Experimental analysis of seasonal processes in shallow landslide through downscaled observations

Shallow landslides are phenomena involving small parts of land and are triggered by huge intensity rainfall events of short duration or more moderate but prolonged over time. The area and thickness of such slips are typically reduced, but they are still harmful because there are no warning signs and no information on their possible evolution.

Since the middle of the 20th century, heavy precipitation events have been more frequent and intense. In light of the current climate crisis, it is crucial to thoroughly examine the effects of these occurrences in order to establish triggering thresholds in mountain regions.  

This work deals with the experimental study of these landslides through the laboratory simulations on a small-scale slope, reproduced at the Gap2 lab of the Lecco Campus.  Different experiments have been performed reproducing the seasonal conditions of the slopes. In particular, extreme rainfall events, soil conditions with different volumetric water content percentages were compared with moderate rainfall events in order to assess the different timing of landslide triggering.

To investigate the behaviour of surface landslides under these conditions and to visualise in detail the processes related to water circulation, a multidisciplinary approach was adopted that consist of observations using geological, geophysical and photogrammetric methodologies and instrumentation. These technologies include modified pressure transmitters for the pore water pressure evaluation, GoPro’s cameras, TDR (Time Domain Reflectometry) for the volumetric water content evaluation and a georesistivimeter (IRIS Syscal Pro). In this way hydrogeological processes can be deeply analysed from different perspectives and can highlight peculiarities and assess in detail their evolution leading to collapse.

Through the information obtained from geophysics, it is possible to visualise the formation of cracks within the landslide body in advance, also allowing considerations regarding the different water contributions of the simulated rainfall and the initial water content in the soil. The experimental results were then compared with a mathematical model.