JP2557952B2 - Gravel filling method in reinforced concrete basket of cast-in-place concrete pile and filling jig directly used for its implementation - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gravel filling construction method in a rebar cage of cast-in-place concrete piles and a filling jig used directly for carrying out the method.

“Prior Art” Cast-in-place concrete piles are constructed by excavating the ground in a circular or rectangular cross-section to the support layer, constructing a rebar cage, and placing underwater concrete. At this time, the vertical bearing capacity generally decreases due to the precipitation of some of the excavated soil on the excavated tip ground, the accumulation of slime by a stabilizing solution such as bentonite solution, and the looseness of the tip ground caused by excavation It also causes uneven settlement of the structure.

That is, if the pile is constructed on the above-mentioned deposit or the ground in a loose state, the supporting force at the tip end thereof is small and the sinking is large and unstable. For the accumulated slime and the loose ground, which are the sources of such inconvenience, there is a means for injecting and consolidating the grout material to solidify it.

However, with mere injection, slime is generally fine sand,
Since it is a mixture of silt and clay, the permeability of the grout material is low, and therefore, the range in which the grout material penetrates into the pores of the soil particles and solidifies is extremely narrow, so that a sufficient effect cannot be obtained.

On the other hand, the recent increase in the height of structures tends to significantly increase the bearing load of a single pile, where the spacing between piles is restricted by legal regulations.

Therefore, various means have been proposed for improving the tip of the pile by injecting and solidifying cement milk into the tip of the pile under high pressure.

Figures 3a-g show one of them. That is, after the excavation of the excavation hole 1, the slime treatment of depositing on the bottom of the hole is performed by the bucket 2 (Fig. A).

Then, the rebar cage 3 with the pressure cell 5 and the gravel chamber 4 attached to the lower end is inserted into the hole 1 (FIG. B).

The structure of the lower end of the above-mentioned reinforcing bar cage 3 is shown in detail in FIGS. That is, the pressure cell 5 is mounted in a manner to shield the lower end surface of the reinforcing bar cage 3 and is a flat box body composed of a pair of upper and lower steel plates 7 and 8 with a spacer 6 interposed therebetween.
A grout pipe 9 is connected to the steel plate 7. Steel plate 8 has through holes 10, ...
An elastically deformable film 11 of a rubber or neoprene sheet is closely attached to the lower surface of the plate.

The membrane 11 has a through hole 1 that is displaced from the through holes 10 ,.
2, ... are evenly drilled over the entire surface. Then, through hole 10 →
Although the flow of 12 is possible, the flow of the through holes 12 → 10 is blocked, forming a check valve.

Gravel (gravel) formed below the overhead pressure cell 5
The chamber 4 is a basket made of reinforced bone and mesh, and is filled with gravel of the same size. In the figure, 13 is a hook for hanging. Insert the tremie pipe 14 and cast concrete 15 (figure f).

After the concrete 15 is hardened, cement milk is pressure-injected into the pile tip (the gravel chamber 4) through the grout pipe 9 and the pressure cell 5 to infiltrate into the gravel chamber 4 and the supporting ground area 16 in contact with the gravel chamber 4, and the pressure is applied. It is cured as it is added (Fig. G).

[Problems to be solved by the invention] As described above, in the system using the pressure cell and the gravel chamber at the lower end of the rebar cage, the injected cement milk enters the gravel chamber through the pressure cell and Pressure will be applied after the voids are filled with cement milk. When the cement milk inlet was closed while pressure was applied, the cement milk hardened as it was and the ground was well tightened at the tip of the pile,
A mixed layer of hardened gravel chamber and cement milk is created, which should be a high-performance pile.

However, the reality is that the expected effect cannot be expected. The reason is that the gravel chamber is created on the ground,
It is provided on the bottom of the hole, and there is a gap between the chamber and the hole wall as shown in FIG. When concreed is placed in this state, as shown in Fig. C, the gap part is filled with concrete placed from the tremie pipe 14 and is effectively compacted when cement milk is injected into the chamber. This is because the area of the pile bottom of the mixed layer of the chamber and cement milk becomes small.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method capable of expanding the area of a pile bottom that is effectively compacted by injection of cement milk to the same level as an excavation hole. And

"Means for Solving the Problem" In order to achieve the above object, in the present invention, the gravel is diffused around the rebar cage on the pressure cell of the rebar cage provided with a gravel chamber having a pressure cell at the lower end. A possible gravel filling hopper (filling jig) is hung and arranged so as to fill the gap between the gravel chamber and the hole wall with gravel.

As a matter of course, after the gravel is filled in the gap between the gravel chabber and the hole wall using the above gravel filling jig, after the concrete is placed by the tremie pipe and the concrete is hardened. High-pressure injection of cement milk and hardening of the cement milk with pressure applied.

[Operation] According to the gravel filling jig, the gravel filling layer of the gravel chamber extends over the entire drill hole bottom.

Further, in this state, the concrete is poured by the tremie pipe and the high pressure injection of the cement milk is performed. Therefore, the area of the pile bottom effectively compacted with the cement milk corresponds to the area of the drill hole bottom.

[Examples] Examples will be described with reference to the drawings.

1 (a) and 1 (b) are schematic views of the gravel filling jig of the present invention shown in the case of a circular pile, and FIGS. 2 (a) to 2 (c) are explanatory views of the procedure of the present invention.

The gravel filling jig 17 shown in FIG. 1a has a bottom plate composed of a conical umbrella-shaped base 18 according to the cross-sectional shape of a pile, and a cylinder 19 is suspended and mounted on the base 18 to form a hopper. Is.

Then, if a predetermined amount of gravel is housed in the cylinder 19 and only the cylinder 19 is pulled up with the stand 18 left, the housed gravel drops on the inclined surface of the stand 18 and pressure is applied. It is spread around the cell 5. The amount of horizontal movement of the gravel to be sprinkled can be adjusted by the conical inclination of the base 18 and the height of the legs 20. The material forming the table 18 and the cylinder 19 is iron or a synthetic resin such as vinyl chloride.

In the figure, 21, ... and 22, ... are tip hooks 21a ,.
This is a case in which a shaped guide column and a ring brought out from the cylinder 19 fitted to the column 21 are used to pull up the cylinder 19 to discharge the gravel, and then the platform 18 is pulled up and collected as it is.

In the figure, 23 is a wire for pulling up the cylinder 19. The stand
If a wire 24 is attached to the hook 21a on the 18th side, the wire 24 can be used in the hole 1 of the reinforcing bar cage 3 without mounting the coordination of the jig 17 on the pressure cell 5 when the reinforcing bar cage 3 is lowered. It can also be done after installation.

On the other hand, in the jig 25 shown in FIG. 1b, a flexible mesh or sheet material 28 is stretched between a circular outer ring 26 and an appropriately shaped inner ring 27 (circular in the figure) with sufficient deflection to form a hopper. The suspension wire 29, 30 is attached to the outer ring 26 and the inner ring 27.

Then, while maintaining the mode in which a predetermined amount of gravel is accommodated in the mesh or sheet material 28 part, the jig 25
Aligning with or following the rebar cage 3 and lowering it to position it on the pressure cell 5 and pulling only the wire 30 of the inner ring 27, the gravel housed on the slanted mesh or sheet material 28. Can be dropped and spread around the periphery of the pressure cell 5.

Fig. 2a shows the construction procedure using the above gravel filling jig
This will be described in detail with reference to c.

 The drawing shows the case of the described jig 17.

After excavating the drill hole 1 as in the conventional procedure described, slime treatment is performed on the bottom of the hole by a bucket, and then the pressure cell 5 of the rebar cage 3 attached to the pressure cell 5 and the lower end of the gbel chamber 4 is attached. A jig 17 in which a predetermined amount of gravel G is put is mounted in a cylinder 19 on the above, and the rebar cage 3 is inserted into the hole 1 (Fig. A).

Once installed at the bottom of the hole 1, the cylinder 19 is pulled up by the wire 23 and the gravel G is put into the periphery of the gravel chamber 4 (Fig. B).

After pulling up the jig 17 and collecting it, a tremie pipe is inserted and concrete 15 is placed (Fig. C).

After the concrete 15 is hardened, cement milk is pressure-injected into the gravel packed layer at the tip of the pile through the grout pipe 9 and the pressure cell 5, and the gravel packed layer has a hole 1 as shown in FIG. Since it is expanded to the bottom, the gravel + cement milk layer extends to the entire bottom of the hole 1.

As described above, the jig 17 may be coordinated on the pressure cell 5 after the rebar cage 3 is installed at the bottom of the hole.

"Effects of the Invention" Since the present invention is configured as described above, it has the effects described below.

It is possible to realize a gravel packed bed that is good to cover the entire bottom of the pile. As a result, when cement milk is injected, gravel +
Cement milk can be spread and the injection effect can be enhanced.

[Brief description of drawings]

1a and 1b are schematic views of the gravel filling jig of the present invention shown in the case of a circular pile, FIGS. 2a to 2c are explanatory views of the construction procedure of the present invention, and FIGS. 3a to 3g are lower ends. It is a construction procedure procedure diagram of the cast-in-place concrete pile using the reinforced cage with which the gravel chamber which interposes the pressure cell was attached. 1 ... Drilling hole, 2 ... Bucket, 3 ... Reinforcing cage, 4 ...
Gravel chamber, 5 ... pressure cell, 6 ... spacer, 7,8 ... steel plate, 9 ... grout pipe, 10 ... through hole, 11 ... membrane, 12 ... through hole, 13 ... for hanging Hook, 14 ... Tremy tube, 15 ... Concrete, 16
…… Supporting ground area, 17 …… Gravel filling jig, 18 …… table,
19 …… Cylinder, 20 …… Leg, 21 …… Guide support, 21a …… Tip hook, 22 …… Ring, 23,24 …… Wire, 25 …… Jig, 26 …… Outer ring, 27 …… Inner ring, 28 …… Mesh or sheet material, 29,30 …… Suspending wire.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Kakai 2-5-14 Minamisuna, Koto-ku, Tokyo Inside Takenaka Corporation Technical Research Institute (72) Inventor Kiyoshi Yamashita 2-5-14 Minamisuna, Koto-ku, Tokyo Takenaka Corporation Technical Research Institute

Claims (3)

(57) [Claims] 1. A hopper body which can be filled with gravel on the pressure cell of a rebar cage provided with a gravel chamber having a grout pipe planting pressure cell at the lower end thereof and which can diffuse the gravel around the rebar cage. After carrying in and constructing the reinforced basket, the hopper was used to fill the gap between the gravel chamber and the hole wall with gravel, and the gravel filling construction in the reinforced basket of cast-in-place concrete piles. Law. 2. A filling jig used directly for carrying out the construction method according to claim 1, wherein an umbrella-shaped legged bottom plate around which guide posts with tip hooks for attaching wires stand upright, and the guide. A filling jig for gravel filling in a reinforced basket of cast-in-place concrete pile, which comprises a hopper composed of a wire-hanging cylinder mounted on the bottom plate that is attached to a pillar through a ring taken out. 3. A filling jig used directly for carrying out the construction method according to claim 1, wherein a flexible mesh or a sheet material is stretched with a bend between an outer ring of wire suspension and an inner ring of wire suspension. Filling jig for gravel filling construction in rebar cages of cast-in-place concrete piles that are composed of a hopper.