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.
The following projects were initially implemented for the protection of the wall:
Weeding the area from indigenous vegetation and cleaning accretions from the drainage system of the South Wall
The aim of these projects was to protect the Circuit Walls and the underlying limestone slope against the destructive mechanical action of the root system of indigenous vegetation, to remove unsafe rock pieces and reveal the current state of the monument. This project was also a prerequisite for the geometric documentation of the Circuit Walls and the Rock.
Geometric documentation of the walls
In 2009 orthophotographs were taken throughout the length of the walls. Moreover, a three-dimensional scanning of the Walls was carried out in order to fully and precisely conduct a geometric documentation of the existing state of the walls.
Geophysical investigations
In 2006 geophysical investigations (electrical tomography, radar) on the walls were conducted by the laboratory of Applied Geophysics of the Aristotle University of Thessaloniki in collaboration with I.M.S. FORTH, in order to look into invisible surfaces. Horizontal and vertical tomographies were taken on specific positions of the south wall. After comparing the measurements and calibrating the materials it was possible to discern the limestone, the backfilling, the rock and a damp area. Geophysical monitoring, in order to detect the depth of backfilling, was carried out in 2014. An important undertaking of the same period, which enriched our knowledge related to the stratification of geomaterials on the Acropolis, was the geophysical investigation using the method of electromagnetic prospecting V.L.F. that observed the total length of 2300m during the period of 2014-2015.
This information is important, on the one hand, because it has revealed the location of areas on the wall where dampness was evident in the backfilling and on the other, to find the width of the wall.
Geotechnical investigation
In addition, a geotechnical investigation was carried out in 2015 in order to investigate the geotechnical characteristics of the buttressed artificial backfilling of the Acropolis rock and the fillings of the physical and mechanical properties of the geological limestone substratum. The Service dug two shafts, each 4m deep; the first one in the box grid excavation south of the Parthenon, adjoining the wall, the other one in the north wall near the Belvedere tower. However the nature of the artificial backfilling in the Acropolis terrace, a result of the extensive excavations conducted at the end of the 19th century did not allow the taking of unperturbed samples. Moreover, sensors taking measurements of geotechnical parameters were placed in the north shaft, near the Belvedere tower, in order to gather information on backfilling materials.