Large slope instabilities: characterisation, dating, triggering, monitoring and modelling
Co-organized as GM7.7/HS11.42, co-sponsored by JpGU
Convener: Giovanni Crosta | Co-conveners: Federico Agliardi, Masahiro Chigira, Irene Manzella
| Tue, 09 Apr, 14:00–18:00
Room L1
| Attendance Tue, 09 Apr, 10:45–12:30
Hall X3

Large slope instabilities have been frequently recognised in areas with different lithological (sedimentary, igneous, metamorphic rocks) and geological domains (cordillera, volcanic, etc.). Slow to very fast moving, complex mass movements have been recognized and sometimes described as strongly interrelated. Many types of slope instabilities can be grouped within this broad class, each presenting different types of hazard and risk. Some major aspects of these slope instabilities are still understudied and debated, namely:
- their regional distribution and relevance;
- triggering and controlling factors, including possible climatic changes;
- hydrological boundary conditions and evolution or control of internal hydrogeological conditions;
- mechanical controls in terms of physical mechanical properties of failure surfaces and shear zones
- dating of initial movements and reactivation episodes;
- style and state of past and present activity;
- passive and/or active control by structural-tectonic elements of the bedrock geology;
- possible styles of evolution and consequent modeling approaches;
- assessment of related hazard;
- influence of external anthropogenic factors and effects on structures and infrastructures (e.g. tunnels, dams, bridges);
- role on the general erosional and sediment yield regime at the local or mountain belt scale;
- best technologies and approaches for implementing a correct monitoring and warning system and for the interpretation of monitoring data in terms of landslide activity and behavior.

Study of these instabilities requires a multidisciplinary approach involving geology, geomorphology, geomechanics, hydro-geochemistry, and geophysics. These phenomena have been recognized on Earth as well as on other planetary bodies (e.g. Mars, Moon).
Trenching and drilling can be used for material characterization, recognition of episodes of activity, and sampling in slow slope movements. At the same time many different approaches can be used for monitoring and establishing of warning thresholds and systems for such phenomena.
Geophysical survey methods can be used to assess both the geometrical and geomechanical characteristics of the unstable mass. Different dating techniques can be applied to determine the age and stages of movement. Many modeling approaches can be applied to evaluate instability and failure (e.g. displacement and velocity thresholds), triggering mechanisms (e.g. rainfall, seismicity, volcanic eruption, deglaciation), failure propagation, rapid mass movements (rock avalanches, debris avalanches and flows), and related secondary failures (rock fall and debris flows).
Studies of hydraulic and hydrologic boundary conditions and hydrochemistry are involved, both at the moment of initial failure and, later, during reactivation. The impacts of such instabilities on structures and human activities can be substantial and of a variety of forms (e.g. deformation or failure of structures and infrastructure, burial of developed areas, etc.).
Furthermore, the local and regional sediment yield could be influenced by the landsliding activity and different landslides (e.g. type, size) can play different roles.