Usually geomorphology, structural geology and engineering geology provide descriptions of slope instability in quite distinctive ways. This new research is based on combined approaches to providing an integrated view of the operative slope processes. ‘Slope Tectonics’ is the term adopted here to refer to those deformations that are induced or fully controlled by the slope morphology, and that generate features which can be compared to those created by tectonic activity. Such deformation can be induced by the stress field in a slope which is mainly controlled by gravity, topography and the geological setting created by the geodynamic context.
The content of this book includes slope-deformation characterization using morphology and evolution, mechanical behaviour of the material, modes of failure and collapse, influence of lithology and structural features, and the role played by controlling factors. The contributions cover broad aspects of slope tectonics that attempt to underline a multidisciplinary approach, which should create a better framework for studies of slope instability.
Inheritance of ductile and brittle structures in the development of large rock slope instabilities: examples from western Norway
Published:January 01, 2011
A. Saintot, I. H. C. Henderson, M.-H. Derron, 2011. "Inheritance of ductile and brittle structures in the development of large rock slope instabilities: examples from western Norway", Slope Tectonics, M. Jaboyedoff
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The high density of slope failures in western Norway is due to the steep relief and to the concentration of various structures that followed protracted ductile and brittle tectonics. On the 72 investigated rock slope instabilities, 13 were developed in soft weathered mafic and phyllitic allochthons. Only the intrinsic weakness of such rocks increases the susceptibility to gravitational deformation. In contrast, the gravitational structures in the hard gneisses reactivate prominent ductile or/and brittle fabrics. At 30 rockslides along cataclinal slopes, weak mafic layers of foliation are reactivated as basal planes. Slope-parallel steep foliation forms back-cracks of unstable columns. Folds are specifically present in the Storfjord area, together with a clustering of potential slope failures. Folding increases the probability of having favourably orientated planes with respect to the gravitational forces and the slope. High water pressure is believed to seasonally build up along the shallow-dipping Caledonian detachments and may contribute to destabilization of the rock slope upwards. Regional cataclastic faults localized the gravitational structures at 45 sites. The volume of the slope instabilities tends to increase with the amount of reactivated prominent structures and the spacing of the latter controls the size of instabilities.