Abstract: Based on results of ground deformation monitored and the numerical simulation, the process of ground deformation is investigated in East Main Shaft of Chengchao Iron Mine; and then the characteristics and mechanism of ground deformation are given. Research results show that: When the underground mined-out area and the collapse pit form a certain scale, under the release and squeezing of horizontal tectonic stress in different directions, the surrounding rock cut columnar structure cut by geological in structures the surrounding rock toppled to collapse pit, then caused the ground deformation in the surface. Ground deformation is mainly dominated by horizontal displacement, and the vertical displacement is very little. With the constantly tilt of columnar structure, the ratio of vertical displacement to horizontal displacement is constantly increasing, and the funnel-shaped deformation curve forms in the surface.

Key words: surface deformation, fast Lagrangian analysis of continua(FLAC), underground mining, deformation monitoring