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The construction of the circuit walls was one of the first works undertaken on the Acropolis as part of the extensive building programme of the 5th century B.C. Based on a unified architectural conception, it is a work on a grand scale. Particularly strong supporting walls were built in the circumference, around the destroyed Mycenaean Wall, for a length of 740 meters, so as to support the heavy fill and to create a new raised terrain for the construction of the sanctuaries. The Acropolis surface was expanded, while the uneven surface of the rock was terraced, acquiring an area of 29,000 sq. m.
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The north fortification wall with its characteristic recessed surface, known generally as the "Themistoclean Wall", was one of the first works to be carried out after the Persian Wars. Architectural members of the ruined sanctuaries were used as building material in its construction: marble blocks from the crepis of the destroyed pre-Parthenon, 26 half-finished unfluted marble column drums, poros column capitals from the "Archaios Naos" (Old Temple), members of the entablature (architrave blocks, triglyphs, metopes and cornice blocks) were laid in a continuous row as crown blocks on the wall. Preserved today is most of the ancient construction, which has been partly filled in with rubble masonry, in recent repairs. |
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The south fortification wall, known as the "Kimonian Wall", was built after the victory in the naval battle of the Eurymedon (466 B.C.). Today it is difficult to discern the original monumental construction on the outer face, since the façade comprises for the most part irregular, mixed courses, made up of marble and small stones, added in later repairs. Despite the change in its outer appearance, the core of the wall has remained authentic and its outline gives a general picture of its ancient form. The south wall is constructed for its full width of large rectangular quarried poros blocks, laid in horizontal courses in the isodomic system, together with reused building material. |
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The east fortification wall has for the most part been reconstructed in more recent times, after collapsing, probably in a severe earthquake of the 18th century. |
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 | During the long, turbulent history of the Acropolis, the circuit walls were repaired again and again. As part of the repairs in mediaeval times, two tall towers were erected on the south and east sides. The eastern one is generally known as the "Belvedere". A row of buttresses against the eastern and southern parts of the walls belong to this same time.
In the 19th century, during the first programme for the restoration of the Acropolis monuments, most of the additional fortifications were removed, the ramparts taken down and a parapet was added to the top of the wall. Between 1899 and 1940, N. Balanos carried out consolidation works.
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Interventions completed |
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 | Continuous repairing of the walls has contributed to their preservation to date. Yet structural damage, such as cracking, gaps and extreme deformations are evident in many parts of the ancient construction, just as in the more recently repaired sections.
During the past 25 years, the condition of the walls has been systematically monitored and the problems noted have frequently been reported. During this time a strategy and programme of an interdisciplinary approach has been formed in order to deal with the problems. To begin with, primary emphasis was placed on documentation of the form and state of preservation of the walls, in order to build the necessary database for evaluating and estimating any future intervention.
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Interventions in process |
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The programme at present under way is concerned with the monitoring of structural damage in the walls. Following research on various methods of instrumental monitoring of the micro-movements, it was decided to use a combination of mechanical methods and other recording systems of advanced technology. For this purpose mechanical crack meters have already been installed on cracks in the walls. The information they provide is local but very useful, since they gather reliable information as to whether and to what extent the cracks are "active".
Additionally, in terms of monitoring the circuit wall, a pilot program including installation of optical fibre sensors has been realized. These sensors aim at the measurement of strains induced from mechanical or thermical actions in characteristic areas of the wall. To be noted that optical fibre sensors are the state of the art in strain monitoring and provide extremely high accuracy. They have been developed mainly around the SE corner of the wall as well as in a certain area of the North Wall in the proximity of Arryphorion filling, where the circuit wall appears intensely deformed. Following this pilot phase, the monitoring program with optical fibre sensors is to be expanded to larger areas of the circuit wall.
Additionally, in terms of monitoring the circuit wall, a pilot program including installation of optical fibre sensors has been realized. These sensors aim at the measurement of strains induced from mechanical or thermical actions in characteristic areas of the wall. To be noted that optical fibre sensors are the state of the art in strain monitoring and provide extremely high accuracy. They have been developed mainly around the SE corner of the wall as well as in a certain area of the North Wall in the proximity of Arryphorion filling, where the circuit wall appears intensely deformed. Following this pilot phase, the monitoring program with optical fibre sensors is to be expanded to larger areas of the circuit wall. |
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At the same time, an underground non-expanding INVAR wire has been installed between the stable foundation of the Parthenon and the south wall. A network of observation points has also been established on the south and east walls for monitoring the micro-movements. The use of electronical systems (crack meters, inclinometers, load cells) for automatic and continuous recording of high accuracy comprises the fourth system of instrumental monitoring that has been programmed. |
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 Photogrammetric recording of the full length of the walls and three-dimensional (3D) scanning of the walls have been programmed in order to have full geometrical documentation of the existing condition of the ancient walls. Geophysical research of the wall surfaces (electrical tomography-radar) in order to investigate the invisible surfaces, has recently been completed. |
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In addition to the use of technologically advanced methods, optical inspection is always a reliable method for directly evaluating the most troublesome areas. Access to these is by means of a suspended work platform accommodating two people. By means of this we have been able to obtain surveys of the cross-sections and deformations of the walls, using traditional methods. This can be combined with weeding, the removal of accretions from the drainage system and, in some cases, improving the drainage system. |
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Programmed interventions |
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 In the future instrumental monitoring of the evolution of the cracks and deformations of the walls is to be continued with a more extensive and denser network than that which has been installed at present. Quality control of the measurements and evaluation of the structural damage is necessary in order to locate the areas of severe danger, and the extent, seriousness and degree of danger in which they may be. Evaluation of all information to be collected will provide the foundation for the special studies on the consolidation of the walls. |
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 Also to be completed is the particularly demanding and time-consuming recording of the architectural members that have been incorporated in the wall. General research on the walls, detecting and dating the numerous repairs, should increase our knowledge of the ancient form, the materials used, the ways of construction and the historical phases of the Acropolis circuit wall, which is in itself a monument of great importance. |
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