STABILITY ANALYSIS OF MINED-OUT AREAS INFLUENCED BY BLASTING VIBRATION WITH FLAC~(3D)

For the reason that Changba lead-zinc mine is severely destroyed by disordered mining,the numerical analysis of mined-out areas under blasting vibration is carried out with FLAC3D . Two different measured velocity time-dependent curves are selected as blasting vibration input according to the in-situ test data;and static calculation and dynamic calculation are carried out,respectively. The analytical results show that the maximum displacement of surrounding rock is 4.75 mm after mined-out areas are excavated,while the maximum displacement of surrounding rock increases to 5.47 mm after the blasting dynamic loading is applied,and amplitude of increasing displacement is proportional to the velocity of blasting vibration. The shape of vibration wave influences the variation of displacement distribution for surrounding rock. When the blasting vibration dynamic loading is appliedt,he second redistribution of stress field of surrounding rock occurs;and the distribution area of plastic zone is expanded obviously. The foot of the right open slope above the mined-out area is also influenced as well. The analytical results are accordant with the observed results. Several suggestions to avoid instability and subside of mined-out areas induced by blasting vibration are brought forward.