Verwendung von Tunnelausbruchmaterial - Geologische und Geotechnische Aspekte
Research output: Thesis › Doctoral Thesis › Research
The focus in recycling of tunnel excavation material lies in the maximum usage of the excavation material at minimum environmental contamination and maximum economics. Beside industrial applications (i.e.: Chemistry, Metallurgy, Glass and Varnish coatings) and usage as gravel in infrastructure engineering, excavation materials are used as aggregates for concrete. Mineralogical, geological and geotechnical properties of different Austroalpine rocks were determined and correlated with results of concrete tests. The aim is the determination of the usability of lithologies as aggregates already in the design phase of a project. The investigations show that all lithologies are qualified for producing inner lining- and tubbingconcrete. Boundary values for uniaxial compressive strength, Young’s modulus, Abrasiveness, longitudinal wave velocity and Mica content were obtained by practical experience. Additionally, the excavation process was analyzed due to major differences in grain size distributions and geometry of excavated rocks from NATM or TBM tunneling. Linear cutting tests, which simulate the chipping process, were done on alpine lithologies to figure out the influence of cutter spacing and cutter penetration on the grain size distribution of the excavated rocks. The results show that there is a significant impact of cutter spacing and almost no influence of cutter penetration on the grain size distribution. Increased cutter spacing provides a coarse grain size distribution. Rocks with low uniaxial compressive strength and high mica content provide a finer grain size distribution. Additionally, a relationship between grain size and the grain size distribution of the excavation material could be observed. The cutting process induces cracks in the rocks which were analyzed macro- and microscopically. Additionally, Schmidthammer test were done on the rock surface. The investigations show that micro crack growth is mainly controlled by the schistosity orientation. A zone of completely destroyed grain bonding is developing directly beneath the indenting disc cutter. This zone is followed by an area of micro-cracks which develop mainly in hard grains (i.e.: quartz, garnet). The lowest region shows cracks along mica-layers, along cleavage properties of minerals, or, if mica is absent, along the grain boundaries of the minerals.