JP6885669B2 - Construction method of pile foundation and pile foundation - Google Patents

Description

This disclosure relates to a method for constructing a pile foundation and a pile foundation.

When constructing a pile foundation using ready-made piles, generally, the pile circumference fixing liquid is injected and then the rooting liquid is injected. Then, the ready-made pile is submerged in the pile hole until the tip (lower end) of the ready-made pile reaches a predetermined depth in the solidification liquid. After that, the root compaction liquid is cured to form a cylindrical root compaction portion so as to surround the tip portion of the ready-made pile.
For example, the depth of embedding of a ready-made pile in the consolidation part is set to about 3 times the diameter of the ready-made pile, and the length of the part deeper than the tip of the ready-made pile in the consolidation part is the diameter of the ready-made pile. It is set to about twice.

On the other hand, the tip ground improvement pile disclosed in Patent Document 1 is composed of a ready-made pile and a cement pillar or a mortar pillar formed in a support layer deeper than the tip of the ready-made pile, and the cement pillar or the mortar pillar is a peripheral surface thereof. It is formed so that the frictional force is regarded as the bearing capacity of the ready-made pile. According to Patent Document 1, when the depth of the support layer is not constant, the depth of the pile hole changes accordingly, but the diameter and length of the soil cement column (the length of the excess dug portion) are adjusted. By doing so, the tip bearing capacity of the ready-made pile can be set to be the same without changing the length of the ready-made pile.

Japanese Unexamined Patent Publication No. 2004-332262

In the method for designing advanced ground improvement piles disclosed in Patent Document 1, each pile hole reaches the inside of the support layer regardless of the depth of the support layer, and the support layer is excavated to form the pile hole. Has been done. In this case, since the support layer is generally hard, there is a problem that it takes time to excavate the support layer. On the other hand, it may be possible to secure the tip bearing capacity of the pile without having to excavate the support layer.

In view of the above circumstances, an object of at least one embodiment of the present invention is to ensure the minimum necessary pile tip bearing capacity while facilitating the excavation of pile holes by avoiding excavation of the support layer. The purpose is to provide a method for constructing a pile foundation and a pile foundation.

(1) The method for constructing a pile foundation according to at least one embodiment of the present invention is
The excavation process to form pile holes in the ground and
The pile circumference fixing liquid filling step of filling the pile hole with the pile circumference fixing liquid,
A root hardening liquid filling step of filling the lower end of the pile hole with a root hardening liquid,
A ready-made pile insertion step of inserting a ready-made pile into the pile hole is provided.
In the excavation step, excavation of the pile hole is stopped when the upper surface of the support layer in the ground is reached, and then only the soft layer portion at the lower end of the pile hole is excavated by expanding the diameter. ,
In the ready-made pile insertion step, the lower end of the ready-made pile is brought into contact with the upper surface of the support layer.
The root hardening liquid was cured in a state where the lower end of the ready-made pile was in contact with the upper surface of the support layer.
The lower end of the root hardening portion formed by hardening the root hardening liquid is brought into contact with the upper surface of the support layer.
The support layer has unevenness and
In the excavation process, a plurality of the pile holes are formed in the ground,
The lengths of the plurality of pile holes are different from each other depending on the unevenness of the support layer.

According to the above configuration (1), since the excavation of the pile hole is stopped when the support layer is reached, it is not necessary to excavate the support layer, and the time required for excavation can be shortened. On the other hand, according to the above configuration (1), since the lower end of the ready-made pile is brought into contact with the support layer, the ready-made pile is surely supported by the support layer. Therefore, the minimum required pile tip bearing capacity can be reliably secured.
Then, according to the above configuration (1), since the lower end portion of the pile hole is enlarged, the root compaction portion of the pile foundation is expanded, and the peripheral frictional force of the root compaction portion is increased. As a result, a larger pile tip bearing capacity can be secured.

(2) In some embodiments, in the above configuration (1),
The N value of the soft layer is less than 30.

( 3 ) The pile foundation according to at least one embodiment of the present invention is
Pile holes formed in the ground and
A ready-made pile provided at the lower end of the pile hole and inserted into the pile hole,
A solidified part surrounding the lower end of the ready-made pile and
With
The lower end of the pile hole is located at the boundary between the soft layer and the support layer.
The diameter of the pile hole is expanded only in the soft layer portion at the lower end portion of the pile hole.
The lower end of the ready-made pile abuts on the upper surface of the support layer.
The lower end of the root compaction abuts on the upper surface of the support layer.
The support layer has unevenness and
A plurality of the pile holes are formed in the ground,
The lengths of the plurality of pile holes are different from each other depending on the unevenness of the support layer.

According to the above configuration ( 3 ), when constructing a pile foundation, excavation of the pile hole may be stopped when the pile foundation is reached, so that it is not necessary to excavate the support layer and the time required for excavation is shortened. can do. On the other hand, according to the above configuration (3 ), since the lower end of the ready-made pile is in contact with the support layer, the ready-made pile is surely supported by the support layer. Therefore, the minimum required pile tip bearing capacity can be reliably secured.
Then, according to the above configuration (3), since the lower end portion of the pile hole is enlarged, the root compaction portion of the pile foundation is expanded, and the peripheral frictional force of the root compaction portion is increased. As a result, a larger pile tip bearing capacity can be secured.

( 4 ) In some embodiments, in the above configuration ( 3 ),
The N value of the soft layer is less than 30.

According to at least one embodiment of the present invention, a method for constructing a pile foundation and a pile that can surely secure the minimum necessary pile tip bearing capacity while facilitating excavation of pile holes by avoiding excavation of a support layer. The foundation is provided.

It is a figure which shows the schematic structure of the structure to which the construction method of the pile foundation which concerns on one Embodiment of this invention is applied. It is a schematic enlarged view of the region II of FIG. It is a flowchart which shows the schematic procedure of the construction method of the pile foundation which concerns on one Embodiment of this invention. It is a figure for demonstrating each process of the pile foundation construction method of FIG. It is a figure corresponding to FIG. 2 of the pile foundation which concerns on other embodiment.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, and are merely explanatory examples. Absent.
For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a state of relative displacement with tolerances or angles and distances to the extent that the same function can be obtained.
For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, an expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also a concavo-convex portion or chamfering within a range in which the same effect can be obtained. The shape including the part and the like shall also be represented.
On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions that exclude the existence of other components.

FIG. 1 is a diagram showing a schematic configuration of the structure 1. The structure 1 has a pile foundation 2 according to an embodiment of the present invention and a superstructure 4 supported by the pile foundation 2. The pile foundation 2 is composed of a plurality of ready-made piles 6.

FIG. 2 is an enlarged view showing the region II in FIG. 1, and is a cross-sectional view schematically showing the lower end portion of the ready-made pile 6 and its periphery. For example, the ready-made pile 6 has a hollow cylindrical shape, and although not shown, it is composed of hollow cylindrical concrete sandwiched between end plates arranged at both ends of the ready-made pile 6.

The ready-made pile 6 is buried in a pile hole 8 dug in the ground. The lower end of the pile hole 8 is located at the boundary between the soft layer 10 and the support layer 12 in the ground, that is, on the upper surface of the support layer 12. For example, the soft layer 10 is a stratum having an N value of less than 30, and the support layer 12 is a stratum composed of sand, gravel or gravel having an N value of 30 or more. The change in the N value at the boundary between the soft layer 10 and the support layer 12 does not have to be discontinuous, and the N value may change continuously.

The lower end of the ready-made pile 6 is surrounded by the root compaction portion 14. The root compaction portion 14 is made of, for example, cement. The outer shape of the root compaction portion 14 is a cylindrical shape. The portion of the ready-made pile 6 above the root consolidation portion 14 is surrounded by the pile peripheral portion 16. The pile peripheral portion 16 is made of, for example, soil cement.
When the ready-made pile 6 is hollow, the cement and soil cement constituting the root consolidation portion 14 and the pile peripheral portion 16, respectively, are also filled inside the ready-made pile 6.
The lower end of the ready-made pile 6 is in contact with the support layer 12.

FIG. 3 is a flowchart showing a schematic procedure of a method for constructing a pile foundation according to an embodiment of the present invention. FIG. 4 is a diagram for schematically explaining each step of the pile foundation construction method.
As shown in FIG. 3, the pile foundation construction method includes an excavation step S1, a pile circumference fixing liquid filling step S2, a root hardening liquid filling step S3, and a ready-made pile inserting step S4.
In the excavation step S1, as shown in FIGS. 4A and 4B, the excavator 18 is used to excavate the ground to form a pile hole 8 in the ground.
Here, in the excavation step S1, as shown in FIG. 4B, the excavation of the pile hole 8 is stopped when the support layer 12 in the ground is reached.

In the pile circumference fixing liquid filling step S2, the pile circumference fixing liquid 20 is stored in the pile hole 8. Therefore, for example, while excavating the ground as shown in FIG. 4B, the pile circumference fixing liquid 20 is injected from the tip of the excavator 18 into the pile hole 8 being excavated. The excavated soil and the pile circumference fixing liquid 20 are mixed and agitated by the excavator 18.

Next, in the root hardening liquid filling step S3, the root hardening liquid 22 is filled in the lower end portion of the pile hole 8. Therefore, for example, as shown in FIG. 4C, the root hardening liquid 22 is filled in the lower part of the pile circumference fixing liquid 20 and replaced with the root hardening liquid 22. In this case, the root hardening liquid 22 is injected from the tip of the excavator 18 into the lower end of the pile hole 8.
After that, as shown in FIG. 4D, the excavator 18 is pulled up from the pile hole 8 and the ready-made pile insertion step S4 is carried out. When the excavator 18 is pulled up from the pile hole 8, the pile circumference fixing liquid 20 may be agitated by the excavator 18 and the pile circumference fixing liquid 20 may be further injected.
In the ready-made pile insertion step S4, as shown in FIGS. 4 (e) and 4 (f), the ready-made pile 6 is inserted into the pile hole 8 by using, for example, a pile driver 24.

Then, in the ready-made pile insertion step S4, the lower end of the ready-made pile 6 is brought into contact with the support layer 12, and the root hardening liquid 22 is cured in a state where the lower end of the ready-made pile 6 is in contact with the support layer 12. When the root hardening liquid 22 is hardened, the root hardening portion 14 is formed, and when the pile circumference fixing liquid 20 is hardened, the pile peripheral portion 16 is formed.
Therefore, if the support layer 12 is shallow, the pile hole 8 becomes shallow and the ready-made pile 6 becomes short, and if the support layer 12 is deep, the pile hole 8 becomes deep and the ready-made pile 6 becomes long.

According to the above configuration, since the excavation of the pile hole 8 is stopped when the support layer 12 is reached, it is not necessary to excavate the hard support layer 12 as compared with the soft layer 10, and the time required for excavation can be shortened. it can. On the other hand, according to the above configuration, since the lower end of the ready-made pile 6 is brought into contact with the support layer 12, the ready-made pile 6 is surely supported by the support layer 12. Therefore, the minimum required pile tip bearing capacity can be reliably secured.
Whether or not the pile hole 8 has reached the support layer 12 is based on the resistance value (current value of the electric motor or the hydraulic value of the hydraulic motor) acting on the drive device (electric motor or hydraulic motor) of the excavator 18. It is possible to judge.

In some embodiments, the diameter of the pile hole 8 is constant over the entire longitudinal direction, as shown in FIGS. 2 and 4.
According to the above configuration, since the diameter of the pile hole 8 is constant, it is not necessary to enlarge the lower end portion of the pile hole 8, and the pile foundation 2 can be constructed in a shorter period of time.

Finally, the present invention is not limited to some of the above-described embodiments, and includes a modified form of the above-described embodiment and a combination of these embodiments as appropriate.
For example, in the above-described embodiment, the case where the root hardening liquid filling step S3 is carried out after the pile circumference fixing liquid filling step S2 has been described, but the present invention is not limited to this, and the pile is piled up after the root hardening liquid filling step S3. Peripheral fixing liquid filling step S2 may be carried out. That is, regardless of the order of the pile circumference fixing liquid filling step S2 and the root hardening liquid filling step S3, after the pile circumference fixing liquid filling step S2 and the root hardening liquid filling step S3, the root hardening liquid is placed at the lower end of the pile hole 8. 22 may be filled, and the pile circumference fixing liquid 20 may be filled above the root hardening liquid 22.
Further, for example, as shown in FIG. 5, the diameter of the pile hole 8 may be enlarged at the lower end portion. That is, the diameter of the lower end of the pile hole 8 may be larger than the diameter of the upper end or the middle of the pile hole 8. In this case, the diameter of the root compaction portion 26 is larger than the diameter of the pile peripheral portion 16.
According to the above configuration, since the lower end portion of the pile hole 8 is enlarged, the root compaction portion 26 of the pile foundation 2 is expanded, and the peripheral friction force of the root compaction portion 26 is increased. As a result, a larger pile tip bearing capacity can be secured.
When expanding the lower end of the pile hole 8, after digging a straight pile hole 8, the diameter can be expanded only at the lower end of the pile hole 8 by using an excavator for expanding the bottom.

1 Structure 2 Pile foundation 4 Superstructure 6 Ready-made pile 8 Pile hole 10 Soft layer 12 Support layer 14,26 Root compaction 16 Pile circumference 18 Excavator 20 Pile circumference fixing liquid 22 Root compaction 24 Pile driver

Claims (4)

The excavation process to form pile holes in the ground and
The pile circumference fixing liquid filling step of filling the pile hole with the pile circumference fixing liquid,
A root hardening liquid filling step of filling the lower end of the pile hole with a root hardening liquid,
A ready-made pile insertion step of inserting a ready-made pile into the pile hole is provided.
In the excavation step, excavation of the pile hole is stopped when the upper surface of the support layer in the ground is reached, and then only the soft layer portion at the lower end of the pile hole is excavated by expanding the diameter. ,
In the ready-made pile insertion step, the lower end of the ready-made pile is brought into contact with the upper surface of the support layer.
The root hardening liquid was cured in a state where the lower end of the ready-made pile was in contact with the upper surface of the support layer .
The lower end of the root hardening portion formed by hardening the root hardening liquid is brought into contact with the upper surface of the support layer.
The support layer has unevenness and
In the excavation process, a plurality of the pile holes are formed in the ground,
A method for constructing a pile foundation, characterized in that the lengths of the plurality of pile holes are different from each other depending on the unevenness of the support layer. The method for constructing a pile foundation according to claim 1, wherein the N value of the soft layer is less than 30. Pile holes formed in the ground and
The ready-made pile inserted in the pile hole and
A root compaction portion provided at the lower end of the pile hole and surrounding the lower end of the ready-made pile,
With
The lower end of the pile hole is located at the boundary between the soft layer and the support layer.
The diameter of the pile hole is expanded only in the soft layer portion at the lower end portion of the pile hole.
The lower end of the ready-made pile abuts on the upper surface of the support layer .
The lower end of the root compaction abuts on the upper surface of the support layer.
The support layer has unevenness and
A plurality of the pile holes are formed in the ground,
A pile foundation characterized in that the lengths of the plurality of pile holes are different from each other depending on the unevenness of the support layer. The pile foundation according to claim 3 , wherein the N value of the soft layer is less than 30.

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