Abstract: Since the ore drop shaft of a copper mine was built, sections have changed from circular to irregular shape and its size have changed from 3 meter to 20 meter. The maximum area nearly approach 300 square meters, and the sidewall distance between the two passes changed from 25 meters to about 13 meters. If the collapse is continued to happen,the danger of caving will be appeared. However,according to the production plan of the mine, the drop shafts have longer service life.Analysis of the stability of the drop shafts is done by numerical simulation method and some relative researches on the mechanism of the collapse process influence of drop shafts is done. Based on MohrCulomb failure criterion, the paper gave the emphasis on the analysis of stress state of surrounding rock changed in the sig3sig1 coordinate plane, getting the variation law of stress preliminarily established stable states of the passes which sets up the basis on later research of reinforcing and support of rocks.

Key words: Drop shafts, Mutual influence of two drop shafts, Numerical simulation, MohrCulomb failure criterion, Stability of surrounding rock