Volume 9, Issue 3

September 2024

Special Contribution
Rapid Load Test on a Gyropress Steel Pipe Pile for Design Purpose
Tatsunori MatsumotoEmeritus Professor
Kanazawa University, Kanazawa, Japan
Reiki Bridge, an old bridge in Gunma Prefecture, Japan, was rebuilt in 2022. Steel pipe piles (SPPs) constructed using theGyropress Method were used for the pile foundations of the abutments of the new bridge. The piles were designed
preliminarily based on the empirical equations specified in Guidelines for design and construction of Gyropress steel pipepiles retaining walls. However, as the number of applications of Gyropress pile is not enough so far, the Hybridnamic rapid
load test was carried out on one of the constructed piles for the purpose of pile design.
Keywords: Gyropsess pile, design, load-displacement relation, rapid load test, case study
1. Introduction
Reiki Bridge crossing Name-kawa River in Gunma Prefecture, Japan was replaced by a new bridge in 2022 [1]. The old
Reiki Bridge (Fig. 1a), a two-span rolled steel beams and reinforced concrete slab bridge, had a span length of 28.09 m
and a width of 3.7 m. The width of the new bridge (Fig. 1b), a single-span simple beam composite floor bridge with aspan length of 26.90 m, was widened to 7.5 m to accommodate increased traffic. The old bridge's pier foundation wasremoved, making the river's flow smooth and mitigating the risk of floods.
Steel pipe piles (SPPs) were adopted for the foundations of the abutments of the new bridge. Because of narrow site
conditions, limited access (as shown in Fig. 1a and 1b), mitigation of noise and vibration, and shortening of theconstruction period, Gyropress Method (Rotary Cutting Press-in Method) was employed to construct the SPPs. In theGyropress Method, an open-ended steel pipe pile with cutting bits at the pile tip is pressed into the ground with rotation
as shown in Fig. 2. The piles were designed preliminarily based on the empirical equations specified in Guidelines fordesign and construction of Gyropress steel pipe piles retaining walls (IPA, 2014) [2]. However, as the number ofapplications of Gyropress pile is not enough so far, it was determined to carry out a load test on the constructed pile.

Fig. 1b The new Reiki bridge

Fig. 1a The old Reiki bridge

The constraints of the narrow space made the conventional static load test (SLT) impractical. And, the construction period
needed to be shortened. Hence, the Hybridnamic Rapid Load Test (Hybridnamic RLT) (Kamei et al., 2022) [3] was carriedout on one of the constructed SPPs to obtain “static” load-displacement curve. The Hybridnamic RLT requires less space
and test period, compared with SLT.

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2 Outline of Rapid Load Test
2.1 Site condition
Fig. 3 shows the results of borehole investigations and theembedment of the instrumented test pile. Beneath the top
filled layer, there exists a very hard gravel layer with SPT Nvalues ≥ 50. Because the borehole terminated at a depth of
10 m, the soil layer below this depth was assumed to be agravel layer similar to the shallower gravel layer.
2.2 Pile specifications
Table 1 shows the specifications of the test steel pipe pile
(SPP). The SPP was installed using the Gyropress Method. The
test pile was instrumented with two pairs of strain gages andaccelerometers near the pile head for the Hybridnamic RLT(see Fig. 3).

Fig. 2 GYRO PILERTM(https://www.giken.com/en/solutions/gyro/)

SPT N-value

0 10 20 30 40 50 60

Table 1. Specifications of test piles
Item
Value
Pile length, L (m)15.0
Embedment length, Ld (m)14.0Outer diameter, Do (mm)1200
Inner diameter, Di (mm)1176
Wall thickness, tw (mm)12.0
Cross-sectional area, A (m2)0.045Young's modulus, E (GPa)206.8
Density, ρ (ton/m3)
7.88
Bar wave velocity, c (m/s)
5123
Mass, m (ton)
4.94

0G.L.

SPT-N
Assumed N -value

Test pile
G.L.

L1

2.3 Preliminary pile design

Depth from sea level, z (m)Fill5Gravel

Ground water table

10Table 2 lists the design working loads on the pile, the factorof safety and the corresponding required pile capacity. The
action of the reaction mass caused during loading is about
5g. Hence, weight of the reaction mass is about 20% of theplanned maximum load. An advantage of the Statnamic testis the high loading capacity which can be as high as 60 MN.
However, repeated loading is difficult in the Statnamic test.
The ultimate bearing capacity of the pile was preliminarily
calculated using the empirical formulas listed in Table 3.
Using N = 50, the following values of ultimate resistancewere roughly obtained:
qd = 2400 kPa, total tip resistance Qd = 2714 kN
fs = 100 kPa, total shaft resistance Qs = 2740 kN
Total pile capacity Q = Qd + Qs = 5454 kN

Gravel(deemed)15

Acceleromete
Strain gage

Fig. 3 Profiles of soil layers and SPT N-values

Table 2. Design loads, factor of safety and required pilecapacity
Working Factor ofRequired
Stateloadsafety pile capacity
Usual1305 kN
33915 kN
L1 earthquake
1440 kN
22880 kN

While the estimated total pile capacity sufficiently
exceeds the required capacity, the limited number of
Gyropress pile applications raises concerns about the reliability of empirical formulas used to estimate tip and shaftresistance. Hence, it was determined to carry out a load test on one of the constructed piles. As mentioned earlier, the5Volume 9, Issue 3

September 2024

narrow site conditions rendered the conventional SLT impractical. For these reasons, it was determined to carry out theHybridnamic RLT to confirm that the pile has a bearing capacity greater than 3915 kN.
3. Interpretation Methods of RLT Signals

Table 3. Empirical formulas to estimate tip and shaft
resistance (IPA, 2014)
Soil type
Tip resistance
Shaft resistanceqd (kPa)fs (kPa)
Sand60 N (≤ 2,400 kPa) 2 N (≤ 100 kPa)
Gravel

3.1 ULPC method
The ULPC (UnLoading Point Connection) method (Kamei etal., 2022) [3] is an extension method of UnLoading Point(ULP) method. In the Hybridnamic RLT, generally, 5 to 7
blows are applied to the pile with increasing the fall heightof hammer h. In each blow, the time variation of the soil
resistance Rsoil(t) is obtained using Eq. (1).
(1)

where Frapid is the measured applied force, α is themeasured pile head acceleration and M is the pile mass.
Rsoil contains dynamic soil resistance depending on the pilepenetration velocity v(t). At the maximum pile
displacement (UnLoading Point, ULP), the pile velocity v =0. Hence, Rsoil at ULT is thought to be the static soil
resistance. By connecting ULPs from multiple blows, staticload-displacement relation is easily constructed.

t - Lm/cF ( xm , t ) − Z v( xm , t )2L L t ) Fd  xm , t − m  + Fu  xm , t + m Rt ( xm ,=c c 
Fu ( xm , t ) =t + Lm/c TimeFdFu

Pile length below
measurement (Lm)

The Case method (Raushe et al., 1985) [4] is a method
based on the one-dimensional stress-wave theory, inwhich the penetration resistance Rt (= Rsoil) of a pile during
driving is estimated. First, the downward traveling wave Fdand the upward traveling wave Fu are calculated from themeasured dynamic signals (axial force F and pile velocity v)
using of Eq. (2) and Eq. (3), respectively. Then, by using Eq.
(4), the time variation of Rt(t) (= Rsoil(t) ) is obtained (Fig. 4).

F ( xm , t ) + Z v( xm , t )2t

Measurement position (xm)

3.2 ULPC_CM method

Fd ( xm , t ) =FdFu2Lm/cForceRsoil (t ) = Frapid (t ) - M α (t )Depth(2)Fig. 4 Case method (Raushe et al. 1985)

(3)
(4)

where, x: Coordinate along the pile axis (pile head = 0), xm: Measurement position, v: Pile velocity,
Lm: Pile length from measurement position to pile tip, F: Axial force, Fd: Downward force wave, Fu: Upward force wave,
Z: Impedance (=EA/c), c: Bar wave velocity, E: Young's modulus of pile, A: Cross-sectional area of pile.
In the ULPC_CM method, multiple blows (rapid load tests) are applied to a pile. The time variation of soil resistance Rsoil
is obtained from the Case method, and the time variation of pile displacement w is directly measured. Hence, Rsoil – w
relation is easily obtained. Rsoil at the maximum pile displacement can be regarded as the static resistance Rw. Similar tothe ULPC method, a static load-displacement curve is constructed by connecting ULPs from the multiple blows.
As the ULPC_CM method is based on the one-dimensional stress-wave theory, it has the advantage of not requiringcorrection for pile inertia Ra. Hence, the ULPC_CM method would be applied to RLTs on piles with relative loading duration
Tr = tL/(2L/c) < 5 (tL is the loading duration).

6Volume 9, Issue 3Forces,
Fd and Fu (kN)

6000
5000
4000
3000
2000
1000
0-1000

Displacement,w (mm)Fig. 5 is the Hybridnamic RLT device used at the site. As
seen from the figure, the usual reaction system such asreaction piles and rection beams are not required and thetesting space is very narrow.

2015
1050-5
2.0
1.5
1.0
0.5
0.0-0.5-1.0-1.52001000-100-200
0.00

Fig. 5 Hybridnamic RLT device used in the site

RLTs were carried out using the device with a hammer
mass mh = 9.5 tons. A total of 6 blows (RLTs) were applied
to the pile with increasing drop height h from 0.30 to 1.80
m. The target maximum load was 4083 kN which wasgreater than the required pile capacity of 3915 kN. The
test was completed within 3 days including preparation,
testing and dismounting of the device.

6000
5000 h = 1.80 m
4000 m = 9.5 ton
3000
2000
1000
tL = 33.3ms0(Tr = 6.1)
-1000

Velocity,v (m/s)4.1 Outline of RLT

Acceleration,α (m/s2)

Rapid load &soil resist.,
Frapid and Rsoil (kN)

4 Rapid load test at the site

September 2024

FrapidRsoil (ULPC)
Rsoil (ULPC_CM)

FdFu

0.02

0.04

0.06

Time, t (s)

0.08

0.10

Fig. 6 RLT signals (h = 1.80 m)

4.2 Test results
The measured test signals were interpreted using two methods, ULPC and ULPC_CM. Fig. 6 shows the measured dynamicsignals, rapid load Frapid, pile head displacement w, velocity v and acceleration α, in the RLT at h = 1.80 m. In the figure,soil resistance Rsoil (ULPC) from the ULPC method and Rsoil (ULPC_CM) from the ULPC_CM method are shown together
with Frapid. Furthermore, Fd and Fu are also shown.
Fig. 7 shows the Frapid, Rsoil (ULPC) and Rw (ULPC) vs w from the ULPC method.
Fig. 8 also shows the Frapid, Rsoil (ULPC_CM) and Rw (ULPC_CM) vs w from the ULPC_CM method.
Fig. 9 shows the static load-displacement relations from ULPC and ULPC_CM. The 2 curves match quite well up to 6 mm
displacement, but start to show some deviation as the displacement increases from 6 mm. Until the 3rd blow the pilehead accelerations were relatively small. Hence the 2 curves match well. After the 4th blow large pile head upward(negative) acceleration was generated resulting in an overestimation of Rsoil when ULPC interpretation method isemployed. On the other hand, as mentioned earlier, because the ULPC_CM method is based on the one-dimensional
stress-wave theory, it has the advantage of not requiring correction for pile inertia Ra. Therefore ULPC_CM is more reliable
than ULPC.
Both of the result from each interpretation method satisfied the required capacity. The initial pile head stiffness Kh fromeach interpretation was almost same, Kh = 501 MN/m.

76000

FrapidRsoil (ULPC)
Rw (ULPC)

5000
4000

Resistance, Rw & Rsoil (kN)Resistance, Rw & Rsoil (kN)

Volume 9, Issue 3

3000
2000
1000
0051015Displacement, w (mm)206000

September 2024

FrapidRsoil (ULPC_CM)
Rw (ULPC_CM)

5000
4000
3000
2000
100000Fig. 7 Frapid, Rsoil and Rw vs w from ULPC

51015Displacement, w (mm)20Fig. 8 Frapid, Rsoil and Rw vs w from ULPC_CM

Due to the low reliability of the empirical formulas forestimating tip and shaft resistance, RLT was carried out toconfirm the required capacity of SPPs constructed using theGyropress Method.
In this study, load-displacement relations of the pile wereobtained from RLT with two interpretation methods, ULPC(the current JGS method) and ULPC_CM (a new and morereliable method). The load-displacement curves from bothinterpretation methods exceeded the required pile capacitywith a pile head displacement of about 14 mm.
It is emphasized that the Hybridnamic rapid load testing wasused as a reliable design tool.

6000

Total pile capacity from the5000 preliminary design stage = 5,454 kN

Static resistance, Rw (kN)

5 Concluding Remark

4000 Required capacity = 3,915 kN
3000
2000

Rw (ULPC)
Rw (ULPC_CM)

1000
00

5

1015Displacement, w (mm)20Fig. 9 Comparison of load-displacement curves fromRLTs with ULPC and ULPC_CM

REFERENCES[1] Mandal, K., Lin, S., Kamei, S., Watanabe, K. and Matsumoto, T.: Rapid load test on a press-in steel pipe pile with
Gyropress Method for confirmation of design bearing capacity, Proceedings of the 3rd International Conference on
Press-in Engineering, Singapore. 7p., 2024.
[2] International Press-in Association (IPA): Guidelines for design and construction of steel pipe pile retaining walls
constructed using Gyropress Method, 2014 (in Japanese).
[3] Kamei, S., Takano, K. and Fujita, T.: Comparison of static load test and rapid load test on steel pipe piles in two sites.
Proceedings of the 11th International Conference on Stress Wave Theory and Design and Testing Methods for DeepFoundations, Rotterdam, 8p., 2022. DOI 10.5281_zenodo.7148489.
[4] Raushe, F., Goble, G. and Likins, G. E. Jr.: Dynamic determination of pile capacity, ASCE Jour. Geotech. Div., 111(3),pp. 367-383, 1985.
[5] Lin, S., Kamei, S., Yamamoto, I. and Matsumoto, T.: Hybridnamic rapid load testing with UnLoading Point Connection
method invoking Case method. Proceedings of the 17th Asian Regional Conference on Soil Mechanics andGeotechnical Engineering 2023, Nur-Sultan, pp.1425-1428, 2023.

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September 2024

◆ A brief CV of Prof. Tatsunori Matsumoto

Tatsunori Matsumoto obtained his Bachelor of Engineering and Master of Science fromKanazawa University, Japan. He joined the Department of Civil Engineering of Kanazawa
University in 1981 as research associate. He became an Associate Professor in 1991 andpromoted to a Professor from August in 1999. He retired from Kanazawa University in 2021
and became Emeritus Professor.
He retains an active involvement in research into pile dynamics and deformation of pilefoundations including piled rafts subjected to load combinations. He has published morethan 200 technical papers including more than 60 Journal papers.

He was the Chairman of IS-Kanazawa 2012: The 9th International Conference on Testingand Design Methods for Deep Foundations held in Kanazawa, Japan, from 18 to 20
September, 2012. He was Vice-President Asia of IPA from 2019 to 2024.

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