Japanese National Committee on Large Dams. Dams in Japan, No. 10

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the core materials were not available near th€

dam site to be used individually, the mixture of fine and coarse

materials

were

used as the core

materials. As fine materials scoria

loam which is volcanic ashes originated ftom Mt. Fuji

and disfibutes v,ridely

around the

dam site were used. On the

other hand, as coa$e materials the debris

provided

quar-

ry were

used. The scoria loam is less impermeable,

so that the

foundation

treatments were carried out by the usual

methods. In the whole

foundation

of the core mne, blanket

grouting

was carried out to

prevent piping

oc.cured in the

core or

the foundation and consolidation

grouting

was adopted to

the foundation treatment of the spillway. i. e.

At the dam

site, river bed was composed of

gravel

sediment

about 10m in thickness

and 800,000m3 in

grouting,

under

the

influence of

the dam for hydrcelect c eisting downstream.

At fiIst, whole of the dver bed was

planned

to be taken

away, but in

consideration of a schedule and cost about @Ea ol

the river bed in volume was

utilized as foundation of the

rock zone.

Rm G

TYPICAL

CROSS

SECTION

50 30

UPSTREAM

VIEW

18.

MIYAMA

DAM

(AND

NUMAPPARA

DAM)

Location

Nearest

City

River

Purpose

Catchment

area

Mean

annual

discharge

Years

of construction

Type

Foundation

Height

Crest

length

Volume

Spillway

Type

and

number

gate

Maximum

discharge

capacity

Reservoir

Gross

capacity

Effective

capacity

Area

Drawdown

range

Owner

Engineering

Construction

Kuroiso-shi, Tochigi-ken

Kuroiso-shi

Nakagawa

Irrigation, Hydroelectric

and Water

supply

53Km'?

3.7m3ls

1969-1974

Rockfill

Rhyolite and

Quartz

andesite

breccia

tuff

76m

334m

1,967,000m3

Controlled

Crest radial

gate

840m3/s

25.8X lClum'

20.9x Lffm'

0.97Km'?

32m

M. A. F.

F., Tochigi-ken and E. P.

Ministry of

Agriculture, Forestry

and Fisheries

Taisei Corporation

The Miyama

dam is

the

largest

asphalt fac€d dam in Japan. It is for multipurpose

including

irrigation, city

water

supply

and hydroelectric power.

Main

purpose

is for irrigation,

and for

power generation

it functions

the lower reser-

voir

of a

pumped-storage

plant

combination with the Numappara reservoir.

The foundation

consists

generally

of rhyolite, but it is deeply cracked and

partly

neathered.

addition, the

broad

valley

overlain

deeply by river deposit,

conqete

dam was first eliminated from

consideration.

According to

inves-

tigations

and experiments

the earth matedal available near the dam site is not suitable

for the impervious zone.

Therefore,

asphalt faced rocKill dam was

constructed

on the river deposit.

-----\

CROSS.

SECT ION.ASPHALT.

FAC I N G

CREST

LENGTH

l=3338O

TYPICAL

CROSS SECTION

NWLEL74880m

LWL

72r

-__l t__l,

EL 743.OO

9.o

€

PROFILE

ALONG

DAM

AXIS

A quarry

near

the dam

site

was

the

source

of most of the rock

material which

was quarried

bench cut

and the

rest

was

by small

undermining

blast. The

embanked

materials were compacted

with

l3t

and

llt

vibraiing

rollers.

The

smal-

ler was

used

for compaction

close to the

slope

surface because of that

trafficability.

The

asphalt

facing has

two cou$es

and four

layerp. Their thickness

and

proportioning

was

designed

to meet

each

fanction

as follows.

1) Binder

course;

filling voids in

the rocks

to bind the facing wall

to the dam

body

Levelling

course;making

the smooth

surface in

preparation

for next layer.

Lower

layer;

the

second impervious

layer which

sandwiches the middle

layer with

the

upper

to make

a drainage

Middle

layer

;

draining

the water

infiltrated

through

the upper

layer

to the

inspection

gallery.

the

ceeds

a certain valve,

it would

indicate damage

of the impervious

layer.

Upper

layer;

the impervious

layer,

the most

important

part

the

facing,

which was

constructed

divided

good

composition.

Protection

layer

;

preventing

the impervious

layer from aging.

Construction

equipments

of the

asphalt wall

such as finished and vibrating

rolle$ were

hanged

by the

cables to be able

to work

the slope.

And the cables were

drived

by the winches travelling

on the top

of the dam.

A dumper

was used

feed

the matedal

to the finishers

also drived by

the

winch.

The

end

asphalt facing

is connected with

the inspection

gallery

which

is based

directly

on the bedrock.

The con-

solidation

grouting

nas carried

out to improve

bearing capacity of the

foundation, and

the curtain grouting

was

done from

the galtery.

The gatlery

is sewing to

collect the seepage water through

the asphalt

facing and

also

to iheck the water

pressure

behind

the

curtain

grouting.

the right bank is relatively

thin, the rim

grouting

was

executed

to ensure rmper-

meability

of it.

Length

of the rim

grouting

amounts to 12,000m.

The diversion

tunnel was utilized

for intake

work. At the

position

of the inlet

an intake

tower

of 66m tall was

instal-

led

with

the

function

of selective intake.

,__-

The Numappara

dam is the upper

regulatiog

reservoir of Numappara

pumped

storage

power

station

(installed

capacity

675MW)

and

a circular

asphalt facing

type dam. The effective storage

capacity is almost

secured

by the excavation

foundation

ground.

In relation to

the Miyama

dam, the Numappara dam is introduced

below.

NUMAPPARA

DAM

Topography

and

Geology

The

upper

pond

located

volcanic

tableland

of the

western

with

about

1,250m

elevation is

called

"Numappara"

which means

cept

eastern

side,

form

very steep

cliffs in

general.

The

geology

of the surounding

of the

pond

consist of

volcanic products

ftom

Nasu Volcano

euaternary

activity.

The foundation

the dam and

pond

comprise mainly lapilli tuff and andesite

lava,

patially

agglomerate,

coa6e volcanic

ash

and volcanic

lake deposits

(caused

by local dammed lake) and

present

stratigraphically

complex

structure.

Most

of these

are

geological

groups

of high

permeability.

Design

2-1.

General

Vadous

investigations

were conducted

from 1968 through early 1970 in order

to obtain

information

on the

properties

of the

foundation

and the embankment

materials. As a result of investigations,

the following

facts were

clarified.

Andesite

lava

and lapilli tuff have

adequate bearing capacity and shearing

strength

for the foundation

of dams of

this

class.

Since

both

of the foundations and

the embankment materials have

high

permeability,

it'was

necessary to

provide

impervious

facing over the

entire surface including bottom of

the

pond.

Excavated

muck

ftom the

pond

area composed of lapilli tuff have high water

content

oI30Vc-50% and

low dry

density

of 1.1-1.4Vm3.

But

since other matedals were not available in

the

vicinity

of the

pond

area, excavated

muck

was

used as embankment

materials after test banking and various

studies taking

into consideration

securing

of trafficability

of heavy equipment

and accel€ration of settlement.

2-2

Asphaltic

impervious

facing

Asphaltic

imPervious

facing was

designed to have an open-graded

asphaltic mncrete

layer as

middle drainage zone

sandwiched

between

two impervious dense-grade

asphaltic conoete layer. Middle drain

layer is

highly

pervious

order

to drain

immediately

leakage

water to an inspection gallery. The facing

is 30cm thick

and is executed

in 6layers on the

slope

and

25cm

thickness of 5 layers at

the bottom.

And

also transition

zone, which is

@cm thickness at the

pond

slope and 50cm thickness

at the bortom,

is arranged in

order

secure

the reinforcement

of dcformation

property

of facing, the drainage

function and

the

preventation

of frost

heaving.

2-3

Structure

of embankment

The

structure

was

designed based on various

investigations

abovc-mentioned

and insitu

expe

mental banking.

Since

the

upstream side of the embankment with

asphaltic impervious facing need

to obtain especially

quick

con-

solidation

effects, altemate Iayers

of lapilli tuff and sand-gravel

were

ernbanked each 30cm in

thickness.

As for

the downstream side, a sand-gavel

layer

of approximately 50cm in thickness is

provided

between every 3m

lapilli tuff

laver.

leakage

ex-

into

two for

fringe

of the Nasu

Volcanic

Belt.

The tableland

highland

marsh.

The

fringes

the tableland,

ex-

PLAN

Furthermore,

order to

facilitate

embankment works, sand-gmvel

zones

of 7.5m

in width

are served

as site roads

at the

middle portion

and downstream

side, and

these zones

concurrently

have

the functions

of vertical

drains.

Construction

The

pond

is of circular shape

of circumference

of approximately 1,6mm with

its east

area

of an excavated

Dortion

and

its

west,

south

and north

side comprising

the embanked

portion

Since

the dam

foundation was

on comparative

soft side,

while

the

pond

area

was

expansive,

it was

necessary

ftom the

aspects

the construction

schedule

for the excavation

line to

be determined

accurately

and

quickly.

Therefore,

the in-situ

C. B. R. test, which

can be

performed

within a short period

time as the

judging

the found-

ation ground,

was

adopted,

And the relation

between the C. B. R. value

and the internal

frictional

ansle was

sousht be-

forehand.

Since the

temperature at the

damsite in winter

season

drops to

a mean of

10t

and a minimum

-20t

it n'as un-

avoidable

suspend works

from December to

March.

Embankment was

started

at the south

area and approximately

years

including

the wintertime discontinuation periods

were required to complete

the works.

Detoil

of focing

H.W.L.l238.OO

Detoilof X

T9.

MIZIJKT.]BO

DAM

Location

Nearest

City

River

Purpose

Catchment

area

Mean

annual

discharge

Years

construction

Type

Foundation

Height

Crest

length

Volume

Spillway

Type

and

number

gate

Maximum

discharge

capacity

Reservoir

Gross

capacity

Effective

capacity

Area

Drawdown

range

Owner

Engineering

Construction

Yonezawa-shi,

Yamagata-ken

Yonezawa-shi

Kariyasu

Irrigation

and

Water

supply

38km'

1.3mr/s

r970-t975

Rockfill

Granite

diorite

62m

205m

1,020,000m,

Controlled

Crest

radial

gatexz

413m3/s

31.0X 106m3

30.5

106m3

'l..7km'

40m

Ministry

Agriculture,

Forestry

and

Fisheries

Ditto

Kajima

Corporation

The Mizukubo

darn is

rockfill dam with center impervious

zone, and has a side spillway in

the left bank.

The

geology

of the

dam site

granite-diorite,

which is overlain

by river deposit

(sand-gravel)

in the valley, and is

weathered

deeper

at th€ higher elevation.

The weathering reaches

as much as 20m at the

top of both abutments. The

river deposit

and the weathered

rock

are

permeable

but have no

problem

in bearing capacity,

so they have been left intact

under

the dam

body except for the

portion

of the core zone.

The

sectional

profile

of the dam

is rather conservative but

the lower

part

of the upstream

filter

omitted

ftom the

zoning

because the matedal

very expensive and it is thought

that the rapid drawdown of water will not happen over th€

full

range of the

available drawdown due to furigation and

water supply

only.

For

the core material,

decomposed

granite

was used mixed

with another clayey earth in

proportion

of 25

percent.

PLAN

)

After

excavating the core trench to sound bedrock, the

foundation treatment was

carried out by the concrete replace-

ment of

several faults and by curtain

gouting.

The main curtain

grouting

has two lines in

the center and

grout

holes

were

drilled

1.5m apart.

The sub curtain

grouting

has three lines on each side of the

former.

The spacing of

grout

holes

yvas

3m. In

grouting

of both abutment, chemical material

was

used

instead of c€ment.

excavation

line

core

filter

transition

rock

rock B

core

(coffer

dam)

@rockA(

)

curtain

lgroutingl

rock

[-T-TTTTT]".

TYPICAL CROSS

SECTION

PROFILE

ALONG

DAM

AXIS

20.

NAGAI44ADO

DAM

Location

Nearest

City

River

Purpose

Catchment

area

Mean annual

discharge

Years of construction

Type

Foundation

Height

Crest length

Volume

Spillway

Nagawa-mura,

Minamiazumi-gun,

Nagano-ken

Matsumoto-shi

Azusa

Hydroelectric

380.5Km'

21.3m'ls

1964-1969

Dome

arch

Granite

155m

355.5m

672.000m'

123x

1ffm3

94X

1ffm3

2.74Km'

55m

The

Tokyo

Electric

Power

Co-,

Inc.

Ditto

Kajima

Corporation

Type

Tunnel

Type and number

gate

Roller

g^texz

Maximum discharge

capacity

1.800m3/s

Reservoir

Gross capacity

Effective capacity

Area

Drawdown

range

Owner

Engineering by

Construction by

gso

"r,

/----\--...\

r.@o'

t.o?5'

t.o50

ttCO

'Qt,

lr)

(\,

ar,

.()'

/17

-o

PLAN

DEVELOPED

UPSTREAM ELEVATION

TYPICAL

CROSS

SECTION