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on. On the other hand, the term mechanical failure applies
mainly to material blocks and comprises block fractures (figure
3), joint dislocations (figure 4), superficial weathering,
disorganization of major areas due to mortar loss, instability of
underlain rockmass, and so on.
The above described structural problems, irrespectively of their
geometric or mechanical nature, constitute what is typically
called, the “pathology” of the monument (Egglezos et al., 2008).
This “pathology” is encountered systematically in large areas at
the current state of the circuit wall.
Figure 3. Characteristic fractures in the SE comer of Acropolis
circuit wall. By D. Egglezos
Figure 4. South part of Acropolis circuit wall. Characteristic
dislocations of joints of structural blocks. By D. Egglezos
Taking into consideration the above mentioned problems, as
well as the severe loading factors acting on the circuit wall (soil
thrust, dead load from its own weight, thermal loading,
foundation instabilities, and -the rather critical load- earthquake
events), it is easily concluded that a systematic intervention has
to be launched. The intervention has to assure a) minimization
of additional deterioration, b) restoration of seriously damaged
areas, c) drastic decrease of the effect of loading factors and d)
safe conditions for a long period of time. This intervention, in
brief, must comprise tasks as, geometric documentation of the
existing state, realization of supporting studies relating to the
walls (systematic geotechnical investigation of the area,
drainage of the superficial plane of the rocky hill, proper
laboratory program for determination of mechanical properties
of structural blocks, seismic hazard evaluation study and so on),
geostructural analyses for interpretation of current state and
proper choice of geotechnical and structural model simulation
for design of stability measures (both for the walls and the
supporting underlain rock), extended instrumentation for
continuous observation of both the current and future (post
intervention) state, continuous conservation of the
repaired/restored monument.
In this paper, the main emphasis from the above mentioned
targets focuses on, how rigorous geometric documentation of
the circuit wall applies directly to geostructural analyses for
interpretation of current state of deformed sections and permits
the calibration of structural model parameters.
3. GEOMETRIC DOCUMENTATION
Geometric recording based on reliable elevation information
and 3D phototextured models are now, perhaps, the standard
photogrammetric products for archaeological and architectural
documentation (Mavromati et al., 2002, Georgopoulos et al.,
2005). An orthophoto constitutes a powerful textured
representation combining geometric accuracy with high visual
quality and a wealth of detail, providing invaluable information
about morphology and deformation. Hence, it is a non-
generalized background arid the vectorized interpretation to be
overlaid is left to the specialists. A fully 3D photo-textured
surface model provides photorealistic visualization, high
geometric accuracy and facilitates geometric or morphological
documentation and analysis (Moullou et al., 2007).
The recording and the documentation of the Acropolis circuit
walls is a vital part of the restoration planning. Due mainly to
its size (~ 760m perimeter, maximum height 18m) and its
inaccessibility (figure 5) the only fast and accurate method that
could be applied is a proper combination of photogrammetry
and 3D laser scanning.
This is the reason why the Acropolis Restoration Service
initiated, in 2007, a project, its objective being the recording,
modelling, visualisation and GIS applications development for
the Acropolis archaeological site.
The project has a dual goal consisting of: firstly the production
of the scientific infrastructure needed for current or future
restoration planning, with the emphasis laid on the Acropolis
circuit walls. The project will cater for the investigation of the
various interventions the walls have sustained across time, for
the location and study of the poros limestone and marble blocks
reused in them and for the examination of their static
sufficiency. And secondly the exposure of all information