AU2018343817B2 - Pile construction method, manifold device, and manifold device design method - Google Patents

Abstract

The purpose of the invention is to provide a pile construction method that can reliably improve pile bearing capacity. Provided is a pile construction method comprising a step of driving a pile by applying vibration with a vibratory hammer while injecting a high-pressure fluid into the ground, wherein one or more high-pressure fluid delivery devices and a manifold device having a cylindrical inner space are disposed, the one or more high-pressure fluid delivery devices are respectively connected to one or more injection holes in the manifold device, and a plurality of discharge holes in the manifold device are respectively connected to a plurality of jet pipe members. With the inner space of the manifold device filled with the high-pressure fluid, the high-pressure fluid is discharged from each of the plurality of discharge holes and, in terms of the discharge rates of the high-pressure fluid discharged from each of the plurality of discharge holes, the difference between the maximum discharge rate and the minimum discharge rate is no more than 5% of the maximum discharge rate.

Description

DESCRIPTION PILE CONSTRUCTION METHOD, MANIFOLD DEVICE, AND MANIFOLD DEVICE DESIGN METHOD

Field

[0001] The present invention relates to a pile

construction method for driving a pile into a hard ground.

Background

[0002] As a method of driving a pile into a hard ground,

there is a water-jet vibro hammer method (hereinafter, "JV

method"). The JV method is a method in which high-pressure

water (hereinafter, "water" includes both pure water and

sea water) is injected to the ground from a plurality of

injection nozzles attached to an end of a pile while

applying vibrations caused by a vibro hammer to the pile so

as to loosen or cut the ground and further move obstacles

such as clods of gravel, thereby driving the pile by the

vibro hammer and the own weight of the pile (for example,

Patent Literature 1).

[0003] However, according to conventional JV methods,

the ground around the pile is loosened by the injection of

high-pressure water and vibrations caused by the vibro

hammer, and the bearing capacity of the pile may decrease.

In order to increase the bearing capacity of the pile in

the JV method, such a method has been conventionally used

that a flowable solidifying material such as cement milk is

injected to the end of the pile and/or to around the pile

so as to form a foot protection block, or a method of

performing peripheral grouting of a pile.

[0004] For example, Patent Literature 2 discloses a

construction method in which a steel pipe pile is driven up to a depth at which peripheral grouting of a pile is required by the JV method, and after reaching the depth at which peripheral grouting of the pile is required, the steel pipe pile is driven by a vibro hammer while injecting a flowable solidifying material instead of water-jet water, thereby performing pile driving and peripheral grouting simultaneously.

[00051 Further, Patent Literature 3 discloses a

construction method in which, after a steel pile is driven

up to a predetermined depth by the JV method, a flowable

solidifying material is injected from an injection nozzle

while pulling up the steel pile, and then the steel pile is

driven again up to a designed depth while injecting the

flowable solidifying material so as to form a foot

protection block at the end of the pile. Further, as

required, the flowable solidifying material is injected to

the periphery of the pile while pulling up the injection

nozzle to perform peripheral grouting of the steel pile.

Citation List

Patent Literatures

[00061 Patent Literature 1: Japanese Patent Application

Laid-open No. H7-238544

Patent Literature 2: Japanese Patent Application Laid

open No. 2001-193068

Patent Literature 3: Japanese Patent Application Laid

open No. 2004-270157

Non Patent Literature

[0007] Non Patent Literature 1: THE BEARING CAPACITIES

OF STEEL PIPE PILES INSTALLED BY WATER JET VIBRATORY TECHNIQUE AND NEW IMPROVING METHODS FOR THE CAPACITIES

(Proceedings of Japan Society of Civil Engineers No.

700/Vl-54, March 2002)

[0007a] Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Summary Technical Problem

[00081 In Patent Literatures 2 and 3, when an outer peripheral length of a target pile is long, a plurality of jet pipes are evenly arranged on an outer periphery of a pile. In order to form a foot protection block at the end of the pile or a grout layer on the periphery of the pile in a uniform size or thickness symmetrically about the pile, it is essential to discharge a flowable solidifying material at an equal discharge rate from each of the jet pipes.

[00091 Particularly, in order to form a uniform grout layer, it is necessary to inject a flowable solidifying material matched with a construction speed (in Patent Literature 2, the driving speed of the pile, and in Patent Literature 3, the pulling-up speed of the injection nozzle). For this purpose, it is necessary to adjust the injection speed as needed, during construction of the pile according to ground conditions and the like. One of effective adjusting methods is, for example, to stop a part of a plurality of delivery devices that deliver the flowable solidifying material, or to adjust a flow rate of delivery devices. Even if a substantial number of devices in operation of the delivery devices is changed in this manner, it is necessary to discharge the flowable solidifying material with an equal discharge rate from each of the jet pipes.

[0010] However, in Patent Literatures 2 and 3 described

above, means for discharging a flowable solidifying

material with an equal discharge rate from each of the jet

pipes is not presented. The same applies to a case where

water is delivered to the jet pipes instead of a flowable

solidifying material.

[0011] The present invention has been achieved in view

of the above problems, and an object of the present

invention is to enable, in a construction method in which a

plurality of jet pipes are attached to a pile to drive the

pile into a ground by discharging a high-pressure fluid,

discharge of the high-pressure fluid from each of the jet

pipes with an equal discharge rate at all times, regardless

of variations of a total discharge rate.

[0011a] It is an object of the present invention to

overcome or ameliorate at least one of the disadvantages of

the prior art, or to provide a useful alternative.

[0011b] Unless the context clearly requires otherwise,

throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed

in an inclusive sense as opposed to an exclusive or

exhaustive sense; that is to say, in the sense of

"including, but not limited to".

Solution to Problem

[0012] In order to realize the above object, the present

invention provides the following configurations.

An aspect of the present invention is to provide a pile construction method comprising: a preparing step of attaching a plurality of jet pipe members and a vibro hammer to a pile; and a constructing step including at least a partial step of moving down or up the pile by giving vibrations caused by the vibro hammer while injecting a high-pressure fluid from ends of the jet pipe members into a ground, wherein in the preparing step, one or plural high-pressure fluid delivery devices and a manifold device having a cylindrical inner space are arranged, the one or plural high-pressure fluid delivery devices are connected respectively to one or plural injection holes in the manifold device, and each of a plurality of discharge holes in the manifold device is connected to each of the jet pipe members, in the constructing step, a high-pressure fluid is injected from at least one of the injection holes and the high-pressure fluid is discharged from each of the discharge holes while maintaining a state in which the inner space of the manifold device is filled with the high pressure fluid, and in terms of discharge rates of a plurality of high pressure fluids discharged from each of the discharge holes, a difference between a maximum discharge rate and a minimum discharge rate is equal to or less than 5% of the maximum discharge rate. In the manifold device in the pile construction method according to the above aspect, it is preferable that a relation among a number n of the discharge holes, a diameter d of the inner space, a diameter do of the discharge hole, a flow rate coefficient A of the discharge hole, an interval L between the two adjacent discharge holes, a dynamic viscosity coefficient v of the high- pressure fluid, and a sum total Q of the respective discharge rates satisfies a following formula.

[Expression 1]

1FA do dd 0.0039_ ( 3 In the pile construction method according to the above aspect, it is preferable that the high-pressure fluid is water or a flowable solidifying material, and the constructing step includes a driving step of driving the pile up to a first depth that is lower than an interfacial surface of a bearing ground by giving vibrations caused by the vibro hammer while injecting water, a pulling-up step of pulling up the pile up to a depth corresponding to a set upper end of peripheral grout of the pile by giving at least vibrations caused by the vibro hammer, and a re-driving step of driving the pile again up to a second depth that is lower than the interfacial surface of the bearing ground while injecting a flowable solidifying material. In the pile construction method according to the above aspect, it is preferable that the high-pressure fluid is water or a flowable solidifying material, and the constructing step includes a driving step of driving the pile up to a first depth that is lower than an interfacial surface of a bearing ground by giving vibrations caused by the vibro hammer while injecting water, a pulling-up step of pulling up the pile up to a depth corresponding to a set upper end of foot protection, by giving vibrations caused by the vibro hammer while injecting a flowable solidifying material, a re-driving step of driving the pile again up to a second depth that is lower than the interfacial surface of the bearing ground while injecting a flowable solidifying material, and a pulling-out step of pulling out the jet pipe member while injecting a flowable solidifying material.

In the pile construction method according to the above

aspect, it is preferable that the high-pressure fluid is

water or a flowable solidifying material, and the

constructing step includes

a driving step of driving the pile up to a depth that

is lower than an interfacial surface of a bearing ground by

giving vibrations caused by the vibro hammer while

injecting a flowable solidifying material.

In the pile construction method according to the above

aspect, it is preferable that the high-pressure fluid is

caused to meander by current plates that are arranged in

the inner space of the manifold device.

In the pile construction method according to the above

aspect, it is preferable that the high-pressure fluid is

agitated by an agitator that is arranged in the inner space

of the manifold device, or vibrations are given to the

high-pressure fluid by a vibrator that is arranged in the

inner space.

In the pile construction method according to the above

aspect, it is preferable that a construction management

device

acquires vertical height data of a pile continuously

transmitted from a total station that tracks a prism attached to the vibro hammer, and flow rate data of a high pressure fluid respectively transmitted continuously from a flowmeter attached to each of delivery ports of the one or plural high-pressure fluid delivery devices, and compares acquired vertical height data of the pile and acquired flow rate data of the high-pressure fluid with execution plan data so as to adjust a moving speed of s pile in each partial step included in the constructing step, switching of water and a flowable solidifying material, or a discharge rate of a high-pressure fluid on a real time basis. In the pile construction method according to the above aspect, it is preferable that the jet pipe member includes a conduit that is connected to the manifold device, an integration pipe with one end being connected to the conduit, and the other end being branched into plural ends, and a plurality of injection nozzles that are connected to each of the branched other ends of the manifold device. Another aspect of the present invention provides a manifold device used in a pile construction method including at least a step of driving a pile attached with a plurality of jet pipe members while injecting a high pressure fluid from each end of the jet pipe members, wherein the manifold device comprises a cylindrical inner space, one or plural injection holes respectively connected to one or plural high-pressure fluid delivery devices, and a plurality of discharge holes respectively connected to each of the jet pipe members, during the pile construction, a high-pressure fluid is injected into the manifold device from at least one of the injection holes and the high-pressure fluid is discharged from each of the discharge holes while the manifold device is maintained in a state in which the inner space thereof is filled with the high-pressure fluid, and in terms of discharge rates of a plurality of high pressure fluids discharged from each of the discharge holes, a difference between a maximum discharge rate and a minimum discharge rate is equal to or less than 5% of the maximum discharge rate. In the manifold device according to the above aspect, it is preferable that a relation among a number n of the discharge holes, a diameter d of the inner space, a diameter do of the discharge hole, a flow rate coefficient A of the discharge hole, an interval L between the two adjacent discharge holes, a dynamic viscosity coefficient v of the high-pressure fluid, and a sum total Q of the respective discharge rates satisfies a following formula.

[Expression 2]

FA do d 000039 Q- (n

A still another aspect of the present invention provides a design method of a manifold device used in a pile construction method including at least a step of driving a pile attached with a plurality of jet pipe members while injecting a high-pressure fluid from each end of the jet pipe members, the manifold device comprises a cylindrical inner space, one or plural injection holes respectively connected to one or plural high-pressure fluid delivery devices, and a plurality of discharge holes respectively connected to each of the jet pipe members, and during the pile construction, a high-pressure fluid is injected into the manifold device from at least one of the injection holes and the high-pressure fluid is discharged from each of the discharge holes while the manifold device is maintained in a state in which the inner space thereof is filled with the high-pressure fluid, wherein when one or plural parameters of a number n of the discharge holes, a diameter d of the inner space, a diameter do of the discharge hole, a flow rate coefficient

A of the discharge hole, an interval L between the two

adjacent discharge holes, and a dynamic viscosity

coefficient v of the high-pressure fluid are respectively

changed in advance, discharge rates of a plurality of high

pressure fluids discharged from each of the discharge holes

are calculated for each case, by designating a sum total of

respective discharge rates as Q,

in terms of discharge rates of a plurality of high

pressure fluids discharged from each of the discharge holes,

(i, $, and 6 in a following formula are set so that a

difference between a maximum discharge rate and a minimum

discharge rate becomes equal to or less than a

predetermined ratio of the maximum discharge rate, and

the manifold device is designed so that a relation

among the number n of the discharge holes, the diameter d

of the inner space, the diameter do of the discharge hole,

the flow rate coefficient A of the discharge hole, the

interval L between the two adjacent discharge holes, the

dynamic viscosity coefficient v of the high-pressure fluid,

and the sum total Q of the respective discharge rates

satisfies a following formula.

[Expression 3]

(FA x do)' _ _

(Q)

Advantageous Effects of Invention

[0013] According to the pile construction method of the

present invention, a manifold device is provided between

high-pressure fluid delivery devices and jet pipe members.

The manifold device according to the present invention is

designed so as to discharge a high-pressure fluid from each

of discharge holes with a substantially equal discharge

rate. As a result, when the high-pressure fluid is a

flowable solidifying material, uniform grout having no

defect or deviation can be formed, and a pile can exert

required bearing capacity. When the high-pressure fluid is

water, equal driving can be performed.

Brief Description of Drawings

[0014] Fig. 1 is a perspective view schematically

showing an example of a construction system for performing

a pile construction method.

Fig. 2 is a diagram schematically showing a piping

configuration in the construction system shown in Fig. 1.

Fig. 3(a) is a plan view schematically showing an

example of a manifold device shown in Fig. 2, (b) is a

longitudinal sectional view of (a), (c) is a transverse

sectional view of (a), and (d) is a longitudinal sectional

view of another example of the manifold device.

Fig. 4(a) is a schematic longitudinal sectional view

for explaining a proper condition of the manifold device, and (b) is a longitudinal sectional view of (a).

Fig. 5 is a graph created based on the simulation in

Table 1.

Fig. 6 is a graph created based on the simulation in

Table 2.

Figs. 7(a) to (h) are diagrams schematically showing

each step in a first embodiment of the pile construction

method according to the present invention.

Fig. 8(a) is a perspective view schematically showing

a configuration example of a jet pipe member near the end

of a steel pipe pile, and (b) is a bottom view of (a).

Fig. 9 is a diagram schematically showing an example

of a construction management method in the pile

construction method shown in Fig. 1.

Figs. 10 are schematic diagrams for calculating a

design injection volume of a flowable solidifying material,

where (a) is a longitudinal sectional view of a pile and

the periphery thereof, and (b) is a horizontal sectional

view of (a).

Figs. 11(a) to (g) are diagrams schematically showing

each step in a second embodiment of the pile construction

method according to the present invention.

Figs. 12(a) to (e) are diagrams schematically showing

each step in a third embodiment of the pile construction

method according to the present invention.

Description of Embodiments

[0015] Embodiments of the present invention will be

described below with reference to the drawings.

(1) Configuration of construction system

A pile construction method according to the present

invention is described here, as an example, for the

construction at a sea for vertically driving a steel pipe pile to a ground on a seabed. However, the present invention is also applicable to the construction on land. Further, the pile can be a pile other than a steel pipe pile and may be, for example, a steel pipe sheet pile or a steel sheet pile. Furthermore, a driving direction may be inclined.

[0016] Fig. 1 is a perspective view schematically showing an example of a construction system for performing the pile construction method. Fig. 2 is a diagram schematically showing an example of a piping configuration in the construction system shown in Fig. 1.

[0017] The construction system is installed on a crane barge 10. Here, the flowable solidifying material is a cement milk. Cement accumulated in a cement silo 11 and water accumulated in a water tank 13 are respectively pressure-fed to one or plural mixing plants 12 by a pump, and in the mixing plants 12, water and cement are kneaded to prepare cement milk.

[0018] A water-cement ratio (W/C%), which is a weight ratio of water and cement in the cement milk, is appropriately set according to the pile application and the ground conditions. The water-cement ratio is generally, for example, in a range from 50% to 150%. Add-in materials related to water reduction, condensation delay, expansion, underwater inseparability, and the like are added to the cement milk as required.

[0019] The cement milk generated in the mixing plants 12 can be supplied to one or plural high-pressure fluid delivery devices 14 by a pump (not shown) via a switching device 18A, as shown in Fig. 2. When the high-pressure fluid delivery device 14 has a suction function, the pump between the mixing plants 12 and the high-pressure fluid delivery devices 14 is not required.

[0020] Meanwhile, water taken from the sea and

accumulated in the water tank 13 can be supplied to the one

or plural high-pressure fluid delivery devices 14 by a pump

via the switching device 18A. When the high-pressure fluid

delivery device 14 has a suction function, the pump between

the water tank 13 and the high-pressure fluid delivery

devices 14 is not required.

[0021] Each of the one or plural high-pressure fluid

delivery devices 14 is supplied with either cement milk or

water by switching by the switching device 18A. Each of

the high-pressure fluid delivery devices 14 can deliver the

supplied cement milk or water with high pressure. A

flowmeter 19 is attached to a delivery port of each of the

high-pressure fluid delivery devices 14.

[0022] Further, the delivery port of the one or plural

high-pressure fluid delivery devices 14 is respectively

connected to one or plural input ports of a second

switching device 18B. One or plural output ports of the

second switching device 18B is respectively connected to

one or plural injection holes of a manifold device 16 via

one or plural high-pressure hoses 15. The cement milk or

water can be delivered from each of the high-pressure fluid

delivery devices 14 to each injection holes of the manifold

device 16 or can be stopped by switching by the second

switching device 18B.

[0023] The cement milk or water delivered from the one

or plural high-pressure fluid delivery devices 14 is

gathered once in one manifold device 16. Thereafter, the

cement milk or water is pressure-fed to a plurality of jet

pipe members via a plurality of high-pressure hoses 17

respectively connected to each of discharge holes of the

manifold device 16.

[0024] The jet pipe members are attached to a steel pipe pile 1. The jet pipe member is configured by a plurality of conduits 9, integration pipes 8 respectively connected to an end of each conduit 9, and injection nozzles 7 respectively connected to respective branched ends of each integration pipe 8. As another example, the jet pipe member can be configured by a plurality of conduits 9 and injection nozzles 7 respectively connected to an end of each conduit 9. In any case, the injection nozzles 7 are arranged in a circumferential direction near the end of the steel pipe pile 1. The injection nozzles 7 can be arranged, for example, for each of 60°, 90°, 120°, and 1800 in the circumferential direction.

[0025] If there is no floating matter such as dust in sea water, the water tank 13 may be omitted. The numbers of mixing plants 12 and high-pressure fluid delivery devices 14 are decided as required based on the construction conditions and the like. The vibro hammer 2 is suspended by a crane. In the example in Fig. 1, a generator 20 is provided in order to drive the vibro hammer 2, which is power-operated, and is operated by an operating unit 21. In the case of construction on land, these devices are all installed in a working yard.

[0026] (2) Configuration and design method of manifold device <Basic configuration of manifold device> The manifold device 16 shown in Fig. 1 and Fig. 2 is described with reference to Figs. 3 and Figs. 4. Fig. 3(a) is a schematic plan view of an example of the manifold device 16 shown in Fig. 2, (b) is a longitudinal sectional view of (a), and (c) is a transverse sectional view thereof.

[0027] As shown in Figs. 3(a), (b), and (c), the manifold device 16 includes a substantially cylindrical casing 16a. The casing 16a has a cylindrical inner space.

One or plural injections holes 16b are provided on one periphery, and a plurality of discharge holes 16c are provided on the other periphery, putting an axis of the casing 16a therebetween, at regular intervals in a direction parallel to the axis. A coupler for connecting, for example, the high-pressure hoses 15 and 17 detachably is provided in each of the injection holes 16b and the discharge holes 16c. When both the injection hole 16b and the discharge hole 16c are provided in plural, these holes can be provided in the same number or in different numbers.

[0028] In the manifold device 16 being used, the entire inner space is maintained in a state filled with a high pressure fluid while the high-pressure fluid flows therein from the one or plural injection holes 16b, and flows out from the discharge holes 16c. It is preferable that the manifold device 16 is designed so that a discharge rate of the high-pressure fluid discharged from each of the discharge holes 16c becomes substantially equal, regardless of the injection volume of the high-pressure fluid from the one or plural injection holes 16b.

[0029] In the case where the injection volume from each of the injection holes 16b varies, for example, the injection volume of a part of the injection holes 16b becomes zero (for example, a part of the high-pressure fluid delivery devices 14 in Fig. 2 stops operation), even if a total injection volume of the high-pressure fluid is intensely narrowed down (for example, all the high-pressure fluid delivery devices 14 are in an idling state), the discharge rate of the high-pressure fluid from each of the discharge holes 16c is substantially equalized by the effect of the manifold device 16.

[0030] Fig. 3(d) shows another example of the manifold device 16. The manifold device 16 in Fig. 3(d) rectifies the flow of the high-pressure fluid to a uniform flow by arranging current plates 16e in the inner space to cause the high-pressure fluid to meander therein. This enables to stabilize the discharge rate from each of the discharge holes 16c. Further, in order to improve the rectification function, one or plural vibrators 16d and/or one or plural stirrers 16f can be arranged in the inner space. In Fig.

3(d), all the current plates 16e, the vibrators 16d, and

the stirrer 16f are shown; however, one or plural of these

elements can be combined and arranged.

[0031] <Proper condition of manifold device: in case of

five discharge holes>

A proper condition of the manifold device for

realizing equalization of the discharge rate in each

discharge hole of the manifold device is described with

reference to Figs. 4. Specifically, conditions required

for the manifold device so that a difference in the

discharge rate of the high-pressure fluid respectively

discharged from the discharge holes of the manifold device

falls within a predetermined range are derived.

[0032] Fig. 4(a) is a schematic sectional view along the

axis in an example of the manifold device, and (b) is a

sectional view in a direction vertical to the axis. The

diameter of a cylindrical inner space of the manifold

device 16 is d (hereinafter, "inner diameter d"). Here, as

an example, the manifold device 16 includes three injection

holes Il, 12, and 13, and five discharge holes Al, A2, A3,

A4, and A5. The discharge holes Al to A5 have the same

inner diameter do. The injections holes Il to 13, and the

discharge holes Al to A5 are arranged at equal intervals as

an example. The interval between the discharge holes Al to

A5 is L. However, in this example, a distance between the

discharge holes Al and A5 at the opposite ends and opposite end walls of the casing 16a is L/2. As an example, the injection hole Il is arranged at a position corresponding to an intermediate between the discharge holes Al and A2, the injection hole 12 is arranged on the opposite side of the discharge hole A3, and the injection hole 13 is arranged at a position corresponding to an intermediate between the discharge holes A4 and A5.

[00331 In an example of Figs. 4, conditions required for the difference in the discharge rate of the high-pressure fluid respectively discharged from five discharge holes Al to A5 during the use of the manifold device 16 to fall within the predetermined range are derived. In the example of Figs. 4, assuming the worst condition, it is supposed that the high-pressure fluid is injected with an injection volume Qi only from the injection hole Il at the endmost position, and the injection holes 12 and 13 are closed. Further, it is supposed that the pressures of the high pressure fluid discharged from each of the five discharge holes Al, A2, A3, A4, and A5 are respectively P1, P1, P2, P3, and P4, and the discharge rates are respectively Q1, Q1, Q2, Q3, and Q4. Since the discharge holes Al and A2 are at positions under the same condition with respect to the injection hole Il, it is supposed that the pressure and the discharge rate are the same. The sum total of the respective discharge rates is designated as Q. The distance and the positional relation between the injection hole Il and the discharge hole Al, and the distance and the positional relation between the injection hole Il and the discharge hole A2 are exactly the same. Therefore, the pressure P1 and the discharge rate Ql of the high-pressure fluid discharged from the discharge hole Al become the same values as those of the discharge hole A2.

[0034] In this example, when there is a variability in the discharge rate from each of the discharge holes, the discharge rate Q1 from the discharge holes Al and A2 closest to the injection hole II is supposed to be the maximum discharge rate, and the discharge rate Q4 from the discharge hole A5 farthest from the injection hole Il is supposed to be the minimum discharge rate. Here, the variability in the discharge rate is defined as a rate R (%) of a difference between the maximum discharge rate Q1 and the minimum discharge rate Q4 to the maximum discharge rate Q1, as shown in the following formula, and is referred to as "discharge rate difference R".

R(%)=((Q1-Q4)/Q1)xlOO

[0035] According to the following procedure, the proper condition of the manifold device so that the discharge rate difference R becomes, for example, equal to or less than 5% can be obtained.

[0036] First, the discharge rates Q1, Q1, Q2, Q3, and Q4 from each of the five discharge holes are calculated by using Formula [1], Formula [2], and Formula [3].

[0037] [Expression 4]

QA Qk-A ndo 21Pkg - - -1] 4 JY

[0038] [Expression 5]

h _ k-1- Pk 321 gd 2 v v -[2

[0039] [Expression 6] k' v = U '? - --[3] - d 4

[0040] Formula [1] is a relational expression between the pressure and the discharge rate in each discharge hole. Formula [2] is a relational expression of pressure between adjacent discharge holes (source "Hydraulics" (second edition) by Tokio UEMATSU, p52). Formula [3] is a formula representing v in Formula [2].

[0041] Respective parameters in Formula [1], Formula [2], and Formula [3] represent physical volumes described below. The inside of brackets represents a unit. Qk: discharge rate of discharge hole (m 3 /sec) (k=1, 2,

3, 4) Qk': partial sum of discharge rate of discharge hole (m3 /sec) A: flow rate coefficient of discharge hole do: inner diameter of discharge hole (m) 2 Pk: pressure in discharge hole (kN/m ) (k=1, 2, 3, 4)

g: acceleration of gravity (m 2 /sec)

y: unit weight of cement milk (kN/m3 )

L: discharge hole interval between adjacent two holes (M)

v: dynamic viscosity coefficient of cement milk (m2 /sec)

d: inner diameter of manifold device (m) v: mean flow rate in manifold device (m/sec) h: coefficient of friction loss (m) The flow rate coefficient A of the discharge hole is a coefficient that varies according to a shape and the like of the discharge hole, and is a dimensionless number of about from 0.5 to 2 generally obtained experimentally.

[0042] The discharge rates Q1, Q1, Q2, Q3, and Q4 of the

five discharge holes Al, A2, A3, A4, and A5 are calculated

by the following procedures (i) to (vi).

(i) First, a pressure P4 in the discharge hole A5 is

obtained from Formula [1] by assuming that the discharge

rate Q4 of the discharge hole A5 is a variable (it is

designated that k=4). Accordingly, P4 is represented by a

function of Q4.

(ii) Next, a pressure P3 in the discharge hole A4 is

obtained by using P4 obtained in (i) and Formula [2] and

Formula [3]. At this time, Pk-1-Pk in Formula [2] is

designated as P3-P4, and Qk' in Formula [3] is designated

as Q4. Accordingly, P3 is represented by the function of

Q4. When P3 is obtained, Q3 is obtained according to

Formula [1]. Accordingly, Q3 is represented by the

function of Q4.

(iii) Next, a pressure P2 in the discharge hole A3 is

obtained by using P3 obtained in (ii) and Formula [2] and

Formula [3]. At this time, Pk-1-Pk in Formula [2] is

designated as P2-P3, and Qk' in Formula [3] is designated

as Q3+Q4. Accordingly, P2 is represented by the function

of Q4. When P2 is obtained, Q2 is obtained according to

Formula [1]. Accordingly, Q2 is represented by the

function of Q4.

(iv) Next, a pressure P1 in the discharge hole A2 is

obtained by using P2 obtained in (iii) and Formula [2] and

Formula [3]. At this time, Pk-1-Pk in Formula [2] is

designated as P1-P2, and Qk' in Formula [3] is designated

as Q2+Q3+Q4. Accordingly, P1 is represented by the

function of Q4. When P1 is obtained, Q1 is obtained

according to Formula [1]. Accordingly, Q1 is represented

by the function of Q4.

(v) A sum total Q of the discharge rate from each of the discharge holes Al to A5 is represented as Q=2Q1+Q2+Q3+Q4. The total discharge rate Q is equal to the injection volume Qi from the injection hole Il, and is calculated from the following Formula [4]. By substituting the results of (ii) to (iv) described above into Q1, Q2, and Q3, a value of Q4 is obtained by convergent calculation. (vi) Lastly, values of Q1, Q2, and Q3 are calculated based on the value of Q4 obtained in (v) and the results of (ii) to (iv).

[0043] Since the injection volume Qi normally corresponds to a maximum discharge flow rate of one high pressure fluid delivery device, the injection volume Qi (m3 /sec) in (v) described above is normally obtained according to the following Formula [4]. In this case, a theoretical maximum discharge rate Qo in Formula [4] is decided according to the specification of the high-pressure fluid delivery device. The injection volume Qi changes

according to the unit weight y of cement milk. The high pressure fluid delivery device is, for example, a water jet cutter (for example, CJ-340ERS manufactured by CHOWA KOGYO Co., Ltd, theoretical maximum discharge rate: 900 liters/min) capable of performing pressure-feed of water or cement milk. When cement milk is injected from a plurality of high-pressure fluid delivery devices, the number of devices is further multiplied to the right-hand side of Formula [4].

[0044] [Expression 7]

QI~ X- W[4

[0045] Each parameter in Formula [4] represents the

following physical amount. 3 Qi: injection volume (M

) 7,: unit weight of water (kN/m 3

) y: unit weight of cement milk (kN/m 3

) Qo: theoretical maximum discharge rate (m3 /min)

[0046] Table 1 is a table in which simulation results

when obtaining Q1 to Q4 according to the procedures in (i)

to (vi) described above are summarized for each of cases 1

to 7 in which each of numerical values of respective

parameters of the inner diameter d of the manifold device,

the inner diameter do of the discharge hole, the flow rate

coefficient A of the discharge hole, and the discharge hole

interval L is appropriately changed. The unit weight y and

the dynamic viscosity coefficient v of cement milk are

calculated, by assuming W/C as 65%. While a variation of

the unit weight y of cement milk causes influence on the

discharge rate of each discharge hole based on Formula [1],

it does not cause influence on the discharge rate

difference R.

[0047] [Table 1]

1 0 0 0 ~~ LO a) CD) ~(NM w.~ % + 0 I 040 M v41 wp op 4) -0 0 4 0 ) .) 7 0v -i v. 0

'3W (; 00 OD O 0C . 07 0) 0

0 00

10 M0( 7 a 0 0 +p 00 4 I ~C, N0 WN ' n o o 0 +I 40 0) i

0)~~~ 0(N 0) 0 ~-4 0 ) e 0 0N. 1 "' 0 . 07 0 40 0) 0

U) 0 4v' 0 0) N' 0 0 0 wp w4 0w 1 in 0 in 0 wr- w) 0) +I w0 0 0 M)( 0 0 0 0 0 (N V 0 4 .0 )0 '0 000 '3' OW0;i 0 00 0 0 3C 7

0 40 CI 0 0 n (0 ) -400 Mp 0N0 v~4 0 0 ) r. i ) 0 0 0.0 0 0 0 0

04 . . o-4O O ', L oo 0 0 00 - 0 - 0 W 0.0 inp 00. 0 0700 0

w0. w U) 70 (N ( 0 0 0 (N M0 ( (N 1-4 0) - 0 0 ' i - -4 U 0 0

0 0 M. 0 0 0 w) 0 0 i

00 000 0 0 0N 0 oo n

U, I in wnI ( 0 0- (N in lp7 I O

I 0 (N 4 00 0 M - w ~- 0) 0Nin 0 0I70 0 CO0 0 0 0 i

0 0 0 0 0 004N 0 H 701 _, 000 000) + I W O O

0 0 (

C,0

01 7 q) q. q)E 70

-4 05 0.2 !2 00 0'-. '0 7.'-.40 40 )4 +

'0 X C17 07 .7 40 07 4 0 ) 4

[048 InTbe1 ae otemxmmdshrert

Q1 of other discharge rates Q2, Q3, and Q4 are displayed (three lower tiers in the table). As shown in Table 1, in cases 1 to 5, the discharge rate difference R from five discharge holes Al to A5 is 5%. According to the same calculation, in the case 6, the discharge rate difference R is 0.5%, and in the case 7, the discharge rate difference R is 15%.

[0049] At this time, when (\Axdo/d)4/(Q/vL) is each

calculated for the cases 1 to 5, a constant value 9x10-5 is obtained (the fourth tier from the bottom in Table 1).

(\Axdo/d)4/(Q/vL) is a dimensionless quantity, and this is referred to as "shape parameter G" of the manifold device. According to the similar calculation, in the case 6, the

shape parameter G becomes 8.0x10-6 , and in the case 7, the

shape parameter G becomes 3.0x10-4 .

[0050] From the results described above, in the example of Figs. 4, the proper condition in which the discharge rate difference R from the five discharge holes Al to A5 becomes equal to or less than 5% is derived from the following Formula [5]. A case where an equality sign is established in Formula [5] corresponds to the case where the discharge rate difference R is 5%.

[0051] [Expression 8]

doI FA 9. 0 X10 - [5]

[0052] Fig. 5 is a graph created based on the simulation

in Table 1. In this graph, \Axdo/d is plotted on a

horizontal axis, and Q/vL is plotted on a vertical axis.

Respective numerical values in the cases 1 to 5 are plotted

on one quartic curve.

[00531 In the design of the manifold device shown in

Figs. 4, in the case of the manifold device in which a

relation between Axdo/d and Q/vL is located in a region

above the quartic curve in Fig. 5 (for example, the case 6

in Table 1), the discharge rate difference R can be set to

be equal to or less than 5%. On the other hand, in the

case of the manifold device in which the relation between

Axdo/d and Q/vL is located in a region below the quartic

curve in Fig. 5 (for example, the case 7 in Table 1), the

discharge rate difference R exceeds 5%.

[0054] In the manifold device having the five discharge

holes Al to A5 shown in Figs. 4, when the discharge rate

difference R is set to be a certain value other than 5%, a

constant of a right-hand side of Formula [5], that is, the

value of the shape parameter G is decided according to the

value of the discharge rate difference R. The value of the

shape parameter G can be also derived by experiments.

[0055] So long as the proper condition in Formula [5] is

satisfied, the parameters d, do, A, and L related to the

manifold device, the parameter v related to cement milk,

and the parameter Q related to the high-pressure fluid

delivery device can be freely combined. As an example, in

the case 1 in Table 1, the inner diameter d is 120

millimeters, the inner diameter do of the discharge hole is

45 millimeters, the flow rate coefficient A of the

discharge hole is 1, the discharge hole interval L is 200

millimeters, the dynamic viscosity coefficient v is 3.3x10

4 m 2 /sec, the total discharge rate Q is 1.4x10-2 m 3 /sec.

Further, the axial length of the manifold device can be set,

for example, to 1000 millimeters, and the inner diameter of the injection hole can be set, for example, to 45 millimeters. However, the length and the inner diameter are not limited thereto.

[00561 In the example shown in Figs. 4, it is assumed

that a high-pressure fluid is injected only from the

injection hole Il located at the end of the manifold device.

When the high-pressure fluid is injected from the center

injection hole 12, it is considered that the discharge rate

difference R naturally becomes smaller than that of the

case where the high-pressure fluid is injected from the

injection hole Il located at the end. Further, for the

injection hole 13 at the opposite end, the same condition

as that of the injection hole Il applies. Therefore, for a

case where the high-pressure fluid is injected from one or

plural injection holes Il, 12, and 13 in any combination,

the proper condition in which the discharge rate difference

R is set to be within 5% is included in Formula [5].

[0057] <Proper condition of manifold device: in case of n

discharge holes>

Next, the proper condition of the manifold device when

the number of discharge holes is extended other than five

is described. In the example of Figs. 4, a case where n

discharge holes Al to An are arranged is assumed, and a

worst condition in which cement milk is injected in an

injection volume Qi only from the injection hole Il is

assumed similarly to the example of Figs. 4.

[00581 Table 2 is a table in which the number n of

discharge holes is set to be any one of 3 to 10 and

similarly to the simulation in Table 1, simulation results

are summarized for each of cases 1 to 10 where each of

numerical values of respective parameters of the inner

diameter d of the manifold device, the inner diameter of do

of the discharge hole, the flow rate coefficient A of the discharge hole, the discharge hole interval L, and the dynamic viscosity coefficient v is appropriately changed.

The discharge rates Q1 to Qn-l (the discharge rates of the

discharge holes Al and A2 are respectively Q1) of each of

the discharge holes Al to A5 are respectively obtained by

using procedures same as (i) to (vi) described above. The

unit weight y and the dynamic viscosity coefficient v of

cement milk are calculated while assuming W/C as 65%.

[0059] [Table 2]

0

O

4~0 0 0 0 0 0 0 I I I ; 3

' 04 0 0Q 0 0 0 0 0 0 ., .ION ...

00~~~~ 0 m 0 0 1- 1 3, o 0 03 40 0 0 w 9 9 3 0 0-4 0 0 0 0 0 0 N00 00 ,0.....

. 0 0 OO. 0 c 0 00N 0 034 O 0 0 0 0 0 40

0 0 , .0 0 0 0 N 40 3, 3 3, , 3, , 3,

, 3, ,0 ~0 0 0 0 0 0 0 0 0 0

5 0 0 00 0 0 0 0 0 T-O 03 03 0 , *~T 0 0 0 N0 0N, 0 3 O 3 3 3 01 0 0 . . . . .

. N 0 0 0 3, 3, 3, 3, 0 , 0 o 3 , 3 3 3 3 3

3,

& .00N II N 343 0 0 0 0 0 0 000 3 0 34 N • 3 3 0•, 3

o 00 00 0 0 0

0 .0000 0 00 00N N 0 O03 3

00~~~~~ N 0 .0 . . 0 0N 0. 340O4 0 0G 00 -,................g 3, N 3, , ,3

it

O 0.3

~ , 34 34 0+ + x0 , 4

0 3, N 0 u0 .e.e.4. e .0.0.0.04 • •. N0 . 9ir 4 0 .o - oO O o 0 0 00a 0 0 3, 0+,0+

S 000 0-4 5555N NN N , 3,3 Nx

[0060] In Table 2, rates to the maximum discharge rate Q1 of other discharge rates Q2 to Qn-1 are displayed (eight lower tiers in the table). The variability in the discharge rate is also defined here as a rate R (%) of a difference between the maximum discharge rate Q1 and the minimum discharge rate Qn-1 to the maximum discharge rate Q1 as in the following formula and is referred to as "discharge rate difference R".

R(%)=((Q1-Qn-1)/Q1)xlOO.

[0061] In cases 1 to 8 in Table 2, the discharge rate difference R is 5%. According to the similar calculation, in the case 9, the discharge rate difference R is 0.65%, and in the case 10, the discharge rate difference R is 32%.

[0062] Here, a model formula in which the discharge rate difference R becomes equal to or less than a predetermined value is set as in the following Formula [6]. A left-hand side of Formula [6] is the shape parameter G. When the discharge rate difference R is set to be the predetermined

value, a set of a, P, and 6 can be decided so that the right-hand side of Formula [6] becomes a constant value according to the value of the discharge rate difference R. For example, when the discharge rate difference R is 5%,

the set of a, $, and 6 can be uniquely decided.

[0063] [Expression 9]

(f A d! Y dd ___

a

[0064] a, , and 6 are decided as described below for the cases 1 to 8 where the discharge rate difference R becomes 5%. Calculation results of the shape parameter G on the left-hand side of Formula [6] are as described in Table 2, when each parameter value of the number n of discharge holes, the inner diameter d of the manifold device, the inner diameter do of the discharge hole, the flow rate coefficient A of the discharge hole, the discharge hole interval L, and the dynamic viscosity coefficient v is changed.

[0065] Next, a and $ are obtained by convergent

calculation so that a variation of 6, which is a value

obtained by multiplying the shape parameter G by (n-x)P, becomes minimum. For the cases 1 to 8 in Table 2, it is

decided that a=1.5 and P=3. 6 is obtained by re calculation using values of a and $, and it is decided that

6=0.0039. Therefore, the proper condition of the manifold device in which the discharge rate difference R becomes equal to or less than 5% is represented by the following Formula [7].

[0066] [Expression 10]

(JAXdIo_. 0M03 (n_-1.5)

[0067] Fig. 6 is a graph created based on the simulation in Table 2. In this graph, the number n of discharge holes is plotted on a horizontal axis, and the shape parameter G

is plotted on a vertical axis, that is, (\Axdo/d) 4/ (Q/vL) .

Respective numerical values in the cases 1 to 8 are plotted on one curve.

[0068] In the case of the manifold device in which a value of the shape parameter G with respect to the number n of discharge holes is located in a region below the curve in Fig. 6 (for example, the case 9 in Table 2), the discharge rate difference R becomes equal to or less than

5%. On the other hand, in the case of the manifold device

in which the value of the shape parameter G with respect to

the number n of discharge holes is located in a region

above the curve in Fig. 6 (for example, the case 10 in

Table 2), the discharge rate difference R exceeds 5%.

[00691 In the manifold device having n discharge holes,

when the discharge rate difference R is set to be a value

other than 5%, values of the set of u, $, and 6 on the

right-hand side of Formula [6] are decided according to the

value of the discharge rate difference R. The parameters n,

d, do, A, and L related to the manifold device, the

parameter v related to cement milk, and the parameter Q

related to the high-pressure fluid delivery device can be

freely combined, so long as Formula [6] is satisfied.

However, the number n of discharge holes is preferably in a

range of 3 to 10.

[0070] The manifold device is designed before the

construction. A specific designing of the manifold device

that realizes the allowable discharge rate difference R is

performed, for example, according to the following

procedures I) to IV).

I) By deciding the high-pressure fluid delivery device

to be used for the construction, the injection volume Qi is

decided according to Formula [4], and simultaneously, the

total discharge rate Q to be used for simulation is decided.

Further, by deciding W/C % of cement milk to be used for

the construction (adopting the smallest value as the worst

condition), the unit weight y and the dynamic viscosity coefficient v to be used for simulation are decided. II) For the simulation, by using a plurality of combinations in which respective parameters of the number n of discharge holes and the inner diameter d of the manifold device, the inner diameter do of the discharge hole, the flow rate coefficient A of the discharge hole, and the discharge hole interval L are set to be appropriate values, and the total discharge rate Q, the unit weight y, and the dynamic viscosity coefficient v in I) described above, the discharge rate of each discharge hole is obtained by performing the procedures similar to (i) to (vi) described above. III) The discharge rate difference R is calculated for each of combinations of parameters based on the obtained discharge rate of each discharge hole. From these results, a plurality of combinations matched with the allowable discharge rate difference R are extracted. IV) The shape parameter G is calculated for each of the extracted combinations. By using Formula [6], a combination of a and $ in which a variation of Gx(n-ax)P being 6 in the case of equality sign becomes minimum is obtained. 6 is obtained again based on the obtained u and $. This enables to obtain Formula [7] of the proper condition, for example, in the case where the allowable discharge rate difference R is 5%. V) The number n of discharge holes and the inner diameter d of the manifold device, the inner diameter do of the discharge hole, the flow rate coefficient A of the discharge hole, and the discharge hole interval L to be actually used are set within a range of, for example, satisfying Formula [7] obtained in Formula [7] in IV) described above. Since the flow rate coefficient A of the discharge hole is a physical constant decided based on the shape and the like of the discharge hole, the flow rate coefficient A of the discharge hole can be obtained based on experiments or previous research results.

[0071] As an example, when the discharge rate difference

R is set to be equal to or less than 5%, for example, in

the case 3 satisfying Formula [7] in Table 2, the number n

of discharge holes is five, the inner diameter d is 150

millimeters, the inner diameter do of the discharge hole is

70 millimeters, the flow rate coefficient A of the

discharge hole is 0.735, the discharge hole interval L is

400 millimeters, the dynamic viscosity coefficient v is

3.3x10-4 m 2 /sec, and the total discharge rate Q is 3.7x10-2

m 3 /sec. The shape parameter G at this time is 9.2x10- 5

. Further, the axial length of the manifold device can be set,

for example, to 2000 millimeters and the inner diameter of

the injection hole can be set, for example, to 70

millimeters. However, these dimensions are not limited

thereto.

[0072] In the actual pile construction, the total

discharge rate of the high-pressure fluid discharged from

the discharge holes of the manifold device varies by being

controlled according to the respective construction stages.

However, the discharge rate difference between respective

discharge holes becomes the allowable discharge rate

difference R used in the design of the manifold device.

[0073] As another embodiment of the manifold device, a

plurality of manifold devices can be provided in one

construction system. In this case, each manifold device is

designed so as to satisfy the proper condition described

above. Accordingly, at least in each manifold device, it

is ensured to deliver the high-pressure fluid from the discharge holes with an equal discharge rate.

[0074] The proper condition of the manifold device described above is described for a case where the high pressure fluid is cement milk. However, the same applies to a case where the high-pressure fluid is water. Respective embodiments of the pile construction method according to the present invention using the construction system including the manifold device described above are explained below.

[0075] (3) First embodiment of pile construction method Figs. 7(a) to (h) are diagrams schematically showing each step in the first embodiment of the pile construction method.

[0076] <Preparing step> Fig. 7(a) shows a preparing step. A pile to be driven here is the steel pipe pile 1. The ground into which the pile is driven includes a bearing ground G1 located on the lower side, and a predetermined ground G2 being present between an interfacial surface DO of the bearing ground and a land surface (in this example, bottom of a sea). The vibro hammer 2 is attached to an upper end of the steel pipe pile 1. Jet pipe members are attached to the steel pipe pile 1. A jet pipe member configured by a plurality of conduits 9, the integration pipe 8 connected to a bottom end of each conduit 9, and a plurality of injection nozzle 7 respectively connected to each of the branched ends of the integration pipe 8 is attached, as an example, around the steel pipe pile 1. A detachable high-pressure hose 17 is each attached to an upper end of each conduit 9 via a coupler. Water of a flowable solidifying material can be pressure-fed to the conduit 9 through the high-pressure hose 17.

[0077] Fig. 8(a) is a perspective view schematically showing a configuration example of the jet pipe member near the end of the steel pipe pile 1, and (b) is a bottom view thereof. In the illustrated example, two pairs of jet pipe members are attached to the steel pipe pile 1. Water or the flowable solidifying material passes through the conduit 9, is branched by the integration pipe 8, and is injected from each injection nozzle 7. The number of the conduits 9, the number of branches of the integration pipe 8, that is, the number of the injection nozzles 7, are not limited to the illustrated example.

[0078] According to the construction method of the first embodiment, the jet pipe member does not need to be detached from the steel pipe pile 1. Therefore, detailed designing is not required in terms of attachment of the jet pipe member, particularly, the injection nozzle to the steel pipe pile 1, and if required strength can be ensured, the injection nozzle can be attached to the steel pipe pile 1 by simple and inexpensive means.

[0079] <Driving step> Figs. 7(b) and (c) show a driving step subsequent to the preparing step. As shown in Fig. 7(b), the driving step is performed by the JV method using water jet. That is, the steel pipe pile 1 is driven into the ground at the end of the pile by giving vibrations caused by the vibro hammer 2 while injecting water (represented by sign W) from the injection nozzle 7 in a driving direction.

[0080] There are some advantages in using water during driving. First, since the specific gravity of water is lighter than that of the flowable solidifying material, the discharge rate can be maintained to be as high as the maximum discharge capacity of the high-pressure fluid delivery device. Therefore, there is a major effect of loosening and cutting the ground. Meanwhile, when the flowable solidifying material is used for driving, jet injection for a long time is required, and as a result, a large amount of flowable solidifying material is used, which is not economical. In many cases, water can be freely obtained from rivers and the sea near the construction site. However, for the flowable solidifying material, there is a limitation in the amount obtained, and thus when the flowable solidifying material is used for driving, shortage of the flowable solidifying material may occur.

[0081] Therefore, in the initial driving of the steel

pipe pile 1, it is preferred to inject high-pressure water

jet as high as possible from the injection nozzle 7 to

assist driving by the vibro hammer 2.

[0082] The vibro hammer 2 has a motion exciter and a

chuck device, and grasps the upper end of the steel pipe

pile 1 by the chuck device. The motion exciter generates

axial vibrations in the steel pipe pile 1 by rotating an

eccentric mass by an electric motor. The electric motor of

the motion exciter has an output of, for example, 30 to 500

kW, and the vibration frequency is, for example, 10 to 60

Hz. In the case of a large pile, a plurality of vibro

hammers can be linked together.

[0083] As shown in Fig. 7(c), the steel pipe pile 1 is

driven until the end thereof reaches a predetermined first

design depth Dl. The first design depth Dl can be set to

be a position that is deeper than the interfacial surface

DO of the bearing ground by a predetermined distance (for

example, about twice the diameter of the pile 1).

[0084] Fig. 9 is referred to here. Fig. 9 is a diagram

schematically showing an example of a construction

management method in the pile construction method. A

construction management system is incorporated in the construction system. A construction management device 26 functions as a key element and collects pieces of data from respective devices such as a measurement device to execute control. The construction management device 26 can be realized by a computer, preferably, a personal computer in which a predetermined program is installed.

[00851 The construction management device 26 includes a wired and/or wireless communication function. Since the present example is the construction at a sea, communication is performed wirelessly between the device on the crane barge 10 and the construction management device 26. Communication with respective devices on land can be either wired or wireless.

[00861 The construction management device 26 continuously receives flow data of water from a flowmeter 19 provided in the delivery port of the high-pressure fluid delivery device 14. Further, a vertical height of the steel pipe pile 1 is measured by a prism 25 attached to the vibro hammer 2 and a total station 24 that tracks the prism. The construction management device 26 continuously receives the measured vertical height data from the total station 24.

[0087] The construction management device 26 compares the water flow data and the vertical height data of the steel pipe pile 1 with execution plan data stored in advance so as to generate control information for adjusting the pile driving speed and the discharge rate of water. This enables construction management on a real time basis during driving. For example, the measurement data and/or the control information are transmitted from the construction management device 26 to a monitor 23 in an operation room of a crane 22.

[00881 The construction management device 26 determines the first design depth Dl, being a driving stop position of the steel pipe pile 1 based on the vertical height data of the steel pipe pile 1. When having reached the first design depth Dl shown in Fig. 7(c), the flow rate of the water jet is decreased up to an idling flow rate to stop driving. The idling flow rate is the lowest flow rate that can be stably discharged in terms of the machine performance. Blockage of the injection nozzle due to backflow of soil particles in a surrounding soil can be prevented by not stopping the water jet. If a backflow prevention device such as a check valve is installed in the injection nozzle, the water jet may be stopped. The water jet is stopped to stop driving. The vibro hammer 2 may be stopped, or may be continuously operated for the following pulling-up step.

[00891 In the driving step in the present example, the flowable solidifying material is not used, and vibrations caused by the vibro hammer are given to drive the pile while injecting water, thereby enabling to maintain the jet discharge rate during pile driving about at the maximum discharge capacity continuously. Therefore, various problems that are caused when the flowable solidifying material is injected during pile driving do not occur.

[0090] <Pulling-up step> Subsequently, a pulling-up step in Figs. 7(d) and (e) are performed. The pulling-up step can be performed by using any of the JV method or a method using vibro hammer only. The steel pipe pile 1 is pulled up by the crane until the end of the steel pipe pile 1 reaches a second design depth D12. The second design depth D12 is a predetermined depth as an upper end of peripheral grout of the pile in a grouting step described later, and is separately defined in the design.

[0091] When the JV method is used in the pulling-up step, the steel pipe pile 1 is pulled up by giving vibrations caused by the vibro hammer while injecting water jet. A main object of using water jet concurrently in the pulling up step is to prevent blockage of the injection nozzle as described above. The discharge rate of water for preventing blockage of the injection nozzle can be a requisite minimum, and is set to be a small amount as compared to that at the time of driving. If the backflow prevention device is installed in the injection nozzle, the method using vibro hammer only can be used to perform the pulling-up step.

[0092] The construction management device 26 in Fig. 9

determines the second design depth D12 being a pulling-up

stop position of the steel pipe pile 1 based on the

vertical height data of the steel pipe pile 1. When the

steel pipe pile 1 has reached the pulling-up stop position,

pulling-up is stopped.

[0093] <Grouting step>

Subsequently, a grouting step in Figs. 7(f) and (g) is

performed. When the steel pipe pile 1 has reached the

pulling-up stop position of the pulling-up step, water is

changed to the flowable solidifying material (represented

by sign C). Here, cement milk is used as the flowable

solidifying material. The water-cement ratio of cement

milk is set as required in a range of, for example, from

50% to 150%. The steel pipe pile 1 is then driven up to a

third design depth D13 by giving vibrations caused by the

vibro hammer 2 while injecting the flowable solidifying

material from an end of the injection nozzle 7. Since the

flowable solidifying material is solidified, peripheral

grout of the pile is formed. The third design depth D13 is

within the bearing ground Gl, and can be substantially the

same position as the first design depth Dl, a position that is slightly deeper than the first design depth Dl, or a position that is slightly shallower than the first design depth Dl. For example, the third design depth D13 can be a position that is deeper than the interfacial surface DO of the bearing ground, for example, by about once the diameter of the pile 1.

[0094] The grouting step is a step of driving again the

pile into the ground to which the pile has been driven once.

Therefore, the ground is loosened and obstacles are removed,

and thus such a state in which the pile cannot be driven in

the grouting step does not occur.

[00951 During re-driving of the steel pipe pile 1, the

flowable solidifying material in a required amount is

injected from the injection nozzle 7 for grouting, for

every depth of the end of the steel pipe pile 1. The re

driving speed of the steel pipe pile 1 cannot be set faster

than the driving capability of the vibro hammer 2 at the

time of injecting the flowable solidifying material.

Therefore, even if the rotating speed of the high-pressure

fluid delivery device 14 shown in Fig. 2 is decreased and

the high-pressure fluid delivery device 14 is operated in

the idling state, the flowable solidifying material is

injected more than necessary, which is not economical. In

such a case, if there are a plurality of high-pressure

fluid delivery devices as shown in Fig. 2, it is preferable

to stop a part thereof. A part of the high-pressure fluid

delivery devices can be stopped as required, according to

the balance between the driving speed of the pile and the

required injection volume of the flowable solidifying

material, thereby enabling to maintain the appropriate

injection volume of the flowable solidifying material and

to realize economization.

[00961 As described above, in the present system, the manifold device 16 shown in Fig. 3 is arranged between one or plural high-pressure fluid delivery devices and the plurality of conduits. Therefore, even if all the high pressure fluid delivery devices are operated in the idling state or a part of the high-pressure fluid delivery devices is stopped, the flowable solidifying material can be discharged equally to each high-pressure hose by a discharge-rate equalizing function of the manifold device

16. As a result, the flowable solidifying material is

equally injected from each injection nozzle, thereby

forming uniform peripheral grout of the pile without any

defect or bias, and a required skin friction force in the

pile can be exerted.

[0097] In the grouting step, since the steel pipe pile 1

once driven in the driving step is driven again, obstacles

such as clods of gravel in the ground have been already

removed. Therefore, even in the case of driving by

injecting the flowable solidifying material, such a state

can be avoided that driving of the steel pipe pile 1

becomes difficult due to obstacles such as clods of gravel.

[00981 In the grouting step, vibrations caused by the

vibro hammer 2 are given to the steel pipe pile 1 and the

surrounding ground. Therefore, in the case where the

surrounding ground is a sandy soil, the injected flowable

solidifying material easily penetrates into gaps of sandy

soil. In the case where the surrounding ground is a

cohesive soil, gaps are formed between the steel pipe pile

1 and the ground by vibrations of the vibro hammer, and the

flowable solidifying material easily penetrates into the

gaps. As a result, a grout layer having a large friction

force is uniformly formed between an outer periphery of the

steel pipe pile 1 and a surrounding soil layer. This

enables to increase the bearing capacity of the steel pipe pile 1 effectively.

[00991 The construction management device 26 shown in

Fig. 9 continuously receives discharge rate data of the

flowable solidifying material from the flowmeter 19

provided in the delivery port of the high-pressure fluid

delivery device 14. Further, the vertical height of the

steel pipe pile 1 is measured by the prism 25 and the total

station 24 attached to the vibro hammer 2, and the

construction management device 26 continuously receives the

data from the total station 24.

[0100] The construction management device 26 generates

control information for adjusting the pile driving speed

and the discharge rate of the flowable solidifying material

by combining the pieces of data of the discharge rate of

the flowable solidifying material and the vertical height

of the steel pipe pile 1 and comparing the data with the

execution plan data stored in advance. This enables to

perform construction management of peripheral grouting of

the pile on the real time basis.

[0101] The construction management device 26 determines

the third design depth D13 being the driving stop position

of the steel pipe pile 1 based on the vertical height data

of the steel pipe pile 1. When the steel pipe pile 1 has

reached the driving stop depth D13 shown in Fig. 7(g), the

vibro hammer 2 and the injection of the flowable

solidifying material are stopped to complete driving.

[0102] The construction management of peripheral

grouting of the pile is performed in order to match the

injection volume of the flowable solidifying material with

that of the execution scheme within an allowable tolerance

for every depth of the end of the steel pipe pile 1.

Specifically, the construction management is performed by

adjusting the re-driving speed of the steel pipe pile 1 and the discharge rate of the flowable solidifying material.

The injection volume of the flowable solidifying material

in the execution scheme is calculated based on Figs. 10.

[0103] Figs. 10 are schematic diagrams for calculating a

design injection volume of the flowable solidifying

material, where (a) is a longitudinal sectional view of the

pile and the periphery thereof, and (b) is a horizontal

sectional view thereof. A diameter p of the steel pipe

pile is, for example, from 600 millimeters to 1500

millimeters, and an injection width q is, for example, from

50 millimeters to 300 millimeters. However, these

dimensions are not limited to these ranges. As an example,

in Non Patent Literature 1, it is reported that the

injection width q is assumed to be 300 millimeters, and a

cement volume in the grout formed in the ground by

injecting cement milk is assumed to be 300 kilograms in 1

m 3 of grout. The water-cement ratio of cement milk in Non

Patent Literature 1 is 100%.

[0104] <Post-processing step>

After the peripheral grouting of the pile is complete

and injection of the flowable solidifying material has

finished, as shown in Fig. 7(h), the high-pressure hose 17

connected to the coupler of the conduit 9 is detached, and

the released joint end is connected to an injection pipe,

for example, to a turbid water treatment facility.

Subsequently, water is injected to the mixing plants 12 in

Fig. 2 to clean the mixing plants 12 by high-pressure

washer, and flushing water is supplied to the high-pressure

fluid delivery device 14 via a pump, and further supplied

from the high-pressure fluid delivery device 14 to the

high-pressure hose 15 to pass through the manifold device

16 and the high-pressure hose 17, and then to the turbid

water treatment facility via an injection pipe from the high-pressure hose 17. Accordingly, cleaning of a pressure feed system of the flowable solidifying material is performed. Further, sludge accumulated in the turbid water treatment facility is disposed to end the entire step.

[0105] The turbid water treatment facility is not

essential. For example, if a water level in a pipe is

sufficiently lower than a crown of the steel pipe pile 1

due to a reason such that the crown of the steel pipe pile

1 is located at a position that is sufficiently higher than

the sea surface, the flushing water can be discharged into

the steel pipe pile to economize the turbid water treatment.

[0106] In the present embodiment, since construction is

completed with the jet pipe member being attached to the

pile without detaching it, a special structure for

attaching the jet pipe member, particularly, the injection

nozzle is not required, as compared with a case where the

jet pipe member is retrieved, thereby enabling cost

reduction. According to the present embodiment, the

bearing capacity of the pile driven by the JV method can be

increased economically and reliably.

[0107] (4) Second embodiment of pile construction method

Figs. 11(a) to (g) are diagrams schematically showing

each step in the second embodiment of the pile construction

method. In the following descriptions of the second

embodiment, there are cases where descriptions of

constituent elements identical to those of the first

embodiment are omitted.

[0108] <Preparing step>

A preparing step shown in Fig. 11(a) is basically as

described in Fig. 7(a) in the first embodiment described

above.

[0109] In the second embodiment, a configuration of the

jet pipe member different from that of the first embodiment is adopted. In the second embodiment, four conduits 9 are arranged for every 90 degrees in the circumferential direction of the steel pipe pile 1, and one injection nozzle 7 is attached to an end of each conduit 9. The injection nozzle 7 is fixed to an outer periphery of the steel pipe pile 1 via a fixing means that can be cut by an application of a predetermined tension. Accordingly, by applying an upward tension to the conduit 9, the injection nozzle 7 and the conduit 9 can be pulled up.

[0110] In the second embodiment, the jet pipe member in

the same form as that of the first embodiment can be

adopted. In this case, a structure that can be cut by an

application of a predetermined tension is inserted into a

boundary portion between the conduit 9 and the integration

pipe 8 in the jet pipe member according to the first

embodiment shown in Figs. 8.

[0111] <Driving step>

Figs. 11(b) and (c) schematically show a driving step

subsequent to the preparing step. It is preferable to

perform the driving step in Fig. 11(b) by the JV method

using water jet. That is, the steel pipe pile 1 is driven

into the ground at the end of the pile by giving vibrations

caused by the vibro hammer 2 while injecting water

(represented by sign W) from the injection nozzle 7.

Similarly to the first embodiment, in the initial driving, it is preferable to use water; however, usage of a flowable

solidifying material such as cement milk is not excluded.

[0112] As shown in Fig. 11(c), the steel pipe pile 1 is

driven until the end thereof reaches a predetermined first

design depth D21. The first design depth D21 is at a

position that is deeper than the interfacial surface DO of

the bearing ground by a predetermined distance (for example,

about twice the diameter of the pile 1).

[0113] After the steel pipe pile 1 has reached the first

design depth D21 shown in Fig. 11(c), a flow rate of water

jet is decreased up to an idling flow rate to complete

driving. The vibro hammer 2 may be stopped, or may be

continuously operated for the next pulling-up step.

[0114] <Pulling-up step>

Subsequently, a pulling-up step in Figs. 11(d) is

performed. First, after completion of the initial driving

in Fig. 11(c), water is changed to the flowable solidifying

material (represented by sign C) such as cement milk. In

the case of cement milk, the water-cement ratio of the

cement milk is set as required in a range of, for example,

from 50% to 150%. The steel pipe pile 1 is then driven up

by a crane until the end of the steel pipe pile 1 has

reached a second design depth D22, by giving vibrations

caused by the vibro hammer 2 while injecting the flowable

solidifying material from an end of the injection nozzle 7.

The second design depth D22 is a predetermined depth as an

upper end of foot protection grout. The second design

depth D22 is a position that is slightly shallower than,

for example, the interfacial surface DO of the bearing

ground by a predetermined distance (for example, about once

the diameter of the pile 1).

[0115] <Foot protecting step>

Subsequently, a foot protection processing in Fig.

11(e) is performed. The steel pipe pile 1 is driven until

the end of the steel pipe pile 1 has reached a third design

depth D23 by giving vibrations caused by the vibro hammer 2

while injecting the flowable solidifying material from the

end of the injection nozzle 7. The third design depth D23

is within the bearing ground and at substantially the same

position as the first design depth D21, at a position that

is slightly deeper than that, or at a position that is slightly shallower than that. For example, the third design depth D23 can be at a position that is deeper than the interfacial surface DO of the bearing ground, for example, about once the diameter of the pile 1.

[0116] The foot protecting step in Fig. 11(e) can be

performed only once or repeatedly performed. When the foot

protecting step is performed repeatedly, after the steel

pipe pile 1 is pulled up again to the second design depth

D22 together with injection of the flowable solidifying

material and vibrations caused by the vibro hammer, the

steel pipe pile 1 is driven up to the third design depth

D23. Particularly, in the case of a hard ground, it is

preferable to repeat the foot protecting step by pulling-up

and driving for an appropriate number of times. By

solidifying the flowable solidifying material, foot

protection grout is formed. As described above, uniform

foot protection grout without any defect or bias is formed

by the manifold device according to the present invention

that uniformly injects a flowable solidifying material to

the circumference of the steel pipe pile 1, thereby

enabling to exert required end bearing capacity of the pile.

[0117] At the time of finishing the foot protecting step

in Fig. 11(e), the end of the steel pipe pile 1 is driven

up to the third design depth D23. At this position, the

vibro hammer is stopped. Preferably, by performing

injection of the flowable solidifying material again at

this position for a predetermined time, foot protection

grout can be reliably formed. After ending the foot

protecting step, the vibro hammer is detached.

[0118] <Injection-nozzle pulling-out step>

Next, an injection-nozzle pulling-out step shown in

Figs. 11(f) and (g) is performed. First, by applying a

predetermined tension to the conduit 9, the injection nozzle 7 is detached together with the conduit 9 from the steel pipe pile 1. Thereafter, while hoisting an upper end of the conduit 9 by the crane, the injection nozzle 7 is pulled out at a predetermined speed. At this time, the injection nozzle 7 is pulled out, while injecting the flowable solidifying material from the injection nozzle 7.

[0119] The water-cement ratio and the flow rate of

cement milk as the flowable solidifying material in the

pulling-out step can be set to be different values from

those in the foot protecting step described above.

[0120] When the end of the injection nozzle 7 has

reached a predetermined fourth design depth D24, injection

of the flowable solidifying material is stopped. The

fourth design depth D24 is an upper end of peripheral grout

of the pile, and is a depth defined separately on the

design.

[0121] Thereafter, the conduit 9 and the injection

nozzle 7 are completely pulled out. Since the flowable

solidifying material is solidified, peripheral grout is

formed. Also in this case, since the manifold device

according to the present invention uniformly injects the

flowable solidifying material to the circumference of the

steel pipe pile 1, uniform peripheral grout without any

defect or bias is formed, and a required skin friction

force in the pile can be exerted.

[0122] <Post-processing step>

In a post-processing step according to the second

embodiment, in addition to the post-processing step

described in the first embodiment, cleaning of the

retrieved conduit 9 and the injection nozzle 7 is performed.

[0123] (5) Third embodiment of pile construction method

Figs. 12(a) to (e) are diagrams schematically showing

each step in the third embodiment of the pile construction method. In the following descriptions of the third embodiment, there are cases where descriptions of constituent elements identical to those of the first embodiment are omitted.

[0124] <Preparing step> A preparing step shown in Fig. 12(a) is basically as described in Fig. 7(a) in the first embodiment described above.

[0125] <Driving step/grouting step> As shown in Figs. 12(b), (c), and (d), in the third embodiment, the grouting step is simultaneously performed at least in a part of the driving step. In the illustrated example, an initial stage of the driving step is performed by the JV method using water jet. That is, the steel pipe pile 1 is driven into the ground at the end of the pile by giving vibrations caused by the vibro hammer 2 while injecting water (represented by sign W) from the injection nozzle 7 in a driving direction. This embodiment can be performed in a case where driving of the pile is relatively easy, for example, the driving ground is relatively soft and any obstacle does not lie buried.

[0126] When the end of the steel pipe pile 1 has reached a predetermined first design depth D31, driving is once stopped, and water is changed to a flowable solidifying material such as cement milk (represented by sign C). In the case of cement milk, the water-cement ratio is set as required, for example, in a range from 50% to 150%. Thereafter, as shown in Fig. 12(c), the steel pipe pile 1 is further driven by giving vibrations caused by the vibro hammer 2 while injecting the flowable solidifying material.

[0127] As shown in Fig. 12(d), the steel pipe pile 1 is driven until the end thereof reaches a predetermined second design depth D32. The second design depth D32 is at a position that is deeper than the interfacial surface DO of the bearing ground by a predetermined distance (for example, about twice the diameter of the pile 1).

[0128] After the steel pipe pile 1 has reached the second design depth D32 shown in Fig. 12(d), injection of the flowable solidifying material and the vibro hammer 2 are stopped to complete driving.

[0129] Since the flowable solidifying material is solidified, peripheral grout is formed. Also in this case, since the manifold device according to the present invention uniformly injects the flowable solidifying material to the circumference of the steel pipe pile 1, uniform peripheral grout without any defect or bias is formed, and a required skin friction force in the pile can be exerted.

[0130] Although not shown, as a modified mode of the third embodiment, the driving step and the grouting step can be simultaneously performed by injecting the flowable solidifying material from the initial stage of the driving step in Fig. 12(b) and giving vibrations caused by the vibro hammer 2. Particularly, this operation is possible when the ground near the land surface is a soft soil layer such as a sandy soil or a cohesive soil.

[0131] <Post-processing step> After the driving step and the grouting step are complete and injection of the flowable solidifying material has finished, as shown in Fig. 12(e), the high-pressure hose 17 connected to the coupler of the conduit 9 is detached, and a post-processing step same as that of the first embodiment described above is performed.

[0132] (6) Summary The pile construction method according to the present invention includes, as a common mode, a preparing step of attaching a plurality of jet pipe members and a vibro hammer to a pile to connect piping of a construction system including the manifold device, and a constructing step including at least a partial step of moving down or up the pile by giving vibrations caused by the vibro hammer while injecting a high-pressure fluid from an end of the jet pipe member into the ground. The present invention is not limited to the configurations of the respective embodiments described above, and the present invention can be modified as appropriate without departing from the scope of the invention.

Reference Signs List

[0133] 1 steel pipe pile

2 vibro hammer

7 injection nozzle

8 integration pipe

8a head portion

8b branched portion

9 conduit

10 crane barge

11 cement silo

12 mixing plant

13 water tank

14 high-pressure fluid delivery device

15 high-pressure hose

16 manifold device

16a casing

16b injections hole

16c discharge hole

16d vibrator

16e current plate

16f stirrer

17 high-pressure hose 18A, 18B switching device 19 flowmeter 20 generator 21 operating unit 22 crane 23 monitor 24 total station 25 prism 26 construction management device

Claims (12)

1. A pile construction method comprising:

a preparing step of attaching a plurality of jet pipe

members and a vibro hammer to a pile; and

a constructing step including at least a partial step

of moving down or up the pile by giving vibrations caused

by the vibro hammer while injecting a high-pressure fluid

from ends of the jet pipe members into a ground, wherein

in the preparing step, one or plural high-pressure

fluid delivery devices and a manifold device having a

cylindrical inner space are arranged, the one or plural

high-pressure fluid delivery devices are connected

respectively to one or plural injection holes in the

manifold device, and each of a plurality of discharge holes

in the manifold device is connected to each of the jet pipe

members,

in the constructing step, a high-pressure fluid is

injected from at least one of the injection holes and the

high-pressure fluid is discharged from each of the

discharge holes while maintaining a state in which the

inner space of the manifold device is filled with the high

pressure fluid, and

in terms of discharge rates of a plurality of high

pressure fluids discharged from each of the discharge holes,

a difference between a maximum discharge rate and a minimum

discharge rate is equal to or less than 5% of the maximum

discharge rate.

2. The pile construction method according to claim 1,

wherein in the manifold device, a relation among a number n

of the discharge holes, a diameter d of the inner space, a

diameter do of the discharge hole, a flow rate coefficient

A of the discharge hole, an interval L between the two adjacent discharge holes, a dynamic viscosity coefficient v of the high-pressure fluid, and a sum total Q of the respective discharge rates satisfies a following formula.

[Expression 1]

1FA do xd)0.0039 ( 3

3. The pile construction method according to claim 1 or 2, wherein the high-pressure fluid is water or a flowable solidifying material, and the constructing step includes a driving step of driving the pile up to a first depth that is lower than an interfacial surface of a bearing ground by giving vibrations caused by the vibro hammer while injecting water, a pulling-up step of pulling up the pile up to a depth corresponding to a set upper end of peripheral grout of the pile by giving at least vibrations caused by the vibro hammer, and a re-driving step of driving the pile again up to a second depth that is lower than the interfacial surface of the bearing ground while injecting a flowable solidifying material.

4. The pile construction method according to claim 1 or 2, wherein the high-pressure fluid is water or a flowable solidifying material, and the constructing step includes a driving step of driving the pile up to a first depth that is lower than an interfacial surface of a bearing ground by giving vibrations caused by the vibro hammer while injecting water, a pulling-up step of pulling up the pile up to a depth corresponding to a set upper end of foot protection, by giving vibrations caused by the vibro hammer while injecting a flowable solidifying material, a re-driving step of driving the pile again up to a second depth that is lower than the interfacial surface of the bearing ground while injecting a flowable solidifying material, and a pulling-out step of pulling out the jet pipe member while injecting a flowable solidifying material.

5. The pile construction method according to claim 1 or 2, wherein the high-pressure fluid is water or a flowable solidifying material, and the constructing step includes a driving step of driving the pile up to a depth that is lower than an interfacial surface of a bearing ground by giving vibrations caused by the vibro hammer while injecting a flowable solidifying material.

6. The pile construction method according to any one of claims 1 to 5, wherein the high-pressure fluid is caused to meander by current plates that are arranged in the inner space of the manifold device.

7. The pile construction method according to any one of claims 1 to 6, wherein the high-pressure fluid is agitated by an agitator that is arranged in the inner space of the manifold device, or vibrations are given to the high pressure fluid by a vibrator that is arranged in the inner space.

8. The pile construction method according to any one of

claims 1 to 7, wherein

a construction management device

acquires vertical height data of a pile continuously

transmitted from a total station that tracks a prism

attached to the vibro hammer, and flow rate data of a high

pressure fluid respectively transmitted continuously from a

flowmeter attached to each of delivery ports of the one or

plural high-pressure fluid delivery devices, and

compares acquired vertical height data of the pile and

acquired flow rate data of the high-pressure fluid with

execution plan data so as to adjust a moving speed of s

pile in each partial step included in the constructing step,

switching of water and a flowable solidifying material, or

a discharge rate of a high-pressure fluid on a real time

basis.

9. The pile construction method according to any one of

claims 1 to 8, wherein

the jet pipe member includes

a conduit that is connected to the manifold device,

an integration pipe with one end being connected to

the conduit, and the other end being branched into plural

ends, and

a plurality of injection nozzles that are connected to

each of the branched other ends of the manifold device.

10. A manifold device used in a pile construction method

including at least a step of driving a pile attached with a

plurality of jet pipe members while injecting a high

pressure fluid from each end of the jet pipe members, wherein the manifold device comprises a cylindrical inner space, one or plural injection holes respectively connected to one or plural high-pressure fluid delivery devices, and a plurality of discharge holes respectively connected to each of the jet pipe members, during the pile construction, a high-pressure fluid is injected into the manifold device from at least one of the injection holes and the high-pressure fluid is discharged from each of the discharge holes while the manifold device is maintained in a state in which the inner space thereof is filled with the high-pressure fluid, and in terms of discharge rates of a plurality of high pressure fluids discharged from each of the discharge holes, a difference between a maximum discharge rate and a minimum discharge rate is equal to or less than 5% of the maximum discharge rate.

11. The manifold device according to claim 10, wherein in the manifold device, a relation among a number n of the discharge holes, a diameter d of the inner space, a diameter do of the discharge hole, a flow rate coefficient A of the discharge hole, an interval L between the two

adjacent discharge holes, a dynamic viscosity coefficient v of the high-pressure fluid, and a sum total Q of the respective discharge rates satisfies a following formula.

[Expression 2]

1FA do dd 0.0039 ((3 v(L

12. A design method of a manifold device used in a pile construction method including at least a step of driving a pile attached with a plurality of jet pipe members while injecting a high-pressure fluid from each end of the jet pipe members, the manifold device comprises a cylindrical inner space, one or plural injection holes respectively connected to one or plural high-pressure fluid delivery devices, and a plurality of discharge holes respectively connected to each of the jet pipe members, and during the pile construction, a high-pressure fluid is injected into the manifold device from at least one of the injection holes and the high-pressure fluid is discharged from each of the discharge holes while the manifold device is maintained in a state in which the inner space thereof is filled with the high-pressure fluid, wherein when one or plural parameters of a number n of the discharge holes, a diameter d of the inner space, a diameter do of the discharge hole, a flow rate coefficient A of the discharge hole, an interval L between the two adjacent discharge holes, and a dynamic viscosity

coefficient v of the high-pressure fluid are respectively changed in advance, discharge rates of a plurality of high pressure fluids discharged from each of the discharge holes are calculated for each case, by designating a sum total of respective discharge rates as Q, in terms of discharge rates of a plurality of high pressure fluids discharged from each of the discharge holes,

(i, $, and 6 in a following formula are set so that a difference between a maximum discharge rate and a minimum discharge rate becomes equal to or less than a predetermined ratio of the maximum discharge rate, and the manifold device is designed so that a relation among the number n of the discharge holes, the diameter d of the inner space, the diameter do of the discharge hole, the flow rate coefficient A of the discharge hole, the interval L between the two adjacent discharge holes, the dynamic viscosity coefficient v of the high-pressure fluid, and the sum total Q of the respective discharge rates satisfies a following formula.

[Expression 3]

FA do)' _ _

(0L