Abstract: In order to effectively reduce rock burst disaster in underground stope and reasonably control the deformation of surrounding rock in stope,tailings are generally used to fill underground goaf. The traditional strength of tailings is difficult to play a role in complex underground space,especially in the freeze-thaw cycle environment of high-cold and high-altitude mining areas. Therefore,it is necessary to ensure that the backfill in freeze-thaw environment has good mechanical properties. In order to study the effect of freeze-thaw cycle on the mechanical behavior of the fiber-modified backfill,firstly,the fiber with the percentage of non-mass (0,0. 2%,0. 4%,0. 6%,0. 8%,1. 0%) was mixed with the filling slurry for mixing,and then the fiberbackfill mixture was mixed for 0,5,10,15 freeze-thaw cycles. The variation trends of slump,uniaxial compressive strength and splitting tensile strength of fiber-modified backfill mixture with fiber content and number of freeze-thaw cycles were also discussed. The results show that the cyclic freeze-thaw can significantly reduce the mechanical properties of the fiber modified backfill mixture,and the appropriate incorporation of fiber plays a major role in improving the mechanical properties of the backfill. When the fiber content is 0~ 0. 6%,the strength of the backfill can be effectively improved,while when the fiber content is more than 0. 6%,the physical properties of the backfill will be degraded. In addition,the incorporation of fiber is easy to fuse with the water in the filling body and play a role in fixing water,thus inhibiting its fluidity.

Key words: filling mining,fiber content,filling body,freeze-thaw cycle,collapse,mechanical property