Screwed steel pile NS ECO-PILETM

Building and Civil Engineering Method ofNIPPON STEEL & SUMIKINENGINEERING

Foundation Structure

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Screwed Steel P i le

NS ECO-PILE

○○○改 １ 大

Large bearing capacityA large vertical bearing capacity is generated by theconsolidation effect of the ground as the pile is screw-driven into the ground and the base enlarging effect ofthe blade as the blade rotates to drill the ground.

Low noise and low vibrationThe screw piling method with a pile driver or casing rotatorcauses no impact when driving a pile into the ground,minimizing noise and vibration during construction.

No waste soilBy screw-driving the pile without excavating the ground,no waste soil is produced.

Overview of NS ECO-PILE

What is NS ECO-PILE?

Structure of NS ECO-PILE

Construction compared with conventional pile method

Many Advantages

Most of the major cities in Japan are built on alluvial plains at thelower reaches of the rivers. Since alluvium is typically soft ground,structures such as high-rise buildings or expressways need to besupported by piles long enough to reach the hard ground base.Industrial waste such as waste soil or slurry as well as noise andvibration arising during the conventional pile construction methodcreate environmental and social problems. NIPPON STEEL& SUMIKIN ENGINEERING's NS ECO-PILE solves all theseproblems and realizes high bearing capacity, excellent earthquakeresistance, cost effectiveness and shorter construction period.This is the piling method of the future.

NS ECO-PILE is a steel pile with a helical blade welded to theedge. During construction, a pile driver or casing rotator, forexample, rotates the pile, and the blade on the edge performs thedigging that drives the pile into the ground like a wood-screw.

Conventional pile

Driven pile: noise and vibration problems

Conceptual illustration of screw piling

1

p.2 p.3

Characteristics

1

2

Blade diameter (Dw)● ●

Short pipe for edge blade part (the wall can be thicker than that of the lower blank pipe)

Lower blank pipe

Pile diameter (Dp)● ●

Blade

Blade diameter● ●

Note

The maximum difference in wall thickness betweenconnecting blank pipes should be 7 mm or less. When blank pipes of different thickness areconnected,a thick wall part should be considered tomitigate stress concentration. The length of thepart inside the blank pipe shall be not less than4(t1-t2). When (t1-t2) is not more than 2 mm, orwhen (t1-t2) is not more than 3 mm in the case ofboth-side welding of the shop circumferentialweld, the cutting may be omitted.When the site circumferential weld of a pile isconnected to another pile, the wall thickness ofthe piles should be the same.

*1 Temporary pieces for dummy piles may beinstalled inside the steel pipe.

*2 Temporary pieces for chucks are used when pile driving penetrating with a three-point pile driver.

Edge blade part

●

●

Blade

Shopcircumferentialweld

Site circumferential weld(welding of blank pipes of the same thick)

Temporary piece for dummy pile*1

Shop circumferential weld (welding of blank pipes of different wall thickness)

●

●

●

●

●

●

●

Site circumferential weld(welding of blank pipes of the same thick)

●

●

Shop circumferential weld

Cutting edge

Rd= Dw is called the blade diameter ratio.Dp

Hanging hook

Cast-in-place pile:Disposal of slurry and waste soil;sludge; and possible collapse of thebored hole wallBored pile: Disposal of slurry and waste soil; orreduction in the bearing capacity at thebottom due to loosening of the ground

2

3

Large pulling resistance capacityA large pulling resistance capacity is maintained asthe passive soil resistance, which acts on the bladepart as propulsive force as the pile penetrates into theground, is wholly turned into pulling resistance.

4

High qualityAt the final embedment stage, the bearing layer canbe confirmed by the torque, thus constructing a pilefoundation of excellent quality and reliability.

5

Excellent earthquake resistanceThe steel pile foundation is highly resistant to deformationand earthquakes.

6

RecyclingTo remove a pile, it is rotated in the direction opposite tothat when driven, allowing easy recycling of usedpiles. NS ECO-PILES can thus also be used astemporary piles.

7

Short construction periodSince this method uses no concrete or cement milkand therefore does not need to wait for hardening, theconstruction period is far shorter than for cast-in-placepiles or bored piles.

8

Low costThanks to their large bearing capacity, piles of asmaller diameter or fewer piles can be used, thusreducing the size of the footing itself. In addition, costsare lower since there is no need to dispose of slurry orresidual earth and the construction period is shorter.

9

Proximity workAs the method drives piles without excavating theground, the subterranean soil around the piles is notloosened. Therefore, pile-driving can be performedwithout affecting the foundation or buried pipes of anexisting structure nearby.

10

Batter pilesUnlike cast-in-place piling, the method drives pileswithout excavating the ground and so there is no risk ofcollapse of the bored hole wall. In the field of structuraldesign, batter piles can reduce the number of pilesmore economically than vertically straight piles.

11

Small area or under height restrictionsThe equipment for pile driving is small and so themethod can be used in small area such as sitesadjacent to existing structures. For example, piles can bedriven by a casing rotator at a site with limited overheadclearance such as under an elevated bridge or aerialwires.

123 Construction Machinery

Major construction machines used with NS ECO-PILE Method

Type Machine Specifications, standard, etc Remark

Constructionmachine 1

Structure of NS ECO-PILE

Upper blank pipe A

Temporary piece for chuck*2

Temporary piece for chuck*2

Upper pile

Middle pile

Lower pile

Casing rotator, 1500 class Maximum torque: 1150 kN・m (117 t・m) φ500 to φ600 mm in dia. (standard outside pile diameter)

φ700 to φ1200 mm in dia. (standard outside pile diameter)

φ1300 to φ1600 mm in dia. (standard outside pile diameter)

400 mm or less in dia. (standard outside pile diameter)

Maximum torque: 2070 kN・m (211 t・m)

Maximum torque: 5100 kN・m (520 t・m)

Maximum torque: 250 kN・m (25.6 t・m)

Casing rotator, 2000 class

Casing rotator, 2600 class

Three-point pile driver/Compact pile driver

Constructionmachine 2

Type of crane Crawler crane Capacity selectable as required Used for pile installation or heavy machinery relocation

Used for backfilling a vacant hole (after removing the temporary pile)Backhoe

Upper blank pipe B

2

p.5

1

Moving of heavy machine (setting of casing rotator)

Installation of lower pile

Driving of lower pile (screw piling)

Driving of lower pile (screw piling)

Driving of upper pile (screw piling)

Driving of middle and upper pile (screw piling)

Installation of middle / upper pileand site circumferential welding

Installation of middle pile andsite circumferential welding

Driving of dummy pile andpiling completion

Driving of dummy pile andpiling completion

Installation of a lower pile, checking and adjustment of verticality

Setting of deflection stopper andadjustment of verticality

Crawler crane

Middle or upper pile

Blade

S T E P - 1 S T E P - 2 S T E P - 3 S T E P - 4 S T E P - 5 S T E P - 6

▲ ▲ ▲ ▲ ▲

Schematic diagram of NS ECO-PILE (casing rotator) procedure

Schematic diagram of NS ECO-PILE (three-point pile driver)

Casing rotator

Deflection stopper

Blade

Auger

Three-point pile driver

Lower pile

Blade

Middle pile

p.4

Construction Procedure

NS ECO-PILE procedures

Construction

Example of Machine Layout

▼ Diagram of the necessary distance during proximity construction

▼ Example of layout when casing rotator is used

Screwed steel pipe pile

Crawler crane

Backhoe

Operation house

Hydraulic unit

Reaction bar

Crawler crane

Casing rotator, φ2000 class

Casing rotator, φ2000 class

Reaction bar

Operation house

Hydraulic unit

Backhoe

Casing rotator, φ2000 class

Crawler crane

Screwed steel pipe pile

Operation house

Hydraulic unit

Backhoe

For pile outside diameter of 1,200mm or less andcasing rotator with boring diameter of φ2,000 class

For pile outside diameter of 1,200mm or less andcasing rotator with boring diameter of φ2,000 class

3

▼ Example of layout when 3-point pile driver is usedBackhoe

Crawler crane

Three-point pile drier

When the leader is assembled

Material and machine yard Screwed steel pile stock yard

Spiral collar(for casing rotator)This is used to insert an NS ECO-PILEfrom above the machinery (patent no.3484653)

Special Jigs for NS ECO-PILES

For driving NS ECO-PILES, the following jigs are used inaddition to the major machines:

Dummy pileA dummy pile is used when the pile head is lower than the working ground level.

Temporary pieces for dummy pileProtrusion on the pile head on which to apply torque to NS ECO-PILE

Start

Preliminary survey

Execution plan

Selection of construction machines

Driving of test pileforⅠ=1 to n

Setting of piling machine

Installation of lower pile

Installation of upper pile

Verticality adjustment

Screw piling

Welding of piles

Screw piling

Confirmation of the capacity of construction machines

Welding inspection

Confirmation of torque

Change

A

No

Yes

No

Yes

End

Completion of the screw piling according to the flow for piling completion

nextⅠ

B

C

n: no. of piles

Start of screw piling

Completion of the screw piling

Is the pile drivento the design depth?

Screw piling while controlling adequate torque

(working torque lower than the managed upper limit torque)

Yes

Yes

Yes

Is the additional pipe lengthbelow the permitted value?

To To

Yes

Yes

No

No

No

No

Yes

No

No

a

b

c

c c

Has the bearing layerbeen confirmed?

Is the embedment into the bearing layer 1 Dp or more?

Consultation withsupervisor

(to determine, for example, to finish piling

by confirming the working torque)

Confirmation of thebearing layer depth

Is the difference in lengthbelow the permitted value?

Confirmation of the difference in length between actuallength and design length

Continuation of piling(notification to the supervisor)

Consultation withsupervisor

(about considering pile splicing, for example)

Comparison between boring dataand working torque record

Is it appropriate to judge that the bearing layer is reached at that depth?

(notification to supervisor)

Review of the possibility of

buried obstacles

Consultation withsupervisor

(about removing obstacles, for example)

Consultation withsupervisor

(about cutting the steel pipe, for example)

Confirmation of thebearing layer depth

Confirmation of theadditional pile length

p.6 p.7

430

Bottom pile

1～4

Root interval keeping bead or spacer

6 t

0～2.4

t

45°min

25

35

H(

h (

Backing ring(field installation)

T

Top pile

Stopper number(shop assembly)

N

Ａ：Driving of test pile

Example of shape and dimensions of backing ring and stopper

Flow of Construction Management

Construction

Fluctuation of working torque is used for allpiles to check whether a pile has reached thebearing layer. A test pile is driven at each site todetermine the management method to confirmarrival at the bearing layer, and the basiccriterion for completion of piling is when thepile is embedded into the bearing layer to adepth equivalent to the pile diameter (1 Dp) ormore.

Test piles are driven to confirm the degree ofworkability of the actual ground condition at thework site, adequacy of machines selected, and thestatus of torque generation. By comparing the status oftorque generation and the results of boring data, thetorque fluctuation which confirms arrival at the bearinglayer is determined.The number and location of test piles are determined tosuit the position of the boring exploration point and thescale of the number of piles. Some initial permanentpiles may be used as test piles in the vicinity of theboring exploration point.

B：Site circumferential weld

Piles are generally connected with welded joints.The backing ring should be that of a standard jointspecified by the Japanese Industrial Standard (JIS A5525).

Welding work

C：Management of the piling completion

●

Actual bearing layer level

●

flow for piling completion

1...When the actual level is closer to the expected level

Expected (design)bearing layer level

2...When the actual level is deeper than the expected level

3...When the actual level is shallower than the expected level

In the standard procedure, a pile is screwed to the design depth and piling is completed when the pile isembedded into the bearing layer to a depth of 1 Dp or more. But when there is a difference between thedepth of the bearing layer determined by a fluctuation of working torque and the depth of the bearing layerdetermined at the time of design or when the bearing layer is a very hard stratum, the piling can becompleted at a depth shallower or greater than the design depth.

The bearing layer is generally confirmed by the fluctuation of working torque for judging the bearing layerdetermined by the test pile, but if the bearing layer is shallower than expected, it may be difficult topenetrate the pile to the design depth. In such cases, piling is sometimes completed at a depthshallower than the design depth if it can be confirmed that the pile has penetrated the bearing layer to asufficient depth (1 Dp or more) and that torque has been generated.

If the bearing layer is too hard to drive a pile to a depth of 1 Dp or more, piling can be completed at anembedment depth of less than 1 Dp providing it can be confirmed that torque has been generated.