ABSTRACT
This chapter provides a general description of the mine site including geological settings, rock mass conditions, in-situ stresses, the layout and geometry of the tunnel system, the used ground control methods, and the field measurements and observations. As an active mine, this underground mine has a remaining life of about 20 years. The deposits are sediment-hosted and are generally controlled by the intersection of mineralized faults and stratigraphic units. The ore zones or altered rocks have low rock mass ratings, while the rock masses outside the ore zones are in better conditions. The layout of the development drifts which are used to extract and transport the ore from the mining area is rather complex. They go through the low rock mass quality areas or major faults. Primary ground control methods used at the mine include the rock and cable bolts, the shotcrete and mesh support, and the cemented rock fill. Field observations showed that failures of the rock masses and supports may be encountered at the wide tunnel intersections and the areas with weak rock mass conditions or fault zones. In the field, rehabilitation works have been conducted repeatedly from time to time to keep the rock mass stable. For the tunnels located in the very weak ground, the shotcrete arch support system was designed.
