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2nd International Workshop on a Far Detector in Korea for the J-PARC Neutrino Beam
July 13 - 14. 2006, International Conference Hall, SNU
Overview of geological situation for a
possible T2KK detector site
2006. 07. 14
Chang-Ha Ryu
Geotechnical Division
Korea Intitute of Geoscience & Mineral Resources (KIGAM)
韓國地質資源硏究院
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General procedure
 Preliminary data collection
- preliminary assessment
- preliminary geotechnical characterization
Feedback loop
 Feasibility study
- engineering classification of rock mass
- feasibility assessment of tunneling problems & alternatives
 Detailed site characterization
 Stability analyses
 Final design and construction
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Requirements
 Area between 2.0 and 2.5 degree off-axis beam ( < 1 deg. ?)
 Depth: ~ 1,000 m (uniform overburden in all direction)
 Size of underground research module: 50 m (dia.) x 280m (l)
cylindrical opening
 Long term safe operation
 Effective (economic) construction
 Research module in good rock mass
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Requirements_Location
2.5 deg. off axis
2.5deg.off-axis beam @Kamioka
JPARC
Off-axis angle
2.0 deg. off axis
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Geology of Korea
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Overview of General Geology
 Throughout the country, mountains are not high, rarely exceeding 1,200
meters, but they are found almost everywhere. The terrain is rugged and
steep, and only near the west and southwest coasts are extensive flat
alluvial or diluvial plains and more subdued rolling hilly lands.
 Korea consists largely of the Precambrian rocks, such as granite gneisses
and other metamorphic rocks. The Gyeongsang Supergroup is
distributed across a wide area within the Gyeongsang-do province which
is one of the area of our concerns.
 The Gyeongsang Supergroup is composed of the Sindong and Hwayang
groups and the Bulguksa Intrusives. The biotite granite intruded in the
Gyeongsang Supergroup is called Bulguksa Granite.
Hwayang Group widely distributed throughout the Gyeongsang-do
province, consists of conglomerates, sandstone, shale, and volcanic rock
such as andesite, basalt, rhyolite, and tuff, especially in the upper part of
the group.
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Site Consideration 1
 Overburden: 1 km deep
 Preferrable site: mountain, mine, tunnel
 Easy slope topograpy requires
- excavation of long tunnel to satisfy gradient condition
- shaft, inclined shaft
too costly !
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Mine Site
Advantages of utilizing abandoned mine
 Reduce costs
 Minimize environmental impacts
 Minimize complaints from residents and
environmentalist
 Easy to get approval and
to get support from local government
 Easy to get information on geological conditions
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URLs for Astrophysics Research_Mine Site
Soudan URL
Old iron mine in Minesota
Depth : 710m (2,080mwe)
Exp. Lab. : 15m x 13m x 82m
SNO (Sudbury Neutrino Observatory) – Canada
Location : Creighton mine, Sudbury
Depth : 2,039m
CUPP Lab. - Finland
Location : Outokumpu mine, Pyhasalmi
Depth : 90~970m (current)
Boulby Mine Lab. - UK
Location : Boulby mine, Cleveland
Depth : 1,100m
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URLs for Astrophysics Research_Tunnel Site
LNGS (Gran Sasso National Lab.) – Italy
besides Gran Sasso tunnel (Teramo – Rome)
Depth : 1,400m Experiment halls : L=100m, H=18m,
LSC-Spain
inside Somport tunnel (Spain – France), Canfranc
Depth : ~ 900m
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Site Consideration_2~2.5deg. off-axis
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Site Consideration_ < 1deg. off-axis
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Geological Sheets
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Possible Sites
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Possible Sites
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Possible Site: Geological map - Eon Yang Sheet
1208m
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Site Consideration_2005
Bohyeon San (1124m)

Bohyeon San in Youngcheon
~1,045 km, 2.0o off, 1124 m high
National Astronomy Observatory on top
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Possible Site: <1 degree off-axis

Guryongpo in Pohang (Gyeongbuk Province)
< 1,000 km
< 1.0o off, no mountains (sea level)

Toham San in Gyeongju
1,000 km
1.0o off, ~500 m high mountains (National Park)
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Description of Geology
EON YANG Sheet:
High mountaineous districts includes the peaks of
Gajisan(1240m), Shinbulsan(1208m), in the western part,
underlain by andesite, granite, and other rocks
GI GAE Sheet:
Southern marginal portion of the Taeback Mountain Range;
the highest peak 960m(Giryoungsan); Bohyounsan(839m),
Suseokbong(820m), Chimgoksan 725m, Unjusan 807m; the
area is underlain by Cretacous sedimentary, volcanic and
plutonic rocks- granite, granodiorite, andesite, rhyolite …
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Geological map of GI GAE sheet _1:50000
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Other Sites
 SHINSHEUNG Sheet:
Noreong mountain range, many peaks attain heights of
between 400-760m; Sinseon-bong(763m), Choowolsan;
gneiss, granite, sedimentary and volcanic rocks
 MIRYANG Sheet
There are comparatively high peaks of Togoksan(855m),
Yomsubong(816m), Muchoksan(700m), Chontaesan(631m),
Kumosan(760m), Hyangrobong(727m), Manosan(670m) etc.
The geology of the area is composed of Yuchon Group and
Bulguksa Intrusive rocks. The Yuchoon group is divided into
andesitic rocks (andesite, ruff), and rhyolitic rocks (rhyolite,
tuff); Miryang andesite is distributed on a large scale.
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Possible Site: <1 degree off-axis
Geological map – Guryogpo/Yeonil Sheet

1:50,000 geological maps of these area: unavailable

Geological data and some detailed site information
available
high speed rail way construction
roadway construction
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Mines
Abandoned Mines
Province
Gangwon-do
Coal mine
Metal, Non-metal mine
A
B
C
D
A
5
1
3
5
Gyeonggi-do
C
D
6
7
3
1
2
2
4
4
Chungbuk-do
Chungnam-do
8
3
Jeonnambuk-do
Gyeongbuk-do
Gyeongnam-do
B
1
2
1
1
2
4
1
1
1
* Possibility of utilization: A>B>C>D
(source: KIGAM report, 2004)
EX) List of Metal Mines in MUJU-gun
(source: KIGAM Mine DB)
가옥, 강창, 고길, 금령(2), 길산, 동왕(1), 무주, 봉소(2),
삼가(1), 삼가(3), 삼가리, 삼봉(3), 삼성(3),
세창(2), 승륭, 쌍봉(1), 쌍봉(2), 쌍봉(3), 영성, 오동, 오산(2),
월성, 적상, 전일(1), 제국(1), 창덕(1), 태성, 태정
Mine layout, Samga mine
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Abandoned Quarry near Miryang
~ 1.5 km
Location: Gyeongsangbuk-do Cheongdo-gun
Rock type: Andesite
Uni-axial compressive strength: 1,500 ~ 1,600 kgf/cm2
tunnel
quarry
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Possible Site
478 m
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Concluding Remarks
 Possible sites
- mountain area
- need to investigate mines thoroughly,
and then find new site
 Geological conditions
- favorable
- if poor but no other choice, solve by engineering
- more detailed geotechnical characterization needed
to reduce potential risks for construction
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Concluding Remarks
 Factors affecting the stability of tunnels
- stress fields
- mechanical properties of rock: strength, E …
- structural characteristics: joints, faults
- groundwater conditions
- method and quality of excavation
- support of rock strata
- size and shape of tunnel, underground chamber
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