Low-angel fracture zones in rapakivi granite at Hästholmen, southern Finland

Olli Okko (Corresponding Author), Kai Front, Pekka Anttila

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)

Abstract

Geological and geophysical borehole data from the site investigation programme for spent nuclear fuel in Finland are integrated to analyse the main engineering geological structures of the rock mass. At the Loviisa nuclear power plant site at Hästholmen, there are 100–150-m-long altered sections with anomalies in geophysical logs along the holes drilled in the orthogonally fractured rapakivi granite. In detail, the high water conductivity is concentrated in narrow sections as observed in the tube wave logs and hydraulic measurements. The TV image locates sporadic subhorizontal fractures that are most probably the main hydraulic conduits in the rock mass. The mean length of the measured fracture traces is 8 m. However, geophysical cross-hole investigations and seismic surveys indicate the continuity of a few fracture patterns between shallow boreholes drilled with spacing of the order of 100 m. Furthermore, the continuity of five gently dipping fractured structures that contain a few sections of broken rock between the 1-km-deep holes drilled approximately 0.5 km apart is suggested according to similarities in the acoustic character in the full waveform sonic borehole logs.
Original languageEnglish
Pages (from-to)171-191
Number of pages21
JournalEngineering Geology
Volume69
Issue number1-2
DOIs
Publication statusPublished - 2003
MoE publication typeA1 Journal article-refereed

Fingerprint

rapakivi
Granite
Boreholes
fracture zone
borehole
granite
Rocks
Hydraulics
rock
hydraulics
Spent fuels
site investigation
Nuclear fuels
seismic survey
nuclear power plant
geological structure
Nuclear power plants
spacing
acoustics
conductivity

Keywords

  • rapakivi granite
  • granite
  • fractures
  • geophysical
  • borehole logs
  • statistical analysis
  • spent nuclear fuel
  • nuclear waste
  • nuclear waste management

Cite this

Okko, Olli ; Front, Kai ; Anttila, Pekka. / Low-angel fracture zones in rapakivi granite at Hästholmen, southern Finland. In: Engineering Geology. 2003 ; Vol. 69, No. 1-2. pp. 171-191.
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abstract = "Geological and geophysical borehole data from the site investigation programme for spent nuclear fuel in Finland are integrated to analyse the main engineering geological structures of the rock mass. At the Loviisa nuclear power plant site at H{\"a}stholmen, there are 100–150-m-long altered sections with anomalies in geophysical logs along the holes drilled in the orthogonally fractured rapakivi granite. In detail, the high water conductivity is concentrated in narrow sections as observed in the tube wave logs and hydraulic measurements. The TV image locates sporadic subhorizontal fractures that are most probably the main hydraulic conduits in the rock mass. The mean length of the measured fracture traces is 8 m. However, geophysical cross-hole investigations and seismic surveys indicate the continuity of a few fracture patterns between shallow boreholes drilled with spacing of the order of 100 m. Furthermore, the continuity of five gently dipping fractured structures that contain a few sections of broken rock between the 1-km-deep holes drilled approximately 0.5 km apart is suggested according to similarities in the acoustic character in the full waveform sonic borehole logs.",
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Low-angel fracture zones in rapakivi granite at Hästholmen, southern Finland. / Okko, Olli (Corresponding Author); Front, Kai; Anttila, Pekka.

In: Engineering Geology, Vol. 69, No. 1-2, 2003, p. 171-191.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Low-angel fracture zones in rapakivi granite at Hästholmen, southern Finland

AU - Okko, Olli

AU - Front, Kai

AU - Anttila, Pekka

PY - 2003

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N2 - Geological and geophysical borehole data from the site investigation programme for spent nuclear fuel in Finland are integrated to analyse the main engineering geological structures of the rock mass. At the Loviisa nuclear power plant site at Hästholmen, there are 100–150-m-long altered sections with anomalies in geophysical logs along the holes drilled in the orthogonally fractured rapakivi granite. In detail, the high water conductivity is concentrated in narrow sections as observed in the tube wave logs and hydraulic measurements. The TV image locates sporadic subhorizontal fractures that are most probably the main hydraulic conduits in the rock mass. The mean length of the measured fracture traces is 8 m. However, geophysical cross-hole investigations and seismic surveys indicate the continuity of a few fracture patterns between shallow boreholes drilled with spacing of the order of 100 m. Furthermore, the continuity of five gently dipping fractured structures that contain a few sections of broken rock between the 1-km-deep holes drilled approximately 0.5 km apart is suggested according to similarities in the acoustic character in the full waveform sonic borehole logs.

AB - Geological and geophysical borehole data from the site investigation programme for spent nuclear fuel in Finland are integrated to analyse the main engineering geological structures of the rock mass. At the Loviisa nuclear power plant site at Hästholmen, there are 100–150-m-long altered sections with anomalies in geophysical logs along the holes drilled in the orthogonally fractured rapakivi granite. In detail, the high water conductivity is concentrated in narrow sections as observed in the tube wave logs and hydraulic measurements. The TV image locates sporadic subhorizontal fractures that are most probably the main hydraulic conduits in the rock mass. The mean length of the measured fracture traces is 8 m. However, geophysical cross-hole investigations and seismic surveys indicate the continuity of a few fracture patterns between shallow boreholes drilled with spacing of the order of 100 m. Furthermore, the continuity of five gently dipping fractured structures that contain a few sections of broken rock between the 1-km-deep holes drilled approximately 0.5 km apart is suggested according to similarities in the acoustic character in the full waveform sonic borehole logs.

KW - rapakivi granite

KW - granite

KW - fractures

KW - geophysical

KW - borehole logs

KW - statistical analysis

KW - spent nuclear fuel

KW - nuclear waste

KW - nuclear waste management

U2 - 10.1016/S0013-7952(02)00281-8

DO - 10.1016/S0013-7952(02)00281-8

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