An investigation on ultrasonic wave velocity of laminated sandstone under freeze-thaw and salt crystallization cycles: Insights from anisotropy effects

Abstract

In this study, the anisotropy effects on the P (Vp) and S (Vs) wave velocities are investigated in laminated sandstone subjected to freeze-thaw (FT) and salt crystallization (SC) processes. For this purpose, cylindrical core specimens were prepared from sandstone at angles (β) of 0°, 30°, 45°, 60°, and 90° to the lamination direction. Next, FT and SC tests were performed up to 60 cycles. After every 10 cycles, the specimens’ Vp and Vs were determined at various β values. The decay constant (λ), half-life (N1/2), and rate of loss (RL) were used to investigate the anisotropy effects on the Vp and Vs of specimens under FT and SC and compare the effects of FT and SC on the Vp and Vs. The results indicated that anisotropy is an important factor in the durability of the specimens against FT and SC. In this respect, the specimens with β = 0° and β = 60° had the least and the highest changes in the Vp and Vs, respectively. Also, it was found that the anisotropic behavior of the specimens is different at various cycles of FT and SC such that it is intensified at higher cycles. Overall, it was concluded that SC had more significant effects on the Vp and Vs compared to FT. Considering the β values, the effect of a single cycle of the SC test in decreasing the Vp and Vs of the specimens corresponds to 1.34 to 1.94 and 1.28 to 1.70 cycles of the FT test, respectively.