Geomechanical studies on slow slope movements in Parma Apennine

The Apennine mountains of the Parma Province (Italy) are characterized by a young geological structure subjected to continuous morphological modification in many areas. As a consequence, several active landslides can be identified in this region. Among others, slow movements occurring over large areas are the typical type of instability in this zone. The slow but constant deformation process can induce major damage when interacting with major civil infrastructures such as bridges, roads and railways, but has a less severe effect on agricultural practice and smaller structures. Four different slope instability phenomena are analyzed in this paper. All the slopes are characterized by similar geological and hydrogeological features and by similar deformation rates. All slopes have been studied by means of experimental tests and numerical modelling in order to understand the failure mechanism and the evolution of slope movement. The deformation of each slope was monitored using superficial topographic control points and inclinometers, while its water level regime is controlled by means of discontinuous piezometric readings. The monitoring results, together with in-situ and laboratory testing, allowed a more detailed understanding of processes such as deformation under a constant active stress. The development of a numerical model was necessary to predict creep rates. Special attention has been given to the mineralogical components of the material involved in the unstable areas, in order to identify the material structure characterizing these types of landslides. This work is aimed to be a methodological study of a type of complex phenomena that are recurrent in a zone of the Apennines. These phenomena can be partly considered as mudslides acting in undrained loading condition along localized shear zones but creep gives a fundamental contribution to mass deformation that must also be considered in the phenomenon modelling to be able to obtain measured displacement rates. For this purpose creep tests have been performed in undrained conditions and modeled by a finite difference code for the calibration of relevant material mechanical parameters. The paper reports the description of the problems encountered to sample and to make experimentation on this kind of complex materials along with the obtained results and, at the end, gives some operative suggestions on how to overcome such difficulties.