JPH0784744B2 - Prestressed concrete foundation slab construction method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a prestressed concrete foundation slab construction method suitable for a foundation slab of a low floor and a large floor area such as factories and warehouses.

"Conventional technology" When setting up a foundation slab such as a factory or warehouse with a large area on the ground where the bearing capacity is insufficient, conventionally, the soil slab was constructed with soil concrete and the independent foundation that receives the column load was directly applied to the ground. Construction method to support (Fig. 13A).

Construction method for constructing an earth slab with earth concrete and supporting an independent foundation that receives a column load with piles (Fig. 14A).

A construction method in which the earth slab is a structural slab and the pile and floor loads are received by the pile (Fig. 15A).

Etc. have been adopted.

Further, according to the published patent publication, it can be adopted even in places with relatively low strength of bearing, i) PC inside the foundation slab to be constructed in contact with soil on the ground
The steel material is arranged, the PC steel material is positioned on the upper side at the intermediate position between the columns, and is bent downward at the position where the concentrated load of the column and the wall is applied, and inserted in a parabolic shape to prevent prestressing. Basic structure to be introduced (Japanese Patent Laid-Open No. 59-55921).

ii) In the basic structure of the above i), the basic slab is bulged downward at the position of the column (Japanese Patent Laid-Open No. 60-102431).

There is.

"Problems to be solved by the invention" However, when uneven settlement occurs, in the case of the above, unevenness and cracks occur in the soil concrete slab due to the difference in the settlement amount (Figs. 13B and 14B), It is very inconvenient to use.

Even if the above i) and ii) are carried out, the problem remains in the ground, so that the cracks of the foundation slab can be reduced in reality.

In the above case (Fig. 15B), if the span is large, it is necessary to use tie beams, slabs, etc. as members with a large cross section, but for that purpose, the weight of the skeleton and the piles that support the foundation also become large. It's not economical.

The present invention seeks to solve these problems.

[Means for Solving the Problems] To achieve the above object, one invention is, as shown in FIG. 1 and FIG. 2, a subslab 4 by improving the surface layer of the ground 1 having insufficient ground bearing capacity. And laying a plastic sheet 5 for trimming on the sub-slab, deploying a PC steel material on the plastic sheet, and providing a gap between the column base and the column base of each column 2. It is characterized in that the foundation slab concrete 7 is cast, and then the prestress is introduced into the foundation slab concrete by the PC steel material.

In another invention, a plurality of anchor bolts 11 are planted at the upper ends of pile foundations 3'provided at various points of the ground 1 having insufficient ground bearing capacity, and the surface layer of the ground 1 is grounded. A subslab 4 having the same level as each of the pile foundations 3'is improved and a plastic sheet 5 for edge cutting is laid on the subslab or each of the pile foundations 3 ', and a PC steel material is placed on the plastic sheet. In addition to the above, a space is provided around each of the anchor bolts 11 to form the foundation slab concrete 7
Then, place the above PCs on the foundation slab concrete.
It is characterized by introducing prestress by steel material.

"Operation" Because of the above configuration, in the first invention, the edges of the foundation slab and the sub slab 4, the column base of each column, and the column foundation are cut by the plastic sheet 5 and the gap. In another invention, the base slab and the sub slab 4, due to the plastic sheet 5 and the gap,
The edges of the pile foundations 3'and the anchor bolts 11 are cut off, and in each case, the foundation slab concrete 7 shrinks without trouble with the introduction of prestress even if the sub-slab 4 or the like exists.

And, the plastic sheet 5 brings good sliding to the finished base slab, and the introduction of pre-stress enables the base slab to be thinned. As a result, the completed basic slab can be provided with deformation followability and resilience, and inconveniences due to differential settlement can be eliminated by injecting grout between the basic slab and the sub-slab 4. Will be possible.

[Example] Part 1. Figs. 3 to 7 show an example of one invention.

In this case, an appropriate number of piles 3 are laid in each of the important points of the ground 1 where the bearing capacity is insufficient, and the pillar foundation is supported on the upper ends of the piles at each important point to construct the pillar 2. Further, the surface layer of the ground 1 is ground-improved by soil cement or the like to construct a sub slab 4 at the same level as the pillar foundation, and a plastic sheet 5 for edging is provided on the sub slab and each pillar foundation. The base slab is laid, and a large number of sheaths 6 having a plurality of PC steel materials inserted therein are arranged vertically and horizontally on the plastic sheet, and joints, which are gaps for edging, are formed around the legs of the columns 2. Concrete 7 is cast, and then prestress is introduced into the basic slab concrete by the above PC steel materials, and then joint concrete 8 is cast in each joint.

In the figure, 9 is an end concrete, and 10 is a connecting rebar.

Part 2. FIGS. 8 to 12 show another embodiment of the invention.

In this case, pillars 2 will be placed at various points on the ground 1 where the bearing capacity is insufficient.
The pile foundations 3'for supporting the piles are provided so that the upper ends thereof coincide with the lower surface level of the foundation slab, and a plurality of anchor bolts 11 are planted at the upper ends of these pile foundations 3 ', and the surface layer portion of the ground 1 thereof. The soil is improved by soil cement or the like to construct a sub slab 4 at the same level as each of the pile foundations 3 ', and a plastic sheet 5 for edging is laid on the sub slabs and each of the column foundations, and the plastic sheet is placed on the plastic sheet. A large number of sheaths 6 in which a plurality of PC steel materials are inserted are arranged vertically and horizontally, and a sheath 12 is fitted into each of the anchor bolts 11 to cast a foundation slab concrete 7, and then each of the above PCs is attached to the foundation slab concrete. A prestress is introduced by a steel material, and then columns 2 are built on the hardened foundation slab concrete 7 so as to correspond to the pile foundations 3 ′. The anchor bolts 11 and the nuts 13 screwed onto these are fastened and fixed.

[Effect of the Invention] According to the present invention, the subslab 4 is provided by improving the surface layer of the ground 1 having insufficient ground resistance, so that even if the ground has insufficient ground resistance, this is required. The sub-slab 4 that is the improved ground can be strengthened to the ground bearing capacity and a predetermined supporting force can be obtained. In addition to this, since the foundation slab on the sub-slab is a prestressed concrete slab, the foundation slab is It can be made extremely strong and can prevent the occurrence of differential settlement in the foundation slab.

Furthermore, since the plastic sheet 5 for cutting the edge is provided on the sub slab 4 and the like, the basic slab does not adhere to the sub slab 4, and good sliding is obtained in the basic slab despite the existence of the sub slab 4, Since the foundation slab can be made thin by introducing the prestress, the foundation slab can have good deformation followability and resilience, and even if uneven settlement occurs, unevenness and cracks will occur. In addition, even if an abnormality occurs due to differential settlement exceeding the allowable limit in the ground, it can be easily repaired by injecting grout between the plastic sheet 5 and the sub-slab 4 laid under the foundation slab, of course. Even if such a repair is carried out, the slip of the basic slab will not be hindered and no inconvenience will be caused in use. Moreover, since the foundation slab is supported by the ground, the pillar foundation can be an independent foundation with piles,
It is economical because there is no need to increase the size of the pile to support the load of the foundation slab.

[Brief description of drawings]

FIG. 1 is a plan explanatory view showing a constitutional point of one invention, and FIG.
1 is a sectional view taken along the line II-II in FIG. 1, FIGS. 3 to 7 are embodiments of the present invention, FIG. 3 is a plan view, FIG. 4 is a line IV-IV in FIG. Sectional view, FIG. 5 is a sectional view taken along line VV of FIG. 3, FIG. 6 is an enlarged view of an essential part of FIG. 4, FIG. 7 is an enlarged view of an essential part of FIG. FIG. 12 shows another embodiment of the invention. FIG. 8 is a plan view and FIG. 9 is FIG. 8 IX-I.
X-ray sectional view, FIG. 10 is a sectional view taken along line XX of FIG. 8, FIG. 11 is an enlarged view of an essential part of FIG. 9, and FIGS. 13 to 15 are explanatory views of conventional examples. . 1 ... Ground, 2 ... Pillars 3 ... Piles, 4 ... Sub slab 5 ... Plastic sheet, 6 ... Sheath with PC steel inserted 7 ... Foundation slab concrete, 8 ... Joint concrete 9 ... End Concrete, 10 ...... Connecting rebar 11 …… Anchor bolt, 12 …… Sheath 13 …… Nut, 3 ′ …… Pile foundation

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ikuo Yamaguchi Ikuo Yamaguchi 2-5-14 Minamisuna, Koto-ku, Tokyo Inside the Takenaka Corporation Technical Research Institute (72) Shinto Ueda 2-5 Minamisuna, Koto-ku, Tokyo No. 14 Incorporated Takenaka Corporation Technical Research Institute (72) Inventor Kiyoshi Yamashita 2-5-14 Minamisuna, Koto-ku, Tokyo Incorporated Takenaka Industrial Engineering Laboratory (72) Inventor Masao Miyaguchi Ginza, Chuo-ku, Tokyo 8-21-1 Takenaka Corporation Tokyo Main Store (72) Inventor Hiroshi Sawada 8-21-1 Ginza, Chuo-ku, Tokyo Takenaka Corporation Tokyo Main Store (56) References JP-A-60- 188538 (JP, A) JP 60-102431 (JP, A) JP 59-55921 (JP, A) Actual development Sho 60-22535 (JP, U)

Claims (2)

[Claims] 1. A subslab 4 is constructed by improving the surface layer of the ground 1 having insufficient bearing capacity, a plastic sheet 5 for edging is laid on the subslab, and a PC steel material is placed on the plastic sheet. In addition to deploying, placing a gap between the column base of each column 2 and the column foundation, placing the basic slab concrete 7, and then introducing prestress to the basic slab concrete with the above PC steel material. Prestressed concrete foundation slab construction method characterized by. 2. A plurality of anchor bolts 11 are respectively provided at the upper ends of pile foundations 3'provided at various points of the ground 1 having insufficient ground bearing capacity.
And the subsurface slab 4 at the same level as each of the pile foundations 3'is constructed by improving the ground surface portion of the ground 1.
A plastic sheet 5 for edge cutting is laid on the sub slab or each of the pile foundations 3 ', a PC steel material is placed on the plastic sheet, and each of the anchor bolts is placed.
A prestressed concrete foundation slab construction method characterized by placing a foundation slab concrete 7 with a gap around 11 and then introducing prestress to the foundation slab concrete with the above PC steel materials.