JPS64531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for removing 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 damage to the structure of the building. This caused unexpected subsidence in the foundation, causing buildings to tilt or crack, or even causing the piles to break.

Conventionally, in areas with subsidence, steel pipe piles were coated with a friction-cutting material such as asphalt and ready-made piles were driven in. However, cast-in-place piles use asphalt as shown in Figure 2. A plurality of plates 12 to which No. 11 etc. are attached are attached to the outer periphery of a reinforcing bar cage 13 with wires 14 and built into the excavation hole 15, so that the plurality of plates 12 are pressed against the wall surface of the excavation hole 15 by the pressure of the poured concrete. At that time, the only known method was to form concrete piles using concrete (see Japanese Patent Publication No. 58-58495).

Problems to be Solved by the Invention In 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 to the pile in advance. However, in the method of using cast-in-place pile plates, it is necessary to prepare a plate to which friction cutting material is attached and attach it movably to the reinforcing bar cage, and since the plate is attached to the reinforcing bar cage, the diameter of the reinforcing bar cage cannot be changed from the conventional method. Because of this, not only did it lack strength against bending and shearing, but there was also the risk that concrete would enter between the plate and the wall of the borehole, 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 that does not require plate materials or the like.

Means for Solving the Problems The means of the present invention for solving the above problems is to construct cast-in-place concrete piles in the ground,
After the concrete hardens, a steel pipe with a larger diameter than the concrete pile and a lubricant attached to the outer circumferential surface is inserted into the concrete pile to remove negative frictional force from a cast-in-place pile. .

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

To explain the state of construction with respect to Figures 1 a to c, Figure 1 a shows the state in which cast-in-place concrete piles 2 have been constructed in the ground 1 and the concrete piles 2 are solidified, and Figure 1 b shows the state in which the concrete piles 2 have been solidified. 3 is the third steel pipe
As shown in the figure, a lubricant 5 such as asphalt or grease is applied to the outer peripheral wall 4 of the steel pipe 3, and the steel pipe 3 is positioned above the concrete pile 2. Then, as shown in Figure c, the steel pipe 3 is inserted from above the concrete pile 2 to a predetermined depth using a drop hammer, vibrohammer, or the like.

In this case, the steel pipe 3 does not have to be the same length as the concrete pile 2, and may be made shorter as shown in Figure c depending on the ground condition. In this state, when the ground 1 sinks as shown in Figure d, the concrete pile 2, the steel pipe 3 surrounding it, and the surrounding ground 1 will cause friction due to the lubricant 5 applied to the outer peripheral wall 4 of the steel pipe 3. Since the force is cut off, the negative frictional force from the surrounding ground 1 does not act on the concrete pile 2, and only the ground 1 sinks, making it possible for the concrete pile 2 to maintain its original state when it was constructed. can.

Effects of the Invention Since this invention uses the above-mentioned means, it is possible to remove the negative frictional force in a cast-in-place pile by a simple means, and the plate can be replaced with a wire as in the conventional cast-in-place pile. There is no need for troublesome work such as movably attaching the steel pipe to the reinforcing bar cage, and the work is simple as all you need to do is drive the steel pipe.Also, since the steel pipe is inserted with a larger diameter than the concrete pile, it is easier to use than the conventional method. There is no need to make the diameter of the reinforcing cage smaller than conventional ones, unlike the case where plates are attached to the rebar cage, and therefore there is no disadvantage such as insufficient strength against bending and shearing, and there is also no need to make the diameter of the reinforcing bar cage smaller than that of the conventional one. The negative frictional force removal effect is ensured without the possibility of concrete entering between the wall surface of the excavation hole and the cutting of the frictional force becoming uncertain.

[Brief explanation of the drawing]

Figures 1 and 3 show one embodiment of the present invention, and Figures 1a to d are explanatory diagrams showing the state of construction of cast-in-place concrete piles and the state of ground subsidence, and Figure 2 is a cutaway front view. 3 is a cutaway plan view showing a conventional cast-in-place concrete pile, and FIG. 3 is an enlarged cutaway plan view of a concrete pile into which a lubricant-coated steel pipe is inserted. 1...Ground, 2...Cast-in-place concrete pile, 3...
Steel pipe, 4... outer peripheral wall, 5... lubricant.

Claims (1)

[Claims] 1. A cast-in-place concrete pile 2 is constructed in the ground 1, and after the concrete hardens, a steel pipe 3 having a diameter larger than the concrete pile 2 and having a lubricant 5 attached to the outer peripheral wall 4 is inserted into the concrete pile 2. A method for removing negative frictional force from cast-in-place piles.