Overview of geological situation for a possible T2KK detector site

1
Overview of geological situation for a possible
T2KK detector site
2nd International Workshop on a Far Detector in
Korea for the J-PARC Neutrino BeamJuly 13 - 14.
2006,   International Conference Hall,   SNU

• 2006. 07. 14
• Chang-Ha Ryu
• Geotechnical Division
• Korea Intitute of Geoscience Mineral Resources
  (KIGAM)
• ? ? ? ? ? ? ? ? ?

2
General procedure

• Preliminary data collection
•     - preliminary assessment
•     - preliminary geotechnical characterization
  
• Feasibility study
• - engineering classification of rock mass
• - feasibility assessment of tunneling
  problems alternatives
• Detailed site characterization
• Stability analyses
• Final design and construction

Feedback loop
3
Requirements

• Area between 2.0 and 2.5 degree off-axis beam ( lt
  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

4
Requirements_Location
2.5 deg. off axis
2.5deg.off-axis beam _at_Kamioka
JPARC
Off-axis angle
2.0 deg. off axis
5
Geology of Korea
6
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.

7
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 !

8
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

9
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
Boulby Mine Lab. - UK Location Boulby mine,
Cleveland Depth 1,100m
CUPP Lab. - Finland Location Outokumpu mine,
Pyhasalmi Depth 90970m (current)
10
URLs for Astrophysics Research_Tunnel Site
LNGS (Gran Sasso National Lab.) Italy besides
Gran Sasso tunnel (Teramo Rome) Depth 1,400m
Experiment halls L100m, H18m,
LSC-Spain inside Somport tunnel (Spain France),
Canfranc Depth 900m
11
Site Consideration_22.5deg. off-axis
12
Site Consideration_ lt 1deg. off-axis
13
Geological Sheets
14
Possible Sites
15
Possible Sites
16
Possible Site Geological map - Eon Yang Sheet
1208m
17
Site Consideration_2005
Bohyeon San (1124m)

• Bohyeon San in Youngcheon
• 1,045 km, 2.0o off, 1124 m high
• National Astronomy Observatory on top

18
Possible Site lt1 degree off-axis

• Guryongpo in Pohang (Gyeongbuk Province)
• lt 1,000 km
• lt 1.0o off, no mountains (sea level)
• Toham San in Gyeongju
• 1,000 km
• 1.0o off, 500 m high mountains (National
  Park)

19
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

20
Geological map of GI GAE sheet _150000
21
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.

22
Possible Site lt1 degree off-axis

• Geological map Guryogpo/Yeonil Sheet
• 150,000 geological maps of these area
  unavailable
• Geological data and some detailed site
  information available
• high speed rail way construction
• roadway construction

23
Mines
Abandoned Mines
Possibility of utilization AgtBgtCgtD
(source
KIGAM report, 2004)
EX) List of Metal Mines in MUJU-gun

(source KIGAM Mine DB) ??, ??, ??, ??(2), ??,
??(1), ??, ??(2), ??(1), ??(3), ???, ??(3),
??(3), ??(2), ??, ??(1), ??(2), ??(3), ??, ??,
??(2), ??, ??, ??(1), ??(1), ??(1), ??, ??
Mine layout, Samga mine
24
Abandoned Quarry near Miryang
1.5 km
tunnel
Location Gyeongsangbuk-do Cheongdo-gun Rock
type Andesite Uni-axial compressive strength
1,500 1,600 kgf/cm2
quarry
25
Possible Site
478 m
26
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

27
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