Quasi-static resonant column (QSRC) method for indirect assesment of natural weathered rock joint surface

Rock mass classification system defined the quality of jointed rock mass by the joint conditions. However, the roughness and waviness characteristics on joint surface cannot be assessed in-situ as it is invisible as compared to other joint conditions. Hence, this study has carried out an experimental setup of Quasi-Static Resonant Column (QSRC) test to characterize the weathered rock joint roughness by P-wave propagation. The characterization was made based on P-wave velocity (VP) that propagated through the continuum columnar multi jointed specimens. The propagation of compression waves in jointed rock masses is heavily affected by the angularity and intensity of roughness profile on joint surfaces. Those profiles that form naturally from weathering process potentially to be measure for classification that made based on range result of VP, thus convinced the rock conditions assessment. The results obtained from this resonance test lead to characteristic of VP with respect to the degree of roughness and waviness for various grades of weathered joint surface which carefully classified into Joint Roughness Coefficient (JRC) index. Comparatively, the assessment of VP trend of characteristics was evaluated between 2-dimentional (2D) sawed surfaces that conventionally applied and 3-dimentional (3D) natural surface that more representative of jointed rock mass. Both methods of joint roughness profiling showed significant reduction of VP as higher the index of JRC due to lesser the contact area as rougher the surface. However, the VP response between 2D and 3D surface profile showed different rate of decrement. It was also found that the variability of joint roughness on the joint surface consequently influences the P-wave propagation by reducing its velocities. A correlation between elastic wave propagation of P-wave and joint conditions was established.