Abstract
In order to extend the already existing subway line U2 to the airport of Nuremberg (Bavaria) tunnels of a total length of 3.3 km had to be built. The advance works encountered mainly sandstones and clay-sillstones of the "Keuper" formation (upper triassic). In some lots the inhomogeneous composition of the sediments led to problems in roadheader excavation. Two case studies are supposed to show how layers of hard calcrete (so called "quacken" layers) as well as soft clay-sillstone-layers reduced the efficiency of the roadheader excavation system. Even if there are a lot of rock properties controlling the excavation performance of a roadheader, a geological phenomenon may cause much more trouble in excavation than "just" higher rock strength values. Therefore, preliminary site investigations should also especially focus on geological conditions and problems. Both geological-mineralogical and geotechnical aspects should be taken into consideration to raise the level of geotechnical contribution to underground construction. Nevertheless the description of some geological and geotechnical influences on the effectiveness of cutting works given in this paper may help to improve the estimation of rock excavation rates and bit consumption in planning future tunnel projects.
| Translated title of the contribution | Experience during roadheader tunnelling of the nuremberg underground |
|---|---|
| Original language | German |
| Pages (from-to) | 8-13 |
| Number of pages | 6 |
| Journal | Felsbau |
| Volume | 19 |
| Issue number | 1 |
| State | Published - 2001 |