Characterization of rock weathering using elastic waves: A Laboratory-scale experimental study

The weathering of rock through various mechanisms can be characterized by multiple techniques. For example, the compressional wave velocity has been mainly used with the advantage of being a non-destructive method. However, the application of shear wave velocity, which is suitable for representing the lithological characteristics of the medium, has rarely been applied to assess the deterioration of rock. The objective of this study is to apply the elastic waves, including both compressional and shear waves, to characterize weathered rock. Furthermore, the technique of weight change is adopted to estimate the weathering of rock based on porosity. Highly concentrated salty water is used to achieve chemical weathering by simulating sea water. In addition, the slake durability test is performed to simulate the mechanical weathering. Compressional waves, shear waves and weight are measured at each weathering step. The average variation in compressional wave velocity, shear wave velocity and porosity after 3 chemical and 9 mechanical weathering steps is approximately 47.4%, 55.5% and 78.2%, respectively. The slake durability index gradually decreases with increasing amounts of mechanical weathering. Furthermore, the statistical and the multiple linear regression analyses were carried out to correlate the slake durability index with the compressional wave velocity, shear wave velocity, and porosity. These tests indicate that the shear wave velocity is highly correlated with the slake durability index. This study demonstrates that the elastic wave velocities can be effectively used to characterize rock weathering.