Based on process mineralogical characteristics of villaninite,a process of "stage grinding,stage flotation,and concentrate discharge from two points" was adopted.

It showed that by using mixed reagent (butyl xanthate/penty1 xanthate ratio was 1∶3)and 9538 collector for sulfide mineral to intensify silver flotation and by adopting the process flow of stage grinding-flotation,the silver recovery rate reached 94.

This thesis, based on a real project, Dongyang-Yongkang expressway, demonstrates the contents that need careful consideration in route scheme study at feasibility study stage, including the determination of the so-called corridor region, technical criterion, selection of the two ends of the roads, and comparative analysis of the route scheme.

In combination with compiling for Techical Code of Investigation for Nuclear Power Plant,the present existing issue of geotechincal engineering investigation in preliminary feasibility stage of nuclear power plant are discussed and relevant approaches are given.