Abstract: The surface movement caused by underground mining can affect the stability of adjacent open-pit slopes. Taking the combined open-pit and underground mining of Dahongshan Iron Mine as an example,various methods such as microseismic observation and surface cracking observation were used for rock movement monitoring and data analysis to explore the laws of rock mass movement and surface cracking caused by underground mining. Firstly,the historical monitoring data of the open-pit underground combined mining project was organized and analyzed,including the development of surface subsidence and cracks. Secondly,based on the deformation characteristics of surrounding rock during underground mining,microseismic monitoring was conducted to obtain information on rock damage and failure. At the same time,based on the geological conditions of the mine and statistical data,the range of changes in subsidence angle is determined. The results indicate that the development stages of rock mass movement in the open-pit underground joint mining of Dahongshan Iron Mine can be divided into: movement stages of caving and surface connectivity,fully developed rock movement stages of subsidence areas,asymmetric development stages of subsidence angles influenced by F2 fault,and rock movement stages under waste rock filling and deep mining. The development range of the northwest subsidence angle is 75°~81°,and the southeast subsidence angle is 65°~82°. The study can provide a certain reference for the analysis of the development law of rock movement in mines under similar geological and engineering conditions.

Key words: Dahongshan iron mine,combined open-pit and underground mining,rock movement,subsidence angle