Abstract: Multi stage mining model can effectively improve the production capacity of low-grade large thick ore-body and reduce the costs.So it is significant to research the step distance of multi-stage synergistic mining.From the view of mine engineering systems,the ideas or methods for computing the step distance of multi-stage synergistic mining were proposed.The exploited computing system was constructed to build the comprehensive fuzzy evaluation system of multi-stage synergistic mining.The hierarchical fuzzy analysis method was adopted to determine the weight value of each factor that influences the multi-stage synergistic mining.Through evaluating the multi-stage synergistic mining scheme,the scheme and its synergistic steps are determined in theory.With the copper zinc ore body in Tongkeng mine,Guangxi Huaxi Group as engineering background,the investigation on the theory and application of the synergistic mining step distance showed that the second stage mining of copper zinc ore-body collaborating with the upper stage ahead two steps distance from the lower stage is the optimal.Research results provided technical guidance for the multi-stage synergistic mining of low-grade large thick ore-body.

Key words: Multi-stage, Synergistic mining, Association synchronous distance, Heavy low-grade ore-body, Comprehensive Fuzzy Evaluation