STATIC ALTERNATING CYCLIC HORIZONTAL LOAD TESTS ON DRIVENSTEEL PIPE PILES OF FOUNDATIONS FOR HIGHWAY BRIDGES
Kouichi TOMISAWA, Civil Engineering Research Institute of Hokkaido, Japan
Satoshi NISHIMOTO, Civil Engineering Research Institute of Hokkaido, Japan
Hirofumi FUKUSHIMA, Civil Engineering Research Institute of Hokkaido, Japan
Eiji KOJIMA, Japan Pile Corporation, Japan
Tatsunori MATSUMOTO, Kanazawa University, Japan

Two bridges were constructed for extension work of Central Hokkaido
Connection Road in 2005 at two different sites. Pile group foundations were
employed for the foundations of abutments of the two bridges. In order toassess the performance of the constructed piles in the sites and to obtain
design parameters for design in future, static alternating cyclic horizontal load
test was carried out on one of the open-ended steel pipe piles constructed ateach site. The ground at one site was characterised as a thick deposit ofvolcanic soils, and the ground at the other site was characterised as a very
soft peat layer near the surface. In this paper the results of static alternating
cyclic horizontal load tests on the piles at the two sites are presented anddiscussed in detail.

INTRODUCTION

results in very low horizontal pile resistancewithin allowable horizontal displacement of thepile. Therefore, soil improvement is often
needed for peat soils in order to gain
appropriate pile performance until the design
horizontal load.

A highway route of 80 km called Central
Hokkaido Connection Road that connects
Chitose City and Otaru City is underconstruction. Several bridges are planned tobe constructed for the highway. Pile groups
were selected for foundations of the bridges,
since volcanic ash and peat soils distributeover the area of the highway route.
Foundations of highway bridges in Japan are
designed according to the Specifications for
Highway Bridges (Japan Road Association,2002). In the Specifications, although designof piles in clayey and sandy soils is prescribed,
the design of piles in volcanic ash and peatsoils is not definitely prescribed. Therefore,
design of piles in volcanic ash soils is madewith an assumption that volcanic ash soil iscategorised as sandy soil at present.

During construction of Central Hokkaido
Connection Road, horizontal load tests of steel
pipe piles were carried out at two sites, Kiusu
site and Shinotsu site, in 2005, to confirm
performance of the constructed piles and to
get appropriate design parameters for future
construction of foundation piles for the
highway bridges. Volcanic ash soil distributes
at Kiusu site, while peat exists at Shinotsu site.
The peat soil layer at Shinotsu site was
improved to increase its strength and stiffness.
In this paper, results of the static horizontal
load tests at the two sites are presented anddiscussion will be made on design of piles insuch particular soils.

Mechanical properties of volcanic ash are
different from those of sand due to highcrushability
andcorresponding
highcompressibility of volcanic ash (for examples,
Kitamura 1999, Miura and Yagi 2002). Hence,
attention will be paid in the application of theSpecifications to design piles in volcanic ash
soils.

DESIGN METHODS FORBRIDGE FOUNDATION

PILES

FOR

As mentioned earlier, pile foundations ofhighway brides in Japan are designed
according to the Specifications for Highway
Bridges. It may be appropriate here to
introduce the Specifications briefly for later
discussions.

Another problem in pile design for this highway
is the existence of peat soil. It has very highwater content and high compressibility that782

Vertical Bearing Capacity

such as rotation of the pile head and horizontal
load and moment given at the pile head aswell as boundary conditions at depth .

The vertical bearing capacity, Ru, of a pile iscalculated as

The value of kH is estimated byRu

qd A U

Lifi

(1)
kH

The first and the second terms of of Equation(1) are the toe capacity and the shaft friction
capacity, respectively. In Equation (1), qd is thetoe resistance per unit area, A and U are thecross-sectional area and the circumference
the pile, and Li and fi are the length and theshaft resistance per unit area of soil layer i.
The shaft resistance f is calculated from SPT
N-value or cohesion c of the soil as follows:fi

2N kPa (max. = 100 kPa) for sand

kH0

BH

(2)

E0

60N (Ld / D) kPa (max. = 1500 kPa)
(4)

0.3

E0 kPa/m

D/

(8)
(9)

2800N kPa

(10)

Figure 1 shows the profiles of soil layers and
SPT N-values at Kiusu site. The soil profile atthis site is characterised by thick deposits of
volcanic soils. SPT N-values are typically lessthan 7, except for gravel at depths from 17.5 m
to 21.2 m and volcanic soils at depths from27.5 m to 31 m. No definite bearing stratum
having N greater than 30 can be found to adepth of 32 m.

Two types of external loads, usual load andearthquake load, are considered in design.
Design pile capacity is estimated with safety
factors of 3 and 2 for usual load andearthquake load, respectively. If a pile load
test is carried out at the site, the safety factors
can be reduced to 2.5 and 1.7, respectively,
for usual and earthquake loads.

Two abutments were constructed here. Eachabutment was supported by 40 driven openended steel pipe piles. Pile design for thevertical load and the horizon load aresummarised in Tables 1 and 2, respectively.

Horizontal Resistance
The horizontal resistance of a pile is usually
determinedfromallowablehorizontal
displacement of the pile head. The use of
Equation (5) is prescribed in the Specifications.

The maximum values of design vertical loads
on piles were 1198 kN and 2267 kN for usualand earthquake loads, respectively. The
design pile capacities considering safety
factors were 3594 kN and 4534 kN without pileload test, and 2876 kN and 3627 kN with pileload test, for usual and earthquake loads.
Finally, piles were designed to have the pile
capacity of 4534 kN at the first stage of pile
design.

{exp( z ) (C1 cos z C2 sin z )z ) (C3 cos z C4 sin z )} /(2EI(7)

KIUSU SITE
Test Site and Test Pile

where Ld is embedment length of the pile toe
into a bearing stratum having N greater 30.

exp(

kPa/m

In the above equations, E0 is Young's modulus
of soil and is correction factor dependent on
method used in estimation of E0. For examples,= 4 if E0 is estimated from borehole lateralpressure test, and = 1 if E0 is estimated froman empirical equation (10).

c or 10N kPa (max. = 150 kPa) for clay
(3)
The toe resistance per unit area qd of driven
open-ended steel pipe pile is given byu

3/4

where kH0 and BH are given by the following
equations:

fi

qd

BH
0.3

kH0

3

)
(5)
In Equation (5), z is the distance from the pilehead and the characteristic length is given
by
1/ 4

kH D
(6)
4EI
where kH is the coefficient of horizontal
subgrade reaction, and D, E and I are thediameter, Young's modulus and the geometricmoment of inertia of the pile. Coefficients C1 to
C4 are determined from boundary conditions

The horizontal loads on a pile in the pile groupwere 187 kN and 555 kN, respectively, forusual and earthquake loads. The design
requirement was that the horizontal pile headdisplacement should not exceed 15 mm for thehorizontal load of 555 kN.

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The specifications of the pile were determined
as shown in Table 3 in order to satisfy theabove design requirements. The expected pile
capacity for vertical loading was 4880 kN andthe expected pile head displacement was 11.4mm for the design horizontal load of 555 kN.

Table 3 Specifications of steel pipe pile
Property
Value
Length (m)Embedment length (m)Outer diameter (mm)
Inner diameter (mm)2

SPT N-value
0
0

10

20

30

Cross-sectional area (cm )

40

50

0

Fill
Valconic ash
Organic silt

2Young's modulus (kN/m )2
Bending rigidity (kN m )Valconic ash

510Depth from G.L. (m)5Silty valconic ash

Pile capacity fromempirical equation (kN)10

In the design stage, it was assumed that thesoil to the depth of the characteristic length,= 3.8 m, is uniform having a coefficient ofhorizontal subgrade reaction kH of 14330
kPa/m, based on the results of borehole lateralpressure tests.

Gravel15

20

15

Valconic silt

20

As mentioned above, in the pile design, thevolcanic soils at the site were treated as sand,because of the lack of design specifications forvolcanic soils in the Specifications for Highway
Bridges. Therefore, the pile performance wasconfirmed by performing vertical andhorizontal load tests of one of the constructed
piles in the site.

Silty sand25

Sandy silt

25

Silty sand
Sandy silt

30

Silty sand
Sandy silt

30.0
29.2
800
770 (upper)
782 (lower)
369.2 (upper)
223.7 (lower)
82.06 ×10
5
5.87×10 (upper)
5
3.61×10 (lower)
4880(perfect friction pile)

30

Silty sandFigure 1 Profiles of soil layers and SPT Nvalues at Kiusu site

Test Method and Test Procedure

Table 1 Design of pile for vertical load at Kiusu
Usual
Design vertical loadon abutment (kN)
Number of piles
Design vertical loadon pile (kN)
Safety factor
Design pile capacity(kN)
Safety factor with pileload test
Design pile capacitywith pile load test(kN)

Dynamic vertical pile load tests were carriedout during pile driving and at 5 hours and one
week after the end of pile driving. Static
alternating cyclic horizontal load test was
carried out 13 days after the pile driving.
Horizontal loads were applied to the pile at 0.5
m above the ground surface by means of two
hydraulic jacks, and horizontal displacement
was measured by means of dial gauges, as
shown in Figure 2. Pairs of axial strains were
measured at 6 levels down the pile shaft toobtain bending moments down the pile axis.

Earthquake

43295

43558
40

978 to 1198

-89 to 2267

3

2

3594

4534

2.5

1.7

2995

3854

Table 2 Design of pile for horizontal load at Kiusu
Usual
Design total
horizontal load on theabutment, H (kN)
Design horizontal
load on a pile (kN)Horizontal pile headdisplacement at
design load (mm)Allowable horizontal
pile headdisplacement (mm)Earthquake

7495

22218

187

555

4.5

11.4
15

15

Figure 2 Horizontal load test set-up at Kiusu

784

Static horizontal load (kN)

Test Results(a) Vertical dynamic load test
The vertical bearing capacity of the pile fromthe dynamic pile load testing was 2100 kN at
the end of driving and 2900 kN at 5 hours after
the end of pile driving. The pile capacity fromthe dynamic load test at 7 days after the endof pile driving exceeded 3900 kN showing socalled 'set-up'. This pile capacity satisfies thedesign pile capacity of 3854 kN for the case of
conducting pile load test at the site. Hence, thedynamic load test was stopped at that time.

600
300
0
-300
-600
0

Figure 2

Loading procedure in horizontal load
test

600

Horizontal load (kN)

Alternating cyclic horizontal loads shown in
Figure 3 were applied to the pile.
Figure 4 shows the relationships between thehorizontal load H and the horizontal
displacement u. The residual displacement
was measured at full recovery of horizontal
load to 0 in each load step, and the elastic
displacement was obtained by subtracting theresidualdisplacement
from
the
total
displacement measured at the maximum loadin each loading step. The residual
displacement and the corresponding elastic
displacement at the maximum load in eachload step are also shown in Figure 4.

3

)

400
200
0
-200
-400

-40

-20

0

20

40

Horizontal displacement (mm)Figure4

Horizontal
load vs horizontal
displacement in Kiusu site

Bending strain ( )-600 -400 -200

Depth from G.L. (m))H /(2EI

Total
Residual
Elaslic-600

It should be noted that the boundary
conditions of the head of a pile in the pilegroup for the abutment and the single pile,which is tested, are totally different. Rotation of
the head of the former pile is constrained,
while the pile head moment of the single pile is
0 and the pile head rotation is free. The
horizontal displacement of a single pile iscalculated by the following equation (Japan
Road Association 2002):(1

100 150 200 250 300 350

Time (min)(b) Horizontal load test

u

50

(11)

The horizontal displacement at the design loadof 555 kN is calculated as 29.4 mm for thecoefficient of horizontal subgrade reaction kH= 14330 kPa/m that has been used in the pile
design. The measured total displacement at H
= 555 kN is almost equal to this predictedvalue. Consequently, it was confirmed that thepile satisfies the design requirement forhorizontal loading.

0

200 400 600

0
-2
-4
-6
-8

-10
-12
76 kN
182 kN
306 kN421 kN552 kN

Figure 5 shows the distributions of bendingstrains down the pile shaft measured at the
maximum load in each loading step. Here,bending strain is defined as the difference-75 kN-182 kN-300 kN-422 kN-541 kN

Figure 5 Distributions of bending strains down
the pile shaft

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between the axial strains measured at thefront and the back sides of the pile shaft
divided by 2. It can be seen from the figurethat the pile body remained in elastic state
during the load test and that the maximum
bending moment was generated at a depth ofabout 3 m below the ground surface
irrespective of load amplitude.

SPT N-value

3

kH (kN/m )Clayey silt

Depth from G.L. (m)Sandy silt

10

15

Clayey silt

15

20

Sandy silt

20

Sand

25

30

40

50

25

Silt

30

Silt
Sand

30

Silt

35

35

Organic soil

Silty gravel

40

Silt

45

Gravel

50

1.0 %

20

5

10

40

45
50

Figure 7 Profiles of soil layers and SPT Nvalues of the original ground at Shinotsu site

3.0% 4.0%

1.875%(15.0mm)-0.5331

60000

5

0

Organic clayey silt

12000080000

Sandy silt

10

Peat

In order to use the results of the horizontal
load test in future, kH was back-calculated fromthe measured horizontal load versus total
horizontal displacement, and plotted against
thenormalised
horizontal
pile
head
displacement u/D in Figure 6. It can be seenthat the kH from back-analysis decreases
exponentially with increasing u/D, and that thevalue of kH = 14330 kPa/m that was used in
the pile design corresponds to u/D = 3 % (u =24 mm).

10000000y = 26503.63 x

20000

11500
6000

5500

3

40000

Design value=14330 kN/m

20000
θ

0
0
1
2
3
4
5
Normalised displacement, u/D (%)

2
20000

45

Figure 6 Values of kH from back-analysis
SHINOTSU SITE

SPP
d = 800 mm
L = 40 m

8000

Figure 7 shows the profiles of soil layers and
SPT N-values. A very soft peat exists to adepth of 5 m. Below the peat, very soft soils of
clayey silt and organic clayey silt exist to adepth of 19 m, of which N-values are very low
from 1 to 2. Soils having N-values from 10 to
30 exist from a depth of 21 m to 36 m. Below adepth of 42 m, gravel having N-values greaterthan 50 exists. The gravel layer was selected
as the bearing stratum for the piles.

19000

Test Site and Test Pile

5500

The purpose of the load test at Shinotsu site
was similar to that at Kiusu site, i.e.
confirmation of the pile design, except for thatsoil improvements were conducted for the peatsoil at Shinotsu site.

Dry Deep Mixing
with Cement

Vacuum Consolidation Method+ Fill5500

Footing

Figure 8 Soil improvements around abutment
and piles

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Table 4

The soil around the piles was improved to adepth of 20 m before construction of piles asshown in Figure 8. Combination of two
methods of soil improvement was employed.
One of them was vacuum consolidation
method with fill on the ground surface. The
height of the fill was 10 m (surcharge of 190kPa). The other method was dry deep mixing
with cement. It was assumed that SPT Nvalues to a depth of 20 m increases to 7 times
the original N-values. Pile design was carriedout based on this assumption.

Design of pile for vertical load at
Shinotsu site
Usual

Design vertical loadon abutment (kN)
Number of piles
Design vertical loadon pile (kN)
Safety factor
Design pile
capacity (kN)
Safety factor withpile load test
Design pile
capacity with pileload test (kN)

Earthquake

16665

14623
12

1058
1718

to

-232 to 2669

3

2

5154

5334

2.5

1.7

4295

4537

Tables 4 and 5 summarises the pile design
against vertical and horizontal loads,
respectively. The coefficient of subgrade
reaction kH = 18485 kPa/m was used to the= 5 m in the pile design
characteristic depth
for horizontal load, considering the increased
N-values by the soil improvements. The valueof E0 was evaluated by means of Equation(10) using increased N-value expected in the
improved soil, because borehole lateralpressure test was not carried out for the
improved soil.

Table 5 Design of pile for horizontal load at
Shinotsu site
Usual
Design total
horizontal load on theabutment, H (kN)
Design horizontal
load on pile (kN)Horizontal pile headdisplacement at
design load (mm)Allowable horizontal
pile headdisplacement (mm)Earthquake

3140

7480

262

623

7.2

13.2

15

15

It is interesting to note that 21 piles (3 × 7
piles) were required from the pile design
without soil improvement. The required
number of piles was decreased to 12 piles (3 ×4 piles) by conducting soil improvement prior
to pile construction.

Table 6 Specifications of pile in Shinotsu site
Property
Value
Length (m)Embedment length (m)Outer diameter (mm)
Inner diameter (mm)

44.0
43.2
800
776 (upper)
782 (lower)
2
Cross-sectional area (cm )297.1 (upper)
223.7 (lower)
2
8Young's modulus (kN/m )2.06×102
5
Bending rigidity (kN m )4.76×10 (upper)
5
3.61×10 (lower)
Pile capacity of the6199
pile from empirical(end capacity = 2006 kN)
equation (kN)(shaft capacity = 4133 kN)

Test Method and Test Procedure
Vertical pile load test was not carried out at
Shinotsu site, because the pile toe was seatedon the very hard gravel layer.
Three piles alone were constructed out of 12
piles required from the pile design. Alternating
cyclic horizontal load test was carried out on
one of the constructed piles, in order toexamine the validity of the pile design. It was
intended to change the design of piles, if theresults of the horizontal load test did notsatisfy the design requirements.
Loading method and measurements of signals
were the same as those at Kiusu site. The setup for the horizontal load test at Shinotsu site
is shown in Figure 9.
Test Results
Figure 8 shows the relationships between thehorizontal load, H, and the horizontal
displacement, u. The residual displacement
and the corresponding elastic displacement at
the maximum load in each loading step arealso shown in Figure 8.

Figure 9 Load test set-up at Shinotsu site

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400
Total
Residual
Elastic

300

Horizontal load (kN)

It can be seen from Figure 8 that the responseof the total horizontal displacement is almost
equal to the elastic response.

200

For the horizontal load test on the single pile inwhich the moment at the pile head was 0, thepredicted horizontal displacement at the pilehead was 12.3 mm at horizontal load H = 262
kN (design usual load) and was 29.3 mm at H
= 623 kN (design earthquake load). The
measured horizontal displacement was 11 mm
at H = 262 kN, which satisfied the design
requirement. The load test was stopped athorizontal load of 322 kN because the pile
displacement exceeded 15 mm at this load
and the tested pile was used as actual
foundation pile for the abutment.

100
0
-100
-200
-300
-400
-25 -20 -15 -10 -5 0 5 10 15 20 25

Horizontal displacement(mm)Figure 10 Horizontal
load vs horizontal
displacement in Shinotsu site

It may be reasonable to apply the test results
until the horizontal load of 623 kN, because
the bending strains down the pile axis at H =322 kN still had enough margin to the bending
failure of the pile (Figure 9). Hence, it can besaid that the design requirements for the pilein the pile group, of which rotation at the pilehead is constrained, for the abutment shown in
Table 5 were confirmed from the horizontal
load test on the single pile.

Bending strain ( )
-500

-250

0

250

500

Depth from G.L. (m)

0
-2
-4

In order to use the results of the horizontal
load test in future, kH was back-calculated fromthe measured horizontal load versus total
horizontal displacement and plotted against
thenormalised
horizontal
pile
head
displacement u/D in Figure 10 in the same
way as at Kiusu site (Figure 5). It can be seenthat the kH from back-analysis decreases
exponentially with increasing u/D, and that thevalue of kH = 18485 kPa/m that was used in
the pile design corresponds to u/D = 2 % (u =16 mm).

-6
-8

-10
-12
39 kN
-39 kN
118 kN-119 kN
201 kN-200 kN
284 kN-278 kN
322 kN-318 kN
Figure 11 Distributions of bending strains
down the pile shaft

It is interesting to mention that total cost of thebridge foundation at Shinotsu site wasdecreased by 20 %, compared with theoriginal design stage in which soil
improvement was not employed.

4000001.0%

3500001.875%(15.0mm)3

KH (kN/m )300000250000

CONCLUSIONS-0.7497y = 28176.19 x

In this paper, the results of alternating cyclic
horizontal load tests on driven open-ended
steel pipe piles constructed for foundations ofbridge abutments at two different construction
sites on the route of the Central Hokkaido
Connection Road, Japan, have beenpresented and discussed. Applicability of thecurrent Specifications for Highway Bridges thatare widely used in Japan to volcanic soils andimproved soils was also discussed, based on
the results of the horizontal load tests.

200000150000100000Design value = 18485 kN/m

3

50000
0
0.0

0.5

1.0

1.5

2.0

2.5

Nomarlised displacement, u/d (%)
Figure 12 Back-figured values of kH

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It was confirmed from the load tests that thepiles at the sites satisfy the design
requirements.
It was also found that the design soil
parameters for sand in the current
Specifications can be applied to volcanic soils
which distribute widely in Hokkaido, and thatthe design soil parameters estimatedempirically from SPT N-value can be applied
to improved soils with enough safety margin.
The design soil parameters in the current
Specifications can accommodate horizontal
pile displacements of more than 2 % of pile
diameter, although the allowable horizontal
displacement is specified as 1 % of pile
diameter or 15 mm. Pile design in which morehorizontal pile displacement is allowed could
be possible using the design soil parametersin the current Specifications, if the design
requirements from the superstructure permit it.
The authors are planning to carry out otherpile load tests to gather more information on
pile design parameters, in order to improve thecurrent pile design towards the framework of
the performance based design or the limit
state design.
REFERENCES
Japan Road Association, 2002. Specificationsfor Highway Bridges Part IV Substructures (inJapanese).
Kitamura, R., 2000. Topics on Crushable Soiland Crushable Ground in GeotechnicalEngineering, Tsuchi-to-Kiso, Vol.48, No.10,
Japanese Geotechnical Society, pp. 3-6 (inJapanese).
Miura, S. and Yagi, K., 2002. Mechanicalbehaviour and particle crushing of volcanic
coarse grained soil in Japan, Proceedings ofConferenceonCharacterization
andEngineering Properties of Natural Soil,
Singapore, pp.1169-1204.

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