Method of Elastic Constant Measurement for Transversely Isotropic Rocks: Application to Banded Gneiss of the Onyang Region

Elastic constants were measured for 70 samples of transversely isotropic banded gneiss from the Onyang region. Anisotropic angles of samples are $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$. Exact values of $E_2$ and ${\nu}_{21}$ can be measured from samples with anisotropic angles of $0^{\circ}$ and those of $E_1$ and ${\nu}_{12}$ from samples with anisotropic angles of $90^{\circ}$. These values are set as reference values. Elastic constants measured from samples with anisotropic angles of $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $75^{\circ}$, using the methods proposed by Jang et al. (2001) and Park et al. (2008), are compared with the reference values to examine the effectiveness of the two methods. $E_1$ were measured correctly from samples with anisotropic angles of $60^{\circ}$ and $75^{\circ}$, and $E_2$ from samples with anisotropic angles of $15^{\circ}$ and $30^{\circ}$, when using the method suggested by Jang et al. (2001). $E_1$ were measured correctly from samples with anisotropic angles of $45^{\circ}$ and $60^{\circ}$, and $E_2$ from samples with anisotropic angles of $15^{\circ}$, $30^{\circ}$, and $60^{\circ}$, when using the method proposed by Park et al. (2008). The effectiveness of the two methods was determined by error rates between exact values and measured values. The effectiveness of the two methods was similar. However, the method suggested by Jang et al. (2001) may be more effective in measuring $E_1$, while the method suggested by Park et al. (2008) may be more effective in measuring $E_2$.

온양지역에 분포하는 호상편마암을 이용한 평면 이방성 암석의 탄성상수 측정방법

충청남도 온양지역에서 채취한 호상편마암으로부터 $0^{\circ}$ 시료 9개, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$ 시료 각 10개, $60^{\circ}$, $75^{\circ}$ 시료 각 11개, $0^{\circ}$ 시료 9개를 획득하여 총 70개의 시료를 이용해 이방성 탄성상수를 측정하였다. 이방성 각 $0^{\circ}$, $90^{\circ}$ 시료에서 측정된 탄성상수($E_1$, $E_2$, ${\nu}_{12}$, ${\nu}_{21}$)를 기준값으로 설정하고 Jang et al. (2001)과 Park et al. (2008)에 의해 제안된 방법을 이용하여 $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$ 시료의 탄성계수($E_1$, $E_2$)를 계산한 후 기준값과 비교하였다. Jang et al. (2001)의 제안법을 사용할 경우 $60^{\circ}$, $75^{\circ}$와 같은 고각의 이방성 시료에서는 $E_1$이 비교적 정확하게 계산되고 $15^{\circ}$, $30^{\circ}$와 같은 저각의 이방성 시료에서는 $E_2$가 비교적 정확하게 계산되었다. Park et al. (2008)의 제안법의 경우 $E_1$은 $45^{\circ}$와 $60^{\circ}$ 시료에서만 비교적 정확한 값을 계산해냈고 $E_2$는 $15^{\circ}$, $30^{\circ}$, $60^{\circ}$ 시료에서 비교적 정확하게 계산되었다. 유효성 검토 결과 두 제안법 모두 총 20개의 유효성 판단구간에서 '유효함(Effective)' 7개(35%), '가능함(Possible)' 5개(25%), '유효하지 않음(Ineffective)' 8개(40%)로 분석되어 두 제안법의 유효성은 같은 수준이었다. 다만 Jang et al. (2001)의 제안법은 $E_1$을, Park et al. (2008)의 제안법은 $E_2$를 계산하는데 상대적으로 더 유효한 것으로 분석되었다.