JPH046813B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing the head of a cast-in-place concrete pile using a static crushing agent, and more specifically, the present invention relates to a method for removing the head of a cast-in-place concrete pile using a static crushing agent. This invention relates to a method for removing cast-in-place concrete pile heads by breaking them into small pieces.

In the case of cast-in-place concrete piles, it is essential to remove the excess concrete at the head of the pile. This removal work is generally carried out manually or mechanically, but this not only causes pollution problems such as vibration, noise, and dust, but is also very time consuming and inefficient. Therefore, it has been proposed to cover the reinforcing bars located in the excess concrete with a covering material in advance to prevent the reinforcing bars from adhering to the concrete, but this alone cannot be said to have sufficiently solved the above problems.

On the other hand, in recent years, a method of crushing and removing concrete using a static crushing agent has been used. The present applicant proposed improvements to this method in Japanese Patent Application No. 57-68070 (Japanese Unexamined Patent Publication No.
-185823), but even though the pile head could be cut from the planned cutting surface of the concrete, the cut pile head had to be further divided into smaller pieces in order to be disposed of.

The present invention is a method that can perform this subdivision work at the same time as cutting the pile cap, and its gist is that protruding members are provided on the reinforcing bars located in the excess concrete, and the reinforcing bars are coated to prevent concrete from adhering. In place casting, concrete is covered with concrete and placed, and after the concrete has hardened, static crushing material is filled into multiple holes made in the planned cut surface of the concrete, and then the static crushing material is expanded and crushed. This is in the method for removing the head of a concrete pile.

When a static crushing agent is filled into multiple holes in the planned cutting surface of cast-in-place concrete and allowed to expand, cracks occur in the horizontal direction of the pile, and at the same time, force is generated in the vertical direction. At this time, if the protruding member firmly attached to the reinforcing steel located in the excess concrete receives the above force, the reaction force will act on the excess concrete, causing vertical cracks in the excess concrete due to a wedge effect. urge In this case, the reinforcing bars are coated with a covering material to prevent concrete from adhering to them, so the above-mentioned force will not be interfered with.

The protruding members installed on the reinforcing bars function in this way, so they can be wedge-shaped, hatchet-shaped, cone-shaped with a circular or star-shaped cross section, or the tip of the reinforcing bar can be bent 180 degrees. You can use bent ones, but if you point the wedge-shaped ones toward the center of the pile, you can make small cuts more efficiently. In addition, the teeth of the protruding members provided on the reinforcing bars are preferably positioned 20 to 30% below the top of the excess concrete.

An appropriate number of protruding members are provided around the reinforcing bars according to the desired size of subdivision.

Commercially available paper coverings for reinforcing bars,
It may be a cylindrical sheathed tube made of styrofoam, or it may be wrapped with adhesive tape around the reinforcing steel.

The method of the present invention will be explained using figures.

Figure 1 is a plan view of the concrete pile head.
FIG. 2 is a side sectional view thereof. A large number of reinforcing bars 1 are planted in concrete and covered with a covering material 5. Wedge-shaped protruding members 2 are provided on some of these reinforcing bars, for example, six in FIG. 1. Third
The figures are enlarged views of a wedge-shaped protruding member of reinforcing bars, with A being a side view and B being a front view of the protruding member.

To crush the excess concrete 8, first, a horizontal crack with a width of about 2 mm is caused at the planned cutting surface 6, and only when the width is further widened is the tooth 3 of the protruding member 2
The distance between the extra concrete 8 and the tooth 3 is approximately 2 in the vertical direction so that the extra concrete acts on the extra concrete.
It is better to allow room for shrinkage of about mm. If this shrinkage room is not provided, horizontal cracking at the planned cutting surface and vertical cracking due to the subdivision of the excess concrete will occur at the same time, which will only require a large amount of expansion pressure. Instead, there is a risk that the vertical cracks will extend to the remaining portion 10 of the pile.

As a means for providing room for this contraction, the teeth of the protruding member may be covered with a covering material 9 that shrinks with a strong force, for example, an elastic material such as styrofoam, rubber, paper, etc., or when the protruding member is attached to a reinforcing bar, the protruding member may be It is also possible to make elongated holes in the member so that the projecting member initially moves vertically along with the approximately 2 mm excess concrete due to the expansion force, but does not move any further.

In this way, the excess concrete is crushed into small pieces at the planned cutting surface by the expansion pressure of the static crushing agent.

According to the present invention, the concrete pile head can be cut into small pieces in the vertical direction at the same time. Therefore, compared to the conventional dicing operation by hand or machine, or the dicing operation in which vertical holes are drilled and crushed using a static crushing agent, the dicing operation can be carried out extremely easily and efficiently.

Next, the present invention will be specifically explained with reference to Examples.

Example Six projecting members were used to remove approximately 1 m of excess concrete from the head of a cast-in-place concrete pile with a diameter of 1400 mm as shown in Fig. 1. This projecting member consists of a tube, teeth, bolts, and sheathing material for fitting into the reinforcing steel. The teeth are 200 mm long, 30 mm thick, 26 mm high, and angled at 60 degrees, and are further covered with approximately 2 mm of covering material (styrofoam). The tube of this projecting member was fitted into the reinforcing bars located in the excess concrete and fixed with bolts. Also reinforcing bars (outer diameter 54
mm) was covered with a polystyrene heat-insulating cylinder (inner diameter 34 mm) on the reinforcing bars to prevent concrete from adhering.

After concrete was placed and hardened, a static crushing agent was filled into the eight holes made on the concrete surface to be cut, and when the static crushing agent was expanded, cracks appeared on the surface to be cut after 16 hours. Shortly thereafter, vertical cracks appeared in the excess concrete and it was broken into six pieces.

[Brief explanation of drawings]

1 and 2 are views of the head of a concrete pile for explaining the method of the present invention, with FIG. 1 showing a plan view and FIG. 2 showing a side view. FIG. 3 is an enlarged view of the wedge-shaped projection member of the present invention, with A being a side view and B being a front view. DESCRIPTION OF SYMBOLS 1...Reinforcement bar, 2...Protrusion member, 3...Teeth of protrusion member, 4...Bolt, 5...Coating material, 6...Planned cutting surface, 7...Hole for static crushing agent, 8... Excess concrete, 9... Covering material for protrusion members, 10...
The remaining part of the concrete.

Claims (1)

[Scope of Claims] 1. Protruding members are provided on reinforcing bars located in excess concrete, the reinforcing bars are covered with a covering material to prevent adhesion of concrete, concrete is poured, and after the concrete hardens, the concrete is cut. Static crushing agent is filled into multiple holes made on the planned surface,
A method for removing a cast-in-place concrete pile head, the method comprising: then expanding the static crushing agent to crush the head. 2. The removal method according to claim 1, wherein the protrusion member is wedge-shaped.