Abstract: Through the research and analysis of extension mining method without expansion side slope from open-pit to underground mining, and combining with the actual situation in Guilaizhuang open-pit mine, the reasonable mining depth in terms of the extension method without expanding side slope was theoretically calculated, and the scheme of different depth for different section was put forward. After the extension mining of open-pit, cement shall be employed as filling stuff, which may serve as the man-made shore for underground mining with an average thickness of 12 m. As for the triangle pillars remained from the upward side, the extraction process should be conducted with the upper inlet cementation filling method. Then the cementation filling with reinforcement shall be used to combine the filling stuff of the extraction room with the man-made shore. This artificial bottom shaped from filling may greatly increase the stability and safety of the original side slope. In this view, the afterward problems, such as the low recovery rate of the isolated pillars, difficulty in mining, may be readily solved, which enables the stable transition from open-pit to underground mining and achieves a high-efficient production.

Key words: Transition from open-pit to underground mining, Extension without expansion side slope, Zoning extension, Cementation filling with reinforcement