Under what circumstances is a box foundation used?

The raft foundation, also known as the slab foundation, is to connect all the independent foundations or strip foundations under the column with connecting beams, and then pour the bottom plate as a whole. Generally speaking, when the bearing capacity of the foundation is uneven or the foundation is weak, a slab foundation is used. Moreover, the buried depth of the slab-type foundation is relatively shallow, and it can even be used as a non-buried foundation.

The box foundation is an overall space structure with a certain height composed of reinforced concrete bottom plate, roof, exterior wall and internal partition wall, which is suitable for high-rise, heavy-duty or buildings with strict requirements for uneven settlement on weak foundations. Compared to raft foundations, box foundations have greater flexural stiffness and can only produce roughly uniform settlement or overall tilt, essentially eliminating the possibility of cracking the building due to foundation deformation.

The box-shaped foundation is a closed box composed of reinforced concrete bottom plate, roof, side wall and a certain number of internal partition walls, and the middle part of the foundation can be used as a basement in the inner partition wall. The integrity and stiffness of this foundation are good, and the ability to adjust uneven settlement is strong, which can eliminate the possibility of cracking the building due to foundation deformation, reduce the original foundation self-weight stress at the base, and reduce the total settlement.

Construction requirements. 1.In order to avoid excessive tilting of the foundation, the box foundation should be as symmetrical as possible in the plane layout to reduce the eccentricity of the load, and the eccentricity should generally not be greater than the ratio of the resistance moment of the base plate area to the base bottom area).

2.The height of the box-shaped foundation is generally 1 8 1 12 of the height of the building, and should not be less than 1 18 of its length.

3.The thickness of the bottom and top plate should meet the requirements of the column or wall punching and shear check, and be determined by calculation according to the actual force. The thickness of the bottom plate is generally 1 10 1 8 of the partition wall spacing, about 30 100cm, the thickness of the roof is about 20 40cm, the thickness of the inner wall should not be less than 20cm, and the thickness of the outer wall should not be less than 25cm.

4.The foundation concrete grade should not be lower than C20, and the impermeability grade should not be lower than S6.

5.In order to ensure the overall stiffness of the box-shaped foundation, there should be certain restrictions on the number of walls, that is, the length of the wall on the average square meter of foundation area shall not be less than 40cm, or the horizontal cross-sectional area of the wall shall not be less than 1 10 of the foundation area, wherein the longitudinal wall configuration shall not be less than 3 5 of the total configuration of the wall.

Features of the box foundation:

The box foundation is a single-layer or multi-layer reinforced concrete foundation with good overall stiffness composed of the bottom plate, the roof plate, the side wall and a certain number of internal partition walls. The internal space of the box foundation can be designed as a basement, an underground garage or an underground equipment layer in combination with the use function of the building. The box-shaped foundation has great stiffness and integrity, can effectively adjust the uneven settlement of the foundation, and because it has a large burial depth, the soil has a good embedding and compensation effect on it, so it has good seismic resistance and compensation, and is one of the foundation types often used in high-rise buildings at present.

Summary. Pro-<>

Hello, the box-shaped foundation interior space can be used as a basement. The presence of this space reduces the pressure on the underside of the foundation, which can increase the number of floors of the building if it is not necessary to reduce the base pressure.

What can be used for the internal space of the box foundation.

Hello <> box-shaped foundation, the internal space can be used as the lower room of Di Chunxiang. The existence of this space reduces the pressure on the underside of the foundation, and if it is not necessary to reduce the pressure on the base, the prime minister should increase the number of floors of the building.

The box foundation is an overall spatial structure composed of reinforced concrete floor slabs, roof slabs, and vertical and horizontal interior and exterior walls. Box foundations have great flexural stiffness and can only produce roughly uniform settlement or overall tilt, which essentially eliminates the possibility of cracking the building due to foundation deformation, and the space within the box foundation is often used as a basement. The existence of this or mausoleum space reduces the pressure on the bottom surface of the foundation, and if it is not necessary to reduce the pressure of the base, the number of layers of the building group can be increased accordingly.

The amount of steel and cement used in the box foundation is very large, and the construction technical requirements are also very high.

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One of the forms of foundation of the house building. Because of its shape, it resembles a box, hence the name.

The so-called box foundation is to hollow out the entire land occupied by the building, dig deep, and then fill it with reinforced concrete. Its advantages are: first, the contact area between the building and the ground is increased, thereby reducing the pressure of the building on the ground, and can effectively prevent the subsidence of the large amount of the ground row wild skin; Second, it lowers the center of gravity of the whole building, increases the stability of the building, and improves the seismic resistance of the building.

There may or may not be piles underneath the box foundation. When there is a pile, it is called a pile box foundation or a pile raft foundation, which is a foundation form that combines a pile foundation and a shallow foundation, and the two jointly bear the upper load. Zhentong.

Classification of foundations and structures: foundations are divided into deep foundations (pile foundations and their ancillary components, pile foundation caps) and shallow foundations (independent foundations, strip foundations, raft foundations, and foundation connecting foundations, connecting beams, underground frame beams, box foundations, basement structures); The structure is divided into frame structure, shear wall structure, frame shear structure, cylinder structure, and frame tube structure;

Detailed description of the basement structure: the basement structure is divided into the foundation part according to the specification, it is a component placed above the foundation and below the superstructure, covering the components of the foundation and the components in the structure, it should be a complex, its lower foundation can be an independent foundation, a strip foundation, a raft foundation, a box foundation, and the superstructure can of course be a frame structure, a shear wall structure, etc.; Here we should focus on the difference between the basement structure and the box-type foundation, first of all, in terms of function, the box-type foundation plays the role of supporting structure, and the basement structure plays the role of using functions; Secondly, in terms of composition, the box-shaped foundation is composed of vertical components composed of external walls and inner walls, and the basement structure is composed of columns and walls.

The composition of the box-shaped foundation: mainly including transverse components (bottom plate, middle layer plate, roof plate), vertical components (external wall, interior wall), other components (post-pouring belt, foundation pit, rectangular opening, rectangular opening opening, circular opening, rectangular niche, wall edge dark column, wall reinforcing longitudinal reinforcement, plate reinforcing longitudinal reinforcement);

The composition of the basement structure: mainly including foundation, transverse components (beams, plates), vertical components (columns, walls), and other structures (other components in the foundation and structure);

Description of whether each component in the basement belongs to the foundation class or the structural class: the components belonging to the foundation class include exterior walls, ramp beams, ramp slabs, and structural components, columns, shear walls, beam plates, etc.;

1. Plane drawing rules.

1) Box-type foundation:

1. Box substrate (including bottom plate, top plate, middle layer board): divided into centralized labeling and in-situ labeling, centralized labeling number, thickness, top and bottom through longitudinal bars, relative height difference, and necessary explanatory text; In the in-situ annotation, the additional reinforcement of the support is mainly marked and the difference is centrally annotated.

2. Outer wall of box base: divided into centralized labeling and in-situ labeling, centralized labeling of wall number, thickness, horizontal and vertical reinforcement on the outside, horizontal and vertical reinforcement on the inside, and tendoning; In-situ annotation, additional reinforcement for transverse support and additional reinforcement for vertical support; It should be noted here that the exterior wall is designed as a component to resist horizontal loads according to the two-way plate, so there is a corresponding additional reinforcement for the support;

3. The inner wall of the box foundation: there are two differences between this and the outer wall, one is that the inner and outer reinforcements are not divided into centralized labeling, and the other is that there is no additional reinforcement of the support in the in-situ labeling, unless there is a horizontal load in the design;

4. Other components of the box base: the annotation of the components is the positioning size of the elevation and the plane;

2) Basement structure.

1. Foundation: It is the agreement in the independent foundation, strip foundation, raft foundation and box foundation;

3. Vertical components: as agreed above;

4. Other components: as agreed above.

It is completely possible, in fact, many high-rise buildings are box-shaped foundations, with two to three floors underground, and the floor height is more than 4 meters, which can be used for civil air defense and underground parking lots.

1. The average length of the wall on the square meter of box-shaped foundation area is not less than 40cm, or the horizontal cross-sectional area of the wall is not less than 1 10 of the box-shaped foundation area, wherein the longitudinal wall configuration is not less than 3 5 of the total configuration.

2. The shape of the upper building should be as regular as possible, the plane should be symmetrically arranged, the load should be evenly distributed, and the center of gravity of the structure should coincide with the center of shape.

3. The height of the box foundation should be greater than the length of the box foundation 1 18, and should not be less than 3m.

Fourth, the thickness of the bottom plate and the anti-laughter wall should not be less than 250, the thickness of the inner wall should not be less than 200, and the thickness of the roof should not be less than 150.

5. Considering the overall bending influence, in addition to meeting the calculation requirements, the reinforcement configuration in the middle of the span should have a total amount of 1 4 connected in the vertical and horizontal direction of the supporting reinforcement, and all the reinforcements in the middle of the span are passed.

6. For the analysis of the internal force of the box-shaped foundation, the overall bending and local bending should be considered as much as possible.

Qichang and box-shaped foundations should check the anti-floating stability and buoyancy partial coefficient in the construction and use stages.

8. The protective layer of steel bars on the surface of the water should not be less than 50, and the width of concrete cracks.