Surrounding rock classification is the foundation of tunnel design and construction. At present, BQ coefficient is used to classify surrounding rock in China, but this coefficient requires drilling rocks and measuring them directly, which is costing high, sampling hard and discontinuously. Using elastic wave continuous detection technology can help solve the above problems. In this paper, the elastic parameters of surrounding rock samples were measured by rock physics test, including: elastic wave velocity (P-wave velocity Vp, S-wave velocity Vs, and Vp/Vs ratio), elastic modulus (bulk modulus K, shear modulus μ, lame constant λ, young's modulus E and Poisson's ratio ν), anisotropic coefficients (ε, γ, δ, anisotropy of P-wave velocity Av, anisotropy of quality factor Aq), quality factor Q. Then, through cross-plot analysis between various parameters and BQ, the R² values comparison shows that 1) P-wave velocity Vp (R²=0.70) and quality factor Q (R²=0.62) are most suitable for surrounding rock classification; 2) S-wave velocity Vs (R²=0.62), shear modulus μ (R²=0.59) and Young's modulus E (R²=0.55) are also suitable; 3) anisotropy parameters are very unsuitable (R²<0.30); 4) other parameters are not suitable (0.20<R²<0.38). The results make the elastic wave continuous detection technology more pertinently used in the surrounding rock classification and have a broad application prospect.

Surrounding rock classification,rock-physics,elastic parameter,quality factor,cross-plot analysis