JP2518122B2 - Construction method of joint between pile and foundation slab - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a joint between a foundation pile and a concrete foundation slab in which prestress is introduced.

[0002]

2. Description of the Related Art There are many foundation structures in which a foundation concrete slab such as a footing is provided on the top of a pile. By the way, in this foundation structure, when a large number of piles are connected with one foundation slab like the foundation of an aboveground tank as shown in Fig. 4, the concrete of the foundation slab is cracked due to drying shrinkage because the restraining force of the piles is large. Is likely to occur. When used as a low temperature liquefied gas tank such as an LNG or LPG tank, the pile restrains the concrete slab from shrinking as it cools, causing cracks in the foundation slab and the amount of reinforcement in the foundation slab. Many are needed.

Further, when joining a pile and a foundation slab, which have been generally practiced in the past, there is often a method in which a reinforced cage is arranged between the pile and the foundation slab and a filling concrete is placed on the upper portion of the pile. By the way, in the structure obtained by this method, from the time of placing the foundation slab concrete, displacement restraint conditions are applied, and tensile forces are often generated due to drying, shrinkage, and temperature decrease, and cracks often occur.

As a measure for solving the above problems, a method of introducing prestress into the concrete of the foundation slab can be considered. However, the conventional method of connecting the pile and the foundation slab cannot effectively introduce prestress into the concrete of the foundation slab due to the restraining force of the pile. Therefore, the present invention has developed a method in which the constraint between the pile and the foundation slab is released during the construction process, and the pile and the foundation slab can be completely rigidly connected after the completion.

[0005]

A method of constructing a joint portion of a foundation slab according to the present invention is to install a support plate at the lower end position of the foundation slab on the outer periphery of the upper portion of a pile, and to insert a reinforcing bar to be inserted into the upper portion of the pile. Cover the top of the pile with a steel pipe with a lid that incorporates a basket,
The lower end of the steel pipe is slidably supported on the supporting plate, then the concrete of the foundation slab is placed, and after hardening of the concrete, the PC steel material reinforced in the concrete is tensioned to introduce prestress to the concrete of the foundation slab. Then, a grout material is injected and fixed in the gap between the inside of the pile upper portion and the outer periphery of the pile upper portion and the steel pipe.

[0006]

EXAMPLE A ring-shaped support plate 1 is provided by welding at the lower end position of a foundation slab B on the outer periphery of the upper portion of a pile A made of a hollow ready-made pile such as a steel pipe pile. Further, a steel pipe 3 with a lid in which a lower half portion is inserted in the upper part of the pile A is covered with a steel pipe 3 with a lid, and the lower end of the steel pipe 3 is supported on the support plate 1 so as to be slidable in the lateral direction. There is.

Next, the concrete 4 of the foundation slab B is cast, the PC steel material 5 arranged in the concrete is tensioned to introduce prestress into the concrete 4 of the foundation slab A, and then the injection pipe arranged in advance. Pile A using 6
The grout material is injected and fixed in the gap between the upper portion of the steel pipe 3, the outer periphery of the upper portion of the pile A, and the steel pipe 3.

[0008]

EFFECTS OF THE INVENTION The present invention has the above-described structure. When prestressing is introduced into the concrete of the foundation slab, the steel pipe with the lid on the upper part of the pile is slidably supported on the support plate on the outer periphery of the upper part of the pile. Since does not restrain the displacement of concrete, the required prestress can be introduced. Further, when the construction is completed, this prestress can act so as not to cause cracks in the concrete of the foundation slab.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part.

FIG. 2 is a cross-sectional view of a main part in an exploded state.

FIG. 3 is a sectional view of the entire foundation.

FIG. 4 is a sectional view of a conventional example.

[Explanation of symbols]

A ... Pile, B ... Foundation slab, K ... Crack 1 ... Support plate, 2 ... Reinforcing cage, 3 ... Steel pipe, 4 ... Concrete, 5 ... PC steel, 6 ... Injection pipe

Claims (1)

(57) [Claims] 1. A support plate is provided at a lower end position of a foundation slab on an outer periphery of an upper portion of a pile, and a steel pipe with a lid incorporating a rebar cage inserted into an upper portion of the pile is covered on the upper end of the pile to support a lower end of the steel pipe. It is slidably supported on the plate, then the concrete of the foundation slab is placed, and after hardening of the concrete, the PC steel material reinforced in the concrete is tensioned to introduce prestress into the concrete of the foundation slab, and then inside the pile top. And a method for constructing a joint between a pile and a foundation slab, characterized by injecting and fixing a grout material into a gap between an upper outer periphery of the pile and the steel pipe.