Evaluating the effect of freezing-thawing cycles on the compressional wavevelocity and dry density of schist rock (Case study: Angouran mine)

The effects of freezing-thawing cycles on the compressional wave velocities and dry density of schist rock have been investigated in this research. For this purpose, 13 boreholes were drilled in the Angouran mine and 25 cylindrical specimens were prepared. Then, the samples were weathered in the laboratory by freezing-thawing process and the compressional wave velocity and dry density of samples were measured in freeze-thaw cycles of 0, 7, 15, 40 and 75. The results analysis indicates an exponentially decrease in the compressional wave velocities (50% reduction) and dry density (30% reduction) with increasing the number of freeze-thaw cycles. Also, wave velocities exponentially increased with increasing the dry density. By fitting the concluded results, two empirical equations to calculate the compressional wave velocity and dry density in schist rock for different numbers of freeze-thaw cycles and also an equation between compressional wave velocity and dry density have been presented. In addition, the texture of samples was studied in intact situation and after 75 cycles of freezing-thawing by an electronic microscope. The obtained results indicated that the samples texture is condensed before weathering, whereas the discontinuities spacing is increased after weathering. Finally, verification results proved that there is a good conformity between the outputs of current study and other investigations.