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| Titel |
Geo-structural modelling for potential large rock slide in Machu Picchu |
| VerfasserIn |
D. Spizzichino, G. Delmonaco, C. Margottini, S. Mazzoli |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027343
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| Zusammenfassung |
| The monumental complex of the Historical Sanctuary of Machu Picchu, declared as World
Heritage Site by UNESCO in 1983, is located in the Andean chain at approx. 80 km from
Cuzco (Peru) and at an elevation of 2430 m a.s.l. along the Urubamba River Valley. From a
geological point of view, the Machu Picchu granitoid pluton, forming part of the larger
“Quillabamba granite”, is one of a series of plutons intruded along the axial zone of the high
Eastern Cordillera Permo-Liassic rift system including a variety of rock types, dominantly
granites and granodiorites. The most evident structures at the outcrop scale consist of planar
joint sets that may be variably reactivated and exhibiting 4 main orientations. At present, the
site is affected by geological risk due to frequent landslides that threaten security and tourist
exploitation. In the last years, the international landslide scientific community has
promoted a multi-discipline joint programme mainly finalised to slope deformation
monitoring and analysis after the warning, launched in 2001, of a potential collapse
of the citadel, caused by a huge rock slide. The contribute of the Italian research
team was devoted to implement a landslide risk analysis and an innovative remote
sensing techniques. The main scope of this work is to present the implementation of a
geo-structural modelling aimed at defining present and potential slope stability conditions
of the Machu Picchu Citadel. Data have been collected by geological, structural
and geomechanical field surveys and laboratory tests in order to reconstruct the
geomorphological evolution of the area. Landslide types and evolution are strictly
controlled by regional tectonic uplift and structural setting. Several slope instability
phenomena have been identified and classified according to mechanism, material
involved and state of activity. Rock falls, debris flows, rock slides and debris slides are
the main surveyed landslide types. Rock slides and rock falls may produce blocks
with dimensions variable from 10-1 to 102m3 that form the toe accumulation on
steeper slopes. The area of the citadel has also been interpreted as affected by a
deep mass movement (>100m) that, if confirmed by the present day monitoring
systems, could be referred to a deep-seated gravitational slope deformation (DSGSD),
probably of the type of the compound bi-planar sagging (CB) described by Hutchinson
(1988). The analysis of active strain processes (e.g. tension cracks) along with the
damage pattern surveyed on archaeological structures (e.g. sinking, swelling, tilting)
suggest that the potential failure of a large rock slide may be located at a depth of
ca. 30m. The various data sets have been integrated in order to obtain a general
geo-structural and geotechnical model (strength and deformation parameters, seismic
input) of the citadel at the slope scale. This represents a first step in implementing a
slope stability analysis capable of reconstructing present and potential landslide
evolution under static and dynamic conditions. This multi-discipline study, based on
geological and structural analysis integrated with geotechnical and geomechanical
interpretation, will aid defining actual landslide hazard and risk levels, indispensable for the
design of low impact mitigation measures to be applied at Machu Picchu Citadel. |
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