JPS6151093B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pile construction method in liquefied ground.

In soft sandy ground, the pore water pressure increases due to an earthquake, and the effective stress, which is the value obtained by subtracting the pore water pressure from the vertical stress, becomes zero, and the sand loses its shear strength and liquefies.

Conventionally, as a method to prevent this liquefaction, a construction method was developed in 1975, in which piles were driven into the casing while supplying gravel, sand, etc., and drainage was carried out through the gravel, sand, etc.
Although disclosed in Publication No. 45285, it is difficult to bring gravel or sand into the ground by driving a pile through gravel, sand, etc., and it is difficult to ensure that a permeable layer is formed around the pile. I can't expect that.

This invention is easier and more reliable to construct than the above-mentioned invention, provides more effective measures against liquefaction by replacing the ground and draining water, and does not require special mechanical equipment like the conventional consolidation method. The structure is easy to pull out and remove, and the details will be explained below using examples.

Ready-made foundation piles 1 such as steel pipe piles and concrete piles are driven into soft gravel ground A to a required depth, for example, to the supporting ground, and pile insertion holes are provided at the tips at required intervals around the foundation 1. A casing 3 provided with a bottom plate 2 is driven into the ground.

This casing 3 is made up of a plurality of plates connected by a joint 4 and tied together by a band 5, and has a spacer 6 for maintaining a required distance between the outer peripheral surface of the foundation pile 1 and the inner surface of the casing 3.

In addition, as a construction order, the casing 3 can be driven in, and the foundation pile 1 can be driven into the center of the excavation after digging. In either case, the driving depth of the casing 3 may be up to the depth of soft sandy ground.

Next, the area around the foundation pile 1 in the casing 3 is filled with highly water-permeable material such as crushed stone, gravel, or other chemical products.

Next, only the casing 3 is pulled up one by one, leaving the bottom plate 2 behind. If the pulling resistance is large, pull out the casing 3 one by one while applying vibration.

This invention has the above-mentioned structure, and replaces the sandy ground around the foundation pile, which is extremely important, with highly permeable materials such as crushed stone, gravel, and other chemical products, and drains water from the surrounding soft sandy ground. can be carried out between these materials. In particular, since a spacer is interposed between the foundation pile and the casing, and the permeable material is introduced after the spacers are buried in the ground, the permeable material can be reliably filled to a constant thickness.

Further, since the casing is divided into pieces and tied together with a band, and when the casing is to be pulled out, it is pulled up one by one, making the work easy.

[Brief explanation of the drawing]

Fig. 1, Fig. 2 a, b, Fig. 3, and Fig. 4 are vertical and cross-sectional views showing an overview of the construction process, and Fig. 5 and Fig. 6 are cross-sectional views of other embodiments. It is. A...Ground, 1...Foundation pile, 2...Bottom plate, 3...
...Casing, 4...Joint, 5...Band, 6...
...Spacer, 7...Aggregate.

Claims (1)

[Scope of Claims] 1. A bottom plate is provided at the tip, a continuous casing of multiple plates is tied together with a band, the casings are placed around the foundation pile with intervals maintained by spacers, and the casing is placed in the ground. A pile construction method for liquefied ground, characterized in that the casing is filled with a highly permeable material around the foundation pile, and the casing is pulled up one by one, leaving the bottom plate.