Abstract: It is difficult to realize increasing production of transition period from open-pit to underground mining by conventional method.So,taking Xiaowanggou iron mine as an example,a new method that forming overburden layers by induced caving is proposed so as to reduce mutual influence scope of open-pit and underground mining and extend the time of open-pit and underground mining.Through optimizing open-pit and underground mining technologies,the ultimate boundary is designed according to the principle of convenience for exploiting and benefit maximization.Besides that,some relative measures are taken to accelerate the underground mining process and realize the goal of transition period production of open-pit to underground mining is increased greatly year by year.

Key words: Open-pit to underground, Transition period, Overburden layers, Boundary optimization