Abstract: A site stability evaluation on the mined out area was performed in order to study the ground subsidence as well as the principal stress change in both the roof and the bottom of a gypsum mine before and after the mined out area. The gypsum mining process was able to be simulated by establishing a threedimensional finite element model using MIDAS/GTS. The results indicate that the maximum vertical displacement at the roof and the bottom of the minedout area are 17.0 mm and 11.8 mm, respectively. The maximum principal stress is 11.75 MPa. All values are within the allowable range. The mining monitoring results and the bore holes demonstrated the consistency among between the simulated values and the measured.

Key words: MIDAS/GTS, Minedout Area, Stability Evaluation, Numerical Simulation