Pile foundation

Abstract

To provide a pile foundation that offers higher bearing capacity while being easy to construct. [Solution] A pile foundation 1 that supports a structure 4 by the bearing force of multiple piles 5, comprising a cylindrical main body part 2 that fixes the shaft portion 41 of the structure 4 in the axial direction, and multiple leg parts 3 provided separately from the main body part 2, wherein multiple first protrusions 22 projecting radially outward are formed on the outer circumferential surface of the main body part 2, and each of the multiple leg parts 3 includes a cylindrical portion 31 into which the piles 5 are inserted, and a second protrusion 32 that projects radially outward from the outer circumferential surface of the cylindrical portion 31, the end of which is connected to the first protrusions 22 by a connector, the pile foundation 1.

Description

Technical Field

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[0001] This disclosure relates to pile foundations.

Background Art

[0002] When erecting columnar members such as lighting poles on the ground, a technique using pile foundations is known. For example, Patent Document 1 discloses a simple foundation for fixing a support column to the ground. The simple foundation of Patent Document 1 has a foundation body and six driving pins. The foundation body includes a hollow cylindrical fixing portion and six legs each formed with a cylinder into which these pins can be inserted.

[0003] During construction, the constructor installs the foundation body on the ground, inserts pins into the plurality of legs respectively, and drives the pins into the ground using an electric hammer or the like. These legs are provided radially on the outer peripheral surface of the fixing portion so as to incline downward, and by driving the pins along this direction, the foundation body is fixed to the ground while restricting movement in the horizontal and vertical directions. Then, the lower end of the lighting pole is fixed to the plate of the foundation body with bolts.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, in order to support a larger structure with a pile foundation, it may be considered to make the pile foundation larger in order to increase its bearing capacity. However, if the size of the pile foundation is increased, the weight will increase accordingly, resulting in a situation where the constructor cannot carry the pile foundation manually, and there is a risk of deterioration in workability.

[0006] In light of these challenges, this disclosure aims to provide a pile foundation that has higher bearing capacity while also being easy to construct. [Means for solving the problem]

[0007] The pile foundation of this disclosure is a pile foundation that supports a structure by the bearing capacity of a plurality of piles, comprising a cylindrical main body part that fixes the shaft portion of the structure in the axial direction, and a plurality of leg parts provided separately from the main body part, wherein a plurality of first protrusions projecting radially outward are formed on the outer circumferential surface of the main body part, and each of the plurality of leg parts includes a cylindrical portion into which the piles are inserted, and a second protrusion projecting radially outward from the outer circumferential surface of the cylindrical portion, the end of which is connected to the first protrusion by a connector, the pile foundation. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide a pile foundation that has higher bearing capacity while also being easy to construct. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram illustrating the overall configuration of the pile foundation according to the embodiment. [Figure 2] This is a perspective view of the pile foundation and multiple piles, seen from an oblique angle above. [Figure 3] This is a plan view of the pile foundation. [Figure 4] This is a cross-sectional view taken along the line IV-IV in Figure 3. [Figure 5] This is a side view of the main body part. [Figure 6] These are plan and cross-sectional views of the leg parts. [Figure 7] This is a diagram illustrating the construction procedure for pile foundations. [Figure 8] These are a plan view and a side view of the leg part related to a modified example. [Figure 9] This is a perspective view of the modified pile foundation and multiple piles, seen from an oblique angle above. [Figure 10]These are a plan view and a side view of the leg part related to a modified example. [Figure 11] This diagram illustrates the differences between the pile foundation according to the embodiment and the pile foundation according to a modified example. [Modes for carrying out the invention]

[0010] <Summary of the embodiments of this disclosure> The embodiments of this disclosure are outlined below.

[0011] (1) The pile foundation of the present disclosure is a pile foundation that supports a structure by the bearing capacity of a plurality of piles, comprising: a cylindrical main body part that fixes the shaft portion of the structure in the axial direction; and a plurality of leg parts provided separately from the main body part, wherein a plurality of first protrusions projecting radially outward are formed on the outer circumferential surface of the main body part, and each of the plurality of leg parts includes a cylindrical portion into which the piles are inserted, and a second protrusion projecting radially outward from the outer circumferential surface of the cylindrical portion, the end of which is connected to the first protrusion by a connector.

[0012] In the pile foundation described herein, the main body part and multiple leg parts are provided as separate components, making it possible to lighten the weight of each individual part to a level that can be carried by hand. This improves the ease of construction, even when the size of the leg parts is increased to create a pile foundation with higher bearing capacity.

[0013] (2) In the pile foundation described in (1) above, when the second protrusion is connected to the first protrusion, the length from the cylindrical portion to the central axis of the main body part may be 300 mm or more.

[0014] In this way, by making the length relatively long, the piles can be driven over a wider area, thereby increasing the bending strength of the pile foundation. This makes it possible to create a pile foundation with higher bearing capacity.

[0015] (3) In the pile foundation of (2) above, in a state where the second convex part is connected to the first convex part, the cylindrical part may be inclined at an angle of 20 degrees or more and 45 degrees or less with respect to the axial direction of the main body part and toward the outside in the radial direction of the main body part.

[0016] By setting the angle to a relatively large angle of 20 degrees or more, the support force in the radial direction can be made particularly strong. On the other hand, if the angle exceeds 45 degrees, the pile may be liable to yield to the load from the axial direction. Therefore, in order to suitably cope with the loads in both the radial and axial directions, the angle is set to 20 degrees or more and 45 degrees or less. Thereby, the support force of the pile foundation can be made higher.

[0017] (4) In any of the pile foundations of (1) to (3) above, the main body part and the plurality of leg parts are each less than 55 kg, and in a state where the second convex part is connected to the first convex part, the pile foundation may be 55 kg or more.

[0018] [[ID=十一]] When the total weight of the pile foundation thus becomes 55 kg or more, it becomes difficult for one constructor to carry it by hand. On the other hand, in the pile foundation of the present disclosure, the main body part and the leg parts are provided separately, and since the main body part and the leg parts are each less than 55 kg, it becomes possible for one constructor to carry it by hand. Thereby, since the pile foundation can be constructed more easily with fewer personnel, the workability of the pile foundation construction can be improved.

[0019] <Details of Embodiments of the Present Disclosure> Hereinafter, details of embodiments of the present disclosure will be described with reference to the drawings. Note that at least a part of the embodiments described below may be arbitrarily combined.

[0020] 〔Overall Configuration of Pile Foundation 1〕 FIG. 1 is a schematic diagram illustrating the overall configuration of a pile foundation 1 according to an embodiment. The pile foundation 1 is a foundation that supports a structure 4, which includes a columnar shaft portion 41, by the bearing capacity of multiple piles 5, in order to erect the structure 4 on the ground G1. In the example in Figure 1, the pile foundation 1 is provided on the ground G1, but the pile foundation 1 may also be provided underground (below the ground G1). Also, although the ground G1 is illustrated as a horizontal plane in Figure 1, the ground G1 may also be a slope.

[0021] Structure 4 is not particularly limited, but for example, it is a small wind turbine installed on the shoulder of a roadway. Structure 4 comprises a shaft portion 41 and a load portion 42. The lower end portion of the shaft portion 41 is fixed to the pile foundation 1 (specifically, the main body part 2 described later), and the load portion 42 is fixed to the upper end portion of the shaft portion 41. The load portion 42 is a part that bears a larger load than the shaft portion 41, such as the wind turbine of a wind turbine. Structure 4 may also be a snow fence, street light, large sign, traffic sign, artificial nesting tower for storks, etc., wooden deck, or boardwalk.

[0022] Figure 2 is a perspective view of the pile foundation 1 and the multiple piles 5 inserted into the pile foundation 1, viewed from diagonally above. The pile foundation 1 comprises a main body part 2 and multiple (e.g., 8) leg parts 3. The main body part 2 and the multiple leg parts 3 are separate parts, and these parts 2 and 3 are connected by connectors including bolts B1 and nuts N1.

[0023] Pile 5 is inserted into the leg part 3 (specifically, the cylindrical part 31 described later) of the pile foundation 1. Pile 5 is a small-diameter steel pipe pile, with diameters of, for example, 48.6 mm, 60.5 mm, or 76.3 mm.

[0024] [Structural elements of pile foundation 1] Figure 3 is a plan view of pile foundation 1. Figure 4 is a cross-sectional view taken along the line IV-IV in Figure 3. Figure 5 is a side view of the main body part 2. Figure 6 shows a plan view and a cross-sectional view of the leg part 3. Figure 6(a) is a plan view of the leg part 3, and Figure 6(b) is a cross-sectional view taken along the BB cutting line in Figure 6(a). The following explanation will describe the individual parts 2 and 3 included in the pile foundation 1, with reference to Figures 1 through 6 as appropriate.

[0025] The main body part 2 is a cylindrical steel part that fixes the shaft portion 41 in the axial direction, and its weight is approximately 52 kg. As shown in Figure 5, the main body part 2 includes a cylindrical body 21, a plurality of first protrusions 22, and a plate 23.

[0026] The cylindrical body 21 is a hollow structural member that fixes the shaft portion 41 along the center line C1. The cylindrical body 21 is, for example, a structural round steel pipe (such as STK400) with an outer diameter of 318.5 mm, a thickness of 6 mm, and a height of 300 mm.

[0027] Here, the direction along the center line C1 is referred to as the "axial direction of the main part 2." The axial direction of the main part 2 includes the direction parallel to the center line C1 (the up and down direction in Figure 5). The direction perpendicular to the center line C1 is referred to as the "radial direction of the main part 2." When the center line C1 is aligned vertically, the radial direction of the main part 2 is horizontal. The direction around the axis centered on the center line C1 is referred to as the "circumferential direction of the main part 2."

[0028] As shown in Figures 3 and 4, the inside of the cylindrical body 21 is provided with an inner cylindrical portion 25 having a smaller diameter than the cylindrical body 21, and a plurality of plate-like portions 24 that fix the inner cylindrical portion 25 to the inner circumferential surface of the cylindrical body 21. The inner cylindrical portion 25 is, for example, a cylinder with an outer diameter of 70 mm and a height of 200 mm, and is provided 20 mm above the lower end of the cylindrical body 21.

[0029] The plate-like portion 24 is, for example, a rectangular plate with a height of 150 mm. One end of the plate-like portion 24 is welded to the inner cylindrical portion 25, and the other end of the plate-like portion 24 is welded to the inner circumferential surface of the cylindrical body 21. The same number of plate-like portions 24 are provided at the same positions as the first protrusions 22 in the circumferential direction of the main body part 2. In this embodiment, eight plate-like portions 24 are provided at 45-degree intervals.

[0030] The multiple first protrusions 22 are plate-like pieces that project radially outward from the main body part 2 on the outer circumferential surface of the cylindrical body 21. In this embodiment, eight first protrusions 22 are provided at 45-degree intervals. The first protrusions 22 are fixed to the outer circumferential surface of the cylindrical body 21 and the lower surface of the plate 23, for example, by welding. Multiple (e.g., two) bolt holes 22a are formed in the first protrusions 22 for attaching connectors.

[0031] The height of the first protrusion 22 is, for example, 250 mm, and the thickness of the first protrusion 22 is, for example, 9 mm. Since the upper end of the first protrusion 22 is in contact with the lower surface of the plate 23, the lower end of the first protrusion 22 is located 34 mm above the lower end of the cylindrical body 21. In this way, the lower ends of the first protrusion 22, the plate-like part 24, and the inner cylindrical part 25 are all positioned higher than the lower end of the cylindrical body 21. With this configuration, when the main body part 2 is placed on the ground G1, even if the ground G1 has some unevenness, the lower ends of the first protrusion 22, the plate-like part 24, and the inner cylindrical part 25 will not interfere with the ground G1, preventing the main body part 2 from becoming unstable, wobbling, or tilting, and the main body part 2 can be easily placed on the ground G1.

[0032] The plate 23 is a disc-shaped member fixed to the upper end of the cylindrical body 21, and its thickness is, for example, 16 mm. The plate 23 is a region for attaching and fixing the lower end portion of the shaft portion 41, and its outer diameter is 480 mm, which is larger than the outer diameter of the cylindrical body 21 (318.5 mm). In the region of the plate 23 that protrudes radially outward from the cylindrical body 21, a plurality (for example, 8) of bolt holes 23a are formed at 45-degree intervals. The bolt holes 23a are located, for example, between two first protrusions 22 that are adjacent to each other in the circumferential direction, and the circumferential angle from the first protrusions 22 to the bolt holes 23a is 22.5 degrees.

[0033] Furthermore, a positioning hole 23b with an inner diameter of 250 mm is formed in the center of the plate 23. The center of the positioning hole 23b is formed to coincide with the center line C1. When the installer looks down at the positioning hole 23b from above, the plate-like part 24, the inner cylindrical part 25, and the ground G1 can be visually seen inside the positioning hole 23b. This allows the installer to visually align the position of the inner cylindrical part 25 with, for example, a marker placed on the ground G1, and to accurately and easily place the main body part 2 in the installation location.

[0034] In this embodiment, the cylindrical body 21 and the plate 23 are circular when viewed from above, but at least one of the cylindrical body 21 and the plate 23 may be rectangular (for example, square) when viewed from above.

[0035] Leg part 3 is a steel part that secures the stake 5, and its weight is approximately 3.5 kg. Up to eight leg parts 3 can be connected to one main body part 2, for example, and the total weight of the main body part 2 and the eight leg parts 3 is approximately 80 kg.

[0036] The leg part 3 includes a cylindrical portion 31 and a second protrusion 32. The cylindrical portion 31 is a hollow structure member that fixes the pile 5 along the center line C2. Here, the center line C2 is inclined at an angle θ1 (for example, θ1 = 20 degrees) radially outward of the main body part 2 with respect to the center line C1, such that when the pile foundation 1 is installed on the ground G1, it slopes downward away from the center line C1. Therefore, when the leg part 3 is connected to the main body part 2, the cylindrical portion 31 and the pile 5 inserted into the cylindrical portion 31 are also inclined at the same angle with respect to the main body part 2.

[0037] Furthermore, as shown in Figure 1, the centerlines C2 of the multiple cylindrical sections 31 coincide at a single point P1 above. In other words, the multiple centerlines C2 radiate downward from point P1 at an angle θ1 with respect to the centerline C1. Point P1 is located where the centerline C1 passes through, that is, where the shaft section 41 stands. Therefore, the multiple piles 5 can evenly support the load transmitted from the shaft section 41, and thus can support the shaft section 41 with strong bearing force in any radial direction.

[0038] The cylindrical section 31 is, for example, a structural round steel pipe (such as STKM13A) with an outer diameter of 70 mm, a thickness of 4 mm, and a height of 200 mm along the center line C2. Bolt holes 31a are formed radially through the cylindrical section 31 through which bolts B2 for fixing the pile 5 are passed.

[0039] The second protrusion 32 is a plate-like piece that protrudes radially outward from the outer circumferential surface of the cylindrical portion 31. The second protrusion 32 is fixed to the outer circumferential surface of the cylindrical portion 31, for example, by welding. The second protrusion 32 is, for example, a steel plate (SS400, etc.) with a height of 150 mm and a thickness of 9 mm along the center line C1. As shown in Figure 6(b), multiple (for example, two) bolt holes 32a are formed at the end of the second protrusion 32 opposite to the cylindrical portion 31.

[0040] As shown in Figures 2 and 3, the end of the second protrusion 32 is connected to the first protrusion 22 by a connector. Specifically, the first protrusion 22 and the second protrusion 32 are overlapped in the circumferential direction, and with the bolt hole 22a of the first protrusion 22 and the bolt hole 32a of the second protrusion 32 communicating in the circumferential direction, a bolt B1 is inserted into the bolt holes 22a, 32a. Then, the first protrusion 22 and the second protrusion 32 are connected by fastening a nut N1 to the end of the bolt B1 protruding from the hole. In this case, the bolt B1 and the nut N1 function as the "connector" in this embodiment.

[0041] In the state where the second protrusion 32 is connected to the first protrusion 22, the length W1 from the cylindrical portion 31 to the center line C1 is 300 mm or more, specifically 350 mm. By making the length W1 relatively long (for example, longer than the outer diameter of the cylindrical body 21), the pile 5 can be driven further away from the center line C1 and over a wider area, thereby increasing the bending strength of the pile foundation 1, as shown in the experimental example described later.

[0042] On the other hand, increasing the length W1 increases the size of the pile foundation 1, which in turn increases its weight, making it inconvenient to transport. For example, the total weight of the pile foundation 1 is approximately 80 kg, as mentioned above, which is too heavy for one worker to carry by hand, and in some cases it may be impossible to transport.

[0043] In contrast, in the pile foundation 1 of this embodiment, the main body part 2 and the multiple leg parts 3 are provided as separate components, so the weight of each individual part 2 and 3 can be made light enough to be carried by hand. Specifically, the weight of each part 2 and 3 can be reduced to less than 80 kg, more preferably 55 kg or less. As a result, the pile foundation 1 can have higher bearing capacity while improving workability during construction.

[0044] Furthermore, when the second protrusion 32 is connected to the first protrusion 22, the cylindrical portion 31 is inclined at an angle of 20 to 45 degrees radially outward with respect to the axial direction of the main body part 2. With such a cylindrical portion 31, the pile 5 can be driven into the ground G1 while inclined downwards away from the center line C1, thereby increasing the radial (horizontal) bearing capacity of the pile 5. In particular, inclining it at a relatively large angle of 20 degrees or more can make the radial bearing capacity especially strong.

[0045] On the other hand, if the angle exceeds 45 degrees, the pile 5 will succumb to the load from the axial direction (vertical direction), and if the limit load is exceeded, the pile 5 may break by bending towards the main body part 2. For this reason, in order to suitably accommodate both radial and axial loads, the inclination should be between 20 degrees and 45 degrees, and more preferably between 20 degrees and 30 degrees. This makes it possible to increase the bearing capacity of the pile foundation 1.

[0046] [Construction procedure for pile foundation 1] Figure 7 is a diagram illustrating the construction procedure for pile foundation 1. Referring to Figure 7, the procedure described in the publication for erecting structure 4 on ground G1 using pile foundation 1 will be explained. The construction procedure shown below is an example, and the order may be changed as appropriate.

[0047] First, as shown in Figure 7(a), the installer places the main body part 2 at an appropriate location on the ground G1. Since the weight of the main body part 2 is less than 55 kg (specifically, about 52 kg), the installer can place the main body part 2 at the installation site manually without using heavy machinery. At this time, the installer can easily and accurately place the main body part 2 at the installation site by checking the markings placed on the ground G1 through the alignment hole 23b of the main body part 2 and then placing the main body part 2 on the ground G1.

[0048] Next, the installer manually carries the leg part 3. Since the leg part 3 also weighs less than 55 kg (specifically, about 3.5 kg), the installer can manually carry the leg part 3 to the vicinity of the main body part 2 without using heavy machinery.

[0049] Next, the first protrusion 22 of the main body part 2 and the second protrusion 32 of the leg part 3 are placed on top of each other. In this state, as shown in Figure 7(b), the bolt B1 is passed through the bolt holes 22a and 32a, and the nut N1 is fastened to the end of the bolt B1 protruding from the hole, thereby connecting the first protrusion 22 and the second protrusion 32. Similarly, the installer sequentially connects the leg parts 3 to the other first protrusions 22.

[0050] Next, as shown in Figure 7(c), the worker inserts the pile 5 into the cylindrical section 31. Since the outer diameter of the pile 5 (e.g., 60.5 mm) is smaller than the inner diameter of the cylindrical section 31 (e.g., 62 mm), the pile 5 is guided by the inner circumferential surface of the cylindrical section 31 and inserted into the cylindrical section 31 along the center line C2. In this state, the worker drives the upper end of the pile 5 into the ground G1 by striking it with a power tool such as a handheld electric hammer.

[0051] After the pile 5 is driven into the ground G1 while being guided in the direction of driving by the cylindrical section 31, the worker uses a power tool such as a handheld drill to create a bolt hole in the pile 5 through the bolt hole 31a. Then, as shown in Figure 7(d), the bolt B2 is inserted through the bolt hole 31a and a nut is fastened to the end of the bolt B2 protruding from the hole, thereby fixing the pile 5 to the cylindrical section 31. Similarly, the worker sequentially inserts and fixes the piles 5 into the other cylindrical sections 31.

[0052] Finally, as shown in Figure 7(e), the lower end of the shaft portion 41 is fixed to the plate 23 with bolts B3. Thus, the pile foundation 1, which supports the shaft portion 41 with the bearing capacity of the multiple piles 5, is constructed.

[0053] As described above, the pile foundation 1 can be transported and constructed manually by dividing it into the main body part 2 and the leg part 3. Here, the appendix to the "Notification from the Director of the Labor Standards Bureau of the Ministry of Health, Labour and Welfare dated September 6, 1994: Guidelines for Preventing Lower Back Pain in the Workplace" stipulates that "the weight that male workers aged 18 or older handle solely by hand shall be 55 kg or less." In Japan, there is a 55 kg limit on the weight that can be handled solely by hand, and if the weight exceeds this limit, it is necessary to transport it by two or more people or by machine. Since the main body part 2 and the leg part 3 each weigh less than 55 kg, which is lighter than the said limit, a wide range of workers can carry them by themselves. This makes it possible to construct the pile foundation 1 more easily with fewer personnel, thus improving the workability of the pile foundation 1.

[0054] [Procedure for dismantling pile foundation 1] Next, the procedure for dismantling pile foundation 1 will be explained. Since pile foundation 1 does not involve the pouring of concrete or other materials, it can be easily dismantled manually. The dismantling procedure shown below is just one example, and the order may be changed as appropriate.

[0055] First, the demolition worker dismantles structure 4 from main body part 2. Next, the bolts B1 and nuts N1 connecting main body part 2 and leg part 3 are removed, and main body part 2 is detached from leg part 3. Since the pile foundation 1 is provided with main body part 2 and leg part 3 as separate components, only main body part 2 can be removed while the pile 5 is inserted into leg part 3.

[0056] Next, the demolition worker uses a pile extractor to remove the pile 5 from the ground along with the leg part 3. Here, the pile extractor may be an electric type or a manual type. For example, the "K-50" pile extractor manufactured by Marusa Co., Ltd. may be used. In particular, since the leg part 3 is fixed to the head of the pile 5, when removing the pile 5, the leg part 3 functions as a "gripping point," making it easier to apply the load from the pile extractor to the pile 5. This makes it easier for the demolition worker to remove the pile 5 from the ground.

[0057] Furthermore, by removing the pile 5 from the ground first while the leg part 3 and the pile 5 remain fixed together, the removal of the pile 5 from the leg part 3 can be carried out later as a single unit. For example, the leg part 3 and the pile 5, which are fixed together, can be placed on a transport vehicle and transported to a materials storage area, and the pile 5 can be removed from the leg part 3 at a later date. This reduces the amount of work required at the demolition site of the pile foundation 1, and allows for the early completion of withdrawal from the demolition site.

[0058] Furthermore, since the main body part 2 and leg part 3 are not damaged during construction or dismantling, they can be reused at other construction sites.

[0059] In this regard, in the case of the simple foundation described in Patent Document 1, since the main body part 2 and the leg part 3 are integrated, the dismantling procedure involves first removing the piles (pins) and then removing the simple foundation. This is because it is difficult to remove the simple foundation first, as the piles are arranged radially. Therefore, the dismantling procedure for the simple foundation involves, for example, first removing the bolts that fix the pins to the simple foundation, then removing the pins from the ground and the simple foundation, and finally removing the simple foundation.

[0060] In particular, in the example of Patent Document 1, since the pins need to be removed while the simple foundation (specifically the main body of the fixing part) is installed, there is a risk that the pile extraction machine and the main body of the fixing part may interfere with each other, and it may be necessary to excavate the ground during demolition in order to secure space for removing the pins.

[0061] In contrast, with a pile foundation 1 as described above, the main body part 2 can be removed first, and then the pile 5 can be removed together with the leg part 3, thus reducing the risk of interference as described above and making the dismantling work easier.

[0062] [Example: Bending strength of pile foundation 1] Here, we will explain the relationship between the length W1 of the pile foundation 1 and its bending strength [kN·m]. For the pile foundation 1 exemplified in Figures 2 to 6, the bending strength F1 was simulated for each length W1 by varying the length W1 from 300 mm to 500 mm under the following conditions. The bending strength F1 is the value of the bending stress calculated based on the maximum load until the pile 5 fails when a load F is applied horizontally to the pile foundation 1, which is installed with its axial direction oriented vertically.

[0063] [Analysis conditions] Geological conditions: Cohesive soil, N-value 10 Specifications for pile 5: Outer diameter 60.5 mm, length 2000 mm, 8 pieces

[0064] [Analysis results] Length W1 = 300 mm: Bending strength F1 = 50 kN·m Length W1 = 350 mm: Bending strength F1 = 54 kN·m Length W1 = 400 mm: Bending strength F1 = 58 kN·m Length W1 = 450 mm: Bending strength F1 = 62 kN·m Length W1 = 500 mm: Bending strength F1 = 66 kN·m

[0065] As shown in the analysis results above, the longer the length W1, the stronger the bending strength F1 becomes. In other words, the longer the leg part 3 is formed horizontally and the wider the pile 5 is driven into the ground G1, the stronger the resistance to horizontal loads becomes. In this embodiment, the length W1 is 300 mm or more, so the pile foundation 1 has a bending strength F1 of 50 kN·m or more under the above conditions. Thus, by making the length W1 relatively long, the bending strength of the pile foundation 1 can be increased, and a higher bearing capacity can be achieved.

[0066] [Variation] The following describes modified examples of the embodiments. In the modified examples, components identical to those in the above embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0067] [Variations of leg parts: Number of connections, connection positions] In the above embodiment, the leg parts 3 are connected to all of the first protrusions 22 provided on the main body part 2. That is, if the main body part 2 has eight first protrusions 22, eight leg parts 3 are attached to each of the first protrusions 22. However, the number of leg parts 3 to be attached may be reduced depending on the load of the structure 4, etc.

[0068] For example, when supporting a lighter structure 4, fewer than eight leg parts 3 may be connected to the eight first protrusions 22, i.e., four leg parts 3. In this case, the leg parts 3 may be attached at 90-degree intervals in the circumferential direction (an interval of one leg part between each other).

[0069] As shown in Patent Document 1, in conventional examples, the main body part 2 and the leg part 3 are integrally formed, making it impossible to vary the number of leg parts 3 used depending on the structure 4. In contrast, in the pile foundation 1, the main body part 2 and the leg part 3 are provided as separate components, so the number of leg parts 3 can be adjusted as appropriate according to the structure 4. This reduces the amount of leg parts 3 used and makes the number of parts required for construction more efficient.

[0070] [Modified leg parts: Lightweight structure] Figure 8 shows a plan view and a side view of the leg part 6 according to a modified example. Figure 8(a) is a plan view of the leg part 6, and Figure 8(b) is a side view of the leg part 6.

[0071] Leg part 6 is a modified version of leg part 3 that is lighter. Leg part 6 includes a cylindrical portion 61 and a second protrusion 62. These 61 and 62 basically have the same structure as the cylindrical portion 31 and second protrusion 32 of leg part 3, but differ in the following respects.

[0072] The cylindrical portion 61 has weight-reducing holes 61a formed in it. As shown in Figure 8(a), the weight-reducing holes 61a are formed in the circumferential direction on the opposite side from where the second protrusion 62 is fixed. The weight-reducing holes 61a are arc-shaped holes and are located in the axial center of the cylindrical portion 61 at a height of, for example, half the height along the center line C2 of the cylindrical portion 61 (for example, about 100 mm). By providing weight-reducing holes 61a in the cylindrical portion 61 in this way, the weight of the cylindrical portion 61 can be reduced.

[0073] The second protrusion 62 is, for example, a plate-like piece with a thickness of 22 mm. In the above embodiment, the second protrusion 32 is connected to the first protrusion 22 by overlapping it on one side in the circumferential direction, whereas the second protrusion 62 connects to the first protrusion 22 by sandwiching it from both sides in the circumferential direction. For this reason, the thickness of the second protrusion 62 is set to 22 mm, which is thicker than that of the second protrusion 32, in order to ensure sufficient thickness for sandwiching.

[0074] The second protrusion 62 includes a thin-walled portion 63 for weight reduction and a weight-reducing hole 63a provided within the thin-walled portion 63. The thickness of the thin-walled portion 63 is thinner than the area of ​​the second protrusion 62 other than the thin-walled portion 63 (thickness 22 mm), for example, 9 mm. The thin-walled portion 63 occupies, for example, about half the area of ​​the second protrusion 62. By providing the thin-walled portion 63 and the weight-reducing hole 63a in the second protrusion 62 in this way, the weight of the second protrusion 62 can be reduced.

[0075] As shown in Figure 8(a), the end of the second protrusion 62 includes a first piece 64 that sandwiches the first protrusion 22 from one side in the circumferential direction, and a second piece 65 that sandwiches the first protrusion 22 from the other side in the circumferential direction. The thickness of the first piece 64 and the second piece 65 is, for example, 6 mm, and a recess D1 with a width of 10 mm is formed between these pieces 64 and 65.

[0076] Furthermore, as shown in Figure 8(b), bolt holes 62a are formed in the first piece 64 and the second piece 65, respectively. In a side view, the end of the second protrusion 62 includes an upper first ear portion 66 and a lower second ear portion 67, and bolt holes 62a are formed in each of these ear portions 66 and 67. In addition, a recess D2 is formed between these ear portions 66 and 67. The recess D2 is a recess for weight reduction.

[0077] When connecting the second protrusion 62 to the first protrusion 22, the first protrusion 22, which has a thickness of 9 mm, is inserted into the recess D1 formed at the end of the second protrusion 62, and bolts B1 are sequentially passed through the bolt holes 62a on one side in the circumferential direction (for example, the bolt hole 62a of the first piece 64), bolt hole 22a, and the bolt hole 62a on the other side in the circumferential direction (for example, the bolt hole 62a of the second piece 65).

[0078] During installation, as shown in Figures 7(a) to 7(b), the leg part 3 must be placed on top of the first protrusion 22 of the main body part 2 in the circumferential direction, and then connected to the main body part 2. Depending on the shape of the leg part 3, it may not be able to stand on its own. In this case, the installer must support the leg part 3 with one hand to keep it upright while inserting the bolt B1 with the other hand.

[0079] In contrast, in this modified example, the first protrusion 22 is sandwiched between the first piece 64 and the second piece 65 from both sides in the circumferential direction. Therefore, even if the installer releases their hands from the leg part 6 before inserting the bolt B1, the leg part 6 can maintain an upright position because it is supported by the first protrusion 22. As a result, when connecting the leg part 6 to the main body part 2, the installer can release their hands from the leg part 6 and proceed with the connection work by holding the bolt B1 and nut N1 with both hands, thereby improving work efficiency.

[0080] [Modified leg part: twisted structure] In the pile foundation 1 according to this embodiment, the centerlines C2 of the multiple cylindrical sections 31 coincide at a single point P1 in the vertical direction upward, as shown in Figure 1. In contrast, the leg section 6a of this modified example guides the piles 5 in a "twisted" positional relationship.

[0081] Figure 9 is a perspective view of the modified pile foundation 1a and the multiple piles 5 inserted into the pile foundation 1a, viewed from diagonally above. The pile foundation 1a comprises a main body part 2 and multiple leg parts 6a. The pile foundation 1a of this modified version differs from the pile foundation 1 mainly in that the leg parts 6a are connected to the main body part 2 instead of the leg parts 3, and is otherwise similar.

[0082] Figure 10 shows a plan view and a side view of the leg part 6a. Figure 10(a) is a plan view of the leg part 6a, and Figure 10(b) is a side view of the leg part 6a. The leg part 6a basically has the same structure as the leg part 6 (Figure 8), but differs in the following respects. As shown in Figure 10(a), the cylindrical portion 61 of the leg part 6a is inclined circumferentially at an angle θ2 with respect to the second protrusion 62. The angle θ2 is, for example, 30 degrees. Therefore, the directions in which the multiple cylindrical portions 61 extend are in a "twisted" relationship with each other, and the piles 5 inserted into these cylindrical portions 61 are also in a "twisted" relationship with each other.

[0083] Figure 11 illustrates the differences between pile foundation 1 and pile foundation 1a. In the construction procedure shown in Figure 7, as shown in Figures 7(c) to 7(e), piles 5 are driven one by one into the ground G1, and after each pile 5 is fully driven in, the next pile 5 is inserted into the cylindrical section 31.

[0084] However, as another example of the construction procedure, multiple piles 5 may be inserted sequentially into the cylindrical section 31, and then these piles 5 may be driven sequentially into the ground G1. With this procedure, the work of inserting the piles 5 into the cylindrical section 31 is performed all at once, and then the worker drives the piles 5 all at once with a power tool, thus eliminating the need to pick up and put down the power tool and improving work efficiency.

[0085] A problem that arises when adopting such a construction procedure is the interference of multiple piles 5. As shown in Figures 1 and 11(a), when multiple piles 5 are inserted into the pile foundation 1, depending on the length of the piles 5 and the angle of the cylindrical portion 31, the multiple piles 5 may interfere with each other at point P1 in the vertical direction above. For this reason, in the pile foundation 1, it may not be possible to adopt the construction procedure of inserting multiple piles 5 into the cylindrical portion 31 as described above and then driving the piles 5 all at once.

[0086] In contrast, as shown in Figure 11(b), in the pile foundation 1a, the multiple piles 5 inserted into the multiple cylindrical sections 61 are in a "twisted" relationship, and the centerlines C2 do not converge at points such as point P1. Therefore, even if multiple piles 5 are inserted into the pile foundation 1a, these piles 5 do not interfere with each other, so a construction procedure can be adopted in which multiple piles 5 are inserted into the cylindrical sections 31 as described above, and then the piles 5 are driven in all at once, thereby improving work efficiency.

[0087] [Note] The embodiments and variations disclosed herein are illustrative in all respects and are not restrictive. The scope of this disclosure is not limited to the embodiments and variations described above, but includes all modifications within the scope of equivalence to the configurations described in the claims. [Explanation of Symbols]

[0088] 1,1a Pile foundation 2 Main body parts 21 Cylinder body 22 First protrusion 22a Bolt hole 23 Plate 23a Bolt hole 23b Alignment hole 24 Plate-shaped part 25 Inner cylinder section 3 Leg section parts 31 Cylinder section 31a Bolt hole 32 Second protrusion 32a Bolt hole 4 Structure 41 Shaft part 42 Load part 5 stakes 6 leg parts 6a leg parts 61 Cylinder portion 61a Weight-reducing hole 62 Second protrusion 62a Bolt hole 63 Thin-walled section 63a Weight-reducing hole 64 1st piece 65 2nd piece 66 1st ear 67 Second ear G1 Ground B1, B2, B3 Bolt N1 Nut C1 Centerline C2 center line θ1 angle θ2 angle

Claims

1. A pile foundation that supports a structure by the bearing capacity of multiple piles, A cylindrical main body part that fixes the shaft portion of the aforementioned structure in the axial direction, Multiple leg parts are provided separately from the main body part, Equipped with, Multiple first protrusions projecting radially outward are formed on the outer circumferential surface of the main body part. Multiple of the aforementioned leg parts are, The cylindrical portion into which the aforementioned pile is inserted, A second protrusion extends radially outward from the outer surface of the cylindrical portion, and its end is connected to the first protrusion by a connector, Pile foundations, each including the respective elements.

2. In the state where the second protrusion is connected to the first protrusion, the length from the cylindrical portion to the central axis of the main body part is 300 mm or more. The pile foundation according to claim 1.

3. The cylindrical portion, when the second protrusion is connected to the first protrusion, is inclined at an angle of 20 degrees or more and 45 degrees or less radially outward with respect to the axial direction of the main body part. The pile foundation according to claim 2.

4. Each of the aforementioned main body parts and the multiple aforementioned leg parts weighs less than 55 kg. In the state where the second protrusion is connected to the first protrusion, the pile foundation weighs 55 kg or more. A pile foundation according to any one of claims 1 to 3.

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