JPS6319651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to pile foundations for civil engineering and architectural structures, particularly to the structure of pile heads.

Prior Art Conventionally, there are two types of pile head structures: one in which the pile head is rigidly connected, and the other in which the pile head is hinged to allow rotation. However, in the case of rigid connections, the stress generated in the pile body, especially the stress applied to the pile head, is large, and the joint with the footing needs to be reinforced against earthquakes and other horizontal forces. It must be designed to withstand all axial forces.

For this reason, hinge connections may be made, for example, by interposing a bearing such as a roller on the bottom surface of the footing, or by separating the footing body and the pile head and connecting them in a hinge-like manner with a spherical unevenness that allows the pile head to rotate. It has been devised. Although these methods can reduce the need to reinforce the pile head, it is difficult to achieve a perfect hinge connection, making design and construction difficult.

Purpose of the Invention This invention was invented under the above-mentioned circumstances, and utilizes the friction between sand and steel under high pressure, the behavior of sand particles when horizontal force is applied, etc. to improve reliability. The purpose is to provide a high-quality and economical pile foundation.

Structure of the Invention Hereinafter, a pile foundation of the present invention will be explained based on an illustrated embodiment.

The embodiment shows the case of an independent footing, in which a steel plate 2 is integrally attached to the lower surface of a footing 1 made of reinforced concrete. As this steel plate 2, it is preferable to use one that has good adhesion to the concrete of the footing 1, such as a striped steel plate having an uneven upper surface. Alternatively, anchor reinforcement may be provided protruding from the upper surface of the outer steel plate 2, and after the necessary reinforcement has been arranged, concrete may be poured to integrate the outer steel plate 2.

On the other hand, an impermeable flexible plate or sheet 4 is installed at the pile head of the plurality of piles 3 that are previously driven below the footing 1 and supports the footing 1, and is placed between the steel plate 2 and the middle. They face each other with a buffer layer 5 in between. In addition to steel pipe piles, ready-made or cast-in-place concrete piles can also be used as the piles 3.

The buffer layer 5 is made of sand, gravel, etc. or a mixture of these laid down to a predetermined thickness, and it transmits the load of the upper structure directly to the piles 3, and also absorbs the horizontal force acting on the footing or the superstructure due to earthquakes, etc. It is transmitted in the form of frictional force between particles. This buffer layer 5
The optimal thickness is designed depending on the load of the superstructure, the ground contact area of the footing 1, the depth of the supporting ground, and other conditions.

Further, as the water-impermeable flexible plate or sheet 4, for example, a synthetic rubber plate or a vinyl sheet can be used. Note that it is preferable to prevent moisture from penetrating into the sand or gravel of the buffer layer 5, and for this purpose, the ends of the plate or sheet 4 are folded back to wrap the buffer layer 5.

Next, the construction procedure in this embodiment will be explained. First, the pile 3 is driven, and the plate or sheet 4 is laid so as to cover the pile head. Next, a buffer layer 5 made of sand or gravel is placed on this board or sheet 4.
Lay down. At this time, if necessary, the buffer layer 5 is vibrated to perform compaction. The plate or sheet 4 is folded back to enclose the buffer layer 5, and then the steel plate 2 is installed, the necessary formwork is assembled, and concrete for the footing 1 is poured. After demolding, the surrounding earth and sand will be backfilled.

In addition, although I have mentioned independent footings above,
It can be similarly applied to cases connected by underground beams or to cases of solid foundations.

Effects of the Invention Under the high pressure of supporting the superstructure, a buffer layer made of sand or gravel is interposed between the steel plate on the lower surface of the footing and the lower pile.
Vertical loads from the superstructure are transmitted to the piles via steel plates and buffer layers, and horizontal forces other than frictional forces are not transmitted to the piles.

Due to the phenomenon of fragmentation of sand or gravel particles, energy can be absorbed in the buffer layer against horizontal forces.

Since the footing and the pile head are separated via a buffer layer, rotation is allowed and the pile head is no longer fixed. Therefore, there is no risk of excessive bending moment acting on the pile head, and no particular reinforcement is required.

It has a relatively simple structure and is easy to construct.
Economical.

It can be applied to steel pipe piles, ready-made concrete piles, and cast-in-place concrete piles.

Fold back the ends of the pile head plate or sheet,
Since the buffer layer is wrapped around the buffer layer, moisture such as ground water is prevented from penetrating into the sand or gravel of the buffer layer, and there is no risk of impairing the function of the buffer layer.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view showing an embodiment of the pile foundation of the present invention. 1...Footing, 2...Steel plate, 3...Pile, 4...Plate or sheet, 5...Buffer layer.

Claims (1)

[Claims] 1. An impermeable flexible plate or sheet is installed on the heads of a plurality of piles driven below the footing, and a steel plate is attached to the lower surface of the footing, and the plate or sheet and the A pile foundation characterized in that a buffer layer made of sand or gravel is provided between the steel plate and the buffer layer is wrapped by folding back the end of the plate or sheet. 2. The pile foundation according to claim 1, wherein the steel plate is a striped steel plate having unevenness on its upper surface.