mass falls in the Wachau-Danube Valley (Bohemian Massif

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not yet proved possible to find the finances necessary to fund an existing, well-defined remedial concept based on the cutback of a total volume of 369 000 m³, to be realised by open mining over a period of several years. The concept in question would provide for a total cutback of all bedding planes which had been undercut by quarrying. The resultant cataclinal slopes above and laterally from the former quarry would extend the longitudinal surface area of mining considerably, dividing the whole valley flank into berms and quarry faces. In Dürnstein the slope geometry between the foot of the rock face and the railway track was redesigned, by constructing an eight metre high protection dam using debris from the failed rock mass. It was thus possible to construct a new reservoir to accommodate further rock-mass falls combined with a 150 metre long and up to eight metre high protection dam without having to transport any construction material to or from the site. The protective effect of the dam was improved considerably by redesigning the slope geometry in the transport and deposit area of possible future rock-mass falls and creating an absorption bench at the foot of the rock face. Additionally, a rockfall protection kit was installed (Fig. 16). Fig. 16 Geomorphological situation in the former quarry at Dürnstein. This was not enough, however, as major failure of certain larger parts of the rock face, especially in the upper sections, could still result in partial damage to the dam. Moreover smaller blocks could bounce over in this case. Therefore these potentially hazardous parts of the rock face were monitored. At the same time, a long-term remedial concept has been devised for cutting back these parts of the rock face by blasting. This concept was implemented in summer 2011, removing a total volume of more than 5000 m³. 18
Conclusions There are two causes of natural and anthropogenic origin for the rock-mass fall and rockslide events in Spitz and Dürnstein. The unfavourable orientation of discontinuities is natural given, whereas the steep slope morphology and loosening of the rock mass was caused by human mining activities. The combination of both factors led to the undercutting of the beds, posing a situation, where block failure is potentially possible from a kinematic point of view and the slope is in a critical state of equilibrium. This allowed heavy rainfall to trigger rock-mass falls. The need for rapid restoration of endangered transport routes required extensive protective measures. Acknowledgements We would like to thank the Austrian Railways, who allowed us to use unpublished data, Michael Bertagnoli (Geological Service of Lower Austria) for fruitful discussions, Wolfgang A. Lenhardt (Seismological Service of Austria) for providing actual seismic data and Klaus Legat (AVT) for providing DEM in figure 15b. Furthermore the comments of Andreas Kellerer-Pirklbauer, Ján Vlcko and an anonymous reviewer, which helped to improve the scientific quality of the paper are gratefully acknowledged. Markus Wiesinger improved the English manuscript. Authors Hans Jörg Laimer, Austrian Federal Railways (ÖBB), Infrastruktur AG, SBM, Weiserstraße 9, A-5020 Salzburg, Austria Martin Müllegger iC consulenten Ziviltechniker GesmbH, Zollhausweg 1, A-5101 Bergheim, Austria Email: m.muellegger@ic-group.org References Abele, G., 1974. Bergstürze in den Alpen. Ihre Verbreitung, Morphologie und Folgeerscheinungen. Wissenschaftliche Alpenvereinshefte, 25. DAV, München. Barton, N.R., 1971. A relationship between joint roughness and joint shear strength. In: Proceedings of the International Symposium on Rock Fracture, paper 1.8. International Society for Rock Mechanics, Nancy. 20 p. Brandmayr, M., Dallmeyer, R.D., Handler, R. and Wallbrecher, E., 1995. Conjugate shear zones in the Southern Bohemian Massif (Austria): Implementations for Variscan tectonothermal activity. Tectonophysics 248, 97- 116. Bruce, I.G., Cruden, D.M. and Eaton, T.M., 1989. Use of a Tilting Table to Determine the Basic Friction Angle of Hard Rock Samples. Canadian Geotechnical Journal 26, 474-479. Cawsey, D.C. and Farrar, N.S., 1976. A Simple Sliding Apparatus for the Measurement of Rock Joint Friction. Geotechnique, The Institution of Civil Engineers 26 (2), 382-386. Figdor, H. and Scheidegger, A.E., 1977. Geophysikalische Untersuchungen an der Diendorfer Störung. Verhandlungen der Geologischen Bundesanstalt 1977(3), 243-270. Fuchs, G. and Matura, A., 1980. Die Böhmische Masse in Österreich. In: Oberhauser, R., (ed.): Der geologische Aufbau Österreichs. Springer, Wien. 121-143. Gattinger, T.E., 1980. Grundwasser und Massenbewegungen. In: Oberhauser, R., (ed.): Der geologische Aufbau Österreichs. Springer, Wien. 580-594. Goodman, R.E. and Shi, G.-H., 1985. Block Theory and its Application to Rock Engineering. Prentice-Hall, Englewood Cliffs, New Jersey. Günther, A., Carstensen, A. and Pohl, W., 2002. The RSS-GIS (Rock Slope Stability GIS): Tools for automated regional sliding susceptibility assessments of hard-rock hill slopes. In: Proceedings 3 MITCH-Workshop, Potsdam, 8 p. Hoek, E. and Bray, J., 1974. Rock slope engineering. Institute of Mining and Metallurgy, London. Kohl, H., 1966. Das Donautal zwischen Passau und Hainburg. Eine geomorphologisch-paläogeographische Betrachtung. Geographische Rundschau 18(5), 186-196. 19
Page 1 and 2: Geomorphological and geotechnical c
Page 3 and 4: Fig. 3 Rock-mass fall near the town
Page 5 and 6: Tectonically, the whole Bohemian Ma
Page 7 and 8: There is not much information on fu
Page 9 and 10: Fig. 8 Monitoring devices in the fo
Page 11 and 12: Fig. 9 (a) Orientation of bedding p
Page 13 and 14: Fig. 11 (a) Orientation of joints a
Page 15 and 16: strength of eight MPa, and a fricti
Page 17: Discussion Interpretation of failur

mass falls in the Wachau-Danube Valley (Bohemian Massif

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