Assessment of the behavior of an active earth-slide by means of calibration between numerical analysis and field monitoring

Abstract

The assessment of hazards associated with active landslides and the related risk management takes advantage nowadays of using the integration of information arising from field monitoring data, including both displacement data, at ground surface and at depth, and pore pressure measurements well distributed throughout the landslide area, along with the results of numerical models. This paper provides an example of the application of this methodological approach to a case study represented by an active sector of the large Montaguto earthslide, located in the Italian Southern Apennines, which has shown in recent years a continuous slow movement, despite the draining interventions executed in 2011 and the general stability of the other portions of the earthslide. The near real-time topographic monitoring network installed in 2010 shows the presence of different kinematic sectors within the same landslide body, characterised by different velocities and evolution trends. After the proper emergency phase occurred in 2010, a specific area has still shown in 2011 and 2012 clear signs of activity, with acceleration stages generally recorded in the Spring. In order to explore the factors that presumably control the activity of this landslide sector, a two-dimensional finite element model has been developed by using PLAXIS-2D code. Based on the available geological information, pore water pressure measurements and soil geotechnical properties, the numerical results indicate the role of geometry of the landslide mass in sector E as a factor promoting the instability of this specific area. The numerical results are in good agreement with the displacement field measured throughout the landslide channel and confirm that numerical modelling can represent a reliable support for the interpretation of the landslide failure mechanism and the corresponding evolution, when calibrated against the in situ landslide behaviour reconstructed through a monitoring system.