Abstract
Abstract. On 12 February 2008, a landslide occurred along a 50 m high bank of the Danube river near Dunaszekcsö, Hungary. The initial state is only incompletely documented and the geodetic data acquired after the mass movement are sparse. A generalized 3-D topographic model of the landslide and its surrounding area was assembled and a representative longitudinal profile extracted. The reconstruction of the original surface is based on an orthophoto as well as on morphological considerations. Recorded observations include the locations of the outcrops of basal sliding surfaces, displacements at the main scarp and in the lower part of the slide, and a value to describe the total mass transport. Such sparse and inhomogeneous data were insufficient to derive a comprehensive documentation of the landslide or obtain adequate constraints for an accurate numerical analysis. Therefore, slider block models were fitted to the field data, which have only a small number of free parameters. A general view on the morphology of the mass movement justifies its classification as a rotational slide. A double slider block model fits all observational parameters within their error margin and supplies valuable information on the geometry of the slide. Estimates of the residual friction angles were derived and the question of reactivation was addressed. Finite Difference (FD) modelling and the application of conventional stability analysis support the geometry of the slider blocks and the computed average residual friction angles. Generally, the results are assumed to represent preliminary information, which could only be attained by the combination of the thinly distributed geodetic data with qualitative morphological observations and the implementation of a model. This type of information can be gained quickly and may be valuable for preliminary hazard mitigation measures or the planning of a comprehensive exploration and monitoring program.
Highlights
When analysing the kinematics of mass movements, experts are frequently confronted with the situation that only sparse, incomplete, and inhomogeneous field data are available
The goal of this study is to explore if the application of a simple mechanical model to this data can result in reliable information on the depth and extent of the mass movement and support mitigation measures, guide further exploration and supply a starting model for detailed numerical studies
At Dunaszekcso, Hungary, 20 km north of the border to Serbia and Croatia, on the right bank of the Danube river is formed by an approx. 50 m high steep cliff of loess layers with brown to red fossil soils accumulated during the Pleistocene (Fig. 1)
Summary
When analysing the kinematics of mass movements, experts are frequently confronted with the situation that only sparse, incomplete, and inhomogeneous field data are available. There may be a lack of accurate documentation of the topography before the initiation of the mass movement in the form of topographic maps and aerial photos, geological maps and borehole profiles, geophysical investigations, geotechnical tests or samples, and – last but not least – a documentation of the movements over time by geodetic measurements. In case of incomplete field data and suitable geological conditions, the application of simple mechanical models with only very few degrees of freedom may be an alternative or first step to achieve a better understanding of the mass movement and to support hazard estimation and mitigation. The goal of this study is to explore if the application of a simple mechanical model to this data can result in reliable information on the depth and extent of the mass movement and support mitigation measures, guide further exploration and supply a starting model for detailed numerical studies
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