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Mine Gianna: a jump back in history

Iron and wood reinforcements
Iron and wood reinforcements
© Archivio Ecomuseo delle Miniere e della Val Germanasca
The rocks stability is good in the first part, where the presence of gneiss allows not to reinforce the gallery, it worsens in proximity of the layer where the rock (mica schist) becomes more pushing and is degraded by water seepages.

Iron and wood reinforcements were mostly used in the haulages. The metallic ribs had a weight of around 12 kg/ms, and they were transported 3 metres at a time, and hooked to the vault centre by a male-female system. This way they could check the cave-in through dynamometric keys. The roof was reinforced with wood beams or salvage plate structures.

The wood frames used in the yards were mainly built with two types of lumber: acacia in the more pushing areas since it is resistant and yielding at the same time, and chestnut where stress was less since such wood is brittler.
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