JPS6347424A - Prestressed concrete foundation slab construction - Google Patents

Abstract

PURPOSE:To prevent the unequal settlement of columns by a method in which an inverse umbrella-shaped recession is formed in and around a place where a column is present, a PC part is penetrated along the recession for erection, and a foundation slab is placed. CONSTITUTION:Improved surface ground 2 is constructed by using soil cement, etc. for the ground 1, and an inverse umbrella-shaped recession 3' is formed in and around a place where a column 7 is present. A plastic sheet 4 is laid on the ground 2 and many PC parts 5 are set horizontally and vertically by penetrating a plurality of PC steels into the sheet 4 curved along the recession 3'. Foundation slab concrete 6 is then placed, a prestress is introduced into the PC parts, the column 7 is erected on the position of the recession 3, and concrete is placed to the surrounding of the column 7. The unequal settlement of the column 7 can thus be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a prestressed concrete foundation slab construction method suitable for foundation slabs of low-rise factories, warehouses, etc. with large floor areas.

``Conventional technology'' When constructing a foundation slab for a low-rise, wide-area factory, warehouse, etc. on the ground where the bearing capacity is insufficient and uneven settlement is expected, the conventional method was to: Build a pillar
A construction method in which the independent foundation that receives the column load relies exclusively on the soil-floor concrete (No. 10 Painter) ■ A construction method in which the earth-floor slab is constructed with soil-floor concrete and the independent foundation that receives the column load is based on foundation piles (No. 1)
(Fig. 1A) ■ A construction method (Fig. 12A) is adopted in which the earthen floor slab is used as a structural slab and the floor load and column load m are supported by foundation piles.

"Problem to be solved by the invention" However, in the case of (■) above, the earthen floor concrete relies on the ground and cannot cope with uneven settlement, resulting in the above (■).

In case (2), foundation piles are used, which increases the cost considerably and lengthens the construction period.

In addition, if uneven settlement occurs, in the case of (1) above, unevenness and cracks will occur in the earthen floor concrete slab due to the difference in the amount of settlement (10Tf!JB, Fig. 11B).
If there is a large difference between the structural slab and the ground (
Fig. 12B) is extremely inconvenient in use.

The present invention seeks to solve these problems.

"Means for Solving Problems" As shown in the illustrated embodiment, the present invention improves the surface layer of the ground where the bearing capacity is insufficient, and also appropriately improves the area where the pillar is located and the surrounding area. Make a depression, spread a plastic sheet on the improved surface ground, place a sheath on top of the plastic sheet and curve downward to follow this in the depression, and inside the sheath, a plurality of plastic sheets are placed. Insert a prestressing steel material, place foundation slab concrete, introduce prestress with the prestressing steel material, and raise a column from the foundation slab at the position of the depression to transfer the column load to the foundation slab. It is supported by being lifted up using prestressed steel.

In addition, it is better to use a flat sheath, and 1.
As the steel material, unbonded PC steel material or the like may be used.

"Action" The state before applying the column load m and introducing prestress (
In Figure 19 A), when prestress is introduced, the foundation slab is separated from the ground by the plastic sheet, so at the same time it contracts, the area around the column is lifted up and rises slightly, and the 8 layers of the foundation slab are lifted up by the column. It is transmitted to the ground in areas other than the surrounding areas (Figure B).

Next, when a column load (!bearing load) is applied, the area around the columns of the raised foundation slab descends again, and this column load is dispersed over the entire area of the foundation slab due to the above-mentioned lifting action. The entire slab supports one column, eliminating the need for foundation piles. In addition, consideration should be given to the distribution of this column load in the design so that it is as even as possible.

In addition, the foundation slab is a pre-stressed concrete slab and can be made thin, so it has deformation followability and recovery properties, and the plastic sheet makes the foundation slab slide well, eliminating inconveniences caused by uneven settlement. Make exclusion possible.

This construction method is effective when used in cases such as reclaimed land, where the entire site has a large amount of subsidence, and using a pile foundation would cause problems due to the difference in subsidence between that area and other areas.

"Example" Part 1 Figures 1 and 2 show the first example. In this case,
In a ground 1 with insufficient bearing capacity that cannot support a large column load as an independent foundation without foundation piles, an improved surface layer 2 of fill cement, etc. is constructed on the surface layer, and the area where the column is located and its surroundings. A recess 3 is formed in the shape of a reverse water, and a plastic sheet 4 is laid on the improved surface ground 2, and the plastic sheet is curved downward to follow this in the j-shaped part. A large number of PC members 5 with multiple PCjg materials inserted into the source.
... are arranged vertically and horizontally, and the foundation slab.

concrete is poured, prestress is introduced using prestressed steel materials, columns are erected from the foundation slab 6 at the position of the depression 3, and the column load is supported by lifting the column load using those prestressed steel materials 5... , post-cast concrete 9 is placed in the recess 8 around the outer 7.

2゜Figures 3 and 4 show the second embodiment, in this case,
Part 1 above. By eliminating post-cast concrete,
The lead portion of the foundation slab 6 is made thick.

3. FIGS. 5 to 8 show a third embodiment in which the column span is narrow in one direction. In this case, the above-mentioned 2. In this case, adjacent depressions 3.3 are made to communicate with each other, a long depression 3' is formed on one side, and the PC member 5... is curved upward between both pillars 7.7 to make it wave.

``Effects of the Invention'' According to the present invention, the column load is supported by the entire foundation slab without causing stress concentration under the column surface. It can be fully addressed and can be constructed at low cost and in a short period of time.

In addition, since the foundation slab is a prestressed concrete slab and can be made thin, the foundation slab can have good deformation followability and resilience, and even if uneven settlement occurs, the foundation slab will not be uneven or crack. do not have.

Furthermore, if an abnormality occurs in the ground due to uneven settlement, it can be easily repaired by injecting grout between the plastic sheet placed under the foundation slab and the improved ground.
No inconvenience occurs during use.

[Brief explanation of the drawing]

1 to 9 show examples of the present invention, FIG. 1 is a plan view of the first example, FIG. 2 is a sectional view taken along the line ■-■ in FIG.
Figure 3 is a plan view of the second example, and Figure 4 is Figure 3 rV.
-TV line sectional view, FIG. 5 is a plan view of the third example, and FIG.
The figure is a sectional view taken along the line Vl-■ in Figure 5, and the figure 7 is a cross-sectional view taken along the line Vl-■ in Figure 5.
■ Line sectional view, Figure 8 is a perspective view of the same example, Figure 9 is
The operation explanatory diagrams and FIGS. 10 to 12 are explanatory diagrams of conventional examples, respectively. 1...Ground 2...Improved surface ground 7...Column 8...Concavity 9...Post-cast concrete Figure 1 Figure 2 Figure 9...Cut concrete Figure 3 Figure 4 7... Figure 7 Figure 8 Figure 9 Figure 7... Figure 10 Δ Figure 11 Δ

Claims (1)

[Claims] In addition to improving the surface layer of the ground where the bearing capacity is insufficient, the area where the pillar is located and its surroundings are appropriately depressed, a plastic sheet is laid on the improved surface layer, and a plastic sheet is placed on top of the plastic sheet along this. At the same time, a sheath is curved downward to follow the concave area, and a plurality of prestressing steel members are inserted into the sheath, and foundation slab concrete is poured to prestress the prestressed steel material. A prestressed concrete foundation slab construction method characterized in that a column is erected from the foundation slab at the position of the depression, and the column load is supported by being lifted by the foundation slab with PC steel.