JPH0352817Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a concrete pile, and particularly to a concrete pile in which a small-diameter lower pile is connected to the lower end of the concrete pile.

[Conventional technology]

When a horizontal force acts on a pile driven into the ground, it is thought that the moment that acts within a range of about 10m from the ground surface is the largest.

Therefore, it is not only economical to use a large-diameter upper pile and connect a small-diameter pile to the lower end of this upper pile, that is, one with a diameter that provides sufficient support, but also to improve construction efficiency. It also becomes easier.

For this reason, conventionally, concrete piles as shown in FIGS. 1 to 3 have been devised.

In other words, the one shown in Fig.
Disclosed in the publication No. 1 and 2.
and a joint 3 that joins both 1 and 2, and the joint 3 consists of a large diameter part 3a, a small diameter part 3b, and a tapered part 3c in between.
A large-diameter upper pile 1 is connected to the small-diameter portion 3b, and a small-diameter lower pile 2 is connected to the small-diameter portion 3b, and is reinforced with anchor reinforcement bars 4 and 5 inside. 1 is designed so that prestress is introduced by tension steel material 6.

The one shown in Fig. 2 is disclosed in Japanese Utility Model Publication No. 51-17682, and has a tapered portion 2' that gradually becomes larger in diameter and thicker toward the upper end of the small-diameter lower scoop 2'. A is integrally formed, and an upper pile 1 having the same diameter as this is connected to the upper end surface.

Furthermore, the one shown in FIG. 3 is disclosed in Japanese Utility Model Publication No. 51-22485, and contrary to the one shown in FIG. It has a structure in which a tapered part 1'a is integrally formed, and a lower peg 2 of the same small diameter is connected to the lower end surface of the tapered part 1'a.

[Problems with conventional technology]

However, in the case shown in FIG. 1, since the joint 3 is a separate member, it is not only troublesome to construct, but also concentrated stress is generated at the joint portion of the joint 3 with the upper pile 1.

Furthermore, in a stake with such a configuration, the diameter of the stake changes suddenly, that is, at the joint 3.
Concentrated stress occurs near the tapered portion 3c,
For example, it is said that the magnitude of stress that occurs at geometrically discontinuous locations is several times greater than the stress that occurs at locations that are continuous.

Therefore, the joint 3 is intensively subjected to two loads: the concentrated stress generated at the joint portion and the concentrated stress generated near the tapered portion 3c. Although it is installed, there are problems in terms of strength.

Furthermore, as mentioned above, there is local disturbance in the concentrated stress occurring near the tapered portion 3c, but this disturbed stress is caused by the small diameter portion 3b.
and is transmitted to the vicinity of the upper end of the lower pile 2 via the joint at its lower end.

Therefore, near the upper end of the small-diameter lower pile 2, which has a weaker supporting capacity than the upper pile 1, the concentrated stress generated at the joint with the joint 3 and the concentrated stress generated near the tapered portion 3c are generated. However, there is a problem in that it cannot withstand locally disturbed concentrated stress and may be destroyed or damaged.

Furthermore, the case shown in FIG. 2 is also used for the same reason as the conventional example shown in FIG.
Concentrated stress occurring at the joint with the lower part 2'
There is a problem in that the area near the upper end of the lower pile 2' may be destroyed or damaged due to locally disturbed concentrated stress generated near the tapered part 2'a.

Furthermore, the conventional device shown in FIG. 3, like the one shown in FIG. There is a problem in that the vicinity of the upper end of the lower pile 2 may be destroyed or damaged due to the disturbed concentrated stress.

[Means for solving problems]

In order to solve these conventional problems, the applicant first filed Utility Application No. 55-181158 (Utility Model Application No. 57-105335).
However, with this invention, problems regarding the strength of the tapered portion and the small diameter portion and the problem of the optimal length of the small diameter portion were not resolved.

In view of the above, the present invention not only improves the ease and reliability of construction without using joints, but also eliminates local stress disturbances that occur near the tapered part of the pile. The purpose of this is to provide a structure that prevents the destruction or damage of the small-diameter pile connected to the lower end of the pile. A tapered part and a small diameter part are integrally connected to the tapered part, and the length of the small diameter part is approximately the same as the diameter of the small diameter part, and the inside of the tapered part and the small diameter part is The concrete pile is characterized by having reinforcing bars thicker than the pile body.

〔Example〕

Hereinafter, the present invention will be explained in detail based on the embodiments shown in FIGS. 4 and 5. In the figures, numeral 10 is a pile body, which is used as a top pile.

At the lower part of the pile body 10, a tapered part 10a that gradually becomes thinner toward the bottom and a small diameter part 10b are integrally connected to the tapered part 10a.
Moreover, the length L of this small diameter portion 10b is
The length is set to be approximately the same as the diameter D of 0b.

In this way, the length L of the small diameter portion 10b is made to be approximately the same length as the diameter D of the small diameter portion 10b in order to eliminate local disturbances in concentrated stress occurring near the tapered portion 10a. It's for a reason.

In other words, the San Penan principle (basic engineering/1)
According to Mechanics of Soil, written by Hideo Shiseki, published by Gendai Rikogaku Shuppan Co., Ltd., published on May 30, 1978), local disturbances in stress are rapidly dispersed as the distance increases. It is assumed that the distance disappears at a distance equal to the maximum dimension of the cross section from the discontinuous point of the shape, and the present invention applies this principle.

Therefore, since the local disturbance of the concentrated stress generated near the tapered portion 10a has already disappeared at the lower end of the small diameter portion 10b, undisturbed stress acts on the joint end surface of the lower step 20. become,
The upper end portion of the lower pile 20 may be configured to withstand only the concentrated stress occurring at this joint.

Reference numeral 11 denotes reinforcement, which is composed of a PC steel bar 12 and a spiral reinforcement 13, and this reinforcement 11 reinforces the pile body 10, but the tapered portion 10a and the small diameter portion 10b are further provided with: In order to withstand concentrated stress with local disturbances applied to the part,
In the embodiment shown in FIG. 4, the pitch width of the spiral reinforcement 13 is made smaller, and in the embodiment shown in FIG. They are each reinforced by In the figure, 15 is an end plate, 16 is a reinforcing band, 21 is an end plate of the lower pile 20, and 22 is a reinforcing band.

In the construction example of the present invention, the lower pile 20 is first driven into the ground, and the upper end plate 21 and the pile body 1 are
0, and the periphery thereof is welded to connect both studs 10 and 20. Then, do more typing.

[Effect of idea]

As mentioned above, the concrete pile according to the present invention has a tapered part that gradually becomes thinner toward the bottom and a small diameter part that is continuous with the tapered part that gradually becomes thinner toward the bottom of the pile body, and this small diameter part. The length of the pile is approximately the same as the diameter of the small diameter portion, and the structure is such that reinforcing bars are provided in the tapered portion and the small diameter portion, which are thicker than the pile body, so construction is easy. In addition, it can sufficiently withstand concentrated stress generated near the tapered portion.

Moreover, since the local disturbance of this concentrated stress is also eliminated, there are various effects such as being able to reliably prevent destruction or damage to the small-diameter lower plinth connected to the lower end.

[Brief explanation of the drawing]

1 to 3 are right half cross-sectional front views showing different conventional examples, and FIGS. 4 and 5 are right half cross-sectional front views showing different embodiments of the present invention. DESCRIPTION OF SYMBOLS 10... Pile main body, 10a... Same tapered part, 10b... Same small diameter part, 11... Reinforcement arrangement, 12...
...PC steel bar, 13... spiral bar, 14... reinforcing reinforcing bar,
20...Go down.

Claims (1)

[Scope of utility model registration request] At the bottom of the pile body, a tapered part that gradually becomes thinner toward the bottom and a small diameter part are connected to the tapered part, and the length of this small diameter part is approximately the same as the diameter of the small diameter part. A concrete pile characterized in that reinforcing bars that are thicker than the pile body are provided in the tapered part and the small diameter part.