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The preparation and compilation of an engineering geological map of Patras city wider area, at a scale of 1:5,000 is presented, prepared as a part of a thorough geotechnical study of the broader area of the city
for urban planning purposes. In this map, eleven (11) engineering geological units were grouped, based on their lithostratigraphy, physical conditions and geomechanical properties. More specifically, two (2) lithological types of man-made deposits (recent and historical fills) of small thickness, which cover at some places the Quaternary formations and Plio-Pleistocene sediments, were distinguished. The recent Quaternary formations were grouped in five (5) lithological types, namely marshy deposits, coastal sands, river bed deposits, Holocene deposits, and the weathering mantle of older formations. The old Quaternary formations were classified as alluvial, diluvial and Pleistocene deposits, while the basement of the area consists of Pliocene sediments. Of the above lithological types, the fill materials and the Holocene deposits constitute the most difficult ground of the city area. The former are loose materials of mixed phases up to 8m thick, while the latter, with a thickness up to
35m, consist of soft, clay to silty clay materials (ML, CL), with SPT 'N' values ranging from 2 to 28 and generally less than 10. In places they include thin lenses of silty sands and gravels (SM, GW-GM and GC). So,
these materials need special treatment in the case of various foundations. Also, the rest of the Quaternary formations (alluvial, diluvial and Pleistocene types), with a thickness of up to 90m and SPT 'N' values from 4 to 50, are of a high heterogeneity and non-uniform geomechanical behaviour and so they should be studied in detail for every case of human activity. Finally, the Pliocene sediments consist of the marly bedrock of the city area, with SPT 'N' values from 20 to more than 50 and a thickness more than 300m. They outcrop mostly in the area surrounding the town, and cause, in some places, instability phenomena.
The 10th IAEG International Congress, Nottingham, United Kingdom, 6-10 September 2006, Paper number 241
NTUA, School of Mineral and Metallurgical Engineer, Athens, Greece
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