Cases of swelling in tunnels excavated through Triassic sulphate-bearing rocks from the Gipskeuper and the Anhydritgruppe are presented and discussed in this series of papers in order to gain a better understanding of the expansive phenomena in these materials and to identify the most relevant ones. Part I deals with main features of swelling in tunnels and alternative supports designs for their control an mitigation, as well as with the phenomenology of swelling in tunnels from Baden-Wurttemberg (Germany) excavated through the Gipskeuper.