Approaches to technical solutions for tunnelling in swellable ground / Lösungsansätze für den Tunnelbau in quellund schwellfähigem Gebirge

"Swelling" is generally taken to mean the expansion of a rock due to water absorption. The main intention of this paper is to point out the significant difference between the swelling of clay and claystone (Tonstein) on one hand and the swelling of claystone and marl containing anhydrite on the other. In the opinion of the author, these differences are so large that they should be described as different phenomena. Leopold Müller has already proposed the introduction of different German terms: "Quellen" for clay and "Schwellen" for anhydrite. Unfortunately, this terminology has not caught on, probably because the word swelling is used in English for both processes. The resulting merging has hindered research into anhydrite swelling for decades, and the development of calculation methods and technical solutions for tunnelling in anhydrite-bearing ground is still at an early stage. In contrast, the problem of clay swelling can be regarded as largely solved.