JP2003064698A - Pile foundation structure having enhanced horizontal frictional force of foundation bottom surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pile foundation structure constructed so that it can always hold the horizontal frictional force of building foundation bottom surface at a constant level despite ground subsidence. SOLUTION: Foundation slab of a building is constructed in a vertically double structure, with the top foundation slab made with the building and fixed by the upper ends of supporting piles through penetration, and the bottom foundation slab separated from the top one is constructed on ground so as to be able to settle on the ground. These top and bottom double slabs are arranged in such a relation that horizontal forces can be transmitted to them in all directions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a pile foundation structure in which a foundation portion of a building that is supported by support piles and does not substantially sink is rooted in the ground.
The present invention relates to a pile foundation structure constructed so that the horizontal frictional force of the bottom surface of a building can be maintained at a constant level even if the ground subsides.

[0002]

2. Description of the Related Art Conventional pile foundation structures are designed to support a building with support piles whose ends reach a support layer, and the piles are designed to bear all vertical forces due to the weight of the building. The ground is designed and constructed so that it does not bear the vertical force even if the bottom of the foundation of the building is in contact with the ground.

Regarding the horizontal force at the time of an earthquake, even if the bottom surface of the foundation of the building is embedded, the support piles still bear the total horizontal force, and the horizontal resistance of the ground contacting the bottom surface of the foundation is ignored in the design. There is. The reason is that even if the surface ground subsides, the support piles are unlikely to subside, and as a result the bottom surface of the foundation and the ground are separated, and horizontal forces may not be transmitted. I do not expect the horizontal resistance of.

For this reason, the support pile is designed to have a cross-section so as to ensure resistance to horizontal force as well as vertical force. When the building is soft and the scale of the building is large, the design horizontal force is considerably large, and the cross-sectional area of the support pile is often determined by the horizontal force. Therefore, as the performance of the support pile, a thick support pile is required, and more than one must be installed, resulting in an increase in cost.

Therefore, a technique for ensuring the horizontal resistance of the bottom surface of a pile foundation building is disclosed as follows.

(I) Japanese Unexamined Patent Publication No. 2000-303482 discloses, as a method for increasing the frictional force on the bottom surface of the foundation, providing a projection on the bottom surface of the foundation to increase the surface area in contact with the ground. (II) JP-A-10-331173 and JP-A-20
In 01-64982 gazette, the head of the support pile constructed in the ground and the lower part of the structure are trimmed so that they can move relative to each other in the up-and-down direction, and an interposing member is provided between them to prevent an earthquake. It prevents the building from floating and keeps the horizontal resistance of the bottom of the foundation to prevent damage to the building and foundation piles. (III) In Japanese Unexamined Patent Publication No. 10-331483, a building that is cut off from a pile foundation is constructed, and a friction damper means, an energy absorbing means, and a horizontal transmission member are provided between the underfloor space of the building and the pile foundation. The horizontal force is transmitted to the ground surface through the bottom surface of the foundation to absorb the energy during the earthquake in the underfloor space of the building.

[0007]

However, it is difficult to say that the above-mentioned prior art is a pile foundation structure that copes with ground subsidence. The above technique (I) is effective in normal times when the bottom surface of the foundation is in contact with the ground surface, but when the ground surface is below the projection provided on the bottom surface of the foundation due to ground subsidence, the effect of the above-mentioned projection is completely eliminated. I can't show it. In other words, the horizontal frictional force borne by the foundation bottom becomes almost zero.

Further, regarding (II) and (III),
When the bottom surface of the foundation and the ground surface are separated due to ground subsidence, no horizontal force is transmitted to the ground surface. Therefore,
It is clear that the horizontal force that the support piles bear increases and that many problems occur in earthquake resistance during an earthquake.

Therefore, an object of the present invention is to make full use of the horizontal frictional force of the ground surface so that both the supporting pile and the bottom surface of the foundation can bear the building inertia force and the horizontal force received from the ground surface caused by an earthquake. A pile foundation constructed by devising the structure of the foundation slab of the foundation building and using a foundation slab that moves downward together with the ground due to ground subsidence so as to always bear a certain amount of horizontal frictional force that resists horizontal force. To provide the structure.

A second object of the present invention is to prevent the lowering of the horizontal frictional force due to the lifting of the lower base slab by making the structure that fills the gap between the upper and lower base slabs caused by the subsidence. Also, by applying a compulsory pushing down force to the lower foundation slab to ensure a certain level of horizontal frictional force even on the ground where it is difficult to secure horizontal force, the horizontal force that the support piles bear An object of the present invention is to provide a pile foundation structure capable of reducing the number of support piles and reducing the diameter thereof.

[0011]

[Means for Solving the Problems] As means for solving the above-mentioned prior art, a pile foundation structure having an increased horizontal frictional force on the bottom surface of the foundation according to the invention described in claim 1 is a building supported by support piles. In the pile foundation structure in which the foundation part of is built in the ground, the foundation slab of the same building is constructed in two layers, the upper foundation slab is integrated with the building, and the upper end of the support pile is attached to the foundation slab. It is embedded and fixed, the lower foundation slab that is cut off from the upper foundation slab,
The foundation slab is constructed so that it can sink together with the ground on the ground, and the upper and lower double foundation slabs are arranged in a relationship capable of transmitting a horizontal force between them in all directions of 360 °.

According to the invention described in claim 2, in the pile foundation structure in which the horizontal frictional force of the bottom surface of the foundation is increased, horizontal force can be transmitted from the lower foundation slab to the upper foundation slab. A receiving part is provided to receive the horizontal force transmission part between the upper and lower base slabs, and a sliding member is interposed at the horizontal force transmission part so that only the horizontal force can be transmitted.

According to a third aspect of the present invention, in the pile foundation structure in which the horizontal frictional force of the bottom surface of the foundation is increased, the horizontal frictional force with the ground is amplified on the bottom surface of the lower foundation slab. It is characterized in that a convex protrusion is formed.

According to a fourth aspect of the present invention, in the pile foundation structure in which the horizontal frictional force of the bottom surface of the foundation is increased according to the first or second aspect, the granular body filling the gap between the upper and lower foundation slabs is on the upper side. The upper and lower foundation slabs are housed in the receiving portion of the foundation slab and are characterized in that horizontal forces are transmitted through the granular bodies interposed therebetween.

According to a fifth aspect of the invention, in the pile foundation structure in which the horizontal frictional force of the foundation bottom surface is increased according to the first or second aspect, the wedges for filling the vertical gap between the upper and lower foundation slabs are vertical. It is characterized in that it is installed downward and follows the lower foundation slab that sinks together with the ground, and the wedge descends to transmit horizontal force.

According to a sixth aspect of the present invention, in the pile foundation structure in which the horizontal frictional force of the bottom surface of the foundation is increased according to the first or second aspect, the inner peripheral surface portion of the receiving portion in the upper foundation slab is sunk. It is characterized in that a plurality of non-return check rods for pressing the upper surface of the lower foundation slab are freely provided in the vertical direction.

According to the invention described in claim 7, in the pile foundation structure in which the horizontal frictional force of the foundation bottom is increased according to claim 1 or 2, a jack is installed vertically between the upper and lower foundation slabs. The feature is that the pressure between the lower foundation slab and the ground is always kept constant by the pushing force of the jack.

The invention described in claim 8 is the pile foundation structure in which the horizontal frictional force of the foundation bottom is increased according to claim 1 or 2, in which a pressure bag is placed between the upper and lower foundation slabs. It is characterized in that the pressure between the lower foundation slab and the ground is always kept constant by the expansion force of the pressure bag body.

[0019]

Embodiments and Examples of the Invention Next, embodiments of a pile foundation structure according to the present invention will be described with reference to the drawings. This pile foundation structure is a pile foundation structure in which the foundation part of the building supported by the support piles is embedded in the ground, and in particular, even if the ground subsides, the horizontal frictional force of the bottom surface of the foundation of the building is kept constant. It is suitably implemented as a pile-structured building that is kept in the height.

In the pile foundation structure shown in FIG. 1, the foundation slab of the building 2 is an upper foundation slab 2b integrally formed with the building 2 and a lower foundation slab 3 which is a separate body. It's built in double up and down. The upper foundation slab 2b and the building 2 are constructed so as to reach the underground support layer 6, and are supported by the support piles 1 whose upper ends are fixed to the upper foundation slab 2b. Upper and lower double slab 2b
And 3 are the ground surface G. L. It is deeply embedded deep into the ground.

The lower foundation slab 3 is constructed so as to be cut off from the upper foundation slab 2b and directly subsided on the ground below the upper foundation slab 2b together with the ground. 1 (a) and 1 (b), the lower foundation slab 3 is formed on the upper foundation slab 2b,
It is constructed in such a manner that a horizontal force can be transmitted in all directions of 360 ° in the receiving portion 4 having a bowl shape downward and having the same planar shape (quadrangle in the illustrated example). A sliding member 5 (slider) that transmits a horizontal force but does not transmit a vertical force is interposed between the vertical wall surfaces between the upper and lower base slabs 2b and 3 (the invention according to claim 2). The sliding member 5 is made of polytetrafluoroethylene for reducing the vertical sliding resistance,
Styrofoam, iron plate, etc. can be used, which facilitates subsidence of the lower foundation slab 3 by accommodating even a slight subsidence.

Therefore, the upper foundation slab 2b and the building 2 supported by the support piles 1 do not go down even if the ground subsides, but the lower foundation slab 3 subsides together with the ground and becomes Always maintain a certain amount of frictional force. Therefore, with respect to the horizontal force at the time of an earthquake, the design can be made by sufficiently considering the resistance force due to the frictional force (weight × friction coefficient) between the lower foundation slab 3 and the ground.

Next, in the pile foundation structure shown in FIG. 2, a protrusion 7 is formed on the bottom surface of the lower foundation slab 3 constructed so as to be able to sink together with the ground, so as to secure a horizontal frictional force with the ground. The embodiment is shown (the invention according to claim 3). Uplift 7
This is to secure the frictional force between the lower foundation slab 3 and the ground due to the dowel effect (bearing pressure).

In the pile foundation structure shown in FIG. 3, the receiving portion 4 of the upper foundation slab 2b and the lower foundation slab 3 are provided with the concavities and convexities 8 which are fitted to each other when seen in a plan view. 3 shows an embodiment in which horizontal forces are transmitted as shear forces.

Next, the pile foundation structure shown in FIG.
It shows an embodiment in which a granular body A is provided between the upper surface of the lower base slab 3 and the receiving portion 4 of the upper base slab 2b. The granules A are promptly submerged when the lower foundation slab 3 is subsided due to ground subsidence, and the upper and lower foundation slabs 2b and 3 are immediately formed.
As shown in an enlarged view, the gaps are generated in the gaps between the two, filling the gaps tightly, preventing inconvenience that the lower base slab 3 floats up, and transmitting the horizontal force to the upper and lower base slabs.
Therefore, the upper surface of the lower base slab 3 is formed as an inclined surface at an angle at which the granular material A easily flows down automatically. on the other hand,
The receiving portion 4 is provided with a holding portion 4b that is substantially parallel to the upper surface (sloping surface) of the lower base slab 3. The granular body A
As such, sand grains, boulders, steel grains and the like can be used.

The pile foundation structure shown in FIG. 4 (b) is between the inclined upper surface 3b around the lower foundation slab 3 and the inclined surface 4c formed on the peripheral side surface of the receiving portion 4 of the upper foundation slab 2b. It shows an embodiment in which the wedge B is installed vertically downward. Like the granular body A, the wedge B quickly slides down into the gap between the upper and lower foundation slabs 2b and 3 as shown in the enlarged view when the lower foundation slab 3 sinks due to ground subsidence. To prevent inconvenience of the lower foundation slab 3 from floating and to transmit horizontal force to the upper and lower foundation slabs. Therefore, the wedge B is formed into a shape that can be fit tightly into the gap between the inclined upper surface 3b around the lower foundation slab 3 that sinks together with the ground and the inclined surface 4c formed on the peripheral side surface of the receiving portion 4.

The pile foundation structure shown in FIG. 4 (c) is
An embodiment is shown in which a check member C that automatically protrudes inward as the lower foundation slab 3 sinks is provided on the inner peripheral surface of the receiving portion 4 in a plurality of stages in the vertical direction. Check member C
Is pushed out by the pushing force of the spring 9 on the back surface and abuts on the upper surface of the lower base slab 3. Therefore, when the lower foundation slab 3 sinks downward along with the ground subsidence, the check member C at the height position corresponding to the upper surface of the lower foundation slab 3 rapidly moves.
The base slab 3 is pushed out by the above to press the upper surface of the base slab 3 to prevent the base slab from being lifted and to secure horizontal frictional force between the lower base slab 3 and the ground.

Next, an embodiment will be described in which it is difficult to secure a horizontal force, for example, a horizontal friction force is secured in sandy ground. First, the pile foundation structure shown in FIG. 5A shows an embodiment in which the jack D is vertically installed between the upper and lower foundation slabs 2b and 3. The jack D applies a forced pushing force to the lower foundation slab 3 to secure a horizontal frictional force with the ground.

The pile foundation structure shown in FIG. 5 (b) shows an embodiment in which a pressure bag E is placed between the upper and lower foundation slabs 2b and 3. A fluid such as water or mortar is supplied to the pressure bag E from the ground side to expand the pressure bag E, and the expansion force thereof forcibly pushes down the lower base slab 3 to secure a horizontal friction force. It is a composition.

In the pile foundation structure shown in FIG. 5 (c), the anchor material F is driven into the ground from the upper surface of the lower foundation slab 3 to transmit the horizontal force of the ground to the lower foundation slab 3 to make it horizontal. The embodiment which secures a frictional force is shown. The lower end portion of the anchor material F is made to enter a storage portion that allows subsidence and has a structure corresponding to the subsidence of the lower base slab 3. Therefore,
The base slab 3 on the lower side can secure a certain amount of resistance force against the horizontal force at the time of the earthquake or even if the ground subsidence occurs.

The pile foundation structure shown in FIG. 5 (d) is
Although the embodiment in which the jack D and the anchor material F are used in combination is shown, the pressure bag E instead of the jack D can be used in combination.

Although the embodiments have been described above with reference to the drawings, the present invention is not limited to the embodiments shown in the drawings. For example, the material of the lower foundation slab 3 is not limited to reinforced concrete, and improved ground can be used. It can also be applied. Further, the arrangement of the lower base slab 3 is not limited to the example shown in the drawing, and a plurality of the base slabs 3 may be provided in a grid pattern between the support piles in accordance with the situation of the ground surface. Furthermore, when it is judged that all the designed horizontal force can be supported by the frictional force of the foundation slab, the horizontal force is transmitted to the support pile by using a pin or roller instead of a rigid connection between the support pile and the foundation slab. Since it can be suppressed, the support pile can have a cross-sectional design only for vertical force.

[0033]

According to the pile foundation structure in which the horizontal frictional force of the bottom surface of the foundation according to the present invention is enhanced, the lower foundation slab moves downward together with the ground as the ground subsides. However, the horizontal frictional force that resists the horizontal force can always be maintained at a certain level, and can be resisted by both the support pile and the bottom surface of the foundation during an earthquake. Therefore, it is possible to provide a pile foundation building in which the horizontal frictional force between the lower foundation slab and the ground is sufficiently taken into consideration.

Further, it is possible to automatically fill the gap between the upper and lower foundation slabs due to the subsidence of the ground to prevent the lowering of the horizontal friction force due to the lifting of the lower foundation slab. Further, the horizontal frictional force can always be maintained at a constant magnitude even on the ground where it is difficult to secure a horizontal force by applying a forced pushing force to the underlying slab. Therefore, the horizontal force borne by the support piles can be reduced, and the diameter of the support piles and the number of the support piles can be reduced.

[Brief description of drawings]

FIG. 1A is an elevation view showing a pile foundation structure in which a horizontal frictional force of a bottom surface of the foundation according to the present invention is enhanced. b is a top view of a.

FIG. 2 is an elevational view in which a protrusion is provided on the bottom surface of a lower foundation slab.

FIG. 3 is a plan view in which unevenness is provided on an outer peripheral surface of a lower base slab.

FIG. 4a is an elevational view with granules between the upper and lower foundation slabs. b is an elevation view with a wedge between the upper and lower foundation slabs. FIG. 3c is an elevation view in which a check member is provided between the upper and lower foundation slabs.

FIG. 5A is an elevation view in which a jack is installed on the upper surface of a lower foundation slab. b is an elevation view in which a pressure bag is installed on the upper surface of the lower base slab. c is an elevation view in which an anchor material is installed on the upper surface of the lower foundation slab. d is an elevation view in which a jack and an anchor material are installed together.

[Explanation of symbols]

1 support pile 2 buildings 2b Upper base slab 3 Lower foundation slab

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Junji Hamada             Chiba Prefecture Inzai City 1-5 Otsuka 1 Stock Association             Takenaka Corporation Technical Research Institute (72) Inventor Keito Takahashi             Chiba Prefecture Inzai City 1-5 Otsuka 1 Stock Association             Takenaka Corporation Technical Research Institute F-term (reference) 2D046 CA01 DA11

Claims (8)

[Claims] 1. In a pile foundation structure in which a foundation portion of a building supported by support piles is embedded in the ground, the foundation slab of the same building is constructed in double layers, and the upper foundation slab is integrated with the building. Is fixed by inserting the upper end of the support pile into the foundation slab, and the lower foundation slab, which is cut off with the upper foundation slab, is constructed so that it can sink together with the ground on the ground, The pile foundation structure having an increased horizontal frictional force on the bottom surface of the foundation, wherein the upper and lower double foundation slabs are arranged in a relationship capable of transmitting horizontal forces in all directions of 360 °. 2. An upper base slab is provided with a receiving portion for receiving a lower base slab capable of transmitting a horizontal force, and a sliding member is interposed at a horizontal force transmitting portion between the upper and lower base slabs. The pile foundation structure having an increased horizontal frictional force on the bottom surface of the foundation according to claim 1, characterized in that only the horizontal force can be transmitted. 3. The horizontal frictional force of the foundation bottom surface according to claim 1 or 2, wherein a protrusion that amplifies the horizontal frictional force with the ground is formed on the bottom surface of the lower foundation slab. Enhanced pile foundation structure. 4. A granular body for filling a gap between upper and lower base slabs is housed in a receiving portion of the upper base slab,
The pile foundation structure according to claim 1 or 2, wherein the upper and lower foundation slabs transmit the horizontal force through the granular bodies interposed therebetween. 5. A wedge is installed vertically downward so as to fill a vertical gap between the upper and lower foundation slabs, and the wedge descends following the lower foundation slab that sinks together with the ground to transmit horizontal force. The pile foundation structure with increased horizontal frictional force on the bottom surface of the foundation according to claim 1 or 2, characterized in that 6. A plurality of vertically movable check members for pressing the upper surface of the sinking lower foundation slab are provided on the inner peripheral surface portion of the receiving portion of the upper foundation slab in a vertical direction. The pile foundation structure with enhanced horizontal frictional force on the bottom surface of the foundation according to claim 1 or 2. 7. A jack is installed vertically between the upper and lower foundation slabs, and the pressure between the lower foundation slab and the ground is always kept constant by the pushing force of the jack. A pile foundation structure in which the horizontal frictional force of the bottom surface of the foundation according to claim 1 or 2 is enhanced. 8. A pressure bag is placed between the upper and lower base slabs, and the pressure between the lower base slab and the ground is always kept constant by the expansion force of the pressure bag. ,
A pile foundation structure in which the horizontal frictional force of the bottom surface of the foundation according to claim 1 or 2 is enhanced.