Geomechanics and Engineering
Volume 30, Number 5, 2022, pages 449-460
DOI: 10.12989/gae.2022.30.5.449
Probabilistic Q-system for rock classification considering shear wave propagation in jointed rock mass
Ji-Won Kim , Song-Hun Chong , Gye-Chun Cho
Abstract
Safe underground construction in a rock mass requires adequate ground investigation and effective determination of rock conditions. The estimation of rock mass behavior is difficult, because rock masses are innately anisotropic and heterogeneous at different scales and are affected by various environmental factors. Quantitative rock mass classification systems, such as the Q-system and rock mass rating, are widely used for characterization and engineering design. The measurement of rock classification parameters is subjective and can vary among observers, resulting in questionable accuracy. Geophysical investigation methods, such as seismic surveys, have also been used for ground characterization. Torsional shear wave propagation characteristics in cylindrical rods are equal to that in an infinite media. A probabilistic quantitative relationship between the Q-value and shear wave velocity is thus investigated considering long-wavelength wave propagation in equivalent continuum jointed rock masses. Individual Q-system parameters are correlated with stress-dependent shear wave velocities in jointed rocks using experimental and numerical methods. The relationship between the Q-value and the shear wave velocity is normalized using a defined reference condition. This relationship is further improved using probabilistic analysis to remove unrealistic data and to suggest a range of Q-values for a given wave velocity. The proposed probabilistic Q-value estimation is then compared with field measurements and cross-hole seismic test data to verify its applicability.
Key Words
rock mass classification; Q-system; jointed rock mass; shear wave velocity; equivalent continuum
Address
- Ji-Won Kim — Disposal Performance Demonstration Research Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea
- Song-Hun Chong — Department of Civil Engineering, Sunchon National University, 255 Jungang-ro, Sunchon, Jeollanam-do 57922, Korea
- Gye-Chun Cho — Department of Civil and Environmental Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Korea
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