Experimental and DEM simulations of the mechanical properties of rock under freeze–thaw cycles

The investigation of the physical-mechanical properties of rock after freeze–thaw (F-T) cycles has important theoretical significance for understanding freeze–thaw disaster mechanisms, disaster prediction, and tunnel protection system design in cold regions. Physical-mechanical tests are carried out to quantify the deterioration of the physical-mechanical properties of sandstone subjected to long-term F-T cycles. The damage mechanism of sandstone subject to F-T cycles is discussed based on scanning electron microscopy (SEM) results. A new three-dimensional discrete element method (DEM) model for simulating freeze–thaw damage of water-saturated rocks is established based on the volume expansion theory. In the new method, a one-dimensional thermal conduction equation is introduced to realistically simulate the distribution of the temperature field in a cylindrical sample during thermal conduction, and the evolution equation of ice volume expansion is introduced to control the volume expansion of ice particles in the sample as the freeze point. The crack development mechanism during the F-T cycle and the correlation between the cracks generated by the F-T cycle and subsequent loading are also analyzed. The results show that approximately 80% of the frost-heave cracks are distributed in the annular column area 10–25 mm from the axis of the sample. In the radial direction, there is a significant correlation between the formatting of cracks during F-T cycles and loading. In the axial direction, due to the relatively uniform distribution of F-T cracks, the formation of cracks under subsequent loading is mainly controlled by stress concentration.