Abstract: It is increasingly thought highly of hazardous assessment and treatment technology on the mined-up regions under the tunnels.In order to treat the goaf under tunnel for transport line of Eastern Open Pit,numerical simulation analysis on stability and treatment program of goaf were carried out with FLAC3D,obtaining the rule of stress and deformation before and after the reinforcement of goaf under tunnel.The optimal reinforcement measure was got through the sensitivity analysis on the invert thickness and the strength of the grouting material.The numerical analysis indicated that：tunnel excavating above the unreinforced goaf made the sides of goaf suffer more vertical load.Shear failure occurred in the root of the tunnel and tensile failure occurred in the middle and roof of the tunnel.Meanwhile,there was a large settlement and unequal settlement in the root of the tunnel.After joint reinforcement of mined-out area grouting and tunnel floor pouring invert,the stress concentration near the mined-out area is well released,which significantly reduces maximum or uneven settlement in tunnel floor and improves overall stability of rock and soil.

Key words: Tunnel, Goaf, Grouting, Invert, Numerical simulation analysis