Engineering geological parameters affecting the response of Τhessalonikiʹs urban fill to a major seismic event

In urban areas where there has been continuous occupation of the land for centuries, there are likely to be large areas of filled ground. Fills may have arisen inadvertently from the rubble of demolished buildings and the slow accumulation of refuse. Old urban fills of this type may contain soil, rubble, refuse and even whole parts of past constructions. Despite the fact that areas covered with such deposits are generally prone to severe problems, especially under conditions of dynamic loading, still their influence, as a foundation material on the seismic behaviour of modern buildings is practically unpredictable. loniki is an old historical city of Macedonia, Greece with no less than 2300 years of continuous urban evolution. A thick and heterogeneous layer of artificial deposits covers the biggest part of the historical centre of the city, as is the case for many old historical cities. The presence of this extensive formation influences the urban development, as it constitutes the foundation of the majority of the buildings of the historical centre, and its investigation is essential for most of the major constructions proposed. The complexity and heterogeneity of Thessalonikiʹs fill makes the assessment of its engineering behaviour a rather complicated task. This is due to the big range of values of accumulated geotechnical data but also to the fact that these data have been produced by unrelated methods and applied tests. m of this paper is to assess the engineering performance of Thessalonikiʹs fill based on its behaviour as foundation material to a major seismic event. This is carried out by the evaluation of the influence of engineering geological parameters to the damage distribution of the 1978 earthquake, based on the official database which recorded the condition of all the buildings of the historical centre. The statistical elaboration of the damage distribution was carried out following a classification scheme for the fill, based on the fillʹs classes produced by this scheme, the fillʹs thickness and the combination of both. sults are given in terms of damage ratios i.e. the ratios of the number of buildings in each damage status per total number of buildings inspected. The correlation of the engineering response with the thickness of the fill showed that there is a significant increase of the percentage of damaged buildings with increasing thickness. However, further analysis of these results showed that the above increase does not apply to all classes equally, which actually suggests that different parts of the fill behave differently in respect to the fill thickness. These results clearly show that a classification scheme and the determination of the boundary conditions should be used as a combined tool from an engineering geological point of view, in order to form a basis for the better understanding of the engineering behaviour of such deposits, the interpretation of geotechnical data and the design of more sophisticated investigations.