JPS5820822A - Concrete pile - Google Patents

Abstract

PURPOSE:To prevent the occurrence of cracks in concrete piles by attaching a columnar body having an adequate mass concentrically to the lower end of the concrete pile so as to reduce tensile stress to be generated in the pile when being driven. CONSTITUTION:Concrete 2d is packed into a space formed by a cylindrical steel plate 2a, an upper steel plate 2b, and a lower steel plate 2c to form a pile body 1. Furthermore, a cylinder 2 is formed through a partition plate 2e below the pile body 1. Then, an elastic buffer material 4 and the cylinder 2 are concentrically connected by means of a piano wire 3' extended in the lower part of the pile body 1. Thus, since ascending tensile stress wave is not joined with descending tensile stress wave inthe inside of the pile 1, no degradation due to cracking occurs in the pile body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a concrete pile that can significantly reduce excessive tensile stress generated inside the pile during pile construction using the impact method on relatively soft ground such as at the beginning of construction.

When the pile head of a concrete pile is hit, ■ appears at the top of Figure 1.
Compressive stress and tensile stress occur alternately in the pile cap. On the other hand, the compressive strength of concrete is 400 kg/cm2 or more, but the tensile strength is about 1/10 of that, and concrete piles are extremely weak against tensile stress. Therefore, when a subordinate concrete pile is driven into soft ground, the compressive stress wave generated at the pile head descends inside the pile, as shown in the lower part of Figure 1, and is reflected at the lower end of the pile, resulting in a tensile stress wave. This tensile stress wave rises as a stress wave, and this tensile stress wave then occurs at the pile cap and meets the descending tensile stress wave at There were drawbacks such as damage. For this reason, in order to prevent excessive tensile stress from occurring during pile driving in soft ground, the impact force is limited based on experience, or the strength is higher than that required to support the superstructure after pile construction. Construction has been carried out using methods such as the use of stronger piles.

This invention improves the above-mentioned drawbacks of conventional concrete piles, reduces the tensile stress generated inside the pile, allows the use of relatively low-strength piles, and improves construction efficiency by utilizing sufficient impact force. The purpose of the concrete pile of the present invention, which meets the above-mentioned purpose, is to provide a concrete pile with a diameter approximately equal to the outer diameter of the concrete pile body at the lower end of the concrete pile body. It is characterized in that cylindrical bodies having an outer diameter and an appropriate mass are attached concentrically.

Hereinafter, one embodiment of the present invention will be specifically described with reference to FIGS. 2 to 4.

1 is a concrete pile body, and the concrete pile 1 is a known prestressed concrete pile pressed with piano wire 3.

2 is a cylindrical body attached to the lower end of the concrete pile body, the space formed by the cylindrical steel plate 2a, the upper steel plate 2b and the lower steel plate 2c is filled with concrete 2d, and a partition plate 2e is provided at the bottom. It is something. The upper part of the cylindrical steel plate 2a protrudes to form a cylindrical part 2a' whose inner diameter is slightly larger than the outer diameter of the concrete pile body 1, and is fitted into the lower part of the concrete pile body 1. Moreover, the cylindrical body 2 is a piano wire 3 which is an extension of the piano wire 3 of the concrete pile body 1.
', it is concentrically crimped and attached to the lower end surface of the concrete pile main body 1 via the elastic buffer material 4 and the partition plate 2e.

As shown in FIG. 4, the elastic cushioning material 4 is made up of square-shaped spring steel tension rings 5 and compression rings 6 alternately stacked and crimped to form a small yet strong cushioning body. In the figure, 7 is a washer and 8 is a tightening nut.

In this invention, when a compressive stress wave traveling inside a pile is reflected at the free end, it is reflected as a tensile stress wave, but when an object with a considerable mass is in contact with the lower end of the pile, it is reflected again. Focusing on the fact that it is reflected as a compressive stress wave, a solid cylindrical body is attached closely to the lower end of the pile to prevent harmful tensile stress from occurring within the pile.

In other words, in Fig. 2, when the compressive stress wave caused by the impact travels downward from the upper end of the concrete pile body and reaches the lower end, a part of it is reflected, moves up inside the concrete pile body as a compressive stress wave, and is reflected again at the upper end. Then, it becomes a weak tensile stress wave, which descends and disappears while gradually attenuating. On the other hand, the other part descends inside the cylindrical body 2 as a compressive stress wave, is reflected at the lower end, rises as a tensile stress wave, is reflected again at the upper end of the cylindrical body 2, becomes a weak compressive stress wave, and continues the same process. The reflection returns to ■ and attenuates and disappears.

In this way, the rising tensile stress waves and the descending tensile stress waves do not meet and overlap inside the concrete pile body 1. Note that when the compressive stress wave from the concrete pile body 1 passes through, the cylindrical body 2 slightly descends with respect to the concrete pile body 1 against the pressure force of the elastic buffer material 4, but immediately the concrete pile The cylindrical portion 2a' is in close contact with the lower end of the main body 1, and maintains the concentricity of the cylindrical body 2 and the concrete pile main body 1.

The concrete pile of this invention has a cylindrical body having an outer diameter approximately equal to the outer diameter of the concrete pile body and an appropriate mass attached concentrically to the lower end of the concrete pile body, as described in detail. Therefore, large tensile stress does not occur inside the concrete pile, which prevents damage to the concrete pile during driving, and reduces impact force unnecessarily to improve construction efficiency. It has many effects such as no need to lower the compressive strength and no need to use expensive concrete piles with more compressive strength than necessary, and can be extremely useful and widely used.

[Brief explanation of the drawing]

Figure 1 is an operational diagram showing the movement of stress waves generated in a conventional concrete pile. FIG. 2 is an operational diagram showing the movement of stress waves generated in a concrete pile according to the present invention. FIG. 3 is a partially broken sectional view of an example of a concrete pile of the present invention. FIG. 4 is a detailed view of the elastic cushioning material shown in FIG. 3. 1... Concrete pile body 2... Cylindrical body 2c... Lower steel plate 2a... Cylindrical steel plate 2d... Concrete 2a'... Cylindrical part
2b Partition plate 2b...Top steel plate 3.3'...Piano wire 4...Elastic buffer material 5...Tension ring 6...Compression ring 7...Washer 8...Tightening nut patent Applicant Tadahiko Miura

Claims (3)

[Claims] (1) A cylindrical body having an outer diameter approximately equal to the outer diameter of the concrete pile body and having an appropriate mass is concentrically attached to the lower end of the concrete pile body. Concrete piles constructed using the impact method. (2) The impact according to claim 1, characterized in that the cylindrical body is attached to the lower end of the concrete pile body by crimping it with a piano wire extending from the concrete pile body through a heating material. Concrete piles constructed using construction methods. (3) Claims 1 and 2, characterized in that the cylindrical body has a cylindrical part formed on the upper part that fits with the outer diameter of the concrete pile main body while maintaining a pincushion. Concrete piles constructed using the impact method described in Section 1.