JPH0220769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing a pile cap from a cast-in-place concrete pile.

Cast-in-place concrete piles are often driven in underground water or muddy water for stabilizing hole walls, and the pile cap is made of extremely deteriorated concrete. It has been decided that an extra 30 to 100 cm of concrete will be added and that part will be removed after the concrete has hardened. This removal work is carried out by hand or by machine, but it not only poses pollution problems such as vibration, noise, and dust, but is also extremely time consuming and inefficient.

In recent years, in order to eliminate these drawbacks, a method has been used in which concrete is crushed and removed using a slow crushing agent made of a substance that expands in volume through a hydration reaction. However, cracks often occur not only in the part of the concrete that is to be removed, but also in the part of the concrete that will remain as a structure.To prevent this, in order to be safe, the concrete should be removed above the planned cutting surface of the concrete. Since the slow crushing agent is loaded at a distance of ~50 cm, a large amount of concrete remains that must be removed, which is further removed by hand or machine chisel.2
Next, crushing work has to be done, causing pollution problems,
Work inefficiency remains unresolved.

The present invention provides a method for removing the pile cap of a cast-in-place concrete pile in order to solve these problems without adversely affecting the concrete portion that remains as a structure. That is, the present invention provides a cast-in-place concrete pile construction method in which a reinforcing bar cage is installed in a hole drilled in the ground and concrete is poured. A crack prevention material of twice as much or more is placed below the planned cutting surface of the concrete, and 2. A pipe for filling the slow crushing agent is placed horizontally at a position where the center line of the pipe almost coincides with the planned cutting surface of the concrete. at least one end thereof is open to the outside of the concrete pile, and 3. A covering material is applied to the entire reinforcing bars of the concrete portion to be removed to prevent adhesion of the reinforcing bars and concrete to the lower end of the covering material. is arranged and covered so that it almost coincides with the planned cutting surface of the concrete, and then concrete is poured,
This is a method for removing cast-in-place concrete pile caps, which comprises filling the pipe with a slow crushing agent after the concrete has hardened, and then expanding the slow crushing agent to crush it.

The present invention will be explained below with reference to the drawings.

First, a crack preventive material 6 is provided as shown in FIGS. 1 and 4 to prevent cracks from occurring in the concrete structure 1 to be left due to the expansion force of the slow crushing agent.

The crack prevention material 6 can prevent cracks in the vertical and horizontal directions in the concrete structure 1 due to its adhesion to concrete. The crack prevention material 6 is made of reinforcing bars or welded wire mesh, etc. so that it will not cause any structural problems even if it is buried in the concrete structure 1, but the thickness of the reinforcing bars or wire mesh depends on the size of the reinforcing bar cage and the crack prevention material. Although the wire diameter is not constant depending on the shape of the reinforcing bar or the opening size of the reinforcing bar or wire mesh, etc., a wire diameter of 9 to 51 mmφ is appropriately selected for reinforcing bars, and a wire diameter of 6 to 13 mmφ for wire mesh. The position where the crack prevention material is placed is from directly below the concrete structure 1 side that is to be left below the planned cutting surface 5 of the concrete and in contact with the lower end of the pipe for filling the slow crushing agent, which will be described later.
A range below 10 cm is suitable. In this case, as shown in FIG. 1, the effect of preventing cracks in the concrete structure 1 is further promoted by providing the reinforcing steel bar 4 located at the top of the concrete structure 1 close to the lower end of the crack prevention material 6. do. In addition, by providing the crack prevention material 6, in order not to impede the fluidity and integration of fresh concrete, the mesh size of reinforcing bars or welded wire mesh should be 1.2 times the maximum grain size of concrete coarse aggregate. As described above, the shape of the eyes is not limited to square. Furthermore, when using reinforcing bars as a crack prevention material, it is not limited to a mesh shape as shown in Figure 4, but a star shape in which the main reinforcing bars 3 of the reinforcing bar cage are tied horizontally,
There is no problem even if it is a polygon such as a hexagon. In addition, when pouring concrete, when using a concrete pile or hose for filling concrete, place a concrete pile with a diameter of 30 cm or more near the center of the cross section as shown in Figure 4 so as not to interfere with the raising and lowering work. An opening 7 for concrete pouring shall be provided.

Next, the slow crushing agent filling pipe (hereinafter simply referred to as the pipe) 8 is fixed using iron wire or the like and placed horizontally so that the position of the planned concrete cutting surface 5 and the center line of the pipe almost coincide with each other. do. When the crack preventing material 6 is disposed in contact with the lower end of the pipe, the crack preventing material 6 can be used as a pipe holder. As a result, in addition to the effect of the crack prevention material, horizontal cracks are generated in the vicinity of the planned concrete cutting surface 5, and no concrete remains to be removed, so there is almost no need for secondary crushing work. As for the material of the tube, commercially available cylindrical tubes with a diameter of about 1 to 10 cm may be used, such as thin iron plates or plastics.

The pipe 8 should be arranged so that it is almost concentric with the concrete pile in the cross section of the concrete pile as shown in Figs. 3, 5 and 6, and it should be arranged so that it faces the center of the cross section of the concrete pile as shown in Fig. 7. They can be placed almost evenly on the cross section of the concrete pile and have a crushing effect, such as arranging them radially (radially) or spirally on the cross section of the concrete pile as shown in Figure 8. You are free to adopt any arrangement you wish. The concentric circles in Figures 3 and 5 are approximately 1 turn, and the concentric circles in Figure 6 are approximately 2 turns, but the number of turns may be 1.5, 2.5 or more depending on the cross-sectional area of the concrete pile, pipe diameter, etc. There is no problem even if it is. In addition, one end of the pipe 8 is provided so as to be in contact with the outer surface of the concrete pile in order to secure a filling port 9 for filling the slow crushing agent, and when filling with a slow crushing agent in the form of a slurry, the pipe 8 is provided to ensure filling. The other end of the pipe 8 is provided in contact with the outer surface of the concrete pile to secure an air vent 10. In addition, when arranging the tubes in a radial or spiral pattern, the arrangement locations are not limited to the number of locations shown in Figures 7 and 8.
The number of locations is increased or decreased as appropriate depending on the concrete pile cross-sectional area, pipe diameter, etc. In these cases, filling ports are provided in the same manner as in the case of concentric circles.

In addition, when using a tremor pipe or hose for concrete filling during concrete pouring, place it near the center of the cross section of the concrete pile as shown in Figures 5 to 8 so as not to interfere with the raising and lowering work. shall be located so that an opening with a diameter of 30 cm or more can be secured. The filling port 9 and the air vent 10 are preferably covered with adhesive tape, cloth, etc. to prevent foreign matter such as fresh concrete from entering the pipe.

Next, in the concrete 2 to be removed, there is a main reinforcing bar 3 with an anchoring length necessary for connection with a superstructure such as a building foundation, but since the concrete and reinforcing bars have a considerable adhesion force, When crushing using a crushing agent, it is difficult to crush as intended if the concrete and reinforcing bars remain attached. In order to solve this problem, the main reinforcing bars 3 are connected to the reinforcing bar sheathing material 11 as shown in Figure 1.
By covering with concrete, the adhesion force between concrete and reinforcing bars is eliminated, making crushing easier. Reinforcement sheathing material 1
If the lower end of 1 is shallower than the planned concrete cutting surface 5, concrete 2 to be removed remains;
Next, crushing is required, and if the lower end is located deeper than the planned concrete cutting surface 5, cracks will occur in the concrete structure 1, which is a structural problem. Therefore, in the present invention, the lower end of the reinforcing bar covering material 11 is made to match the planned concrete cutting surface 5, so that the concrete can be cut horizontally on the planned cutting surface 5. In addition, reinforcing bar covering material 1
1 may be a commercially available cylindrical sheath tube made of paper, iron, or plastic, or may be wrapped with adhesive tape around the reinforcing bar. Further, the upper and lower ends of the sheath tube have lids 12 to prevent foreign matter such as fresh concrete from entering, but the purpose can also be achieved by covering the lids with adhesive tape, cloth, etc. instead.

After performing the above processing on the reinforcing bar cage, concrete is poured. However, it is also possible to perform various processing on the reinforcing bar cage on the ground and then place it in the hole drilled and pour concrete. After placing it in the hole, various processing may be performed and concrete may be poured.

After concrete is poured and the concrete hardens, the slow crushing filling pipe is filled with a slow crushing agent.
The purpose is achieved by generating reliable cracks horizontally at the location of the concrete cutting surface 5 due to volumetric expansion.

After the crushing is completed, it is necessary to divide the concrete into small pieces in order to facilitate the transportation of the concrete 2 to be removed.
As shown in the figure, a pipe 13 filled with a crushing agent for subdivision (hereinafter abbreviated as a small pipe) is installed vertically in the concrete section 2 to be removed, and the pipe is similarly filled with a slow crushing agent and its expansion This purpose can be achieved by crushing with pressure (the material is the same as the tube 8). The number of pipes to be installed is not limited to four as shown in Figure 9, but can be increased or decreased depending on the degree of planned subdivision. established,
The upper end is brought out further than the upper end of the concrete 2 to be removed so that a slow crushing agent filling port 9 can be secured. In this case as well, the filling port 9 is covered with a lid or covered with adhesive tape, cloth, etc. to prevent foreign matter such as concrete from entering.

Furthermore, by embedding lifting hooks 16 made of reinforcing bars as shown in FIG. 11 in each of the concrete pieces 15 that have been broken into small pieces by the cracks 14 in FIG. 10, the removal and transportation of the concrete pieces becomes easy. Work efficiency can be further improved.

By the method of the present invention, it is not necessary to use machinery as well as manpower for crushing concrete, and there is no need to drill holes.Therefore, pollution problems caused by vibration, noise, dust generation, etc. can be solved, and in addition, slow crushing The use of the agent, the combination of the pipe filled with the agent and the anti-crack material, and the setting of their relative positions make it possible to perform crushing as desired, thereby sufficiently improving work efficiency, and the significance of the present invention is extremely significant.

The present invention is not limited to the removal of pile heads of cast-in-place concrete piles, but can also be extremely effectively applied to the removal of temporary concrete structures.

Next, a concrete explanation will be given with reference to examples.

Example: Reinforcement cage on the ground (main reinforcing bar 22mmφ, band reinforcing bar 13mmφ,
A crack prevention material (reinforced bar basket, 9 mm diameter mesh, 15 cm opening) was installed at a position 24 mm below the planned cutting surface of the concrete, and then a pipe made by Kurimoto Iron Works Co., Ltd. was used to fill the slow crushing agent. "Winding Sheath" (Product name) (Ultra-thin steel plate thickness 0.23mm, 30mm
φ) was wrapped in two concentric circles as shown in Figure 6 and installed on the planned cutting surface of the concrete, and then used as reinforcing bar covering material "Fuji Void" (product name) manufactured by Fujimori Sangyo Co., Ltd.
(35mmφ made of paper) was coated on the main reinforcing bars up to the planned cutting surface of the concrete.

This reinforcing cage was lowered into a pre-drilled underground hole and concrete was placed to obtain a pile with a diameter of 1.2 m and a length of 15 m. After 7 days, the concrete had hardened, and the pipe was filled with 6 kg of Nippon Cement Co., Ltd.'s slow crushing agent "Calmite" (trade name). After 12 hours, the slow crushing agent expanded and crushed the concrete 80 cm from the originally planned top end. It was observed that the crushing at this time was carried out almost in line with the planned cutting plane. The time required to remove the crushed material after crushing was 10 minutes per pile, and the time required to finish the cut surface of the concrete for pouring concrete thereon was approximately 10 minutes per pile.

On the contrary, a method carried out according to the conventional method,
In other words, in order to avoid cracking below the planned cutting surface since no crack prevention material is used, the pipe for filling the slow crushing agent is placed 30 cm above the planned cutting surface and wrapped in two concentric circles as shown in Figure 6. In addition, concrete was poured without using a covering material to prevent adhesion of concrete to the reinforcing bars in the part where concrete was removed, and 7 days after pouring, the same amount of slow crushing agent as in the example was used. When the concrete was crushed, a portion 30 cm above the planned cutting surface remained intact, and the concrete above it was crushed, but in order to remove the crushed material, one pile was used because the adhesion between the concrete and the reinforcing bars was strong. It takes 60 minutes to win,
Furthermore, the remaining unbroken concrete is removed using a concrete breaker up to the planned cutting surface.
It took 50 minutes for each pile to finish the cut surface so that concrete could be poured over it.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, and Fig. 1 is a cross-sectional view of the head of a cast-in-place concrete pile, and Fig. 2 is Fig. 1A.
-A cross-sectional view, Figure 3 is a B-B cross-sectional view in Figure 1,
Figure 4 is a cross-sectional view taken along the line C-C in Figure 1, Figures 5 to 8 are plan views of various shape patterns of pipes for filling slow crushing agents, and Figure 9 is for crushing into small pieces in cast-in-place concrete piles. FIG. 10 is a cross-sectional view showing how the agent filling pipe is installed, FIG. 10 is a plan view taken along the line D--D in FIG. 9, and FIG. 11 is a diagram showing how the lifting hook is buried. 1... Concrete structure, 2... Concrete to be removed, 3... Main reinforcing bars, 4... Band reinforcing bars, 5...
...Concrete planned cutting surface, 6...Crack prevention material,
7... Opening for concrete placement, 8... Pipe for filling slow crushing agent, 9... Filling port, 10... Air vent,
11...Reinforcing bar covering material, 12...Lid, 13...Pipe filled with crushing agent for dividing into small pieces, 14...Cracks, 15...Small concrete pieces, 16...Lifting hook.

Claims (1)

[Scope of Claims] 1. In a cast-in-place concrete pile construction method in which a reinforcing bar cage is installed in a predetermined hole drilled in the ground and concrete is poured, the reinforcing bar cage has a 1-mesh opening, which is the maximum coarse aggregate used for concrete. A crack preventive material with a grain size of 1.2 times or more is placed below the planned cutting surface of the concrete, and 2. A pipe for filling the slow crushing agent is placed horizontally at a position where the center line of the pipe almost coincides with the planned cutting surface of the concrete. and at least one end of the pipe is arranged so as to open to the outside of the concrete pile, and 3. A covering material is applied to the entire reinforcing bars of the concrete portion to be removed to prevent adhesion of the reinforcing bars and concrete. The tube is placed so that its lower end almost coincides with the planned cutting surface of the concrete, and then covered with concrete. After the concrete has hardened, the pipe is filled with a slow crushing agent, and then the slow crushing agent is filled in. A method for removing cast-in-place concrete pile heads characterized by expanding and crushing them. 2. The removal method according to claim 1, wherein the crack prevention material is a reinforcing bar or a welded wire mesh. 3. The removal method according to claim 1, wherein the slow crushing agent filling pipe is arranged so as to face the center of the cross section of the concrete pile. 4. The removal method according to claim 1, wherein the slow crushing agent filling pipe is arranged so as to be substantially concentric with the concrete pile in a cross section of the concrete pile. 5. The removal method according to claim 1, wherein the pipe for filling the slow crushing agent is arranged in a spiral shape in the cross section of the concrete pile. 6 Claim 1 in which the covering material is a sheath pipe
Removal method described in section. 7. The removal method according to claim 1, wherein the slow crushing agent is made of a substance that expands in volume through a hydration reaction, such as quicklime or calcined dolomite.