Effects of stoping activities on tunnel conditions in a deep, hard rock mine in Austria

In a deep Austrian hard rock mine, the effect of stoping activities on a mine tunnel situated in the abutment area of a stoping panel, was investigated by means of underground observations and numerical modelling using FLAC 2D and 3D to assess the stress changes resulting from the advancing stopes. This paper discusses the difficulties encountered in quantifying in situ mechanical properties of sheared and jointed rock mass, numerical modelling of the complex geological conditions and relating calculated stress changes to in situ tunnel conditions. It was found that the rockwall condition factor (RCF) tunnel assessment criteria developed to evaluate tunnel conditions in deep South African gold mines, worked remarkably well under very different geological conditions. The focus of this paper is on the approaches adopted to deal with the uncertainties encountered in back analyses and case studies of situations involving behaviour of slender stope pillars, paste fill and regional effects of stoping activities on mine tunnels.