Abstract: Aiming at the layered rock mass with certain impact damage but incomplete breakage caused by mining operation in mine production,the freeze-thaw damage of layered rock mass with impact cracks was studied. Through the impact test of layered rock mass with incident amplitudes of 60,70,80 and 90 mV,the freeze-thaw cycle damage and NMR test were carried out on the specimens that were not completely broken after impact,and the freeze-thaw damage law was analyzed. The results show that when the incident amplitude of 60 mV and 70 mV is cycled for 1 to 3 times,cracks appear on the surface of rock specimens,and rock specimens with 80 mV and above are broken. With the increase of impact times,the peak stress of layered rock mass specimens decreases,and the maximum strain and strain rate increase,resulting in the deepening of damage and the weakening of the ability to resist damage. The distribution of initial porosity after impact is dominated by small pores, followed by medium pores,and the least is large pores. With the increase of freeze-thaw times,the development of medium and large pores leads to the decrease of small pore porosity component. By fitting the final damage variable after impact with the damage variable of 30,60 and 90 freeze-thaw cycles,the exponential distribution is presented,and the impact damage promotes the development of freeze-thaw damage. The research results can provide theoretical support for the prevention of geological disasters in mines in cold regions containing layered rock mass. 

Key words: layered rock,SHPB,freeze-thaw cycle,NMR,porosity