Volume 8, Issue 3

September 2023

Directors’ research and development activities

R & D activities on the structures constructed by the press-inmethod
Yukihiro Ishihara, Nanase Ogawa, Masashi Eguchi, Kazunori Toda
Scientific Research Section, GIKEN LTD.
Some of the IPA events in Kochi this July were held in the newly opened facility of GIKEN “RED HILL 1967” (GIKEN, 2023).
This facility is mainly composed of an exhibition area showing the real-scale “Implant™” structures constructed by thepress-in method and two innovative buildings of steel sheet piles, and provides a variety of information on a “seeing isbelieving” basis. This article will briefly introduce some examples of the researches on these structures, conducted by
the research team in GIKEN or by other researchers. Please note that it does not provide a comprehensive review ofrelated research on each structure.

1. Implant Bell Cap Bridge – a bridge on a hatted tubular pile constructed with special press-in pilingsystemThe “Implant Bell Cap Bridge” is a bridge utilizing the “hatted tubularpile” (Fig. 1) as its pier pile and securing the bridge function by settling
the deck panels on the hatted tubular piles via the T-shaped beams,constructed by a special press-in construction system (Fig. 2). The hatted
tubular pile consists of an open-ended tubular pile (a “pile part”) and abell-shaped cap (a “hat part”), with the hat part being connected to thepile part near the ground surface. This bridge can be constructed in asmall space within a short period, since (1) the construction system canbe positioned and move on the bridge and (2) the embedment depth ofthe pier pile can be smaller than the conventional tubular pile due to theeffect of the hat part. The construction procedure of the bridge is to (1)install the hatted tubular pile, (2) settle the T-shaped beam on the pierpile, (3) settle the deck panels on the T-shaped bars and (4) move theconstruction machine forward on the deck panels. The removal of thebridge can be conducted by following the reverse procedure.
The vertical and horizontal resistance of the hatted tubular pile wereinvestigated by the 1-g model tests and full-scale field tests (Ishihara etal., 2016).
In the full-scale field tests, the static vertical and horizontal load tests
were conducted on the tubular pile (with the outer diameter Do being
0.8 m) and the hatted tubular pile (with Do being 0.8 m and the outer
diameter of the hat part being 2.2 m). The hat part was rigidly connectedto the pile part. The embedment depths of the tubular pile and thehatted tubular pile were 4.4 m and 4.7 m respectively.
The vertical load displacement curves obtained in the field tests areshown in Fig. 3. The vertical capacity of the hatted tubular pile wasaround 1.7 times greater than that of the tubular pile, if the capacity wasdefined as the resistance at the base displacement of 1/10 of Do. One of
the mechanisms to increase the vertical capacity of the hatted tubular
pile was expected to be the increase in the soil stress beneath the hatted
part and the subsequent increase in the shaft resistance of the pile part.
This mechanism was investigated in the field test by comparing the axial
stresses of the pile part or the tubular pile at several levels, but was notclearly observed. The initial vertical stiffness (when the basedisplacement was smaller than 1/100 of Do) was comparable in thehatted tubular pile and the tubular pile. This was thought to be becausea certain displacement was necessary to achieve the fully plugged
condition of the hat part and the full mobilization of the strength of the9Fig. 1. Hatted tubular pileFig. 2. Press-in construction system
for the Implant Bell Cap Bridge

Fig. 3. Results of full-scale vertical load
tests (after Ishihara et al. (2016))

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September 2023

soil beneath the hat part.
The horizontal load displacement curves obtained in the field tests areshown in Fig. 4. The horizontal capacity, defined as the resistance when
the horizontal displacement of the pile at the ground surface level
reached 15 mm, of the hatted tubular pile was around 1.5 times greaterthan that of the tubular pile. The initial horizontal stiffness of the hatted
tubular pile was also greater than that of the tubular pile.

2. Confined Ground Seismic Damper – aseismic technology
using a pressed-in sheet pile wall with a closed shapeFig. 4. Results of full-scale horizontal load
tests (after Ishihara et al. (2016))

The “Confined Ground Seismic Damper” consists of a pressed-in sheet
pile wall with a closed shape and the ground confined by the wall. As
exemplified in Fig. 5, it can be used beneath the structure (Fig. 5a) or asa structural component of the whole structure (Fig. 5b). It is expected toreduce the displacement of the structure due to the liquefaction of theground, by preventing or mitigating (1) the sliding failure of the soil, (2)the deformation of the soil inside the wall, (3) the lateral movement ofthe liquefied soil, (4) the transmission of the excess pore water pressureand (5) the uneven settlement of the structure. It is also expected toprovide a seismic damping function, by taking advantage of its structural
flexibility in the liquefied ground.
As for the effectiveness for reducing the settlement and the inclination(a)of the structure due to liquefaction, Kato et al. (2014) carried out 1-g
model tests, centrifuge model tests and numerical analyses. The housemodels having the uneven load (Fig. 6) were used, with the sheet pilewall being connected to the spread foundation of the house. The ratio ofthe embedment length of the sheet pile wall to the thickness of theliquefiable layer (embedment ratio, zemb / Hliq) was varied. The results aresummarized in Fig. 7. When the embedment ratio was 1, the settlement(b)and the inclination of the house were reduced by 90 % and 80 %Fig. 5. Application examples of Confined
respectively, as compared with the house having no sheet pile wall. In
Ground Seismic Damper (GIKEN (2023))
addition, the settlement and the inclination were confirmed to bereduced even when the embedment ratio was smaller than 1.
Toda et al. (2022, 2023) and Haigh (2022) conducted a series of 1-g largescale model tests to investigate the vertical and horizontal resistance ofthe slab with a square sheet pile wall in a liquefiable ground. The tests
were conducted using a soil tank shown in Fig. 8, where the liquefactionof the ground (the reduction of the effective stress) is simulated by using
the seepage force generated by the water injection at the bottom of thesoil tank (Ogawa et al., 2018). The extent of liquefaction was judged by
the excess pore water ratio (ru). The static vertical and horizontal load
tests were conducted, with ru being controlled constant during the tests
either at 0, 0.3 or 0.6. Both the vertical and horizontal resistance wereFig. 6. House model used in the model
found to be smaller in the tests with larger ru values. If plotted against ru
test (after Kato et al. (2014))
as shown in Fig. 9, both the verticaland the horizontal capacity were
found to vary roughly linearly withru. These trends were consistent
with those found for the single
closed-ended
tubularpile(Willcocks, 2021). These findings
would be suggesting that theresistance of these structures in aliquefied ground could be estimatedfrom their resistance in a nonliquefied ground.
Haigh (2022) conducted centrifuge
Fig. 7. Experimental results on the effect of square sheet pile wall on reducing
tests and numerical analyses tosettlement and inclination of house due to liquefaction (Kato et al. (2014))
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Volume 8, Issue 3(a) Plan view(b) Side viewFig. 8. Large-scale test apparatus for liquefaction (Ogawa et al. (2018))
investigate the vertical andhorizontal resistance of thesame structure as was treatedin the above-mentioned largescale model tests, by applying a0.36 g seismic loading to themodel. She showed that acolumn of non-liquefied soil iscreated in and beneath thesheet pile wall a s shown in Fig.
10, and suggested that this will
be one of the mechanisms forthe structure to exhibit someresistance in a liquefied ground.

September 2023

Fig. 9. Horizontal capacity vs. ru(after Toda et al. (2023))(a) Slab only(b) Slab with sheet pile wallFig. 10. Results of numerical analysis (in kPa) (after Haigh (2023))

3. Preload Retaining Wall – a preloaded retaining wall consisting of steel sheet piles
The “Preload Retaining Wall” is a retaining steel sheet pile wall having an inclination angle and a bow shape. As shown inFig. 11, the construction procedure of this wall is to (1) install the sheet piles by the press-in method at a certain inclination
angle, (2) excavate one side of the wall, (3) apply a horizontal load (Preload) to the wall in its head, (4) fill the gap behind
the wall with a backfill material and (5) remove the Preload.
Gao (2014) and Ishihara et al. (2015) conducted 1-g model tests and field tests to compare the deformation of a normalwall (a retaining sheet pile wall having no inclination), a slanting wall (a retaining sheet pile wall having an inclination
angle of 5 degrees) and the Preload Retaining Wall having the same inclination angle with the slanting wall, when aFig. 11. Construction procedure of Preload Retaining Wall (Ishihara et al. (2015))
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backside surcharge was applied behind each wall. The results areillustratively summarized in Fig. 12. The horizontal displacement
caused by the surcharge of 20 kPa was smaller in the Preload
Retaining Wall than in the slanting wall, by 99 % at the wall head
and 74 % for the entire wall. The deformation pattern of thePreload Retaining Wall was different from that of the slantingwall. The maximum horizontal displacement was found near theexcavation bottom in the Preload Retaining Wall, while it was
found in the wall head in the slanting wall.
Ishihara et al. (2015) conducted numerical analyses to investigate
the mechanisms for the smaller deformation of the Preload
Retaining Wall confirmed in the field tests. They suggested basedon the analysis results that the possible mechanisms were (1) theenhanced stiffness of the soil in the excavation bottom as a resultof the loading history due to the Preload and (2) the improved
shear strength of the backside soil as a result of the increased
horizontal stress due to the elastic reaction of the steel sheet pilewall to the Preload, as summarized in Fig. 13.
A simple method to determine the amount of Preload wasproposed by focusing on the first of the above-mentioned twomechanisms (Ishihara et al., 2015). The appropriate amount ofPreload was assumed to correspond to the amount of thesurcharge to be experienced in service, in terms of the effect on
the soil in the excavation side. A conceptual two-dimensional
diagram was introduced as shown in Fig. 14, where the effect of
the Preload or the surcharge is expressed by the combination of
the horizontal load and the moment at and around the cross pointof the wall and the excavation bottom (in the vertical axis), while
the deformation of the soil in the excavation side is representedby the summation of the horizontal displacement of the wall
below the excavation bottom (in the horizontal axis).

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(a) Slanting wall(b) Preload Retaining Wall
Fig. 12. Field test results (Ishihara et al. (2015))

Fig. 13. Mechanisms of smaller deformation ofPreload Retaining Wall (Ishihara et al. (2015))

4. Implant Barrier – a protective wall consisting of strut
members (steel tubular piles) and wall members(concrete, metal, fiber etc.)
The “Implant Barrier” is a protective wall to be used for thedisaster prevention and mitigation, by reducing thehydrodynamic load of tsunamis, wave surges and so on. As shownin Fig. 15, it mainly consists of the strut members (steel tubularpiles) and wall members (made of concrete, metal or fiber). The
strut members are aligned with a certain distance with eachother, by being installed into the ground by the press-in method.
The wall members are made either of concrete, metal or fiber,
and are fixed to the strut members. The structural stability of theImplant Barrier is supposed to be assured by the strut members
and optionally by the sheet piles.
The wall members of the Implant Barrier (hereinafter called“Barrier”) can be porous sheets made of fiber. In this case, thereduction of the hydrodynamic load will be achieved by theenergy loss of the flow when it passes through the Barrier. Suzuki
et al. (2016) proposed a theoretical approach shown in Fig. 16 toconsider the energy loss of the flow by introducing the “lossfactor” (η), defined by η = f / λ2 where f is the friction factor andλ is the aperture ratio of the Barrier. They confirmed its validity
by conducting a series of two-dimensional hydraulic model tests
in the apparatus shown in Fig. 17, using a surge-type tsunami. As
shown in Fig. 18, the estimated and the measured tsunami loadon the Barrier (FB) and the flowrate of the tsunami after passing
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Fig. 14. Conceptual diagram for design of Implant
Preload Wall (Ishihara et al. (2015))

Fig. 15. Basic structure of Implant Barrier(after GIKEN (2023))

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Fig. 16. Theoretical approach for Implant Barrier(after Suzuki et al. (2016))

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Fig. 17. Experimental apparatus to simulate tsunami(after Ishihara et al. (2018))

Fig. 18. Experimental results in comparison with estimated results(after Suzuki et al. (2016))

Fig. 19. Shapes of wall members(after Toda et al. (2021))

the Barrier (Qt) were confirmed to agree with each other to some extent, if tsunami did not overflow the Barrier. A tradeoff relationship was confirmed between FB and Qt with regard to the loss factor η, where increasing the η value (i.e.
reducing the aperture ratio λ) led to greater FB and smaller Qt values. In addition, an experimental method to obtain η
was also introduced to cope with the difficulty in defining the λ value of the porous sheet made of fiber.
Toda et al. (2021) proposed a method to apply the theoretical approach of Suzuki et al. (2016) to the tsunami overflowing
the Barrier, by introducing the “equivalent aperture ratio” and the “equivalent loss factor”. Its validity was assessed bycomparing with the results of the hydraulic model tests conducted in the same apparatus. As a result, the water depthbehind the Barrier was well estimated, while the water depth in front of the Barrier and the tsunami load on the Barrier
were underestimated.
Toda et al. (2021) also investigated the effect of the shape of the wall members of the Barrier (flat or flexural, as shownin Fig. 19) on reducing the tsunami load behind the Barrier (FD), by using the porous sheet made of fiber for the wallmembers. They confirmed that the flexural shape was slightly more effective. For example, the Barrier with λ = 24 % wasconfirmed to reduce FD by 75 % if the wall members were flat and by 80% if they were flexural.

References
Gao, G. 2014. Comparing performance of different sheet pile walls. M.Eng. Thesis, University of Cambridge, 50p.
GIKEN. 2023. GIKEN RED HILL 1967, Akaoka Kochi, Japan. https://redhill1967.giken.com/en/
Haigh, A. 2022. Performance of Implant structures. M.Eng. Thesis, University of Cambridge, 52p.
Ishihara, Y., Ogawa, N., Okada, K. and Kitamura, A. 2015. Implant Preload Wall: a novel self-retaining wall with highperformance against backside surcharge. Press-in Engineering 2015, pp. 68-82.
Ishihara, Y., Ogawa, N., Okada, K., Inomata, K., Yamane, T. and Kitamura, A. 2016. Model test and full-scale field test on
vertical and horizontal resistance of hatted tubular pile. Proceedings of the Third International Conference Geotec
Hanoi 2016 - Geotechnics for Sustainable Infrastructure development, pp. 131-139.
Kato, I., Hamada, M., Higuchi, S., Kimura, H. and Kimura, Y. 2014. Effectiveness of the sheet pile wall against housesubsidence and tilting induced by liquefaction. Journal of Japan Association for Earthquake Engineering, Vol. 14, No.
4, pp. 35-49. (in Japanese)
Ogawa, N., Ishihara, Y., Ono, K. and Hamada, M. 2018. A large-scale model experiment on the effect of sheet pile wall on
reducing the damage of oil tank due to liquefaction. Proceedings of the First ICPE 2018, Kochi, pp. 193-202.
Suzuki, N., Ishihara, Y. and Isobe, M. 2016. Experimental study on influence of porosity and material of pile-type porous
tide barrier on its tsunami mitigation effect. Journal of Japan Society of Civil Engineers, Ser. B3 (Ocean Engineering),
Vol. 72, No. 2, pp. I-491-I-496. (in Japanese)
Toda, K., Mori, A., Ishihara, Y. and Suzuki, N. 2021. Experimental study on tsunami mitigation effect of pile-type porous13

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tide barrier. Proceedings of the Second International Conference on Press-in Engineering 2021, Kochi, pp. 444-453.
Toda, K., Ishihara, Y., Eguchi, M. and Mori, A. 2022. Experimental study on a foundation reinforced by square sheet pilewall. Japan Society of Civil Engineers 2021 Annual Meeting, 2p. (in Japanese)
Toda, K., Ishihara, Y., Eguchi, M. and Mori, A. 2023. Horizontal resistance of a slab reinforced by square sheet pile wall ina liquefied ground. Japan Society of Civil Engineers 2023 Annual Meeting, 2p. (in Japanese)
Willcocks, F. 2021. The vertical and horizontal performance of pressed-in tubular piles in liquefied ground. M.Eng. Thesis,
University of Cambridge, 52p.

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