Mechanisms of slope movements are always the result of a complex stress-strain field induced by factors depends on soil properties and initial conditions and is categorised by different landslide styles. The major aim of this report is to stress the relationship existing between mechanisms and mechanics of slope movements induced by changes of boundary conditions.
The word mechanism in the context of slope stability is generally used to describe the modes of deformation and rupture of slopes. It is hence essentially related to geomorphological features of slopes and to their changes induced by movements. For this reason, even if devoted to the mechanisms of slope movements, this paper is also mechanically based, because it deals with the quantitative stress-strain-time response of slopes to changes ofi i) stress boundary conditions (e.g. by erosion, static and dynamic loading or unloading etc.); ii) hydraulic boundary conditions (e.g. by rainfall, snowmelting etc.); iii) environmental conditions (e.g. by weathering, climatic changes, infiltration of pollutant waters etc.), which determine a change of soil properties. To stress these aspects, in this report the word mechanics will be also widely used. The main topic of the report is the relationship existing between mechanisms and mechanics of slope movements in fine grained soils (stiff fissured or jointed clays, clay shales and indurated fine grained soils, as mudrocks, degradable marls etc.). In particular, it will be shown that the main landslide styles described by well known geomorphological classifications (slides, earthflows, spreads etc.) have a bearing in the mechanics of processes which develop as a consequence of changes of boundary conditions. This goal will be pursued through examples, sometimes taken from the experience of the writer, concerning well documented cases of landslides, numerical analyses of slope behaviour and any other element useful to clarify such a relationship.
