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| Titel |
Basic processes and factors determining the evolution of collapse sinkholes: a sensitivity study |
| VerfasserIn |
Douchko Romanov, Georg Kaufmann |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250142577
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| Publikation (Nr.) |
 EGU/EGU2017-6213.pdf |
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| Zusammenfassung |
| Collapse sinkholes appear as closed depressions at the surface. The origin of these karst
features is related to the continuous dissolution of the soluble rock caused by a focussed
sub-surface flow. Water flowing along a preferential pathway through fissures and fractures
within the phreatic part of a karst aquifer is able to dissolve the rock (limestone, gypsum,
anhydrite). With time, the dissolved void volume increases and part of the ceiling above the
stream can become unstable, collapses, and accumulates as debris in the flow path. The
debris partially blocks the flow and thus activates new pathways. Because of the low
compaction of the debris (high hydraulic conductivity), the flow and the dissolution rates
within this crushed zone remain high. This allows a relatively fast dissolutional and
erosional removal of the crushed material and the development of new empty voids.
The void volume expands upwards towards the surface until a collapse sinkhole is
formed.
The collapse sinkholes exhibit a large variety of shapes (cylindrical, cone-, bowl-shaped),
depths (from few to few hundred meters) and diameters (meters up to hundreds of meters).
Two major processes are responsible for this diversity: a) the karst evolution of the
aquifer - responsible for the dissolutional and erosional removal of material; b) the
mechanical evolution of the host rock and the existence of structural features, faults
for example, which determine the stability and the magnitude of the subsequent
collapses.
In this work we demonstrate the influence of the host rock type, the hydrological and
geological boundary conditions, the chemical composition of the flowing water, and the
geometry and the scale of the crushed zone, on the location and the evolution of the growing
sinkhole. We demonstrate the ability of the karst evolution models to explain, at least
qualitatively, the growth and the morphology of the collapse sinkholes and to roughly predict
their shape and location. Implementing simple rules that describe the mechanical collapse, we
come to the conclusion that a complete quantitative and qualitative description of a collapse
sinkhole is possible, but for this it is necessary to take into account also the mechanical
properties of the rock and the processes determining the mechanics of the collapses. |
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