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

Reinforcement of Damaged Bridge Pier by Scouring Using Steel Pipe PilesYusuke KUROKIAssistant Senior Researcher, Structures Technology Division, RTRI, Tokyo, Japan

Hidetoshi NISHIOKA
Senior Researcher, Structures Technology Division, RTRI, Tokyo, Japan
Email:nishioka.hidetoshi.58@rtri.or.jp

Kei KUMABE
Acting Manager, Construction Division, JR Kyushu, Fukuoka, Japan

Masayuki KODA
Director, Structures Technology Division, RTRI, Tokyo, Japan
Email:koda.masayuki.81@rtri.or.jp

ABSTRACTThis report introduces a case where railways bridge piers were damaged by scouring and restored using steel pipe piles.
The Kumanouegawa Bridge of JR Kyushu was damaged by flooding in July, 2012, one of the bridge piers settled andtilted to the upper stream. Regarding the permanent repair intended for train operation at a normal speed after theimmediate repair intended for the resumption of train operation at a slow speed, it was judged to be optimal to install
steel pipe piles into the river bed in such a manner that they surround the footing of existing foundation and to connect
them with the side surface of footing by reinforced concrete. In the actual construction, since the height of the lower
surface of the girder of the bridge from the river bed is only about 4.0 m, the driving method of the piles had to beapplied even at a construction site with low-height space. For this reason, steel pipe piles, were installed by press-in
method which enables construction in this small space. The driving of the steel pipe piles was started in winter when thewater level of the river was low, and the construction of the connecting concrete was finished about one month later.
Key words: Steel Pipe Piles, Reinforcement, scouring, Bridge pier1. Outline of the project1.1. Kumanouegawa Bridge
The Kyudai Line on which Kumanouegawa Bridge
stands is a railway line crossing northern Kyushu that has
linked Kurume Station in Kurume City in Fukuoka
Prefecture with Oita Station in Oita City in Oita
Prefecture since 1934 when it was fully opened (Fig. 1).
Kumanouegawa Bridge is located between Ukiha Station
and Chikugo Oishi Station in the Kyudai Line as a bridgecrossing the Kumanouegawa River, which is a main river― Kyudai Line★ Kumanouegawa Bridgein the Chikugogawa river system.
Kumanouegawa Bridge was constructed in 1931. Its
superstructure is a seven-span deck-type deck girder witha total bridge length of 71.18 m, and a maximum spanFig. 1

Locatoion of Kyudai line

and Kumanouegawa Bridge- 549 -Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

length of 9.14 m.

Its substructure consists of six

elliptical bridge piers supported by a spread foundation.

piers P3 to P6 that were not damaged by the flooding had
been prone to be destabilized by past scouring, andvarious countermeasures including those by the footprotection method had been taken. However, the bridge

1.2. Outline of the disaster
The Northern Kyushu Downpour of July 2012pier P2 had been shorter than the other bridge piers andrecorded a maximum hourly rainfall of 78.5 mm and a

had been covered with an earth cover from its footing

maximum continuous rainfall of 336.0 mm, causing

crest to a height of about 1.5 m, so countermeasures had

severenot been taken at this bridge pier.

damageinnorthern

Kyushu.

OntheKumanouegawa River, as shown in Fig. 2, the waterlevel rose as high as it almost reached the crest of thebridge piers under the impact of this downpour. At

1.3. Immediate repair for slow train operation
Regarding the repair of the damaged bridge pier P2,

Kumanouegawa Bridge, the foundation was scoured, andsuch tentative work as is described in the following was

the fine-grain component of the bottom surface grounddone to quickly reopen the bridge for slow-moving train

was sucked out at the elliptical bridge pier P2 with aoperation before the work to be done for train operationfooting thickness of 0.6 m and a bridge pier height ofon the bridge at the prescribed speed.

3.76 m, causing the bridge pier to settle (about 300 mm)

・Clarifying the natural frequency by an impact vibrationand lean (49/1,000 rad upstream and 21/1,000 rad toward

test to confirm the state of the bottom surface of theOita Station) (Fig. 3). The revetment near the bridge pierfoundation

P1 was washed away. It has been pointed out that bridge

・Preloading work forremoving the looseness on thebottom surface of the foundation.
・Repairing the concrete of the bearing supports
・Trial driving by a test train
After completing the above-mentioned work, a train
was run across the bridge at a slow speed of 15 km/h

P2

during which time the displacement of the bridge pier P2
was monitored. The train operation resumed at the slow
speed 1.5 months after the disaster.
2. Repair method for usual train operation
2.1. Site condition
As stated above, the bridge pier P2 was a short bridgepier, and it was only possible to ensure overhead working

Fig. 2 View during the floodspace of about 4.0 m under the girders. Also, during theTo Kurume

To OitaP2(settlement)

Fig. 3

Overview of the damaged bridge pier- 550 -Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

permanent reconstruction work, although traveling

directly under the bridge girder between the bridge pierslowly, trains were already crossing the bridge, requiring

P2 and the bridge pier P3 of Kumanouegawa Bridge.

that the work be done directly under the bridge piers

At this location, there is a gravel layer mixed withwhile trains were in operation. Also, the work done forround stones with a N-value of 19 near the design riverbed

the retrofit bridge pier P2 was to be done in the river,level, but there is also a sandy layer with a N-value of 4

which necessitated blocking the river partially by afrom 2.0 m to 3.0 m below the designed riverbed level.

cofferdam, and as a result of the consultations with theBelow the sandy layer, there is another gravel layer mixed

river manager, approval for executing the retrofit waswith round stones with a N-value over 50, and theobtained on the condition that the retrofit be executed indiameter of some of the round stones exceeds 300 mm.

a short period during the dry season.
2.3. Required performance
The following two points were designated as the2.2. Ground condition
Fig. 4 shows the results of boring near the bridge
pier P2. The boring locations is, as shown in Fig. 5,

required performance of the reinforcement methods to be
used to restore the damaged bridge piers.
[1] Form a foundation that will be stable under the actionof scouring of the bridge piers during future flooding ofthe same severity.
[2] Form a foundation that will obstruct the cross sectionof the river to less extent than the adjoining bridge piers.
2.4. Structural type and piling methodAs specific foundation retrofitting work methods
for the bridge pier P2, [1] ground improvement on thebottom surface of the foundation and [2] retrofitting thefoundation using steel sheet piles were considered. [1]was removed from the choices of little expectation ofrainforcement. Because the foundation of the bridge pierP2 was a spread foundation and the embedded depth after
the disaster was extremely shallow, it would be difficult

Fig. 4

Borehole log

to ensure adequate resistance against future flooding byexecuting only ground improvement work. It wasconcluded that [2] reinforcement of the foundation withsteel sheet piles could sharply improve the bearing
capacity at the time of a future flood or sinking of theriverbed, because it has been applied many times in thepast and the foundation is supported by a gravel layer
containing round stones below the sandy layer with aN-value of 4 located from 2.0 m to 3.0 m under thedesigned riverbed level, as stated in Section 2.2 above.
However, as stated in Section 2.1, because, at the bridge

P2

P3

pier P2, workspace of only approximately 4.0 m in height
could be ensured under the girders, and the execution
would have been impossible without using an auger

Fig. 5

Location of boring

capable of crushing round stones larger than 300 mm indiameter, as mentioned in Section 2.2. This problem was- 551 -Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

resolved by adopting the gyropress work method using
steel pipes instead of steel sheet piles, as shown in Fig. 6,
permitting the execution in the reduced space.
At first, execution using steel pipes only near thegirders where the workspace was narrow and execution
using steel sheet piles at other locations were considered.
However, it is possible to reduce the thickness of thefooting if the number of steel pipes is increased and theirdiameter is reduced. This is a structure that would not
greatly obstruct the river cross-section, so steel pipes wereinstalled on the entire surface of the bridge pier, as shownin Fig. 7, and the tops of the steel pipes were connected toFig. 6

the bridge pier with reinforced concrete. The restoration

Overview of the gyropress work methodof P2 was completed with 37 steel pipes 600mm indiameter and 4.0 m long.
3. Press-in piling3.1. Layout
Fig. 8 shows the layout of the machines that pressedin the steel pipe sheet piles, and Fig. 9 is a photo of theDump Truck

T1
H=47.117

Rough Terrain Crane 50t

・パイラー掴み代確保のため・斜線部内を常設帯とHP

φ700

ラフテレー
アウトリガ
ブーム長
作業半径
定格総重ジャイロパ25tフック
補巻
合計

A1
H=48.694
土のうGyropiler(a) Front view

R10000
5PL2
5PL1

RL=50.156

RL=50.148
71PC1

RL=50.155

5PC1

RL=50.148

1PR1

5PR1
5PR2

P2P3

B1
H=50.016

Fig. 8Layout of the restoration execution machines(b) Plan viewFig. 7

General drawing of the restoration
Fig. 9 View of the steel pipe pile press-in work- 552 -Proceedings of the First International Conference on Press-in Engineering 2018, Kochi

execution. For this execution, part of the river wasmachinery, as shown in Fig. 8.

blocked with a cofferdam, as explained in Section 2.1.

Fig.10 is a photograph of the work completed.

The cofferdam was executed by arranging large sandbags
so that they enclose the bridge pier P2 and construction

3.2. Limit value of tiltingDuring press-in of the steel pipes, trains started torun across the bridge at a slow speed, as explained inSection 2.1. If the bridge pier P2 had tilted under the
impact of the press-in of the steel pipes, the tracks might
have been displaced, so, during the execution, the tilting
was continually measured to check its values against thecontrol values.
The control values were calculated based on the
track’s maintenance reference values and warning values,
work stoppage values, and limit values, were set asshown in Table 1.

Fig. 103.3. Monitoring data
Fig.11 shows the fluctuation of the tilting of theWork completed

bridge pier P2 of the Kumanouegawa Bridge after theTable 1.

Control values of tilting during the restoration work

Alignment irregularly
Tilt at right angles
Tilt in the line direction
River levelof the track
to the line
9mm (22.0mm×0.4）
9mm (22.0mm×0.4）
0.08°
0.08°
15mm （22.0mm×0.7）
15mm （22.0mm×0.7）
0.13°
0.13°
22mm （22.0mm×1.0）
22mm （22.0mm×1.0）
0.20°
0.20°
3.4ｍ

Longitudinal level irregularityof the trackWarning Value
Work stop Value
Suspention Value

Alignment irregularly
Tilt at right angles
Tilt in line direction
River levelof track
to line
9mm (22.0mm×0.4）
9mm (22.0mm×0.4）
0.08°
0.08°
15mm （22.0mm×0.7）
15mm （22.0mm×0.7）
0.13°
0.13°
22mm （22.0mm×1.0）
22mm （22.0mm×1.0）
0.20°
0.20°
3.4ｍ

Longitudinal level irregularityof track

Warning Value
Work stop Value
Suspention Value

Fig. 11

Change in tilting- 553 -

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

completion of the immediate work. When trains wereriver cross-section to a minimum. In addition, this was afirst allowed to cross the bridge at a slow speed after thecase where the construction of a steel pipe pile

execution of the immediate work, a slight advance offoundation structure was completed using a gyropiler astilting upstream and toward Oita Station was seen.

a method for constructing structures when only a small

About four months later, tilting tended to converge atconstruction space is available.

about 1/1,000 rad (approximately 0.06°) in both theThe retrofitting was completed without anydirection of the railway line and the direction at right

accidents in a work period of about one month, during

angles to it.

which time the tilting and settlement of the bridge pierAfter the restoration work started, the advance ofwere monitored constantly, so that the train operation attilting (tilting toward Oita and upstream) was seen during

thethe steel pipe press-in work and during the excavation

Kumanouegawa Bridge. None of the displacement,

between the steel pipes and the body concrete after thedeformation and other abnormality of the bridge at thecompletion of the press-in work.

Nevertheless, even theprescribed speed were found.

cumulative

exceededtilting(approximately0.1°),

neverwhichmeans

1.6/1,000
that

thework-stopping value was not reached and that the work

prescribed

speed

could

beresumedon

The authors hope that this report will be of use as areference concerning the restoration of bridge piers
damaged by flooding.

was completed successfully without obstructing the train
service. After the steel pipes and the body wereconnected by reinforcing bars following the completion

References
Yosho, N. 2014-1. Soundness Evaluation of Railwayof the excavation, the progress of the measured values

Bridge which was damaged by scouring. The

showed a tendency to converge. This is considered to be

Journal of Japan Railway Civil Engineeringa result of the integration of the steel pipes and the body.

Association, pp. 75-77, (洗掘被害を受けた鉄道橋の健全度評価).

Later, the measured values did not change verymuch until the slow train operation was discontinued

Nishioka, H., Shinoda, M., Sumi, Y. and Yamate, H.

after completion of the restoration.

2013-7. The Vertical Loading Test and Train
Running Test to the Bridge Pier of Spread

3.4. Productivity
The ground supporting the bridge pier P2 was, asFoundation which was Damaged by Scouring

explained in Section 2.2, a gravel layer containing round

Geotechnical Engineering, (洗掘により沈下した直stones whose diameter exceeded 300 mm, but the接基礎橋脚に対する鉛直載荷試験および列車走

adoption of the gyropress work method allowed the行試験).

press-in of the steel pipe piles without any impact by theSettlement. 48th Japan National Conference on

GIKEN LTD. Home Page Retrieved December 22, 2017

round stones and other objects. Specifically, although theconstruction work was done under a bridge where trains
were operated, 5piles were installed per day, which led tothe completion of the press-in of 37 steel pipes in 8 days.
4. Concluding remarks
This report introduced the case of Kumanouegawa
Bridge in the Kyudai Main Line operated by JR Kyushu
as an example of the permanent restoration of a bridge
damaged by flooding.
Thanks to the restoration of Kumanouegawa Bridge,
the structure will be able to withstand future floodings ofsimilar severity, and it will keep the obstruction of the- 554 -from https://www.giken.com/en/.