[Technical Field of the Invention]
[0001]
The present invention relates to a steel pipe pile and a steel pipe pile
construction method.
Priority is claimed on Japanese Patent Application No. 2013-128351s filed on
June 19, 2013, the content of which is incorporated herein by reference.
[Related Art]
[0002]
A steel pipe pile can be classified into several types according to construction
methods. For example, a pile driven by hammer is a steel pipe pile which is driven to
a bearing stratum by a pile driving by hammer. A frictional force (an in-pipe
fi-ictional force) occurring between the inner peripheral surface of a leading end portion
of a steel pipe pile and the ground increases in proportion to a pile diameter. On the
other hand, the cross-sectional area (the closed cross-sectional area) of the leading end
portion of the steel pipe pile increases in proportion to the square of a pile diameter.
Therefore, the larger the pile diameter of the steel pipe pile, the smaller the in-pipe
frictional force of the steel pipe pile becomes relatively with respect to the closed
cross-sectional area of the steel pipe pile, and thus a sufficient leading end plugging
effect cannot be obtained. As a result, the leading end bearing capacity of the steel
pipe pile also decreases.
[0003]
In the. related art, as a method of increasing the in-pipe frictional force of the
- 1 -
steel pipe pile in order to improve the leading end plugging effect of the steel pipe pile,
a method of increasing the total surface area of the leading end portion of the steel pipe
pile by mounting a dividing member which divides a cross section of the steel pipe pile,
on the inside of the leading end portion of the steel pipe pile, is known (refer to, for
example, Non-Patent Document 1 described below).
[0004]
FIG. 13A is a diagram schematically showing a state where a dividing
member 110 configured with a plurality of steel plates orthogonal to each other is
mounted on the inside of a leading end portion of a steel pipe pile 100. The dividing
member 110 is welded to the inner peripheral surface of the leading end portion of the
steel pipe pile 100.
[0005]
In order to reliably improve the leading end plugging effect of the steel pipe
pile 100, it is desirable that the length of the dividing member 110 in a length direction
(an axial direction) of the steel pipe pile 100 is set to be greater than or equal to twice
an outer diameter D of the steel pipe pile 100. However, in a case where the dividing
member 110 having a length greater than or equal to twice the outer diameter D of the
steel pipe pile 100 is mounted on the inside of the steel pipe pile 100, it is necessary for
a worker to enter the inside of the steel pipe pile 100 and perform welding work. As
a result,-:a problem In that the physical burden of the worker increases arises.
[0006]
Further, due to the mounting of the dividing member 110, the leading end
plugging effect of the steel pipe pile 100 is improved.and resistance occurring between
the leading end portion of the steel pipe pile 100 which is driven into the ground by a
pile driving by hammer and the ground also increases. As a result, even if impact
- 2 -
force by the hammer is applied to the steel pipe pile 100, there is a case where
penetration is not possible (driving becomes impossible) before the steel pipe pile 100
reaches a target bearing stratum.
[0007J.
In this case, as a countermeasure, it is conceivable to increase a striking force
which is applied to the steel pipe pile 100. However, in a case of adopting a pile
driving by hammer, heavy machinery such as a pile driver is increased in size. For
this reason, an increase in facility cost or a decrease in workability is caused. Further,
a large amount of noise and vibration are generated, and therefore, in an area in which
environmental regulations are strict, like an urban area, it is difficult to simply increase
a striking force. Therefore, even if the dividing member 110 is mounted on the steel
pipe pile 100 having a large pile diameter (the outer diameter D), there is a case where
it becomes difficult to drive the steel pipe pile 100 to a bearing stratum by a pile
driving by hammer.
[0008]
On the other hand, in an area in which environmental regulations are strict, an
inner excavation method or a bored pile method, in which it is possible to suppress
noise and vibration occurring during the driving of a steel pipe pile, is widely used.
In these construction methods, in a state where a drilling rod is inserted into the inside
of a steel pipe pile, drilling of the ground by the drilling rod and sinking of the steel
pipe pile are performed at the same time, and a fluidity solidifying material (cement
milk of the like) is injected into a bearing stratum disturbed by the drilling rod. The
.^•fluidity solidifying material injected into the bearing stratum is solidified, whereby a
foot protection block is constructed so as to cover a leading end portion of the steel
pipe pile. Due to the construction of the foot protect! oitblock, the leading end
- 3 -
portion of the steel pipe pile is plugged and the ground disturbed by the drilling rod is
restored (refer to, for example, Patent Documents 1 to 5 described below and Non-
Patent Document 1 described below).
[0009]
FIG. 13B is a diagram schematically showing a state where the steel pipe pile
100 is driven by an inner excavation method. The ground is dug by a drilling rod 120
inserted into the inside of the steel pipe pile 100, until the leading end portion of the
steel pipe pile 100 reaches a bearing stratum. After the leading end portion of the
steel pipe pile 100 reaches the bearing stratum, a fluidity solidifying material (cement
milk or the like) is injected from a leading end portion of the drilling rod 120 into the
bearing stratum disturbed by the drilling rod 120 and the leading end portion of the
steel pipe pile 100, and thus a foot protection block 130 is constructed.
[0010]
By adopting the inner excavation method or the bored pile method, it is
possible to suppress noise and vibration occurring during the driving of the steel pipe
pile 100, and therefore, it is possible to drive the steel pipe pile 100 in an area in which
environmental regulations are strict, such as an urban area. However, as described
above, in the inner excavation method and the bored pile method, it is necessary to
insert the drilling rod 120 into the inside of the steel pipe pile 100, and therefore, it is
••-. - not possible to Ttiotint the dividing member 110 for-increasing the leadingxnd plugging
effect on the steel pipe pile 100. -, ,
[ o o i i ] ••-• -
The leading end portion of the steel-pipe .pile 100 driven by the inner
excavation method or the bored pile method is confined by a factional force occurring
- between soil cement filled into the leading end portion of the steel pipe pile 100 and
• - 4 -
the surface of the steel pipe pile 100. This confining force exerts the leading end
plugging effect.
[0012]
The larger the outer diameter D of the steel pipe pile 100, the further the
leading end plugging effect decreases. Therefore, in order to obtain the abovedescribed
confining force, it is necessary to increase the length of the soil cement (the
length of the foot protection block) on the inside of the leading end portion of the steel
pipe pile 100. Further, it is necessary to inject a large amount of cement milk or the
like into the steel pipe pile 100 and the ground according to the extension of the foot
protection block, and therefore, construction hours become longer, and construction
costs increase.
[Prior Art Documents]
[Patent Document]
[0013]
[Patent Document 1] Japanese Unexamined Patent Application, First
Publication No. 2009-057817
[Patent Document 2] Japanese Unexamined Patent Application, First
Publication No. 2009-068326
[Patent Document 3] Japanese Unexamined Patent Application, First
Publication No. 2010-209516 ' • * - - •" ~ -
[Patent Document 4] Japanese Unexamined Patent Application, First
Publication No. 2012-097511 '
[Patent Document 5] Japanese Unexamined Patent Application, First
Publication No. 2012-127082
[Non-Patent Document] <•=• -
- 5 -
[0014]
[Non-Patent Document 1] "Steel pipe pile - design and construction
thereof (12th edition revised on April 1, 2009) issued by the Japanese Technical
Association for Steel Pipe Piles and Steel Sheet Piles, pp 328 to 329 and 469 to 470
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
[0015]
In recent years, under strict environmental regulations, applications of the
inner excavation method or the bored pile method in which it is possible to suppress
noise and vibration occurring during the driving of a steel pipe pile have increased.
However, unlike in the pile driving by hammer, in the inner excavation method or the
bored pile method, it is necessary to insert the drilling rod into the inside of the steel
pipe pile, and therefore, it is not possible to attach the dividing member for increasing
the leading end plugging effect, to the inside of the leading end portion of the steel
pipe pile.
[0016]
For this reason, in a case of adopting the inner excavation method or the bored
pile method, in order to improve the confining force of the steel pipe pile by the foot
protection block constmcted by the solidification of the fluidity solidifying material, it
is necessary to'increase the length of the foot protection block'in the leading end
portion of the-steel pipe pile as the outer diameter of the steel pipe pile becomes larger.
In a case where the length of the foot protection block is not appropriate with respect to
the outer diameter of the steel pipe pile, it is not possible to obtain the bearing capacity .
of the steel pipe pile from the bearing stratum to a maximum extent. For this reason,
it is necessary to increase* the number of steel pipe piles in order to obtain the required
- 6 -
bearing capacity for the entire structure, and thus an economical burden such as an
increase in construction costs and a prolonged construction period increases.
[0017]
The present invention has been made in view of the above-mentioned
circumstances and has an object to provide a steel pipe pile and a steel pipe pile
construction method in which leading end bearing capacity can be obtained to a
maximum extent by increasing a confining force of a steel pipe pile by a foot
protection block constructed by solidification of a fluidity solidifying material.
[Measures for Solving the Problem]
[0018]
In order to achieve an object by solving the problem, the present invention
adopts the following measures.
(1) According to an aspect of the present invention, there is provided a steel
pipe pile including a pile main body configured with a steel pipe, a dividing member
which is mounted on the inside of a leading end portion of the pile main body, thereby
dividing a cross section of the pile main body into a plurality of sections, an injection
nozzle which is mounted on at least one of an outer peripheral surface of the leading
end portion of the pile main body and an inner peripheral surface of the leading end
portion of the pile main body and selectively injects water and a fluidity solidifying
• - Jmaterial;and a pipe which selectively supplies the water and the'fluidity solidifying
material to.the injection nozzle.
[0019] :
(2) In the steel pipe pile according to (1), the dividing member may he a .. -^
member for constructing a foot protection block by solidification of the fluidity
solidifying material. -
- 7 -
[0020]
(3) In the steel pipe pile according to (1) or (2), the dividing member may be a
steel plate mounted on the inside of the leading end portion of the pile main body so as
to be parallel to an axial direction of the pile main body.
[0021]
(4) In the steel pipe pile according to any one of (1) to (3), the injection nozzle
may be mounted on the dividing member as well.
[0022]
(5) In the steel pipe pile according to any one of (1) to (4), an injection
direction of the injection nozzle may be parallel to an axial direction of the pile main
body and may be directed to the inside of an inner peripheral surface of the pile main
body.
[0023]
(6) In the steel pipe pile according to any one of (1) to (5), a plurality of the
injection nozzles may be mounted on at least one of the outer peripheral surface and
the inner peripheral surface of the leading end portion of the pile main body, and each
injection direction of the plurality of injection nozzles may intersect an axial direction
of the pile main body.
[0024]
(7) In the steel pipe pile according to any one of (1) to (6), the outer peripheral
surface of the pile main body may be provided with a projection.
' [0025]
(8) In the steel-pipe pile according to any one of (1) to (7), the-dividing-,- *
member and the inner peripheral surface of the pile main body may be provided with a
projection. *. • -
- 8 -
[0026]
(9) In the steel pipe pile according to any one of (1) to (8), the dividing
member may be provided with a through-hole.
[0027]
(10) In the steel pipe pile according to any one of (1) to (9), a length of the
dividing member in an axial direction of the pile main body may be less than twice an
outer diameter of the pile main body.
[0028]
(11) In the steel pipe pile according to any one of (1) to (10), the injection
nozzle and the pipe may be detachably mounted on the pile main body.
[0029]
(12) According to another aspect of the present invention, there is provided a
steel pipe pile construction method including a process of driving the steel pipe pile
according to any one of (1) to (10) to a maximum drilling depth in a bearing stratum
while injecting the water from the injection nozzle, a process of pulling up the steel
pipe pile to a predetermined pull-up depth while injecting the fluidity solidifying
material from the injection nozzle, a process of driving the steel pipe pile to a fixing
depth in the bearing stratum while continuing to inject the fluidity solidifying material
from the injection nozzle, and a process of constructing a foot protection block of the
steel pipe pile by solidification of the fluidity solidifying material.- :--.--
[0030]
(13) According to still another aspect of the present invention, there is
provided^ steel.pipe-pile construction method including a process of driving the steel
pipe pile according to (11) to a maximum drilling depth in a bearing stratum while
injecting the water from the injection nozzle, a process of pulling up the steel pipe pile
- 9 -
to a predetermined pull-up depth while injecting the fluidity solidifying material from
the injection nozzle, a process of driving the steel pipe pile to a fixing depth in the
bearing stratum while continuing to inject the fluidity solidifying material from the
injection nozzle, a process of separating the injection nozzle and the pipe from the steel
pipe pile in a state where injection of the fluidity solidifying material from the injection
nozzle is temporarily stopped, a process of pulling up the injection nozzle and the pipe
to the ground while injecting the fluidity solidifying material from the injection nozzle,
and a process of constructing a foot protection block of the steel pipe pile by
solidification of the fluidity solidifying material.
[0031]
(14) According to still another aspect of the present invention, there is
provided a steel pipe pile construction method including a process of driving the steel
pipe pile according to (11) to a maximum drilling depth in a bearing stratum while
injecting the water from the injection nozzle, a process of pulling up the steel pipe pile
to a predetermined pull-up depth while injecting the fluidity solidifying material from
the injection nozzle, a process of driving the steel pipe pile to a fixing depth in the
bearing stratum while continuing to inject the fluidity solidifying material from the
injection nozzle, a process of separating at least a portion of the pipe from the steel
pipe pile in a state where injection of the fluidity solidifying material from the injection
nozzle is temporarily stopped, a process of pulling up a portion of the-separated pipe to
the ground while injecting the fluidity solidifying material from a leading end of the
separated pipe,' and a process of constructing a foot protection block of the steel pipe
pile by solidification of the fluidity solidifying material. _. -., :.•>,<. >
[0032]
(15) in the steel pipe pile construction method according to any one of (12) to
- 10 -
(14), after the process of driving the steel pipe pile to the maximum drilling depth and
before the process of pulling up the steel pipe pile to the pull-up depth, a process of
pulling up the steel pipe pile while injecting the fluidity solidifying material or the
water from the injection nozzle, and then driving the steel pipe pile, may be performed
at least once.
[Effects of the Invention]
[0033]
According to the above aspects, the contact area between the foot protection
block constructed by the solidification of the fluidity solidifying material and the inside
of the leading end portion of the pile main body (the leading end portion of the pile
main body and the dividing member) increases, and therefore, it is possible to increase
the confining force of the steel pipe pile on the foot protection block.
Therefore, according to the above aspects, in a case where the outer diameter
of the steel pipe pile (the pile main body) is large, even if the length of the foot
protection block on the inside of the pile main body is shortened, the contact area is
secured, and thus it is possible to sufficiently obtain the confining force of the steel
pipe pile. Therefore, it is possible to obtain the leading end bearing capacity of the
steel pipe pile from the bearing stratum to a maximum extent.
[Brief Description of the Drawings]
[0034] - :r. - - . • * • :'
FIG. 1A is a side view of a steel pipe pile 1 according to an embodiment of the
present invention.
... .***„ 'PIG. IB is a cross-sectional view as seen from a direction of.arrow A-A of the
steel pipe pile 1 shown in FIG. 1 A.
, *iEIG 2 A is a first diagram schematically showing a method of constructing the
- 11 -
steel pipe pile 1 according to the embodiment of the present invention.
FIG. 2B is a second diagram schematically showing the method of
constructing the steel pipe pile 1 according to the embodiment of the present invention.
FIG. 2C is a third diagram schematically showing the method of constructing
the steel pipe pile 1 according to the embodiment of the present invention.
FIG. 3 is a diagram schematically showing a foot protection block FPB
constructed by the method of constructing the steel pipe pile 1 according to the
embodiment of the present invention.
FIG. 4 is a diagram schematically showing a modified example in which
injection nozzles 4 are mounted on both an outer peripheral surface 2b and an inner
peripheral surface 2a of a leading end portion of a pile main body 2.
FIG. 5 is a diagram schematically showing a modified example in which a
plurality of through-holes 3a is provided in a dividing member 3.
FIG. 6A is a diagram schematically showing a modified example in which the
injection nozzles 4 are disposed on the outer peripheral surface 2b of the pile main
body 2 and the cross section of the pile main body 2 is divided into three sections by
three dividing members 6 (flat steel plates) joined to each other at the center of the pile
main body 2.
FIG. 6B is a diagram schematically showing a modified example in which the
injection nozzles 4 are disposed on the outer peripheral surface' 2b of the pile main
body 2 and the cross section of the pile main body 2 is divided into three sections by *
two arc-shaped dividing members 7.
. FIG. 7A is a diagram schematically showing ^-modified example in which the
injection nozzles 4 are disposed on the outer peripheral surface 2b and the inner
peripheral surface 2a of the pile main body 2 and the cross section of the pile main
- 12 -
body 2 is divided into three sections by the three dividing members 6 (flat steel plates)
joined to each other at the center of the pile main body 2.
FIG. 7B is a diagram schematically showing a modified example in which the
injection nozzles 4 are disposed on the outer peripheral surface 2b and the inner
peripheral surface 2a of the pile main body 2 and the cross section of the pile main
body 2 is divided into three-sections by the two arc-shaped dividing members 7.
FIG. 8 is a diagram schematically showing a modified example in which two
injection nozzles 4 are also disposed on both sides of the dividing member 3 which is a
sheet of flat steel plate as shown in FIG. IB.
FIG. 9 A is a diagram schematically showing a modified example in which one
injection nozzle 4 is disposed on one side of each of the three dividing members 6 as
shown in FIG. 6A.
FIG. 9B is a diagram schematically showing a modified example in which one
injection nozzle 4 is disposed on one side of each of the two arc-shaped dividing
members 7 as shown in FIG. 6B.
FIG. 10 is a diagram schematically showing a modified example in which
injection directions of a plurality of injection nozzles 4 intersect an axial direction AX
of the pile main body 2.
FIG 11A is a schematic diagram when the pile main body 2 with four
'projections 11" (steelplates) provided on the outer peripheral surface 2b*is viewed from*
the axial direction AX. •> . .*.- -.» *.•
FIG. 11B is a schematic diagram when the pile main body 2 with four
projections 11 (steel plates) provided on.fhe outer peripheral surface 2b is viewed from
a direction orthogonal to the axial direction AX.
FIG. 12 is a diagram schematically showing a modified example in which a
- 13 -
projection 12 (a reinforcing bar) is provided at the dividing member 3 which is a sheet
of flat steel plate.
FIG. 13A is a diagram schematically showing a state where a dividing
member 110 configured with two steel plates orthogonal to each other is mounted on
the inside of a leading end portion of a steel pipe pile 100.
FIG. 13B is a diagram schematically showing a state where the steel pipe pile
100 is driven into the ground by an inner excavation method.
[Embodiments of the Invention]
[0035]
Hereinafter, an embodiment of the present invention will be described in
detail with reference to the drawings.
[0036]
FIG. 1A is a side view of a steel pipe pile 1 according to an embodiment of the
present invention. FIG. IB is a cross-sectional view as seen from a direction of arrow
A-A of the steel pipe pile I shown in FIG. 1 A. As shown in FIGS. 1A and 1B, the
steel pipe pile I according to this embodiment is provided with a pile main body 2, a
dividing member 3, a plurality of (for example, six) injection nozzles 4, and a plurality
of (for example, six) pipes 5.
[0037]
The pile main body 2 is configured with a steel pipe having:an outer diameter
D which is constant .along an axial direction AX. In the following, an endportion on
one side on which the dividing member 3 is mounted, in two end portions of the pile
main body 2, is referred to as a leading=end portion, and an end portion on the other
side is referred to as a rear end portion.
[0038]
- 14 -
The dividing member 3 is a single flat steel plate having a rectangular shape.
The dividing member 3 is mounted so as to divide the cross section of the pile main
body 2 into two sections on the inside of the leading end portion of the pile main body
2. The dividing member 3 is welded to an inner peripheral surface 2a of the pile main
body 2 so as to be parallel to the axial direction AX of the pile main body 2. As will
be described later, it is preferable that a length L of the dividing member 3 in the axial
direction AX of the pile main body 2 be less than twice the outer diameter D of the pile
main body 2.
[0039]
As described above, as the dividing member 3, it is preferable to use a flat
plate-shaped metal member. In particular, it is preferable that a steel plate which is
used as the dividing member 3 have a strength and a plate thickness capable of
withstanding driving of the steel pipe pile 1 and a pile leading end bearing capacity.
A method of joining the dividing member 3 to the pile main body 2 is not particularly
limited. For example, it is possible to adopt a bolt joint. However, as a method of
joining the dividing member 3 to the pile main body 2, welding is preferable. In this
case, it is preferable that the quality of a material of a steel plate which is used as the
dividing member 3 be the same as the quality of a material of the pile main body 2.
However, as long as it is the quality of a material having good weldability, the quality
of a material which is different from that of the pile main body 2 is also acceptable.
[0040.].,
The six injection nozzles 4 are mounted at regular intervals along a:
circumferential direction of.the pile^main body 2 on an outer peripheral surface 2b of -
the leading end portion of the pile main body 2. Each of the injection nozzles 4
selectively injects water and a fluidity solidifying material (for example, cement milk)
- 15 -
along the axial direction AX of the pile main body 2. That is, an injection direction
JD of each of the injection nozzles 4 is a direction parallel to the axial direction AX
and outward in the axial direction AX. In a case where the water is injected from
each of the injection nozzles 4, the ground which is included in a drilling range 4a
shown in Fig. IB is dug. In this embodiment, each of the injection nozzles 4 is
detachably mounted on the pile main body 2.
[0041]
The six pipes 5 correspond to the six injection nozzles 4 on a one-to-one basis.
That is, one pipe 5 is connected to one injection nozzle 4. Each of the pipes 5 is
disposed so as to extend along the axial direction AX of the pile main body 2 on the
outer peripheral surface 2b of the pile main body 2. The water and the fluidity
solidifying material are selectively supplied to the injection nozzle 4 through the pipe 5.
In this embodiment, each of the pipes 5 is detachably mounted on the pile main body 2,
similarly to the injection nozzle 4. In addition, in the steel pipe pile 1 according to
the embodiment of the present invention shown in FIGS. 1A and IB, an example in
which the pipes 5 and the injection nozzles 4 correspond to each other on a one-to-one
basis is shown. However, there is no limitation thereto, and pipes branched from one
pipe may be connected to the plurality of injection nozzles 4, and a plurality of pipes
may be connected to one injection nozzle 4.
[0042] :'• • —• —'- - * • - -
*-.i-Next, a method of constructing the steel pipe pile 1 according to this
embodiment .configured as described above will be described.
First, as-shown in.a first process in FIG. 2A, after the steel pipe pile Lis, •« - - ..• ,
provided to be erect on a surface of ground GS in a state where the leading end portion
of the steel pipe pile 1 (that is, the leading end portion of the pile main body 2) is in *»
- 16 -
contact with the surface of ground GS, a vibratory hammer BH is mounted on a rear
end portion of the steel pipe pile 1 (that is, a rear end portion of the pile main body 2).
The vibratory hammer BH is suspended by a crane (not shown).
[0043]
Further, each of the pipes 5 of the steel pipe pile 1 is connected to a fluid
supply device (not shown). The fluid supply device has a function to selectively
supply the water and the fluidity solidifying material to each of the pipes 5 according
to an operation by a worker. At this point of time, a fluid which is supplied from the
fluid supply device to each of the pipes 5 is set to be the water.
[0044]
Subsequently, as shown in a second process in FIG. 2A, vibration which acts
in the axial direction AX is applied to the steel pipe pile 1 by the vibratory hammer BH
while high-pressure water (water jet) WJ is injected from each of the injection nozzles
4 of the steel pipe pile 1. The ground which is present in a driving direction (a
vertically downward direction) from the steel pipe pile 1 is dug by the injection of the
high-pressure water WJ and the vibration of the steel pipe pile 1, and thus a driving
hole DH of the steel pipe pile 1 is formed along the driving direction. The steel pipe
pile 1 settles along the driving hole DH due to its own weight and the weight of the
vibratory hammer BH.
• [0045] ...........
IM* :•
stopped and a vibration generating operation of the vibratory hammer BH is also
stopped. In this way, thcsteel pipe pile 1 is stopped at the maximum drilling depth-.
- 17 -
In a state where the steel pipe pile 1 has been stopped at the maximum drilling depth in
this manner, the fluid which is supplied from the fluid supply device to each of the
pipes 5 is switched from the water to the fluidity solidifying material (for example,
cement milk).
[0046]
Subsequently^ as shown in a fourth process in FIG. 2B, the vibration
generating operation of the vibratory hammer BH is resumed, and while a fluidity
solidifying material SM is injected from each of the injection nozzles 4 of the steel
pipe pile 1, the vibratory hammer BH is pulled up by the crane until the steel pipe pile
1 returns to a predetermined pull-up depth. When the steel pipe pile 1 is pulled up
from the maximum drilling depth to the pull-up depth in this manner, the section
between the maximum drilling depth and the pull-up depth in the driving hole DH is
filled with the fluidity solidifying material SM.
[0047]
As shown in a fifth process in FIG. 2B, the pull-up of the vibratory hammer
BH (that is, the pull-up of the steel pipe pile 1) by the crane is stopped while injecting
the fluidity solidifying material SM from each of the injection nozzles 4 even after the
steel pipe pile 1 reaches the pull-up depth. The steel pipe pile 1 starts settling again
along the driving hole DH due to its own weight and the weight of the vibratory
hammer BH. Then, as shown in a sixth process in FIG. 2B, when the steel pipe pile 1
i_4« ..-.reaches a fixing depth, a wire of the crane is fixed,-, and, thus the position of the steel
pipe pile 1 in the driving hole DH is maintained at the fixing depth.
Jn addition^ the fixing depth is set at a position shallower^han. the maximum
drilling depth and deeper than the pull-up depth, in the bearing stratum. Further, it is
preferable that the distance between the fixing depth and the pull-up depth be longer
- 18 -
than the length L of the dividing member 3 in the axial direction AX of the pile main
body 2.
[0048]
Then, as shown in a seventh process in FIG. 2C, in a state where the position
of the steel pipe pile 1 is maintained at the fixing depth, the injection nozzles 4 and the
pipes 5 are pulled up to the ground while the fluidity solidifying material SM is
injected from each of the injection nozzles 4 of the steel pipe pile 1. Before the
injection nozzles 4 and the pipes 5 are pulled up, it is necessary to separate the
injection nozzles 4 and the pipes 5 from the steel pipe pile 1 in a state where the
injection of the fluidity solidifying material SM from the injection nozzles 4 is
temporarily stopped. In the seventh process in FIG. 2C, an example in which the
injection nozzles 4 and the pipes 5 are pulled up to the ground is shown. However, an
example is also possible in which the pipe 5 is separated from a joint portion between
the injection nozzle 4 and the pipe 5 and only the pipe 5 is pulled up to the ground.
Otherwise, an example is also possible in which at least a portion of the pipe 5 is
separated from the steel pipe pile 1 in a state where the injection of the fluidity
solidifying material SM from the injection nozzles 4 is temporarily stopped, and only a
portion of the separated pipe is pulled up to the ground while injecting the fluidity
solidifying material SM from the leading end of the separated pipe.
Then,-as shown in an eighth process in FIG. 2C, after the pull-up (recovery) of
the injection nozzles 4 and the pipes 5 is completed and the fluidity solidifying
material SM is solidified, the vibratory hammer BH is removed from the pile main
body 2yand-thus the construction (driving) of the steel pipe.pile.l i&completed.
[0049]
- : As shown in FIG. 2C, after the recovery of the injection nozzles 4 and the
- 19 -
pipes 5 is completed, the pile main body 2 and the dividing member 3 (in FIG. 2C, not
shown) mounted on the inner peripheral surface 2a of the leading end portion of the
pile main body 2, among the constituent elements of the steel pipe pile 1, remain in the
driving hole DH, and the section between the pull-up depth and the surface of ground
GS in the driving hole DH is also filled with the fluidity solidifying material SM.
That is, a region which is included between the surface of ground GS and the
fixing depth, of the outer peripheral surface 2b of the pile main body 2, is covered with
the fluidity solidifying material SM, and a space between the pull-up depth and the
fixing depth, of an internal space (also including spaces divided by the dividing
member 3) of the pile main body 2, is filled with the fluidity solidifying material SM.
[0050]
As shown in FIG. 3, when the fluidity solidifying material SM is solidified in
such a state, a foot protection block FPB (soil-cement solidified body) is constructed so
as to cover the leading end portion of the pile main body 2. The foot protection block
FPB also penetrates the space between the pull-up depth and the fixing depth, of the
internal space (also including the spaces divided by the dividing member 3) of the pile
main body 2, without a gap.
[0051]
The foot protection block FPB described above is constructed, whereby the
inner peripheral-surface 2a of the-pile main body 2 and the surface of the dividing " •-• *
member 3 come into contact with the foot-protection block FPB, that is, the soilcement
solidified body. As a result, the contact area between the foot protection
blocMPB and the inside of the leading end portion of thenpile-main body 2 increases,
and therefore, a confining force of the pile main body 2 by the foot protection block
FPB is increased. - • • ., -•=.-
- 20 -
[0052]
As already described, in the related art, in a case where the outer diameter of a
steel pipe pile is large, in order to obtain a sufficient leading end plugging effect
(leading end bearing capacity) by increasing a confining force of the steel pipe pile by
a foot protection block, it is necessary to increase the length of the foot protection
block (the length of a soil-cement solidified body) on the inside of the steel pipe pile.
[0053]
However, as described above, according to this embodiment, it is possible to
increase the confining force of the pile main body 2 by the foot protection block FPB
by an increase in the contact area between the foot protection block FPB and the inside
of the leading end portion of the pile main body 2. Therefore, according to this
embodiment, in a case where the outer diameter D of the pile main body 2 is large,
even if the length of the foot protection block FPB on the inside of the pile main body
2 is set to be short, it is possible to sufficiently secure the confining force of the pile
main body 2 by the foot protection block FPB, and as a result, it is possible to obtain a
leading end plugging effect (leading end bearing capacity) of the pile main body 2 to a
maximum extent.
[0054]
In particular, in a case where the outer diameter D of the pile main body 2
exceeds 1000 mm, the confining force of the pile main body 2 by the foot protection
block FPB greatly varies according^to the presence or absence of the dividing member \>.» -.-,,
3 in the leading end portion of the pile main body 2, and therefore, the effect of
>. ^ ..-improving the leading end bearing capacity which-is obtained by the mounting of the
dividing member 3 is remarkable.
, , - . [0055]
- 21 -
Further, in this embodiment, the distance between the fixing depth and the
pull-up depth is set to be longer than the length L of the dividing member 3 in the axial
direction AX of the pile main body 2. For this reason, as shown in FIG. 3, the foot
protection block FPB penetrates to a space above the dividing member 3, of the
internal space of the pile main body 2. In this manner, according to this embodiment,
an upper end of the dividing member 3 is covered with the foot protection block FPB,
whereby an anchor effect by the foot protection block FPB is also obtained, and
therefore, it is possible to further improve the leading end bearing capacity of the pile
main body 2.
[0056]
Here, the length L of the dividing member 3 which is integrated with the foot
protection block FPB will be described. As already described, in a case where a
dividing member is mounted on a steel pipe pile which is driven by a pile driving by
hammer, it is preferable that the length of the dividing member be set to be greater than
or equal to twice the outer diameter of the steel pipe pile. However, as shown in FIG.
3, in this embodiment, the dividing member 3 is integrated with the fluidity solidifying
material SM, and thus the foot protection block FPB is constructed along with the
leading end portion of the pile main body 2, and therefore, it is sufficient if the length
L of the dividing member 3 is a length which is integrated with the fluidity solidifying
- *: material SM. •- ~ * - - ,--.- • . . . . _ « . ..
[0057]
The upper limit of the length L of the dividing member 3 depends on the state
,**>«,» ? of the ground and the outer diameter D of the.pik-main body 2. According to the
results of the tests carried out by the inventors of this application, in order to
•w - sufficiently secure the confining force by the foot protection block FPB, it is preferable
- 22 -
that the length L of the dividing member 3 be less than twice the outer diameter D of
the pile main body 2. In a case where the length L of the dividing member 3 is
greater than or equal to twice the outer diameter D of the pile main body 2, since it is
necessary for a worker to enter the inside of the pile main body 2 and perform work of
welding the dividing member 3, working hours for the mounting of the dividing
member 3 become longer, and thus the physical burden of a worker increases.
[0058]
On the other hand, if the length L of the dividing member 3 is too short, even
if the dividing member 3 is integrated with the fluidity solidifying material SM, it is
difficult to constiiict a robust foot protection block FPB, and it is difficult to secure the
quality and the strength of a welded portion between the pile main body 2 and the
dividing member 3. The lower limit of the length L of the dividing member 3
depends on the state of the ground, the outer diameter D of the pile main body 2, and
the number of divisions by the dividing member 3. According to the results of the
tests carried out by the inventors of this application, it is preferable that the lower limit
of the length L of the dividing member 3 be greater than or equal to 0.5 times the outer
diameter D of the pile main body 2.
[0059]
The present invention is not limited to the above-described embodiment and
the following modified examples can be given/ .- - *
(1) In the above-described embodiment, an example that the injection nozzles
4 are mounted on only the outer peripheral surface 2b of the leading end portion of the
pile main body 2 is explained, However^it-i&enough if the injection nozzles 4 are
mounted on at least one of the outer peripheral surface 2b of the leading end portion of
the pile main body 2 and the inner peripheral surface 2a of the leading end portion of
- 23 -
the pile main body 2.
[0060]
FIG. 4 is a diagram showing an example in which the injection nozzles 4 are
mounted on both the outer peripheral surface 2b and the inner peripheral surface 2a of
the leading end portion of the pile main body 2. In the example shown in FIG. 4,
three injection nozzles 4 are mounted along the circumferential direction of the pile
main body 2 on the outer peripheral surface 2b of the leading end portion of the pile
main body 2, and three injection nozzles 4 are mounted along the circumferential
direction of the pile main body 2 on the inner peripheral surface 2a of the leading end
portion of the pile main body 2.
[0061]
By injecting high-pressure water from the injection nozzles 4 mounted on the
inner peripheral surface 2a of the pile main body 2, it is possible to efficiently dig the
ground which is present in the driving direction of the steel pipe pile 1. Further, since
the inner peripheral surface 2a of the pile main body 2 is cleaned, adhesion between
the fluidity solidifying material SM and the inner peripheral surface 2a of the pile main
body 2 increases.
[0062]
In addition, in a case of preferentially blocking the leading end portion of the
j steel pipe pile l-(that is, the leading end portion of the pile main'body 2% the crosssectional
area^of .the leading end portion of the pile main body 2 is divided into small
areas by the dividing member 3. Therefore, by injecting the fluidity solidifying
material SM from the injection nozzles.4 while pulling up the injection nozzles 4
disposed on the inner peripheral surface 2a of the pile main body 2, it becomes
possible to construct the foot protection*block FPB which integrates the inner
- 24 -
peripheral surface 2a of the pile main body 2, the surface of the dividing member 3,
and the fluidity solidifying material SM with each other.
[0063]
(2) In the above-described embodiment, an example that the number of
injection nozzles 4 is six is explained. However, it is favorable if the number, the
positions, the disposition interval, and the like of the injection nozzles 4 are
appropriately set according to the state of the ground, the outer diameter D of the pile
main body 2, and the like.
[0064]
(3) As shown in FIG. 5, a plurality of through-holes 3a may be provided in the
dividing member 3. The through-holes 3a are provided in the dividing member 3 (a
steel plate), whereby the fluidity solidifying material SM solidified on the inside of the
pile main body 2 is integrated with the dividing member 3 through the through-holes
3a, and therefore, a confining force on the dividing member 3 is further improved and
the bearing capacity of the pile main body 2 is also improved. It is enough if at least
one through-hole 3a is provided in the dividing member 3. There is no limit to the
number of through-holes 3a. However, it is preferable to appropriately set the
number of through-holes 3a in consideration of the strength of the dividing member 3
and a confining force of the solidified fluidity solidifying material SM on the dividing
member 3. • - * ~ *' • "
..--,[0065] ^ •.,.-•
- (4) In the above-described embodiment, an example that the cross section of
the pile main body 2 is.divided into two sections by using a single flat steel plate.as the.» •.
dividing member 3 is explained. However, it is favorable if the number of divisions
of the cross section of the pile main body 1 and the disposition of the dividing member -«-*
- 25 -
3 are appropriately set according to the state of the ground or the outer diameter D of
the pile main body 2.
[0066]
FIG. 6A shows an example in which the injection nozzles 4 are disposed on
the outer peripheral surface 2b of the pile main body 2 and the cross section of the pile
main body 2 is divided into three sections by three dividing members 6 (flat steel
plates) joined to each other at the center of the pile main body 2. FIG. 6B shows an
example in which the injection nozzles 4 are disposed on the outer peripheral surface
2b of the pile main body 2 and the cross section of the pile main body 2 is divided into
three sections by two arc-shaped dividing members 7.
[0067]
If the number of divisions of the cross section of the pile main body 2
increases, the surface areas of the dividing members 6 (or 7) increase, and therefore,
the confining force of the pile main body 2 by the foot protection block FPB increases.
However, work of mounting the dividing members 6 (or 7) becomes complicated, and
therefore, it is preferable to appropriately set the number of divisions of the cross
section of the pile main body 2 so as not to inhibit the workability of construction of
the steel pipe pile 1, after the consideration of the outer diameter D of the pile main
body 2.
[0068] --_.•....
•i-i jtv Further, if the number of divisions of the cross section of the pile main body 2
increases, the surface areas of the dividing members 6 (or 7) increase, and therefore,
the confining forceof the pile main body 2 by the foot protection block FPB. increases.
For this reason, the length of each of the dividing members 6 (or 7) in the axial '
direction AX of the pile main body 2 may be shorter than the length L of the dividing
- 26 -
member 3. .
[0069]
FIG. 7 A shows an example in which the injection nozzles 4 are disposed on
the outer peripheral surface 2b and the inner peripheral surface 2a of the pile main
body 2 and the cross section of the pile main body 2 is divided into three sections by
the three dividing members 6 (flat steel plates) joined to each other at the center of the
pile main body 2. FIG. 7B shows an example in winch the injection nozzles 4 are
disposed on the outer peripheral surface 2b and the inner peripheral surface 2a of the
pile main body 2 and the cross section of the pile main body 2 is divided into three
sections by the two arc-shaped dividing members 7.
[0070]
In the examples shown in FIGS. 7A and 7B, the injection nozzles 4 are
disposed on the outer peripheral surface 2b and the inner peripheral surface 2a of the
pile main body 2, and therefore, it is possible to reliably inject the fluidity solidifying
material SM to divided portions in the leading end portion of the pile main body 2 by
the injection nozzles 4 disposed on the inner peripheral surface 2a, and thus the leading
end plugging effect is significantly improved.
[0071]
(5) As described above, it is enough if the injection nozzles 4 are mounted on
• at least one of the outer peripheral surface 2b and the inner peripheral surface 2a of the
s;, >T. pile main body 2. However, in order to quicken a driving speed of the steel pipe pile
1 and improve the leading end plugging effect, the injection nozzles 4 may be mounted
on the dividing member 3 (or, 6 or 7) as well. ... ..« ;..^ >•
[0072]
- = FIG. 8 shows an example in which two injection nozzles 4 are also disposed
- 27 -
on both sides of the dividing member 3 which is a single flat steel plate as shown in
FIG IB. FIG 9A shows an example in which one injection nozzle 4 is disposed on
one side of each of the three dividing members 6 as shown in FIG. 6A. FIG 9B
shows an example in which one injection nozzle 4 is disposed on one side of each of
the two arc-shaped dividing members 7 as shown in FIG. 6B.
[0073]
The disposition of the injection nozzles 4 is not limited to the examples shown
in FIGS. 8, 9A, and 9B. For example, in the example shown in FIG. 8, two injection
nozzles 4 may be disposed on one side of the dividing member 3. In the example
shown in FIG. 9A, for example, a total of two or more injection nozzles 4 may be
disposed on both sides of one dividing member 6. In the example shown in FIG. 9B,
at least one injection nozzle 4 may be disposed on the inside of one arc-shaped
dividing member 7.
[0074]
(6) In the above-described embodiment, an example that the injection
direction JD of each of the injection nozzles 4 is a direction parallel to the axial
direction AX of the pile main body 2 and outward in the axial direction AX is
explained. However, the injection directions JD of the injection nozzles 4 may be
directions parallel to the axial direction AX of the pile main body 2 and toward the
inside of the inner peripheral surface 2a of the pile main body 2. It isrpreferable that
the injection directions JD of the injection nozzles 4 be set in consideration of the state
of the ground, the drilling efficiency, and the like. In addition, the injection directions
JD of each.Qif.the injection nozzles 4 may be different from each.other.»
[0075]
In particular, in a case of driving the steel pipe pile 1 into hard-ground, there is
- 28 -
also a possibility that the ground of a central portion of the steel pipe pile 1 cannot be
dug. Therefore, in a case where the plurality of injection nozzles 4 are mounted on at
least one of the outer peripheral surface 2b and the inner peripheral surface 2a of the
leading end portion of the pile main body 2 in order to easily dig the ground, it is
preferable that the injection directions JD of the plurality of injection nozzles 4
intersect the axial direction AX of the pile main body 2.
[0076]
FIG. 10 shows an example in which the injection directions of the two
injection nozzles 4 intersect the axial direction AX of the pile main body 2. In the
example shown in FIG. 10, the injection direction JD of an injection nozzle 4b
disposed at the dividing member 3 which is a sheet of steel plate is parallel to the axial
direction AX of the pile main body 2 and is directed to a point X on the line of the
axial direction AX of the pile main body 2. On the other hand, the injection
directions JD of two injection nozzles 4c and 4d facing each other, which are disposed
on the outer peripheral surface 2b of the pile main body 2, intersect each other at the
point X on the line of the axial direction AX of the pile main body 2.
[0077]
(7) At least one projection may be provided on the outer peripheral surface 2b
of the leading end portion of the pile main body 2. In a case where a projection is
provided" on the outer peripheral surface 2b of the leading end portion of the pile main *'
body 2, the contact area between the foot .protection block FPB which covers the
leading end portion of the pile main body 2 and the surface of the pile main body 2 is
.. enlarged, .and therefore, the bearing capacity of the pile rnain-body 2 from the ground
increases. Further, at least one projection may also be provided on the inner
peripheral surface 2a of the leading end portion of the pile maimbody 2 and the
- 29 -
7
dividing member 3 (or, 6 or 7).
[0078]
FIG. 11A shows a schematic diagram when the pile main body 2 with four
projections 11 (steel plates) provided on the outer peripheral surface 2b is viewed from
the axial direction AX. FIG. 11B shows a schematic diagram when the pile main
body 2 with the four projections (steel plates) provided on the outer peripheral surface
2b is viewed fi-om a direction orthogonal to the axial direction AX. In FIGS. 11A and
11B, the four projections 11 which are steel plates are welded to the outer peripheral
surface 2b of the leading end portion of the pile main body 2 which is buried in the
foot protection block FPB, along the axial direction AX.
[0079]
In addition, it is favorable if the number of projections is appropriately set in
consideration of the state of the ground, the drilling efficiency, and the like. Further,
the shape of the projection is not limited to a plate shape. However, it is preferable
that the shape of the projection be a plate shape.
[0080]
FIG. 12 shows an example in which a projection 12 (a reinforcing bar) is
provided at the dividing member 3 which is a single flat steel plate. As shown in FIG.
12, a plurality of the projections 12 which are reinforcing bars are welded to the
surface of the dividing member 3 at regular intervals along~the axial direction AX and'
so as to extend in a direction orthogonal to the axial direction AX.
[0081]
•»-,< *. In addition, it is favorable if the number af.prejections.which are provided at
the dividing member 3 (or, 6 or 7) is appropriately set-in consideration of the state of
-ths.ground, the drilling efficiency, and the like. Furtheivas the projection which is
- 30 -
provided at the dividing member 3 (or, 6 or 7), instead of the reinforcing bar, a rib steel
plate may be provided. Further, the projection may be formed with a bolt joint or the
like without being limited to welding.
[0082]
(8) In the above-described embodiment, an example that the injection nozzles
4 and the pipes 5 are detachably mounted on the pile main body 2 is explained. In
this case, as described in the above-described embodiment, a method of constructing
the steel pipe pile 1 includes: a process of driving the steel pipe pile 1 to the maximum
drilling depth in the bearing stratum while injecting the high-pressure water WJ from
the injection nozzles 4; a process of pulling up the steel pipe pile 1 to a predetermined
pull-up depth while injecting the fluidity solidifying material SM from the injection
nozzles 4; a process of driving the steel pipe pile 1 to the fixing depth in the bearing
stratum while continuing to inject the fluidity solidifying material SM from the
injection nozzles 4; a process of separating the injection nozzles 4 and the pipes 5 from
the steel pipe pile 1 in a state where the injection of the fluidity solidifying material
SM from the injection nozzles 4 is temporarily stopped; a process of pulling up the
injection nozzles 4 and the pipes 5 to the ground while injecting the fluidity solidifying
material SM from the injection nozzles 4; and a process of constructing a foot
protection block of the steel pipe pile (that is, the pile main body 2 remaining in the
••;_ ground) by solidification of the fluidity solidifying material SM. .... ^ , . .
With respect to the above-described embodiment, a configuration of i.*. A
separating the pipe 5 at a joint portion between the injection nozzle 4 and the pipe 5
.., .**.-*, - and pulling up only the pipe 5 to the ground,.-ratherUhan pulling up the injection
nozzles 4 and the pipes 5, is also acceptable. Otherwise, a configuration of separating
-n> at least a portion of the pipe 5 from the steel pipe pile 1 in a state where the injection of
- 31 -
the fluidity solidifying material SM from the injection nozzle 4 is temporarily stopped
and pulling up only a portion of the separated pipe 5 to the ground while injecting the
fluidity solidifying material SM from the leading end of the separated pipe is also
acceptable.
Further, after the process of driving the steel pipe pile 1 to the maximum
drilling depth in the bearing stratum while injecting water from the mjection nozzles 4
and before the process of pulling up the steel pipe pile 1 to a predetermined pull-up
depth while injecting the fluidity solidifying material SM from the injection nozzles 4,
a process of pulling up the steel pipe pile 1 while injecting the fluidity solidifying
material SM or the water from the injection nozzles 4, and then driving the steel pipe
pile 1, may be performed at least once. In the case of hard ground, it is possible to
sufficiently secure a construction area of the foot protection block FPB by stirring the
ground by repeating this process. In this process, from the viewpoint of delaying
solidification, it is preferable to use water, rather than the fluidity solidifying material
SM.
[0083]
In addition, with respect to the above-described embodiment, the injection
nozzles 4 and the pipes 5 may be fixed to the pile main body 2. In a method of
constructing the steel pipe pile 1 in this modified example, the injection nozzles 4 and
the pipes 5 stfe-buried-in the ground along with the pile main body 2J without being
pulled up to the ground.. •?* ^ •
Specifically, the method of constructing the steel pipe pile 1 in this modified
example includes: a process of driving the*steel pipe pile 1 to the maximum drilling
depth in the bearing stratum while injecting the high-pressure water WJ from the
injection nozzles 4; a process of pulling up th© steel pipe pile 1 to a predetermined
- 32 -
pull-up depth while injecting the fluidity solidifying material SM from the injection
nozzles 4; a process of driving the steel pipe pile 1 to the fixing depth in the bearing
stratum while injecting the fluidity solidifying material SM from the injection nozzles
4; and a process of constructing a foot protection block of the steel pipe pile 1 by
solidification of the fluidity solidifying material SM.
[0084]
That is, in the method of constructing the steel pipe pile 1 in this modified
example, the first to sixth processes shown in FIGS. 2A and 2B are the same as those
in the construction method of the above-described embodiment. However, the
seventh process shown in FIG. 2C is omitted, and the foot protection block is
constructed in a state where all the constituent elements of the steel pipe pile 1 remain
in the ground.
[Examples]
[0085]
Next, an example of the present invention will be described. However, the
conditions in the example are one example case adopted in order to verify the
feasibility and the effects of the present invention, and the present invention is not
limited to the one example case. The present invention can adopt various conditions
without departing from the gist of the present invention, as long as they achieve the
• object'bf the present invention. - - . - - . - . - - -
[0086] n
(Example!) - - . - -
A pile main body (a.steel pipe.) having an outer diameter D of 1300 mm was.
prepared and a steel plate dividing the cross section of the pile main body into two
sections was welded to a leading end portion of the pile main body as a dividing :
- 33 -
member. A length L of the dividing member in an axial direction of the pile main
body was set to be 0.5 times the outer diameter D of the pile main body (that is, to be
650 mm).
[0087]
Six injection nozzles were mounted on the outer peripheral surface of the pile
main body and four injection nozzles were mounted on the dividing member. Ten
pipes which selectively supply water and a fluidity solidifying material to these ten
injection nozzles were also mounted on the pile main body. The pipes for the
injection nozzles mounted on the outer peripheral surface were extended along the
outer peripheral surface of the pile main body and connected to the injection nozzles.
The pipes for the injection nozzles mounted on the dividing member were extended
along the inner peripheral surface of the pile main body and the dividing member, bent
at a joint portion between the pile main body and the dividing member, and connected
to the injection nozzles. In this manner, the steel pipe pile in this example was
configured with the pile main body having the outer diameter D of 1300 mm, the
dividing member mounted on the inside of the leading end portion of the pile main
body, the ten injection nozzles, and the ten pipes.
[0088]
The steel pipe pile in this example was driven while digging the ground by
injecting water from the ten injection nozzles. After the steel pipe pile had reached
the bearing .stratum, a foot protection block was constructed bytswitching a fluid which
was injected from the injection nozzles from the water to a fluidity solidifying material
(cement milk). ... .<* >--,>.. .,_ .*« ;,-*
[0089]
The inventors of this application confirmed that the leading end bearing
- 34 -
capacity of the steel pipe pile in this example was about 11000 kN. Further, when the
inside of the steel pipe pile was dug by boring and the construction shape of the foot
protection block was investigated, it could be confirmed that the foot protection block
having a length greater than or equal to twice the outer diameter D of the pile main
body, which could be integrated with a required maximum length (less than twice the
outer diameter D of the pile main body) of the dividing member, was constructed.
[0090]
When a core was collected from the foot protection block and the strength of
soil cement of the foot protection block expressing the leading end bearing capacity
(11000 kN) was measured with an uniaxial compression test, the strength of the soil
cement was in a range of 15 MPa to 40 MPa.
[0091]
Here, if the leading end bearing capacity (11000 kN) is divided by the crosssectional
area (1.3 m ^ l . 3 m/2)zXTc) of the pile main body, 8.3 MPa is obtained as a
required strength of the soil cement.
Since the strength of the foot protection block in this example is in a range of
15 MPa to 40 MPa, it significantly exceeds the required strength of 8.3 MPa.
[0092]
Therefore, it was possible to confirm that a foot protection block more robust
than that in the related art could be constructed by'adopting the steel pipe pile in this
example in which the.dividing member and the injection-nozzles were mounted on the
leading end portion of the pile main body. . . .:
[Industrial Applicability] ... / ... „ : ..r>;<,
[0093]
As described above, according to the present invention, a confining force of
- 35 -
the leading end plugging effect of the steel pipe pile is improved by the fluidity
solidifying material (for example, cement milk) and the dividing member, and thus the
bearing capacity of the steel pipe pile from the beanng stratum increases. In
particular, in the case of a steel pipe pile having the outer diameter D exceeding 1000
mm, the confining force greatly varies according to the presence or absence of the
dividing member in a leading end portion of a pile main body, and therefore, an
increase in the beanng capacity of the bearing stratum due to the present invention is
remarkable.
[0094]
Therefore, according to the present invention, the number of piles which are
driven can be reduced by improvement in bearing capacity per single pile, and thus it is
possible to obtain economical effects such as a reduction in material cost, shortening of
a construction period, and a reduction in construction costs. In addition, in a case of
driving a steel pipe pile by using an injection nozzle, a driving speed is fast compared
to a drilling rod, and therefore, construction costs can be further reduced, and this
contributes to improvement in an economical effect. Accordingly, the present
invention is highly applicable in the civil engineering industry and the building
industry.
[Brief Description of the Reference Symbols]
1: steel pipe pile ^ ^ •
2: pilemainbody "
3,6, 7: dividing member ., .,-..',..<
4: injection nozzle
- -' - 5: pipe _*> - - - - = -^
- 36 -
3a: through-hole
4a: drilling range
11, 12: projection
WJ: high-pressure water
SM: fluidity solidifying material
FPB: foot protection block
D: outer diameter of pile main body
AX: axial direction of pile main body
JD: injection direction of injection nozzle
L: length of dividing member
DH: driving hole
BH: vibratory hammer

[Document Type] CLAIMS
1. A steel pipe pile comprising:
a pile main body configured with a steel pipe;
a dividing member which is mounted on the inside of a leading end portion of
the pile main body, thereby dividing a cross section of the pile main body into a
plurality of sections;
an injection nozzle which is mounted on at least one of an outer peripheral
surface of the leading end portion of the pile main body and an inner peripheral surface
of the leading end portion of the pile main body and selectively injects water and a
fluidity solidifying material; and
a pipe which selectively supplies the water and the fluidity solidifying
material to the injection nozzle.
2. The steel pipe pile according to Claim 1,
wherein the dividing member is a member for constructing a foot protection
block by solidification of the fluidity solidifying material.
3. The steel pipe pile according to Claim 1 or 2,
wherein the dividing member is a steel plate mounted on the inside of the
leading end portion of the pile main body;so as to be parallel to an axial direction of
the pile main body.
4. The steel pipe pile according to any one of Claims 1 to 3,
^wherein the injection nozzle is mounted on the dividing-member as well.
- 38 -
5. The steel pipe pile according to any one of Claims 1 to 4,
wherein an injection direction of the injection nozzle is parallel to an axial
direction of the pile main body and is directed to the inside of an inner peripheral
surface of the pile main body.
6. The steel pipe pile according to any one of Claims 1 to 5,
wherein a plurality of the injection nozzles are mounted on at least one of the
outer peripheral surface and the inner peripheral surface of the leading end portion of
the pile main body, and
each injection direction of the plurality of injection nozzles intersects an axial
direction of the pile main body.
7. The steel pipe pile according to any one of Claims 1 to 6,
wherein the outer peripheral surface of the pile main body is provided with a
projection.
8. The steel pipe pile according to any one of Claims 1 to 1,
wherein the dividing member and the inner peripheral surface of the pile main
body are provided with a projection. • . . . . . . . ..
9. The steel pipe pile according to any one of Claims 1 to 8,
wherein the dividing member is provided with a- through-hole.
- -\> 10. The steel pipe pile according to any one of Claims 1 to 9,
- 39 -
wherein a length of the dividing member in an axial direction of the pile main
body is less than twice an outer diameter of the pile main body.
11. The steel pipe pile according to any one of Claims 1 to 10,
wherein the injection nozzle and the pipe are detachably mounted on the pile
main body.
12. A steel pipe pile construction method comprising:
a process of driving the steel pipe pile according to any one of Claims 1 to 10
to a maximum drilling depth in a bearing stratum while injecting the water from the
injection nozzle;
a process of pulling up the steel pipe pile to a predetermined pull-up depth
while injecting the fluidity solidifying material from the injection nozzle;
a process of driving the steel pipe pile to a fixing depth in the bearing stratum
while continuing to inject the fluidity solidifying material from the injection nozzle;
and
a process of constructing a foot protection block of the steel pipe pile by
solidification of the fluidity solidifying material.
13. A steel-pipe pile construction method comprising:
a process of driving the steel pipe pile according to Claim 11 to a maximum .
drilling depth in a bearing stratum while injecting the water from the injection nozzle;
a process of pulling up the steel pipe pile to a predetermined pull-up depth
while injecting the fluidity solidifying material from the injection nozzle;
a process of driving the steel pipe pile to a-fixing depth in the bearing stratum
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while continuing to inject the fluidity solidifying material from the injection nozzle;
a process of separating the injection nozzle and the pipe from the steel pipe
pile in a state where injection of the fluidity solidifying material from the injection
nozzle is temporarily stopped;
a process of pulling up the injection nozzle and the pipe to the ground while
injecting the fluidity solidifying material from the injection nozzle; and
a process of constructing a foot protection block of the steel pipe pile by
solidification of the fluidity solidifying material.
14. A steel pipe pile construction method comprising:
a process of driving the steel pipe pile according to Claim 11 to a maximum
drilling depth in a bearing stratum while injecting the water from the injection nozzle;
a process of pulling up the steel pipe pile to a predetermined pull-up depth
while injecting the fluidity solidifying material from the injection nozzle;
a process of driving the steel pipe pile to a fixing depth in the bearing stratum
while continuing to inject the fluidity solidifying material from the injection nozzle;
a process of separating at least a portion of the pipe from the steel pipe pile in
a state where injection of the fluidity solidifying material from the injection nozzle is
temporarily stopped;
aprocess of pulling up a portion of the separated pipe to the ground while
injecting the fluidity-solidifying material from a leading end of the separated^pipe; and
a process of constructing a foot protection block of the steel pipe pile by
solidification of the fluidity solidifying material.
15. The steel pipe pile construction method according to any one of Claims
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12 to 14,
wherein after the process of driving the steel pipe pile to the maximum
drilling depth and
before the process of pulling up the steel pipe pile to the pull-up depth,
a process of pulling up the steel pipe pile while injecting the fluidity
solidifying material-or the water from the injection nozzle, and then driving the steel
pipe pile, is performed at least once.