TW202012747A - Plie foundation - Google Patents

Abstract

A pile foundation includes: a pile that supports a towering structure and that extends along a vertical direction, a pile top projecting further upward than the ground; and ribs provided near the ground surface in the ground of the pile and projecting radially outward from the outer peripheral surface of the pile.

Description

Pile foundation

The present invention relates to a foundation structure, and more specifically a pile foundation structure.

Japanese Unexamined Patent Publication No. 2005-232694 (hereinafter referred to as Patent Document 1) discloses a method of forming an in-situ infusion in a pile foundation having a rotary press-fitting steel pipe pile so as to cover the head and outer peripheral surface of the steel pipe pile The structure of the concrete pile, wherein the front end of the tubular pile body of the steel pipe pile is provided with a spiral wing. In addition, Japanese Patent Application Laid-Open No. 7-127053 discloses a pile penetrating a liquefied formation portion, and a ground disturbance body is formed on the peripheral surface of the pile corresponding to the liquefied portion.

However, a pile foundation supporting a tower-like structure requires a structure that can ensure resistance to horizontal forces without increasing the diameter of the pile. As an example of this structure, there is a structure in which a concrete pile is formed on a pile head of a steel pipe pile that is rotated and pushed as described in Patent Document 1. However, in order to rotate the rotating steel pipe pile, a large-scale device is required. In addition, in order to pour the concrete, it is necessary to dig the site around the pile head, so there is still room for improvement in terms of construction period.

The present invention takes this fact into consideration, and aims to provide a pile foundation capable of shortening the construction period while ensuring resistance to horizontal forces.

The pile foundation of the first aspect of the present invention has: a pile that extends in a vertical direction, and whose pile head protrudes upward from the ground to support a tower-like structure; and a rib, which is provided near the ground surface in the ground The pile protrudes radially outward from the outer circumferential surface of the pile.

In the pile foundation of the first aspect of the present invention, the pile extends in the vertical direction, and the pile head of the pile protrudes upward more than the ground. In addition, a rib is provided on the pile near the ground surface of the ground, and the rib protrudes radially outward from the outer circumferential surface of the pile. Thereby, when a horizontal force is input to the pile, the sliding surface of the pile can be moved from the circumferential surface of the pile to the tip end side of the rib. As a result, the resistance received from the ground becomes larger, and the resistance to the horizontal force can be ensured.

In addition, since the resistance to the horizontal force can be increased only by forming the rib, it is possible to carry out the construction in the same manner as the case where the rib is not provided, and the construction period can be shortened.

The pile foundation of the second aspect of the present invention is the first aspect, in which a plurality of the ribs are provided at equal intervals in the circumferential direction of the pile.

In the pile foundation of the second aspect of the present invention, even when the horizontal force is input to the pile from various directions, the resistance to the horizontal force can be ensured.

The pile foundation of the third aspect of the present invention is in the first aspect or the second aspect, and the upper end of the rib is located below the ground surface of the ground.

In the pile foundation of the third aspect of the present invention, since the rib does not extend above the ground surface of the ground, it is possible to provide a floor or the like on the ground surface.

The pile foundation of the fourth aspect of the present invention is in any of the first aspect to the third aspect, the pile system is formed of a steel pipe, and the rib system is formed of steel material.

In the pile foundation of the fourth aspect of the present invention, steel is used to form the pile and the rib. Therefore, when fixing the rib to the pile, in addition to the method of fixing the rib by mechanical fastening methods such as bolts and nuts, It is also possible to use welding or the like to fix the rib to the pile.

The pile foundation of the fifth aspect of the present invention is in any of the first aspect to the fourth aspect, and the tower-shaped structure constitutes the leg of the wind power generator.

In the pile foundation of the fifth aspect of the present invention, even when an external force in the dumping direction is input to the pile by a heavy object such as a wind power generator, the resistance to the horizontal force can be secured by the rib.

The pile foundation of the sixth aspect of the present invention is in any of the first aspect to the fifth aspect, the pile is cylindrical, and the pile foundation has an internal rib, and the internal rib is separated from the pile The inner circumference of the part buried in the ground surface protrudes radially inward.

In the pile foundation of the sixth aspect of the present invention, in addition to the ribs on the outer circumferential surface of the pile, the rigidity of the pile can be further improved by the inner ribs provided on the inner circumferential surface of the pile. As a result, even if the pile is miniaturized, the necessary resistance can be ensured.

As described above, according to the pile foundation of the present invention, the construction period can be shortened while ensuring the resistance to the horizontal force.

>First Embodiment>

The pile foundation 10 according to the first embodiment will be described with reference to the drawings. As shown in FIG. 1, the pile foundation 10 of this embodiment serves as a foundation for supporting the wind power generator 12.

The wind power generator 12 includes a leg portion (tower) 14 as a tower-shaped structure extending from the pile foundation 10 in the vertical direction, and a windmill portion 16 provided at the upper end of the leg portion 14. In addition, the windmill section 16 includes a nacelle 18, a hub 20 and blades 22.

The diameter of the leg portion 14 gradually decreases upward, and the lower end of the leg portion 14 is connected to the pile foundation 10. In addition, a nacelle 18 constituting the windmill portion 16 is rotatably attached to the upper end portion of the leg portion 14, and a generator and an amplifier (not shown) are housed inside the nacelle 18.

The nacelle 18 is connected to the hub 20 via a rotor shaft (not shown). Furthermore, blades 22 as a plurality of rotor blades are attached to the hub 20. In this embodiment, as an example, three blades 22 are attached to the peripheral surface of the hub 20.

The leg portion 14 of the wind power generator 12 as described above is supported by the pile foundation 10. Here, the pile foundation 10 of this embodiment includes a pile 24 and a rib 28.

The pile 24 is formed of a steel pipe, extends in the vertical direction as an axial direction, and is provided substantially coaxially with the leg portion 14 of the wind power generator 12. In addition, in addition to the pile head 24A provided in the upper part, the other part of the pile 24 is driven into the ground 26 by the striking method. Here, in this embodiment, since it is the pile foundation 10 applied to the offshore wind power generator 12, the pile 24 is driven into the seabed, and the diameter of the pile driven into the pile 24 from the site 26 is about 4 to 6 times depth. In this embodiment, as an example, a pile 24 having a pile diameter of 8 m can be used, and the pile 26 can be driven into a depth of about 40 m from the ground 26.

As shown in FIG. 2A, the pile head 24A protrudes upward more than the ground 26. In addition, a plurality of ribs 28 are provided on the pile 24 near the ground surface of the ground 26. The ribs 28 each extend in the axial direction (vertical direction) of the pile 24. In the present embodiment, the ribs 28 each extend downward from the position of the ground surface of the floor 26. That is, the upper end portion of the rib 28 is located on the ground surface of the ground plate 26 and is arranged so as not to protrude further above the ground surface.

As shown in FIG. 2B, in this embodiment, eight ribs 28 are provided at equal intervals in the circumferential direction of the pile 24. Each rib 28 protrudes radially outward from the outer circumferential surface of the pile 24.

Here, the rib 28 is formed of steel material, and the rib 28 is fixed to the outer peripheral surface of the pile 24 by welding or the like before driving into the pile 24. Furthermore, in the state where the rib 28 is fixed, the pile 24 is driven into the ground 26 by the striking construction method. It is worth mentioning that, besides welding, the method of fixing the ribs 28 may also be a method of mechanically fastening with bolts and nuts.

(effect)

Next, the function of this embodiment will be described.

In the pile foundation 10 of the present embodiment, since a plurality of ribs 28 protrude radially outward from the outer circumferential surface of the pile 24, even when an external force (horizontal force) in the dumping direction is input from the wind power generator 12 to the pile 24 Next, the sliding surface of the pile 24 can also be displaced by the rib 28 from the circumferential surface of the pile 24 to the front end side of the rib 28. As a result, resistance to the horizontal force can be ensured. The function will be described below with reference to FIG. 3.

As shown in FIG. 3A, the case of the pile 100 of the comparative example in which the rib 28 is not provided is discussed below. In this structure, when a horizontal force is input to the pile 100, the boundary portion between the circumferential surface of the pile 100 and the ground 26 becomes the sliding surface P1.

On the other hand, as shown in FIG. 3B, in the pile 24 constituting the pile foundation 10 of the present embodiment, since the rib 28 is provided, the boundary between the front end portion of the rib 28 and the ground 26 becomes the sliding surface P2. As a result, in the pile foundation 10 of the present embodiment, compared with the comparative example in which the rib 28 is not provided, it is possible to withstand greater resistance from the ground 26. It is worth mentioning that, in FIG. 3B, for convenience of description, only the ribs 28 that bear the resistance from the ground 26 are shown, and the illustration of the other six ribs 28 is omitted.

In addition, when driving the pile 24 using a hammering method, the ground 26 near the peripheral surface of the pile 24 becomes softer due to the driving of the pile 24. That is, the frictional force becomes smaller. In such a structure, if the rib 28 is not provided as in the comparative example, the sliding surface P1 becomes a portion where the frictional force on the peripheral surface of the pile 100 is small, and therefore the resistance may become small.

In the present embodiment, since the sliding surface P2 is located outside the circumferential surface of the pile 24, the resistance from the ground 26 can be obtained at the portion where the friction force is greater, and the resistance to the horizontal force can be ensured.

In addition, in the present embodiment, the resistance to the horizontal force can be increased only by the rib 28, so the diameter of the pile 24 is not increased. In addition, since the rib 28 is designed to extend in the vertical direction, it is possible to suppress the resistance from the rib 28 when driving the pile 24 by the hammering method. As a result, construction can be performed in the same manner as when the rib 28 is not provided, and the construction period can be shortened.

Furthermore, in this embodiment, as shown in FIG. 2B, a plurality of (8) ribs 28 are provided at equal intervals in the circumferential direction of the pile 24. Thereby, even when the horizontal force is input to the pile 24 from various directions, the resistance to the horizontal force can be ensured.

In addition, in this embodiment, the upper end of the rib 28 is located below the ground surface. That is, the rib 28 does not extend to the upper side than the ground surface. With this, a floor or the like can be provided on the ground surface to increase the resistance to horizontal forces (see FIG. 8 ). On the other hand, the pile 24 near the ground surface of the ground plate 26 is a portion where the moment increases, so by providing the rib 28 in this portion, it is possible to ensure the resistance to the horizontal force.

In addition, in the present embodiment, the pile 24 is formed of a steel pipe, and the rib 28 is formed of a steel material. Thereby, when fixing the rib 28 to the pile 24, in addition to the method of fixing the rib 28 to the pile 24 by mechanical fastening methods such as bolts and nuts, a method of fixing the rib 28 to the pile 24 by welding or the like can also be used .

It is worth mentioning that in the present embodiment, the interior of the steel pipe used to form the pile 24 is designed to be hollow, but it is not limited to this, and for example, the structure of the first modification shown in FIG. 4 may be adopted. In addition, regarding the shape and number of the ribs, the structures of the second to eighth modification examples shown in FIGS. 5 to 7 may also be adopted.

(First modification)

As shown in FIG. 4A, in this modification, the inside of the pile 24 formed of a steel pipe is filled with concrete 32, that is, so-called CFT (Concrete-Filled Steel Tube: concrete-filled steel tube structure). As shown in FIG. 4B, by filling the interior of the pile 24 with concrete 32, the concrete 32 is in close contact with the inner circumferential surface of the steel pipe.

As shown in FIG. 4A, the concrete 32 is filled from the pile head 24A located higher than the ground surface of the ground 26 to the lower side than the lower end of the rib 28. In this way, by filling the concrete 32 in the portion of the pile 24 where the yield strength is required, the thickness of the pile 24 and the diameter of the pile 24 can be reduced.

(Second modification)

As shown in FIG. 5A, in this modification, 16 ribs 28 are provided at equal intervals in the circumferential direction of the pile 24. Each rib 28 protrudes radially outward from the outer circumferential surface of the pile 24. In addition, the length of each rib 28 protruding outward from the circumferential surface of the pile 24 is the same.

(Third modification)

As shown in FIG. 5B, the present modification has an internal rib 34 that protrudes radially inward from the inner circumferential surface of the portion of the pile 24 buried in the ground 26. In this way, in addition to the ribs 28 on the outer circumferential surface of the pile 24, the rigidity of the pile 24 can be further improved by the inner ribs 34 provided on the inner circumferential surface of the pile 24. As a result, even if the pile 24 is designed to be small, the necessary resistance can be ensured.

It is worth mentioning that, in FIG. 5B, the inner side of the pile 24 is designed as a hollow, but in reality, by driving the pile 24 into the ground 26 by using a striking method, the sand will enter the inside of the pile 24.

(Fourth modification)

As shown in FIG. 5C, in this modification, the length of the rib 28 protruding outward from the circumferential surface of the pile 24 is shorter than in the first embodiment. For example, in the case where the ground 26 is relatively hard, by shortening the length of the rib 28, it is possible to drive the pile 24 more easily.

(Fifth Modification)

As shown in FIG. 6A, in this modification, the rib 40 protrudes radially outward from the circumferential surface of the pile 24, and the lower end portion of the rib 40 gradually decreases in length in the radial direction toward the lower side. Furthermore, the lower end portion of the rib 40 in this modification is inclined so as to be located radially outward as it goes downward.

(Sixth modification)

As shown in FIG. 6B, in this modification, the rib 42 protrudes radially outward from the circumferential surface of the pile 24, and the lower end portion of the rib 42 is inclined so as to be located radially inward as it goes downward. As shown in the fifth modified example and the sixth modified example, by inclining the lower end portion of the rib, the pile 24 can be driven more easily.

(The seventh modification)

As shown in FIG. 7A, in this modification, the rib 44 protrudes radially outward from the circumferential surface of the pile 24, and the lower end portion of the rib 44 is curved so as to be located radially inward as it goes downward.

(The eighth modification)

As shown in FIG. 7B, the rib 46 of this modification is curved in the opposite direction to the seventh modification. That is, the lower end portion of the rib 46 is curved so as to be located radially outward as it goes downward.

>Second embodiment>

Next, the pile foundation 50 of the second embodiment will be described with reference to the drawings. It is worth mentioning that the same configuration as that of the first embodiment is denoted by the same symbol, and the description is omitted as appropriate.

The pile foundation 50 of this embodiment includes a pile 24, a rib 28, and a floor 52. The structure of the pile 24 and the rib 28 is the same as that of the first embodiment. In addition, a floor 52 is provided on the pile head 24A of the pile 24, and the floor 52 includes a base 54 and a triangular plate 56.

The base 54 is formed with the axial direction (vertical direction) of the pile 24 as a thickness direction, and is provided on the ground 26. In addition, as shown in FIG. 8B, the base 54 has a substantially circular shape concentric with the pile 24 in a plan view. Furthermore, in the present embodiment, as an example, the base 54 is formed of steel material and fixed to the circumferential surface of the pile head 24A. As a method of fixing the base 54 to the pile head 24A, in addition to welding, a method of mechanically fastening with bolts, nuts, or the like may be used.

A plurality of triangular plates 56 are provided on the upper surface side of the base 54. Eight triangular plates 56 are provided at equal intervals along the circumferential direction of the pile 24, and each triangular plate 56 is formed in a substantially triangular shape so as to form a linear portion in the direction of the pile 24 and in the direction of the base 54. In addition, in this embodiment, the position of the triangular plate 56 coincides with the position of the rib 28. Therefore, in a plan view, the triangular plate 56 and the rib 28 are located at a position overlapping with each other.

The lower end surface of the triangular plate 56 extends in the radial direction of the pile 24 along the base 54 and is fixed to the upper surface of the base 54. In addition, the side surface of the triangular plate 56 on the center side of the pile 24 extends in the vertical direction along the pile head 24A and is fixed to the pile head 24A. As a method of fixing the triangular plate 56 to the base 54 and the pile head 24A, it is the same as the base 54, and besides welding, a method of mechanical fastening with bolts, nuts, etc. can also be used.

As described above, the floor 52 is provided on the ground 26 and fixed to the pile head 24A. Therefore, the external force acting on the pile 24 is transmitted to the ground 26 via the floor 52.

(Construction method of pile foundation)

Next, an example of the construction method of the pile foundation 50 of this embodiment will be described. First, in a state where the pile 24 and the floor 52 are separated, the rib 28 is fixed to the pile 24 in advance. Then, the driving method is used to drive the pile 24 into the ground 26 to a predetermined depth. If such a strike method is adopted, the site 26 is not limited to a sand site or a relatively loose stone site, and the pile 24 can be constructed (driven) even if it is soft rock.

Next, the floor 52 is fixed to the driven pile 24. Here, in this embodiment, since the floor 52 is fixed to the pile head 24A in the sea, the floor 52 may be formed by attaching a triangular plate 56 to the base 54 in advance, and in this state, the pile 24 The method of setting the floor 52 on the ground 26 through the pile head 24A on the upper side of the building.

After the floor 52 is installed on the ground 26, the base 54 and the triangular plate 56 are fixed to the pile head 24A in a prescribed method. In this way, the pile foundation 50 is constructed.

(effect)

Next, the function of this embodiment will be described.

In the pile foundation 50 of this embodiment, a floor 52 is provided on the ground 26. The floor 52 is fixed to the pile 24 and transmits the force acting on the pile 24 to the ground 26. Thereby, even when an external force in the direction of the dumping of the pile 24 is input to the pile 24 from the leg 14 of the wind turbine generator 12 as a tower-like structure, at least a part of the external force can be transmitted to the ground 26 via the floor 52 , The resistance of the pile 24 to the horizontal force can be ensured. Other functions are the same as in the first embodiment.

The first to second embodiments and modifications have been described above, but they can be implemented in various ways without departing from the gist of the present invention. For example, in this embodiment, the pile foundation supporting the wind power generator as a tower-shaped structure has been described, but it is not limited to this. That is, it may be applied to a pile foundation supporting other tower-shaped structures, and may also be applied to a pile foundation supporting tower-like structures such as an iron tower. In this case, by driving a plurality of piles into the ground, a tower-shaped structure such as an iron tower can be supported.

In addition, in this embodiment, a single pile foundation using one pile to support the wind power generator is described, but it is not limited to this, and may be applied to other foundations. For example, it is possible to drive three piles into the ground and connect these piles to apply to a tripod type foundation supporting a wind power generator. In this case, by separately providing the floor to each pile, it is possible to exert the same effect as that of this embodiment.

Furthermore, in this embodiment, the pile is formed of a steel pipe, but the material of the pile is not particularly limited, and other materials may be used to form the pile. For example, a wooden pile or a concrete pile made of concrete may be used. In addition, piles combining these materials can also be used.

In the above embodiment, the upper end of the rib is located on the ground surface of the floor 26, but it is not limited to this, and the rib may be projected to the upper side than the ground surface.

In addition, in the fifth to eighth modifications shown in FIGS. 6 and 7, the structure in which the shape of the lower end portion of the rib is changed is described, but the tip portion of the rib may be further sharpened. For example, in the rib 28 shown in FIG. 2A, the thickness of the lower end portion of the rib 28 may be designed to gradually become thinner toward the lower side. In this way, since the lower end portion of the rib 28 is sharpened, the resistance received from the rib 28 when driving the pile 24 can be reduced.

10: Pile foundation 12: Wind power generator 14: Feet (tower structure) 24: Pile 24A: Pile head 26: Site 28: rib 34: inner rib 40: rib 42: Rib 44: Rib 46: Rib 50: Pile foundation

FIG. 1 is an overall schematic diagram showing a wind power generator to which a pile foundation of the first embodiment is applied.

Fig. 2A is an elevation view of the pile foundation in the first embodiment.

2B is a plan cross-sectional view showing a state cut along the line 2B-2B of FIG. 2A.

FIG. 3A is a schematic diagram showing the sliding surface when an external force acts on the pile of the comparative example.

3B is a schematic diagram showing the sliding surface when an external force acts on the pile of the first embodiment.

4A is an elevation view of a pile foundation in a first modification of the first embodiment.

4A is a plan cross-sectional view showing a state cut along the line 4B-4B of FIG. 4A.

5A is a plan cross-sectional view of a pile foundation in a second modification of the first embodiment.

5B is a plan cross-sectional view of a pile foundation in a third modification of the first embodiment.

5C is a plan cross-sectional view of a pile foundation in a fourth modification of the first embodiment.

6A is a vertical cross-sectional view of a pile foundation in a fifth modification of the first embodiment.

6B is a vertical cross-sectional view of a pile foundation in a sixth modification of the first embodiment.

7A is a vertical cross-sectional view of a pile foundation in a seventh modification of the first embodiment.

7B is a vertical cross-sectional view of a pile foundation in an eighth modification of the first embodiment.

8A is an elevation view of a pile foundation in the second embodiment.

8B is a plan view of the pile foundation of the second embodiment.

no

10: Pile foundation

12: Wind power generator

14: feet

16: Windmill Department

18: cabin

20: Wheel

22: Blade

24: Pile

24A: Pile head

26: Site

28: rib

Claims (6)

A pile foundation comprising: A pile, which extends in a vertical direction, wherein the pile head of the pile protrudes upward more than the ground to support a tower-like structure; and a rib, which is provided on the pile near the ground surface in the ground, from The outer circumferential surface of the pile protrudes radially outward. The pile foundation according to claim 1, wherein a plurality of the ribs are provided at equal intervals in the circumferential direction of the pile. The pile foundation of 2, wherein the upper end of the rib is located below the ground surface of the ground plate. The pile foundation of 2, wherein the pile system is formed of steel pipes, and the rib system is formed of steel materials. The pile foundation of 2, wherein the tower-shaped structure constitutes the foot of the wind power generator. The pile foundation of 2, wherein the pile has a cylindrical shape, and the pile foundation has an inner rib that protrudes radially inward from an inner circumferential surface of a portion of the pile buried in the ground.

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