JPS6383314A - Method for preparing cast-in place pile - Google Patents

Abstract

PURPOSE:To unnecessitate chipping of a pile head section and strengthen peripheral ground, by forming the excavation recess of a large diameter on the outer periphery of the upper section of a pile head, and by permitting concrete including slime to overflow the excavation recess of the large diameter when the concrete is cast in the vertical shaft for pile. CONSTITUTION:After the first stand pipe 1 of a diameter larger than a pile diameter is penetrated into ground and the interior section is excavated, the pile shaft 5 for a specified pile diameter is excavated. After that, a resin-forced cage 7 with a partition cylinder 6 fitted firmly on an upper section is inserted into the pile shaft 5, and concrete is cast in the pile shaft 5 with a tremie tube or the like. Then, concrete C2 including slime pushed upward by the concrete C1 of good quality overflows the upper edge of the parting cylinder 6, and is contained on the outer periphery of the partition cylinder 6. After that, the first stand pipe 1 is drawn out, and the void section is backfilled with earth 11 and is cured. As a result, the chipping of a pile head section is unnecessitated, and strength on the outer periphery of the pile head section is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a cast-in-place pile construction method that eliminates the need for grinding of pile head excess concrete or removal work in an uncured state.

[Conventional technology]

The cast-in-place pile construction method, which eliminates the need for grinding concrete piles on pile heads or removing them in an uncured state, was developed by the Special Publication Publication No. 61-1.
This is already known from Publication No. 6810 and the like. As shown in Figure 4, this cast-in-place pile construction method uses stand pipe a
After excavating the inside, a reinforcing bar cage d to which a cylindrical steel frame C having a flange with an outer diameter approximately equal to the inner diameter of the standpipe a is attached is inserted, and an extra layer is placed on the outer periphery of the cylindrical steel frame C. Concrete is poured with an annular gap having a volume equivalent to the amount of concrete formed, and the defective concrete mixed with slime corresponding to the excess concrete that has been raised by the stand vibrator a is poured from the upper edge of the cylindrical 1i4 frame C. It overflows into the annular gap and is cured at this position.

[Problem that the invention seeks to solve]

However, the above conventional example has the following problems.

In other words, in -&i, for cast-in-place support, the pile diameter is the one that ensures a predetermined concrete covering thickness around the outer periphery of the reinforcing bar corner, so even in the conventional example shown in Fig. 4, the inner diameter is the pile diameter, but in reality, as shown in the figure, a pile hole corresponding to the inner diameter of standpipe a was excavated, resulting in a large waste of excavation and concrete usage.

An object of the present invention is to solve the problems of the conventional example.

[Means for solving problems]

In order to achieve the above object, the present invention provides a large-diameter excavated hole below the design pile top, which has an inner diameter larger than the pile diameter and has a volume approximately twice or more than the amount of excess concrete on the pile head, After that, the central part of the bottom of the large diameter excavation hole is excavated to form a pile hole having the same diameter as the pile diameter, and a reinforcing bar cage is inserted into the pile hole, and a partition whose upper edge matches the top of the designed pile. Concrete is poured with a tube separating the portion corresponding to the pile cap from the large-diameter excavation hole, and an amount of concrete equivalent to the excess concrete overflows from the upper edge of the partition tube into the large-diameter excavation hole around it. As a result, a large-diameter portion made of the overflowing concrete was formed on the outer periphery of the pile head.

[Effect]

According to the above configuration, the slime-containing concrete (corresponding to excess concrete) that has been pushed up by high-quality concrete during concrete placement overflows from the upper edge of the partition tube that is aligned with the top of the set pile.

The overflowing concrete is accommodated in the annular gap around the outer periphery of the partition tube, and only high-quality concrete is located inside the partition tube.

Further, the concrete accommodated in the annular cavity is left behind and hardens in that position, forming a large-diameter portion around the pile head.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

As shown in Fig. 1 (a), the first stand pipe 1 whose inner diameter is larger than the pile diameter is penetrated into the ground, the inside of it is excavated, and the pile cap is reconcrete below the designed pile top p. (If it is too large, the amount of excavation and the amount of concrete used will be wasted, so please
It is desirable to make it twice as large or slightly larger than that. > A large-diameter excavated hole 2 is formed.

Next, as shown in FIGS. 1(B) and 1(C), a disk-shaped member 3 having a through hole 3a having approximately the same diameter as the pile diameter is installed at the bottom of the large-diameter excavated hole 2. The member 3 may be made of steel plate or may be a concrete molded product.

After that, as shown in FIG. 1(d), install the second stand pipe 4 that will serve as a pile hole excavation guide, and insert its lower end into the through hole 3a of the disc-shaped member 3. The lower end of the second stand pipe 4 is positioned by the disk-shaped member 3, and the upper end of the second stand pipe 4 and the upper end of the first stand vibe 1 are connected with a connecting fitting (not shown). , the upper end of the second standpipe 4 is positioned and prevented from falling. In this state, the central part of the bottom of the large-diameter excavated hole 2 is excavated using the earth drill method, reverse circulation method, etc., and a predetermined pile diameter is formed. 1 pile hole 5 is formed.

Next, the second standpipe 4 is pulled out and recovered, and at the same time, as shown in FIG. . The upper edge of the partition tube 6 is made to coincide with the design pile top p. As a result, as shown in FIG. 2, the portion corresponding to the pile g and the large-diameter excavated hole 2 are separated by the partition tube 6, and the outer periphery of the partition tube 6 has a volume equivalent to the amount of excess concrete. An annular void is formed. 8 in Figure 2 is the reinforcing bar cage 7,
The bolts 9, which are eccentrically fixed so as not to interfere with the tremie tube, are nuts that are screwed into both ends of the bolts, and the partition tube 6 is fixed to the reinforcing bar cage 7 by these bolts. The partition tube 6 may be made of any material such as a synthetic resin sheet, a thin steel plate, a galvanized iron plate, etc., but the partition tube 6 may be made of any material such as a synthetic resin sheet, a thin steel plate, a galvanized iron plate, etc., but the material strength or reinforcing means that can withstand the concrete lateral pressure of the pile head is required. The lower end may be in contact with or close to the upper surface of the disc-shaped member 3, but if a thin walled material such as a galvanized iron plate is used as the partition tube 6, it may be placed in contact with or close to the upper surface of the disc-shaped member 3. In addition, it is desirable that the lower end of the partition tube 6 be inserted into the through hole 3a of the disc-shaped member 3.

In this state, as shown in Figure 1 (f), the tremie tube 1
0. Place underwater concrete. The slime-containing concrete (corresponding to excess concrete >CX) pushed up by high-quality concrete CI during concrete pouring overflows from the upper edge of the partition tube 6, as shown in Figure 1 (G). It is accommodated in the annular gap on the outer periphery of the partition tube 6, and only high-quality concrete C1 is located inside the partition tube 6.Drilling fluid and hole wall stabilizing liquid are discharged to the ground as concrete is placed. However, water may be actively pumped out in parallel with concrete pouring.

Thereafter, the first standpipe 1 is pulled out and recovered, and as shown in FIG. 1 (h), it is backfilled with earth and sand 11 for curing.

The slime-containing concrete C2 that overflowed from the partition tube 6 and was accommodated in the annular gap is left behind, hardens at that position, and forms a large-diameter portion 12 around the pile head.

Next, another embodiment of the present invention will be described based on FIGS. 3(A) to 3(G).

As shown in Fig. 3 (a), the first stand vibrator 1 whose inner diameter is larger than the pile diameter is penetrated into the ground, the inside of it is excavated, and the pile cap is placed below the design pile or @p. A large-diameter excavated hole 2 having a volume approximately twice or more than the amount of reconcrete is formed.

After that, as shown in Figure 3 (b) and (c), the pile diameter l
A steel frame A consisting of a partition tube 6 having an inner diameter approximately equal to , and a disk-shaped member 3 having an outer diameter approximately equal to the inner diameter of the first stand vibe 1 which is integrally bent outward from the lower end of the partition tube 6 is enlarged. The partition tube 6 is installed at the bottom of the diameter excavation hole 2 so that the upper edge of the partition tube 6 matches the designed pile top p. This W4 frame body A is constructed to have sufficient strength so that it can serve as the lower half of the second stand vibe 4 described in the previous embodiment. And as shown in Figure 3 (c) and (d),
A stand vibe 4a corresponding to the upper half of the second stand vibe 4 is added to the partition tube 6 of the steel frame A, and the lower end of the stand vibe 4a is positioned by the steel frame A. The upper end of the stand vibe 4a and the upper end of the first stand pipe 1 are connected by a connecting fitting (not shown) to position the lower end of the stand pipe 4a.

In this state, using the stand pipe 4a and the partition tube 6 as excavation guides, as shown in FIG. A pile hole 5 having a predetermined pile diameter l is formed by excavating the pile hole 5.

Next, the stand vibrator 4a is pulled out and collected.

In this state, an annular gap corresponding to the amount of excess concrete is formed around the outer periphery of the partition tube 6.

Thereafter, as shown in FIG. 3(E), the reinforcing bar cage 7 is inserted and underwater concrete is poured using the tremie pipe 10. Concrete mixed with slime was pushed up by high quality concrete C3 during concrete pouring (
C2 (corresponding to excess concrete) overflows from the upper edge of the partition tube 6 and is accommodated in the annular gap on the outer periphery of the partition tube 6, as shown in FIG.
Only high quality concrete C1 will be located inside.

Next, the first stand vibrator 1 is pulled out and recovered, and as shown in FIG. 3 (G), it is backfilled with earth and sand 11 for curing. The slime-containing concrete C2 that overflowed from the partition tube 6 and was accommodated in the annular gap is left behind, hardens at that position, and forms a large-diameter portion 12 around the pile head. The other configurations are the same as in the previous embodiment.

〔Effect of the invention〕

Since the present invention has the above-described configuration, in addition to the advantage that there is no need to grind the pile head excess concrete or remove it in an uncured state, the present invention can exhibit the following effects.

■ A large-diameter excavation hole with an inner diameter larger than the pile diameter and a volume more than twice the amount of excess concrete on the pile head is provided below the design pile top, and then the center of the bottom of the large-diameter excavation hole is to form a pile hole with the same diameter as the pile diameter, insert a reinforcing bar cage into the pile hole, and use a partition tube whose upper edge matches the top of the designed pile to connect the portion corresponding to the pile cap and the large diameter excavated hole. Concrete is placed in a partitioned state, and an amount of concrete equivalent to the excess concrete is allowed to overflow from the upper edge of the partition tube into the large-diameter excavated hole around it to ensure the quality of the concrete at the pile head. Therefore, only the minimum necessary amount of excavation is required, and compared to the conventional example, it is possible to significantly reduce the cost by reducing the excavation work cost and the amount of concrete used.

■Since a large diameter section is formed on the outer periphery of the pile head using concrete that has overflowed from the upper edge of the partition, the outer periphery of the pile head is reinforced or the ground is improved, reducing the horizontal resistance of the pile head. can be increased.

[Brief explanation of the drawing]

FIGS. 1(A) to 1(H) are process explanatory diagrams showing one embodiment of the present invention, and FIG. 2 is a vertical sectional side view of the main part in a state where a reinforcing bar cage is inserted. FIGS. 3(A) to 3(G) are process explanatory diagrams showing another embodiment of the present invention. FIG. 4 is a longitudinal sectional side view of the main parts of a conventional example. 2... Large diameter excavation hole, 5... Pile hole, 6... Partition tube, 7... Rebar cage, 12... Large diameter part, L... Inner diameter,! ...Pile diameter.

Claims (1)

[Claims] A large-diameter excavation hole having an inner diameter larger than the pile diameter and a volume approximately twice or more than the amount of excess concrete on the pile head is provided below the designed pile top, and then the center of the bottom of the large-diameter excavation hole is A pile hole with the same diameter as the pile diameter is formed by excavation, a reinforcing bar cage is inserted into the pile hole, and a partition tube whose upper edge matches the top of the designed pile is used to connect the portion corresponding to the pile cap and the large diameter excavated hole. Concrete is placed in a state where the pile is partitioned, and an amount of concrete equivalent to the excess concrete is overflowed from the upper edge of the partition cylinder into the large diameter excavated hole around it, and the above-mentioned overflow is poured onto the outer periphery of the pile head. A cast-in-place pile construction method characterized by forming a large-diameter section of concrete.