the top-down method, we often encounter underground water, making construction very difficult. Usually, people have to lower the water level of the pump.
The excavators here are small specialized machines, small graders, and small ground rollers.
The steel reinforcement of the floor and beams is connected to the wall by drilling through the wall and sliding the steel in behind. Then use cement mortar mixed with "glue" and spray it into the drilled hole where the steel is placed.
According to the Vietnam Construction Association, some advantages of top-down technology are: No need for a large foundation excavation area or the cost of having to build an independent retaining wall. Allows to speed up construction progress. While working on the basement, you can still work on the upper part at the same time, saving time.
No extra protection costs. Temporary shoring systems are often very complicated, blocking construction space and very expensive. Compared to traditional excavation methods, the cost of supporting 3 basement floors and supporting scaffolding materials is quite high. The top-down construction plan solves the problem of excavation roof slipping, cracking, etc., reducing the negative effects of weather, even though during construction it is necessary to install ventilation and artificial lighting systems because there is a lack of light deep underground. bright.
According to the Vietnam Construction Association, this technology was applied in Vietnam for the first time in Ho Chi Minh City. Dozens of projects in Hanoi also continue to apply successfully.
According to Chinhphu.vn

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