JP2001081791A - Foundation structure for building - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce weight and increase strength by supporting a single mat supporting all legs of a tower building at the upper end of a steel sheet pile provided in the lower ground. SOLUTION: When the upper layer part 16 of a ground G is a liquefiable soft sandy soil and the lower layer part 14 is a soft cohesive soil, the lower end edge 12a of a steel sheet pile 12 is driven to reach the lower layer 14. A single mat slab 13 is integrally supported at the upper end edge 12b and the legs 4 of a tower structure 3 is integrally supported by the slab 13 to constitute a foundation structure 11. Then, the ground of the upper layer 16 is improved by a sand compaction pile or the like. When a wind load or the like acts on the tower 3, the tower is prevented from falling dowm by the dead weight of the slab 13 and the pulling resistance resulting from the peripheral friction of the sheet pile 12. In this way, the weight of a mat slab can be reduced and the bottom slab thickness can be made thin. The structure can be easily constructed, and ground improvement can be reduced. Further, the settlement depth can be reduced and further, since the ground is surrounded by steel sheet piles, the ground is prevented from liquifying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foundation structure applied to a tower-like building such as a power transmission tower, and more particularly to a foundation having a thick soft layer and a relatively deep support layer. According to.

[0002]

2. Description of the Related Art Generally, a pile foundation or a direct foundation is used as a foundation type of a tower-like building such as a power transmission tower, but in a ground where a soft layer is thick and a support layer is relatively deep. From the viewpoint of concrete work, excavation work, temporary work, construction work period, etc., it is better to adopt a foundation directly than a pile foundation,
It may be economically advantageous.

When the direct foundation is used on soft ground, as shown in FIGS. 6 and 7, from the viewpoint of measures for liquefaction of the ground and ground stabilization measures such as bearing capacity, as shown in FIGS.
To the ground improvement to form ground improvement soil 2,
From the viewpoint of suppressing uneven displacement between legs on the improved ground G, legs 4, 4 (in this case, four places) of the tower structure (building) 3
It is conceivable to construct a basic form in which is integrally supported by a single mat slab 5.

[0004]

However, in such a basic type, the mat slab 5 does not have a weight (self-weight) at least capable of resisting the acting load (wind load or the like) of the tower structure. However, not only does the bottom plate become very thick, which causes problems from the viewpoint of concrete work and excavation work, but also increases the weight of the mat slab 5, which may increase the settlement amount of the foundation.

In view of such circumstances, in the present invention, even when building on soft ground, it is possible to reduce the weight and the thickness of the bottom plate, and furthermore, to construct a tower-like building. An object of the present invention is to provide a foundation structure of a building capable of sufficiently resisting an applied load.

[0006]

Means for Solving the Problems To solve the above problems, the present invention employs the following means. That is,
The building substructure according to claim 1, wherein all legs of the tower-like building are supported by a single mat slab,
A steel sheet pile is driven into the ground below the mat slab, and at least a part of the mat slab is supported by an upper edge of the steel sheet pile.

[0007] With such a configuration, in the foundation structure of this building, it becomes possible to resist not only the own weight of the mat slab but also the peripheral friction of the steel sheet pile against an applied load such as a wind load. .

According to a second aspect of the present invention, there is provided a foundation structure of a building according to the first aspect, wherein at least a part of the mat slab is formed hollow.

With such a configuration, it is possible to reduce the load acting on the area below the mat slab.

According to a third aspect of the present invention, there is provided a foundation structure of a building according to the second aspect, wherein the inside of the hollow mat slab has a predetermined area when viewed in a plan view. It is characterized by being filled with earth and sand.

With this configuration, even when an eccentric load acts, the load acting on the area below the mat slab can be kept substantially constant.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, the same reference numerals are given to configurations common to the above-described conventional technology, and description thereof will be omitted.

FIGS. 1 and 2 show an embodiment of the present invention in the case where the upper layer 16 of the ground G is a soft sandy soil which liquefies, and the lower layer 14 of the ground G is a soft clayey soil. It is a figure which shows typically, The code | symbol 11 shows the foundation structure employ | adopted as the foundation of the steel tower structure 3. As shown in FIG. As shown in the figure, the foundation structure 11 includes steel sheet piles 12, which are driven into the ground G,.
And a mat slab 13 supported by a steel sheet pile 12.

The sheet pile 12 is provided such that its lower edge 12a reaches the lower layer 14 in the ground G, and its upper edge 12b is integrated with the mat slab 13 to form the mat slab 13 Is supported.

Further, the mat slab 13 is used for the steel tower structure 3.
. Are supported integrally by a single mat slab 13.

The upper layer 16 of the ground G located around the mat slab 13 is subjected to ground improvement such as a sand compaction pile from the viewpoint of ground liquefaction countermeasures and ground stabilization countermeasures such as supporting force. ing. On the other hand, the ground G located below the mat slab 13 is not subjected to ground improvement.

In the basic structure 11 having such a configuration, when a wind load or the like acts on the tower structure 3, the tower structure 3 is caused to fall by the weight of the mat slab 13 and the circumferential friction of the steel sheet pile 12 when the tower structure 3 falls. It can be prevented by pull-out resistance. As a result, the weight of the mat slab 13 can be reduced as compared with the conventional mat foundation, and as a result, the thickness of the bottom slab can be reduced, and concrete work, excavation work, temporary work, construction work, and the like can be performed. Can be reduced. In addition, since it is not necessary to perform the ground improvement on the ground below the mat slab 13, it is advantageous also in the ground improvement work. Further, since the weight of the mat slab 13 can be reduced, the settlement amount of the foundation can be reduced as compared with the related art.

Further, in the foundation structure 11, the ground G below the mat slab 13 is surrounded by the steel sheet pile 12, thereby suppressing liquefaction of the portion surrounded by the steel sheet pile 12 during an earthquake. Can be highly secure.

The examination of whether the basic structure 11 can be adopted and the determination of the design items of each part of the basic structure 11 are performed based on the flowchart shown in FIG.

That is, in FIG. 3, the reaction force of the steel sheet pile 12 is calculated by assuming the shape of the foundation structure 11 (step S1) by using the applied load (wind load, etc.) of the tower structure 3 (step S1). Step S2), comparing the pushing force and the allowable supporting force of the steel sheet pile 12 among the obtained reaction forces (Step S3),
If the pushing force is small, it is designed as a pile foundation (step S4). On the other hand, if the pushing force is large, it is determined whether or not a pulling force is generated among the obtained reaction forces (step S5).

When it is determined that a pulling force is generated,
The drawing force acting on the steel sheet pile 12 is compared with the allowable supporting force of the steel sheet pile 12 (step S6). If the drawing force is larger, the process returns to step S1 and the assumption of the basic shape is redone. . When it is determined that the pulling force is smaller, the frictional resistance of the steel sheet pile 12 is considered (step S7).

On the other hand, if it is considered that no pulling force is generated, the steel sheet pile 12 is designed without regard to the pulling resistance (step S8).

Next, when the frictional resistance of the steel sheet pile 12 is considered in step S7, and in step S8
In any case where the pull-out resistance of the steel sheet pile 12 is neglected in (3), the stability calculation of the supporting force, overturn, sliding, etc. is performed (Step S9), and it is determined whether the foundation structure 11 is stable (Step S10). . Here, regarding the supporting force and the fall, the analysis is performed by focusing on the lower end of the mat slab 13. The allowable bearing capacity of the ground is determined with respect to the lower end of the mat slab 13 and the lower edge 12a of the steel sheet pile 12, and in the case where there is a weak layer in the ground G further below the lower edge 12a of the steel sheet pile 12. In addition, the bearing capacity of the weak layer is also determined. When it is determined that the sheet pile 12 is stable, the steel sheet pile 12 is designed (step S11), and based on this, it is determined whether the bending stress of the steel sheet pile 12 is within an allowable range. (Step S1
2).

If the bending stress of the steel sheet pile 12 is within the allowable range, the bottom slab, ie, the mat slab 1
The design of No. 3 is performed using an elastic bearing upper beam model or a friction pile model or the like (step S13), and based on this, it is examined whether or not the reinforcing bars can be arranged in the mat slab 13 (step S13). Step S14).

In step S14, the mat slab 13
If it is determined that rebar arrangement is possible, the subsidence amount is calculated in step S15, and the design of the foundation structure 11 is completed.

If it is not determined in step S10 that the basic structure 11 is stable, the process proceeds to step S10.
In step S12, when it is determined that the bending stress of the steel sheet pile 12 is not within the allowable range, and when it is determined that it is not possible to arrange the reinforcing bar in the mat slab 13 in step S14, step S1 is performed again. And the assumption of the basic shape is redone.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and other configurations may be adopted as necessary for design or the like. Is also possible.

For example, the basic structure 11 'shown in FIGS.
Is an example in which a mat slab 15 having a hollow inside is employed instead of the mat slab 13 of the above embodiment. As shown in the figure, this mat slab 15
Has a configuration in which a certain area when viewed in a plan view is filled with earth and sand S in a hollow interior.

In the basic structure 11 'having such a structure, since the inside of the mat slab 15 is hollow, the load acting on the area below the mat slab can be further reduced, and as a result, The settlement amount can be further reduced. Furthermore, since a certain area in the plan view is filled with earth and sand inside the mat slab 15, even when an eccentric load is applied, the load acting on the area below the mat slab 15 is substantially constant. , Whereby uneven settlement can be prevented, and the stability of the tower structure can be further increased.

[0030]

As described above, in the basic structure of a building according to the first aspect, when a wind load or the like acts on the tower-like building, the falling of the building together with its own weight of the mat slab, This can be prevented by pulling resistance due to friction of the peripheral surface of the steel sheet pile. As a result, the weight of the mat slab can be reduced compared to the conventional mat foundation, and as a result, the thickness of the bottom slab can be reduced, and concrete work, excavation work, temporary work, construction work, etc. can be reduced. can do. In addition, since the ground below the mat slab is surrounded by steel sheet piles, it is not necessary to improve the ground below the mat slab as a measure against liquefaction, which is advantageous in terms of ground improvement work. Further, since the weight of the mat slab can be reduced, the settlement amount of the foundation can be reduced as compared with the related art.

In the foundation structure for a building according to the second aspect, since the inside of the mat slab is hollow, the load acting on the area below the mat slab can be further reduced, and as a result, The settlement amount can be further reduced.

In the foundation structure for a building according to the third aspect, since a predetermined area in a planar view is filled with earth and sand inside the mat slab, the eccentric load acts on the mat slab. Also, the load acting on the area below the mat slab can be kept almost constant,
Thereby, uneven settlement can be prevented, and the stability of the tower structure can be further increased.

[Brief description of the drawings]

FIG. 1 is an elevational sectional view of a basic structure schematically showing an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a flowchart showing a procedure for determining whether or not to adopt the basic structure of the present invention and design items of each unit.

FIG. 4 is an elevational sectional view of a basic structure schematically showing another embodiment of the present invention.

FIG. 5 is a sectional view taken along the line II in FIG. 4;

FIG. 6 is an elevational sectional view of a basic structure schematically showing a conventional technique of the present invention.

FIG. 7 is a plan view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed area 2 Ground improvement soil 3 Steel tower structure (building) 4 Leg 5 Mat slab 11, 11 'Foundation structure 12 Steel sheet pile 12a Lower edge 12b Upper edge 13, 15 Mat slab 14 Lower layer 16 Upper layer G Ground S Earth and sand

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuaki Ishikawa 1 Higashi-Shinmachi, Higashi-ku, Nagoya City, Aichi Prefecture Inside Chubu Electric Power Company (72) Inventor Mamoru Kawabe 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation Co., Ltd. (72) Inventor Haruo Kubo 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Nobuyuki Yui 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Toshiyuki Nakasa 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation F-term (reference) 2D046 DA36

Claims (3)

[Claims] 1. All towers of a tower-like building are supported by a single mat slab, and a steel sheet pile is driven into the ground below the mat slab, and at least one of the mat slabs is provided. A base structure of a building, wherein a portion is supported by an upper edge of the steel sheet pile. 2. The basic structure of a building according to claim 1, wherein at least a part of the mat slab is formed hollow. 3. The foundation structure of a building according to claim 2, wherein a predetermined area is filled with earth and sand inside the hollow mat slab when viewed in a plan view. The basic structure of a building.