U.S. patent application number 17/272900 was filed with the patent office on 2021-07-15 for pile foundation.
This patent application is currently assigned to TOKYO ELECTRIC POWER SERVICES CO., LTD.. The applicant listed for this patent is TOKYO ELECTRIC POWER SERVICES CO., LTD.. Invention is credited to Hideharu Nakamura, Shigeru Tanabe.
Application Number | 20210214909 17/272900 |
Document ID | / |
Family ID | 1000005540502 |
Filed Date | 2021-07-15 |
United States Patent
Application |
20210214909 |
Kind Code |
A1 |
Nakamura; Hideharu ; et
al. |
July 15, 2021 |
PILE FOUNDATION
Abstract
The present invention relates to a pile foundation including: a
pile that extends in a vertical direction, and whose pile head
protrudes above the ground, and that supports a tower-type
structure, and ribs that are provided at the pile in a vicinity of
a surface of the ground, and that protrude outwardly in radial
directions from an outer circumferential surface of the pile.
Inventors: |
Nakamura; Hideharu;
(Koto-ku, Tokyo, JP) ; Tanabe; Shigeru; (Koto-ku,
Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO ELECTRIC POWER SERVICES CO., LTD. |
Koto-ku, Tokyo |
|
JP |
|
|
Assignee: |
TOKYO ELECTRIC POWER SERVICES CO.,
LTD.
Koto-ku, Tokyo
JP
|
Family ID: |
1000005540502 |
Appl. No.: |
17/272900 |
Filed: |
August 22, 2019 |
PCT Filed: |
August 22, 2019 |
PCT NO: |
PCT/JP2019/032856 |
371 Date: |
March 2, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02D 2300/0029 20130101;
E02D 27/12 20130101; E02D 2600/40 20130101; E02D 5/285 20130101;
E02D 2200/1685 20130101; E02D 27/425 20130101 |
International
Class: |
E02D 5/28 20060101
E02D005/28; E02D 27/42 20060101 E02D027/42; E02D 27/12 20060101
E02D027/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2018 |
JP |
2018-164264 |
Claims
1. A pile foundation comprising: a pile that extends in a vertical
direction, that has a pile head protruding above the ground, and
that supports a tower-type structure; and ribs that are provided at
the pile in a vicinity of a surface of the ground, and that
protrude outwardly in radial directions from an outer
circumferential surface of the pile.
2. The pile foundation according to claim 1, wherein a plurality of
the ribs are provided at equidistant intervals in a circumferential
direction of the pile.
3. The pile foundation according to claim 1, wherein upper end
portions of the ribs are positioned on a lower side of the surface
of the ground.
4. The pile foundation according to claim 1, wherein: the pile is
formed by a steel pipe, and the ribs are formed from a steel
material.
5. The pile foundation according to claim 1, wherein the tower-type
structure forms a leg portion of a wind power generator.
6. The pile foundation according to claim 1, wherein: the pile is
formed in a tubular shape, and internal ribs that protrude inwardly
in radial directions from an inner circumferential surface of a
portion of the pile that is embedded in the ground are provided.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a pile foundation.
BACKGROUND ART
[0002] Japanese Patent Application Laid-Open (JP-A) No. 2005-232694
discloses a structure in which, in a pile foundation that is
provided with a screwed steel pile in which spiral blades are
provided at a distal end of a cylindrical pile main body, a
cast-in-place concrete pile is formed so as to cover a pile head
and an outer circumferential surface of this steel pile. Further,
Japanese Patent Application Laid-Open (JP-A) No. H7-127053
discloses a pile that penetrates a ground layer portion where
liquefaction is generated. A ground agitator is formed on a
circumferential surface of this pile that corresponds to the
liquefaction portion.
SUMMARY OF INVENTION
Technical Problem
[0003] In a pile foundation that supports a tower type of
structure, a structure that ensures sufficient resistance to
horizontal force without increasing the diameter of the pile is
required. As described in JP-A No. 2005-232694, a structure in
which a concrete pile is formed around a periphery of a pile head
of a screwed steel pile is as one example of such a structure.
However, large-scale equipment is required in order to screw in a
screwed steel pile. Moreover, it is also necessary to firstly
excavate the ground around the periphery of the pile head in order
to place the concrete so that, from the standpoint of construction
time, there is considerable room for improvement.
[0004] The present disclosure provides a pile foundation that
ensures sufficient resistance to horizontal force while enabling
the construction time to be shortened.
Solution to the Problem
[0005] A first aspect of the present disclosure is a pile
foundation including: a pile that extends in a vertical direction,
and whose pile head protrudes above the ground, and that supports a
tower-type structure, and ribs that are provided on the pile in a
vicinity of a ground surface of the ground, and that protrude
outwardly in radial directions from an outer circumferential
surface of the pile.
[0006] In the pile foundation according to the first aspect of the
present disclosure, a pile extends in a vertical direction, and a
head portion of this pile protrudes above the ground. Further, ribs
are provided on the pile in a vicinity of a ground surface of the
ground, and these ribs protrude outwardly in radial directions from
an outer circumferential surface of the pile. Due thereto, in a
case in which horizontal force is input into the pile, it is
possible to shift a slip plane of the pile from the circumferential
surface of the pile to a distal end side of the ribs. As a result,
it is possible to increase resistance received from the ground, so
that sufficient resistance to horizontal force may be ensured.
[0007] Moreover, because it is possible to increase resistance to
horizontal force simply by forming these ribs, construction may be
performed in the same manner as when ribs are not provided so that
the construction time may be shortened.
[0008] In a pile foundation according to a second aspect of the
present disclosure, in the first aspect, a plurality of the ribs
are provided at equidistant intervals in a circumferential
direction of the pile.
[0009] In the pile foundation according to the second aspect of the
present disclosure, even in a case in which horizontal forces are
input into a pile from various different directions, it is still
possible to ensure sufficient resistance to these horizontal
forces.
[0010] In a pile foundation according to a third aspect of the
present disclosure, in the first aspect or second aspect, upper end
portions of the ribs are positioned on a lower side of the ground
surface of the ground.
[0011] In the pile foundation according to the third aspect of the
present disclosure, because the ribs extends above the ground
surface of the ground, a floor slab or the like may be provided on
this ground surface.
[0012] In a pile foundation according to a fourth aspect of the
present disclosure, in anyone of the first through third aspects,
the pile is formed by a steel pipe, and the ribs are formed from a
steel material.
[0013] In the pile foundation according to the fourth aspect of the
present disclosure, because the pile and the ribs are formed from a
steel material, when fixing the ribs to the pile, in addition to a
method in which the ribs are fixed by being mechanically fastened
thereto using nuts and bolts and the like, it is also possible to
fix the ribs to the pile using a method such as welding or the
like.
[0014] In a pile foundation according to a fifth aspect of the
present disclosure, in anyone of the first through fourth aspects,
the tower-type structure forms a leg portion of a wind power
generator.
[0015] In the pile foundation according to the fifth aspect of the
present disclosure, even in a case in which an external force from
a heavy object such as a wind power generator that is acting in a
direction that might cause the pile to topple over is input into
the pile, the ribs make it possible to ensure sufficient resistance
to such a horizontal force.
[0016] In a pile foundation according to a sixth aspect of the
present disclosure, in any one of the first through fifth aspects,
the pile is formed in a tubular shape, and internal ribs that
protrude inwardly in radial directions from an inner
circumferential surface of a portion of the pile that is embedded
in the ground are provided.
[0017] In the pile foundation according to the sixth aspect of the
present disclosure, the rigidity of the pile may be further
improved by providing internal ribs on the inner circumferential
surface of the pile in addition to the ribs on the outer
circumferential surface of the pile. As a result of this, even if
the size of the pile is reduced, it is still possible to ensure the
required resistance.
Advantageous Effects of the Invention
[0018] As has been described above, according to the pile
foundation and method of constructing a pile foundation of the
present disclosure, it is possible to ensure sufficient resistance
to horizontal force while enabling the construction time to be
shortened.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic view illustrating an overall view of a
wind power generator in which a pile foundation according to a
first exemplary embodiment has been applied.
[0020] FIG. 2A is an elevational view of the pile foundation
according to the first exemplary embodiment.
[0021] FIG. 2B is a plan cross-sectional view illustrating a state
across a line 2A-2A illustrated in FIG. 2A.
[0022] FIG. 3A is a schematic view illustrating a slip plane when
an external force is acting on a pile of a comparative example.
[0023] FIG. 3B is a schematic view illustrating a slip plane when
an external force is acting on the pile of the first exemplary
embodiment.
[0024] FIG. 4A is an elevational view of a pile foundation
according to a first modified example of the first exemplary
embodiment.
[0025] FIG. 4B is a plan cross-sectional view illustrating a state
across a line 4B-4B illustrated in FIG. 4A.
[0026] FIG. 5A is a plan cross-sectional view of a pile foundation
according to a second modified example of the first exemplary
embodiment.
[0027] FIG. 5B is a plan cross-sectional view of a pile foundation
according to a third modified example of the first exemplary
embodiment.
[0028] FIG. 5C is a plan cross-sectional view of a pile foundation
according to a fourth modified example of the first exemplary
embodiment.
[0029] FIG. 6A is an elevational cross-sectional view of a pile
foundation according to a fifth modified example of the first
exemplary embodiment.
[0030] FIG. 6B is an elevational cross-sectional view of a pile
foundation according to a sixth modified example of the first
exemplary embodiment.
[0031] FIG. 7A is an elevational cross-sectional view of a pile
foundation according to a seventh modified example of the first
exemplary embodiment.
[0032] FIG. 7B is an elevational cross-sectional view of a pile
foundation according to an eighth modified example of the first
exemplary embodiment.
[0033] FIG. 8A is an elevational view of a pile foundation
according to a second exemplary embodiment.
[0034] FIG. 8B is a plan view of the pile foundation according to
the second exemplary embodiment.
DESCRIPTION OF THE EMBODIMENTS
First Exemplary Embodiment
[0035] A pile foundation 10 according to a first exemplary
embodiment will now be described with reference to the drawings. As
is illustrated in FIG. 1, the pile foundation 10 of the present
exemplary embodiment serves as a foundation to support a wind power
generator 12.
[0036] The wind power generator 12 is structured to include a leg
portion (i.e., a tower) 14 serving as a tower-type structure that
extends in a vertical direction from the pile foundation 10, and a
wind turbine portion 16 that is provided on an upper end portion of
the leg portion 14. The wind turbine portion 16 is structured to
include a nacelle 18, a hub 20, and blades 22.
[0037] The leg portion 14 is formed so as to become progressively
smaller in diameter approaching the upper portion thereof, and a
lower end of this leg portion 14 is connected to the pile
foundation 10. The nacelle 18 that forms part of the wind turbine
16 is mounted on the upper end portion of the leg portion 14 so as
to be able to rotate freely around this upper end portion, and an
electricity generator and an amplifier and the like (not
illustrated in the drawings) are housed within this nacelle 18.
[0038] The nacelle 18 is connected to the hub 20 via a rotor shaft
(not illustrated in the drawings). A plural the rotating blades 22
are attached to the hub 20 and, in the present exemplary
embodiment, as an example, three blades 22 are attached to a
circumferential surface of the hub 20.
[0039] The leg portion 14 of the wind power generator 12 that is
formed in the above-described manner is supported on the pile
foundation 10. Here, the pile foundation 10 of the present
exemplary embodiment is structured to include a pile 24 and ribs
28.
[0040] The pile 24 is formed by a steel pipe whose axial direction
extends in a vertical direction, and is disposed on substantially
the same axis as the leg portion 14 of the wind power generator 12.
Portions of the pile 24 other than a pile head 24A that is provided
in an upper portion thereof are driven into the ground 26 using a
pile-driving construction method. Here, in the present exemplary
embodiment, since the pile 24 is used in the pile foundation 10 of
an offshore wind power generator 12, the pile 24 is driven into the
ocean bed, and is pile-driven to a depth of approximately 4 to 6
times the pile diameter of the pile 24 from the ground surface of
the ground 26. In the present exemplary embodiment, as an example,
a pile 24 having a pile diameter of 8 meters is used, so that the
pile 24 is driven to a depth of approximately 40 meters from the
surface of the ground 26.
[0041] As is illustrated in FIG. 2A, the pile head 24A protrudes
above the ground 26. The plural ribs 28 are provided on the pile 24
in a vicinity of a ground surface of the ground 26. Each one of the
ribs 28 extends in the axial direction of the pile 24 (i.e., in a
vertical direction) and, in the present exemplary embodiment,
extends downwards from the position of the ground surface of the
ground 26. In other words, an upper end portion of each rib 28 is
positioned at the ground surface of the ground 26, and is disposed
so as to not protrude above this ground surface.
[0042] As is illustrated in FIG. 2B, eight ribs 28 are provided at
equidistant intervals from each other in the circumferential
direction of the pile 24. Each one of the ribs 28 protrudes
outwardly in a radial direction from an outer circumferential
surface of the pile 24.
[0043] Here, the ribs 28 are formed from a steel material, and are
fixed using a method such as welding or the like to the outer
circumferential surface of the pile 24 before the pile 24 is driven
into the ground. Once the ribs 28 have been fixed to the pile 24,
the pile 24 is driven into the ground 26 using a pile-driving
construction method. Note that, the method employed to fix the ribs
28 may be a method such as mechanically fastening the ribs 28 using
nuts and bolts.
[0044] (Actions)
[0045] Next, actions of the present exemplary embodiment will be
described.
[0046] In the pile foundation 10 of the present exemplary
embodiment, because the plural ribs 28 protrude outwardly in a
radial direction from the outer circumferential surface of the pile
24, even in a case in which external force (i.e., a horizontal
force) acting in a direction that might cause the pile 24 to topple
over is input from the wind power generator 12 to the pile 24, it
is possible to shift a slip plane of the pile 24 from the
circumferential surface of the pile 24 to a distal end side of the
ribs 28. As a result, sufficient resistance to horizontal force may
be ensured. This action will now be described in detail with
reference to FIG. 3.
[0047] As is illustrated in FIG. 3A, a case of a pile 100 of a
comparative example in which the ribs 28 are not provided will now
be considered. In this structure, in a case in which horizontal
force is input into the pile 24, a slip plane P1 is formed at a
boundary portion between the circumferential surface of this pile
24 and the ground 26.
[0048] In contrast to this, as is illustrated in FIG. 31, in the
pile 24 that forms part of the pile foundation 10 of the present
exemplary embodiment, by providing the ribs 28, a slip plane P2 is
formed at a boundary portion between the distal end portion of the
ribs 28 and the ground 26. In this way, in the pile foundation 10
of the present exemplary embodiment, compared to the comparative
example in which the ribs 28 are not provided, it is possible for a
greater degree of resistance to be received from the ground 26.
Note that in FIG. 3B, for reasons of convenience, only the ribs 28
that receive resistance from the ground 26 are illustrated, and the
remaining six ribs 28 have been omitted from the drawing.
[0049] Moreover, in a case in which the pile 24 is being
pile-driven using a pile-driving construction method, the ground 26
in the vicinity of the circumferential surface of the pile 24
becomes softer as a result of the pile-driving performed on the
pile 26. In other words, there is a reduction in the friction force
thereof. In a structure such as this, in a case in which the ribs
28 are not provided, as the case in the comparative example, the
slip plane P1 is generated in the portion of the circumferential
surface of the pile 100 where there is little friction force.
Because of this, there is a possibility that the resistance thereof
will be reduced.
[0050] In the present exemplary embodiment, because the slip plane
P2 is further to the outer side than the circumferential surface of
the pile 24, it is possible to obtain resistance from the ground 26
in portions where the friction force thereof is greater, so that
the required resistance to horizontal force may be ensured.
[0051] Furthermore, in the present exemplary embodiment, because it
is possible to increase resistance to horizontal force simply by
forming the ribs 28, it is not necessary to increase the diameter
of the pile 24. Further, by extending the ribs 28 in the vertical
direction, when the pile 24 is being driven into the ground using a
pile-driving construction method, it is possible to reduce
receiving resistance from the ribs 28. As a result, construction
may be performed in the same way as in a case in which the ribs 28
are not provided, so that it is possible to shorten the
construction time.
[0052] Furthermore, in the present exemplary embodiment, as is
illustrated in FIG. 2B, a plural (i.e., eight) the ribs 28 are
provided at equidistant intervals in the circumferential direction
of the pile 24. Due to the above, even in a case in which
horizontal forces are input from various different directions into
the pile 24, it is still possible to ensure sufficient resistance
to these horizontal forces.
[0053] Additionally, in the present exemplary embodiment, the upper
end side of each rib 28 is positioned on the lower side of the
ground surface. In other words, the ribs 28 do not protrude above
the surface of the ground. Consequently, it is possible to provide
a floor slab or the like on the ground surface, and to thereby
increase resistance to horizontal force (see FIG. 8). In contrast,
since the portion of the pile 24 that is located in the vicinity of
the ground surface of the ground 26 is a portion where moment is
increased, by providing the ribs 28 in this portion, it is possible
to secure sufficient resistance to horizontal force.
[0054] Moreover, in the present exemplary embodiment, the pile 24
is formed by a steel pipe, and the ribs 28 are also formed from a
steel material. Due to the above, when the ribs 28 are being fixed
to the pile 24, in addition to a method in which the ribs 28 are
fixed to the pile 24 by being mechanically fastened thereto using
nuts and bolts and the like, it is also possible to fix the ribs 28
to the pile 24 using a method such as welding or the like.
[0055] Note that, in the above-described exemplary embodiment, the
interior of the metal pipe used to form the pile 24 is a hollow
cavity, however, the present disclosure is not limited to this, and
it is also possible, for example, to employ the structure of a
first modified example which is illustrated in FIG. 4. Moreover,
the structures of a second modified example through an eighth
modified example, which are illustrated in FIG. 5 through FIG. 7,
may also be employed for the shape and number of the ribs.
First Modified Example
[0056] As is illustrated in FIG. 4A, in the present modified
example, what is known as a CFT (Concrete-Filled Steel Tube)
structure in which the interior of the pile 24, which is formed by
a steel pipe, is filled with concrete 32 is employed. As is
illustrated in FIG. 4B, as a result of the interior of the pile 24
being filled with concrete 32, the concrete 32 adheres to the inner
circumferential surface of the steel pipe.
[0057] As is illustrated in FIG. 4A, the concrete 32 fills the pile
24 from the pile head 24A, which is positioned on the upper side of
the ground surface of the ground 26, as far as the lower side of a
lower end portion of the ribs 28. By filling this portion where the
pile 24 requires superior yield strength with the concrete 32 in
this way, it is possible to reduce the thickness of the pile 24, or
to reduce the diameter of the pile 24.
Second Modified Example
[0058] As is illustrated in FIG. 5A, in the present modified
example, 16 ribs 28 are provided at equidistant intervals from each
other in the circumferential direction of the pile 24. Each one of
the ribs 28 protrudes outwardly in a radial direction from the
outer circumferential surface of the pile 24. Additionally, the
lengths of the ribs 28 from the circumferential surface of the pile
24 are all the same length.
Third Modified Example
[0059] As is illustrated in FIG. 5B, in the present modified
example, internal ribs 34 that protrude inwardly in radial
directions from an inner circumferential surface of a portion of
the pile 24 that is embedded in the ground 26 are provided. As a
result of the internal ribs 34 being provided in this way on the
inner circumferential surface of the pile 24 in addition to the
ribs 28 on the outer circumferential surface of the pile 24, the
rigidity of the pile 24 may be further improved. As a result of
this, even if the size of the pile 24 is reduced, it is still
possible to ensure the required resistance.
[0060] Note that, in FIG. 5B, the interior of the pile 24 is
illustrated as a hollow cavity, however, because the pile 24 is
driven into the ground 26 by a pile-driving construction method,
the interior of the pile 24 actually contains dirt and sand.
Fourth Modified Example
[0061] As is illustrated in FIG. 5C, in the present modified
example, the length of each rib 28 from the circumferential surface
of the pile 24 is made shorter than in the first exemplary
embodiment. For example, in a case in which the ground 26 is
comparatively hard, by shortening the length of the ribs 28, it
becomes possible to pile-drive the pile 24 more easily.
Fifth Modified Example
[0062] As is illustrated in FIG. 6A, in the present modified
example, ribs 40 protrude outwardly in radial directions from the
circumferential surface of the pile 24, and a lower end portion of
each rib 40 is formed such that a length thereof in the radial
direction becomes progressively shorter the closer it is to the
lower side. Further, the lower end portion of each rib 40 in the
present modified example is inclined so as to be located further to
the outer side in a radial direction the closer it is to the lower
side.
Sixth Modified Example
[0063] As is illustrated in FIG. 6B, in the present modified
example, ribs 42 protrude outwardly in radial directions from the
circumferential surface of the pile 24, and a lower end portion of
each rib 42 is inclined so as to be located further to the inner
side in a radial direction the closer it is to the lower side. By
forming the lower end portion of each rib such that they are
inclined in the manners illustrated in the fifth modified example
and the sixth modified example, it is possible to pile-drive the
pile 24 more easily.
Seventh Modified Example
[0064] As is illustrated in FIG. 7A, in the present modified
example, ribs 44 protrude outwardly in radial directions from the
circumferential surface of the pile 24, and a lower end portion of
each rib 44 is curved so as to be located further to the inner side
in a radial direction the closer it is to the lower side.
Eighth Modified Example
[0065] As is illustrated in FIG. 7B, ribs 46 of the present
modified example are curved in the opposite direction from those in
the seventh modified example. In other words, a lower end portion
of each rib 46 is curved so as to be located further to the outer
side in a radial direction the closer it is to the lower side.
Second Exemplary Embodiment
[0066] Next, a pile foundation 50 according to a second exemplary
embodiment will be described with reference to the drawings. Note
that component elements that are similar to those of the first
exemplary embodiment are given the same descriptive symbols and any
description thereof is omitted when this is appropriate.
[0067] The foundation pile 50 of the present exemplary embodiment
is formed so as to include the pile 24, the ribs 28, and a floor
slab 52, and the pile 24 and ribs 28 have a similar structure as
those of the first exemplary embodiment. The floor slab 52 is
provided on a pile head 24A of the pile 24, and is structured to
include a base 54 and triangular plates 56.
[0068] The base 54 is formed such that a thickness direction
thereof extends in the axial direction of the pile 24 (i.e., in the
vertical direction), and the base 54 is installed on the ground 26.
As is illustrated in FIG. 8B, the base 54 is formed in a
substantially circular shape so as to be concentric with the pile
24 when looked at in plan view. In the present exemplary
embodiment, as an example, the base 54 is formed from a steel
material, and is fixed to a circumferential surface of the pile
head 24A. A method employing mechanical fastening using nuts and
bolts or the like may be employed as the method used to fix the
base 54 to the pile head 24A.
[0069] A plural the triangular plates 56 are provided on an upper
surface side of the base 54. Eight of the triangular plates 56 are
provided at equidistant intervals from each other in a
circumferential direction of the pile 24, and each of the
triangular plates 56 is formed substantially in a triangular shape
such that one rectilinear portion thereof extends in a direction
along the pile 24, and another rectilinear portion thereof extends
in a direction along the base 30. Moreover, in the present
exemplary embodiment, the position of each triangular plate 56
coincides with the position of the corresponding rib 28. Due to the
above, when looked at in plan view, the triangular plates 56 and
the ribs 28 are positioned so as to mutually overlap each other
vertically.
[0070] A lower end surface of each triangular plate 56 extends in a
radial direction of the pile 24 along the base 54, and is fixed to
the upper surface of the base 54. A side surface of each triangular
plate 56 that is positioned closest to the center of the pile 24
extends in the vertical direction along the pile head 24A, and is
fixed to the pile head 24A. A method employing mechanical fastening
using nuts and bolts or the like may be employed, in the same way
as for the base 54, as the method used to fix the triangular plates
56 to the base 54 and the pile head 24A.
[0071] As is described above, the floor slab 52 is laid on top of
the ground 26, and is fixed to the pile head 24A. Due to the above,
a structure is created in which external force acting on the pile
24 is transmitted to the ground 26 via the floor slab 52.
[0072] (Method of Constructing a Pile Foundation)
[0073] Next, an example of a method of constructing the pile
foundation 50 of the present exemplary embodiment will be
described. Firstly, while the pile 24 and the floor slab 52 are
still in a state of mutual separation from each other, the ribs 28
are fixed in advance to the pile 24. Next, the pile 24 is driven to
a predetermined depth into the ground 26 using a pile-driving
construction method. If this type of pile-driving construction
method is employed, then the ground 26 is not restricted to being
sandy ground or comparatively soft gravel ground, and the pile 24
may even be constructed in (i.e., pile-driven into) soft rock.
[0074] Next, the floor slab 52 is fixed to the driven pile 24.
Here, in the present exemplary embodiment, because this operation
involves fixing the floor slab 52 to the pile head 24A under the
sea, a method may be employed in which the floor slab 52 is formed
with the triangular plates 56 attached in advance to the base 54,
and in this state, the floor slab 52 is fitted over the pile head
24A from the upper side of the pile 24, and is then installed on
the ground 26.
[0075] After the floor slab 52 has been installed on the ground 26,
the base 54 and the triangular plates 56 are fixed to the pile head
24A using a predetermined method. In this manner the pile
foundation 50 is constructed.
[0076] (Actions)
[0077] Next, actions of the present exemplary embodiment will be
described.
[0078] In the pile foundation 50 of the present exemplary
embodiment, the floor slab 52 is installed on the ground 26, and
this floor slab 52 is fixed to the pile 24 and is formed so as to
transmit any force acting on the pile 24 to the ground 26. As a
result, even in a case in which external force acting in a
direction that might cause the pile 24 to topple over is input from
the leg portion 14 of the wind power generator 12, which is a
tower-type structure, to the pile 24, at least a portion of this
external force may be transmitted to the ground 26 via the floor
slab 52, so that the ability of the pile 24 to withstand horizontal
force may be secured. The remaining actions are similar to those of
the first exemplary embodiment.
[0079] First and second exemplary embodiments of the present
disclosure as well as modified examples thereof have been described
above, however, it should be understood that various modifications
and the like may be made thereto insofar as they do not depart from
the spirit or scope of the present disclosure. For example, in the
above-described exemplary embodiments, a description is given of a
pile foundation that supports a wind power generator that is
serving as a tower-type structure, however, the present disclosure
is not limited to this. In other words, the present disclosure may
instead be applied to a pile foundation that supports another
tower-type structure, or to a pile foundation that supports a
tower-type structure such as a steel tower. In this case, by
pile-driving a plural piles into the ground, it is possible to
support a tower-type structure such as a steel tower.
[0080] Moreover, in the above-described exemplary embodiments, a
monopile foundation that supports a wind power generator by a
single pile is described, however, the present disclosure is not
limited to this and may be applied to other types of foundations.
For example, the present disclosure may also be applied to a tripod
type of foundation in which three piles are pile-driven into the
ground, and these three piles are linked together so as to support
a wind power generator. In this case, by providing ribs
respectively for each of the piles, the same type of actions as
those demonstrated in the above-described exemplary embodiments may
be obtained.
[0081] Furthermore, in the above-described exemplary embodiments,
the piles are formed by steel pipes, however, the material used to
form the piles is not limited to this, and the piles may instead be
formed from another type of material. For example, wooden piles
made from wood and concrete piles made from concrete may also be
used. It is also possible to use a combination of these
materials.
[0082] Moreover, in the above-described exemplary embodiments, the
upper end portion of each rib is located at the ground surface of
the ground 26, however, the present disclosure is not limited to
this, and it is also possible to employ a structure in which the
upper end portion of each rib protrudes above the ground
surface.
[0083] In the fifth through eighth modified examples illustrated in
FIG. 6 and FIG. 7, a structure in which the shape of the lower end
portion of the ribs is altered is described, however, it is also
possible to additionally form the distal end portion of each rib as
a sharp point. For example, in the ribs 28 illustrated in FIG. 2A,
it is also possible to form the lower end portion of each rib 28
such that the thickness thereof becomes progressively thinner the
closer it is to the lower end side thereof. By employing this type
of structure, because the lower end portion is sharpened, it is
possible to reduce the resistance from the ribs 28 when the pile 24
is being pile-driven.
[0084] Priority is claimed on Japanese Patent Application No.
2018-164264, filed Sep. 3, 2018, the disclosure of which is
incorporated herein by reference.
[0085] All references, patent applications and technical
specifications cited in the present specification are incorporated
by reference into the present specification to the same extent as
if the individual references, patent applications and technical
specifications were specifically and individually recited as being
incorporated by reference.
* * * * *