Freeze-thaw test and triaxial compression test are carried out for model samples with pre-existing single fracture by the rock mechanical servo-controlled testing system

freeze-thaw damage degradation model is studied based on the freeze-thaw test

and crack coalescence mechanism is discussed under the triaxial compression condition. Tests reveal that: freeze-thaw damage deterioration modes of fractured rock masses are scattered to particle model

crack model and prefabricated crack fracture mode. Under the triaxial loading condition

there are four coalescence modes of fractured rock samples due to freeze-thaw cycles: tensile mode，shear mode，compression mode and mix mode

which are closely related to the freeze-thaw cycles

confining pressure and the crack dip angle. With the increase of freeze-thaw cycles and confining pressure

more and more surface ruptures are found

at the same time

crack coalescence mode has experienced from single to mix; the failure modes of rock samples show tensile and compression mode when confining pressure reaches the values of 2 MPa and 6 MPa

while tensile mode are presented when the confining pressure reaches the value of 4 MPa. Rock samples with smaller fissure angle which equals 30° are taken on tensile mode

however

the rock samples with the longer fissure angle of 60° take on shear mode.