JPH09111758A - Cast-in-place concrete pile and construction method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to construct a tension member easily and definitely by providing a dia-expanded area on a concrete pile whose head is exposed and excavating a boring hole and fixing a fixture grip at the tip of the tension member with the dia-expanded area. SOLUTION: A pile reinforcing bar 2 is placed into an excavation hole 1 where concrete 3 is cast only in an area which is the foundation of an underground skeleton. An evacuated area in the upper part is backfilled. After that, underground excavation is executed down to the foundation surface, thereby exposing the head of a pile 4 and constructing the pile 4. Then, a boring hole 5, which is opened in the upper end of the pile 4 and forms a dia-expanded area 5a at the lower part, is bored in the longitudinal direction of the pile 4. A tension member 6, on which a thick plate-like fixture grip 7 is mounted at the tip, is inserted into the boring hole 5 where a grout material is injected in the dia-expanded area and a primary grout filling work is executed. After the tension member 6 is strained, secondary grout filling work is further executed. At that time, the fixture rip 6 is fixed with the size expansion area so that it may act as a support member of tensile force, thereby introducing the tensile force to the pile 4 by way of the grout material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast-in-place concrete pile and its construction method.

[0002]

2. Description of the Related Art As is well known, cast-in-place concrete piles are formed by setting a reinforced basket in an excavation hole and placing concrete. The cast-in-place concrete piles are used as a tensile resistance material. In order to prevent cracking of concrete due to tensile force acting at the time of earthquake, etc., a tensile material such as PC steel stranded wire is embedded in the pile body and a tensile force is applied to this to pre-compress the concrete pile. (Prestress) may be given.

The above-mentioned tensile member is usually a bundle of one or a plurality of PC steel wires, which cannot be easily joined like a reinforcing bar. Therefore, one having a required length is assembled on the ground and placed in concrete. Before inserting the reinforced steel cage into the drill hole, fix it to the reinforced steel cage and insert the sheath tube.After placing concrete, insert a tension material into the sheath tube and tension it to compress the concrete (pre-press). stress)
give.

As described above, at the time of reinforced cage construction, only the sheath tube which can be easily joined is embedded in the pile hole excavated from the ground, the tension material is inserted into the sheath tube after the concrete is placed, and then the mortar or the like is used. The solidification material is injected into the sheath pipe to integrate the pile concrete and the tension material.

[0005]

When an underground skeleton such as a basement is constructed, the foundation surface is located below the ground surface, and the piles are located only below the foundation surface with respect to the entire length of the excavation hole. The actual length is reached, and the concrete is also driven only to a depth corresponding to the actual length of the pile in the lower part inside the drill hole, and the empty part inside the drill hole above that part is backfilled with sand or the like.

For this reason, when a tension member is inserted into the sheath pipe from the ground after placing concrete as in the conventional case, the tension member is also disposed in the blank driving portion, and the ground portion above the actual length of the pile is grounded. Moreover, the construction of the tension member is from the ground and the workability is not good, so in order to eliminate this, it is only necessary to extend the sheath tube to the ground. Similar to the above case, it will be arranged at the blanking portion. Then, the construction of this tensile member is a work during the pile construction, which makes the construction complicated.

The object of the present invention is to eliminate the disadvantages of the above-mentioned conventional example, and when the underground structure such as a basement is constructed, the tension members can be easily and surely constructed, and the tension members can be constructed during the pile construction. Another object is to provide a cast-in-place concrete pile and a construction method thereof that can eliminate the complexity of construction work and have good workability.

[0008]

[Means for Solving the Problems] To achieve the above object, firstly, in the case where an underground skeleton is constructed, a boring hole is provided in a longitudinal direction in a concrete pile whose pile head is exposed by underground excavation. The gist is that a hole is drilled so that its upper end opens to the upper end of the pile, and a tensile member is inserted into the boring hole.

Secondly, the boring hole for inserting the tensile member has a lower end portion formed with an enlarged diameter portion. Thirdly, the boring hole for inserting the tensile member has a spiral groove formed in the hole wall at the lower end portion. Is the gist.

Fourthly, the tension member is folded back in a U shape in the middle, and the folded back portion is positioned at the bottom of the pile and inserted into the hole. The gist is that the folded-back portion is hooked on the connecting portion.

Fifth, in the case where an underground skeleton is constructed, a pile head is exposed by underground excavation and a lower part is formed in a diameter-expanded part by a boring hole formed in the concrete pile in the longitudinal direction. The gist of the invention is to insert a sheath tube having a spiral groove formed therein, and to insert a tension member having a thick plate-shaped fixing body as a pressure bearing body attached to the tip in the sheath tube.

Sixth, in the case where an underground skeleton is constructed, concrete is placed only in the lower part of the pile hole excavated from the ground, which will be the foundation of the underground skeleton, and then underground excavation is performed. The purpose is to expose the head, form a boring hole in the concrete pile, and insert the tensile member there.

Seventh, in the case where an underground skeleton is constructed, after a sheath pipe is built only in a portion which is a base of the underground skeleton in a lower portion in a pile hole excavated from the ground, concrete is poured, Underground excavation exposes the pile head, and either the expanded part or the spiral groove is formed by boring in the lower part of the sheath pipe, and the tensile material is inserted into the expanded part or spiral groove formed inside these sheath pipes and by the boring. What is done is the gist.

According to the present invention as set forth in claims 1 and 6, when an underground skeleton is constructed, concrete is poured only into a portion which is a base portion of the underground skeleton in a lower portion in a pile hole excavated from the ground. After installation, underground excavation is performed to expose the pile head,
After that, by forming a boring hole in the concrete pile and inserting the tension member into this, the tension member can be inserted after the pile work is completed, and the work during the pile work is eliminated, and the workability is good.

According to the second and third aspects of the present invention, in addition to the above action, the boring hole into which the tensile member is inserted has a lower end portion having a diameter-increasing portion, or a spiral groove in the hole wall at the lower end portion. Since it is formed, even if dust such as concrete powder adheres to the hole wall when boring the boring hole, it is possible to prevent the adhesion strength with the grout material injected into the boring hole from decreasing, and the concrete and grout material are integrated. Can be secured.

According to the present invention as set forth in claim 4, the U-shaped folded portion of the tension member is attached to the bearing body and fixed to the bottom of the pile, and the tension force for tensioning the tension member is supported. The pressure body is supported and dispersed by a pair of thick plate-shaped members connected to face each other. Therefore, the tensile stress is not concentrated on the bottom of the pile, and the prestress can be uniformly introduced to the entire pile.

According to the fifth aspect of the present invention, when a thick plate-shaped fixing member is attached to the tip of the tension member as a pressure bearing member, stress tends to concentrate near the fixing member. Since the spiral groove is formed on the tube wall of the sheath tube into which is inserted and the lower part of the boring hole for building the sheath tube is formed in the expanded diameter portion, the stress is dispersed and the prestress is uniformly introduced.

According to the present invention of claim 7, claim 6 is provided.
In addition to the operation according to the present invention described, since the sheath pipe is built in advance in the portion that will be the foundation part of the underground structure in the pile hole, a hole for inserting a tensile member after placing concrete is provided in the pile hole. It is not necessary to perform boring over the entire length, and it suffices to form either the expanded diameter portion or the spiral groove when constructing the tensile member, which further improves the constructability.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a vertical sectional front view showing a first step of the first embodiment of the method for constructing a cast-in-place concrete pile of the present invention, and FIG. 2 is a plan view of the same as above, which is carried out when constructing an underground skeleton such as a basement. is there. First, drill hole 1
After digging holes from the ground, building pile rebars 2 here, and placing concrete 3 only in the lower part of the excavation hole 1 that will be the foundation part of the underground structure, and then in the upper part of the excavation hole 1. The blank part is backfilled with sand or the like, and then underground excavation is performed to the foundation surface to expose the pile head, and the pile body 4 is constructed.

Next, concrete boring is performed on the pile body 4 in the lengthwise direction, and the boring hole 5 is drilled in the lengthwise direction. The lower portion of the boring hole 5 is formed in the expanded diameter portion 5a, or as shown in FIG. 5, a spiral groove 5b is formed in the hole wall as the second embodiment. The expanded diameter portion 5a and the spiral groove 5b are formed by using a mechanical expanded diameter pit or a horizontal jet of high-pressure water jet. On the other hand, the upper end of the boring hole 5 opens at the upper end of the pile body 4.

As shown in FIG. 3, a tension member 6 made of PC steel wire or the like is inserted into the boring hole 5. A thick plate-shaped fixing grip 7 is attached to the tip of the tension member 6, and the grouting material 8 such as mortar is injected into the expanded diameter portion 5a at the tip of the boring hole 5 as shown in FIG. After tensioning the tension member 6, the grout member 8 is further injected into the boring hole 5 to perform the secondary grout.

At this time, since the fixing grip 7 is attached to the tip of the tension member 6, it is fixed to the tip of the boring hole 5 via the grout material 8 and acts as a pressure bearing member for the tension force. Stress is uniformly introduced into the pile body 4 through the grout material 8.

In addition, dust such as concrete powder produced during boring by boring often adheres to the hole wall, but the lower end of the boring hole 6 is formed in the expanded diameter portion 5a,
Or, since the spiral groove 5b is formed here, the grout material 8
The contact area between the concrete and the concrete 3 becomes large, and the integrity can be ensured, so that the introduction of pre-stress is also ensured.

The order of inserting the pulling material 6 and injecting the grout material 8 may be opposite to that described above such that the grout material 8 is injected and then the pulling material 6 is inserted.

In the above-described embodiment, the boring hole 5 was drilled over substantially the entire length of the pile body 4, but in the third embodiment, the lower portion of the borehole 1 excavated from the ground is the lower end portion of the underground structure. Only after pre-building a sheath pipe made of thin-walled steel pipe, etc., after placing concrete, underground excavation is performed to expose the pile head, and only the lower part of the sheath pipe is bored so that either the expanded part or the spiral groove is formed. It can also be formed.

In this case, it is not necessary to drill the boring hole 5 over substantially the entire length of the pile 4, and only the diameter expansion or the scoring of the spiral groove may be performed at the time of applying the tension member 6, so that the workability is improved. .

FIG. 6 shows a fourth embodiment. When the fixing grip 7 is used as a bearing member, the tension member 6 to which the fixing grip 7 is attached is not directly inserted into the boring hole 5, but the spiral groove 9a is formed on the pipe wall. The formed sheath tube 9 is inserted into the boring hole 5 whose lower portion is formed in the expanded diameter portion 5a, the tension member 6 is inserted into the sheath tube 9, and the grout material 8 is inserted into the sheath tube 9 and the boring hole 5. Filled.

As a result, the fixing grip 7 serves as a bearing member.
When using, the tensile stress is likely to concentrate in this portion, but this stress causes the sheath tube 9 in which the spiral groove 9a is formed,
The prestress can be evenly introduced into the entire pile body 4 by being dispersed by the boring hole 5 having the expanded diameter portion 5a.

7 and 8 show another example of the pressure bearing member, in which the tension member 6 is folded back in a U shape in the middle, and the folded back portion 6a is formed.
Position on the bottom of the pile and insert it into the hole, facing each other and connecting member 10b
The pressure-bearing body 10 is formed by a pair of thick plate-shaped members 10a facing each other connected by
And the folded-back portion 6a was hooked on the connecting member 10b.

As a result, the tension member 6 has its U-shaped folded-back portion 6a hooked on the pressure bearing member 10 and fixed to the bottom of the pile, and the tension force when tensioning the tension member 6 causes the tension member 6 to be tightened. It is supported and dispersed by the pair of thick plate-shaped members 10b which are connected so as to face each other. Therefore, the tensile stress is not concentrated on the bottom of the pile, and the prestress can be uniformly introduced to the entire pile.

[0031]

As described above, the cast-in-place concrete pile and the construction method thereof according to the present invention can easily and reliably perform the construction of the tensile member when the underground structure such as the basement is constructed, and the The construction of the tension material can be eliminated, the complexity of the construction can be eliminated, the workability is good, and the prestress can be evenly introduced into the entire pile body.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of a first step showing a first embodiment of a method for constructing a cast-in-place concrete pile of the present invention.

FIG. 2 is a plan view of a first step showing the first embodiment of the method for constructing a cast-in-place concrete pile of the present invention.

FIG. 3 is a vertical sectional front view of a second step showing the first embodiment of the method for constructing a cast-in-place concrete pile of the present invention.

FIG. 4 is a vertical sectional front view of a third step showing the first embodiment of the method for constructing a cast-in-place concrete pile of the present invention.

FIG. 5 is a vertical sectional front view of a main portion of a pile showing a second embodiment of the method for constructing a cast-in-place concrete pile of the present invention.

FIG. 6 is a vertical sectional front view of a main portion of a pile according to a third embodiment of the method for constructing a cast-in-place concrete pile of the present invention.

FIG. 7 is a vertical sectional front view showing an example of a pressure bearing body of a cast-in-place concrete pile of the present invention.

FIG. 8 is a plan view showing an example of a bearing member of a cast-in-place concrete pile of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Excavation hole 2 ... Pile reinforcement 3 ... Concrete 4 ... Pile body 5 ... Boring hole 5a ... Expanded part 5b ... Spiral groove 6 ... Tensile material 6a ... Folding part 7 ... Fixing grip 8 ... Grout material 9 ... Sheath tube 9a ... Spiral groove 10 ... Bearing body 10a ... Thick plate member 10b ... Connecting member

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hideo Hayashi 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Within Kashima Construction Co., Ltd. (72) Masataka Fukushima 1-2-7 Moto-Akasaka, Minato-ku, Tokyo No. Kashima Construction Co., Ltd.

Claims (7)

[Claims] 1. When an underground skeleton is constructed, a boring hole is drilled in a length direction in a concrete pile whose pile head is exposed by underground excavation so that its upper end opens at the upper end of the pile. A cast-in-place concrete pile characterized by having a tensile member inserted in it. 2. The concrete pile according to claim 1, wherein the boring hole into which the tensile member is inserted has a lower end portion formed in a diameter-expanded portion. 3. The concrete pile according to claim 1, wherein the boring hole into which the tensile member is inserted has a spiral groove formed in the hole wall at the lower end. 4. The tension member is folded back in a U shape in the middle, and the folded portion is positioned at the bottom of the pile and inserted into the hole. The cast-in-place concrete pile according to claim 1, wherein the folded-back portion is hooked on. 5. When an underground skeleton is constructed, the pile head is exposed by underground excavation, and the lower part of the concrete pile is formed in the lengthwise direction by boring holes formed in the expanded part, and the pipe wall is spiraled. A cast-in-place concrete pile in which a sheath tube having a groove is inserted, and a tensile member having a thick plate-shaped fixing body as a pressure bearing body attached to the tip is inserted into the sheath tube. 6. In the case where an underground skeleton is constructed, concrete is placed only in the lower portion of the pile hole excavated from the ground, which will be the foundation of the underground skeleton, and then underground excavation is performed to remove the pile head. Exposed, forming a boring hole in the concrete pile,
A method of constructing cast-in-place concrete piles, characterized by inserting a tensile member here. 7. In the case where an underground skeleton is constructed, a sheath pipe is laid only in a portion which will be a foundation of the underground skeleton in a lower portion of a pile hole excavated from the ground, and concrete is then poured, followed by underground excavation. To expose the pile head and form either an expanded diameter part or a spiral groove by boring in the lower part of the sheath tube, and insert a tension material inside these sheath tubes and in the expanded diameter part or spiral groove formed by boring. Construction method for cast-in-place concrete piles.