The fractured rock mass in cold areas is damaged and deteriorated due to crevice-water frost heaving

which seriously threatens the safety of engineering construction in cold regions. In this study

freeze-thaw cycling tests were conducted on green sandstone

red sandstone and granite samples of different porosities. The strain changing with time and temperature of saturated fracture during freeze-thaw cycling under influences of fracture length

width and lithology were analyzed. The changing rules of the characteristic values of fracture strains and the failure mechanism of fractured rock were also studied. Experimental results show that the change rule of freeze-thaw strain of fractured rock mass with different fracture geometry parameters can be divided into seven stages: the cool shrinkage stage

the frost heave stage

the frost heave stabilization stage

the thermal expansion stage

the thaw shrinkage stage

the thaw shrinkage rebound stage

and the thaw shrinkage stabilization stage. The curve of freeze-thaw strain versus temperature of saturated fractured rock mass is an unclosed hysteresis loop. The phenomenon of “freeze-thaw hysteresis” occurs

and with the increase of freeze-thaw cycles

the hysteresis loop gradually moves up

leading to a gradual increase of the residual strain. Characteristic values of freeze-thaw strain of saturated fractured rock mass include: the maximum microstrain

the residual strain

the frost heave amplitude

and the thaw shrinkage amplitude. The characteristic value of strain is related to the fracture length

the width and lithology of rock mass

and the freeze-thaw failure of fractured rock mass is caused by gradual accumulation of the residual strain.