l Geophysical investigation of landslides
—— Prof. Hans Balder Havenith
Detailed investigations of landslides for back-analysis calculations typically include geotechnical tests in situ and in the laboratory, but there is often also a need to apply geophysical methods in order to provide additional data on the subsurface geology. The relatively rapid acquirement of information over large areas up to a depth of several tens of metres turns geophysical prospecting into an important complementary tool for the investigation of landslides. In this lecture, the geophysical techniques that will be presented here include the electrical resistivity and seismic methods. The latter are subdivided into active methods, i.e. seismic refraction technique (analysed in terms of P-wave tomographies and multi-channel analysis of surface waves), and passive methods, i.e. the use of microseismic ambient noise with single or multiple station configurations. Presented field experiments (in the Tien Shan, Carpathians and Ardennes region) combine geophysical, geotechnical and geological investigations, and for most sites, results are now visualised within 3D geomodels.
l Regional physically-based landslide modelling - parametrization of the input data and validation of the results
——Prof. Veronica Tofani
In this lecture applications of a physically-based model, namely the HIRESSS (High REsolution Stability Simulator) model will be shown, to forecast the occurrence of shallow landslides at regional scale. The software is made of two parts: hydrological and geotechnical. The hydrological model is based on an analytical solution of an approximated form of the Richards equation while the geotechnical stability model is based on an infinite slope model that takes into account the unsaturated soil condition. The lecture will particularly deals with: i) to properly characterize the geotechnical and hydrological parameters of the soil to feed the HIRESSS model and to spatialize this punctual information in order to have spatially-continuous maps of the model input data ii) to test the HIRESSS code in different areas for elected rainfall events that have triggered several shallow landslides and to validate the model results.