Dams in Japan
Overview 2018

Tokuyama Dam

JAPAN COMMISSION ON LARGE DAMS

CONTENTS
Japan Commission on Large Dams
History … ……………………………………………………………………
Operation … …………………………………………………………………
Organization… ………………………………………………………………
Membership… ………………………………………………………………
Publication… …………………………………………………………………
Annual lecture meeting… ……………………………………………………
Contribution to ICOLD… ……………………………………………………

1
1
1
1
2
2
2

Dams in Japan
Development of dams … …………………………………………………… 3
Major dams in Japan… ……………………………………………………… 4
Hydroelectric power plants in Japan… ……………………………………… 5
Dams completed in 2014 − 2016 in Japan … ……………………………… 6
Isawa Dam… ……………………………………………………………… 7
Kyogoku Dam … ………………………………………………………… 9
Kin Dam…………………………………………………………………… 11
Yubari-Shuparo Dam… …………………………………………………… 13
Tokunoshima Dam………………………………………………………… 15
Tsugaru Dam… …………………………………………………………… 17
Introduction to Dam Technologies in Japan
Trapezoidal CSG dam … …………………………………………………… 19
Sediment bypass tunnel (SBT)… …………………………………………… 19
Preservation measures of dam reservoirs… ………………………………… 19
Advancement of flood control operation… ………………………………… 20
Dam Upgrading Vision… …………………………………………………… 21
Utilization of ICT in construction of dam… ………………………………… 22
Papers in ICOLD & Other Technical Publications
Theme 1 Safety supervision and rehabilitation of existing dams…………… 23
Theme 2 New construction technology … ………………………………… 26
Theme 3 Flood, spillway and outlet works… ……………………………… 29
Theme 4 Earthquakes and dams… ………………………………………… 30
Theme 5 Reservoir sedimentation and sustainable development…………… 33
Theme 6 Geology and rock foundation……………………………………… 38

1

DAMS IN JAPAN - OVERVIEW 2018

Japan Commission on Large Dams
History

Membership

In 1931, three years after the International Commission
on Large Dams (ICOLD) was established, Japan joined
ICOLD as the Japan National Committee on Large Dams.
In 1944, Japan withdrew from ICOLD during the WorldWar II, then rejoined in March 1953. On September 13,
1962, the Japan Commission on Large Dams (JCOLD)
was established, and in January 2012, it became a General
Incorporated Association.

The members of JCOLD are incorporated bodies
involved in dam construction. They include government
bodies concerned with dam construction, electric powercompanies, survey and research bodies, academic
associations, industrial associations, construction
consultants, construction companies, and manufacturers (78members as of January 2018).

Operation
JCOLD is involved in operations such as surveys, research,
international technology exchanges, etc. concerning large
dams and related facilities (below, “large dams”), in
order to improve the design, construction, maintenance,and operation of large dams and to contribute to thedevelopment of the Japanese economy. Responsibilities
include:(1) C ollection of information, surveying, and researchconcerning large dams(2) Exchange of technology and guidance concerning largedams(3) Participation in ICOLD, assistance to its activities, andinternational exchange of technology concerning largedams(4) D issemination of and spreading awareness of theachievements of surveys and research concerning largedams(5) O ther activities necessary to achieve the goals of
JCOLD
In recent years, JCOLD has actively conducted a programof surveys and research on methods of harmonizing dam
development with the environment and on ways to mitigate
their environmental impacts to achieve the sustainable
development of dams.

Organization
Under the leadership of the Chairman, there is a Planning
Committee, Technical Committee, and Administrative
Office. These committees undertake work in their respective
areas.

President

Managing
Director
Vice
President(3)Senior Managing
Director

Advisor/Counselor

Directors

GeneralMeeting

AuditorAdministrative OfficePlanning Committee(Sub Committees)
Public Relations/
Environment
Editorial
Technical Committee(Sub Committees)
International affairsa
Dam Concrete Frost Damage Testing and Research
Maximizing functions of existing dams
Revision of current JCOLD technical guidelines

Figure-1 Organization Chart of JCOLDDAMS IN JAPAN - OVERVIEW 20182

Publication
JCOLD publishes its Journal, “Large Dams”, four times ayear (January, April, July, October), which is distributed tomembers and subscribers. At ICOLD Congresses held once
every three years, JCOLD publishes Current Activities on
Dams in Japan in English, which introduces the state ofdams and dam technologies in Japan, and distributes it toCongress participants (1997, 2000, 2003, 2006, 2009, 2012
and 2015).
Figure-3 Dam Technology Lecture and Discussion Meeting
Study TourTo increase mutual awareness among engineers, including
JCOLD members and others concerned with dams, on
improving dam and hydroelectric power plant technologies
and the construction of dams, JCOLD holds tours of dams
and hydroelectric power plants still under construction withthe cooperation of various organizations.

Figure-2 Publicaitons of JCOLD

Annual lecture meeting

Figure-4 Tour of the site of the Hirase Dam (2017)

Dam Technology Lectures and Discussion Meetings

Contribution to ICOLD(Held jointly with the Japan Association of Dam & Weir
Equipment Engineering)

JCOLD submitted 357 ICOLD Congress papers until now.
In addition, Many Japanese engineers participate in ICOLD
Annual Meeting and Congress.

At the meeting, the results of surveys and research by thevarious JCOLD technical sub committees, papers presented
to the ICOLD Congress, and results of activities by theJapan Association of Dam & Weir Equipment Engineering
are reported widely to people concerned with dams. In
addition, the lecturers and participants in the Technology
Lecture and Discussion Meeting discuss the reports in orderto improve the technologies, maintenance, and operation ofdams.

JCOLD participates in 24 technical committees at Annual
Meeting and exchanges technical information.
JCOLD held Annual Meeting in 1960(Tokyo) and1984(Tokyo), and Congress in 2012(Kyoto).
Susumu NAGATA(1957-1960), Masayoshi NOSE (19661969), Shigeru ICHIURA (1982-1985), Kyohei BABA
(2001-2004), Norihisa MATSUMOTO(2007-2010) andTadahiko SAKAMOTO(2011-2014) served as a vicepresident of ICOLD.

3

DAMS IN JAPAN - OVERVIEW 2018

Table-1 Number of participants from Japan
Year
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017

Host country(Host city)
India (New Delhi)
Turkey (Antalya)
China (Beijing)
Germany (Dresden)
Brazil (Iguazu)
Canada (Montreal)South Korea (Seoul)
Iran (Tehran)
Spain (Barcelona)
Russia (St. Petersburg)
Bulgaria (Sofia)
Brazil (Brasilia)
Vietnam (Hanoi)
Switzerland (Lucerne)Japan (Kyoto)
USA (Seattle)
Indonesia (Bali)
Norway (Stavanger)
South Africa(Johannesburg)
Czech Republic (Prague)

Number ofparticipantsfrom Japan
43
56
87
60
47
49
143
77
107
79
63
46
75
70
398
73
79
80
58
84

Table-2 Number of submitted Congress papers
Year

No.

Host country(Host city)

1933
1936
1955
1958
1961
1964
1967
1970
1973
1976
1979
1982
1985
1988
1991
1994
1997
2000
2003
2006
2009
2012
2015

1
2
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

Sweden (Stockholm)
United States (Washington)
France (Paris)
United States (New York)
Italy (Rome)
United Kingdom (Edinburg)
Turkey (Istanbul)
Canada (Montreal)
Spain (Madrid)
Mexico (Mexico)
India (New Delhi)
Brazil (Rio de Janeiro)
Switzerland (Lausanne)
United States (San Francisco)
Austria (Vienna)
South Africa (Durban)
Italy (Florence)
China (Beijing)
Canada (Montreal)
Spain (Barcelona)Brazil (Brasilia)
Japan (Kyoto)
Norway (Stavanger)

Number ofsubmitted
papers
3
5
4
13
8
13
11
8
12
9
11
12
17
22
29
25
28
16
20
23
15
37
16

Dams in Japan
Development of dams
In Japan, the major purpose of dams was irrigation fromancient times to the end of the feudal period in the mid
nineteenth century. The Sayama-ike irrigation pond (Osaka
Prefecture), which is considered to be Japan’s oldest dam,
was completed in 616, and is recorded in the official
historic documents.

in recent years, redevelopment projects, such as raising
the height of dams, excavating reservoirs, and upgrading
discharge facilities, are being carried out more and more.

As Japan was modernized and urbanized after the Meiji
Revolution (1867), Japan started to build dams with modern
technology, to meet the increased demand for water andelectric power. In 1900, the Nunobikigohonmatsu Dam(Hyogo Prefecture) was completed as water supply dam.
As for hydropower, the Chitose No.1 Dam (Hokkaido) was
first completed in 1910. Later, multi-purpose dams withflood control capacity were constructed, with the first, theKodo Dam (Yamaguchi Prefecture), completed in 1940.
To make more efficient use of water resources and control
of flood, comprehensive projects are promoted under theconcept of integrated development of river systems. Also,

Figure-5 Nunobikigohonmatsu Dam

4
DAMS IN JAPAN - OVERVIEW | 2018

DAMS IN JAPAN - OVERVIEW 2018

Figure-6 Development of Dams, Economy of Japan and Population
Figure-6 Development of Dams, Economy of Japan and Population

Major dams in Japan
Major dams in Japan
There aredams
over
100 100
metershigh inhigh
Japan,
There
aremany
many
dams
over
metersin though,Japan,
theirreservoir
capacities
aresmaller
than
those
of
other
dams
though, their reservoir capacities are smaller than thoseofaroundtheworld,
reflecting
thegeographicalfeaturesofother dams around the world, reflecting the geographicalJapan(narrowislands
andsteep
terrain).
features of Japan (narrow islands and steep terrain).
Table-3 Ranking of dams by height in Japan
1
2
3
4
5
6
6
6
9
10

Dam name
Kurobe Dam
Takase Dam
Tokuyama Dam
Naramata Dam
Okutadami Dam
Miyagase Dam
Urayama Dam
Nukui Dam
Sakuma Dam
Nagawado Dam

Type
Arch
Rockfill
Rockfill
Rockfill
Gravity
Gravity
GravityArch
GravityArch

Height (m)
186
176
161
158
157
156
156
156
155.5
155

Dam
Figure-7
Figure-7 Ｎaramata
Naramata Dam

Table-4 Ranking of dams by reservoir capacity in Japan
Dam name
1
2
3
4
5
6
7
8
9
10

Tokuyama Dam
Okutadami Dam
Tagokura Dam
Yubari Shuparo Dam
Miboro Dam
Kuzuryu Dam
Sakuma Dam
Ikehara Dam
Sameura Dam
Hitotsuse Dam

Reservoir capacity(million m3)
660
601
494
427
370
353
343
338
316
261

Figure-8 Miyagase Dam
Figure-8 Miyagase Dam

455
DAMS IN JAPAN - OVERVIEW 2018
DAMS IN JAPAN - OVERVIEW | 2018
Table-6 Electric power output ranking of Pumped
Storage hydropower plants

Hydroelectric power plants in JapanThe output of hydroelectric power plants in Japan accounts
The output of hydroelectric power plants in Japan accounts
for about 19% of all electric power sources, and pumped
for about 19% of all electric power sources, and pumped
storage hydroelectric power occupies top 10s of the electric
storage hydroelectric power occupies top 10s of the electric
power output rankings.
power output rankings.

Hydroelectric
power plant

Electric
power
output(MW)

1

Okutataragi

1,932

2

Okukiyotsu

1,600

3

Okumino1,500

Dam name4

Shintakasegawa

1,280

Okutadami Dam
Tagokura Dam
Sakuma Dam
Kurobe Dam
Arimine Dam
Tedorigawa Dam
Miboro Dam
Miyanaka Dam
Hitotsuse Dam
Nishiotaki Dam

4

Okouchi

1,280

6

Okuyoshino

1,206

7

Tamahara
Tambara1,200

7Matanogawa

1,200

7

Omarugawa

1,200

7

Kazunogawa

1,200Table-5 Electric power output ranking of Conventionalhydropower plants
Hydroelectric power
plant
1
2
3
4
5
6
7
8
9
10

Okutadami
Tagokura
SakumaKurobegawa 4
Arimine 1
Tedorigawa 1
MiboroShinojiya
Hitotsuse
Shinanogawa

Electric
power
output
(MW)
560
400
350
335
265
250
215
206
180
177

Figure-9 Okutadami Dam

Dam name(upper reservoir /lower reservoir)
Kurogawa Dam /Tataragi Dam
Kassa Dam /Futai Dam
Kaore Dam /Kamiosu Dam
Takase Dam /Nanakura Dam
Ota Dam /Hase Dam
Seto Dam /Asahi Dam
Tamahara
Dam//
Tambara Dam
Fujiwara Dam
Doyo Dam /Matanogawa Dam
Ouseuchi Dam /Ishikawauchi Dam
Kamihikawa Dam/
Kazunogawa Dam

Figure-10 Kurobe Dam

DAMS IN JAPAN - OVERVIEW 20186Dams completed in 2014 - 2016 in Japan
Dams completed in 2014-2016 in Japan are counted in 15 dams. The features are summarized below. Several dams areillustrated in the following pages.
Dam
Dam name

Location

Purpose(s)Type

Height（ｍ）

Length ofReservoirCrestcapacity（ｍ） （million ㎥）

OwnerCompleted

1 Toppu

Hokkaido

CSI

PG

78.4

309

36 Hokkaido Pref.

2014

2 Yofudo

Hyogo

CS

PG

54.4

145

1.1 Hyogo Pref.

2014

3 Rogi

Kumamoto

CS

PG

53

169

2.3 Kumamoto Pref.

2014

4 Isawa

Iwate

CSIH

ER

127

723

143

5 Naganuma

Miyagi

CS

TE

15.3

1050

31.8 Miyagi Pref.

2014

6 Kyogoku

Hokkaido

H

ER

54

332.5

5.5 Hokkaido Electric Power Co.,Inc.

2014

7 Kin

Okinawa

CSI

CSG

39

461.5

8.6 Okinawa General Bureau

2014

8 Yubari Shuparo Hokkaido

CSIH

PG

110.6

390

9 Kirimegawa

Wakayama

CS

PG

44.5

127

10 Kurikara

Hyogo

CS

PG

26.7

172

11 Tokunoshima

Kagoshima

I

ER

56.3

266.9

12 Hamada 2

Shimane

CS

PG

97.8

218

15.5 Shimane Pref.

2016

13 Shobara

Hiroshima

CS

PG

42

118.5

0.7 Hiroshima Pref.

2016

14 Tsugaru

Aomori

CSIH

PG

97.2

342

15 Gima

Okinawa

CS

TE

24.5

539

Purpose: C - flood control, S - water supply, I - Irrigation, H - hydroelectricity
Type: PG - gravity in masonry or concrete, ER - rock fill, TE - earth, CSG - CSG*1 Ministry of Land, Infrastructure, Transport and Tourism*2 Ministry of Agriculture, Forestry and Fisheries

427

The Tohoku Regional
Development Bureau, MLIT*1

Hokkaido Development Bureau,
MLIT*1

4 Wakayama Pref.
0.4 Hyogo Pref.
8.1

140.9

Kyushu Regional Agricultural
Administration Office, MAFF*2

The Tohoku Regional
Development Bureau, MLIT*1

0.6 Okinawa Pref.

2014

2015
2015
2015
2015

2016
2016

7

DAMS IN JAPAN - OVERVIEW 2018

Isawa Dam

＠ The Tohoku Regional Development Bureau, MLITLo
Up wer D
peri
Div versi
ers on tionutun nnel
nel

Figure-1 PlanDAMS IN JAPAN - OVERVIEW 2018

Axis of dam

S.W.L EL. 356.500

Cresat elevation EL. 364.000

DFWL EL. 361.000
N.H.W.L EL. 345.600

H.W.L in Flood Season
EL. 342.900
Surface Protection
L.W.L EL. 304.500

External
Rockfill
SectionSurface Protection

Internal
Rockfill
SectionInternal
Rockfill
SectionCore
Clay
FilterZone

Filter
Zone

External
Rockfill
SectionAuxiliary Dam
Blanket Grouting
Main Curtain Grouting

Figure-2 Typical section

Left Bank Entrance(Access road toAdministration
Building)

Right Bank Entrance

Crest length

Cresat elevation EL. 364.000
DFWL EL. 361.000
S.W.L EL. 356.500
N.H.W.L EL. 345.600
H.W.L in Flood Season

EL. 342.9

Upper Diversion Tunnel
Access Road to Lower Elevator

Lower Diversion Tunnel

Figure-3 Longitudinal Cross Section

8

9

DAMS IN JAPAN - OVERVIEW 2018

Kyogoku Dam（Pumped-storage Hydroelectric Power Station ）＠ Hokkaido Electric Power. Co., Inc.

Cresat elevation

Crest length of dam

Figure-1 Plan of upper reser voir

DAMS IN JAPAN - OVERVIEW 2018

Figure-2 Section of upper reser voir

Crest length of dam

Axis of dam
Cresat elevation

Figure-3 Plan of lower Dam（Kyogoku）
Axis

am

of d

Cresat elevation

Figure-4 Typical section of lower reser voir（Kyogoku）

Figure-5 Longitudinal Cross Section

10

11

DAMS IN JAPAN - OVERVIEW 2018

Kin Dam＠ Okinawa General Bureau

Cresat elevation
NWL

DFWL
SWL

Figure-1 PlanDAMS IN JAPAN - OVERVIEW 2018

0

10

20

30

12

40m

( 1: 500)

EL(m)X+240
80

X+200

X+220

X+180

X+160

X+150

X+140

X+120

X+100

X+60

X+80

X+40

X+20

X- 40

X- 0

15000

13500

BL29

J 29

BL28

J 28

BL27

J 27

BL26

J 26

BL25

J 25

BL24

J 24

Emergency spillways 36500
BL23

J 23

X- 12027@15000=405000

Non Overflow section 187000

60

X- 80

Spillways 30000

Crest length 461500

BL22

J 22

BL21

J 21

BL20

J 20

BL19

J 19

Overflow section 81500
13000

BL18

J 18

2000

13000

BL17

J 17

2000

12900

BL16

J 16

2200

X- 200X- 180

2200

12900

2000

BL14

J 14

6500

15000

13000

15000 Emergency spillways

BL13

J 13

X- 240X- 220Non Overflow section 193000

12800

BL15

J 15

X- 160

BL12

BL11

J 12

J 11

BL10

J 10

BL9

J9

BL8

J8

BL7

J7

BL6

J6

BL5

J5

BL4

J4

BL3

J3

BL2

J2

BL1

J1

J0

Water intake facility

40

EL29. 000
28. 0

27. 0
25. 5

18. 0

Spillways

Ｂ3. 20× Ｈ2. 15

EL13. 000

EL9. 000

1: 0. 821. 0

EL15. 000

EL4. 500

0EL2. 000

EL1. 000

EL3. 500
EL0. 000

EL0. 000

導水管

1: 0. 81: 0. 8

24. 0

20

22. 5

18. 75EL15. 000
EL11. 000

EL12. 000

EL17. 000

EL14. 000

EL9. 000EL- 2. 000

φ 1100EL- 2. 000

- 20

- 40

- 60

- 80

Figure-2 Upstream elevation

Axis of dam
1900
EL（m）

8000

6000

30

EL29. 000

27.20025.600NWL

21.50025. 600
0
1.
1:

1500

DFWL
SWL

0
00
R6

E L21. 000

8
0.
1:

1:
0.
8

20

ＣＳＧ

1000

1000
10

EL 9. 000

LWL 6.000
1500

EL0. 750

0
1.
1:

1:
1.
5

1500
2000
2500 2000

E L 2. 7000EL 0. 000
EL - 2. 000- 10

Figure-3 Typical Section

M

ⅰ＝10.0％ⅰ＝10.0％

車庫棟

埋設

犬走 ﾀﾝｸ
り

ｵｲﾙ

1：
1.5

EL=30

8.575

15％

EL=30

1.500

EL=29

7.000

EL=

.00

277

0

Figure-1 Plan

EL 210.500

EL 213.500

EL 212.000

EL.23
5.00

EL.225.000

EL.216.000

220

Emergency spillways
56000
Spillways57600

12900×4+2000×3

6.00

EL.21

仮排水路ﾄﾝﾈﾙ

2000

EL.25
5.00

EL.22
5.00

2

210

8

26

0

1:1.2

1:1.2

1:1.2

2

26

4

26

6

26

0
5.0

.27
EL

0

28

0
3.0

1:1.

.28

1:1.0

0
26 8
25 6
25

1:1.2

EL297.0EL291.0

EL293.0EL295.0EL289.0

EL283.0

EL287.0EL275.0 EL278.0

EL270.0 EL272.0

EL272.0 EL274.0

EL273.0 EL276.0

EL255.0

EL256.0EL257.0

EL261.0EL265.0

EL267.0

EL268.0EL270.0

EL251.0 EL253.0

EL252.0 EL254.0

EL253.0 EL255.0

EL248.0

EL248.0

EL249.0EL250.0EL250.0 EL251.0

EL241.0

EL215.0

EL209.0EL234.0

EL232.0EL230.25

EL228.0

EL225.0

EL222.0

EL241.0 EL243.0

EL239.0 EL241.0

EL237.0 EL239.0

EL235.0 EL237.0

1：0.8

EL261.0

EL278.0EL275.0EL272.0

EL268.0EL265.0EL281.0J23EL295.00

EL289.0

EL283.0 EL285.0

EL282.0 EL284.0

EL.285.00 EL281.0 EL282.0

EL279.0

EL252.0 EL255.0

EL249.0 EL251.0

EL247.0 EL249.0

EL245.0 El247.0

EL243.0 EL245.0

J22EL.275.00

210

EL234.0 EL236.0

EL232.0 EL234.0

EL230.25

EL.215.00

EL210.5

EL216.0EL220.5EL225.0

EL238.0 EL240.0

EL236.0 EL238.0

EL239.0EL240.0EL242.0

EL219.0

5.00

EL.24

1:0.5

220

230

0

27

EL

EL299.0 EL301.0

J24

EL293.0EL305.0EL301.0EL295.0EL295.0EL305.0EL301.0EL301.0EL297.0EL299.0EL297.0EL289.0EL285.0EL281.0

EL277.0EL275.0EL273.0

EL267.0

EL268.0EL272.0EL270.0

1:0.82EL266.0

EL247.0

EL249.0

EL251.0

EL255.0EL258.0

EL262.0EL265.0

EL267.0

EL269.0EL272.0EL275.0

EL278.0EL281.0EL285.0

EL287.0

EL255.000

EL297.0 EL299.0

EL251.000

EL276.0 EL279.0

EL249.000

EL303.0 EL305.0

EL238.0

EL239.0EL240.0

EL241.0

EL243.000

EL301.0 EL303.0

EL251.000

EL237.000

300

EL234.000

EL.297.00

EL244.000

580

EL248.000
EL231.000

ⅰ＝12.0％EL252.000

EL250.000.57
5EL259.000

EL241.000

EL227.0000

Crest length 390000

15000 12500 21200
2500
12500×3+2000×24500
24@15000=360000

M

M

M

EL228.000.50EL240.000

EL241.000

308

EL254.000

EL255.000

EL238.000
EL224.000

EL252.000

EL246.000

EL245.000

585

EL275.0560

EL213.500

1:1.

作業構台

EL206

J21+320

1：1.2

EL206.0

EL267.000

EL218.000

EL266.50
EL217.000

Emergency spillways
41500

EL207.5
EL217.000

EL235.000

EL223.000

取水塔
EL229.000

232

EL263.000

EL235.000

234

EL270.0EL265.0EL260.0

EL255.0EL250.0

ＥＬ225.00

500

EL22

4

10.0％

EL.287.00

236

J20

10%

街灯

EL241.0

壁

238

擁

0

10%

トラ

0.0

EL218
ーブ

.24
光ケ

EL

60°

ル柱

600

Power station
流
ム放
張ダ
大夕 看板

EL242.0ーブEL243.0
光ケEL=EL297.00

308

ＥＬ297.00

EL=NTT

EL244.0

壁

護岸ブロック
土留

0

J19

.8

Control officeEL245.0J180EL246.0

J17

5.0
.28

250

J16

EL

244

J15

1：0

124000EL247.0

J14EL267.000

4.075

EL.255.00

J13

EL265.000

4.150

.00

J12

EL263.000

255

EL.

J11

EL262.000

EL=28

65.0

J10

EL260.000

EL=28

EL.2

.00

EL=29

1.150

1:1.2

1.225

.2

J9

EL256.000

1:1

260

1:1.2

EL=29

1:0.8

.00

5.0%

EL=29

7.075

Water intake facility

EL252.000.2J8EL247.000

1:1

J7EL242.000

1:1.2

J6
EL238.000

EL277.0J5EL232.000

U形側溝工

J4

EL.240

8.500

1:1.2

5
1：1.

EL=30

J3

EL.250EL264.00

20000

J2

EL243.0

EL215.0

EL232.000

EL226.000

ロ－プ

擁壁

EL217.5226

EL225.0

EL

Auxiliary dam
023.0EL220.000

EL235
EL213.500

EL291.0EL244.0.0EL232.000

EL306.6

J1

EL245.0
EL237
EL229.000

EL305.0

EL246.0

1:2.0

EL225.000

EL306.6

1:2.0

EL221.000

Ｊ0
1:2.0

EL241.000

J0

1:2.0

EL238.000

Axis of dam
1:2.0

EL

22
225

Grouting tunnel

EL235.000

ガ－ド

路
進入
8.1%

EL

LEV

EL2

18

EL2

18

ル配

線

フ3

00

電柱

1

1：1.2

13
DAMS IN JAPAN - OVERVIEW 2018

Yubari-Shuparo Dam

＠ Hokkaido Development Bureau, MLIT

8

EL21

S=1:1000

電柱

Valve chamber

Energy dissipation

1:2.0
EL225.0

J25

EL306.6

J26

J26

Grouting tunnel

EL207.5

EL212.0EL306.6

1:1.2

EL 218.000

右岸崖錘斜面対策工

1:1.5

EL.230.00

12500×4+2000×3

53200

10000

Axis of dam

DAMS IN JAPAN - OVERVIEW 201814

Overflow section S=1:1000
Spillways

am

fd

is o

Oyubari Dam

Ax

155000

EL（m）
320

2500

8000

Cresat elevation EL306.600
EL304.400
DFWL
SWL
EL301.500

300

NWL

EL297.000

EL297.000

280

00

76600

EL266.500
F.W.L 264.500

L.W.L 240.000
EL237.000

LWL

ダム高 H=110600

EL256.000

EL259.600

Dam body Energy dissipation

82
0.
1:

260

15

240

EL230.000

0.

1:

L.W.L 230.000

77EL226.000

1:
0.
80

34000

EL213.500
EL206.000
2000.5EL205.700

1:0

.5

90036

39800

0

1:0

88000

1.

Apron
Foundation rook EL196.000
27200

6750

EL220.000

EL215.500

EL208.000

EL206.000
200

EL199.000.0

Auxiliary dam
1:

1:0.10EL214.000

R=

EL216.750

1:2

0

00

20

220

5464

78963

13300

11723616000

118727180

Figure-2 Typical section

Crest length 390000

EL（ｍ）
10000

53200

Emergency spillways 56000

24@15000=360000

Spillways 57600

2000

21200

Emergency spillways 15000

12900×4＋2000×3

12500×4＋2000×3

12500

4500

12400012500×3＋2000×2

Water intake facility
26BL

J26
300

20000

Emergency spillways 41500

2500

320

J25

25BL

24BL

J24

23BL

J23

22BL

J22

EL304.600
EL301.500

21BL

J21

20BL

J20

19BL

J19

18BL

J18

17BL

J17

16BL

J16

15BL

J15

13BL J12 12BL J11

14BL

J14

J13

11BL

9BL

10BL

J10

J9

8BL

J8

7BL

J7

6BL

5BL

J6

J5

4BL

J4

1BL

HWL 304.400
SWL 301.500

EL301.500

EL301.500
EL297.000

3BL

2BL

J3

J2

1BL

J1

EL295.000
EL289.000

EL280.000

280
EL275.000
1：0.82

1:0.2

EL273.000
EL266.500

EL266.000
EL263.000
LWL 259.600

1:0.15260

EL258.000

EL258.000

EL250.000
EL246.000
EL243.000

EL245.000

240

EL240.000

EL242.000

EL241.000

EL235.500

EL235.000
EL231.000
EL227.000

EL227.000
EL225.000

EL228.000

EL226.000

EL221.500

220

EL206.000

EL204.000

200

EL205.500

EL200.000 EL200.000

EL200.000
EL196.000

S=1：600
0

180

Figure-3 Downstream elevation

J0
EL299.850

NWL 297.000

5

10

20

30

40

50

Cresat elevation
EL306.600

5000

15

DAMS IN JAPAN - OVERVIEW 2018

Tokunoshima Dam

＠ Kyushu Regional Agricultural Administration office, MAFF

＠ Kyushu Regional Agricultural Administration office, MAFF

DAMS IN JAPAN - OVERVIEW 201816

Intake tower
Control officeOutlet works

Power station

Spillways

Figure-1 Plan
EL.120.0m

EL.120.0m

10,000
4,000
3,000

1,000

3,000

1,000

EL.110.0m

EL.110.0m▽

HWL 103.50m ▽EL.100.0m

Cresat elevation EL.106.30m

13.3m

SWL 102.80m▽

NWL F.W.L.100.30m

EL.100.30m

EL.94.00m
EL. 90.0m

1

2.60

2

EL. 80.0m▽

LWL D.W.L.79.60m

1
1

1.20

2.60

EL. 70.0m

Rock1

1
0.20

1

EL. 80.0m

1.30

0.20

Core

EL83.0m

1

1

Filter

Rock2

EL. 90.0m

0.20

1Filter

0.20

1

k
Roc

EL.100.0m

2.00

Rock1

Rock2

EL. 70.0m
EL.67.50m

Foundation rookEL. 60.0m

EL. 60.0m

EL. 50.0m

LeakageEL.50.00m

EL. 50.0m

Blanket grouting
Blanket grouting

EL. 40.0m

Curtain grouting
2,000

26,3202,000

Curtain grouting

Figure-2 Typical section

EL. 40.0m

17DAMS IN JAPAN - OVERVIEW 2018

159.6

.9

0
14

189.0

0
16

Ｇ
136.50139.42.5

139.19148.39144.98T-18

137.36

150

（岩）

0
1:1.

0
00
12
00
150

+EL135.000

139.45

Ｇ

189.0
194.3
200.4
212.9

207.26230 測線

218.02

210

216.4

186.1

192.1

220

T-206

7

143.67

T-54

T-247
171.19165.50135.99138.74（岩）

209.13213.54211.46215.49180.49No.

199.9198.04139.40J8

211.44

T-245

R=10
0

139.00136.63137.400158.500T-212

142.82144.1820EC.2

157.07

T-179

i=10
.000
L=61
％
.000

J1
J9

T-207

147.32174.86179.52

6

143.58T-180

170
178.94184.02

T-213

No.

120

167.04224.72

T-144

202.92.200

158.18167.42
175.65

212.3

200.4

川原平幹線76160

218.63

211.2

211.5

169.13

219.0

IP.

0
00
11

180

177.7

184.0

188.8

+EL150.000

2139.34SP.

ジャカゴ

143.48BC

145.21

153.230198.5

260 測線

2

149.81

212.7

T-246

T-214

137.23137.06164.16

No

149.11

10

T-17

169.56

R=

183.7

14
8.
48 250
.0
00
)

184.2

194.06146.09151.59

(1

190

T-208

159.78

T-14

190

T-58
148.98218.22202.2

0170.58156.90

T-15
215.6

206.4

E L170.0

17138.92

189.0

161.5

170.6

179.0

E L170.0

184.4
198.3

204.0

149.25

.3

199.6

.4

1:2.
12

No

137.24143.15

1:0

198.0

185.4

185.26145.19T-16

260 測線

210.5

193.3

164.84Ｇ

138.68145.32

T-19

0.3

202.4

205.6

180

T-215

(休）

153.25

213.0

201.6

15

0

143.85

188.4

176.9

159.4
169.3

170.5

L=9 LEVEL
6.0
65

187.6

138.69136.77

1:1.
25

156.78.3

184.5

168.56No

191.0

159.70150.97

1:

209.6

200.6

T-225

T-209

159.68

209.7

199.3

70

143.77

T-20

139.95234.76

192.7

185.1
1 47

151.02

Ｇ

156.77

T-143

181.6

R-210

168.00156.6

ｗ

153.21150.73

EL

195.3

155.7

162.7

171.8

181.4

184.4

146.25.2

187.4

137.25138.73151.73149.90

191.8

T-40

180.1

185.0

194.6

T-226
149.72

1:1.0

194.1

R-180

R-150

R-120

146.50144.67

T-22
193.4

R-165

142.20142.85T-216

140.48

203.7

176.1

158.0

R-135

R-90

R-105

R-45

152.5

159.6

161.5

165.6

181.1

196.2

140.84137.88136.74138.18

IP.1

161.2

R-75

R-15

R-30

CL

L-15

R-60

137.14147.25152.49

T-21

204.0

167.7

148.6

153.4

154.9

169.4

L-30

L-45

168.1

L-60

L-75

L-105

L-90
165.5

166.98137.66138.40152.48150.60230 測線

173.7

L

L
171.0

171.2

177.1

178

L

L

（空）

177.0

182.3

183.7

192.4

181.1

179.7

L-135

180.2

183.7

189.1

L-165

L-150

199.6

L-180

L-210

L-120

L

L

L
213.1

L

219.8

227.0

231.5

L-240

197.8

135.31

T-24

Ｗ

138.31

T-224

163.58145.17

No

207.4

.1

198.8

（岩）

60

215.8

EC

136.50

No.1
SP.1

206.7

140.73T-23

152.49166.68137.49

R=

216.2

BC.1

134.97137.87

140

220.2

T-38
146.54

＠ The Tohoku Regional Development Bureau, MLIT

138.43139.89152.67152.13214.3

164.99

T-217

R=60

223.4

No.0-10.000

231.8

142.36

No.7

226.5

136.21134.62138.44138.28No.0(No.7+7.417)
148.300(148.000)

L

Tsugaru Dam

220

180

182.79231.53217.80218.15136.93160.78218.59208.82139.62

T-248

146.73223.82137.55

T-53

No.8

IP.3

135.81139.7600

136.88

15

0

1:0.5

200

210

220

230

EL200.000

EL190.000

EL180.000

EL220.000

1:0.
8
1:0.

5

0

0

1:1.

1:1.0

210.97

1:1.

175.98

3級

1:1.

0

200.88231.68

BM.1

1:0.5

2
283.10252.06

256.62
192.59178.47224.28248.550201.52187.93187.90187.92187.90257.940 測線

270.50284.06272.48283.41274.81285.56T-128
174.21

173.15185.43241.54T-126
188.57

T-91

211.56227.41204.70195.26

T-93
T-92

188.24T-158

187.91

187.87

T-79

209.72190.74No.1（ﾌ （№ﾞﾚｰｷ 0+
ﾎﾟ 10.4
ｲﾝ
93
ﾄ））

225.11

(As)

川原平35

181.78175.45189.99204.79245.75264.45225.74211.98

T-127

188.8619

T-125

186.02266.60

T-95

（岩）

T-160

No.2

258.07189.33

T-124

No.3

176.06222.90T-161

262.43

270No.4

271.97187.539185.501:1.0
176.45174.90230.74

No.5

20 測線

171.89178.13182.45223.23231.76285.10265.72（岩）

209.73185.49237.21

No.6

1.
1:
2
275.17260.46

0

1:1.0
180

1:1.0

164.39

1:1.0

1:0.5

0

T-273

188.24T-159

233.70287.12

T-272

1:1.

0

191.60187.95237.00230.76257.19278.31

177.930233.29247.4850 測線

192.09EL180.000
EL180.000

177.11179.43

1:1.

.0236.49

T-270

T-269
265.55235.94165.30

T-156

0

0

0

No

236.53239.77157.09

1:1.

60 測線
C 測線

259.71

EL227

0.00

229.36

1:1.

0
235.00247.29

0.00

1:0.5

240

25
0

EL21

244.980.00

210.13230.08

1:1.0

1:1. 174.65
0158.46

156.67244.101:0.738

EL170.000
EL170.000

0147.98155.93

1:0.

235.46

EL22

0.00

5

1:0.

5

EL19
EL20

245.54254.70248.80

1:1.

146.45

192.39T-94

7

263.97211.54187.68155.93166.71

T-157

1:0.

5

233.56T-150
253.54244.59169.06

Meya dam

144.93149.40145

00206.300

1:1.

235.40247.070.00

177.61290.33

23

1.

17

0

5

1:0.5

T-173

0.00

1:0.

5

0.00

1:0.

EL18
210.24

T-114

No.7

EL

EL

1:

160
160

141.92EL16EL17209.69224.20T-151

EL180.000

187.24

1:1.0

150

1:0.5

5
199.16

T-155

229.78

1:0.5

0
T-153

0
1:1.

230

（岩）

223.17288.03279.66264.73

1:0.697201.27

1:T-2811.0EL160.000
EL160.000

172.11

T-187

155

1:0.5

床 固

1:0.5

230.20242.56258.46

1:0.899186.84

1:0.8

1:0.5

EL140.000

1:0.5

65 測線

268.59Inspection gallery

T-274

EL170.000

1:1.0

172.26+EL160.000

264.02

T-271

T-280

190.13169.43

T-188

166.49

1:0. 8141.96

1:1.

T-149

230

278.36

T-236

242.11+EL.221.80
217.25

1:1.0

141.6255212.91

236.62139.58140.19163.96200.82190.02

2185.5717（岩）

140.45

T-192

190.67

T-154

T-113

233.2780 測線

272.75T-235

1:0.182

1:0.182

1:0.182

1:0.182

1:0.182

171.191.

160.681:

140.23179.340
1:1.

252.67230.73

1:0.5

L=34.167

LEVEL
L=10.000

1:0.74

T-237
264.31EL220.000

139.32

1:0.

1:0.

222.250 測線

Intake tower

140.13162.99170.18220251.84273.21241.83266.40000

176.39

T-172

5
1:0.

213.09

5
1:0.

T-152

248.753
1:0.69+EL227.000

EL210.
000

184.585
1:0.

210
214.97

T-112

243.59286.56

T-275
1:0.634

EL200.

Cresat elevation EL226.700

191.62

1:1.0
1:1.0
234.05255.42274.35270.04265.61

1:0.724

1:0.8

216.58200.56EL190.
000

199.88200

256.3020 測線

i=12.000％150

1:0.182

1:0.182

1:0.182

1:0.182

1:0.182201.22

1:1.0

266.07261.52

T-234

タ

268.16268.93

Ｇ

1:0.

1:1.0

213.47T-167

259.09

T-279

T-282

184.30169.74

1:0.5

EL247.000
EL247.000

EL257.000

3NO.1

172.88283.86T-238

142.47

EL190.
000

236.34

1:1.0
1:1.0

268.68158.65

1:0.8

265.41

184.401:0.182257.72257.72267.7450 測線

139.48

T-291
1:0.8

270.09266.27

246.67

床 固

床 固139.15273.66

1:0.8

110 測線

266.48189.36

EL237.000
EL237.000

60 測線
C 測線

T-1
264.77167.29

T-170

1:0.5

265.51

T-278

T-276

170

182.67

T-168

65 測線

（岩）

270.38T-283
183.05

190

Axis of dam

262.25180

EL220.000

1:0.74190.36

Control
office245.39（空）

Spillways
170.52

床 固

T-169
214.15

1:0.8

240

1:0.8

237.581:0.8

219.14250

260.30

1:0.8

1:0.8

Grouting
tunnel Inspection gallery

259.34

1:1.0

197.38

T-96

T-189

148.83

T-191（岩）
137.5280 測線

181.72

Conduit gate
137.06174.80183.58260.31

259.94LEVEL
L=28.800

0

000
21

15000

1:0.74

EL190.000

Spillways

166.45T-171
193.45WC

173.271275418

EL220.000

EL200.000

1:0.5

1:0.8

EL210.000

15000

253.0
266.6

212.84234.16154.85145.34138.64260

254.42

T-277

1:1.0

181.51

T-186
137.70T-292

269.69

1:0.5

T-230

180.55162.03143.86137.45138.78263.09T-293

268.40

EL257

8
1:0.

T-130

265.0815140.32

T-174

171.02174.57259.94

T-295

EL247

T-183

T-139

182.06193.15140 測線

257.50T-239

261.53G
174.91

1:0.8

1:0.5

EL16
0.00

1

0

8
186.18200.59268.02272.37

1:0.8
268.6215

192.57208.90245.63240.26

1:0.8

1:0.75

EL237

0.00

T-136

1:0.

196.67234.43260
217.66

1:1.0

1:1.0
177.10EL210.000

8

EL17223.64

T-132

1:0.8

271.93
195.48

1:1.0
179.60174.31T-137

8

208.00243.77249.53

1:0.8

219.72179.02

172.19(Co)

251.32150 測線

253.60215.21
178.48T-185

167.06173.25

T-175

2

250

267.13161.20T-190

EL160.000

0.

160 測線

222.34170

EL18244.14244.32EL242.5

T-296
EL237

T-240

1:1.0
185.91

1:1.0

153.581:0.

227.45245.82

255.35160

149.23139.96170 測線

248.65216.37141.26J0
142.25

8
1:0.

1:0.

T-251
177.93174.51152.80133.20137.51138.89175.47000

259.34110 測線

142.55133.10178.151:0.50203.40

1:0.8
231.88Ｇ

160.21

1:0.5
0.00

216.19207.53176.95

No.11

1:0.5

0.00

EL19

245.62265.68J1

202.480T-135+EL150.000

146.52

Valve chamber

T-182

137.44

0

EL237

1:1.0

No.11
+10.022

0.00

1:0.8

T-241

270.63150.000

EL21

EL20216.97

1:1.0

1:1.0

0″

T-134

1:1.0

T-133

8
1:0.

1:1.0
230.850240.13

T-131

266.250′

224.00229.62232.41

24

252.26138.76176.59253.18T-242

260.60201.6111°

241.72

256.968
1:0.

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川原平幹線78155.04139.75

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195.62261.12244.32173.6816138.14150.300(150.000)

190

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8

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180.99

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8

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253.53265.160136.34141.08

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190.55

BL 8

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BL11

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207.45青森県

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Figure-1 Plan
J11

J12

J13

BL17

BL18 181.07

BL19

BL20

BL21

BL22

BL23
202.23

J15

J14

J16

J17

J18

J19

J20

J21

250.20J23

262.01273.05

T-304
T-123

208.82190.01

R-150

R-135

R-115

186.35

R-120

R-110

R-105

R-100

(Co)

R-95

R-90

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R-45

224.69J22

川原平幹線86
174.45

R-60

R-15

R-30

CL

L-30

L-45

L-60

L-50

L-55

L-75

L-70

L-65

L-90

L-105

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7

DAMS IN JAPAN - OVERVIEW 2018

18

am

a d

Mey

f
s o

am

f d

s o

Axi

EL.(m)

Axi

240
60000

9000

Cresat elevation
EL 226.700
DFWL EL 224.500
220

SWL EL 216.300
NWL EL 204.900
200

1:Cresat elevation
EL 187.500

0.

DFWL EL 186.000
NWL EL 183.000

74

180

Dam body Energy dissipation

LWL

97473

R=1

EL 160.000

00
50
R=1

12058

3700

EL 152.500(Right bank)

1:
0.

EL 153.500(Left bank)

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.0

000

EL 142.000

EL 135.000

2000

1000

0
1.
1:

EL 135.00

16000

1000

5000 4000

1:
0.
6

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R=1

0
000
R=1

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EL 146.00

140

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0
500

1500

160

Left bank 152974（Right bank 92780）

LWL EL 170.000

17500

HWL in flood season
EL 170.500

Foundation rook EL129.500
Diversion conduit
B5.0×H4.5m
120
87.0m

44000
11100

71928

45473

3490

10000

89473

62.8m

24000

123473Figure-2 Typical section

R - 1 65

R - 180

R - 13 5

R - 150

R-110

R - 120

R-105

R-100

R-95

R-90

R - 60R - 75R - 30R - 45R - 15

CL

L - 30L - 15

L-45 L-50 L-55 L-60 L-65 L-70 L-75

L - 90L - 10 5

L - 1 35

L - 120

L - 15 0

L - 1 80

L - 165

EL(m)

EL(m)

320

320

300

300

Crest length 342000

280
10@15000=150000

16000

2000

2000

13000

2000

13000

2000

13000

2000

13000

13000

2000

13400

2000

12700

2000

12700

8500
1418

6100

12200

6100

BL23

J21
BL22

J20
BL21

J19
BL20

J18
BL19

J17
BL18

J16

J15

BL17

240

BL16

J14
BL15

5000

Non Overflow section 118900
2000

12700

12700

2000

13400

2000

13000

2000

13000

2000

13000

2000

13000

2000

1418
5665

J13
BL14

8500

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1418
5665

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9@15000=135000

Overflow section 96200

260

J23

280

2@18000=36000

Non Overflow section 126900

J12
BL13

260

J11
BL12

J10

J 9

BL11

J 8

BL10

BL 9

J 7
BL 8

J 6

J 5
BL 6

BL 7

J 4

J 3

BL 5

BL 4

J 2
BL 3

J 1

J 0
BL 1

BL 2

240

取水設備

Cresat elevation EL226.700
EL220.000

1:0.182

1:0.182

1:0.182

EL221.000
220

220EL205.000
EL201.756
200

12000

EL201.756

3000

200

EL193.000

Spillways

Spillways

B4.3×H4.4m

EL187.000

12000

1:0.74

1:0.74

EL198.000
EL1944.000
EL188.750

B4.3×H4.4m

4000

EL176.000
3000

1:0.74180
EL175.000

6000

EL177.000

EL170.000

呑口：φ6.019m
EL167.000
12000

160

3000

吐口：B3.9m×H3.6m

5625
2000

EL154.000

EL160.000

EL159.577

EL158.577

EL157.000

12000

EL150.000

3000
EL145.250

EL144.000

12000
3000

EL143.000

140
3000

EL142.000

5000
5000

EL135.000
2000

EL133.000
EL130.000
EL129.500

DiversionDiversion
conduitconduit

12000

12000

B5.0×H4.5m

3000
12000
3000

160

EL154.000

EL153.500

EL152.500
EL150.000

120

3000

6375

10000
3000

180

Conduit gate

6000

7400

3100

15000

4500

3000

2250

15000
750

3000

100

9100

15000

15000

18000

18000

15000

6100

80

Figure-3 Downstream elevation

140

19

DAMS IN JAPAN - OVERVIEW 2018

Introduction
toto
DamTechnologies
in in
Japan
IntroductiontoDamTechnologies
Japan
Introduction
Dam
Technologies
Japan
Trapezoidal
CSG
dam
Trapezoidal
CSG
dam
Trapezoidal
CSGdam

the dammaterials
requireless strength,
the required
performanceofthematerial
is
and
there
are few
the body
dam body
materials
requirelesslowstrength,
the required
performanceof on
theofthematerial
is low
andare few
restrictions
selectionof ismaterials,”
performancethematerial
low there
and “Rationalization
there
are few
on theof materials,”“Rationalization
onselection
the selectionof materials,”“Rationalizationofrestrictions
design:The
trapezoidal
shape
improves
seismic stability,
Thetrapezoidal
trapezoidal
CSG
dam developed
in is
Japan
is a new restrictions
The
CSG
dam
in Japana new
The trapezoidal
CSGdeveloped
dam developedin Japanis atype
new typeof design:The
trapezoidal
shapeshape
improves
seismic
stability,of design:The
trapezoidal
improves
seismic
stability, is
and
so
the
strengthrequired
of
the
dam
body
materials
type
of
dam
which
combinesthecharacteristicsofaof damcombines
the characteristics
of a trapezoidalof which
dam whichcombines
the characteristics
of a trapezoidal
and sothesostrength
requiredof theofdambodymaterials
isandthe strength
requiredthedam body
materials
islower,”
and“Rationalizationof
construction:
Construction
trapezoidal
Dam
and
the
CSG
(Cemented
Sand
andGravel)Dam Damand andthe CSG(Cemented
Sand Sand
and andGravel)the CSG(Cemented
Gravel)lower,”
and“Rationalizationof
construction:
Construction
lower,”
and“Rationalizationof
construction:
Construction
work
can
be
executed
rapidlybysimplified
construction
construction
method.
Itrationalizes
theconstructionofconstruction
method.
It rationalizes
the construction
of ofconstruction
method.
It rationalizes
the construction
workfacilities.”
can berapidly
by simplified
construction
work
canexecuted
be executed
rapidly
by simplified
construction
damsdams
three
ways:
“Rationalizationmaterials:
becausedams
ininthreeways:“Rationalizationof ofmaterials:
becausein threeways:“Rationalizationof materials:
becausefacilities.”
facilities.”
the dam body materials require less strength, the requiredProtectionProtection
concrete concrete

CSG

CSG

ProtectionProtection
concrete concrete

Structural Structuralconcrete concrete
InspectionInspection
gallery gallery
Seepage control
concrete
Seepagecontrol concreteRich mix CSG
Rich mix CSG

Auxiliary curtain
grouting
Auxiliarycurtain grouting
Foundation
drain holedrain hole
Foundation
Curtain grouting
Curtain grouting

Figure-11
Conceptof Trapezoidal
CSG
dam damFigure-11
Conceptof Trapezoidal
CSG
Figure-1
Conceptof Trapezoidal
CSG
dam

Sediment bypass tunnel (SBT)
SBTs are one sustainable and effective strategy against
sedimentation. The SBT connects upstream anddownstream of a dam and bypasses sediment-laden floods
into downstream. They are mainly operated in Japan,
Switzerland and Taiwan.
In Japan, SBTs are operated at the oldest

Figure-12
Tobetsu
DamDamFigure-12
Tobetsu
Dam
Figure-2
Tobetsu

concrete dam in Japan, Nunobikigohonmatsu Dam (1900),
Tachigahata Dam (1905), Asahi Dam (1998), Miwa Dam(2005). Also, they are currently undergoing trial operation
at Koshibu Dam and Matsukawa Dam. The problem
of SBTs is countermeasure against invert abrasion andelucidation of sediment hydrological behavior, and research
is currently under way.

Figure-3 Sediment bypass tunnel (SBT)

Figure-4 Miwa Dam

Preservation measures of dam reservoirs

One of water quality preservation measures for the dam
reservoir is conducted by controlling outflow of pollutant
and nutrient salts from the catchment area.

Water quality issues are closely associated with the size ofthe dam reservoir, and operation of the dam reservoir.

DAMS IN JAPAN - OVERVIEW 2018

Fence
Fence
Fence

Aerating circulation
Aerating
circulation
Aerating
circulationTo change water temperature distribution or otherTo prevent the spread of algae or to shift thenutrient flow away from surface to middle layer

conditions inadequate for algae growth
To changewatertemperature
distribution
To changewatertemperature
distributionororotherotherconditions
inadequate
forforalgae
growthconditions
inadequate
algae
growthNo operation
operation
No No
operation

20

Topreventpreventthethespreadspreadalgae
to shift
To
of of
algae
or or
to shiftthethenutrientflow
flowawayaway
fromsurfaceto middle
layer
nutrient
fromsurfaceto middle
layer

Operation
Operation
Operation
Upper stream

UpperstreamUpper
streamLower stream

Lower
stream
(Dam
side)
Lower
stream(Dam side)(Dam side)

Figure-19Reservoir
ReservoirWater
Waterquality
qualityfacilities
facilities
Figure-5
Figure-19
Reservoir Water
quality facilities
Figure-19 Reservoir Water quality facilities

Inflow of
Inflowofnutrients
Inflowofnutrients
nutrients

Sunlight
Sunlight
Sunlight
Algae blooms
Algae blooms
Algae blooms

Shading
Shading
Shading

Fence

Fence

Auxiliary
Dam
Auxiliary Dam

Algae blooms
Algae blooms
Algae blooms

Selective

Selective
Discharge
Discharge
Selective

Discharge
To select adequate water depth to

To select adequate water depth tointake better quality of water
intakebetteradequate
quality of water
To select
water depth tointake better quality of water

Fence

Auxiliary
Damthe load ofTo
To reduce
reduce theload ofnutrients
to aa dam
dam reservoir
reservoir
nutrients to
To reducetheload ofnutrientswithwith particulate
particulate nutrientsnutrients
toadam
reservoirsettledsettledwith particulate nutrients
settledform
AirAirform
Air form

Air Air
formform
Air form

Aerating
circulation
Aerating
circulation

BypassBypassBypassTonutrients
inflow
Tocut
cutoffoffthethenutrients
inflow

Aerating circulation

Figure-20
of ofqualityconservation
measures
Figure-20Example
Examplequalityconservation
measures
Figure-20 Example of quality conservation measures
Figure-6 Example of quality conservation measures
to time.
to time.
Advancement ofAdvancementof flood
floodcontrol
controloperation
operation
Therefore,theappropriate
operationis conductedallAdvancementof
flood
control
operation
totime.
Therefore,
the theappropriate
operationis conducted
at allat
Advancement of flood control operation
Therefore,
appropriate
operationis conducted
at alltimes,
makinguseoftherainfallprediction
technologies
Recently, flood
flood disasters
times,
makinguseof therainfallprediction
technologies
Recently,
disasters caused
caused byby heavy
heavyrains
rainsoccur
occur Therefore,times,
makinguseoftherainfallprediction
technologies
theoutflow
appropriate
operation
isand
conducted
at allRecently,
disasters
by
heavy
occur
flood
analysismodel
maximizing
frequently floodin Japan.
It is set caused
that the flood
controlrains
operation
andandflood
outflow
analysismodel andmaximizing
the flood thefrequently
inJapan.
It
is
set
that
the
flood
control
operationandflood
outflow
analysismodel
andmaximizing
the
flood
Recently,flood
disasterscaused
by
heavy
rains
occur
times,
makinguseoftherainfallprediction
technologies
frequently
Japan. work
It is set
thateffectively
the flood forcontrol
operation
flood capacity
control capacityof thethe preventionof the daminshould
mostdesignflood
controlof the dam
so damthat sothe that
prevention
or
of
the
dam
shouldwork
mosteffectively
fordesignflood
control
capacity
of
the
dam
so
that
the
preventionorfrequently
inJapan.
It
is
set
that
the
flood
control
operationandflood
outflow
analysismodel
andmaximizing
the
flood
ofscalethe anddamdesign
shouldwork
effectively
for design
or mitigationof flood
damagescanachieved
be achieved
wave
form.mostHowever,as the rainfall
is amitigationof flood
damagescan bein thein thescaledamanddesignwave
form.
However,astherainfallisamitigationofflood
damagescanbeachievedintheof floodtheshouldwork
mosteffectively
fordesignflood
control
capacity
of
the
dam
so
that
the
preventionoror phenomenonhydrograph.theHowever,as the rainfall
a natural
downstream
areas.
naturalrainfall condition
varies isfromtime
downstream
areas.
naturalphenomenon
thecondition
rainfallcondition
time
downstream
areas. damages can be achieved in thescale
and designform.
However,
as from
thevaries
rainfallamitigationof flood
phenomenon
thewave
rainfallvariestimefrom
toistime.
natural phenomenon the rainfall condition varies
from
time
downstream
areas.
Avoidance of inundation
To cut off the nutrients inflow

Avoidance of inundation

Nabari River

Nabari River

Avoidance of inundation
About 1.5 m
of About
drawdown
1.5 m
8.0
of
drawdown
Design
high
Water
level
About
1.5
m
8.0
of
drawdown
Designhigh Water level

Nabari City
Urban areaof Nabari
Urban
area
City

of NabariUrban areaCityof NabariCity

Nabari City
Hinachi Dam 8.0
Nabari City
Design high Water level
Hinachi Dam
ShorenjiDam
HinachiDam

Shorenji Dam
Shorenji Dam

Murou Dam

Murou Dam

Water Level (m)Water Level (m)Water Level (m)Nabari River

Actual water level

WaterActuallevel withoutdams
water level
WaterWater
Level oflevel without dams
Actuallevel
normal water
dam operation
Water Level of
Waternormal
level without
dams
dam operation
Water Level ofnormal dam operation

6.0

6.0

6.0

Water level at Nabari City, downstream of 3 dams

Water
at NabariCity, downstream
3 dams･Heavyrain due to big typhoon threatened
to levelcause
inundationin Nabari ofRiveron
Murou Dam
Water level at Nabari City, downstream of 3 dams
October 8, 2009.
･Heavy rain due to big typhoon threatened to cause inundation in Nabari River on･Japan Water Agency’s O&M offices conducted collaborative operations in view of water
October
8, 2009.
･Heavyrain
duetoto threecausedams
inundation
Nabari control.
River onlevel,
rainfall,andbigdamtyphoon
capacitythreatenedof each of theunder its in
integrated･JapanWater
Agency’s O&M offices conducted collaborative operations in view of water
October
8,
2009.
･The above figures show that the water level of urban area was kept below the designlevel,
rainfall,anddamcapacityof each of thethree damsoperations
under its integrated･JapanWater
Agency’s
officescollaborativein view ofcontrol.
water
flood
water
level
at O&M
NabariCity. conducted･Therainfall,above figuresthat oftheeachwater
levelof urbanarea waskept below
the designlevel,and damshow
capacityof thethreedams under
its integrated
control.
levelatNabari
City.
･The flood
abovewater
figures
show
that
the
water
level
of
urban
area
was
kept
below
the
Figure-21 Flood control through integrated and collaborativedesign
operation of three dams
flood water level at Nabari City.

Figure-21 Flood control through integrated and collaborative operation of three dams
Figure-7Flood
Flood
controlthrough
integrated
andcollaborative
operation
three
dams
Figure-21
controlthrough
integrated
andcollaborative
operation
of of
three
dams

21

DAMS IN JAPAN - OVERVIEW 2018

Dam Upgrading Vision
It is important to effectively use existing stocks while
controlling total costs. Various technologies will beadvanced as the number of cases of the effective use ofexisting dams grows. On the other hand, more frequentand intense flood damage and more frequent droughts
are concerns. Under this context, dam upgrading will bepromoted by effectively using existing dams applying
both hard and soft measures according to each basin’s
characteristics and issues. Typical examples are shown infigures. These exhibit that dam upgrading to effectively
use existing dams has features and effects such as greatly
increasing water storage capacity with the slight raising of
dam bodies, or the economic completion of work in a shortperiod of time, to show effects more quickly.

Figure-8 Projects and Technologies to effectively use dams

DAMS IN JAPAN - OVERVIEW 2018

The “Dam Upgrading Vision” which provides a strategy
for the further promotion of dam upgrading efforts that
effectively utilize existing dams has been formulated in2017. These strategies for the vision are categorized below.
1) Dam Life Extension
2) Promoting Efficiency and Advancement of Maintenance3) Flexible and Reliable Operation to Optimally Utilize the
Capacity of the Facility4) Improving Facilities for a more Advanced Functionality
5) Responding to Climate Change

Utilization of ICT in construction of dam

Utilization of ICT in construction of dam

The construction industry in Japan aims at drastically
improvingproductivityof all aims
construction
production
The constructionindustryin Japanat drasticallyby utilizing
and its approachis called iimproving processes
productivityof allICT,
construction
production
Construction.
processes byutilizing ICT, and its approach is called
Even in the construction of dams, the utilization of ICT has
i-Construction.
Even in thebeen
constructionof dams,
the utilizationof ICTadvanced toward
improving
quality, safe sitework,
has been advanced
improving
quality,safe siteof
shortening towardof construction
period,and reduction
work, shorteningof construction
period, and reduction of
construction
cost.

22

6) Addition of Hydropower
7) Protection and Revitalization of River Environment8) Regional Development utilizing the Dams
9) Promoting Dam Upgrading Technologies Overseas
10) Development and Implementation of Technologies toPromote Dam Upgrading

In addition, using ICT to share information in real time andInusingaccumulate
ICT to share3-dimensional
information in realtime
toaddition,utilize anddata
can contributeandtoutilizeandaccumulate
3-dimensionaldatacan
to a dramatic rationalization of actions throughout the dam
contributea dramatic
rationalization
actions
life cycleto fromthe design
stage, ofthe
construction stage tothroughout
the
dam
life
cycle
from
the
designthe operation and maintenance stage. stage, theconstruction stage to the operation and maintenancestage.

construction cost.

Figure-●ApplicationofofICTICT forConstruction
Figure-9
Application
forDamDam
Construction

23

DAMS IN JAPAN - OVERVIEW 20152018

Papers in ICOLD & Other Technical Publications
Theme 1    Safety supervision and rehabilitation of existing dams
A. ICOLD 84th Annual Meeting International Symposium in Johannesburg, May 2016
Development of emergent monitoring system for leakage
from the dam

External deformation monitoring of five rockfill dams inthe same radar satellites data

T. Higuchi, T. Sugai, T. Sato, and T. Kayukawa

H. Sato, T. Sasaki1, T. Kobori, Y. Enomura, Y. Yamaguchi, W. Sato,In this paper, the development of 24-hour monitoring system forleakage from the dam by using goods on the market will be introduced. From the middle of November in 2013, the IWAYA Dam
Management Office had conducted 24-hour alert condition becauseof unexpected increasing leakage from the dam body and its shallow foundation. The initial monitoring system for leakage volume
had some drawbacks in terms of conducting 24-hour alert condition. Some engineers of the IWAYA Dam assembled ad-hoc monitoring and alert system developed by using goods on the market,
such as a smartphone.

Suggestions for dam crisis management learned throughThe 2011 off the Pacific Coast of Tohoku Earthquake
H. Okumura, T. Matsumoto, and K. Koyama
On 11th of March, 2011, the 2011 off the Pacific coast of Tohoku
Earthquake, with a moment magnitude of 9.0, hit on Numappara
dam. Immediately, more than 1,000 l/min of leakage increasing
which was assumed to run through caused cracks on the asphaltic
facing was detected. To avoid a possible serious failure, the waterlevel was drawn down to the safe one. This paper describes thesuggestions for dam crisis management learned through these
responses taken for the Earthquake and also focuses on the importance of the usual dam monitoring.

N. Mushiake, K. Honda and N. Shimizu
It is important to research new methods of conducting effective
measurements of the external deformation of embankment dams.
External deformations of five rockfill dams in the same SAR data
were measured in about four years, and the results of external
deformations using SAR data were compared with those by GPSor conventional survey data. We found that the results of external
deformations using SAR data agreed well with those by GPS orconventional survey data and the average error of the external
deformations between SAR and GPS or conventional survey was
about five millimeters.

Inspection of submerged area with the use of anunderwater camera survey vehicle
Y. Sakamoto, S. Akimoto and K. Kera
Japan Water Agency (JWA) has the standard for the dams as rivermanagement facilities managed by the JWA. All the daily patrol,
inspection, maintenance and repair work, etc. are being implemented based on this standard. But for the areas not exposed, there
has been no measure of conducting the visual inspection. JWA
therefore came up with an idea of using an underwater-camera to
inspect the usually submerged part of the facilities and conducted
the test at concrete arch dam and rockfill dam. As a result, it wasproved that with both dams there were no damage or degradation.

B. 4th Asia Pacific Group Symposium and 9th East Asia Dam Conference, September 2016
Dynamic characteristics of dams evaluated using
earthquake monitoring data for safety assessment
M. Kashiwayanagi, H. Onishi, N. Osada and S. Hayakawa
Earthquake monitoring is normally conducted in high dams inJapan. Detailed analysis of dam behaviour during an earthquake
helps to identify the mechanical properties of the dam which could
reflect its current soundness. This paper focuses on the effective
utilization of earthquake monitoring data for the safety management of dams. Data on concrete gravity dams, arch dams androckfill dams are examined so as to elaborate the management criteria in terms of the response characteristics and the predominantfrequency. Such dynamic characteristics of concrete dams are formulated with influential factors, which are finally identified as thedam height, dam-reservoir interaction and mechanical propertiesof the transverse joints. In addition, the applicability of microtremor measurement is verified for another method of identifying thepredominant frequency of dams through the in-situ measurementof an arch dam. It is concluded that the dynamic characteristics ofthe dam examined can be utilized as management indices to reveal
an abnormal situation or degradation of the dam by detecting theirdeviations.

Study on the deformation mechanism of an ageing dam
aiming at future deformation prediction
H. Onishi, M. Kashiwayanagi and M. Yoda
In evaluation of dam behaviour, deformation monitoring is es-

DAMS IN JAPAN - OVERVIEW 20152018
sential. Although most dams show a stable deformation trend, it
is highly important to confirm whether these trends will continue
in the future assuming that the lifespan of a dam is more than 100
years. If unique deformation behaviours have been encountered ina dam, such as monotonic increase toward the stream direction of
the dam and variation in the deformation degree corresponding toreservoir water level or the ambient temperature, the current deformation mechanism, future dam behaviour, and also the necessity ofcorrespondence should be addressed considering dam safety in the
future. In this report, we studied the deformation and related dataof a 50-year-old concrete gravity dam and interpreted the deformation mechanism with the aid of numerical analysis, and conducteda simulation of dam behaviour in an elastic and steady mannerconsidering the three parameters of reservoir water level, ambient
temperature, and sediment depth. The results of the simulation
show the consistent dam behaviour against these loads acting on
the concrete gravity dam usually.

Application of global positioning system for dam
deformation monitoring
H. Arizono, H. Okumura, H. Onishi and N. Shimizu
Renovation of safety monitoring system of existing dams has
been becoming one of main issues for dam owners. In this regard,
Global Positioning System (GPS) has been applied for dam external deformation monitoring in considerable numbers of existingdams in Japan. Electric Power Development Co., Ltd. which is oneof the electricity utility companies in Japan, and owns rather olddams for hydropower stations, has started to utilize GPS for dam
deformation monitoring for some years, and it has been applied infive dams. Since GPS enables to obtain the data more frequently
than those obtained by the conventional manual measurement,
it is useful to figure out deformation characteristics and its longterm trends more precisely. In addition, since digital data can beobtained automatically and transmitted online, it is also useful toacquire the status in real time, even if personnel cannot access todams. On the other hand, the accuracy of GPS data is prone to beaffected by some external factors such as climate conditions, surrounding plants growth. This paper shows continuous monitoringdata of dam deformation by GPS through case histories in fivedams and their effectiveness as well as countermeasures actuallyprovided to improve foresaid matters.

24

Investigation and repair on deteriorated transverse joint of
Kasabori dam
H. Kawasaki and S. Iwasaki
Kasabori dam is a concrete gravity dam with height of 74.5m
completed in 1964 by Niigata prefectural government in a snowy
region, for the purposes of flood control and hydropower. It was
redeveloped in 1973-79 and again in 2011-17 to upgrade its flood
control function. The present work, which started in 2014, includes
heightening the dam by 4m, placing concrete on its downstream
surface to increase its thickness by 2m, renewing its two gates, andextending its spillway. However, a visual inspection confirmed aserious increase of water leakage around the J2 transverse joint,
and the extension of cracks along J2 since the first repair in 197379. Thus, before the main work, repair work started in 2014 and,cutting down around J2 by line drilling was performed after lowering the reservoir level. After water-stop installation and steel-bar
reinforcement, the concrete was placed, and the J2 repair work was
finished by June 2015. Experientially, there were some difficulties
coping with the transverse joint trouble (Kawasaki, H., et al. 2014).
In this paper, we introduce the investigation process and the repair
work on the traverse joint, and try to explain the mechanism of deterioration by earthquakes and heavy freezing-thawing.

Improvement of deformation prediction of Rock-fill dam
with GPS measurement
H. Soda, S. Nigo and N. Sato
Accurate and continuous data accumulation of deformation measurement of dam body is important for proper dam safety management. Regarding the improvement of the accuracy of rock-fill
dam deformation survey, there are problems that the measurement
frequency is low and the accuracy may be affected by slight differences in measurement techniques and by observer. In recent
years, Global Positioning System (GPS) measurement system
which enables us to measure the exterior deformation of rock-filldam bodies continuously, accurately and three-dimensionally havebeen developed and is experimentally introduced in about 20 damsin Japan. The authors, based on the approximate expressions corresponding to the long-term settlement of the embankment, haveproposed approximate expressions of settlement and the horizontal
displacement by using the GPS measurement data in Tokuyama
Dam. As a result, predicted deformation by using the approximate
expressions well matched to the value measured by GPS measurement system. Based on the research results in Tokuyama dam, it ispossible to monitor other dams by proposing approximate expressions using the same method that utilizes the features of the GPS ofhigh precision and continuous observation data.

C. ICOLD 85th Annual Meeting International Symposium in Prague, July 2017
Technical solutions on concrete for Kasabori damheightening
H. Kawasaki, S. Iwasaki, T. Miyano and Y. Hagiwara
Kasabori dam is a gravity-type concrete dam with height of 74.5m
constructed in 1964 by Niigata Prefecture for the purpose of flood
control, power generation, etc.. After a serious flood damage in2011, the redevelopment project started to upgrade the flood con-trol function by heightening the dam by 4 m. On the other hand,
this project term was limited to seven years due to disaster restoration grant project, and the workable days of a year are largely
restricted because of avoiding heavy snow season and flood season.
So, the major challenge is how to complete the construction in ashort period. The project includes various works such as concrete
placing on the downstream face and crest, renewal of two crest
gates, improvement of the spillway and energy dissipater, repairof the transverse joint, and grouting to the dam foundation. In thispaper, we focus on the rational designing of dam heightening and25

DAMS IN JAPAN - OVERVIEW 20152018

the seismic safety evaluation, the crack control measures and unification of new and old concrete, and the speed up and facilitation ofcomplicated work site by precast forms.

Inspection of construction joints in the concrete dam bodyby the impact elastic wave method
S. Ichikawa, T. Kamada, T. Sugiura and N. Hayashi
The deterioration of the horizontal construction joints, which may
affect the stability of the dam body is one of the phenomena of theaging concrete dams. The inspection by boring survey has beenused to verify the state of the construction joints in the dam body.
However, there are some problems in taking boring survey because
it is costly, it needs to destroy even a very small portion of the dam
body, and it can just check the spots, not the area. Therefore, thestudy was made on the non-destructive survey method to use thereflective wave of the elastic wave input by the impact, this method
was applied for the survey of dam body of which the horizontal
construction joints might be deteriorated. The following points
were revealed: Estimation of the state of the construction joints
by this method coincided with that from the boring survey from apractical standpoint.; This method enabled us to grasp the deteriorated construction joint area in the concrete dam body. Additionally, proper set-up of the strength of sound portion and deteriorated
portion of the construction joints enabled us to judge the safety ofthe dam body.

Deformation monitoring of rockfill dams in normal times
and after earthquakes using satellite SAR data
H. Sato,T. Sasaki,

M. Kondo,

T. Kobori, A. Onodera,

Y. Yamaguchi, K. Yoshikawa, D. Sango and Y. Morita
For development of efficient and advanced deformation monitoring
methods for rockfill dams in normal times and after earthquakes,
we studied monitoring methods using satellite SAR (Synthetic Aperture Radar) data. Because satellite SAR doesn’t need any sensors
on dam surfaces and it can observe entire surface of rockfill dams
and obtain data regardless of weather conditions, it is expected tocontribute in monitoring of deformation of rockfill dams. In thispaper, we evaluate external deformation of a rockfill dam using
satellite SAR data in about four years. The dam has three targets on
the crest for survey and we compared the results of external deformations by satellite SAR and survey at the points. We found the results of external deformations using satellite SAR data agreed wellwith those by survey and the average error of the external deformations between SAR and survey was about several millimeters. We
also investigated tendency of external deformations of dam surface
where survey had not been conducted. In addition, we conductedstudies of deformation monitoring after earthquakes using satellite
SAR data to grasp damage on rockfill dams by 2016 Kumamoto
earthquake. We found satellite SAR data could detect small deformation of rockfill dams by the earthquake.

D. ICOLD 86th Annual Meeting International Symposium and 26th ICOLD World Congress in Vienna, July 2018
External deformation monitoring of nineteen rockfill dams
using satellite SAR data
H. Sato, M. Kondo, T. Koboir, R. Ishikawa, T. Sasaki, W. Sato,N. Mushiake, T. Sato and K. Honda
It is important to research new methods of conducting effective
measurements of the external deformation of embankment dams.
In this paper, based on data collected by Synthetic Aperture Radar(SAR) satellite, a basic examination was carried out regarding theapplicability of SAR to the external deformation measurementof rockfill dams. Because no measurement facilities on the dam
surfaces are needed for SAR, SAR technique will lead to cost reduction for external deformation measurements of embankment
dams. This paper reports the results of satellite SAR based external
deformation monitoring of nineteen rockfill dams in Japan in about
two years from late 2014 to early 2016. The results of external
deformations using satellite SAR data were compared with thoseby GPS or electro-optical survey data. We found that the results ofexternal deformations using satellite SAR data agreed well withthose by existing geodetic data and the average error of the external
deformations between SAR and existing geodetic survey was about
five millimeters.

The risk management of thermal cracking for concretedams subjected to unprecedented temperature fluctuations
due to climate change
E. Hasegawa, Y. Miyata and T. Kase
Temperature data used in thermal stress analysis are usually deter-

mined on the basis of data accumulated over a period of several
tens of years. Because of considerable temperature fluctuations,however, that are thought to be attributable to climate change inrecent years, assumed temperature fluctuations have become increasingly greater. Consequently, analytical results tend to deviate
from actual concrete conditions so that thermal cracking risk is
growing not only in the block under consideration but also at otherlocations. To address this problem, therefore, a three-dimensionalmodel covering the entire dam structure including the foundation
bedrock is constructed to conduct thermal stress analysis and determine the thermal cracking index distribution over the entire dam.
On the basis of the results thus obtained, multiple blocks having a
relatively high probability of occurrence of thermal cracking are
identified, and detailed two-dimensional thermal stress analysis isconducted. At the time of concrete placement, changes in concretetemperature are monitored continuously by use of temperature
sensors installed in the dam body, and the measurement results arechecked against concrete temperature history simulation results
based on past atmospheric temperature data. If the temperature
difference is greater than predicted, appropriate control measures
such as regulation of temperature and cooling can be taken. In the
newly developed system, the relationship between the temperature
difference between the exterior and interior of dam concrete andthe thermal cracking index is determined so that thermal cracking
risk can be managed quantitatively by use of the thermal cracking
index calculated from the temperature difference.

Empirical evaluation of seepage ofreservoir level and rainfall

fill-dams using

H. Soda, J. Ishiguro, K. Otagaki and K. Kishida
Seepage of fill dams is generally measured by observation equip-

DAMS IN JAPAN - OVERVIEW 20152018
ment installed on the downstream side of the cutoff zone in thedam body and at the toe of the slope. Seepage is an important item
measured to evaluate the safety of a dam, but seepage of a dam
is impacted by noise such as the rise or fall of the RWL or therainfall, so safety of a dam is evaluated only during a period whenthese impacts can be ignored and assuming that seepage has notincreased from the past level at the same level. The authors haveattempted to evaluate seepage behavior based on the range of past
RWLs and seepage quantity at a sampled dam that was constructed
30 years ago. This paper presents the rangeof seepage based on past RWLs and rainfall and proposes an evaluation method based on this range.

History and present state of investigations on landslides
caused by reservoir filling: A review
Y. Wakizaka
The internationally most famous landslide caused by reservoir
landslide is the landslide at the Vajont Dam in Italy in 1963. Before the occurrence of the landslide at the Vajont Dam, reservoir
landslides occurred at many Japanese dams such as the Ishibuchi
Dam, Shichikawa Dam, Naruko Dam, Kanogawa Dam and Futase
Dam. Since the occurrence of the landslide at the Vajont Dam,
reservoir landslides occurred at the Shimokubo Dam, Shingu
Dam, Yanase Dam, Odo Dam, Hachisu Dam and Takizawa Dam.
In 1995, a manual titled “Investigations and countermeasures for26

landslides around reservoirs” was published by the Japan Instituteof Construction Engineering. This manual was revised in July 2009as the guideline titled “Technical Guideline for investigations andcountermeasures of a landslide around a reservoir” by the Ministryof Land, Infrastructure and Transportation. Uniform and systematicinvestigations and stability analyses can be performed based on the
manual and the guideline. Not one disaster has ever been caused
by a reservoir landslide in Japan, because suitable countermeasures
are taken based on the results of many kinds investigations of reservoir landslides.

Application of the transfer function matrix method in adam engineering
M. Kashiwayanagi and Z. Cao
Transfer function is essential for the seismic design and safety
evaluation, etc. of structures. In order to improve the evaluation
accuracy of the transfer function, the authors proposed the transfer
function matrix method considering mutual interference between
vibration directions. In this study, the applicability of the proposed
method in the field of dam engineering is investigated. It has beenconcluded that the proposed method can give out more recognizable dynamic characteristics than the conventional method. It isapplicable to the earthquake response prediction of dams at low
cost without relying on a numerical model. Furthermore, it shows
the possibility for utilizing in the deterioration diagnosis of dams.

Theme 2    New construction technology
A. 4th Asia Pacific Group Symposium and 9th East Asia Dam Conference, September 2016
The underwater excavation by the shaft-style underwater
excavator T-iROBO UWConstruction of a coastal levee at Hamamatsu city
coastline using trapezoidal CSG dam technology

N. Yachi, H. Miura,and A. Ueyama

N. Itoh, T. Suzuki, S. Terada, T. Fujisawa, Y. Kinouchi and

In order to solve the problems caused by deterioration and the inefficiency of the conventional method in redevelopment of existing
dams, a shaft-style underwater construction machine (T-iROBO
UW) was developed and utilized in the Amagase Dam redevelopment project in Uji city, Kyoto prefecture. The machine is operated
remotely to ascend, descend, rotate, to crash and gather the rockusing a power shovel that is fixed to a shaft that goes down fromthe barge to the lake bottom, for underwater works. The underwater
excavation is carried out while observing several monitors at thesame time. One of the monitors shows landform of the lake bottom
in 3D graphics, using the data obtained by investigation of sonar
device. On the 3D graphics of landform, the movement of thepower shovel is featured in animation, by measuring the angles of
the arm of the power shovel. The ultrasonic camera is used to provide the operator a real-time image on the other monitor. It is also
possible to replace attachments of the power shovel, and currently
the underwater breaker, bucket, and pump are being used. This is areport of the development of T-iROBO UW and its performance.

N. Yasuda
In order to mitigate giant tsunami damage predicted to occur on the
Hamamatsu city coastline, a coastal levee higher than Level-1 tsunami is being constructed about17.5 km from Lake Hamana to themouth of the Tenryu river. Here, Level-1 tsunami is a tidal wave
which occurs as the result of an earthquake of magnitude (M) 8with the return period of roughly 100-year to 150-year along Suruga-trough and Nankai-trough. The planned coastal levee is locatedon a long sandy beach with a seaside protection forest parallel to iton the north side. Considering the conservation of valuable plants
and animals, the seriously eroded shoreline, and the scenic appearance of the site, basically the ground level of the seaside protection
forest is raised and CSG (Cemented Sand and Gravel) is placed at
the center of the levee section and the outer sections are constructed as earth dikes. The planned coastal levee is required to havetenacity enabling it to withstand overflow of Tsunami but, strength
equal to that of a concrete structure is not needed, so a CSG structure, which has been developed by dam engineering, is adopted forthe internal portion of the levee.

27

DAMS IN JAPAN - OVERVIEW 20152018

Construction of Gokayama Dam by the cruising RCD
construction method
R. Nishiyama, M. Yugeta, T. Toyomasu, H. Yotsumoto, T. Fujisawa,
Y. Kinouchi and N. Yasuda
RCD (Roller Compacted Dam-Concrete) construction method wasdeveloped as a rationalizing dam concrete placing method and has
been used to speed up the construction works of concrete gravity
dams. The cruising RCD construction method adopted to construct
Gokayama Dam has been developed to aim for even more rationalizing dam concrete placing, and which improves construction work
efficiency by advancing the placing procedure of the internal RCD,
so it enables the continuous placement of dam concrete and enables placement of concrete more speedily. In Gokayama Dam, theslumping concrete is placed in the outer concrete and RCD is placein the inner concrete. Originally, the RCD is not placed unless theplacement of slumping concrete is finished in one lift. The cruising
RCD construction method is that the placement of RCD starts fromone side of the dam site, while the slumping concrete is placed at
the other side of the dam site. In that case, the RCD is placed at
the next lift. Simultaneously, the RCD and slumping concrete areplaced at different two lifts. The placement of RCD antecedent tothat of the slumping concrete enables this execution, unlike theconventional RCD construction method in which the slumping
concrete is placed antecedent to that of RCD.

Construction of Apporo trapezoidal CSG dam
S. Yoshimura, S. Takasugi, M. Konno, T. Fujisawa, H. Yoshida andN. Yasuda
The Apporo Dam is the second trapezoidal CSG dam in Hokkaido,
following the Tobetsu Dam. At the Apporo Dam, the shale is usedas the CSG material, which is the dam body material, and the dam
is constructed on the foundation of the shale and shale-sandstonealternative layer. Shale has the characteristic which causes the slaking phenomenon when it is dried, so various technical studies wereconducted to prepare for its use. For the concrete gravity dam, shaleor mudstone cannot be used as the aggregates, so the aggregate for
the Apporo Dam with original concrete gravity type was planned topurchase from quarry place. Furthermore, the foundation surface ofthe dam is extremely uneven and bumpy, so the investigation was
carried out to select the execution machinery. According to the extent and depth of undulation, the proper spreading and compaction
machinery are used in the Apporo Dam. As existing Tobetsu Dam
and Kim Dam with trapezoidal CSG type had an even foundation
surface, large-size construction machine was chosen. So, this kindof investigation has an important role for the construction of the
new Trapezoidal CSG dams.

water content of fine-grained and wet soils is an important issue forthe improvement of core quality. In this background, we developed
a machine called “Mantis”, which can blend fine-grained soil andcoarse-grained material efficiently even though the mix has a very
high content of fines and water. We used a crawler type soil mixing
machine, called “Stabilizer” which was improved with a fan forsending hot air produced with engine’s exhausted heat. Finally, we
carried out a trial blending test at the stock yard. We found that theprocessed material was well mixed and its water content was reduced.

Large-scale dam body
redevelopment project

drilling

byTsurudaDam

K.Kaji, K. Oobayashi, K. Miyahara, T. Fujisawa, H. Yoshida andN. Yasuda
The Ministry of Land, Infrastructure, Transport and Tourism is
now redeveloping Tsuruda Dam. The objective of the project is toimprove its flood control function by increasing its flood control
capacity and installing 3 additional large outlets for flood control.
Remarkable features of the project are its large scale: 6m diameterholes and 4.8m diameter outlet. And the height of the dam crest
above the holes is more than 60m. This work had to be executed
while ensuring Tsuruda Dam’s flood control and water supply
functions, requiring the construction of a cofferdam in the reservoir
before drilling the dam body. Because underwater work at the large
depth was necessary, we developed a new type of floating cofferdam. This report introduces an outline of large-scale dam body
drilling at Tsuruda Dam redevelopment project.

Proposal of the rationalization of dam construction quality
control
H. Yoshida and M. Kusumi
The Dam Construction Technology Research Group of the Japan
Society of Dam Engineers studied rationalization of the quality
control of the dam construction work. We surveyed many cases ofquality control of dam construction executed in recent years andconducted a study based on execution data concerning the possibility of rationalizing quality control. Based on the results of thisstudy, we proposed the rationalization of quality control of future
dam construction work.

Development of embankment material grading control
continuous management system using three-dimensional
image processor

Development of a crawler type soil mixing machine withdryer function

M. Fujiwara, W. Nakane, I. Miyairi, M. Omata, T. Otake,

S. Yamada, T. Temmyo, T. Koshida, I. Sandanbata, H. Itoh andIn dam construction, grading control of embankment material isof vital importance in quality control. The conventional practice is
to take samples and carry out sieve analyses at regular intervals,
which is both labor- and time-consuming. When constructing a
trapezoidal dam with cemented sand and gravel, it is standard practice to produce embankment material by mixing locally available
earth material such as riverbed deposits and excavated material
with cement and water. In order to achieve the required strength ofembankment material, therefore, grading control checks need to bemade to ensure that its strength is kept within the allowable range.
The authors have developed a new continuous grading manage-

A. Yamagishi
This paper describes a newly developed soil mixing machine withdryer function. Regarding the core embankment of rock-fill dams,
fine-grained soil and coarse-grained gravel must be mixed uniformly and efficiently in the stockpile. When the fine-grained soil
is relatively wet, compared to optimum water content, blended soil
becomes difficult to be mixed uniformly because fine-grained soil
tends to become what is called “clay lumps”. Therefore reducing

I. Kobayashi, T. Hashizume and A. Nakamura

DAMS IN JAPAN - OVERVIEW 20152018
ment system using three-dimensional image processing technology. The newly developed system makes real-time monitoring of
grading possible by irradiating line laser light onto the material on
the conveyor, calculating the volume of particles of each size fromthe image data continuously acquired with a digital camera and28

thereby determining particle size distribution. The usefulness of thesystem has been verified by using it for a countermeasure against
landslide in which cemented sand and gravel embankment material
was used. This paper introduces the new system and reports thefield verification results.

B. ICOLD 85th Annual Meeting International Symposium in Prague, July 2017
Dam concrete compaction management system Analyzing
concrete vibration to decide when to stop compacting
K. Uekoua, H. Furuyab, W. Nakanec and S. Sakazume
Compaction of concrete is of vital importance in dam construction
when trying to attain the required water-tightness, durability andstrength of the dam body. Viback concrete vibrator systems areusually used to compact conventional slumpable mixes. Decision
as to when to stop compacting, however, is largely dependent oncompaction time and empirical judgment based on visual observation, and there are no established quantitative criteria. There isconcern, therefore, about problems such as segregation resulting
from inadvertent failure to perform compaction, incomplete compaction and excessive compaction. To solve these problems, a new
dam concrete compaction management system has been developed.
The new system directly measures changing concrete vibration
with acceleration sensors and analyzes vibration waveforms so thatan objective judgment can be made as to when to stop compacting
and numerical data can be recorded. The system makes it possible
to make the best decision as to when to stop compacting, regardlessof the operator’s experience or expertise.

Construction of a tunnel spillway at large water depth
K. Takahata, R. Yoshioka and A. Konagai
To increase of the flood control capacity of the dam which has
passed through the half century after completion, the large-scaletunnel spillway with a diameter of 11.5m was newly constructedat the abutment of dam under water of 33m. The most importanttask was a construction of intake shaft of steel pipe sheet pile at theupper end of the tunnel which act as an intake part of new spillway
and also serves as a temporary coffering, and measures to stop gushout of water at the joint part with tunnel. For solving these engineering problems, we performed stress analysis and quantitatively
grasp the stress distribution of the intake shaft in the constructing
stage and joint excavation of tunnel that has been constructed fromthe downstream. Based on the result of the analysis, we made monitoring plan of shaft displacement and performed countermeasures
for reliable water tightness around the intake shaft and tunnel jointing part. As a result of these countermeasures, the construction of
the tunnel under the water was safely completed without suffering
by large water gush out from the intake shaft.

Proposing a fully automatic cementitious mix production
systemM. Fujiwara, I. Miyairi and S. Sakazume
The authors have developed a continuous grading management system using a three-dimensional image processor capable of irradiating line laser light to CSG (cemented sand and gravel) materials
on a belt conveyor, calculating the volumes of particles of different

sizes from continuous image data obtained with a digital cameraand determining particle size distribution in real time. By using
particle size distribution measurements obtained from the newly
developed system in combination with moisture content measurements obtained with radioisotope moisture meters, the quantities
of cement and water to be added to produce cemented fill materials
can be controlled in real time. This report deals with functions of afully automatic cementitious mix production system consisting ofthese components.

Construction of a coastal levee in Natsui District,
Fukushima Prefecture using trapezoidal CSG dam
technology
T. Okeda, H. Igari, N. Yasuda, Y. Kobayashi and A. Takei
The coastal area of Fukushima Prefecture suffered enormous
damage from the tsunami caused by the 2011 off the Pacific coastof Tohoku Earthquake, and most of the coastal levees were damaged catastrophically. Completed in October 2013, Natsui District
Coast was the first coastal levee to be constructed in Fukushima
Prefecture as a restoration and reconstruction project. The lengthof the coastal levee is 920 m, and the crest height (TP; Tokyo Peil)is 7.2 m. The levee volume is 60,000 m3, and 40,000 m3 of that is
made using CSG (Cemented Sand and Gravel), which was madewith concrete debris from the earthquake together with cement andwater. This is the world’s first application of the design and construction method of trapezoidal CSG dams to a coastal levee. By
adopting this method, not only does it have a “persistent” structure
toward overflows of sea wave, but both material cost and disposal
cost were reduced by using concrete debris from the earthquake,
which has to be handled as general waste. In addition, we wereable to greatly shorten the construction period: it took about sevenmonths to complete the main part of the coastal levee.

Trial mix and full-scale trial embankment for RCC dam at
Nam Ngiep 1 hydropower projectY. Aosaka, T. Seoka, B. A. Forbes, J. Cockcroft, Y. Murakami
and M. Asakawa
The Nam Ngiep 1 Hydropower Project (290MW) in Lao PDR ispresently under construction (2014-2019). A Roller Compacted
Concrete (RCC) gravity dam, 167m height is being built in a narrow V-shaped gorge. A total of 2.3 million cubic metres of RCC isplanned to be placed in 26 months, as a continuous process throughwet and dry seasons using the Slope Layer Method (SLM) for
placing RCC. The principal materials are cement and fly ash, imported from Thailand, and locally quarried sandstone/conglomerate
aggregate. This Paper discusses the programme of off-site and onsite trial mixes that were conducted between 2008-2015 to obtaina stable, durable and economical RCC mix design, the full-scale
trial embankment, and the construction of the left bank wing wall

29

DAMS IN JAPAN - OVERVIEW 20152018of the regulating dam and the secondary upstream cofferdam to themain dam, that were carried out from 2015-2016. The full-scale
trial embankment confirmed and evaluated the variability of RCC
and the Grout Enriched RCC (GE-RCC), the placement characteristics, with respect to the machinery used, the layers thickness,compaction amount, joint treatment, compressive and direct tensile
strength, in-situ permeability testing, and finally as observed in full
section cuts made through the trial embankment by band sawing
cutting.

C. ICOLD 86th Annual Meeting International Symposium and 26th ICOLD World Congress in Vienna, July 2018
Design of a Tsunami coastal levee using trapezoidal CSG
technology and quality control during CSG production(Coastal of Hamamatsu city)
N. Itoh, T. Takada, S. Terada, N. Yasuda, T. Nakashima and M.
TanakaIn order to mitigate giant tsunami damage predicted to occur on
the Hamamatsu City Coastline, a coastal levee higher than Level-1
Tsunami is being constructed about 17.5 km from Lake Hamana
to the mouth of the Tenryu River. Here, Level-1 Tsunami is a tidal
wave which occurs as the result of an earthquake of magnitude (M)8 with the return period of roughly 100 year-150 year cycle along

Suruga-trough and Nankai-trough. The planned coastal levee is located on a long sandy beach, parallel to a seaside protection foreston the north side. Its location imposed the design requirements forthe conservation of valuable fauna and flora, and scenic appearance, and for the restoration of the seriously eroded shoreline. The
levee of CSG (Cemented Sand and Gravel) placed at the center andsurrounded with embankment are applied for raising the groundelevation of the seaside protection forest. The planned coastal levee is required to have tenacity enabling it to withstand overflowof Tsunami, but strength equal to that of a concrete structure is notneeded, so a CSG structure, which has been developed by dam engineering, is adopted for the internal portion of the levee. Furthermore, the usage of ICT is also attempted to rationalize and advancequality control of CSG material.

Theme 3    Flood, spillway and outlet works
A. ICOLD 84th Annual Meeting International Symposium in Johannesburg, May 2016
Planning and design of additional discharge facilities inJapan
N. Hakoishi, T. Sakurai and T. Ikeda
Additional discharge facilities to the existing dam are hardly
planned in the design and construction stages of the existing dam.

The arrangement of additional discharge facilities is restricted dueto the layout of the existing facilities of the dam. In this paper,
we explain the considerations in the planning and design of theadditional discharge facilities in accordance with purposes andtypes of a facility. In addition, we describe the design approach ofadditional discharge facilities which are to be installed by drilling a
concrete gravity dam.

B. 4th Asia Pacific Group Symposium and 9th East Asia Dam Conference, September 2016
Gate operation support table of Ohno flood control dam
against excess flood inflow
J. Kashiwai, T. Kubozonoand T. Takada
Flood control operation requires smaller discharge than inflow.
This operation raises water level of a reservoir, and cannot be
continued until reservoir water level reaches to the dam design
flood stage. Flood control operation mode should be changed into
overtopping prevention mode in an appropriate way at a certain
inflow and water level condition during excess flood inflow. Modechanging timing and the gate operation ways for increasing dis-charge to prevent overtopping are one of the most serious mattersfor operation managers. In above situation, MOPO (minimum outflow to prevent overtopping) table, which was developed by Public
Works Research Institute Japan, was employed by Ohno dam forsupporting the operation judgment. MOPO is obtained throughthe gate operation simulation in the large inflow condition whichreaches to the design inflow. If the outflow at the time in the pair of
inflow and water level condition is greater than MOPO, future water level must be controlled under the dam design flood stage without extreme outflow increase. This paper will show the simulation
conditions for the Ohno dam’s MOPO table. They consist of the
inflow condition, gate movement restrictions and outflow increase
limitations.

DAMS IN JAPAN - OVERVIEW 2015
2018

30

C. ICOLD 85th Annual Meeting International Symposium in Prague, July 2017
Experimental study of ski jump spillway at the Nam
Ngiep1 Hydropower Project in Laos

Study on scouring phenomena at downstream of dam
during flood control

T. Takahashi, Y. Murakami, M. Asakawa, S. Tsutsui and Y. Aosaka

Y. Kitamura and S. Takagi

The Nam Ngiep 1 Hydropower Project in Laos is under construction: two dams and two powerhouses with total installed capacityof 290MW. A 167 m roller compacted (RCC) dam is being constructed in the narrow valley and will be equipped with a ski jump
spillway with multiple flip bucket. Hydraulic model tests have been
carried out in order to confirm the effect of deflectors and alternative flip bucket geometries which promote increased longitudinal
dispersion of the water jets and diving zones downstream in theriver course.

Funagira Dam was built at the most downstream of the Tenryu
River in 1977. The spillway facilities were designed to handle thedesign discharge of up to 11,130 m3/s under gross head of 10m
to 18m. The energy dissipation at downstream of the dam wasdesigned as the hydraulic jump-type on the bed protection blocks.
The dam has been experienced several large flood events during
the last about 40 years after the completion. The protection blocks
were damaged and the scouring downstream foundation of the dam
was begun in the early stage, and up to 6,300 measure blocks were
continually put on. In recent time, nonetheless, the flood events in
2011, was larger and longer period of flood with maximum flood
about 6.396 m3/s, and the scouring increased to the severe condition at the foot and stability of dam. In this paper the experimental
study results and knowledge with the field observation, mathematical model tests, and the vertical 2-dimensional and the fully 3-dimensional hydraulic scale model tests were introduced to evaluate
the scouring processes and to determine the long-term measures.

Development of new maintenance program for scouring
measures at downstream of dam
S. Takagi, M. Sato and Y. Kitamura
Energy dissipations at downstream of dam have to be sufficient to
reduce the stream power and to pass the flood discharge safely. The
scouring at downstream foundation of dam and spillway structureis especially a major topic in presence of hydraulic structures forflood control. By utilizing the obtained information, we will further and continuously make our all efforts to securely carry out theexisting erosion measures and long-term measures at downstreamof dam to stabilize the dam, to thoroughly keep and control theenvironment including the dam and the river, and to respond to the
problems found as the results of the measures. They are including
checks and reviews for the maintenance and control standards,
plans, and countermeasures. In this paper the new maintenanceprogram was explained and introduced the process of setting up
by the experimental study with the field observation, mathematicalmodel tests, and the hydraulic scale model tests. The program wasappropriately to be examined through the various observation andtests about the topics of during construction of scouring measuresand maintenance for the existing dam.

Study on validity of the hydroelectric dam operation
adopted GSM and the information about typhoons
H. Takakura, T. Matsubara, E. Nakakita and N. Takada
In recent years, unusual rainfalls and floods have increased, andsocial demands are increasing that hydroelectric power dams,
which have no function for flood-control originally, function as theflood-control dam. The long-term rainfall forecast is needed forthe hydroelectric power dam to have the flood-control function bylowering reservoir water level with power generation. In this study,
a new proposed weather and flood forecasting method, which
combines the efficient formulation of GSM (Japan Meteorological Agency’s Global Spectral Model) and the information about
typhoons, was applied to Ikehara and Kazeya hydroelectric powerdams at Kumano river basin and evaluated. The results showedthat the new flood-control method had the applicability to the dam
operations in terms of the reductions of the max discharge from thedams.

Theme 4    Earthquakes and dams
A. ICOLD 84th Annual Meeting International Symposium in Johannesburg, May 2016
The seismic analysis of an earth-fill dam on thickliquefiable ground and countermeasures against a large
earthquake
T. Kato, T. Honda and S. Kawato
This paper introduces the seismic analysis of an earth-fill dam on a
thick layer of liquefiable ground and countermeasures that can betaken to counteract the effect of a large earthquake by using effec-

tive stress with dynamic analyses using Finite Element Methods(FEM). According to these analyses, the dam’s crest subsidence islimited after the earthquake due to the restriction of the liquefaction potential by adopting the counterweight filling method.

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B. 4th Asia Pacific Group Symposium and 9th East Asia Dam Conference, September 2016
Experimental study on seismic response behavior of filldams influenced by dam’s shapes and input wave’s directions
Y. Hayashida, S. Masukawa, I. Asano and H. Tagashira
The characteristics of the seismic behaviour of fill-type dams were
examined by shaking table tests, in which three shapes of dam
models, namely, symmetric about both a maximum cross section
and a dam axis, symmetric about only a dam axis, and asymmetric
about both a maximum cross section and a dam axis, were shaken
separately in the stream direction and in the dam axis direction, andthen the effects of the dam’s shape and the direction of the input
wave on the seismic response behaviour were verified. From theresults of the experiment, the point at which the maximum acceleration values were recorded during the shaking in the stream and thedam axis directions was found to be right above the deepest part ofthe dam’s valley. It was clarified that the response orthogonal to theshaking direction could arise depending on the shapes of the dam,the direction, and the dominant frequencies of the input waves.
In particular, in the case of shaking in the dam axis direction, thepoint at which no response could be incited appeared on the crestof the dam depending on the shape of the dam and the dominantfrequencies of input waves.

C. ICOLD 85th Annual Meeting International Symposium in Prague, July 2017
Study of seismic performance evaluation method for
concrete gravity dams on low stiffness foundation

Efficient repairing and reinforcement method for AFRD
damaged by the earthquake

T. Shiono, C. Yamaguchi, Y. Nakano and T. Tsukada

T. Tsukada, M. Shimazaki and T. Mizuno

For evaluation of seismic performance of concrete gravity dams
which are constructed on low-stiffness foundation, we should
consider the permanent settlement of foundation due to earthquake loading in addition to stress of dam body and foundation.
However the Guidelines for Seismic Performance Evaluation ofDams against Large Earthquakes (draft) in Japan don’t mention
how to estimate the permanent settlement of foundation. So, we
studied the evaluation method, which is using FEM dynamic analysis by equivalent linearizing method, modeling the foundation as
non-linear material and calculating the settlement by cumulative
damage. Then we conducted the centrifugal loading vibration test
and numerical analysis to estimate that the method we studied was
reliable enough to be used for the first stage evaluation of seismic
performance of concrete gravity dams on low-stiffness foundation.

We developed the effective repairing method for asphalt facing of
the Yashio dam, asphalt facing rock fill dam (AFRD) constructed
for the upper reservoir of the Shiobara pumped storage power
plant of Tokyo Electric Power Company Holdings, where cracks
occurred by the 2011 Tohoku earthquake, to complete repairing
works in a short period so as to resume power generation immediately. The developed repairing method was consisted of asphalt
mastic using asphaltic material developed for the purpose of improving deformation performance under a low temperature, hereinafter we call it “low elastic asphalt”, and asphalt impregnated
non-woven sheet. We completed the repairing works in about only
one month, because we limited the removing area by covering thelow elastic asphalt mastic of 10 cm width and 5 cm thickness, as abuffer part absorbing the strain, on the cracks leaving in the layer
underneath from the forth layer to the bottom layer of the asphalt
facing consisted of seven layers. In addition, it was estimated thatthe cracks occurred by the strain concentration of the crest concrete block joint connecting the asphalt facing, the facing near theconcrete block joints were also reinforced using low elastic asphalt
mixtures.

An experimental study on permeability of soils under shear
deformation using remodeled torsional shear apparatus
A. Hisano and M. Takabatake
We remodeled the apparatus for torsional shear test on hollow cylindrical specimen of soils in order to examine the relationship between the shear deformation and the permeability of the impervious
material for rock fill dams. As a fundamental approach concerning
the permeability change of impervious materials deformed by thevertical offset, we conducted the permeability test using the apparatus. Firstly, we conducted TEST 1 that was the permeability test
method for test material deformed by turning the swivel in steps,
while keeping the test pressure constant. We assumed that the coefficient of permeability obtained from TEST 1 was similar to thatobtained from JIS A 1218:2009. Secondly, we conducted TEST 2
whose purpose is evaluation of water resistance of deformed test
material against high water pressure as severe condition beyond
realistic situation. As the result of TEST 1, test material was notmeasured the increasing characteristics of coefficient of permeability under shear deformed condition. The result of TEST 2 indicatesthat consolidation pressure has a influence on the increasing characteristic of coefficient of permeability of test material.

Seismic analysis based on results of the laboratory shaking
table tests for the dam-model
M. Matsuura, H. Ieda, H. Tagashira and S. Sato
As Japan frequently suffers large earthquakes, a safety collationof performance against earthquake for aged fill-dams is an urgent
issue. But an application of technique to maintain high resistanceto earthquake based on results of quantitative analysis is limited.
First we have taken one step of arranging examples which analyzed
conditions and problems about present design techniques for earthquake-resistance. The series of the example of the seismic-stability
analysis for the fill-dams is shown in this paper, in which reductionof undrained strength in saturated zone, liquefaction of dam bodyand foundation and the non-linear property of loose dam body weretaken into account. Then we introduce the results for the shaking
table tests, which we can demonstrate and inspect the applicabilityof examination methods for earthquake-resistance. In the tests, six

DAMS IN JAPAN - OVERVIEW 20152018
cases using silica sand were carried out on the 1G field of a small
dam with many sensors and centrifugal force field of 60G corresponding to an actual dam height. Three cases of the tests wereconducted in the seepage condition. The response acceleration, the32settlement and the deformation for the tests were investigated. And
we present consideration about diagnosis and its procedure to support a rational and appropriate evaluation.

D. ICOLD 86th Annual Meeting International Symposium and 26th ICOLD World Congress in Vienna, July 2018
Three-dimensional behavior properties and reproduction
analysis of an arch dam during large-scale earthquakes

Study on the mechanism of the peculiar behaviors ofAratozawa Dam in The 2008 Earthquake

H. Sakamoto, N. Sato and N. Tomida

N. Yasuda, N. Matsumoto, M. Naruoka and , Z. Cao

This study analyzed the following earthquake records at the Yagisawa Dam, which is managed by the Japan Water Agency, in orderto clarify the three dimensional behavior of arch dams during
large-scale earthquakes: (a) microtremor records measured simultaneously at 14 points, (b) small earthquake measurement records
obtained simultaneously by seismographs installed at 6 points, and(c) maximum earthquake records (6.56m/s2 at center of dam crest).
The behavior at the Yagisawa Dam found in (c) during a 6.56m/s2
earthquake record was difficult to reproduce based on three-dimensional FEM analysis, which is generally used in Japan, but were reproduced with high precision by analysis using revised foundation
ground – dam body – reservoir coupling conditions.

During the 2008 Iwate-Miyagi Earthquake (M7.2) of June 14,
2008, seismic motions with the maximum acceleration of 10.24
cm/s2 in the stream direction were recorded at the foundation bedrock of Aratozawa dam, a rockfill dam located approximately 16km
from the epicenter. However, the maximum response accelerationin the same direction near the center of the dam crest was 5.25 m/
s2, and the acceleration amplification ratio of the dam body was
far lower than that normally considered for a rockfill dam. Furthermore, it was measured that the crest settled down 19.8 cm after theearthquake. In this study the dynamical properties of the embankment materials have been identified with the reproduction analysisof the past earthquakes, and the recorded behaviors of the dam
body during the mentioned strong earthquake have been simulated.
The generating mechanism of the peculiar earthquake behavior has
been investigated based on the results of earthquake response analysis. Furthermore, in order to understand the deformation mechanism, sliding stability analysis and cumulative damage analysis are
performed. According to the results, the residual deformation of thedam body after the strong earthquake is inferred to be caused by
the shaking settlement of the embankment materials.

Studies on extensibility of asphalt face and effective
reinforcement based on AFRD damaged by the earthquake
T. Tsukada, M. Shimazaki, T. Mizuno and Y. Matsumoto
The 2011 Tohoku Earthquake triggered cracking in the asphalt faceof Yashio Dam, which extended for 70-80 m from the crest almost
running parallel to the abutment on both sides. This asphalt-facerock-fill dam was located about 300 km from the epicenter. The
maximum observed acceleration was around 0.05 m/s 2 at thefoundation and around 0.25 m/s2 at the crest, not necessarily intensecompared to the levels envisaged in the design (0.266 m/s2
at the foundation and 1.0 m/s2 at the crest). Nevertheless, the dam
was damaged. Therefore, the conditions of cracking were studied
in detail on site in combination with indoor testing and dynamic
response analysis to reproduce and compute the behavior of thedam during the earthquake. As a result, the cracking was presumed
to have appeared when strains concentrated on a block joint of
the crest concrete. The further downward propagation along theslope was probably caused by strains from displacement by theearthquake and thermal contraction from the drop in the waterlevel, which concentrated at the tips of the cracks. Indoor tests andsimulations by dynamic analysis were conducted to validate thepresumed causes of crack propagation. A method was devised to
repair the cracks while ensuring adequate performance of the asphalt face consisting of a total of seven layers. In this method, only
three layers were cut out and replaced with a material resemblinga joint sealant that contained polymer-modified asphalt with great
deformation following performance even in cold temperatures.
The material’s composition was also determined by taking theworkability into account. Before the repair work, a simulation test
was conducted with a sample to make sure that the method not
involving cutting and replacement down to the bottom layer would
provide comparable or greater deformation following performance
than the existing asphalt face. The same material from the repair
work was used at the crest area that experienced the strain concentration. A structure was devised and constructed to follow even alarge strain after a simulation by numerical analysis.

Centrifugal model test for destruction of dam body inducedby the liquefaction of its foundation
Y. Hayashida, H. Tagashira and S. Masukawa
Huge earthquakes have been occurred frequently in Japan and there
are about 1200 irrigation fill dams which have passed over 50 years
after construction. Some of such irrigation fill dams (especially,
earth dams) have the problem about leakage and loss of cross section by aging. In these dams, countermeasures to constructing impervious zone on the upper slope of dam body as countermeasureagainst leakage and reinforcement are adopted frequently. Purposeof this study is to acquire the fundamental scientific knowledge
about deformation and destruction behaviors of dam body withinclined core zoning, especially, in sight of the liquefaction of its
foundation which is one of principal factor to induce large deformation during earthquake. Destruction mechanism of dam bodydeveloped by interactions among liquefiable foundation, dam bodyand reserved water are verified by the centrifugal liquefaction experiment. From results, it is clarified that dam body effects to the
behavior of pore water pressure in the liquefiable layer. Increased
value of pore water pressure under shaking become several times
when dam body exists. However, retrofitting at the toe of downstream slope of dam body can inhibit the typical increasing of porewater pressure. And it is supposed that behavior of pore water pressure in liquefiable layer closely related to the deformation behaviorof dam body. Fracture of dam body with inclined core develop
progressively according to the interactions among liquefiable foundation and dam body. And it is supposed that deformation of upstream slope of dam body is dominant factor to induce catastrophic

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destruction of dam body. Retrofit at the toe of downstream can
restrain such deformation and, even though dam body damage severally, catastrophic destruction inducing over topping is prevented.

Discussion on the mechanism of the destruction of a smallscale dam by The 2011 Great East Japan Earthquake andreconstruction and reinforcement
T. Miura, M. Matsuura, T. Tanaka, F. Tatsuoka and Y. Mohri
In Japan, where rice farming is the main agricultural activity, theadvancement of civil engineering technology has facilitated thedevelopment of new paddy fields and new agricultural facilities
and there are approximately 210,000 small-scale dams that irrigate farmland in areas where there are no large rivers. Many ofthese small-scale dams are earthfill dams. Because of the shortageof suitable embankment materials, the embankments of many ofthese small-scale dams have an insufficient degree of compaction.
The reconstruction of the Fujinuma Dam, a small-scale dam in
Fukushima Prefecture, which was destroyed by the Great East Japan Earthquake, incurring loss of human lives, is described in thispaper. The safety standard for the reconstruction of the Fujinuma
Dam was defined as “constructing a safe and reliable dam that isoverwhelmingly more seismic resistant than the failed old dam,”based on the results of analysis of the causes of the failure of theold dam. The technical goal for the reconstruction was defined as“ensuring the safety of the dam against the largest possible groundmotion expected in future.” As the new dam had to be constructed
as a high-quality dam with a larger degree of compaction than theold one to satisfy the standard and achieve the goal, a standard forthe degree of saturation, which had not been used in the conventional dam construction, was defined for the reconstruction of the
Fujinuma Dam. The design and the results of the execution control
tests are discussed in this paper.

Theme 5     Reservoir sedimentation and sustainable development
A. ICOLD 84th Annual Meeting International Symposium in Johannesburg, May 2016
Positive effects of reservoir sedimentation management on
reservoir life: Examples from Japan

Development of a bedload transport measuring system for
sediment bypass tunnels in JapanC Auel, SA Kantoush and T Sumi

T. Koshiba, T. Sumi, D. Tsutsumi, S. Kantoush and C. Auel

The effectiveness of different strategies against reservoir sedimentation is demonstrated herein using data sets of Asahi, Nunobiki
and Dashidaira reservoirs in Japan. The applied strategies encompass sediment routing with a bypass tunnel, drawdown flushing
during floods and sabo dam construction in the catchment. It isshown that bypassing and flushing are very efficient strategies
enlarging reservoir life by 3 to 21 times up to many hundreds ofyears. Furthermore, it is revealed that also efforts in the catchment,
e.g. sabo dam construction, is effective enlarging reservoir life by
2.4 times.

Sediment Bypass Tunnels are operated to divert sediment aroundreservoirs reducing reservoir sedimentation. A major drawbackof these tunnels is severe invert abrasion due to high velocity andsediment flows. There is an urgent need to establish innovative
measurement systems of sediment transport rates in SBTs. In thispaper, three bedload measuring systems, namely hydrophones,
geophones, and newly developed plate microphones are introduced
and compared. The Koshibu SBT is planned to operate from 2016.
Plate microphones combined with geophones and other plannedsystems are installed in the tunnel. Results of preliminary tests andinstallation plans of bedload measurement are presented.

2D reproduction analysis of reservoir sedimentation
caused by flood
N Sorimachi, K Hashimoto and T Sato
Reservoir sedimentation of an existing hydroelectric dam was
reproduced by two-dimensional numerical analysis. To make thecalculation simple, numerical analysis was based on parametricstudies. As a result, reservoir sedimentation was reproduced by
two-dimensional analysis, in terms of sediment’s volume. In addition, relation between reservoir level and inflow, for the effective
dredging of sediments, were estimated to some extent. We willconduct additional experimental operation and numerical analysis
to obtain more information about moving sediments into the deadstorage effectively.

A practical example change of river bed environment
downstream from dam reservoir by sediment
replenishment
Y. Musashi, Y. Nakata, T. Suzuki, M. Oshima and S. Demizu
We reviewed the case of the Nakagawa River, which had one of
the largest scales of sediment replenishment. Its monitoring results
are composed of river survey, river bed material survey, biologicalresearch and so on. The results show the changes of river bed condition such as restoration of river bed materials, the increase in theratio of fine sediment on the armored river bed and the expansionof riffle. We estimated the amount of transported sediment by one
dimensional analysis of river bed variation. We also examined theeffects of sediment replenishment on amount of sediment yield bygrain size.

DAMS IN JAPAN - OVERVIEW 2015
2018

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B. 4th Asia Pacific Group Symposium and 9th East Asia Dam Conference, September 2016
Vertical Multi-Holed Double-Pipe system: A new sedimentsuction method utilizing a natural head

Abrasion and corrective measures of a sediment bypass
system at Asahi Dam

A. Hisano, S. Oota and K. Maeda

T. Nishikawa, Y. Yamane and Y. Omoto

At present, the sediment removal method using a suction pipe isthe subject of research as an effective method for discharge of accumulated sediment in dam reservoirs. Vertical Multi-Holed Double-Pipe system is one of these methods and has been researchedby the authors for the application to an actual reservoir. This system
is expected to reduce the cost of removing sediment accumulated
repeatedly around a local place such as the neighborhood of the intake. This paper explores the following topics: methods and resultsof the laboratory tests of the system; the hydraulic design method
based on the laboratory tests; and the estimation of sediment concentration in the discharge flow.

At the Asahi Dam of Kansai Electric Power Co., Inc., a sediment
bypass system was built and in operation in 1998 to take a fundamental measure to mitigate impacts by prolonged water turbidity
and sedimentation ascribable to collapse of mountain slopes in the
upstream caused by a great flood in 1990. The effectiveness of the
bypass system has been verified and reported in the past. In themeantime, the tunnel invert has been worn notably by a significant
sediment transport at high velocity and how to improve the efficiency of periodical maintenance is an issue. This paper describes
the abrasion of the tunnel invert of the sediment bypass systemat the Asahi Dam that has been in operation for approximately 15
years, and evaluates possible tunnel maintenance methods using
the life-cycle cost based on monitored data of abrasion.

C. ICOLD 85th Annual Meeting International Symposium in Prague, July 2017
An examination of efficient turbid water coagulation
method using natural coagulant
M. Miyakawa, M. Kusumi, T. Ishigami and K. Motoyama
Long term persistent turbidity is a major problem in reservoirs ofJapan and other countries. We are examining the practical methods
using natural coagulants, such as allophane (clay), which can bedeposited in the reservoirs, to prove experimentally the effectiveness of allophanes coagulation performance, and to develop a useful and environmental friendly coagulation method for turbid water.
The experiments conducted in this study provided two important
findings. The first is that, through the laboratory experiments, we
proved that the new practical dispersers, which are a cavitation
mixer and a high pressure water sprayer, can be used effectively todisperse allophane. And we confirmed the usage of these dispersers raises the zeta potential of allophane. This effect is presumed
to promote coagulation. The second is that the coagulation effectat the depth of more than 10 m was confirmed through the field
experiment, where the new dispersers were used. As mentioned
above, we can propose more practical, useful, and environmental
friendly treatment method for turbid water using allophane at dam
reservoirs.

Grouting method for dam reservoir foundation by effective
use of ground water flow
F. Kawashima, T. Tsukada and S. Tsuruta
In the bedrock of the Yashio dam reservoir foundation, the upper
reservoir of the Shiobara Pumped Storage Power Plant of Tokyo
Electric Power Company Holdings, the high dip angle open fissures
are distributed to the deep area, there was relatively large amountof leakage due to these fissures and we needed to reduce leakage.
As the leakage reduction measure, we selected the cement grouting
at the bottom of the reservoir filled with water, with relatively wideborehole spacing by effective use of ground water flow. We confirmed its applicability by the field tests, research and laboratory

tests by parallel plates which simulating the open fissure in the bedrock, and applied it to leakage reduction works. We completed theleakage reduction works and we were able to reduce the leakage to
our target level.

Measures against the predicted degradations of water
quality of Makio dam by the volcanic eruption
K. Onoshima, H. Imamoto, T. Miyashita and Y. Ishiguro
Mt. Ontake erupted on September 27, 2014 and it was the second
time in recorded history. The distribution and volume of productsby the volcanic eruption were almost similar to those of the previous eruption in 1979. The catchment of Makio Dam is located at
the foot of Mt. Ontake, therefore the influence of the eruption on
the water quality of the dam reservoir was predicted to be continuing over a long period. In response to this situation, Japan Water
Agency (JWA), the management body for Makio Dam, has collaborated with local governments/municipalities concerned and water
users/stakeholders to implement not only efficient water quality
monitoring but also appropriate measures for water quality conservation while making accurate forecast of discharged turbidity. As aresult, the dam has kept supplying water to the downstream continuously without any particular trouble in water use at the moment.

Sediments discharging using siphon system demonstration
test at the Republic of Indonesia Wonogiri multipurposedam
T. Sumi, H. Itoh, T. Sase, T. Satoh and S. Kantoush
The countermeasures by machines for excavation and dredging reservoir sediments have been often used in the past but in the future
the total cost, including operation and maintenance costs as wellas construction costs and the inhibitory effect of shoreline retreatof the coastal region have come to be required in the sediments
countermeasure. In this paper, we report the results of demon-

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DAMS IN JAPAN - OVERVIEW 20152018

stration tests of sediments countermeasure in Indonesia Wonogiri
dam including sediments reduction of the reservoir sediments todownstream river by the siphon system using water level difference between reservoir and downstream river water level, not only
construction costs but also aims to reduce energy consumption for
operation and maintenance costs by the siphon system in Indonesia
Wonogiri dam. A sufficient water level difference for the drought inthe test cannot be reserved by using sediments discharge pipe witha diameter of 400mm, the system can transport sediments with amaximum particle size of about 130mm, with an average transportcapacity of 30m3/h in the transport distance of 250m and withsediments discharge per unit power of about 8.1m3/kwh. Siphon
system has 27 times processing capacity compared the dredging
system with small pump with a capacity of 0.3m3/kwh.

Density current flux due to bubble plume using a new airenergy system
E. Furusao, H. Kawasaki, S. Takasu and S. Uchizato
The Dam Air-energy System (DAS) is a new energy system using
compressed air with high efficiency in dams. Several countermeasure facilities were installed in the Haneji Dam for water quality
improvement as the first full-scale system using DAS. DAS facilitates artificial circulation of water by using a bubble plumecaused by the production of compressed air by the DAS. Due tothe efficiency of DAS, a large amount of compressed air (9.7 m3/min) can create a bubble plume. Field experiments were conductedto elucidate the flux in the horizontal density currents caused by the
bubble plume. Based on temporal changes in the vertical profiles ofwater temperatures, flow rates of surface currents and intrusion as
the middle layer flow were estimated. This method is applicable to
the Haneji Dam due to the long residence time of water as hydrologic characteristics of the Haneji Dam reservoir. It was observedthat a large amount of current flux was produced by the DAS-bubble plume system. By comparison of the experimental results withmany previous studies, empirical equations for estimating the fluxin current due to the bubble plume are proposed.

Control method of water bloom using characteristics ofreservoir ecosystem
Y. Iseri, M. Mori, K. Kudo and S. Yamamoto
In the management of the dam reservoir, water bloom is often
produced by an abundance of nutrient salts and causes significant
damage on water supply including poor scenery, unfavorable water
taste and production of toxic substance. Cyanobacteria belongs
to bloom forming Microcystis and most frequently occurs in thereservoirs. They are also known to grow rapidly in high temperature environment and are, in fact, in increasing trend in the world
because of the green house effect. This paper introduces the control
method of the bloom, including Jet-Shock System for dispersing
colony cells into the isolated cells, UV radiation Ship for stoppingcell division and cooperation system to improve ecological purification function.

Field experiment of bedload transport rate measurement at
sediment bypass tunnel
T. Koshiba, S. Kantoush and T. Sumi
For advanced maintenance of sediment bypass tunnels (SBTs), particularly concerning on the abrasion of the tunnel invert, a monitoring of sediment through tunnel is essential. We developed new bedload measurement systems, namely a plate microphone and a plate
vibration sensor. After confirming the high sensitivity and robustness of these systems by flume experiments, these systems were
installed at the outlet of Koshibu SBT, which started operation in2016, in Japan. Prior to its commencement of the SBT, on-site calibration experiment was conducted. In the experiment, sediment is
input in the SBT artificially by truck beforehand and flushed themout with clear water from the upstream. The experiment is repeatedfor 10 times with different grain size (5, 10 and 50 mm), volume(1, 3, 5 and 9 m3) and water discharge (5, 10 and 50 m3). Seven
sensors of the measurement systems, which installed evenly along
the width, successfully recorded the signals of passing sediment.
In this paper, practical calibration formula of predicting sedimenttransport rate by recorded data are developed by analyzing the pattern of the 10 experiment cases. Finally, a method to quantify sediment transport rate and a desirable operation of those measurement
systems on-site are discussed.

D. ICOLD 86th Annual Meeting International Symposium and 26th ICOLD World Congress in Vienna, July 2018
Observation and Estimation Method of Sediment
Production in Kamanashigawa Basin, Fujikawa River
System (Toward an Accurate Estimation of Dam SedimentVolume)K. Tomita, Z. Ye, T. Hikita and T. Sumi
The sediment storage in a dam is usually designed based on thecases which have similar watershed condition or sediment discharge in the nearby area, but not calculated directly from the sediment observation data in the watershed. Furthermore, the inflow
of sediment due to flood events after dam construction is only
accounted by total sediment volume. Besides, the sediment thatflow into dam reservoir during a flood and the unstable sediments
reserved in upstream that will become the supply resource in the

future, are not under observation yet. In this paper, some consideration to improve the estimation method for sediment discharge
in a watershed were conducted for sediment management in dam
operation, by combining observation data of the sediment transportobtained by various equipment such as hydrophone, turbidimeter,
and that predicted by satellite SAR image interference analysis, inOmukawa River, a right branch of Kamanashigawa, Fujikawa river
system, Japan. Using the middle to downstream section of Omukawa River (extension L = 8.3 km, gradient 1/58) as a study site,
a comparison between the volume of sediment transport obtainedby SAR image interference analysis using 9 SAR images acquiredby the ALOS-2 satellite passing over JAPAN, and the sediment
discharge observed by hydrophone, turmidimeter and sediment trap
pit during 2014-2016 period, is conducted. Some considerations
were made for the results. The result shows that, although the data
show relatively large scattering, an approximate linear correlation
was recognized. The reason of the difference between two data is

DAMS IN JAPAN - OVERVIEW 20152018
assumed that sediment discharge is measured in only 2.0m wide
area with respect to the river width of 72 m, which is not adequate
for representing the entire river cross section.

Case analysis of sediment bypass tunnels (Switzerland,
Taiwan, Japan)
H. Ohori, M. Ono, Y. Takata, G. Nagatani and T. Sumi
Until now, the planning and design of SBT has been performed
individually, in accordance with the circumstances of a particulardam. In order to systematize design methods for SBT, with thisresearch we created a database of the purpose and specificationsof SBT. We then applied classifications by structural types, andanalyzed related characteristics. The target was a set of 15 SBT in
Switzerland, Taiwan and Japan. Classification of structures was
performed based on the sediment discharge form, the purpose of
the dam, and the main purpose of the SBT. Here, the sediment discharge form refers to whether or not sediment entering upstreamof the reservoir is passed through the reservoir. For the analysis of
SBT characteristics, we analyzed the tunnel design discharge, thetunnel structure, and the target grain size of sedimentation, basedon the prior structural classifications. We then organized considerations to be taken into account with future SBT planning anddesign.

Research on sediment sluicing operations through dam
discharge operations in consideration of upstream/
downstream riverbed characteristics
Y. Kitamura and S. Takagi
Sediment environment changes due to sedimentation in a dam reservoir not only cause changes within the reservoir but also affect awide range of the dam’s upstream/downstream. Sedimentation in adam reservoir greatly changes the upstream/downstream riverbed
environment, with effects such as increasing the flood level in the
upstream area, armor coating and degradation of riverbed of thedownstream riverbed, and even coastal retreat. Due to this, the importance of comprehensive sedimentation management, which includes not only sedimentation measures targeting the environments
within the dam reservoir but also sediment flushing and sedimentsluicing (hereinafter referred to as “sluicing”) measures comprehensive sediment management, has been increasing. Sedimentation
sluicing measures, which are comprehensive sediment management, have often been implemented. In this paper, the authors analyze data obtained from hydraulic model experiments and results ofnumerical analyses regarding measures against riverbed erosion inareas downstream the Funagira Dam, and discuss sediment flushingand sluicing techniques based on dam discharge operations taking
the riverbed characteristics upstream and downstream the dam into
account. The results obtained indicate that it is possible to estimate
the amount of sediment outflow from the average riverbed level upstream the dam reservoir and the flood volume; to forecast changes
in the flow downstream the dam from the estimated amount of sediment outflow and the average riverbed level downstream the dam;and to maintain and control the flow. On the basis of the numericalanalysis results, the authors also propose adequate gate operations
and discharge level operations to control dam sedimentation andsluicing as well as the flow downstream the dam.

36

Analysis of sedimentation countermeasures in hydropowerdams considering properties of reservoir sedimentation
C. Onda, H. Okumura and T. Asahi
Sedimentation in hydropower reservoir is one of the most important problems for sustainable power generation. Many our company’s dam and reservoirs were installed in post war reconstruction
period, then for decades reservoirs have stored much sedimentation
inside up to sedimentation ratio about 10% because of high degreeof sediment production and river flow regime. We have trying to
excavate sedimentation out of reservoirs to avoid aggradations of
upstream riverbed and obstacle for intake and outlet functions.
Reprehensive five different type reservoir sediment managements
considering sediment properties have been really carried out. In
comparatively large Sakuma dam, provisional transporting insidereservoir is main countermeasure, in near future radical management will be required. In comparatively small Futatsuno andTaki dam, current excavating sedimentation volume is enough formaintaining reservoir size for flow sedimentation. So that sedimentrouting methods as bypassing will be planned in a hurry. In smaller
Setoishi and Yambara dam, sediment sluicing or hydro-suction sediment removal systems have been already started as test. In spiteof no quick remedy to countermeasure reservoir sedimentation
dramatically, some methods exist that select suitable options foreach reservoir considering with reservoir size, life and basin. Not
only the technical feasibility, but also the economic advantages andecological acceptability should be considered. For sustaining reservoir and hydropower, reservoir sedimentation management will be
active and adaptive more and more.

Prediction of environmental effect due to sediment sluicing
at a series of three dams
T. Yoshimura, H. Shinya, T. Sumi and N. Onikura
With the flood disaster experienced in the Mimikawa River system
due to Typhoon Nabi in 2005, various problems caused by sediment in the river basin became clear, including increased risk offlooding with rising riverbed levels in damregulating reservoirs,
grain coarsening in the downstream river channel with the entrapment of sediment in dams, and the destabilization of bridge piersin the downstream river channel. As part of an effort to resolve allthese problems simultaneously, from sediment sluicing at a seriesof dams was implemented. Sluicing is an operation carried out
when there is river flooding due to typhoons. Dam-regulating reservoir drawdown is carried out, and sediment flowing into these reservoirs from the upstream is allowed to flow downstream of dams.
This paper principally covers 1) an overview of sediment sluicing
at dams in the Mimikawa River system, 2) understanding and analysis of the river environment prior to sluicing, 3) predictions of theeffect on the river environment due to sluicing, and 4) testing ofthese predictions.

New development of technology for countermeasuresagainst barren ground by dam reservoir sediments (Super
fulvic acid iron)T. Toyoda, J. Takimoto, T. Sumi, S. Horiya, Y. Sakai and
M. Sueyoshi
This time, our research group focused on the effect of high concentrations of fulvic acid produced at the bottom of the dam, using ahigh concentration fulvic acid iron elution unit, in a real sea area

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DAMS IN JAPAN - OVERVIEW 20152018

where barren ground is progressing. By conducting demonstration
experiments on the algae field recovery of the dam reservoir, it
is going to develop for the practical application of technologicaldevelopment for effective utilization of lake bottom deposits. We
have used steelmaking slag made from blast furnace as a material
to promote dissolution of divalent iron ions in the past development
process, but from this time we have found more effective materials,
we have manufactured from electric furnace converter A material
containing high concentration divalent iron ions was adopted. Thisis a material containing high concentrations of divalent iron ionswhich is 100 times higher than the steelmaking slag that has been
adopted so far. Regarding the commercialization of this researchand development overseas, it is scheduled to apply in Korea thefirst time in East Asia. In addition, we propose a new calculation
formula for CO2 absorption (carbon conversion) by seaweed bed
construction, and the annual fixing by the algae of Japan is estimated to be about 3 million tons. It is expected that future development of research and development utilizing this technology will becommercialized in areas such as tidal banks as a port conservation
technology and construction for forming seaweed bed and seawall
maintenance etc. Research and development in this area has attracted attention as a technique for improving the quality of cultured
laver as application technology in recent years, technology for restoring seaweed beds and improving the production of agricultural
products in recent years.

Plan and operation results of Koshibu Dam sediment
bypass tunnel
T. Sakurai, T. Tsujimoto, I. Kunimura, H. Takeuchi and K. Ishida
In order to prevent sedimentation in the reservoir and ensure thecontinuity of sediment transport at the river, the Koshibu dam
sediment bypass tunnel was planned and completed in September
2016. From the viewpoint of structure, environment and sedimentbudget, monitoring plan was examined by the monitoring committee and several trial operations have been carried out. Since thepurposes of the Koshibu dam is including flood control, irrigationand power generation, the sediment bypass tunnel is planned tooperate during the flood control. In order to adapt to the flood control rule, two crests placed on the two orifices is designed for the
inlet structure. The target bypassing sediments are gravel having
a grain size of about 100 mm or less, sand and silt (clay). As acountermeasure against abrasion damage caused by the sedimenttransport, around the gate with a relatively low flow velocity wasprotected with “rubber steel” and the downstream section with highflow velocity was protected with steel lining. In the monitoring
plan, the objectives of monitoring at each viewpoint were arranged
by selecting suitable methods. In sediment budget monitoring, as
the first case of the sediment bypass tunnel in Japan, sediment observation devices were installed on the bottom of the tunnel outlet
part. After completion of the bypass facility, several trial discharge
operations were carried out. Even though the trial discharge was asmall scale compared with the planned maximum bypass discharge
and comparatively short time, as a result of monitoring, it was
confirmed that there was no problem in gate operation, and no significant abrasion damage and environmental changes in the downstream river. Moreover, it was able to estimate the sediment budget
and sediment transport characteristics during bypass operations.
Regarding abrasion damages, long-term monitoring is needed since
the flow rate and operation time in the trial discharge was limited.

Sediment derivation by bypass tunnel restores downstream
environment
S. Kobayashi, H. Fukuroi, T. Sumi and Y. Takemon
We reviewed studies of the effect of SBT on the downstream environment to clarify whether SBT has a positive effect on downstream, and to understand the key features of SBT that promote theenvironmental recovery of the degraded reaches. Major results ofthe studies are listed as follows.
1. Below-SBT site in the downstream of dam was more like upstream of dam than above-SBT site in the downstream of dam, in
terms of bed grain size, microhabitat composition, and invertebrate
community.
2. Environmental recovery of downstream reaches, evaluated by
upstream-downstream similarity in microhabitat composition
and invertebrate community, corresponded with the years of SBT
among the 4 dams. 3. Comparison of among-sites dissimilarity ininvertebrate community among 3 types of rivers (non-dam, dam
without SBT, dam with SBT) suggested a positive effect of SBT on
habitat fragmentation.
4. Turbidity of downstream during and after floods and red tide occurrence in the reservoir decreased after the start of SBT.
5. Although bed level didn’t increase constantly, grain size,
pool-riffle structure, gravel-bar changed as expected within a several years after the start of SBT.
6. Invertebrate community of downstream became more like thatof upstream of dam within 2-3 years after the SBT in terms of bothtaxon richness and taxonomic composition.
7. Sediment releases by SBT acted as natural pulse disturbancesthat lower invertebrates and ecosystem functions, followed by theirrapid recovery.
8. Numerical and field studies showed that the downstream channel
becomes steeper and the riverbed becomes unarmored conditions
by SBT. Surface grain
size distribution can change quickly even by one SBT release.
9. Turbidity decreased after the SBT operation. Algae, invertebrates, and fish decreased after each event but they recovered to apre-event level soon.
10. Although test-run of SBT had been done for several years, there
was no evidence of the recovery in the invertebrate community ofdownstream reaches towards an upstream state.
Downstream environment is expected to recover to a pre-dam state
within a few to several years after the start of SBT if surface bed
materials are reworked and exchanged. The downstream recovery
by SBT that release mainly fine sediment will be examined by ongoing monitoring in multiple Japanese dams.

Challenges of Dam Reservoirs for the Coming JapaneseSociety and Several Proposals
T. Hamaguchi, H. Mori and H. Ishii
This communication is to introduce the core contents of the reportcompiled by the special committee of Japan Society of Dam Engineers (JSDE) in 2016, which aims to clarify important targets inplanning, operation and maintenance of dam reservoirs, with fulland adaptive utilization of dam stock for the coming Japanese society in mind. Approx. 2,700 existing dam reservoirs play indispensable role in supply of water, energy, mitigation of flood damage,
maintenance of normal function of the river flow, and recreational
function. With increase of aged dams, there is an increasing number of re-development project of dams, whose major purpose isenhancement of flood control capability and recovery from excessive sedimentation. Importance of “backup” capacity is pointed out
here.

DAMS IN JAPAN - OVERVIEW 20152018
After examining three influencing factors, namely decline in population, climate change, and rare but devastating disasters, major
issues will be mitigation of flood damages, maintenance of normal
function of the river flow, hydropower, and sediment management.
Necessity of flood control capacity for long-term river improvement plan is confirmed. Hydropower’s stabilizing function for solar and wind power is also focused. A basic framework consistingof four phases is presented, to make the stock of dam reservoirs
function fully, with proper maintenance and adaptive operation tochanges. They are 1) Long service life, 2) Wise use, 3) Capacity
increase, and 4) Network use.
Finally, nine proposals of high priority are shown as follows.

38

1. Enhancement of flood control capacity
2. Securing water supply in a crisis situation
3. Promotion of hydropower
4. Networking of dam reservoirs at a basin level and efforts forconsensus building
5. A method to concretize backup capacity
6. Improvement in reservoir operation
7. Securing dam safety
8. Technology development for longer service life of dams
9. Better understanding of dams and fostering engineers of next
generation

Theme 6.    Geology and rock foundation
A. 4th Asia Pacific Group Symposium and 9th East Asia Dam Conference, September 2016
Reduction of ground water flow by promoting clogging
effect of soil particles
T. Tamai, T. Shiono, N. Sorimachi, T. Tsukada and F. Kawashima
Grouting was conducted to reduce groundwater flow in the bedrockof a reservoir of a pumped storage power plant, located in the sitewhere the ground water level is low. We conducted grouting aroundthe bottom of the reservoir, due to difficulty of forming the grout
curtain reaching the low permeable layer of the bedrock. To reduce
the permeability of bed rock with the smaller volume of grout,
we invented a method to promote clogging effect artificially by
spreading soil particles into reservoir water. The soil particles wereobtained from the residual horticultural soil after being screened,collected near the reservoir, in order to reduce the cost. This paper
summarizes the results and evaluation of laboratory tests, field tests
and application of the invented method.

B. ICOLD 85th Annual Meeting International Symposium in Prague, July 2017
Dam foundation design for the main dam at Nam Ngiep1
hydropower project in Laos
T. Tabuchi, Y. Murakami, M. Asakawa, T. Seoka and K. Ueda
A roller compacted concrete (RCC) gravity dam of 167 m height isunder construction in Laos. Due to a folded zone in the geology of
the right abutment, several weak horizontal layers are distributed
below the river bed and these were considered to have potential toseriously impact the dam stability. In order to evaluate the mechanical properties and the distribution and formation of these weaklayers, detailed geological investigations were instigated by conducting core drilling, rock property tests, X-ray diffraction (XRD)
analysis and computed tomography (CT) scanning. Through amultiple-wedge stability analysis and finite element analysis (FEA),a shear key was designed to penetrate part of the weak layers andbe incorporated into the dam body to improve the dam stability
against sliding.

C. ICOLD 86th Annual Meeting International Symposium and 26th ICOLD World Congress in Vienna, July 2018
Evaluation of the dam geology and geological risk at the
Namngiep 1 hydropower plant
T. Seoka, Y. Aosaka, Y. Yoshizu and T. Tabuchi
The surface of the mountain at the dam site is covered by talus
and a stratified structure below has alternating layers of sandstone
and mudstone having rock class of CM to CH. On this has beendeveloped the dam site. As general the bedding planes on the bothabutment are moderately dipping with 8° in downstream direction
and 8° in riverbed direction. And around the middle of the dam
axis the dip angle of the bedding plane is 15° to 25° in the same
direction. On the right abutment the fold axis is continuous in the
upstream and downstream directions and geological formationshows a steep profile, but it becomes moderate again at the higher

elevation. No outstanding fault has been observed and a box foldhas been formed at the steep slope area. Flexural-slip associatedwith fold formation has developed around the fold axis. It is extrapolated that flexural-slip occurred before solidification based on
the observation that blocks formed by joint sets intersecting withthe bedding planes are observed in the sandstone layer and ductile
deformation are frequently observed in the mudstone layer. Simultaneously definite striation of reverse-fault sense harmonized wellwith flexural-slip observed in some fine sandstone indicates thatcoarse sandstone and fine mudstone had flexural-slip developed insemi-brittle and ductile condition in geological time respectively.
The weak layers are 8 in number and are confirmed on the bottomof the dam and both the abutments, and they are issues to consider
specific strength and continuity of weak layers. Physical propertiesof the rock were determined based on observation of outcrops anddrilling cores, in-situ block shear tests and laboratory tests. Physi-

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DAMS IN JAPAN - OVERVIEW 20152018

cal properties of rock mass were evaluated based on Hoek-Brown
failure criterion for each part of the foundation rock. Physical properties of weak layers were determined based on the shear box testsof the disturbed samples, liquid limit tests and plastic limit tests.
The total strength of the weak layer can be estimated from the component of weak layers. In addition, X-ray diffraction analysis was
conducted in order to verify that these fine particle fractions in the
weak layers do not include any swelling clay (for example, Smectite) which might significantly degrade physical properties. Besides
detailed observation by means of CT scanning was conducted inorder to examine the continuity of a fractured part. Geologicalrisk should be evaluated adequately for the dam construction in
the BOT scheme project. The risk to a hydropower project is highcompared with other infrastructure projects because large amountof project cost depends on geological condition. Therefore, adequate evaluation of geological risk and diversification of geologicalrisk are very important factors. In addition, highly accurate geological data helps adequate evaluation of geological risk. Drilling
technology especially is one of the most important factors to support geological evaluation. In this paper, the methods to evaluate
the dam foundation rocks are discussed in the feasible study phaseto the execution phase. Evaluation of the geological risk and themethod to reduce the geological risk are discussed based on actual
geological data.

Slaking countermeasures related to rock contact execution
at the soft rocks foundation
S. Yoshimura, S. Takasgi, N. Yasuda, H. Satoh
Apporo dam is a multi-purpose dam now under construction at
the Azuma river in Horonai frontage of Atsuma town, Yufutsu
district of Hokkaido prefecture as part of comprehensive development of the Azuma river. The dam is a trapezoidal CSG dam withof 47.2m in height, 47,400,000m3 in total reservoir capacity, and43,100,000m3 in effective reservoir capacity. Apporo dam uses softrock as the CSG material of dam body, and its dam foundation is
also soft rock. Properties of the soft rock surrounding Apporo dam
include slaking caused by cyclic wetting and drying, so various
technical studies were conducted in order to use soft rock as thefoundation bedrock. The dam foundation is extremely uneven so
the excavation procedure was also studied. Slaking tests during thesurvey and slaking confirmation tests before construction works
showed clearly the slaking characteristic of this bedrock and leads
to the effective countermeasures. The construction works werecompleted and the first impoundment started in October.

Behavior analysis of the underground powerhouse basedon precise displacement measurement
M. Kashiwayanagi, K. Maeda, N. Shimizu
A few damaged pre-stressed anchors were identified in the 40year aged underground powerhouse, while no other deteriorationin the cavern was found. The underground powerhouse includes
output of 220 MW and two generator units. The cavern located
100 m beneath the reservoir has the dimension of 23 m wide, 42.25
m high and 70.2 m long. The monitoring of the convergence has
been conducted at two generator sections of the cavern to clarify
its long-term performance using a newly developed laser range
finder since then. The monitored convergences have behaved stably
reproducible and been clearly consistent with the yearly and/or theseasonal fluctuations of the reservoir water depth and the ambient
temperature in the cavern. These are less than the unusual convergence which is designated under the assumption of the entire lossof the support effect as the risk scenario. No concerns are found in
the current situation of the cavern so far.

DAMS IN JAPAN - OVERVIEW 20152018

Editorial Committee for Dams in Japan
Chef editor: Mr. Shigeru ARIGA
Advisor: Mr. Yoshiaki MORIKITA
Member: Dr. Masayuki KASHIWAYANAGI
Mr. Koutatsu TATEICHI
Mr. Yoshihiro KAMEO
Mr. Kazuo SAKAMOTO
Dr. Shigeru IKEDA
Mr. Toru NISHIKAWA
Mr. Tatsuya MIZUNO
Mr. Toru HINO
Mr. Junichi FUKUWATARI
Dr. Norihisa MATSUMOTO

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