An ultrasonic time-frequency method for evaluating the freezing state and frozen-section thickness of sandstone

The aim of the present study is to evaluate the freezing state and frozen-section thickness of sandstone blocks by UT under controlled laboratory conditions. The objectives are to describe and interpret the results concerning the change of acoustic parameters during laboratory experiments involving (1) upward freezing and (2) complete freezing of the blocks. We measured the ultrasonic properties of a sandstone in experiments on both unfrozen and upward freezing conditions in order to simulate artificial frozen-wall development in a progressively freezing sandstone layer. Some physical parameters (water content, porosity and density) were estimated for different stages of upward freezing to determine water migration, porosity and density change. In addition, frozen sandstone was tested at different negative temperature to investigate the relationships between acoustic parameters (waveform, wave velocity, amplitude and frequency spectrum) and temperature.