Pile construction method, pipe pile and pile structure

Abstract

To provide a pile construction method that is simpler and cheaper than conventional methods, in which a pipe pile with a slit formed in a peripheral wall is pressed into the ground and expanded from an inside, and to provide a pipe pile that can be used for the method.SOLUTION: A hollow and straight pipe pile 1 is prepared by forming multiple slits 12 extending in the longitudinal direction of the material in a peripheral wall of the pipe pile 1, forming easily expandable sections 11, and closing off a tip of the pipe pile 1. The pipe pile 1 is buried to a predetermined depth in the ground by pressing or driving, and a flange-shaped anti-subsidence device 3 is attached to a head thereof so as to abut against the ground surface. Crushed stone 4 is poured into the pipe pile 1, and pressure is applied from above the pipe pile 1, causing the easily expandable sections 11 to bulge outward in the radial direction, increasing the peripheral friction force within the ground.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The invention disclosed in this application relates to a pile construction method for burying pipe piles made of steel pipes or other hollow straight pipes in the ground to obtain bearing capacity, the pipe piles used in this method, and pile structures constructed using this method. [Background technology]

[0002] When constructing houses and other small to medium-sized buildings, small-diameter (approximately φ100mm to φ200mm) steel pipe piles are often used to ensure sufficient ground bearing capacity. The following methods are used to construct small-diameter steel pipe piles: (1) A method of construction in which a steel pipe pile with a spiral impeller attached to the tip of the pile is rotated to penetrate the ground while excavating, and the tip of the pile reaches a hard layer, thereby obtaining bearing capacity. (2) A pile construction method in which a straight pipe without stirring blades is pressed into the ground without rotating or while rotating, and bearing capacity is obtained by the frictional resistance of its periphery. are typical examples.

[0003] The pile construction method (1) requires a large construction machine to drive the steel pipe pile into the ground, and depending on the ground condition, the tip of the pile must reach a deep, hard layer, which often results in a large pile length and high construction costs. In addition, the rotation of the mixing blades disturbs the soil in the ground, so surface friction cannot be obtained.

[0004] On the other hand, the pile construction method (2) is simpler and cheaper to construct than the pile construction method (1), but if the ground is soft, sufficient surface friction force cannot be obtained, and construction may be difficult if there are obstacles such as rocks in the shallow part of the ground.

[0005] Therefore, a construction method has been proposed in which a straight steel pipe pile is driven into the ground, and then the circumferential surface of the steel pipe pile is expanded radially outward from the inside to increase the circumferential friction force.For example, Patent Documents 1 to 4 disclose techniques in which a steel pipe pile with slits formed in the circumferential wall at the tip or middle part is driven into the ground, and then a mechanical diameter expansion device is inserted into the steel pipe pile or an expansive material is filled in to expand the diameter of the slit portion. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 55-009953 [Patent Document 2] Japanese Patent Application Publication No. 57-108314 [Patent Document 3] Japanese Patent Publication No. 63-233117 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-070478 Summary of the Invention [Problem to be solved by the invention]

[0007] The invention disclosed in this application aims to provide a pile construction method that employs a diameter expansion means that is simpler and less expensive to construct than conventional methods, as well as a pipe pile that can be suitably used in this method, and a pile structure constructed by this method, in relation to the pile construction method in which a steel pipe pile or the like with a slit formed in the surrounding wall is pressed into the ground and expanded from the inside, as described above. [Means for solving the problem]

[0008] The pile construction method adopted by the present application to achieve the above-mentioned object is characterized as including the following [Step 1] to [Step 6]. [Step 1] By forming multiple slits in the peripheral wall of a hollow straight pipe, extending in the longitudinal direction of the straight pipe and penetrating the peripheral wall in an inward and outward direction, the peripheral wall in that part becomes an easily expandable section, and a pipe pile is prepared with the tip of the straight pipe closed. [Step 2] The pipe pile is buried in the ground to a predetermined depth by pressing or driving. [Step 3] Attach a subsidence prevention device to the head of the pipe pile and abut the subsidence prevention device against the ground surface. [Step 4] Crushed stone is poured into the pipe pile, filling it up to at least the height of the easily expandable portion. [Step 5] A pressure device is used to apply pressure to the crushed stone from above the pipe pile, causing the easily expandable portion to expand and deform in the radially outward direction. [Step 6] Stop applying pressure to the crushed stone, remove the pressure device, and remove the anti-settling device.

[0009] In this pile construction method, the following [Step 7] and [Step 8] may be carried out following the above [Step 1] to [Step 6]. [Step 7] Adjust the head of the pipe pile to the specified height. [Step 8] The foundation of the building is constructed on top of the adjusted pipe piles.

[0010] Furthermore, the pile construction method adopted in the present application is characterized in that in the above-mentioned [Step 2], the pipe pile is embedded while being rotated and pressed in a certain direction.

[0011] In this pile construction method, the pipe pile prepared in [Step 1] is formed so that the penetration direction of the slit appearing in a cross section perpendicular to the material axis of the easy-to-expand section is inclined at a predetermined angle relative to the radial direction of the pipe pile, and in [Step 2], it is preferable to construct the pipe pile so that the inside of the penetration direction of the slit is ahead in the rotation direction of the pipe pile.

[0012] Furthermore, the pipe pile invention disclosed in this application can be characterized as a pipe pile consisting of a hollow straight pipe, the tip of which is closed and the peripheral wall of which is provided with an easily expandable diameter portion having a plurality of slits formed therein that extend in the longitudinal direction of the straight pipe and penetrate the peripheral wall in an inward and outward direction, and the easily expandable diameter portion is formed so that the penetrating direction of the slits as seen in a cross section perpendicular to the material axis is inclined at a predetermined angle relative to the radial direction of the straight pipe.

[0013] Furthermore, the pipe pile may be one in which the easily expandable diameter portions are provided at a plurality of locations at predetermined intervals in the material axial direction.

[0014] Furthermore, the pile structure invention disclosed in this application is characterized as having an easily expandable portion formed on the peripheral wall of a pipe pile consisting of a hollow straight pipe with a closed tip, with multiple slits extending in the longitudinal direction of the pipe pile and penetrating the peripheral wall in an inward and outward direction, the pipe pile being buried in the ground, crushed stone being filled inside the pipe pile, and the crushed stone being pressurized, causing the easily expandable portion to bulge and deform in a radially outward direction within the ground.

[0015] Furthermore, the easily expandable diameter portion is characterized in that the penetration direction of the slits, as seen in a cross section perpendicular to the material axis, is inclined at a predetermined angle with respect to the radial direction of the straight pipe. [Effects of the Invention]

[0016] According to the pile construction method configured as described above, the impact of obstacles in the ground can be reduced by embedding the pipe pile in the ground by pressing or driving it in. Then, by the simple process of applying pressure to the crushed stone filled inside the pipe pile from the head side of the pipe pile, the easily expandable portion formed in the pipe pile is deformed radially outward, increasing the peripheral frictional force of the pipe pile against the ground, thereby obtaining excellent bearing capacity.

[0017] Furthermore, by using a pipe pile configured as described above, it is possible to prevent surrounding soil and sand from entering the inside of the pipe pile through the slits formed in the peripheral wall when the pipe pile is rotary-driven into the ground.

[0018] Furthermore, with the pile structure configured as described above, the frictional force of the peripheral surface of the pipe pile against the ground increases, and excellent bearing capacity can be obtained. [Brief explanation of the drawings]

[0019] [Figure 1]1 is an explanatory diagram showing the construction method from [Step 1] to [Step 4] in the pile construction method disclosed in the present application, in which (a) to (c) are external views and (d) is a cross-sectional view. [Figure 2] Similarly, this is an explanatory diagram showing the construction method from [Step 5] to [Step 7], (E) and (F) are cross-sectional views, and (G) and (H) are half cross-sectional and half external views. [Figure 3] Similarly, this is an explanatory diagram showing the construction method of [Step 8], with (K) to (K) being half cross-sectional and half external views. [Figure 4] This is a cross-sectional view of an easily expandable portion of a pipe pile according to one embodiment of the invention disclosed in the present application, taken perpendicular to the material axis. [Figure 5] FIG. 2 is a perspective view showing an example of the head of the pipe pile and an attachment attached to the head. [Figure 6] FIG. 10 is a perspective view showing an example of a subsidence prevention device attached to the head of the pipe pile. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the invention disclosed in the present application will be described.

[0021] [Pipe pile] This pile construction method uses small-diameter steel pipes with hollow circular cross sections as pipe piles. The specifications for steel pipes used for supports, scaffolding, piles, etc. in architectural and civil engineering work are stipulated in the Japanese Industrial Standard (JIS) G3444:2015 "General Structural Carbon Steel Pipes." "Small-diameter steel pipe piles" usually refer to a pile construction method that uses steel pipe piles with an outer diameter of 101.6 mm to 267.4 mm. However, this pile construction method is intended to use steel pipes with an outer diameter of approximately 139.8 mm and a wall thickness of 4.5 mm to 267.4 mm and a wall thickness of 6.0 mm.

[0022] However, the invention disclosed in this application does not limit the size of the steel pipe to the above range. Metallic pipes other than steel pipes can also be used. Resin pipes made of fiber-reinforced plastic (FRP), carbon fiber-reinforced plastic (CFRP), and other materials can also be used as long as they have sufficient rigidity and undergo appropriate plastic deformation. A pipe material that is easily plastically deformed can be used for the easily expandable diameter section (described below), and a pipe material of the same diameter with high rigidity can be used for the other general sections, and these can be joined in appropriate places. In this specification and claims, these hollow pipe materials are collectively referred to as "straight pipes."

[0023] 1 to 3 are explanatory diagrams showing the pile construction method disclosed in the present application in the order of steps. The steps will be explained below with reference to these drawings. Note that these drawings are schematic representations, and the thickness, length, and other details of the pipe piles are appropriately exaggerated to fit the page size.

[0024] [Process 1]~[Process 2] In this pile construction method, prior to on-site construction, a pipe pile 1 is prepared in which an easily expandable section 11 is formed in the peripheral wall of the straight pipe near the tip or in the middle, as described above. The easily expandable section 11 is a section in which multiple slits 12 extending in the longitudinal direction of the pipe pile 1 and penetrating the peripheral wall of the pipe pile 1 in an inward-outward direction are formed at regular intervals around the circumference of the pipe pile 1. The pipe pile 1 illustrated in Figure 1(A) has two easily expandable sections 11 provided at an appropriate interval in the middle part in the longitudinal direction. Each easily expandable section 11 has four slits 12 extending parallel to the axis of the pipe pile 1, which are aligned in length and spaced apart by 90 degrees in central angles in a cross section perpendicular to the axis of the pipe pile 1 (see Figure 4). However, the number of slits 12 is not limited to four, and can be selected as a guideline from about 2 to 12 (more preferably about 4 to 8) within a range that allows for balanced expansion in the circumferential direction without compromising the compressive strength of the peripheral wall of the pipe pile 1. Furthermore, the number of easily expandable portions 11 provided in the material length direction of one pipe pile 1 is not limited to two, and may be one, three, or more. Furthermore, different numbers of slits 12 may be formed in multiple easily expandable portions 11.

[0025] The dimensions of the slits 12 are selected appropriately depending on the material, pipe diameter, wall thickness, etc. of the straight pipe that constitutes the pipe pile 1, but the length is generally 2 to 5 times the pipe diameter, and the width is approximately 5 mm to 12 mm. It is preferable that the multiple slits 12 lined up in the circumferential direction in one easy-to-expand diameter section 11 are all formed to the same length and width. However, if there are a large number of slits, it is also possible to select a configuration in which long slits 12 and short slits 12 are arranged alternately.

[0026] Furthermore, the slits 12 do not necessarily have to be formed parallel to the material axis of the pipe pile 1, and may be slightly inclined relative to the material axis as long as they extend roughly in the longitudinal direction of the pipe pile 1. Even if they are inclined, it is preferable that the multiple slits 12 lined up in the circumferential direction in one easy-to-expand diameter portion 11 be arranged parallel to each other at equal intervals.

[0027] Furthermore, in this invention, it is assumed that the pipe pile 1 will be pressed into the ground while being rotated in the next step [Step 2]. To prevent soil from entering the interior through the slits 12 during rotation, the slits 12 are formed to penetrate the peripheral wall of the pipe pile 1 at an angle. That is, as shown in FIG. 4, the penetration direction of each slit 12 appearing in a cross section perpendicular to the material axis of the easily expandable portion 11 is not in the radial direction of the pipe pile 1, but is formed so as to be inclined at a predetermined angle α (approximately 50 degrees in the illustrated embodiment) relative to the radial direction. This inclination angle α can also be set within a range of approximately 30 to 60 degrees depending on the material, pipe diameter, wall thickness, etc. of the straight pipe that constitutes the pipe pile 1. Then, in [Step 2], the pipe pile 1 is rotated so that the inner side of the slit 12 in the penetration direction leads the rotation direction of the pipe pile 1.

[0028] When driving a pipe pile 1 into the ground, a roughly cylindrical attachment 2, such as that shown in Figure 5, is attached to the head of a pile driver (not shown), and placed over the head of the pipe pile 1. The connecting protrusion 13 on the side of the pipe pile 1 is then engaged with the engagement groove 21 of the attachment 2, and the pipe pile is set in place. The tip (bottom end) of the pipe pile 1 is sealed in advance by attaching a pointed cap 14 to prevent soil and sand from entering the inside. The pipe pile 1 is then basically driven into the ground while being rotated. The direction of rotation is as described above (Figure 4). If the soil is soft and the pipe pile 1 can be driven in without being rotated, it may be driven without being rotated.

[0029] As shown in Figure 1(a), when the head of the pipe pile 1 reaches the vicinity of the design ground level GL, the press-in is stopped and the attachment 2 is removed from the head of the pipe pile 1. If a bearing capacity equal to or greater than a predetermined value is achieved before the head of the pipe pile 1 reaches the design ground level GL, the press-in of the pipe pile 1 can be stopped at that point and the excess portion of the pipe pile 1 can be cut off.

[0030] [Process 3]~[Process 4] Next, as shown in Figure 1(c), a subsidence prevention device 3 is attached to the head of the pipe pile 1. As shown enlarged in Figure 6, this subsidence prevention device 3 has a hollow tubular portion 31 that fits over the head of the pipe pile 1, similar to the attachment 2 used in the aforementioned [Step 2]. The lower part of the tubular portion 31 is formed with an engagement groove 32 that can engage with the connecting protrusion 13 of the pipe pile 1. A flange-shaped pressure plate 33 that protrudes radially outward is attached to the middle part of the tubular portion 31. The subsidence prevention device 3 is set on the pipe pile 1 so that this pressure plate 33 abuts against the design ground surface GL. Note that if the excess portion of the pipe pile 1 is removed in the aforementioned [Step 2], the engagement groove 32 of the subsidence prevention device 3 cannot be engaged with the connecting protrusion 13 of the pipe pile 1. Therefore, the subsidence prevention device 3 may be connected to the pipe pile 1 by bolt and nut joints, etc.

[0031] Next, as shown in Figure 1(d), crushed stone 4 is poured into the pipe pile 1 through the top opening of the subsidence prevention device 3. If the inside diameter of the pipe pile 1 is small, a funnel-shaped loading aid 5 may be attached to the top opening of the subsidence prevention device 3. Crushed stone 4 to be poured can be crusher run (C-30) with a maximum particle size of approximately 30 mm, or recycled crushed stone (RC-30) mixed with concrete waste. However, other materials are also available, such as sized crushed stone, natural boulders, and blast furnace slag, as long as they can withstand pressure. In this specification and claims, these materials are collectively referred to as "crushed stone." Crushed stone 4 is filled up to near the head of the pipe pile 1 (the position reached by the pressure device in the next step [Step 5]).

[0032] [Step 5] Next, as shown in Figures 2(e) to 2(f), pressure is applied from above the pipe pile 1 to the top surface of the crushed stone 4 filled in the pipe pile 1 using a pressure device. The pressure device used is a hammer 6 with a diameter smaller than the inner diameter of the pipe pile 1, for example, connected to the head of a pile driver. The subsidence prevention device 3 attached to the head of the pipe pile 1 prevents the entire pipe pile 1 from settling due to this pressure, and acts to concentrate pressure on the easily expandable portion 11 of the pipe pile 1. This pressure then causes the easily expandable portion 11, which has slits 12 formed therein, to bulge outward in the radial direction, increasing the peripheral friction of the pipe pile 1 against the ground.

[0033] Furthermore, for example, if the overall length of the pipe pile 1 is large and there are multiple easily expandable sections 11, it is possible to adopt a construction procedure in which crushed stone 4 is not poured all at once up to near the head of the pipe pile 1, but rather crushed stone is first poured up to the height of the lower easily expandable section 11 and pressurized, causing the lower easily expandable section 11 to swell and deform, and then additional crushed stone is poured and pressurized again, causing the upper easily expandable section 11 to swell and deform.

[0034] [Process 6]~[Process 7] When the top surface of the crushed stone 4 settles to a certain extent due to pressure, it is determined that the easily expandable portion 11 has bulged and deformed, and pressure is stopped, the pressure device is removed, and the settlement prevention device 3 is also removed. Then, as shown in Figure 2(g), excavation is carried out around the head of the pipe pile 1 to match the level of the bottom of the foundation, and adjustments are made by cutting the head of the pipe pile 1, etc. If further necessary, the excavated area is backfilled as shown in Figure 2(h).

[0035] [Step 8] After this, the foundation work for the building begins. As shown in Figure 3 (K) to (K), the area around the head of the pipe pile 1 whose height has been adjusted is again uprooted, and the foundation 7 of the building is constructed on top of it using an appropriate construction method.

[0036] This pile construction method, in which crushed stone 4 is filled inside a pipe pile 1 buried in the ground by rotary pressing or driving, and pressure is applied to the crushed stone 4 from above to cause the easily expandable portion 11 to expand and deform, is far simpler and less expensive than conventional methods that use complex expansion equipment or large-scale heavy machinery. Because this is a so-called "dry" construction method that does not use fluid materials such as cement milk or mortar, there are fewer constraints on the construction schedule (arrangement), and construction site management is easy. This method thus significantly improves the ease of construction in building pile construction.

[0037] The technical scope of the invention disclosed herein should not be construed as being limited by the exemplified embodiments, but should be construed conceptually based on the claims. The names of elements used in the claims and the specification are for convenience in making the invention easier to understand, and the names do not unnecessarily limit the concepts or properties of the elements. When implementing the invention disclosed herein, the detailed shape, dimensions, structure, materials, quantity, connection form with other elements, relative positional relationship, etc. of elements not specifically specified in the claims may be appropriately modified within the scope of utilizing an operating principle substantially equivalent to the exemplified embodiments or within the scope of obtaining effects substantially equivalent to or greater than those of the exemplified embodiments.

[0038] For example, in the above-described embodiment, a process of attaching a cap to the tip of the pipe pile before the pipe pile is pressed into place was exemplified, but the process of blocking the tip of the pipe pile may be carried out in parallel with the processing of the slit, or the slit may be processed in a straight pipe whose tip has already been blocked with an appropriate blocking member.

[0039] In the above embodiment, rotary press-in was used as an example of the method for embedding the pipe pile in Step 2, but the method for embedding the pipe pile is not limited to this, and other press-in or driving methods may be used. For example, the method may involve excavating the ground to a predetermined depth in advance and then inserting the pipe pile into the excavated hole.

[0040] Furthermore, the embodiments and other matters disclosed in this specification can also be understood as the technical ideas described in the following supplementary notes.

[0041] (Appendix 1) A pile construction method including the following [Step 1] to [Step 6]. [Step 1] By forming multiple slits in the peripheral wall of a hollow straight pipe, extending in the longitudinal direction of the straight pipe and penetrating the peripheral wall in an inward and outward direction, the peripheral wall in that part becomes an easily expandable section, and a pipe pile is prepared with the tip of the straight pipe closed. [Step 2] The pipe pile is buried in the ground to a predetermined depth by pressing or driving. [Step 3] Attach a subsidence prevention device to the head of the pipe pile and abut the subsidence prevention device against the ground surface. [Step 4] Crushed stone is poured into the pipe pile, filling it up to at least the height of the easily expandable portion. [Step 5] A pressure device is used to apply pressure to the crushed stone from above the pipe pile, causing the easily expandable portion to expand and deform in the radially outward direction. [Step 6] Stop applying pressure to the crushed stone, remove the pressure device, and remove the anti-settling device.

[0042] (Appendix 2) In [Step 2] of the pile construction method described in Appendix 1, The pipe pile is buried while being rotated and pressed in a certain direction. A pile construction method characterized by the above.

[0043] (Appendix 3) In the pile construction method described in Appendix 2, The pipe pile prepared in [Step 1] is formed so that the penetration direction of the slit appearing in the cross section perpendicular to the material axis of the easy-to-expand diameter portion is inclined at a predetermined angle with respect to the radial direction of the pipe pile, In [Step 2], the pipe pile is rotated so that the inner side in the penetration direction of the slit leads in the rotation direction of the pipe pile. A pile construction method characterized by the above.

[0044] (Appendix 4) A pipe pile consisting of a hollow straight pipe, The straight pipe has a peripheral wall provided with an easily expandable diameter portion formed by forming a plurality of slits extending in the material length direction of the straight pipe and penetrating the peripheral wall in an inward and outward direction, The easily expandable diameter portion is formed so that the penetration direction of the slits, which appears in a cross section perpendicular to the material axis, is inclined at a predetermined angle with respect to the radial direction of the straight pipe. A pipe pile characterized by:

[0045] (Appendix 5) In the pipe piles described in Appendix 4, The easily expandable diameter portions are provided at a plurality of locations at predetermined intervals in the material axial direction. A pipe pile characterized by:

[0046] (Appendix 6) An easily expandable diameter portion is provided on the peripheral wall of a pipe pile made of a hollow straight pipe with a closed tip, in which a plurality of slits extending in the material length direction of the pipe pile and penetrating the peripheral wall in an inward and outward direction are formed, The pipe pile is buried in the ground, The inside of the pipe pile is filled with crushed stone, When the crushed stone is pressurized, the easily expandable portion is deformed by expanding in the radially outward direction within the ground. A pile structure characterized by:

[0047] (Appendix 7) In the pile structure described in Appendix 6, The easily expandable diameter portion is formed so that the penetration direction of the slits, which appears in a cross section perpendicular to the material axis, is inclined at a predetermined angle with respect to the radial direction of the straight pipe. A pile structure characterized by: [Industrial Applicability]

[0048] The invention disclosed in this application can be widely used as a technique for obtaining ground bearing capacity in construction work for small to medium-sized buildings and the like. [Explanation of symbols]

[0049] 1 pile pipe 11 Easy-to-expand diameter section 12 Slit 13 Connecting protrusion 14 Cap 2 Attachments 21 Engagement groove 3. Anti-sinking devices 31 Cylinder part 32 Engagement groove 33 Presser plate 4. Crushed Stone 5 Feeding aid 6 Hammer 7 Basics

Claims

1. A pile construction method including the following [Step 1] to [Step 6]. [Step 1] By forming multiple slits in the peripheral wall of a hollow straight pipe, extending in the longitudinal direction of the straight pipe and penetrating the peripheral wall in an inward and outward direction, the peripheral wall in that part is made into an easily expandable section, and a pipe pile is prepared with the tip of the straight pipe blocked. [Step 2] The pipe pile is buried in the ground to a predetermined depth by pressing or driving. [Step 3] Attach a subsidence prevention device to the head of the pipe pile and abut the subsidence prevention device against the ground surface. [Step 4] Crushed stone is poured into the inside of the pipe pile, filling it up to at least the height of the easily expandable portion. [Step 5] A pressure device is used to apply pressure to the crushed stone from above the pipe pile, causing the easily expandable portion to expand and deform in the radially outward direction. [Step 6] The pressure on the crushed stone is stopped, the pressure device is removed, and the anti-settling device is removed.

2. In [Step 2] of the pile construction method described in claim 1, The pipe pile is buried while being rotated and pressed in a certain direction. A pile construction method characterized by the above.

3. The pile installation method according to claim 2, The pipe pile prepared in [Step 1] is formed so that the penetration direction of the slit appearing in the cross section perpendicular to the material axis of the easy-to-expand diameter portion is inclined at a predetermined angle with respect to the radial direction of the pipe pile, In [Step 2], the pipe pile is rotated so that the inner side in the penetration direction of the slit leads in the rotation direction of the pipe pile. A pile construction method characterized by the above.

4. A pipe pile consisting of a hollow straight pipe, The straight pipe has a closed tip, and a peripheral wall of the straight pipe has a plurality of slits extending in the longitudinal direction of the straight pipe and penetrating the peripheral wall in an inward and outward direction, and the easily expandable diameter portion is provided in the peripheral wall. The easily expandable diameter portion is formed so that the penetration direction of the slits, which appears in a cross section perpendicular to the material axis, is inclined at a predetermined angle with respect to the radial direction of the straight pipe. A pipe pile characterized by:

5. The pipe pile according to claim 4, The easily expandable diameter portions are provided at a plurality of locations at predetermined intervals in the material axial direction. A pipe pile characterized by:

6. An easily expandable diameter portion is provided on the peripheral wall of a pipe pile made of a hollow straight pipe with a closed tip, in which a plurality of slits extending in the material length direction of the pipe pile and penetrating the peripheral wall in an inward and outward direction are formed, The pipe pile is buried in the ground, The inside of the pipe pile is filled with crushed stone, When the crushed stone is pressurized, the easily expandable portion is deformed by expanding in the radially outward direction within the ground. A pile structure characterized by:

7. The pile structure according to claim 6, The easily expandable diameter portion is formed so that the penetration direction of the slits, which appears in a cross section perpendicular to the material axis, is inclined at a predetermined angle with respect to the radial direction of the straight pipe. A pile structure characterized by:

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