Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

Bearing Capacity Recovery Rate of Square Steel Tubular Pipe Piles Based onLoading Test Results
Noriyuki KAWABATA
Director, Nippon Steel & Sumikin Metal Products Co., Ltd. Civil Engineering Div. Tokyo, Japan

Shinji NISHIMURAManager, Nippon Steel & Sumikin Metal Products Co., Ltd. Civil Engineering Div, Tokyo, Japan

Yutaka KUBO
CEO, System Keisoku Co., Ltd, Head Office, Tokyo, Japan

Yukichi KANEHIRA
General Manager, System Keisoku Co., Ltd, Head Office, Tokyo, JapanABSTRACTSeveral vertical loading tests were performed to establish the bearing capacity design formula of the square steel tubepile. At the same time, the relations between the bearing capacity of each pile and the final press-in force of each pile
construction were measured. The set-up rate which is determined by the ratio of the bearing capacity and the final
press-in force were calculated. The average set-up rate of 8 test piles is obtained around 2.3 both for the sandy groundand the clayey ground. Also the minimum value of the set-up rate is around 1.6 both for sandy and clayey ground. Theminimum set-up rate of 1.6 is applied to the press-in construction control method to ensure each pile bearing capacity
performance.
Keywords: Steel pipe pile, Loading tests, Bearing capacity, Set-up rate, Construction control method

1.1. Introduction

1. Outline of this paper
This paper represents the bearing capacity design

In Japan there are several types of steel piles such as

formula and the press-in piling construction control

H-shape steel piles, round pipe steel piles, steel-concrete

method of a newly developed square tubular steel pilecomposite piles, and screw type steel piles and so on.

called Kakuske-pile.

Square tubular steel pipes have not been applied toFirst we introduce the outline of Kakuske-pile andfoundation piles although some square precast concrete

explain the several loading tests results in order topiles

have

been

usedforbuilding

foundations.

establish the design bearing capacity formula of

Kakuske-pile which is made of square tubular steel pipe

Kakuske-pile.

by press-in piling method was developed recently.

Secondly, the bearing capacity recovery rate after

This paper describes the design bearing capacity

piling construction date will be discussed from aformulation of Kakuske-pile and its construction control

viewpoint of the piling construction control.

methods. The set-up rate which is defined by the ratio

Finally, DEM trial simulation will be applied to

between the ultimate bearing capacity and the final press

Kakuske –pile press-in construction procedure. As DEM

in resistance at the end of construction will be discussed

modeling analysis for piles has not yet been a fully

based on the loading tests results.

developed technique, the calculation results may not give
us enough information to explain the set-up phenomena.

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Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

2. Loading tests of Kakuske-piles
2.1. Test piles
To establish the design bearing capacity formula of thesquare tubular steel piles by press-in piling construction,
8 verticalloading tests have been performed indifferent construction sites. The test pile properties areshown in Table 1 and Table 2. The pile toe ofKakuske-pile is closed ended by steel flat plate shown inFig. 1, Fig. 2 is the press-in piling construction site forhouses.

CrossWall
Depth ofSoil property N-value
thickness section area pile toe
at pile toe
at pile toe
2(mm)
(m)
(mm )
Clayey fine3.2
100
1511.9sand
Clayey fine
2.3
156
5.8
6.5
sand
Clayey fine
1.6
25
5.5
6
sand

Site

S-3

KR

100

S-4

KR

125

S-5

MK50

S-6

BD

125

3.2

156

8.73

Fine sand

3.4

S-7

NB

100

2.3

100

6.3

Clayey gravel

29.9(mm)Table 2.
NO

Site

Width(mm)Fig. 3 SPT results of Loading test site KRN value

Loading test piles on clayey groundKR50

1.6254

Clay

1.6

C-4

MK125

3.2

156

7.65Clay

5.6

C-5

NB

125

2.3

156

4.3

Clay

1.4

Fig. 1 Pile Tip of Kakuske-pile

C-405Clayey fine sandCrossWall
Depth ofSoil property N-value
thickness section area pile toe
at pile toe
at pile toe
2(mm)
(m)
(mm )

C-3

S-50 10 20 30 40 50

Depth (m)

NO

5.5m

WidthLoading test piles on sandy ground

7.65m

Table 1.

Clay

< Site MK >10Fig. 4

SPT results of Loading test site MK

Fig. 2 Press-in pile driver

2.2. Ground condition
Loading tests sites’ ground conditions are shown inFig. 3 to Fig. 6. 8 loading tests of Kakuske-piles areperformed in 4 test sites. The lengths of each test pile isrepresented next to the boring logs.

- 86 -Fig. 5

SPT results of Loading test site BDProceedings of the First International Conference on Press-in Engineering 2018, Kochi

Where,
P t: Axial force transferred to the pile tip
St : Pile toe settlement
B: Width of square pipe pile
N : Averaged SPT –N value at the pile toe:

Normalized P-S relations at the pile tips are plotted inFig. 8 for sandy ground tests, Fig. 9 for clayey ground.
The ultimate bearing capacity equation

for the pile tip

is formulated as below.

Ra  q p  Ap 3 N  Ap(3)Ra : Allowable design capacity at pile toekN

qp : Pile tip capacity ofkN/m2

allowable base

Ap : Pile tip effective area in m2
Fig. 6

N :Averaged N value around the pile tip

SPT results of Loading test site NB

 :Pile bearing capcity factor to N value
After Fig. 8 and Fig. 9 the bearing capacity factor of2.3. Test pile press in construction
Test piles of Kakuske-pile are pressed into the groundpile tip in Eq. (3) can be determined as 410 for sandy

by ordinary piling machines which are equipped withstratum and 450 for clayey bearing stratum as minimum

100-200kN hydraulic jacks. Fig. 5 is a photograph of avalue.

construction scene at a loading test site.
Uni t r esi st ance / N-val ue ( kN/m2)( Sandy)

Kakuske –pile driver

Fig.7

2000

S-6
1500

1000

S-4
500

S-30
0. 00

3.1. Load – Settlement Relations
Vertical static loading tests are performed according toultimate bearing capacity of pile toe is determined bymeasured axial force by strain gauges corresponding to
the settlement of 10% equivalent diameter D of the piles.
D can be calculated by D=2B/ Observed P-S relations are normalized by the following
calculations.

S

(1)

NB

2St
0.1  B 2

Uni t r esi st ance / N-val ue ( kN/m2)

Fig. 8the Japanese pile loading test standard(JGS,2012). ThePt

0. 02

0. 04

0. 06

0. 08

0. 10

0. 12

Nor mal i zed t oe di spl acement ( 1/D)

3. Loading tests results of Kakuske-piles

P

S-5

S-7( Cl ayey)

2000

1500

C-4

1000

C-3
C-5500

0
0. 00

(2)
Fig. 9- 87 -Normalized P-S curves of sandy ground

0. 02

0. 04

0. 06

0. 08

0. 10

Nor mal i zed t oe di spl acement ( 1/D)

Normalized P-S curves of clayey ground0. 12

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

3.2 Set-up rate between Bearing Capacity and the300

Ultimate capacity at pile top (kN)final press-in resistanceIn Table 3 and Table 4, the set-up rate which indicatesthe recovery rate of the bearing capacity after pile
installation as defined by Eq. (4).

SUR RuREOD(4)SUR: Set-up rate

Ru

: Ultimate bearing capacity of pile top (kN)

ave:2.3
200

min:1.5
100

00

20

40

60

80

100

120

140

Pressing resistance at E.O.D.(kN)

REOD : Final press in resistance at EOD (kN)In Table 3 and Table 4 press-in resistance at EOD isFig. 10 Set-up Rate relations of sandy groundmeasured by the hydraulic pressure gauge. Also, SLT
denotes the static loading test.
Ultimate capacity at pile top (kN)

200

From Fig.10 and Fig.11 the average set up rate forsandy ground was 2.3 and the minimum value of themwas 1.59. Also the average set-up rate for clayey groundwas 2.18 and the minimum value of them was 1.63.
Bearing capacity recovery rate of each pile withdays after driving are plotted in Fig. 12. There seems tobe quite small correlations between them.
The set-up rate must have some tendency with theave:2.18150

min:1.63100

50

0duration days,permeability of soils, and the pile diameter.

0In Fig. 13 the set-up rate is plotted to the days/D ,in the4060

80

100120140

Fig. 11 Set-up Rate relations of clayey groundsame manner as proposed by Randolph & Wroth(1979).

Table 3.

20

Pressing resistance at E.O.D. (kN)2loading test summary of sandy ground

Sa ndy s oi l
WallToe
Equivalen
Widtht diameter thickness depth
(mm)
(mm)
(mm)
(m)

Soil property

Press-in

S-3

100

113

3.2

15.00

Clayey fine sand

56.6

220.6

3.90

2015/5/26 2015/6/25

30

49.2

11.9

413

S-4
S-5
S-6

125
5012514156141

2.3
1.6
3.2

5.80
5.50
8.73

Clayey fine sandFine sand

51
20.1
94.7

108
47.4
150.3

2.12
2.36
1.59

2015/5/25 2015/9/25
2015/5/29 2015/6/24
2015/5/27 2015/6/30

12326
34

64.2
8.5
89.7

6.5
6.0
3.4

632
565
1674

S-7

100113

2.3

6.30

Clayey gravel

98

165.8

1.69

2015/6/4 2015/6/10

6125.629.9

420

Clayey fine sandUltimateavemin

Table 4.

Aging

resistance at capacity of Set up rate
E.O.D.(kN)
SLT(kN)

Instration date

SLT date

Toetime(days)

N-value

resistance at pile(kN)toe

α

2.33
1.59

loading test summary of clayey groundCl a y ey s oi lWidth(mm)Equivalen

WallToet diameter thickness depth(mm)
(mm)
(m)

Press-inSoil property

Ultimate

Aging

resistance at capacity of Set up rate
E.O.D.(kN)

Instration date

SLT date

SLT(kN)Toe

time

N-value

resistance at pile(days)

(kN)

αtoe

C-3

50

56

1.6

4.00

Sandy clay

5.1

15.7

3.08

2015/5/25 2015/6/26

32

3.1

1.6

749

C-4125141

3.2

7.65

Clay95.5

174.4

1.83

2015/5/29 2015/6/23

25

121.5

5.61389C-5

125141

2.3

4.30

Clay

28.2

46.1

1.63

2015/6/4

5

9.9

1.4

451

ave
min- 88 -

2.18
1.63

2015/6/9

Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

10m2/year. Fujita&Ueda(1971) summarized many static

4.5

loading test results from a viewpoint of theSet up rate at pile top

4

set-up rate,

and formulated the bearing capacity recovery rate as in

3.5

Eq. (5)., and the maximum set-up limited by 2.0.

32.5

  501  0.5ogT 2
1.5(5)

β：Bearing capacity recovery rate

1(%)

T : Duration time after pile driving until SLT (days)

0.5

3.3 Press-in piling construction control method for

00

20

40

60

80

100120Kakuske –pile
By considering the static loading tests and the set-up

140

Time（days）

phenomena, we understand that the press-in pilingFig. 12 Set-up rate to aging days

resistance at EOD is strongly related to the bearing
capacity after aging. After Fig. 13 and other test results,

4.5

reliable set-up rate is around 2 to 3.

Set up rate at pile top

4The

3.5

most advantageofthepress-in piling3

construction method is that the simple and direct

2.5

measurement of the final resistance of EOD of each pile .

2

That is, Kakuske-piles are surely installed by observing

1.5

their capacity at EOD. And multiplying the SURc to the1

final press-in resistance, we could ensure the long-term

0.5

capacity of the pile. Here, we choose 2.5 as SURc for a0
10.0

100.0

1000.010000.0

100000.0

construction control method.

Time（days/D^2）

RudSURc(5)

Rud  3  Ra(6)REOD Fig. 13 Set-up rate to aging days/D2

REOD :

Final press in resistance at pile top at EOD

Rud:Design ultimate bearing capacity at

Ra: Allowable bearing capacity at pile top

pile top

SURｃ :Construction control set up rate (=2.5)
4. DEM simulation of pile press-in construction.
Recently DEM is considered to be effective method
to understand the soil pile interaction problem such as piledriving. Here we tried to see how the press-in resistancevaries with press-in velocity and the soil void ratio.
Model piles dimensions are shown in Table 5, DEMFig. 14 Pile bearing capacity recovery rate with days

modeling factors such as particle elastic modulus, friction
By Fig. 13 we understand that the slightly better
correlation between the set-up rate and the characteristiccoefficient, dumping factor and so on are set after
H.Kuwabara et al.,(2002).

days. According to Randolph &Wroth, the pile set-up
phenomenon can be calculated by the consolidation
theory . They plotted the bearing capacity recovery rate
as in Fig. 14 by using the consolidation coefficient of- 89 -Table 5.

DEM press in piling model dimensions

Pile width Soil model width Dia. of perticle penetration depth
125mm
1250mm
6.25mm
1000mmProceedings of the First International Conference on Press-in Engineering 2018, Kochi

Soil particle

square pipe pile

Pile width 125mm

Fig. 17 Penetration resistance with displacement

Fig. 15

Configuration of DEM simulation model

The configuration of the simulation pile and particle
ground is shown in Fig. 15. As the soil was modeled by
6mm diameter, the pile tip is contacted by 20 particles.
Press-in penetration analyses were done by threedifferent conditions as in Table 6 by opensource DEM

CASE-1

code called LIGGGHTS,2011(Kloss et al.,2012).
Table 6.
casecase-1
case-2case-3Fig. 18

DEM press in analysis conditions

particle size
6.25mm
6.25mm
6.25mm&3.12mm

CASE-2

CASE-3DEM stress distribution around tip at EOD

5. Concluding & remarks
1) Bearing capacity design formula of square steelpress in velocity
comment
1.5m/minquick pressing
0.5m/minslow pressing
1.5m/mindense sandtubular pile was developed, by several SLT results.
2) Kakuske-pile press in piling control method wasproposed by the set-up consideration based onFig. 16 and Fig. 17 represent the relations between
press in resistance and penetration length. It is clear thatthe penetration velocity does not have much impact toconsolidation process.
3) DEM analysis applied to the press in piling to see thethe resistance, i.e. bearing capacity. On the other hand,the particle arrangement has affected to the resistancemuch. Fig. 18 shows the stress distribution around thevelocity affection to the resistance.
References
JGS 1811-2002. Method for Static Axial Compressive

pile toe. Slightly larger stress concentration was observed

Load Test of Single Pilesin case 3 after press-in piling, after press in piling.

Randolph,M.F. and Wroth,C.P. 1979. An analyticalsolution for the consolidation around a driven pile,
Int.J.Num.and Anal.Methods in Geomech., 3.
Fujita,K.&Ueda,K. 1971. Pile Bearing Capacity andDuration days after Driving, Annual research reportof Hazama Corporation.
Kuwabara,H., Aso,T., and Hironaka,M. 2002. Pile
Driving

Analysis

Using

Distinct

ElementMethod,Yamaguchi Univ. Research Report.
Kloss,C.,Goniva,C.,Hager,A.,Amberger,S.and2012.
Fig. 16 Penetration resistance with displacement

Models,Algorithms

opensource

DEMandandPirker,S.

Varidation

Prog.inComp.Fluid Dynamics,Vol. 12, Nos. 2/3.

- 90 -for

CFD-DEM,