Effect of Freeze-Thaw Damage on the Physical, Mechanical, and Acoustic Behavior of Sandstone in Urumqi

Abstract

The Urumqi area in China is a seasonally cold region, and the rock structures in the region are susceptible to freeze-thaw (F-T) weathering. Therefore, this study investigated the effect of F-T on the physical, mechanical, and fracture behavior of sandstone from Urumqi. The acoustic emission method (AE) was used to determine the stress thresholds for the initiation and development of cracks in the samples under cyclic F-T action. The results suggested that parameters such as P-wave velocity, elastic modulus, and peak stress presented a significant negative correlation with F-T damage, while porosity exhibited a close positive correlation. The elastic modulus of the sample was more sensitive to the F-T action with the smallest half-life (27 cycles) and the largest decay factor (0.0254). In addition, the stress threshold for micro-cracks development and macro-cracks initiation in the samples decreased with increasing F-T damage. After 30 F-T cycles, the stress threshold for micro-cracks propagation in the samples decreased from 20.73 MPa to 5.02 MPa by approximately 76%. The normalized stress threshold for the macro-cracks initiation was also decreased from 0.93 to 0.71. Moreover, the macro-cracks damage zone of the samples showed an increasing trend with F-T damage, from 7% under natural conditions to 29% after 30 cycles. It is concluded that F-T action lowers the stress thresholds for cracks development in sandstone in the Urumqi area, posing serious safety concerns for mass rock engineering in this area.