Abstract: The investigation of the physical and mechanical properties of stones in monuments needs non-destructive methods and small quantity of testing material. In this framework, P & S waves ultrasonic velocities can be used for both in situ and laboratory measurements. These methods are used for studying properties such as the mechanical anisotropy, and the modulus of elasticity of the materials. In this paper, the P-wave velocities were used for the estimation of the depth of weathered or artificially consolidated layers as well as the depth of cracks at the surface of the building stone. This estimation was performed in relation to the lithology and texture of the materials, given that in many cases different lithological data create similar diagrams. All tests were performed on representative monuments in Greece.

Brief Biography of the speaker:
Professor Basile Christaras was born in 1954, in Thessaloniki.
He is a) Professor of Engineering Geology b) Director of the Geological Department and c) President of the Postgraduate Course on “Applied & Environmental Geology” in the School of Geology, of the Aristotle University of Thessaloniki (AUTH). He is also Chairman of the Join Technical Committee on “Ancient Monuments/Historic Sites” of the Federation of the International Geo-engineering Societies (IAEG, ISSMGE & ISRM).
He studied in the Aristotle University of Thessaloniki and the University P. et M. Curie of Paris. He has a very good knowledge of English and French languages and quite good knowledge of the Italian one, additionally to his Greek mother tongue.
During his carrier, he was President of the Board of Directors of the Greek Geological Survey (IGME), member of the Greek National Advisory Council of Research and Technology, member of the Boards of Directors of several National Institutions and member of European and international committees of experts. Scientifically, he is President of the Commission 16, for the protection of monuments, of the International Association of Engineering Geology.
He is responsible for the courses of soil mechanics, at graduate and postgraduate level, in the School of Geology of AUTH.
His research concerns geotechnical aspects related to a) the construction of public works, b) natural hazards c) environmental management, d) natural building stones and protection of monuments, especially with the use of non-destructive methods.
In this framework, he performed (and continues to coordinate) research projects, in Greece and abroad. Apart from Greece, his research is related to studies of St. Sophia church in Istanbul, the Cathedrals of Bari and Cadiz, small churches in Malta, the orthodox rock-hewn churches of Lalibela, in Ethiopia, fieldwork related Tree Gorges Dam in China, in collaboration with the Chinese Academy of Sciences, deep drilling construction in the Pacific Ocean and other geotechnical activities.
He is author of two books on soil mechanics, published by the Aristotle University of Thessaloniki and the Technical Chamber of Greece, and 120 scientific papers, published in international scientific journals. Furthermore, he participated in numerous international congresses (in many of them as invited speaker).