The problems of stability of surface movement and deformation as time goes on and residual distortion are always important aspect of mining cover-rock subsidence study.

But because of hard to fix test ring in bedrock, so report of domestic deep worked-out area overlying rock subsidence observation by layers have not yet been heard so far.

The mining subsidence mechanism of metal mine with fractured blocky rock mass is different from that of coal mine with layered rock mass.