JP7089928B2 - How to build cast-in-place concrete piles - Google Patents

Description

The present invention relates to a method for constructing cast-in-place concrete piles.

Conventionally, cast-in-place concrete expansion piles are often used as pile foundations in heavy buildings such as skyscrapers.

The cast-in-place concrete expanded pile (cast-in-place concrete pile) is provided with a shaft portion having a substantially constant diameter and a substantially conical stand-shaped expanded bottom portion in which the tip end side of the shaft portion is expanded according to the required bearing capacity. By providing a bottom-expanded portion at the tip of the pile, the bearing capacity can be significantly improved (see, for example, Patent Document 1).

When constructing a cast-in-place concrete expansion pile, for example, an excavator is used to excavate and form an excavation hole having a diameter substantially constant from the ground surface while filling a predetermined depth with a stabilizing liquid. Next, at the stage where the bottom-expanding excavator (bottom-expanding machine such as a bottom-expanding bucket) connected to the tip of the rod is inserted and placed at the tip of the excavator, the rod is moved around the central axis while expanding the bottom-expanding excavator. The ground of the hole wall is excavated by rotating it, and the tip of the hole is expanded. Then, a reinforcing bar cage is built in the expanded excavation hole, and concrete is placed so as to replace the stabilizer using a tremie pipe, and if necessary, the pile head side is backfilled or the pile head foundation is constructed. Construction of cast-in-place concrete expansion piles is completed.

Japanese Patent No. 4120478

Here, when constructing a plurality of expanded piles 1, the pile spacing of adjacent expanded piles 1 is generally secured at least (shaft diameter (average diameter of shaft portion 2) + bottom expanded diameter (average diameter of expanded bottom portion 3)). ..

On the other hand, as shown in FIG. 3, due to the design, there may be a portion where the distance between the pillars 5 of the building body 4 (= the distance between the piles 1) is narrower than the diameter of the expanded bottom. Since unstable portion 6 is generated due to floating of soil, the positions of adjacent bottom expansion piles 1 can be shifted in a plane (sideways) as shown in FIG. 4, or adjacent to each other as shown in FIG. The bottom expansion portion 3 of the bottom expansion pile 1 is displaced in the vertical direction (up and down) so that the bottom expansion portions 3 do not overlap.

However, if the adjacent bottom-expanded piles 1 are displaced in a plane, the position of the pillar 5 of the building body 4 and the position of the pile 1 are displaced, which causes a large moment to be generated in the bottom-expanded pile 1, which is processed. In order to do so, it becomes necessary to thicken the foundation 7 (Fig. 4).

Further, if the bottom expansion portion 3 of the adjacent bottom expansion pile 1 is displaced in the vertical direction, the lower pile 1 is excavated directly under the upper pile bottom 1a, which is caused by the loosening of the ground G of this portion R. There is a risk that the bearing capacity of the upper pile 1 will be insufficient, or the load P of the upper pile 1 will be transmitted to the lower pile 1 and the bearing capacity of the lower pile 1 will be insufficient (FIG. 5).

On the other hand, as shown in FIG. 6, excavation holes of adjacent bottom-expanded piles (expanded pile portions) 1 are excavated and formed at least at intervals where the shaft portions 2 do not overlap, and the ground between the excavation holes of the adjacent bottom-expanded piles 1 is formed. It is also conceivable to excavate and connect two adjacent expanded pile portions (1) with a wall portion 14 to construct one expanded pile portion 1 (see, for example, Patent Document 1).

However, as shown in FIG. 7, when excavating the connecting pile portion 8, the excavator 9 bends toward the excavation hole 10 side of the expanded pile portion (1) previously excavated (the excavation direction shifts). There is a possibility that the ground G of the connecting pile portion 8 cannot be excavated suitably.

On the other hand, if the ground G of the connecting pile portion 8 between the drilling holes 10 of the adjacent bottom-expanded pile portions (1) is excavated by a machine for constructing an underground continuous wall, the drilling holes do not bend and the connecting pile portion 8 is excavated. Excavation work can be done.

However, since the excavator of pile 1 (earth drill, etc.) and the excavator of continuous underground wall (reverse, etc.) have different machines, it will be necessary to put two types of large dedicated machines on site, and continuous underground. The work using the excavator for the wall is expensive and requires a large area for the attached equipment, so that the total cost for constructing the pile 1 becomes very high. In addition, the space required for construction will be extremely large.

In view of the above circumstances, the present invention makes it possible to excavate and form the excavation holes of the adjacent bottom-expanding piles and the connecting piles with the same excavator, and efficiently and economically from the plurality of bottom-expanding piles and the connecting piles. It is an object of the present invention to provide a method for constructing cast-in-place concrete piles capable of constructing a bottom-expanded pile.

In order to achieve the above object, the present invention provides the following means.

The method for constructing a cast-in-place concrete pile of the present invention is provided at a predetermined interval from a bottom-expanded pile portion consisting of a columnar shaft portion and a substantially conical stand-shaped bottom-expanded portion formed by expanding the tip portion of the shaft portion. It is a method of constructing a cast-in-place concrete pile provided with a connecting pile portion connecting the adjacent bottom-expanded pile portions, and at least the excavation hole of the adjacent bottom-expanded pile portion is made by using an excavator for piles. The expansion pile excavation process of excavating at predetermined intervals so that the shafts of the adjacent expansion piles do not overlap, and the side surface along the axial total length of each expansion pile in the excavation hole of each expansion pile. Excavation for piles while being guided in the vertical direction by the excavator guide member installation process of inserting and installing the excavator guide member provided with Using a machine, excavate the ground of the connecting pile portion between the drilling holes of the adjacent bottom-expanded pile portions to form an excavation hole of the connecting pile portion, and connect the excavation holes of the adjacent bottom-expanded pile portions to communicate with each other. The excavator guide member comprises a pile portion excavation step and a concrete placing step of placing concrete in a connecting excavation hole composed of an excavation hole of the adjacent bottom-expanded pile portion and an excavation hole of the connecting pile portion. It is characterized in that a recess is formed only on the surface for guiding the excavator in the excavation of the connecting pile portion .

In the method for constructing a cast-in-place concrete pile of the present invention, one excavator guide member inserted into the excavation hole of one of the adjacent bottom-expanded pile portions is a pile excavator on the surface facing the excavation hole of the other bottom-expanded pile portion. The other excavator guide member is formed with one guide surface for engaging and vertically guiding the excavator for the pile, and the other excavator guide member to be inserted into the excavation hole of the other expanded pile portion. It is desirable that the side surface of the excavator for piles is engaged with the surface of the expanded pile portion facing the excavation hole and provided with the other guide surface for guiding the excavator for piles in the vertical direction. ..

According to the method for constructing cast-in-place concrete piles of the present invention, excavation holes for adjacent bottom-expanded piles and connecting piles can be excavated and formed by the same excavator, and a very large column axial force such as a skyscraper is suitable. It is possible to efficiently and economically construct cast-in-place concrete expansion piles with high bearing capacity that can be supported.

It is a figure which shows the procedure of excavating the ground between adjacent bottom-expanded pile portions in the method of constructing a cast-in-place concrete pile which concerns on one Embodiment of this invention. It is a figure which shows the cast-in-place concrete pile which concerns on one Embodiment of this invention. It is a figure which shows the case which the part where the space between columns (= the space between piles) of a building body is narrower than the expanded bottom diameter occurs. It is a figure which shows the state which the position of the adjacent bottom expansion pile is shifted in a plane. It is a figure which shows the state which the expanded part of the adjacent bottom-expanded pile is shifted in the vertical direction. It is a figure which shows the state which connected the two adjacent bottom-expanded pile parts by the wall part, and constructed as one bottom-expanded pile part. It is a figure which shows the state which the bending occurred at the time of excavating the ground between two adjacent bottom expansion pile parts.

Hereinafter, a method for constructing a cast-in-place concrete pile according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In the method of constructing a cast-in-place concrete pile of the present embodiment, as shown in FIGS. 1 (a) to 1 (c), a conventional excavator 9 for piles is used, and a columnar shaft portion having a substantially constant diameter is used. The excavation hole 10 of the bottom-expanded pile portion 1 composed of the substantially conical platform-shaped bottom-expanded portion 3 formed by expanding the tip of the shaft portion 2 and the shaft portion 2 is predetermined so that at least the shaft portions 2 of the adjacent bottom-expanded pile portions 1 do not overlap. Pre-excavation at intervals (pre-excavation process). The excavation holes 10 of the pair of expanded pile portions 1 are such that the central axis O1 of the shaft portion 2 of each expanded pile portion 1 and the excavated holes 10 of the pair of adjacent expanded pile portions 1 adjacent to each other are connected to each other. Excavation is performed so that the central axis O2 of the excavation hole 11 of the connecting pile portion 8 that excavates and forms the ground G between the excavation holes 10 is arranged on a straight line S1 in a plan view.

Then, at this stage, the excavator guide member 12 is inserted into each of the excavator holes 10 of the adjacent bottom-expanded pile portions 1 (excavator guide member installation step).

The excavator guide member 12 is formed by using, for example, a reinforcing bar 12a and a steel plate 12b, and the excavator guide member 12 inserted into the excavation hole 10 of one of the adjacent bottom-expanded pile portions 1 has the other excavator guide member 12. One guide surface 12c for vertically guiding the excavator 9 for piles is formed on the surface of the bottom-expanded pile portion 1 facing the excavation hole 10, and the other is inserted into the excavation hole 10 of the other bottom-expanded pile portion 1. The excavator guide member 12 is formed with the other guide surface 12c for vertically guiding the excavator 9 for piles on the surface of one of the expanded pile portions 1 facing the excavation hole 10.

When the pair of excavator guide members 12 are inserted into the excavation holes 10 of one of the adjacent bottom-expanded pile portions 1 and the other of the other-bottom-expanded pile portions 1, the guide surfaces 12c of the pair of excavator guide members 12 excavate for the pile. They are arranged facing each other at predetermined intervals according to the size and shape of the machine 9. Further, in the present embodiment, the guide surface 12c of each excavator guide member 12 is part of a concentric circle so as to correspond to the excavator 9 for piles (the side surface of the excavator 9 for piles is engaged) in a plan view. It is formed in an arc shape along it.

At the stage where the pair of excavator guide members 12 are inserted into the excavation holes 10 of the adjacent bottom-expanded pile portions 1 and submerged in the stabilizing liquid, the piles are used between the pair of excavator guide members 12 (pair of guide surfaces 12c). Excavate the ground G between the excavation holes 10 (connecting piles 8) of the adjacent bottom-expanded piles 1 while guiding them to the pair of guide surfaces 12c so as to insert the excavator 9 (connecting pile excavation process). ..

At this time, the excavator 9 is guided by the guide surface 12c of the excavator guide member 12 and guided in the vertical direction. As a result, even when excavating the ground G of the connecting pile portion 8 between the adjacent bottom-expanded pile portions 1, no bending occurs and the ground G between the adjacent bottom-expanded pile portions 1 is suitably excavated. Then, the excavation holes 10 of the pair of expanded pile portions 1 can be connected by the excavation holes 11 serving as the connecting pile portions 8.

Then, the excavation hole 10 of the adjacent bottom-expanded pile portion 1 composed of the shaft portion 2 and the bottom-expanded portion 3 and the excavation hole 11 of the connecting pile portion 8 composed of the shaft portion 2 and the bottom-expanded portion 3 are formed in communication with each other to form a stabilizing liquid. The excavator guide member 12 is pulled out from the connected excavation hole filled with the excavator, and the excavator guide member 12 is removed, a reinforcing bar cage is built, and concrete is placed so as to replace the stabilizing liquid using a tremie pipe (concrete placing step). In addition, if necessary, the pile head side is backfilled, the pile head foundation is constructed, and the construction of the cast-in-place concrete pile 1'is completed.

As shown in FIG. 2, the cast-in-place concrete pile 1'of the present embodiment constructed in this manner has three expanded piles 1 and 8 composed of a shaft portion 2 and a bottom expanded portion 3, and these three expanded bottoms. The central axes O1 and O2 of the shaft portions 2 of the piles 1 and 8 are arranged on the same straight line S1 in a plan view, and the shaft portions 2 and the bottom expansion portions 3 of the adjacent bottom expansion piles 1 and 8 overlap each other. It is constructed in an integrated form.

In other words, the cast-in-place concrete pile 1'of the present embodiment has one side surface 18a and another side surface 18b of the side surface of the shaft connecting portion 18 in which the substantially cylindrical shaft portion 2 of the three expanded piles 1 and 8 is integrated. It extends from the upper end to the lower end of the shaft connecting portion 18 and is formed so as to exhibit an arc uneven shape in which three convex arcuate surfaces 19 having substantially constant diameters are connected in parallel. Conical uneven shape in which one surface 20a and the other surface 20b of the side surface of the bottom-expanding connecting portion 20 in which the bottom-expanding portion 3 is integrated are connected in parallel with three conical surfaces whose diameter gradually increases from the upper end to the lower end of the bottom-expanding connecting portion 20. It is formed to exhibit.

The cast-in-place concrete pile 1'formed in this way can realize a pile having a high bearing capacity by having a large bottom area. Further, in addition to the one surface 20a and the other surface 20b of the side surface of the bottom-expanded connecting portion 20 being formed in a conical uneven shape, the one surface 18a and the other surface 18b of the side surface of the shaft connecting portion 18 are formed in an arc uneven shape. , The frictional resistance of the pile 1'can be significantly improved, and from this point, it becomes possible to realize the pile 1'with a higher bearing capacity.

The bottom area of each of the expanded piles 1 and 8, and the total bottom area of the pile 1'consisting of the shaft connecting portion 18 and the expanded bottom connecting portion 20, may be determined by the required bearing capacity of the pile 1'.

Therefore, in the method of constructing the cast-in-place concrete pile of the present embodiment, it is possible to construct the cast-in-place concrete pile 1'that gives the necessary bearing capacity even when the pillars 5 of the building body 4 are close to each other by design. Further, the excavation of the adjacent bottom-expanded pile portions 1 and the excavation of the connecting pile portions 8 can be performed by using the same excavator 9 for piles such as an excavator without bending the excavation hole 10.

Therefore, according to the method for constructing a cast-in-place concrete pile of the present embodiment, a cast-in-place concrete pile 1'with a high bearing capacity that can suitably support a very large column axial force such as a skyscraper is more efficient than the conventional one. It will be possible to build it economically and economically.

Although one embodiment of the method for constructing a cast-in-place concrete pile according to the present invention has been described above, the present invention is not limited to the above-mentioned one embodiment and can be appropriately changed without departing from the spirit of the present invention. ..

For example, the excavator guide member 12 inserted and arranged in the excavator holes 10 of the adjacent bottom-expanded pile portions 1 may guide the excavator 9 for piles in the vertical direction to excavate the connected pile portion 8. For example, it is not always necessary to limit the shape and configuration as in the present embodiment.

Further, the connecting pile portion 8 does not necessarily have to have a bottom-expanded pile shape including the shaft portion 2 and the bottom-expanded portion 3. That is, if a desired bearing capacity can be obtained, it may be formed and configured only by the shaft portion 2.

1 Cast-in-place concrete pile (expanded pile, expanded pile)
1'Casting concrete pile 1a Pile bottom 2 Shaft 3 Expanded bottom 4 Building body 5 Pillar 7 Foundation 8 Connecting pile 9 Excavator 10 Excavation hole for expanding pile 11 Excavation hole for connecting pile 12 Excavator guide member 12a Reinforcing bar 12b Steel plate 12c Guide surface 14 Wall part 18 Axis connecting part 18a One side 18b Other side 19 Convex arc surface 20 Expanded bottom connecting part 20a One side 20b Other side G Ground O1 Central axis O2 Central axis P Load S1 Straight line

Claims (2)

A connection that connects a bottom-expanded pile portion consisting of a columnar shaft portion and a substantially conical platform-shaped bottom-expanded portion formed by expanding the tip portion of the shaft portion, and adjacent bottom-expanded pile portions provided at predetermined intervals. A method of constructing cast-in-place concrete piles with piles.
Using an excavator for piles, a bottom-expanded pile excavation process for excavating the excavation holes of the adjacent bottom-expanded piles at a predetermined interval so that at least the shafts of the adjacent bottom-expanded piles do not overlap.
An excavator guide member installation process of inserting and installing an excavator guide member having a side surface along the axial length of each of the expanded pile portions in the excavation hole of each expanded pile portion .
While guiding in the vertical direction by the excavator guide member inserted and installed in the excavation hole of each bottom-expanded pile portion, the connecting pile portion between the excavation holes of the adjacent bottom-expanded pile portions is used by using the excavator for piles. The excavation process of the connecting pile part, in which the ground is excavated to form the excavation hole of the connecting pile part and the excavation holes of the adjacent bottom-expanded pile parts are communicated with each other.
It is provided with a concrete placing step of placing concrete in a connecting excavation hole composed of an excavation hole of the adjacent bottom-expanded pile portion and an excavation hole of the connecting pile portion .
The excavator guide member is a method for constructing a cast-in-place concrete pile, characterized in that a recess is formed only in a surface for guiding the excavator in excavation of the connecting pile portion . In the method for constructing cast-in-place concrete piles according to claim 1,
One of the excavator guide members to be inserted into the excavation hole of one of the adjacent bottom-expanded piles is a pile excavator in which the side surface of the excavator for piles engages with the surface of the other of the expanded piles facing the excavation hole. Formed with one guide surface for guiding in the vertical direction,
The other excavator guide member to be inserted into the excavation hole of the other expanded pile portion is vertically engaged with the side surface of the excavator for piles on the surface facing the excavation hole of one expanded pile portion. A method of constructing cast-in-place concrete piles, characterized in that they are formed with the other guide surface for guiding in the direction.

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