Limestone is one of the most important mineral resources, and it is only one mineral that can be fully supplied by domestic producers. Generally, a certain amount of ores is stored in the ore passes temporally after blasting excavation, and extraction is carried out from the bottom of the ore pass. However, the hang-up phenomena in the ore passes sometimes occurred and some cases are recently reported. Once the hang-up phenomena in the ore passes occur, it will cause serious problems. In this study, ore flow experiments in the vertical ore passes were conducted using ore pass models which was composed of transparent acrylic tubes, and the conditions of hang-ups were discussed. Since the ore passes were assembled with transparent tubes, it was also possible to observe the hang-up phenomenon directly. To discuss the effect of cross-sectional shapes of ore passes, two kinds of ore-passes, that is, circular and square shapes of cross-sections, are prepared. Using various sizes of ores, the relation between ore size and cross-sectional area was also discussed. It was found that the hang-up phenomenon almost did not occur when the ratio of ore pass size to the mean grain size of ores exceeds the value of 5. It was also found that the circular-shaped ore passes were a little preferable to avoid ore pass hang-ups compared with the square ore pass. The same procedure was applied to the mixed ores which two types of ores with different mean diameters are mixed. In this case, also, the results were almost the same as the results obtained by single-size ores. 3D-DEM analysis was also conducted, and the validity of the experiments was discussed.
