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

Load History of Cedar Foundation Pile in the Mietsu Naval Facility World
Heritage
Takaharu SHOGAKI
Professor, Civil and Environmental Engineering, National Defense Academy, Yokosuka, Japan
Email: shogaki@nda.ac.jp

Daishi OKUDA
Graduate students, Civil and Environmental Engineering, National Defense Academy, Yokosuka, Japan
Email: panappu237@gmail.com

ABSTRACTThe Mietsu Naval Facility (MNF) is a Dutch Western-style naval base constructed in 1858 by the Saga clan at Hayatsue
River 6 km north of the Ariake Sea. The MNF is divided into three sections: the shipbuilding/repair docks and metal
working section, the training grounds, and the small boat docks section (SBD). All elements have been maintained inlargely good condition. Furthermore, archaeological surveys have shown that underground structural remains in this site
have been preserved in good condition and have retained their positions. In 2015, the MNF was registered as one of aseries of sites that make up the World Heritage Sites of Japan’s Meiji Industrial Revolution. The SBD contains traces oflarge wooden buildings, and excavation of the remains commenced in January 2017.
As part of an engineering investigation of the remains, this study involved the measurement of the consolidation
properties of a sample obtained through tube sampling, the undrained shear strength cu obtained from cone penetration
tests for the vertical walls of the trench cut around the pile and changes in the natural water content wn around the cedar
foundation pile. The load history of the cedar foundation pile preserved in the SBD was examined using these measured
values to determine the building weight and how the pile was installed.
The changes in cu and wn measured in the area around the cedar foundation pile indicated that the cedar pile was driven
into the clay ground. The ultimate load was estimated to be 1.15 to 2.15 times the consolidation stress of the layer ofsoil under the pile. The total energy required to drive the pile to a penetration depth of 30 mm with a hammer of 500 N
in weight from a height of 2 m was calculated as 49.7 kN・ m, and 50 hammer blows were required to drive the pile to adepth of 1.5 m.
Key words: World Heritage, pile foundation, load history, ultimate load, total energy, Hasuike clay

used as a maritime academy from 1902 until 1933. During

1. Introduction
In the nineteenth century, Saga clan established athis time, no major changes were made to the groundWestern-style navy and built Western-style ships based on

surface; therefore, a number of remaining structures,

the Western naval knowledge and technologies that it had

which can provide insights into the nature of the MNF

acquired at the Tokugawa government’s Nagasaki Naval

when it was in operation, are well preserved underground.

Training Institute. The Mietsu Naval Facility (MNF)

Archaeological surveys and document reviews

provided the optimal location for developing suchcarried out since 2009 indicate that the Mietsu Naval

operations. The MNF is thought to have closed down after

Dock (MND) was the operation base for the Saga clan

the abolition of the feudal clans and the establishment ofnavy from 1859 to 1871. The investigations showed that

prefectures at the beginning of the Meiji era. The site wasthe construction of the Ryofu-maru, Japan’s second- 603 -

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

steamship, was completed at the MND throughexcavated ground surface (Shogaki et al., 2018). The

independent efforts of the Saga clan; and that at the end of

5-m-thick clay layer changes to sand at T.P. level -4.4 m.

the Edo period, it was the first place in Japan where
Western-style ships were repaired using a combination ofWestern and traditional Japanese technologies. In 2015
the MNF was registered as a world heritage site as part of
the group of sites named the World Heritage Sites ofJapan’s Meiji Industrial Revolution: Iron and Steel,Fig. 1 Layout of the foundation piles at the small boat docks
site

Shipbuilding and Coal Mining.
The small-boat docks section (SBD) of the MNF

The number of standard penetration test blows

contains traces of large wooden buildings, and excavation(N-value) in the clay layer ranged from 3 to 5 (Shogaki etof the remains commenced in January 2017. As part of anal., 2018).

engineering

investigation

of

the

remains,theThe cu values obtained in the CPT from theconsolidation properties of a clay sample were obtained

penetration resistance are plotted against the elevation E

through tube sampling. The undrained shear strength cuin Fig. 2 The clay at the test site is Hasuike clay. The cu

was derived from a cone penetration test of the verticalvalues at E = 1.5-1.8 m reached 25-50 kN/m2, caused bywalls of the trench cut around one of the piles and changes

the excavations down to about 2 m and the hardenedin the natural water content wn were measured around theground surface. The cu values at E = 0.48-1.58 m were incedar foundation pile. However, the loading history andthe range of 10-20 kN/m2. The horizontal continuity of

the installation method of the cedar foundation piles

the Hasuike clay at the SBD site is higher along the A

preserved in the SBD remained unclear.

piles (43 m) as shown in Fig. 1. At E = 0-0.3 m the CPT

In this paper, the deformation behavior around the

did not penetrate under the weight of two people (=1.08

foundation piles is examined based on the movement ofkN); this layer corresponds to the clay layer with shells

soil particles in a laboratory model of Kawasaki clay

observed at Bors. 6 and 7.

penetrated by a foundation pile. The experiment results

The layout of the CPTs around Bor. 6 and their

are compared with measurements of the changes of wn andresults are shown in Figs. 3 and 4, respectively. The

cu around the pile in the SBD to infer the installation

variation of the cu obtained from nineteen CPT tests

method of the cedar foundation piles preserved in the(A2-1 to A2-19) is smaller than that of Fig. 2 because theSBD.

former tests covered a smaller area and the cu values
gradually decreased with depth. The mean values 𝑐 u of

2. Soil properties of the small-boat docks section site
Fig. 1 shows the layout of the foundation piles
found during the excavation at the SBD. Piles A1–A11
are 1.5-m-long cedar piles stripped of bark with adiameter of 20 cm. Piles B1–B11 consist of groups ofthree pine piles 10 cm in diameter with the bark. Twobore samples were taken using a two-chambered
hydraulic piston sampler (45-mm) (Shoghaki and
Sakamoto, 2004) according to Japanese standards (JGS,
2015a) at boreholes #6 (Bor. 6) and #7 (Bor. 7), and threeportable cone penetration tests (PCPTs) according toJapanese standards (PCPT: JGS 2015b) were taken
between the cedar foundation piles. The SBD area
comprises a clay layer with 70%–80% shells at a depth

Fig. 2 Relationship between cu from PCPTs and elevation forof 1.4 m (Tokyo Pail (T.P.) level of -0.7 m) from the- 604 -

piles A1 to A12

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

depth (Dp) is 40 cm. The construction method of the pilesof line A can be inferred from these cu results, assumingthat the load history from the construction of thefoundation piles remains as the variable strength of thesoil around the foundation piles.

Fig. 3

Layout of the PCPT site (A2-1 to A2-19)

cu are 17 kN/m2 at E = 0.6 m and 19 kN/m2 at E = 1.5 m,
and the variation of cu is 7 kN/m2 unrelated to depth.
Photo 1.

Bottom end of cedar pile A1

Photo 2.

Group of three pine piles (B8)

Photo 3.

Bottom end the pine pile (B8)Fig. 4 Relationship between cu and elevation based on PCPTs
A2-1 to A2-19

3. Changes in the natural water content and strength
aof the soil around the pile
The bottom of the excavated cedar pile is cut off
horizontally (Photo 1). A group of three pine piles in the
B-line is shown in Photo 2. Each pile is about 2 m longand the bottom ends are cut at an angle of about 30°(Photo 3), indicating these were driven piles. Fig. 5
shows the layout of the site where the CPTs wereconducted at the trench cut around pile A11. The tests
were performed along five horizontal levels at the
excavated surface (Photo 4). The test results of the CPTs
for lines (a) to (f) on the southern wall of the trench are
shown in Figs. 6 (a) to (f), respectively. The penetration- 605 -

2.0

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

South wall (cm)
80

60

40

20

. 20
（1.74m）

West wall(cm)
40

60

80

100

A11杭
pile
A11

1.0

West wall

0.5
0Elevation. E (m)

1.5

100

A11

Fig. 5

Symbol記号凡例（+0.28m）

Trenchトレンチ
South wall

：a
：b
：c
：d
：e
：f

Layout of the PCPT and wn measurements around pile(a) At line (a) on the southern wall of the trench

A11(b) At line (b) on the southern wall of the trench
Photo 4.

PCPT site at the excavated vertical surface

cu decreases with increasing Dp along the CPTline(a), 2cm from the foundation pile (Fig. 6 (a)). This
indicates that the cu values are greatest close to thefoundation pile. A similar trend was observed for theplots of E = 33, 85 and 112 cm, 5-8 cm from thefoundation pile. However, along CPT line (e), 50 cm
from the foundation pile (Fig. 6 (e)) cu = 9-18 kN/m2 andis almost constant at for the different elevations. The wn(c) At line (c) on the southern wall of the trenchvalues obtained from the southern and western walls areplotted against the distance from the surface of pile A11(Ds) in Fig. 7 wn decreases by about 30% from Ds = 60
cm to Ds = 2 cm. This decreasing trend may reflect thedraining effect of the cedar piles and/or the dissipation of
the pore-water pressure caused by the movement of thesoil particles driven by the penetrating pile. The cu
behavior in Fig. 6 corresponds to the change of wn. Thisis supported by the visual assessment that the soils
around the piles were dense. Therefore, the cedar
foundation pile is considered to be a driven pile based on
the changes in cu and wn measured in the area around it.

- 606 -(d) At line (d) on the southern wall of the trenchProceedings of the First International Conference on Press-in Engineering 2018, Kochi

200
Water content, w(%)

Bor.6

: No.1 C-1: No.1 C-2: No.2 C-1: No.2 C-2'
: Remolded

100
74.6

160

0
1

(e) At line (e) on the southern wall of the trench

486

10
100
1000 2
Consolidation pressure, p(kN/m )10000(a) Borehole 6200: No.2-2 C-1: No.2-1 C-2: No.2-2 C-2: No.2-2 C-3: Remolded

Water content, w(%)

Bor.7

100
74.6

200

(f) At line (f) on the southern wall of the trench
Fig. 60
1

Relationship between cu and Dp around pile A11

599

10
100
1000
Consolidation pressure, p(kN/m 2)

10000(b) Borehole 7
Fig. 8 Relationship between wn and ppressure (σ’v0) of 41 kN/m2.
Fig. 9 shows a sketch of a basic structure that may
have stood over the piles of lines A and B. The lower
ends of the A-line piles are located 20 cm above the shelllayer and the B-line pillars penetrate 30 cm into the shelllayer. The wn value of the clay under the A-line piles is
74.6%, which is less than wn = 110%-140% for the clay
Fig. 7

not affected by the driven pile. The clay with wn = 74.6%

Relationship between wn and Ds around pile A11

is hard and could not be penetrated by the CPT. The main
4. Estimation of the driven load for the pile
The relationship between wn and the consolidation

reason for the decrease in wn is most likely the driven

pressure (σ’v) on the incremental loading oedometer test

the piles and the drainage effect of the piles. These load

(Japanese Standard Association, 1993) for the samples

histories equivalent to the wn of the clay below the A-line

obtained from the 45-mm core are shown in Figs. 8 (a)piles can be estimated as 160-486 kN/m2 (mean value ofand (b) for Bor. 6 and Bor. 7, respectively. The

323 kN/m2) and 200-599 kN/m2(mean value of 400

over-consolidation ratios (OCRs) of the samples obtained

kN/m2) from Figs. 8 (a) and (b) (Bors. 6 and 7),

from Bors. 6 and 7 are 1.1 and 1.3, respectively. These

respectively. These values were usedload of the piles, the weight of the building supported by

are normal values for normally consolidated clay
deposits, indicating that the clay layer was not affected

Ra = 1/3(6cuAp+Ns/3•Ls•ψ + qu/2•Lc•ψ)−Wp

by a load greater than that of the effective overburden- 607 -

(1)

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

Ns is the mean N-value obtained from a standard
penetration test for the pile in sand layer, Ls is the lengthof the pile surface in contact with the sandy soil (m), Lc is
the length of the pile surface in contact with the clayey
layer (m), qu is the unconfined compressive strength
under the clayey layer for the pile (kN/m²), provided thatqu ≤ 157 kN/m², cu is the undrained shear strength of theclayey layer (kN/m²), ψ is the circumference of the pile(m), Wp is the weight of the pile defined as the effective
weight minus the displaced effective soil weight (kN).
The weight of the wooden building is estimated at 1.962
kN/m2 based on the first floor of a wooden structure froma plan of the mid-nineteenth century.
Table 1 shows the values of qu, cu, Wp and thedimensions used to calculate Ra, and the Ra values I
obtained from Bors. 6 and 7, respectively. cu (cone) is the cu
obtained from the PCPT and qu(I)/2 is the estimated insitu cu obtained using the Shogaki method (Shogaki,2006). Table 2 shows the estimated results for I, II and
Fig. 9Sketch of a basic building assumed to have been

III, where III is the allowable stress for a pile, in kN/m²

constructed on top of A- and B-line pile

Equation (1) describes the long-term vertical allowablebearing capacity of a pile; thus, II represents the ultimate

to estimate the set-up of the driven pile and the load

bearing

capacityas

3Ra/Ap.

The

value

III

=

2

288.387kN/m is the allowable vertical stress for a pileincluding the building in next section.

and the long-term vertical allowable bearing capacity of
5. Ultimate bearing capacity, load history and driving

the pile weight of a one-story wooden house (1.962

energy of the piles

kN/m2 (in kN), is estimated from Eq. (1) established by

The load history estimated from Fig. 8 is calculated

the Architecture Society of Japan (Japan Architectural

as the sum of the weight of the building and theSociety, 1961). The ratio of (II+III) / I is 2.23–3.13 forallowable bearing capacity (Ra) of the piles. Ra, thequ(I)/2 and 1.55-1.82 for qu/2. The ratio II / I islong-term vertical allowable bearing capacity (Ra) of the

1.07-1.23 for cu (= qu/2) and 1.75-2.54 for cu (= qu(I)/2). If

pile (in kN), is estimated from Eq. (1) established by thethese ratios are considered as the safety factor for similar

Architecture Society of Japan (Japan Architectural

current construction methods. The ultimate bearing

Society, 1961), where Ap is the area of the pile tip (m2),capacity is estimated to be 1.15 to 2.15 times the

Table 1.

Long-term vertical allowable bearing capacity of a pile

Borehole
Undrained shear strength, c u(Ⅰ): R a （kN/m²） Maximum value（w n =74.6%）
Mean value(Ⅱ): 3R a/A p（kN/m²）

6
470
323
597.000(Ⅲ): Allowable stress of pile
qqqq（1.962kN/m² for one-storied)
Maximum value
Mean value
Ⅱ/Ⅰ(Maximum value)(Ⅱ+Ⅲ)/Ⅰ

7

6

q u/2

7

6

q u(I)/2560
400
642.000

470
323
1234.0007c u(cone)

560
400
1047.000

470323
606.000

560
400
515.000

288.387(1.962 kN/m² for one-storied)
3.310
4.816
1.230

2.846
4.935
1.070

- 608 -

6.971
10.143
2.540

5.634
9.768
1.750

3.418
4.973
1.250

2.494
4.324
0.860

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

Table 2.

Estimated value for load history of a pile

Borehole
Undrained shear strength, c u
R a (kN)z =0.2～0.8m
c u (kN/m²)
z =0.9～1.5m
A p (m²)
ψ (m)L c (m)W p (kN)
Pile diameter (m)(Ⅰ): R a from Bor.6 (kN/m²)(Ⅰ): R a from Bor.7 (kN/m²)(Ⅱ) : R a /A p（kN/m²）

Table 3.

6

7

6

7
6
7
q u(I)/2c u(cone)
48.81050.011102.861
99.05650.40643.81820.21322.47339.64129.58420.22516.96616.01516.17431.57331.363
16.53114.726
0.031
0.031
0.031
0.031
0.031
0.031
0.628
0.628
0.628
0.628
0.628
0.628
1.5
0.638
0.2
486 (Maximum value)
543 (Mean value)
599 (Maximum value)
1554.470 1592.716 3275.834 3154.638 1605.274 1395.464
q u/2

Driving energy of a pile

H (m)
1
2
3

Hammer weight W H (kN)
kgf
101
51
34

kN
0.995
0.497
0.332

Dropped height H (m)23
Driving energy (kN・m)
0.995
0.990
2.985
0.497
0.994
1.491
0.332
0.664
0.996
1

consolidation stress of the clay under the pile.

550-N hammer dropped from a 2-m height is calculated

The ultimate bearing capacity (Rd) of a pile based on
the Basic Architectural Structure Design Standards andas 49.7 kN•m; thus, 50 hammer blows would be required
to drive the pile to a depth of 1.5 m.

commentary (Japan Architectural Society, 1961) isestimated as
Rd = (0.6WH•H) / (S + 0.02)

6. Conclusions
The conclusions obtained in this study can be(2)summarized as follows.
1) The natural water content wn decreased by about 30%

in (t), where WH is the hammer weight (t), H is theat a distance of 2 cm from the pillar surface. This is

dropped height of the hammer (m), and S is the final

likely caused by the draining effect of the cedar pilepenetration length of the pile (m).

and/or the dissipation of the pore-water pressurecaused by movement of soil particles as a result ofTable 3 shows the relationship between H and WH
estimated for S = 0.015 m. For H = 2 m, WH for I ispile penetration.

calculated with 51 kgf. The driving energy of I at H = 1-3

2) The deformation around the pile caused by pileis also shown in Table 3. The driving energy of WH = 51

penetration increased within the range equal to the

kgf at H = 2 m is 0.994 kN・m. The total driving energy

pile diameter. This is likely due to the decreased

to drive the pile to a depth of 1.5 m is 99.4 kN・m,water content and increased shear strength caused byassuming S = 15 mm in all the cases; therefore, 100

increased pore-water pressure and dissipation.

impacts would be required to drive the pile into the clay3) The area influenced by the pile penetration as

ground to a depth of 1.5 m. It is possible to underestimate

measured on site was similar to the affected area in

S since qu in the soft clay layer is 40 kN/m2. If we assume

the model (adjusted to the model scale of 20:3.5) forfor pile driving, they can be used as design criteria S =clays with qu = 57 and 77 kN/m2. Thus, based on the

0.03 m, the total energy and number of impacts would bechanges in cu and wn measured around pile A11 and49.7 kN•m and 50, respectively. The total energy

the model test results, we conclude that the cedar

required to drive the pile to a depth of 30 mm with afoundation pile was driven into position.

- 609 -

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

4) The ultimate bearing capacity was estimated to be 1.15

Japanesestandards

forgeotechnicalandto 2.15 times the consolidation stress of the layer ofgeoenvironmental investigation methods –Standards

soil under the pile. The total energy required to driveand explanations-, 290-295. (in Japanese)the pile to a penetration depth of 30 mm with aJapanese Standard Association. 1993. Test method forhammer of 500 N in weight dropped from a 2-m

one-dimentional consolidation properties of soils,

height was calculated as 49.7 kN•m. Thus, 50

JIS A 1217-1990, 1-13. (in Japanese)

hammer blows would be required to drive the pile to

Shogaki, T, 2006. An improved method for estimatinga depth of 1.5 m.

in-situ undrained shear strength of natural deposits,
Soils and Foundations, Vol. 46, No. 2, pp. 1-13.

References
Japanese Architectural Society. 1961. Basic architectural

Shogaki, T. 2017. Mechanism of sample disturbancecaused by tube penetration (Model test on Toyoura

structure design standards and commentary. (inJapanese)sand), Soils and Foundations, 57 (3), 527-542.
Shogaki, T. and Sakamoto. R. 2004. The applicability ofJapanese Geotechnical Society. 2015a. Method fora small diameter sampler with a two-chamberedobtaining soil samples using thin-walled tube

hydraulic piston for Japanese clay deposits, Soils

sampler with fixed piston (JGS 1221-1995),

and Foundations, 44 (1), 115-126.

Standard of Japanese Geotechnical Society for Soil
Sampling-Standards

andExplanations-,

Shogaki, T., Okuda, D., Nakano, Y., and Suzuki, M. 2018.

1-7(English version)

Strength and deformation properties of Ariake clay
deposit in Mietsu Naval Facilities, The 53rd Annual

Japanese Geotechnical Society. 2015b. Method for
portable cone penetration test (JGS 1431-2003),- 610 -

Conference on Japanese Geotechnical Conference,
335-336. (in Japanese)