Kanayama 10-14-12 Kanayama

7/30/2019 Kanayama 10-14-12 Kanayama

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Application of Environmental

Dredging

System to

Harbor

Development Works in Japan

S.Kanayama

Penta‐Ocean Co. Ltd. ,Japan



Introduction(1)

・Reduction of water pollution

・Reduction of disposal volume

Important problems for dredging operation



Introduction(2)Our choice for tackling these difficult tasks is

‘’Environmental Clamshell

Bucket’’ , introduced from

Cable Arm Inc.of USA

‘’Dredge Positioning System’’

, developed by ourselves

and

the combination of



Features of the

‘’Environmental Clamshell Bucket’’



Venting system

Venting system reduces

the disturbance of seabed while grab lowering

and also reduces

the entrainment of surplus water

while lowering while pulling up



Over lapping side plates

Over lapping side plates and rubber seal reduces

the leak of grasped sediments

tightly grasp the dredged sediment

Over lapping side plates



Level‐cutting feature

Level‐cutting feature reduces the surplus

dredging volume

Ordinal grab Environmental grab



Dredge Positioning System

For the best performance of

the ‘’Environmental Clamshell Grab’’ ,exact control of Grab movement is indispensable

‘’Dredge Positioning System’’

・Horizontal positioning of bucket

←GPS at the top of crane boom

・Vertical positioning of bucket

← Pressure gage attached to the bucketwith tide level compensation



Schematic figure of

the Dredge Positioning System

Horizontal positioning of bucket

(GPS)Vessel positioning

(GPS)

Vertical positioning of bucket(pressure gage)

GPS reference Station

Tidal data



A screen of Dredge positioning system



The line up of the employed

‘’Environmental Clamshell Bucket’’

Volume Size Excavation area

4m3class 3.7m×3.5m 13m2

7m3class 5.7m×4.0m 23m2

24m3

class 7.1m×5.2m 37m2



Field verification sites

Sakaiminato port for the 4m3 bucket

Hroshima port

for the 7m3 bucket

Kobe port

for the 24m3

bucket



Verifications for

Thin layer dredging

Non-exceedance probability of dredge thickness for 24m3bucket(Hiroshima Port),excepting the area with designed dredge thickness exceed 60cm

→ 24m3bucket can execute

thin layer dredging of 60cm

by the probability of 90%

Suitable for rapid execution of dredging operation

with wide area and thin dredging thickness



Verifications for

Thin layer dredgingBy the same analysis , our conclusion is…

・The possible thin layer dredging thickness

of 4m3 and 7m3bucket is about 30cm

・The possible thin layer dredging thicknessof 24m3 bucket is about 60cm



Verifications for

evenness of finished surface

Definition of unevenness of dredged trace94％

90％

94% of unevenness are less than 30cm90% of unevenness are less than 20cm



Verifications for

less water entrainment into dredged sediment

V0 : Daily dredged volume

of In-situ sediment

(by sounding data)

V1 : Daily volume of dredged

sediment loaded on barge

V0 /V1 → 72.1～93％ →exceed 80％ on average

（only for 4m3bucket in SakaiminatoPort）

Only when the dredging thickness conform to the size of bucket,

so that dredged sediment just fill the bucket



Verifications for

less production of suspended solid(1)

Ideal pattern for estimating re-suspension product

whole section of turbidity

plume can be captured

We could obtain this situation in

Sakaiminato Port (4m3bucket) and Hiroshima Port(7m3bucket)

turbidity meters



Standard unit of turbidity generation ω0

4m3 bucket : ω0= 5.2 kg/m3

(in Sakaiminato Port)

7m3 bucket : ω0= 7.1 kg/m3

(in HiroshimaＰort)

ω0＝W o/Qo

W o: Turbidity generation amount (kg/h)

Qo: Handled sediment volume (m

3

/h)



In the case of the 24m3bucket

In Kobe Port(24m3bucket) ,

we were not allowed to remove the frame type silt curtain

turbidity meters

W1: remained components

W2: passed components

→ evaluated from flow velocity

and the time series of turbidity

Frame typesilt curtain

→ measured immediately after bucket stopped.



Results for 24m3bucket

1st Run 2nd Run Average

C1(mg/L) :Av. conc. of remained components 23 38 ‐

C2(mg/L) :Av. conc. of passed components 12 10 ‐

U (cm/s): Av. velocity under the curtain 4.2 6.3 ‐

V(m3): Handled sediment volume 57.6 ‐

ω0(kg/m3)：Standard unit of turbidity

generation

3.9 6.2 5.1

24m3

bucket :ω

0= 5.1 kg/m3

(in KobeＰort)



Standard unit of turbidity generation

of

environmental grab dredging

and

ordinary grab dredging.



conclusion

・Excellent futures of the ‘’Environmental

Dredging System ‘’were verified by field data in

Japan.

・Japanese governmental authorization was

obtained by the ‘’Examination and Certification Service of New Coastal Technologies developed

by Private Companies’’

・This allows the smooth spreading of excellent

environmental dredging technologies of U.S.A.

into Japan

Documents

Kanayama 10-14-12 Kanayama