Japanese Dam Technologies
Contributing to the World 2018

JCOLD

JAPAN COMMISSION ON LARGE DAMS

It’s our honor to introduce
the following expertise¾

Japanese Original CSG Technology¾

Upgrading Dams with Japanese Advanced Technologies
under Operation¾

࡮࡮࡮࡮࡮P.1

࡮࡮࡮࡮࡮P.33

Japanese Advanced Technologies for Sediment Management࡮࡮࡮࡮࡮P.41

Appendix࡮࡮࡮࡮࡮P.52

Japanese Original CSG Technology

1CSG Structures in JAPAN① Natsui Coastal Levee④ Yokokawa Sediment Check Dam

China

Map of Japan

Russia⑤ Taiho Sub Dam② Hamamatsu Coastal Levee④

North Korea⑧

Kyoto,JAPAN③⑥ Kasegawa Sub Dam

South Korea①⑦②⑧ Landslide countermeasure（Isawa dam Reservoir）⑥⑦ Nagashima Sediment Check Dam⑤○：Coastal Levee○：Sediment Check Dam, Sub Dam,etc○：Landslide countermeasure

CSG Coastal Levee
StatusCompleted

Under
Construction

Top level(Above sea level)(m)Length(m)

Volume
(CSG)
3
(m )

Raw
Materials

Unit of Cement3(kg/m )

①Natsui Coastal Levee

7.2

920.0

60,000(40,000)

Quake concrete
wreckage80~100②Hamamatsu Coastal Levee

13.0

17,5002,000,000

Terracedeposit40~100③Sendai Bay South Coastal Levee

7.2

1,179

50,500

Excavated rockand sand material

40~100Name of Structure

CSG Small Dam (Sub Dam, Sediment Check Dam, Coffer Dam)
StatusName of Structure

Height (m)Length(m)

Volume
(CSG)
3
(m )

Raw
Materials

Unit of Cement3(kg/m )

Completed④Yokokawa Dam Upstream cofferdam

12.4

26.0

3,200

Dam excavationmaterial

60

Completed⑤Taiho Sub Dam

30.0

110.5

34,000Weathered rocks

60,100Completed⑥Kasegawa Sub Dam

29.3

115.5

68,000Weathered rocks

80

Completed⑦Nagashima Sediment Check Dam

33.0

127.0

23,100River bed graveland sand80

2

Trapezoidal CSG Dams in JAPANMap of Japan② Tobetsu Dam③

Russia

②
China

⑧

⑤

North Korea④③ Sanru Dam⑥⑦

South Korea⑨④ Apporo Dam① Kin Dam①

List of Trapezoidal CSG Dams
StatusName of Dam

Height(m)

Length(m)

Dam Body
Volume (m 3 )Under
Designing

Unit of Cement(kg/m 3 )① Kin Dam

39.0

461.5

300,000

Weathered rocks

80～100② Tobetsu Dam

52.4

432.0

803,000

Riverbed sand andgravel60～100③ Sanru Dam

46.0

350.0

495,000

Riverbed sand andgravel60～100④ Apporo Dam

47.2

516.0

480,000

Weathered rocks

60～100⑤ Naruse Dam

114.5

778.5

4,760,000⑥ Chokai Dam

81.0

365.0

1,688,000⑦ Tsutsusago Dam

105.0

345.8

1,870,000⑧ Mikasa-ponbetsu Dam

53.0

160.0

480,000⑨ Honmyo-gawa Dam

64.0

385.0

750,000

Completed

Under
Construction

Raw
Materials

3Japanese Original Technology of Trapezoidal CSG Dam①The trapezoidal CSG dam is a new type of dam which differs from the conventional concrete gravity
dams, embankment dams, and hard-fill dams. The dam body is made of cemented sand and gravel(CSG).
Protection concrete
Protection concrete

CSG

Structural concrete

Gallery
Seepage control concrete
Seepage control concreteRich mix CSG
Foundation drain hole
Auxiliary curtain grouting
Curtain grouting

The outlet works, gallery, etc. can beplaced inside the CSG dam body.

②The trapezoidal shaped body requires less strength, so the material strength may be low, permitting
the use of low-quality materials.

Compressive stress distribution

Tensile stress distribution③CSG can be produced easily by mixing cement ④The trapezoidal CSG dam is designed in range
and water with materials obtained nearbyof an elastic body behavior of CSG, (so like aconcrete dam).
without gradation adjustment and washing.
8

As long as the gradation and unit watercontent of material remain in this area, thedesign strength is automatically satisfied.
Curve forcoarsest material

If there is an excess ofwater, its workability
may deteriorate.

6

Stress応力(N/mm2)

Strength of CSG (MPa)

Design Strength
If there is a lack of water,
CSG strength may beinsufficient.

σE：弾性領域強度
Elastic Region Strength5

Diamond-shapearea

Curve forfinest material

σp：ピーク強度
Peak Strength

7

4Gradient:
傾き：弾性係数
Elastic Modulus

32

Elastic
Region弾性領域

1Allowable range ofunit water content

03Unit water content (kg/m )In consideration of the larger scatter in CSG properties compared
to concrete, "Diamond Shape Theory" has been established todesign and control CSG strength.

4

0

2,000

4,000

6,000

Strain
ひずみ

8,000

10,000

The Construction Results of Trapezoidal CSG Dams in Japan
Up to present, four trapezoidal CSG dams have been constructed in Japan. Currently, five more
trapezoidal CSG dams are under construction or being designed. The highest of the completed
trapezoidal CSG dams in Japan is 52m, however, those currently under construction are designed to
be over 100m in height.
List of the Trapezoidal CSG Dams

Completed

Kin
Tobetsu
Sanru
ApporoHeight
(m)
39.0
52.4
46.0
47.2

Length
(m)
461
432
350
516

Dam Body Volume(m3)
300,000
803,000
495,000
480,000

Under Construction

Naruse

114.5

778.5

4,760,000

StatusUnder Designing

Name of Dam

Chokai81.0

365

1,688,000

Tsutsusago

105.0

345.8

1,870,000

Mikasa-ponbetsu

53.0

160

480,000

Honmyo-gawa

64.0

385

750,000

Tobetsu Dam

Kin DamApporo Dam

Sanru Dam

5

Application of the CSG Technology
The CSG Technology and the CSG construction method have also been to various structures.

CSG Sub Dam

CSG Sediment Check Dam

CSG Coastal Levee

Landslide Countermeasure

6

CSG materials
CSG is produced using simple equipment by mixing cement and water with material obtainable
nearby without classification, gradation adjustment or washing. When CSG is manufactured, gradation
adjustment of CSG material such as sorting, blending, etc. is not carried out, other than removing or
crushing oversized pieces, and cleaning. Thus, the equipment required to manufacture CSG is
minimal: a simple continuous CSG mixing system.

CSG Manufacturing Process
CSG Material
Raw material

MachineryContinuous Mixer

Gravel which was excavated in the riverbed isused as raw material

Producing CSG is conducted with a highperformance continuous mixer

CSG Manufacturing Processes for a Trapezoidal CSG Dam

7

Stock Yard of Concrete Wreckage（Raw Materials of CSG）

CSG Manufacturing Processes for Small CSG Structures

8

The Raw Materials of CSG
CSG consists of is rock-like raw materials such as material excavated to form the foundation, riverbed
sand and gravel, terrace deposits, weathered rocks and concrete wreckage all of which can beobtained relatively easily.
CSG requires less strength than concrete, so the CSG raw materials may be lower quality than therock used as concrete aggregate.
Many kinds of rock-like materials can be used as CSG materials. But we should decide theapplicability of the materials proposed, as CSG materials, considering the strength, mixing condition,
execution condition and so on. For example, when the material proposed contains high fine particle
contents, there is high possibility of low strength and workability.

River Bed Gravel and Sand

Terrace Deposits

Concrete Wreckage

Excavated RockThe Raw Materials of CSG

9

Construction Flow for a Trapezoidal CSG Dam
The CSG construction method can, like the RCD or RCC method, be executed by the layer placing
method using general-purpose machines such as dump trucks, bulldozers, and vibrating rollers.
The unit cement content is small and almost no bleeding occurs, so green-cutting is unnecessary.
CSG is made by mixing cement and water with CSG material. A continuous mixing system is used,which is simpler than a normal concrete mixing system.

Construction Flow for a Trapezoidal CSG Dam

CSG Mixing System for a Trapezoidal CSG Dam

10

Construction Flow for small CSG structures(Example of CSG coastal levee)
The CSG construction method for small structures can be executed by utilizing widely available
small size general-purpose machines.

Raw Materials:
Riverbed gravel, terrace
deposits, excavated rock,concrete wreckage etc.

Concrete wreckage

Quarrying
Terrace deposits

Crushing
Crawler crushing machine

Fresh CSG

MixingMobile soil remediation machineCompacting

Bulldozing

Transportation

Vibrating Roller(4t class combined type)

Bulldozer (7t class)

Dump Trucks(10t class Crawler type)11

１．Feature of The Trapezoidal CSG Dam
What's the trapezoidal CSG dam ?＊1
The trapezoidal CSG dam is a new type of dam which differs from the conventional concrete gravity dams
and embankment dams, and its dam body is trapezoidal in shape and made of cemented sand and gravel(Fig.-1), which is mixture of cement, water and material obtained near the dam construction site. This type ofdam has been developed in Japan.
CSG can be produced easily by mixing cement and water with material obtained nearby without gradation
adjustment and washing, but it is not as strong as concrete. To overcome this shortcoming, it was combinedwith a trapezoidal shape, which does not require great strength.
The trapezoidal CSG dam simultaneously leads to "rationalization of materials", "rationalization ofdesign", and "rationalization of execution". And the feature of the trapezoidal CSG dam is shown in Fig.-1.

Fig.-1 The Feature of the Trapezoidal CSG Dam

Standard Cross Section of the trapezoidal CSG dam-body (Fig.-2)
The trapezoidal CSG dam is made using CSG (Photo-1) for the main part of dam body, and protection
concrete is placed on its surface to increase durability. A structural concrete for gallery and a seepage control
concrete for securing seepage pass length are placed on the upstream side. CSG on the bottom surface ofthe dam body is rich-mix CSG selected to ensure durability.

＊1 This paper is prepared on "Engineering Manual for Design, Construction, and Quality Control of Trapezoidal CSG
Dam 2012" which Japan Dam Engineering Center published. We forbid the reproduction of figures and photographs in thispaper without permission.

12

CSG Material

Specimen of CSG

Protection concrete
Protection

concrete

CSG
Structural concrete

Gallery
Seepage control concreteRich mix CSG
Foundation drain hole
Auxiliary curtain grouting
Curtain grouting

Fig.-2 Standard Cross Section of the trapezoidal CSG dam

Photo-1 CSG Material and CSG

Advantages of the Trapezoidal CSG dam
1. An required condition for a trapezoidal dam is that the vertical stress generated on the bottom of dam isalways on the compressive side, so the dam body and foundation bedrock need not be integrated for theuse of cohesion of rock foundation. Because the cohesion of the foundation bedrock needs not be used,
it is possible to relax the conditions for the foundation bedrock.
2. In addition to the lower strength required for the dam body material, a trapezoidal CSG dam has fewer
requirements for the foundation bedrock, increasing the flexibility for dam site selection.
3. A trapezoidal CSG dam can be built with a simple CSG manufacturing plant, permitting rapid execution
by a continuous mixing system.
4. The construction cost depends upon each dam condition, but based on the previous cases, theconstruction cost of trapezoidal CSG dams is estimated to be 20 to 25% reduction compared to concrete
gravity dams.

The Construction Results of the Trapezoidal CSG Dams in Japan
Two trapezoidal CSG dams were completed in Japan. At present, seven trapezoidal CSG dams are underconstruction or designing. The maximum height of completed trapezoidal CSG dams in Japan is 52m.
However, the design of 100m-high class trapezoidal CSG dams is now designing in Japan (Table-1, Photo-2,
Fig.-3).

StatusCompleted

Under Construction

Under Designing

Table-1 List of the Trapezoidal CSG Dams
HeightLengthName of Dam(m)(m)① Kin Dam
39.0
461

Dam Body Volume(m3)
300,000② Tobetsu Dam

52.4

432

803,000③ Sanru Dam

46.0

350

495,000④ Apporo Dam

47.2

516

480,000⑤ Naruse Dam

114.5

778.5

4,760,000⑥ Chokai Dam

81.0

365

1,688,000⑦ Tsutsusago Dam

105.0

345.8

1,870,000⑧ Mikasa-ponbetsu Dam

53.0

160

480,000⑨ Honmyo-gawa Dam

64.0

385

750,00013

Tobetsu Dam

Kin Dam

Sanru Dam

Apporo Dam
Photo-2 The Trapezoidal CSG Dams②③

RussiaChina

North Korea⑤⑥

South Korea⑨①
Fig.-3 Map of the Trapezoidal CSG Dams in Japan

14

④
⑧
⑦

Kyoto,JAPANApplication of the CSG Technology
The CSG Technology and the CSG construction method were also applied to sediment check dams forreservoir sediment management (Photo-3), sub dams (Photo-4), upstream cofferdams (Photo-5), etc. In
addition, considering the advantages of the CSG technology, such as rapid execution and easy supply ofmaterials, we have applied this technology to the coastal levees (Photo-6,7), landslide countermeasures(Photo-8), seepage control works in reservoir, and so on.

Photo-3 CSG Sediment Check Dam(Nagashima Dam Reservoir)

Photo-4 CSG Sub Dam (Taiho Dam)

Under construction

After overflow

Photo-5 Upstream Cofferdam (Yokokawa Dam)

Photo-6 Coastal Levee (Natsui Coastal Levee, Fukushima Pref.)15

W=5000
W=4000Top concrete
Embankment

Embankment

Soil cover

Soil cover

CSG

Rich mix CSG

Photo-7 Coastal Levee (Hamamatsu Coastal Levee, Shizuoka Pref.)Photo-8 Landslide Countermeasure (Isawa Dam Reservoir)

Table-2 List of CSG Coastal Levees and CSG Small Dams
StatusCompleted

Under
Construction

StatusVolume(CSG)(m3)
60,000(40,000)

Top level(Above sea
level) (m)Length(m)

Natsui Coastal Levee

7.2

920.0

Hamamatsu Coastal Levee

13.0

17,5002,000,000

Terrace deposit

Sendai Bay South Coastal Levee

7.2

1,179

50,500

Excavated rock and sand material

Name of coastal levee

Nam of Structure

CSG Raw Materials
Quake concrete wreckage

Height(m)

Length(m)

Volume(CSG)(m3)

Raw Materials

Unit of Cement(kg/m3)Completed

Yokokawa Dam Upstream
cofferdam

12.4

26.0

3,200

Dam excavation material

60

Completed

Taiho Sub Dam

30.0

110.5

34,000Weathered rocks

60,100Completed

Kasegawa Sub Dam

29.3

115.5

68,000Weathered rocks

80

Completed

Nagashima Sediment Check
Dam

33.0

127.0

23,100River bed gravel and
sand

80

16

ChinaRussiaNorth Korea④Yokokawa Sediment
Check Dam

⑦ Landslide countermeasure（Isawa dam Reservoir）③ Sendai Bay South Coastal Levee

South Korea① Natsui Coastal Levee
Kyoto,JAPAN② Hamamatsu Coastal Levee⑦ Nagashima Sediment Check Dam⑥ Kasegawa Sub Dam○：Coastal Levee○：Check dam, Sub Dam,etc○：Landslide countermeasure⑤ Taiho Sub Dam

Fig.-4 Map of the CSG Structures in Japan

17

２．Design of The Trapezoidal CSG Dam
Different points from the Concrete gravity dam and the Hardfill dam
The trapezoidal CSG dam is designed in range of an elastic body behavior of CSG, so like a concretedam (Fig.-5), the outlet works, gallery, etc. can be placed inside the dam body, and the emergency spillway,
etc. placed at the crest.
Besides, in consideration of the larger scatter in CSG properties compared to concrete, "Diamond
Shape Theory (Fig.-6)" has been established to design and control CSG strength.
The strength of CSG depends on the materials used and cement content. According to previous cases,
the CSG strength of riverbed deposit is about 2N/mm2 or higher, and that of weathered rock is about
2N/mm2 or higher. However, these values are not the upper limitation of the CSG strength of thesematerials.
As long as the gradation and unit watercontent of material remain in this area, thedesign strength is automatically satisfied.

8
σp：ピーク強度
Peak Strength

7

Curve fo r
coa rsest material

6
σE：弾性領域強度
Elastic Region Strength

Stress応力(N/mm2)

S tre ngth of CSG (MPa)54Gradient:
傾き：弾性係数
Elastic Modulus

32

Elastic
Region弾性領域

10

If there is an excess ofwater, its workability
may deteriorate.

0

2,000

4,000

6,000

8,000

10,000Curve forfinest material

Diamond-shapea rea

Design Strength
If the re is a la ck o f water ,CS G strength may beinsufficient.

Allowable range ofunit water content
3

Unit water con ten t (kg/m )Strainひずみ

Fig.-5 Definition of the Strength of CSG

Fig.-6 Diagram of Diamond Shape Theory

How to decide the Standard cross section of the Trapezoidal CSG
dam body.
 A trapezoidal CSG dam is a new type of dam, which is different from conventional concrete dams orembankment dams, and so is designed using an appropriate method for this shape instead of theexisting method. The trapezoidal CSG dam is designed using the finite element method (FEM) anddynamic analysis method to consider the earthquake effects. An example of FEM analysis is shownas in Fig.7.
 A trapezoidal CSG dam is designed with upstream and downstream slope gradients set such that bothduring normal condition and during an earthquake, the vertical stress is compression along the entire
base (Fig.-8).
 Upstream surface gradient: Selected based on the strength of the materials obtained, dam height,
and foundation bedrock conditions. Based on previous and present cases, it is generally set to be
1:0.8.
 Crest width: Set considering constraints of construction works near crest. Based on previous andpresent cases, it is generally set to be 8m (Fig.-9).

18

Fig.-7 An example by FEM Analysis(Distribution of maximum stresses, comparison of the concrete gravity dam and the trapezoidal CSG dam)

Fig.-8 Distribution of Vertical Stress over Bottom of the Dam body19

Fig.-9 Necessary Width of Execution of the Trapezoidal CSG Dam Crest

Zoning of the Trapezoidal CSG Dam-body
The trapezoidal CSG dam is made of CSG for the main part of dam body, and protection concrete isplaced on its surface to increase durability. A structural concrete for gallery and a seepage control
concrete for securing seepage pass length are placed on the upstream side. The CSG on the bottom
surface of the dam body is rich-mix CSG to ensure durability.
Zoning of the Trapezoidal CSG Dam-body is as shown Fig.-10~13.
 Protection concrete: The permeability of CSG is generally low, but water tightness of trapezoidal
CSG dam body depend on protection concrete. Concrete placed on the dam surface to ensure
durability. Its thickness is a horizontal thickness of about 1.0～2.0m.
 Seepage control concrete: Concrete placed on the upstream side of the dam base to ensure watertightness of the contact rock surface from seepage flow. The length in stream direction are set
according to dam height and permeability of rock foundation. The thickness is more than 2 m(Fig.-15).
 Rich-mix CSG: Cement with a higher cement content than used generally in the dam body, toaccommodate irregularities of the bedrock. Its thickness is basically 1 m, but the thicker layer will be
adapted based on topographical conditions.
 Transversal joints: Joints are installed in the CSG near the abutments on the left and right banks. In
the middle, if the dam crest is long, they are installed about every about 100 m in the dam axis
direction (Fig.-16).

Fig.-10 Standard Cross Section of the Trapezoidal CSG Dam

20

Fig.-11 Standard Cross Section of Tobetsu Dam

Fig.-12 Standard Cross Section of Kin Dam

Fig.-13 Standard Cross Section of Sanru Dam

21

Fig.-14 Width of Protection Concrete

Fig.-15 Layout of Seepage Control Concrete (Dam Axis Direction Section)

Fig.-16 Example of Locations of Transverse Joints

How to Detail Design
The trapezoidal CSG dam is a new type of dam, which is different fromconventional concrete dams or embankment dams, and so is designed using
an appropriate method for this shape instead of the existing method. The
trapezoidal CSG dam is designed using the finite element method (FEM) anddynamic analysis method to consider the earthquake effects.
In designing the trapezoidal CSG dams, you should have a detailed
knowledge of design concept and procedure. The details are summarized in"Engineering Manual for Design, Construction, and Quality Control ofTrapezoidal CSG Dam 2012" which Japan Dam Engineering Center
published (you can purchase it here), or, please do not hesitate to contact with
JCOLD*2.

*2 https://search.jcold.or.jp/contacts/new, Tel. +81-3-5614-0968, Fax. +81-3-5614-0969

22

In the trapezoidal CSG dam design, the physical properties of the CSG (strength, deformability) must be
clarified. The design is conducted as follows.
1. First, the usable quantities of materials which can be obtained near the dam site are surveyed,accompanied by investigation and testing of the engineering properties of the material and the hardened
CSG which will be made using the material (surface dry density and water absorption of CSG material,
strength, elastic modulus and unit weight of CSG).
2. Next, the shape of the trapezoidal CSG dam (upstream/downstream slope gradients) is decided basedon the physical properties of the hardened CSG obtained.
3. Analysis is performed based on the physical properties of CSG and the shape decided, to confirm theexternal stability and internal stability. If there is surplus stability, the gradient is set steeper within a range
which ensures that the stress at the dam bottom remains compressive, or the unit cement quantity islowered. If the stability is insufficient, a study is conducted on either relaxing the gradient or increasing theunit cement content, and the most rational overall shape is finally decided.

For the following reasons, FEM analysis are used (Fig.-17).
1. Both external and internal stabilities can be clarified more directly and rationally than by the conventional
design method.
2. The finite element method permits consideration of the deformation properties of the foundation bedrock,allowing rational analysis.
3. Dynamic analysis permits direct and detailed determination of the effect of the shape of the dam body,and along with [2], rationally obtains the stresses inside the dam body, along the dam bottom, etc.

Fig.-17 Example of an FEM Analysis Model

23

３．Feature of The CSG Material
What is The CSG material ?
CSG is produced using simple equipment by mixing cement and water with material obtainable nearby
without classification, gradation adjustment or washing. When CSG is manufactured, gradation adjustmentof CSG material such as sorting, blending, etc. is not carried out, other than removing or crushing oversizedpieces, and cleaning. Thus, the equipment required to manufacture CSG is minimal: a simple continuous
CSG mixing system (Photo-6~9).

Fig.-18 CSG Manufacturing Process

Photo-6 CSG Manufacturing Process of Apporo Dam

24Machinery
Continuous Mixer

CSG Material
Raw material

Gravel which was
excavated in the riverbed isused as raw material

Producing CSG isconducted with a highperformance continuous
mixer (SP-Mixer)

Photo-7 CSG Manufacturing Process of Tobestu Dam

CSG Material
Raw material

MachineryZcross Mixer

Gravel which was
excavated in the riverbed isused as raw material

Producing CSG isconducted with highperformance mixer

Photo-8 CSG Manufacturing Process of Kin Dam

Concrete wreckage

Manufacture of CSG

Wreckage crushing

CSG mixing

Photo-9 CSG Manufacturing Process of Small CSG Structure (Coastal Levee)25

Raw Materials of CSG
CSG consists of is rock-like materials such as material excavated to form the foundation, riverbed sandand gravel, terrace deposits, weathered rocks, and quake concrete wreckage; all of which can be obtained
relatively easily (Photo-10).
CSG requires less strength than concrete, so the CSG raw materials may be lower quality than the rockused as concrete aggregate.
Many kinds of rock-like materials can be used as CSG materials. However, we should decide theapplicability of candidate materials, as CSG materials, considering the strength, mixing condition, execution
condition and so on. For example, when the material proposed contains high fine particle contents, there ishigh possibility of low strength and workability.

(River Bed Gravel and Sand)(Terrace Deposits)(Quake concrete Wreckage)(Excavated Rock)Photo-10 The Raw Materials of CSG

Quality control of the CSG material
The quality control for CSG contains three main items:
 Quality control of CSG
 Quality control of raw material
 Quality control of CSG material
Quality control of CSG is performed at the mixing equipment site and at the placing site.
At the mixing equipment site, unit water content and gradation are controlled by simple methods(Photo-11). The frequency of measurement is set to be high at the early stage of execution, and then thedata analyses of the results are conducted in order to set an appropriate frequency. And in the mixing
equipment, weights of water, cement, CSG materials are controlled. In principle, the material is supplied
continuously so weighing should be done in real time.
Next, at the placing site, the roller compaction frequency is controlled as compaction energy control(Photo-12). As an extra precaution, an on-site density test is done to confirm that the control system isoperating normally, for example, to check whether the quality of the material has changed, or if the weighing,spreading, and roller compaction, etc. are being done appropriately.

26

A strength test of specimens is also done in a laboratory (Photo-13), which is for the same purpose as
the on-site density test, and the younger age strength, such as a 7-day strength test is usually used to checkthis as early as possible.

(Grain size distribution)(Unit water content)
Photo-11 Quality Control Management Tests of the CSG Material(At the mixing equipment site)

Photo-12 Control of Roller Compaction Energy(At the placing site)

Photo-13 Strength Test of CSG Specimens(In Laboratory)

Quality control Method of the raw material and the CSG material
Quality control of the raw material is done to confirm whether or not the quality of the raw material haschanged greatly, and considering the time required to remake the Diamond Shape according to changes ofquality, this is done to clarify the quality at least one month before execution.

27

The items controlled for CSG materials are surface dry density, absorption coefficient, gradation, andsurface water content.
Quality control of CSG material is performed in the primary stock yard (quantity scheduled to be used in 3
to 5 days) and in the secondary stock yard (enough for the next day’s work).
Sufficient material for the next 3 to 5 days is stocked in the primary stockyard, considering the timerequired (approx. 3 days) to test the surface dry density and absorption coefficient.

Table- 3 Considering the time required to do the test
Day
1 day
2nd day
3rd dayst

Item
24hour water absorption
Measuring surface density, 24hour for drying
Measuring absolute dryness

Fig.-19 Flow from Stocking of CSG Material to Production of CSG

Photo-14 Primary Stock of CSG Material

Photo-15 Secondary Stock of CSG Material

28

4．Construction
Construction Flow for a Trapezoidal CSG Dam
The CSG construction method can, like the RCD method, be executed by the layer placing method using
general-purpose machines such as dump trucks, bulldozers, and vibrating rollers. The unit cement content issmall and almost no bleeding occurs, so green-cutting is unnecessary.
CSG is made by mixing cement and water with CSG material. A continuous mixing system is used, which
is simpler than a normal concrete mixing system.
The unit cement content is small and almost no bleeding occurs, so green-cutting is unnecessary.

Photo-16 Construction Flow for a Trapezoidal CSG Dam

29

Construction Flow for small CSG structures (Example of CSG coastal levee)
The CSG construction method for small structures can be executed by utilizing widely small size
general-purpose machines.

Raw Materials:
Riverbed gravel, terrace
deposits, excavated rock,concrete wreckage etc.

Concrete wreckage

Quarrying
Terrace deposits

Crushing
Crawler crushing machine

Fresh CSG

MixingMobile soil remediation machineCompacting

Bulldozing

Transportation

Vibrating Roller(4t class combined type)

Bulldozer (7t class)

Dump Trucks(10t class Crawler type)30

Manufacturing Facilities of CSG
When CSG is manufactured, gradation adjustment of CSG material such as sorting, blending, etc. is notdone, other than removing or crushing oversized particles, and washing is also not done, so the equipment
required to manufacture CSG is very simple: simple continuous CSG mixing systems are used
(Photo-17,18).

Photo-17 CSG Production Equipment (Tobetsu Dam)

Zcross Mixer (Kin Dam)

Mobile Soil Remediation Machine (For Small structure; Natsui Coastal Levee)
Photo-18 CSG Mixing Systems

Construction Facilities
For rapid execution, there are almost no restrictions on equipment for material production and mixing of
CSG. Therefore, the manufacturing equipment for CSG material and CSG can be selected flexibly to suit theexecution speed.
Next, the placing work of the trapezoidal CSG dam consists of:1) CSG placing work,
2) Protection concrete placing work, and

313) Formwork installation work, but performing these works at the same location greatly reduces efficiency.
Therefore, these placing works are done at different times to avoid interference and ensure smooth
construction of the dam body.
Simplified Equipment

Material easily obtained near the

Raw Material

CSG Material

CSG Mixing devices

Spreading and(new type mixers)

Compaction

Raw Material

CSG Material (RockRiverbed gravel,

based material used

Excavated rock etc.

General Purpose Equipment(newly developed)

construction site

Fresh CSG

CSG

for CSG)

Removing large stones

Mixing Adding Cement

Crushing etc., as necessary

and Water

Placing Curing

No grading, no cleaning of raw material= necessity to deal with wide gradation range of material in design and construction

Fig.-20 Manufacturing Flow of CSG

Photo-17 CSG Placing Work

Photo-18 Protection Concrete Placing Work

References

Engineering Manual for Construction and Quality Control of Trapezoidal CSG Dam 2007, Japan Dam
Engineering Center
Engineering Manual for Design, Construction, and Quality Control of Trapezoidal CSG Dam 2012,
Japan Dam Engineering Center

32

Upgrading Dams with JapaneseAdvanced Technologies under Operation

33

Controlled blasting technique with an electronic detonator
In the conventional blasting technique with a DS (decisecond‐level) electric detonator, the gas created by the previous blast escapes through the construction
joints before the next blast occurs, which makes this technique not suitable for concrete demolition. Therefore, by adopting the MS (millisecond‐level) electric
detonator, the next blast is successfully detonated before the gas escapes.
However, there were concerns about a blast vibration at private residence area exceeding the limit value set by management standard. Our solution was todeploy an electronic detonator (product name eDev II) and set one‐hole one‐step blasting with a time difference of 15 milliseconds, which enabled demolition
blast to generate moderate vibration that was significantly lower than the standard limit value.

Upstream side

25m

Downstream side

45.5m

Procedure of Demolition by Blasting

Part to Be Demolished by Blasting

Drilling

Charging explosives

Blasting completion【Characteristic】∙ Time setting in arbitrary milliseconds for each detonator is possible on the spot.
∙ Time setting can be set in 1 ms increments within range from 0 to 20,000 ms.
∙ The precision of the set time is ± 0.1%.
∙ Includes safety devices to protect integrated circuits in the detonator from high voltage such as static electricity or induced current due to lightning strike.
∙ Includes a capacitor that stores the energy necessary for communication with the explosive device as well as for ignition.
∙ Each explosive device can detonate up to 500 electronic detonators.
This technique is effective in cases such as blast vibrations need to be suppressed, especially when other properties are in close proximity, or in whenconstruction time is too limited to deploy conventional blasting technique.
【Regarding Environment, Surroundings, etc.】(Plan) Vibration level: not to exceed management standard value of 75 dB(Actual) Vibration level: actual value of 61 dB (average)【Future Prospects】∙ Among controlled blasting methods for demolition, this technique is the most superior at present.
∙ In the introduced case, we set 15 ms as the time difference, however, we are still working on finding the optimal setting.

【Dam】 Arase【Type】 Concrete gravity dam【Dimensions】 Height 25 m Length 210.8 m Volume 47, 167 m3【Purpose】 Power generation

Work Description【Phase2】Gate, Right Bank Gatepost and Management Bridge's Removal【Phase1】
Drawdown Equipment's Installation and Gate's Removal【Phase5】
Left Bank Gatepost and Management Bridge Removal【Phase4】
Right Bank's Removal【Phase6】
Left Bank's Removal【Phase3】Gate and Right Bank Water-Route Section's Removal

34【Purpose】
To remove water intake facilities and drainage
lines, which are structures inside the river, due tothe shutdown of the hydroelectric power station.

LIBRA-S Method: Temporary piers oblique tie installation method【Purpose】 To streamline the submerged brace installation work for temporary platforms.
【Background of selection of the method】
The brace installation work had been carried out using divers. However, the small range of visibility of the dam interior significantly harmed the work
efficiency. The high turbidity of water after floods suspended the work for several days. Due to these, this work method to streamline theunderwater operations was developed.
【Construction conditions】 Construction depth: 0 ‐ 30m【Outline of work method】
In constructing the substructure (brace) of a temporary platform, unit substructure members are assembled above water and slid downward andinstalled, thereby considerably reducing the diving operation.
・ Most of the braces are assembled on stages installed above water, which reduces submerged operations, leading to an increase in theconstruction efficiency and safety.
・ Once the work is completed, only bolts are loosened under water then the substructure members are collected in succession and demolishedabove water. This also results in higher safety and efficiency.
(1) Preparation work
（１）準備工electric chain (2) Temporary brace assembly work above water（２）ブレース材気中仮組立工
blocks

電 動ﾁ ｪｰﾝ ﾌﾞ ﾛｯｸ

ブレースバンド
brace bands

Temporary brace

ブレース材仮組立（気中施工）

仮止めバンド

作業用足場
working stage（３）ブレース材スライド(3)
Sliding down of braces(4) Repeating of sliding（４）スライド繰返し

スライド後仮固定(1) Preparation work
Install a hanging working stage above water.
Mount electric chain blocks onto the upper structure girder.
Tie brace bands onto steel pipe piles to couple braces andsteel pipe piles.
(2) Temporary brace assembly work above water
Install horizontal and diagonal members.
Hook the chain on a hanging jig on the upper horizontal
members.
(3) Sliding down of braces
Run the electric chain blocks to slide the braces one level
downward.
(4) Repeating of sliding
Repeat the above steps from tying brace bands in (1) to therest.

・ブレース材仮組立
Repeating of sliding・スライド（繰返し施工）Run the electric chain
blocks to slide the braces

ブレース材スライド
one level downward.
（気中⇒水中）Assemble members.

Mount electric chain blocks.

Slide downward.

Summary of the project【Dam】Kanogawa dam【Type】Gravity concrete dam【Specifications of the dam】
Height：61m、Crest length：167.9m、Volume：161,000m3【Purpose】
Flood control、hydropower【Purpose of work】
A tunnel spillway will be constructed on the right bank of the dam inorder to increase the flood regulation capacity of the existing Kano
River Dam 1.4‐fold.
Tunnel spillway:
Standard finished inner diameter: 11.5m; maximum cross section of
excavation: 320m2
Source: Ministry of Land, Infrastructure, Transport and Tourism,
Shikoku Regional Development Bureau pamphlet

35Full Rotation and Full Casing Method【Purpose】To bore holes for installing steel pipe sheet piles in the bedrock under water.

Construction site view with rotary excavator RT‐300【Background of selection of the work method】
・Relatively economical for the excavation of 2m‐dia. and max. 30m‐deep holes in submerged bedrock.

Stand pipe
Ø2300

・Has an operational record.
・Applicable to a wide range of bedrocks.
Excavation scale:
Width 10m x length 45m x maximum depth 30m
Excavation volume: 4,900m3
Excavation shape:
Width 11m x length 11m x average depth 10m

Rotary excavator
RT‐300Submerged pump

Excavator rack

Slush tank

Crawler craneOperator’s cabin
Ramp for fresh concrete vehicle

Revolving hydraulic unit

Hammer grab

Casing tube

Revolving jackTremie pipe

WeightConstruction equipment overview【Characteristics】
・This method can apply to a wide rangeof soils and also allows for greater
construction depth and excavation
diameter than other methods.
(Excavation depth: about 50m;
excavation diameter: 3,000mm)
・The method supports most soil
conditions.
・Clayey soil deposits on the outer
periphery of the casing could increase afriction resistance, possibly hampering or
preventing the revolving of the casing.

Summary of the project【Dam】Kanogawa dam【Type】Gravity concrete dam【Specifications of the dam】
Height：61m、Crest length：167.9m、Volume：161,000m3【Purpose】
Flood control、hydropower【Purpose of work】
A tunnel spillway will be constructed on the right bank of the damin order to increase the flood regulation capacity of the existing
Kano River Dam 1.4‐fold.
Tunnel spillway:
Standard finished inner diameter: 11.5m; maximum cross sectionof excavation: 320m2

Source: Ministry of Land, Infrastructure, Transport and Tourism,
Shikoku Regional Development Bureau pamphlet

36Underwater wire saw method【Purpose】A part of underwater concrete structure was cut and removed by the wire saw,
which was then placed above water level.
【Selection process of method】
Because of the lack of visibility in the reservoir (only 0〜1m), the original method, that themain body was set underwater was changed to the alternative method that the main bodywas set on the barge above water level and extend wire into water , since it will be difficult
to cope with incase of cutting the wire, and it has less ability of cutting, etc.
(Adopted wire saw：K‐WAC‐04､32.2Kw）【Conditions】 Water depth：0～30m、Concrete strength：Approximately 30N/mm2【Features】
・Under water concrete structure was cut by wire saw and was placed above water level.
・It is possible to execute when that the reservoir has the lack of visibility and it isdifficult to work underwater.
・Maintenance work is easy because the wire saw itself is placed above water level.
・It is not necessary for the wire saw to replace every place to cut off.
・Great depth result in the increasing the risk of cutting wire because the length of thewire saw is long.
・Since the method use crane, restraint
time will be longer.

Cutting parts by wire saw under water

Cutting of the concrete structure

Cutting of the concrete structure undrewater by wire saw【Procedure of the work】(ⅰ) Set the wire saw body (cutting machine) on the barge and cut the concrete in theunderwater block into blocks of 20 t or less.
(ⅱ) Cut the concrete block by lifting it with a crawler crane (120 t) placed on the temporary
gantry.
(ⅲ) Dispose of the removed concrete lumps in large trucks after handling them to apredetermined location.

Lifting cut concrete mass in water

Summary of the project【Dam】Kanogawa dam【Type】Gravity concrete dam【Specifications of the dam】
Height：61m、Crest length：167.9m、Volume：161,000m3【Purpose】
Flood control、hydropower【Purpose of the project】
A tunnel flood discharge is newly constructed on the right bank of thedam, with the aim of setting the flood control capacity of the existing
Kanogawa dam 1.4 times.
A tunnel flood discharge:
Standard inside diameter 11.5m, Maximum excavate section 320m2
In the Kano River dam remodeling project, new low water discharge
facility "and "selective water intake facility" are constructed for the
purpose of preventing cold water discharge and prolongation of turbid
water discharge and suppressing eutrophication of reservoir.

Image of the project"Reprinted from the pamphlet of Yamasakizaka Dam Construction Office, Shikoku Regional
Development Bureau, Ministry of Land, Infrastructure and Transport"

37

Drilling the existing dam body using road header
In the existing dam, a total five holes were drilled: three forthe expansion of discharge pipes and two to move thepower generation intake pipes.
To drill five locations in the same dam‐body is the largest
scale in Japan, as a dam upgrading work.
The drilling depth per hole is approx. 60 m, which contains asection of 1 m of upstream non‐vibration penetration
section (hole size: vertical 6 m, horizontal 6 m).
To drill the general section, a 200 to 240 kW class roadheader was used.
The vibration value on the dam‐body was mesured toconfirm if there are any effects on the dam‐body.
This picture shows the drilling work performed by a roadheader.
As it was reported from similar construction that vibration
would be the strongest at the time of penetration, the non‐vibration penetration technique was adopted to avoid
impact from vibration during penetration.

Summary of the project【Dam Specifications】
Type：Concrete gravity dam
Height：117.5m
Length：450.0m
Volume：1,119,000m3
purpose：flood control and power generation

The concept of the project is to increase flood capacity and discharge facilities.
The increase in flood storage will increase to a total capacity of between 75 million m3 and 98
million m3 by transferring the power generation capacity during flood season of 2.5 million m3
and dead water storage of 20.5 million m3, for a total of 23 million m3, to flood storage.The
discharge facility was expanded to enhance discharge capacity by adding three conduit gateson the right dam‐body (EL 115.6) at a location lower than the current discharge facility (EL130.0) in accordance with the decline of the lowest water level.

38

Floating type temporary cofferdam method
Overview of New Technologies

The cofferdam construction requires long diving hours at a very
deep water depth, large temporary equipment, and a long
construction timeframe.
For the floating type temporary cofferdam method, steel plates(skin plates) are attached to both the inside and outside of thebulkhead to make an airtight structure, and this becomes thebuoyancy chamber to make the bulkhead float.
It is important to maintain the balance between buoyancy
forces and dead weight by filling and draining the bulkheads
blocks in the proper order.
And this new method was used for the first time in the Tsuruda
Dam upgrading.

Efficiencies of the technologies
Construction Method

For actual construction, bulkhead blocks made at local factories will be assembled
on the reservoir to standardize them and they will be towed to the installation
position by a ship, and subsequently pulled by a winch and secured.
And then, water is drained from the cofferdam.

Efficiencies of this method :This is dependent on scale of the cofferdam and construction
depth, as large temporary facilities, such as pedestal concrete andsupport framework, are unnecessary and diving work can begreatly reduced, costs and processes can be reduced, and safety
can be improved, leading to an increase in construction efficiency.
Moreover, when drilling holes in the same dam, it is necessary
with conventional methods to dissemble and then reassemble
the bulkheads, but with this method there is no need todisassemble the bulkheads; flood the cofferdam and detach thebulkheads from the dam‐body and tow it as is to the next
construction site where it can be installed.

Summary of the project【Dam Specifications】
Type：Concrete gravity dam
Height：117.5m
Length：450.0m
Volume：1,119,000m3
purpose：flood control and power generation

The concept of the project is to increase flood capacity and discharge facilities.
The increase in flood storage will increase to a total capacity of between 75 million m3 and 98 million m3
by transferring the power generation capacity during flood season of 2.5 million m3 and dead water
storage of 20.5 million m3, for a total of 23 million m3, to flood storage.The discharge facility was
expanded to enhance discharge capacity by adding three conduit gates on the right dam‐body (EL 115.6)
at a location lower than the current discharge facility (EL 130.0) in accordance with the decline of thelowest water level.

39Underwater Work Method by Shaft-Style Equipment
Remote Controlled Multifunctional Underwater Equipment
Underwater Operation Using an Equipment with Apprratures①Erection of Shaft②Instllation of Equipment, LaunchRemote control

Machine guidance

SummaryThis equipment enables a series of underwater operations such as rock crushing,excavation, debris, disposal, precise sounding, photography, etc. in a safe andreliable condition through remote controlling. These are carried out by using
various apparatus on a machine attached to a shaft which is lowered from a barge.
The machine moves up and down along the shaft.
The equipment has been developed to conduct various underwater works
without divers. It is especially advantageous for works in deep, steep and limited
visibility areas such as dam reservoirs. Significant improvements of safety andoperational efficiency are observed through remote controlled visualization
technology and computerized technology.

③Rock crushing, Debris collecting

Specific Features
a. Enables deep underwater ( ‐50m) works without divers
b. Applicable for all types of reservoirs
c. Applicable for very steep areas via an equipped casing auger
d. Applicable for deep and dark reservoir bases via equipped ultrasonic camera
e. Enables precise execution via equipped sounders④Dredging

Various Apparatuses

Summary of the projectThis method was adopted for the construction of the inflow and vestibule area of the tunnel discharge facility
in the Amagase Dam Redevelopment Project.

Amagase Dam Specifications
Model: Arched concrete dam
Dam height: 73.0ｍ
Crest length: 254.0m
Dam volume: 122,000m3

天ヶ瀬再開発完成予想図

ﾄﾝﾈﾙ放流設備

Total reservoir capacity:
26,280,000m3
Effective reservoir capacity:
20,000,000m3
Purpose : Flood control,
Waterworks,
Power generation

40

Japanese Advanced Technologies
for Sediment Management41

Replenishing to the river by artificially removing sediment andtemporary placing this to the downstream– Countermeasures for sedimentation –①Sediment excavation■ Outline○ Temporary sediment placing is a method of artificiallyremoving sediment of reservoir and check dam, trucking
and temporary placing them to the downstream riverbed
and flushing down by natural or artificial flood.
○ This method can be implemented without using special
facilities and is adopted by many dams in Japan for
sediment management measures and environmental
improvement.
○ The amount of replenishing to the river is around 1 to 10
thousand m3 per year, which is 1 to 10% of the annual
average sedimentation.

②Sediment trucking③Temporary sediment placing■ Case on Countermeasures for sedimentation at Nagayasuguchi dam○ Nagayasuguchi dam is a multipurpose dam
completed in 1956 in the Nakagawa River.
○ The progression of sedimentation of the dam isremarkable. The sediment volume as of 2016 was
16,078 thousand m3 and those sedimentation for
approximately 30% of total water storage capacity.
○ As a countermeasure for sedimentation, 1,372
thousand m3 sediments from 2007 to 2016 have been
temporary placed downstream.
○ In the downstream river, various environments are
created, including rapids, pools and dry riverbed due
to sediment replenishing to the river by temporary
placing to the downstream.

Nagayasuguchi Dam● The placed sediments are flushed by natural flood
Jul. 2014

DS1

Jul. 2014

DS2● The change of riverbed
Jan. 2009

Unit3(60.5kp)

Flood of 5,384 m3/s
Aug. 2014

Sep. 2012

Flood of 5,384 m3/s

Most of the water area
were placed by pooldue to the sediment
shortage in 2009.

Aug. 2014
Pool changed
into rapids

Pool changed
into dry river bed

Dec. 2014

85,000m3 sediments out of
85,000m3 were flushed out.

88,000m3 sediments out of
185,000m3 were flushed out.

(Data provided by Nakagawa River Office. Ministry of Land, Infrastructure,
Transport and Tourism Shikoku Regional Development Bureau)■ Performance: We have temporary placed 1,372 thousand m3 of sediments todownstream rivers in 10 years.
42

Replenishing to the river by artificially removing sediment andtemporary placing this to the downstream– Improvement of the river environment –①Sediment excavation■ Outline○ Temporary sediment placing is a method of artificiallyremoving sediment of reservoir and check dam, trucking
and temporary placing them to the downstream riverbed
and flushing down by natural or artificial flood.
○ This method can be implemented without using special
facilities and is adopted by many dams in Japan for
sediment management measures and environmental
improvement.
○ The amount of replenishing to the river is around 1 to 10
thousand m3 per year, which is 1 to 10% of the annual
average sedimentation.

②Sediment trucking③Temporary sediment placing■ Case on improvement of the river environment at Shimokubo dam○ Shimokubo dam is a multipurpose dam completed in 1968 in
the Kanna River, a tributary of the Tone River.
○ Sediment supply to the downstream river was blocked by theconstruction of the dam. As a result, river bed degradation,
bed materials coarse grain progressed and the boulders of
Sanbaseki-kyo, the scenic spot, were covered with moss.
○ Since 2003 we have replenished sediments to downstream
rivers by temporary replacing them to the downstream of dam.
○ On the downstream river, sandbar shaping and cleansing
effects (recovery of river landscape) have been confirmed by
sediment replenishment to downstream.

Shimokubo Dam Replenished sediments bytemporary placing them

● Cleansing effects (recovery of river landscape)Jul. 2005

Sand and gravel washed away from the river bed

Before dam constructed(1960’s)● Sandbar shaping

After 44 years constructedof dam (current)

Jun. 2004

Before the supplying
H

Oct. 2007

Deposition

Deposition

Deposition

Jun. 2007

After the supplying■ Performance: We have replenished about 20 thousand m3 of sediments to downstream rivers in
4 years and improved the river environment.
43

Countermeasure for sedimentation using sediment sluicing- Total sediment management in the Mimikawa river basin -■ Outline

The vision of coordinated sediment management in a basin

Through coordinated sedimentmanagement of dams

Suppression of sediment
discharge by forest preservation○ (Mountain zone) Suppression of discharge of
sediment and driftwood by forest preservation,
erosion control works and sabo works.

Suppression ofdriftwood occurs
and washed away

Reduction / Solutionof discontinuous ofsediment
transportation by
dam upgrading○ (Dam area) Recover the continuity of sediment
Ensuring safety
degree of rivercourse against floodtransportation by dam upgrading andappropriate operation management.
○ (River course zone) Realize safety and biodiversity

Sediment flowing
under natural
conditions

through appropriate river management.
○ (River mouth and shore zone)
Conservation of sustainable estuaries and coasts■耳川の事例
through appropriate management of consistentsediment in the water system.

■ Contents

maintaining functionsof port facilities

Restoration and safetyof sandy beach

Before upgrading

After upgrading

Scheme of dam upgrading
Implementation of dam upgrading to partial
cutting down of existing dam within a range where
there is no structural problem.
Cutting down height :Saigo Dam = 4.3m , Yamasubaru Dam = 9.3m

Saigo Dam

Sediment sluicing operation

Cutting downheight : 4.3m

○ Drawing down the water level of the reservoir
beforehand at the time of large-scale flooding,and making flow conform to the ordinary rivercondition and sediment inflow into the reservoir.

Saigo Dam (Sept. 9. 2017)
Normal water level

Water level during flooding○ On the Mimikawa, River sluicing operation
conducts at downstream 3 dams.
Location of Dam
Moroduka Dam

Yamasubaru Dam
Now planning

Saigo Dam
Ohuchibaru Dam
Now operating

44

Sediment Flushing at Dashidaira Dam■ Outline○ The Kurobe River is known in Japan to produce numerous
sediment due to its poor geology and heavy rainfall.
○ Dashidaira Dam, located 28 km upstream from the river mouth of
the Kurobe River, was constructed in 1985 as the first dam
equipped with full-scaled sediment flushing gates in Japan.
○ The flushing gate operation is optimized by lowering the waterlevel and reaching the free-flow river condition during floods.
○ An environmental assessment committee has been in operation
involving academic experts, which has functions of authorizing
the scheme of flushing operation and evaluating theenvironmental impacts of flushing based on sampled data.

Flushing
Gates andChannels■ Procedure for Sediment Flushing Operation
After floods

Decline stage of floods

After peak of floods< Lowering water level >< Recover water level >< Free flow >Continuous
discharge

Flushing
sediment

ErosionSedimentation
Erosioni) Lowering water levelii) Free-flow conditioniii) Recovering water level

After confirmation of the peak of
the inflow, the flushing gatesstart opening, and then sediment
upstream of the reservoir only
starts to move.

Once free-flow river condition
appears during the decline stageof floods, more sediment moves by
the large tractive force of the flow
and is discharged downstream
through the flushing gates.

When the inflow decreases tocertain level – before dilution
effect of water dramatically drops,
the flushing gates start closing.

■ Environmental Sampling
Location of sampling points○ Numerous sampling surveys have been carriedout, covering the downstream part of the Kurobe
River as well as the coastal areas of the Japan
Sea expanding from the river mouth of the
Kurobe River.
○ Sampling is periodic, providing three statuses:
before, during and after flushing operation, tomonitor the environmental impacts of flushing.

Aimoto weir
Unazuki Dam(owned by MLIT)

Sediment flushing andsluicing co-operation

Dashidaira Dam(Legend): Water quality: Bed material: Aquatic organisms■ Historical Records in Effects of Sediment Flushing Operation○ Coordinated flushing and sluicing operation
has been carried out since 2001 with
Unazuki Dam, owned by MLIT, located 7 km
downstream from Dashidaira Dam.
○ Annual flushing volume of sediment is 380
×103 m3 on average.

MLIT: the Ministry of Land, Infrastructure, Transport and Tourism(conducted in 2010)

MLIT: the Ministry of Land, Infrastructure,
Transport and Tourism

Records of sediment flushed by Operation [10,000 m3]
0Date Volume [10000m3]
Dec-9146
Feb-948
Jul-952
Oct-95172
Jun-9680
Jul-9746
Jun-9834
Sep-9970
Jun-01
59
Jul-02
6
Jun-03
9Jul-0428
Jun-0551
Jul-0624
Jun-0712
Jun-0835
Jul-0937
Jul-092
Jun-1016
Jul-105
Jun-11
39
Jun-12
44
Jun-1318
Jul-1432
Jul-1519
Jun-16
30

45

50

100

150

200

A big flood occurredin July 1995.

Coordinated flushing operation wasstarted with Unazuki Dam.
380,000 m3

Hydro-suction sediment dredging■ Outline
The mobile siphon dredging system which
consists of three parts: a siphon intake unit, aconveyance unit and an outlet unit.
The siphon dredging system which uses thedifference in the reservoir water level and thesediment transport destination outlet level to
excavate/dredge and convey sediments.
The Siphon Barge forming the siphon intake
unit is able to move reservoir area anddredging sediments.

Conceptual drawing of siphon dredging
Siphon intake unit
Conveyance unit

Outlet unit

■ System features○Transferable
A Siphon Barge equipped with a suction unit
is freely transferable on the reservoir.
○Simple structure
Since there is no impeller unlike the pump,
the sucked dust can pass through the insideof the pipe as it is.

コメント
Siphon intake unit - Siphon Barge

Conveyance unit - Sediment discharge
pipeline & pressure regulator○Powerless
Using the siphon principle so, there is noneed mechanical power.
●○○（小見出し等）○Cost reduction
Low energy consumption and running cost.
Outlet unit - View of Sediment dredging【WONOGIRI DAM】

Dredged & transported
sediment from reservoir【Upstream】

コメント【Downstream】

View of dredging site

View of siphon dredging facility■ Performance: Dredging volume = 77 m3/hour,
The sediment concentration = 2 %, Sediment discharge pipe = φ 600 mm
46Model experiment of hydro-suction sediment dredging■ Outline of Hydro-suction sediment dredging○ The method of sucking and removing sediments is using the difference water level between
reservoir and the downstream water levels.
○ Since it does not require mechanical power, the initial cost and running cost can be reduced.
Normal time

Sediment discharging time
Water level
difference■ Outline of model experiment○Reproduce the water level
difference at the model,
generate water flow inside thepipe, and suck sedimentsfrom the suction holes at thebottom of the pipe by using
negative pressure.

Water level
difference■ View of model experiment

Before suction

During suction■ Cases of Hydro-suction sediment dredging

The fixed typeThe mobile type47

The surface installation type

Sediment Bypass at Asahi Dam■ Outline○ Asahi Dam had suffered prolonged turbid water, caused by collapsed sediment brought by large typhoons,since its start in 1978, and KANSAI ELECTRIC POWER adopted the bypassing method as a drastic
measure against the problem of prolonged turbid water in the reservoir.
○ This method takes full advantage of the characteristics of Asahi Dam that there is no function of storingwater because it is a lower dam of the associated pumped-storage power station. Turbid water coming fromupstream is diverted before the reservoir to downstream through the bypass tunnel, which can also
contribute to controlling reservoir sedimentation conveying bed load as well as suspended load.

■ Procedure for Sediment Bypass Operation
Before operation

After operation
IntakeBypassing turbid water andsediment from the upstream

Prolonged turbid water

IntakeWeirTunnelView around the intake of the bypass tunnel
Desilting prolonged turbid
water and sedimentaccumulation

Sediment accumulation

Asahi Dam

weir

Asahi Dam

intakeOutletSupply of sand to
the downstream

Riverbed degradation

Outlet①

Beginning of floods②

OrificeDuring floods
Rise water
surface③

End of floods

TunnelModerate sedimentation
Open channel flow

A lot of sedimentaccumulation
Orifice flow

The locally retained
sediment is graduallyeroded by open
channel flow

Open channel flow

A well-designed combination of structures of a weir and an orifice is the key to this bypassing method.
At beginning of floods, there occurs moderate sedimentation in front of the orifice, followed by sedimentaccumulation as the water level rises in front of the weir during floods. As a flood eases off and thewater level goes down, the locally retained sediment is gradually eroded by open channel flow andconveyed to the tunnel, where erosion helps prevent the tunnel from being clogged with sediment.

(Patent:No.3347104)【Patentee: Kansai Electric powerCo., Inc. and NEWJEC Inc.】■ Historical Records in Effects of Sediment Bypass Operation
Introduction of the sediment bypass system has improved the reservoir environments as follows:○ The annual number of days of occurrence of prolonged turbid water - over 5 ppm - has decreased from 81
days to 14 days on average, and○ The annual sedimentation rate has decreased from 78 x 103 m3 to 17 x 103 m3 on average.
Annual Rate on Reservoir Sedimentation③: 81 days/year
on average

120

After operation of the bypass system

100
80
60
40
20
0

①Upstream of reservoir③: 14 days/year
on average

No measurement

Number of Days when turbidity
is measured over 5ppm

140

700

①Upstream of reservoir②Downstream of reservoir③Difference (②－①)

93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17
9

2

8

5

6

8

5

6

2

1

2

3

14

②Downstream of reservoir 146 79 76

76 19 14

6

19

8

14 40

8

10

4

6

6

8

73 28 14 17 42 13 26③Difference (②－①)

18 25 16

62

4

11

3

8

3

4

2

5

4

5

59 20

128 54 60

14 10
9

5

32

8

6
8

6

17 12 1211 25

1Annual sedimentation volume [1,000 m3]

160

600
500

By‐passed sedimentation volume (estimated)
Annual sedimentation volume
Accumulated sedimentation volume

(440)

400

100
0

‐100

14

(216)
After operation of the bypass system

89' 90' 91' 92' 93' 94' 95' 96' 97' 98' 99' 00' 01' 2' 3' 4' 5' 6' 7' 8' 9' 10' 11' 12' 13' 14' 15'

Year

48

1000

600
400

(105)
(108)
(83) (70) (83) (78)200(53) (46) (14)(8) (68)(61)(40) (28)(15) (0)035
43 133123131 27 79 57 32 -2 10 10 4 25 9 8 14 6 6 9 16 23 51 226 6-36 -86

Sediment volume in Asahi Reservoir

Data: over 5 ppm

1200

800

300
200

1400

Accumulated sedimentation volume [1,000 m3]

Days of occurrence of Prolonged Turbid water‐200

Sediment Bypass - Bypassing of clay and silt ■ Outline○ Sediment bypassing is a method to divert all or part of flood watercontaining sediment at the diversion weir constructed upstream of areservoir, and route this via the bypass tunnel to the downstream
reaches.
○ This method is adopted for 4 dams in Japan for the purpose ofpermanent sedimentation countermeasure for dams with large
sedimentation and relatively plentiful discharge.
○ The target sediment materials can correspond according to thecharacteristics of the dam, such as in the case of only wash road or all
grain size.
● Operation rule of Miwa Dam sediment bypassing○ Miwa dam is a multipurpose dam complete in1959 in the Tenryu river basin Mibu River.
○ Because of the reservoir sedimentation isquickly, we started sediment bypass operation in
2005, and it is showing its effect.
○ At the Miwa Dam, among the incoming
sediment material, only the wash road are flowedfrom the upstream of the reservoir by sediment
bypass tunnel to the downstream of the dam andcoarse grain material is trapped by the check dam
and the diversion weir.
○ On the downstream river, monitoring is carriedout to ascertain the effect and impact of sediment
bypassing.

1,200m3/s
Inflow (Planed flood)
Outflow after flood control
BypassDischarge rate

■ Case on Miwa Dam

500m3/s
300m3/sTime● Operational performance
Maximum flow rate

Wash load amount

Inflow

BypassBypassdischarge time

Inflow

BypassJuly 2006

366 m3/s

242 m3/s

47 hours

326,000 m3

150,000 m3

July 2007

166 m3/s

136 m3/s

35 hours

37,000 m3

14,000 m3

Sept. 2007

568 m3/s

264 m3/s

48 hours

462,000 m3

155,000 m3

July 2010

229 m3/s

199 m3/s

146 hours

131,000 m3

80,000 m3

Sept. 2011

218 m3/s

178 m3/s

87 hours

99,000 m3

60,000 m3

Flood name● Miwa Dam and Sediment bypass tunnel
Sediment check dam
IntakeMibu weir (Diversion weir)
Dam type
Dam Height
Crest LengthIntercept coarse sand and gravel(sedimentation) and make it easy to
excavate out after flooding.

Typical cross section of tunnel

Specification of Tunnel
Max. Discharge 300m3/s
Tunnel Length

4,300m

Slope

1/100

Concrete gravity
20.5m
244.5mBypass outlet

It is overflowing to draw asemicircle radially from theenergy dissipater and it isbeing energy dissipated.

Outlet■ Performance: Along with the operation of the sediment bypass, increase in sedimentation
volume could be suppressed in general.
49Sediment Bypass - Bypassing of clay, silt, fine sand ■ Outline○ Sediment bypassing is a method to divert all or part of flood watercontaining sediment at the diversion weir constructed upstream of areservoir, and route this via the bypass tunnel to the downstream
reaches.
○ This method is adopted for 4 dams in Japan for the purpose ofpermanent sedimentation countermeasure for dams with large
sedimentation and relatively plentiful discharge.
○ The target sediment materials can correspond according to thecharacteristics of the dam, such as in the case of only wash road or
all grain size.
● Change over the years of reservoir sedimentation situation■ Case on Matsukawa Dam

Period sediment○ From 2016, experiment operation of the sediment
bypass was started.
● Matsukawa dam & sediment bypass tunnel

Plan sediment volume
Unloaded amount∙ Period sediment [1000m3]

Unloaded amount● Overview of experiment operation of the sediment bypass (FromNov.11, 2016 to Dec.31,2016 )Inflow

Outflow

BypassSpecification of Tunnel
IntakeTunnel length

200m3/s
1,417m

Slope

1/25

Max. Discharge● Sediment bypass facility① Trap weir

② Diversion weir

③ Bypassing canal④ OutletMatsukawa
Dam
Outlet■ Performance: Along with the experiment operation of the sediment bypass, anincrease in sedimentation volume can be suppressed.
50

water level

water level[EL.m]○ Among the incoming sediment material, finesediment are flowed from the upstream of thereservoir by sediment bypass tunnel to thedownstream of the dam with running water andreducing sediment inflow into the reservoir.

Sediment volume ∙ Accumulated sediment volume ∙ Plan sediment volume[1000m3]○ Because the upper stream of Matsukawa Dam is
steep in the topography and fragile in the geology,
due to repeated floods including Typhoon No.10 in
1983, design sediment storage of dam flowed into
the reservoir and accumulated.

Sediment volume
Accumulated sediment volume

quantity of flow[m3/s]○ Matsukawa dam is a multipurpose dam completed
in1974 in the Tenryu river basin Matsukawa River.

Sediment Bypass - Bypassing from clay to gravel ■ Outline○ Sediment bypassing is a method to divert all or part of flood watercontaining sediment at the diversion weir constructed upstream of areservoir, and route this via the bypass tunnel to the downstream
reaches.
○ This method is adopted for 4 dams in Japan for the purpose ofpermanent sedimentation countermeasure for dams with large
sedimentation and relatively plentiful discharge.
○ The target sediment materials can correspond according to thecharacteristics of the dam, such as in the case of only wash road or
all grain size.
● Effect of Koshibu dam sediment bypassing■ Case on Koshibu Dam○ As of 2015, the sedimentation rate of the reservoir is 89%,and if in such a situation sedimentation proceeds, it ispredicted that the sedimentation rate will be 100% after
another 15 years.

Design sediment storage volume (20 million m3)
SEDIMENT VOLUME[1000m3]○ Koshibu dam is a multipurpose dam completed in June
1969.

Flood in 1982
Without bypass it will exceed the design
sediment storage volume in about 15 years.
With bypass, it will exceed the designvolume in about 75 years.
Actual sediment volume○ By operating sediment bypass, it is possible to extend thelife of the reservoir by about 60 years.

(Estimated based on actual results of 2014 years since completion of dam)

● Conceptual diagram of sediment bypassing facility
River
Flood surcharge water level
Sediment check dam
Diversion weir
Capture coarse sediment
Limited water level

Koshibu dam● Sediment bypass inlet area and diversion weir

Kosibu River

Without bypass

TIME○ The incoming sediment material without large stone areflowed from the upstream of the reservoir by sediment bypass
tunnel to the downstream of the dam with running water andreducing sediment inflow into the reservoir.

View of diversion weir gate (stop log)

With bypass

at flood season

Inlet gate control house

Sediment check dam

Gravel digging● Koshibu dam and sediment bypass tunnel outlet

The diversion weir gate stop log
which operate down for lowering
water level of diversion pool during
inspection etc.

Specification of Tunnel
Max. Discharge
370m3/sDiversion weir gate

Tunnel length

Diversion pool

Slope

Dam

3,999m
1/50

Kosibu River● View of sediment bypassing① Intake② OutletWater flow

Outlet■ Performance: Three bypass discharges were carried out in 2016, bypassing almost the same amount of
sediments as the incoming from the upstream to suppress the inflow of sediment into the reservoir.
51

Appendix
We have Original Advanced Technologies

52Current Dam Technology in Japan
Improvement of Sediment Transportation in Dam_
1. Reservoir Sediment Restoration for Fish Habitat in Downstream of Hiranabe Dam
1.1 Background
J-POWER has three dams for hydropower plants in Nahari river
basin having 61 kilometers of the length and 311 square
kilometers of river catchment area as shown in Figure 1. Due to its
steep gradient;1/250, the Nahari river is suitable site forhydropower and hydropower development was commenced in
1960s.

However,terminatedbytransportation

the

dams;

of

riverbed

consequently,

material

wasdegradation

andYanase Dam

Kouchi pre.

granulation of river bed (armor coating) had been caused in the

Nagayama
Plant

downstream of dams. Although the Nahari was famous for fishery×of Sweet fish (Ayu), it was damaged seriously.

Tokushima
pre.
Kuki Dam× × Hiranabe Dam

× restoration position

Against this situation, J-POWER, fishermen, residents and an
expert of Ayu jointly started river improve activities from 2004.

Figure 1 Dams in Nahari river

1.2 Contents of Improve Activities
The main activities executed are as illustrated in Table 1. Considering length to be improved; that isfrom dam to river mouth and early appearance of activities effect, measures has been taken at threepositions in the downstream of Hiranabe dam, which is located in the most downstream site in thethree dams.
Table 1 River Improve Activities
Contents
To make Ayu spawn bed, sediment having appropriate grain size is
supplied on the riverbed covered by hard and large sized grain,
before November in every year. November is Ayu spawn season.

PositionStart Year

Mouth of River

2005

Intermediate
Point from Dam
to Mouth

2006

Sediment taken from the reservoir is supplied to the riverbed, which
was done in 2006 and 2010.

Downstream of
Dam

2017

Sediment taken from the reservoir is supplied to immediate
downstream of Dam. Equipment was installed in 2016, shown in
Figure 2. Larger amount of sediment will be supplied in 2018.

1.3 Result
It is observed that the assumed number of Ayu has been gradually increasing since 2004 as shownin Figure 3, which is investigated in May every year before fishing season. Accordingly, it is judgedthat the taken measures have positive effect to restoration of habitat in downstream river of dams.
1.4 For the Future
It is planed that sediment supply to immediate downstream of Hiranabe dam and monitoring of Ayu
number are continuously conducted and enhanced. if necessary, in order to Improve all section ofriver from dam to mouth.
Ayu habitat number(×1,000)

Hiranabe Dam

Equipment (close)

Figure 2 Equipment of Sediment Restoration

Figure 3 Secular Change of Ayu Habitat Number

53

Current Dam Technology in Japan
2. Draw-Down Operation in Setoishi Dam
2.1 Background
J-POWER has Setoishi dam for hydropower plant,as shown in Figure4 in Kuma river having 115
kilometers of the length and 1,880 square kilometersof river catchment area. The Kuma flows into
Yatsushiro sea, having problems such as water
quality deterioration and much mud on the bottom.
One of the reasons for the problems is sedimenttermination by dam, then improvement of sedimentcontrol in dam is needed.
Setoishi reservoir has flooding risk around itself
because of aggradation of riverbed by reservoir

Figure 4 Setoishi Dam, Hydropower Plant
and Reservoir

sedimentation, and it is planned that in flooding Table 2 Setoishi Draw-Down Operation Rules
Items
Contents
draw-down operation to control sedimentation will be
From June to September
conducted. Downstream of Setoishi dam, there was
Period(avoiding going upstream andArase dam in possession of Kumamoto prefecture,
spawning season of Ayu)
which had been under removal work between 2012
Low Water Level - 4.0m.
and 2018. In 2017 water channel appeared in dam Draw-Down
Draw-Down rate is under
Water Level
removal site, then we started draw-down operation in
0.5m/hr.
Setoishi dam by way of experiment.
When dam inflow volume ispredicted over 2,000m3/s on
2.2 Draw-Down Operation
Entry Criteria
our own rainfall prediction
To make inflow sediment run out of reservoir throughsystem.
spillway gate, draw-down operation in flooding has toWhen dam inflow volume is
be conducted to get bigger tractive force in all area of Exit Criteria
under 1,000m3/s on record.
reservoir than usual operation.
Interruption
When Dissolved Oxygen of is
During draw-down operation, power generation has
standard
under 5mg/liter on record.
to be kept stopped. It is the most important for
Rules are grounded on result
effective use of renewable hydropower to make anof numerical analysis
effective operation rules. We made the operation
Groundconsidering balance between
inflow sediment and output
rules as shown in Table 2, using our own rainfall
sediment.
prediction system.
2.3 Result
Experiment operation in 2016 and 2017 told us that our operation rules were available. Because we
did not have large rainfall during two years, effect in sediment control of draw-down operation was notclear.
2.4 For the Future
Full-scale operation will be started in 2018 and it is expected that environmental improvement inYatsushiro sea and Kuma river will appear. Also operation rules will be checked and revised byestimation of effect of draw-down operation. (End)J‐POWERContact Person:

Hirofumi OKUMURA

E‐mail:Hirofumi_okumura@jpower.co.jp

Phone:+81‐3‐3546‐9405

URL:

www.jpower.co.jp

54

Current Dam Technology in JapanNew Construction Technologies
SP-TOM (Special Pipe Transportation Method)
This method can transport large quantities of concrete,soil and stone stably and continuously, by rotating asteel-pipe which several hard rubber blades are installed
in a spiral pattern inside. The pipeline is installed on theslope.

SP mixer (Special Pipe mixer)
This mixer was developed to mix CSG materials.
This method is to mix materials passing throughthe interior by rotating a mixing tube equippedwith blades inside the mixer.
The mixing tube is installed to incline. The
self-weight of the CSG materials cause them toflow through the mixer. This mixer has two
mixing effects inside its mixing tube; forced
agitation by drive power and falling.

Patent:Incorporated Administrative Agency Japan Water
Agency; KAJIMA CORPORATION; OBAYASHICORPORATION; TOBISHIMA COPORATION;
Kumagai Gumi Co., Ltd.; The Zenitaka
Corporation;
Osakasaiseki
Engineering
Corporation

Contact Person:

Construction Management Dept.
Takayuki KAMBE

E‐mail:tkambe@kajima.com

Phone:+81‐3‐5544‐0664

URL:

https://www.kajima.co.jp/english/welcome.html

55

Current Dam Technology in Japan

Floating Type Temporary Cofferdam Method
Innovative Dam Redevelopment – A New Coffering System for Underwater Work–

Feature of technology
With the floating type temporary cofferdam
method, steel plates (skin plates) are attached
to both the inside and outside of the bulkhead,
the temporary cofferdam barrier that is
integrated into the base is floated, and is
supported by installing an anti-buoyancy braceon the top barrier of the dam body. The
construction assembles barrier blocks made at
the site on the reservoir surface, tows them tothe installation position, pulls them by winch
and secures them. The floating type temporary
cofferdam method--assembling and installingwhile adjusting the ballast by filling anddraining water from a reservoir--is the first of its
kind in the world.

Figure of Structure

Figure of Structure

Technology developers:
Kajima Corporation; Hitachi Zosen Corporation
Joint developers:
Ministry of Land, Infrastructure, Transport and Tourism

Contact Person:

Kyushu Regional Bureau; Japan Dam Engineering
CenterConstruction Management Dept.
Takayuki KAMBE

E‐mail:tkambe@kajima.com

Phone:+81‐3‐5544‐0664

URL:

https://www.kajima.co.jp/english/welcome.html

56

Current Dam Technology in Japan
CRT（The Continuous Rotary Tube）Mixer System
The Continuous Rotary Tube (CRT) Mixer System provides using the Cemented Sand andGravel (CSG) Method. By attaching agitating blades inside the steel drum and maintaining
specified rotation speeds and angles, the mixer is capable of producing mixtures of consistent andstable quality.

Contact Person:

Public Relations Department

E‐mail:kouhoubu@nishimatsu.co.jp

Phone:+81‐3‐3502‐7642

URL:

https://www.nishimatsu.co.jp/eng/

57

Current Dam Technology in Japan
Newly Developed High-performance CSG Mixer: Double Rotation Continuous Mixer
The newly developed double-rotation mixer combining the characteristics of a tilting mixer and a forced
circulating mixer produces high-quality CSG (Cemented Sand and Gravel) mixes at a rate exceeding
200 m3/hDrum

How Mixing Takes Place
PaddlesMaterial movement

Example of Concrete Plant Layout

Constant feeder

Cement silo
Receiving hopper

Double-rotation mixer

Backhoe

Cement silo
Double-rotation
mixer

Receiving hopper

58

BackhoeCurrent Dam Technology in Japan

Mixer Specifications
Rotating Drum Specifications
Drum inside diameter and height
Rotation speed and direction
Motive power
Drive system

φ1800×4200L
10 rpm (clockwise looking in the direction of movement)
37kw×220V
Chain drive
Roller (φ400 × 145L) × 4
Thrust roller (φ250 × 90L) × 2

Support system

Inner Paddle Specifications
Mixer outside diameter, pitch and number of paddle shafts
Rotation speed and direction
Motive power
Drive system

φ1100 × P1000 (two shafts)
38 rpm (counterclockwise looking in the direction of movement)
45kw×220V
Chain coupling drive, chain drive
Bearing
Plummer block (φ135)
30t-220-220
36 pcs.

Support system
Paddle inserts

Size
Quantity

Internal
paddles

Rotating
drum

MixingSectional View

Side View

SHIMZ CORPORATION
Contact Division:

Dam Engineering Dept.

E-mail:e.hasegawa@shimz.co.jp

Phone:+81-3-3561-3883

URL:

https://www.shimz.co.jp/en/59Current Dam Technology in Japan
New Water Filtration System (Advanced Membrane Filtration Process)In construction projects such as tunnel and dam construction and site preparation, proper treatment of
turbid water generated from construction work is important in order to protect the environment. There
has also been growing demand for higher water treatment performance than required by the current
standards of the local governments.
Conventional turbid-water treatment processes relied mainly on coagulation and sedimentation.
Shimizu's newly developed filtration system effectively removes suspended solids by use of amembrane filtration process to achieve higher water quality in an environmentally considerate mannerand provide solutions to current and emerging problems.
Features
・The filtration process reduces the SS concentration of turbid water to 5 mg/L.
・High turbidity (SS1000–3000 mg/L) water can be treated directly.
・The process is environmentally friendly because it does not use any organic polymer coagulant.
・The system footprint is compact because sand filtration is not used.
・The water treatment system is environmentally considerate because it requires only a small amountof electricity.
Turbid Water Treatment Test Data

SS concentration (mg/L)

2500

2000

1500

1000
SS of raw water (mg/L)
SS of treated water (mg/L)
500

0
0

5

10

15

20

25

Time (hr)

30

35

40

45

60

50

Raw water and treated water

Current Dam Technology in Japan
System Flow
Inorganic coagulant
PAC storage tank
Membrane filtration unit
Filter tank

Raw water tank

Hydraulic head200～300mm

PAC reaction
chamber

ReleaseTreated water tank

Dewatering facility

Slurry storage tank

Dewatered cake

How Membrane Filtration Works

Membrane Filtration Capacity
Let A (m2) represent the area of themembrane surface. Then, membrane filtration
capacity V (m3/day) can be calculated asfollows:
V = A × 2 m3/day

Clean waterCore material
Filter fabric
Dirty
water

Dirty
water

Filtering membrane
Deposited turbidity

SHIMZ CORPORATION
Contact Division:

Dam Engineering Dept.

E‐mail:e.hasegawa@shimz.co.jp

Phone:+81‐3‐3561‐3883

URL:

https://www.shimz.co.jp/en/61Current Dam Technology in Japan
Remote Controlled Multifunctional Underwater Equipment
Underwater Operation Using an Equipment with Apparatus (T-iROBO UW)Remote control, Machine guidance

SummaryThis equipment enables a series of underwater operations such as rock crushing, excavation, debris
disposal, precise sounding, photography, etc.in a safe and reliable condition through remote controlling.
These are carried out by various apparatuses on a machine attached to a shaft which is lowered from abarge. The machine moves up and down along the shaft.
The equipment has been developed to conduct various underwater works without divers. It is especiallyadvantageous for works in deep, steep and limited visibility areas such as dam reservoirs. Significant
improvements of safety and operational efficiency are observed through remote controlled visualization
technology and computerized technology.

Specific Features
a.
b.
c.
d.
e.
f.
g.

Enables deep underwater works without divers
Applicable for all types of reservoirs
Applicable for very steep areas via an equipped casing auger
Enables a series of works to be carried out by various apparatuses
Equipped with I.T, machine guidanceApplicable for deep and dark reservoir bases via equipped ultrasonic camera
Enables precise execution via equipped sounders
TAISEI CORPORATION
Contact Division:

62

Dam Engineering Section

E‐mail:arai@ce.taisei.co.jp

Phone:+81‐3-5381-5282

URL:

http://www.taisei.co.jp/english/

Current Dam Technology in Japan
Various Apparatuses
Applicable for a series of works via various
apparatuses attached to a machine

Rock crushing with a breaker

Sand pump suctioning

Cleaning by an ejector

Examples of applicable works
Precise sounding

Edge cutting

Crushing concrete
Shaft

Shaft
Dam body

Sounding

Shaft

Grab dredging

Surface treatment
Shaft

Instrument

Grab bucket
Foundation

Air lift

Other applications

a. Drilling by an air drifterb. Surface cleaning by a rotary brushc. Rock & concrete cutting by wire-saw
d. Steel beam & pipe and reinforced concrete cutting by nibbler

63

Current Dam Technology in Japan

TAISEI CORPORATION
Contact Division:

64

Dam Engineering Section

E‐mail:arai@ce.taisei.co.jp

Phone:+81‐3-5381-5282

URL:

http://www.taisei.co.jp/english/

Current Dam Technology in Japan

65

Hydrodynamic Pressure on the Gate
The hydrodynamic pressure acting on the Gate is larger thanwhich acting on the Dam body (Westergaard’s formula)①Entire System Analysis Model (Dam-Gate-Rock-Reservoir)
Reservoir （Fluid element）

Analytical model： Dam-Gate-Rock-Reservoir Model
Analysis approach：3-Dimensional Linear Dynamic Analysis
Number of nodes and elements：About 250,000475

Gate（Shell element）
Dam（Solid element）
470

SectionAHigh

Elevation（m）

Rock（Solid element）
SectionB465

460

Westergaard’s formula

455

450
0

SectionA SectionB

Low

Distribution of hydrodynamic pressure

0.05

0.1

0.15

Dynamic Water pressure（MPa）②Gate Analysis Model
High

Analytical model：Gate Model
Analysis approach： 3-Dimensional Linear Dynamic Analysis
Number of nodes and elements：About 20,000

Low

Distribution of stress and displacement

 The hydrodynamic pressure acting on the Gate is derived from the entire
system analysis model.
 High reliable value of the stress on the Gate is calculated by Detail Gate
Analysis Model.

66㼀㼔㼑㻌㻺㼛㼚㻙㼘㼕㼚㼑㼍㼞㻌㻭㼚㼍㼘㼥㼟㼕㼟㻌㼛㼒㻌㻼㼕㼑㼞㻌㻼㼘㼍㼟㼠㼕㼏㻌㼐㼑㼒㼛㼞㼙㼍㼠㼕㼛㼚㻌㼕㼟㻌㼢㼕㼟㼡㼍㼘㼕㼦㼑㼐㻌㻌㻌䐟㻮㼑㼒㼛㼞㼑㻌㼍㼟㼑㼕㼟㼙㼕㼏㻌㼞㼑㼕㼚㼒㼛㼞㼏㼕㼚㼓㻌㼣㼛㼞㼗㻌㻌㻌㻌㻌㻰㼍㼙㼍㼓㼑㼐㻌㼍㼞㼑㼍㻌㻌㻌㻰㼕㼟㼜㼘㼍㼏㼑㼙㼑㼚㼠䠄㼙㼙䠅

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㻝㻠

㻝㻡

㻰㼕㼟㼜㼘㼍㼏㼑㼙㼑㼚㼠㻌㼞㼑㼟㼜㼛㼚㼟㼑㻌㼍㼠㻌㼠㼔㼑㻌㼠㼛㼜㻌
8

㻌

㻌
㻌
㻌
䕔䠖㻾㼑㼕㼚㼒㼛㼞㼏㼑㼐㻌㼏㼛㼚㼏㼞㼑㼠㼑㻌㼑㼘㼑㼙㼑㼚㼠㻌㻌䕔䠖㻯㼛㼚㼏㼞㼑㼠㼑㻌㼑㼘㼑㼙㼑㼚㼠㻌㻌䐠㻭㼒㼠㼑㼞㻌㼍㼟㼑㼕㼟㼙㼕㼏㻌㼞㼑㼕㼚㼒㼛㼞㼏㼕㼚㼓㻌㼣㼛㼞㼗㻌㻌㻿㼠㼞㼑㼟㼟䠄㻺㻛㼙㼙㻞䠅

6

㻌
㻌

4
2
0
Ͳ2
Ͳ4
Ͳ6
Ͳ8
㻙㻡㻘㻜㻜㻜

㻜㻡㻘㻜㻜㻜㻝㻜㻘㻜㻜㻜
㻿㼠㼞㼍㼕㼚䠄䃛䠅

15

4.5m

䖃㻱㼤㼕㼟㼠㼕㼚㼓㻌㼞㼑㼎㼍㼞㻌䖃㻭㼐㼐㼑㼐㻌㼞㼑㼎㼍㼞㻌㻞㻜㻘㻜㻜㻜

㻾㼑㼕㼚㼒㼛㼞㼏㼑㼙㼑㼚㼠㻌㼑㼒㼒㼑㼏㼠㻌䠄㼕㼚㼕㼠㼕㼍㼠㼕㼛㼚㻌㼟㼠㼞㼍㼕㼚㻌㼐㼑㼏㼞㼑㼍㼟㼑䠅㻌

10

1.9m
㻾㼑㼕㼚㼒㼛㼞㼏㼑㼙㼑㼚㼠㻌㼍㼞㼑㼍㻌㻝㻡㻘㻜㻜㻜

㻿㼠㼞㼑㼟㼟㻙㻿㼠㼞㼍㼕㼚㻌㼞㼑㼘㼍㼠㼕㼛㼚㻌㻿㼠㼞㼑㼟㼟䠄㻺㻛㼙㼙㻞䠅

㻌
㻌
㻌
㻌
㻌
㻌
㻌

NonͲLinear
Linear㻯㼛㼚㼏㼞㼑㼠㼑㻌㼏㼞㼍㼏㼗㻌

50
Ͳ5Reinforcementratio×1.0
Reinforcementratio×2.0
Reinforcementratio×3.0

Ͳ10
Ͳ15㻙㻡㻘㻜㻜㻜

㻜㻡㻘㻜㻜㻜㻝㻜㻘㻜㻜㻜
㻿㼠㼞㼍㼕㼚䠄䃛䠅㻝㻡㻘㻜㻜㻜

㻞㻜㻘㻜㻜㻜

㻌㻿㼠㼞㼑㼟㼟㻙㻿㼠㼞㼍㼕㼚㻌㼞㼑㼘㼍㼠㼕㼛㼚㻌
㻌
㻌
㻌
㻌
㻌
㻰㼕㼟㼜㼘㼍㼏㼑㼙㼑㼚㼠㻌㼞㼑㼟㼜㼛㼚㼟㼑㻌㼍㼠㻌㼠㼔㼑㻌㼠㼛㼜㻌㻌㻌
¾ 㻼㼔㼥㼟㼕㼏㼍㼘㻌㼎㼑㼔㼍㼢㼕㼛㼞㻌㼛㼒㻌㼠㼔㼑㻌㼜㼕㼑㼞㻌㼏㼛㼚㼏㼞㼑㼠㼑㻌㼍㼒㼠㼑㼞㻌㼏㼞㼍㼏㼗㼕㼚㼓㻌㼕㼟㻌㼐㼑㼞㼕㼢㼑㼐㻌㼍㼚㼐㻌㼢㼕㼟㼡㼍㼘㼕㼦㼑㻌㻌
¾ 㻿㼠㼞㼡㼏㼠㼡㼞㼍㼘㻌㼞㼑㼟㼕㼐㼡㼍㼘㻌㼐㼑㼒㼛㼞㼙㼍㼠㼕㼛㼚㻌㼛㼚㻌㼠㼔㼑㻌㼜㼕㼑㼞㻌㼍㼒㼠㼑㼞㻌㼠㼔㼑㻌㼑㼍㼞㼠㼔㼝㼡㼍㼗㼑㻌㼕㼟㻌㼐㼑㼞㼕㼢㼑㼐㻌㼍㼚㼐㻌㼢㼕㼟㼡㼍㼘㼕㼦㼑㻌㻌㻌㼀㼛㼗㼥㼛㻌㻱㼘㼑㼏㼠㼞㼕㼏㻌㻼㼛㼣㼑㼞㻌㻿㼑㼞㼢㼕㼏㼑㼟㻌㻯㼛㻚㻘㻌㻸㼠㼐㻚㻌㻌㻮㼡㼟㼕㼚㼑㼟㼟㻌㻰㼑㼢㼑㼘㼛㼜㼙㼑㼚㼠㻌㻰㼑㼜㼠㻚㻌㻌㻯㼛㼚㼠㼍㼏㼠㻌㻼㼑㼞㼟㼛㼚㻦㻌㻾㼥㼛㼡㼠㼍㼞㼛㼡㻌㻹㻭㼀㻿㼁㻹㻻㼀㻻㻌㻌㻱㻙㼙㼍㼕㼘㻦㻌㻌 㼞㻙㼙㼍㼠㼟㼡㼙㼛㼠㼛㻬㼠㼑㼜㼟㼏㼛㻚㼏㼛㻚㼖㼜㻌㻼㼔㼛㼚㼑㻦㻌

㻗㻤㻝㻌㻟㻌㻢㻟㻣㻞㻌㻡㻝㻣㻡㻌㼁㻾㻸㻦㻌㼣㼣㼣㻚㼠㼑㼜㼟㼏㼛㻚㼏㼛㻚㼖㼜㻌67

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