Pile construction method, pipe pile, and pile structure

Abstract

The present invention provides: a pile construction method which is simpler and less expensive than conventional methods and in which a pipe pile having a slit formed in a peripheral wall is press-inserted into the ground and expanded in diameter from the inner side; and a pipe pile that can be used for the method. A pipe pile (1) is prepared which comprises a hollow straight pipe which has a closed tip and in which a plurality of slits (12) extending in a direction along the length of the material are formed in a peripheral wall of the pipe pile (1) to form an easily enlarged diameter part (11). The pipe pile (1) is embedded up to a prescribed depth in the ground by being press-inserted or driven, and a flange-shaped settlement prevention tool (3) is attached to the head part to be brought into contact with the ground surface. Crushed stones (4) are charged into the pipe pile (1) and pressurized from above the pipe pile (1), whereby the easily enlarged diameter part (11) is expanded and deformed in the radially outward direction to increase the peripheral surface frictional force within the ground.

Description

Pile construction methods, pipe piles and pile structures

[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.

[0002] In the construction of houses and other small- to medium-sized buildings, small-diameter (approximately 100 mm to 200 mm) steel pipe piles are often used to ensure sufficient ground bearing capacity. Typical pile construction methods using small-diameter steel pipe piles include: (1) 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 achieving bearing capacity; and (2) a straight pipe without impellers is pressed into the ground with or without rotation, and bearing capacity is achieved by the frictional resistance of the periphery.

[0003] The pile construction method (1) requires a large construction machine to rotate and penetrate the steel pipe pile, and depending on the ground, the tip of the pile needs to 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 peripheral friction force 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 pressed 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 a slit formed in the circumferential wall at the tip or middle part is pressed into the ground, and then the diameter of the slit part is expanded by inserting a mechanical diameter expansion device into the steel pipe pile or by filling it with an expansive material.

[0006] Japanese Patent Laid-Open No. 55-009953 Japanese Patent Laid-Open No. 57-108314 Japanese Patent Laid-Open No. 63-233117 Japanese Patent Laid-Open No. 2014-070478

[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.

[0008] The pile construction method adopted by the present application to achieve the above-mentioned object is characterized by including the following [Steps 1] to [Steps 6]. [Step 1]: Prepare a pipe pile 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 / outward direction, thereby forming an easily expandable portion in the peripheral wall at that portion and closing the tip of the straight pipe. [Step 2]: Bury the pipe pile to a predetermined depth in the ground 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]: Fill the pipe pile with crushed stone, filling it up to at least the height of the easily expandable portion. [Step 5]: Apply pressure to the crushed stone from above the pipe pile using a pressure device, thereby causing the easily expandable portion to bulge outward in the radial direction. [Step 6]: Stop applying pressure to the crushed stone, remove the pressure device, and detach the subsidence prevention device.

[0009] In this pile construction method, the following steps 7 and 8 may be carried out after steps 1 to 6. Step 7: Adjust the head of the pipe pile to a predetermined height. Step 8: Construct the foundation of a building on top of the adjusted pipe pile.

[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 axial direction of the material.

[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.

[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.

[0019] [Correction based on Rule 91 10.02.2025] This is an explanatory diagram showing the construction method from [Step 1] to [Step 4] in the pile construction method disclosed herein, where (a) to (c) are external views and (d) is a cross-sectional view. Similarly, this is an explanatory diagram showing the construction method from [Step 5] to [Step 7], where (e) and (f) are cross-sectional views and (g) and (h) are half-sectional and half-external views. Similarly, this is an explanatory diagram showing the construction method for [Step 8], where (i) to (k) are half-sectional and half-external views. This is a cross-sectional view taken perpendicular to the axis of the easily expandable portion of a pipe pile according to one embodiment of the invention disclosed herein. This is a perspective view showing the head of the pipe pile and an example of an attachment attached to the head. This is a perspective view showing an example of a subsidence prevention device attached to the head of the pipe pile.

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

[0021] [Pipe piles] In this pile construction method, small-diameter steel pipes with hollow circular cross sections are used as pipe piles. The specifications for steel pipes used for supports, scaffolding, piles, etc. in architectural and civil engineering works are defined in the Japanese Industrial Standards (JIS) G3444:2015 "General structural carbon steel pipes." A "small-diameter steel pipe pile" typically refers to a pile construction method using 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 approximately 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), etc. 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 following describes the order of steps 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] [Correction Based on Rule 91, 10.02.2025] [Steps 1] to [Steps 2] In this pile construction method, prior to on-site construction, a pipe pile 1 is prepared with an easily expandable diameter section 11 formed in the peripheral wall near the tip or in the middle of the straight pipe, as described above. The easily expandable diameter section 11 is a section in which multiple slits 12 extending longitudinally of the pipe pile 1 and penetrating the peripheral wall in an inward-outward direction are formed at regular intervals around the pipe pile 1. The pipe pile 1 illustrated in Figure 1(a) has two easily expandable diameter sections 11 at an appropriate interval in the middle of its longitudinal direction. Each easily expandable diameter section 11 has four slits 12 extending parallel to the pipe pile 1's axis, aligned in length, and spaced 90 degrees apart in a cross section perpendicular to the pipe pile 1's axis (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 circumferential expansion without impairing the compressive strength of the peripheral wall of the pipe pile 1. Furthermore, the number of easily expandable portions 11 provided in the 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 portion 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 generally 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, this invention assumes that the pipe pile 1 will be rotated while being pressed into the ground 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 Figure 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 constituting 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 of the pipe pile 1.

[0028] When driving the pipe pile 1 into the ground, a generally cylindrical attachment 2, such as that shown in FIG. 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 engaging 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 with 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 (FIG. 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] [Correction based on Rule 91 10.02.2025] As shown in Figure 1(b), when the head of the pipe pile 1 reaches near 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 part of the pipe pile 1 can be cut off.

[0030] [Correction based on Rule 91 10.02.2025] [Steps 3] to [Steps 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 is similar to the attachment 2 used in the above-mentioned [Step 2] and has a hollow tubular portion 31 that fits over the head of the pipe pile 1, and 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 presser plate 33 that protrudes radially outward is attached to the middle part of the tubular portion 31, and the subsidence prevention device 3 is set on the pipe pile 1 so that this presser plate 33 abuts against the design ground surface GL. In addition, if the excess portion of the pipe pile 1 is cut off in the above-mentioned [Step 2], the engagement groove 32 of the subsidence prevention device 3 will no longer be able to engage with the connecting protrusion 13 of the pipe pile 1, so the subsidence prevention device 3 may be connected to the pipe pile 1 using a bolt and nut joint or the like.

[0031] [Correction pursuant to Rule 91, 10.02.2025] Next, as shown in Figure 1(d), crushed stone 4 is poured into the pipe pile 1 through the top opening of the anti-subsidence device 3. If the inner diameter of the pipe pile 1 is small, a funnel-shaped loading aid 5 may be attached to the top opening of the anti-subsidence device 3. Crushed stone 4 can be suitably used, such as 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 the top of the pipe pile 1 (the position reached by the pressure device in the next step [Step 5]).

[0032] [Correction based on Rule 91 10.02.2025] [Step 5] Next, as shown in Figures 2(e)-2(f), a pressure device is used to apply pressure to the top surface of the crushed stone 4 filled in the pipe pile 1 from above the pipe pile 1. The pressure device 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 anti-subsidence device 3 attached to the head of the pipe pile 1 prevents the entire pipe pile 1 from settling due to this pressure and concentrates the 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 circumferential 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 multiple easy-to-expand sections 11 are provided, it is also 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 easy-to-expand section 11 and pressurized, causing the lower easy-to-expand section 11 to swell and deform, and then additional crushed stone is poured and pressurized again, causing the upper easy-to-expand section 11 to swell and deform.

[0034] [Correction based on Rule 91 10.02.2025] [Steps 6] to [Steps 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 expanded and deformed, and the pressure is stopped, the pressure device is removed, and the settlement prevention device 3 is also removed. Then, as shown in Figure 2(g), excavate around the head of the pipe pile 1 to match the level of the bottom of the foundation, and adjust by cutting the head of the pipe pile 1, etc. If necessary, the excavated area is backfilled as shown in Figure 2(h).

[0035] [Correction based on Rule 91 10.02.2025] [Step 8] From this point onwards, the foundation work for the building begins. As shown in Figures 3(i) to 3(k), the area around the head of the pipe pile 1 whose height has been adjusted is again cut off, 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 the 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 much simpler and less expensive than conventional methods that use complex expansion devices 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 easier. This 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 exemplified as 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] 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.

[0041] REFERENCE SIGNS LIST 1 pile pipe 11 easily expandable portion 12 slit 13 connecting protrusion 14 cap 2 attachment 21 engaging groove 3 settling prevention device 31 cylindrical portion 32 engaging groove 33 holding plate 4 crushed stone 5 loading aid 6 hammer 7 foundation

Claims

1. A pile construction method including the following [Steps 1] to [Steps 6]. [Step 1]: Prepare a pipe pile 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 / outward direction, to form an easily expandable section in the peripheral wall and closing off the tip of the straight pipe. [Step 2]: Bury the pipe pile to a predetermined depth in the ground 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]: Fill the inside of the pipe pile with crushed stone, filling it up to at least the height of the easily expandable section. [Step 5]: Apply pressure to the crushed stone from above the pipe pile using a pressure device, thereby causing the easily expandable section to bulge outward in the radial direction. [Step 6]: Stop applying pressure to the crushed stone, remove the pressure device, and detach the subsidence prevention device.

2. A pile construction method according to claim 1, characterized in that in step 2, the pipe pile is embedded while being rotated and pressed in a fixed direction.

3. A pile construction method as described in claim 2, characterized in that 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 easily expandable portion is inclined at a predetermined angle relative to the radial direction of the pipe pile, and in [Step 2] the pipe pile is rotated so that the inside in the penetration direction of the slit is ahead in the rotation direction of the pipe pile.

4. A pipe pile consisting of a hollow straight pipe, the straight pipe having a closed tip, and an easily expandable diameter section formed in the peripheral wall of the straight pipe by forming a plurality of slits that extend in the longitudinal direction of the straight pipe and penetrate the peripheral wall in an inward and outward direction, the easily expandable diameter section being formed so that the penetration 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.

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

6. A pile structure characterized in that an easily expandable portion is provided on the peripheral wall of a pipe pile consisting of a hollow straight pipe with a closed tip, with a plurality of slits formed in the peripheral wall that extend in the longitudinal direction of the pipe pile and penetrate the peripheral wall in an inward and outward direction, the pipe pile is buried in the ground, crushed stone is filled inside the pipe pile, and the crushed stone is pressurized, causing the easily expandable portion to bulge and deform in an outward radial direction within the ground.

7. A pile structure as described in claim 6, characterized in that the easily expandable portion is formed so that the penetration 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.

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