JPH05339940A - Cast-in-place concrete pile - Google Patents

Abstract

PURPOSE:To increase the supporting force, by providing continuous ribs to form rings at a part or the whole outer peripheral face of a cast-in-place concrete pile to actuate the shearing force of the applied ground of the pile on the outer peripheral face of the pile body. CONSTITUTION:Continuous ring-form ribs with semi-spherical section surrounding the whole periphery of a pile body 1 are provided at a part or on the whole outer peripheral face of the pile body 1 of a cast-in-place concrete pile. In this way, the bearing force of the pile can be increased because the adhesive force between the pile and the ground is not brought by the sum of frictional forces but the shearing force of the ground is actuated on the peripheral face of the pile.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of cast-in-place concrete piles.

[0002]

2. Description of the Related Art Conventionally, a pile peripheral surface resistance value of a cast-in-place concrete pile, an ultimate peripheral surface frictional force fu of the pile is expressed by the following equation as a sum of adhesion force and frictional force between the pile and soil. fu = Ca + Ph · tanδ where Ca: adhesive force between pile and ground Ph: lateral pressure acting on pile and peripheral surface δ: friction angle between pile peripheral surface and ground Generally, the ultimate peripheral surface friction force fu In order to obtain, the adhesive force between the pile and the ground is set to 0, and fu = Ph · tan
δ. Further, in order to obtain the ultimate circumferential surface frictional force fu of the cohesive soil layer, the friction angle δ of the sand layer is set to 0 and fu = Ca.

On the other hand, as a method of utilizing the strength of the ground as it is, a twisted pile, which is a kind of ready-made pile, has been developed in the low noise and low vibration construction method. In the case of cast-in-place pile, after burying the corrugated shell in the ground, concrete is placed inside, or the concrete is poured while gradually pulling out the corrugated shell from the ground. There is a method to inject cement milk around.

[0004]

However, even if a screwed pile is buried in the ground by screwing, soil between adjacent ribs on the outer circumference of the pile is disturbed, and the yield strength of the ground between the ribs is expected. It cannot be done and the pile peripheral strength is adhesive force, frictional force, or less, and the shearing force of the soil originally possessed by the ground cannot be expected. The same applies to the above-mentioned conventional method using a corrugated shell.

Further, in a normal straight pile (straight pile), as the ground strength increases, the solidification property of soil increases,
Since slumping occurs between the outer peripheral surface of the pile and the surrounding ground, the pile peripheral strength corresponding to the strength of the ground cannot be expected. On the other hand, in order to increase the bearing capacity of the pile, a method of widening the tip of the pile is usually adopted, but considering the amount of subsidence of the pile, the bearing capacity corresponding to the widening cannot be expected.

The present invention has been proposed in view of the above problems of the prior art, and the object thereof is to significantly increase the bearing strength of cast-in-place concrete piles according to the ground strength. The point is to provide a cast-in-place concrete pile that can control the amount of subsidence at the pile head.

[0007]

In order to achieve the above object, a cast-in-place concrete pile has a ring-shaped continuous rib provided on a part or all of the outer peripheral surface of the pile body, and the continuous rib is formed on the outer peripheral surface of the pile body. Construction of piles It is configured to exert a shearing force on the ground.

[0008]

As described above, the cast-in-place concrete pile according to the present invention is provided with a continuous rib that surrounds the entire circumference of the pile-body in a ring shape in a part or all of the outer peripheral surface of the pile-body, so that Peripheral surface strength, by applying the shearing force of the soil on which the concrete pile is constructed on the pile circumferential surface, not the sum of the adhesive force and the frictional force between the pile and the soil on which the pile is constructed. The bearing capacity of the pile can be greatly increased.

If a larger supporting force is required,
A ring-shaped continuous rib is provided on the outer peripheral surface of the pillar widened pile.

[0010]

The present invention will be described below with reference to the illustrated embodiments. In FIG. 1, a ring-shaped continuous rib 2 having a hemispherical cross section is provided on the outer peripheral surface of a pile body 1 of a cast-in-place concrete pile so as to surround the entire circumference of the pile body 1 partially or entirely. In the embodiment shown in FIG. 2, the ribs have a pyramidal cross section. In the embodiment shown in FIG. 3, the lower surface of the rib of FIG. 3 is formed into a flat surface.

The balance equation as the external force and the resistance of the pile in the cast-in-place concrete pile is shown by the following equation (1).
(Refer to FIG. 4) P = R _F + R _P (1) where P: External force or ultimate bearing force of pile (tf) R _F : Peripheral friction force of pile (tf) R _P : Tip bearing force of pile (Tf) Further, the peripheral frictional force R _F of the pile is expressed by the following formula. (Fig. 4
Reference) R _F = UΣf _i · L _i (2) where U: Perimeter of pile (m) f _i : in the i-th soil layer when the soil layer is divided into n equal parts in the depth direction Peripheral frictional stress of pile (tf / m ² ) L _i : Pile length in the i-th soil layer (m) Therefore, peripheral frictional stress f of the pile in the i-th soil layer f
_i is given by the following equation (3) as the sum of the adhesive force and the frictional force between the pile and the soil around the pile.

F _i = Ca + Ph · tan δ (3) where f _{i is the} frictional stress on the peripheral surface of the i-th soil layer (tf /
m ² ) Ca: Adhesive force between the pile and the ground (tf / m ² ) Ph: Lateral pressure acting on the peripheral surface of the pile (tf / m ² ) (Ph = P _K · P _V , K: Lateral pressure coefficient, P _V : Overlay pressure) δ: Friction angle between pile peripheral surface and ground (°) In formula (3), the ultimate peripheral surface frictional force of clay ground is f _i = Ca when the friction angle δ is 0. Shown.

F _i = Ca = αCu (4) where α: Adhesive force coefficient (α <1) Cu: Average undrained shear strength of soil in the embedded part of piles and ultimate surface friction of sandy ground The degree is expressed by f _i = Ph · tan δ from the equation (3) with the adhesive force Ca being 0.

As described above, the normal pile pile surface resistance of a normal straight pile (straight pile) is that the soil has a consolidation property (cementation phenomenon) when the shear strength τ of the soil increases, so that the pile circumference is the same as that of the pile. Since shavings occur between the surface soils, hard cohesive soils, etc. are less likely to adhere to the pile material, and as the soil strength increases, the pile surface resistance decreases. On the other hand, when a ring-shaped continuous rib 2 surrounding the entire surface of the pile body 1 is provided on the outer peripheral surface of the pile body 1 as shown in the embodiment of the present invention, the shear strength of the ground represented by the following formula (5) is obtained. The pile surface resistance can be obtained according to τ.

Τ = Cu + σ · tanφ _u (5) where σ: total vertical stress Cu, φu: adhesive force and internal friction angle expressed by total stress of each of them. A comparative study shows that formula (3) is f _i = Ca + Ph · tan δ Formula (5) is τ = Cu + σ · tan φ Ph · tan δ = Pk · Pv · tan δ≈0.5 Pv ·
2/3 tanφ≈0.3 Pvtanφ Ca = αCu≈ (1.0 to 0.2) Cu. That is, f _i ≈ (1 to 0.2) Cu + 0.3P
It is represented by vtanφ≈0.3τ and, in addition, the normal pile has an upper limit for the adhesive force and the upper limit for the friction force.

The ribs are constructed by, for example, Japanese Patent Application No. 4-126203 (a pile body widening device for cast-in-place concrete piles) proposed by the present inventor.

[0017]

As described above, according to the present invention, by providing a ring-shaped continuous rib that surrounds a part or all of the outer surface of the pile body of a cast-in-place concrete pile, the entire circumference of the pile body is provided. , The shear strength of the soil around the pile, which is based on the ground strength, can be used for the resistance force on the pile peripheral surface, rather than the frictional force between the pile and the soil, thus significantly increasing the bearing capacity of the pile. be able to.

Further, according to the present invention, the supporting force of the pile is
Since it depends heavily on the peripheral surface, the support layer thickness at the tip of the pile may be thin. In particular, the strength of the cohesive ground with solidification can be evaluated as it is, which makes it possible to construct a rational and economical pile. It will be possible. By increasing the diameter of the pile body part, a larger supporting force can be obtained, and since the amount of subsidence at the pile head can be controlled, it is possible to eliminate uneven settlement of the building.

[Brief description of drawings]

FIG. 1 is a left half longitudinal sectional front view showing an embodiment of a cast-in-place concrete pile according to the present invention.

FIG. 2 is a left half longitudinal sectional front view showing another embodiment of the cast-in-place concrete pile according to the present invention.

FIG. 3 is a left half vertical sectional front view showing still another embodiment of the cast-in-place concrete pile according to the present invention.

FIG. 4 is an explanatory diagram of mechanical properties of a straight pile.

FIG. 5 is an explanatory view of mechanical properties of cast-in-place concrete according to the present invention.

[Explanation of symbols]

 1 pile structure 2 rib

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[Procedure amendment]

[Submission date] October 29, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Conventionally, a pile peripheral surface resistance value of a cast-in-place concrete pile, an ultimate peripheral surface frictional force fi of the pile is expressed by the following equation as a sum of adhesion force and frictional force between the pile and soil. fi = Ca + Ph · tan δ where Ca: Adhesive force between pile and ground Ph: Lateral pressure acting on pile and surrounding surface δ: Friction angle between pile peripheral surface and ground Generally, the limit circumferential surface friction force of sand layer fi To obtain, fi = Ph · tan with the adhesive force between the pile and the ground as 0
δ. Further, in order to obtain the limit circumferential frictional force fi of the cohesive soil layer, the friction angle δ of the sand layer is set to 0 and fi = Ca.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

F _i = Ca + Ph · tan δ (3) where f _{i is the} frictional stress on the peripheral surface of the i-th soil layer (tf /
m ² ) Ca: Adhesive force between pile and ground (tf / m ² ) Ph: Lateral pressure acting on the peripheral surface of the pile (tf / m ² ) (Ph = K · P _V , K: Lateral pressure coefficient, P _V : Top load pressure) δ: Friction angle between pile peripheral surface and ground (°) In formula (3), the ultimate peripheral surface frictional force of clay ground is indicated by f _i = Ca, where the friction angle δ is 0. Be done.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

Τ = Cu + σtanφ _u (5) where σ: total normal stress Cu, φ _u : adhesive force and internal friction angle expressed by respective total stresses. Here, equation (3) above (5) (3) Equation f _i = Ca + Ph · tan δ Equation (5) τ = Cu + σ · tan φ _u Ph · tan δ = K · Pv · tan δ≈0.5 Pv · 2
/ 3 tanφ _u ≈0.3 Pvtanφ _u Ca = αCu≈ (1.0 to 0.2) Cu. That is, f _i ≈ (1 to 0.2) Cu + 0.3P
It is represented by vtanφ≈0.3τ and, in addition, the normal pile has an upper limit for the adhesive force and the upper limit for the friction force.

[Procedure amendment 4]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 4

[Correction method] Change

[Correction content]

[Figure 4]

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (1)

[Claims] 1. A ring-shaped continuous rib is provided on a part or all of the outer surface of the pile body of a cast-in-place concrete pile so that the shearing force of the construction ground of the pile can be applied to the outer surface of the pile body. Cast-in-place concrete pile characterized by being made.