JP2003193465A - Bottom widening method for pile and its structure - Google Patents

Abstract

(57) [Summary] [Problem] To expand a tubular pile capable of increasing a bearing capacity by expanding a pile tip and reinforcing a pile tip ground without disturbing a ground at a peripheral portion and a tip portion outside the pile. Methods and structures are provided. SOLUTION: A pile 2 into which a pile expanding device 3 for expanding the tip of a pile and reinforcing the ground at the tip of a pile 2 having a hollow cross section can be inserted or inserted into a ground without previously drilling the ground. After that, the reinforcing member 4 attached to the bottom expanding device 3 is inserted into the pile tip ground to increase the pile tip support force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for expanding the bottom of a tubular pile, which expands the cross section of the pile without disturbing the ground, and a structure thereof.

[0002]

2. Description of the Related Art Pile foundations have long been used as one of the basic types of building structures and civil engineering structures. The main structural elements that make up the pile foundation are ready-made piles manufactured by factory using steel materials and concrete materials, and cast-in-place piles that are constructed by placing concrete in holes drilled in the ground. It is (hereinafter referred to as a pile collectively).

FIG. 11 shows a conceptual diagram of the supporting force mechanism of the pile, and FIG. 12 shows a typical example of using the pile.

The supporting force Q of the pile 101, which is the resistance performance against external load, is determined by the frictional resistance between the peripheral surface of the pile 101 and the ground.
Friction force Q _{f of} 01 and tip support force Q that supports the tip of the pile
Determined by the sum of _P.

The pile 101 safely supports the structure by transmitting various assumed loads such as the self-weight of the structures 104 and 105 constructed on the upper part of the foundation and the seismic load to the ground 103, and also supports the load. It is used for the purpose of suppressing the displacement caused by the structure within a range that does not hinder the usage conditions of the structure.

Most of the above-mentioned examples of the use of the pile 101 are used as a foundation type for the soft ground 102, but the magnitude of the load per pile (supporting the pile 101 installed in the soft ground 102 ( In most cases, the bearing capacity will be much smaller than the strength of the pile body. In order to support the foundation safely and to satisfy the use performance, it is generally dealt with by increasing the number of piles installed. ing.

[0007] This is one of the main factors that hinder the reduction of the construction cost of the conventional pile foundation construction method, and a construction method that can secure the bearing capacity of the pile as close as possible to the strength of the pile body is desired. ing. Especially, soft ground 1 which is relatively thick near the ground surface
When a relatively lightweight building structure 104 such as a house is built on the ground where 02 exists, the basic cost occupying the entire construction cost must be limited, so that the cross section has a long length. The reality is that you can't use a big pile of. For this reason, in the construction of a house on the soft ground 102, a technique for securing a supporting force by a short pile having a small cross section is important for providing a high-quality and economical house.

However, a pile having a short cross-section can hardly expect frictional resistance on the peripheral surface of the pile, and the pile 101
In many cases, the tip is located in the soft layer, and sufficient tip support force cannot be expected.

On the other hand, as a construction method for securing the pile tip supporting force, a construction method for expanding the pile tip portion has been developed and put into practical use.

[0010]

However, in any of the above-mentioned conventional construction methods, when expanding the bottom of the pile tip or when installing a ready-made pile having a structure such as a bottom expanding wing,
It has the drawback of disturbing the ground (hereinafter also referred to as looseness of the ground).

Furthermore, the conventional method for increasing the bearing capacity of ready-made piles or cast-in-place piles without improving the ground around the piles is as follows:
There are roughly two methods (A) and (B), but the methods and problems are as follows.

(A) Method of excavating bottom of pile tip soil This method is a method of placing a cast-in-place concrete after excavating the soil of pile tip soil in advance, as shown in FIG.

In FIG. 13, FIG. 13 (a) is a view showing the power transmission shaft 201 and its bottom expanding bit 202, FIG.
(B) is a figure which shows the pile tip shape 203 after bottom expansion.

The major drawbacks of this method are:

Lowering of peripheral frictional resistance due to loosening of the ground around the pile outside due to excavation Lowering of pile tip supporting force due to loosening of pile tip ground due to bottom expanding excavation Lowering of pile tip supporting force due to slime accumulation Hole during excavation Degradation of the quality of wall collapsed concrete The construction process is complicated by excavation, hole wall protection, bottom expansion of the pile, slime treatment, reinforcement bar installation, concrete placing or installation of ready-made piles, and pile heads, and shortening the construction period. It is difficult to reduce the construction cost. Among these problems, especially ,,, are considered to be inevitable as the fatal drawback of the method (A).

(B) Method of attaching steel plate blades or bottom expanding device to ready-made piles In this method, as shown in FIG. This is a method in which the support force is increased by anticipating the vertical pressure bearing resistance between the steel plate and the ground by screwing or driving while rotating in the ground 303.

The major drawbacks of this method are:

Since the ground around the pile is shear fractured or disturbed by the steel plate blades or the like at the time of screwing or driving, almost no frictional resistance against the peripheral surface can be expected.

It is almost impossible to install piles without damaging or loosening the pile tip ground, in other words, such control / management in construction is almost impossible, and even if the pile tip supporting force can be secured to the expected level. Even so, a large long-term consolidation settlement occurs due to the disturbance of the tip ground.

These problems are due to the shape of the pile resulting from attaching steel plate blades having an area larger than the outer peripheral cross-sectional area of the pile itself to the prefabricated pile. I think it is inevitable as a fatal flaw.

In view of the above situation, the present invention can increase the supporting force by expanding the pile tip and reinforcing the pile tip ground without disturbing the soil around the pile outer periphery and the tip. An object of the present invention is to provide a method for expanding the bottom of a tubular pile and a structure thereof.

[0022]

In order to achieve the above-mentioned object, the present invention provides [1] a method of expanding a bottom of a tubular pile, wherein inside the pile having a hollow cross section, the bottom of the pile tip is expanded and the ground of the tip portion is reinforced. Perform a pile with a built-in or insert bottom expanding device, without penetrating the ground in advance, after penetrating into the ground to a predetermined depth, then insert the reinforcing member attached to the bottom expanding device into the pile tip ground By doing so, the pile tip supporting force is increased.

[2] In the method of expanding the bottom of a tubular pile, a pile having a hollow member and having a bottom expanding device having a reinforcing member for expanding the bottom of the pile tip and reinforcing the tip ground is built in the pile. And a step of inserting a rod inside the pile having the hollow cross section, pushing down the rod, and pushing the reinforcing member out of the inside of the pile into the ground, and the reinforcing member is planned to penetrate. When inserted to the position, pull out the rod,
A step of filling the inside of the pile having the hollow cross section with an injection material, and combining the bottom expanding device and the reinforcing member with the pile by the injection material to integrate them.

[3] In the method of expanding a tubular pile according to the above [1] or [2], the reinforcing member is inserted into the pile tip ground by using the tip shoe of the pile as a guide.

[4] In the bottom expanding method for a tubular pile according to the above [1] or [2], the reinforcing member is inserted into the pile tip ground by using a slit formed in the pile as a guide. .

[5] In the method for expanding the bottom of a tubular pile according to the above [1] or [2], the bottom expanding device is provided in the middle of the pile to increase the supporting force of the pile in the middle of the pile. And

[6] An expanded bottom structure of a tubular pile, in which the pile is grounded in order to safely support the structure and suppress displacement caused by a load within a range that does not hinder the usage conditions of the structure. In the laying of a tubular pile that penetrates and secures the pile tip supporting force, a bottom expanding device having a reinforcing member that is extruded from a pile having a hollow cross section through a guide and penetrates into the ground, and in the pile having the hollow cross section. And an injection material that is injected and that joins and integrates the bottom expanding device and the reinforcing member with the pile.

[7] In the expanded bottom structure for a tubular pile according to the above [6], the guide is a tip shoe provided at the tip of the pile.

[8] In the expanded structure for a tubular pile according to the above [6], the guide is a slit formed in the pile.

[0030]

[9] In the expanded structure for tubular piles according to the above [6], the reinforcing member is a long member whose upper end is fixed to the head.

[10] Above

In the bottom expanded structure for a tubular pile described in [9], the elongated member is a plate-shaped member.

[11] Above

In the bottom expanded structure for a tubular pile described in [9], the elongated member is a rod-shaped member.

[12] Above

In the structure for expanding the bottom of a tubular pile according to [9], the elongated member is bent to the outside in advance and attached to the hollow pile.

[13] In the bottom expanding structure for a tubular pile according to any one of [6] to [12], the bottom expanding device having the reinforcing member is arranged at an intermediate position of the pile.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

FIG. 1 is a diagram showing a pile tip supporting force increasing mechanism by a bottom expanding device showing an embodiment of the present invention, and FIG. 2 is a pile peripheral surface friction resistance increasing mechanism when the bottom expanding device is applied to the middle part of the pile. And FIG. 3 are process diagrams of the bottom expanding method according to the present invention.

In these figures, 1 is the ground, 2 is a tubular pile (steel pipe pile or control pipe: hereinafter simply referred to as pile),
3 is a bottom expanding device pre-mounted on the tip of the pile 2, 4 is a reinforcing member mounted on the bottom expanding device 3, 5 is a reinforcing member 4, and the ground 1
A tip shoe that serves as a guide for penetrating into a predetermined position inside, 6
Is a penetrating rod for pushing down the bottom expanding device 3, 7 is an injection material such as mortar for filling the periphery of the bottom expanding device 3 and the inside of the pile 2,
Reference numeral 8 indicates the direction of penetration of the reinforcing member 4 inserted into the ground 1.

In FIG. 1, FIG. 1 (a) is an enlarged view showing the bearing cross-sectional area A2 of the tip of the pile 2 with respect to the outer peripheral cross-sectional area A1 of the pile 2, and FIG. 1 (b) is the pile tip ground due to the action of load. It is a reinforcement conceptual diagram of the shear fracture surface generated inside.

When the bottom expanding device 3 according to the method of the present invention is installed at the tip of the pile 2, the apparent cross-sectional area of the tip of the pile 2 projected on a horizontal plane by a plurality of radially open reinforcing members 4 (hereinafter referred to as a support). And the reinforcing member 4
Increases the pile tip supporting force by the double effect of acting as a reinforcing effect of resisting shear failure of the ground 1.

Further, as shown in FIG. 2, when the bottom expanding device 3 is installed at an appropriate position above the tip of the pile 2,
Since the pile diameter at the bottom of the bottom expanding device is apparently increased, it can be expected to increase the frictional resistance of the pile peripheral surface.

Next, the bottom expanding method according to the present invention will be described with reference to FIG.
Will be described with reference to.

Here, FIGS. 3A to 3F show a specific example of the order of performing the bottom expanding method according to the present invention. That is, FIG. 3A is just before the pile 2 is penetrated into the ground 1,
A bottom expanding device 3 having a reinforcing member 4 and a tip shoe 5 are attached to the tip of the pile 2.

FIG. 3 (b) shows immediately after the completion of the penetration of the pile 2 into the ground 1. Until this point, the bottom expanding device 3 and the tip shoe 5 remain in the state of FIG. 3 (a), and therefore the reinforcing member. Four
Is stored inside the pile 2.

FIG. 3C shows a state in which a penetrating rod 6 for pushing the reinforcing member 4 out of the pile 2 and penetrating it into the ground 1 is inserted into the pile 2.

FIG. 3D shows the bottom expanding device 3 with the penetrating rod 6
It is in a state of being pushed down by and the reinforcing member 4 is penetrating into the ground 1, and the reinforcing member 4 is inserted to the expected penetration position along the penetrating direction 8 shown by the broken line.

FIG. 3 (e) shows a state in which the reinforcing rod 4 is pulled out after the reinforcing member 4 has been completely penetrated into the ground 1, and the pile 2 and the bottom expanding device 3 are not yet joined at this point.

FIG. 3 (f) shows a state in which the pile 2 is filled with the filling material (mortar or the like) 7. The bottom expanding device 3 and the reinforcing material 4 are connected to the pile 2 by the filling material 7 to be integrated.

According to the method of expanding the bottom of the pile tip,
There is no protrusion on the outer peripheral surface of the pile 2 from the time when the penetration of the pile 2 is started to the ground 1 until the penetration is completed to a predetermined depth, so that the pile 2 has an amount equivalent to its cross-sectional area. It only pushes the soil away and penetrates into the ground 1. For this reason, when the pile penetrates, as in the conventional bottom-expanding method in which a device having a plate shape or the like that becomes some kind of protrusion is provided on the outer peripheral surface of the pile 2,
It is possible to avoid the drawback that the ground 1 near the outer periphery of the pile 2 is disturbed by these protrusions.

Further, in the construction method in which the ground of the pile installation portion is drilled in advance such as cast-in-place pile, the ground 1 is disturbed due to the collapse of the hole wall that occurs during drilling, or the stability of the hole wall is stabilized. Due to the fact that an extremely soft coating consisting of fine particles in muddy water used for the purpose of
Although it has drawbacks such as reduced frictional resistance of the pile peripheral surface and reduced resistance to displacement, the method according to the present invention does not require pre-drilling, and therefore,
Further, since no stabilizing solution such as muddy water is used, these drawbacks can be avoided. For this reason, the strength and resistance to deformation of the ground 1 can be maintained at the state of natural ground, and at least do not fall below that. Rather, the strength of the ground 1 is improved by the consolidation and compaction of the ground 1 by the penetration of the piles 2. It can also be expected that the deformation resistance will increase.

The method according to the invention, in which the ground 1 is not drilled before the installation of the pile, does not have the drawback of slime depositing on the tip of the pile 2 after the penetration has been completed. Furthermore, after the penetration of the pile 2 is completed, the reinforcing member 4 inserted into the ground at the lower end of the pile 2 that spreads outward beyond the outer circumference of the pile 2 using the tip shoe 5 as a guide is struck by the ground 1. 2 also increases the bearing cross-sectional area A2 that supports the tip of the pile 2, and also serves as a reinforcing material that suppresses shear failure of the ground around the tip of the pile.

As a result, both the effect of increasing the bearing capacity of the pile 2 and the decrease of the settlement amount are exhibited. The reinforcing member 4 attached to the bottom expanding device 3 is the penetration rod 6 inserted into the pile 2.
Since it penetrates into the ground 1 in a predetermined curved shape 9 by the impact force or the pressure input transmitted via
It does not disturb or destroy the ground at the tip of the pile,
The above effect becomes more certain.

As a bottom expanding device having the reinforcing member 4 attached, for example, the examples shown in FIGS. 4 to 7 can be considered.

In FIGS. 4 (a) and 4 (b), a plate-shaped reinforcing member 12 is fixed to a hexagonal head 11, and the tip 12a of the reinforcing member 12 is slightly bent outward. There is.

In FIG. 5, a linear reinforcing member 22 is fixed to the outer circumference of a cylindrical head 21, and a tip 22a of the reinforcing member 22 is slightly bent in advance.

In FIG. 6, a protruding rod 32 is formed at the bottom of a cylindrical head 31, and a linear reinforcing member 33 is fixed to the outer peripheral surface of the cylindrical head 31. The tip 33a of 33 is bent slightly outward in advance. Here, the lower end of the rod 32 comes into contact with a tip shoe (not shown), and functions as a stopper that restricts the downward movement range of the reinforcing member 33.

FIG. 7 shows a reinforcing member 42 formed by bundling thick linear members 41, which has a simple structure. The tip 41a of the linear member 41 is also bent slightly outward in advance.

Further, as a method of penetrating these reinforcing members into the ground in a predetermined curved shape, for example, as shown in FIGS. 8 (a) and 8 (b), the tip shoe 5 and the pile are When the reinforcing member 4 is pushed out from the tip of the pile 2 by appropriately adjusting the opening width with the tip of the pile 2 or by appropriately selecting the opening width of the slit 10 opened in the pile 2, The reinforcing member 4 can be bent in a curved shape by using the tip shoe 5 and the slit 10 as a guide.

Alternatively, as shown in FIG. 9, the reinforcing member 4 processed in advance into the curved shape 9 is attached to the bottom expanding device 3, and this is pushed into the tip end of the pile 2 to be mounted again. When the bottom expanding device 3 is pushed out from the pile 2, the reinforcing member 4 penetrates into the ground 1 while recovering to the original curved shape due to its restoring force. That is,
This example is a method that does not necessarily require a guide like the above-mentioned method, and when this reinforcing member is extruded from the inside of the pile again, it can penetrate into the ground while recovering the shape during processing by its restoring force.

The above embodiment is an example in which the bottom expanding device is mounted at the tip of the pile or at a position close to the tip, but the installation position of the bottom expanding device according to the present invention is not limited to the vicinity of the tip of the pile. It can be installed at any position along the pile axis.

FIG. 10 is a view showing an example in which a bottom expanding device is installed in the middle of such a pile. The same parts as those shown in FIGS. 1 to 3 are designated by the same reference numerals and the description thereof will be omitted.

In this figure, 51 is the lower soft ground formation, 5
2 is a good quality intermediate formation, and 53 is an upper soft formation.

For example, as shown in FIG. 10, a good quality intermediate formation 52 sandwiched between soft formations 53 and 51 at the top and bottom.
When the pile 2 exists through the high quality intermediate formation 52, the bottom expanding device 3 is placed at the position of the high quality intermediate formation 52.
Is an example of installation in the same manner as in the above-mentioned embodiment. In addition, here, the reinforcing means provided in the middle of the tubular pile is also defined as the bottom expanding device.

According to such an embodiment, the good quality intermediate formation 52 which could not be positively used in the conventional pile can be effectively used as a part of the supporting layer. That is, since the pile diameter apparently expands in the section of the high-quality intermediate stratum 52 below the reinforcing member 4 extruded by the bottom expanding device 3 installed in the middle portion of the pile 2, it is expected that the frictional resistance of the peripheral surface of the pile increases. it can. Further, since the load transmitted from the pile 2 to the ground is widely dispersed by the intermediate formation 52, the vertical pressure generated in the soft formation 51 existing therebelow is reduced, and the consolidation settlement of the soft formation 51 is suppressed. Expected to work.

The present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these modifications are not excluded from the scope of the present invention.

[0065]

As described in detail above, according to the present invention, the following effects can be achieved.

(A) Since the bottom expanding device and the reinforcing member are configured to be housed or inserted at least inside the pile so as not to come into contact with the ground, until the time when the penetration of the pile into the ground is completed, There are no protrusions due to members or devices attached to the outer peripheral surface of the pile for the purpose of improving the supporting force. Therefore, since the pile can be penetrated without disturbing the ground around the pile, the circumferential friction resistance of the pile and the lateral resistance against horizontal displacement are not reduced. In addition, since it is not necessary to drill the ground before or during the penetration of the pile, slime or the like having low strength and large compressibility does not remain in the pile tip at the point where the pile tip and the ground contact, and the pile tip It is possible to prevent a decrease in bearing capacity and a large settlement.

(B) After completing the penetration of the pile, the reinforcing member built into the pile tip or attached to the bottom expanding device inserted from the pile head crosses the pile outer circumference without disturbing the ground at the pile tip. It can be inserted into the ground below the pile tip while spreading outward. Such a reinforcing member increases the effective bearing cross-sectional area of the pile tip supported by the ground as in the case where the pile tip is expanded, and prevents the shear failure of the ground around the pile tip. Has a role. As a result, the bearing capacity of the pile can be increased, and the sinking amount of the pile can be reduced.

The reinforcing member mounted on the bottom expanding device is inserted into the ground by a hitting penetration rod inserted into the pile or a press-fitting device. At this time, the reinforcing member penetrates the reinforcing member. By moving only along the penetrating direction or the penetrating shape without moving in the direction orthogonal to the direction, it is possible to prevent disturbance due to shear failure or the like of the ground around the reinforcing member.

[Brief description of drawings]

FIG. 1 is a diagram showing a bottom spreading condition of a pile tip portion and a reinforcing condition of a pile bottom lower ground according to the present invention.

FIG. 2 is an explanatory view of a mechanism for increasing the frictional resistance of the peripheral surface of the pile when the bottom expanding device according to the present invention is applied to the middle portion of the pile.

FIG. 3 is a process drawing of a bottom expanding method according to the present invention.

FIG. 4 is a view showing a first embodiment of a bottom expanding device equipped with a reinforcing member of the present invention.

FIG. 5 is a view showing a second embodiment of the bottom expanding device equipped with the reinforcing member of the present invention.

FIG. 6 is a view showing a third embodiment of the bottom expanding device equipped with the reinforcing member of the present invention.

FIG. 7 is a view showing a fourth embodiment of the bottom expanding device equipped with the reinforcing member of the present invention.

FIG. 8 is a diagram showing an embodiment of a guide for a reinforcing member of the present invention.

FIG. 9 is a view showing an embodiment of a bottom expanding device equipped with a reinforcing member which is bent in advance into a predetermined shape according to the present invention.

FIG. 10 is a view showing an example in which a bottom expanding device is installed in the middle portion of the pile of the present invention.

FIG. 11 is a conceptual diagram of a supporting force mechanism for a pile.

FIG. 12 is a diagram showing a typical usage example of a pile.

FIG. 13 is an explanatory view of a conventional method for placing cast concrete after excavating the ground at the tip of the pile in advance.

[Fig. 14] A steel plate wing is attached to the peripheral surface or near the tip of a conventional ready-made pile, and it is screwed while rotating it into the ground to expect vertical pressure resistance between the steel plate and the ground, thus enhancing the bearing capacity. It is explanatory drawing of the method to be tried.

[Explanation of symbols]

1 ground 2 tubular piles 3 Bottom expanding device 4 Reinforcement member 5 Tip shoe 6 Penetration rod 7 Injection material 8 Reinforcement member penetration direction 9 curved shape 10 slits 11 Hexagonal head 12 Plate-shaped reinforcing member 12a, 22a, 33a Tip of reinforcing member 21,31 Cylindrical head 22,33 Linear reinforcing member 32 protruding rod 41 Thick linear member 41a Tip of linear member 42 Reinforcement member made of a bundle of thick linear members 51 Lower soft strata 52 High quality middle strata 53 Upper soft strata

Claims (13)

[Claims] 1. A pile in which a bottom expanding device that expands the bottom of the pile and reinforces the ground at the tip of the pile is incorporated or inserted inside a pile having a hollow cross section is provided in the ground without preliminarily drilling the ground. The method for expanding the bottom of a tubular pile is characterized in that the pile tip supporting force is increased by inserting the reinforcing member mounted on the bottom expanding device into the pile tip part ground after penetrating to the depth of. 2. (a) A step of penetrating into the ground a pile having a hollow section, which can incorporate or insert a bottom expanding device having a reinforcing member for expanding the bottom of the pile and reinforcing the ground at the tip. , (B) a step of inserting a rod into the pile having the hollow cross section, pushing down the rod, and pushing the reinforcing member out of the pile to penetrate into the ground, and (c) the reinforcing member penetrates. When inserted into a predetermined position, pulling out the rod, filling the inside of the pile having the hollow cross section with an injection material, and combining the bottom expanding device and the reinforcing member with the injection material by the injection material to integrate them. A method for expanding the bottom of a tubular pile, which is characterized by applying it. 3. The method for expanding a tubular pile according to claim 1, wherein the reinforcing member is inserted into the pile tip portion ground using the tip shoe of the pile as a guide. . 4. The method for expanding the bottom of a tubular pile according to claim 1, wherein the reinforcing member is inserted into the pile tip portion ground by using a slit formed in the pile as a guide. Method. 5. The method for expanding the bottom of a tubular pile according to claim 1, wherein the bottom expanding device is provided in the middle of the pile to increase the supporting force of the pile in the middle of the pile. Bottom expansion method. 6. A tubular shape for safely supporting a structure and suppressing a displacement caused by a load within a range that does not hinder the use condition of the structure by penetrating a pile into the ground to secure a supporting force at the tip of the pile. In the laying of piles, a bottom expanding device having a reinforcing member that is extruded from a pile having a hollow cross section through a guide and penetrates into the ground, and is injected into a pile having the hollow cross section, and the bottom expanding device and the reinforcing member are An expanded bottom structure for tubular piles, comprising: an injection material that is combined with and integrated with the piles. 7. The bottom expanding structure for a tubular pile according to claim 6, wherein the guide is a tip shoe provided at the tip of the pile. 8. The bottom expanding structure for a tubular pile according to claim 6, wherein the guide is a slit formed in the pile. 9. The bottom expanding structure for a tubular pile according to claim 6, wherein the reinforcing member is an elongated member having an upper end fixed to a head. 10. The bottom expanding structure for a tubular pile according to claim 9, wherein the elongated member is a plate-shaped member. 11. The bottom expanding structure for a tubular pile according to claim 9, wherein the elongated member is a rod-shaped member. 12. The bottom expanding structure for a tubular pile according to claim 9, wherein the elongated member is preliminarily bent to the outside and attached to the hollow pile. 13. The bottom expanding structure for a tubular pile according to claim 6, wherein a bottom expanding device having the reinforcing member is arranged at an intermediate position of the pile. object.