Abstract: Water-ice phase transition often produces frost heaving pressure in fractured rock mass in cold regions. The repeated action of frost heaving pressure will drive crack propagation, coalescence and even fracture failure of rock mass. Through prefabrication of single open crack with different inclination angles in quasi-sandstone specimens, freeze-thaw and uniaxial compression experiments are conducted on those crack-containing specimens under precooling and non-precooling conditions, to investigate the influence of freezing mode and crack inclination angle on the process of frost propagation, rupture characteristics and uniaxial compressive strength. The experimental results show that: the frost heaving pressure is the main driving force of frost propagation, which is closely related to the freezing mode of crack water. It is hard to produce frost-heaving cracks under precooling conditions, because most of the crack water is squeezed out. Generally, the frost-heaving cracks propagate along the coplanar direction of the prefabricated cracks; and then they gradually turn to the short sides due to the boundary effect. There is a positive correlation between the length of coplanar propagation and the inclination angle of crack. When the prefabricated crack inclination angle is 60°-90°, the rock mass can easily be compressed and destroyed along the direction of frost-heaving crack, resulting in the reduction of uniaxial compressive strength of rock mass. The research results can provide reference for revealing the freeze-thaw damage mechanism of fractured rock mass and developing rock engineering in cold regions.

Key words: fractured rock mass, water-ice phase transition, frost-heaving expansion, fracture characteristics, strength loss