Abstract: The upper-medium part of the north wall of Ansteel Yanqianshan Iron Open-Pit Mine is composed of soft rocks such as carbonaceous phyllite and chlorite-phyllite and a large area deformation and cracking of about 110m rockmass have been formed due to mining unloading and rainfall. The deformation scope, sliding trend and significant rainfall-related features of the rockmass are determined by surface displacement monitoring. The deformation monitoring of the sliding body, the sliding law of the deformation zone and the corresponding measures taken to ensure the production safety are described.

Key words: Displacement monitoring, Sliding law, Rockmass slope