Stability analysis of goaf group is a complicated geological problem; there is some “group effect”. An accurate grasp of cavity shape

size and its change is the premise to this problem. In the engineering background of Shirengou iron mine

using the cavity monitoring system (CMS) to detect the goaf group precisely. Then the cavity model and geological model of the mine are constructed using the 3Dmine software based on the detection results. A method of constructing numerical computing model with the coupling of 3Dmine and FLAC3D is put forward. The stress and strain fields are analyzed according to the simulation calculation results; and the “group effect” is discussed. The research results show that the “group effect” increases the stress and strain larger than the single goaf; and this effect is not only simple addition but improve the goaf’s hazard grade. This paper combinates the advantages of CMS

3Dmine and FLAC3D

and provides a new and effective way for numerical simulation research on the stability of rock engineering.