JPS6290443A - Chipping work for head of in-situ pile - Google Patents

Abstract

PURPOSE:To curtail the cost of labor as well as shorten the period of construction by a method in which an in-situ pile is constructed under a condition that a covering film is beforehand spread over the periphery of main reinforcing bars positioned on the chipping level of the pile head, and the head of the pile is broken by an oil-pressure packer. CONSTITUTION:The periphery of main reinforcing bars 3 positioned on the chipping level of the pile head in the upper end portion of a reinforcing bar cage 2 inserted into an excavated pit 1 is covered with a covering material 4 of synthetic resin tube or tape. Concrete 5 is then placed into the pit 1 and hardened, and pits 7 are then provided in the side of nearby pile 5A where the lower end of the covering material 4 is positioned. A wedge-type oil-pressure packer 8 is inserted into the pits 7 and operated to break the pits 7, and the pit head concrete 5B is then lifted up by using a hanging ring 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for efficiently sharpening the head of a cast-in-place pile.

[Conventional technology and its problems]

When constructing cast-in-place piles as the foundation of a building, the concrete is filled with hentonite solution in the excavated hole to prevent the wall from collapsing, so after the concrete hardens, the pile cap is filled with bentonite. Due to the solution being mixed in, the strength of the pile is inadequate, and the head of the pile is generally ground down after the pile is constructed.

The conventional method of crushing the pile caps has been to use a breaker to crush the concrete, but recently, the method of crushing the concrete using an expanding material such as plyster has become more popular. This can also be done by dividing it into small pieces using a breaker.

However, since the concrete is attached to the internal reinforcing steel, grinding of the pile cap requires breaking down a large chunk of concrete little by little using a breaker or other means. This method requires a lot of time and effort, and also has the problem of being noisy.

c Means for Solving the Problems] The present invention solves the problems in the conventional pile head pile work as described above, and provides a new method that can efficiently sharpen the pile head at a predetermined position. Specifically, the outer periphery of each main reinforcing bar located at the cutting height of the shaft is coated with a coating material such as glass wool to prevent adhesion to concrete, and then the piles are cast in place. After concrete 1 has hardened, multiple holes are drilled with a rock drill in the radial direction inside the pile from the outer periphery of the pile cap where the lower end of the coating +4 is located. By inserting a tree-shaped hydraulic packer into the drilled holes and splitting each drilled hole, the concrete pile head is fractured horizontally, and the fracture head is then lifted up and removed along each main reinforcing bar. This is a characteristic feature.

[Effect]

In this invention, cast-in-place piles are constructed by coating the outer periphery of each main reinforcing bar located at the height of the pile head with a coating material such as glass wool to prevent adhesion to concrete.
The main reinforcing bars covered with this coating material will not substantially adhere to the concrete even after the concrete has hardened, and the fracture surface will be horizontal to the concrete head section where the lower end of this coating material is located. If this is done, as long as all the main reinforcing bars are in a vertical state without bending, the fractured concrete part of the pile head can be lifted and removed in one direction along the main reinforcing bars.

〔Example〕

Next, the head-height construction method according to the present invention will be explained with reference to an embodiment shown in the drawings. First, as shown in FIG.
After the completion of excavation, attach glass wool, synthetic resin tubes such as vinyl chloride, or tape to the outer periphery of all the main reinforcing bars 3 located at the height of the head at one end of the reinforcing bar cage 2 to be inserted into the hole. The coating material 4 consisting of is inserted or wrapped in advance, and then mixed with the concrete that will be placed later.
= Prevent I-wearing.

At this time, the ten end portions of each main reinforcing bar 3 are pretreated to ensure that the end face is edged and to correct any bends so that the upper ends of all the main reinforcing bars 3 are in a parallel state without bending.

The length of the coating material 4 is set to a predetermined length by determining the expected grinding height depending on conditions such as the soil quality of the pile construction site.

After concrete 5 is poured into the hole and hardened as shown in FIG. 2, a rock drill 6 is used from the side of the pile 5A near where the lower end of the coating material 4 is located, as shown in FIG. A plurality of holes 7 are drilled in the radial direction inside the pile. This drilling hole 7 is about 3 to 4 holes for a pile with a diameter of 1500Φ.
For a 2000Φ type, it is sufficient to provide about 6 locations. Also,
The hole 7 may be formed at any position as long as the coating material 4 is provided, but it may be located directly below the lower end of the coating material 4.

Next, as shown in FIG. 4, a tree-shaped hydraulic backer 8 is inserted into each of the drilled holes 7, and the drilled holes 7 are
split into pieces. This packer 8 has a structure in which a gasket 8a is sandwiched between a pair of pressure pieces 8b as shown in Fig. 6a.
As shown in the same figure, when the shaft 8a is advanced by hydraulic pressure, the pressurizing pieces 8b on both sides expand, thereby splitting the drilled hole 7 part and cutting the counter head concrete 5B horizontally from this part. Ru.

Next, when pouring the 2-liter concrete 5, the suspension ring 9, which has been installed in advance so as to be embedded in the head concrete, is used to lower the head concrete 5B as shown in Fig. 5.
along each main reinforcing bar 3. When this lifting force is applied, each main reinforcing bar 3 and the concrete 5B are separated by the covering material 4, and since no adhesive force is substantially acting, the covering material 4 is separated from the main reinforcing bar 3. The concrete 5B is pulled along each main reinforcing bar 3 while being peeled off, thereby completing the placement work.

[Effect] As described above, in the present invention, a coating material 4 such as glass wool is applied to the upper end of each main reinforcing bar 3 before concrete is poured.
It is necessary to pre-process the concrete to prevent it from adhering to the main reinforcing bars 3 and to correct the bending of each main reinforcing bar 3, but even if such pre-processing steps are included, Since the main reinforcing bars and concrete are not attached, it is sufficient to simply drill a horizontal hole 7 and break the concrete using a hydraulic backer. Since there is no need for the painstaking work of crushing the grain at all, it is possible to expect a significant efficiency improvement in the head grinding work, as well as a reduction in labor costs and time.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing the sequence of steps in the pile head grinding work according to the present invention, and FIG. 6 is an enlarged cross-sectional view showing the configuration of a projected hydraulic backer used in this construction method. 1: Drilling hole, 2: Rebar cage, 3: Main reinforcing bar, 4: Coating material, 5: Concrete, 7: Drilling hole, 8: Projection hydraulic packer, 8: Hanging ring.

Claims (1)

[Claims] (1) Construct cast-in-place piles with the outer periphery of each main reinforcing bar located at the height of the pile cap covered in advance with a coating material such as glass wool to prevent adhesion to concrete, and after the concrete hardens, A rock drill is used to drill multiple holes from the outer periphery of the pile cap where the lower end of the coating material is located in the radial direction inside the pile, and then a wedge-shaped hydraulic packer is inserted into each of these holes. A pile head drilling method for cast-in-place piles, which is characterized in that the concrete pile head is fractured horizontally by splitting the drilled hole, and then the fractured pile head is lifted up and removed along each main reinforcing bar.