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Seismic Velocity Change Due to Micro-crack Accumulation of Rock Samples from Seokmo Island, Korea

손상 진행에 따른 석모도 암석 시험편의 탄성파속도 변화

  • Lee, Sang-Kyu (Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Choi, Ji-Hyang (Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Cheon, Dae-Sung (Korea Institute of Geoscience and Mineral Resources (KIGAM)) ;
  • Lee, Tae-Jong (Korea Institute of Geoscience and Mineral Resources (KIGAM))
  • Received : 2011.11.01
  • Accepted : 2011.11.21
  • Published : 2011.11.30

Abstract

Seismic wave velocity change has been monitored due to the accumulation of micro-cracks by uniaxial loads on the rock samples from Seokmo Island with stepwise increase in 5 stages. After the load was applied up to 95% of UCS, P- and S-wave velocities varied in ranges of 0.9 ~ 18.3% and 2.8 ~ 14.8% of fresh rock sample velocities, respectively. Unlike seismic velocity of the dry rock samples that showed overall decreases after the loading, velocity changes of saturated rock samples were much more complicated. These seemed to be due to the mixture of two contradictory mechanisms; i.e. accumulation of micro-crack causes an increase in porosity and a decrease in wave velocity, while saturation causes an increase in wave velocity. Most of tested rocks showed a trend of velocity increase with low axial load and then velocity decrease at later stages. Starting stage of velocity decrease differs from samples to samples. After the failure of rock occurred, noticeable increases of porosity and decreases of wave velocity have been observed. It showed overall trend that the more the quartz contents and the lower the silicate, the higher the Young's modulus.

Acknowledgement

Supported by : 한국에너지기술평가원(KETEP)

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