Abstract: The blasting practice in recent years showed that with the mining depth increasing in Sijiaying Open-pit Iron Mine, slopes at different lithology and different positions were becoming unstable in varying degree.By the co-action principle of the compression stress wave and the quasi static gas pressure, and based on Langefors' research, how to select the parameters for pre-split blasting near final slope of severely-weathered chlorite are analyzed and discussed.Moreover, according to the field tests and practical application in Sijiaying Open-pit Iron Mine, the basic principle of selecting the parameters for pre-split blasting is proposed and good pre-split and vibration reducing effect were achieved finally.

Key words: Pre-split blasting, Pre-split hole, Weathered chlorite, Half-hole rate, Vibration reduction ratio