SOME EFFECTS ON NATURAL SLOPE STABILITY INDUCED BY THE 1980 ITALIAN EARTHQUAKE. PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON SOIL MECHANICS AND FOUNDATION ENGINEERING, SAN FRANCISCO, 12-16 AUGUST 1985

On November 23rd, 1980, a strong earthquake in Irpinia triggered numerous landslides and caused deformations in natural slopes composed of rocks, clays or structurally complex formations such as are widespread along the Apennine chain. With the exception of rock falls, the movements involved large ancient, slide masses and because they have a low margin of safety these formations are periodically mobilized by the earthquakes that successively affect the area. This paper deals with three typical cases concerning two large landslides and the deformation of a hill, which involve stiff overconsolidated clays or structurally complex formations where clay is the predominant component. The main features of the movements and the results of geotechnical surveys and direct surface observations emphasize the complexity of the phenomena which can only be explained on the basis of hypotheses concerning the stress fields and their evolution in time. For the covering abstract of the conference see IRRD 287689. (TRRL)