2128 cause instabilities in the rock mass, which can lead to an increase in shear stresses in the mining area. Figure 1 gives a schematic overview on the geological setting in Hochfilzen. This geological setting can primarily influence the stability of stopes and pillars. For this reason, this circumstance must be taken into account when dimensioning the stopes and pillars. Porphyroid can also be problematic in terms of quality control, as the high silicate content reduces the quality of the magnesite extracted in the chambers. For this reason, attention must also be paid to minimizing dilution during mining. At the same time, the different qualities of magnesite are distributed unevenly throughout the deposit. This means that besides the rock engineering challenges, selective mining is also a major goal in Hochfilzen. Due to the rather small size of the deposit, it is of major importance, to optimize the recovery of the mine. However, mine safety should be one of the major topics. This implies that safe mining conditions are given to any time during the mining process in Hochfilzen. Figure 1 – Simplified vertical section of the geology in the alpine environment in Hochfilzen. 3.1.2 Historical Mining As described in section 2, the first underground mining activities have been started in the early 1960s. Some of the old underground workings are still in use for material transport and most of them are still accessible. The ability to access these workings is a big advantage for the planning process. Especially when it comes to investigations of the rock mass. Rock mass classification could be directly done in the deposit where future drifts and stopes will be mined. Moreover, the stability of old mine workings can be judged and also included in the planning process. Additionally, there is the big advantage, that existing drifts and shafts can be included in the new mine for the purpose of mine ventilation and material transport.
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