JPS60246918A - Method of removing negative friction force of cast-in-place concrete pile - Google Patents

Abstract

PURPOSE:To remove a negative friction force, by a method wherein a steel pipe pile, to the outer periphery of which a lubricant is adhered, is buried in a ground, and after a pile hole is formed through excavation of the interior of the pile, a reinforcing cage is built in the pile hole to place concrete. CONSTITUTION:A lubricant 2, such as grease, is coated on the outer peripheral surface of a steel pipe pile 1 to cover it with a film 3 such as polyester, and molten asphalt and the like is coated. After the pile 1 is buried in a ground 4, a pile hole 5 is formed through excavation of the interior of the pile 1 by means of a drill 6. After a reinforcing cage 9 is built in the pile hole 5, a tremie 10 is inserted into the reinforcing cage 9 to place concrete 11 therethrough to build a concrete pile 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for removing the negative frictional force that tends to pull in cast-in-place piles such as foundation piles of buildings due to ground subsidence.

Conventional technology Foundation piles constructed on soft ground such as reclaimed land are subject to negative frictional force that tries to pull the foundation piles together as the ground sinks due to the consolidation action of the ground, causing the foundation of buildings, etc. This can cause unexpected subsidence and cracks in buildings, etc.
Or it caused the pile to break. Conventionally, in such areas of subsidence, double steel pipes were used, or steel pipes were coated with a friction cutting material such as asphalt beforehand and ready-made piles were driven into them. This method is not used, and as shown in Figure 2,
A plurality of plate materials α2 with υ etc. attached are attached to the outer periphery of the reinforcing bar cage (131 with wire I and erected in the excavation hole (15),
The only known method (see Japanese Patent Publication No. 58-58495) is to form a concrete pile by pressing a plurality of plates α2 against the wall of an excavated hole (19) using the pressure of poured concrete.

Problems to be Solved by the Invention In the conventional technology, with ready-made piles, it is possible to apply a frictional cutting material such as asphalt to the pile, but with cast-in-place piles, it is not possible to apply a frictional cutting material in advance, The method of using plate materials for cast-in-place piles requires that the plate material with the friction cutting material attached be movably attached to the reinforcing bar cage, which is a troublesome work.Also, since the plate body is attached to the reinforcing bar corner, The diameter needed to be smaller than the conventional one, and not only did it lack strength against bending, but there was also a risk that concrete would enter between the plate and the excavation hole, preventing the frictional force from cutting.

In view of the above points, the present invention aims to provide a simple and reliably effective method for removing negative frictional force using cast-in-place piles.

Means for Solving the Problems The means of the present invention for solving the above-mentioned problems is to bury a steel pipe pile in the ground with a lubricant attached to its outer periphery, and then excavate the inside of the steel pipe pile to form a pile hole. This method consists of a method for removing negative frictional force from cast-in-place concrete piles by placing reinforcing bars in the pile holes and pouring concrete.

Example An embodiment of the invention will be described with reference to the drawings.

In Figure 1 (a), (1) is a steel pipe pile, and its outer peripheral surface is coated with a lubricant (2) such as grease and covered with a film (3) such as polyester, or coated with molten asphalt, etc. This is applied and is buried in the ground (4) by driving or embedding. Next, the same figure (b
) As shown in I/j, drill a pile hole (5) inside the steel pipe pile (1) using an earth drill excavator, reverse circulation excavator, etc. to a depth equivalent to the length of the concrete pile. After excavating to a predetermined depth, the drill (6) is pulled up with a Kerryper or drill pipe f (7). Pile hole (5
) is filled with muddy water (8).

Next, as shown in the same figure (c), insert the reinforcing bars (9) into the pile holes (5).
However, depending on the case, the length of the reinforcing bars (9) may be from the middle of the steel pipe pile (1) to the tip instead of the entire length of the pile.

Next, a tremie pipe (QO) is inserted into the reinforcing bar cage (9), concrete aD is cast, and a concrete pile α is constructed ((d) in the same figure) ((e) in the same figure). Concrete pile α
2 is integrally connected with the steel pipe pile (1) coated with the lubricant (2), so the negative frictional force of the ground (4) is cut off, and the ground ( Even if the concrete pile (2) sinks and a negative frictional force is generated, the concrete pile (2) can maintain its original state when it was placed.

Effects of the Invention Since the present invention uses the above-mentioned means, (1) negative frictional force can be removed without any uncertainty in cutting the frictional force unlike in conventional cast-in-place piles that use plate materials; (2) Since the steel pipe pile is installed on the outside of the concrete pile, there is no need to reduce the diameter of the reinforcing bar corners, unlike when plates are attached to reinforcing bars, so there is insufficient strength against bending and shearing. (3) Since concrete piles are covered with steel pipe piles, the steel pipe piles collectively bear the bending stress and shear stress, and can withstand large horizontal forces. Compared to concrete piles without piles, they can withstand the same horizontal force even with smaller diameter piles, so they are economical because they save on materials.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the present invention, (a) to (
e) is an explanatory diagram showing the construction order of concrete piles, and is a cutaway front view, and FIG. 2 is a cutaway plan view showing a conventional cast-in-place concrete pile. (1)...Steel pipe pile, (2)...Lubricant, (4)...
・Soil, (5)...Pile holes, (9)...Reinforcing bars, (
11) Concrete. Representative: Kiyoshi Sakai, Patent Attorney Page 1 continued 0 Inventor: Kiyoshi Yamashita Minamisuna 2-Jitsu Research Institute, Koto-ku, Tokyo

Claims (1)

[Claims] A steel pipe pile (1) with a lubricant (2) attached to its outer periphery is placed in the ground (
4), then excavate the inside of the steel pipe pile (1) to form a pile hole (5), erect a reinforcing bar cage (9) in this pile hole (5), and pour concrete (11). A method for removing negative friction force from cast-in-place concrete piles.